Process for preparation of cyclic organohydrosiloxanes
AssigneeDow Corning Corporation
InventorsSteven K. Freeburne, David E. Puckett
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Abstract
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.
Claims11
A process of cyclic organohydrosiloxanes, the process comprising:
- (A) contacting an organohydrodihalosilane described by formula
- RHSiX.sub.2
- with a substantially stoichiometric quantity of water at a temperature within a range of about 0.degree. C. to 50.degree. C. to form a first mixture;
- (B) distilling the first mixture to recover a second mixture comprising cyclic organohydrosiloxanes and short-chained polyorganohydrosiloxanes;
- (C) contacting the second mixture with water to effect polymerization of the short-chained polyorganohydrosiloxane to long chain polyorganohydrosiloxanes and forming a third mixture;
- (D) distilling the third mixture to recover cyclic organohydrosiloxanes described by formula
- (RHSiO).sub.n ;
- where each R is a radical independently selected from a group consisting of alkyls comprising one to 20 carbon atoms, alkenyls comprising one to 20 carbon atoms, and aryls;
- X is a halogen;
- and n=3 to 12.
A process for preparation of cyclic organohydrosiloxanes, the process comprising:
- (A) contacting an organohydrodihalosilane described by formula
- RHSiX.sub.2
- with about 0.8 mole of water to 1.2 mole of water per mole of organohydrodihalosilane at a temperature within a range of about 10.degree. C. to 30.degree. "C. to form a first mixture;
- (B) distilling the first mixture to recover a second mixture comprising cyclic organohydrosiloxanes and short-chained polyorganohydrosiloxanes;
- (C) contacting the second mixture with about 0.05 to 1.0 volume of water per volume of the second mixture to effect polymerization of the short chained polyorganohydrosiloxane to long-chain polyorganohydrosiloxanes and forming a third mixture;
- (D) distilling the third mixture to recover cyclic organohydrosiloxanes described by formula
- (RHSiO).sub.n ;
- where R is methyl, X is chlorine, and n=4 to 8.
Dependencies are inferred from the claim text.