Patent GB-683182-A (GB)
Title: Process for dehalogenating organo halogenosilanes to form silanols and siloxanes
IPC: C08G77/00
Filed: 1950-12-12
Abstract: Polymeric organosiloxanes are obtained by treating an organohalogenosilane with an alkali metal bicarbonate or bisulphite under substantially anhydrous conditions.  Sodium or potassium bicarbonate or bisulphite may be used and the reaction may be carried out in a non-aqueous solvent, e.g. ethyl ether, acetone, toluene, xylene, petroleum ether or mixtures of these solvents.  The preferred organohalogenosilanes are the organochlorosilanes.  The formation of the siloxanes is favoured by the use of an excess of the halogenosilane.  In the examples, diphenoxypolysiloxane is obtained from the reaction of diphenoxydichlorosilane and sodium bicarbonate in acetone, low molecular weight OH-terminated polysiloxanes are obtained from the reaction of diethyldichlorosilane and sodium bicarbonate in ether, a condensation product is obtained by allowing a film of an isopropanol solution of the reaction product of ethyltrichlorosilane and sodium bicarbonate in acetone to stand for a few days, siloxane polymers are obtained by treating a mixture of bis (trichlorosilyl) ethane, phenyltrichlorosilane, ethyltrichlorosilane and diethyldichlorosilane with sodium bicarbonate in a mixture of toluene and acetone, and a polymer corresponding to the formula (C2H5)2Si0,65(OH)0,7 is obtained by treating diethyldichlorosilane with sodium bisulphite in ether and a small amount of water Other organohalogenosilane reactants mentioned are ethyl-, amyl-, phenyl-, vinyl-gamma - chloropropyl -, and nonyl - trichloro-silanes, and dimethyl- and ethylpropoxydichlorosilanes.  Copolymers derived from amyltrichlorosilane and trichlorosilane may be prepared by the above method.ALSO:Organosiloxanes and/or organosilanols substantially free from halogen are prepared by reacting organohalogenosilanes with an alkali metal bicarbonate or bisulphite under substantially anhydrous conditions.  Sodium or potassium bicarbonate or bisulphite may be used.  The reaction may be carried out in the presence of a non-aqueous solvent, e.g. ethyl ether, acetone, toluene, xylene, petroleum ether or mixtures of these.  The halogenosilane employed may be a chlorosilane.  When an excess of alkali metal bicarbonate is used, the principal product is the silanol, and when an excess of the halogenosilane is used, the principal product is the siloxane.  In the examples: (1) hexaethylcyclotrisiloxane is prepared from diethyldichlorosilane; (2) cyclic diphenoxypolysiloxanes are prepared from diphenoxydichlorosilane; (3), (7) diethylsilanediol is prepared from diethyldichlorosilane; (4) ethylsilanetriol is prepared from ethyl trichlorosilane; (5) ethyldichlorosilane is treated with an acetone solution of sodium bicarbonate; (6) a mixture of bis-(trichlorosilyl) ethane, phenyltrichlorosilane, ethyltrichlorosilane and diethyldichlorosilane is reacted with sodium bicarbonate in a mixture of toluene and acetone; (8) a compound of the formula (C2H5)2SiO0.65(OH)0.7 is formed from diethyldichlorosilane by reaction with sodium bisulphite in a mixture of ether and water.  Other organohalogenosilanes which may be used are ethyl-, amyl-, phenyl-, vinyl-, gamma - chloropropyl-, and nonyl - trichlorosilanes, dimethyldichlorosilane and ethylpropoxydichlorosilanes.  Diphenoxydichlorosilane is prepared by the reaction of silicon tetrachloride and phenol.