Patent GB-978654-A (GB)
Title: Improvements in or relating to laminated material and method and apparatus for the manufacture thereof
IPC: B29C51/22
Filed: 1960-12-14
Abstract: 978,654. Laminates and laminating. M. A. CHAVANNES. Dec. 14, 1960, No. 42983/60. Heading B5N. [Also in Division B8] A laminated structure having hollow closed cells and suitable for use as a cushioning material is made by heat-treating two films of thermoplastics until at least one surface of each is at its fusing temperature, passing one film over an embossing roller provided with surface cavities, a surface of the film at fusing temperature being turned away from the embossing roller, depressing the first film into the surface cavities, applying the other film under pressure with its surface at fusing temperature touching the non-depressed parts of the surface of the first film so that the two films are welded together, without rupture of either, and stripping the product from the embossing roller by means of a separate non- embossing roller. As shown, the first film 11 is passed around rollers 12, 13 and 14, which are heated to successively higher temperatures, to the vacuum-moulding roller 10. The vacuum draws the film into the recesses of the roller, but the non-recessed portions are kept hot by a heater 15, and by the fact that the surface 10<SP>1</SP> of the roller is of heat-insulating material. The second film 16 passes round the rollers 17, 18 and 19, which are heated to successively higher temperatures, and is pressed on to the first film by the roller 19, so sealing the depressions in it. The laminated structure 21 is stripped off the roller 10 by the stripping roller 20. In other embodiments (Figs. 2-5, not shown), one or both of the films may be freshly extruded and fed round a cooling roller to the roller 10, thus avoiding the need for reheating; or the second film is also moulded on a vacuum-moulding belt to form recesses in register with those of the first film. The process may be carried out at superatmospheric pressure to avoid the partial collapse of the sealed cells on cooling. The laminate may have additional layers bonded to it, e.g. a third film overlying the extremities of the depressions of the first film and substantially parallel to the second; or a layer of paper, textile fabric, rubber or foamed plastics material secured to that surface of the second film that is away from the first; or may be enclosed, by edge-sealing around its whole periphery, between barrier layers, e.g. of aluminium foil, that protect it against gas or water vapour; or may be enclosed within a resilient material, which may be natural or synthetic rubber or a foamed material. Each cell may contain a powdered material, which may be fire-retardant or desiccant. Two of the laminated structures may be secured together face to face, with the cells of one located between the cells of the other. Thermoplastics materials referred to are: polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polyethylene, polystryrene, polypropylene, polyvinylidene chloride and polyvinyl butyral. Use can also be made of thermosetting plastics materials that have a thermoplastic stage or materials which are mouldable before curing or vulcanizing, such as natural or butyl rubber.