PRODUCTION OF SILICA GLASS POWDER AND SILICA GLASS MOLTEN MOLDING

PURPOSE:To obtain a silica glass molten molding of good transparency without opaqueness by hydrolyzing and gelling alkoxysilane to get wet gel, crushing the gel and removing fine particles before forming the dried silica glass powder into a molding by fusion. CONSTITUTION:2 to 50 times by mol of water is added to alkoxysilane (e.g. tetramethoxysilane) and the mixture is subjected to hydrolysis and gelation under atmospheric pressure at 20-60 deg.C for 20min to 10hr. The formed wet gel is crushed to form particulate of 100-1000mum average particle diameter. The particulate is fed to a washing tower 1 equipped with an agitator 2 and a water medium (e.g. ultrapure water) is put in from a feed opening 3 to subject the mixture to suspension washing while turning agitation blades of the agitator 2 at about 300rpm for about 10min. The suspension stands still for about 5min to precipitate the wet gel and supernatant which is turbid with fine particles is removed by a siphon pipe 4. This operation is repeated about fine times to remove fine particles of