PRODUCTION OF POROUS DRYING GEL

摘要

PURPOSE:To eliminate the occurrence of volume shrinkage and crack by washing wet gel obtd. from a hydrolyzate of silicon alkoxide by a specified method, with liq. CO2 and by removing the liq. CO2 through the supercritical state. CONSTITUTION:The hydrolyzate (sol) of silicon alkoxide such as Si(OC2H5)4, Si(OCH3)4, preferably hydrolyzate of Si(OC2H5)4, to which is added silica fine particles (50mum particle size), is subjected to ultrasonic wave to disperse the silica fine particles and centrifuged to remove huge particles. The wet gel is obtd. by controlling the obtd. sol in <=4pH value, preferably in 2.0-3.0, and at 5-10 deg.C. The wet gel is washed with liq. CO2 to substitute the volatile component in the gel body with liq. CO2. Thereafter, the porous drying gel is obtd. by bringing the gel body in the supercritical condition to remove the liq. CO2 in the gel body.