CN118765261A - Precipitated silica and method thereof - Google Patents

Abstract

The present disclosure relates to precipitated silica characterized by a primary particle size average of greater than 80nm, a BET surface area of 10-40m ²/g, a total mercury intrusion volume of 0.75-2.00cc/g, and an oil absorption of 60-120cc/100 g. The silica of the present invention is produced by a process comprising (a) continuously feeding an acid and an alkali metal silicate or an alkaline earth metal silicate into a liquid medium with stirring at a silicate addition rate V1 and a temperature of 70-96 ℃ to form silica particles, (b) stopping feeding the alkali metal silicate or the alkaline earth metal silicate and the acid, and then raising the temperature to 90 to 100 ℃ with stirring, (c) adding the alkali metal silicate or the alkaline earth metal silicate and the acid with stirring, wherein the silicate addition rate is 1 to 40% of the silicate addition rate V1, and the pH value of 9.0 to 10.0 is kept constant by adjusting the acid rate during the addition of the alkali metal silicate or the alkaline earth metal silicate, (d) stopping the addition of the alkali metal silicate or the alkaline earth metal silicate, and adding the acid with stirring until the pH of 5.0 to 7.0 is reached. The precipitated silicas of the invention are useful in cosmetics, anti-caking free/flowing, food, carrier applications, dentifrices and mouthwashes.

Description

Precipitated silica and method thereof

Technical Field

The present disclosure generally relates to precipitated silica and methods of making and using the same.

Background Art

Porous precipitated silica is usually prepared by the reaction of an alkaline silicate solution (e.g., sodium silicate) with an inorganic acid. Sulfuric acid is mainly used commercially, although other acids such as hydrochloric acid may also be used. Acid and sodium silicate solution are added to water simultaneously under stirring. When silica is precipitated from the dispersion due to the neutralization reaction and the generation of a byproduct sodium salt (sodium sulfate), precipitated silica is produced. Precipitated silica is composed of aggregates (secondary particles) of primary (or final) colloidal silica particles. Primary particles are mostly spherical and generally have a diameter in the range of 5 to 50 nm. The primary particles in the aggregates are covalently bonded to each other by forming siloxane bonds. Aggregates are three-dimensional clusters of these primary particles. Aggregates have a diameter of up to 500 nm. During the preparation process, aggregates are not chemically connected to form a huge gel network. Aggregates themselves can be physically connected to larger agglomerates with a diameter of up to 100 μm before grinding by forming hydrogen bonds between silanol groups on their surfaces. The median size of the agglomerates is about 20-50 μm in diameter (before grinding). The porosity and surface area of these precipitated silica particles vary with the size of the primary particles and how they aggregate and agglomerate. The pores are formed by the spaces between the primary particles and the aggregates. The typical surface area of commercial precipitated silicas is 5-800 ^m2 /g. They are sold in the form of powders. The tapped density, which is a measure of the weight of these porous powders, is in the range of 50-500 kg/ ^m3 . They have a high absorption capacity of about 175-320 g/100 g.

U.S. Pat. No. 8,597,425 reports that porous precipitated silica with a primary particle size of 10-80 nm can be used in applications including rubber and tires, battery separators, anti-caking agents, matting agents for inks and paints, carriers for agricultural products and feed, coating materials, printing inks, fire extinguisher powders, plastics, non-impact printing sectors, articles in the pulp or personal care sectors, etc.

J. Soc Cosmet. Chem August 1978, 29, 497-521 reports that precipitated silica having a primary particle size of 12-51 nm can be used in cosmetic applications including toothpaste.

The commercial product SIPERNAT 22, which can be used as a carrier and anti-caking free-flowing additive in food and feed applications, is reported to have a primary particle size of 18 nm (Degussa literature No. 64, Physiological Behavior of highly dispersed Oxides of Silicon, Aluminum and Titanium 1978, page 26-27).

U.S. Patent No. 6,946,119 discloses a precipitated silica product comprising silica particles having a median diameter of 1 to 100 micrometers supporting a surface deposit thereon, the surface deposit comprising active precipitated amorphous silica, a material present in an amount effective to provide the silica particles with a BET specific surface area of 1 to 50 ^m2 /g. The precipitated silica is used in oral care applications.

U.S. Patent No. 7,255,852 describes a precipitated silica comprising a silica particle product having a porous surface, the silica particles having a cumulative surface area of all pores having a diameter greater than 500 Å less than 8 ^m2 /g (as measured by mercury intrusion porosimetry), a BET specific surface area less than about 20 ^m2 /g, and a percent compatibility of cetylpyridinium chloride (%CPC) greater than 55%. The precipitated silica is used in oral care applications.

