Production of coated film

1,134,876. Coated films. IMPERIAL CHEMICAL INDUSTRIES Ltd. 27 Feb., 1967 [29 March, 1966], No. 13859/66. Heading B2E. [Also in Division C3] A heat-seal coated organic thermoplastic polymeric film is produced by subjecting a film to a treatment to improve the bonding properties of its surface and then coating the film on at least one surface with a resin comprising a composition obtained by condensing a monoaldehyde with an interpolymer of acrylamide or methacrylamide with at least one other unsaturated monomer in the presence of an alkanol containing from one to six carbon atoms such that the composition has at least some amino hydrogens replaced by -ROR' groups, the R and R' groups being alkylene and alkyl groups corresponding to those of the monoaldehyde and the alkanol respectively, further coating the coated surface or surfaces with a heat-seal coating and heating to set the resin so that it becomes adhesively bonded to the heatseal coating and to the base film. The film may be of any organic thermoplastic polymeric material, for example polymers and copolymers of alpha olefines such as ethylene, propylene, butene and 4-methyl pentene- 1; linear polyesters such as polyethylene terephthalate and polyethylene-1:2-diphenoxyethane-4:4'-dicarboxylate and polymers and copolymers containing vinyl chloride. The film may be unoriented or oriented in one or equally or unequally both directions. The pretreatment of the film may be a physical or chemical treatment which oxidises the film surface. Examples of suitable chemical treatment are to treat the surface of the film with oxidising agents such as chromic acid in sulphuric acid, hot nitric acid or exposure of the surface to ozone. Alternatively the surface of the film may be subjected to exposure of the surface to corona discharge (such treatment is described in British Specification No. 715,914); exposure of the surface to ionising radiation, or exposure of the surface to a flame for a sufficient time to cause superficial oxidation. Examples of unsaturated monomers which may be copolymerised with acrylamide or methacrylamide include acrylic acid and its esters; for example methyl, ethyl butyl, 2-ethyl-hexyl. isobutyl, hexyl or octyl acrylates; methacrylic acid and its esters for example methyl, ethyl or butyl methacrylate. Other suitable monomers include acrylonitrile, styrene, monomethyl styrene; vinyl toluene. acidic materials such as maleic anhydride, vinyl ethers; dienes such as butadiene or chloroprene.