GB921276A - Improving the surface properties of polyolefine films - Google Patents

Abstract

<PICT:0921276/IV(a)/1> Polyolefin films are subjected in the presence of chlorine and sulphur dioxide to a high voltage electric stress accompanied by corona discharge. Specified polyolefins include polymers of olefines having 2-6 carbon atoms, e.g. polyethylene and polypropylene, especially isotactic polypropylene. Treatment may be carried out in the presence of air or other diluent gas, the concentration of chlorine, sulphur dioxide and the other gas being preferably within the area enclosed by the chain-dotted line on the triangular diagram, and especially within the shaded area. Treatment enhances the adhesiveness of the film for synthetic organic polymer coatings, inks and dyes. The treated film may be coated with a synthetic organic heat seal or moisture proof coating polymer, especially a vinyl acetate polymer or a copolymer of vinylidene chloride and acrylonitrile containing 80-95% vinylidene chloride, 5-20% acrylonitrile, and 0-5% of another monomer, e.g. itaconic acid, methacrylic acid or an alkyl acrylate. Other suitable polymers are polyvinyl alcohol, butadiene-acrylonitrile copolymers, methyl methacrylate-methacrylic acid copolymers, copolyesters of terephthalic acid and another dicarboxylic acid, e.g. sebacic acid with a glycol, N-alkoxy-methyl polyamides, gelatin, nitrocellulose, vinyl chloride-vinylidene chloride copolymers, vinyl acetate-vinyl chloride copolymers, vinyl acetate-ethylene copolymers and vinyl chloride-ethylene copolymers. The above are especially suitable as heat seal coating polymers, but may also be used as moisture proof coatings, especially if there is added to such polymers a small proportion of a thermosetting resin precondensate, e.g. a urea-formaldehyde, phenol-formaldehyde or melamine-formaldehyde precondensate, the coating then being heated to induce cross-linking. Alternatively a thermosetting resin precondensate may be used as such. These coatings may be applied as aqueous dispersions which are dried off under conditions under which the thermosetting resin is cross-linked. The heat seal or moisture proof coatings are applied by known solution or dispersion coating techniques, preferably as aqueous dispersions. Specification 715,914 is referred to.