TECHNICAL FIELD

The present invention relates generally to compositions of, processes for manufacturing, and uses of microfibrillated cellulose in forming fibres and non-woven materials comprising such microfibrillated cellulose-containing fibres. The fibres may

additionally comprise at least one inorganic particulate material that may optionally be used in the processing of the microfibrillated cellulose. The compositions of microfibrillated cellulose or microfibrillated cellulose and at least one inorganic particulate material may additionally comprise a water soluble or dispersible polymer, which compositions may also be used in forming fibres and non-woven materials comprising such fibres.

BACKGROUND OF THE INVENTION

Microfibrillated cellulose may be added to various compositions and products in order to reduce the use of another component of the composition and consequently reduce cost, which must be balanced with the physical, mechanical and/or optical requirements of the end-product. It is desirable to utilize compositions of microfibrillated cellulose and compositions comprising microfibrillated cellulose and a water soluble or dispersible polymer for use in the manufacture of fibres and non-woven materials comprising those fibres. Advantages associated with the use of microfibrillated cellulose, and, optionally inorganic particulate material, in the manufacture of fibres and nonwoven products made therefrom include higher mineral loading, higher

microfibnllated cellulose loading, no substantial deterioration in elastic modulus and/or tensile strength of the fibre; improvement in elastic modulus and/or tensile strength of the fibre; improved temperature resistance, biodegradable and/or flushable and biodegradable compositions; and water-based (not solvent-based) compositions.

Additional advantages associated with the use of microfibnllated cellulose, and, optionally inorganic particulate material, in the manufacture of fibres and nonwoven products made therefrom include the ability of such fibres and nonwoven materials to be composted and that the fibres and nonwoven materials come from a sustainable source.

SUMMARY OF THE INVENTION

The present invention relates generally to compositions comprising, consisting essentially of, or consisting of microfibrillated cellulose, and methods utilizing such microfibrillated cellulose compositions to manufacture fibres and non-woven materials made from and comprising such fibres.

Microfibrillated cellulose suitable for the compositions and methods of the present invention may, for example, have a fibre steepness ranging from about 20 to about 50. The microfibrillated cellulose may, for example, be processed with a grinding material of a size greater than 0.5 mm in a grinding vessel followed by a second stage processing in a refiner, homogenizer or by sonification with an ultrasonic device resulting in microfibrillated cellulose having a median diameter (d50) less than 100 μm, an increased percentage of material finer than 25 μηι and a lower percentage of material coarser than 300 μm, by the methods of the present invention. The microfibrillated cellulose

obtained or obtainable by the foregoing two-stage processing may be readily extruded through an extruder, dried by an attenuating gas, such as one or more streams of hot air, and collected as fibres. The collected fibres may be used to make various nonwoven materials, including nonwoven bonded fabrics and articles.

Microfibrillated cellulose suitable for the compositions and methods of the present invention may, for example, have a fibre steepness ranging from about 20 to about 50. The microfibrillated cellulose may, for example, be processed with a grinding material of a size greater than 0.5 mm in a grinding vessel followed by a second stage processing in a refiner, homogenizer or by sonification with an ultrasonic device resulting in microfibrillated cellulose having a median diameter (d50) less than 100 μm, an increased percentage of material finer than 25 μηι and a lower percentage of material coarser than 300 μπι, by the methods of the present invention. The microfibrillated obtained or obtainable by the foregoing two-stage processing may be mixed with a water soluble or dispersible polymer and may be readily extruded through an extruder, dried by an attenuating gas, such as one or more streams of hot air, and collected as fibres. The collected fibres may be used to make various nonwoven materials, including nonwoven bonded fabrics and articles.

Similarly, the microfibrillated cellulose of the present invention may be ground (co-processed) with at least one inorganic particulate material in the presence or the absence of grinding material of a size greater than 0.5 mm in a grinding vessel followed by a second stage processing in a refiner, homogenizer or by sonification with an ultrasonic device resulting in microfibrillated cellulose having a median diameter (d50) less than 100 μm, an increased percentage of material finer than 25 μm and a lower percentage of material coarser than 300 μm, by the methods of the present invention. The

microfibrillated cellulose may exhibit higher tensile strength performance, thereby permitting such microfibrillated cellulose compositions to be readily extruded through an extruder, dried by an attenuating gas, such as one or more streams of hot air, and collected as fibres. The collected fibres may be used to make various nonwoven materials, including nonwoven bonded fabrics and articles.

The microfibrillated cellulose of the present invention may be ground (co-processed) with at least one inorganic particulate material in the presence or the absence of grinding material of a size greater than 0.5 mm in a grinding vessel followed by a second stage processing in a refiner, homogenizer or by sonification with an ultrasonic device resulting in microfibrillated cellulose having a median diameter (d50) less than 100 μm, an increased percentage of material finer than 25 μm and a lower percentage of material coarser than 300 μηι, by the methods of the present invention. The

microfibrillated cellulose may exhibit higher tensile strength performance, thereby permitting such microfibrillated cellulose compositions to be readily extruded through an extruder, dried by an attenuating gas, such as one or more streams of hot air, and collected as fibres. The microfibrillated obtained or obtainable by the foregoing two-stage processing may optionally be mixed with a water soluble or dispersible polymer and may be readily extruded through a extruder, dried by an attenuating gas, such as one or more streams of hot air, and collected as fibres. The collected fibres may be used to make various nonwoven materials, including nonwoven bonded fabrics and articles.

In accordance with a first aspect of the present invention, there is provided a fibre comprising, consisting essentially of, or consisting of microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate comprising cellulose in a grinding vessel and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising microfibrillated cellulose; wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μπι.

In certain embodiments of the first aspect, the grinding vessel may be a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the first aspect, the refiner may be a single disc, conical, twin disc or plate refiner.

In certain embodiments of the first aspect, the ultrasonic device may be an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

In accordance with a second aspect of the present invention, there is provided a fibre comprising (a) a microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate comprising cellulose in a grinding vessel and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the fibrous substrate comprising cellulose; wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size; and (b) a water-soluble or dispersible polymer.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μιη.

In certain embodiments of the second aspect, the grinding vessel may be a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the second aspect, the refiner may be a single disc, conical, twin disc or plate refiner.

In certain embodiments of the second aspect, the ultrasonic device may be an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

In certain embodiments of the second aspect, the water soluble or dispersible polymers include water soluble polymers, natural and synthetic latex, colloidal dispersions of polymer particles, emulsions, mini-emulsion, micro-emulsions or dispsersion polymerization.

In accordance with a third aspect of the present invention, there is provided a fibre comprising, consisting essentially of, or consisting of microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate comprising cellulose in a grinding vessel, wherein the grinding of the fibrous substrate comprising cellulose is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the fibrous substrate comprising cellulose and at least one inorganic particulate material; wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μπι.

In certain embodiments of the third aspect, the refiner may be a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the third aspect, the grinding vessel may be a Stirred media detritor, screened grinder, tower mill, SAM or IsaMill.

In certain embodiments of the third aspect, the ultrasonic device may be an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

In accordance with a fourth aspect of the present invention, there is provided a fibre comprising, consisting essentially of, or consisting of microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate comprising cellulose in a grinding vessel, wherein the grinding of the fibrous substrate comprising cellulose is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the fibrous substrate comprising cellulose and at least one inorganic particulate material; wherein the grinding is carried out in an aqueous environment in the absence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μm.

In certain embodiments of the fourth aspect, the refiner may be a single disc, conical, twin disc or plate refiner.

In certain embodiments of the fourth aspect, the grinding vessel may be a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the fourth aspect, the ultrasonic device may be an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

In accordance with a fifth aspect of the present invention, there is provided a fibre comprising, consisting essentially of, or consisting of: (a) microfibnllated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate comprising cellulose in a grinding vessel, wherein the grinding of the fibrous substrate comprising cellulose is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the fibrous substrate comprising cellulose and at least one inorganic particulate material; wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size; and (b) a water-soluble or dispersible polymer.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μιη.

In certain embodiments of the fifth aspect, the refiner may be a single disc, conical, twin disc or plate refiner.

In certain embodiments of the fifth aspect, the grinding vessel may be a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the fifth aspect, the ultrasonic device may be an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

In certain embodiments of the fifth aspect, the water soluble or dispersible polymers include water soluble polymers, natural and synthetic latex, colloidal dispersions of polymer particles, emulsions, mini-emulsion, micro-emulsions or dispsersion polymerization.

In accordance with a sixth aspect of the present invention, there is provided a fibre comprising, consisting essentially of, or consisting of: (a) microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate comprising cellulose in a grinding vessel, wherein the grinding of the fibrous substrate comprising cellulose is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the fibrous substrate comprising cellulose and at least one inorganic particulate material; wherein the grinding is carried out in an aqueous environment in the absence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and

wherein the grinding medium is 0.5 mm or greater in size; and (b) a water-soluble or dispersible polymer.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μm.

In certain embodiments of the sixth aspect, the refiner may be a single disc, conical, twin disc or plate refiner.

In certain embodiments of the sixth aspect, the grinding vessel may be a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the sixth aspect, the ultrasonic device may be an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

In certain embodiments of the sixth aspect, the water soluble or dispersible polymers include water soluble polymers, natural and synthetic latex, colloidal dispersions of polymer particles, emulsions, mini-emulsion, micro-emulsions or dispsersion polymerization.

In certain embodiments of the first to sixth aspects, the grinding medium other than inorganic particulate material has a minimum size of 0.5 mm or greater. The grinding medium, when present, may be of a natural or a synthetic material. The grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300°C to about 1800°C. For example, in some embodiments a Carbolite® grinding media is preferred. Alternatively, particles of natural sand of a suitable particle size may be used.

In other embodiments, hardwood grinding media (e.g. woodflour) may be used.

Generally, the type of and particle size of grinding medium to be selected for use in the methods may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground. In some embodiments, the particulate grinding medium comprises particles having an average diameter in the range of from about 0.5mm to about 6.0mm, or in the range of from about 0.5mm to about 4.0mm. The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.

In certain embodiments of the first to sixth aspects, the microfibrillated cellulose has a fibre steepness equal to or greater than about 10, as measured by Malvern (laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd) or by other methods which give essentially the same result.

The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern (laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd) or by other methods which give essentially the same result. Fibre steepness (i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula:

Steepness = 100 x (d30/d70).

The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

In certain embodiments of the first to the sixth aspects, the microfibrillated cellulose has a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

In certain embodiments of the first to the sixth aspects, the microfibrillated cellulose has a modal fibre particle size ranging from about 0.1-500 μm.

In certain embodiments of the first to the sixth aspects, the microfibrillated cellulose has a modal fibre particle size ranging from about 0.1-500 μιη and a modal inorganic particulate material particle size ranging from 0.25-20 μιη.

In certain embodiments of the first to the sixth aspects, the microfibrillated cellulose in the first grinding stage is obtained or obtainable with a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the first to the sixth aspects, the microfibrillated in the second refining stage is obtained or obtainable with a single disc, conical, twin disc, or plate refiner, for example, a single disc refiner (manufactured by Sprout) having a 12 in (30cm) single disc.

In accordance with a seventh aspect of the invention, there is provided a method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) extruding the microfibrillated cellulose from step (1) through an extruder;

(3) attenuating the extruded microfibrillated cellulose with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μιη.

In accordance with an eight aspect of the invention, there is provided a method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) mixing the composition of microfibrillated cellulose with a polymer to form a second mixture;

(3) extruding the second mixture through an extruder;

(4) attenuating the extruded second mixture with an attenuating gas, for example, hot air; and

(5) collecting the extruded fibres.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μπι.

In accordance with a ninth aspect of the invention, there is provided a method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material; wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) extruding the microfibrillated cellulose and at least one inorganic particulate material from step (1) through an extruder;

(3) attenuating the extruded microfibrillated cellulose and at least one inorganic particulate material with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μηι.

In accordance with a tenth aspect of the invention, there is provided a method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material; wherein the grinding is carried out in an aqueous environment in the absence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) extruding the microfibrillated cellulose and at least one inorganic particulate material from step (1) through an extruder;

(3) attenuating the extruded microfibrillated cellulose and at least one inorganic particulate material with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μm.

In accordance with an eleventh aspect of the invention, there is provided a method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) mixing the composition of microfibrillated cellulose and at least one organic particulate material with a polymer to form a second mixture;

(3) extruding the second mixture through an extruder;

(3) attenuating the extruded second mixture with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μπι.

In accordance with a twelfth aspect of the invention, there is provided a method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material;

wherein the grinding is carried out in an aqueous environment in the absence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) mixing the composition of microfibrillated cellulose and at least one inorganic particulate material with a polymer to form a second mixture;

(3) extruding the second mixture through an extruder;

(4) attenuating the extruded second mixture with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

In certain embodiments, the microfibrillated cellulose has a median diameter (d50) less than 100 μπι.

In certain embodiments of the seventh to the twelfth aspects, the grinding medium other than inorganic particulate material has a minimum size of 0.5 mm or greater. The grinding medium, when present, may be of a natural or a synthetic material. The grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300°C to about 1800°C. For example, in some embodiments a Carbolite® grinding media is preferred. Alternatively, particles of natural sand of a suitable particle size may be used.

