Process for the preparation of silica spheres

Abstract

Silica spheres are prepared in a process comprising: (a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate with an aqueous solution of an acid; (b) converting the hydrosol into droplet form; (c) aging the droplets in a fluid to produce hydrogel particles; (d) partially drying the hydrogel particles at 10.degree. to 60.degree. C. in air having a relative humidity in the range of from 45 to 95%, to a water content in the range of from 0.3 to 1.3 kg/kg solids; (e) decreasing the cation content of the hydrogel particles by ion-exchange in an aqueous medium to less than 10% w, calculated on dry material; and (f) finally drying the hydrogel particles to obtain silica spheres.

Dependencies are inferred from the claim text.