| abstract |
1364488 Non-woven fabrics BAYER AG 7 July 1971 [11 July 1970] 31826/71 Heading D1R [Also in Division B5] A process for covering a fibrous web with a polymeric coating comprises the steps of:- (a) applying to a temporary support a layer of a reaction mixture which comprises (1) at least one polyisocyanate and (2) at least one compound containing active hydrogen atoms and which will undergo a polyaddition reaction with the polyisocyanate to form a microporous polyurethane and/or polyurea layer; (b) applying to the layer before the polyaddition reaction is complete, a fibrous web, and (c) removing the fibrous web with the adhering polymeric layer from the temporary support. The polyurethane and/or polyurea may be produced in the presence of a non-solvent for the product by a single-stage process or a twostage process, the second stage of the twostage process being effected in the presence of a chain lengthening agent. Many suitable reactants for forming the layer are specified. The temporary support may be a separating paper, a glass plate, a steel plate or a conveyor belt and may carry a finish to be applied to the layer or be embossed. The fibrous web may be a woven or knitted fabric, natural leather e.g. split leather, grain leather or suede or a fibre fleece which may after application to the layer but before step (c) be impregnated with 10 to 98% by weight (based on the fleece) of a polymeric binder and the binder coagulated. The fleece may be made from polyester, polyamide, polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, cotton, staple rayon, collagen, regenerated cellulose or polyurethane fibres or mixtures thereof. The binding agent may be a copolymer of butadiene with styrene, acrylonitrile and/or acrylic or methacrylic acid, polychloroprene, an acrylic or methacrylic acid ester copolymer or a polyurethane. The finish may be a polyurethane latex or a polyacrylonitrile. In the drawing, a reaction mixture is applied to a temporary support from a mixing gear 2 to form a polyurethane layer 5 to which is applied a non- bonded fibre fleece 3, a polymeric binder from mixing gear 6 being introduced into the fleece by roller 7, the product passed under a heating means 8 prior to removal from the support 1 and drying in heating chamber 9. The apparatus may also comprise a roller 10 for applying a leather finish to the temporary support. |