SILICA SOL AND PROCESS FOR PRODUCING THE SAME

摘要

[PROBLEMS] To provide a silica sol which is suitable for use as a material for, e.g., an abrasive material for electronic materials, silicon wafers, and the like which are required to have a high purity, has excellent sol stability, can hence be easily made to have an increased silica concentration, and can be regulated so as to have a silica concentration equal to or higher than that of silica sols produced from water glass. [MEANS FOR SOLVING PROBLEMS] The silica sol comprises water and fine silica particles dispersed therein, and is characterized in that the fine silica particles have a secondary-particle diameter of 10-1,000 nm, a metal impurity content of 1 ppm or lower, and a silica concentration of 10-50 wt.%. Also provided is a process for producing a stable silica sol characterized by comprising the following steps (a) and (b). (a) A first step in which a hydrolyzable silicon compound is hydrolyzed and condensation-polymerized to produce a silica sol. (b) A second step in which the silica sol obtained in the first step is concentrated to a silica concentration not higher than a certain value according to the particle diameter and the dispersion medium and alkali catalyst in the silica sol are replaced with water to regulate the pH to 6.0-9.0.