Peroxide compatible silica

Abstract

The invention relates to peroxide compatible heat-treated precipitated silica and a method of making the same. The invention also relates to the use of peroxide compatible silica in oral care formulations, in particular to improve the whitening performance of the toothpaste by controlling the time of peroxide decomposition in the toothpaste formulation.

Description

[0001] Technical Field of the Invention This invention relates to precipitated silica suitable for whitening oral care formulations and methods for preparing the same, wherein the formulations have peroxide compatibility that improves over time. Background of the Invention I've always wanted to use toothpaste that offers improved whitening performance.

[0003] Bright white teeth and a bright smile are important to many people around the world. For this purpose, combinations of cleaning silica with chemical cleaners have been used to provide whitening; however, these are ineffective if the underlying tooth color is not bright white. Therefore, peroxide-based whitening agents are currently used in formulations to not only clean the teeth but also increase the whiteness of the base teeth.

[0004] Peroxides typically function by forming free radicals as they decompose, and these free radicals are highly effective at removing organic-based stains and whitening teeth as they continue to decompose to form oxygen and water. The timing of peroxide decomposition is important because it needs to occur during brushing, not in the tube before use. If decomposition begins too early in the tube, it can cause the tube to rupture due to excessive pressure from the oxygen formation. Although pyrolytic silica thickeners are used in these oral care preparations to achieve the desired rheological properties, conventional precipitated silica abrasives and thickeners are incompatible with peroxides. When precipitated silica is used, it promotes the decomposition of peroxides shortly after preparation, which often leads to ruptured tubes or loss of active peroxide material. Therefore, calcium pyrophosphate abrasives and stable forms of peroxides are typically used to avoid this decomposition. Calcium pyrophosphate can be expensive, and sodium monofluorophosphate is required as a fluoride source, which is less effective than sodium fluoride in preventing cavities. The desired outcome is the presence of precipitated silica compatible with peroxides, which would allow sodium fluoride to be used to increase caries prevention, enhance formulation flexibility related to cleaning and abrasion, and provide a more palatable taste similar to traditional toothpaste.

[0005] US Patent 2015 / 0209252 A1 discloses a dental cleaning composition comprising a heat-treated precipitated silica (containing cristobalite) for compatibility with peroxides and improved stability, for use as a substitute for calcium pyrophosphate.

[0006] WO 2022 / 101015 A1 patent publication also discloses heat-treated silica for improving compatibility with peroxides. This compatibility has been achieved by reducing the number of OH groups per unit surface area.

[0007] WO 1993 / 023007 A1 discloses dehydroxylated silicone for enhancing oral care compatibility.

[0008] US Patent 2003 / 0124069 A1 discloses a silica / metal phosphate composite material for improving chemical cleaning.

[0009] US Patent 2014 / 271900 A1 discloses a dental cleaning composition comprising a heat-treated precipitated silica, wherein the precipitated silica has a particle size of less than 90 μm. 2 / g of BET SA, which has reduced wear characteristics.

[0010] US Patent 2014 / 127145 A1 discloses a method of subjecting silica particles to temperatures above 800°C. 0 A method to improve the stability of precipitated silica materials by adjusting the temperature (C).

[0011] Although many existing technologies mention compatibility or specific peroxide compatibility, they do not mention using phosphate-containing additives to achieve the peroxide compatibility required in oral care formulations.

[0012] Therefore, the object of the present invention is to provide a novel precipitated silica with specific BET surface area, phosphate content and loss on ignition (LOI) that provides a higher level of compatibility with peroxides under accelerated aging tests compared to existing products on the market.

[0013] Brief Overview of the Invention Because calcium pyrophosphate abrasives are expensive components and primarily require sodium monofluorophosphate as a fluoride source, there is a need to improve upon another abrasive compatible with peroxides. After thorough research, the inventors of this invention surprisingly discovered that abrasive silica as defined in claim 1 solves the aforementioned technical problem because it provides a higher level of peroxide compatibility under accelerated aging tests compared to calcium pyrophosphate.

[0014] The precipitated silica commonly used in dental compositions typically contains trace amounts of metallic impurities, which may be in the form of metal hydroxides / oxides (oxidation promoters) that can react with peroxides in the dental preparation over time, leading to tube rupture.

[0015] Advantageously, the present invention provides a novel heat-treated precipitated silica abrasive having a reduced BET surface area and LOI, and containing a certain amount of phosphate, which is believed to form insoluble metal phosphates under heat treatment, providing a higher level of compatibility with peroxides. Using heat-treated precipitated silica with a lower BET surface area and additional phosphate material reduces the reaction with peroxides over time. It is believed that the addition of phosphate forms metal pyrophosphate complexes on the silica surface with trace metal impurities after the heating step. The resulting impurities will be insoluble and do not react with peroxides, which significantly increases stability during aging at elevated temperatures.

[0016] Therefore, in a first aspect, the present invention relates to precipitated silica abrasives having specified BET surface area, loss on ignition (LOI), and phosphate content as defined in claim 1.

[0017] A second aspect of the present invention is a method for preparing the heat-treated precipitated silica.

[0018] A third aspect of the invention is the use of silica in oral care formulations to improve peroxide compatibility.

[0019] Another aspect of the present invention is an oral care preparation comprising the heat-treated precipitated silica.

[0020] Detailed Description of the Invention This invention relates to the field of peroxide-compatible precipitated silica abrasives, their preparation methods, and applications.

[0021] Several key differences exist between pyrolytic silica and precipitated silica. First, pyrolytic silica has a much higher purity. Precipitated silica can have an iron content ranging from 50 to 400 ppm, which functions in a Fenton-type mechanism to rapidly catalyze the decomposition of peroxides. A second difference is the lower density of silanols (-OH) on pyrolytic silica, a result of synthesis in a flame rather than an aqueous precipitation process. Furthermore, pyrolytic silica primarily functions as a thickener and does not provide any abrasive or cleaning effects. Therefore, precipitated silica is preferred as an abrasive in oral care formulations.

[0022] Preparation of peroxide-compatible silica: Reducing the surface area can be effective in decreasing the total number of -OH groups on precipitated silica. However, simply reducing the surface area has been found to be ineffective in achieving peroxide compatibility. To further reduce the -OH density per unit area, heat treatment or calcination is required. Silica is heated to up to 1000°C. 0Temperature (C) leads to further polymerization of the silica framework and a reduction in Q2 and Q3 silanol groups. Even when calcining low-surface-area silica, compatibility with peroxides increases from hours to days, and sometimes weeks, provided the BET surface area of ​​silica is low enough.

