The present invention relates to a method for the preparation of inorganic particles by grinding a mineral material in the presence of a particular anionic polymer. The polymer used is obtained by polymerization in the presence of sodium hypophosphite, dipropionate disodium trithiocarbonate (DPTTC) and at least one radical-generator compound. The invention also relates to an aqueous composition comprising comminuted inorganic material particles and such a polymer, in particular a paper coating composition.

EP 2900708 and EP 3074436 describe anionic preparation methods of molecular weight and polydispersity index are controlled.

Discloses inorganic material grinding methods, particularly for the grinding of mineral materials used in paper industry. In particular, there are known methods for grinding mineral material which implement grinding aid agents, including polymers derived from unsaturated monomers comprising one or more carboxylic acid functions. These grinding aid agents are used to control the rheology of the suspension during the grinding operation. Typically, these grinding aid agents are used to minimize the yield stress of the suspension of mineral filler to be ground while maintaining a sufficient level of viscosity during the grinding operation.

In general, methods of inorganic material grinding must be effective and capable of controlling the particle size of the particles obtained.

In addition, methods of inorganic material grinding must have a high efficiency in terms of milling time for a particular particle size and a defined amount of mineral matter. Indeed, for the preparation of a defined quantity of mineral particles of particular particle size, a usage time reduces grinding plants allows an improved overall efficiency of the grinding method.

Similarly, it is important to have methods of mineral grinding which allow the preparation of aqueous suspensions of mineral particles from low viscosity that are stable soon after grinding but also several hours or days after grinding. The viscosity drift phenomena must be controlled because they can lead to gelling of the suspensions prepared which would make handling difficult or impossible. Such viscosity differences should be the lowest possible. Similarly, the phenomena of sedimentation of particles must be prevented or greatly slowed.

Furthermore the stability control, the control of the viscosity of aqueous suspensions of ground mineral material particles is also essential. In general, control of the viscosity of aqueous suspensions of ground mineral material particles must achieve a low viscosity.

It is also important to be able to prepare aqueous suspensions of mineral particles having a high solids content. A high solids content of these aqueous suspensions of mineral matter particles makes it possible in particular to increase the productivity of these suspensions preparation methods.

Moreover, from an environmental point of view, it is important to have available agents grinding aid for the preparation of mineral material suspensions of particles comprising an amount of water reduced while maintaining or improving the properties these suspensions.

Furthermore, during the manufacture of coated and surfaced papers, aqueous compositions of paper coatings are used for depositing a layer of inorganic material particles and binder on the surface of the paper sheet in order to modify its surface state to improve printability, brightness, or opacity. For example, for a coated paper for printing, the layer is obtained from an aqueous dispersion consisting mainly of binders and pigments also known as mineral fillers. The most commonly used pigments for paper coating are kaolin, calcium carbonate, titanium dioxide, talc and organic pigments, such as plastic pigments. Within these compositions, the inorganic filler is in the form of particles. The use of such paper coatings possible in particular to improve the physical properties of the paper, in particular to improve its optical properties.

Improving the efficiency of the papermaking process is also permitted through the use of these paper coatings.

Improve the compatibility of various compounds used in the preparation of the paper should also be sought.

Thus, although there are wet milling processes of mineral implementing polymers as grinding aid agent, the methods of the prior art do not always provide a satisfactory solution to the problems met. There is therefore a need for improved methods of mineral grinding in water.

The method of the invention to provide a solution to any or all of the problems of the methods of the art.

Thus, the invention provides an inorganic material particles preparation method comprises grinding in the presence of water, at least one mineral in the presence of at least one molecular weight polymer material weight Mw (measured by SEC ) of less than 8000 g / mol and polydispersity index IP or polydispersity index less than 3, obtained by a radical polymerization reaction in water, at a temperature above 50 ° C, of ​​at least one monomer anionic comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function, in the presence:

- d'hypophosphite de sodium,

de dipropionate trithiocarbonate disodique (DPTTC) and

d 'au moins un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio an ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 and leurs mélanges.

When the grinding method according to the invention, the mineral implementation may be in various forms including the form of coarse grain size from blocks or pieces of crushed mineral material. During grinding according to the invention, the size of grains including grains of coarse size of inorganic material or pieces of mineral material used is reduced to obtain particles. The method according to the invention is particularly effective for controlling the size of particles produced during the grinding of the mineral. According to the invention, particle size is measured by sedimentation.

For the method according to the invention, the particle size may be defined by their median diameter dso at which half by weight of a population of particles has a size lower than a given value. Thus, the particles having a size less than 50 μιη are particles belonging to a population whose half by weight has a diameter less than 50 μιη. Preferably, the method according to the invention relates to the preparation of particles whose size is less than 50 μιη or ranging in size from 0.05 to 50 μιη μιη.

More preferably, the method according to the invention relates to the preparation of inorganic material particles having a size less than 10 μιη or less than 5 or 2 μιη μιη. More preferably, the size of inorganic material particles is less than 1 or less than 0.5 μιη μιη. Also preferably for the method according to the invention, at least 50% by weight of the particles have a size ranging from 0.5 to 50 μιη μιη or smaller than 10 μιη. In particular, at least 50% by weight of the particles have a size less than 5 μιη or 2 μιη, or even less than 1 μιη.

