Patent GB-703613-A (GB)
Title: Process for spinning artificial fibres
IPC: D01D5/14
Filed: 1950-02-06
Abstract: <PICT:0703613/IV (a)/1> <PICT:0703613/IV (a)/2> Artificial filaments are produced by extruding viscose at 35-67 DEG C. through a spinneret into an acid regenerating liquid at 40-75 DEG C. in contact with the face of the spinneret, the draw off ratio, i.e. the ratio of the linear speed of the filaments at the rotor which draws them from the spinneret to the linear velocity of extrusion (as determined by the rate of pumping of the viscose through the spinneret and the diameter and number of the spinneret orifices), being 0.2-1.25.  After extrusion, the filaments travel in a straight path to a thread advancing device.  The acid regenerating liquid is formed, at a point not more than 5 cm. from the spinneret face, into a jet or stream having substantially the same speed as the filaments and flows through mid-air from this point along the straight path of the filaments for a distance of at least 15 cm., the amount of liquid in the liquid stream being limited to ensure that all of the liquid adheres to and travels substantially at the same speed as the filaments throughout at least the first 15 cm. portion of the straight path through mid-air.  A part of the liquid is then removed from the filaments at a position along or at the end of the straight path.  As shown in Fig. 1, viscose flows through a line 4, pump 3, line 5, filter 7, and conduit 8 having a coiled section 10, and is extruded from a spinneret 9.  An adjustable detent means 16 is provided to control the depth of immersion of the spinneret 9 below the surface of the liquid in the spinning bath 11.  The regenerating liquid enters the bath at inlets 13 and overflows through the discharge pipe 14, the depth of the liquid in the bath being thus kept constant.  The spinneret face is not more than 5 cms., and preferably only 1-3 cms., below the surface of the spinning bath, and the length of the path of travel of the filament bundle from the surface of the bath to the thread-advancing, thread-storage reel 17 is 15-75 cms., preferably 20-35 cms.  In an example the temperature of the acid regenerating liquid is 60 DEG C. and the viscose in passing through the coiled conduit 10, is warmed to 35 DEG C.  The spinneret face is immersed to a depth of 0.5 inch in the bath liquid and the length of the path of mid-air travel of the filaments from the surface of this liquid to the reel 17 is 33 cms.  The draw-off ratio is 0.86.  The liquid discharged downwardly from the reel 17 is caught by the receptacle 19.  The reactive portion of the acid liquid remaining on the turns of the filaments about the reel 17 is partially consumed by regenerating the cellulose xanthate of the filament between 50 and 70 per cent., but not over 70 per cent.  The filament bundle is drawn from reel 17 by a reel 20 and stretched, and on reel 20 and subsequent reels the regeneration of the filaments is completed and they are subjected to the usual after treatment.  As shown in Fig. 2, viscose from the supply pipe 37 is extruded through the spinneret 36 into a chamber 42 into which coagulating liquid may be supplied at a controlled rate either by a metering pump 48 or by means of a predetermined constant pressure via the conduit 47, which directs the liquid across the face of and around the body of the spinneret.  The liquid joins the bundle of extruded filaments and passes with them through the tapered bore 44a in the guiding member 44 and the opening 44b, the diameter of which may be 0.5-3 mm.  The distance from the opening 44b to the face 36a of the spinneret is preferably 1-3 cm. or less.  The spinneret assembly may be arranged to discharge the filaments and their accompanying stream of coagulating liquid in any direction.  The filaments leave the orifice 44b accompanied by a stream of coagulating liquid travelling at substantially the same speed and are drawn through the air in a straight path by the rotating reel or cylindrical screen 17a.  The distance between the orifice 44b and the reel 17a should be 15-75 cm. and is preferably 20-30 cm.  The reel 17a preferably has a peripheral speed substantially the same as that of the filaments, the spinning speed being from 75 metres up to 200 to 350 metres per minute.  Part of the surplus liquid may be removed from the filaments before they reach the reel 17a by means of a rotary screen or drum 171 pressed lightly against the filaments, surplus liquid being sucked through the screen or wiped off the drum.  Alternatively or in addition, surplus liquid may be removed from the filaments by centrifugal force as the filaments travel round the reel 17a and caught in the guard member 19a surrounding most of the reel 17a.  The filaments then pass upwardly to a thread advancing device 20a.  In general the amount of coagulating liquid accompanying the bundle of filaments in their path of mid-air travel from the spinneret to the first reel should not exceed 0.001 gram, preferably 0.0006 gram, per cm. per filament for bundles containing up to about 300 filaments.  For coagulating liquids of specific gravity 1.3-1.4 the filament-containing liquid stream should not exceed 3 mm. in diameter and preferably should not exceed 2 mm.  When spinning upwardly with spinneret assemblies of the type shown in Fig. 2, the spacing between the spinneret orifices may be 0.15 to 0.3 mm., preferably not exceeding 0.2 mm.  The process enables the filaments to be continuously spun at high speeds and stretched to obtain high tenacity without production of irregularities in the yarn.  Specification 664,829 and U.S.A. Specifications 2,359,749-50 are referred to.