DE1769904

1,174,328. Coated films. IMPERIAL CHEMICAL INDUSTRIES Ltd. 23 July, 1968 [3 Aug., 1967], No. 35763/67. Heading B2E. [Also in Division C3] Heat-sealable film comprises a base film of an organic thermoplastic polymeric material which has been subjected to a surface oxidation treatment to improve the bonding properties of its surface, coated with a heat-sealable coating material, and an intermediate layer of a resin comprising an interpolymer of the product obtained by condensing acrylamide or methacrylamide with a monoaldehyde in the presence of an alkanol containing from one to six carbon atoms with at least one other unsaturated monomer. The heat-sealable film is produced by subjecting the film to a surface oxidation treatment to improve the bonding properties of its surface and then coating that surface with a resin comprising a composition obtained by condensing a monoaldehyde with acrylamide or methacrylamide in the presence of an alkanol containing from one to six carbon atoms so that at least some of the amino hydrogens are replaced by -ROR' groups, the R and R' groups being alkylene and alkyl groups respectively and subsequently interpolymerising the condensation product with at least one other unsaturated monomer and then overcoating the coated surface or surfaces with a heat-seal coating and heating to set the resin so that it becomes adhesively bonded to the heat-seal coating and the base film. Examples of aldehyde and unsaturated monomer are given. The coating composition may contain up to 50% by weight of the solids content of the resin of an epoxy resin, or a melamine-formaldehyde resin. The copolymer may contain up to 90% of styrene, up to 80% of an alkyl acrylate, up to 15% of methacrylic acid and 5% to 25% of acrylamide which has been condensed with a solution of formaldehyde in n-butanol containing from 0.2 to 3 equivalents of formaldehyde for each amide group. The thermoplastic polymeric material may comprise a polymer or copolymer of an α-olefine e.g. ethylene, propylene, butene, 4-methyl pentene-1; linear polyesters e.g. polyethylene terephthalate and polyethylene-1:2-diphenoxy-ethane-4:4'-dicarboxylate; and polymers and copolymers containing vinyl chloride. The films may be unoriented or oriented in one or both directions in the plane of the film, and the oriented film may be heat set before or after coating. The heatseal coating may comprise copolymers of vinylidene chloride e.g. with acrylonitrile or vinyl chloride, which may contain