Improvements in or relating to the production of artificial filament

A continuous filament of large cross-section is produced by passing a thread of fibres of finer cross-section upwards in a straight line into and through a body of volatile solvent liquid for the substance of at least some of the fibres and causing the thread to continue substantially in a straight line beyond the body of liquid until it is set by the drying off of the solvent liquid picked up by it. The original thread may be composed of fine continuous filaments and may be twisted to impart a round cross-section to the product. Excess solvent liquid may be stripped from the thread mechanically and the evaporation of the solvent may be accelerated by passing the thread through a current of a heated evaporative medium. The thread may contain filaments of cellulose acetate or other cellulose esters such as cellulose propionate, acetate-propionate, or acetate-butyrate, or of cellulose ethers such as ethyl cellulose. Examples of solvents for use with cellulose acetate threads are acetone, triacetin, ethyl lactate, diacetone alcohol and mixtures of diacetone alcohol with water or alcohol. The solvent may contain dyes or other effect materials (see Group IV (c)). As shown, a thread 6 (Fig. 1) of continuous filaments of cellulose acetate is drawn from the bobbin 5 and passes upwards via thread guide pulley 7 through a die hole 8 (Fig. 2) in the floor of the trough 9 into which a continuous flow of acetone is fed by way of supply pipe 10 and control valve 12 from the reservoir 11. The surplus acetone overflows down pipe 13 into the receiver 14. The thread passes upwards and may pass through a stripper die 15 in a die-plate 16 secured to a stand 18 by wing nuts 17 by means of which the height of die 15 above the trough 9 may be adjusted. The two dies 8 and 15 are carefully aligned with the thread guide pulley 7 so that the thread is not deflected by the die 8. From the die 15 the thread 6 passes upwards in free air, in the course of which evaporation of the acetone from the thread takes place. The thread then passes through a further guide 20 (Fig. 1), substantially in alignment with the two dies 8, 15 but adapted to be traversed over a short distance so as to distribute the treated thread 19 on the surface of a take-up swift 21 by means of which the thread is drawn through the apparatus. Instead of drying the moistened thread in free air it may be passed through a tube 26 (Fig. 3), closed at