GB1262796A - Method for producing highly crimped regenerated cellulose fibers by solvent stretching - Google Patents

Abstract

1,262,796. Crimped viscose filaments. MITSUBISHI RAYON CO. Ltd. 23 June, 1970 [24 June, 1969], No. 30468/70. 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 non- aqueous liquid having a boiling point of at least 80‹ C. and maintained at a temperature of 60‹ to 150‹ C., preferably between 70‹ and 130‹ C.; relaxing said filaments having a regeneration degree of less than 89% and preferably between 20 and 80%, in solution having a swelling action on the filaments and maintained at a temperature of 30‹ to 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. Suitable non-aqueous solvents for the stretching process are liquid paraffins, silicone oil, white oil, glycerine, polyethylene glycol, xylene, toluene and styrene, the filaments being stretched at a ratio between 0À25 and 0À8 times their maximum stretch ratio. The relaxation step is preferably accomplished in aqueous solutions maintained at pH between 2À0 and 10À5, suitably in aqueous solutions containing either inorganic or organic salts of alkali or alkaline earth metals or organic N- and S-containing solvents, soluble ketones or cyclic ethers. In some of the examples the relaxation step is carried out after the filaments produced according to the above process have been cut into staple lengths.