Claims:1. A silica composite comprising zinc oleate, calcium oleate, zinc stearate, and a precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25.
2. The silica composite as claimed in claim 1, wherein zinc oleate, calcium oleate, zinc stearate, and the precipitated silica are in a weight ratio in the range of 36:18:6:40 to 42:21:7:30.
3. The silica composite as claimed in claim 1 or claim 2, wherein the composite is in a powder form.
4. The silica composite as claimed in claim 3 having an average primary particle size in the range of 50 to 400 nm.
5. The silica composite as claimed in any one of claims 1-4, having an average pore diameter in the range of 50-150 nm.
6. The silica composite as claimed in any one of claims 1-5, having a moisture content in the range of 4-9%.
7. The silica composite as claimed in any one of claims 1-6, having a zinc content in the range of 3-6% w/w, a calcium content in the range of 1-2.5% w/w and an organic content in the range of 1.86-4.05% w/w.
8. The silica composite as claimed in any one of claims 1-7, having a pH value in the range of 7-8.
9. The silica composite as claimed in any one of claims 1-8, having a tap density in the range of 300-500 g/l.
10. The silica composite as claimed in any one of claims 1-9, wherein the precipitated silica has a BET surface area in the range of 150-250 m2/g and a CTAB surface area in the range of 145-230 m2/g.
11. The silica composite as claimed any one of claims 1-10, wherein the precipitated silica has a BET/CTAB ratio in the range of 1.0 to 1.4.
12. The silica composite as claimed in any one of claims 1-11, wherein the precipitated silica has a DBP oil absorption in the range of 230-300 ml/100g.
13. The silica composite as claimed in any one of claims 1-12, wherein the precipitated silica has a sears number in the range of 15-35 ml/5g.
14. The silica composite as claimed in any one of claims 1-13, wherein the precipitated silica has a CDBP coefficient (DA) in the range of 0.4-0.8.
15. The silica composite as claimed in claim in any one of claims 1-14, wherein the precipitated silica is a nano-silica.
16. The silica composite as claimed in claim 15, wherein the precipitated silica has an average primary particle size in the range of 8-50 nm.
17. The silica composite as claimed in any of claims 1-16, wherein the silica composite has an average particulate aggregate size having D90 value in the range of 200-300 µm, D50 value in the range of 5-20 µm and D10 value in the range of 0.5-3.0 µm.
18. A process for preparing a silca composite, the process comprising:
mixing zinc oleate, calcium oleate, zinc stearate, and a precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25 to form a homogenized blend;
subjecting the homogenized blend to drying to form a solid mass; and
milling the solid mass to obtain the silica-composite.
19. The process as claimed in claim 18, wherein zinc oleate, calcium oleate, zinc stearate, and the precipitated silica are mixed in a weight ratio in the range of 36:18: 6:40 to 42:21:7:30.
20. The process as claimed in claim 18 or claim 19, wherein zinc oleate, calcium oleate, zinc stearate, and the precipitated silica are mixed simulanteously or sequentialy by stirring at a rate of 100-300 rpm.
21. The process as claimed in any one of claims 18-20, wherein the mixing is performed at a temperature in the range of 25-40oC for 15-20 minutes.
22. The process as claimed in any one of claims 18-21, wherein the drying is performed at a temperature in the range of 40 to 70 oC for 3-5 hours.
23. The process as claimed in any one of claims 18-22, wherein the precipitated silica is in the form of an aqueous slurry or a powder.
24. The process as claimed in claim 23, wherein the aqueous slurry has a silica content in the range of 15-25%
25. The process as claimed in claim 23 or claim 24, wherein the aqueous slurry has a pH value in the range of 3-6.
26. The process as claimed in any one of claims 18-25, wherein the precipitated silica has a BET surface area in the range of 150-250 m2/g and a CTAB surface area in the range of 145-230 m2/g.
27. The process as claimed in any one of claims 18-26, wherein the precipitated silica has a BET/CTAB ratio in the range of 1.0-1.4.
28. The process as claimed in any one of claims 18-27, wherein the precipitated silica has a DBP oil absorption in the range of 230-300 ml/100g.
29. The process as claimed in any one of claims 18-28, wherein the precipitated silica has a sears number in the range of 15-35 ml/5g.
30. The process as claimed in any one of claims 18-29, wherein the precipitated silica has a CDBP coefficient (DA) in the range of 0.4-0.8.
31. The process as claimed in any one of claims 18-30, wherein the precipitated silica is a nano-silica.
32. The process as claimed in claim 31, wherein the precipitated silica has an average particle size in the range of 8-25 nm.
33. The process as claimed in any one of claims 18-32, wherein the silica composite has an average particulate aggregrate size having D90 value in the range of 200-300 µm, D50 value in the range of 5-20 µm and D10 value in the range of 0.5-3.0 µm.
34. The process as claimed in any one of claims 18-33, wherein zinc oleate, calcium oleate, and zinc stearate are in a powder form.
35. The process as claimed in any one of claims 18-34, wherein zinc oleate has a zinc content in the range of 8-12% w/w and calcium oleate has a calcium content in the range of 5.5-7.5% w/w.
36. The process as claimed in claim 19, wherein the drying is carried out till the moisture of the solid mass is less than 5%.
, Description:TECHNICAL FIELD

