Patent GB-924517-A (GB)
Title: Artificial yarn, and method and means for its production
Inventor: SCRAGG FREDERICK
IPC: B29C69/02
Filed: 1960-12-06
Abstract: <PICT:0924517/IV(a)/1> <PICT:0924517/IV(a)/2> <PICT:0924517/IV(a)/3> <PICT:0924517/IV(a)/4> <PICT:0924517/IV(a)/5> <PICT:0924517/IV(a)/6> <PICT:0924517/IV(a)/7> <PICT:0924517/IV(a)/8> Artificial filaments consist of at least one continuous filament trunk and a number of filament branches formed integrally therewith and of a minimum length at least equal to, preferably at least twice, the average diameter of the trunk and extending in succession therefrom.  The length of the branches may be at least five times, preferably at least ten times, the average trunk diameter.  The filaments may be made by extruding a strip of molten filament-forming material from an extruder 16 (Fig. 1) into the nip of rolls 11 and 12 the peripheral surfaces of one or both of which are engraved with a branched mould pattern such as 13, 14 or 15 (Fig. 2).  The strip of molten or plastic material is forced into the branched engravings and the branched filaments thereby formed are withdrawn from the rolls, cooled and solidified by a stream of air supplied by the blower 17 and discharged between the baffles 18 and 19, and wound up to form packages 21.  The roll 11 may be replaced by an endless travelling belt urged against part of the periphery of the roll, and the roll and/or the belt may be engraved to constitute a mould for the filaments.  The filaments may be made by means of an apparatus comprising an engraved roll 31 (Fig. 4) rotating in a vessel 32 containing filament-forming material 34 maintained in a molten condition by the electric heater 33.  The excess melt picked up by the roll 31 is removed by a doctor 35 and the residual melt in the mould engraved on the roll is cooled and solidified by a stream of air from the nozzle 36.  The solidified branched filaments are withdrawn from the roll and wound up to form a package 37.  In a third method of forming the branched filaments, molten or hot plastic filament-forming material is extruded from an extruder 41 (Fig. 5) having an extrusion orifice 42 which is of annular shape and is provided with a number of short radial branches (Fig. 6).  The extruded material (or extrudate) is continuously cut by a rotating tool 43 mounted on a shaft 44 driven by a motor 45 to produce a branched filament 50 (Fig. 7).  In a modified extrusion cutting machine the die orifice is a peripheral slot 51 (Fig. 8) defined by die faces (Fig. 9) at least one of which contains a series of deep radial grooves 52.  A cutting tool 53 which revolves round the slot 51 while the filament-forming material is being extruded produces a branched filament (Fig. 10).  Two or more branched filaments may be simultaneously produced by the use of two or more cutting tools 53.  The filament-forming material used, in the case of one or more of the methods described, may be in solution in a volatile solvent which is subsequently evaporated off or in a solvent from which the filament-forming material may be deposited in the recesses of an engraved roll by spraying the roll with a liquid coagulant.  In a fourth method of forming the branched filaments the filament-forming material is cast in a mould to form a continuous filament having a central cylindrical main portion integral with one or two thinner radially extending webs or fins.  The finned filaments are given a high twist sufficient to break the edge of the fin or fins, the resulting yarn having a central non-extendable core surrounded by a series of thin fluffy projections composed of the broken webs.  The filament may then be drawn and doubled with others to make a yarn. In all cases, by whichever process they have been produced, a number of branched filaments may be twisted together to form a yarn, the twisted yarn either hot or cold drawn to improve its tenacity, the drawn yarn nearly wholly untwisted, or even reverse twisted, and the filament branches brushed loose from the filament structure, so as to project from the resultant yarn.  The yarn may then be twisted to a rather higher degree.  Yarns made with the filaments of the invention have a soft springy handle without a tendency for pulling when woven into fabrics.