[0023] When examining methods for removing elemental impurities from silica, washing with different acids and chelating agents was attempted. It was found that while acid washing of silica is an effective way to remove metal ion impurities, peroxide compatibility is actually reduced if they are not completely washed away from the silica surface, as metal ions are more readily involved in peroxide decomposition mechanisms. Some benefits were observed when washing with phosphoric acid; however, it was difficult to determine whether all metal ion impurities were washed away from the silica surface, and an improvement in peroxide compatibility was not always observed.

[0024] During further testing to improve the method, it was found that adding a phosphate-containing material with a concentration higher than 200 ppm of a polyphosphate, such as sodium tripolyphosphate (STPP), prior to the calcination (heating) step was sufficient to significantly increase the surface area of ​​low-surface-area silica (BET surface area equal to or less than 20 m²). 2 / g, preferably less than 6m 2 / g, more preferably below 4m 2 The compatibility of polyphosphates with a concentration of 5000 ppm or higher can significantly increase the compatibility of silica with a higher surface area (BET surface area greater than 20 m²). 2 / g, preferably at 20m 2 / g to 100m 2 Compatibility (within the range of / g). Even with no restrictions on the use of high surface area silica in high concentration phosphate-containing materials, it is desirable to use low surface area silica, which requires a smaller amount of phosphate addition for peroxide compatibility.

[0025] Unbound by any particular theory, it is believed that residual phosphates left on the silica surface after calcination appear to passivate metal ion impurities (potentially forming metal pyrophosphates) on the silica surface, preventing them from participating in the peroxide decomposition reaction. Adding phosphates to silica prior to calcination resulted in a significant increase in compatibility with peroxides, with the precipitated silica prototype exceeding the calcium pyrophosphate control by up to 10 times.

[0026] Oral care composition Precipitated silica and / or silicate particles can be used in any suitable composition and for any suitable end-use application. Typically, silica and / or silicate particles are used in oral care applications, such as in dental floss compositions. Dental floss compositions may contain any suitable amount of silica and / or silicate particles, such as about 0.5 to about 50% by weight, about 1 to about 50% by weight, about 5 to about 35% by weight, about 10 to about 40% by weight, or about 10 to about 30% by weight of precipitated silica and / or silicate particles. These weight percentages are based on the total weight of the dental floss composition.

[0027] The dental cleaning composition may be in any suitable form, such as liquid, powder, or paste. In addition to silica and / or silicate particles, the dental cleaning composition may also contain other ingredients or additives, non-limiting examples of which may include humectants, solvents, binders, therapeutic agents, chelating agents, thickeners other than silica and / or silicate particles, surfactants, abrasives other than silica and / or silicate particles, sweeteners, colorants, flavorings, preservatives, etc., and any combination thereof.

[0028] Humectants are used to enhance the texture or "mouth texture" of dental floss and to prevent it from drying out. Suitable humectants include polyethylene glycol (of various molecular weights), propylene glycol, glycerin (glycerol), erythritol, xylitol, sorbitol, mannitol, lactitol, and hydrogenated starch hydrolysates, as well as mixtures thereof. In some formulations, the humectant is present in an amount from about 20% to about 50% by weight, based on the weight of the dental floss composition.

[0029] Solvents may be present in the dental cleaning composition in any suitable amount, and typically the solvent comprises water. When used, the water is preferably deionized and free of impurities, and water may be present in the dental cleaning composition in an amount of 5 to about 70% by weight, or about 5 to about 35% by weight, based on the weight of the dental cleaning composition.

[0030] Therapeutic agents can also be used in the compositions of the present invention to provide, for example, prevention and treatment of dental caries, periodontal disease, and temperature sensitivity. Suitable therapeutic agents may include, but are not limited to, fluoride sources such as sodium fluoride, sodium monofluorophosphate, potassium monofluorophosphate, stannous fluoride, potassium fluoride, sodium fluorosilicate, ammonium fluorosilicate, etc.; condensed phosphates such as tetrasodium pyrophosphate, tetrapotassium pyrophosphate, disodium dihydrogen pyrophosphate, trisodium monohydrogen pyrophosphate; tripolyphosphates, hexametaphosphates, trimetaphosphates, and pyrophosphates; antimicrobial agents such as triclosan; biguanides such as alexicon, chlorhexidine, and chlorhexidine gluconate; enzymes such as papain, bromelain, glucosylamylase, amylase, dextranase, mutanase, lipase, pectinase, tanninase, and protease; quaternary ammonium compounds such as benzalkonium chloride (BZK), benzyl chloride (BZT), cetylpyridine chloride (CPC), and domiphen bromide. bromide; metal salts, such as zinc citrate, zinc chloride, and stannous fluoride; sanguisorba extract and sanguisorbine; volatile oils, such as eucalyptol, menthol, thymol, and methyl salicylate; fluorinated amines; peroxides, etc. Therapeutic agents can be used alone or in combination in dental cleaning formulations at any therapeutically safe and effective level or dose.

[0031] Thickeners can be used in dental cleaning compositions to provide a gel-like structure that stabilizes the toothpaste and prevents phase separation. Suitable thickeners include silica thickeners; starch; starch glycerin; gums, such as gum arabic (Sterculia foetida), gum tragali, gum arabic, gum acacia, xanthan gum, guar gum, and cellulose gum; magnesium aluminum silicate (Veegum); carrageenan; sodium alginate; agar; pectin; gelatin; cellulose compounds, such as cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl cellulose, hydroxymethyl carboxypropyl cellulose, methyl cellulose, ethyl cellulose, and sulfated cellulose; natural and synthetic clays, such as lithium montmorillonite clay; and mixtures thereof. The typical content of a thickener or binder is up to about 15% by weight in the toothpaste or dental cleaning composition.

[0032] Useful silica thickeners for use in toothpaste compositions include, for example, amorphous precipitated silica, such as ZEODENT® 153, 163, 165, 167, 168 and AEROSIL® 200 pharma, which are available from Evonik Corporation as non-limiting examples.

[0033] Abrasive silica used in toothpaste compositions includes, for example, ZEODENT 103, 113, 120, 124, 115, 116, SPHERILEX 145, 148, which are available from Evonik Corporation as non-limiting examples.

