GB796344A - Improvements relating to the manufacture of cellulose acetate crimped fibres - Google Patents

Abstract

Crimped cellulose triacetate filaments are given an increased degree of crystallinity by subjecting them to the action of dry heat, wet steam, hot water or an organic liquid which is a swelling agent for cellulose triacetate. The treatment may be given during and/or after the crimping operation and may be termed "setting." The filaments may be in the form of a tow of 5000-20,000 or more denier and the crimp may be imparted by the stuffing-box method. The whole or part of the setting operation may be carried out on the tow while it is still in the stuffing-box. The filaments may also be crimped by passing the tow between toothed wheels or rollers slightly spaced apart. The preferred method of setting the crimp is by means of wet steam or hot water at 120-145 DEG C. or up to about 160 DEG C., for example, for 3-8 minutes at 120-130 DEG C. or 20-60 seconds at 140-145 DEG C. When the setting is effected with dry heat, the temperature used may be 180-250 DEG C., preferably 200-230 DEG C., and the treating time may be 0.5-3 minutes, the heating medium being hot air or other gas. The setting may also be effected with a liquid organic swelling agent under the conditions set out in Specification 776,346. In a modification, in which the crystallinity of the cellulose triacetate is not as a rule significantly increased, the crimp retentivity of the crimped tow is increased by treating the tow with hot water or wet steam below 120 DEG C., particularly 90-120 DEG C. The treatment time may then be 15-40 minutes. In an example, a 10,000 denier tow of cellulose triacetate, made by melt-spinning, as described in Specification 748,772 and having a filament denier of about 3, is crimped by the stuffing-box technique to form 14-16 crimps per inch of filament. Portions of the crimped tow are then treated with wet steam at temperatures and for times ranging from 30 minutes at 100 DEG C. to 30 seconds at 142 DEG C. A method of determining the crimp retentivity of the treated filaments is described. Specification 758,442 also is referred to.