Patent GB-1435588-A (GB)
Title: Process
IPC: B32B15/08
Filed: 1973-05-30
Abstract: 1435588 Laminating apparatus and method MITSUI PETROCHEMICAL INDUSTRIES Ltd 30 May 1973 25691/73 Headings B5N and B5A [Also in Division G3] A process for producing a laminated sheet composed of a thermosplastic resin and metal sheet comprises feeding a metal sheet having a thickness of 0À01 to 1À0 mm. to the nip between a pair of heated rollers, feeding a heated thermoplastic resin to the rollers so that an accumulation of resin is produced upstream of the rollers at the nip thereof, pressing the metal sheet to the resin sheet while the resin forms said accumulation and cooling the product at a cooling rate, of less than 200‹ C./min. The metal sheet, which may be wider than the resin sheet may be made of aluminium, iron, lead or an alloy thereof and may be coated with zinc, tin or chromium or may have a coating of a resin, e.g. an epoxy, acrylic or melamine-aldehyde resin on the face which is not adhered to the resin sheet. The resin may be a polyolefine, e.g. polyethylene, polypropylene or polystyrene, a defined copolymer, e.g. an ethylene (propylene copolymer, polyvinyl chloride, an acrylonitrile-butadiene-styrene copolymer, a polyamide, a polyurethane or a butadienestyrene block copolymer and may be fed directly from an extruder to the nip. In a preferred embodiment, the resin sheet is sandwiched between two metal sheets. An apparatus for producing a laminated sheet comprises a pair of heated rollers, first feeding means for feeding a metal sheet to the nip between the rollers, second feeding means for feeding a sheet of heated thermoplastic resin to the rollers, means for detecting the presence of an accumulation of resin at the upstream side of the rollers at the nip thereof, control means for controlling the second feeding means in dependance upon said detection and means for cooling the laminated sheet down stream of the rollers. In the embodiment described with reference to Fig. 1, a heated sheet 3 of the resin extruded from die 2 of extruder 1 is passed between rollers 4 and 4<SP>1</SP>, thin metal sheets 5 and 5<SP>1</SP> being fed by guide rollers 6 and 6<SP>1</SP> and pressed and heat-adhered to the sheet 3 by the rollers, the metal sheets being optionally pre-heated by heaters 7 and 7<SP>1</SP> and the amount of resin extruded and the drawing speed being controlled so that an accumulation 8 of resin is formed at the nip of rollers 4 and 4<SP>1</SP>. The resultant laminated sheet is gradually cooled by an air-knife whilst tensioned by pinch rollers 10 and 10<SP>1</SP> or steel belts, further cooling, after the temperature of the metal has been reduced to 90‹ to 110‹ C. being effected in a cooling water bath 12 and optionally in a further cooling apparatus prior to cutting to width and length in a flash removing and cutting apparatus 14. Fig. 2 shows a control device for regulating the amount of resin in the accumulation, numeral 2 showing molten resin from extruder 1 passing through calender rollers 3, numeral 4 showing the accumulation. A light source 5 is situated at one side of the rollers 3 and light passes from the source to a photocell 7 situated on the side of the rollers opposite the light source, a series of slits being arranged at spaced intervals in front of the photocell. The size of the accumulation is determined by measuring the amount of light reaching the photocell and detected by the detector 8 connected to an automatic circuit control 9 which adjusts the rate of rotation of the extruder shaft, means being provided for manual operation.