Patent GB-831077-A (GB)
Title: Self-supporting multi-layer articles and method of making the same
IPC: B63B5/24
Filed: 1956-07-02
Abstract: 831,077. Laminates. LONZA ELECTRIC & CHEMICAL WORKS Ltd. July 2, 1956 [July 2, 1955 (2); Sept. 8, 1955 (2); Dec. 28, 1955], No. 20471/56. Drawings to Specification. Class 140. [Also in Group XXXIII] A self-supporting, curved, multi-layer body, such as a shell for a boat, refrigerator, motor car or aeroplane, is made by deforming under slight pressure against a curved, open mould a closedcell, cellular, synthetic, non-vulcanizable plastic sheet of low specific gravity by placing pressureexerting bodies on the sheet while it is in a soft, deformable condition, hardening the deformed cellular plastic sheet while it is held in the mould, and joining to both faces of the curved sheet a solid, substantially continuous plastic layer of a self-hardening synthetic resin. The sheets of cellular material, which may comprise a polymer or copolymer of vinyl chloride, polystrene, or cellulose acetate, preferably have their outer skins removed or provided with moulded or cut ribs before deformation, which may be effected by placing bodies such as sandbags on the sheets which have been softened e.g. by moderate heating or by the use of solvents or softeners, either present in the freshly manufactured sheet, or applied subsequently. Heated pressure-exerting bodies such as warm sand bags may be used to press cold and still hard cellular sheets against a mould. Hardening of the sheet after deformation is effected by replacing the warm sand bags by cool sand bags, by evaporation of the solvent, or by chemical action. For example, in the case of a cellular material formed from polyvinyl chloride, phenyl diisocyanate, and azo-isobutyric acid dinitrile, the phenyl diisocyanate acts at first as a softener for the polyvinyl chloride, but the material hardens on exposure to moisture e.g. atmospheric moisture, or additional moisture from moist fabrics placed against the surfaces of the sheet. The shaping of the sheet may be effected with the aid of light moulds of gypsum, wood, sheet metal, reinforced synthetic resin, or the multi-layer material made according to the invention. Felt may be placed between the mould and the cellular sheet to be shaped. Several cellular sheets may be deformed and adhesively joined at the edges before or during the application of the cover layers. The self-hardening synthetic resin for the cover layers may be a urea or melamine resin, one derived from isocyanates, or a solution of an unsaturated polyester, e.g. a glycol-maleic acid polyester, in a solvent acting as a cross-linking component, e.g. styrene. Reinforcement such as fabric, synthetic foil, wire netting, or glass fibres may be embedded in the cover layers. As described, one cover layer is built up on the surface of the mould from alternate layers of polyester resin and glass fibres, cellular polyvinyl chloride plates softened by exposure to acetone vapour are caused to conform to the surface of the cover layer formed in the mould, thin felt being interposed. After hardening, the shaped plates and felt are removed, and the shaped plates secured to the cover layer, and their edges joined, by means of polyester resin. A further cover layer is built up on the exposed surface of the cellular layer by applying layers of polyester resin and glass fibres. Specification 694,964 is referred to.