Improvements in or relating to the dry spinning of artificial threads

摘要

PICT:0788194/IV (a)/1 Artificial threads, particularly of polyacrylonitrile, are dry-spun by extruding a spinning solution through a spinneret into an externally heated spinning cell through which is blown a current of a hot gas in the direction of travel of the extruded filaments, the current being of laminar flow free from turbulence and eddy currents and the temperature of the gas first entering the cell being 10-70 DEG C. (preferably 20-40 DEG C.) above that of the inner surface of the portion of the cell wall in the vicinity of the spinneret; the hot gas is introduced into the end of the spinning cell in such a manner that the stream of extruded filaments is surrounded by a substantially uniform cylindrical sheath of the gas travelling at a linear velocity below that at which the flow of the gas becomes turbulent. In the example and as shown in Fig. 2, a 20 per cent solution of polyacrylonitrile in dimethyl formamide is extruded through a spinneret 6 into a cylindrical spinning cell 1 maintained at 160 DEG C. by a jacket 2 through which a heating medium enters at 3 and leaves at 4. Air at 200 DEG C. is blown into the top of the spinning cell through the perforated annular pipe 7, nickel gauze screen 8 and hollow truncated cone 14, the wide upper end of which is in gas-tight contact with the wall of the spinning cell and at about the level of the spinneret face. The truncated cone 14 narrows in the direction of travel of the filaments 5 and is coaxial with the spinneret. A secondary current of air at 200 DEG C. is supplied to the cell 1 through a tube 10 and an annular duct 11 having openings 12 and is downwardly directed by the annular baffle 9, the rate of supply of the primary and secondary hot air currents being equal. Both air streams leave the cell through the perforated annular tube 15, and the thread is collected on the wind-up reel 16. Specification 614,959 is referred to.