Patent GB-1484584-A (GB)
Title: Manufacture of filaments
IPC: D04H13/02
Filed: 1974-08-15
Abstract: 1484584 Non-woven fabrics; electrostatic web formation BATTELLE MEMORIAL INSTITUTE 15 Aug 1974 [16 Aug 1973 6 Nov 1973 12 Dec 1973 28 Jan 1974] 36052/74 Headings D1K D1N and D1R A layer of molten dielectric material is formed upon the surface of a substrate and the material subjected to an electrostatic field orientated perpendicular to the surface of said substrate so that portions of said material are torn away and drawn in the direction of the field whilst cooling to form a plurality of filaments.  In the embodiment of Fig. 1 hopper 6 delivers powdered thermoplastic material upon metal conveyor belt 1. Belt 1 is connected to a high voltage whilst belt 4 is earthed. The filaments formed are collected upon belt 4 in the form of a non-woven fabric. Preferably the distance separating the belts is e.g. 2 cm, such that the filaments are collected whilst still tacky and hence fuse together to give an autogeneously bonded fabric. Monofilaments are formed at low viscosities whilst at higher viscosities the filaments branch out to form tree like structures comprising a main filaments. The filaments are cooled by a stream filaments are of the order of 1 micron diameter. They may be obtained from polyamide polyethylene, polystyrene, polyurethane, polyvinyl chloride, acrylic resins, tar, sugar and chocolate. In the embodiment of Fig. 2 belt 4 is replaced by a rotating tubular metal grid 13 so that a layer of filaments is deposited on the outside of the grid. Filaments are also deposited on the inside of the tubular grid from material coated onto travelling wire 9. In the embodiment of (Fig. 4, not shown) the filaments are deposited upon a rotating mandrel placed between the charged belt carrying molten material and an earthed electrode. In the embodiment of Fig. 5 branched filaments are deposited on belt 29 followed by fibres obtained by cutting monofilament filaments. The fibrous layer is subsequently needled, or calendered into the filamentary layer. To a non-woven layer formed from molten polyethylene on belt 25 may be applied cellulose fibres by flocking or from a solution of cellulose and the product calendered to form a paper. Pile fabrics. The surface of thermoplastic strip 37, Fig. 8 is melted by heater 36. Portions are attracted by electrode 34 and form filaments. The filaments are cooled by a stream of air before they contact electrode 34. The product resembles fur. The filaments may be cut to the same length by cutter 35. Filaments are produced preferentially from irregularities in the molten layer. Such irregularities can be produced by passing the molten layer supported upon a conveyor belt through the nip of a pair of rollers (50, Fig. 10, not shown). In the embodiment of (Fig. 12, not shown) grains of solid thermoplastic material are dropped onto the layer of molten thermoplastic material just before application of the electric field. The grains do not melt completely and thus act as filament initiators. In a portable apparatus the material is stored in powdered form in a hopper in which the bottom is formed by a conductive roller (41, Fig. 9, not shown) charged by a brush (42) and heated by radiation from a heater (45) placed below the roller. On placing the apparatus close to an earthed surface the coating of molten material on the roller yields filaments which are deposited on the earthed surface.