The present disclosure relates to silica composites. Specifically, the present disclosure relates to silica composites comprising silica and fatty acids of metal salts and processes for preparing such composites.

BACKGROUND

Silica is well known for use as a reinforcing filler in elastomer and polymer applications. When used as a reinforcing filler it helps in strengthening the rubber network and results in an increase in stiffness, and tensile strength. This results in improved wear resistance and modulus of the elastomeric compositions. However, silica particles in their powder form are agglomerated in nature. The agglomerated silica has less surface area in contact with the elastomers or polymers, which affects the properties of the elastomeric or polymeric compositions. It is important that the agglomerates of silica break down while mixing in elastomers and polymers for efficient dispersibility of the silica particles.

Several attempts have been made to overcome the tendency of agglomeration of the precipitated silica. For examples, silanes such as aminosilanes and phenylsilanes have been used to prevent aggregation of silica and to improve surface modification.

US 5,226,930 discloses use of trialkylhalosilanes and hexaalkyldisilazane for preventing agglomeration of colloidal silica.

US 5,009,874 discloses use of organosilicon compounds for preventing aggregation of silica and for improving the surface modification.

US 3,904,787 discloses a method involving treatment of an aqueous suspension of precipitated silica with an organohalosilane at a temperature in the range of 15 °C up to 70 °C.

DE 60109579 T2 discloses a process for stabilizing the surface of colloidal silica by esterification in the presence of a catalyst; and mixing the surface-stabilized silica with a solution of a rubbery polymer and an additive to substantially prevent agglomeration of the silica.

SUMMARY

The present disclosure relates to a silica composite comprising zinc oleate, calcium oleate, zinc stearate, and a precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25.

The present disclosure also relates to a process for preparing a silica composite. The process comprises mixing zinc oleate, calcium oleate, zinc stearate, and a precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25 to form a homogenized blend; subjecting the homogenized blend to drying to form a solid mass; and milling the solid mass to obtain the silica composite.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the disclosed composition and method, and such further applications of the principles of the disclosure therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.

Reference throughout this specification to “one embodiment”, “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms “a,” “an,”, and “the” are used to refer to “one or more” (i.e. to at least one) of the grammatical object of the article.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion and are not intended to be construed as “consists of only”, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof. It will be further understood by those skilled in the art that the parameters such as BET surface area, CTAB surface area, bulk density, PSD (%V) in µm, DOA, CDBP coefficient (DA), DBP absorption, Wk coefficient, sears number, have the same meaning as generally understood in the art, unless specifically stated otherwise.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described.

The present disclosure relates to silica composites. Specifically, the present disclosure relates to a silica composite comprising zinc oleate, calcium oleate, zinc stearate, and a precipitated silica in a weight ratio in the range of 30:15:5:50 to to 45:22:8:25.

In accordance with an embodiment, the disclosed silica composite comprises zinc oleate, calcium oleate, zinc stearate, and the precipitated silica in a weight ratio in the range of 36:18: 6:40 to 42:21:7:30.

In accordance with an embodiment, the silica composite is in a powder form. In accordance with an embodiment, the silica composite has an average primary particle size in the range of 50 nm to 400 nm. In a specific embodiment, the silica composite has the average primary particle size in the range from 70 nm to 120 nm. In accordance with an embodiment, the silica composite has an average pore diameter in the range of 50-150 nm.

In accordance with an embodiment, the silica composite has a moisture content in the range of 4-9%. In a specific embodiment, the moisture content is 4-5%.

In accordance with an embodiment, zinc oleate has a zinc content in the range of 8-12% w/w. In an embodiment, zinc stearate has a zinc content in the range of 9-11% w/w. In accordance with an embodiment, calcium oleate has a calcium content in the range of 5.5-7.5% w/w.

