GB860327A - Preparation of graft co-polymers - Google Patents

Abstract

Graft polymers are made by (a) exposing an organo-siloxane polymer of the unit formula <FORM:0860327/IV (a)/1> wherein n is 1, 2 or 3 and each R is a monovalent hydrocarbon, halohydrocarbon, hydrocarbonoxy or hydroxy radical or a hydrogen atom, at least some of the R's being organic radicals, to ionizing radiation at a temperature at least as low as the second order transition temperature of the polymer and in the substantial absence of oxygen diffusion into the polymer, and thereafter (b) contacting the irradiated polymer with a grafting material, and (c) raising the temperature of the reactants above the second order transition temperature. The siloxanes used may be polymers, copolymers or mixtures, may be resins (cured or uncured), liquids or eleastomers, and may contain conventional fillers and other additives provided that they are inert to the ionizing radiation. The grafting material can be the same as the trunk material but preferably is a different material, e.g. vinyl chloride, butadiene, acrylonitrile, acrylamide, styrene, vinylidene dichloride, vinylcarbazole, isoprene, ethylene, polypropylene, natural rubber, tetrafluoroethylene and chlorotrifluoroethylene, and can be used in the solid, liquid or vapour form. The radiation may be b -, g or X-rays, neutrons, accelerated electrons or heavy particles. The grafting may be effected in the presence of chain transfer agents, e.g. mercaptans, CCl4 and HCBr3, which, if desired, may form part of the siloxane, e.g. as in haloalkyl radicals. The whole siloxane or just the surface thereof can be subjected to grafting. The process results in grafting as well as vulcanizing or cross-linking of the siloxanes. In typical Examples, (1) a mixture of a dimethylsiloxane gum, fume silica and a hydroxy-terminated dimethylsiloxane, was compounded on a mill and formed into sheets which were immersed in liquid nitrogen and exposed to g -rays; the irradiated sheets were removed and immediately dropped into liquid methylmethacrylate, acrylonitrile, vinyl acetate, a 50% solution of acrylonitrile in dimethylformamide, and styrene, all at room temperature; the sheets while still immersed were heated on a steam bath; (2) a liquid dimethylsiloxane, contained in a test tube, was immersed in liquid nitrogen and exposed to g -rays; methyl methacrylate was then added to the still frozen siloxane (after removal of the liquid nitrogen) whereupon rapid and vigorous reaction took place; (6) an uncured methylphenylsiloxane copolymeric resin was cooled in dry ice and exposed to g -rays and then immersed in acrylonitrile at room temperature. Uses.-For making new materials; surface treatment of shaped forms; modifying polymers and their properties; and vulcanizing elastomeric stocks.