Patent GB-1142920-A (GB)
Title: Method and apparatus for spinning elastic yarn
IPC: D02G1/06
Filed: 1967-11-07
Abstract: 1,142,920. Elastic polyurethane filaments. TOYO BOSEKI K.K. 7 Nov., 1967 [8 Nov., 1966], No. 50644/67. Heading B5B. [Also in Division D1] In a process for the production of a coalesced multifilament elastic polyurethane yarn a plurality of spun elastic polyurethane filaments is passed through an orifice eccentrically positioned in a twisting plate placed on a hollow rotating device so as to impart a false twist to the filaments, the false twist being allowed to extend back to a point where the filaments are in a plastic state so that the spun filaments will coalesce into a single yarn. Preferably the spun filaments are formed by extruding a solution of polyurethane extruded through a spinneret into a spinning cell to form a plurality of separate filaments which are then passed downwardly through the spinning cell, solvent is evaporated from the filaments by contacting them with a heated inert gas which is introduced into the spinning cell, and the filaments are withdrawn from the bottom of the spinning cell. The hollow rotating device is suitably rotated by a synchronous electric motor, and the diameter of the eccentrically positioned orifice is suitably from 0À5 to 1.5 mm. when the coalesced multifilament yarn denier is from 30 to 1300. In apparatus as shown, the spinning solution is extruded from a spinneret into the spinning cell 2 and the separate filaments passed downwardly therethrough and are continuously withdrawn from the bottom of the cell 2, into which a heated inert gas is introduced through a gas inlet 6 and discharged therefrom through a gas outlet 7. The filaments withdrawn from the cell 2 are passed over a finish roll 4 which is partly dipped in a lubricant reservoir and the filaments are wound up on a bobbin 41 via rolls 3 and 3<SP>1</SP>. The false twister 5 comprises a hollow rotating device having a twisting plate provided with an eccentrically positioned orifice, the filaments passing through the orifice and the opening of the hollow rotating device. Thus a false twist is imparted to the filaments, which extends back into the spinning cell 2 as shown in Fig. 1, to a point where the filaments are in a plastic state and thus adhere to one another, so coalescing the filaments into a single yarn. In Fig. 2, the twister 5 comprises a synchronous electric motor 8 having a central hollow shaft 9. A false twisting plate 11 having an eccentrically positioned orifice 12 is mounted on the top portion of the hollow shaft 9 by means of a holder 10 (Fig. 3, not reproduced). The eccentrically positioned orifice 12 communicates with the hollow shaft. As shown in Fig. 4 (also Figs. 5a and 5b), orifice 12 is circular and is deviated from the centre of the circular plate 11 by a small distance e. A straight or bent slit 14 is cut in plate 11 to communicate with the orifice 12 forming a keyhole-like opening. Slit 14 facilitates the insertion of the filaments into orifice 12. The diameter of the eccentrically positioned orifice 12 may be varied according to the denier of the extruded filaments, and when the total denier of the coalesced multifilament bundle is from 30 to 1300, the diameter of orifice 12 is suitably from 0À5 to 1À5 mm. Suitably, the point to whioh the false twist extends back is preferably that where the solvent content in the filament is from 2 to 6%, and this point is generally in the middle of the spinning cell 9. Thus the number of revolutions of the false twisting plate 11 may be from 7000 to 16,000 r.p.m. when the yarn denier is from 30 to 1300, spinning speed is from 200 to 600 m. per min., and the temperature of the inert heated gas within the spinning cell is from 150‹ to 300‹ C. A synchronous electric motor shown in Fig. 2 is preferably employed as a hollow rotating device, since the number of twists and retroactive length of the false twist can be accurately controlled by using a frequency control in connection with the electric motor. Alternatively, the hollow shaft 9 may be rotated by a mechanical driving means. Thus shaft 9 may be journalled in bearings 17, 17 and a pulley 18 fitted on the shaft between the upper and lower bearings as shown in Fig. 7. A driving belt (not shown) is engaged around pulley 18 so that the hollow shaft and hence the plate 11 is rotated. Alternatively, the hollow shaft may also be rotated through a gear train.