Patent GB-932482-A (GB)
IPC: D01D10/04
Abstract: 932,482. Fibrous fabrics. E. I. DU PONT DE NEMOURS & CO. Dec. 14, 1960 [Dec. 15, 1959 (2)], No. 42991/60. Drawings to Specification. Class 42 (2). [Also in Group IX] A non-woven filamentary structure e.g. a batt, mat, web or sheet, comprises continuous synthetic organic filaments disposed in a random, loopy configuration uniformly throughout the structure without a pattern of parallelism between the filaments. The filaments may have crimp e.g. 30-100 three-dimensional helical crimps per inch, as may be induced or modified by controlled relaxation or shrinkage of the structure, and the surface of the structure may bear an embossed pattern. Normal finishing treatments e.g. buffing, felting, shearing, brushing, printing, napping may be applied. A process for making the structure comprises electrostatically charging a zero- or low-twist bundle of continuous synthetic organic filaments (generally containing less than 5% by weight of moisture) forwarding the bundle under tension toward a receiving surface, reducing the amount of tension to permit separation of the individually charged filaments by mutual repulsion thereof before they reach the surface which is so positioned that the direction of movement of the filaments is changed when they impinge thereagainst so that the filaments are deposited on the surface according to the specified pattern. The surface, which may be earthed or charged oppositely to the filaments in order to hold securely the filaments deposited thereon, is provided by a solid or foraminous plate, screen, belt or rolls, or by a liquid: it may move continuously or intermittently with or without reciprocal and/or circular motion or be shaped to produce a preformed article or predetermined contour. The filaments may be charged by a corona discharge maintained in the vicinity of the bundle, or by triboelectric contact e.g. with guides and/or a forwarding aspirator, and the charge may be uniformly maintained or alternate (to produce transverse loops in the structure). The filaments may be of polyamides such as polyhexamethylene, adipamide, polycaproamide and/or copolymers thereof; polyesters such as polyethylene terephthalate, poly(hexahydro-pxylene terephthalate) and/or copolymers thereof; polyhydrocarbons such as polypropylene polyethylene, polyurethanes, polycarbonates; polyacetals, polyacrylics, vinyl polymers, vinylidene polymers, cellulosics. Additives e.g. conductive salts such as lithium chloride, or minor quantities of a comonomer e.g. 2% of sulphoisophthalate ester incorporated during preparation of polyethylene terephthalate, to render the filaments responsive to the electrostatic treatment, may be employed. Conductivity may be imported to freshly formed filaments by spinning or grafting a conducting sheath thereabout. Filaments of different materials may be blended. The cross-section of individual filaments may be modified e.g. as a Y or ribbon cross-section, to provide enhanced triboelectric contact with a charging surface. A binder is applied to the structure by spraying on to the charged filaments (and the binder particles may be oppositely charged to the fibres) dipping in a solution or dispersion, or as low melting fibres (which are rendered adhesive by heat or solvents) introduced by aspiration or cospinning. The filaments may be bonded at spaced points throughout the structure. Binder fibres may be of polycaproamide or copolymers or melt blends thereof (with polyhexamethylene) or isophthalate copolymers, or filaments of reduced orientation of, polyethylene terephthalate for the latter. In the preparation of one binding material, an aqueous dispersion of an elastomer containing polyethylene acrylate and polyvinyl acetate, to which is added diepoxide resin, butylated melamine formaldehyde resin and titanium dioxide, is converted to fibrids which are used in the form of a slurry. A batt may be compacted by pressing, and stabilized by heating to fuse individual filaments at points of filament crossings or by a controlled electric discharge at intervals throughout the main structure, or by needle punching.