Preparation of Polysiloxanes by the Silylation of Silicic Acid Extracted with Tetrahydrofuran

Abstract

Silicic acid, prepared by sodium metasilicate and hydrochloric acid, was extracted from an aqueous solution by means of organic solvents. The extraction with tetrahydrofuran (THF)was most effective. The amount of silicic acid extracted into THF increased with an increase in the concentration of hydrochloric acid in the solution.
Silylation of extracted silicic acid by trimethylchl orosilane at room temperature gave silylates with molecular weights of about 1900. The infrared measurement of the relative degree of silylation of the silylates indicated that partially or fully silylated siloxanes were formed depending on the molar ratio of trimethylchlorosilane. Possible structures of the silylates were indicated. When the silylates with a low degree of silylation were heated under reduced pressure, a polysiloxane was obtained with a molecular weight which was nearly three times higher than that before heating.