Patent GB-748772-A (GB)
Title: Improvements in the production of artificial fibres
Inventor: SAMMONS CHARLES WILLIAM
IPC: D01D1/04
Filed: 1953-04-24
Abstract: <PICT:0748772/IV(a)/1> <PICT:0748772/IV(a)/2> <PICT:0748772/IV(a)/3> Melt-spinning is effected by pressing a coherent block of filament-forming material against a heated perforated plate and collecting the filaments so formed.  Suitable apparatus comprises a perforated plate heated to a temperature higher than any other part of the apparatus in contact with the filament-forming material, e.g. by passing an electric current through the plate itself, a vessel for containing a block of filament-forming material and for laterally confining it to the size of the perforated plate which closes one end of the vessel, and means for pressing the block against the plate. The filament-forming material may be pre-heated immediately before reaching the perforated plate, either by conduction from the heated plate, which may be restricted by interposing insulating material between the heated plate and the vessel containing the material, or by providing separate heating means.  The material may be fed by hydraulic or pneumatic pressure or by a weight.  The perforated plate may be laminated and include layers such as wire gauze or expanded metal.  A single spinning unit is shown in Fig. 1, wherein a hydraulic cylinder 11 and ram 14 press a preformed rod of filament-forming material housed in metal cylinder 20 against a perforated plate 25, heated by the passage therethrough of a current of 200-250 amps. from the bus-bars 31.  The resulting filaments are drawn off by roller 33 and wound up by a ring-spinning device 36. Fig. 2 shows in detail the perforated plate 25 and electrical connections 30 for heating it.  The plate rests on a layer 26 of heat-insulating material and above it are two layers 28 of stainless steel wire gauze of 200 mesh and 60 mesh.  Conduction of heat upwardly is restricted by interposing layers of asbestos paper 27 between the heated plate and gauze and the vessel 23 containing the filament-forming material 38.  A thermocouple 39 may be provided for checking the temperature of the plate.  As shown in Fig. 1 hydraulic pressure may be applied to raise or lower the ram 14 by manipulation of valve 17, and the movement of the ram may be kept at a constant linear rate by feeding the cylinder through a constant volume pump 16. Alternatively, hydraulic fluid from a separate source may be used to raise the ram quickly.  In the modification shown in Fig. 3, pressure is supplied pneumatically by two-way valve 55 to a cylinder 11 to actuate ram 14.  In this modification the upper part of the vessel for holding the filament-forming material is duplicated at 43, 44, whereby one may be re-charged whilst the other is in operation. The vessels 43, 44 are mounted at their ends about a centrally-disposed vertical pivot 46.  The filament-forming material may be pre-formed into either tablets or rods.  Suitable tablets may be formed in a conventional tabletting press at about 15 tons p.s.i. from powdered cellulose acetate having a moisture content of about 3 per cent to assist their formation, but the moisture content should be reduced to less than 0.1 per cent before use.  Suitable rods may be formed by moulding oven-dried powdered cellulose triacetate under pressure in a stainless steel cylinder for several minutes under heat and further drying the shaped rod.  Suitable filament-forming materials, in addition to cellulose acetate, are cellulose propionate, acetopropionate and acetobutyrate, also polyaminocaproic acid, polyaminotriazole, polyhexamethylene adipamide, polyureas, 4,4-polyurethanes and polyethylene. Mixtures of different materials may be used, e.g. 10 per cent cellulose acetate and 90 per cent polyhexamethylene adipamide. Specification 719,853 is referred to.