GB813814A - Improvements in the production of aqueous dispersions of polymerisation products of ethylene - Google Patents

Abstract

Aqueous dispersions of ethylene polymer are made by polymerizing ethylene alone or in admixture with one or more other ethylenically-unsaturated monomers, soluble in water at most up to 10 per cent. in aqueous emulsion in the presence of a free radical forming polymerization catalyst and a water-soluble ethylenically-unsaturated compound in an amount up to 1 per cent with reference to the water in the polymerization medium. The water-soluble compound is a sulphonic or carboxylic acid or the water-soluble salts, especially alkali salts, or amides thereof and may be a vinyl sulphonate, e.g. the sodium salt, acrylic acid or its salts, acrylamide, or maleic or fumaric acids or their salts, e.g. sodium maleate. The comonomer may be methyl, ethyl or butyl acrylates or methacrylates, vinyl esters, e.g. vinyl acetate, vinyl halides, e.g. vinyl chloride, vinyl ketones or lactams, e.g. vinyl caprolactam or vinyl caprylic lactam, vinylidine halides, acrylonitrile or maleic or fumaric esters, e.g. diethyl maleate or mixtures thereof. The free radical forming catalyst may be an azo compound or a peroxide. Azo catalysts specified are alpha, alpha1-azo-bis-isobutyronitrile; alpha, alpha1-azo-bis-isobutyric acid esters, e.g. the methyl, ethyl or butyl esters; alpha, alpha1-azo-bis-alpha, gamma-dimethylvaleronitrile; alpha, alpha1-azo-bis-cyclohexane carbonitrile; alpha, alpha1 - azo - bis - alpha - methyl - gamma - diethylamino - butyronitrile; alpha, alpha1 - azo - bis - alpha - methyl - deltapiperidino-valeronitrile and alpha, alpha1-azo-bis - alpha - methyl - gamma - ethoxy - butyronitrile. Peroxide catalysts specified are lauroyl, benzoyl and di-t-butyl peroxides, cumene and t-butyl hydroperoxides and t-butyl perlaurate. Emulsifying agents specified are the alkali palmitates, stearates and oleates, e.g. the potassium salts, isopropyl and di-isobutyl naphthalene sulphonic acid salts, the alkali salt of sulphonated castor oil, hydroxyethylation products of high molecular weight fatty alcohols and alkyl phenols, paraffin sulphonic acid salts, benzyl dimethyl phenyl ammonium chloride, stearyl amidomethyl pyridinium chloride and stearyl ammonium chloride. Polymerization is effected at raised temperatures and preferably raised pressures and may be carried out, e.g. at a pH of 10-12 continuously or discontinuously, or the ethylene may be added portionwise. The polymer dispersions may be concentrated by evaporation or creaming, e.g. by the addition of substances such as methyl cellulose. The dispersions can be used for coating or impregnating fabrics, paper or leather or for obtaining solid ethylene polymers by precipitation.