Precipitated silica and method thereof

Abstract

The present disclosure relates to precipitated silica characterized by an average primary particle size of from 80 nm to 140 nm, a BET surface area of less than 40 m2 / g, and an oil absorption of from 160 cc / 100 g to 250 cc / 100 g. The silica according to the invention is prepared by a process comprising (a) dispersing colloidal seed particles having a primary particle size of 40-100 nm, preferably 50-80 nm, in water, (b) adding an electrolyte at a concentration of 2.5-4.0 wt%, based on the total mass of the colloidal seed particles added in step (a), (c) heating the suspension to 65-100 DEG C, preferably 85-95 DEG C, and (d) cooling the suspension to the room temperature. The present invention relates to a process for the preparation of a water-soluble polymer, comprising the steps of (a) adding an acid and a silicate, while maintaining the pH at 7.5-10, preferably 8-9, for a time of 60-180 minutes, (d) adding 1.8-5.0% of an electrolyte, based on the initial volume of water, during the addition of the acid and silicate (c), (e) stopping the addition of the silicate, (f) adding an acid until the pH is reached to 3-6, (g) filtering, drying and optionally grinding. The precipitated silica of the present invention is useful in cosmetics, anti-caking free / flow, food, carrier applications, dentifrice and mouthwash.

Description

Technical Field

[0001] The present disclosure generally relates to precipitated silica and methods for its preparation and use. Background Art

[0002] Porous precipitated silica is typically prepared by the reaction of an alkaline silicate solution such as sodium silicate with an inorganic acid. Commercially, sulfuric acid is mainly used, but other acids such as hydrochloric acid can also be applied. The acid and the sodium silicate solution are simultaneously added to water under stirring. When silica precipitates from the dispersion by a neutralization reaction and a by-product sodium salt (sodium sulfate) is produced, precipitated silica is generated. Precipitated silica consists of aggregates (secondary particles) of primary (or ultimate) colloidal silica particles. The primary particles are mostly spherical and typically 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. The aggregates are three-dimensional clusters of these primary particles. The aggregates have a diameter of at most 500 nm. During the preparation process, the aggregates are not chemically linked into a huge gel network. Before grinding, the aggregates themselves can be physically linked to larger agglomerates with a diameter of at most 100 μm by forming hydrogen bonds between the silanol groups on their surfaces. The median agglomerate size has a diameter of about 20 - 50 μm (before grinding). The porosity and surface area of these precipitated silica particles depend on 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 commercially available precipitated silica is 5 - 800 m 2 / g. They are sold as powders. The tapped density is a measure of the weight of these porous powders and ranges from 50 - 500 kg / m 3 . They have a high absorption capacity of about 30 - 320 g / 100 g.

[0003] U.S. Patent No. 4,708,859 reports silica with a CTAB of 20 - 120 m 2 / g, an oil absorption of 250 to 500 ml / 100 g, and a projected area greater than 8000 nm 2 .

[0004] U.S. Patent No. 8,597,425 reports that porous precipitated silica with a primary particle size of 10 - 80 nm can be used in the following applications, including rubber and tires, battery separators, antiblocking agents, matting agents for inks and paints, carriers for agricultural products and feeds, coating materials, printing inks, dry powder fire extinguishers, plastics, in the field of non-impact printing, pulp, or articles in the personal care field.

[0005] In J.Soc Cosmet.Chem August 1978, 29, 497 - 521, it was reported that precipitated silica with a primary particle size of 12 - 51 nm can be used in cosmetic applications, including toothpaste.

[0006] Commercially available products that can be used in food and feed applications as carriers and anti - caking free - flowing additives 22 has a primary particle size of 18 nm (Degussa Document No. 64, Physiological Behavior of highly dispersed Oxides of Silicon, Aluminum and Titanium 1978, pp. 26 - 27).

[0007] U.S. Patent No. 6,946,119 discloses a precipitated silica product comprising silica particles, the silica particles having a median diameter of 1 - 100 microns and having a deposit loaded on its surface, the deposit comprising an active precipitated amorphous silica material present in an effective amount to provide a BET surface area of 1 - 50 m 2 / g to the silica particles. This precipitated silica is used in oral care applications.

[0008] U.S. Patent No. 7,255,852 describes a precipitated silica comprising silica product particles having a porous surface, the cumulative surface area of all pores in the silica particles with a diameter greater than 500 Å being less than 8 m 2 / g as measured by mercury porosimetry, the BET surface area being less than about 20 m 2 / g, and the percentage of cetylpyridinium chloride (% CPC) compatibility being greater than 55%. This precipitated silica is used in oral care applications.

[0009] 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 it coats, and wherein the coated precipitated silica material exhibits a median particle size of 5.5 to 8 microns, the pore area of pores with a diameter greater than 500 Å being at most about 2.4 m 2 / g, and the percentage of cetylpyridinium chloride compatibility being at least 90% after aging the material at 140°F for 7 days.

