Patent GB-1424163-A (GB)
Title: Method of laminating warp and weft of fibrous materials
IPC: D04H3/04
Filed: 1974-01-18
Abstract: 1424163 Laminates POLYMER PROCESSING RESEARCH INSTITUTE Ltd 18 Jan 1974 [18 Jan 1973] 02526/74 Heading B5N [Also in Divisions D1-D2] In a method of preparing a heat or adhesively bonded net or a laminate incorporating warp and weft arrays a weft array 13, Fig. 1, comprising individual filaments or yarns or a fibrillated film is placed on the top run of an endless belt 2 which has been moistened with water optionally containing surfactant or binder. The surface tension of the liquid maintains the orientation of the weft array as it is moved around by the belt. The weft array is released from the belt by the downward movement of linear members 15 transverse to the belt and situated in recesses in the belt or between the belt and the weft array. In three embodiments the wefts fall upon a warp array 1 travelling perpendicular to the motion of the belt. The speeds may be arranged so that successive weft arrays fall upon the warp without leaving gaps. Alternatively the weft arrays overlap on the warp, the overlapping regions of each weft array having a pitch half that of the central regions. The warp array may be transported upon a moistened endless belt similar to belt 2. Suction may be applied from below the warp array. In Fig. 1 continuous weft filaments 8 are cut to lengths equal to the width of the warp by a heated rod 12 in an endless belt 9 of length equal to that of the warp width and successive weft arrays 13 are deposited upon belt 2 which travels at a faster speed than belt 9 and thus creates gaps between successive weft arrays. The belt may be a lattice, a single endless sheet or a plurality of narrower endless sheets 2<SP>1</SP>, Fig. 2a each supported and moved by a pair of pulleys 21. Strings 15, Fig. 1 or 28, Fig. 2a may be stretched across the belt, tensioned by springs 26, 27 and moved with the belt by circulating chains 24, 25. Ski-shaped members 14, Fig. 1, 29, Fig. 2a are vertically reciprocated to depress the strings and thus release successive warp arrays from the belt. As shown there is one ski member 29 at each side of the belt; alternatively there may be one member between each of the sub-belts. In the embodiment of Fig. 4a a continuous weft array 52 is fed on to the moistened belt before being cut. Organic filaments may be cut by a heated wire (62, Fig. 4c, not shown) contained in a belt (61) of length equal to the width of the warp and pressed against the weft array 52 whilst it is on the main belt. Glass filament arrays may be cut by a knife 57 which rotates about axis 53 with the same peripheral speed as the belt and presses the weft against a rubber plate 59 mounted on selected lattice members 58 of the belt. In the embodiment of Fig. 3a the belt comprises lattice members 4 of length 1200 mm. and width 5-30 mm. attached to two circulating chains, one (42) being shown. Strings 48 are held under tension between lattice members 41 by supporting members 45 having one end held up by spring 43 and the other end in frictional contact with lattice member 41. The vertical reciprocation of ski members 49 displaces support member 45 and hence lowers string 48 to free the weft array. In another amendment the weft array 71, Fig. 5a, is deposited upon square cross-section lattice members 72. At the lower run of the belt ski members 78, Fig. 5d, are lowered striking U cross-section plates 76, thereby forcing them downwards against springs 75 so as to release weft 71. In Fig. 6 warp 83 is pressed on to thermoplastic film 82, weft 85 is dropped on to warp 83, a second warp 87 and a second film 82<SP>1</SP> are applied. The product is dried and heated by passage around heated drums 88 and hot pressed between rollers 89. The films may melt completely to act merely as an adhesive or they may retain their integrity to provide an impervious laminate. An additional sheet may be laminated on to the top and another on to the bottom of the product during its course of travel on the heated drums 88. The weft array may be deposited upon film 82 before a warp array is introduced. In example 3 the warp array comprises 320 stretched tapes each of which is formed from a fibrillated sheet, the weft array is identical and the films are unstretched quenched polypropylene of lower melting point. In similar embodiments the warp and weft arrays are of high density stretched polyethylene and the films are of quenched low density polyethylene or of an ethylene-vinyl acetate copolymer. The warp and weft arrays may comprise spun yarns, monofilament yarns, glass fibre yarns, carbon fibre yarns, metal wire yarns, metal filament yarns and fibrillated films. Each warp and weft component may comprise one S and one Z twist yarn to prevent untwisting. In Example 1 the warp and weft arrays are fibrillated polyethylene films. Cotton linters are deposited upon the net and the net autogeneously bonded by hot pressing. In Example 2 glass fibre warps and wefts are bonded by application of a liquid comprising polyvinyl alcohol.