US Patent 7985392 Cake of easily dispersible precipitated silica

An easily dispersible cake of precipitated silica, wherein the precipitated silica has a BET specific surface area of at least 220 m2/g. When the cake is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration to 1.5% by weight, the dispersion has a light-scattering index (n-value) of at least 2. The easily dispersible cake can be obtained by simultaneously adding an alkali silicate and a mineral acid to a reaction liquid whose pH is being maintained at a fixed value within a range of 7.5-11.5 and whose temperature is being maintained at 92-98° C., thus forming precipitated silica through their reaction, and separating the precipitated silica from the reaction liquid in wet state.