Patent GB-661939-A (GB)
Title: Improvements in and relating to the production of viscose rayon threads
IPC: D01F2/06
Filed: 1949-05-27
Abstract: <PICT:0661939/IV (a)/1> In a continuous process for the manufacture of viscose rayon threads by extruding viscose through a jet into an aqueous acid coagulating bath, withdrawing the thread so formed from the bath while it is in an incompletely regenerated state, passing the still incompletely regenerated thread to a thread-advancing thread-storage device on which the thread advances in a number of consecutive turns and supplying an aqueous acid treating liquid to the turns of the advancing thread, the thread-advancing, thread-storage device is maintained at at least 75 DEG  C. in the acid treating zone and the aqueous acid liquid is supplied to the thread at a temperature below that of the thread-advancing device so that heat is supplied from the heated device to the acid on the device and on the advancing turns of thread.  The thread-advancing thread-storage devices may be supported at one end only and tilted downwards from the horizontal towards the take-up end.  Heat may be supplied to the device by extraneous heating devices such as infra-red ray lamps or steam coils placed near to the thread so that the thread is heated on the device and also, if desired, while passing between co-operating parts of the advancing device, for example between two canted rollers.  Internally-heated thread-advancing thread-storage devices in which the heating is effected by a heated fluid such as steam, hot gases, hot solutions or hot water passed through the interior of the device may also be used. Aqueous solutions of sulphuric, phosphoric, nitric or hydrochloric acid may be applied to the advancing threads. Aqueous solutions containing 0.05-15 per cent by weight of sulphuric acid are preferred.  The aqueous acid may be delivered from tubes at very low rates to an aqueous medium already present on the heated advancing thread so that rapid dilution of the delivered acid occurs on the device.  After the hot acid treatment to complete the regeneration of the thread has been effected, the thread may be washed free from acid and other water-soluble impurities while it is still being advanced and stored as a helix, for example by using a reel having two or more processing zones, the acid zone and preferably also the washing zone of which are heated.  Alternatively, the completely regenerated thread may be washed while it is being advanced and stored on a second independent thread-advancing device, preferably also heated. Suitable washing liquids are water and dilute aqueous alkaline solutions which may contain thread lubricants such as mineral or fatty oils and waxes, or surface-active compounds for removing sulphur impurities from the regenerated thread, e.g. sulphonated aryl, long chain alkyl or alkyl-aryl substituted compounds, solubilized amines or amides containing aryl or long chain alkyl radicals, highly polymerized ethylene oxide and long chain hydrocarbons modified with polyethylene oxide radicals.  The washing solutions preferably have a pH value of 6.5-11.  The regenerated and washed yarn is preferably dried on the last zone of a single multi-stage reel but may be dried on a separate heated reel or other device.  An aqueous desulphurizing zone may be provided between the acid and the washing zones, where aqueous solutions of desulphurizing agents, such as sodium sulphide, tri-sodium phosphate or sodium sulphite may be applied.  Aqueous solutions containing 0.05-0.7 per cent by weight of sodium sulphide are preferred.  The processing liquids applied to the thread may be restricted (by mechanical means or by the provision of intermediate aqueous washing zones) to specific areas on the thread-advancing device so as to prevent mingling of the liquids, but it is preferred to allow the liquids in the various zones to mingle and flow towards the beginning of the thread helix so that the thread passes through a liquid zone of gradually decreasing acid content.  The thread may be stretched, e.g. about 10-50 per cent before or during the treatment.  As shown, viscose is extruded through a jet 11 into an acid coagulating bath 12, and the thread 14 thereby formed is withdrawn from the bath by means of a godet 15 around which it is lapped once.  The thread, while still in an incompletely regenerated state and while still wet with acid bath liquid is transferred to a thread-storage, thread-advancing reel 19 which is tilted downwards from the horizontal towards the take-up end.  The reel 19 is driven at a higher peripheral speed than the godet 15 so that the thread is stretched about 20 per cent between the two.  Reel 19 is heated internally by introducing steam at about 10-12 p.s.i. through a hollow shaft 20, the steam being exhausted through a concentric shaft 21, and the heat from the steam being conducted to the thread-bearing metal bar members 26 of the reel 19 to heat the thread 14.  A 1 per cent salt-free aqueous sulphuric acid solution at ordinary temperature is delivered to the helix by tube 22 and an aqueous oil emulsion at ordinary temperature containing about 0.5 per cent of a mixture of 70 per cent mineral and vegetable oils and 30 per cent sulphonated fatty acid esters and having a pH of 7.5 is delivered at the same rate from tubes 23 and 24.  The applied solutions are allowed to mingle on the reel 19 to form a continuous film 25 enveloping most of the thread helix and flowing towards the take-up end of the reel, whence most of the excess liquid drips into the tray 28.  Under these conditions the thread advances through an aqueous-acid medium the acidity of which progressively diminishes as the thread advances on the heated reel and emerges from the film 25 as a substantially completely regenerated lubricated thread substantially free from impurities. After emerging from the film 25 the thread is dried by passing over a heated zone of the reel 19 to the discharge end of the reel, whence it passes through a guide 30 to the twisting and collecting device 31 and 32.  In a second and similar illustrated example the godet 15 is heated internally by steam introduced through a hollow shaft 17 and exhausted through a concentric shaft 18, and the thread is treated on the godet 15 with dilute aqueous salt-free sulphuric acid solution from the tube 16 as well as on the reel 19.  In a third illustrated example the godet 15 is replaced by an unheated thread-advancing reel and from this the thread passes to a second unheated thread-advancing reel before reaching the main thread-advancing reel 19.  The thread is treated on the second thread-advancing reel with water at 75 DEG  C.  In a fourth illustrated example the reel 19 is heated by means of infra-red ray lamps fixed in enclosures which serve to retain the heat within the vicinity of the thread turns.  In a fifth illustrated example the reel 19 is replaced by a pair of tilted superimposed parallel drums internally heated with steam and heated also by a stationary steam heater placed between the drums and within the thread helix.  In a sixth illustrated example the stationary heater is replaced by infra-red lamps fixed in enclosures on either side of the thread helix.  In a seventh illustrated example the infra-red lamps are replaced by a second pair of rotatable internally steam-heated drums adjacent and parallel to the first pair of drums and in contact with the major part of the two sections of the advancing helical thread package which are out of contact with the first pair of drums.  In an eighth illustrated example the thread from the spinning bath passes in succession over two of the thread-advancing and treating devices described in the fifth example, and in a ninth illustrated p  example the thread passes over two pairs of horizontal unheated superimposed drums before reaching the thread advancing and treating device used in the fifth example.  In other examples the various modifications of the apparatus described above are also used, but the compositions and concentrations of the treating and washing solutions and other conditions differ somewhat. Specifications 413,413, 413,414, [Group IX], 423,152 and 661,940, and U.S.A. Specification 2,294,866 are referred to.  The Specification as open to inspection under Sect. 91 comprises also the treatment of the thread on the unheated godet 15 with aqueous sulphuric acid, the thread being treated on the thread-advancing reel 19 with water only. This subject-matter does not appear in the Specification as accepted.