Patent CS-203915-B2 (CS)
Title: Needle-punched fabric and method of manufacturing same
Inventor: SMITH ALEXANDER M
IPC: D04H1/46
Filed: 1973-01-26
Abstract: 1418061 Artificial leather FIBERWOVEN CORP 3 Jan 1973 [28 Jan 1972] 377/73 Heading B2E [Also in Divisions B5 and D1] An artificial leather comprises a coated needled non-woven fabric having an overall bulk density of at least 6 lbs/ft<SP>3</SP> e.g. 20 to 45 lbs/ft<SP>3</SP> and its axis of flexure is within 0.3 of the distance from the face surface to the back surface. Preferably there is a density gradient across the fabric thickness, the face region having the greatest density. The fabric is bonded, dried, buffed, sanded and a coating of polyurethane applied to the face side of the fabric by means of a doctor blade. The fabric is dried and stood at room temperature for 3 hours whilst the polyurethane becomes 30% cured and then embossed between an upper belt at 400‹F and a lower belt at 75‹C so that the upstanding fibres at the surface are orientated in the plane of the fabric and form with the polyurethane a porous surface layer. Three coats of pigment plus an aqueous emulsion of 74/20/3/3 copolymer of ethyl acrylate, methyl acrylate, methylol acrylamide and methacrylic acid are sprayed onto the face side, the fabric embossed at 345‹F to give a grained texture then sprayed on the face side with a nitrocellulose laquer and on the back surface with an aqueous solution of sulphonated fats as a softener. In an alternative embodiment an impervious coating of P.V.C. or polyurethane may be sprayed on.  As shown in Fig. 1 a plurality of corded webs are laid one on top of the other, the middle webs having fibres of greater length and/or denier than those of the outer webs The sandwich is compacted, needled and split into two. Each split web now has a fibre pick up gradient i.e. the fibres of the face region are of the smaller length and/or density than those of the back region. Needling thus densifies the face region more than the back region. (Where splitting is not used a 2 or 3 layer composite web is given its first needling from the face side only.) Two corded layers of # to ¥ inch length and ¢ to 2 denier fibres are applied to the face surface, the second layer preferably having the fibres of smallest length and denier. The fabric is needled a second time, dipped in a concentrated aqueous solution of a wetting agent soap or thickening agent so as to facilitate a third needling, then washed and dried. Preferably no more than # inch of each needle penetrates through the thickness of the fabric during needling. The fabric is then passed between a roll having a plurality of upstanding wires and a friction roll, there being a difference of 1 to 100% in their peripheral speeds, the friction roll preferably rotating faster. Alternatively the fabric is transversely stretched on a tenter and then heated with hot air. The fibre entanglement is thereby lessened, fibre relaxation encouraged, the ratio of longitudinal transverse stressstrain modulus reduced to 2 or even to unity, and heat shrinkage of the face region facilitated. The fabric is hot pressed between two belts. In example 1 the first portion of the upper belt is maintained at 460‹F. The lower belt and the second portion of the upper belt is maintained below 200‹C by circulating cooling water through heat exchanger over which the belts pass. The fibres preferably have 3 to 28 crimps per inch and are nylon, polyester, polyacrylic, polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, cotton, collagen, wool and combinations thereof. The fabric may comprise 5 to 200% by weight of the fibres of a filler, giving a total bulk density of 20-45 lbs/ft<SP>3</SP>. Preferably the filler is an organic polymer such as collagen. Natural rubber, silicone or fluorosilicon rubber, polyacrylonitrile, polyethylene polypropylene, chlorosulphonated polyethylene, plasticised P.V.C., copolymers of tetrafluoroethylene and chlorotrifluoroethylene, polysulphides, polychloroprene, polymers and copolymers of butadiene, isobutylene butene and pentene and copolymers of alkyl acrylates with vinyl ethers. Alternatively finely divided chalk, bentonite, kaolin, talc, clays, asbestos, diatomaceous earth, silica flour, mica, magnesium silicate, zeolites, carbon black, zinc oxide, barytes, or ferric oxide may be bonded to the fibres with P.V.C., natural rubber or butadiene, polychloroprene, polyurethane or silicon rubber. In example 1 a natural rubber latex is padded onto the fabric and coagulated by 10 minutes treatment with steam at 218‹F. Preferably the filler forms spheres arranged in groups and loosely bonds the fibres.