| 摘要 |
A polyurethane foam is rendered readily weldable by heat or high frequency welding technique to a thermoplastic sheet by applying thereto, over at least those areas of it to which the sheet is to be caused to adhere, a coating of a welding aid comprising a thermoplastic synthetic resin which is readily weldable to itself or another thermoplastic synthetic resin and which adheres strongly to polyurethane, the thickness of the coating being such as not to seal the porous surface of the polyurethane to which it is applied. The welding aid may be applied in the form of a solution in a volatile solvent or an aqueous emulsion, the solvent or the liquid phase of the emulsion being allowed to evaporate or being driven off before the welding is effected; in the form of a plastisol; or in powder form which is caused to adhere to the polyurethane foam by the welding operation. The welding aid or an essential ingredient thereof may be polyvinyl chloride; a copolymer of vinyl chloride with vinyl acetate, polyvinylidene chloride or a copolymer of vinylidene chloride with vinyl chloride or acrylonitrile. The welding aid may also include a colouring pigment to assist in identification of those areas of the polyurethane surface to which it has been applied. A sheet of a thermoplastic, e.g. polyvinyl chloride, may be welded to the coated surface, or only at selected areas of the surface, or two sheets of polyurethane foam to each of which has been applied a coating of a thermoplastic synthetic resin, as above, the two coated surfaces may be caused to adhere to each other, by heat or high frequency welding techniques. The welding aid may be applied by brushing, spraying, roller, reverse roller or gravure roll coating. |
