Patent GB-554689-A (GB)
Title: Improvements in or relating to the manufacture of regenerated cellulose yarns, filaments, films and the like
IPC: D01F2/06
Filed: 1941-12-03
Abstract: 554,689. Artificial silk, films &c. BRITISH CELLOPHANE, Ltd. Dec: 3, 1941, No. 15596. Convention date, Dec. 3, 1940. [Class 2 (ii)] Regenerated cellulose yarns, filaments, or films, including sheets, tubes, or the like, are obtained by extruding viscose from a shaping extrusion device, preferably at a high spinning speed of at least 5,000 inches per minute, into an acid coagulating bath heated to at least 60 C., and passing the yarns, filaments, films, or the like so obtained immediately into a second acid bath containing 7-15 per cent. of sulphuric acid or an equivalent amount of another mineral acid, and maintained at a lower temperature, preferably at least 10 C. lower, in order to complete the coagulation and regeneration of the cellulose. The acid baths employed may contain in addition to sulphuric acid also glucose, or ammonium, sodium, zinc, nickel, or iron sulphate. The two baths may be of the same or different composition. The viscose may be partially or fully ripened. The travel of the yarn in the first bath is preferably short, e.g. 1-10 inches. The length of travel in the second bath may be 12-50 or more inches. Spinning speeds up to 15,000 inches per minute may be used and the first bath temperature may be as high as 85 or 100 C. or more. The temperature of the second bath is preferably about 45 C. or lower. Spinning may be carried out under sufficient tension to obtain products of high tenacity. The completely regenerated materials may be subjected to stretching in a separate bath maintained at elevated temperature. In examples, viscoses having salt indices of 4-7.3 are used with spinning speeds of 5,300 to 9,500 inches per minute and spinning bath temperatures of 65-98 C. The process results in the production of yarns and other materials of high quality factor, i.e. the product of the numerical values of the tenacity and elongation, both measured in the dry state. As shown in Fig. 2, viscose is extruded from a spinning nozzle which is immersed in a small tank 4 mounted within the main tank 1. Hot coagulating liquid is introduced continuously into tank 4 through tube 5 and is discharged with the filaments through a small hole 7 into the tank 1, or is led to drain through outlet pipe 6. Coagulating liquid at a lower temperature is introduced into tank 1 through pipe 2 and is discharged through outlet pipe 3. The filaments pass through the tank 1 and are then led to collecting roller 12. A number of guides may be disposed so as to cause the filaments to pursue a zig-zag path while immersed in the coagulating liquid in tank 1. The apparatus may be modified by fixing the spinning nozzle so that only the face of the spinneret protrudes into the coagulating liquid. Local heating may be effected by mounting a heating device in close proximity to the spinneret. A spinning funnel may be used of the type used in the cuprammonium process, the hot liquid being contained within this funnel. Specifications 264,161, [Class 2 (ii)], and 370,943 are referred to.