GB671140A - Organo-silicon co-polymers and their manufacture - Google Patents

Abstract

A siloxane copolymer which contains silicon atoms bonded to oxygen and silicon atoms all the bonds of which are satisfied by carbon, and contains an average of 1.98 to 2.1 (inclusive) organic radicals per siloxane silicon atom, over 50 per cent of the organic radicals being CH3-radicals, the remaining radicals being [(CH3)3SiCH2-] or [(CH3)2.C6H5SiCH2-], to the extent of at least 0.25 per cent of the organic radicals, the remaining valencies of the silicon atoms being satisfied by siloxane linkages, may be made (a) by reacting a chloromethyl methyl polysiloxane with trimethyl or dimethyl phenyl silicon chloride using sodium by a Würtz reaction; (b) by cohydrolysis and co-condensation of R(CH3)2SiCH2SiCH3Y2 and (CH3)2SiY2, where each R is a CH3- or C6H5 radical and each Y is an alkoxy radical or halogen atom, either with or without a catalyst and in the presence or absence of a solvent, such as benzene, or (c) by separately hydrolysing and condensing the reactants in (b) and mixing and copolymerizing (by contacting them with oleum) the resulting products, a solvent being used, if desired. Minor amounts of methylsilsesquioxane or trimethylsiloxane may be included as units in the copolymer. The copolymers vary from mobile liquids (2.1 radicals) to products which are elastic and non-flowing (2.0 rads.) at room temperature, and may be used for damping media, hydraulic fluids, liquid dielectrics, and for rendering surfaces water-repellent, and they may be thickened by adding fillers, e.g. silica aerogel, for use as electric sealing compositions, while the copolymers containing less than 2.0 radicals per siloxane silicon are cross-linked elastic solids, and may be used for the production of silicone rubber. The copolymers may be mixed with benzoyl peroxide or tertiary butyl perbenzoate (as catalyst) and a filler, such as titania, ferric oxide, zinc oxide or silica, with subsequent milling and vulcanization by heating to 100-300 DEG C. In examples: (1 to 6) a mixture of [(CH3)2SiO]4, <FORM:0671140/IV (a)/1> and [(CH3)3Si]2O was contacted with oleum; (7) cyclic [(CH3)2SiO]3SiO(CH3)CH2Cl and (CH3)3 SiCl were reacted with sodium and distilled to give <FORM:0671140/IV (a)/2> (8) a mixture of [(CH3)2SiO]4 and cyclics of <FORM:0671140/IV (a)/3> and (9) [(CH3)2 SiO]4 and <FORM:0671140/IV (a)/4> were contacted with oleum. Specification 579,408 is referred to.