GB624019A - Improvements in and relating to the preparation of polysiloxane resins - Google Patents

Abstract

Polysiloxane resins are prepared by hydrolysing a mixture of chlorosilanes containing a major proportion of methylchloro-silanes and having a hydrocarbon-to-silicon ratio between 1 and 1.5, with a mixture of water, an ether selected from the group dioxane, diethyl cellosolve ("Cellosolve" is a Registered Trade Mark), and diethyl carbitol and a hydrocarbon having a higher boiling point than the ether. Suitable hydrocarbons are petroleum white spirit (B.R. 140-220 DEG C.) and petroleum solvent naphtha (B.R. 155-210 DEG C.). Methyltrichlorosilane is the chief methylchlorosilane present. Other ingredients of the starting mixture may be ethyl, propyl, butyl, allyl or phenyl chlorosilanes. The presence of phenyl chlorosilanes is particularly beneficial. Some silicon tetrachloride may also be included. Hydrolysis may be performed under reflux. HCl gas liberated may be recovered. At the conclusion of the hydrolysis, water and ether are distilled off leaving a hydrocarbon solution of resin. The example describes a preparation of a copolymer from dimethyldichlorosilane and methyltrichlorosilane. Specifications 585,627 and 585,628 are referred to. The Specification as open to inspection under Sect. 91 states that the hydrocarbon-to-silver ratio may exceed 1.5. This subject-matter does not appear in the Specification as accepted.