GB406016A - Improvements in or relating to the manufacture of artificial filaments, films and the like - Google Patents

Abstract

Artificial filaments, threads, ribbons, foils, or films of organic derivatives of cellulose are subjected during or after their formation to the action of a medium containing in a non-solvent diluent a liquid organic solvent for the cellulose derivative in high concentration and in low concentration a dissolved solid substance which has at least some solvent or swelling action on the cellulose derivative, and simultaneously or subsequently the materials are subjected to a stretching operation. The medium referred to may be the coagulating liquid employed in the production of the materials by a wet spinning process. The solid solvent or swelling agent may be urea, thiourea, guanidine, or an alkyl or aryl derivative thereof, or it may be an inorganic salt such as zinc chloride or potassium thiocyanate. The liquid organic solvent may be of low, medium, or high boiling point. The non-solvent diluent may be water, ethyl alcohol or other mono- or polyhydric alcohol, or a coal-tar or petroleum hydrocarbon, or a chlorinated compound sych as carbon tetrachloride. Stretching may take place in stages and the materials may be treated with softening liquid prior to or during each stage. Filaments may be stretched while in warp formation, or in hanks, or while travelling from bobbin to bobbin, or continuously with their production by dry or wet spinning processes. The process may be carried out at room or higher temperature. Filaments and threads of cellulose esters may be subjected to shrinking or saponifying treatment continuously with the softening and stretching operation. The stretching tension may be applied continuously or intermittently and differentially strained yarns may be obtained. The softening liquid may be completely or partially removed from the materials by washing prior to drying and solvents, swelling agents, or salts may be present in the washing liquid in order to avoid delustring. The washing step may be omitted in order that the solid substance may be left in the materials after the liquid solvent has evaporated. In an example, cellulose acetate solution is extruded into an aqueous solution containing 5 per cent potassium thiocyanate and 45 per cent diacetone alcohol. The filaments are stretched, washed, dried, twisted, and wound. In other examples the coagulating bath or subsequent treatment bath contains about 3 per cent urea and a high concentration of ethyl lactate or dioxane. Specifications 177,868, 179,234, 277,089, 323,790, 336,217, [all in Class 2 (ii)], 340,324, 340,436, 340,437, 370,430, 371,461, 371,910, 375,423, 375,424, 378,858, 380,819, 389,823, 392,185, 400,589, 400,597, 400,938, 400,946, 401,679, 402,106, 402,141, 403,106, 405,619, and 405,676 are referred to. The Provisional Specification describes also processes in which instead of using a coagulating bath containing a liquid solvent and a dissolved solid solvent or swelling agent, one or both of these substances is contained in the spinning solution or in a subsequent treatment bath.