Patent GB-1358412-A (GB)
Title: Laminated product and method of preparing same
IPC: D04H3/045
Filed: 1971-08-25
Abstract: 1358412 Laminates; seaming non-metallic sheet material POLYMER PROCESSING RESEARCH INSTITUTE Ltd and NIPPON PETROCHEMICALS CO Ltd 25 Aug 1971 [25 Aug 1970] 39997/71 Headings B5N and B5K  A laminated product comprising a first and a second layer of parallel spaced stretched tapes of a fibrillatable polymer, the first and second layers being bonded to one another in face-toface arrangement with the tapes 1 of the first layer extending at an angle to and crossing the tapes 3 of the second layer, by a polymer film having a lower melting point than that of the tapes, the laminated product having perforations 5 in portions thereof surrounded by the crossed tapes and the polymer film material of the portions being gathered by melting towards the tapes, comprises the steps of thermally bonding a first layer of parallel spaced stretched tapes of a fibrillatable polymer to a second layer of parallel spaced stretched tapes of a fibrillatable polymer placed in face-to-face arrangement on the first layer with the tapes of the first layer extending at an angle to and crossing the tapes of the second layer, by a polymer film having a lower melting point than that of the tapes and laminated with the first and second layers, and heating the resultant laminate sufficiently to melt the polymer film whereby the molten polymer material gathers towards the tapes, covering the tapes and forming perforations at portions of the product surrounded by the crossed tapes. Laminated products according to the invention may be in the form of:- (1) a three-layer structure comprising a tape layer, a polymer film and a tape layer; (2) a four-layer structure comprising a tape layer, a polymer film, a tape layer and a polymer film; (3) a five-layer structure comprising a polymer film, a tape layer, a polymer film, a tape layer and a polymer film; or (4) a three-layer structure comprising a polymer film, a tape layer and a tape layer. In preferred embodiments, the tapes are crossed either at a right angle or at an angle of 45 degrees. The size of the perforations may be adjusted by varying the intensity of the heating, which may be effected by hot air, a high rate of heating leading to the formation of perforations of a size almost equal to that of the areas bounded by the tapes, a lower rate leading to the retention of unmelted film parts 6. A product with smaller perforations or with increased thermal insulation may be made by thermally bonding a web of fibrous material, e.g. a web of carded jute fibres, a web of synthetic fibres, a web of garnetted fibres, a web of carded new and reclaimed short fibres, a layer of crimped filaments or a layer of warp and weft threads either to one composite product or between two composite products. The stretched tapes may be made of high density polyethylene and the film of low density polyethylene, an ethylene-vinyl acetate copolymer or an ethylene-acrylamide copolymer; alternatively, the tapes may be made of polypropylene and the film of low melting polypropylene, an ethylene-propylene copolymer or a plasticized polyvinyl chloride. Other polymers from which the tapes may be made are homo- and copolymers of vinyl chloride, vinyl alcohol, acrylonitrile or vinylidene chloride, nylon, polyesters and regenerated cellulose. In the embodiment shown in Fig. 3, a product having diamond shaped perforations is made by spacing a large number of tapes in parallel, placing a polymer film slightly wider than the tape layer upon one surface thereof, bonding the film and the face layer under heat and pressure, cutting the resultant product at a predetermined angle to prepare lengths 21 of tape assembly which are held, e.g. on a suction plate prior to deposition with overlapping ends upon porous cloth belt 22 which is driven around a drive roller 23 and a heating roller 24 and has a suction chamber 25 provided below its upper span. The deposited overlapping lengths being fed via roller 26 to the heating roller 24 and pressed between the heating roller and pressure roller 27 to bond the overlapped edges and form a tape assembly 29 which is then cooled, a laminated perforated product being made by superposing two tape assemblies 29 with crossed tapes, bonding the assemblies under heat and pressure, transferring the resultant product to a hot air chamber and melting the polymer film by hot air blown at right angles to the product. Stretched polyethylene tapes for use in making the product of the invention may be made by melt extruding a tubular polyethylene film, water quenching the film whilst passing it through nip rollers, cutting both ends of the folded film, passing the resultant cut films through pinch rollers and a wave-form curved slit, stretching the films to four times their original length to form an assembly of two superposed films, passing the assembly through pinch rollers, placing the films in side-by-side parallel arrangement, passing the films through a drier drum, through a wave-form curved slit and into a hot air chamber in which hot air is blown against each surface of the parallel films and the films stretched to a total of nine times their original length. The two films are again arranged in parallel and split fibre yarns inserted between two successive wound layers of the films in a zig-zag manner whilst traversing split fibre yarns beyond the edges of the film in an arc shape, a weak tension is applied to the films which are then wound in a cylindrical form, the films being then unwound, separated from the fibres, subjected to tension in a hot air chamber and slit into tapes.