[0010] U.S20080160053 describes a method for manufacturing abrasive silica materials, wherein the method involves the following sequential steps: reacting a first amount of silicate with a first amount of acid under high shear mixing conditions, optionally in the presence of at least one electrolyte present in an amount of from 5% to 25% by weight relative to the dry weight of the first amount of silicate, to form a first silica material; and reacting a second amount of silicate with a second amount of acid in the presence of the first silica material, optionally in the presence of at least one electrolyte present in an amount of from 5% to 25% by weight relative to the dry weight of the second amount of silicate, 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 any one of the steps or during both steps, and wherein the second step is optionally carried out under high shear mixing conditions.

[0011] U.S. Patent No. 10,328,002 discloses a dentifrice composition, the dentifrice composition comprising: an abrasive, the abrasive comprising precipitated silica particles, the precipitated silica particles being characterized by: a BET surface area in the range of from about 0.1 m 2 / g to about 9 m 2 / g; a bulk density in the range of from about 35 lb / ft 3 to about 55 lb / ft 3 ; an Einlehner wear value in the range of from about 8 mg loss / 100,000 revolutions to about 25 mg loss / 100,000 revolutions; a total mercury intrusion pore volume in the range of from about 0.4 cc / g - 1.2 cc / g; and a stannous compatibility in the range of from about 70% to about 99%; wherein the abrasive comprises macropores having a size of about 1000 Å or greater and no micropores having a size less than about 500 - 1000 Å.

[0012] WO 2018114280 describes silica particles having a BET surface area in the range of from about 0.1 m 2 / g to about 7 m 2 / g; a packed density in the range of from about 35 to about 55 lb / ft 3 ; an Einlehner wear value in the range of from about 8 to about 25 mg loss / 100,000 revolutions; a total mercury intrusion pore volume in the range of from about 0.7 to about 1.2 cc / g; and (v) a stannous compatibility in the range of from about 70% to about 99%.

[0013] U.S. 20190374448 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.

[0014] 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; and (v) a loss on ignition (LOI) in the range of about 3 to about 7 wt%.

[0015] EP 22160705.4 describes precipitated silica characterized by an average primary particle size greater than 80 nm, a BET surface area of 10 - 40 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.

[0016] US 4,708,859 A describes precipitated silica characterized by a high oil absorption greater than 300 cc / 100 g and lower and higher BET surface areas. This US application does not provide compatibility and viscosity data for the use of silica in toothpaste formulations.

[0017] In toothpaste formulations, it is important that precipitated silica provides compatibility with the ingredients while providing the right balance of cleaning and abrasion. None of the prior arts have addressed the problems of lack of compatibility with other ingredients such as CPC and BAC and flavor compatibility, while not achieving PCR (80 - 110) and RDA (100 - 220) values within the normal range. Summary of the Invention

[0018] The inventors of the present invention have now found that, compared with conventional thickening silica, in oral care applications, silica with a high primary particle size can achieve high compatibility with CPC, BAC, and / or flavor and have an acceptable increase in viscosity.

[0019] Accordingly, the subject matter of the present invention is precipitated silica characterized by an average primary particle size greater than 80 nm, preferably greater than 100 nm, more preferably greater than 115 nm, and most preferably 115 nm to 130 nm, and a BET surface area of less than 40 m 2 / g, preferably less than 35 m² / g 2 / g, more preferably less than 30 m² / g 2 / g, most preferably 15 m² / g 2 / g to 30 m² / g 2 / g, and the oil absorption is higher than 160 cc / 100 g, preferably higher than 175 cc / 100 g, more preferably higher than 200 cc / 100 g, and most preferably 200 cc / 100 g to 250 cc / 100 g.

[0020] The subject of the present invention is also a method, which includes:

[0021] (a) Dispersing colloidal seed particles with a primary particle size of 40 - 100 nm in water,

[0022] (b) Adding an electrolyte at a concentration of 2.5 wt% - 4.0 wt% based on the total mass added in step (a),

[0023] (c) Heating the suspension to 65 °C - 100 °C,

[0024] (d) Adding an acid and a silicate while maintaining the pH at 7.5 - 10 for a period of 60 - 180 minutes,

[0025] (e) Stopping the addition of the silicate,

[0026] (f) Adding an acid until a pH of 3 - 6 is reached,

[0027] (g) Filtering, drying, and optionally grinding.

[0028] Another subject of the present invention is the use of the silica of the present invention in cosmetics, anti-caking free / flow agents, food, carrier applications, dentifrices, and mouthwashes.

[0029] Another subject of the present invention is an oral care agent containing the silica of the present invention. Detailed Description

[0030] The average primary particle size of the precipitated silica of the present invention is greater than 80 nm, preferably greater than 100 nm, more preferably greater than 115 nm, and most preferably 115 nm to 130 nm, and the BET surface area is less than 40 m² 2 / g, preferably less than 35 m² / g 2 / g, more preferably less than 30 m² / g 2 / g, most preferably 15 m² / g 2 / g to 30 m² / g 2 / g, and the oil absorption amount is higher than 160 cc / 100 g, preferably higher than 175 cc / 100 g, more preferably higher than 200 cc / 100 g, and most preferably 200 cc / 100 g to 250 cc / 100 g.

