GB914712A - Improvements relating to bonded fibrous sheet material and its production - Google Patents

Abstract

914,712. Coated bonded fibrous material. DU PONT DE NEMOURS & CO., E. I. July 3, 1959 [July 3, 1958; Feb. 3, 1959], No. 23030/59. Class 140. A flexible moisture-permeable sheet material having the properties of soft suede comprises a ligated fibrous mat comprising at least 50%, based on weight of fibres in the mat, of in situretracted synthetic fibres, the said mat having been shrunk by 30% to 80% of its original planar area, and dispersed throughout the said mat 10% to 90% based on the weight of fibres in the mat, of a synthetic polymer binder for said fibres, said binder being in such a form that in the absence of the fibres it would have a tensile stress of 5% elongation of 5 to 150 pounds per square inch. The sheet material may be made by forming a mat or web of retractable synthetic staple fibres some of which are positioned substantially perpendicular to the plane of the mat, treating the mat so as to retract the fibres to effect a reduction in the surface area of the mat of from 30 to 80% and then impregnating the shrunken mat with from 10 to 90% of the binder based on the weight of fibres in the mat. The shrinking is done with hot water or other means capable of retracting the fibres without fusing or damaging them. The mat may comprise several layers, the fibres of which may be mainly oriented in different directions. The binder may be introduced into the mat in the form of a solution or aqueous dispersion, or as a dry powder or as a slurry of fibrils, after whi h it is coagulated by immersing the mat in a coagulant or other appropriate means and the mat is thereafter dried. By the term " ligated " and " ligating " is meant the binding together of adjacently disposed fibres lying substantially parallel to the plane of the mat by forcibly orienting sufficient fibres to a position substantially perpendicular to the plane of the mat so that a unitary dense coherent structure is formed. The required fibre orientation may be accomplished by punching the mat with fine barbed needles in a needle loom. Specified fibres and shrinking agents (the latter in brackets) are cellulose acetate (aqueous acetone), nylon (dilute nitric acid), polyethylene (hot water), polyethylene terephthalate (hot water or hot air), polystyrene, polytetrafluoroethylene, copolymer of acrylonitrile and vinyl chloride, and copolymer of vinyl chloride and vinylidene chloride (hot air). A suitable binder is an elastomer formed by employing a compound having two active hydrogen atoms bonded to amino-nitrogen atoms to chain-extend the reaction product of a polyalkylene ether glycol and an organic diisocyanate. Suitable glycols are those of polyethylene ether, polypropylene ether, polytetramethylene ether, polyhexamethylene ether, polyoctamethylene ether, polynonomethylene ether or polydecamethylene ether. Suitable diisocyanates are tolylene- 2,4; tolylene-2,6; m-phenylene ; bi-phenylene- 4,4<SP>1</SP>; methylene bis-(4-phenyl isocyanate); 4-chloro- 1,3-phenylene; naphthalene-1,5; tetramethylene-1,4; hexamethylene-1,6; decamethylene-1,10; cyclohexylene-1,4; methylene bis-(4-cyclohexylene) ; tetrahydronaphthalene. Suitable chain-extending compounds are hydrazine, mono-substituted hydrazines, dimethyl piperazine, 4-methyl-m-phenylene diamine, 4,4<SP>1</SP>-diamino-diphenylmethane, ethylene diamine, hexamethylene diamine. The binder may be dissolved in a solvent such as N,N- dimethylformamide, dimethyl sulphoxide, tetrahydrofuran, tetramethyl urea, N,N-dimethyl acetamide. The treated mat may be coated with polyvinyl chloride or a polyurethane elastomer, or may be dyed, pressed, buffed, napped, embossed, printed or otherwise subjected to fabric-treatment processing. Specifications 712,950, 788,560, 875,052, 914,711 and U.S.A. Specifications 2,336,797, 2,515,834, 2,758,908 and 2,910,763 are referred to.