[0034] The disclosed abrasive silica and / or silicate particles can be used alone as an abrasive in toothpaste compositions, or as an additive, or as a co-abrasive with other abrasive materials known in the art. Therefore, any number of other conventional types of abrasive additives can be present in the dental cleaning compositions of the present invention. Other such abrasive particles include, for example, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), chalk, bentonite, dicalcium phosphate or its dihydrate form, silica gel (in itself and of any structure), precipitated silica, amorphous precipitated silica (in itself and of any structure), perlite, titanium dioxide, dicalcium phosphate, calcium pyrophosphate, alumina, hydrated alumina, calcined alumina, aluminum silicate, insoluble sodium metaphosphate, insoluble potassium metaphosphate, insoluble magnesium carbonate, zirconium silicate, particulate thermosetting resins, and other suitable abrasive materials. Such materials can be introduced into dental cleaning compositions to tailor the polishing properties of the target formulation.

[0035] Surfactants can be used in the dental cleaning compositions of the present invention to make the compositions more sensorily acceptable. The surfactants are preferably cleaning materials that impart cleaning and foaming properties to the compositions. Suitable surfactants are anionic, cationic, nonionic, amphoteric, amphoteric, and betaine surfactants in safe and effective amounts, such as sodium lauryl sulfate, sodium dodecylbenzene sulfonate, lauroyl sarcosine, myristoyl sarcosine, palmitoyl sarcosine, stearoyl sarcosine, and oleoyl sarcosine in alkali metal or ammonium salts, polyoxyethylene sorbitan monostearate, isostearate, and laurate, sodium lauryl sulfoacetate, sodium, potassium, and ethanolamine salts of N-lauroyl sarcosine, N-lauroyl, N-myristoyl, or N-palmitoyl sarcosine, alkylphenol polyoxyethylene condensates, cocamidopropyl betaine, lauramidopropyl betaine, palmityl betaine, etc. Sodium lauryl sulfate is a preferred surfactant. Surfactants are typically present in the compositions of the invention in amounts of about 0.1 to about 15% by weight, about 0.3 to about 5% by weight, or about 0.3 to about 2.5% by weight.

[0036] Sweeteners can be added to dental cleaning compositions (such as toothpaste) to give the product a pleasant taste. Suitable sweeteners include saccharin (such as sodium, potassium, or calcium saccharin), cyclamate (such as sodium, potassium, or calcium salts), acesulfame K, sematrandole, neohesperidin dihydrochalcone, ammoniated glycyrrhizin, dextrose, levulose, sucrose, mannose, and glucose.

[0037] Colorants can be added to improve the appearance of a product. Suitable colorants include, but are not limited to, those approved by appropriate regulatory agencies such as the FDA and those listed in the EU Food and Drugs Directive, and include pigments such as TiO2, as well as dyes such as FD&C and D&C dyes.

[0038] Flavoring agents can also be added to dental cleaning compositions. Suitable flavoring agents include, but are not limited to, wintergreen oil, peppermint oil, spearmint oil, safrole oil and clove oil, cinnamon, anethole, menthol, thymol, eugenol, eucalyptol, lemon, orange, and other such flavoring compounds to add fruity, spice, and other aromas. These flavoring agents typically include mixtures of aldehydes, ketones, esters, phenols, acids, and aliphatic alcohols, aromatic alcohols, and other alcohols.

[0039] Preservatives can also be added to the compositions of the present invention to prevent bacterial growth. Suitable preservatives approved for use in oral compositions, such as methylparaben, propylparaben, and sodium benzoate, can be added in safe and effective amounts.

[0040] Other ingredients can be used in dental cleaning compositions, such as desensitizers, healing agents, other anti-caries agents, chelating agents / isolation agents, vitamins, amino acids, proteins, other anti-plaque / anti-tartar agents, light-blocking agents, antibiotics, anti-enzyme agents, enzymes, pH control agents, oxidants, antioxidants, etc.

[0041] Implementation Plan Therefore, this invention relates to heat-treated precipitated silica materials, characterized in that: Phosphate content ranging from 1 to 1500 ppm, Loss on ignition less than 1.4% by weight, preferably less than 1.25% by weight, and 20m or less 2 / g BET surface area.

[0042] In one embodiment, the heat-treated precipitated silica material is characterized by: The phosphate content is from 25 ppm to 1500 ppm, preferably from 50 to 1300 ppm. Loss on ignition less than 1.25% by weight, preferably less than 1% by weight. Less than 6m 2 / g, preferably less than 4m 2 / g, more preferably 2-4m 2 / g BET surface area.

[0043] In another embodiment of the invention, the precipitated silica material is characterized by: Phosphate content of 1 to 200 ppm Less than 1.25% by weight of loss on ignition, and Less than 2m 2 / g, preferably less than 1m 2 / g BET surface area.

[0044] In one embodiment of the invention according to any of the foregoing embodiments, the median particle size (D50) of silica is 7 to 15 μm, preferably 8 to 11 μm.

[0045] In one embodiment of the invention according to any of the foregoing aspects / implementations, the oil absorption value of silica is 20 to 80 cc / 100g; preferably 30 to 60 cc / 100g.

[0046] In another aspect of the invention, the precipitated silica material is characterized by: A phosphate content of at least 1500 ppm, preferably 1500 to 2500 ppm, is required. Loss on ignition less than 1.4% by weight, preferably less than 1.25% by weight, and Greater than 20m 2 / g, preferably greater than 20 to 100m 2 / g BET surface area.

[0047] In one embodiment of the invention, the precipitated silica material has, on the other hand, a median particle size (D50) of 10 to 25 μm and an oil absorption value of 100 to 250 cc / 100g.

[0048] In one aspect of the invention, according to the above-defined embodiments, heat-treated precipitated silica is obtained by adding phosphate to an aqueous medium to precipitate silica and then calcining the silica.

[0049] Another aspect of the present invention is a method for preparing heat-treated precipitated silica material, comprising the following steps: a) Provide precipitated silica materials in aqueous media, b) Add phosphate material to the precipitated silica slurry and mix. c) Spray dry the silica to a moisture content of less than 10%, and optionally grind and... d) Calcine silica at a temperature greater than 700°C to reduce LOI to less than 1.4 wt.%.

[0050] In one embodiment of the present invention, the method for preparing the treated precipitated silica material according to the present invention includes the following steps: a) Synthesize silica according to methods known in the art, followed by a washing step to remove sodium sulfate. b) Add an appropriate amount of phosphate to the silica slurry before drying. c) Spray dry the silica to a moisture content of less than 10%, and optionally grind it to a particle size of 3-25 μm. d) Calcine silica at a temperature greater than 700°C to reduce the LOI to less than 1.4% by weight.

