GB388400A - Improvements in the manufacture of artificial silk and other artificial products - Google Patents

Abstract

To obtain non-scintillating dry spun artificial filaments, yarns, &c., the spinning solution is made with a solvent mixture containing as regards its main bulk a liquid which is a solvent for the cellulose derivative at normal temperatures, and also a minor proportion of a more volatile liquid. In the case of acetone-soluble cellulose acetate, this volatile liquid may be a solvent for the cellulose derivative, such as methyl or ethyl formate, or a latent solvent such as methylene chloride, or a weakly-acting or strongly-acting precipitant such as an ether especially diethyl ether, although low boiling petroleum fractions such as petrol ether may also be used; and suitable proportions are say 6-12 per cent of diethyl ether, and 10 per cent to 2 per cent or less of petrol ether. A small percentage of water or alcohol may also be added to facilitate the draw-down of the filaments. With the use of the above solvent mixtures, it is not essential that the spinning solutions contain a high percentage of the cellulose derivative, and concentrations below 25 per cent down to 15 per cent or less may be used while still producing non-scintillating filaments; and with these latter solutions, spinning speeds up to 400 metres per min. or higher may be employed. It is advantageous to employ cellulose derivatives of high viscosity characteristics, for example, cellulose acetates obtained according to the process of Specification 207,562, [Class 2 (ii), Cellulose &c.]. To obtain the desired cross section of filament, it is important that the evaporation of the solvent should be rapid during the earlier part of its travel, say, the first two inches; and such rapid evaporation may be secured by introducing additional evaporative medium, heated or not, at the region of the spinning nozzle as described in Specification 325,233, [Class 2 (ii), Cellulose &c.], or by the use of the collector devices of Specifications 300,998, 304,674, 326,232, [all in Class 2 (ii), Cellulose &c.], and 352,922, or by the employment of reduced pressure within the spinning cell, see Specification 324,061, [Class 2 (ii), Cellulose &c.]. Specifications 209,125 and 210,108, [both in Class 2 (ii), Cellulose &c.], also are referred to.