GB795175A - Coated boxboard - Google Patents

Abstract

795,175. Coated boxboard or paper. LOWE PAPER CO. Sept. 26, 1955 [July 19, 1955], No. 27357/55. Class 140. A coated boxboard or paper comprises a base coat of a hydrophobic thermoplastic material bonded to boxboard or paper, a portion of which at least is reprocessed wood pulp, and applied thereover a water-suspension of a mineral pigment with an adhesive component which by weight is 10 to 35 per cent of the weight of pigment used. The base coat may be of polyethylene or one or more of the following materials : acrylonitrile polymers and copolymers, plasticized polyvinylchloride, vinyl chloride and its copolymers, vinylidene chloride and its copolymers, acrylic polymers and copolymers, butadiene-acrylonitrile, cellulose acetate and polyvinyl butyral. The mineral pigments may be one or a combination of kaolin clay, titanium dioxide, barium sulphate, zinc sulphide, calcium carbonate or metallic powder such as aluminium or bronze powder. The adhesives used are selected from casein, starch, protein, butadiene styrene copolymer, acrylic polymers and copolymers or polyvinyl alcohol. To render the hydrophobic base coat acceptable to the aqueous suspension it is pressed while still plastic against a rough surface then cooled; it is stated that in this way polythene surfaces may be made readily print-acceptable. The aqueous top coat is applied to the base coat and dried at temperatures between 120‹ and 200‹ F., after which it is fused with the base coat by heating at a temperature high enough to soften the base coat, and a highly glossy surface may be achieved by pressing against a rotating polished drum maintained at 80‹ to 300‹ F. and with a pressure of 100-1000 1bs. per linear inch.