[0051] In the first step, it can begin with pre-existing silica that has been wetted (as described in the previous section) and continue with the same steps: adding an appropriate amount of phosphate to the silica slurry, re-drying, and then calcining to achieve the same particle size and LOI range.

[0052] In one embodiment of the present invention, precipitated silica can be obtained by any method known in the art following the steps: a) Provide an alkaline silicate solution containing alkali metal silicates such as sodium silicate and water. b) Add sulfuric acid and alkaline silicate solution together with stirring. c) After precipitation, the precipitated silica is recovered by filtration and washing with salt.

[0053] Another aspect of the invention is a heat-treated precipitated silica material obtained by further adding phosphate according to the method defined above and then calcining.

[0054] In one embodiment of the invention, silica is precipitated by the following steps using methods known in the art, and subsequently treated with phosphate followed by calcination to obtain heat-treated precipitated silica: a) Provide an alkaline silicate solution containing alkali metal silicates such as sodium silicate and water. b) Add sulfuric acid and alkaline silicate solution together with stirring. c) Precipitate silica and filter the precipitated silica, followed by washing with salt. d) Add an appropriate amount of phosphate (e.g., STTP) to the silica slurry before drying. e) Spray dry the silica to a moisture content of less than 10%, and optionally grind it to a particle size of 3-25 μm. f) Calcine silica at a temperature greater than 700°C to reduce the LOI to less than 1.4% by weight.

[0055] In one embodiment of the invention, according to the foregoing embodiment, the phosphate material is added to the mixture at a level higher than 200 ppm; for a BET surface area equal to or less than 20 m² 2 / g of silica, phosphate materials are preferably added to the mixture at a level higher than 200ppm; and for BET surface areas greater than 20m² 2 / g of silica, phosphate materials are added to the mixture at levels higher than 5000ppm, and for BET surface areas less than 1m² 2 / g of silica, without the addition of phosphate.

[0056] In one embodiment of the present invention, according to the aforementioned embodiment, calcination is carried out at a temperature of 700-1000°C for 1-120 minutes, preferably at 825°C for 60 minutes.

[0057] According to the present invention, any type of phosphate material can be used, as long as it is soluble in water. Preferably, the phosphate material is selected from polyphosphates, orthophosphates, or pyrophosphates, such as sodium tripolyphosphate (STTP), tetrasodium pyrophosphate (TSPP), and any mixture thereof. The phosphate material can be selected from metal or organophosphates, hydrogen phosphates, dihydrogen phosphates, or phosphoric acid, and any mixture thereof. The phosphate material can also be selected from polyphosphates, such as sodium polyphosphate, potassium polyphosphate, and sodium hexametaphosphate.

[0058] The amount of phosphate added depends on the surface area of ​​silica, where the BET surface area is equal to or less than 20 m². 2 / g, preferably less than 6m 2 / g, more preferably less than 4m 2 Low surface area silica ( / g) requires low levels of phosphate addition, but BET surface area is greater than 20m². 2 High surface area silica ( / g) requires higher levels of phosphate addition. Therefore, the phosphate level in the final silica product will be at least 25 ppm, preferably 50 ppm, for low BET surface area silica, and at least 1500 ppm for silica with a high BET surface area. For silica with very low surface area, i.e., less than 1 m², further phosphate addition is necessary. 2 For silicon dioxide of / g, phosphate addition is not required.

[0059] In a preferred embodiment of the invention, according to the foregoing embodiments, STPP is preferably used in an amount sufficient to deliver at least 25 ppm, preferably at least 50 ppm, of elemental P in the final silica product, wherein the BET surface area is equal to or less than 20 m². 2 / g, preferably less than 6m 2 / g; and preferably STPP is used in an amount sufficient to deliver 0 to 200 ppm of elemental P in the final silica product, wherein the BET surface area is less than 2m². 2 / g, preferably less than 1m 2 / g.

[0060] In a preferred embodiment, according to the aforementioned embodiments, the final amount of elemental phosphate in the silica product is 0-1500 ppm, more preferably 25-1500 ppm, and even more preferably 50-1300 ppm, wherein the BET surface area is equal to or less than 20 m². 2 / g, preferably less than 6m 2 / g.

[0061] In a preferred embodiment of the invention, according to the foregoing embodiments, STPP is preferably used in an amount sufficient to deliver at least 1500 ppm, preferably 1500-2500 ppm, of elemental P in the final silica product, wherein the BET surface area is greater than 20 m². 2 / g.

[0062] Another aspect of the present invention is the use of precipitated silica materials according to the present invention in oral care compositions.

[0063] In one embodiment of the invention, the precipitated silica material given in the above embodiments or the precipitated silica material treated according to the given method (phosphate treatment followed by calcination) is used in an oral care composition, wherein the oral care composition is a toothpaste formulation containing a peroxide-releasing compound.

[0064] In one embodiment of the invention, the oral care composition comprises 3 to 35% by weight of precipitated silica treated according to the above embodiments.

[0065] In one embodiment of the invention, the oral care composition may include additional abrasive precipitated silica, solvents, thickeners such as pyrolytic silica thickeners, therapeutic agents, surfactants, sweeteners, colorants, fluoride sources, and / or other ingredients such as desensitizers, healing agents, other caries prevention agents, chelating / isolating agents, vitamins, amino acids, proteins, other anti-plaque / anti-tartar agents, opacifiers, antibiotics, anti-enzyme agents, enzymes, pH control agents, oxidants, antioxidants, etc.

[0066] In another embodiment, the oral care composition is a toothpaste formulation having tube stability at 60°C for at least about 5 days, preferably at least 14 days or more.

[0067] Although the invention has been described according to preferred embodiments thereof, it is known that the invention can be practiced by modifications within the scope of the claims.

[0068] Experimental Section The present invention will be further described in detail below with reference to embodiments and comparative embodiments, but is not intended to limit the scope of the invention.

[0069] abbreviation LOI: Loss on Ignition STPP: Sodium tripolyphosphate MR: Molar ratio Methods for determining the properties of silicon dioxide The BET surface area disclosed herein was determined on a Micromeritics TriStar II 3020 V1.03 using the BET nitrogen adsorption method of Brunaur et al. (J. Am. Chem. Soc., 60, 309 (1938)), and this technique is well known to those skilled in the art.

[0070] The D50 median particle size refers to the particle size at which 50% of the samples have smaller sizes and 50% have larger sizes. The median particle size (d50), average particle size (mean), and d95 were determined using laser diffraction on a Horiba LA 300 instrument. Dried particles were fed into the instrument for analysis.

