Dow Corning S.a.

Dow Corning Corporation

Eric Damme

Patrick Leempoel

Fabrice Lebecq

Francois De Buyl

Takao Takemasa

David J Wilson

Jean-Marc Gilson

Jean De Habimana

A compound of formula (I) is disclosed for use as a silylating agent: ##STR1## wherein each R.sup.1 is independently a hydrogen atom, an alkyl group or an alkenyl group with at least one R.sup.1 being a hydrogen atom or alkenyl group, and R.sup.2 is a hydrogen atom or an alkyl group. Also disclosed is a method of making the compound, and a method of using the compound as a silylating agent.

Silylating agent

This specification describes and claims a process for preparing chain-extended organopolysiloxanes. The process comprises the steps of: A) mixing organopolysiloxanes having at least one silicon-bonded hydroxyl group per molecule with a polymerization catalyst to form a mixture, B) allowing the mixture of step A to react so as to produce a reaction product comprising polymerized organopolysiloxanes of which some have at least one silicon-bonded hydroxyl group per molecule and C) allowing the silicon-bonded hydroxyl group containing organopolysiloxanes of the reaction product of step B to react with a nitrogen-containing silylating agent capable of chain-extending to produce a chain-extended organopolysiloxane. Preferably the silylating agent is a cyclosilazane. Organopolysiloxanes having terminal groups other than silicon-containing hydroxyl groups and which are capable of equilibrating with the mixture of step A and/or the reaction product of step B may also be introduced prior to step C. The chain-extended organopolysiloxanes are suitable for use in sealant compositions.

Process for preparing chain-extended organopolysiloxanes

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').sub.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 --Si (R').sub.3 group and C) adding a substituted alkenylsilane in the presence of a hydrosilylation catalyst to the reaction product obtained from step B to form a polydiorganosiloxane partially end-blocked with substituted silethylene groups. A chain extender may also be included with the reaction mixture of step A and/or the reaction product of step B. The polydiorganosiloxanes are suitable for use in sealant compositions.

Method for preparing polydiorganosiloxanes partially end-blocked with

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Brussels, Belgium

Eric Damme