In accordance with an embodiment, the silica composite has a zinc content in the range of 3-6% w/w.

In accordance with an embodiment, the silica composite has a calcium content in the range of 1-2.5% w/w.

In accordance with an embodiment, the silica composite has an organic content in the range of 1.86-4.05% w/w.

In accordance with an embodiment, the silica composite has a pH value in the range of 7-8. In an example, the silica composite has the pH value of 7.

In accordance with an embodiment, the silica composite has a tap density in the range of 300-500 g/l. In an example, the tap density is 350 g/l.

In accordance with an embodiment, the precipitated silica has a BET surface area in the range of 150-250 m2/g. In a specific embodiment, the BET surface area is in the range of 160-210 m2/g.

In accordance with an embodiment, the precipitated silica has a CTAB surface area in the range of 145-230 m2/g. In a specific embodiment, the CTAB surface area is in the range of 150-190 m2/g.

In accordance with an embodiment, the precipitated silica has a BET/CTAB ratio in the range of 1.0-1.4. In a specific embodiment, the BET/CTAB ratio is in the range of 1.0-1.2.

In accordance with an embodiment, the precipitated silica has a DBP oil absorption in the range of 230-300 ml/100g. In a specific embodiment, the DBP oil absorption is in the range of 240-280 ml/100g.

In accordance with an embodiment, the precipitated silica has a CDBP coefficient (DA) in the range of 0.4-0.8. In a specific embodiment, the CDBP coefficient (DA) is in the range of 0.4-0.6.

In accordance with an embodiment, the precipitated silica has a sears number (V2) in the range of 15-35 ml/5g. In a specific embodiment, the sears number is in the range of 20-30 ml/5g.

In accordance with an embodiment, the silica composite is a nanocomposite. In accordance with an embodiment at least one of the zinc oleate, calcium oleate, zinc stearate, and the precipitated silica in the silica composite are nanosized. In accordance with an embodiment, the precipitated silica is nanosized. In accordance with an embodiment, the precipitated silica has an average primary particle size in the range of 8-50 nm. In a specific embodiment, the average particle size is in the range of 10-20 nm.

In accordance with an embodiment, the silica composite has an average particle aggregate size having D90 value in the range of 200-300 µm.

In accordance with an embodiment, the silica composite has an average particle aggregate size having D50 value in the range of 5-20 µm.

In accordance with an embodiment, the silica composite has an average particle aggregate size having D10 value in the range of 0.5-3.0 µm.

Any suitable particle analyzer may be used for measuring the average particle size. For example, a Transmission Electron Microscope (TEM), or a Malvern particle size analyzer.

The term “D90” as used herein signifies that 90% of the particles have a diameter equal to or below the provided value. For example, D90 value of 200 µm signifies that 90% of the particles have a size equal to or below 200 µm.

The term “D50” as used herein signifies that 50% of the particles have a diameter equal to or below the provided value.

The term “D10” as used herein signifies that 10% of the particles have a diameter equal to or below the provide value.

The present disclosure also relates to a process for preparing a silica composite. In accordance with an embodiment, the process is for preparing the silica composite described above. The process comprises mixing zinc oleate, calcium oleate, zinc stearate, and the precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25 to form a homogenized blend; subjecting the homogenized blend to drying to form a solid mass; and milling the solid mass to obtain the silica composite.

In accordance with an embodiment, zinc oleate, calcium oleate, zinc stearate and the precipitated silica are mixed in a weight ratio in the range of 36:18: 6:40 to 42:21:7:30.

Zinc oleate, calcium oleate, zinc stearate and the precipitated silica can be mixed sequentially in any order or simultaneously. In an example, zinc oleate, calcium oleate, and zinc stearate are mixed prior to the addition of the precipitated silica. In accordance with an embodiment, zinc oleate, calcium oleate, zinc stearate, and the precipitated silica are mixed simultaneously. In accordance with an embodiment the mixing is performed by stirring at a rate of 100-300 rpm.

In accordance with an embodiment, zinc oleate, calcium oleate, zinc stearate, and the precipitated silica are mixed at a temperature in the range of 25-40°C for 15-20 minutes.

Zinc oleate may be used in a form of a cake or as a powder. In accordance with a specific embodiment, zinc oleate is in the powder form. In accordance with an embodiment, the powder form of zinc oleate has a moisture content of less than 5%. In another embodiment, zinc oleate is in the cake form. In accordance with an embodiment, the cake form of zinc oleate has a solid content of about 30% w/w. In accordance with an embodiment, zinc oleate is in the form of nanoparticles. In accordance with an embodiment, zinc oleate has a pH value in the range of 5.5-9.5. In a specific embodiment, zinc oleate has the pH value of 7 ± 2. In accordance with an embodiment, zinc oleate has a zinc content in the range of 8-12%w/w. In a specific embodiment, the zinc content is 10 ±1%.

