GB815088A - Improvements in a process for the production of halogenated hydrocarbons - Google Patents

Abstract

Normally solid, semi-solid or tacky olefin polymers in which the unsaturation is predominantly of the trans-internal or terminal vinyl type and which are substantially insoluble in low-boiling chlorinated solvents at temperatures at which such solvents exist as liquids at atmospheric pressure may be halogenated, e.g. with elemental chlorine, bromine or iodine, either (a) in homogeneous solution in low-boiling chlorinated solvents, e.g. carbon tetrachloride, chloroform, methylene chloride and 1,1,1-trichlorethane, at superatmospheric pressure at temperatures above the normal boiling-point of the solvent, or (b) in the molten state. Catalysts, e.g. benzoyl peroxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, dimethyl and diethyl alpha, alpha1-azodiisobutyrate, alpha, alpha1-azodiisobutyronitrile, alpha, alpha1-azobis-(alpha, gamma-dimethylvaleronitrile) and ultra-violet light may be present. Alternatively the temperature may be reduced and the pressure reduced to atmospheric when a partially halogenated polymer soluble in the chlorinated solvents has been obtained, and the product further halogenated. The first stage may be conducted with the polymer in solution in tetrachlorethane, chlorobenzene or dichlorobenzene which may be substantially removed before further halogenation in solution in the low-boiling solvents. Specified polymers are those of ethylene, propylene, 1-butene, 1-pentene, 1-hexene and copolymers thereof, e.g. of ethylene and propylene, which may be prepared by polymerization, e.g. in isooctane, in the presence of chromium oxidesilica and/or alumina catalysts as described in Specification 790,195. Alternatively the polymers may be halogenated and, if desired, at least partially dehalogenated in substantially a single step to produce vulcanizable products by reacting the polymer in the molten state at temperatures of 150-300 DEG C. with a halogenating agent, e.g. chlorine, bromine, iodine, carbon tetrachloride, carbon tetrabromide, carbon tetraiodide, hexachlorethane, chloroform, iodoform, bromoform or phosgene, optionally in the presence of a dehydrohalogenating catalyst, e.g. magnesium, zinc, magnesium chloride, zinc chloride, barium chloride or ultra-violet light. The dehalogenation may be effected by raising the temperature when substantial halogenation has occurred, preferably while flushing the reactor with carbon dioxide or nitrogen to remove the hydrogen halide formed. The products may be vulcanized by incorporationg conventional vulcanizing ingredients, e.g. sulphur, zinc oxide, magnesium oxide, stearic acid and N,N-dimethyl - S - tert - butylsulphenyl dithiocarbamate, and stabilizers, e.g. hydroquinone monobenzyl ether, and heating. Pigments, e.g. carbon black, graphite, titanium dioxide, malachite and iron oxide, may be incorporated and the products moulded, extruded to form pipes, tubes and wire insulation, or used as coating materials or heat insulation.