Patent GB-1243512-A (GB)
Title: Method of producing filaments, fibres or fibre networks
Inventor: RASMUSSEN OLE-BENDT
IPC: B29C48/18
Filed: 1967-08-09
Abstract: 1,243,512. Filamentary structures. O-B. RASMUSSEN. 9 Aug., 1968 [9 Aug., 1967], No. 37930/68. Divided out of 1,240,661. Heading B5B. [Also in Division C1] Fibres, including yarn, are made by splitting strips comprising a plurality of materials in a sandwich-like arrangement, the strips being made by extruding a continuous sheet composed of the materials in a sandwich-like arrangement having its layers extending substantially in the longitudinal direction of the sheet and substantially parallel to the surface of the sheet, and longitudinally subdividing the sheet in the extrusion device into strips having their longer cross-sectional dimension at an angle to the layers. At least one of the materials may be an organic polymeric material, especially a splitresistant organic polymeric material, e.g. a polyamide, polyester, block copolymer of alternate crystalline and elastomer segments, or graft copolymer having an elastomer backbone and crystalline grafts; one of the materials may be a polyamide and the other a polyester; or one of the materials may be either a polyamide or a polyester and another a polyolefin present in a proportion of higher than 50% by weight. Alternatively, where one of the materials is a split-resistant organic polymeric material, another may be a polymeric material exhibiting high splittability in the oriented state. By selection of split-resistant and splittable materials it is possible to obtain strips, and hence fibres, of bicomponent nature; for this purpose it is advantageous to introduce a third component, suitably a mixture, graft-copolymer or block-copolymer between the two materials, to act as adhesive and sometimes a fourth material to assist delamination. The invention may also be applied to glass, and in this case waterglass is suitable as layers in the sandwich to effect disruption. During the subdivision step, the dimensions of the strip laterally of the sheet may be substantially reduced, and/or the dimension of the strips perpendicularly to the sheet increased, advantageously, the reduction and increase of dimensions may be so chosen as to invert thickness into width and vice versa; and prior to such subdivision, each layer may be subdivided by means of a grid into strands finer than the division between the means forming the strips. In the preferred method, the sheet is produced by feeding a first fluid, extrudable material to a circular row of first orifices 7 in the extruder head of Fig. 5, feeding a second fluid extrudable material to second orifices 8 which are interspersed with orifices 7, extruding the fluid materials through the orifices into an annular collecting chamber 9 extending along the length of the circular row (thus forming radially arranged lamellµ) and rotating one side of the collecting chamber relative to the other, thereby shearing the sides of the extruded lamellµ to substantially reduce their thickness while they advance in the direction of extrusion. Thus the lamellµ are drawn out to form a sandwich-like arrangement in which the layers will traverse the thickness of the sheet, but under a very small angle. If desired the layers so formed may be divided into very narrow ribbons by means of a row of radial wires or blades provided in the path of the extruded tube. The extrudate from the annular collecting chamber 9 is then passed immediately through the device shown diagrammatically in Fig. 6, so inverting its dimensions. The inlet width of each of the chambers for inversion of the structure is 5 mm., and the outlet width 1 mm. The product so formed is then oriented at 165 C. to a draw ratio of 2À5:1, and the resulting structure disrupted to a split fibre network by flexing and rubbing. The example illustrates the production of such a network from melts of polycaprolactam and polyethylene in a proportion of 40 : 60.