Patent EA-000508-B1 (EA)
Title: Silica capable of being used in toothpaste compositions
Inventor: AMICHE FREDERIC
IPC: A61K8/66
Filed: 1997-06-04
Abstract: 1. An abrasive precipitation silica having: a BET specific surface ranging from 15 to 300 m<2>g, preferably from 20 to 250 m<2>g; a DOP oil absorption ranging from 40 to 160 ml/g, preferably from 50 to 140 ml/g; a median particle diameter of at least 10 μm, generally ranging from 12 to 30 μm; a particle cohesion factor of at least 85 % about for a median particle diameter ranging from 12 to 20 μm. 2. Silica as claimed in Claim 1, characterized in that having a CTAB specific surface ranging from 10 to 120 m<2>/g, preferably from 15 to 100 m2/g. 3. A method for preparing silica by reacting an alkaline metal silicate M with ratio SiO2/M2O ranging from 2 to 4, preferably from 3 to 3,8 with an acidifying agent, to form a silica slurry, separating and optionally drying the recuperated silica suspension and optionally grinding, characterized in that the operation for forming the slurry being effected according to the following steps: - a first step consisting in using one initial heel solution constituted of water, an electrolyte salt of the alkaline or alkaline-earth metal group and optionally of one acidobasic agent at temperature ranging from 70 to 98 degree C, preferably from 80 to 95 degree C, while the quantity of the present electrolyte ranges from 0,1 to 1 of alkaline metal salt or ranges from 10 to 100 mmole of alkaline-earth metal per litre of initial heel solution; - a second step consisting in introducing in said initial heel solution an aqueous solution of the alkaline metal and the acidifying agent at such conditions that the reaction medium pH remaining constant from 4 to 7, preferably from 5,5 to 7 and particularly from 5.8 to 6.7, wherein said reagents are introduced to obtain the required silica concentration in said reaction medium and the reaction medium is maintained at temperature ranging from 70 to 98 degree C, preferably from 80 to 95 degree C; - and, a third optional step, consisting in acidifying the reaction medium until a silica slurry with a pH of less than 6, preferably less 5 and particularly of 4 is obtained. 4. A method as claimed in Claim 3, characterized in that the alkaline metal silicate is sodium or potassium silicate. 5. A method as claimed in Claim 3 or 4, characterized in that the alkaline metal silicate is sodium silicate used in the form of aqueous solution, having the concentration regarding SiO2 from 150 to 400 g/l, preferably from 200 to 400 g/l. 6. A method as claimed in any one of Claims 3-5, characterized in that the acidifying agent is mineral or organic acid. 7. A method as claimed in Claim 6, characterized in that the acidifying agent is sulfuric acid, nitric acid, hydrochloric acid, acetic acid, formic acid or carbonic acid. 8. A method as claimed in Claim 7, characterized in that the acidifying agent is sulfuric acid, used in the form of an aqueous solution, having concentration of from 60 to 400 g/l. 9. A method as claimed in any one of the preceding Claims 3-8, characterized in that electrolyte is a salt of initial metal silicate and the acidifying agent, preferably sodium sulfate. 10. A method as claimed in any one of the preceding Claims 3-9, characterized in that the acidobasic agent is acid phosphate of the alkaline metal. 11. A method as claimed in any one of the preceding Claims 3-10, characterized in that the second step consisting in adding to the initial heel solution, maintained by agitation, silicate solution and acidifying agent simultaneously, wherein the respective quantities of the alkaline metal silicate and the acidifying agent are chosen so as to maintain reaction medium pH to remain constant from 4 to 7, preferably from 5.5 to 7 and particularly from 5.8 to 6.7 during introduction of two reagents. 12. A method as claimed in any one of the preceding Claims 3-11, characterized in that the third step consisting in adding the acidifying agent in the reaction medium during agitation to obtain a pH of less than 6, preferably less 5 and particularly of 4. 13. A method as claimed in any one of the preceding Claims 3-12, characterized in that the medium, obtained at the end of the second step after stopping the introduction of the silicate solution is left to age during at least 10 minutes, preferably from 10 minutes to 2 hours. 14. A method as claimed in any one of the preceding Claims 3-13, characterized in that at the end of the third step after stopping the introduction of the acidifying agent the reaction medium is left to age during the time from 10 minutes to 2 hours. 15. A method as claimed in any one of the preceding Claims 3-14, characterized in that during formation of the silica slurry the temperature ranges from 70 to 98 degree C, preferably from 80 to 95 degree C. 16. Use of silica as claimed in Claim 1 or 2, obtained according to any 3-15 Claims as an abrasive agent in toothpaste compositions. 17. A toothpaste composition, comprising 5-50% silica, described in Claim 1 or 2, or obtained according to any one of the preceding Claims 3-15. 18. A toothpaste composition as claimed in Claim 17, characterized in that further comprising at least one ordinary ingredient, chosen between other abrasive agents, thickening agents, moistening agents, surfactants, detergents, colorants, anti-bacteria agents, fluorinated derivatives, opacifiants, aromatic agents, sweetening agents, anti-tartar agents, anti-plaque agents, whitening agents, sodium bicarbonate, antiseptics, enzymes, natural extracts.