Patent GB-1437001-A (GB)
Title: Laminates
IPC: F25D23/06
Filed: 1972-08-21
Abstract: 1437001 Laminates SIDAPLAX SA NV 11 July 1973 [21 Aug 1972] 38944/72 Heading B5N [Also in Divisions B2 and F4] A laminate comprises a sheet of thickness at least 200 microns of a rubber-modified polystyrene bonded to a biaxially oriented film of thickness less than 200 microns of a rubbermodified copolymer of styrene and acrylonitrile the other surface of which is bonded to a layer of polyurethane foam. The rubber may be incorporated into the polymers during or after polymerization preferably by polymerizing styrene or a mixture of styrene and acrylonitrile in the presence of natural or synthetic rubber to produce a graft copolymer of rubber and styrene or styrene and acrylonitrile. An alkyl substituted acrylonitrile or substituted styrene may be used. The synthetic rubber may be produced from butadiene, isoprene, 2,3-dimethyl butadiene, 1-phenyl butadiene or myrcene. The preferred rubber-modified polymers are polybutadiene-modified polystyrenes and ABS copolymers. The sheet and the film may be bonded together by the application of heat and pressure. Adhesion may be improved by subjecting the surface of the sheet or film or both to an electric discharge, to the action of a gaseous mixture of boron trifluoride and an oxidizing agent, to flame treatment, to the action of a strong oxidant, e.g. nitric acid, to ultra-violet radiation, to the action of a photosensitiser, e.g. benzophenone or acetophenone, and then ultra-violet radiation, to sand-blasting or other roughening treatment or to treatment with a solvent or etchant. An adhesive, e.g. an epoxy resin, polyurethane, synthetic rubber latex or acrylonitrile-acrylic ester copolymer, applied in discrete bands may be used. The layer of polyurethane foam may be poured or sprayed on to the film of rubber-modified styrene-acrylonitrile copolymer as a foamable or foaming composition and allowed to set. In Fig. 1 film 2 of rubber-modified styrene-acrylonitrile copolymer is passed over smoothing rollers 4 and 5, heated on one surface by passage over heated roller 6 and on the other side by infra-red heater 7, subjected to corona discharge emitted from electrode and bonded to rubber-modified polystyrene sheet 1 fed from an extruder by the application of heat and pressure applied by rollers 6 and 9, the resultant laminate 10 being cooled and passed to conveyer 12 where it is cut into lengths. In an alternative arrangement a heated film of biaxially or monoaxially oriented polystyrene is also fed to the nip of the rollers 6 and 9 to produce a three layer laminate in which the rubbermodified polystyrene sheet is positioned between the films of polystyrene and rubber modified styrene-aerylonitrile copolymer. The laminates of films and sheets may be vacuum formed and used in the production of refrigerator cabinets having a thermally insulating structure in the form of a box having one open side which prdvides access to the interior of the cabinet, the other sides having interior and exterior spacedapart walls, the interior wall being of the laminate with the rubber modified styrene/ acrylonitrile copolymer film facing the exterior walls, the exterior walls being of metal, wood, plastics laminates, paper, cardboard or other paper pulp materials and the space between the walls being filled with polyurethane foam. Panels or doors may also be produced by sandwiching polyurethane foam between the laminate of the film and sheet and a layer of metal, wood, paper, cardboard or other paper pulp material, the foam being cured by heating, e.g. microwave heating.