U.S. Patent No. 7,438,895 discloses an abrasive precipitated silica material having a precipitated silica coating thereon, wherein the precipitated silica coating is denser than the material to which it is applied, and wherein the coated precipitated silica material exhibits a median particle size between 5.5 and 8 microns, a pore area of pores having a diameter greater than 500 Å of up to about 2.4 ^m2 /g, and a cetylpyridinium chloride compatibility percentage of at least 90% after aging the material at 140°F for 7 days.

U.S20080160053 describes a method for making an abrasive silica material, wherein the method comprises the following sequential steps: reacting a first amount of a silicate and a first amount of an acid together, optionally in the presence of at least one electrolyte present in an amount of 5 to 25% (on a weight/weight basis) compared to the dry weight of the first amount of the silicate, under high shear mixing conditions to form a first silica material; and reacting a second amount of a silicate and a second amount of an acid together, optionally in the presence of at least one electrolyte present in an amount of 5 to 25% (on a weight/weight basis) compared to the dry weight of the second amount of the silicate, in the presence of the first silica material, to form a dense phase coating on the surface of the first silica material, thereby forming a silica-coated silica material; wherein the at least one electrolyte is present in either of the steps "a" or "b" or during both steps, and wherein the step "b" is optionally performed under high shear mixing conditions.

U.S. Pat. No. 10,328,002 discloses a dentifrice composition comprising: an abrasive comprising precipitated silica particles characterized by: a BET surface area in the range of about 0.1 to about 9 ^m2 /g; a pack density in the range of about 35 to about 55 lb/ft3; an Einlehner abrasion value in the range of about 8 to about 25 mg loss/100,000 revolutions; a total mercury intrusion pore volume in the range of about 0.4-1.2 cc/g; and a stannous compatibility in the range of about 70 to about 99%; wherein the abrasive comprises macropores of about 1000 angstroms or greater in size and lacks micropores of less than about 500-1000 angstroms in size.

WO 2018114280 describes silica particles having: a BET surface area in the range of about 0.1 to about 7 m ² /g; a bulk density in the range of about 35 to about 55 lb/ft 3; an Einlehner abrasion value in the range of about 8 to about 25 mg loss/100,000 revolutions; a total mercury intrusion pore volume in the range of about 0.7 to about 1.2 cc/g, and a stannous compatibility in the range of about 70 to about 99%.

US20190374448 discloses a dentifrice composition comprising: a binder; a surfactant; silica particles; wherein the silica particles comprise: a d50 median particle size in the range of about 4 to about 25 μm; a BET surface area in the range of 0 to about 10 m ² /g; and a total mercury intrusion pore volume in the range of about 0.2 to about 1.5 cc/g.

WO 2019238777 describes silica particles characterized by: (i) a d50 median particle size in the range of about 8 to about 20 μm; (ii) a sphericity coefficient (S80) greater than or equal to about 0.9; (iii) a BET surface area in the range of about 0.1 to about 8 m ² /g; (iv) a total mercury intrusion pore volume in the range of about 0.35 to about 0.8 cc/g; (v) a loss on ignition (LOI) in the range of about 3 to about 7 weight %.

Precipitated silica provides compatibility with ingredients while providing the right balance of cleaning and abrasion, which is important in toothpaste formulations. None of the prior art addresses the lack of compatibility with other ingredients (such as CPC and BAC) and flavor compatibility, while also failing to achieve PCR (80-110) and RDA (100-220) values within the normal range.

Summary of the invention

The inventors of the present invention have now discovered that silica with a high primary particle size can result in high compatibility with CPC, BAC and/or flavors in oral care applications with acceptable PCR/RDA values within the range of current silica cleansers.

The subject of the present invention is therefore a precipitated silica characterized by a mean primary particle size of greater than 80 nm, preferably greater than 90 nm, more preferably greater than 100 nm, still preferably greater than 110 nm, most preferably between 120 nm and 500 nm, a BET surface area of 10-40 m ² /g, preferably 10-26 m ² /g, more preferably 10-23 m ² /g, most preferably 10-20 m ² /g, a total mercury intrusion volume of 0.75-2.00 cc/g, preferably 0.80-1.80 cc/g, more preferably 0.85-1.65 cc/g, more preferably 0.90-1.50 cc/g, and an oil absorption of 60-120 cc/100 g, preferably 60-110 cc/100 g, more preferably 60-100 cc/100 g, most preferably 60-90 cc/100 g.

The subject of the invention is also a method comprising:

(a) feeding an acid and an alkali metal silicate or an alkaline earth metal silicate continuously into a liquid medium under stirring at a silicate addition rate V1 and a temperature of 70-96° C. to form silica particles,

(b) stopping the feeding of alkali metal silicate or alkaline earth metal silicate and acid, and then raising the temperature to 90 to 100° C., preferably 94 to 96° C., under stirring,

(c) adding alkali metal silicate or alkaline earth metal silicate and acid under stirring, wherein the silicate addition rate is 1 to 40%, preferably 1 to 30%, more preferably 2 to 10%, still preferably 3 to 5% of the silicate addition rate V1, and during the addition of the alkali metal silicate or alkaline earth metal silicate, the pH value of 9.0 to 10.0, preferably 9.5 to 9.9, more preferably 9.6 to 9.8 is kept constant by adjusting the acid rate,

(d) The addition of alkali metal silicate or alkaline earth metal silicate is stopped and acid is added with stirring until a pH of 5.0 to 7.0, preferably 5.5 to 6.5, is reached.