Advantageously for the method according to the invention, at least 60% by weight of the particles have a size ranging from 0.5 to 50 μιη μιη or smaller than 10 μιη. In particular, at least 60% by weight of the particles have a size less than 5 μιη or 2 μιη, or even less than 1 μιη. Also advantageously for the method according to the invention, at least 75% by weight of the particles have a size ranging from 0.5 to 50 μιη μιη or smaller than 10 μιη. In particular, at least 75% by weight of the particles have a size less than 5 μιη or 2 μιη, or even less than 1 μιη.

Also advantageously for the method according to the invention, at least 90% by weight of the particles have a size ranging from 0.5 to 50 μιη μιη or smaller than 10 μιη. In particular, at least 90% by weight of the particles have a size less than 5 μιη or 2 μιη, or even less than 1 μιη.

For the method according to the invention, a population of inorganic particles may also be defined by an equivalent spherical diameter (esd). Preferably according to the invention, the spherical equivalent diameter of particles having a size less than 50 μιη is equal to 50% by weight. In this case, 50% by weight of the particles have a size less than 50 μιη. Also preferably according to the invention, the spherical equivalent diameter of particle size from 0.05 to 50 μιη μιη or less than 50 μιη is equal to 60% by weight or equal to 70% by weight or equal to 80% by weight or equal to 90% by weight.

More preferably according to the invention, the spherical equivalent diameter of the particles to a size less than 10 μιη is equal to 60% by weight or equal to 70% by weight or equal to 80% by weight or equal to 90% in weight.

More preferably well according to the invention, the spherical equivalent diameter of the particles to a size less than 5 μιη is equal to 60% by weight or equal to 70% by weight or equal to 80% by weight or equal to 90 % in weight.

Even more preferably according to the invention, the spherical equivalent diameter of the particles to a size less than 2 μιη is equal to 60% by weight or equal to 70% by weight or equal to 80% by weight or equal to 90 % in weight.

Very particularly preferably according to the invention, the spherical equivalent diameter of the particles to a size less than 1 μιη is equal to 60% by weight or equal to 70% by weight or equal to 80% by weight or equal to 90% in weight.

Also preferably according to the invention, the spherical equivalent diameter of the particles to a size less than 0.5 μιη is equal to 60% by weight or equal to 70% by weight or equal to 80% by weight or equal to 90 % in weight.

Preferably, the method according to the invention uses at least one synthetic inorganic material or of natural origin.

De manière également favorite, selon la methode the invention met en oeuvre au moins une matière mineral choisie parmi les carbonates of alkali metal-Slovenian, de préférence Calcium carbonate (carbonate of calcium carbonate or naturel de calcium precipite) of strontium carbonate, carbonate of magnesium, de baryum carbonate, dolomite, kaolin, de titane dioxide, talc, chaux, calcium sulphate, baryum sulphate. De manière plus music, selon la méthode the invention met en oeuvre au moins une matière mineral choisie Models carbonate Calcium naturel de calcium carbonate precipitous, dolomite, kaolin, calcine kaolin, de titane dioxide, talc, Chaux.

The method of the invention may implement a single inorganic material or more inorganic materials. Thus, the method of the invention may implement two or three mineral materials. In particular, the method according to the invention can implement calcium carbonate and at least another mineral material selected from dolomite, kaolin, calcined kaolin, titanium dioxide, talc, lime, notably calcium carbonate and kaolin or of calcium carbonate and lime. Similarly, the method according to the invention can implement titanium dioxide and at least one other mineral material selected from calcium carbonate, dolomite, kaolin, talc, lime, including titanium dioxide and kaolin or dioxide titanium and lime. Also, the method of the invention may implement kaolin or calcined kaolin and at least one other mineral material selected from dolomite, talc, lime. The method according to the invention may also implement talc and lime or talc and dolomite.

In addition to an inorganic material, the method according to the invention uses at least one particular polymer derived from a radical polymerization reaction in the presence

of sodium hypophosphite de, de dipropionate trithiocarbonate disodique (DPTTC) et au moins d'un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio a ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 et leurs mélanges.

Preferably, the polymerization reaction is carried out in water or in a mixture solvent with water, in particular an alcoholic solvent, in particular isopropyl alcohol. More preferably, the polymerization reaction is carried out in water only.

According to the invention sodium hypophosphite (CAS No. 7681-53-0 or 10039-56-2 for the monohydrate) is a sodium salt of hypophosphorous acid.

According to the invention, the DPTTC is disodium 2,2 '- (thiocarbonylbisthio) -dipropanoate

(CAS No. 864970-33-2). Its sodium salts are used according to the invention.

Also preferably, the polymerization reaction implements a radical generator compound selected from hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and mixtures thereof. More preferably, the polymerization reaction implements a radical generator compound selected from hydrogen peroxide and sodium persulfate.

Also preferably, the polymerization reaction uses, relative to the quantity by weight of monomer:

- 2% by weight to 8% by weight, preferably from 2.5 wt% to 7% by weight or 2.5% by weight to 6% by weight of sodium hypophosphite or

0.01% by weight to 1.5% by weight, preferably from 0.01 wt% to 1.2 wt% or 0.05 wt% to 1.5 wt%, more preferably 0.05 wt% to 1.2 wt% or 0.1 wt% to 1 wt% dipropionate disodium trithiocarbonate (DPTTC) or

0.1% by weight to 5% by weight of compound or radical generator, preferably, from 0.5 wt% to 4.5 wt% hydrogen peroxide or 0.1% by weight 4% by weight of sodium persulfate, potassium persulfate or ammonium persulfate.