In other embodiments, hardwood grinding media (e.g. woodflour) may be used.

Generally, the type of and particle size of grinding medium to be selected for use in the methods may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground. In some embodiments, the particulate grinding medium comprises particles having an average diameter in the range of from about 0.5mm to about 6.0mm, or in the range of from about 0.5mm to about 4.0mm. The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.

In certain embodiments of the seventh to the twelfth aspects, the microfibrillated cellulose has a fibre steepness equal to or greater than about 10, as measured by Malvern (laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd) or by other methods which give essentially the same result. The fibrous substrate comprising cellulose alternatively may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern (laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd) or by other methods which give essentially the same result. Fibre steepness (i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula:

Steepness = 100 x (d3o/d7o).

The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

In certain embodiments of the seventh to the twelfth aspects, the microfibrillated cellulose has a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

In certain embodiments of the seventh to the twelfth aspects, the microfibrillated cellulose has a modal fibre particle size ranging from about 0.1-500 μη .

In certain embodiments of the seventh to the twelfth aspects, the microfibrillated cellulose has a modal fibre particle size ranging from about 0.1-500 μπι and a modal inorganic particulate material particle size ranging from 0.25-20 μπι.

In certain embodiments of the seventh to the twelfth aspects, the microfibrillated cellulose in the first grinding stage is obtained or obtainable with a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In certain embodiments of the seventh to the twelfth aspects, the microfibrillated in the second refining stage is obtained or obtainable with a single disc, conical, twin disc, or plate refiner, for example, a single disc refiner (manufactured by Sprout) having a 12in (30cm) single disc.

In certain embodiments of the first to twelfth aspects, the median diameter (d$ ) is less than 100 μηι, and has an increased percentage of material finer than 25 μιη and a lower percentage of material coarser than 300 μπι, by the methods of the present invention compared to methods not employing a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material.

In certain embodiments of the first to twelfth aspects, the median diameter (d50) is less than 100 μπι, and has an increased percentage of material finer than 25 μιη and a lower percentage of material coarser than 300 μιη, by the methods of the present invention compared to methods not employing a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material; and wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size.

In certain embodiments of the seventh to the twelfth aspects, the method comprises extruding the composition comprising, consisting essentially of, or consisting of microfibrillated cellulose, by attenuating or drying extruded fibres with an attenuating gas, preferably, one or more stream of hot air.

In further embodiments of the ninth to the twelfth aspects, the method comprises extruding the composition comprising, consisting essentially of, or consisting of microfibrillated cellulose and at least one inorganic particulate material, by attenuating or drying extruded fibres with an attenuating gas, preferably, one or more stream of hot air.

In still further embodiments of the eleventh to the twelfth aspects, the method comprises extruding the composition comprising, consisting essentially of, or consisting of microfibrillated cellulose and at least one inorganic particulate material and a water soluble or dispersible polymer, by attenuating or drying extruded fibres with an attenuating gas, preferably, one or more stream of hot air..

In certain embodiments of the seventh to the twelfth aspects, the attenuating gas comprises one or more streams of hot air, which dries the extruded fibre comprising microfibrillated cellulose. In other embodiments of the ninth to the twelfth aspects, the attenuating gas comprises one or more streams of hot air, which dries the extruded fibre comprising microfibrillated cellulose and at least one inorganic particulate material.

In certain embodiments of the eleventh and twelfth aspects, the attenuating gas comprises one or more streams of hot air, which dries the extruded fibre comprising microfibrillated cellulose and at least one inorganic particulate material and polymer.

In certain embodiments of seventh to the twelfth aspects, the extrusion rate is about 0.3 g min to about 2.5 g/min, or in other embodiments the extrusion rate may be about 0.4 g min to 0.8 g/min.

In certain embodiments seventh to the twelfth aspects, the fibres may be extruded at a temperature at or below 100° C.

In certain embodiments seventh to the twelfth aspects, the fibres have an average diameter of from about 0.1 μπι to about 1 mm. In other embodiments, the fibres have an average diameter of from about 0.1 μπι to about 180 μπι.

In certain embodiments of the first to the twelfth aspects, the fibres have an elastic modulus from about 5 GPa to about 20 GPa. In still further embodiments, the fibres have a fibre strength of about 40 MPa to about 200 MPa. In some embodiments, the fibres may have an increase in elastic modulus over fibres made from compositions lacking microfibrillated manufactured by the two stage process of the method of the second aspect of the present invention.

In certain embodiments, the fibres are spunlaid fibres. In still further embodiments the spunlaid fibres are formed by spunbonding. In further embodiments the spunbonding step may be selected from the group consisting of flash-spinning, needle-punching and water punching.

In certain embodiments of the seventh to the twelfth aspects, the collecting step is deposition of the fibres onto a foraminous surface to form a nonwoven web. In still further embodiments, the foraminous surface is a moving screen or wire.

In certain embodiments of the seventh to the twelfth aspects, the nonwoven web is bonded by hydro-entanglement. In still further embodiments, the nonwoven web is bonded by through-air thermal bonding. In a certain embodiment, the nonwoven web is bonded mechanically.

In certain embodiments of the preceding aspects of the present invention, the inorganic particulate material used to prepare the composition of microfibrillated cellulose is selected from the group consisting of alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, huntite, hydromagnesite, ground glass, perlite or diatomaceous earth, or wollastonite, or titanium dioxide, or magnesium hydroxide, or aluminium trihydrate, lime, graphite, or combinations thereof.

In certain embodiments of the preceding aspects of the present invention, the composition of microfibrillated cellulose further comprises one or more additives selected from the group consisting of starch, carboxymethyl cellulose, guar gum, urea, polyethylene oxide, and amphoteric carboxymethyl cellulose.

In certain embodiments of the preceding aspects of the present invention, the composition of microfibrillated cellulose further comprises one or more additive

selected from the group consisting of dispersant, biocide, suspending agent, and oxidising agents.

In a thirteenth aspect of the present invention, the use of fibres according to the method of the seventh to the twelfth aspects to manufacture a nonwoven product is

contemplated.

In certain embodiments, the use of the thirteenth aspect of the present invention to prepare nonwoven products selected from the group consisting of: diapers, feminine hygiene products, adult incontinence products, packaging materials, wipes, towels, dust mops, industrial garments, medical drapes, medical gowns, foot covers, sterilization wraps, table cloths, paint brushes, napkins, trash bags, various personal care articles, ground cover, and filtration media, is contemplated. In further embodiments, the nonwoven products prepared by the thirteenth aspect of the present invention are biodegradable.

In accordance with a fourteenth aspect of the present invention, there is provided a method for making a fabric according to any foregoing aspects or further embodiments of the present invention described herein. In certain embodiments, the method comprises dispersing one or more fibres according to any aspect or embodiment of the present invention such that they form a web and bonding the one or more fibres at the points where they intersect. In certain embodiments, the method comprises weaving one or more fibres according to any aspect or embodiment of the present invention.

Certain embodiments of the present invention may provide one or more of the following advantages: higher mineral loading; higher MFC loading; no substantial deterioration in elastic modulus and/or tensile strength of composition; temperature resistance, improvement in elastic modulus and/or tensile strength of composition; biodegradable and/or flushable compositions; and water-based (not solvent-based) compositions.

The details, examples and preferences provided in relation to any particular one or more of the stated aspects of the present invention apply equally to all aspects of the present invention. Any combination of the embodiments, examples and preferences described herein in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein, or otherwise clearly contradicted by context.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a summary of the effect of the use of a single disc refiner on dried composition comprising microfibrillated cellulose and calcium carbonate materials.

Figure 2 shows the effect of exposure to an ultrasonic bath on MFC viscosity.

Figure 3 shows the effect of exposure to an ultrasonic probe on FLT index (Nm/g).

Figure 4 shows the effect of exposure to an ultrasonic probe on MFC viscosity.

Figure 5 shows the effect of exposure to pulsed ultrasound on MFC.

Figure 6 shows the effect of ceramic media contamination on MFC exposed to ultrasonification.

Figure 7 shows the effect of ultrasonification on a 50% POP pressed cake.

Figure 8 shows the effect of high shear and ultrasonification on a mineral-free belt pressed cake.

Figure 9 shows the effect of ultrasonification on a high solids dry milled belt pressed cake.

Figure 10 shows the effect of ultrasonification on a high solids dry milled belt pressed cake.

DETAILED DESCRIPTION

The present invention relates generally to the use of microfibrillated cellulose in various fibres and non-woven products made from such fibres. The present invention also relates generally to the use of microfibrillated cellulose as a filler in various non-woven products made by molding or deposition.

The microfibrillated cellulose may have any one or more of the features of the microfibrillated cellulose described in WO 2010/131016 and WO 2012/066308, which are hereby incorporated by reference. Alternatively or additionally, the microfibrillated cellulose may be made by any one or more of the methods described in these documents.

The microfibrillated cellulose may, for example, be made by grinding a fibrous substrate comprising cellulose in an aqueous environment in the presence of a grinding medium, wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size. The fibrous substrate comprising cellulose may, for example, be ground in the presence of an inorganic particulate material to form a co-processed microfibrillated cellulose and inorganic particulate material composition.

As used herein, "co-processed microfibrillated cellulose and inorganic particulate material composition" refers to compositions produced by the processes for

microfibrillating fibrous substrate comprising cellulose in the present of an inorganic particulate material as described herein.

The fibrous substrate comprising cellulose may, for example, be ground in the absence of a grindable inorganic particulate material.

The fibrous substrate comprising cellulose may, for example, be ground in a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed, preferably in a stirred media detritor.

The microfibrillated cellulose may, for example, have a fibre steepness ranging from about 10 to about 100 or from about 20 to about 50.

Microfibrillated Cellulose and Methods of Making Microfibrillated Cellulose

• Microfibrillation in the presence of inorganic particulate material

In certain embodiments, a cellulose pulp may be beaten in the presence of an inorganic particulate material, such as calcium carbonate.

The microfibrillated cellulose may, for example, be made by a method comprising a step of microfibrillating a fibrous substrate comprising cellulose in the presence of an inorganic particulate material. The microfibrillating step may be conducted in the presence of an inorganic particulate material which acts as a microfibrillating agent.

By microfibrillating is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as smaller aggregates as compared to the fibres of the pre-microfibrillated pulp. The microfibrillated cellulose may be obtained by microfibrillating cellulose, including but not limited to the processes described herein. Typical cellulose fibres (i.e., pre-microfibrillated pulp) suitable for use in making fibres and non-woven materials from such fibres, include larger aggregates of hundreds or thousands of individual cellulose microfibrils. By microfibrillating the cellulose, particular characteristics and properties, including but not limited to the characteristic and properties described herein, are imparted to the microfibrillated cellulose and the compositions including the microfibrillated cellulose.

For preparation of microfibrillated cellulose useful for making fibres and nonwoven materials from such fibres, the fibrous substrate comprising cellulose may be preferably treated in a two stage fibrillation process. The fibrous substrate may be added to a grinding vessel in a dry state. The grinding may be accomplished in a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed. Preferably, the grinding is carried out in a screened grinder, such as a stirred media detritor. For example, a fibrous substrate may be added directly to a grinding vessel. The aqueous environment in the grinding vessel will then facilitate the formation of a pulp. The second stage of microfibrillating the fibrous substrate may be carried out in any a refiner, or a homogenizer or by sonication with an ultrasonic device, for example, an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn. The refiner may be a single disc, conical, twin disc, or plate refiner, for example, a single disc refiner (manufactured by Sprout) having a 12in (30cm) single disc.

In one embodiment, the microfibrillating step is conducted in a grinding vessel under wet-grinding conditions.

Wet-grinding

The grinding is suitably performed in a conventional manner. The grinding may be an attrition grinding process in the presence of a particulate grinding medium of 0.5 mm or greater size, or may be an autogenous grinding process, i.e., one in the absence of a grinding medium. By grinding medium is meant a medium other than the inorganic particulate material of 0.5 mm or greater in size, which is co-ground with the fibrous substrate comprising cellulose.

The particulate grinding medium, when present, may be of a natural or a synthetic material. The grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300°C to about 1800°C. For example, in some embodiments a Carbolite® grinding media is preferred. Alternatively, particles of natural sand of a suitable particle size may be used. In other embodiments, hardwood grinding media (e.g. woodflour) may be used.

Generally, the type of and particle size of grinding medium to be selected for use in the methods may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground. In some embodiments, the particulate grinding medium comprises particles having an average diameter in the range of from about 0.5mm to about 6.0mm, or in the range of from about 0.5mm to about 4.0mm. The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.

The grinding may be carried out in one or more stages. For example, a coarse inorganic particulate material may be ground in the grinder vessel to a predetermined particle size distribution, after which the fibrous material comprising cellulose is added and the grinding continued until the desired level of microfibrillation has been obtained.

The coarse inorganic particulate material initially may have a particle size distribution in which less than about 20% by weight of the particles have an e.s.d of less than 2μιη, for example, less than about 15% by weight, or less than about 10% by weight of the particles have an e.s.d. of less than 2μηι. In another embodiment, the coarse inorganic particulate material initially may have a particle size distribution, as measured using a Malvern Mastersizer S machine, in which less than about 20% by volume of the particles have an e.s.d of less than 2μπι, for example, less than about 15% by volume, or less than about 10% by volume of the particles have an e.s.d. of less than 2μπι.

