Process for preparation of linear organo-polysiloxane having hydroxyl group at its molecular ends

摘要

A process for preparation of a linear organopolysiloxane having a hydroxyl group at both molecular ends thereof, comprising the steps of: mixing a dialkoxysilane having the following general formula (1): Si(R1)(R2)(OR3)2 (1) wherein R1 and R2 are each a substituted or unsubstituted monovalent hydrocarbon group, and R3 is a methyl or ethyl group, or a partial hydrolyzate of said dialkoxysilane with an aqueous acid solution of ph 1.0-5.0, thereby permitting hydrolysis and condensation to take place; adding a metal oxide to the reaction mixture to adjust the reaction system to pH 6.0-9.0; and removing water and by-produced alcohols from the reaction mixture. By the process, linear organopolysiloxanes having a hydroxyl group at both molecular ends thereof can be prepared extremely easily from dialkoxysilanes, such as dimethoxydimethylsilane, which are inexpensive. The process is highly advantageous for preparation of low molecular weight, terminal hydroxyl-containing linear organopolysiloxanes useful as dispersing agent for silicone rubber.