Patent GB-695457-A (GB)
Title: Improvements in or relating to poly-siloxane resins
IPC: C08G77/00
Filed: 1950-04-25
Abstract: Polysiloxane resins are made by mixing a compound or a mixture of compounds of the average general formula RSi(OB)nX3-n with a hydrolysate of a compound of the general formula R1R11SiX2 and reacting the mixture with a strong dehydrating mineral acid, e.g. sulphuric or ortho-phosphoric acid.  The resulting product is eventually hydrolysed and the product condensed.  In the above formul R and B are each an alkyl, aryl, alkaryl, aralkyl or heterocyclic radical, R1 and R11 are each an alkyl, aryl, alkaryl or aralkyl radical, n is 1 to 2, and X is halogen.  It is postulated that hydroxyl groups in the hydrolysate of R1R11SiX2 react with the halogen of RSi(OB)nX3-n with elimination of hydrogen halide, the final hydrolysis of the product involving the OB radicals with elimination of BOH.  By varying the ratio in which RSi(OB)nX3-n and the dihalogenosilane hydrolysate are reacted, products ranging from thick viscous liquids through rubbery solids to hard tough resins may be obtained.  The resins may be compounded with silica, glass (fibres or particles), mica, magnesium oxide, asbestos, galena, lead sulphate, basic lead carbonate, antimony sulphide, barium sulphate, carbon black or calcium carbonate (fillers), or with copolymers of butadiene and acrylonitrile or polymerized acrylic acid esters.  In a modification the product from the acid reaction is mixed with compounds of the formula RaSiX4-a, where a is 1, 2 or 3 and the mixture then hydrolysed and condensed.  In examples: (1) a rubber-like solid is obtained by curing the hydrolysate of the product obtained by reacting, in the presence of sulphuric acid, hydrolysed dimethyl silicon dichloride, 5 parts, and the esterification product from three mols. methyl silicon trichloride and six mols. methyl alcohol, 70 parts.  (2) A flexible solid is obtained by curing the hydrolysate of the product obtained by reacting, in the presence of phosphoric acid, hydrolysed phenyl ethyl silicon dichloride, 5 parts, and the partial methyl ester of ethyl silicon trichloride, 70 parts.  (3) A hard tough resinous material is obtained by curing a product derived as in (1) but using 5 parts of the partial methyl ester of phenyl silicon trichloride and 70 parts of hydrolysed dimethyl silicon dichloride.  (4) 24 parts of hydrolysed dimethyl silicon dichloride are reacted with 192 parts of the partial methyl esters of a mixture of phenyl and ethyl silicon trichlorides in the presence of sulphuric acid; the product is hydrolysed, condensed and cured for 30 minutes at 4000 p.s.i. and 180 DEG  C.  (5) 5 parts of the hydrolysate of diethyl silicon dichloride are reacted in the presence of sulphuric acid with 70 parts of a partial methyl ester of benzyl silicon trichloride to give, after hydrolysis and partial condensation, a stable viscous liquid.  (6) A mixture of 60 parts of the partial methyl ester of phenyl silicon trichloride and 10 parts of the partial methyl ester of ethyl silicon trichloride are reacted with hydrolysed dimethyl silicon dichloride and the product hydrolysed and condensed to give a hard resinous solid on curing.  (7) A mixture of 400 parts dimethoxy phenyl silicon chloride and 78 parts dimethoxy ethyl silicon chloride is reacted with 35 parts of hydrolysed dimethyl silicon dichloride and the product hydrolysed and condensed.  On curing a tough resinous body is obtained.  (8) 15.5 parts of hydrolysed phenyl ethyl silicon dichloride are reacted with the product of 224 parts benzyl silicon trichloride and 64 parts methyl alcohol.  10 parts of the product are co-hydrolysed and condensed with 40 parts of a mixture of phenyl and ethyl silicon trichlorides.  An elastic product is obtained on curing.  (9) The product from the partial esterification of a mixture of phenyl and ethyl silicon trichlorides with methyl alcohol are reacted with hydrolysed dimethyl silicon dichloride.  The product is hydrolysed and condensed to give a hard friable foam which is powdered and cured to give a hard product.  The Specification gives examples of other combinations of reactants suitable for various types of product.  Triethanolamine is used in various examples as a condensation catalyst.