The coarse inorganic particulate material may be wet or dry ground in the absence or presence of a grinding medium. In the case of a wet grinding stage, the coarse inorganic particulate material may be ground in an aqueous suspension in the presence of a grinding medium. In such a suspension, the coarse inorganic particulate material may preferably be present in an amount of from about 30% to about 70% by weight of the suspension. In some embodiments, the inorganic particulate material may be absent. As described above, the coarse inorganic particulate material may be ground to a particle size distribution such that at least about 10% by weight of the particles have an e.s.d of less than 2μπι, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% by weight of the particles, have an e.s.d of less than 2μηι, after which the cellulose pulp is added and the two components are co-ground to microfibrillate the fibres of the cellulose pulp.

In another embodiment, the coarse inorganic particulate material is ground to a particle size distribution, as measured using a Malvern Mastersizer S machine such that at least about 10% by volume of the particles have an e.s.d of less than 2μηι, for example, at least about 20% by volume, or at least about 30% by volume or at least about 40% by volume, or at least about 50% by volume, or at least about 60% by volume, or at least about 70% by volume, or at least about 80% by volume, or at least about 90% by volume, or at least about 95% by volume, or about 100% by volume of the particles,

have an e.s.d of less than 2μm, after which the cellulose pulp is added and the two components are co-ground to microfibrillate the fibres of the cellulose pulp

In one embodiment, the mean particle size (d50) of the inorganic particulate material is reduced during the co-grinding process. For example, the d50 of the inorganic particulate material may be reduced by at least about 10% (as measured by a Malvern Mastersizer S machine), for example, the d50 of the inorganic particulate material may be reduced by at least about 20%, or reduced by at least about 30%, or reduced by at least about 50%, or reduced by at least about 50%, or reduced by at least about 60%, or reduced by at least about 70%, or reduced by at least about 80%, or reduced by at least about 90%. For example, an inorganic particulate material having a d50 of 2.5 μπι prior to co-grinding and a d50 of 1.5 μιη post co-grinding will have been subject to a 40% reduction in particle size. In embodiments, the mean particle size of the inorganic particulate material is not significantly reduced during the co-grinding process. By 'not significantly reduced' is meant that the d50 of the inorganic particulate material is reduced by less than about 10%, for example, the d50 of the inorganic particulate material is reduced by less than about 5%.

The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d50 ranging from about 5 μιη to about 500 μπι, as measured by laser light scattering. The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d50 of equal to or less than about 400 μm, for example equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μπι, or equal to or less than about 125 μηι, or equal to or less than about 100 μπι, or equal to or less than about 90 μηι, or equal to or less than about 80 μηι, or equal to or less than about 70 μηι, or equal to or less than about 60 μη , or equal to or less than about 50 μm, or equal to or less than about 40 μηι, or equal to or less than about 30 μm, or equal to or less than about 20 μηι, or equal to or less than about 10 μηι. Preferably, the fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d50 of equal to or less than about 100 μm, more preferably equal to or less than about 90 μm , or equal to or less than about 80 μm, or equal to or less than about 70 μηι, or equal to or less than about 60 μπι.

The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 μm and a modal inorganic particulate material particle size ranging from 0.25-20 μm . The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 μπι, for example at least about 10 μm , or at least about 50 μπι, or at least about 100 μιη, or at least about 150 μm , or at least about 200 μm , or at least about 300 μm , or at least about 400 μm .

The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern (laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd) or by other methods which give essentially the same result. Fibre steepness (i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula:

Steepness = 100 x (d30 d70).

The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

The grinding is suitably performed in a grinding vessel, such as a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In one embodiment, the grinding vessel is a tower mill. The tower mill may comprise a quiescent zone above one or more grinding zones. A quiescent zone is a region located towards the top of the interior of tower mill in which minimal or no grinding takes place and comprises microfibrillated cellulose and inorganic particulate material. The quiescent zone is a region in which particles of the grinding medium sediment down into the one or more grinding zones of the tower mill.

The tower mill may comprise a classifier above one or more grinding zones. In an embodiment, the classifier is top mounted and located adjacent to a quiescent zone. The classifier may be a hydrocyclone.

The tower mill may comprise a screen above one or more grind zones. In an

embodiment, a screen is located adjacent to a quiescent zone and/or a classifier. The screen may be sized to separate grinding media from the product aqueous suspension comprising microfibrillated cellulose and inorganic particulate material and to enhance grinding media sedimentation.

In an embodiment, the grinding is performed under plug flow conditions. Under plug flow conditions the flow through the tower is such that there is limited mixing of the grinding materials through the tower. This means that at different points along the length of the tower mill the viscosity of the aqueous environment will vary as the fineness of the microfibrillated cellulose increases. Thus, in effect, the grinding region in the tower mill can be considered to comprise one or more grinding zones which have a characteristic viscosity. A skilled person in the art will understand that there is no sharp boundary between adjacent grinding zones with respect to viscosity.

In an embodiment, water is added at the top of the mill proximate to the quiescent zone or the classifier or the screen above one or more grinding zones to reduce the viscosity of the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material at those zones in the mill. By diluting the product microfibrillated cellulose and inorganic particulate material at this point in the mill it has been found that the prevention of grinding media carry over to the quiescent zone and/or the

classifier and/or the screen is improved. Further, the limited mixing through the tower allows for processing at higher solids lower down the tower and dilute at the top with limited backflow of the dilution water back down the tower into the one or more grinding zones. Any suitable amount of water which is effective to dilute the viscosity of the product aqueous suspension comprising microfibrillated cellulose and inorganic particulate material may be added. The water may be added continuously during the grinding process, or at regular intervals, or at irregular intervals.

In another embodiment, water may be added to one or more grinding zones via one or more water injection points positioned along the length of the tower mill, or each water injection point being located at a position which corresponds to the one or more grinding zones. Advantageously, the ability to add water at various points along the tower allows for further adjustment of the grinding conditions at any or all positions along the mill.

The tower mill may comprise a vertical impeller shaft equipped with a series of impeller rotor disks throughout its length. The action of the impeller rotor disks creates a series of discrete grinding zones throughout the mill.

In another embodiment, the grinding is performed in a screened grinder, for example a stirred media detritor. The screened grinder may comprise one or more screen(s) having a nominal aperture size of at least about 250 μηι, for example, the one or more screens may have a nominal aperture size of at least about 300 μπι, or at least about 350μηι, or at least about 400 μπι, or at least about 450 μιη, or at least about 500 μπι, or at least about 550 μηι, or at least about 600 μιη, or at least about 650 μπι, or at least about 700 μπι, or at least about 750 μηι, or at least about 800 μηη, or at least about 850 μηι, or at or least about 900 μπι, or at least about 1000 μηι.

The screen sizes noted immediately above are applicable to the tower mill embodiments described above.

As noted above, the grinding may be performed in the presence of a grinding medium. In an embodiment, the grinding medium is a coarse media comprising particles having an average diameter in the range of from about 0.5 mm to about 6 mm, for example about 2 mm, or about 3 mm, or about 4 mm, or about 5 mm.

In another embodiment, the grinding media has a specific gravity of at least about 2.5, for example, at least about 3, or at least about 3.5, or at least about 4.0, or at least about 4.5, or least about 5.0, or at least about 5.5, or at least about 6.0.

In another embodiment, the grinding media comprises particles having an average diameter in the range of from about 1 mm to about 6 mm and has a specific gravity of at least about 2.5.

In another embodiment, the grinding media comprises particles having an average diameter of about 3 mm and specific gravity of about 2.7.

As described above, the grinding medium (or media) may present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by

volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.

In one embodiment, the grinding medium is present in amount of about 50% by volume of the charge.

By 'charge' is meant the composition which is the feed fed to the grinder vessel. The charge includes of water, grinding media, fibrous substrate comprising cellulose and inorganic particulate material, and any other optional additives as described herein.

The use of a relatively coarse and/or dense media has the advantage of improved (i.e., faster) sediment rates and reduced media carry over through the quiescent zone and/or classifier and/or screen(s).

A further advantage in using relatively coarse grinding media is that the mean particle size (d50) of the inorganic particulate material may not be significantly reduced during the grinding process such that the energy imparted to the grinding system is primarily expended in microfibrillating the fibrous substrate comprising cellulose.

A further advantage in using relatively coarse screens is that a relatively coarse or dense grinding media can be used in the microfibrillating step. In addition, the use of relatively coarse screens (i.e., having a nominal aperture of least about 250 μm) allows a relatively high solids product to be processed and removed from the grinder, which allows a relatively high solids feed (comprising fibrous substrate comprising cellulose and inorganic particulate material) to be processed in an economically viable process. It has been found that a feed having a high initial solids content is desirable in terms of energy sufficiency. Further, it has also been found that product produced (at a given energy) at lower solids has a coarser particle size distribution.

In accordance with one embodiment, the fibrous substrate comprising cellulose and inorganic particulate material are present in the aqueous environment at an initial solids content of at least about 4 wt. %, of which at least about 2 % by weight is fibrous substrate comprising cellulose. The initial solids content may be at least about 10 wt.%, or at least about 20 wt. %, or at least about 30 wt. %, or at least about at least 40 wt. %. At least about 5 % by weight of the initial solids content may be fibrous substrate comprising cellulose, for example, at least about 10 %, or at least about 15 %, or at least about 20 % by weight of the initial solids content may be fibrous substrate comprising cellulose.

In another embodiment, the grinding is performed in a cascade of grinding vessels, one or more of which may comprise one or more grinding zones. For example, the fibrous substrate comprising cellulose and the inorganic particulate material may be ground in a cascade of two or more grinding vessels, for example, a cascade of three or more grinding vessels, or a cascade of four or more grinding vessels, or a cascade of five or more grinding vessels, or a cascade of six or more grinding vessels, or a cascade of seven or more grinding vessels, or a cascade of eight or more grinding vessels, or a cascade of nine or more grinding vessels in series, or a cascade comprising up to ten grinding vessels. The cascade of grinding vessels may be operatively linked in series or parallel or a combination of series and parallel. The output from and/or the input to one or more of the grinding vessels in the cascade may be subjected to one or more screening steps and/or one or more classification steps.

The circuit may comprise a combination of one or more grinding vessels and

homogenizer.

The total energy expended in a microfibrillation process may be apportioned equally across each of the grinding vessels in the cascade. Alternatively, the energy input may vary between some or all of the grinding vessels in the cascade.

A person skilled in the art will understand that the energy expended per vessel may vary between vessels in the cascade depending on the amount of fibrous substrate being microfibrillated in each vessel, and optionally the speed of grind in each vessel, the duration of grind in each vessel, the type of grinding media in each vessel and the type and amount of inorganic particulate material. The grinding conditions may be varied in each vessel in the cascade in order to control the particle size distribution of both the microfibrillated cellulose and the inorganic particulate material. For example, the grinding media size may be varied between successive vessels in the cascade in order to reduce grinding of the inorganic particulate material and to target grinding of the fibrous substrate comprising cellulose.

In an embodiment the grinding is performed in a closed circuit. In another embodiment, the grinding is performed in an open circuit. The grinding may be performed in batch mode. The grinding may be performed in a re-circulating batch mode.

The grinding circuit may include a pre-grinding step in which coarse inorganic particulate ground in a grinder vessel to a predetermined particle size distribution, after which fibrous material comprising cellulose is combined with the pre-ground inorganic particulate material and the grinding continued in the same or different grinding vessel until the desired level of microfibrillation has been obtained.

As the suspension of material to be ground may be of a relatively high viscosity, a suitable dispersing agent may be added to the suspension prior to grinding. The dispersing agent may be, for example, a water soluble condensed phosphate, polysilicic acid or a salt thereof, or a polyelectrolyte, for example a water soluble salt of a poly(acrylic acid) or of a poly(methacrylic acid) having a number average molecular weight not greater than 80,000. The amount of the dispersing agent used would generally be in the range of from 0.1 to 2.0% by weight, based on the weight of the dry inorganic particulate solid material. The suspension may suitably be ground at a temperature in the range of from 4°C to 100°C.

Other additives which may be included during the microfibrillation step include:

carboxymethyl cellulose, amphoteric carboxymethyl cellulose, and oxidising agents.

The pH of the suspension of material to be ground may be about 7 or greater than about 7 (i.e., basic), for example, the pH of the suspension may be about 8, or about 9, or about 10, or about 11. The pH of the suspension of material to be ground may be less than about 7 (i.e., acidic), for example, the pH of the suspension may be about 6, or about 5, or about 4, or about 3. The pH of the suspension of material to be ground may be adjusted by addition of an appropriate amount of acid or base. Suitable bases included alkali metal hydroxides, such as, for example NaOH. Other suitable bases are sodium carbonate and ammonia. Suitable acids included inorganic acids, such as

hydrochloric and sulphuric acid, or organic acids. An exemplary acid is

orthophosphoric acid.

The amount of inorganic particulate material and cellulose pulp in the mixture to be co-ground may vary in a ratio of from about 0:100 to about 30:70, based on the dry weight of inorganic particulate material and the amount of dry fibre in the pulp, or a ratio of from 50:50 based on the dry weight of inorganic particulate material and the amount of dry fibre in the pulp.

