GB832047A - Improved laminated sheet materials - Google Patents

Abstract

832,047. Laminates. IMPERIAL CHEMICAL INDUSTRIES Ltd. Jan. 15, 1958 [Feb. 22, 1957], No. 6118/57. Class 140. A laminated sheet comprising two or more layers of thermoplastic material, with or without one or more fabric interlayers, fused together by heat and pressure or cemented by means of adhesive, is characterized in that before the layers of thermoplastic material are fused or cemented together a discrete layer of an electrically-conducting carbon in finely divided form is interposed between at least two of said layers and/or between at least one of said layers and an adjacent fabric interlayer if used. The thermoplastic material may be polyvinyl chloride, vinyl chloride interpolymers, e.g. with vinyl acetate or vinylidene chloride, polyvinylidene chloride, polystyrene, polythene, nylon or polyester, such as polyethylene terephthalate, and may be highly plasticized or may contain little or no plasticizer. Other ancillary ingredients such as stabilizers, antioxidants, fillers, extenders, dyes and pigments may also be present. At least the surface layers of thermoplastic material may contain an antistatic agent e.g. a condensation product of ethylene oxide and a long-chain fatty alcohol or acid, particularly lauryl, oleyl or cetyl alcohol or lauric acid, or an ester of pentaerythritol, glycerol or a polyethylene glycol with a longchain fatty acid, particularly lauric or oleic acid, in amount which may be between 1 and 8% by weight. The fabric interlayers may be of cotton, rayon, nylon or polyester. The electrically-conducting carbon may be graphite, which may be deposited from colloidal solution in a volatile solvent upon a thermoplastic or fabric layer, or may be a carbon black. When the laminate comprises more than two laminµ a layer of electrically-conducting carbon may be interposed close to each surface, e.g. immediately under the top layer of thermoplastic material on each surface, or immediately over or under the second, layer of thermoplastic material from each surface of a laminate made from more than four laminµ. The laminated sheet may be made by fusing together a number of fabric interlayers coated with a paste of vinyl chloride polymer and a plasticizer and may be used as conveyer belting. The layer of electrically conducting material may be applied by passing a fabric interlayer through a colloidal solution of the material either before or after coating with paste or by spreading, brushing or spraying a suspension in any convenient liquid vehicle, or may be employed in solid form, e.g. as a powder or in gaseous suspension. The laminated sheet may contain reinforcing layers e.g. of wire netting. Adhesive if used may be a solution in an organic solvent of a thermoplastic material similar to that in the layers to be cemented together or may be natural or synthetic rubber. According to the Provisional Specification, the electrically conducting layer may be of materials other than carbon, provided that they are inert under the processing conditions employed; examples are finely divided metals, particularly copper and silver in colloidal form. In another method, a metallized film or foil of thermoplastic material, which may be perforated with a large number of small closely-spaced holes, is interposed between two or more layers of thermoplastic material which are to be fused together in the production of a laminated sheet.