Cake of easily dispersible precipated silica and process for producing the same

Abstract

A silica cake formed of easily dispersible precipitated silica having small primary particle size is provided, from which highly transparent silica dispersion can be effectively obtained. This silica cake is characterized by being a cake of precipitated silica having BET specific surface area of at least 220 m2/g, and when it 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 having a light-scattering index (n-value) of at least 2. This silica 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 not lower than 90° C., whereby forming precipitated silica through their reaction, and separating said precipitated silica from the reaction liquid in wet state.

Dependencies are inferred from the claim text.