[0031] The precipitated silica according to the present invention is characterized in that the average primary particle size (a) is 80 nm ≤ (a) ≤ 140 nm, preferably 110 nm ≤ (a) ≤ 140 nm, and the BET surface area (b) is less than 40 m 2 / g, preferably less than 27 m 2 / g, and the oil absorption amount (c) is 160 cc / 100 g ≤ (c) ≤ 250 cc / 100 g.

[0032] The total mercury intrusion volume of the precipitated silica according to the present invention can be 2.5 cc / g - 5.3 cc / g, preferably 3.0 - 5.3 cc / g, more preferably 4.0 - 5.3 cc / g.

[0033] The CTAB surface area of the precipitated silica according to the present invention can be lower than 40 m 2 / g, preferably lower than 35 m 2 / g, more preferably lower than 30 m 2 / g.

[0034] The packed density of the precipitated silica according to the present invention can be < 0.32 g / cm 3 , preferably 0.11 - 0.24 g / cm 3 .

[0035] The precipitated silica according to the present invention can have an average primary particle size of 100 - 125 nm, a BET surface area of 15 - 30 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption amount of 200 - 250 cc / 100 g.

[0036] The precipitated silica according to the present invention can have an average primary particle size greater than 80 nm, a BET surface area of 10 - 40 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption amount of 175 - 250 cc / 100 g.

[0037] The precipitated silica according to the present invention can have an average primary particle size greater than 100 nm, a BET surface area of 10 - 26 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption amount of 175 - 250 cc / 100 g.

[0038] The precipitated silica according to the present invention may have an average primary particle size greater than 100 nm, a BET surface area of 10 - 23 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 175 - 250 cc / 100 g.

[0039] The precipitated silica according to the present invention may have an average primary particle size greater than 80 nm, a BET surface area of 10 - 30 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 175 - 250 cc / 100 g.

[0040] The precipitated silica according to the present invention may have an average primary particle size greater than 100 nm, a BET surface area of 10 - 23 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 175 - 250 cc / 100 g.

[0041] The precipitated silica according to the present invention may have an average primary particle size of 120 - 135 nm, a BET surface area of 10 - 20 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 175 - 250 cc / 100 g.

[0042] The precipitated silica according to the present invention may have an average primary particle size greater than 100 nm, a BET surface area of 10 - 30 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 175 - 250 cc / 100 g.

[0043] The precipitated silica according to the present invention may have an average primary particle size of 120 - 135 nm, a BET surface area of 10 - 20 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 175 - 250 cc / 100 g.

[0044] The precipitated silica according to the present invention may have an average primary particle size (a) of 85 nm ≤ (a) ≤ 100 nm, a BET surface area of 10 - 35 m 2 / g, a total mercury intrusion volume of 2.5 - 5.3 cc / g, and an oil absorption of 170 - 250 cc / 100 g.

[0045] The method according to the present invention comprises at least the following steps:

[0046] (a) Dispersing colloidal seed particles having a primary particle size of 40 - 100 nm, preferably 50 - 80 nm, in water,

[0047] (b) Based on the total mass of the colloidal seed particles added in step (a), an electrolyte is added at a concentration of 2.5 wt% - 4.0 wt%.

[0048] (c) The suspension is heated to 65°C - 100°C, preferably 85°C - 95°C.

[0049] (d) An acid and a silicate are added while maintaining the pH at 7.5 - 10, preferably 8 - 9, for a period of 60 - 180 minutes.

[0050] (e) The addition of the silicate is stopped.

[0051] (f) An acid is added until a pH of 3 - 6 is reached.

[0052] (g) Filtering, drying, and optionally grinding are carried out.

[0053] The filtering in step (g) can be carried out in a plate filter, a rotary vacuum filter, a belt filter, etc.

[0054] The drying in step (g) can be carried out in a spray dryer, a flash dryer, etc.

[0055] The grinding in step (g) can be carried out in an impact mill, such as a Raymond mill, an air jet mill, etc.

[0056] The colloidal seed particles in step (a) can be 40 - 100 nm, such as Nexsil from Nyacol NanoTechnologies, Inc; AmSol from Applied Material Solutions, Inc; Levasil from Nouryon; Snowtex from Nissan Chemical.

[0057] The dispersion in step (a) can be carried out in a baffled reactor with stirring sufficient to keep the particles dispersed.

[0058] The temperature range in step (a) can be 20 - 95°C, preferably 40 - 95°C, more preferably 60 - 85°C, and even more preferably 70 - 80°C.

[0059] Based on the total volume added in step (a), the colloidal seed particles in step (a) can be used in an amount of 0.15 - 5 wt%. Colloidal silica can account for 5 - 10% of the total silica product prepared in steps (a) to (g) of this method.

[0060] The silicate addition rate in step (d) can be 0.5% to 2.2% of the total volume of silicate added per minute with respect to the total volume of silicate added.

[0061] The alkali metal silicate in step (d) can preferably be an alkaline earth metal silicate or an alkali metal silicate, and more preferably sodium silicate.

[0062] The acid in steps (d) and (f) can preferably be sulfuric acid.

[0063] The time period of step (d) can be 60 - 180 minutes, preferably 90 - 120 minutes.