Also preferably, the polymerization reaction uses, relative to the quantity by weight of monomer:

2% by weight to 8% by weight, preferably from 2.5 wt% to 7% by weight or 2.5% by weight to 6% by weight of sodium hypophosphite or

0.01% by weight to 1.5% by weight, preferably from 0.01 wt% to 1.2 wt% or 0.05 wt% to 1.5 wt%, more preferably 0.05 wt% to 1.2 wt% or 0.1 wt% to 1 wt% dipropionate disodium trithiocarbonate (DPTTC) or

0.5 wt% to 4.5 wt% hydrogen peroxide or 0.1% by weight to 4% by weight of sodium persulfate, potassium persulfate or ammonium persulfate.

More preferably, the polymerization reaction uses, relative to the quantity by weight of monomer:

2% by weight to 8% by weight, preferably from 2.5 wt% to 7% by weight or 2.5% by weight to 6% by weight of sodium hypophosphite,

0.01% by weight to 1.5% by weight, preferably from 0.01 wt% to 1.2 wt% or 0.05 wt% to 1.5 wt%, more preferably 0.05 wt% to 1.2 wt% or 0.1 wt% to 1 wt% dipropionate disodium trithiocarbonate (DPTTC) and

0.1% by weight to 5% by weight of compound or radical generator, preferably, from 0.5 wt% to 4.5 wt% hydrogen peroxide or 0.1% by weight 4% by weight of sodium persulfate, potassium persulfate or ammonium persulfate.

Also most preferably, the polymerization reaction uses, relative to the quantity by weight of monomer:

2% by weight to 8% by weight, preferably from 2.5 wt% to 7% by weight or 2.5% by weight to 6% by weight of sodium hypophosphite,

0.01% by weight to 1.5% by weight, preferably from 0.01 wt% to 1.2 wt% or 0.05 wt% to 1.5 wt%, more preferably 0.05 wt% to 1.2 wt% or 0.1 wt% to 1 wt% dipropionate disodium trithiocarbonate (DPTTC) and

0.5 wt% to 4.5 wt% hydrogen peroxide or 0.1% by weight to 4% by weight of sodium persulfate, potassium persulfate or ammonium persulfate.

During the implementation of hydrogen peroxide associated with an ion selected from Fe 11 , Fe m , Cu 1 , Cu 11 , these ions can be introduced by means of different chemical compounds. Examples of chemical compounds for introducing ions Fe 11 , Fe m , Cu 1 , Cu include iron sulfate, iron sulfate hydrate, sulphate hemi-hydrate iron, iron sulfate heptahydrate, iron carbonate, carbonate hydrated iron carbonate, hemi-hydrate iron, iron chloride, copper carbonate, carbonate hydrated copper carbonate, hemi-hydrate, copper acetate, copper sulfate, copper sulfate pentahydrate, copper hydroxide, halide of copper.

The average molecular weight Mw (measured by SEC or Chromato graphy Steric Exclusion) of the polymer used according to the invention is less than 8000 g / mol, it may vary quite widely. Also preferably, the polymer according to the invention has an average molecular weight Mw of less than 7500 g / mol, preferably less than 6500 g / mol, less than 6000 g / mol, more preferably less than 5 500 g / mol.

Also preferably, the polymer according to the invention has an average molecular weight Mw higher than 1000 g / mol or greater than 1 200 g / mol or greater than 1 500 g / mol.

Thus, the polymer of the invention preferably has an average molecular weight M w of from 1000 g / mol to 7500 g / mol, 6500 g / mol, 6000 g / mol or 5500 g / mol. More preferably, the polymer according to the invention has an average molecular weight M w of from 1200 g / mol to 7500 g / mol, 6500 g / mol, 6000 g / mol or 5500 g / mol. Even more preferably, the polymer according to the invention has an average molecular weight Mw ranging from 1500 g / mol to 7500 g / mol, 6500 g / mol, 6000 g / mol or 5500 g / mol.

Particularly preferably, the polymer according to the invention has an average molecular weight Mw ranging from 3500 g / mol to 5500 g / mol. Also preferably, the polymer according to the invention has an average molecular weight Mw ranging from 4500 g / mol to 5500 g / mol.

According to the invention, the polymolecularity index IP, or molecular weight distribution, the polymer used is less than 3. Preferably, the IP polymolecularity index of the polymer is less than 2.8. Also preferably, the IP polymolecularity index of the polymer ranges from 1.5 to 3. More preferably, the molecular weight distribution of IP polymer ranges from 1.5 to 2.8 or 1.5 to 2 5.

An essential step in the preparation of the polymer used according to the invention is the radical polymerization reaction of at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function. The

polymerization reaction is known as such. Preferably, it can be carried out at a temperature above 80 ° C or above 95 ° C. It can be performed in a solvent selected from water, organic solvents and mixtures thereof, preferably in water.

Preferably according to the invention, the anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function is selected from acrylic acid, methacrylic acid, an acrylic acid salt, methacrylic acid salt and mixtures thereof.

Particularly preferably according to the invention, the anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid is acrylic acid. More preferably according to the invention, the radical polymerization reaction does not implement as acrylic acid.

