Patent GB-830441-A (GB)
Title: Process for extruding a synthetic fibre-forming liquid and a spinneret assembly for use in the process
IPC: D01D4/06
Filed: 1956-06-18
Abstract: <PICT:0830441/IV (a)/1> <PICT:0830441/IV (a)/2> <PICT:0830441/IV (a)/3> In the production of a synthetic fibre by extruding a synthetic fibre-forming liquid through a spinneret having one or more extrusion orifices, the liquid is caused to flow radially towards each extrusion orifice from all directions in a plane substantially perpendicular to the axis of the orifice.  As shown in Fig. 1, a generally cylindrical spinneret assembly for spinning fibres in the above manner comprises a front plate 1 having orifices 2, a back plate 3 having a central aperture 4, and an annular gasket 5 located between the two plates.  The plates 1, 3 are retained at the end of a cylindrical housing 12 by means of an open cap 11 threaded on to the housing.  Except in the vicinity of the orifices 2, the plates 1, 3 are separated from one another by a relatively unconstricted region 6.  About each orifice 2, a cylindrical protrusion 7 concentric with the orifice rises from the rear face of the front plate 1 to terminate in a circular plateau 8 close to but out of contact with the back plate 3, thus forming a constricted region 9 therebetween. In operation, a fibre-forming liquid is forced through a filtering medium 19, a retaining screen 10 and the aperture 4 in the back plate 3 into the relatively unconstricted region 6.  From there, the liquid passes out through the orifices 2 of the front plate 1 after having flowed over the top of each plateau 8 to converge radially on to the orifice entrances.  The back plate 3 may be provided with more than one aperture, but no aperture is located above any of the plateaus 8. The relatively unconstricted region 6 may be composed of recesses surrounding the protrusions 7 and having supply channels for the fibre-forming liquid as shown in Fig. 5, which is a plan of the rear face of a front plate of this type. Protrusions corresponding to the protrusions 7 shown in Fig. 1 may occur on the front face of the back plate, the rear face of the front plate being flat or being provided with similar protrusions, opposite to and closely spaced from the protrusions on the front face of the back plate.  In either case the orifices in the front plate are located opposite the centres of the protrusions on the front face of the back plate.  Two component or "sheath-core" filaments may be produced by causing a second fibre-forming liquid to flow centrally into the radially converging flow towards an orifice entrance of the first fibre-forming liquid, using, for example, the spinneret assembly shown in Fig. 11.  In this assembly a front plate 101 provided with orifices 102 is recessed at the back about cylindrical protrusions 104.  A back plate 107 is sealed against and spaced from the front plate 101 by a gasket 106 and a shim 116.  A relatively unconstricted region 112 between the two plates is interrupted at intervals by constricted regions 115 between the opposing face of the back plate 107 and plateaus 105 of the protrusions 104 from the front plate 101, in the same manner as shown in Fig. 1.  The back plate 107 is partitioned on top by an outer wall 119 and an inner wall 129 into an annular p  chamber 108 and a central chamber 109.  The annular chamber 108 communicates with the constricted regions 115 between the two plates by counterbored apertures 110, and the central chamber 109 communicates with the intervening relatively unconstricted region 112 through holes 111. Supply of the fibre-forming liquid which is the sheath-forming component from the central chamber 109 to the space 112 between the plates occurs as in the spinneret assembly shown in Fig. 1.  The second fibre-forming liquid or core-forming component is injected from the annular chamber 108 through the apertures 110 into the centre of each of the radially converging flows of the sheath-forming component to pass centrally through the extrusion orifices 102 consisting of a capillary 121 at the exit end and a larger counterbore 122.  The apparatus enables filaments of improved uniformity of denier to be obtained.  Specifications 578,079, 586,796, 586,881, 830,442 and U.S.A. Specification 2,530,962 are referred to.