Patent GB-1041904-A (GB)
Title: Improvements in or relating to the manufacture of heterofilaments
Inventor: HUDGELL ALFRED WILLIAM DAVID
IPC: D01D4/06
Filed: 1963-10-19
Abstract: 1,041,904. Spinnerets. BRITISH NYLON SPINNERS Ltd. Oct. 9, 1964 [Oct. 19, 1963], No. 41382/63. Heading B5B. In a spinneret for spinning conjugate filament, the component polymers, especially melts, are fed from meter pumps (not shown) to the polymer ducts 2 and 3 of cover 1 and meet below 1 to form a liquid interface, passing through the filtering medium and the gauze 5 without mixing, and thence flow into the divided channel system 9, one polymer to each side, in the top of the distributer plate 7 (Fig. III, not reproduced), and thence via ducts 11 into alternate channels 12 in the underside of the said distributer plate. The polymers then pass from the relatively unconstricted zones of the channels 12 through the restricted zones formed by the gaps 15 and then into the relatively unconstricted zone of the channels 13 in the spinneret plate 6. The restricted zones formed by the gaps 15 maintain the pressure in the channels 12 at a higher level than that in the channel 13 and so reduce the tendency of polymer in the channels 12 to flow from them into the channels 13 and on into the next channel, so that the tendency for uncontrolled mixing of the polymers between the distributer plate 7 and the spinneret plate 6 is reduced and a substantially straight interface is formed in the channels 13. The polymers are finally extruded through orifices 16 via the counter bores 17 in the form of uniform side-by-side conjugate filaments. Gap 15 should be within defined limits so as to avoid uncontrolled mixing of the polymer components between the distributer plate and the spinneret plate 6. For polymers of melt viscosity 300-500 poises, the gap should not exceed 0À003 inch, with extrusion orifices of 0.015 inch diameter. A larger gap may be used with larger diameter orifices and higher melt viscosity polymers. Channels 13 ensure the maintenance of a substantially straight interface above the spinneret holes 16, and thus permit the formation of conjugate filaments of uniform composition. The parts 11 are preferably arranged as shown in Figs. I and II, to feed polymer into the channels 12 along a line perpendicular to those channels to ensure that at opposite points in any two adjacent channels the pressures will be equal. Since the polymers are fed to channels 12 from a single source, i.e. feed ports 11, the pressure along the channels diminishes to some extent towards the ends thereof so that the denier of filaments extruded from each row of orifices tends to decrease. This may be avoided by making the annular spacer disc 8 in the form of an overall disc containing slots which are perpendicular to and connect each channel 12 with one adjacent channel 13. The width of the slot then controls the denier of the corresponding filament. Figs. IV-VII (not reproduced) show an alternative design of spinneret comprising modified distributer and spinneret plates. Face 31 of distributer plate 30 (Figs. IV and V, not reproduced), is recessed and contains channel systems 32 and 33 to direct molten polymers from each side of the spinneret plate to rows of polymer ports 34 and 35 which are angled through the distributer plate as shown in Fig. V to form a single row of holes on the underside of the plate. A recessed shoulder 36 is formed on the underside of the plate. Spinneret plate 50 has a raised shoulder 42 on its upper face 41 which co-operates with the recessed shoulder 36 of the distributer plate. The upper face carries two series of parallel channels, polymer channels 43 and orifice channels 44 having in the base thereof orifice 45. Polymer channels 43 are spaced on either side of orifice channels 44 and arranged to be perpendicular to the line of polymer ports 35 and 34. Shoulders 36 and 42 are machined to depths giving the required gap between the upper face of the spinneret plate and the lower face of the distributer plate when the plates are in co-operation so that the portions 46 of the spinneret plate between the orifice channels and polymer channels provide restricted zones between the said channels equivalent to gap 15 of Fig. II. Alternatively the depth of shoulders 36 and 42 may be the same and the dimensions of the gap and restricted zones determined by a spacer disc similar to that described with reference to Figs. II and III. In operation the two polymers issue through alternating ports in the lower face of the distributer plate and pass into the corresponding alternate polymer channels in the spinneret plate. The polymers then pass from the relatively unconstricted zones of the polymer channels through the restricted zones formed between the portions 46 of the spinneret plate and the lower face of the distributer plate into the relatively unconstricted zones of the orifice channels. Two polymers enter each channel from opposite sides and meet to form an interface above the orifices through which they are extruded in the form of side-byside conjugate filaments. In the apparatus described the molten polymer components are filtered through an undivided filter pack. When such a pack is used, both components should have nearly the same melt viscosities otherwise the interface formed between the components in the filter pack tends to move across the pack in the direction of the polymer having the lowest viscosity. In these circumstances the channel systems of the polymer ports in the distributer plate may be redesigned to accommodate this movement to maintain the alternate feed to the polymer channels, or alternatively, such redesign may be obviated by fitting a dividing septum within the pack body 4 to keep the polymer components separate until they reach the distributer plate. Although the spinneret and distributer plates shown have channels and orifices in the form of straight lines they can also be in the form of concentric lines, or in any other desired arrangement. Spinneret orifices may be circular in crosssection or may be non-circular, e.g. slot or Y-shaped. An example describes the manufacture of conjugate filaments comprising polyhexamethylene adipamide and an 80/20 copolymer of polyhexamethylene adipamide and polyepsilon caprolactam.