Patent GB-914714-A (GB)
Title: Non-woven fabrics
IPC: B29C70/30
Filed: 1960-12-14
Abstract: 914,714. Non-woven fabrics; paper containing synthetic filaments. DU PONT DE NEMOURS & CO., E. I. Dec. 14, 1960 [Dec. 15, 1959], No. 42992/60. Classes 96 and 140. [Also in Group IX] A non-woven fabric comprises crimped synthetic organic polymer fibres having at least 30 crimps per inch which are bonded together at random fibre cross-over points by a synthetic organic polymer binder which is dispersed throughout the fabric, the average free fibre length between bond points being at least 1.25 times the average straight line distance between these bond points, the binder having an initial tensile modulus (Mi) of from 0.002 to 25 and being present in an amount such that it constitutes from 3 to 50% by weight of the fabric and such that percentage binder Î <SP>3</SP>#Mi(binder) < 40 the fabric having a density of from 0.28 to 0.7 grams per c.c., a drape stiffness of less than 1.0 inch and a sonic velocity transmission of 6% elongation of the fabric equal to at least 1.3 times its value at 0% elongation. The fibres may be deposited to form a batt or sheet from a slurry by paper-making technique or from a stream of gas or filaments may be continuously spun and deposited by apparatus as described below. As shown in Fig. 1, freshly formed filaments 1 issuing from spinneret 2 are passed through aspirator jet 3 to which is supplied air under pressure through inlet 4. The air flows concurrently with the filaments to attenuate, orient and forward them. Aspirate jet 3 is charged to a high positive potential by a source 5 of electrostatic potential through lead 6, the opposite pole being earthed through lead 7. Upon passing aspirator jet 3 the changed filaments 8 are collected into sheet 9 on receiver 10 which is supported by means indicated fragmentarily at 11. Receiver 10 is either earthed through lead 12 or is charged opposite to the charge of filaments 8 by lead 13 from source 5, the lead 12 to earth then being interrupted at switch 14. Under the influence of the electrical charge the individual filaments separate and lay down as a web in a completely random configuration and they also spontaneously crimp. Bonding of the web may be effected by spinning lowmelting binder filaments along with the filaments to be bound and then heating to fuse the lowmelting filaments, or by spraying or flocking fibrids on to the web during its formation. By the term " fibrid " is meant a non-rigid, wholly synthetic fibre-like or film-like polymeric particle capable of forming paper-like structures. Fibrid binders effect bonding by physical entanglement and also, if low-melting fibrids and heat are used, by fibrid fusion. Spontaneously elongatable fibres may be used which, upon thermal treatment, undergo a substantial increase in length, e.g. condensation polymers such as polyesters, polyamides and polymethanes and also acrylic and polyolefinic addition type polymers. Specified binders are butadiene-styrene copolymers; terpolymers of butadiene, styrene and acrylonitrile ; copolymers and terpolymers of poly(methyl acrylate) together with other acrylates and acrylic acid; a mixture of polymethyl methacrylate, glycidyl methacrylate and an acrylate ester copolymer ; a terpolymer of methyl acrylate, methyl methacrylate and acrylic acid; a copolymer of ethyl acrylate and acrylic acid; a mixture of polyhexylmethacrylate, polyethyl acrylate and polyacrylic acid; poly(ethylene/propylene) containing dicumyl peroxide; a reaction product of poly(tetramethylene ether) glycol, tolylene 2,4- diisocyanate, methylene bis-(4-phenyl-isocyanate) and hydrazine; polyhexamethylene adipamide, polycaproamide and copolymers thereof; poly-N-methoxy hexamethylene adipamide; polyethylene terephthalate, polyethylene isophthalate and copolymers thereof; poly(hexahydro-p-xylylene terephthalate) ; methanes formed by reacting piperazine and ethylene bischloroformate; and polyurethanes of hexamethylene diamine and ethylene bis-chloroformate. Specifications 841,230, 849,154, 849,156, 868,651 and 914,711 are referred to.