GB1289526A - - Google Patents

Abstract

1289526 Carbanion-polymerization of cyclic organosiloxanes DOW CORNING Ltd 15 April 1970 [18 April 1969] 19879/69 Headings C3P and C3T An organopolysiloxane is obtained by (1) polymerizing in the presence of a carbanion-producing initiator a cyclic organosiloxane [R 2 SiO] n , wherein each R is H or a methyl, phenyl, vinyl or CF 3 -CH 2 -CH 2 - radical and n is 3, 4 or 5, not more than 50% of the substituents R being H, and (2) reacting the product with a silane R<SP>1</SP> 2 R<SP>11</SP>SiX, wherein each R<SP>1</SP> is a C 1-4 alkyl or alkenyl radical or a phenyl radical, R<SP>11</SP> is an alkyl radical of at least 5 C atoms, and X is Cl, Br or I. Suitable initiators include the alkali metals and their hydrocarbon derivatives and complexes; a solvent, e.g. tetrahydrofuran, tetrahydropyran, dioxan, diethoxyethane dimethyl acetamide, dimethyl formamide or dimethyl sulphoxide, is preferably used; the amount of initiator is preferably such as to give a molecular weight of 400-40,000. The silane is added when the desired molecular weight is reached; it will react with one or both ends of the polymer according to the initiator, butyl lithium, for instance giving a monofunctional polymer, an alkali metal giving a difunctional polymer. In the example butyl lithium is used to polymerize hexamethylcyclotrisiloxane in tetrahydrofuran at 22‹ C.; after 2 hrs. dimethyldecylchlorosilane in benzene is added. The product, precipitated by addition of methanol is When 1% by weight of this is incorporated into polyethylene or polystyrene, reduced solid surface tension is observed.