A further subject of the present invention is the use of the silicas according to the invention in cosmetics, anti-caking free/flow, foods, carrier applications, dentifrices and mouthwashes.

DETAILED DESCRIPTION

The precipitated silica of the present invention has a mean primary particle size of greater than 80 nm, preferably greater than 90 nm, more preferably greater than 100 nm, still preferably greater than 110 nm, most preferably between 120 nm and 500 nm, a BET surface area of 10-40 ^m2 /g, preferably 10-26 ^m2 /g, more preferably 10-23 ^m2 /g, most preferably 10-20 ^m2 /g, a total mercury intrusion volume of 0.75-2.00 cc/g, preferably 0.80-1.80 cc/g, more preferably 0.85-1.65 cc/g, more preferably 0.90-1.50 cc/g, and an oil absorption of 60-120 cc/100 g, preferably 60-110 cc/100 g, more preferably 60-100 cc/100 g, most preferably 60-90 cc/100 g.

The silica of the present invention has a high primary particle size.

The precipitated silica according to the invention may have a CTAB surface area of 10 to 35 m ² /g, preferably 20 to 30 m ² /g.

The precipitated silica according to the present invention may have a bulk density of 0.40-0.80 g/cm ³ , preferably 0.48-0.75 g/cm ³ .

The precipitated silica according to the invention may have an Einlehner value of less than 18 mg loss/100 k revolutions, preferably from 3 to 18 mg loss/100 k revolutions.

The C content of the silica according to the present invention may be lower than 3%, preferably lower than 1%, more preferably from 0% to 0.5%, most preferably from 0% to 0.1%.

The precipitated silica according to the present invention may have a mean primary particle size greater than 90 nm, a BET surface area of 10-26 m ² /g, a total mercury intruded volume of 0.75-2.00 cc/g, and an oil absorption of 60-120 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size greater than 80 nm, a BET surface area of 10-30 m ² /g, a total mercury intrusion volume of 0.80-1.80 cc/g, and an oil absorption of 70-110 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size greater than 90 nm, a BET surface area of 10-26 m ² /g, a total mercury intrusion volume of 0.80-1.80 cc/g, and an oil absorption of 70-110 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size greater than 100 nm, a BET surface area of 10-23 m ² /g, a total mercury intrusion volume of 0.75-2.00 cc/g, and an oil absorption of 60-120 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size greater than 80 nm, a BET surface area of 10-30 ^m2 /g, a total mercury intrusion volume of 0.85-1.65 cc/g, and an oil absorption of 60-100 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size greater than 100 nm, a BET surface area of 10-23 m ² /g, a total mercury intrusion volume of 0.85-1.65 cc/g, and an oil absorption of 60-100 cc/100 g.

The precipitated silica according to the present invention may have a primary particle size mean of 120-500 nm, a BET surface area of 10-20 m ² /g, a total mercury intrusion volume of 0.75-2.00 cc/g, and an oil absorption of 60-120 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size greater than 80 nm, a BET surface area of 10-30 ^m2 /g, a total mercury intrusion volume of 0.90-1.50 cc/g, and an oil absorption of 60-90 cc/100 g.

The precipitated silica according to the present invention may have a mean primary particle size of 120-500 nm, a BET surface area of 10-20 m ² /g, a total mercury intrusion volume of 0.90-1.50 cc/g, and an oil absorption of 60-90 cc/100 g.

The method according to the invention comprises at least four steps:

(a) continuously feeding an acid and an alkali metal silicate or an alkaline earth metal silicate into a liquid medium under stirring at a silicate addition rate V1 and a temperature of 70-96° C. to form silica particles

(b) stopping the feeding of alkali metal silicate or alkaline earth metal silicate and acid, and then raising the temperature to 90 to 100° C., preferably 94 to 96° C., under stirring,

(c) adding alkali metal silicate or alkaline earth metal silicate and acid under stirring, wherein the silicate addition rate is 1 to 40%, preferably 5 to 30%, more preferably 7 to 25%, still preferably 10 to 20% of the silicate addition rate V1, and during the addition of the alkali metal silicate or alkaline earth metal silicate, the pH value of 9.0 to 10.0, preferably 9.5 to 9.9, more preferably 9.6 to 9.8 is kept constant by adjusting the acid rate,

(d) The addition of alkali metal silicate or alkaline earth metal silicate is stopped and acid is added with stirring until a pH of 5.0 to 7.0, preferably 5.5 to 6.5, is reached.