However, besides the anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid, the radical polymerization reaction may implement at least one other monomer. Preferably, the polymerization reaction can also implement at least one monomer selected from:

another anionic monomer comprising at least one different olefinic unsaturation selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, their salts and mixtures thereof,

a nonionic monomer comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and including a polymerizable vinyl group, more preferably a nonionic monomer selected from esters of an acid comprising at least one monocarboxylic acid function, especially an ester of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof, for example styrene, vinylcaprolactam, alkyl acrylate, in particular acrylate Ci-Cio-alkyl, preferably acrylate, Ci-C 4 alkyl, more preferably methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, n-butyl acrylate, alkyl methacrylate, especially methacrylate Ci-Cio-alkyl, preferably methacrylate Ci-C 4 alkyl , more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate,

methacrylate, isobutyl methacrylate, n-butyl, aryl acrylate, preferably phenyl acrylate, benzylacrylate, phenoxyethylacrylate, aryl methacrylate, preferably phénylméthacrylate, benzylméthacrylate, phénoxyéthylméthacrylate, a compound of formula (I):

(I)

in which :

o R 1 represents a polymerizable acrylate group or a polymerizable methacrylate,

o R 2 represents an OH group or an OCH 3 ,

o L 1 and L 2 , identical or different, independently represent an ethyloxy group or a propyloxy group and

om and n, identical or different and at least one is different from 0, are lower or equal to 150 and the sum m + n is less than 150 and

acid 2-acrylamido-2-methylpropanesulfonic acid salt 2-acrylamido-2-methylpropanesulfonic acid

2- (methacryloyloxy) ethanesulfonic acid, an acid salt

2- (methacryloyloxy) ethanesulfonic acid (CAS No. 010595-80-9), sodium methallyl sulfonate, styrene sulfonate and mixtures thereof.

During the polymerization reaction, the amounts of anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid can vary quite widely. Preferably, the polymerization reaction implements 100% by weight of said anionic monomer.

Similarly, the amounts of other monomers may also vary quite widely. Preferably, the polymerization reaction can then implement 70% to 99.5% by weight of anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function and from 0.5% to 30% by weight at least one monomer chosen from:

- another anionic monomer different selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, their salts and mixtures thereof, a nonionic monomer comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and including a function polymerizable vinyl, more preferably a nonionic monomer selected from esters of an acid comprising at least one monocarboxylic acid function, in particular an ester of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof, for example styrene, vinylcaprolactam , alkyl acrylate, in particular acrylate Ci-Cio-alkyl, preferably acrylate, Ci-C 4 alkyl, more preferably methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, n butyl, alkyl methacrylate, especially methacrylate Ci-Cio-alkyl, preferably meth acrylate, Ci-C 4 alkyl, more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, aryl acrylate, preferably phenyl acrylate, benzylacrylate, phenoxyethylacrylate, methacrylate aryl, preferably phénylméthacrylate, benzylméthacrylate, phénoxyéthylméthacrylate, a compound of formula (I):

^-(L CL R2

(D

in which :

o R 1 represents a polymerizable acrylate group or a polymerizable methacrylate,

o R 2 represents an OH group or an OCH 3 ,

o L 1 and L 2 , identical or different, independently represent an ethyloxy group or a propyloxy group and

om and n, identical or different and at least one is different from 0, are lower or equal to 150 and the sum m + n is less than 150 and

acid 2-acrylamido-2-methylpropanesulfonic acid salt 2-acrylamido-2-methylpropanesulfonic acid

2- (methacryloyloxy) ethanesulfonic acid, an acid salt

2- (methacryloyloxy) ethanesulfonic acid, sodium methallyl sulfonate, styrene sulfonate and mixtures thereof.

Preferably, the grinding method according to the invention implements a totally or partially neutralized polymer. According to the invention, neutralization of the polymer used is formed by neutralizing or salifying or all of the carboxylic acid functions present in the polymer.

Preferably, neutralization is achieved by means of a base, for example by means of an alkali metal compound or an alkaline earth metal compound. Preferred bases are selected from NaOH, KOH, NH 4 OH, Ca (OH) 2 , Mg (OH) 2 , monoisopropylamine, triethanolamine, triisopropylamine, 2-amino-2-methyl-l-propanol (AMP), triethylamine, diethylamine , monoethylamine. Particularly preferably, the neutralization is carried out with NaOH, Ca (OH) 2 , Mg (OH) 2 alone or in combination.

When preparing the polymer according to the invention, a separation step can also be implemented. According to the invention, separation may be carried out after the total or partial neutralization of the polymer used according to the invention. It can also be implemented before the neutralization of the polymer.

The aqueous solution of the polymer, wholly or partially neutralized, can be treated according to static or dynamic fractionation methods known as such. then using one or more polar solvents belonging in particular to the group comprising methanol, ethanol, n-propanol, isopropanol, butanols, acetone, tetrahydrofuran, thereby producing a separation into two phases. Upon separation, the less dense phase contains the major fraction of the polar solvent and the fraction of low molecular weight polymers, the most dense aqueous phase comprises the fraction of higher molecular weight polymers. The temperature at which performs processing of selection of the polymer fraction may influence the partition coefficient. It is generally between 10 ° C and 80 ° C, preferably between 20 ° C and 60 ° C. During the separation, it is important to control the relative amounts of water dilution and polar solvents. When the implementation of a dynamic separation method, for example by centrifugation, the ratios of the extracted fractions generally depend on the centrifugation conditions. The selection of the polymeric moiety can also be improved by treating again the most dense aqueous phase, by means of a new amount of polar solvent, which may be different. It can also be a mixture of polar solvents. Finally, the liquid phase obtained after treatment can be subjected to distillation to remove the solvent used for the treatment.

Further provides a method of grinding, the invention also relates to a method for preparing an aqueous suspension of inorganic material particles comprising the implementation of the grinding method according to the invention.

