Claims:1. A process for preparing a surface modified silica, the process comprising,
preparing an aqueous slurry of silica having a silica content in the range of 18-22%, and a pH value in the range of 3-6;
mixing a silica composite with the aqueous slurry of silica in an amount in the range of 4 to 10% w/w, at a temperature in the range of 15-45 °C to obtain a mixture, the silica composite comprising zinc oleate, calcium oleate, zinc stearate and precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25; and
drying the mixture to obtain the surface modified silica.
2. The process as claimed in claim 1, wherein the aqueous slurry of silica is prepared by mixing precipitated silica with water.
3. The process as claimed in any of claims 1-2, wherein the pH of the aqueous slurry of silica is adjusted by adding a mineral acid selected from the group consisting of sulfuric acid and hydrochloric acid.
4. The process as claimed in claim 3, wherein the mineral acid is sulfuric acid having concentration in the range of 10-20% w/v.
5. The process as claimed in any of claims 1-4, wherein the 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.
6. The process as claimed in any of claims 1-5, wherein the amount of the silica composite is in the range of 6-9% w/w.
7. The process as claimed in any of claims 1-6, wherein the silica composite is mixed with the aqueous slurry of silica under continuous stirring at a rate of 500-1000 rpm.
8. The process as claimed in any of claims 1-7, wherein the silica composite is in a powder form.
9. The process as claimed in claim 1-8, wherein the silica composite has an average primary particle size in the range of 50 to 400 nm.
10. The process as claimed in any of claims 1-9, wherein the silica composite has an average pore diameter in the range of 50-150 nm.
11. The process as claimed in any of claims 1-10, wherein the silica composite has a moisture content in the range of 4-9%.
12. The process as claimed in any of claims 1-11, wherein the silica composite has 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.
13. The process as claimed in any of claims 1-12, wherein the silica composite has a pH value in the range of 7-8.
14. The process as claimed in any of claims 1-13, wherein the silica composite has a tap density in the range of 300-500 g/l.
15. The process as claimed in any of claims 1-14, wherein the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have 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.
16. The process as claimed in any of claims 1-15, wherein the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a BET/CTAB ratio in the range of 1.0-1.4.
17. The process as claimed in any of claims 1-16, wherein the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a DBP oil absorption in the range of 230-300 ml/100g.
18. The process as claimed in any of claims 1-17, wherein the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a sears number in the range of 15-35 ml/5g.
19. The process as claimed in any of claims 1-18, wherein the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a CDBP coefficient (DA) in the range of 0.4-0.8.
20. The process as claimed in any of claims 1-19, wherein the precipitated silica present in the silica composite is nanosilica.
21. The process as claimed in claim 20, wherein the precipitated silica present in the silica composite has a particle size in the range of 8-50 nm.
22. The process as claimed in any of claims 1-21, wherein the surface modified silica has an average particulate aggregate size having D90 value in the range of 35-80µm, D50 value in the range of 15-45 µm and D10 value in the range of 5-10 µm.
23. The process as claimed in any of claims 1-22, wherein the drying comprises spray drying, vacuum drying, splash drying, flash drying, or tray drying.
24. The process as claimed in claim 23, wherein the drying is performed in a spray drying unit having an inlet temperature in the range of 300-700 oC and an outlet temperature in the range of 100-120 oC.
25. The process as claimed in any of claims 1-24, wherein the moisture content of the surface modified silica is less than 5.0 after the drying.
26. The process as claimed in any of claims 1-25, wherein the surface modified silica has:
- a zinc content in the range of 0.12-0.7%;
- a calcium content in the range of 0.02-0.25%;
- an organic content in the range of 1.86-4.05%;
- a BET surface area in the range of 150-250 m2/g;
- a CTAB surface area in the range of 145-230 m2/g;
- a pH value in the range of 6-7;
- a bulk density in the range of 200-250 g/l;
- a DOA oil absorption value in the range of 230-300 ml/100g; and
- a CDBP coefficient in the range of 0.8;
- a sears number in the range of 15-35 ml/5g; and
- a total pore volume in the range of 1.0-2.5 ml/g.
