Patent DE-10005664-A1 (DE)
Title: Melt spinning assembly has larger spinneret drillings for the outer filaments which shroud the inner filaments in the cooling station but with a constant flow throughput of the molten polymer
Inventor: SCHULZ DETLEV
IPC: D01D5/088
Filed: 2000-02-09
Abstract: In the melt spinning process, for synthetic filaments, the outer group of filaments from the spinneret are subjected directly to the flow of coolant while the inner group of filaments are shrouded by them. The filaments of the outer group are extruded through the spinneret drillings with a thicker cross section than the drillings for the inner filaments.  The outer and inner filaments are spun through the spinneret with the same molten flow throughput, using drillings of different lengths to give equal flows and compensate for different filament thicknesses. The outer filaments are spun through spinneret drillings at equal intervals in a row, and pref. in a ring row. The inner filaments, shrouded by the spun outer filaments, are spun through equidistant drillings in a row, and pref. a ring row, or in a number of concentric ring rows. The extrusion drillings for the outer filaments have a larger dia. than those for the inner filaments, with a constant molten material flow throughput at all the spinneret drillings. The bundled filaments are carried through a preliminary and a final cooling zone, to be exposed to a coolant flow. The coolant flow supports the filament movement, before the filaments have hardened. The coolant flow speed is equal to or faster than the filament movement speed before hardening. Before the filaments set, they are passed through a concentrator with its smallest cross section at the outlet, linked to a cooling tube with a diffuser, with an under pressure to generate the coolant flow. The extruded filaments, before setting in the preliminary cooling zone, pass through a cooling shaft where wall openings link its interior with the ambient atmosphere. Directly after extrusion, the spun filaments pass through a heated zone where they are exposed to heat. An Independent claim is included for a filament melt spinning assembly with drillings (37,38) at the spinneret of different dias. The drillings (37) for the outer filaments have a larger cross section than the drillings (38) for the inner filaments in the extruded filament bundle. Preferred Features: The extrusion drillings (37,38) have an equal flow resistance despite their different sizes, to give an equal molten flow throughput at all the drillings (37,38). The drillings (37) for the outer filaments are longer than the drillings (38) for the inner filaments. The drillings (37) for the outer filaments are equidistant in a row (39), and pref. in a ring row. The drillings (38) for the inner filaments are shrouded by the outer filament drillings (37). The inner filament drillings (38) are equidistant in a row (40), and pref. a ring row or a number of concentric ring rows. The extrusion drillings (37,38) are offset from each other in neighboring drilling rows (39,40). The filament cooling station (4) has an entry cylinder (7) under the spinneret (2), with gas-permeable walls (10). A cooling tube is below the cylinder (7), in the direction of filament travel. The cylinder (7) and/or tube are linked to an air flow generator, to give a coolant air flow in the direction of filament movement. The cooling tube has a concentrator at the entry, and a diffuser at the exit. The air flow generator is an under pressure source, linked to the diffuser. The walls (10) of the cylinder have different levels of permeability, to control the air vol. passing into the cylinder (7). A heating unit, to heat the spun filaments, is between the spinneret and the cylinder leading into the cooling stage. A further Independent claim is included for a spinneret with a drilled plate (33) for melt spinning a number of filaments (5) from a molten polymer. The drillings (37,38) are in groups with a different cross section. Preferred Features: The longer drillings (37) are around the edge of the plate.