METHODS FOR PRODUCING PURIFIED ACTIVE SILICIC ACID SOLUTION AND SILICA SOL

摘要

There is provided a method for producing an active silicic acid solution in which the existing amount of foreign matters as plate-like fine particles is reduced and a method for producing a silica sol in which such foreign matters are reduced. A method for producing an active silicic acid solution fulfilling the following condition: (1) the existing amount of plate-like fine particles having a length of one side of 0.2 to 4.0 µm and a thickness of 1 to 100 nm is measured to be 0% to 30% in accordance with measuring method A, the method characterized by including the steps of: preparing an active silicic acid solution by subjecting an alkali silicate aqueous solution having a silica concentration of 0.5% by mass to 10.0% by mass to cation-exchange to remove alkaline components; and filtering the active silicic acid solution through a filter whose removal rate of particles having a primary particle size of 1.0 µm is 50% or more.