, Description:FIELD OF INVENTION
The present disclosure relates to processing of silica. Specifically, it relates to a process for preparing a surface modified silica.
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 process for preparing a surface modified silica. The process comprises preparing an aqueous slurry of silica having a silica content in the range of 18-22%, and a pH value in the range of 3-6; mixing a silica composite with the aqueous slurry of silica in an amount in the range of 4 to 10 % w/w, at a temperature in the range of 15-45 °C to obtain a mixture, the silica composite comprising zinc oleate, calcium oleate, zinc stearate and precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25; and drying the mixture to obtain the surface modified silica.
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. 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.
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.
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 a process for preparing a surface modified silica. The process comprising preparing an aqueous slurry of silica having a silica content in the range of 18-22%, and a pH value in the range of 3-6; mixing a silica composite with the aqueous slurry of silica in an amount in the range of 4 to 10 % w/w, at a temperature in the range of 15-45 °C to obtain a mixture, the silica composite comprising zinc oleate, calcium oleate, zinc stearate and precipitated silica in a weight ratio in the range of 30:15:5:50 to 45:22:8:25; and drying the mixture to obtain the surface modified silica.
In accordance with an embodiment, the aqueous slurry of silica is prepared by mixing precipitated silica with water. In accordance with an embodiment, the pH of the aqueous slurry of silica is adjusted by adding a mineral acid. Any suitable mineral acid may be used in the process. Suitable examples of the mineral acid include sulfuric acid and hydrochloric acid. In accordance with an embodiment, the mineral acid is sulfuric acid. In accordance with an embodiment, sulfuric acid has a concentration in the range of 10-20% w/v.
In accordance with an embodiment, the silica composite is mixed with the aqueous slurry of silica in an amount in the range of 6-9% w/w. In accordance with an embodiment, the silica composite is mixed with the aqueous slurry of silica under continuous stirring at a rate of 500-1000 rpm.
In accordance with an embodiment, the 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 silica composite has the moisture content of 4-5%.
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 accordance with an embodiment, the silica composite has a tap density in the range of 300-500 g/l.
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 precipitated silica has the average primary particle size 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.
In accordance with an embodiment, the surface modified silica has an average particulate aggregate size having D90 value in the range of 35-80µm, D50 value in the range of 15-45 µm and D10 value in the range of 5-10 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.
In accordance with an embodiment, the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have same properties. In accordance with an embodiment, both have a BET surface area in the range of 150-250 m2/g. In specific embodiments, the BET surface area in the range of 160-210m2/g.
In accordance with an embodiment, the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a CTAB surface area in the range of 145-230 m2/g. In specific embodiments, the CTAB surface area is in the range of 150-190 m2/g.
In accordance with an embodiment, the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a BET/CTAB ratio in the range of 1.0-1.4. In specific embodiments, both have the BET/CTAB ratio in the range of 1.0-1.2.
In accordance with an embodiment, the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a DBP oil absorption in the range of 230-300 ml/100g. In specific embodiments, the DBP oil absorption is in the range of 240-280 ml/100g.
In accordance with an embodiment, the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a CDBP coefficient (DA) in the range of 0.4-0.8. In specific embodiments, the CDBP coefficient (DA) is in the range of 0.4-0.6.
In accordance with an embodiment, the precipitated silica used for preparing the aqueous slurry of silica and the precipitated silica present in the silica composite both have a sears number (V2) in the range of 15-35 ml/5g. In specific embodiments, the sears number is in the range of 20-30 ml/5g.
Any suitable drying method may be used for drying the mixture. Examples of suitable method include but are not limited to spray drying, vacuum drying, splash drying, flash drying, and tray drying. In accordance with an embodiment, the mixture is dried by splash drying or flash drying to obtain the surface modified silica. In accordance with an embodiment, the drying is performed in a spray drying unit having an inlet temperature in the range of 300-700 oC and an outlet temperature in the range of 100-120 oC. In accordance with an embodiment, the moisture content of the surface modified silica is less than 5.0% after the drying.
