GB415055A - Improvements in yarn manufacture - Google Patents

Abstract

The process of the parent Specification for obtaining artificial filament yarns resembling staple fibre yarns, which consists of stretching a bundle of filaments in a softened state so that individual filaments are broken, is applied to the production of regenerated cellulose yarns. The process may be carried out with filaments obtained by the viscose, cuprammonium, or nitrocellulose processes, or to filaments of organic cellulose derivatives by saponification of the yarns obtained by the process of the parent Specification or by saponification of continuous filament yarns of cellulose esters and stretching in a softened state during or subsequent to saponification. The process may be carried out at any stage of the production of the filaments, or it may constitute a separate operation. The yarns may be treated in hanks or other packages, or while travelling, or while in warp formation. They may be treated before or after twisting. The degree of softening is preferably such that the filaments undergo a high degree of elongation before the requisite breakages in the bundle have been attained. The softening agent may be sulphuric acid, caustic alkali, zinc chloride, or a thiocyanate. The yarn may be subjected to a gassing operation to remove superfluous projecting ends, or it may be passed over a roughened surface to produce increased hairiness. The yarns may be subjected to after-treatments such as delustring, mordanting, or shrinking. They may be doubled together or with other yarns. They may be employed in woven or knitted fabrics, and may constitute the whole or part of such fabric. The warp or weft may comprise normal or imitation spun yarns of regenerated cellulose, the weft or warp comprising normal or imitation spun yarn of cellulose acetate. In an example, cellulose acetate yarn is passed through an aqueous solution of dioxane and stretched between rollers. The yarn is allowed to slip on the take-up roller so that individual filaments are broken, but not the yarn as a whole. The yarn is washed, dried, twisted, and converted into regenerated cellulose yarn by passage through caustic soda solution containing sodium chloride. In another example, viscose yarn is passed through strong sulphuric acid solution and stretched. In another example, cuprammonium cellulose solution is extruded into a precipitation bath and the thread obtained is stretched between the spinning funnel and the hardening bath by rollers so that individual filaments are broken. The yarn is subsequently hardened, shrunk, washed, and twisted.