Preferably, the preparation method according to the invention allows to prepare an aqueous suspension which inorganic material solids content is greater than 60% by weight. More preferably, the method of preparation according to the invention allows to prepare an aqueous suspension which inorganic material solids content is greater than 70% by weight. Much more preferably, the preparation method according to the invention allows to prepare an aqueous suspension which inorganic material solids content is greater than 75% by weight or 80% by weight of the suspension.

The particular features, advantageous or preferred for the grinding method according to the invention establish methods of preparation of an aqueous suspension according to the invention are also special, advantageous or preferred.

The invention also provides an aqueous composition comprising inorganic material particles ground and at least one polymer defined for the grinding method according to the invention.

Advantageously, the composition according to the invention may also comprise at least one additive, in particular at least one adjuvant selected from dispersants, anti-foaming agents, biocides, coloring agents, lubricating agents and optical brightening agents.

Advantageously, the composition according to the invention may also comprise at least one binder, in particular a natural binding agent such as starch or a synthetic binder such as a latex.

The invention also provides a method for preparing a paper coating comprising milling in the presence of water, at least one mineral material in the presence of at least one polymer obtained by a radical polymerization reaction in water at a temperature above 50 ° C, of ​​at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function, in the presence:

- d'hypophosphite de sodium,

de dipropionate trithiocarbonate disodique (DPTTC) and

d'au moins un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio an ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 and leurs mélanges.

The invention also relates to the use as a grinding aid agent of at least one mineral material, at least one polymer obtained by a radical polymerization reaction in water, at a temperature above 50 ° C, at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function, in the presence:

d'hypophosphite de sodium,

- de dipropionate trithiocarbonate disodique (DPTTC) and

d'au moins un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio an ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 and leurs mélanges.

Preferably for use as a grinding aid agent according to the invention, the polymer used is the anionic polymer of the grinding method according to the invention.

The invention also provides a method of preparing paper comprising using an aqueous composition according to the invention.

The particular, advantageous or preferred features of the grinding method according to the invention define aqueous compositions, uses and methods of preparation according to the invention are also special, advantageous or preferred.

The following examples illustrate various aspects of the invention. The methods and techniques used are known or described.

EXAMPLES

molecular weight by chromatography size exclusion (CES)

The molecular weight and polydispersity index of the polymers obtained by a radical polymerization reaction in water, at a temperature above 50 ° C, of ​​at least one monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function are determined by chromatography size exclusion.

A test sample of the polymer corresponding to 90 mg dry matter solution is introduced into a 10 mL vial. Is added to the mobile phase, treated with 0.04% of dimethylformamide (DMF), to a total mass of 10 g. The composition of the mobile phase is: NaHC0 3 : 0.05 mol / L, NaN0 3 : 0.1 mol / L triethanolamine: 0.02 mol / L, 0.03% NaN mass.

The CES chain consists of an isocratic pump Waters 510 type, whose flow rate is set at 0.8 mL / min, a Waters 717+ autosampler, an oven containing a precolumn Guard type column Ultrahydrogel Waters 6 cm in length and 40 mm in inside diameter, followed by a linear column type Ultrahydrogel Waters 30 cm in length and 7.8 mm internal diameter.

Detection is performed by means of a type of differential refractometer RI Waters 410 The furnace is heated to a temperature of 60 ° C and the refractometer is heated to a temperature of 45 ° C.

The ESC system is calibrated with a set of sodium polyacrylate standards provided by Polymer Standard Service molecular weight at the top of the peak between 1000 g / mol and 1.10 6 g / mol and polydispersity index between 1, 4 and 1.7 and with a molecular weight sodium polyacrylate equal to 5 600 g / mol and polydispersity index equal to 2.4. The calibration curve is linear, and takes into account the correction obtained using the flow marker: dimethylformamide (DMF).

The acquisition and processing of the chromatogram are performed by using the PSS WinGPC Scientific v 4.02 software. The chromatogram obtained is integrated in the region corresponding to molecular weights greater than 65 g / mol.

grinding technique and measuring the particle size

Using a peristaltic pump, suspensions of coarse grains of mineral material prepared in the presence of a polymer according to the invention or a comparative polymer are introduced into a Type KDL Dyno Mill crusher pilot 1, 4 L containing 2850 g of ceramic ball type ER 120 S 0.6 mm to 1.0 mm in diameter from the Zirpro society. The grinding conditions are adjusted so as to obtain a suspension of inorganic material particles of desired particle size. The required amount of polymer introduced into the system is adjusted to achieve the desired particle size. This suspension is then characterized by a particle size measurement, a Brookfield viscosity measurement followed by a stability test. This stability test consists in measuring the Brookfield viscosity of the slurry ground after a rest period of 8 days at a temperature of 25 ° C ± 1 ° C.

The particle size characteristics for the preparation of inorganic material particles are determined using a Sedigraph III 5120 apparatus (Micromeritics, USA). In known manner, this method and this measuring instrument for measuring particle size distribution of suspensions of inorganic material particles. They allow in particular to determine the mass fraction percentage of a population of inorganic particles having an equivalent spherical diameter less than 1 μιη or 2 μιη (esd <Ιμιη or esd <2 μιη, both expressed in%) . These measurements are made from an inorganic material particle suspension diluted to a concentration of about 33 g dry matter per liter of solution of a molecular weight of sodium polyacrylate equal to 4 000 g / mol and concentration equal to 1.6 g of dry sodium polyacrylate per liter of solution. This sample was dispersed and sonicated before the measurement.

Brookfield Viscosity Measurement

Brookfield viscosities (mPa.s) of suspensions of inorganic material particles prepared by the method of the invention are measured after the grinding operation (VB0) and after 8 days of rest (VB8) at 25 ° C ± 1 ° C and a rotational speed of 100 rev / min using a Brookfield DVIII equipped with a suitable module, for example 2 to 5.