[0071] The oil absorption value (oil absorbed in cc per 100g of particles) is determined using the rub-out method described in ASTM D281 using linseed oil. Generally, a higher oil absorption level indicates that the particles have a higher level of macroporosity, also described as a higher structure.

[0072] The concentration of phosphate on silica was determined by ICP analysis, which directly determined the phosphorus content based on the polyphosphate content. The P% (phosphorus concentration) was determined as follows: 2.0000 g of silica was moistened with a few drops of deionized water in a platinum crucible. 10 ml of perchloric acid (72%) and 10 ml of hydrofluoric acid (48-50%) were added, and the platinum dish was slowly heated on a stirring plate in a fume hood. As the platinum dish was heated, dense white fumes were produced. The sides of the crucible were then carefully rinsed with boric acid (4%) and heated until fuming. After cooling, the contents of the crucible were transferred to a 250 ml volumetric flask, and the crucible was washed with deionized water to ensure that all remaining contents were quantitatively transferred. The dish was then rinsed with 5 ml of hydrochloric acid (36%), and the washings were added to the volumetric flask. Approximately 200 ml of deionized water was added to the volumetric flask, and if the resulting solution was turbid, it was heated on a low-temperature hot plate until it became clear. After cooling, add 2.50 ml of scandium internal standard solution, and fill the volumetric flask to the mark with deionized water. Then determine the concentration of the metal in the solution by ICP / OES.

[0073] The percentages of silica (%), LOI (Lower Ignorance), and moisture (Lower Ignorance) were determined by recording the weight of a clean, dry platinum dish (Weight 1). Approximately 1 g of silica was added, and the weight of the silica and the platinum dish was recorded to four decimal places (Weight 2). The platinum dish was heated to 105°C for 2 hours. It was cooled and weighed to four decimal places (Weight 3). The platinum dish was heated to 1000°C in a muffle furnace for 2 hours. It was cooled in a desiccator, and the weight after ignition was recorded to four decimal places (Weight 4). The sample was then moistened with a few drops of deionized water, 6 drops of sulfuric acid, and approximately 10 mL of hydrofluoric acid. It was heated to dryness on a hot plate in a fume hood. The platinum dish was then placed in a muffle furnace and heated at 1000°C for 1 hour. It was cooled in a desiccator, and its weight was recorded to four decimal places (Weight 5). The moisture percentage and LOI percentage could be calculated as follows: Moisture % = (weight 3)(100) / (weight 2 - weight 1) LOI% = (weight 4)(100) / weight 3 - weight 1).

[0074] The percentage of silica can be determined by assessing the apparent silica loss: Apparent silica loss % = weight 4 - weight 5. Since the addition of sulfuric acid converts sodium ions interacting with the silica surface into sodium sulfate, increasing the sample weight, the apparent silica loss must be corrected for. pH and conductivity were determined by measuring a 5% silica slurry.

[0075] Example Group 1: Comparison of the low surface area silica of the present invention (silica added with phosphate and calcined) with an untreated control example in toothpaste formulations. Low surface area silica can be produced by many methods in the art; however, the ability to produce low surface area spherical materials with controlled particle size distribution is desirable. Therefore, specific methods for producing low surface area precipitated silica are described below in Examples 1 and 4. Commercially available silica is also treated with phosphate and followed by a calcination step, as shown in Example 4.

[0076] This invention is not limited to any particular precipitated silica. The following methods for preparing precipitated silica are given as examples of preparing low surface area silica and do not constitute any limitation on the invention. Many other commercially available low surface area silicas can be used with phosphate and calcination treatments. ZEODENT® 103, 120, or 124 will have too strong an abrasive effect due to their density and particle shape after the calcination step. Therefore, low surface area silica is obtained according to the preparation method described below.

[0077] Preparation of precipitated silica in Example 1 Initial setup / pretreatment steps (applied to silica, such as ZEODENT 103 (described below), where...) Control milleclipse The reduced BET SA is obtained prior to phosphate treatment and / or calcination steps. Before introducing the acid and silicates into the system, precipitated silica, sodium sulfate, sodium silicate, and water can be added and circulated at 80 L / min. This step is performed to fill the circulation loop with approximately the contents and concentration of a typical batch, minimizing washing time before the desired product can be collected. This step is used to avoid the possibility of gel formation in the reactor. There are no restrictions; the acid and silicates can be added directly to the water-filled loop without gelling or clogging the system.

[0078] 1.5 kg of Zeodent® 103 (from Evonik Corporation), 1.34 kg of sodium sulfate, 11.1 L of sodium silicate (3.3 MR, 19.5%), and 20 L of water were added to the circulation loop and heated to 90 °C at a circulation rate of 60 L / min, with the Silverson operating at 30 Hz (1742 RPM), where the stator screen was removed. Sodium silicate (3.3 MR, 19.5%) and sulfuric acid (17.1%) were added to the loop simultaneously at a silicate rate of 1.7 L / min and an acid rate sufficient to maintain a pH of 7.5. If necessary, the acid rate was adjusted accordingly to maintain the pH. The addition of acid and silicate under these conditions was carried out over 40 minutes to remove unwanted silica from the system before the desired material was collected. After 40 minutes, the collection container was emptied and its contents discarded. The silica product was then collected in a container stirred at 40 RPM while maintaining the temperature at approximately 80 °C. After collecting the required amount of product (700 L), stop adding acid and silicate and circulate the contents of the loop.

[0079] The silica product in the collection container was transferred to a batch reactor and heated to 95°C with stirring at 80 RPM. Sodium silicate (3.3 MR, 19.5%) was added to the reactor until the pH reached 9.5 (+ / - 0.2). Once pH 9.5 (+ / - 0.2) was reached, sodium silicate (3.32 MR, 20.0%) and sulfuric acid (17.1%) were added at rates of 1.66 L / min and 0.80 L / min, respectively. If necessary, the acid rate was adjusted to maintain pH 9.5 (+ / - 0.2). After a total time of 60 minutes, the flow of sodium silicate was stopped, and the pH was adjusted to 7.0 by continuing to add sulfuric acid (17.1%) at 0.81 L / min. The batch was digested at pH 7.0 for 15 minutes, then filtered and washed until the conductivity was <1500 μS. Before drying, the pH of the silica slurry is adjusted to 5.0 with sulfuric acid and then spray-dried to the target moisture content of 5.0%.

