Patent GB-455534-A (GB)
Title: Process and apparatus for the production of cuprammonium silk
IPC: D01D5/14
Filed: 1935-11-13
Abstract: <PICT:0455534/IV/1> In a process for the production of cuprammonium silk filaments of crinkled and woolly character, e.g. for staple fibres by the stretch-spinning method a group of filaments are spun in a freely descending column of precipitant liquid, without negative pressure in the spinning bowl, to a joint thickness which is a function of the aperture of the discharge nozzle for the precipitant, characterized in that the resulting filament bundle is stretched by a column of the same precipitant flowing at a higher velocity than that of the first mentioned column in the upper part of a second bowl, and the tension of the stretched filament bundle is relaxed in the lower part of the said second bowl.  The operation may therefore be carried out at high velocity (about 100 metres per minute), the filament descending with the current of precipitant.  In suitable apparatus, the cellulose solution is supplied through a pipe 25 to nozzle heads 26 in a vat 27. Screwed into said vat are bowls 28, 29 fitted with nozzles 30 which extend into a vessel 31 from the bottom of which extend upwardly a trough 32 carrying a taper bowl 33 provided at its lower end with a discharge tube 34 bent at right angles and opening into a bath 35.  The vessels 27, 28, 29, 31, 33 and 35 are all filled with flowing precipitant.  From the nozzles 26, the solution passes to form filaments 36 into bowls 28, 29 and thence to trough 32 where it is subjected to further stretching.  The filament bundle 37 is relaxed in bowl 33, the bent tube 34 checking the flow of precipitant.  The bundle 37 is straightened out again in the lower part of the bowl and the discharge tube 34 whence it is led over a roller 38 to a perforated drying drum 39 mounted above a vessel 40 and covered with a hood 41 with openings 42, 43 for passage of the thread.  The vessel 40 collects liquid ammoniacal copper hydroxide separating from the filament and ammonia gases liberated therefrom by a heating coil 45, which also heats drum 39, pass out of the exhaust pipe 44 while copper hydroxide collects in the conical bottom of vessel 40 to be re-used in the dissolving process.  From the drying roller, the bundle 37 passes over a roller or rod 46, and through a thread guide 47 to one of a pair of rollers 48, 49.  It is washed with dilute sulphuric acid discharged through nozzles 50 on to the rollers 48, 49.  The filament layer on the rollers may be cut off, washed, mangled, and if desired, cut to staple fibre.  The Specification as open to inspection under Sect. 91 comprises also a form of the invention for producing smooth yarns wherein the filaments are only stretched in the second bowl, tension being relaxed in a third collector bowl in which the filaments are received on a moving band.  An apparatus with a plurality of spinning jets is shown, the second vessel being divided by partitions into a corresponding number of compartments.  After being wound on the cylindrical receiving drums, the filament bundles are cut off, superimposed in several layers and subjected thus to a variety of liquid treatments.  The bundles are then dried and mangled, with smooth or fluted rollers at ordinary or higher temperature to give a soft, open, smooth or undulating material which can be cut into any convenient known length of staple fibres which are put through an opener, either alone or in admixture with cotton or wool, then through an opener combined with a beater to furnish a compact fleece which after several passages through a beater gives a finer and more uniform lap which is carded and passed repeatedly through coarse medium and fine drawing frames.  The sliver then passes through slubbing, intermediate and roving frames to the spinning frame.  This subject-matter does not appear in the Specification as accepted.