Patent GB-1384556-A (GB)
Title: Synthetic papers and method of making the same
IPC: B32B27/00
Filed: 1971-12-22
Abstract: 1384556 Laminates; seaming non-metallic sheet material MITSUBISHI PETROCHEMICAL CO Ltd 22 Dec 1971 59786/71 Headings B5N and B5K A synthetic paper-like laminate is produced by uniaxially orientating a base film layer of thermoplastic resin in the longitudinal direction by longitudinally stretching it to at least 1À3 times its original length, laminating thereto a second film layer of a thermoplastic resin having 0À5-65% by weight of particles of a fine inorganic filler of 0À3-30 micron particle size substantially uniformly dispersed therein, and stretching the laminate while in a heated state in the transverse direction by at least 2À5 times its original dimension to biaxially orientate the base film layer and uniaxially orientate the second film layer to develop microvoids in the second film layer open to a surface thereof free from the base film and distributed in the resin to define therein a cellular fibrous structure so that the second film becomes a paper-like film layer. The base film layer may also contain up to 20% by weight of fine inorganic filler of particle size 0À3-30 microns. A paper-like film layer may be laminated to each surface of the base film layer. The particles of filler may be of clay, talc, asbestos, gypsum, barium sulphate, calcium or magnesium carbonate, kieselguhr, titanium dioxide, zinc or magnesium oxide, silica or diatomaceous earth. The base film layer and paper-like film layers may be a homopolymer or copolymer of ethylene, propylene, butene-1, vinyl chloride, vinylidene chloride or styrene, polyethylene terephthalate or a polyamide, which may also contain an antistatic agent, stabilizer, dispersion agent and ultra-violet light proofing agent. In Fig. 2, base film layer 2 produced by extruding thermoplastic resin from extruder 7 through die 8 is passed over rolls 10, 11, 12 and 13 to longitudinal stretching zone where it passes over a heated roll 15a, is stretched by at least 1À3 times its length by rolls 15b and 15c and cooled over roll 15d. Layer 3 produced by extruding thermoplastic resin containing inorganic filler is laminated to one surface of layer 2 by means of rolls 20 and 21 and a further layer 5 also of thermoplastic resin containing filler similarly laminated to the other surface thereof by means of rolls 30 and 31. Laminate 1 is then passed over rolls 35, 36 and 37 to stretching apparatus 39 where in a preheating zone thereof it is heated with hot air or infra-red heating to 140-180 C., in a second zone stretched transversly by at least 2À5 times its original dimension and in a third zone cooled at 120-160 C. The ink adherence of the surfaces of the laminate may be improved by applying thereto a corona discharge treatment by means of electrodes 41 and 42. Alternatively ink adherence may be improved by subjecting the paper-like film layers to oxidation or applying thereto an electrostatic charge. The adhesion of the layers may be improved by applying to the base film layer a polyisocyanate or polytitanate prior to lamination. The synthetic paper-like laminate may be used in the production of bags by folding the laminate sheet into a bag and seaming with electrically heated bars, suitably for 2-3 seconds at a pressure of 2 kg./cm.<SP>2</SP> and temperature of 200-220 C., or by ultrasonic heat sealing. The laminate may also be used as a wallpaper or wrapping material.