AMORPHOUS SILICA OR SILICA-ALUMINA SPHERICAL PARTICLES AND PROCESS FOR PREPARATION THEREOF

摘要

PURPOSE:To obtain amorphous silica or silica alumina particles having fine primary particle size, and distinct spherical shape together with notched surface, having also superior dispersibility for resin and satisfactory compatibility to resin. CONSTITUTION:The particles comprise substantially amorphous silica or silica- alumina based on the X-ray diffractometric analysis, and each particle has spherical shape which is distinct as a whole and notched surface. The circularity (A) of the particles defined by the formula 1 (wherein r1 is a radius of circum scribed circle given by the contour of an electron microscopic photograph of the particle; r2 is a radius of inscribed circle there) is 0.90-1. The degree of notch (B) expressed by the formula: B=DELTAt/r1X100 (wherein DELTAt is a depth be tween a crest and a root in the radial direction of the notched unevenness in a contour of said particle in the electron microscopic photograph; r1 is same as defined for formula 1) is 1-10%. Further, the primary particle size (2r1) measured by the electron-microscopic photography is 0.1-20mum.