The present disclosure also relates to the surface modified silica obtained from the above method. The surface modified silica obtained in accordance with the present disclosure has a zinc content in the range of 0.12-0.7%, a calcium content in the range of 0.02-0.25%, an organic content in the range of 1.86-4.05%, a BET surface area in the range of 150-250 m2/g, a CTAB surface area in the range of 145-230 m2/g, a pH value in the range of 6-7, bulk density in the range of 200-250 g/l, a DOA oil absorption value in the range of 230-300 ml/100g, a CDBP coefficient in the range of 0.4-0.8, a sears number in the range15-35 ml/5g, and a total pore volume in the range of 1.0-2.5 ml/g.
EXAMPLES
The following examples are provided to explain and illustrate the preferred embodiments of the present disclosure and do not in any way limit the scope of the disclosure as described:
Example 1: Preparation of the Surface Modified Silica
Step: 1: Preparation of the precipitated silica
A sodium silicate solution having a solid content of approximately 30% by weight (Na2O to SiO2 ratio of 1:3, silica percentage by weight of 23%, Na2O percentage by weight of 7.0%) and a pH value of 12.5 was prepared.
5 litres of 50 percent sulfuric acid solution was prepared by slowly adding 5 litres of 98% sulfuric acid solution having (specific gravity of 1.84g/cc) to 5 litres of distilled water.
A surfactant solution was prepared by adding 12.5 millilitre of a C8 to C20 sulfosuccinate blend surfactant to 600 millilitres of distilled water and stirring.
12.5 litres of distilled water was taken in a properly cleaned 30 litre reactor. The heater was set at 85 °C and the stirrer of the reactor was set at a stirring rate of 200 rpm. One litre of the 50% sulfuric acid solution, 4 litres of the sodium silicate solution, 4 litres of the distilled water, and 600 millilitre of the surfactant solution were taken in four separate beakers. Four metering pumps of each of the above were calibrated as follows:

Pump Solution/Water Addition rate
First Pump The 50% sulfuric acid solution 10 ml/min
Second Pump The sodium silicate solution 88 ml/min
Third Pump The distilled water 266 ml/min
Fourth Pump The surfactant Solution 20 ml/min
When the temperature of the reactor reached 85 °C, the second, third and the fourth pump were switched on simultaneously at the above-mentioned flow rates for 2 to 3 minutes to form a reaction mixture. The pH of the reaction mixture was checked. At this point, it was ensured that the pH of the reaction mixture was between pH 10.6 to 10.8.
The reaction was carried out in three phases or stages. In the first stage, the first pump was switched on and the 50% sulfuric acid solution was added at an addition rate of 10 ml/min to the reactor, while continuing the addition of the sodium silicate solution, the surfactant solution and the distilled water at the above-mentioned flow rates. The reaction mixture was continuously stirred at 200 rpm at 85 °C. After 15 minutes, the flows of all the four pumps were stopped while continuing the stirring at 200 rpm at 80°C. The reaction mixture was allowed to age for 15 minutes to form a slurry. The pH of the slurry in the reactor was checked to ensure that the pH of the slurry is between pH 10.1 to 10.2. In the second phase, the first, second and the third pumps were switched simultaneously at the above-mentioned flow rates for 15 minutes. The slurry was continuously stirred at 200 rpm at 85 °C. After 7.5 min, the fourth pump was switched on at the above-mentioned flow rate. The pH of the slurry in the reactor was checked. It was ensured that the pH of the slurry was between pH 10.1 to 10.2. After 15 minutes, the flows of all the four pumps were stopped. The slurry was then allowed to age for 15 minutes with continuous stirring at 85 °C. In the third phase, the first, second, third and the fourth pump were started simultaneously at the above-mentioned rates for 15 minutes. The slurry was continuously stirred at 200 rpm at 85 °C. After 7.5 min, the fourth pump was stopped. It was ensured that the pH of the slurry was between pH 10.1 to 10.2. The slurry was then allowed to age for 15 minutes with continuous stirring at 85 °C. After 15 minutes of ageing, the addition of the sulfuric acid solution was started at a flow rate of 100 millilitre/minute. The pH of the slurry was brought down rapidly from 10.1 to10.2 to 3.5-4.0. After the pH adjustment, the addition of sulfuric acid solution was stopped. The slurry was then allowed to age for another 30 minutes at 85 °C with continuous stirring. The precipitated slurry was then collected from the reactor.