Calcium oleate may be used in a form of a cake or as a powder. In accordance with an embodiment, calcium oleate used is in the powder form. In accordance with an embodiment, the powder form of calcium oleate has a moisture content of less than 5%. In accordance with an embodiment, calcium oleate is in the form of nanoparticles. In an another embodiment, calcium oleate used is in the cake form. In accordance with an embodiment, the cake form of calcium oleate has a solid content of about 15% w/w. In accordance with an embodiment, calcium oleate has a pH value in the range of 5.5-9.5. In a specific embodiment, calcium oleate has the pH value of 7 ± 2. In accordance with an embodiment, calcium oleate has a calcium content in the range of 5.5-7.5%w/w. In a specific embodiment, the calcium content is in the range of 6.5 ±1 % w/w.

Zinc stearate may be used in a form of a cake or as a powder. In accordance with an embodiment, zinc stearate used is in the powder form. In accordance with an embodiment, the powder form of zinc stearate has a moisture content of less than 5%. In accordance with an embodiment, zinc stearate is in the form of nanoparticles. In an alternate embodiment, zinc stearate used is in the cake form. In accordance with an embodiment, zinc stearate has a pH in the range of 5.5-9.5. In accordance with an embodiment, zinc stearate has a zinc content in the range of 9-11% w/w.

In accordance with an embodiment, the precipitated silica may be used in a form of an aqueous slurry or as a powder.

In accordance with an embodiment, the precipitated silica used is in a form of an aqueous slurry. In accordance with an embodiment, the aqueous slurry is prepared by mixing a precipitated silica cake or powder with water. In accordance with an embodiment, the aqueous slurry has a silica content in the range of 15-25% w/w. In a specific embodiment, the silica content is in the range of 18-22%. In accordance with an embodiment, the aqueous slurry has a pH value in the range of 3-6. In a specific embodiment, the pH value is in the range of of 3-4.

In accordance with an embodiment, the precipitated silica has a BET surface area in the range of 150-250 m2/g. In a specific embodiment, the BET surface area is in the range of 160-210 m2/g.

In accordance with an embodiment, the precipitated silica has a CTAB surface area in the range of 145-230 m2/g. In a specific embodiment, the CTAB surface area is in the range of 150-190 m2/g.

In accordance with an embodiment, the precipitated silica has a BET/CTAB ratio in the range of 1.0-1.4. In a specific embodiment, the BET/CTAB ratio is in the range of 1.0-1.2.

In accordance with an embodiment, the precipitated silica has a DBP oil absorption in the range of 230-300 ml/100g. In a specific embodiment, the DBP oil absorption is in the range of 240-280 ml/100g.

In accordance with an embodiment, the precipitated silica has a CDBP coefficient (DA) in the range of 0.4-0.8. In a specific embodiment, the CDBP coefficient (DA) is in the range of 0.4-0.6.

In accordance with an embodiment, the precipitated silica has a sears number (V2) in the range of 15-35 ml/5g. In a specific embodiment, the sears number is in the range of 20-30 ml/5g.

In accordance with an embodiment, the precipitated silica has an average particle size in the range of 8-25 nm. In a specific embodiment, the average particle size is in the range of 10-20 nm.

In accordance with an embodiment, the silica composite has an average particle aggregate size having D90 value in the range of 200-300 µm.

In accordance with an embodiment, the silica composite has an average particle aggregate size having D50 value in the range of 5-20 µm.

In accordance with an embodiment, the silica composite has an average particle aggregate size having D10 value in the range of 0.5-3.0 µm.

Any suitable drying method may be used for drying the homogenized blend. Examples of suitable method include but are not limited to spray drying, hot air oven drying or tray drying. In an embodiment, the homogenized blend is dried by tray drying. In accordance with an embodiment, the homogenized blend is dried at a temperature in the range of 40 to 70 oC for 3-5 hours. In accordance with an embodiment, the drying is carried out till the moisture of the solid mass is less than 5% as detetcted by loss in weight method at 120 °C.

The milling may be carried out in any suitable milling apparatus. Such apparatus includes but is not limited to mortar mills, vibrator mills and ball mills.