The silica from step (d) can be filtered (e), for example in a filter press.

The silicon dioxide of step (e) can be dried (f), for example in a spray dryer.

The silica of step (f) may be ground.

Preferably 35 to 65% of the total volume of the alkali metal silicate or alkaline earth metal silicate is added during step (a).

The liquid medium in step (a) may be an alkali metal silicate or an alkaline earth metal silicate and water.

The temperature in step (a) may range from 70 to 95°C, preferably from 70 to 90°C, more preferably from 80 to 90°C.

The acid rate in step (a) may be sufficient to maintain the pH between 8.5 and 10.5, more preferably 9.5 to 10.2.

The silicate rate in step (c) may be slowed to 5 to 30%, more preferably 10 to 20% of the rate in step (a).

The alkali metal silicate in steps (a) and (c) may preferably be sodium silicate.

The silicate addition rate in step (c) may be adjusted so that the %/hr of silicate added in this step is less than 30%/hr, preferably 15 to 25%/hr, based on the total amount of silicate added during the batch. The %/hr of silicate added is calculated by: volume of silicate used in step (c)/time in hours of step (c)/volume of silicate used in steps (a) and (c)*100.

The acid in steps (a), (c) and (d) may preferably be sulfuric acid.

The time of step (c) may be 100 to 500 minutes, preferably 150 to 300 minutes.

The precipitated silica of the present invention can be produced by the method of the present invention.

The precipitated silica of the present invention can be used in cosmetics, anti-caking free/flowing, food, carrier applications, dentifrices and mouthwashes.

The precipitated silica of the present invention has improved compatibility with cetylpyridinium chloride (CPC), benzalkonium chloride (BAC) and flavors in oral care applications.

Example

The average primary particle size was determined by SEM.

Images were taken with a scanning electron microscope at a magnification of 50,000 times. The images were sputtered with platinum and care was taken so that the sputtering did not cause texturing of the particle surface, as this could be mistaken for primary structure. The images had to represent the entire sample and contain a minimum of 30 particles. The primary particles were then measured. If the particles were not completely round, the minimum diameter across each particle was used. Particles on the edges of the image that could not be fully observed should not be used. The mean and median values were then calculated based on the data set.

Carbon content

Carbon content was measured on a LECO SC832 carbon/sulfur analyzer.

brightness

The silica samples were pressed into smooth-surfaced pellets and analyzed using a Technidyne Brightmeter S-5/BC. The instrument has a dual-beam optical system where the sample is illuminated at an angle of 45° and the reflected light is observed at 0°. It complies with TAPPI test methods T452 and T646, and ASTM standard D985. The powdered material was pressed into pellets of approximately 1 cm with sufficient pressure to provide a smooth surface to the pellets without loose particles or sheen.

Moisture

Moisture was determined by heating silica at 105°C for 2 hours.

BET surface area

The BET surface area of the silica of the present invention is determined using a Micromeritics TriStar 3020 instrument by the BET nitrogen adsorption method of Brunaur et al., J. Am. Chem. Soc., 60, 309 (1938), which is known in the art of particulate materials such as silica and silicate materials.

Oil absorption

Oil absorption values are determined using linseed oil (cc of oil absorbed per 100 g of particles) according to the rub-out method described in ASTM D281. Generally, higher oil absorption levels indicate higher structure particles, while lower values generally indicate lower structure particles.

Total mercury intrusion volume

Mercury intrusion volume or total pore volume (Hg) is measured by mercury porosimetry using a Micromeritics AutoPore IV 9520 (or Micromeritics AutoPore V 9620) device. The pore diameter is calculated by the Washburn equation using a contact angle Theta (θ) equal to 130° and a surface tension gamma equal to 484 dynes/cm. Mercury is forced into the voids of the particles due to the pressure, and the volume of mercury intruded per gram of sample is calculated at each pressure setting. The total pore volume expressed herein represents the cumulative volume of mercury intruded at pressures from vacuum to 60,000 psi. The volume increment (cm ³ /g) at each pressure setting is plotted against the pore radius or diameter corresponding to that pressure setting increment. The peak in the intrusion volume versus pore radius or diameter curve corresponds to the mode in the pore size distribution and determines the most common pore size in the sample. Specifically, the sample size is adjusted to achieve a stem volume of 25 to 90% in a powder penetrometer with a 5 mL sphere and a stem volume of about 1.1 mL. The sample is evacuated to a pressure of 50 μm Hg and maintained for 5 minutes. Mercury fills the pores at a pressure of 4.0 to 60,000 psi, with a 10 second equilibrium time for each data collection point. The total pore volume as described above collects the volume of intra-particle porosity generated by the pore structure within each particle, as well as the volume of inter-particle porosity formed by the interstitial spacing of the filled particles under pressure. In order to better separate and measure the actual intra-particle porosity of the produced amorphous silica, the pore volume of pores <0.11 μm can be used.

