Patent GB-740585-A (GB)
Title: Improvements in or relating to the production of filamentary material by melt-spinning
IPC: B29C48/38
Filed: 1953-08-19
Abstract: Solid fusible filament-forming material is introduced intermittently into a chamber, wherein it is subjected to a vacuum to remove gases and water vapour from the material, the vacuum being applied to the chamber intermittently in alternation with the entry of solid material therein, and the material is fed from the chamber through a heated jacket so that it is melted, and the molten material is passed to a spinneret and extruded to form filaments.  The chamber may be heated to a temperature above the boiling-point of water under the degree of vacuum applied but below that at which the filament-forming material melts.  The filamentforming material may be conveyed from the chamber and through the heated jacket by means of a screw.  The filament-forming material may be a polyamide, polyurethane, polytriazole or polyester, e.g. it may be a polyurethane <PICT:0740585/IV(a)/1> obtained by the reaction of 1,4-tetramethylene diamine with the bis-chloroformate of 1,4-butanediol.  As shown, chips, flakes or powder of a filament-forming material are fed through conduit 11 to a feed-valve 12, which is rotated continuously or intermittently, and down a conduit 16 to the main part of the spinning apparatus 17.  A feed-screw 28 has a shank 27 which is mounted in bearings 26 in a tubular fitting 23.  The screw 28 is rotated through a drive coupling 33.  Positioned inside the tubular member 19 below the tubular fitting 23 is another tubular member 34. A sleeve 35, secured to disc 36, rides inside tubular member 34. Members 34, 35 have openings 37, 38 so that, when rotation of the sleeve 35 brings the openings into alignment, a charge of filamentforming material enters the chamber 39.  When the openings are not in alignment, the chamber 39 is sealed from the atmosphere. The chamber 39 is connected to a vacuum conduit 41 through apertures in the tubular members 19, 34 and disc 36. To avoid drawing filament-forming material into the vacuum system, a block 45 is fastened to the feed-screw 28.  This block is smaller than the internal diameter of member 34 around the major portion of its periphery but bears against member 34 at a point diametrically opposite the position of opening 38 so that, when the openings 37, 38 are in alignment, the block closes the aperture 43 so as to seal of the vacuum line 41 from the chamber 39.  A screen 47 further ensures that particles of filamentforming material are not drawn into the vacuum system. The material is moved by the screw 28 into a jacket 51 which fits closely round the flight 48.  Both the jacket and the flight of the screw are tapered so that a larger quantity by volume of material tends to be fed into the entrance to the jacket than through the remainder of the jacket, and the pressure which is thereby built up tends to eliminate voids in the solid material before melting begins.  The taper of the jacket and flight of the screw also permits the clearance between these members to be finely adjusted, e.g. by inserting a shim 52 between flanges 21 and 24.  The first portion of jacket 51 is heated by means of a fluid which flows from pipe 53 into a chamber 54 and then out through pipe 55.  It is heated to such a temperature that the filament-forming material does not melt but moisture and gases in the material are expelled.  The material is melted as it passes through the next two portions of the jacket, which are separately heated by fluids passing through chambers 62 and 65.  The molten material passes through screen 71 to gear-pump 72 and then through a filter pack 73 to a spinneret 74.