[0080] The sample was then treated with phosphate and subsequently calcined according to the conditions given in Table 2 below, as described below.

[0081] Example 7 of the present invention: SPHERILEX® 145 from Evonik Corporation is processed according to the conditions in Table 2 below, without any pretreatment steps.

[0082] Phosphate treatment steps: The precipitated silica prepared in Example 1 was treated with a phosphate additive (acid or salt). 250 g of precipitated silica was added to 1 L of deionized water. Phosphate (STTP) was added at a concentration higher than 200 ppm to achieve an elemental phosphate content in the final silica product ranging from 0 to 1500 ppm, and the solution was mixed for 30 minutes. After mixing for 30 minutes, the silica was dried overnight at 105°C.

[0083] Calcination steps: Place 250g of phosphate-treated silica in a crucible (container) and heat at 825°C for 60 minutes. After the 60-minute heating time, allow the silica to cool slowly to room temperature.

[0084] The calcined and phosphate-treated silica samples were formulated into toothpaste preparations, filled into tubes, and aged at 60°C. The tubes were checked daily to observe for any signs of failure.

[0085] Calcination can be applied by heating in a furnace, and there are no restrictions on applying other calcination methods such as spray calcination.

[0086] Toothpaste preparations: Toothpaste formulations, such as those described in detail in US 10,363,210 B2, were used. Examples of the present invention, heat-treated silica, were added to toothpaste formulations in place of calcium pyrophosphate as an abrasive, and peroxide compatibility was tested.

[0087] Table 1: Toothpaste formulations of comparative examples and examples of the present invention

[0088] Peroxide compatibility test: To test the compatibility of silica materials with peroxides, toothpaste formulations (as shown in Table 1) were prepared, placed in toothpaste tubes, and sealed for aging at 60°C. The tubes were observed daily, and the failure time was determined when the tube broke and toothpaste began to leak from its seam. Failure was reported as soon as signs of tube failure appeared. The calcium pyrophosphate control formulation (Formulation A) typically failed between 14 and 21 days. For the experimental silica used in Formulations B or C, ideally, its stability should be comparable to, and even more ideally, superior to, that of the calcium pyrophosphate abrasive in Formulation A.

[0089] The following examples of precipitated silica (1A to 1E) were prepared according to the present invention (phosphate addition and calcination) and used in toothpaste formulation B shown in Table 1. Examples 1A to 1E were prepared by adding phosphate before the calcination step (as explained in the phosphate treatment and calcination steps above), 1F (comparative) was prepared by phosphate treatment but without a calcination step, and 1H (comparative) was prepared by adding phosphate after the calcination step, and no phosphate addition or calcination step was applied to Example 1G (comparative).

[0090] Example 7A (of the present invention) relates to a Spherilex 145 sample, which was directly treated with phosphate and then calcined, as described above.

[0091] The last two examples relate to comparative example formulations containing calcium pyrophosphate and prepared according to comparative formulation A and formulation B of the present invention as given in Table 1 above.

[0092] Table 2: Peroxide compatibility test results

[0093] Table 3: Physical and chemical characterization of the silica of the present invention and / or comparative silica used in toothpaste formulations

[0094] As is evident from Table 2, adding phosphate (e.g., STPP) before the calcination step results in increased peroxide compatibility compared to formulations containing calcium pyrophosphate as an abrasive component in toothpaste formulations or to formulations in which phosphate is added to precipitated silica after calcination (1H). Adding STPP after the calcination step, whether in calcined silica or directly in uncalcined toothpaste formulations, results in toothpaste that is incompatible with peroxides because the tubes rupture before the end of day 1 (1F-G).

[0095] Furthermore, it is evident from Table 3 that, as we see in Examples 1A to 1E, the amount of phosphate in the resulting silica also influences the improvement of compatibility. At 600 Silica materials that are compatible with peroxides for 14 days or more under C conditions can be considered effective examples of silica. Since the failure time of toothpaste tubes increased to 91 days compared to 21-25 days for formulations containing calcium pyrophosphate abrasives as a comparative example, the increased phosphate content contributes to a significant increase in compatibility (as seen in Examples 1C to 1E).

[0096] Example 7 shows that when commercially available SPHERILEX® 145 is treated with phosphate and calcined at 825°C, the peroxide compatibility can be improved to up to 42 days when the BET surface area is 19.

[0097] Example Group 2: Comparison of the high surface area silica of the present invention (treated ZEODENT® 113 and ZEODENT® 165 examples) with untreated control examples in toothpaste formulations Examples 2A-C: ZEODENT®113 from Evonik Corporation was treated in the following experiments.

[0098] Examples 3A-B: ZEODENT®165 from Evonik Corporation was treated in the following experiments.

[0099] Samples 2B, 2C and 3B were mixed with STPP by phosphate treatment according to the procedures described in Examples 1 and 7, then calcined and formulated into toothpaste formulations B or C according to Table 1.

[0100] Table 4: Peroxide compatibility test results of Examples 2B, 2C, and 3B of the present invention compared with control Examples 2A and 3A

[0101] Table 5: Physical and chemical characterization of Examples 2 and 3 of the present invention

[0102] As is evident from Table 4, adding phosphate (e.g., STPP) before the calcination step resulted in increased peroxide compatibility compared to the examples where no phosphate was added prior to calcination (Examples 2A, 3A) (Examples 2B, 2C, and 3B). As is evident from Table 5, a higher amount of phosphate is required as the BET surface area of ​​silica increases. Therefore, high-BET SA silica requires 1500 ppm or more of phosphate to achieve the desired compatibility, i.e., at least 14 days of compatibility. Furthermore, the best results were observed in Example 3B, which used ZEODENT® 165 and added phosphate prior to calcination, compared to the calcium pyrophosphate control example and also to other examples using ZEODENT® 113.

[0103] Conversely, Tables 4 and 5 above show that higher surface area silica requires more phosphate addition and does not provide the same compatibility improvements observed with lower surface area silica (see Examples 1 and 4). However, the calcium pyrophosphate control showed an improvement in compatibility up to the 14-21 day range. Since calcium pyrophosphate is currently used as an abrasive in peroxide-containing formulations, it remains necessary to achieve performance comparable to higher surface area silica. Lower surface area silica is required to achieve the highest level of compatibility.

