| 摘要 |
<p>804,286. Coated thermoplastic films. DU PONT DE NEMOURS & CO., E. I. Dec. 1, 1955 [Dec. 9, 1954], No. 34472/55. Class 140. A packaging film comprises a base film of thermoplastic polymeric material, e.g. polyethylene teraphthalate or polyethylene, subcoated with an elastoprene, elastolene or elastothiomer and top-coated with a copolymer obtained from 80-97 per cent of vinylidene chloride and 3-20 per cent of at least one other polymerizable mono-olefinic monomer. The Specification defines an " elastoprene " as a derivative of butadiene, e.g. butadiene rubbers, piperylene rubbers, isoprene rubbers, dimethylbutadiene rubbers and haloprene rubbers ; an " elastolene " as including polymers such as polyisobutylene and an " elastothiomer " as including the polyalkylene sulphides. The polymerizable mono-olefinic monomers preferred are those of general formula CH 2 =C(R)X, where R is halogen, hydrogen or a saturated aliphatic radical, and X may be selected from the following groups: 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> and -CON(R<SP>1</SP>), where R<SP>1</SP> is alkyl. Many examples of such compounds are listed in the Specification. It is stated that the preferred compound of this type is an alkyl acrylate, e.g. methyl acrylate. The top-coating may contain additionally from 0.5-3 per cent, based on the total weight of vinylidene chloride and alkyl acrylate in the top coating, of an unsaturated aliphatic acid, e.g. preferably itaconic acid, but also acrylic or methacrylic acid. Both sub- and top-coating layers may contain in addition, pigments, dyes, delustrants and plasticisers, and are applied to the base film by conventional methods either from aqueous dispersions or solutions of the polymers in organic solvents. Before being coated, the base film, if of polyethylene teraphthalate, may be stretched and/or rolled and may be heat set, and if of polyethylene, may be treated with ozone at above 150‹ C. to improve the adhesion of the coating compositions to the base film. Specifications 718,422 and 758,461 are referred to.</p> |
