| 摘要 |
<p>Coating compositions suitable for improving the heat sealability of polyolefin structures comprise water, 5 to 20% by weight of an alkali soluble copolymer of a vinyl ester and an ethylenically unsaturated carboxylic acid, a sufficient amount of at least one volatile, water-soluble base to render the copolymer soluble in water and 3 to 15% by weight of a finely-divided, water-insoluble, inorganic material. The vinyl ester may be vinyl acetate, vinyl propionate or vinyl butyrate. The carboxylic acid may be acrylic, crotonic, isocrotonic, methacrylic, tiglic or angelic acid, or a monoalkyl ester of a dibasic acid such as monomethyl, monoethyl or monobutyl maleate, fumarate, itaconate or citraconate. The volatile base may be ammonia, an aliphatic amine or alkylolamine. The inorganic material may be colloidal silica, diatomaceous earth, calcium silicate, bentonite or finely-divided clay. The compositions may also contain anti-blocking material, e.g. paraffin wax, microcrystalline wax, bee's wax, carnauba wax, japan wax, montan wax, hydrogenated castor oil, chlorinated hydrocarbon waxes and long chain fatty acid amides, and finely-divided polymers, e.g. vinyl chloride homopolymers and copolymers, polystyrene and polymethyl methacrylate. The compositions may be used for coating films of polyolefins, e.g. polyethylene and polypropylene, to provide packaging materials.</p> |