EXAMPLES

The following examples are provided to explain and illustrate the present disclosure and do not in any way limit the scope of the disclosure as described.

Example 1: Preparation of silica composite comprising zinc oleate, calcium oleate, zinc stearate, and precipitated silica in a weight ratio of 40:20:6.7:33

Zinc oleate cake having a solid content of 30% by weight and a zinc content of 10% was prepared by mixing 45.8 gms of zinc sulphate heptahydrate and 103.2 gms of sodium oleate in an aqueous solution at 65 oC. The pH value of the zinc oleate cake was 7.0.

Calcium oleate cake having a solid content of 15% by weight was prepared by mixing 24.4 gms of calcium chloride dihydrate and 99 gms of sodium oleate in an aqueous solution at 65 oC. The pH of the calcium oleate cake value was 7.0.

Commercial grade zinc stearate having a zinc content of 10% was used. Zinc stearate was used in a powder form.

Precipitated silica having a surface area of 175 m2/g was used. The pH of the precipitated silica was 6.5. The BET surface area and the CTAB surface area of the precipitated silica were 175 m2/g and 155 m2/g respectively. The average primary particle size of the precipitated silica was 20 nm.
80 gms of the zinc oleate cake i.e. 50% solid content in cake (40 % with respect to the total dry powder), 100 gms of the calcium oleate cake i.e. 20% solid content in cake (20% with respect to the total dry powder) and 6.7 gms of the zinc stearate powder (6.7 % with respect to the total dry powder) were mixed using a cone blender. 33.3 gms of the precipitated silica in a powder form (33.3 % with respect to the total dry powder) was added into the cone blender. The mixing of the zinc oleate cake, the calcium oleate cake and the zinc stearate powder, and the precipitated silica were performed at a stirring rate of 100 rpm at 25oC for 15 minutes to obtain a homogenized blend. The homogenized blend so obtained was dried in an oven at 60oC for 4 hr to form a solid mass. The drying was carried out till the moisture content of the solid mass was less than 5%. The moisture content was determined by loss in weight method at 120 oC. The solid mass was milled using a multi-mill to obtain a dry powder of the silica composite. In the multi-mill, the mesh size of 1 mm was used. The particles having a particle size below 1 mm were collected. The moisture content of the dry powder of the silica composite was less than 5%. A detailed characterization of the silica composite powder was carried out. The properties are tabulated in Table 1.

Example 2: Preparation of silica composite comprising zinc oleate, calcium oleate, zinc stearate, and precipitated silica in a weight ratio of 40: 20:6.7:33

Zinc oleate cake having a solid content of 30% by weight and a zinc content of 10% was prepared by mixing 45.8 gms of zinc sulphate heptahydrate and 103.2 gms of sodium oleate in an aqueous solution at 65 oC. The pH value of the zinc oleate cake was 7.0.

Calcium oleate cake having a solid content of 15% by weight and a calcium content of 6.5% was prepared by mixing calcium chloride dihydrate and sodium oleate in an aqueous solution at 65 oC. The pH of the calcium oleate cake was 7.0.

Commercial grade zinc stearate having a zinc content of 10% was used. Zinc stearate was used in powder form.

Precipitated silica cake having a solid content of 20% and a surface area of 175 m2/g was used. The pH of the precipitated silica was 7.5. The BET surface area and the CTAB surface area of the precipitated silica was 175 m2/g and 155 m2/g respectively. The average primary particle size of the precipitated silica was 20 nm.

166.5 gms of the precipitated silica cake i.e. 20% solid content in cake (33.3% with respect to the total dry powder) was converted to form an aqueous slurry of the precipitated silica. The temperature was set at 25oC with the stirring rate of 100 rpm. The pH of the aqueous slurry of the precipitated silica was 6. Thereafter, 80 gms of the zinc oleate cake i.e. 50% solid content in cake (40 % with respect to the total dry powder), 100 gms of the calcium oleate cake i.e. 20% solid content in cake (20% with respect to the total dry powder) and 6.7 gms of the zinc stearate powder (6.7 % with respect to the total dry powder) was added into the prepared aqueous slurry of the precipitated silica. The mixing of the zinc oleate cake, the calcium oleate cake and the zinc stearate powder, and the precipitated silica was performed at a stirring rate of 100 rpm at 25oC for 15 minutes to obtain a homogenized blend. The homogenized blend so obtained was dried in an oven at 60oC for 4 hr to form a solid mass. The drying was carried out till the moisture content of the solid mass was less than 5%. The moisture content was determined by loss in weight method at 120 oC. The solid mass was milled using a multi-mill to obtain a dry powder of the silica composite. In the multi-mill, the mesh size of 1 mm was used. The particles having a particle size below 1 mm were collected. The moisture content of the dry powder of the silica composite was less than 5%. A detailed characterization of the silica composite powder was carried out. The properties are tabulated in Table 1.

