GB417327A - Improvements in the manufacture of artificial filaments, yarns, ribbons, films and like materials - Google Patents

Abstract

Artificial filaments, threads, ribbons, and the like are formed by extruding a solution of a film-forming base in a volatile solvent into an evaporative atmosphere, the filaments and the like being passed, while they still retain substantial quantities of a volatile stretch-assisting agent contained in the solution, into a bath containing the same stretch-assisting agent and stretched, the stretching being effected during their passage through said bath. The proportion of stretch-assisting agent retained in the materials when they are passed into the bath is at least 20 per cent and may be from 25 to 50 per cent. The spinning may be carried out in the apparatus of Specification 165,519, [Class 2 (ii)], but using a reduced length of travel of the filaments through the spinning zone. The retention of the desired amount of stretch-assisting agent in the filament may also be brought about by reducing the flow of evaporative medium through the spinning zone, by reducing the temperature of the spinning zone, by increasing the proportion of volatile solvents to cellulose acetate or the like in the dope, or by increasing the speed of spinning. As solvents, there may be used single liquids or mixtures of liquids provided that the liquid remaining in the materials is capable of facilitating the stretching thereof. Where strong solvents are employed, the presence of a diluent in the bath may be necessary, for example, when the spinning solution comprises a solution of cellulose acetate in dioxane, the products may be stretched in the presence of a 40--50 per cent aqueous solution of dioxane. The materials may be stretched, for example, to 200--500 per cent or more of their original length. The materials may comprise organic or inorganic esters of cellulose, or cellulose ethers, and preferably those having a high viscosity. In an example, a solution of cellulose acetate in dioxane is extruded at such a rate that the filaments emerging from the spinning zone contain 25--35 per cent of dioxane. They are then passed around three rollers immersed in a bath containing 40--45 per cent aqueous dioxane, whereby they are stretched. The Provisional Specification refers generally to a continuous process in which the spinning is carried out so that the formed materials emerging from the spinning zone retain a proportion of the solvent, or of a volatile stretch-assisting agent contained in the solution, and in which the products are treated with a further proportion of the same or different stretch-assisting agent and stretched; it refers also to the production of the materials by dry or wet methods, and to the saponification of the materials continuously with their production and stretching. Specifications 277,089, 323,790, 336,217, [all in Class 2 (ii)], 342,712, 351,718, 370,430, and 389,823 also are referred to.