GB912124A - Improvements in viscose process and improved low-shrink viscose rayon - Google Patents

Abstract

Viscose is spun in an acid regenerating spin bath and the filaments are stretched progressively at least 90%, preferably about 100%, but not over 150% in a primary stage while in contact with the spin bath. They are then contacted while in an incompletely regenerated plastic state with an acid bath at 80 DEG -100 DEG C., preferably about 90 DEG C., containing 1 to 6% preferably about 4% by weight of sulphuric acid while stretching them an additional 5 to 50%, preferably about 30%, to completely fix and regenerate them prior to any relaxation resulting in filaments having an appreciable amount of "skin". They are subsequently immersed in an aqueous solution containing 0,1 to 2% of sodium hydroxide at about 80 DEG to 100 DEG C. while free from tension to effect complete relaxation of the filaments. The completely regenerated filaments prior to washing may be cut into staple fibres, the fibres washed, immersed in a 1% aqueous sodium hydroxide solution at about 90 DEG C. for about five minutes, and then washed and finished in the conventional manner. Conventional acid regenerating spin baths may be used, either the viscose or the spin bath containing an active regeneration retardant to ensure the formation of a high proportion of "skin". A mixture of polyethylene glycol and dimethylamine, preferably in equal proportions of from 0,05 to 0,5% each based on the weight of the viscose, may be used as a regeneration retardant, as described in Specification 912,123. The spin bath is preferably maintained at a temperature of 40 DEG to 70 DEG C., and the stretching in the primary stage may be effected in the spin-bath itself or in the spinbath carryover. The filaments have practically no shrinkage and can be converted into yarns and woven fabrics exhibiting dimensional stability during repeated severe laundering.