[0104] Example Group 3: Comparison of treated and untreated examples of Tixosil 63 & 73 (from prior art WO 2022 / 101015 A1) with control examples in toothpaste formulations. Comparative examples showing the effect of burn-off on compatibility The embodiments disclosed in prior art WO 2022 / 101015 A1 (heat-treated silica with a reduced number of OH groups per unit surface area) are used in the following set of embodiments 3 to demonstrate that exemplary high BET SA embodiments in the prior art do not provide the desired compatibility even with phosphate treatment and / or calcination.

[0105] Tixosil 63 (Example 1 of WO 2022 / 101015 A1) and Tixosil 73 (WO 2022 / 101015 A1) Unprocessed embodiment of embodiment 2) Examples 1A, 1B - Tixosil 63 prepared according to Rhodia patent application (WO 2022 / 101015 A1) Examples 2A and 2B - Tixosil 73 was also prepared according to Rhodia patent application (WO 2022 / 101015 A1). Examples of Tixosil 63 and 73 processed Example 4A - Tixosil 63 was treated with STPP and calcined at 600°C according to the method described in Example 1 of the present invention.

[0106] Example 5A - Tixosil 73 was treated with STPP and calcined at 600°C according to the method described in Example 1 of the present invention.

[0107] Table 6: Peroxide compatibility test results of Tixosil 63 and Tixosil 73 examples

[0108] Table 7: Physical and chemical characterization of Tixosil 63 and Tixosil 73 examples with high surface area

[0109] As can be seen from Table 6, the heat-treated examples of Tixosil 63 and Tixosil 73 (with higher surface areas) from prior art WO 2022 / 101015 A1 did not provide improved peroxide compatibility, even though they were treated with phosphate and / or calcined at higher temperatures than described in the application. For 25-35m 2 The BET surface area value in the range of / g requires additional phosphate and calcination at temperatures above 600°C to reduce the LOI value and improve compatibility to the range of the calcium pyrophosphate control.

[0110] When the physical and chemical characterizations of the Tixosil 63 and Tixosil 73 embodiments are compared with those of the embodiments of the present invention, it can be understood that, in order to improve peroxide compatibility, a lower surface area requires less P from phosphate-containing additives to be present on the silica surface prior to the heat treatment step (calcination).

[0111] Example Group 4: Comparison of the silica of the present invention (in which the silica is added with phosphate and calcined) having a very low surface area in toothpaste formulations with an untreated control example. Preparation of silicon dioxide in Example 6 of the present invention Initial setup (same as in Example 1 of the present invention, involving silicon dioxide) Before introducing the acid and silicates into the system, precipitated silica, sodium sulfate, sodium silicate, and water can be added and circulated at 80 L / min. This step is performed to fill the circulation loop with approximately the contents and concentration of a typical batch, minimizing washing time before the desired product can be collected. This step is used to avoid the possibility of gel formation in the reactor. There are no restrictions; the acid and silicates can be added directly to the water-filled loop without gelling or clogging the system.

[0112] 1.5 kg of Zeodent® 103 (from Evonik Corporation), 1.34 kg of sodium sulfate, 11.1 L of sodium silicate (3.3 MR, 19.5%), and 20 L of water were added to the circulation loop and heated to 90 °C at a circulation rate of 180 L / min, with the Silverson operating at 60 Hz (3480 RPM), where the stator screen was removed. Sodium silicate (3.3 MR, 26.0%) and sulfuric acid (22.8%) were added to the loop simultaneously at a silicate rate of 2.0 L / min and an acid rate sufficient to maintain a pH of 7.5. If necessary, the acid rate was adjusted accordingly to maintain the pH. The acid and silicate were added under these conditions for 40 minutes to remove unwanted silica from the system before collecting the desired material. After 40 minutes, the collection container was emptied and its contents discarded. The silica product was then collected in a container stirred at 40 RPM while maintaining the temperature at approximately 80 °C. After collecting the required amount of product (500 L), stop adding acid and silicate and allow the contents of the loop to circulate.

[0113] The silica product in the collection container was transferred to a batch reactor and heated to 95°C with stirring at 80 RPM. Sodium silicate (3.3 MR, 19.5%) was added to the reactor until the pH reached 9.5 (+ / - 0.2). Once pH 9.5 (+ / - 0.2) was reached, sodium silicate (3.32 MR, 26.0%) and sulfuric acid (22.8%) were added at rates of 1.66 L / min and 0.80 L / min, respectively. If necessary, the acid rate was adjusted to maintain pH 9.5 (+ / - 0.2). After a total time of 60 minutes, the flow of sodium silicate was stopped, and the pH was adjusted to 7.0 by continuing to add sulfuric acid (22.8%) at 0.80 L / min. The batch was aged at pH 6.0 for 10 minutes, then filtered and washed until the conductivity was <1500 μS. Before drying, the pH of the silica slurry is adjusted to 5.0 with sulfuric acid and then spray-dried to the target moisture content of 5.0%.

[0114] The sample was then treated with phosphate as in Example 1 above, followed by calcination. Treatment conditions The components and test results are provided in Table 8 below.

[0115] Comparative Example 8 The silicon dioxide from Example 6 of the present invention was treated under different conditions as shown in the table below.

[0116] Table 8: Peroxide compatibility test results for Examples 6, 7 and 8

[0117] Table 9: Physical and chemical characterization of Examples 6, 7 and 8

[0118] Examples 6A-D show that even when using BET SA<1m 2 / g of silica still requires calcination. Calcination of silica helps to bind metal ion impurities more tightly to the silica surface, even in the absence of phosphate. This is evident in the improved compatibility between Example 6D (uncalcined for 1 day) and Example 6A (calcined for 29 days). When phosphate is added to silica before calcination, a significant improvement in peroxide compatibility is observed, as shown in Examples 6B and 6C. Example 8 demonstrates that heat treatment at 600°C and lower is insufficient to improve peroxide compatibility, even when the BET surface area of ​​silica is less than 5m². 2 / g, regardless of the presence of phosphate. This means: very low surface area (less than 1m²). 2 / g), no phosphate is needed to achieve greater compatibility than calcium pyrophosphate. However, when phosphate is added to these very low-SA materials, compatibility of up to 120 days can be achieved.

[0119] Example Group 5 Cleaning and Abrasion Properties in Toothpaste Formulations To verify that the silica of the present invention has acceptable cleaning and abrasion properties in toothpaste, the silica of Example 6C was used in a toothpaste formulation and tested with PCR (Pellicle Cleaning Ratio) and RDA (Relative Dentin Abrasion) at Indiana University School of Dentistry.