Example 1 Preparation of co-neutralized polymers of the invention

In a stirred reactor, a mixture of (R) water and sodium hypophosphite. Then, the mixture 1 is prepared (Ml), the mixture 2 (M2) and the mixture 3 (M3) from water, acrylic acid (AA), hydrogen peroxide or sodium persulfate, of sodium hypophosphite and DPTTC. then the reactor was heated so as to reach the temperature (T in ° C) and polymerization is introduced in parallel mixtures 1, 2 and 3 into the reactor. Finally, the reactor was cooled and the polymer is neutralized by injecting the mixture (MN) neutralization previously prepared. The quantity (in grams) of reactants, reaction conditions and the characteristics of the polymers (solids content ES, molecular weight Mw and polydispersity index PI) prepared are shown in Tables 1, 2 and 3.

Table 1

Example 2-1 2-2 2-3 2-4 2-5 2-6

R Water 198 198 198 198 198 198

NaH 2 P0 2 .H 2 0 11 11.5 12 13 14 15

AA 208,65 208,65 208,65 208,65 208,65 208,65

Ml DPTTC 20% 13.41 13.41 13.41 13.41 13.41 13.41

Water 23.18 0 23.18 23.18 23.18 23.18

H 2 0 2 to 35% 7,1 7,1 7,1 7,1 7,1 7,1

M2 persulfate Na 0 0 0 0 0 0

Water 130 130 130 130 130 130

NaH 2 P0 2 .H 2 0 0 0 0 0 0 0

M3 DPTTC à 20% 0 0 0 0 0 0

Water 0 0 0 0 0 0

Water 170 170 170 170 170 170

MN NaOH à 50% 160,66 159,85 160,66 159,03 159,85 159,85

Ca (OH) 2 97% 33.52 33.35 33.52 33.18 33.35 33.35

T (°C) 90+2 90+2 90+2 90+2 90+2 90+2

ES (%) 31.69 32.5 31.69 31.68 31.38 31.5

Mw (g/mol) 6 165 5 465 5 640 5 225 5 145 4 590

IP 2,4 2,5 2,3 2,3 2,3 2,2

Table 2

Table 3

Example 2 Preparation of comparative co-neutralized polymers

Analogously to Example 1, are prepared comparative polymers. The quantity (in grams) of reactants, reaction conditions and the characteristics of the polymers prepared are shown in Table 4.

Table 4

Example 3: grinding calcium carbonate with esd less than 1 μιη equal to 80% weight

The polymers according to the invention and a comparative polymer are used as agent for assisting grinding of natural calcium carbonate. The different polymers are used at the same doses and in the same operating conditions.

Aqueous suspensions of natural calcium carbonate having a solid weight content of 76% + 1%. They are prepared in the presence of an amount of 1.07% by dry weight of an aqueous polymer solution, as an agent for assisting grinding as compared to the amount of dry calcium carbonate involved in the operation of grinding in order to achieve the targeted particle size. The polymer solutions have a concentration of 35% ± 1% of active material and a pH of 8.5 ± 0.5. The raw material for preparing the aqueous suspension is an aqueous suspension of coarse calcium carbonate at 75% ± 1% solids content by weight. Calcium carbonate is a crude marble (commercial product Omyacarb 10 Omya AV) from the Carrara region (Italy). The grinding conditions are adjusted so as to obtain a suspension of mineral particles of which 80.0% ± 0.5% by weight of the population has an equivalent spherical diameter less than 1 μιη (esd <Ιμιη = 80.0% ± 0 , 5%).

The suspensions according to the invention and the comparative suspension is then analyzed and characterized by Brookfield viscosity measurements after the grinding operation and after 8 days of standing at 25 ° C. The results are presented in Table 5.

Table 5

The use of grinding aid agents according to the invention allows the preparation of calcium carbonate slurries of comminuted low viscosity. The viscosities of these suspensions evolve over time over a period of 8 days of lower order than that of the suspension prepared in the presence of the comparative polymer. The suspensions prepared according to the invention have lower viscosities than those of the suspension of the trial. They are more stable.

Example 4: grinding calcium carbonate with esd less than 1 μιη equal to 80% by weight

The polymers according to the invention and a comparative polymer are used as agent for assisting grinding of natural calcium carbonate. The different polymers are used at the same doses and in the same operating conditions.

Thereby preparing aqueous suspensions of natural calcium carbonate having a solid weight content of 76% ± 1%. They are prepared in the presence of an effective amount (QE - expressed in% dry / dry) by dry weight of an aqueous polymer solution based on 100 g of dry calcium carbonate, as a grinding aid agent in order to achieve the target particle size. The polymer solutions have a concentration of 35% ± 1% of active material and a pH of 8.5 ± 0.5. The raw material for preparing the aqueous suspension is an aqueous suspension of coarse calcium carbonate at 75% ± 1% solids content by weight. Calcium carbonate is coarse calcite (commercial product Omya BL 200) from the region of Orgon (France). The grinding conditions are adjusted so as to obtain a suspension of mineral particles of which 80.0% ± 0.5% by weight of the population has an equivalent spherical diameter less than 1 μιη (esd <Ιμιη = 80.0% ± 0 , 5%).

calcium carbonate suspensions were then analyzed and characterized by Brookfield viscosity measurements after the grinding operation and after 8 days of standing at 25 ° C. The effective amount (QE) of dry polymer to achieve the target particle size is also measured. The results are presented in Table 6.

