PRODUCTION OF SILICA SOL CONTAINING SILICA PARTICLE HAVING LARGE PARTICLE SIZE

摘要

PURPOSE:To obtain a silica sol containing silica particles, having an uniform particle size distribution, large particle diameter and shape close to that of a true sphere, by preparing a seed solution under specific condition and adding an acidic silicic acid solution to the seed solution at a specific addition rate. CONSTITUTION:A silica sol containing silica particles having a large particle diameter is obtained by the following steps (a) and (b). That is (a) a step of blending a silica sol containing silica particles having a relatively small particle diameter dispersed in a dispersing medium with an aqueous solution of an alkali silicate and/or aqueous solution of an alkali and adjusting the molar ratio of the total SiO2/M2O (M is alkali metal) in the blend solution to 10-70 to prepare a seed solution and (b) a buildup step of adding an acidic silicic acid solution thereto while keeping the seed solution at =70 deg.C at an addition rate satisfying formula 1 [W is the addition rate of the acidic silicic acid solution (number of g SiO2 in the acidic silicic acid solution/hr.g initial silica sol SiO2 in the seed solution); D is average particle diameter (mmu) of silica particles in the seed solution before adding the acidic silicic acid solution] to grow the particle diameter of silica particles having a small particle diameter.