GB1385716A - Method of manufacturing laminates of expanded thermoplastic resins - Google Patents

Abstract

1385716 Laminates LAVORAZIONE MATERIE PLASTICHE SpA 24 July 1972 [10 Aug 1971] 34488/72 Heading B5N A laminate comprising a layer of rigid, closedcell foam thermoplastic at least one of the faces of which is heat sealed to a backing sheet is produced by heating a backing sheet to a temperature above the fusion temperature of the thermoplastic foam and continuously pressing the heated backing sheet into contact with a surface of a layer of rigid closed cell thermoplastic foam so that the heated backing sheet causes fusion of the surface of the foam layer with which it is in contact and the backing sheet becomes bonded to the foam layer without the use of an adhesive. The backing sheet may be of paper, cardboard, fabric, aluminium sheet or plastics film and the foam may be of polystyrene of thickness 1-10 mm. The foam may be made by extruding, e.g. through an annular slit, a heat-softened pressurized mass of polystyrene having dissolved or dispersed therein an expanding agent, e.g. isopentane, drawing it tranversely and longitudinally before or during cooling, optionally slitting, subjecting it to pressure, stabilization of its cells by storing it for at least 24 hours at atmospheric or slightly superatmospheric pressure and then subjecting it to expansion by heating it to a temperature 10‹-30‹ C. less than its softening temperature and to quick cooling, e.g. to less than 50‹ C. by means of jets of cool air. In Fig. 1 foam layer 12 is passed under the action of mutually parallel pairs of chain entrainers 14, 16 between heat radiators 20 so that it increases in thickness and its density decreases, cooled by means of fans 21 and trimmed by knives 22, the cuttings 24 being sent for remelting. Strips of paper 32 and 34 run over arcuate shields 36 and 38 heated by electrical resistances 40 and provided with pressure feet 36A and 38A which press the paper against the foam web. The temperature of the pressure feet may fall progressively in the direction of travel of the laminate to below the melting point of the foam resin and subsequently to below the softening point of the resin. Rollers 42, which may be heated, form a calibrated passage of width less than the thickness of laminate 12A to anneal the bond between the components. The laminate is then heated by infra-red radiators 44 to cause further expansion of foam web 12 while the laminate is kept stretched by the traction exerted by rollers 26, passed between cooled rollers 46 and calibrator rollers 50 each associated with cooling fan 52 and cut into sheets of the desired length by cutting device 54. Shields 36 and 38 may be replaced by one or more pairs of heating rolls.