Example 3: Preparation of silica composite comprising zinc oleate, calcium oleate, zinc stearate, and precipitated silica in a weight ratio of 40: 20:6.7:33

Zinc oleate powder having a moisture content of less than 5% and a zinc content of 10% was prepared by mixing 45.8 gms of zinc sulphate heptahydrate and 103.2 gms of sodium oleate in an aqueous solution at 65 oC. The pH value of the zinc oleate powder was 7.0.

Calcium oleate powder having a moisture content of less than 5% and a calcium content of 6.5% was prepared by mixing 24.4 gms of calcium chloride dihydrate and 99 gms of sodium oleate in an aqueous solution at 65 oC. The pH of the calcium content powder was 7.0.
Commercial grade zinc stearate having a zinc content of 10% was used. Zinc stearate was used in powder form.

Precipitated silica powder having a surface area of 175 m2/g was used. The pH of the precipitated silica was 7.5. The BET surface area and the CTAB surface area of the precipitated silica was 175 m2/g and 155 m2/g respectively. The average primary particle size of the precipitated silica was 20 nm.

80 gms of the zinc oleate cake i.e. 50% solid content in cake (40 % with respect to the total dry powder), 100 gms of the calcium oleate cake i.e. 20% solid content in cake (20% with respect to the total dry powder) and 6.7 gms of the zinc stearate powder (6.7 % with respect to the total dry powder) were mixed using a cone blender. 33.3 gms of the precipitated silica in a powder form (33.3 % with respect to the total dry powder) was added into the cone blender. The mixing of the zinc oleate cake, the calcium oleate cake and the zinc stearate powder, and the precipitated silica performed at a stirring rate of 100 rpm at 25oC for 15 minutes to obtain a homogenized blend. The homogenized blend so obtained was dried in an oven at 60oC for 4 hr to form a solid mass. The drying was carried out till the moisture content of the solid mass was less than 5%. The moisture content was determined by loss in weight method at 120 oC. The solid mass was milled using a multi mill to obtain a dry powder of the silica-composite. In the multi mill, the mesh size of 1 mm was used. The particles having a particle size below 1 mm were collected. The moisture content of the dry powder of the silicacomposite was less than 5%. A detailed characterization of the silica composite powder was carried out. The properties are tabulated in Table 1.

Example 4: Preparation of silica composite comprising zinc oleate, calcium oleate, zinc stearate, and precipitated silica in a weight ratio of 30:15:5:50

Zinc oleate powder having a moisture content of less than 5% and a zinc content of 10% was prepared by mixing 45.8gm gms of zinc sulphate heptahydrate and 103.2gm gms of sodium oleate in an aqueous solution at 65 oC. The pH value of the zinc oleate powder was 7.0.

Calcium oleate powder having a moisture content of less than 5% and a calcium content of 6.5% was prepared by mixing 24.4 gms of calcium chloride dihydrate and 99 gms of sodium oleate in an aqueous solution at 65 oC. The pH of the calcium oleate powder was 7.0.

Commercial grade zinc stearate having a zinc content of 10% was used. Zinc stearate was used in powder form.

Precipitated silica powder having a surface area of 175 m2/g was used. The pH of the precipitated silica was 7.5. The BET surface area and the CTAB surface area of the precipitated silica were 175m2/g and 155m2/g respectively. The average primary particle size of the precipitated silica was 20 nm.

60 gms of the zinc oleate cake i.e. 50% solid content in cake (30 % with respect to the total dry powder), 75 gms of the calcium oleate cake i.e. 20% solid content in cake (15% with respect to the total dry powder) and 5 gms of the zinc stearate powder (5 % with respect to the total dry powder) were mixed using a cone blender. 50 gms of the precipitated silica in a powder form (50 % with respect to the total dry powder) was added into the cone blender. The mixing of the zinc oleate cake, the calcium oleate cake and the zinc stearate powder, and the precipitated silica performed at a stirring rate of 100 rpm at 25oC for 15 minutes to obtain a homogenized blend. The homogenized blend so obtained was dried in an oven at 60 oC for 4 hr to form a solid mass. The drying was carried out till the moisture content of the solid mass was less than 5%. The moisture content was determined by loss in weight method at 120 oC. The solid mass was milled using a multi mill to obtain a dry powder of the silica-composite. In the multi mill, the mesh size of 1mm was used. The particles having a particle size below 1 mm were collected. The moisture content of the dry powder of the silica composite was less than 5%. A detailed characterization of the silica composite powder was carried out. The properties are tabulated in Table 1.

