GB1065680A - Improvements in or relating to coated films - Google Patents

Abstract

Synthetic, organic thermoplastic films are coated with an aqueous dispersion of a heat-sealable polymer containing 0.5 to 5.0% by weight of an ionic antistatic agent comprising the metal, ammonium or amine salt of the sulphonated condensation product of formaldehyde and an aromatic hydrocarbon and thereafter dried so that a continuous layer of the heat-sealable coating is deposited on the films. The films may comprise polymers of propylene, ethylene, butene-1, 4-methyl pentene-1, or block copolymers thereof, polyesters such as polyethylene terephthalate, polyamides such as polyhexamethylene adipamide, sebacamide, or polycaprolactam, oxymethylene polymers and copolymers. The polymers or copolymers may be mixed with stabilisers, pigments. The surface of the films may be activated by say corona discharge, ozone treatment or treatment with chemical oxidizing agents such as halogen, potassium permaganate and chromic acid. The films may be oriented in one or both directions with equal or unequal orientation in these directions. The highest degree of orientation may be in the longitudinal direction. The oriented films may be heat set before or after coating. The heat sealable polymer may be: copoymers of vinylidene chloride in major amounts with another mono ethylenically unsaturated compound copolymerisable therewith such as methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylamide, methyl, ethyl vinyl ether, methyl vinyl ketone, acrylonitrile e.g. copolymers containing 80 to 95% vinylidene chloride and up to 20% acrylonitrile, terepolymers of vinylidene chloride with the above monomers in the presence of 0.5 to 5% by weight of an ethylenically unsaturated monocarboxylic acid or polycarboxylic acid or a partial ester of a monoethylenically unsaturated polycarboxylic acid such as acrylic methacrylic, maleic, fumaric, itaconic, aconitic, ciltraconic, mesaconic acid; polyvinyl acetate, partially hydrolysed polyvinyl acetate; butadiene/acrylonitrile, butadiene/styrene, butadiene/methyl methacrylate, butadiene/methyl methacrylate/styrene copolymers; methyl methacrylate methacrylic acid copolymers; copolyesters of terephthalic acid and an other dicarboxylic acid with a glycol e.g. those containing up to 4.0 molecular proportions of combined terephthalic acid for one molecular proportion of combined sebacic acid; copolymers of vinylidene chloride and vinyl chloride, or with methyl, ethyl acrylate; copolymers of vinyl acetate with ethylene, vinyl proprionate; copolymers of vinyl chloride with ethylene, vinyl acetate. It is preferred to use the alkali, or alkaline earth metal salt of the sulphonated condensation product as the antistatic agent, the preferred aromatic hydrocarbons being naphthalene and alkyl naphthalenes. Up to 0.5% of other anionic or cationic surface active agents such as the alkali metal salts of sulphated or sulphonated long chain aliphatic alcohols such as the oleyl and cetyl alcohols active agent such as condensation products of ethylene oxide with fatty acids, fatty acid amides, ethylene oxide/propylene oxide copolymers, polyoxyethylated nonyl phenol, polyoxyethylated octyl cresol, polyoxyethylated alkyl alcohols such as the oleyl and cetylal cohols and hydrolysed polyvinyl acetate, may be included in the dispersion. The dispersion may also contain antioxidants, dyes, pigments, lubricants, u.v. light stabilisers, slip agents such as starch, talc, zinc oxide, calcium carbonate, magnesium carbonate, diatomaceous earths, silica, kaolin, titanium dioxide, triferric tetroxide and other inorganic oxides, carbonates, silicates, aluminates, alumino silicates, polypropylene, polyvinyl chloride, antiblocking agents such as natural waxes, paraffin wax, microcrystalline waxes, beeswax, carnauba wax, montan wax and synthetic waxes such as hydrogenated castor oil, chlorinated hydrocarbon waxes, long chain fatty acid amides. The coatings may be applied by say roller coating, spraying, doctor-knife or air-knife coating. In the Examples, the coated films are tested for heat seal strength and blocking values.