[0064] During step (d), additional electrolyte can be added in an amount of 1.8 - 5.0% based on the starting water volume.

[0065] The electrolyte in step (b) can be an alkali metal salt, preferably sulfates, chlorides, etc. of sodium or potassium.

[0066] The precipitated silica of the present invention can be prepared by the method of the present invention.

[0067] The precipitated silica of the present invention can be used in cosmetics, anti - caking free - flowing agents, foods, carrier applications, dentifrices, and mouthwashes.

[0068] An oral care composition comprising the precipitated silica of the present invention.

[0069] The oral care composition of the present invention can comprise a second precipitated silica having an average primary particle size of greater than 80 nm, a BET surface area of 10 - 40 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.

[0070] The oral care composition of the present invention can comprise a second silica having a BET surface area of less than 5 m 2 / g.

[0071] The precipitated silica of the present invention has improved compatibility with cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), and flavorants, while providing acceptable rheology in oral care applications.

[0072] Average primary particle size determined by SEM

[0073] Images were taken at a magnification of 50,000 times using a scanning electron microscope. The images were sputtered with platinum, taking care to ensure that the sputtering did not cause texturing of the particle surface, as this could be mistaken for the primary structure. The images must represent the entire sample and contain a minimum of 30 particles. The primary particles were then measured. If the particles were not perfectly round, the minimum diameter on each particle was used. Particles on the edge of the image that could not be fully observed should not be used. The mean and median were then calculated based on the data set.

[0074] Figure 2 The SEM image of Comparative Example 1 is shown.

[0075] Figure 3 and Figure 4 The SEM images of Invention Example 3 and Invention Example 9 are shown.

[0076] Brightness

[0077] The silica samples were pressed into pellets with a smooth surface and analyzed using a Technidyne brightness meter S-5 / BC. The instrument has a double-beam optical system in which the sample is irradiated at an angle of 45° and the reflected light is observed at 0°. It conforms to TAPPI test methods T452 and T646, as well as ASTM standard D985. The powder material was pressed into pellets of about 1 cm with sufficient pressure to obtain a pellet surface that was smooth and free of loose particles or gloss.

[0078] Moisture

[0079] The moisture was determined by heating the silica at 105 °C for 2 hours. The moisture is the percentage of weight loss based on the undried silica.

[0080] BET surface area

[0081] The BET surface area of the silica of the present invention was 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 method is known in the field of particulate materials such as silica and silicate materials.

[0082] Oil absorption

[0083] The oil absorption value was determined using linseed oil (cc of oil absorbed per 100 g of particles) according to the rub-out method described in ASTM D281. Generally, a higher oil absorption level indicates particles with a higher structure, while a lower value usually indicates particles with a lower structure.

[0084] Total mercury intrusion volume

[0085] Using a Micromeritics AutoPore IV 9520 (or Micromeritics AutoPore V 9620) device, the mercury intrusion volume or total pore volume (Hg) was measured by mercury porosimetry. The pore size was calculated by the Washburn equation, with the contact angle Theta (θ) equal to 130° and the surface tension γ equal to 484 dynes / cm. Due to the action of pressure, mercury was pressed into the voids of the particles, and the volume of mercury pressed into per gram of sample was calculated at each pressure setting. The total pore volume expressed in this article represents the cumulative volume of mercury pressed in from vacuum to a pressure of 60,000 psi. The volume increment (cm 3 / g) at each pressure setting was plotted against the pore radius or diameter corresponding to the pressure setting increment. The peak in the intrusion volume versus pore radius or diameter curve corresponds to the mode of the pore size distribution and determines the most common pore size in the sample. Specifically, the sample size was adjusted to achieve 25 - 90% of the stem volume in a powder penetrometer with a 5 mL bulb and a stem volume of approximately 1.1 mL. The sample was evacuated to a pressure of 50 μm Hg and held for 5 minutes. From 4.0 to 60,000 psi, mercury filled the pores, and the equilibrium time at each data collection point was 10 seconds. The total pore volume as described above encompasses the volume of intragranular porosity resulting from the pore structure within each particle, as well as the volume of intergranular porosity formed by the interstitial spacing of the packed particles under pressure.

[0086] CTAB surface area

[0087] The CTAB surface area disclosed in this article was determined by the adsorption of CTAB (cetyltrimethylammonium bromide) on the silica surface. The excess was separated by centrifugation, and the amount was determined by titration with sodium lauryl sulfate using a surfactant electrode. Specifically, approximately 0.5 g of silica particles were placed in a 250 mL beaker containing 100 mL of CTAB solution (5.5 g / L), mixed on a magnetic stirrer for 1 hour, and then centrifuged at 10,000 RPM for 30 min. 1 mL of 10% Triton X - 100 was added to 5 mL of the clear supernatant in a 100 mL beaker. The pH was adjusted to 3 - 3.5 with 0.1N HCl, and the sample was titrated with 0.01M sodium lauryl sulfate using a surfactant electrode (Brinkmann SUR1501 - DL) to determine the end point.

[0088] Particle size

[0089] The particle size of the silica of the present invention was measured by the angle of scattered laser on a HORIBA laser scattering dry particle size distribution analyzer LA - 960.

