Patent GB-1328062-A (GB)
Title: Metl spinning process and apparatus
IPC: D01D5/092
Filed: 1972-01-12
Abstract: 1328062 Melt-spinning apparatus E I DU PONT DE NEMOURS & CO 12 Jan 1972 [13 Jan 1971] 1519/72 Heading B5B A melt spinning apparatus includes a spinneret 1 having orifices arranged in a generally circular pattern for forming a hollow bundle of filaments, a cylinderical quenching chamber 2 positioned below and spaced from the spinneret, a deflector 3 extending downwardly from the spinneret along its central axis having a crosssectional area at the spinneret smaller than the circular pattern and diminishing downwardly into the chamber, the quenching chamber being axial alignment with the gas flow deflector and having its top end positioned in the vicinity of the bottom end of the deflector, the quenching chamber also including gas flow restrictors 5 and 6 at its upper and lower ends which partially seal the ends against the filaments and act as guides to provide convergence of the bundle of filaments, the deflectors being sized so that more than 50% of the quench gas exits through the top of the chamber and a quenching gas supply means for directing quench gas radially inward toward the filaments. Thus quenching gas passes radially inwardly toward the centre of the hollow bundle to cool the filaments, a portion of the gas is directed upwardly through the hollow part of the bundle and the portion is deflected outwardly through the bundle, as indicated by the arrows. The deflected portion of quenching gas is more than 50%, especially 60 to 75%, of the radial inward flow. Thus in Fig. 1, filaments 4 are converged into a hollow filament bundle by passage in contact with the guide surfaces of flow restrictor 5. The openings of flow restrictors 5 and 6 are so sized that the major resistance to flow occurs at the bottom end of the quench device, forcing a major part of the quench air through the upper end of the quench apparatus. Quench air is admitted at 7 and passes upwardly through the annular plenum chamber 19 and hence radially inwards through perforated cylindrical element 20 and cylindrical foraminous member 16, suitably a number of layers of fine mesh screen, to provide a uniform radially inward flow o cooling gas into the quenching chamber and hence against the filament threadline. The major portion of quench air emerging from the upper end of quench chamber 2 flows upwards through the centre of the bundle of hollow filaments 4 and then meets the conical flow deflector 3 and is redirected radially outwardly through the threadline. The apparatus of Fig. 2 is similar except that deflector 3 is of different shape and is surrounded by a smoke removal apparatus 8; sealed against quench chamber 2 and the spinneret to form a substantially air tight chamber around filament 4. The smoke removal device is useful in the melt spinning of polypropylene, which is exemplified and also assists in controlling the relative amounts of air going out through the top and bottom of the quench apparatus. The device consists of an annular exhaust chamber 9 formed between inner and outer wall members 10 and 11. Located at the top of inner wall member 10 is a funnel-shaped, perforated deflector 12, which traps the filaments at start-up and directs them through inner wall 10. The perforations allow some air to flow through thus reducing the velocity over the deflector. Outer wall member 11 is shaped to form a flared smoke diverting ring, providing an open area for air flow over the funnel-shaped deflector 12 and allowing the air to change directions smoothly so as to minimize turbulence in the spinning zone and the risk of breaking the molten filaments. Conduit 14 is connected to a source of suction and perforated baffle 13 provides symmetrical distribution of the suction in exhaust chamber 9 to provide uniform flow at the spinneret. The modified flow director of Fig. 3 (not shown) has discs (22), (23), (24) and (25) attached to it, which cause a greater portion of the quench air to be deflected into the bundle at points successively distant from the spinneret, thus changing the air flow distribution. Fig. 4 (not shown) illustrates a bullet-nosed cylindrical flow deflector. Fig. 5 illustrates a spinning capillary of a cross-section especially suitable for the melt spinning of high molecular weight polypropylene at high throughputs. The tapering portions 27 and 28 have included angles of 60 and 20 degrees respectively.