| 摘要 |
533,781. Coated fabrics; cartons; wrappers. DEWEY & ALMY, Ltd. (Dewey & Almy Chemical Co.). Aug. 15, 1939, No. 23576. Drawings to Specification. [Class 140] [Also in Group XVII] In forming a sealed paper or paper-board container or wrapping, one or both of two co-operating sealing surfaces are provided with a layer of a thermoplastic adhesive composition underlying the coating of fusible air- and moisture-excluding substances and the surfaces are subjected in contact to pressure and heat whereby the outer coating is melted and the thermoplastic composition softened to effect adhesion. Suitable air- and moisture-excluding substances are wax or waxrubber compositions. Suitable thermoplastic adhesives are polyvinyl acetate and chloride and their co-polymers ; polyacrylic acid and its esters, derivatives or homologues; polyvinyl acetates and plasticized cellulose derivatives. In an example a solution of polyvinyl acetate in ethylene dichloride, acetone or ethyl or methyl alcohol is applied to carton flaps by brushing, spraying or roll-coating and the carton is flooded with molten paraffin wax and allowed to drain in an inverted position. A portion .only of the flaps may be coated. Sealing is effected by conventional hot-plate sealing apparatus. |