[0090] Water-corrected AbC value

[0091] The water absorption value was determined using an Absorptometer “C” torque rheometer from C.W.Brabender Instruments, Inc. Approximately 1 / 3 cup of the silica sample was transferred to the mixing chamber of the Absorptometer and mixed at 150 RPM. Then water was added at a rate of 6 mL / min, and the torque required to mix the powder was recorded. As the water was absorbed by the powder, the torque reached a maximum when the powder changed from free-flowing to a paste. The total volume of water added when the maximum torque was reached was then normalized to the amount of water that could be absorbed by 100 g of the powder. Since the powder was used as received (not pre-dried), the free moisture value of the powder was used to calculate the “moisture-corrected water AbC value” by the following equation.

[0092]

[0093] 5 wt% pH

[0094] Weigh out 5.0 g of the sample to the nearest 0.1 g and transfer the weighed sample to a 250 mL beaker to measure the 5% pH. Add 95 mL of DI water and stir the sample for 5 min. Then measure the pH using a pH meter while stirring the sample.

[0095] Pack density and pour density

[0096] The pack density and pour density were measured by placing 20.0 g of the sample into a 250 mL graduated cylinder with a flat rubber bottom. Record the initial volume and calculate the pour density by dividing the weight of the sample used by this volume. Then place the graduated cylinder on a tap density machine and rotate it at the specified RPM on the cam. The cam is designed to raise and lower the graduated cylinder a distance of 5.715 cm per second once until the sample volume is constant, usually for 15 min. Record this final volume and calculate the pack density by dividing the weight of the sample used by this volume.

[0097] Examples

[0098] Comparative Example 1:

[0099] 4000 mL of water and 60.0 g of NexSil 125-40 (80 nm colloidal silica, 40 vol%) were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 98 °C. Approximately 5 mL of 50% sodium hydroxide was added to adjust the pH of the solution to 10.0. Thereafter, sodium silicate (3.3M R 19.5%) was added at 12 mL / min and sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 9.80 - 9.95. After 150 minutes, the silicate flow was stopped and sulfuric acid was added at 2.0 mL / min until a pH of 9.4 was reached. Once the pH of 9.4 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0100] The analysis results are described in Table 1.

[0101] Table 1

[0102] Unit Comparative Example 1 AbC cc / 100g 171.6 BET <![CDATA[m 2 / g]]> 26 CTAB <![CDATA[m 2 / g]]> 25 Packing Density <![CDATA[g / cm 3 > 0.285 Tapped Density <![CDATA[g / cm 3 > 0.218 Average Particle Size μm 14.3 Median Particle Size μm 13.1 <![CDATA[Na2SO4]]> ％ 2.52 <![CDATA[Na2SO4, conductivity]]> μmhos / cm 2000 Oil Absorption Cc / 100g 148 pH 5% 11.0 Average Primary Particle Size nm 50

[0103] Comparative Example 2:

[0104] 4000 mL of water and 60.0 g of NexSil 125-40 (80 nm colloidal silica, 40 vol%) were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 98 °C. Approximately 5 mL of 50% sodium hydroxide was added to adjust the pH of the solution to 10.0. Thereafter, sodium silicate (3.3M R 19.5%) was added at 3 mL / min and sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 9.80 - 9.95. After 600 minutes, the silicate flow was stopped and sulfuric acid was added at 2.0 mL / min until a pH of 9.4 was reached. Once the pH of 9.4 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0105] The analysis results are described in Table 2.

[0106] Table 2

[0107] Unit Comparative Example 2 BET <![CDATA[m 2 / g]]> 16 CTAB <![CDATA[m 2 / g]]> 16 Average Particle Size μm 9.7 Median Particle Size μm 8.9 Oil Absorption Cc / 100g 84 pH 5% 10.9 Average Primary Particle Size nm 140

[0108] Comparative Example 3:

[0109] 4000 mL of water and 60.0 g of NexSil 125-40 (80 nm colloidal silica, 40 vol%) were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 98 °C. Approximately 5 mL of 50% sodium hydroxide was added to adjust the pH of the solution to 10.0. Thereafter, water and sodium silicate (3.3 MR 19.5%) were added at 6 mL / min and 6 mL / min, respectively. Sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 9.80 - 9.95. After 256 minutes, the silicate stream was stopped and sulfuric acid was added at 2.0 mL / min until a pH of 5.7 was reached. Once the pH of 5.7 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0110] The analysis results are described in Table 3.

[0111] Table 3

[0112] Unit Comparative Example 3 AbC 161 BET <![CDATA[m 2 / g]]> 48 CTAB <![CDATA[m 2 / g]]> 42 Packing Density <![CDATA[g / cm 3 > 0.203 Tapped Density <![CDATA[g / cm 3 > 0.096 Average Particle Size μm 7.8 Median Particle Size μm 7.3 <![CDATA[Na2SO4]]> ％ <0.69 <![CDATA[Na2SO4, conductivity]]> μmhos / cm 134 Oil Absorption Cc / 100g 139 pH 5% 7.7 Average Primary Particle Size nm 85

[0113] Inventive Example 1:

[0114] 5508 mL of water, 100.0 g of NexSil 125-40 (80 nm colloidal silica, 40 vol%) and 192.5 g of sodium sulfate were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 95 °C. Sodium silicate (3.3 MR 19.5%) was added at 6 mL / min and sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 9.5 - 9.9. After 180 minutes, the silicate stream was stopped and sulfuric acid was added at 2.0 mL / min until a pH of 5.5 was reached. Once the pH of 5.5 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0115] The analysis results are described in Table 4.