The precipitate was centrifuged at 4000 rpm for 5 minutes followed by washing with distilled water to remove soluble salt like sodium sulphate. The washing was continued till the total solid content of the filtrate reached 1000 ppm or less. The solid content of the washed wet silica cake thus obtained was 12-15% by weight.
Step 2: Preparation of the Surface Modified Silica.
An aqueous slurry of silica having a silica content of 20%, a moisture content of 80% was prepared by mixing 1000 gms of the precipitated silica cake obtained above with water. Dilute sulfuric acid (15% w/w) was added to the aqueous slurry in a reaction vessel. The aqueous slurry had a pH in the range of 3-6.
1000 gms the aqueous slurry of silica was taken in a reaction vessel and 18 gms (9% w.r.t. dry silica) of a silica composite comprising comprises zinc oleate, calcium oleate, zinc stearate, and precipitated silica in a weight ratio of 30:15:5:50 was added, followed by uniform mixing to obtain a mixture. The temperature was set at 35 ºC with a stirring rate of 600 rpm. The pH of the mixture was maintained at 3 by addition of sulfuric acid. The resultant mixture was then spray dried. The inlet temperature of a spray drying unit was set at 500 oC and the outlet temperature was set at 85 oC to obtain spray dried surface modified silica. The moisture content of the spray dried silica was in the range of 2-5%. Post synthesis, a detailed characterization of the synthesized surface modified silica was carried out. The properties were tabulated in the below, Table 1.
Table 1: Properties of the Surface Modified Silica
Sr. No Properties Example-1
1 BET surface area (m2/g) 175
1 CTAB (Titration) (m2/g) 155
2 pH of 5% silica 6.5
3 Bulk density (g/l) 225
4 DOA (ml/100g) 270
5 Loss on drying, 105oC / 2hr, % 5
6 CDBP value 0.5
7 Loss on ignition, 1000oC/2hr, % 12
Example 2: Preparation of the Surface Modified Silica
Step: 1: Preparation of the precipitated silica
A sodium silicate solution having a solid content of approximately 30% by weight (Na2O to SiO2 ratio of 1:3, silica percentage by weight of 23%, Na2O percentage by weight of 7.0%) and a pH value of 12.5 was prepared.
5 litres of 50 percent sulfuric acid solution was prepared by slowly adding 5 litres of 98% sulfuric acid solution having (specific gravity of 1.84 g/cc) to 5 litres of distilled water.
A surfactant solution was prepared by adding 12.5 millilitres of a C8 to C20 sulfosuccinate blend surfactant to 600 millilitres of distilled water and stirring.
15.8 litres of distilled water was taken in a properly cleaned 30 litre reactor. The heater was set at 78 °C and the stirrer of the reactor was set at a stirring rate of 200 rpm. One litre of the 50% sulfuric acid solution, 4 litres of the sodium silicate solution, 2.8 litres of the distilled water, and 600 millilitres of the surfactant solution were taken in four separate beakers. Four metering pumps of each of the above were calibrated as follows:

Pump Solution/Water Addition rate
First Pump The 50% sulfuric acid solution 10 ml/min
Second Pump The sodium silicate solution 88 ml/min
Third Pump The distilled water 186 ml/min
Fourth Pump The surfactant Solution 20 ml/min
When the temperature of the reactor reached 78 °C, the second, third and the fourth pump were switched on simultaneously at the above-mentioned flow rates for 2 to 3 minutes to form a reaction mixture. The pH of the reaction mixture was checked. At this point, it was ensured that the pH of the reaction mixture was between pH 10.6 to 10.8.
