GB902825A - Improvements in and relating to the production of unitary shaped composite plate structures - Google Patents

Abstract

902,825. Laminates and laminating. LONZA ELECTRIC & CHEMICAL WORKS Ltd. Feb. 11, 1959 [Feb. 11, 1958; April 12, 1958 (3)], No. 4670/59. Class 140. [Also in Group V] Unitary-shaped composite layered structures suitable for example for parts of boats or cars, for tanks or pipes, for structural elements, or for furniture, are made by jointly deforming by pressure a composite material including at least one layer of rigid or other cellular thermoplastic material and at least one layer of non-cellular thermoplastic material, the temperature of the non-cellular material being raised to within the range of plastic deformability, the temperature of the adjacent surface portion of the cellular material being also raised to within the range of plastic deformability, but a major portion of the cellular material being maintained below the deformation temperature. The cellular material may be of the open- or closed-cell type and may be of polyvinyl chloride, polyvinyl acetate, polystyrene, polyethylene, polyacrylates, cellulose acetate, polyamide, polyurethane or polycarbonate, or copolymers, or natural or synthetic elastomers. The non-cellular material may be rigid or flexible and of polyvinyl chloride, polycarbonate, polyethylene or cellulose acetate. Both layers may contain plasticizers pigments and the like. A layer of cellular material may be enclosed between two layers of non-cellular material. The non- cellular layer or layers may be stuck to the cellular layer before or during the shaping operation by means of an adhesive which may be appilied to either of the surfaces to be bonded in the form of a powder or of a solution, may be applied all over the surface or on selected parts, e.g. as dots or stripes, and may be of a polymer or copolymer of vinyl chloride, vinyl acetate, styrene, acrylonitrile or butadiene, or a thermosetting adhesive based on a polyester, epoxy resin or isocyanate. When an adhesive-containing solvent is used, vacuum may be applied to the edges of the plate, or the non-cellular layer may be perforated, to assist the escape of solvent vapours. The non- cellular layer may alternatively be applied to the surface of the cellular layer in liquid or paste form and then solidified. In a preferred method, the cellular material is of the gascontaining closed-cell type and the composite plate is deformed by applying to one surface a pressure greater than the pressure of the gas in the cells, and to the other surface a deforming pressure greater still. As shown, Fig. 2, a layer 3 of polyvinyl chloride is placed on the flange 1 of a mould 2 and held by an annular spacer 4 having a vent 5 while being coated with an acetone solution of a vinyl chloride/ acetate copolymer subsequently dried. A core 6 of cellular p.v.c. is then superposed, followed by a second layer 8 of adhesive coated p.v.c., and the mould closed with a flanged cover 9. Hot air is supplied to the cover and withdrawn through a valve-controlled central tube 11 having a terminal baffle close to the laminate to heat the surface of the latter uniformly. At the same time hot air is circulated through the mould 2. Air pressure is then raised in both mould and cover to secure adherence of the softened layers, any air or solvent remaining escaping through vent 5. Pressure is then raised further in the cover to force the laminate against the mould, air being discharged from the latter to maintain the pressure beneath the laminate constant. Finally, cold air or water is admitted to the cover to set the moulded laminate. In a modification the cover 9 may be dispensed with, moulding being effected by vacuum forming, and heating by infra-red radiation. In a further modification, a flanged hemispherical mould and corresponding cover, clamped together, each have inlets and outlets for air or water for the purpose of heating, pressure moulding, and cooling, a diametricallypositioned peripherally clamped laminate. In Fig. 4, layers of p.v.c., cellular material, p.v.c., and aluminium foil are applied in succession to the inner wall of a cylinder 28 forming part of a bag-moulding apparatus and having a wider portion at the top. Hot air is circulated on both sides of the layers via connections 21, 22, 26, 27, in the walls and cover 22 of the apparatus, and a cylindrical rubber bag 19 is then inflated via connection 25 to laminate the layers and mould them into a cylinder with flared mouth, the bag engaging the layers from their mid-point 17b outwards to express entrapped air. In another modification a heated die is used to heat, and then press into a mould, a p.v.c./cellular core/p.v.c. laminate the surface engaging the mould of which is perforated to release entrapped air and solvent. Specification 694,964 is referred to.