Continuous Casting of Particulate Silica Gels

Particulate silica gels have been used to prepare glass articles significantly larger than those made by the alkoxide process unless an autoclave is used. Usually the sols are cast in stoppered molds and pushed out from the mold after gelation. This is a slow process, and so we have carried out a study into the feasibility of transforming the batch process into a continuous process. In our process, the sol is pumped from a reservoir by a large metering pump, while the gelling agent is added by a smaller pump and admixed. The sol is delivered into a cylindrical mold where it gels while moving though the mold, either with or without heating. The activation energy for the gelation process was determined to be about 40 KJ/mol.