Einlehner

The Einlehner AT-1000 Abrader was used as follows: (1) a pre-cleaned and dried Fourdrinier brass screen was weighed and exposed to the action of a 10% silica suspension in water for a fixed length of time, specifically 100 g of sample in 900 g of deionized water; (2) the amount of wear was then measured as milligrams of brass lost per 100,000 revolutions of the Fourdrinier screen. The result measured in mg loss was characterized as the 10% brass Einlehner (BE) wear value.

CTAB surface area

The CTAB surface area disclosed herein is determined by the absorption of CTAB (hexadecyltrimethylammonium bromide) on the silica surface, the excess separated by centrifugation, and the amount measured by titration with sodium dodecyl sulfate using a surfactant electrode. Specifically, about 0.5 g of silica particles are placed in a 250 mL beaker containing 100 mL of CTAB solution (5.5 g/L), mixed on an electric stirring plate for 1 hour, and then centrifuged at 10,000 RPM for 30 minutes. 1 mL of 10% Triton X-100 is added to 5 mL of clear supernatant in a 100 mL beaker. The pH is adjusted to 3 to 3.5 with 0.1 N HCl, and the sample is titrated with 0.01 M sodium dodecyl sulfate using a surfactant electrode (Brinkmann SUR1501-DL) to determine the endpoint.

Particle size

The particle size of the silicon dioxide of the present invention is measured by the angle of scattered laser light using a HORIBA laser scattering dry particle size distribution analyzer LA-960.

Water-corrected AbC values

The water absorption value is determined using an Absorptometer "C" torque rheometer from C.W.Brabender Instruments, Inc. A sample of about 1/3 cup of silica is transferred to the mixing chamber of the Absorptometer and mixed at 150RPM. Water is then added at a rate of 6mL/min, and the torque required to mix the powder is recorded. The torque reaches a maximum value when the powder changes from free flowing to a paste as the water is absorbed by the powder. The total volume of water added when the maximum torque is reached is then standardized to the amount of water that 100g of powder can absorb. Since the powder is used on an as is basis (not pre-dried), the free moisture value of the powder is used to calculate the "moisture-corrected water AbC value" by the following equation.

5 wt% pH

5% pH was measured by weighing 5.0 g of sample (accurate to 0.1 g) and transferring the weighed sample into a 250 mL beaker. 95 mL of DI water was added and the sample was stirred for 5 minutes. The pH was then measured with a pH meter while the sample was stirred.

Bulk density and pouring density

The sample of 20.0g is put into the 250mL graduated cylinder with flat rubber bottom to measure bulk density and pour density.Record initial volume and be used for calculating pour density by the weight of used sample divided by this volume.Then graduated cylinder is placed on the tap density machine that rotates on cam with specific RPM.Cam is designed to raise and lower the distance of 5.715cm by graduated cylinder per second, until sample volume is constant, usually lasts 15 minutes.Record this final volume and be used for calculating bulk density by the weight of used sample divided by this volume.

Example 1A: (Inventive Example)

383 mL of sodium silicate (2.65 MR, 1.193 g/mL) and 957 mL of water were added to a 7 L laboratory scale reactor and heated to 85° C. with stirring at 350 RPM from an overhead stirrer equipped with a propeller blade. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 39.0 mL/min and 16.4 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) was added at 10.2 mL/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 150 minutes. After this additional 150 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 5.1 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and dried at 105°C overnight.

Example 1B: (Inventive Example)

273 mL of sodium silicate (2.65 MR, 1.193 g/mL) and 681 mL of water were added to a 7 L laboratory scale reactor and heated to 85° C. with stirring at 350 RPM from an overhead stirrer equipped with a propeller blade. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 27.7 mL/min and 11.7 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) was added at 10.7 mL/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 210 minutes. After this additional 210 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 5.1 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and dried at 105°C overnight.

Example 1C: (Inventive Example)

273 mL of sodium silicate (2.65 MR, 1.193 g/mL) and 681 mL of water were added to a 7 L laboratory scale reactor and heated to 85° C. with stirring at 350 RPM from an overhead stirrer equipped with a propeller blade. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 43.8 mL/min and 18.4 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) was added at 9.8 mL/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 120 minutes. After the additional 120 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 4.7 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and dried at 105°C overnight.

Example 2A: (Inventive Example)

320 mL of sodium silicate (2.65 MR, 1.193 g/mL) and 824 mL of water were added to a 7 L laboratory scale reactor and heated to 85° C. with stirring at 350 RPM from an overhead stirrer equipped with a propeller blade. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 33.8 mL/min and 15.1 mL/min, respectively, for 47 minutes. After 47 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL) was added at 10.4 mL/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 150 minutes. After this additional 150 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 5.0 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and dried at 105°C overnight.

