GB580498A - Improvements in the manufacture of artificial filaments - Google Patents

Abstract

Artificial filaments having a basis of an organic derivative of cellulose are stretched by at least 100 per cent of their original length with the aid of a softening agent comprising an active substance in a concentration between that which dissolves the materials or destroys their structure and about 2 per cent by volume below such concentration, the softening agent being employed under such conditions as to give slip stretch as defined below. Alternatively, the filaments are stretched by at least 100 per cent of their original length with the aid of a softening agent containing an active substance in such concentration that the stretching tension required is between 0.1 and 0.5 grams per 100 denier, under such conditions that slip stretch is obtained. Slip stretch denotes stretch by which the extension of the yarn is not reduced by more than 25 per cent on stretching the yarn by at least 100 per cent of its original length. Suitable softening agents for filaments made from cellulose acetate are a mixture of acetone and benzene containing 37 to 41 per cent of acetone at 20-25 DEG C., a 90/10 ethyl acetate-toluene mixture at 30 DEG C., and a 95/5 ethyl acetate-carbon tetrachloride mixture at 30 DEG C. In general, the materials are preferably treated with a mixture of a hydrophile organic softening liquid and an inert hydrophobe organic liquid. The materials may be pretreated with a softening agent containing a slightly lower concentration of softening liquid or with a softening agent used at a slightly lower temperature. In example (1), yarn made of acetone-soluble cellulose acetate of 54 per cent acetyl value and having an extensibility of about 25 per cent is immersed in a mixture of 90 per cent ethyl acetate and 10 per cent toluene at 30 DEG C. for 30 seconds. It is then stretched 100 per cent of its original length, rinsed with toluene and allowed to dry without tension. In example (2), the softening agent consists of 95 per cent ethyl acetate and 5 per cent carbon tetrachloride at 30 DEG C. In example (3), a similar yarn is stretched while passing through a mixture of 41 per cent acetone and 59 per cent benzene at 20 DEG C., and the rate of travel is adjusted so that the stretching tension is about 0.3 grams per 100 denier. Specifications 421,614 and 570,588 are referred to.