Patent GB-720187-A (GB)
Title: Improvements in or relating to the manufacture of filamentary materials of a cellulose ester or other thermoplastic substance
Inventor: SOWTER PERCY FREDERICK COMBE
IPC: D01D5/06
Filed: 1951-12-07
Abstract: <PICT:0720187/IV (a)/1> A solution of a cellulose derivative or other thermoplastic substance is extruded into a coagulating liquid moving at a linear speed below the extrusion speed, and the filaments obtained are drawn at a maximum speed higher than the extrusion speed (so stretching them) through a column of the coagulating liquid which, beginning at a point between 1.5 and 4 inches from the point of extrusion, flows in a substantially streamline and non-turbulent manner in the direction of travel of the filaments at an increased linear speed which is uniform along the length of the column and is between the extrusion speed and the speed at which the filaments are drawn from the column, and is controlled by means independent of the friction between the filaments and the liquid. The spinning solution may be a solution of cellulose acetate in acetone and the coagulating bath may be aqueous acetone or aqueous diethylene glycol diacetate. Preferably the whole of the coagulating liquid flows, and the filaments travel, successively through two zones, the first (in which extrusion takes place) being short and of relatively large cross-section, and the second being much longer and of very small cross-section so that the flow of liquid therein is substantially streamlined and non-turbulent.  In the first zone, the speed of the liquid th preferably less than one-tenth of the extrusion speed, and in the second zone, the speed of the liquid is preferably at least 1.5 times the extrusion speed and between 40 and 120 metres per minute below the speed at which the filaments are withdrawn from the column of coagulating liquid.  The stretching may be 500-1000 per cent.  If desired the filaments may be further stretched after leaving the column of coagulating liquid.  The process may be applied to upward or downward spinning.  As shown in Fig. 1, filaments 13, formed by extrusion from nozzle 18, pass upwardly through coagulating liquid contained in vessel 11 which comprises an extrusion chamber 15 and a setting tube 16 of very small diameter, provided with a flared end 17 extending into the extrusion chamber.  A yarn guide 23 is positioned so as to wipe off from the filament bundle or yarn a substantial portion of the adhering liquid.  If desired the amount of liquid carried by the filaments may be reduced by subjecting the yarn to a false twist as it rises from the surface of the coagulating liquid.  The coagulating liquid enters chamber 15 through inlets 20 and flows continuously through tube 16 to the gutter 21.  The yarn passes over godet 12 to the washing device 14 which comprises a bath 25 and thread-advancing rollers 26, 27.  When downward spinning is adopted, the setting tube may be provided at its lower end with a constriction or plug having an orifice just large enough for egress of the filaments, and a separate lead-off for the liquid may be provided in the side of the tube just above the constriction or plug. Specifications 695,559 and 697,967, [Group IV (c)], are referred to.