Process for preparing cyclic organohydrogensiloxanes
AssigneeDow Corning Corporation
InventorsGregory R. Haines, David E. Puckett, Larry H. Wood
Life of this patent
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Abstract
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.
Claims20
A process for preparing cyclic organohydrogensiloxanes, the process comprising:
- (A) contacting a silane described by formula
- RHSiCl.sub.2
- with about a stoichiometric equivalent of water to form a hydrolyzate comprising cyclic organohydrogensiloxanes and linear organohydrogensiloxanes,
- (B) contacting the hydrolyzate with an acidic rearrangement catalyst in the presence of an inert solvent thereby increasing the ratio of the cyclic organohydrogensiloxanes to linear organohydrogensiloxanes in the hydrolyzate, and
- (C) recovering the cyclic organohydrogensiloxanes;
- where R is selected from a group consisting of saturated monovalent hydrocarbon radicals comprising one to 12 carbon atoms and aryl radicals.
A process for preparing cyclic methylhydrogensiloxanes, the process comprising:
- (A) contacting methylhydrogendichlorosilane with water at a temperature within a range of about 0.degree. C. to 50.degree. C., where the water is present within a range of minus seven to plus five percent of stoichiometric equivalence, to form a hydrolyzate comprising cyclic methylhydrogensiloxanes and linear methylhydrogensiloxanes,
- (B) contacting the hydrolyzate with a heterogeneous rearrangement catalyst at a temperature within a range of about 0.degree. C. to 40.degree. C. in the presence of 30 weight percent to 90 weight percent of an inert solvent selected from a group consisting of alkanes and mixtures of alkanes having a boiling point above that of hexamethylcyclohexasiloxane, thereby increasing the ratio of the cyclic methylhydrogensiloxanes to linear methylhydrogensiloxanes in the hydrolyzate,
- (C) recovering the cyclic methylhydrogensiloxanes by separation from the linear methylhydrogensiloxanes and solvent, and
- (D) recycling the linear methylhydrogensiloxanes and solvent from Step (C) to Step (B).
Dependencies are inferred from the claim text.