Example 5: Preparation of composite ‘A’ comprising zinc oleate, calcium oleate, and zinc stearate in a weight ratio of 60:30:10.

Zinc oleate powder having a moisture content of less than 5% and a zinc content of 10% was used. The pH value of the zinc oleate powder was 7.0.

Calcium oleate powder having a moisture content of less than 5% and a calcium content of 6.5% was used. The pH of the calcium oleate powder was 7.0.

Commercial grade zinc stearate having a zinc content of 10% was used. Zinc stearate was used in powder form.

60 gms of the zinc oleate powder (60% with respect to the total dry powder), 30 gms of the calcium oleate powder (30% with respect to the total dry powder) and 10 gms of zinc stearate powder (10% with respect to the total dry powder) were mixed using a cone blender. The mixing of the zinc oleate powder, the calcium oleate powder and the zinc stearate powder, was performed at a stirring rate of of 100rpm at 25oC for 15 minutes to obtain a homogenized blend. The homogenized blend so obtained was dried in an oven at 60oC for 4 hr to form a solid mass. The drying was carried out till the moisture content of the solid mass was less than 5%. The moisture content was determined by loss in weight method at 120 oC. The solid mass was milled using a multi mill to obtain a dry powder of the composite ‘A’. In the multi mill, the mesh size of 1 mm was used. The particles having a particle size below 1 mm were collected. The moisture content of the dry powder of the composite ‘A’ was less than 5%. A detailed characterization of the composite ‘A’ was carried out. The properties are tabulated in Table 1.

Example 6: Preparation of composite ‘B’ comprising zinc oleate, and calcium oleate in a weight ratio of 70:30.

Zinc oleate powder having a moisture content of less than 5% and a zinc content of 10% was used. The pH value of the zinc oleate powder was 7.0.

Calcium oleate powder having a moisture content of less than 5% and a calcium content of 6.5% was used. The pH of the calcium oleate powder was 7.0.

70 gms of the zinc oleate powder (70 % with respect to the total dry powder), and 30 gms of the calcium oleate powder (30% with respect to the total dry powder) were mixed using a cone blender. The mixing was performed at a stirring rate of 100 rpm at 25oC for 15 minutes to obtain a homogenized blend. The homogenized blend so obtained was dried in an oven at 60 oC for 4 hr to form a solid mass. The drying was carried out till the moisture content of the solid mass was less than 5%. The moisture content was determined by loss in weight method at 120 oC. The solid mass was milled using a multi mill to obtain a dry powder of a composite ‘B’. In the multi-mill, the mesh size of 1 mm was used. The particles having a particle size below 1 mm were collected. The moisture content of the dry powder of the composite ‘B’ was less than 5%. A detailed characterization of the composite ‘B’ was carried out. The properties are tabulated in Table 1.

Table: 1: Properties of the silica composite of the present disclosure and the composite ‘A’ and composite ‘B’

Sr. No Analysis Silica Composite of Example 1 Silica Composite of Example 2 Silica Composite of Example 3 Silica Composite of Example 4 Composite ‘A’ of Example 5 Composite ‘B’ of Example 6
3 Total loss on ignition @ 1000 C Wt. remained, % 60.3 60.7 60.5 55.1 87.4 87.3
4 Zinc content (%) 4.9 4.9 4.9 4.1 10.23 10.34
5 Calcium content (%) 1.33 1.3 1.3 1.25 2.3 2.31
6 Moisture (%) 2 2 2 4 4 4
7 pH of 1% aqueous silica composite/ composites slurry 7.3 7.5 7.4 7.5 7.5 7.4
8 Sieve residue of powder silica composite (>50 mesh), % 5.1 5.3 5.1 4.9 6.8 7

Example 8: Preparation of rubber compositions A and B comprising silica filler functionalized with the composite ‘A’ and the composite ‘B’

Virgin precipitated silica was functionalized with the composite ‘A’ and the composite ‘B’ to prepare dispersible silica A and dispersible silica B respectively. Dispersible silica A and dispersible silica B were compounded in rubber compositions to prepare rubber composition A and rubber composition B respectively. The ingredients used for preparing the rubber compositions A and B are given in below table 2. The rubber compositions A and B were prepared in an internal mixer with mixing conditions of fill factor 0.7, initial mixer temperature setting of 60 oC, and rotor speed of 60 rpm. The discharge temperature after the mixing step of all mixes was 150°C. A detailed characterization of the physiochemical properties and the performance parameters of the virgin silica, the rubber composition A and the rubber composition B were carried out.