Table 1 shows the analysis values of Examples.

Table 1

Comparative Example 5A:

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 85° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 25.3 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 25.3 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 5B:

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 85° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 21.6 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 21.6 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 5C:

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 85° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 29.2 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 29.2 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 5D:

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 85° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 29.2 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 29.2 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 5E:

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 85° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 19.1 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 19.1 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Table 2 shows the analytical values of Examples.

Table 2

Comparative Example 6A

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 80° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 21.6 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 21.6 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 6B

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 85° C.) and 1483 mL of water were added to a 7 L reactor and heated to 90° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 85° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 21.6 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 21.6 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 6C

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 90° C.) and 1483 mL of water were added to a 7 L reactor and heated to 95° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 90° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 21.6 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 21.6 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Table 3 shows the analytical values of Examples.

Table 3

Comparative Example 7A:

594 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1483 mL of water were added to a 7 L reactor and heated to 85° C. with stirring at 650 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 60.4 mL/min and 25.4 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 25.4 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Table 4 shows the analytical values of Examples.

Table 4

Comparative Example 8A

510 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1310 mL of water were added to a 7 L reactor and heated to 80° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 53.7 mL/min and 24.0 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 24.0 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 8B

510 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1310 mL of water were added to a 7 L reactor and heated to 80° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 53.7 mL/min and 27.5 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 27.5 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 8C

510 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1310 mL of water were added to a 7 L reactor and heated to 80° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 53.7 mL/min and 20.4 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 20.4 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 8D

510 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1310 mL of water were added to a 7 L reactor and heated to 80° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 53.7 mL/min and 19.2 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 19.2 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Comparative Example 8E

510 mL of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 1310 mL of water were added to a 7 L reactor and heated to 80° C. with stirring at 350 RPM. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 53.7 mL/min and 18.0 mL/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 18.0 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed with 14 L of water and oven dried overnight.

Table 5 shows the analytical values of Examples.

Table 5

Example 10A: (Inventive Example)

62 L of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 154 L of water were added to the 1200 L reactor and heated to 85° C. with stirring at 80 RPM and recirculation at 80 L/min. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 6.27 L/min and 2.24 L/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) was added at 1.63 L/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 150 minutes. After the additional 150 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 0.82 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed until the conductivity was <1500 μS, spray dried to a target moisture of 5%, and ground to a particle size of approximately 10 μm.

Example 10B: (Inventive Example)

53 L of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 133 L of water were added to the 1200 L reactor and heated to 85° C. with stirring at 80 RPM and recirculation at 80 L/min. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 5.42 L/min and 1.82 L/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) was added at 1.63 L/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 180 minutes. After this additional 180 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 0.82 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed until the conductivity was <1500 μS, spray dried to a target moisture of 5%, and ground to a particle size of approximately 10 μm.

Example 10C: (Inventive Example)

44 L of sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and 115 L of water were added to the 1200 L reactor and heated to 85° C. with stirring at 80 RPM and recirculation at 80 L/min. Once 85° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) and sulfuric acid (1.121 g/mL) were added simultaneously at rates of 4.48 L/min and 1.51 L/min, respectively, for 38 minutes. After 38 minutes, the flow of sodium silicate and sulfuric acid was stopped and the reaction mixture was heated to 95° C. Once 95° C. was reached, sodium silicate (2.65 MR, 1.193 g/mL, heated to 80° C.) was added at 1.73 L/min and sulfuric acid (1.121 g/ml) was added at a rate sufficient to maintain pH 9.6 (+/- 0.1) for an additional 210 minutes. After the additional 210 minutes, the flow of sodium silicate was stopped and the pH was adjusted to pH 6.0 by continuing to flow sulfuric acid (1.121 g/mL) at a rate of 0.82 mL/min. Once the pH stabilized at pH 6.0, the batch was filtered, washed until the conductivity was <1500 μS, spray dried to a target moisture of 5%, and ground to a particle size of approximately 10 μm.

Tables 6a and 6b show the analytical values for the Examples.

Table 6a

Table 6b

Example 11: Toothpaste formulation

The inventive silica from above was incorporated into toothpaste for rheology and PCR/RDA measurements. The formulation and results (Table 7a) are shown below. The stannous compatibility and fluoride compatibility of the inventive examples are shown in Table 7b.

Table 7a

(PCR/RDA run at Indiana University School of Dentistry)

Table 7b

The data in Table 7a show that toothpastes containing silica of the present invention achieve PCR and RDA values within the normal range.

