GB841708A - Improvements in or relating to regenerated cellulose structures - Google Patents

Abstract

Regenerated cellulose filaments are obtained by extruding viscose into a coagulating bath in the presence of a coagulation modifier, (i.e., an organic compound which reduces gel swelling) the bath containing from 10-20% by wt. of a znSO4/Na2SO4 mixture, at least 1,0% by wt. of Na2SO4 being present and the ratio of znSO4: Na2SO4 being at least 0.4, and sufficient sulphuric acid being present to provide an acid/alkali factor of 1,0-1,76. The acid/alkali ratio is defined as per cent. Bath acidity/(per cent Viscose alkalinity-1). Coagulation modifiers specified include salts of N-substituted dithiocarbamic acids, and quaternary ammonium compounds of the formula [R1R2R3R4N]+,X-, R being an organic group with not more than 4 aliphatic carbon atoms, at least three of the R groups containing only aliphatic carbon atoms and the fourth containing not more than one phenyl radical, and X-being an anion with substantially no surface activity. Certain aliphatic monoamines and diamines, certain ethers and polyethylene glycols are among other coagulation modifiers mentioned. The coagulation modifier preferably limits the gel swelling ratio to a value not over 0,9, this ratio being defined as gel swelling in the presence of a coagulation modifier/gel swelling in the absence of a coagulation modifier. The bath preferably contains 6-12 % Na2SO4 and the acid/alkali factor is preferably 1,20-1,76. Viscose may be extruded at a temperature of at least 40 DEG C. and a total stretch of at least 100% may be applied to the regenerated cellulose filament. Filaments produced are characterised by having at least 75% skin, a lateral order from 15-40, a minimum point in the force/temperature curve of from 60 DEG -95 DEG C. and substantially uniform orientation across the filament cross section, the difference in orientation numbers of the centre and outside portions of the filament being no greater than 2; such a filament may be made into a yarn or cord of enhanced tenacity. Specifications 652,741,6654,083, 712,623, 723,435, 730,542, 741,727, 762,772, U.S.A. Specification 2,801,998 and Belgian Specification 535,699 are referred to.