Dow Corning Corporation

David E Puckett

Larry Herbert Wood

Gary N Bokerman

Steven K Freeburne

Charles E Neal, Jr

Gregory R Haines

A process for preparing cyclic organohydrogensiloxanes. The process comprises contacting an organohydrogendichlorosilane with about a stoichiometric equivalent of water to form a hydrolyzate. The hydrolyzate is diluted in an inert solvent and contacted with an acidic rearrangement catalyst to effect formation of cyclic organohydrogensiloxanes. The cyclic organohydrogensiloxanes are separated from inert solvent and linear organohydrogensiloxanes. The inert solvent and linear organohydrogensiloxanes are then recycled to the process for further contact with the acidic rearrangement catalyst.

Process for preparing cyclic organohydrogensiloxanes

The present invention is a process for the preparation of organofunctional-terminated polydiorganosiloxane polymers and organofunctional polydiorganosiloxane copolymers. The process comprises reacting a hydroxyl-terminated polydiorganosiloxane polymer with: (1) an organofunctional chlorosilane end-blocker to form an organofunctional terminated polydiorganosiloxane polymer and (2) a mixture of organochlorosilane end-blocker and organofunctional dichlorosilane to form an organofunctional polydiorganosiloxane copolymer. The process can be conducted in the presence of an aqueous solution of hydrogen chloride, where the water is present in stoichiometric excess in relation to the hydrolyzable silicon-bonded chlorine. The present process is particularly useful for producing 5-hexenyl-terminated polydimethylsiloxane polymers and for producing siloxane copolymers comprising poly-5-hexenylmethylsiloxy and polydimethylsiloxy blocks.

Condensation process for preparation of organofunctional siloxanes

The present invention is an anhydrous process for preparing organosiloxy end-blocked polyorganosiloxanes from chlorine end-terminated polyorganosiloxanes. The process comprises contacting an anhydrous mixture comprising a chlorine end-terminated polyorganosiloxane and an organodisiloxane with a rearrangement catalyst, where the rearrangement catalyst facilitates a chlorine and organosiloxy exchange between the chlorine end-terminated polyorganosiloxane and the organodisiloxane forming a organochlorosilane as a by-product. The organochlorosilane is continuously removed from the process providing a means by which the chlorine displaced from the chlorine end-terminated polyorganosiloxane can be effectively removed from the organosiloxy end-blocked polyorganosiloxanes in a useable form. The present process is especially useful for the rearrangement of chlorine end-terminated polyorganosiloxanes having one or more hydrogen atoms bonded to silicon to organosiloxy end-blocked polyorganohydrosiloxanes.

Anhydrous process for preparation of polyorganosiloxanes

The present invention is a process for the preparation of organofunctional-terminated polydiorganosiloxane polymers and organofunctional polydiorganosiloxane copolymers. The process comprises reacting a chlorine-terminated polydiorganosiloxane polymer with: (1) an organofunctional chlorosilane end-blocker to form an organofunctional terminated polydiorganosiloxane polymer and (2) a mixture of organochlorosilane end-blocker and organofunctional dichlorosilane to form an organofunctional polydiorganosiloxane copolymer. The process is conducted in the presence of an aqueous solution of hydrogen chloride, where the water is present in stoichiometric excess in relation to the hydrolyzable silicon-bonded chlorine. The present process is particularly useful for producing 5-hexenyl-terminated polydimethylsiloxane polymers and for producing siloxane copolymers comprising randomly distributed poly-5-hexenylmethylsiloxy and polydimethylsiloxy blocks.

Process for preparation of organofunctional siloxanes

The present invention is a process for preparation of cyclic organohydrosiloxanes. The process comprises contacting an organohydrodihalosilane with a substantially stoichiometric quantity of water to form a mixture containing cyclic and short-chain linear organohydrosiloxanes. This mixture is distilled to separate the cyclic and short-chain linear organohydrosiloxanes from other components of the mixture. The separated cyclic and short-chain linear organohydrosiloxanes are then contacted with an additional quantity of water to effect hydrolysis and condensation of the short-chain linear organohydrosiloxanes to higher molecular weight linear organohydrosiloxanes which are easily separated from the cyclic organohydrosiloxanes by a second distillation step.

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Taylor Mill, KY, United States of America

David E Puckett