Table 6

The implementation of the polymers according to the invention allows a reduction in the effective amount of grinding aid agent. Again, the use of grinding aid agents according to the invention allows the preparation of calcium carbonate slurries of comminuted low viscosity. The viscosities of these suspensions evolve over time over a period of 8 days of lower order than that of the suspension prepared in the presence of the comparative polymer. The suspensions prepared according to the invention have lower viscosities than those of the suspension of the trial. They are more stable.

Example 5: grinding calcium carbonate with esd less than 2 μιη equal to 60% by weight

The polymers according to the invention and a comparative polymer are used as agent for assisting grinding of natural calcium carbonate. The different polymers are used at the same doses and in the same operating conditions.

Thereby preparing aqueous suspensions of natural calcium carbonate having a solid weight content of 74% ± 1%. They are prepared in the presence of an amount of 0.26% by dry weight of an aqueous polymer solution, as an agent for assisting grinding as compared to the amount of dry calcium carbonate involved in the operation of grinding in order to achieve the targeted particle size. The polymer solutions have a concentration of 35% ± 1% of active material and a pH of 8.5 ± 0.5. The raw material for preparing the aqueous suspension is an aqueous suspension of coarse calcium carbonate at 75% ± 1% solids content by weight. Calcium carbonate is a crude marble (commercial product Omyacarb 10 Omya AV) from the Carrara region (Italy). The grinding conditions are adjusted so as to obtain a suspension of mineral particles of which 60.0% ± 0.5% by weight of the population has an equivalent spherical diameter less than 2 μιη (esd <2μιη = 60.0% ± 0 , 5%).

calcium carbonate suspensions were then analyzed and characterized by Brookfield viscosity measurements after the grinding operation and after 8 days of standing at 25 ° C. The results are presented in Table 7.

Table 7

Again, the use of grinding aid agents according to the invention allows the preparation of calcium carbonate slurries of comminuted low viscosity. The viscosities of these suspensions evolve over time over a period of 8 days of lower order than that of the suspension prepared in the presence of the comparative polymer. The suspensions prepared according to the invention have lower viscosities than those of the suspension of the trial. They are more stable.

CLAIMS
1. inorganic material particles preparation method comprising milling in the presence of water, at least one mineral material in the presence of at least one molecular weight polymer Mw (measured by SEC) of less than 8000 g / mol and polydispersity index less than 3 IP obtained by a radical polymerization reaction in water, at a temperature above 50 ° C, of ​​at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid, in the presence:

- d'hypophosphite de sodium,

de dipropionate trithiocarbonate disodique (DPTTC) and

d 'au moins un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio an ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 and leurs mélanges.

2. Method according to claim 1 for which:

the particles have a size less than 50 μιη or a size ranging from 0.05 to 50 μιη μιη or smaller than 10 μιη, preferably less than 5 μιη or 2 μιη, more preferably less than 1 μιη or less 0.5 μιη or - the spherical equivalent diameter of the particles to a size ranging from 0.05 to μιη

50 μιη or less than 50 μιη, preferably to a size less than 10 μιη, more preferably less than 5 μιη or 2 μιη, even more preferably less than 1 or less than 0.5 μιη μιη is equal to 60% by weight not exceeding 70% by weight or equal to 80% by weight or alternatively equal to 90% by weight.

3. Method according to one of claims 1 and 2 wherein:

one mineral material or two or three mineral materials are used, or for which:

the inorganic material is synthetic or of natural origin, preferably selected from alkaline earth metal carbonates, preferably calcium carbonate

(Carbonate of calcium carbonate or naturel de calcium precipite) of strontium carbonate, magnesium carbonate de, de baryum carbonate, dolomite, kaolin, de titane dioxide, talc, Chaux, calcium sulphate, baryum sulphate.

4. Method according to one of claims 1 to 3 wherein the polymerization reaction is carried out in water or in a mixture solvent with water, in particular an alcoholic solvent, in particular isopropyl alcohol, preferably in the water only.

5. Method according to one of claims 1 to 4 wherein the polymer:

has an average molecular weight Mw of less than 7500 g / mol, preferably less than 6500 g / mol, less than 6000 g / mol, more preferably less than 5500 g / mol or

has an average molecular weight Mw higher than 1000 g / mol or greater than 1 200 g / mol or greater than 1 500 g / mol or

has a polydispersity index less than 2.8 IP or IP polydispersity index ranging from 1.5 to 3, 1.5 to 2.8 or from 1.5 to 2.5.

6. Method according to one of claims 1 to 5 wherein the anionic monomer is selected from acrylic acid, methacrylic acid, an acrylic acid salt, methacrylic acid salt and mixtures thereof, preferably acrylic acid.