[0116] Table 4

[0117]

[0118]

[0119] Comparative Examples 4 - 5 and Inventive Examples 2 - 3:

[0120] 5508 mL of water, 100.0 g of NexSil 125-40 (80 nm colloidal silica, 40 vol%) and sodium sulfate (see Table 5) were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 95 °C. Sodium silicate (2.5 M R 20.0%) was added at 6 mL / min and sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 9.5 - 9.9. After 120 minutes, the silicate stream was stopped and sulfuric acid was added at 2.0 mL / min until a pH of 5.5 was reached. Once the pH of 5.5 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0121] Table 5

[0122] Example # Sodium Sulfate Added (g) Initial Conductivity (uS / cm2) Comparative Example 4 50 2500 Comparative Example 5 100 4840 Inventive Example 2 150 6240 Inventive Example 3 200 7100

[0123] The analysis results are described in Table 6.

[0124] Table 6

[0125] Unit Comparative Example 4 Comparative Example 5 Inventive Example 2 Inventive Example 3 AbC cc / 100g 75.3 138.8 189.1 237.4 BET <![CDATA[m 2 / g]]> 26 20 18 12 CTAB <![CDATA[m 2 / g]]> 34 46 22 15 Packing Density <![CDATA[g / cm 3 > 0.59 0.32 0.28 0.41 Tapped Density <![CDATA[g / cm 3 > 0.45 0.20 0.18 0.21 Average Particle Size μm 61.2 12.0 11.0 10.7 Median Particle Size μm 42.3 7.7 10.5 10.2 <![CDATA[Na2SO4]]> Wt.-% <0.69 <0.69 <0.69 <0.69 <![CDATA[Na2SO4, conductivity]]> μmhos / cm 291 512 549 41 Oil Absorption Cc / 100g 64 142 193 209 pH 5% 8.3 8.4 6.5 7.9 Average Primary Particle Size nm 105 105 110 120 Average Projected Area of Aggregates <![CDATA[(nm 2 )]]> - - - 213,775

[0126] Inventive Examples 4 - 6:

[0127] 5000 mL of water, NexSil 125-40 (80 nm colloidal silica, 40 vol%) (see Table 7) and 200 g of sodium sulfate were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 95 °C. Sodium silicate (2.5 M R 20.0%) was added at 6 mL / min and sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 9.5 - 9.9. After 120 minutes, the silicate stream was stopped and sulfuric acid was added at 2.0 mL / min until a pH of 5.5 was reached. Once the pH of 5.5 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0128] Table 7

[0129] Inventive Example # NexSil 125 - 40 (80nm Colloidal Silica) Added (g) 4 25 5 50 6 100

[0130] The analysis results are described in Table 8.

[0131] Table 8

[0132] Unit Inventive Example 4 Inventive Example 5 Inventive Example 6 AbC cc / 100g 166.1 185.2 237.4 BET <![CDATA[m 2 / g]]> 9 8 12 CTAB <![CDATA[m 2 / g]]> 16 17 15 Packing Density <![CDATA[g / cm 3 > 0.370 0.384 0.408 Tapped Density <![CDATA[g / cm 3 > 0.250 0.263 0.213 Average Particle Size μm 13.4 13.7 10.7 Median Particle Size μm 12.9 13.3 10.2 <![CDATA[Na2SO4]]> ％ <0.69 <0.69 <0.69 <![CDATA[Na2SO4, conductivity]]> μmhos / cm 31 215 41 Oil Absorption Cc / 100g 161 170 209 pH 5% 7.6 6.8 7.9 Average Primary Particle Size nm 110 140 120 Average Projected Area of Aggregates <![CDATA[(nm 2 )]]> - 407,620 -

[0133] Inventive Examples 7 - 9:

[0134] Water, Silbond VPS XK-NF 60 (60 nm colloidal silica, 20.7% solids), and sodium sulfate (see Table 9) were added to an 8 L reaction vessel and stirred at 350 rpm at a temperature of 95 °C. Sodium silicate (2.5 M R 20.0%) was added at 12 mL / min, and sulfuric acid (17.1%) was added at a rate sufficient to maintain the pH at 8.4 - 8.7. After the time specified in Table 9, the silicate stream was stopped, and sulfuric acid was added at 2.0 mL / min until a pH of 5.5 was reached. Once the pH of 5.5 was reached, the batch was filtered and washed with 4 L of deionized water and dried overnight at 125 °C.

[0135] Table 9

[0136]

[0137] The analysis results are described in Table 10. The chemical and physical properties of 165 and 153 are also provided in the same table.

