GB1262797A - Method for producing highly crimped regenerated cellulose fibers by steam stretching - Google Patents

Abstract

1,262,797. Crimped viscose filaments. MITSUBISHI RAYON CO. Ltd. 23 June, 1970 [24 June, 1969 (2)], No. 30469/70. Heading B5B. A method for producing highly crimped regenerated cellulose fibres involves stretching filaments containing the reaction product of cellulose xanthate and formaldehyde in a humidified atmosphere having a relative humidity of more than 50% and kept at a temperature of 40‹ to 130‹ C., relaxing said filaments while in a state of regeneration degree of less than 89%, preferably between 20% and 80%, in a liquid having a swelling action on said filaments and maintained at a temperature of between 30‹ and 90‹ C. and then subjecting the filaments to regeneration treatment to complete regeneration. The filaments are preferably obtained by extruding viscose containing 2 to 8% total alkali and having a salt point of at least 16 into a coagulation bath maintained at a temperature less than 45‹ C. containing 20 to 250 g./l. sodium sulphate, less than 0À3 g./l. zinc sulphate and a sulphuric acid concentration in the range 3A+8 to 8A+16 g./l., A being the total alkali concentration (%) in the viscose. When formaldehyde is added to the viscose, preferably in amount of from 0À2 to 2% by weight based on the viscose, its concentration in the coagulation bath may be in the range 1 to 6 g./l. When it is absent from the viscose solution either the coagulation bath contains between 4 and 20 g./l. formaldehyde or after coagulation in a bath consisting of 14 to 50 g./l. sulphuric acid, 20 to 250 g./l. sodium sulphate and less than 1 g./l. zinc sulphate at a temperature below 35‹ C. the coagulated filaments are treated with an aqueous solution containing between 15 and 70 g./l. formaldehyde. Preferably, the stretching step is carried out at a stretch ratio of 0À25 to 0À8 times the maximum stretching ratio in a humidified atmosphere kept at a temperature between 80‹ and 100‹ C. or in saturated steam at a temperature above 80‹ C. The relaxation process is preferably accomplished in aqueous solutions maintained at a pH of between 2À0 and 10À5, suitably in aqueous solutions containing either inorganic or organic salts of alkali or alkaline earth metals or an organic solvent or it may be carried out in an organic solvent alone. In examples, the relaxation step is carried out after the filaments produced according to the above process have been cut into staple lengths.