The total energy input in a typical grinding process to obtain the desired aqueous suspension composition may typically be between about 100 and 1500 kWht- 1 based on the total dry weight of the inorganic particulate filler. The total energy input may be less than about 1000 kWht-1, for example, less than about 800 kWht-1, less than about 600 kWht-1, less than about 500 kWht-1, less than about 400 kWht-1, less than about 300 kWht-1, or less than about 200 kWht-1. As such, it has surprisingly been found that a cellulose pulp can be microfibrillated at relatively low energy input when it is co-ground in the presence of an inorganic particulate material. As will be apparent, the total energy input per tonne of dry fibre in the fibrous substrate comprising cellulose will be less than about 10,000 kWht-1, for example, less than about 9000 kWht-1, or less than about 8000 kWht-1, or less than about 7000 kWht-1, or less than about 6000 kWht-1, or less than about 5000 kWht'1, for example less than about 4000 kWht-1, less than about 3000 kWht-1 , less than about 2000 kWht-1 , less than about 1500 kWht-1 , less than about 1200 kWht-,1 less than about 1000 kWht-1, or less than about 800 kWht-1. The total energy input varies depending on the amount of dry fibre in the fibrous substrate being microfibrillated, and optionally the speed of grind and the duration of grind.

The amount of inorganic particulate material, when present, and cellulose pulp in the mixture to be co-ground may be varied in order to produce a slurry which is suitable for use as the top ply slurry, or ply slurry, or which may be further modified, e.g., with additional of further inorganic particulate material, to produce a slurry which is suitable for use as the top ply slurry, or ply slurry.

Homogenizing

Microfibrillation of the fibrous substrate comprising cellulose may be effected under wet conditions in the presence of the inorganic particulate material by a method in which the mixture of cellulose pulp and inorganic particulate material is pressurized (for example, to a pressure of about 500 bar) and then passed to a zone of lower pressure. The rate at which the mixture is passed to the low pressure zone is sufficiently high and the pressure of the low pressure zone is sufficiently low as to cause microfibrillation of the cellulose fibres. For example, the pressure drop may be effected by forcing the mixture through an annular opening that has a narrow entrance orifice with a much larger exit orifice. The drastic decrease in pressure as the mixture accelerates into a larger volume (i.e., a lower pressure zone) induces cavitation which causes

microfibrillation. In an embodiment, microfibrillation of the fibrous substrate comprising cellulose may be effected in a homogenizer under wet conditions in the presence of the inorganic particulate material. In the homogenizer, the cellulose pulp-inorganic particulate material mixture is pressurized (for example, to a pressure of about 500 bar), and forced through a small nozzle or orifice. The mixture may be pressurized to a pressure of from about 100 to about 1000 bar, for example to a pressure of equal to or greater than 300 bar, or equal to or greater than about 500, or equal to or greater than about 200 bar, or equal to or greater than about 700 bar. The homogenization subjects the fibres to high shear forces such that as the pressurized cellulose pulp exits the nozzle or orifice, cavitation causes microfibrillation of the cellulose fibres in the pulp.

Additional water may be added to improve flowability of the suspension through the homogenizer. The resulting aqueous suspension comprising microfibrillated cellulose and inorganic particulate material may be fed back into the inlet of the homogenizer for multiple passes through the homogenizer. In a preferred embodiment, the inorganic particulate material is a naturally platy mineral, such as kaolin. As such,

homogenization not only facilitates microfibrillation of the cellulose pulp, but also facilitates delamination of the platy particulate material. An exemplary homogenizer is a Manton Gaulin (APV) homogenizer. A laboratory scale homogenizer suitable for preparation of the microfibrillated cellulose compositions, optionally including inorganic particulate material, is a GEA ANiro Soavi Technical Datasheet Ariete NS3030 available from GEA Mechanical Equipment, GEA Niro Soavi, Via A. M. Da Erba Edoari, 29- 1, 43123 Parma, Italy. Other commercial scale homogenizers are available from GEA Niro Soavi, GEA United Kingdom, Leacroft Road, Birchwood, Warrington, Cheshire UK WA3 6JF. These include the Ariete Series - 2006, 3006, 3011, 3015, 3037, 3045, 3055, 3075, 3090, 31 10*,5132, 5180, 5250, 5355 in addition to the 3030 model. Homogenizers are also available from Microfluidics, 90 Glacier Drive Suite 1000, Westwood, MA 02090 (US) denominated as Microfluidizer, 700 series and Models- M-7125, M-7250.

A platy particulate material, such as kaolin, is understood to have a shape factor of at least about 10, for example, at least about 15, or at least about 20, or at least about 30, or at least about 40, or at least about 50, or at least about 60, or at least about 70, or at least about 80, or at least about 90, or at least about 100. Shape factor, as used herein, is a measure of the ratio of particle diameter to particle thickness for a population of particles of varying size and shape as measured using the electrical conductivity methods, apparatuses, and equations described in U.S. Patent No. 5,576,617, which is incorporated herein by reference.

A suspension of a platy inorganic particulate material, such as kaolin, may be treated in the homogenizer to a predetermined particle size distribution in the absence of the fibrous substrate comprising cellulose, after which the fibrous material comprising cellulose is added to the aqueous slurry of inorganic particulate material and the combined suspension is processed in the homogenizer as described above. The homogenization process is continued, including one or more passes through the homogenizer, until the desired level of microfibrillation has been obtained. Similarly, the platy inorganic particulate material may be treated in a grinder to a predetermined particle size distribution and then combined with the fibrous material comprising cellulose followed by processing in the homogenizer. An exemplary homogenizer is a Manton Gaulin (APV) homogenizer.

After the microfibrillation step has been carried out, the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material may be screened to remove fibre above a certain size and to remove any grinding medium. For example, the suspension can be subjected to screening using a sieve having a selected nominal aperture size in order to remove fibres which do not pass through the sieve. Nominal aperture size means the nominal central separation of opposite sides of a square aperture or the nominal diameter of a round aperture. The sieve may be a BSS sieve (in accordance with BS 1796) having a nominal aperture size of 150 μm, for example, a nominal aperture size 125μm, or 100μm, or 90μm, or 74μm, or 63μm, or 53μm, 45μm, or 38μm. In one embodiment, the aqueous suspension is screened using a BSS sieve having a nominal aperture of 75μm. The aqueous suspension may then be optionally dewatered.

It will be understood therefore that amount (i.e., % by weight) of microfibrillated cellulose in the aqueous suspension after grinding or homogenizing may be less than the amount of dry fibre in the pulp if the ground or homogenized suspension is treated to remove fibres above a selected size. Thus, the relative amounts of pulp and inorganic particulate material fed to the grinder or homogenizer can be adjusted depending on the amount of microfibrillated cellulose that is required in the aqueous suspension after fibres above a selected size are removed.

• Microfibrillation in the absence of grindable inorganic particulate material

In certain embodiments, the microfibrillated cellulose may be prepared by a method comprising a step of microfibrillating the fibrous substrate comprising cellulose in an aqueous environment by grinding in the presence of a grinding medium (as described herein), wherein the grinding is carried out in the absence of inorganic particulate material. In certain embodiments, the grinding medium is removed after grinding. In other embodiments, the grinding medium is retained after grinding and may serve as the inorganic particulate material, or at least a portion thereof.

A method for preparing an aqueous suspension comprising microfibrillated cellulose may comprise a step of microfibrillating a fibrous substrate comprising cellulose in an aqueous environment by grinding in the presence of a grinding medium of 0.5 mm or greater in size (as described herein) which is to be removed after the completion of grinding, wherein the grinding is performed in a tower mill or a screened grinder, and wherein the grinding is carried out in the absence of grindable inorganic particulate material.

A grindable inorganic particulate material is a material which would be ground in the presence of the grinding medium. The grinding is suitably performed in a conventional manner. The grinding may be an attrition grinding process in the presence of a particulate grinding medium, or may be an autogenous grinding process, i.e., one in the absence of a grinding medium. By grinding medium is meant a medium other than grindable inorganic particulate.

As mentioned previously, the particulate grinding medium may be of a natural or a synthetic material. The grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300°C to about 1800°C. For example, in some embodiments a Carbolite® grinding media is preferred. Alternatively, particles of natural sand of a suitable particle size may be used. In other embodiments, hardwood grinding media (e.g., woodflour) may be used.

Generally, the type of and particle size of grinding medium to be selected for use in the methods disclosed herein may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground. In some embodiments, the particulate grinding medium comprises particles having an average diameter in the range of from about 0.5 mm to about 6 mm, for example from about 0.2 mm to about 4 mm. In one embodiment, the particles have an average diameter of at least about 3 mm.

The grinding medium may comprise particles having a specific gravity of at least about 2.5. The grinding medium may comprise particles having a specific gravity of at least about 3, or least about 4, or least about 5, or at least about 6.

The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.

The fibrous substrate comprising cellulose may be microfibrillated to obtain

microfibrillated cellulose having a d50 ranging from about 5 μιη about 500 μηι, as measured by laser light scattering, equal to or less than about 200 μιη, or equal to or less than about 150 μm, or equal to or less than about 125 μιη, or preferably, equal to or less than about 100 μm, or equal to or less than about 90 μιη, or equal to or less than about 80 μm , or equal to or less than about 70 μm, or, more preferably, equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm.

The fibrous substrate comprising cellulose may be microfibrillated to obtain

microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 μιη. The fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 μπι, for example at least about 10 μηι, or at least about 50 μιη, or at least about 100 μηι, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.

The fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern. Fibre steepness (i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula:

The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.

The grinding may be performed in a grinding vessel, such as a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.

In one embodiment, the grinding vessel is a tower mill, as previously described and under the conditions explained previously.

In another embodiment, the grinding is performed in a screened grinder, for example a stirred media detritor, in the manner and under the conditions specified previously in this specification for grinding fibrous substances comprising cellulose in the presence of inorganic particulate material.

• The fibrous substrate comprising cellulose used to prepare the microfibrillated cellulose

The microfibrillated cellulose is derived from fibrous substrate comprising cellulose. The fibrous substrate comprising cellulose may be derived from any suitable source, such as wood, grasses (e.g., sugarcane, bamboo) or rags (e.g., textile waste, cotton, hemp or flax). The fibrous substrate comprising cellulose may be in the form of a pulp (i.e., a suspension of cellulose fibres in water), which may be prepared by any suitable chemical or mechanical treatment, or combination thereof. For example, the pulp may be a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or a recycled pulp, or a papermill broke, or a papermill waste stream, or waste from a papermill, or a combination thereof. The cellulose pulp may be beaten (for example in a Valley beater) and/or otherwise refined (for example, processing in a conical or plate refiner) to any predetermined freeness, reported in the art as Canadian standard freeness (CSF) in cm3. CSF means a value for the freeness or drainage rate of pulp measured by the rate that a suspension of pulp may be drained. For example, the cellulose pulp may have a Canadian standard freeness of about 10 cm3 or greater prior to being

microfibrillated. The cellulose pulp may have a CSF of about 700 cm3 or less, for example, equal to or less than about 650 cm , or equal to or less than about 600 cm , or equal to or less than about 550 cm , or equal to or less than about 500 cm , or equal to or less than about 450 cm , or equal to or less than about 400 cm , or equal to or less than about 350 cm , or equal to or less than about 300 cm , or equal to or less than about 250 cm , or equal to or less than about 200 cm , or equal to or less than about 150 cm , or equal to or less than about 100 cm3, or equal to or less than about 50 cm3. The cellulose pulp may then be dewatered by methods well known in the art, for example, the pulp may be filtered through a screen in order to obtain a wet sheet comprising at least about 10% solids, for example at least about 15% solids, or at least about 20% solids, or at least about 30% solids, or at least about 40% solids. The pulp may be utilised in an unrefined state that is to say without being beaten or dewatered, or otherwise refined.

The fibrous substrate comprising cellulose may be added to a grinding vessel or homogenizer in a dry state. For example, a dry paper broke may be added directly to the grinder vessel. The aqueous environment in the grinder vessel will then facilitate the formation of a pulp.

The inorganic particulate material which may be used in the microfibrillating process

The inorganic particulate material may, for example, be an alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, huntite, hydromagnesite, ground glass, perlite or diatomaceous earth, or wollastonite, or titanium dioxide, or magnesium hydroxide, or aluminium trihydrate, lime, graphite, or combinations thereof.

In certain embodiments, the inorganic particulate material comprises or is calcium carbonate, magnesium carbonate, dolomite, gypsum, an anhydrous kandite clay, perlite, diatomaceous earth, wollastonite, magnesium hydroxide, or aluminium trihydrate, titanium dioxide or combinations thereof.

In certain embodiments, the inorganic particulate material may be a surface-treated inorganic particulate material. For instance, the inorganic particulate material may be treated with a hydrophobizing agent, such as a fatty acid or salt thereof. For example, the inorganic particulate material may be a stearic acid treated calcium carbonate.

A preferred inorganic particulate material for use in the microfibrillation methods disclosed herein is calcium carbonate. Hereafter, the invention may tend to be discussed in terms of calcium carbonate, and in relation to aspects where the calcium carbonate is processed and/or treated. The invention should not be construed as being limited to such embodiments.

