| 摘要 |
810,721. Coated films. DU PONT DE NEMOURS & CO., E. I. Nov. 22, 1955 [Nov. 22, 1954], No. 33491/55. Class 140. A packaging film comprises a base film of a thermoplastic polymeric material, e.g. polyethylene teraphthalate or polyethylene, subcoated with a copolymer of 50-80 per cent vinylidene chloride and 20-50 per cent of an alkyl acrylate where the alkyl group contains more than 2 carbon atoms, and top coated with a copolymer of 80-97 per cent vinylidene chloride and 3-20 per cent of a polymerizable mono-olefinic monomer i.e. those compounds having a single CH 2 = C = group. The specification states that the most useful monomers in this class have a general formula CH 2 = C(R)X, where R is halogen, hydrogen or a saturated aliphatic radical, and X is selected from: halogen, cyanide, phenyl, carboxyl, -CO(OR<SP>1</SP>), -CO(R<SP>1</SP>), -CHO, -OC 6 H 5 , -CONH 2 , -CONHR<SP>1</SP>, -CONR<SP>1</SP> 2 in which R<SP>1</SP> is alkyl. Many such compounds are listed in the specification, although it is preferred to use an alkyl acrylate e.g. methyl or ethyl acrylate. The base film may be pretreated before coating If of polyethylene it may be treated with ozone at above 150‹ C. in order to improve adhesion of the coating layer, and if of polyethylene paraphthalate it may be stretched and heat set, stretched and not heat set or neither stretched nor heat set to provide coated films with differing characteristics and uses. The coating compositions, which may be applied by conventional methods from either aqueous dispersions or solutions of the polymers in organic solvents, preferably contain 0.5 to 3 per cent by weight, based on the total weight of the two components of the copolymer, of an unsaturated aliphatic acid, e.g. itaconic, acrylic or metbacrylic acids, and other components may include dyes, pigments, delustrants and plasticizers. Specifications 718,422, 788,461, 810,722 and U.S.A. Specification 2,160,943 are referred to. |
