GB1340846A - Process and apparatus for melt spinning hollow filaments - Google Patents

Abstract

1340846 Hollow filaments E I DU PONT DE NEMOURS & CO 16 March 1972 12418/72 Heading B5B In a process for melt-spinning hollow fibres of synthetic organic polymer, the molten polymer is extruded in the form of thin-walled hollow filaments from spinneret orifices having an annular melt-passageway surrounding a central gas channel, and gas is fed into the filament hollow through the gas channel at a controlled pressure relative to pressure outside the filament by venting the gas supply from beneath a head of liquid in an open container to limit the pressure and passing the gas from beneath a head of liquid in a closed container connected to the gas channel, to adjust the gas pressure in the gas channel to a value controlled by the differential between the heads of liquid in the two containers. The polymer may be a polyamide, especially nylon-6 or nylon-66, or a polyester, especially polyethylene terephthalate. Preferably the supply of gas to the closed container and that to the container from which gas is vented are at substantially equal pressures. In apparatus as shown, a source of gas, e.g. nitrogen cylinder 27 fitted with a conventional pressure regulator 29 is connected to a tubing 31 and hand-adjustable throttling-valve 33. Valve 33 connects to tee 45, which is connected on one side via shut-off valve 35 to direct-acting dip tube 47 immersed in water or other suitable liquid 37 in open-top container 38. The other side of the tee is connected to reverse-acting dip tube 39 in liquid filled closed container 41 to adjust the gas pressure. Line 43 leads to the spinneret assembly of Figure 2. Depth of immersion of dip tube 47 in the liquid in container 38 determines the pressure at which gas will be supplied to the second dip tube 39, excess gas venting through 38. The difference in depth of immersion between dip tube 39 and dip tube 47 determines the pressure at which gas will be supplied through conduit 43 to the spinneret. Hence precise control of the pressure differential relative to atmospheric pressure around the spinneret assembly can be maintained. Spinneret plate 1 of Fig. 2 is sealed against spinning block 2 by gasket 3, and the spinneret melt passageway 7 has an insert 5 which channels liquid polymer into annular melt passageway 9. Gas from conduit 43 enters heater-passage 11, which is equipped with a heating jacket 13, so that the gas temperature is raised to approximately polymer temperature at the heater exit. Heated gas passes through channel 12 and enters annular chamber 14, extending around the spinneret periphery. Gas from 14 enters passage 15 and thence channel 17 positioned centrally within melt-passageway 9, and enters the filament gas channel 25 created by insert 5, maintaining a uniform hollow in the filament.