The particulate calcium carbonate used in the present invention may be obtained from a natural source by grinding. Ground calcium carbonate (GCC) is typically obtained by crushing and then grinding a mineral source such as chalk, marble or limestone, which may be followed by a particle size classification step, in order to obtain a product having the desired degree of fineness. Other techniques such as bleaching, flotation and magnetic separation may also be used to obtain a product having the desired degree of fineness and/or colour. The particulate solid material may be ground autogenously, i.e. by attrition between the particles of the solid material themselves, or, alternatively, in the presence of a particulate grinding medium comprising particles of a different material from the calcium carbonate to be ground. These processes may be carried out with or without the presence of a dispersant and biocides, which may be added at any stage of the process.

Precipitated calcium carbonate (PCC) may be used as the source of particulate calcium carbonate in the present invention, and may be produced by any of the known methods available in the art. TAPPI Monograph Series No 30, "Paper Coating Pigments", pages 34-35 describes the three main commercial processes for preparing precipitated calcium carbonate which is suitable for use in preparing products for use in the paper industry, but may also be used in the practice of the present invention. In all three processes, a calcium carbonate feed material, such as limestone, is first calcined to produce quicklime, and the quicklime is then slaked in water to yield calcium hydroxide or milk of lime. In the first process, the milk of lime is directly carbonated with carbon dioxide gas. This process has the advantage that no by-product is formed, and it is relatively easy to control the properties and purity of the calcium carbonate product. In the

second process the milk of lime is contacted with soda ash to produce, by double decomposition, a precipitate of calcium carbonate and a solution of sodium hydroxide. The sodium hydroxide may be substantially completely separated from the calcium carbonate if this process is used commercially. In the third main commercial process the milk of lime is first contacted with ammonium chloride to give a calcium chloride solution and ammonia gas. The calcium chloride solution is then contacted with soda ash to produce by double decomposition precipitated calcium carbonate and a solution of sodium chloride. The crystals can be produced in a variety of different shapes and sizes, depending on the specific reaction process that is used. The three main forms of PCC crystals are aragonite, rhombohedral and scalenohedral, all of which are suitable for use in the present invention, including mixtures thereof.

In certain embodiments, the PCC may be formed during the process of producing microfibrillated cellulose.

Wet grinding of calcium carbonate involves the formation of an aqueous suspension of the calcium carbonate which may then be ground, optionally in the presence of a suitable dispersing agent. Reference may be made to, for example, EP-A-614948 (the contents of which are incorporated by reference in their entirety) for more information regarding the wet grinding of calcium carbonate.

In some circumstances, minor additions of other minerals may be included, for example, one or more of kaolin, calcined kaolin, wollastonite, bauxite, talc or mica, could also be present.

When the inorganic particulate material is obtained from naturally occurring sources, it may be that some mineral impurities will contaminate the ground material. For example, naturally occurring calcium carbonate can be present in association with other minerals. Thus, in some embodiments, the inorganic particulate material includes an amount of impurities. In general, however, the inorganic particulate material used in the invention will contain less than about 5% by weight, preferably less than about 1% by weight, of other mineral impurities.

The inorganic particulate material used during the microfibrillating step of the methods disclosed herein will preferably have a particle size distribution in which at least about 10% by weight of the particles have an e.s.d of less than 2μm, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% of the particles have an e.s.d of less than 2μπι.

Unless otherwise stated, particle size properties referred to herein for the inorganic particulate materials are as measured in a well known manner by sedimentation of the particulate material in a fully dispersed condition in an aqueous medium using a Sedigraph 5100 machine as supplied by Micromeritics Instruments Corporation, Norcross, Georgia, USA (telephone: +1 770 662 3620; web-site:

www.micromeritics.com), referred to herein as a "Micromeritics Sedigraph 5100 unit". Such a machine provides measurements and a plot of the cumulative percentage by weight of particles having a size, referred to in the art as the 'equivalent spherical diameter' (e.s.d), less than given e.s.d values. The mean particle size d50 is the value determined in this way of the particle e.s.d at which there are 50% by weight of the particles which have an equivalent spherical diameter less than that d50 value.

Alternatively, where stated, the particle size properties referred to herein for the inorganic particulate materials are as measured by the well known conventional method employed in the art of laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result). In the laser light scattering technique, the size of particles in powders, suspensions and emulsions may be measured using the diffraction of a laser beam, based on an application of Mie theory. Such a machine provides measurements and a plot of the cumulative percentage by volume of particles having a size, referred to in the art as the 'equivalent spherical diameter' (e.s.d), less than given e.s.d values. The mean particle size d50 is the value determined in this way of the particle e.s.d at which there are 50% by volume of the particles which have an equivalent spherical diameter less than that d50 value.

In another embodiment, the inorganic particulate material used during the

microfibrillating step of the methods disclosed herein will preferably have a particle size distribution, as measured using a Malvern Mastersizer S machine, in which at least about 10% .by volume of the particles have an e.s.d of less than 2μπι, for example, at least about 20% by volume, or at least about 30% by volume, or at least about 40% by volume, or at least about 50% by volume, or at least about 60% by volume, or at least about 70% by volume, or at least about 80% by volume, or at least about 90% by volume, or at least about 95% by volume, or about 100% of the particles by volume have an e.s.d of less than 2μm.

Unless otherwise stated, particle size properties of the microfibrillated cellulose materials are as are as measured by the well known conventional method employed in the art of laser light scattering, using a Malvern Mastersizer S machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result).

Details of the procedure used to characterise the particle size distributions of mixtures of inorganic particle material and microfibrillated cellulose using a Malvern Mastersizer S machine are provided below.

Another preferred inorganic particulate material for use in the microfibrillating methods disclosed herein is kaolin clay. Hereafter, this section of the specification may tend to be discussed in terms of kaolin, and in relation to aspects where the kaolin is processed and/or treated. The invention should not be construed as being limited to such embodiments. Thus, in some embodiments, kaolin is used in an unprocessed form.

Kaolin clay may be a processed material derived from a natural source, namely raw natural kaolin clay mineral. The processed kaolin clay may typically contain at least about 50% by weight kaolinite. For example, most commercially processed kaolin clays contain greater than about 75% by weight kaolinite and may contain greater than about 90%, in some cases greater than about 95% by weight of kaolinite.

Kaolin clay may be prepared from the raw natural kaolin clay mineral by one or more other processes which are well known to those skilled in the art, for example by known refining or beneficiation steps.

For example, the clay mineral may be bleached with a reductive bleaching agent, such as sodium hydrosulfite. If sodium hydrosulfite is used, the bleached clay mineral may optionally be dewatered, and optionally washed and again optionally dewatered, after the sodium hydrosulfite bleaching step.

The clay mineral may be treated to remove impurities, e. g. by flocculation, flotation, or magnetic separation techniques well known in the art. Alternatively the clay mineral may be untreated in the form of a solid or as an aqueous suspension.

The process for preparing the particulate kaolin clay may also include one or more comminution steps, e.g., grinding or milling. Light comminution of coarse kaolin is used to give suitable delamination thereof. The comminution may be carried out by use of beads or granules of a plastic (e. g. nylon), sand or ceramic grinding or milling aid. The coarse kaolin may be refined to remove impurities and improve physical properties using well known procedures. The kaolin clay may be treated by a known particle size classification procedure, e.g., screening and centrifuging (or both), to obtain particles having a desired d50 value or particle size distribution.

• The aqueous suspension

The aqueous suspensions produced in accordance with the methods described herein are suitable for use in various compositions and fibre and methods for making these fibres and nonwoven materials from such fibres.

The aqueous suspension may, for example, comprise, consist of, or consist essentially of microfibrillated cellulose and optional additives. The aqueous suspension may

comprise, consist of, or consist essentially of microfibrillated cellulose and an inorganic particulate material and other optional additives. The other optional additives include dispersant, biocide, suspending aids, salt(s) and other additives, for example, starch or carboxy methyl cellulose or polymers, which may facilitate the interaction of mineral particles and fibres during or after grinding.

The inorganic particulate material may have a particle size distribution such that at least about 10% by weight, for example at least about 20% by weight, for example at least about 30% by weight, for example at least about 40% by weight, for example at least about 50% by weight, for example at least about 60% by weight, for example at least about 70% by weight, for example at least about 80% by weight, for example at least about 90% by weight, for example at least about 95% by weight, or for example about 100% of the particles have an e.s.d of less than 2μm.

In another embodiment, the inorganic particulate material may have a particle size distribution, as measured by a Malvern Mastersizer S machine, such that at least about 10% by volume, for example at least about 20% by volume, for example at least about 30% by volume, for example at least about 40% by volume, for example at least about 50% by volume, for example at least about 60% by volume, for example at least about 70% by volume, for example at least about 80% by volume, for example at least about 90% by volume, for example at least about 95% by volume, or for example about 100% by volume of the particles have an e.s.d of less than 2μm.

The amount of inorganic particulate material and cellulose pulp in the mixture to be co-ground may vary in a ratio of from about 0:100 to about 30:70, based on the dry weight of inorganic particulate material and the amount of dry fibre in the pulp, or a ratio of from 50:50 based on the dry weight of inorganic particulate material and the amount of dry fibre in the pulp.

In an embodiment, the composition does not include fibres too large to pass through a BSS sieve (in accordance with BS 1796) having a nominal aperture size of 150μm, for example, a nominal aperture size of 125μm, 106μm, or 90μm, or 74μm, or 63μm, or 53μm, 45μm, or 38μm. In one embodiment, the aqueous suspension is screened using a BSS sieve having a nominal aperture of 75μm.

It will be understood therefore that amount (i.e., % by weight) of microfibrillated cellulose in the aqueous suspension after grinding or homogenizing may be less than the amount of dry fibre in the pulp if the ground or homogenized suspension is treated to remove fibres above a selected size. Thus, the relative amounts of pulp and inorganic particulate material fed to the grinder or homogenizer can be adjusted depending on the amount of microfibrillated cellulose that is required in the aqueous suspension after fibres above a selected size are removed.

In an embodiment, the inorganic particulate material is an alkaline earth metal carbonate, for example, calcium carbonate. The inorganic particulate material may be ground calcium carbonate (GCC) or precipitated calcium carbonate (PCC), or a mixture of GCC and PCC. In another embodiment, the inorganic particulate material is a naturally platy mineral, for example, kaolin. The inorganic particulate material may be a mixture of kaolin and calcium carbonate, for example, a mixture of kaolin and GCC, or a mixture of kaolin and PCC, or a mixture of kaolin, GCC and PCC.

• Dry and Semi-Dry Compositions

In another embodiment, the aqueous suspension is treated to remove at least a portion or substantially all of the water to form a partially dried or essentially completely dried product. For example, at least about 10 % by volume of water in the aqueous suspension may be removed from the aqueous suspension, for example, at least about 20% by volume, or at least about 30% by volume, or least about 40% by volume, or at least about 50% by volume, or at least about 60% by volume, or at least about 70% by volume or at least about 80 % by volume or at least about 90% by volume, or at least about 100% by volume of water in the aqueous suspension may be removed. Any suitable technique can be used to remove water from the aqueous suspension including, for example, by gravity or vacuum-assisted drainage, with or without pressing, or by evaporation, or by filtration, or by a combination of these techniques. The partially dried or essentially completely dried product will comprise microfibrillated cellulose and inorganic particulate material and any other optional additives that may have been added to the aqueous suspension prior to drying. The partially dried or essentially completely dried product may be stored or packaged for sale. The partially dried or essentially completely dried product may be used in any of the compositions or products disclosed herein. The partially dried or essentially completely dried product may be optionally re-hydrated and incorporated in any of the compositions or products disclosed herein.

In certain embodiments, the co-processed microfibrillated cellulose and inorganic particulate material composition may be in the form of a dry or at least partially dry, re-dispersable composition, as produced by the processes described herein or by any other drying process known in the art (e.g., freeze-drying). The dried co-processed microfibrillated cellulose and inorganic particulate material composition may be easily dispersed in aqueous or non-aqueous medium (e.g., polymers).

The dried and at least partially dried microfibrillated cellulose compositions may, for example, be made by mechanical dewatering, optionally followed by drying an (never before dried) aqueous composition comprising microfibrillated cellulose, optionally in the presence of an inorganic particulate and/or other additive as herein described. This may, for example, enhance or improve one or more properties of the microfibrillated cellulose upon re-dispersal. That is to say, compared to the microfibrillated cellulose prior to drying, the one or more properties of the re-dispersed microfibrillated are closer to the one or properties of the microfibrillated cellulose prior to drying than it/they would have been but for the combination of dewatering and drying. Incorporation of inorganic particulate material, or a combination of inorganic particulate materials, and/or other additives as herein described, can enhance the re-dispersibility of the microfibrillated cellulose following initial drying.

Thus, in certain embodiments, the method of forming a dried or at least partially dry microfibrillated cellulose or method of improving the dispersibility of a dried or at least partially dried microfibrillated cellulose comprises drying or at least partially drying an aqueous composition by a method comprising:

(i) dewatering the aqueous composition by one or more of:

(a) dewatering by belt press, for example, high pressure automated belt press, (b) dewatering by centrifuge, (c) dewatering by tube press,

(d) dewatering by screw press, and (e) dewatenng by rotary press; followed by drying, or

(ii) dewatering the aqueous composition, followed by drying by one or more of:

(f) drying in a fluidized bed dryer, (g) drying by microwave and/or radio frequency dryer, (h) drying in a hot air swept mill or dryer, for example, a cell mill or an Atritor® mill, and (i) drying by freeze drying; or

(iii) any combination of dewatering according to (i) and drying according to (ii), or

(iv) a combination of dewatering and drying the aqueous composition.