[0138] Table 10

[0139]

[0140] According to the present invention, the desired compatibility can only be achieved by a reduced BET SA, an increased primary particle size, and an oil absorption range. An extremely high oil absorption value will not provide the desired compatibility because it is technically unlikely to provide a high oil absorption silica with a very low BET SA without increasing the primary particle size of the silica to > 80 nm. The BET SA and the oil absorption value are related and generally run parallel to each other; when one increases, the other also increases. It is not possible to separate these parameters to such an extent by conventional synthesis techniques.

[0141] According to the present invention, the method involves (1) a solution of colloidal silica particles of the correct size (preferably 45 - 85 nm), (2) adding sodium sulfate and water to the solution of colloidal silica primary particles, and (3) carefully adding sodium silicate and sulfuric acid under suitable conditions so that the primary particles grow to > 80 nm. This growth of the primary particles reduces the BET SA and also enhances the primary aggregates in order to provide the particles with structural integrity, thus achieving a sufficient increase in viscosity in toothpaste. This level of aggregate enhancement can be measured by the average projected area of the aggregates, such as in the range of about 189,000 nm 2 to 480,000 nm 2 .

[0142] Example 10: BAC

[0143] BAC titration:

[0144] To determine the capacity of a given silica for quaternary ammonium compounds, ζ-potential titration is carried out. In the titration, a 5 wt% suspension of the required silica is prepared by taking the required amount of dry silica and diluting it to 160 g with deionized water. To obtain as close as possible to the required 5 wt% (8 g) of silica in the 160 g suspension, the amount of as-received silica used is adjusted to compensate for the free moisture present (drying loss) and the amount of sodium sulfate. The suspension is magnetically stirred at 500 rpm for 10 minutes to fully wet the silica, and then the suspension is adjusted to pH ~8.5 with 0.5 M NaOH or 0.5 M HCl to facilitate consistency in the initial surface chemistry and more direct comparison.

[0145] Compared to conventional toothpaste thickening silicas with similar oil absorption (Zeodent 153 and Zeodent 165) or higher oil absorption (Sipernat 50), the silicas of the present invention in Examples 7 and 9 require significantly less BAC (benzalkonium chloride) to cross the "0" saturation point (Table 11, Figure 1 ). This indicates that despite having higher oil absorption and thickening ability, they have better compatibility with cationic surfactants. This is attributed to the aggregation of larger primary particle sizes resulting in a significant reduction in surface area.

[0146] In addition to Invention Examples 7 and 9, the BAC compatibility of Zeodent 153, Zeodent 165, 50 and two other silicas of the present invention (3 and 5) are shown in Table 11 below.

[0147] Table 11

[0148]

[0149] Example 11: Flavor

[0150] Method: Place 500 mg of silica into a headspace vial. Add 10 μl of flavor (lime oil, batch number MKCF9356 flavor matrix), and equilibrate the vial overnight. Incubate the sample at 60 °C for 60 minutes while gently shaking, and then sample the headspace. In a GC / MS equipped with a Stabilwax column (0.25 mm × 60 m), analyze 1 mL of the headspace sample at a column flow rate of 1.606 mL / min and a temperature ramp rate of 6 °C / min in the temperature range of 40 °C to 230 °C (HS sampling: take 1 ml of the headspace sample into a gas-tight syringe at 65 °C). Normalize the peak area relative to the peak intensity of 165.

[0151] The results are shown in Table 12.

[0152] Table 12

[0153]

[0154] The high pore volume silica of the present invention was incorporated into a standard toothpaste formulation to judge their performance in terms of increasing toothpaste viscosity (Table 13).

[0155] Table 13

[0156]

[0157] They were compared with the standard 153 and the viscosity was measured over 9 weeks. The results are shown in Table 14.

[0158] Table 14

[0159]

[0160] Example 12: Free - flowing Food Application

[0161] Loose Bulk Density

[0162] The sample was poured through a funnel into a pre-peeled and weighed 100 ml graduated cylinder until it overflowed. The excess sample was gently scraped off and the weight of the graduated cylinder / sample was determined. The weight of the sample was then divided by its volume to calculate the density. Samples with an increased loose bulk density value generally exhibit improved flow characteristics as the particles are "less sticky" and can pack together more efficiently in a given space.

[0163] Pressure / Thermal / Moisture Caking

[0164] Pressure, heat and moisture caking are tests used to determine the tendency of a powder to agglomerate and form lumps (or cakes) when subjected to pressure, heat and / or moisture from processing, packaging, transportation or storage. 5.0 g of the sample was placed in an aluminum tray and subjected to pre-determined conditions. The resulting cake was then transferred to a 12-mesh sieve and shaken for 1 minute. The remaining cake was then weighed and the percentage of the original 5.0 g sample it represented was recorded.

[0165] Flodex Flowability Index

[0166] Flodex is an instrument designed to evaluate the flow of a powder through an orifice, such as the conditions experienced when a silo is emptied. The orifice size in the instrument is gradually decreased until the powder no longer flows. The smaller the orifice size, the better the flow ability of the powder. The Flodex powder flowability tester is from Teledyne Hansen, Chatsworth, CA.