7. Method according to one of claims 1 to 6 wherein the polymerization reaction also implements at least one monomer chosen from:

- another anionic monomer different selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, their salts and mixtures thereof, a nonionic monomer comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and including a function polymerizable vinyl, more preferably a nonionic monomer selected from esters of an acid comprising at least one monocarboxylic acid function, in particular an ester of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof, for example styrene, vinylcaprolactam , alkyl acrylate, in particular acrylate Ci-Cio-alkyl, preferably acrylate, Ci-C 4 alkyl, more preferably methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, n butyl, alkyl methacrylate, especially methacrylate Ci-Cio-alkyl, preferably meth acrylate, Ci-C 4 alkyl, more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate,

methacrylate, isobutyl methacrylate, n-butyl, aryl acrylate, preferably phenyl acrylate, benzylacrylate, phenoxyethylacrylate, aryl methacrylate, preferably phénylméthacrylate, benzylméthacrylate, phénoxyéthylméthacrylate, a compound of formula (I):

(D

in which :

o R 1 represents a polymerizable acrylate group or a polymerizable methacrylate,

o R 2 represents an OH group or an OCH3 group,

o L 1 and L 2 , identical or different, independently represent an ethyloxy group or a propyloxy group and

om and n, identical or different and at least one is different from 0, are lower or equal to 150 and the sum m + n is less than 150 and

acid 2-acrylamido-2-methylpropanesulfonic acid salt 2-acrylamido-2-methylpropanesulfonic acid

2- (methacryloyloxy) ethanesulfonic acid, an acid salt

2- (methacryloyloxy) ethanesulfonic acid, sodium methallyl sulfonate, styrene sulfonate and mixtures thereof.

8. Method according to one of claims 1 to 7, for which the polymerization reaction implements:

100% by weight anionic monomer or

- from 70% to 99.5% by weight of anionic monomer and from 0.5% to 30% by weight of at least one monomer selected from:

other anionic monomer different selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, their salts and mixtures thereof, a nonionic monomer comprising at least one polymerizable olefinic unsaturation, preferably at least one polymerizable ethylenic unsaturation and include vinyl function polymerizable, more preferably a nonionic monomer selected from esters of an acid comprising at least one monocarboxylic acid function, in particular an ester of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof, for example styrene, vinylcaprolactam, alkyl acrylate, in particular acrylate Ci-Cio-alkyl, preferably acrylate, Ci-C 4 alkyl, more preferably methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, n-butyl alkyl methacrylate, especially methacrylate Ci-Cio-alkyl, preferably méthac rylate Ci-C 4 alkyl, more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, aryl acrylate, preferably phenyl acrylate, benzylacrylate, phenoxyethylacrylate, methacrylate aryl, preferably phénylméthacrylate, benzylméthacrylate, phénoxyéthylméthacrylate, a compound of formula (I):

^-(L CL R2

(D

in which :

o R 1 represents a polymerizable acrylate group or a polymerizable methacrylate,

o R 2 represents an OH group or an OCH3 group,

o L 1 and L 2 , identical or different, independently represent an ethyloxy group or a propyloxy group and

om and n, identical or different and at least one is different from 0, are lower or equal to 150 and the sum m + n is less than 150 and

acid 2-acrylamido-2-methylpropanesulfonic acid salt 2-acrylamido-2-methylpropanesulfonic acid

2- (methacryloyloxy) ethanesulfonic acid, an acid salt

2- (methacryloyloxy) ethanesulfonic acid, sodium methallyl sulfonate, styrene sulfonate and mixtures thereof.

9. Method according to one of claims 1 to 8 wherein the compound radical generator is chosen from hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and mixtures thereof.

10. Method according to one of claims 1 to 9 wherein the polymerization reaction uses, relative to the quantity by weight of monomer:

2% by weight to 8% by weight, preferably from 2.5 wt% to 7% by weight or 2.5% by weight to 6% by weight of sodium hypophosphite or

- 0.01% by weight to 1.5% by weight, preferably from 0.01 wt% to 1.2 wt% or 0.05 wt% to 1.5 wt%, more preferably from 0.05 wt% to 1.2 wt% or 0.1 wt% to 1 wt% dipropionate disodium trithiocarbonate (DPTTC) or

0.1% by weight to 5% by weight of compound or radical generator, preferably, from 0.5 wt% to 4.5 wt% of hydrogen peroxide or

0.1% by weight to 4% by weight of sodium persulfate, potassium persulfate or ammonium persulfate.

11. A method of preparing an aqueous suspension of inorganic material particles comprising the implementation of the grinding method according to one of claims 1 to

10, preferably an aqueous suspension which inorganic material solids content is greater than 60% by weight, preferably greater than 70% by weight, more preferably greater than 75% by weight or 80% by weight of the suspension .

12. An aqueous composition comprising inorganic material particles ground and at least one polymer defined according to one of claims 1 to 10.

13. The composition of claim 12 further comprising at least one additive, in particular at least one adjuvant selected from dispersants, anti-foaming agents, biocides, coloring agents, lubricating agents and optical brightening agents or at least one binder agent, in particular a natural binder such as starch or a synthetic binder such as a latex.

14. A method of preparing a paper coating comprising milling in the presence of water, at least one mineral material in the presence of at least one polymer obtained by a radical polymerization reaction in water, a temperature above 50 ° C, of ​​at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function, in the presence: of sodium hypophosphite,

de dipropionate trithiocarbonate disodique (DPTTC) and

d'au moins un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio an ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 and leurs mélanges.

15. The use as a grinding aid agent of at least one mineral material, at least one polymer obtained by a radical polymerization reaction in water, at a temperature above 50 ° C, of ​​at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and a carboxylic acid function, in the presence: of sodium hypophosphite,

de dipropionate trithiocarbonate disodique (DPTTC) and

d 'au moins un composé de générateur radicaux Das Models peroxyde of hydrogène, persulfate of ammonium, a persulfate of metal alkalisch du peroxyde of hydrogène periscio an ion Das Models Fe 11 , Fe 111 , Cu 1 , Cu 11 and leurs mélanges.

16. Use according to claim 15 wherein the polymer is defined according to one of claims 1 to 10.

17. A method of preparing paper comprising using an aqueous composition according to one of Claims 12 and 13.