GB906414A - Improvements in or relating to laminates - Google Patents

Abstract

906,414. Coated metal. BRITISH IRON & STEEL RESEARCH ASSOCIATION. April 27, 1961 [May 11, 1960], No. 16604/60. Class 140. A moving metal strip is coated with a heat-curable adhesive, the strip is heated to cure the adhesive, a uniform layer of mixed plasticized and stabilized thermoplastic resin is applied to the adhesive coating, the coated strip is then passed under a heated roll, the temperature at this point being sufficiently high to melt the thermoplastic powder on the entry side of the nip without causing adhesion at the exit side, the pressure of the heated roll being insufficient to deform the metal but sufficient to maintain a pool of molten thermoplastic at the entry side, the coated strip is partially cooled and passed under a roll to provide the desired surface finish. As shown, a steel strip 12 is passed through an alkaline degreasing bath 14 and then to a washing device 16 comprising water sprays 17, 18 and squeegees 19. It is then passed through a bath of hot water 20, and squeegee rolls 22 to the adhesive applicator device 23. This comprises a roller 24 in fixed bearings dipping into a bath of adhesive, e.g. an uncured phenolformaldehyde resin, nitrile rubber and sulphur, the layer of adhesive picked up by 24 being passed via roller 27 to roller 28 which applies it to the metal strip. The thickness of the adhesive layer is controlled by roller 29 mounted in movable bearings. The strip then passes to a drier 30 and furnace 31 when the temperature is raised to about 250‹ C. to cure the adhesive. It then passes to a powder applicator 32 comprising cooled rolls 33 and 34 so mounted that powdered thermoplastic material, e.g. polyvinyl chloride, can pass steadily through the gap between them through a vibrating sieve 38 and on to the heated strip. The coated strip carrying the powder passes through heated rolls 39, 40, the upper one 39 being made of polytetrafluoroethylene to prevent sticking and the lower one 40 of silicone rubber, and then to a second heated polytetrafluoroethylene roll 41 which can be rotated at any speed in either direction and supported on a silicone rubber roll 42. The roll 41 maintains a pool of molten plastic at the entry side of the nip, and overflowing is prevented by polytetrafluoroethylene side-guides 43. After leaving the nip the coated sheet is allowed to cool, passed beneath a finishing roll 44 and after further cooling wound up on a coiler 45. The Provisional Specification describes a different form of powder applicator.