Patent GB-794119-A (GB)
Title: Condensation process for organopolysiloxanes
IPC: C08G77/00
Filed: 1955-05-04
Abstract: Quaternary phosphonium hydroxides may be made by reacting a Grignard reagent with PCl3, isolating the resulting phosphine by fractional distillation and reacting it with an alkyl iodide to give the corresponding phosphonium iodide, and converting the iodide to the hydroxide by reaction with aqueous silver oxide, with subsequent filtration of silver iodide and concentration to give a 40 to 60 per cent (by weight) aqueous solution of the hydroxide.  The corresponding alkoxides may be made by reacting a quaternary phosphonium chloride with sodium alcoholate in absolute alcohol.  In examples: (1) an ether solution of PCl3 is added to an icecold ether solution of the Grignard reagent of 1-bromobutane and the mixture refluxed to form tri-n-butyl phosphine, which is isolated by adding aqueous NH4Cl, separating the ether layer, evaporating the ether and distilling the phosphine.  The phosphine is then dissolved in ethanol and mixed with an alcoholic solution of n-butyl iodide to yield, after evaporation of the solvent, tetra-n-butyl phosphonium iodide. This is converted to the hydroxide by adding silver oxide and water and filtering off the AgI formed.  The resulting solution is concentrated by boiling off water under a stream of nitrogen to give a solution containing 40 to 60 per cent by weight of tetra-n-butyl phosphonium hydroxide, decomposition of the hydroxide occurring when further concentration is attempted; (12) n-butyl tricyclohexyl-, (13) tetraethyl- and (14) tetramethyl-phosphonium hydroxides are made in a similar way; (16) tetra-n-butyl phosphonium butoxide is made by reacting tetra-n-butyl phosphonium chloride, prepared from tri-n-butyl phosphine and n-butyl chloride by the method of Example 1, with sodium butoxide in n-butanol, filtering off the NaCl precipitated and concentrating the solution to about 40 per cent by weight.ALSO:A liquid organopolysiloxane of the average general formula R11aSiO 4-a/2 , where each R11 is an alkyl, aryl, alkaryl aralkyl or haloaryl radical and a has an average value from 1.2 to 2.5, is polymerized to higher molecular weight siloxane oil, gum, gel or resin by contacting it with an organophosphorus catalyst of the formula R4POR1, wherein each R is an alkyl, cycloalkyl, aryl, aralkyl or alkaryl radical and R1 is a hydrogen atom or an alkyl radical, at a temperature below the decomposition temperature of the catalyst, and subsequently removing the catalyst by heating the products to a temperature above the decomposition temperature of the catalyst. Catalysts specified are tetramethyl-, tetraethyl-, tetra-n-butyl-, tetraoctyl-, diethyldimethyl-, phenyltrimethyl- and butyltricyclohexyl-phosphonium hydroxides, tetramethylphosphonium methoxide and tetrabutylphosphonium butoxide.  The quaternary phosphonium hydroxide catalyst is used either as a concentrated aqueous solution (40 to 60 per cent) or as a solution in a liquid organopolysiloxane, and the quaternary phosphonium alkoxide catalyst is preferably used as a concentrated alcoholic solution, the catalyst being used in amount of from 0.001 to 0.5 per cent by weight of the total siloxanes present.  The temperature of the reaction may vary from room temperature to just below that at which the catalyst decomposes.  The reaction is preferably effected under a stream of an inert gas, e.g. nitrogen, helium or argon, since the presence of moisture lowers the degree of polymerization. Decomposition of the catalyst is effected by heating the polymerized product preferably at 150 DEG  to 250 DEG  C.  In examples siloxanes such as octamethyl- or octaphenyl-cyclotetrasiloxane or mixtures thereof are converted to gums in the above manner.