GB975179A - Coating of olefine polymer films - Google Patents

Abstract

A dispersion, used for coating an olefine e.g. ethylene, polymer film, comprises a carboxylated butadiene copolymer comprising butadiene-1, 3, and 25 to 70% styrene, acrylonitrile, and/or methyl methacrylate, and containing from 0.05 to 13.5%, by weight of the copolymer, of free carboxyl groups, and a thermosetting resin in the uncured or partially cured state. The carboxyl groups may be introduced into the copolymer by inclusion of an ethylenically unsaturated carboxylic acid e.g. acrylic, methacrylic, ethacrylic and other substituted acrylic acids, cinnamic, maleic, fumaric and itaconic acid; or by the hydrolysis of methyl methacrylate when present by inclusion of hydrolysing agents in the polymerisation recipe, or by treating the copolymer with a hydrolysing agent when polymerization is complete. Examples of hydrolysing agents are hydrochloric and sulphuric acid, dichloracetic acid, sodium and potassium hydroxides, quaternary ammonium bases, and primary, secondary and tertiary amines. The thermosetting resin may be phenol-, urea-, or melamine-formaldehyde, epoxy resin, N-alkoxy methyl polyamide resin, cross-linkable or thermosetting acrylic resin such as that made by reacting formaldehyde with acrylamide-styreneethyl acrylate copolymer. The butadiene copolymer is preferably prepared by an aqueous emulsion process. The coated olefine polymer film may be further coated with a dispersion of a thermoplastic polymer which may be a copolymer comprising vinylidene chloride, from 5 to 30%, by weight of the copolymer, of acrylonitrile, vinyl chloride, vinyl acetate and/or low alkyl acrylates, and from 0 to 10%, by weight of copolymer, of an ethylenically unsaturated acid or derivative thereof e.g. vinylidene chloride with from 7.5 to 15% methyl acrylate and 0 to 2.5% maleic acid; polyvinyl acetate, partially hydrolysed polyvinyl acetate, methyl methacrylate-methacrylic acid copolymers, copolyesters of terephthalic acid and another dicarboxylic acid e.g. sebacic acid, with a glycol, copolymers of vinyl acetate with vinyl chloride or ethylene, and copolymers of vinyl chloride with ethylene. The dispersion may be obtained by polymerizing the monomers by an aqueous emulsion process in the presence of an emulsifying agent preferably an anionic emulsifying agent.ALSO:A coated olefine polymer film is produced by applying to the film surface a coating dispersion of a carboxylated butadiene copolymer which comprises butadiene-1,3 and from 25 to 70% by weight of the copolymer, of a comonomer or mixture of comonomers selected from styrene, acrylonitrile, and methyl methacrylate, and containing from 0,05 to 13,5% by weight of the copolymer of free carboxyl groups, and a thermosetting resin in the uncured or partially cured state, and a coating of a thermoplastic polymeric material, the coatings either being applied consecutively and dried between applications, or being applied mixed together with subsequent removal of the dispersing medium, and in either case curing the thermosetting resin. The olefine polymer may be a homopolymer or copolymer of ethylene including low, intermediate and high density polyethylene, and the crystallizable polymers and copolymers of aliphatic alpha-olefines having at least 3 and preferably 3-6 carbon atoms in the molecule, particularly polymers and copolymers of propylene and butene-1 where the polypropylene or polybutene-1 is at least 75% soluble in boiling n-heptane, e.g. isotactic polypropylene or isotactic polybutene-1. The carboxyl groups may be introduced into the copolymer by inclusion of an ethylenically unsaturated carboxylic acid, e.g. acrylic, methacrylic, ethacrylic and other substituted acrylic acids, cinnamic, maleic, fumaric and itaconic acid; or by the hydrolysis of methyl methacrylate when present. The thermosetting resin may be phenol-, urea-, or melamine-formaldehyde, epoxy resin, N-alkoxymethyl polyamide resin, cross-linkable or thermosetting acrylic resin such as that made by reacting formaldehyde with acrylamidestyrene-ethyl acrylate copolymer. The preferred thermoplastic polymers are copolymers comprising vinylidene chloride, from 5 to 30% by weight of copolymer, of acrylonitrile, vinyl chloride, vinyl acetate and/or low alkyl acrylates, and from 0 to 10% by weight of copolymer, of an ethylenically unsaturated acid or derivative thereof, e.g. vinylidene chloride with from 7,5 to 15% methyl acrylate and 0 to 2,5% maleic acid; polyvinyl acetate, partially hydrolysed polyvinyl acetate, methyl methacrylate-methacrylic acid copolymers, copolyesters of terephthalic acid and another dicarboxylic acid, e.g. sebacic acid, with a glycol, copolymers of vinyl acetate with vinyl chloride or ethylene, and copolymers of vinyl chloride with ethylene. The film may be unorientated or orientated in one direction or equally or unequally in both directions, may be subjected to surface oxidizing conditions by chemical or physical means, e.g. treatment with sulphuric acid, hot nitric acid, chromic acid; with halogens under free radical forming conditions; by exposure to ozone; by exposure to high voltage stress accompanied by corona discharge in the presence of oxygen; exposure in the presence of oxygen, particularly at temperatures above 100 DEG C., to ionizing radiations such as ultraviolet, x-, a -, b - or g -radiation; or by exposure to flame. The coatings may be applied as aqueous dispersions by roller coating, reverse roll coating, gravure roller coating, air knife coating or doctor blade coating. The orientated films may be heat set before, during or after the coating treatment.