Stannous compatibility (%)

The stannous compatibility of the above samples was determined as follows. A stock solution containing 431.11 g of 70% sorbitol, 63.62 g of deoxygenated deionized water, 2.27 g of stannous chloride dihydrate and 3 g of sodium gluconate was prepared. 34 g of the stock solution was added to a 50 mL centrifuge tube containing 6 g of the silica sample to be tested. The centrifuge tube was placed on a rotating wheel at 5 RPM and aged for 1 week at 40° C. After aging, the centrifuge tube was centrifuged at 12,000 RPM for 10 minutes, and the stannous concentration in the supernatant was determined by ICP-OES (inductively coupled plasma emission spectrometer). Stannous compatibility is determined by expressing the stannous concentration of the sample as a percentage of the stannous concentration of a solution prepared by the same procedure but without the addition of silica.

Fluoride compatibility (%)

The fluoride compatibility of the above samples was determined as follows. A fluoride stock solution containing 1624ppm was prepared. 30.0g of the stock solution was added to a 50mL centrifuge tube containing 7.0g of the silica sample to be tested. The centrifuge tube was placed on a rotating wheel at 5RPM (or equivalent stirring mode) and aged for 1 hour at 60°C. After aging, the centrifuge tube was centrifuged at 12,000RPM for 10 minutes (or until the supernatant was clear). The fluoride concentration in the supernatant was determined by first taking an aliquot and transferring it to a plastic bottle containing a magnetic stirring bar and an equal volume of TISAB II buffer. The concentration was then measured using a pre-calibrated fluoride specific ion electrode (Orion model #96-09BN or equivalent). Fluoride compatibility was determined by expressing the fluoride concentration of the sample as a percentage of the fluoride concentration of the stock solution.

Relative dentin wear (RDA)

The RDA values of the dentifrice compositions of Examples DC1-DC14 containing the silica of the present invention were determined according to the method set forth in Hefferen, Journal of Dental Res., July-August 1976, 55(4), pp. 563-573 and described in Wason U.S. Pat. Nos. 4,340,583, 4,420,312 and 4,421,527, the contents of which are incorporated herein by reference in their entirety.

Biofilm Cleaning Ratio (“PCR”)

The cleaning performance of a dentifrice composition is usually expressed as a Pellicle Cleaning Ratio ("PCR") value. The PCR test measures the ability of a dentifrice composition to remove bacterial film from teeth under fixed brushing conditions. The PCR test is described in "In Vitro Removal of Stain with Dentifrice" G.K.Stookey, et al., J.Dental Res., 61, 12-36-9, 1982. Both PCR and RDA results vary depending on the nature and concentration of the components of the dentifrice composition. PCR and RDA values are unitless.

Example 12: CPC and BAC Compatibility

In order to determine the given silica capacitance (capacity) for quaternary ammonium compounds, a zeta potential titration was performed. In the titration, a 5 wt% suspension of the desired silica was prepared by taking the required amount of dry silica and diluting to 160 g with deionized water. In order to get as close as possible to the required 5 wt% (8 g) of silica in 160 g of suspension, the amount of raw silica used was adjusted to compensate for the amount of free moisture (drying loss) and sodium sulfate present. The suspension was magnetically stirred at 500 rpm for 10 minutes to completely wet the silica, and then the suspension was adjusted to a pH of ~8.5 with 0.5 M NaOH or 0.5 M HCl to help consistency of initial surface chemistry and more direct comparison.

The suspension was then titrated with 0.25 mL increments of either 5 wt% cetylpyridinium chloride (CPC) or 5 wt% benzalkonium chloride (BAC), and the capacitance of each silica was determined by the volume of CPC or BAC required to reach a zeta potential of 0 mV. Given that most experiments showed artifacts near the 0 mV crossover point, the capacitance was defined as the first point at which the zeta potential became positive. The volume at this point was then used to determine the mass of CPC or BAC per gram of silica in mg/g.

Inventive Examples 10A, 10B and 10C showed lower CPC and BAC values and therefore showed improved CPC/BAC compatibility (Table 8).

Table 8

Example 13: Fragrance

Method: 500 mg of silica was placed in a headspace vial. 10 μL of flavor (lime oil, Lot MKCF9356 flavor matrix) was added and the headspace vial was equilibrated overnight. The samples were incubated at 60°C with gentle shaking for 60 minutes before sampling the headspace vial. 1 mL of headspace was analyzed in a GC/MS equipped with a Stabilwax column (0.25 mm x 60 m) with a column flow rate of 1.606 mL/min and a temperature gradient of 6°C/min over the temperature range of 40°C to 230°C (HS sampling: 1 mL of headspace was sampled into a gas-tight syringe at 65°C). Peak areas relative to The peak intensity of 113 was normalized.

Inventive Examples 10A, 10B and 10C show higher values and therefore show improved fragrance compatibility (Table 9).