Example 9: Preparation of rubber compositions C and D comprising silica filler functionalized with the silica composite of Examples 3 and 4.

Virgin precipitated silica functionalized with the silica composite of Examples 3 and 4 was used to prepare a highly dispersible precipitated silica X and a highly dispersible precipitated silica Y. The highly dispersible precipitated silica X and the highly precipitated dispersible silica Y were compounded in rubber compositions to prepare rubber composition C and rubber composition D. The ingredients used for preparing the rubber composition C and the rubber composition D are given in below table 2. The rubber compositions were prepared in an internal mixer with mixing conditions of fill factor 0.7, initial mixer temperature setting of 60oC, and rotor speed of 60 rpm. The discharge temperature after the mixing step of all mixes was 150°C. A detailed characterization of the physiochemical properties and the performance parameters of rubber composition C and rubber composition D were carried out.

Table 2: Ingredients
Ingredients Unit Rubber composition A Rubber composition B Rubber composition C Rubber composition D Virgin silica based rubber composition
Rubber compounds
Synthetic Rubber Styrene Butadiene Rubber (SSBR) phr*

70 70 70 70 70
Polybutadiene Rubber (PBD) 30 30 30 30 30
Silica 70 70 70 70 70
Carbon black (N234) 5 5 5 5 5
Processing oil 14 14 14 14 14
Si69 6 6 6 6 6
Stearic acid 2 2 2 2 2
Microcrystalline (MC) wax 1.5 1.5 1.5 1.5 1.5
Zinc Oxide (ZnO) 3 3 3 3 3
6PPD 2 2 2 2 2
TMQ 1 1 1 1 1
Sulfur 1.5 1.5 1.5 1.5 1.5
CBS 1.7 1.7 1.7 1.7 1.7
TBzTD 0.3 0.3 0.3 0.3 0.3
DPG 1.5 1.5 1.5 1.5 1.5
*phr: parts per hundred rubber

Table 3 provides a comparison of the properties of dispersible silicas A and B with the highly dispersible precipitated silicas X and Y and the comparison of the physical properties and dynamic properties of the rubber compositions A, and B, with the rubber compositions C and D

Particle properties Unit Dispersible silica A Dispersible silica B Highly dispersible precipitated silica X Highly dispersible precipitated silica Y Virgin silica
Physicochemical properties
Appearance White powder White powder White powder White powder White powder
BET surface area m2/g 235 235 230 220 175
CTAB Surface area m2/g 220 221 200 190 160
Ingredients Zinc oleate and calcium oleate Zinc oleate, calcium oleate, and
zinc stearate Zinc oleate, calcium oleate, zinc stearate, and precipitated silica Zinc oleate, calcium oleate, zinc stearate, and precipitated silica silica
Ratio of the ingredients 70:30 60:30:10 40:20:6.7:33.3 30:15:5:50 -
Silica-composite dosage % 4.5 4.5 4.5 4.5 00
Rubber compounding data
Rubber composition A Rubber composition B Rubber composition C Rubber composition D Virgin silica rubber composition
Mooney viscosity ML 1+ 4 @100°C) 75 81 48.1 42 88
Elongation break
(Physical properties) % 408 402 510 515 375
Tensile strength
(Physical properties) kg/cm2 145 145 196 176 174
Hardness
(Physical properties) Shore A 66 65 61 58 66
Tan d@0°C
(Dynamic properties) 0.355 0.34 0.13 0.13 0.343
Tan d@60°C
(Dynamic properties) 0.18 0.172 0.053 0.067 0.129

Observations: The rubber compounding studies clearly indicate that rubber compositions C and D showed improved processing and physical rubber properties over rubber compositions A and B. Also significant improvement in dispersibility was observed, as evident from the Mooney viscosity.

INDUSTRIAL APPLICABILITY

The disclosed silica composite allows preparation of a highly dispesible silica that can be used as a reinforcing filler in elastomeric and polymeric compositions. The disclosed silica composite can be mixed uniformly in a precipitated silica to obtain surface modified silica making the process for obtaining surface modified silica highly efficient and consistent. The surface modified silicas so obtained when added during a polymeric/ elastomeric processing along with reinforcement fillers, improves filler processing and physical parameters.