[0120] Relative dentin wear (RDA) The RDA values ​​of the dental cleaning compositions of Examples 9A-9C were determined according to the methods proposed by Hefferen (Journal of Dental Res., July-August 1976, 55(4), pp. 563-573) and described in Watson’s U.S. Patents 4,340,583, 4,420,312 and 4,421,527, the contents of which are incorporated herein by reference in their entirety.

[0121] Biofilm cleanliness ratio (PCR) The cleaning performance of the dental cleaning compositions of Examples 9A-9C is expressed as a biofilm removal ratio (“PCR”) value. The PCR test measures the ability of the dental cleaning compositions to remove biofilm from teeth under fixed brushing conditions. The PCR test is described in “In Vitro Removal of Stain with Dentifrice” by GKStookey 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 in the dental cleaning composition. PCR and RDA values ​​are unitless, and the toothpaste formulations are shown in Table 10.

[0122] Table 10 Toothpaste formulations used for PCR / RDA testing

[0123] The PCR value of formulation 9B was observed to be higher than that of ZEODENT shown in Example 9A. ® The control formulation 103 was approximately 20 units higher. At a loading level of only 10%, Example 9C showed a similar level of cleanliness to Control Example 9A, indicating excellent cleaning performance. The RDA values ​​of Examples 9B and 9C of the present invention are similar to the ZEODENT of 9A. ® A level of 103 or lower than the control formulation indicates an acceptable level of wear.

[0124] Overall Assessment It has been found that reduced LOI, lower BET SA, and the presence of phosphate allow for improved compatibility with peroxides. The lower surface area requires less phosphorus from phosphate-containing additives to be present on the silica surface prior to the heat treatment step (calcination) to improve compatibility. Silica with a surface area value of less than 1 m²... 2 At a concentration of / g, it was found that phosphate was not needed prior to the calcination step to improve compatibility with peroxides. However, even with these very low BET SA silicas and the addition of phosphate, compatibility up to 120 days could be achieved.

[0125] Regardless of surface area, a calcination step is required to improve peroxide compatibility, which leads to a decrease in the LOI value of silica. Without being bound by any particular theory, it is believed that heat treatment causes all impurities found on the silica surface to transform into less soluble forms, making divalent and trivalent ions less likely to decompose peroxides. Therefore, it also reduces the -OH density on the silica surface.

[0126] It is unclear at this point whether the decrease in -OH density is necessary, but it occurs as a result of the heat treatment step. Equally crucial is the presence of P on the silica surface. P may form metal pyrophosphate substances on the silica surface, which further prevents metal ion impurities from participating in Fenton-type reactions to decompose the peroxide and essentially passivates the silica surface with a peroxide protective layer, thereby increasing peroxide compatibility.

Claims

1. A heat-treated precipitated silica material, characterized in that: The phosphate content is 25 to 1500 ppm, preferably 50 to 1300 ppm. Loss on ignition less than 1.4% by weight, preferably less than 1.25% by weight, and 20m or less 2 / g, preferably less than 6m 2 / g, more preferably less than 4m 2 / g BET surface area.

2. The heat-treated precipitated silica material according to claim 1, characterized in that: The phosphate content ranges from 25 to 200 ppm. Less than 1.25% by weight of loss on ignition, and Less than 2m 2 / g, preferably less than 1m 2 / g BET surface area.

3. The heat-treated precipitated silica material according to any one of the preceding claims, wherein: The median particle size (D50) is 7 to 15 μm, preferably 8 to 11 μm.

4. The heat-treated precipitated silica material according to any one of the preceding claims, wherein... Oil absorption value is 20-80cc / 100g; preferably 30-60cc / 100g.

5. A heat-treated precipitated silica material, characterized in that: A phosphate content of at least 1500 ppm, preferably 1500 to 2500 ppm, is required. Loss on ignition less than 1.4% by weight, preferably less than 1.25% by weight, and Greater than 20m 2 / g, preferably greater than 20m 2 / g to 100m 2 / g BET surface area.

6. The heat-treated precipitated silica material according to claim 5, wherein: The median particle size (D50) is between 10 μm and 25 μm.

7. The heat-treated precipitated silica material according to claim 5 or 6, wherein... The oil absorption value is in the range of 100-250cc / 100g.

8. The heat-treated precipitated silica according to claims 1 to 7, wherein the silica is obtained by adding phosphate to an aqueous medium to precipitate the silica and then calcining the silica.

9. A method for preparing heat-treated precipitated silica material according to claims 1-8, comprising the following steps: a) Provide precipitated silica materials in aqueous media, b) Add the phosphate material to the precipitated silica slurry and mix it. c) Spray-dry the silica to a moisture content of less than 10% and optionally grind it. d) Calcine the silica at a temperature greater than 700°C to reduce the LOI to less than 1.4 wt.%.

10. The method for preparing heat-treated precipitated silica according to claim 9 may further include the following steps: a) Provide an alkaline silicate solution containing alkali metal silicates such as sodium silicate and water. b) Add sulfuric acid and alkaline silicate solution together with stirring. c) Precipitate the silica and filter the precipitated silica, then wash with salt. d) Add an appropriate amount of phosphate to the silica slurry before drying. e) Spray-dry the silica to a moisture content of less than 10%, and optionally grind and... f) Calcine the silica at a temperature greater than 700°C to reduce the LOI to less than 1.4% by weight.

11. The method for preparing heat-treated precipitated silica according to claim 9 or 10, wherein for a BET surface area equal to or less than 20 m² 2 / g silica, with phosphate materials added to the mixture at a level higher than 200ppm; or for BET surface areas greater than 20m² 2 / g of silica, phosphate materials were added to the mixture at a level higher than 5000ppm.

12. The method for preparing heat-treated precipitated silica according to claims 9 to 11, wherein... The calcination is carried out at a temperature of 700 to 1000°C for 1 to 120 minutes, preferably at 825°C for 60 minutes.

13. The method for preparing precipitated silica materials according to claims 9 to 12, wherein the additional phosphate material is selected from polyphosphates, orthophosphates, or pyrophosphates, such as sodium tripolyphosphate (STTP), tetrasodium pyrophosphate (TSPP), and any mixture thereof.

14. Use of the precipitated silica material according to any one of claims 1 to 8 in an oral care composition, wherein the oral care composition is a toothpaste formulation comprising a peroxide-releasing compound and optionally present abrasive silica, a pyrolytic silica thickener, and / or a fluoride source.

15. An oral care composition comprising heat-treated precipitated silica according to claims 1 to 8, wherein the composition comprises 3-35% silica by weight of the total composition.

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