GB1025623A - Improvements relating to multi-ply structures - Google Patents

Abstract

1,025,623. Laminates. E. I. DU PONT DE NEMOURS & CO. June 6, 1963 [May 20, 1963], No. 22644/63. Heading B5N. A tear resistant laminate comprises two layers of polymeric sheet material bonded to each other, each sheet having a ratio of tear initiation to tear propagation strength above 200 and having a plurality of parallel weak channels, the channels of one sheet being disposed at an angle of at least 20 degrees to the channels of the other sheet and being arranged so that a tear in any straight line will encounter at least one channel and each channel in one sheet will intersect at least one channel in the other sheet. The weak channels may be formed by spaced slits 12, 13, rows of perforations, stretching the sheet in one direction until weak channels form, lines of reduced thickness, e.g. embossing or by density inhomogeneities. Suitable polymeric sheet materials are polyethylene or polypropylene in plain or cellular form, polyethylene terephthalate, polyhexamethylene adipamide, polyvinyl fluoride, regenerated cellulose, polyvinyl chloride, polyimides and copolymers of tetrafluoroethylene with hexafluoropropylene. The sheets may be bonded by adhesives such as chloroprene rubber, ethylene-vinyl acetate copolymers, branched polyethylene, styrene butadiene rubber and polyalkylene ether glycol polyurethanes. The thermoplastic sheet materials may be bonded together by heat-sealing. The tear resistant sheet may have additional layers such as an interposed layer of a vapour impermeable material or surface layers such as plastics films, paper or burlap fabrics. The laminate may be used as a packaging material such as bags or wrapping and may be used for reinforcing tear susceptible sheets or as a backing material for carpets.