Improvements in or relating to the manufacture of moistureproof, heat-sealable films

A composition suitable for the production of a moisture-proof, heat-sealable, self-sustaining film comprises an organic solvent-soluble, film-forming vinylidene chloride copolymer and a slip-agent therefor comprising, incorporated in a proportion of between 1.0 per cent and 5.0 per cent (based on the total weight of solids), a solid ketone comprising in its molecule, and attached directly to the carbon atom of the ketonic group, at least one alkyl group comprising a straight chain of at least 8 carbon atoms, the preferred ketone being laurone. The slip-agent may also contain between 0.05 per cent and 1.0 per cent (based on the total weight of solids) of finely-divided polymer of vinyl chloride or finely-divided copolymer obtained by the polymerization of a mixture containing 90 per cent by weight or more of monomeric vinyl chloride, and/or between 0.5 and 3 per cent (based on the total weight of solids) of a long-chain alkyl amine derivative of bentonite. The vinylidene chloride copolymer may be a copolymer of vinylidene chloride and one or more of acrylonitrile, methacrylonitrile, vinyl chloride, vinyl acetate, acrylates and methacrylates, and the monomeric mixture may also contain a small proportion of one or more of citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride, and mesaconic acid. The composition may be dissolved in methyl ethyl ketone or a mixture of equal parts of methyl ethyl ketone and toluene, and employed for the production of films and coatings. Specification 655,006 is referred to.