In certain embodiments, if drying is by freeze drying, dewatering comprises one or more of (a) to (e).

Upon subsequent re-dispersal, e.g., following transportation to another facility, of the dried or at least partially dried microfibrillated cellulose in a liquid medium, the re-dispersed microfibrillated cellulose has a mechanical and/or physical property which is closer to that of the microfibrillated cellulose prior to drying or at least partial drying than it would have been but for drying according to (i), (ii), (iii) or (iv).

Thus, the microfibrillated cellulose may be re-dispersed, the method comprising re-dispersing dried or at least partially dried microfibrillated cellulose in a liquid medium, wherein the dried or at least partially dried microfibrillated cellulose was prepared by dewatering and drying an aqueous composition comprising microfibrillated cellulose whereby the re-dispersed microfibrillated cellulose has a mechanical and/or physical property which is closer to that of the microfibrillated cellulose prior to drying or at least partial drying than it would have been but for said dewatering and drying,

optionally wherein the dried or at least partially dried microfibrillated cellulose comprises: (i) inorganic particulate material, (ii) a combination of inorganic particulate materials, and/or (iii) an additive other than inorganic particulate material, the presence of which during re-dispersing enhances a mechanical and/or physical property of the re-dispersed microfibrillated cellulose; and optionally wherein dewatering is selected from one or more of:

(a) dewatering by belt press, for example, high pressure automated belt press;

(b) dewatering by centrifuge;

(c) dewatering by tube press;

(d) dewatering by screw press; and

(e) dewatering by rotary press;

and/or wherein drying is selected from one or more of:

(f) drying in a fluidized bed dryer;

(g) drying by microwave and/or radio frequency dryer

(h) drying in a hot air swept mill or dryer, for example, a cell mill or an Atritor® mill; and

(i) drying by freeze drying.

In certain embodiments, if drying was by freeze drying, dewatering comprises one or more of (a) to (e).

References to "dried" or "drying" includes "at least partially dried" or "or at least partially drying".

In certain embodiments, the aqueous composition comprising microfibrillated cellulose is dewatered by belt press, for example, high pressure automated belt press, followed by drying, for example, via one or more of (f) to (i) above.

In certain embodiments, the aqueous composition comprising microfibrillated cellulose is dewatered by centrifuge, followed by drying, for example, via one or more of (f) to (i) above.

In certain embodiments, the aqueous composition comprising microfibrillated cellulose is dewatered by tube press, followed by drying, for example, via one or more of (f) to (i) above.

In certain embodiments, the aqueous composition comprising microfibrillated cellulose is dewatered by screw press, followed by drying, for example, via one or more of (f) to (i) above.

In certain embodiments, the aqueous composition comprising microfibrillated cellulose is dewatered by rotary press, followed by drying, for example, via one or more of (f) to (i) above.

In certain embodiments, the aqueous composition is dewatered, for example, via one or more of (a) to (e) above, and then dried in a fluidized bed dryer.

In certain embodiments, the aqueous composition is dewatered, for example, via one or more of (a) to (e) above, and then dried by microwave and/or by radio frequency drying.

In certain embodiments, the aqueous composition is dewatered, for example, via one or more of (a) to (e) above, and then dried in a hot air swept mill or dryer, for example, a cell mil or an Atritor® mill. Suitable mills and dryers are available from Atritor Limited, 12 The Stampings, Blue Ribbon Park, Coventry, West Midlands, England. These mills and dryers include an Atritor Dryer-Pulveriser (any model including the 8A), Atritor Cell Mill, Atritor Extended Classifier Mill, and an Atritor Air Swept Tubular (AST) Dryer, Such mills may be used to prepare the aqueous composition of microfibrillated cellulose which is subsequently dried and then re-dispersed.

In certain embodiments, the aqueous composition is dewatered, for example, via one or more of (a) to (e) above, and then dried by freeze drying. In certain embodiments, dewatering is by one or more of (a)-(e) described above.

Dewatering and drying may be carried out for any suitable period of time, for example, from about 30 minutes to about 12 hours, or from about 30 minutes to about 8 hours, or from about 30 minutes to about 4 hours, or from about 30 minutes to about 2 hours. The period of time will be depend on factors such as for example, the solids content of the aqueous composition comprising microfibrillated cellulose, the bulk amount of the aqueous composition comprising microfibrillated cellulose and the temperature of drying.

In certain embodiments, drying is conducted at a temperature of from about 50 °C to about 120 °C, for example, from about 60 °C to about 100 °C, or at least about 70 °C, or at least about 75 °C, or at least about 80 °C.

In certain embodiments, the method further comprises re-dispersing the dried or at least partially dried microfibrillated cellulose in a liquid medium, which may be aqueous or non-aqueous liquid. In certain embodiments, the liquid medium is an aqueous liquid, for example, water. In certain embodiments, the water is a waste water or a recycled waste water derived from the manufacturing plant in which the re-dispersed

microfibrillated cellulose is being used to manufacture an article, product or

composition. For example, in paper/paper board manufacturing plants, the water may be or comprise recycled white water from the paper making process. In certain embodiments, at least portion of any inorganic particulate material and/or additive other than inorganic particulate material be present in the recycle white water.

In certain embodiments the dried or at least partially dried microfibrillated cellulose comprises inorganic particulate material and/or an additive, the presence of which enhances a mechanical and/or physical property of the re-dispersed microfibrillated cellulose. Such inorganic particulate materials and additives are described herein in below.

The aqueous composition comprising microfibrillated cellulose may be dewatered and dried in order to reduce water content by at least 10 % by weight, based on the total weight of the aqueous composition comprising microfibrillated cellulose prior to dewatering and drying, for example, by at least 20 % by weight, or by at least 30 % by weight, or by at least 40 % by weight, or by at least about 50 % by weight, or by at least 60 % by weight, or by at least 70 % by weight, or by at least 80 % by weight, or by at least 80 % by weight, or by at least 90 % by weight, or by at least about 95 % by

weight, or by at least about 99 % by weight, or by at least about 99.5 % by weight, or by at least 99.9 % by weight.

By "dried" or "dry" is meant that the water content of the aqueous composition comprising microfibrillated cellulose is reduced by at least 95 % by weight.

By "partially dried" or "partially dry" is meant that the water content of the aqueous composition comprising microfibrillated cellulose is reduced by an amount less than 95 % by weight. In certain embodiments, "partially dried" or "partially dry" means that the water content of the aqueous composition comprising microfibrillated cellulose is reduced by at least 50 % by weight, for example, by at least 75 % by weight or by at least 90 % by weight.

The microfibrillated cellulose may, for example, be treated prior to dewatering and/or drying. For example, one or more additives as specified below (e.g. salt, sugar, glycol, urea, glycol, carboxymethyl cellulose, guar gum, or a combination thereof as specified below) may be added to the microfibrillated cellulose. For example, one or more oligomers (e.g. with or without the additives specified above) may be added to the microfibrillated cellulose. For example, one or more inorganic particulate materials may be added to the microfibrillated cellulose to improve dispersibility (e.g. talc or minerals having a hydrophobic surface-treatment such as a stearic acid surface-treatment (e.g. stearic acid treated calcium carbonate). The additives may, for example, be suspended in low dielectric solvents. The microfibrillated cellulose may, for example, be in an emulsion, for example an oil/water emulsion, prior to dewatering and/or drying. The microfibrillated cellulose may, for example, be in a masterbatch composition, for

example a polymer masterbatch composition and/or a high solids masterbatch composition, prior to dewatering and/or drying. The microfibrillated cellulose may, for example, be a high solids composition (e.g. solids content equal to or greater than about 60 wt. % or equal to or greater than about 70 wt. % or equal to or greater than about 80 wt. % or equal to or greater than about 90 wt. % or equal to or greater than about 95 wt. % or equal to or greater than about 98 wt. % or equal to or greater than about 99 wt. %) prior to dewatering and/or drying. Any combination of one or more of the treatments may additionally or alternatively be applicable to the microfibrillated cellulose after dewatering and drying but prior to or during re-dispersion.

The re-dispersed microfibrillated cellulose may have a mechanical and/or physical property which is closer to that of the microfibrillated cellulose prior to drying or at least partial drying than it would have been but for drying in accordance with (i), (ii), (iii) or (iv) above.

In certain embodiments, the re-dispersed microfibrillated cellulose has a mechanical and/or physical property which is closer to that of the microfibrillated cellulose prior to drying or at least partial drying than it would have been but for drying in accordance with (i), (ii) or (iii).

The mechanical property may be any determinable mechanical property associated with microfibrillated cellulose. For example, the mechanical property may be a strength property, for example, tensile index. Tensile index may be measured using a tensile tester. Any suitable method and apparatus may be used provided it is controlled in order to compare the tensile index of the microfibrillated cellulose before drying and after re-dispersal. For example, the comparison should be conducted at equal concentrations of microfibrillated cellulose, and any other additive or inorganic particulate material(s) which may be present. Tensile index may be expressed in any suitable units such as, for example, N.m/g or kN.m/kg.

The physical property may be any determinable physical property associated with microfibrillated cellulose. For example, the physical property may be viscosity.

Viscosity may be measured using a viscometer. Any suitable method and apparatus may be used provided it is controlled in order to compare the viscosity of the microfibrillated cellulose prior to drying and after re-dispersal. For example, the comparison should be conducted at equal concentrations of microfibrillated cellulose, and any other additive or inorganic particulate material(s) which may be present. In certain embodiments, the viscosity is Brookfield viscosity, with units of mPa.s.

In certain embodiments, the tensile index and/or viscosity of the re-dispersed microfibrillated cellulose is at least about 25 % of the tensile index and/or viscosity of the aqueous composition of microfibrillated cellulose prior to drying, for example, at least about 30 %, or at least about 35 %, or at least about 40 %, or at least 45 %, or at least about 50 %, or at least about 55 %, or at least about 60 %, or at least about 65 %, or at least about 70 %, or at least about 75 %, or at least about 80 % of the tensile index and/or viscosity of the microfibrillated cellulose prior to drying.

For example, if the tensile index of the microfibrillated cellulose prior to drying was 8 N.m/g, then a tensile index of at least 50 % of this value would be 4 N.m/g.

In certain embodiments, the tensile index of the re-dispersed microfibrillated cellulose is at least about 25 % of the tensile index of the aqueous composition of microfibrillated cellulose prior to drying, for example, at least about 30 %, or at least about 35 %, or at least about 40 %, or at least 45 %, or at least about 50 %, or at least about 55 %, or at least about 60 %, or at least about 65 %, or at least about 70 %, or at least about 75 %, or at least about 80 % of the tensile index of the microfibrillated cellulose prior to drying.

In certain embodiments, the viscosity of the re-dispersed microfibrillated cellulose is at least about 25 % of the viscosity of the aqueous composition of microfibrillated cellulose prior to drying, for example, at least about 30 %, or at least about 35 %, or at least about 40 %, or at least 45 %, or at least about 50 %, or at least about 55 %, or at least about 60 %, or at least about 65 %, or at least about 70 %, or at least about 75 %, or at least about 80 % of the viscosity of the microfibrillated cellulose prior to drying.

In certain embodiments, inorganic particulate material and/or an additive other than inorganic particulate material is present during the dewatering and drying. The inorganic particulate material and/or additive may be added at any stage prior to dewatering and drying. For example, the inorganic particulate material and/or additive may be added during manufacture of the aqueous composition comprising

microfibrillated cellulose, following manufacture of the aqueous composition comprising microfibrillated cellulose, or both. In certain embodiments, the inorganic particulate material is incorporated during manufacture of the microfibrillated cellulose (for example, by co-processing, e.g., co-grinding, as described here) and the additive other than inorganic particulate material is added following manufacture of the aqueous composition comprising microfibrillated cellulose. In certain embodiments, additional inorganic particulate material (which may be the same or different than the inorganic particulate added during manufacture of the microfibrillated cellulose) may be added following manufacture of the microfibrillated cellulose, for example,

contemporaneously with the addition of additive other than inorganic particulate material. In certain embodiments, the microfibrillated cellulose of the aqueous composition has a fibre steepness of from 20 to 50. Details of the inorganic particulate material, additives and amounts thereof are described below.

In a further aspect, the method of re-dispersing microfibrillated cellulose comprises re-dispersing dried or at least partially dried microfibrillated cellulose in a liquid medium and in the presence of an additive other than inorganic particulate material which enhances a mechanical and/or physical property of the re-dispersed microfibrillated. The microfibrillated cellulose prior to being to be dried or at least partially dried has a fibre steepness of from 20 to 50.

In yet a further aspect, the method of re-dispersing microfibrillated cellulose comprises re-dispersing dried or at least partially dried microfibrillated cellulose in a liquid medium and in the presence of a combination of inorganic particulate materials, wherein the combination of inorganic particulate materials enhances a mechanical and/or physical property of the re-dispersed microfibrillated. In certain embodiments, the combination of inorganic particulate materials comprises calcium carbonate and a platy mineral, for example, a platy kaolin, or talc.

