FIBROUS SILICA AND ITS PRODUCTION

PROBLEM TO BE SOLVED: To facilitate mixing in a resin, etc., by adding an acid to a mixture of fibrous silica gel having a specified fiber length, aspect ratio and specific surface area and calcium carbonate obtd. by blowing gaseous CO2 into a aq. dispersion slurry of wollastonite as a starting material to decompose the calcium carbonate. SOLUTION: CO2 in a supercritical state under 80-220 kg/cm2 at 40-120 deg.C is blown for 5 min to 24 hr into an aq. dispersion slurry prepd. by dispersing wollastonite having 1-200 μm fiber length, an aspect ratio of 5-100 and 0.5-10 m2/g specific surface area to obtain a mixture of fibrous silica gel and calcium carbonate. The calcium carbonate is then decomposed by adding an acid to the mixture to obtain the objective fibrous silica having 1-200 μm, preferably 5-100 μm fiber length, an aspect ratio of 5-100, preferably 5-20 and 20-80 m2/g specific surface area. When the fibrous silica is heat-treated at 1,150-1,250 deg.C, fibrous amorphous silica is obtd.