| 摘要 |
<p>1413656 Coated sheet materials STAR PAPER LTD 23 Feb 1973 [8 March 1972] 10817/72 Heading B2E A process in which a moulded smooth polymeric coating is formed on a sheet substrate by applying to the substrate an aqueous coating comprising an aqueous emulsion or dispersion of polymeric material, forming a continuous film of the polymeric material in the presence of water, and subsequently evaporating at least some of the water by heating the aqueous coating, without application of pressure, to a temperature above the film forming temperature of the polymeric material, and moulding the film by pressing it aganst a moulding surface under a pressure at least 5 kg/cm<SP>2</SP> at greater than 100‹C. The substrate may be permeable, e.g. paper and paperboard, or impermeable, e.g. aluminium foil. The paper or paperboard may contain synthetic resin fibres. The polymeric emulsion, which generally has a viscosity of 40 to 80 units (by Mooney viscometer), may comprise polyvinyl acetate, polyvinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polystyrene copolymers, polyurethanes, polyacrylates, polymethacrylates, polyacrylonitriles, polyamides, polyethylenes or plasticised polystyrene. Tack reducing agents such as sodium carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose, or polyvinyl pyrrolidone may be used in amounts of 10% by wt. of the main polymer while sodium alginate may be used in amounts of 2%. Other materials that can be used in minor amounts include wax, polyethylene, or stearates, or acrylic copolymers such as butadiene/ methyl methacrylate copolymer, styrene/acrylic copolymers, styrene/maleic anhydride copolymers, or ammonium salts of acrylic copolymers. The polymer may be clear and have a second order transition temperature of above -10‹C but less than 70‹C. The polymer surface may be matt, glossy or embossed, and the coated article may be a wood grain effect sheet or picture postcard. The preferred process applies the emulsion or dispersion by air knife.</p> |
