Method for preparing polydiorganosiloxanes partially end-blocked with substituted silethylene groups

Abstract From the Canadian patent

This specification describes and claims a method for producing polydiorganosiloxanes partially end-blocked with substituted silethylene groups. The method comprises the steps of: A) mixing a hydroxyl end-blocked polydiorganosiloxane with a silicon-containing compound having at least two silicon-bonded hydrogen atoms and a -Si(R')3 end-blocked siloxane in the presence of an acidic polymerisation catalyst to form a mixture wherein each R' independently denotes a monovalent hydrocarbon or halohydrocarbon having 1 to 6 carbon atoms B) conducting, a reaction with the mixture of step A so as to produce a polydiorganosiloxane having at least one silicon-bonded hydrogen atom and at least one …