Patent ID: 6761867
Filing Date: 2004-07-13
Classification: C01B,C01P,C04B,C09D,G09B

Abstract:
A method for the preparation of an aqueous suspension of precipitated silica, having a solids content between 10 and 40% by weight, a viscosity lower than 4Ã—10âˆ’2 Pa.s at a shear rate of 50 sâˆ’1 and wherein the amount of silica present in the supernatant obtained after centrifuging said suspension at 7500 revolutions per minute for 30 minutes represents more than 50% of the weight of the silica present in the suspension, consisting of the steps of:(A) precipitating silica by reacting an acidifying agent with an alkali metal (M) silicate, by: (i) providing an initial base stock of a proportion of the total amount of the alkali metal silicate introduced into the reaction, the silicate concentration expressed as SiO2 in said base stock being lower than 20 g/l, (ii) adding said acidifying agent to said initial base stock until at least 5% of the amount of M2O present in said initial base stock is neutralized, (iii) adding said acidifying agent to the reaction mixture simultaneously with the remaining amount of alkali metal silicate such that the ratio (amount of silica added)/(amount of silica present in the initial base stock) is between 10 and 100; (B) separating from the reaction mixture a precipitation cake which has a solids content of between 10 and 40%, and, optionally, adding to said precipitation cake, an amount of silica powder such that the solids content of the silica-enriched cake is between 10 and 40%; and (C) deagglomerating said cake to obtain a suspension of low viscosity and wherein said deagglomerating is conducted under conditions that result in a silica suspension which has a stability such that the amount of silica in the supernatant obtained after centrifuging said suspension at 7500 revolutions per minute for 30 minutes represents more than 50% of the weight of the silica initially present in the suspension.