[0167] The studies conducted were aimed at evaluating the efficacy of the silica of the present invention in delaying caking and how they affect the flow properties of these model systems. Importantly, performance equivalent to that of the standard anti-caking free-flow agent ( 22S) could be maintained, at least. However, it was observed that, similar to 22S, the inventive examples functioned very well in preventing caking in the salt and sweet whey systems. In both food systems, the maximum allowable addition (loading) permitted in food (2%) was used. Clearly, even lower addition levels of the conditioning agent could be used (Tables 15 + 16).

[0168] Table 15

[0169]

[0170] Table 16

[0171]

Claims

1. Precipitated silica, characterized in that The average primary particle size (a) is 80 nm ≤ (a) ≤ 140 nm, the BET surface area (b) is less than 40 m 2 / g, and the oil absorption (c) is 160 cc / 100 g ≤ (c) ≤ 250 cc / 100 g.

2. The precipitated silica according to claim 1, wherein the BET surface area (b) is 8 m 2 / g ≤ (b) ≤ 35 m 2 / g.

3. The precipitated silica according to claim 1, wherein the CTAB surface area of the precipitated silica is less than 40 m 2 / g, preferably less than 35 m 2 / g, more preferably less than 30 m 2 / g.

4. The precipitated silica according to claim 1 or 2, wherein the packing density of the precipitated silica is < 0.32 g / cm 3 , preferably 0.11 - 0.24 g / cm 3 .

5. The precipitated silica according to claim 1, wherein the average primary particle size of the precipitated silica is 100 - 125 nm, the BET surface area is 15 - 30 m 2 / g, the total mercury intrusion volume is 2.5 - 5.3 cc / g, and the oil absorption is 200 - 250 cc / 100 g.

6. The precipitated silica according to claim 1, wherein the average primary particle size (a) of the precipitated silica is 110 nm ≤ (a) ≤ 140 nm, the BET surface area is 10 - 40 m 2 / g, the total mercury intrusion volume is 2.5 - 5.3 cc / g, and the oil absorption is 175 - 250 cc / 100 g.

7. The precipitated silica according to claim 1, wherein the average primary particle size (a) of the precipitated silica is 110 nm ≤ (a) ≤ 140 nm, the BET surface area is 10 - 26 m 2 / g, the total mercury intrusion volume is 2.5 - 5.3 cc / g, and the oil absorption is 175 - 250 cc / 100 g.

8. The precipitated silica according to claim 1, wherein the average primary particle size (a) of the precipitated silica is 85 nm ≤ (a) ≤ 100 nm, the BET surface area is 10 - 35 m 2 / g, the total mercury intrusion volume is 2.5 - 5.3 cc / g, and the oil absorption is 170 - 250 cc / 100 g.

9. Precipitated silica obtained by the following method, the method comprising at least the following steps; (a) Dispersing colloidal seed particles with a primary particle size of 40 - 100 nm, preferably 50 - 80 nm, in water, (b) Based on the total mass of the colloidal seed particles added in step (a), an electrolyte is added at a concentration of 2.5 wt% - 4.0 wt%. (c) The suspension is heated to 65°C - 100°C, preferably 85°C - 95°C. (d) An acid and a silicate are added while maintaining the pH at 7.5 - 10, preferably 8 - 9, for a period of 60 - 180 minutes. (e) The addition of the silicate is stopped. (f) An acid is added until a pH of 3 - 6 is reached. (g) Filtration, drying, and optionally grinding are carried out. Wherein the silica is characterized in that the average primary particle size (a) is 80 nm ≤ (a) ≤ 140 nm, the BET surface area (b) is less than 40 m 2 / g, and the oil absorption (c) is 250 cc / 100 g ≥ (c) ≥ 160 cc / 100 g.

10. The method for preparing precipitated silica according to claim 9, wherein the temperature range in step (a) is 40 - 95°C, preferably 60 - 85°C, more preferably 70 - 80°C.

11. The method for preparing precipitated silica according to claim 9, wherein based on the total volume added in step (a), the colloidal seed particles in step (a) are used in an amount of 0.15 - 5 wt%.

12. The method for preparing precipitated silica according to claim 9, wherein the rate of addition of the silicate in step (d) is 0.5% to 2.2% of the total volume of the silicate added per minute with respect to the total volume of the silicate added.

13. The method for preparing precipitated silica according to claim 9, wherein the alkali metal silicate in step (d) is an alkaline earth metal silicate or an alkali metal silicate, more preferably sodium silicate, and the acid in steps (d) and (f) is preferably sulfuric acid.

14. The method for preparing precipitated silica according to claim 9, wherein the electrolyte in step (b) is an alkali metal salt, preferably sulfates, chlorides, etc. of sodium or potassium.

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

16. An oral care composition comprising the precipitated silica according to claim 1.

17. The oral care composition according to claim 16, which comprises a second precipitated silica, the average primary particle size of the second precipitated silica being greater than 80 nm and the BET surface area being 10 - 40 m 2 / g, the total mercury intrusion volume is 0.75 - 2.00 cc / g, and the oil absorption is 60 - 120 cc / 100 g.

18. The oral care composition according to claim 16, which comprises a second silica having a BET surface area of less than 5 m 2 / g.

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