The reaction was carried out in three phases or stages. In the first stage, the first pump was switched on and the 50% sulfuric acid solution was added at an addition rate of 10 ml/min to the reactor, while continuing the addition of the sodium silicate solution, the surfactant solution and the distilled water at the above-mentioned flow rates. The reaction mixture was continuously stirred at 200 rpm at 78 °C. After 15 minutes, the flows of all the four pumps were stopped while continuing the stirring at 200 rpm at 78 °C. The reaction mixture was allowed to age for 15 minutes to form a slurry. The pH of the slurry in the reactor was checked to ensure that the pH of the slurry is between pH 10.1 to 10.2. In the second phase, the first, second and the third pumps were switched simultaneously at the above-mentioned flow rates for 15 minutes. The slurry was continuously stirred at 200 rpm at 78 °C. After 7.5 min, the fourth pump was switched on at the above-mentioned flow rate. The pH of the slurry in the reactor was checked. It was ensured that the pH of the slurry was between pH 10.1 to 10.2. After 15 minutes, the flows of all the four pumps were stopped. The slurry was then allowed to age for 15 minutes with continuous stirring at 78 °C. In the third phase, the first, second, third and the fourth pump were started simultaneously at the above-mentioned rates for 15 minutes. The slurry was continuously stirred at 200 rpm at 78 °C. After 7.5 min, the fourth pump was stopped. It was ensured that the pH of the slurry was between pH 10.1 to 10.2. The slurry was then allowed to age for 15 minutes with continuous stirring at 78 °C. After 15 minutes of ageing, the addition of the sulfuric acid solution was started at a flow rate of 100millitre/minute. The pH of the slurry was brought down rapidly from 10.1 to 10.2 to 3.5-4.0. After the pH adjustment, the addition of sulfuric acid solution was stopped. The slurry was then allowed to age for another 30 minutes at 78 °C with continuous stirring. The precipitated slurry was then collected from the reactor.
The precipitate was centrifuged at 4000 rpm for 5 minutes followed by washing with distilled water to remove soluble salt like sodium sulphate. The washing was continued till the total solid content of the filtrate reached 1000 ppm or less. The solid content of the washed wet silica cake thus obtained was 12-15% by weight.
Step 2: Preparation of the Surface Modified Silica
An aqueous slurry of silica having a silica content of 20%, a moisture content of 80% was prepared by mixing 1000 gms of the precipitated silica cake obtained above with water. Dilute sulfuric acid (15% w/w) was added to the aqueous slurry in a reaction vessel. The aqueous slurry had a pH in the range of 3-6.
1000 gms the aqueous slurry of silica was taken in a reaction vessel and 18 gms (9% w.r.t. dry silica) of a silica composite comprising comprises zinc oleate, calcium oleate, zinc stearate, and precipitated silica in a weight ratio of 30:15:5:50 was added, followed by uniform mixing to obtain a mixture. The temperature was set at 35 ºC with a stirring rate of 600 rpm. The pH of the mixture was maintained at 3 by addition of sulfuric acid. The resultant mixture was then spray dried. The inlet temperature of a spray drying unit was set at 500 oC and the outlet temperature was set at 85 oC to obtain spray dried surface modified silica. The moisture content of the spray dried silica was in the range of 2-5%. Post synthesis, a detailed characterization of the synthesized surface modified silica was carried out. The properties were tabulated in the below, Table 1.
Table 2: Properties of the Surface Modified Silica
Sr. No Properties Example-2
1 BET surface area (m2/g) 219
1 CTAB (Titration) (m2/g) 199
2 pH of 5% silica 6.5
3 Bulk density (g/l) 220
4 DOA (ml/100g) 275
5 Loss on drying, 105oC / 2hr, % 5
6 CDBP value 0.52
7 Loss on ignition, 1000oC/2hr, % 11.8

INDUSTRIAL APPLICABILITY

The disclosed process is highly efficient and consistent. The process yields surface modified silica, which can be used as a reinforcing filler in elastomeric and polymeric compositions. The surface modified silica obtained from the disclosed process is highly dispersible and mixes uniformly in the elastomeric and polymeric compositions. The surface modified silicas so obtained when added during a polymeric or elastomeric processing along with improves filler processing and physical parameters.