Table 9

Claims (19)

1. Precipitated silica characterized by a primary particle size average of more than 80nm, preferably more than 90nm, more preferably more than 100nm, still preferably more than 110nm, most preferably between 120nm and 500nm, a BET surface area of 10-40m ²/g, preferably 10-26m ²/g, more preferably 10-23m ²/g, most preferably 10-20m ²/g, a total mercury intrusion volume of 0.75-2.00cc/g, preferably 0.80-1.80cc/g, more preferably 0.85-1.65cc/g, more preferably 0.90-1.50cc/g, and an oil absorption of 60-120cc/100g, preferably 60-110cc/100g, more preferably 60-100cc/100g, most preferably 60-90cc/100 g.

2. The precipitated silica of claim 1, wherein the precipitated silica has a CTAB surface area of 10-35m ²/g, preferably 20-30m ²/g.

3. Precipitated silica according to claim 1 or 2, wherein the precipitated silica has a bulk density of 0.40-0.80g/cm ³, preferably 0.48-0.75g/cm ³.

4. A precipitated silica according to any one of claims 1-3, wherein the precipitated silica has an Einlehner value of less than 18mg loss per 100k revolutions, preferably 3 to 18mg loss per 100k revolutions.

5. The precipitated silica of any one of claims 1-4, wherein the precipitated silica has a C content of less than 3%, preferably less than 1%, more preferably from 0% to 0.5%.

6. The precipitated silica of claim 1, wherein the precipitated silica has a primary particle size average of greater than 90nm, a BET surface area of 10 "26 m ²/g, a total mercury intrusion volume of 0.75" 2.00cc/g, and an oil absorption of 60 "120 cc/100 g.

7. The precipitated silica of claim 1, wherein the precipitated silica has a primary particle size average of greater than 80nm, a BET surface area of 10-30m ²/g, a total mercury intrusion volume of 0.80-1.80cc/g, and an oil absorption of 70-110cc/100 g.

8. The precipitated silica of claim 1, wherein the precipitated silica has a primary particle size average of greater than 90nm, a BET surface area of 10-26m ²/g, a total mercury intrusion volume of 0.80-1.80cc/g, and an oil absorption of 70-110cc/100 g.

9. The precipitated silica of claim 1, wherein the precipitated silica has a primary particle size average of greater than 100nm, a BET surface area of 10-23m ²/g, a total mercury intrusion volume of 0.75-2.00cc/g, and an oil absorption of 60-120cc/100 g.

10. The precipitated silica of claim 1, wherein the precipitated silica has a primary particle size average of greater than 80nm, a BET surface area of 10-30m ²/g, a total mercury intrusion volume of 0.85-1.65cc/g, and an oil absorption of 60-100cc/100 g.

11. The precipitated silica of claim 1, wherein the precipitated silica has a primary particle size average of greater than 100nm, a BET surface area of 10-23m ²/g, a total mercury intrusion volume of 0.85-1.65cc/g, and an oil absorption of 60-100cc/100 g.

12. A process for producing precipitated silica comprising

(A) Acid and alkali metal silicate or alkaline earth metal silicate are continuously fed into the liquid medium with stirring at a silicate addition rate V1 and a temperature of 70-96 ℃ to form silica particles,

(B) The alkali metal silicate or alkaline earth metal silicate and the acid are stopped from being fed and then the temperature is raised to 90 to 100 c, preferably 94 to 96 c with stirring,

(C) Adding an alkali metal silicate or alkaline earth metal silicate and an acid with stirring, wherein the silicate addition rate is 1 to 40%, preferably 1 to 30%, more preferably 2 to 10%, still preferably 3 to 5% of the silicate addition rate V1, and the pH value of 9.0 to 10.0, preferably 9.5 to 9.9, more preferably 9.6 to 9.8 is kept constant by adjusting the acid rate during the addition of the alkali metal silicate or alkaline earth metal silicate,

(D) The addition of alkali metal silicate or alkaline earth metal silicate is stopped and the acid is added with stirring until a pH of 5.0 to 7.0, preferably 5.5 to 6.5 is reached.

13. The process for producing precipitated silica according to claim 12, wherein the silica of step (d) is filtered (e) and dried (f) in a spray dryer.

14. The method for producing precipitated silica according to claim 13, wherein the silica of step (f) is ground.

15. The method for producing precipitated silica according to claim 12, wherein the liquid medium in step (a) is an alkali metal silicate or an alkaline earth metal silicate and water.

16. The method for producing precipitated silica according to claim 12, wherein the temperature in step (a) is in the range of 70 to 95 ℃, preferably 70 to 90 ℃, more preferably 80 to 90 ℃.

17. The method for producing precipitated silica according to claim 12, wherein the period of time of step (c) is 100 to 500 minutes, preferably 150 to 300 minutes.

18. Use of the precipitated silica according to claim 1 for cosmetics, anti-caking free/flowing, food, carrier applications, dentifrices and mouthwashes.

19. A dentifrice composition comprising the precipitated silica of any of claims 1-11.