Patent GB-654466-A (GB)
Title: Improvements in or relating to processes for the preparation of siloxanes
IPC: C08G77/06
Filed: 1948-02-21
Abstract: Siloxanes are prepared by reacting an organic halogeno-silane with methyl alcohol, the quantity of alcohol employed being at least twice the quantity theoretically necessary to form methyl halide using all the halogen atoms present in the silane, and the temperature of the reaction being between room temperature and 65 DEG  C., and isolating the siloxane from the reaction mixture.  The organic halogeno-silane may be of the general formula RnSiX4-n, where R is a monovalent hydrocarbon radical, X is a halogen atom and n is 1, 2 or 3.  The reaction may be carried out at a temperature between 40 DEG  and 65 DEG  C.  The reaction may be allowed to proceed at the elevated temperature until evolution of methyl halide is substantially complete, and the remaining methyl alcohol may then be distilled off and the siloxane separated from the residual mixture.  When the evolution of methyl halide is substantially complete, a large excess of water may be added to the reaction mixture and the siloxane layer is then separated from the product.  A methyl chlorosilane may be used in the above process.  In the example, a siloxane is obtained from dichlorosilane.  The Specification as open to inspection under Sect. 91 refers to the use of any alcohol for the above process, e.g. ethyl, tertiary butyl or benzyl alcohol may be used, the temperature of the reaction being between room temperature and the boiling point of the alcohol.  A number of other halogeno-silanes which may be used are also specified.  This subject-matter does not appear in the Specification as accepted.ALSO:Siloxanes are prepared by reacting an organic halogeno - silane with methyl alcohol, the quantity of alcohol employed being at least twice the quantity theoretically necessary to form methyl halide using all the halogen atoms present in the silane, and the temperature of the reaction being between room temperature and 65 DEG  C., and isolating the siloxane from the reaction mixture.  The organic halogeno-silane may be of the general formula RnSiX4-n, where R is a monovalent hydrocarbon radical, X is a halogen atom and n is 1, 2 or 3.  The reaction may be carried out at a temperature between 40 DEG  and 65 DEG  C.  The reaction may be allowed to proceed at the elevated temperature until evolution of methyl halide is substantially complete and the remaining methyl alcohol may then be distilled off and the siloxane separated from the residual mixture.  When the evolution of methyl halide is substantially complete, a large excess of water may be added to the reaction mixture and the siloxane layer is then separated from the product.  A methyl chloro silane may be used in the above process. In the example, a siloxane is obtained from dimethyl-dichlorosilane. The Specification as open to inspection under Sect. 91 refers to the use of any alcohol for the above process, e.g. ethyl, tertiary butyl or benzyl alcohol may be used, the temperature of the reaction being between room temperature and the boiling point of the alcohol.  A number of other halogeno silanes which may be used are also specified.  This subject-matter does not appear in the Specification as accepted.