PROCESS FOR PRODUCING SILICA PARTICLES SUITABLE FOR USE AS FILLER FOR PAPER

摘要

The present invention relates to a process for easily and efficiently producing silica particles having a narrow particle size distribution and a high porosity from inexpensive starting materials such as sodium silicate. The silica particles of the present invention can be obtained in the form of a slurry containing them by (1) forming a slurry by mixing first particles difficultly soluble in an alkali and soluble in an acid, with an aqueous alkali silicate solution to form a first slurry containing the first particles, (2) neutralizing the first slurry with a mineral acid to prepare a second slurry containing second particles wherein silica.is deposited on the first particles, and (3) adding a mineral acid to the second slurry to dissolve the first particles from the second particles, to prepare a third slurry containing silica particles. When the silica particles of the present invention are used as a filler even in a small amount for paper making, the resultant papers have excellent brightness, opacity, opacity-after-printing, etc.