| 摘要 |
773,231. Moisture-proof coated films. BRITISH CELLOPHANE, Ltd. Nov. 21, 1955 [Nov. 25, 1954], No. 34231/54. Class 140. A smooth, transparent non-moistureproof surface coating comprising imperfectly coalesced particles of a normally crystalline synthetic organic polymer (said particles being capable of further coalescence by heat treatment) is formed on a flexible base film of water sensitive, organic non-fibrous material, the coated film is dried by evaporation by heat at a temperature too low to promote further rapid coalescence of the polymer particles and then heated at a temperature sufficiently high to fuse the polymer particles into a smooth transparent moistureproof coating. The base film may comprise regenerated cellulose, polyvinyl alcohol, lowly etherified cellulose, lowly esterified cellulose, gelatin, casein and alginic acid derivatives. Specified organic polymers suitable for the surface coating include polyvinylidene chloride and copolymers of vinylidene chloride with acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, butyl acrylate, isobutylacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, vinyl chloride and vinyl acetate. Itaconic, citraconic and mesaconic acids and their anhydrides may be copolymerized with the above to form three component systems. Preferably the vinylidene chloride content of the copolymer should not be less than 80 per cent. The polymer may be applied as an aqueous colloidal dispersion, which should be aged until diffraction rings become clearly discernible in the X-ray pattern of the dispersed polymer. In an example an aqueous dispersion of a vinylidene chloride/acrylonitrile/itaconic acid copolymer prepared by emulsion polymerization and aged for 4 days is applied to both sides of a softened film of regenerated cellulose by the method described in Specification 663,645, the water of the dispersion being wholly absorbed by the base film. The coated film is dried at 95‹ C. for 15 seconds and finally heated at 160‹ C. for 3 seconds to coalesce the polymer particles. Specification 655,732 also is referred to. |