In certain embodiments, the additive, when present, is a salt, sugar, glycol, urea, glycol, carboxymethyl cellulose, guar gum, or a combination thereof.

In certain embodiments, the additive, when present, is a salt, sugar, glycol, urea, glycol, guar gum, or a combination thereof.

In certain embodiments, sugar is selected from monosaccharides (e.g. glucose, fructose, galactose), disaccharides (e.g. lactose, maltose, sucrose), oligosaccharides (chains of 50 or less units of one or more monosaccharides) polysaccharides and combinations thereof.

In certain embodiments, the salt is an alkali metal or alkaline earth metal chloride, for example, sodium, potassium, magnesium and/or calcium chloride. In certain embodiments, the salt comprises or is sodium chloride.

In certain embodiments, the glycol is and alkylene glycol, for example, selected from ethylene, propylene and butylene glycol, and combinations thereof. In certain embodiments, the glycol comprises or is ethylene glycol.

In certain embodiments, the additive comprises or is urea.

In certain embodiments, the additive comprises or is guar gum.

In certain embodiments, the additive comprises or is carboxymethyl cellulose. In certain embodiments, the additive is not carboxymethyl cellulose.

In certain embodiments, the microfibrillated cellulose prior to drying or at least partially drying is not acetylsed. In certain embodiments, the microfibrillated cellulose prior to drying or at least partially drying is not subjected to acetylation.

The inorganic particulate material may be added at one or more of the following stages: (i) prior to or during manufacture of the aqueous composition comprising

microfibrillated cellulose; (ii) following manufacture of the aqueous composition comprising microfibrillated cellulose; (iii) during dewatering of the aqueous

composition of microfibrillated cellulose; (iv) during drying of the aqueous composition of microfibrillated cellulose; and (v) prior to or during re-dispersing of the dried or at least partially dried microfibrillated cellulose.

The re-dispersed microfibrillated cellulose has a mechanical and/or physical property which is closer to that of the microfibrillated cellulose prior to drying and re-dispersal than it would have been but for the presence of the inorganic particulate and/or additive. In other words, the presence of the inorganic particulate material and/or additive other than inorganic particulate material enhances a mechanical and/or physical property of the re-dispersed microfibrillated.

In certain embodiments, the re-dispersed microfibrillated cellulose has a mechanical and/or physical property which is closer to that of the microfibrillated cellulose prior to drying or at least partial drying than it would have been but for the presence of the inorganic particulate material and or additive.

As described above, the mechanical property may be any determinable mechanical property associated with microfibrillated cellulose. For example, the mechanical

property may be a strength property, for example, tensile index. Tensile index may be measured using a tensile tester. Any suitable method and apparatus may be used provided it is controlled in order to compare the tensile index of the microfibrillated cellulose before drying and after re-dispersal. For example, the comparison should be conducted at equal concentrations of microfibrillated cellulose, and any other additive or inorganic particulate material(s) which may be present. Tensile index may be expressed in any suitable units such as, for example, N.m/g or kN.m/kg.

The physical property may be any determinable physical property associated with microfibrillated cellulose. For example, the physical property may be viscosity.

Viscosity may be measured using a viscometer. Any suitable method and apparatus may be used provided it is controlled in order to compare the viscosity of the microfibrillated cellulose prior to drying and after re-dispersal. For example, the comparison should be conducted at equal concentrations of microfibrillated cellulose, and any other additive or inorganic particulate material(s) which may be present. In certain embodiments, the viscosity is Brookfield viscosity, with units of mPa.s.

In certain embodiments, the tensile index and/or viscosity of the re-dispersed microfibrillated cellulose is at least about 25 % of the tensile index and/or viscosity of the aqueous composition of microfibrillated cellulose prior to drying, for example, at least about 30 %, or at least about 35 %, or at least about 40 %, or at least 45 %, or at least about 50 %, or at least about 55 %, or at least about 60 %, or at least about 65 %, or at least about 70 %, or at least about 75 %, or at least about 80 % of the tensile index and/or viscosity of the microfibrillated cellulose prior to drying.

For example, if the tensile index of the microfibrillated cellulose prior to drying was 8 N.m/g, then a tensile index of at least 50 % of this value would be 4 N.m/g.

In certain embodiments, the tensile index of the re-dispersed microfibrillated cellulose is at least about 25 % of the tensile index of the aqueous composition of microfibrillated cellulose prior to drying, for example, at least about 30 %, or at least about 35 %, or at least about 40 %, or at least 45 %, or at least about 50 %, or at least about 55 %, or at least about 60 %, or at least about 65 %, or at least about 70 %, or at least about 75 %, or at least about 80 % of the tensile index of the microfibrillated cellulose prior to drying.

In certain embodiments, the viscosity of the re-dispersed microfibrillated cellulose is at least about 25 % of the viscosity of the aqueous composition of microfibrillated cellulose prior to drying, for example, at least about 30 %, or at least about 35 %, or at least about 40 %, or at least 45 %, or at least about 50 %, or at least about 55 %, or at least about 60 %, or at least about 65 %, or at least about 70 %, or at least about 75 %, or at least about 80 % of the viscosity of the microfibrillated cellulose prior to drying.

The inorganic particulate material and/or additive, when present, are present in sufficient amounts in order to enhance the re-dispersibility of the microfibrillated cellulose, i.e., enhances a mechanical and/or physical property of the re-dispersed microfibrillated.

Based on the total weight of the aqueous composition comprising microfibrillated cellulose (including inorganic particulate when present) prior to drying, the additive may be added in an amount of from about 0.1 wt. % to about 20 wt. %, or from about 0.25 wt. % to about 15 wt. %, or from about 0.5 wt. % to about 10 wt. %, or from about 0.5 wt. % to about 7.5 wt. %, or from about 0.5 wt. % to about 5 wt. %, or from about 0.5 wt. % to about 4 wt.%, or from about 9.5 wt. % to about 4 wt. %, or from about 1 wt. % to about 3 wt. %.

The aqueous composition comprising microfibrillated cellulose and optional inorganic particulate material may have a solids content of up to about 50 wt. % prior to drying, for example, up to about 40 wt. %, or up to about 30 wt. %, or up to about 20 wt. %, or up to about 15 wt. %, or up to about 10 wt. %, or up to about 5 wt. %, or up to about 4 wt. %, or up to about 3 wt. %, or up to about 2 wt.%, or up to about 2 wt. %.

Based on the solids content of the aqueous composition microfibrillated cellulose prior to drying, the inorganic particulate may constitute up to about 99 % of the total solids content, for example, up to about 90 %, or up to about 80 wt.%, or up to about 70 wt.%, or up to about 60 wt. %, or up to about 50 wt.%, or up to about 40 %, or up to about 30 %, or up to about 20 %, or up to about 10 %, or up to about 5 % of the total solids content.

In certain embodiments, the weight ratio of inorganic particulate to microfibrillated cellulose in the aqueous composition is from about 10:1 to about 1 :2, for example, from about 8:1 to about 1 :1, or from about 6:1 to about 3:2, or from about 5: 1 to about 2:1, or from about 5 : 1 to about 3 : 1 , or about 4: 1 to about 3 : 1 , or about 4: 1.

In certain embodiments, the aqueous composition of microfibrillated cellulose prior to drying or at least partially drying has a solids content of up to about 20 wt. %, optionally wherein up to about 80 % of the solids is inorganic particulate material.

In certain embodiments, the aqueous composition is substantially free of inorganic particulate material prior to drying.

The inorganic particulate material may, for example, be an alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, huntite, hydromagnesite, ground glass, perlite or diatomaceous earth, or wollastonite, or titanium dioxide, or magnesium hydroxide, or aluminium trihydrate, lime, graphite, or combinations thereof.

In certain embodiments, the inorganic particulate material comprises or is calcium carbonate, magnesium carbonate, dolomite, gypsum, an anhydrous kandite clay, perlite, diatomaceous earth, wollastonite, magnesium hydroxide, or aluminium trihydrate, titanium dioxide or combinations thereof.

In certain embodiments, the inorganic particulate material may be a surface-treated inorganic particulate material. For instance, the inorganic particulate material may be treated with a hydrophobizing agent, such as a fatty acid or salt thereof. For example, the inorganic particulate material may be a stearic acid treated calcium carbonate.

In certain embodiments, the inorganic particulate material is or comprises a platy mineral, for example, kaolin and/or talc, optionally in combination with another inorganic particulate material, such as, for example, calcium carbonate.

By 'platy' kaolin is meant kaolin a kaolin product having a high shape factor. A platy kaolin has a shape factor from about 20 to less than about 60. A hyper-platy kaolin has a shape factor from about 60 to 100 or even greater than 100. "Shape factor", as used herein, is a measure of the ratio of particle diameter to particle thickness for a population of particles of varying size and shape as measured using the electrical conductivity methods, apparatuses, and equations described in U.S. Patent No.

5,576,617, which is incorporated herein by reference. As the technique for determining shape factor is further described in the '617 patent, the electrical conductivity of a composition of an aqueous suspension of orientated particles under test is measured as the composition flows through a vessel. Measurements of the electrical conductivity are taken along one direction of the vessel and along another direction of the vessel transverse to the first direction. Using the difference between the two conductivity measurements, the shape factor of the particulate material under test is determined..

In certain embodiments, the inorganic particulate material is or comprises talc, optionally in combination with another inorganic particulate material, such as, for example, calcium carbonate.

In certain embodiments, the inorganic particulate material is calcium carbonate, which may be surface treated, and the aqueous composition further comprises one or more of the additives other than inorganic particulate material as described herein.

The inorganic particulate material may have a particle size distribution in which at least about 10% by weight of the particles have an e.s.d of less than 2μιη, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% of the particles have an e.s.d of less than 2μιη.

In another embodiment, the inorganic particulate material has a particle size

distribution, as measured using a Malvern Mastersizer S machine, in which at least about 10% by volume of the particles have an e.s.d of less than 2μπι, for example, at least about 20% by volume, or at least about 30% by volume, or at least about 40% by volume, or at least about 50% by volume, or at least about 60% by volume, or at least about 70% by volume, or at least about 80% by volume, or at least about 90% by volume, or at least about 95% by volume, or about 100% of the particles by volume have an e.s.d of less than 2μηι.

In certain embodiments, the aqueous composition comprising microfibrillated cellulose is free of inorganic particulate material, and the aqueous composition further comprises one or more of the additives other than inorganic particulate material as described herein.

The various methods described herein provide for the manufacture of re-dispersed microfibrillated cellulose having advantageous properties.

Thus, in a further aspect, there is provided a composition comprising re-dispersed microfibrillated cellulose dispersed in a liquid medium and which is obtainable by a method according to any one of method aspects described herein, and having, at a comparable concentration, a tensile index and/or viscosity which is at least 50 % of the tensile index and/or viscosity of the aqueous composition of microfibrillated cellulose prior to drying, wherein either (i) the microfibrillated cellulose of the aqueous composition has a fibre steepness of from 20 to 50, and/or (ii) the aqueous composition of microfibrillated cellulose comprises inorganic particulate material, and optionally further comprises an additive other than inorganic particulate material.

The re-dispersed microfibrillated cellulose may be used, in an article, product, or composition, for example, paper, paperboard, polymeric articles, paints, and the like.

• Exemplary procedures to characterise the particle size distribution of mixture of minerals (GCC or kaolin) and microfibrillated cellulose pulp fibres

- calcium carbonate

A sample of co-ground slurry sufficient to give 3 g dry material is weighed into a beaker, diluted to 60g with deionised water, and mixed with 5 cm3 of a solution of sodium polyacrylate of 1.5 w/v % active. Further deionised water is added with stirring to a final slurry weight of 80 g.

- kaolin

A sample of co-ground slurry sufficient to give 5 g dry material is weighed into a beaker, diluted to 60g with deionised water, and mixed with 5 cm3 of a solution of 1.0 wt.% sodium carbonate and 0.5 wt.% sodium hexametaphosphate. Further deionised water is added with stirring to a final slurry weight of 80 g.

The slurry is then added in 1 cm aliquots to water in the sample preparation unit attached to the Mastersizer S until the optimum level of obscuration is displayed (normally 10 - 15%). The light scattering analysis procedure is then carried out. The instrument range selected was 300RF : 0.05-900, and the beam length set to 2.4 mm.

For co-ground samples containing calcium carbonate and fibre the refractive index for calcium carbonate (1.596) is used. For co-ground samples of kaolin and fibre the RI for kaolin (1.5295) is used.

The particle size distribution is calculated from Mie theory and gives the output as a differential volume based distribution. The presence of two distinct peaks is interpreted as arising from the mineral (finer peak) and fibre (coarser peak).

The finer mineral peak is fitted to the measured data points and subtracted

mathematically from the distribution to leave the fibre peak, which is converted to a cumulative distribution. Similarly, the fibre peak is subtracted mathematically from the original distribution to leave the mineral peak, which is also converted to a cumulative distribution. Both these cumulative curves may then be used to calculate the mean particle size (dso) and the steepness of the distribution (d3o/d7o x 100). The differential curve may be used to find the modal particle size for both the mineral and fibre fractions.

