Patent GB-1336201-A (GB)
Title: Non-woven fabrics
IPC: D04H5/04
Filed: 1971-08-03
Abstract: 1336201 Laminated non-woven fabric HERCULES Inc 3 Aug 1971 36513/71 Heading B5N A non-woven laminated fabric comprises two outer layers 14, 16 of staple fibres sandwiching an inner reinforcing layer of scrim 12, the scrim layer being unwoven and comprising, laid one over the other at least two webs 18, 20 of a plurality of substantially parallel, low denier, continuous mono-filament strands of a thermoplastic, hydrophobic, material, the strand directions of adjacent webs being non parallel, and wherein bonding is effected by the inherent bonding and adhesive characteristics of the fibres or by the application of an adhesive, between the outer staple fibre layers through openings in the scrim, the strands of the scrim webs being substantially unbonded either to strands of an adjacent web or to the outer staple fibre layers thereby to be free to move and distribute stress applied to the fabric. The term substantially unbonded is defined as including temporary bonding either of the strands of one web to the other web or of the strands of the webs to the outer plies, the temporary bonding being of such low strength that the bonds are broken as soon as an external stress is applied to the fabric. The outer plies which may be creped or embossed may be made by air-laying or wet-laying, may be the same or different and may be made from asbestos or cellulosic fibres, e.g. wood pulp fibres, cotton fibres or regenerated cellulose fibres or mixtures thereof. The scrim which may comprise more than two webs may be made from synthetic thermoplastic hydrophobic materials e.g. polyethylene, polypropylene, poly-(butene-1), polyvinylidene chloride, a vinyl chloride-vinyl acetate copolymer, nylon, polyethylene terephthalate, cellulose acetate, cellulose butyrate or polyacrylonitrile, the strands of the individual webs being made of one or more materials of the same or differing denier. In one embodiment, the strands of one web are of one material and the strands of another web of a different material. In a preferred embodiment, a web comprises a fibrillated film of polypropylene, nylon, polyethylene terephthalate and/or polyacrylonitrile. The adhesives used are flexible materials which adhere well to the fibres of the outer plies and poorly or not at all to the strands of the scrim e.g. co- and ter-polymers of vinyl acetate, vinyl butyrate, vinyl propionate, maleic anhydride, monobutyl maleate, dibutyl maleate, vinyl chloride, vinyl bromide, allyl chloride, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylene, propylene, isobutylene, styrene, alphamethyl styrene and acrylonitrile, polyethyl acrylate, natural rubber and synthetic rubbers. The laminated fabric of the invention may be made by air laying two plies of cellulosic fibres on screens, spraying the top surface of each ply with an aqueous dispersion of the adhesive, placing the scrim between the two damp plies, passing the resultant sandwich through a press roll, drying and removing the screens. In a second method, adhesive is applied to dry naturally bonded sheets of cellulosic fibres or to the scrim and the sandwich structure pressed and dried. In a third method, a non-woven scrim is sandwiched between two plies of undried waterlaid wood pulp fibres to provide an assembly which is pressed and dried. Examples are given of the preparation of products according to the invention.