| 摘要 |
<p>A barrier, non blocking, and/or heat sealable coating is produced on a shaped article e.g. a film, sheet, moulding extrusion or section of a rigid or semi-rigid nature, of any size, shape or thickness of an oriented alkenyl aromatic resin, by applying to a hydrophyllic surface of the article a continuous coating consisting of or containing an aqueous dispersion of a copolymer of (a) from 40 to 60% by weight of a monovinyl aromatic hydrocarbon compound having from 8 to 10 carbon atoms and wherein the vinyl group is attached directly to the benzene ring e.g. styrene, vinyltoluene, vinylxylene, and vinylethyl benzene, (b) from 35 to 50% by weight of an alkyl acrylate containing up to 14 carbon atoms in the alkyl group, or a mixture of such alkyl acrylates, and (c) from 0.25 to 10% by weight of acrylic, methacrylic or itaconic acid, or a mixture thereof, drying the coating, applying over the dried coating a second coating of an aqueous dispersion of a film forming vinylidene chloride copolymer, and drying the second coating. "Alkenyl aromatic resin" is defined as being a polymer which may have an essentially linear molecular configuration or be in a cross-linked form and which contains at least 50% by weight of at least one polymerized alkenyl aromatic compound or monomer of general formula Ar-Cr = CH2 wherein R is hydrogen or methyl, and Ar is an aromatic radical, advantageously of the benzene series, of from 8 to 10 carbon atoms (including the carbon atoms in any ring substituents on the aromatic nucleus), e.g. thermoplastic polymers and copolymers of styrene, polymers and copolymers of x-methyl styrene, vinyltoluene, mono- or dichlorostyrenes and ar-dimethylstyrenes, including copolymers thereof with such materials as vinylidene chloride and acrylonitrile; and graft copolymers thereof with other polymeric substances such as other elastomeric polymers. The surface of the article may be rendered hydrophyllic by surface sulphonation of chlorination, corona discharge or flame treatment. The first aqueous copolymer coating may be dried at a temperature of from about 50 DEG C. to below the deorientatism temperature of the oriented alkenyl aromatic resin shaped article. The film forming vinylidene chloride copolymer may contain at least 70% by weight of vinylidene chloride with, for example, acrylonitrile, vinyl chloride and alkyl acrylate. The coatings may be applied by brushing, spraying, roller coating, dipping or other means. Excess coating may be removed by means of a doctor blade, squeeze rolls, air knife or doctor.</p> |