The ultrasonification process

In brief, sonication, ultrasonication or ultrasonification (herein used interchangeably unless otherwise noted) is the irradiation of a liquid sample with ultrasonic (>20 kHz) sound waves which results in agitation of the liquid. The sound waves propagate into a liquid media resulting in alternating high-pressure (compression) and low-pressure (rarefaction) cycles. During rarefaction, high-intensity sonic waves create small vacuum bubbles or voids in the liquid, which then collapse violently (cavitation) during compression, creating very high local temperatures, and agitation. The combination of these events results in high shear forces capable of breaking down or reducing materials into smaller constituents essentially emulsifying the material. This process may change physical properties of the material depending on the operation parameters chosen. Ultrasonication also aids in mixing of materials through the agitation of the material. Although the present invention is not limited to the use of any sonication particular device, ultrasonication is most typically performed by use of an ultrasonic bath or an ultrasonic probe (or transducer). Suitable devices know in the art also include, and are not limited to an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

Any effects of ultrasonication-induced cavitation on a material are controlled through a combination of parameters including different frequencies, displacement or vibration amplitudes, time of exposure to the process and mode of administration of the process (e.g., pulsed or continuous administration). Frequencies used typically range from about 25 to 55 kHz. Amplitudes used typically range from about 22 to 50 μιη. The choice of using an ultrasonic bath, ultrasonic probe or other device can also influence the end result of the process.

CLAIMS

1. A fibre comprising (a) a microfibrillated cellulose, wherein the

microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substance comprising cellulose in a grinding vessel and (ii) refining in a refiner or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose; wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size.

2. The fibre of claim 1, wherein the microfibrillated cellulose has a median diameter (d5o) less than 100 μηι.

3. The fibre of claim 1 , wherein the fibre further comprises a water soluble or dispersible polymer.

4. The fibre of claim 1 , wherein the fibrous substrate comprising cellulose is ground in the presence of an inorganic particulate material and a grinding medium to form a co-processed microfibrillated cellulose and inorganic particulate material composition.

5. The fibre of claim 4, wherein the microfibrillated cellulose has a median diameter (d50) less than 100 μιη.

6. The fibre of claim 4, wherein the fibre further comprises a water soluble or dispersible polymer.

7. The fibre of claim 4, wherein the fibrous substrate comprising cellulose is ground in the absence of a grindable inorganic particulate material.

8. The fibre of claim 6, wherein the fibre has a higher elastic modulus than a corresponding fibre that does not comprise the polymer.

9. The fibre of claim 4, wherein the fibre has a higher fibre strength than a corresponding fibre that does not comprise the polymer.

10. The fibre of claim 6, wherein the fibre has a higher fibre strength than a corresponding fibre that does not comprise the polymer.

11. The fibre of claim 1 , having a diameter ranging from about 0.1 μπι to about 1 mm.

12. The fibre of claim 4, having a diameter ranging from about 0.1 μπι to about 1 mm.

13. The fibre of claim 6, having a diameter ranging from about 0.1 μιη to about 1 mm.

14. The fibre of claim 1, wherein the fibre is an extruded fibre.

15. The fibre of claim 4, wherein the fibre is an extruded fibre.

16. The fibre of claim 6, wherein the fibre is an extruded fibre.

17. A method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of: (1) preparing a composition comprising a microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50; wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding in a grinding vessel and (ii) refining in a refiner or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium; wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size; (2) extruding the microfibrillated cellulose from step (1) through an extruder; (3) attenuating the extruded microfibrillated cellulose with an attenuating gas; and

(5) collecting the extruded fibres.

18. The process of claim 17, wherein the microfibrillated cellulose has a median diameter (d50) less than 100 μηι.

19. A method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) mixing the composition of microfibrillated cellulose with a water soluble or dispersible polymer to form a second mixture;

(3) extruding the second mixture through an extruder;

(4) attenuating the extruded second mixture with an attenuating gas; and

(5) collecting the extruded fibres.

20. The process of claim 19, wherein the microfibrillated cellulose has a median diameter (d5o) less than 100 μπι.

21. The process of claim 19, wherein the attenuating gas is one or more streams of hot air.

22. The process of claim 19, wherein the ultrasonic device is selected from the group consisting of an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

23. The process of claim 19, wherein the grinding vessel is screened grinder.

24. The process of claim 23, wherein the screened grinder is a stirred media detritor.

25. The process of claim 19, wherein the water soluble or dispersible polymer is selected from the group consisting of water soluble polymers, natural and synthetic latex, colloidal dispersions of polymer particles, emulsions, mini- emulsion, micro-emulsions or dispersion polymerization.

26. The process of claim 19, wherein the water soluble or dispersible polymer is selected from the group consisting of polyvinyl alcohol (PVA), co- polyamides, polyolefins, polyesters and polyvinyl chlorides.

27. The process of claim 19, wherein the water soluble or dispersible polymer is selected from the group consisting of polypropylene and polyethylene homopolymers and copolymers, including copolymers with 1-butene, 4- methyl-l-pentene, and 1-hexane; and blends thereof.

28. A method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose,

wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) extruding the microfibrillated cellulose and at least one inorganic particulate material from step (1) through an extruder;

(3) attenuating the extruded microfibrillated cellulose and at least one inorganic particulate material with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

29. The process of claim 28, wherein the microfibrillated cellulose has a median diameter (d50) less than 100 μm.

30. The process of claim 28, wherein the attenuating gas is one or more streams of hot air.

31. The process of claim 28, wherein the ultrasonic device is selected from the group consisting of an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

32. The process of claim 28, wherein the grinding vessel is screened grinder.

33. The process of claim 32, wherein the screened grinder is a stirred media detritor.

34. A method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material;

wherein the grinding is carried out in an aqueous environment in the absence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) extruding the microfibrillated cellulose and at least one inorganic particulate material from step (1) through an extruder;

(3) attenuating the extruded microfibrillated cellulose and at least one inorganic particulate material with an attenuating gas, for example, hot air; and

(4) collecting the extruded fibres.

35. The process of claim 34, wherein the microfibrillated cellulose has a median diameter (d5o) less than 100 μη .

36. The process of claim 34, wherein the attenuating gas is one or more streams of hot air.

37. The process of claim 34, wherein the ultrasonic device is selected from the group consisting of an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

38. The process of claim 34, wherein the grinding vessel is screened grinder.

39. The process of claim 34, wherein the screened grinder is a stirred media detritor.

40. A method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the ground fibrous substrate comprising cellulose and at least one inorganic particulate material;

wherein the grinding is carried out in an aqueous environment in the presence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) mixing the composition of microfibrillated cellulose and at least one organic particulate material with a polymer to form a second mixture;

(3) extruding the second mixture through an extruder;

(4) attenuating the extruded second mixture with an attenuating gas, for example, hot air; and

(5) collecting the extruded fibres.

41. The process of claim 40, wherein the microfibrillated cellulose has a median diameter (d5o) less than 100 μπ\.

42. The process of claim 40, wherein the attenuating gas is one or more streams of hot air.

43. The process of claim 40, wherein the ultrasonic device is selected from the group consisting of an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

44. The process of claim 40, wherein the grinding vessel is screened grinder.

45. The process of claim 44, wherein the screened grinder is a stirred media detritor.

46. The process of claim 40, wherein the water soluble or dispersible polymer is selected from the group consisting of water soluble polymers, natural and synthetic latex, colloidal dispersions of polymer particles, emulsions, mini- emulsion, micro-emulsions or dispersion polymerization.

47. The process of claim 40, wherein the water soluble or dispersible polymer is selected from the group consisting of polyvinyl alcohol (PVA), co- polyamides, polyolefins, polyesters and polyvinyl chlorides.

48. The process of claim 40, wherein the water soluble or dispersible polymer is selected from the group consisting of polypropylene and polyethylene homopolymers and copolymers, including copolymers with 1-butene, 4- methyl-l-pentene, and 1-hexane; and blends thereof.

49. A method for preparing a fibre comprising microfibrillated cellulose, the method comprising the steps of:

(1) preparing a composition comprising a microfibrillated cellulose, wherein the microfibrillated cellulose has a fibre steepness ranging from about 20 to about 50;

wherein the microfibrillated cellulose is obtainable by a two-stage process of (i) grinding a fibrous substrate in a grinding vessel is in the presence of at least one inorganic particulate material and (ii) refining in a refiner, or homogenizing in a homogenizer, or sonicating with an ultrasonic device the

ground fibrous substrate comprising cellulose and at least one inorganic particulate material;

wherein the grinding is carried out in an aqueous environment in the absence of a grinding medium;

wherein the term "grinding medium" means a medium other than inorganic particulate material and is 0.5 mm or greater in size;

(2) mixing the composition of microfibrillated cellulose and at least one inorganic particulate material with a polymer to form a second mixture;

(3) extruding the second mixture through an extruder;

(4) attenuating the extruded second mixture with an attenuating gas, for example, hot air; and

(5) collecting the extruded fibres.

50. The process of claim 49, wherein the microfibrillated cellulose has a median diameter (d50) less than 100 μηι.

51. The process of claim 49, wherein the attenuating gas is one or more streams of hot air.

52. The process of claim 49, wherein the ultrasonic device is selected from the group consisting of an ultrasonic probe, an ultrasonic water bath, an ultrasonic homogenizer, an ultrasonic foil and an ultrasonic horn.

53. The process of claim 49, wherein the grinding vessel is screened grinder.

54. The process of claim 53, wherein the screened grinder is a stirred media detritor.

55. The process of claim 49, wherein the water soluble or dispersible polymer is selected from the group consisting of water soluble polymers, natural and synthetic latex, colloidal dispersions of polymer particles, emulsions, mini- emulsion, micro-emulsions or dispersion polymerization.

56. The process of claim 49, wherein the water soluble or dispersible polymer is selected from the group consisting of polyvinyl alcohol (PVA), co- polyamides, polyolefins, polyesters and polyvinyl chlorides.

57. The process of claim 49, wherein the water soluble or dispersible polymer is selected from the group consisting of polypropylene and polyethylene homopolymers and copolymers, including copolymers with 1-butene, 4- methyl-l-pentene, and 1-hexane; and blends thereof.

58. The method of claim 17, wherein the fibres are extruded at a temperature from about 80°C. to about 100°C.

59. The method of claim 17, wherein the fibres have an average diameter of from about 0.1 μπι to about 1 mm.

60. The method of claim 17, wherein the fibres have an elastic modulus from about 5 GPa to about 20 GPa

61. The method of claim 17, wherein the fibres have a fibre strength of about 40 MPa to about 200 MPa.

62. The method of claim 17, wherein the fibres are spunlaid fibres.

63. The method of claim 17, wherein the spunlaid fibres are formed by spunbonding.

64. The method of claim 17, wherein the collecting step is deposition of the fibres onto a foraminous surface to form a non-woven web.

65. The method of claim 64, wherein the foraminous surface is a moving screen or wire

66. The method of claim 64, wherein the non-woven web is bonded by hydro-entanglement.

67. The method of claim 64, wherein the non-woven web is bonded by through-air thermal bonding.

68. The method of claim 64, wherein the non-woven web is bonded mechanically.

69. The method of claim 19, wherein the inorganic particulate material is selected from the group consisting of alkaline earth metal carbonate or sulphate, a hydrous kandite clay, an anhydrous (calcined) kandite clay, or combinations thereof.

70. The method of claim 19, wherein the inorganic particulate material is selected from the group consisting of calcium carbonate, magnesium carbonate, dolomite, gypsum, kaolin, halloysite, ball clay, metakaolin, fully calcined kaolin, talc, mica, huntite, hydromagnesite, ground glass, perlite, diatomaceous earth, wollastonite, titanium dioxide, magnesium hydroxide, aluminium trihydrate, lime, graphite, or combinations thereof.

71. The method of claim 17, wherein the composition of microfibrillated cellulose further comprises one or more additive selected from the group consisting of starch, carboxymethyl cellulose, gum, urea, ethylene, propylene and butylene glycol, and amphoteric carboxymethyl cellulose.

72. The method of claim 17, wherein the composition of microfibrillated cellulose further comprises one or more additive selected from the group consisting of dispersant, biocide, suspending agent, oxidising agents, and wood degrading enzymes

73. Use of the fibres according to the method of claim 17, to manufacture a non- woven product.

74. Use of the fibres according to the method of claim 19, to manufacture a non-woven product.

75. The use of claim 73, wherein the non-woven product is selected from the group consisting of: diapers, feminine hygiene products, adult incontinence products, packaging materials, wipes, towels, dust mops, industrial garments, medical drapes, medical gowns, foot covers, sterilization wraps, table cloths, paint brushes, napkins, trash bags, various personal care articles, ground cover, and filtration media.

76. The use of claim 73, wherein the non- woven product is selected from the group consisting of: diapers, feminine hygiene products, adult incontinence products, packaging materials, wipes, towels, dust mops, industrial garments, medical drapes, medical gowns, foot covers, sterilization wraps, table cloths, paint brushes, napkins, trash bags, various personal care articles, ground cover, and filtration media.

77. The use of claim 75, wherein the non-woven product is biodegradable

78. The use of claim 76, wherein the non-woven product is biodegradable