| 摘要 |
Viscose, having a g -value above 60 and a viscosity of at least 400 poises, is extruded into a coagulating bath of acid concentration 10-15 grams per litre at 15-30 DEG C., and the filamentary product which is obtained is thereafter fixed by treatment with a hot aqueous liquid. The g -value is the number of CSS groups per 100 C6H10O5 units in the cellulose xanthate. The viscose used may be obtained from an unripened alkali cellulose and it may have a cellulose content of 6-10 per cent by weight. Alternatively, viscose of a cellulose content of 10-15 per cent by weight and made from ripened alkali cellulose may be used. The high g -value may be achieved by xanthogenation with a large excess of carbon disulphide, i.e. at least 50 per cent by weight of the a -cellulose content. The viscose may have a viscosity of 600 poises or more and a g -value of 70-80. The spinning nozzle is preferably immersed in the coagulating bath and the extruded filaments may pass through a straight tube immersed in the bath. The spinning speed may be 50-100 metres per minute. The coagulated but still plastic filaments may be stretched by 100-200 per cent. Fixing may be effected by hot dilute acids or saline solutions or hot water. The fixing may be effected while the filaments are under or free from tension or after the filaments have been cut to form staple fibre. In an example, sheets of cellulose pulp having a degree of polymerization greater than 800 are steeped in caustic soda lye and pressed. The alkali cellulose is shredded but not ripened and then xanthated. The cellulose xanthate is dissolved in dilute caustic soda at 0-5 DEG C. to form a viscose containing 9.5 per cent of cellulose and 5 per cent of caustic soda. The viscose has a viscosity of 900 poises and a salt point of 15-16. Its g -value is 70. The solution is spun into sulphuric acid solution of a strength of 10 grams per litre. The coagulated filaments are stretched and set in dilute sulphuric acid solution at 75-80 DEG C. The process may be applied to the production of rayon, staple fibre, artificial hair, braid, and like filamentary products. Filaments having a tenacity higher than 5 grams per denier when dry and of about 4 grams per denier when wet, with elongation higher than y per cent, may be obtained. Specification 655,516 and French Specification 890,575 are referred to.
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