GB570588A - Improvements in or relating to the treatment of yarns, foils and similar materials made of organic derivatives of cellulose - Google Patents

Abstract

<PICT:0570588/IV/1> Artificial yarns, foils and like materials of an organic derivative of cellulose, e.g. cellulose acetate, acetate-propionate, acetate-butyrate and ethyl cellulose, are stretched during their passage through wet steam or hot water under pressure, by passing them over a positively driven feed device into an end chamber containing water under pressure, and at a temperature at which it is inert to the cellulose derivative, then directly into a stretching chamber containing steam or hot water under pressure and over a second positively-driven feed device which withdraws the materials from the chamber at a greater rate than that at which they enter the end chamber. The pressure of the water in the end chamber is higher than that of the wet steam or hot water in the stretching chamber. Yarn is fed by nip-rollers 2 through the orifice 3 to the end chamber 5 containing water under pressure. It then is passed through orifice 7 into the stretching chamber 6 containing wet steam or hot water under pressure. It leaves the chamber through outlet orifice 11 and is collected on conical roller 15 from which it passes to a take-up device (not shown). Any change in degree of stretch is effected by traversing the yarn along the roller 15. Chamber 6 is provided with baffles 9 and 10. The cross-sectional area and length of the inlet orifice 3 are preferably smaller than those of the intermediate orifice 7, and the dimensions of the outlet orifice 11 may vary from slightly more than those of the inlet orifice to several times those of the intermediate orifice. In order to treat several ends of yarn simultaneously, a plurality of orifices may be employed. The temperature of the end chamber water may be as high as 70 DEG C., and the wet steam temperature is preferably higher than 105 DEG C. The apparatus may also be employed in other treatments of yarns, foils and the like. Thus, it may be used in a saponification process effected with the vapour of ammonia or a volatile organic base, or with a solution of sodium hydroxide or other base; or it may be used in a shrinking process employing methylene dichloride as the treating fluid. The end chamber liquid in the latter process may be an organic liquid such as benzene. In the Provisional Specification it is stated that the process is also applicable to yarns or foils of other thermoplastic materials, e.g. an interpolymer of polyvinyl chloridepolyvinyl acetate. Specifications 443,707, 443,773, 537,962, 558,958 and 569,669 are referred to.