Production of crimped tows of polyacrylonitrile filamentary material

摘要

In a continuous process for producing a crimped tow of filaments of polyacrylonitrile containing a major portion, e.g. 75 per cent by weight, of acrylonitrile combined in the polymer molecule, a dry uncrimped tow is wetted (100-700 per cent by weight of water) and heated by an aqueous fluid at a temperature of 155-205 DEG F. and is continuously fed under uniform tension (0.005-0.5 grams per denier) to and crimped within a zone which is within said temperature range. The hot crimped tow is passed, while it is relaxed, to and through a separate cooling zone in which it is cooled to a temperature below 120 DEG F. to set the crimp. The aqueous fluid may contain an "effect" agent, e.g. an anti-static material containing a low viscosity oil or a lubricant. The tow fed to the crimping zone may have a residual shrinkage of 0-3 per cent or may be pretreated to remove such shrinkage by continuous passage, FORM:0809039/IV (c)/1 in a relaxed state, through a liquid at a temperature of 210-230 DEG F. with a dwell therein of 5 seconds to 30 minutes and tensioning the tow to align the filaments thereof. Cooling may be effected by passage through air at "room" temperature or exposure to blasts, sprays or a circulation of cooling fluid during which the tow may be supported on a porous conveyer. As shown in Fig. 1, tow 10 is led from a tunnel or apron dryer 12 by an apron 14 and passed continuously through a shrinkage removal zone provided by a J-box 16 which may have, on each side at 24, alternately operating liquid sprays which deposit the tow in a spiral form 26 which is subjected, in a jacketed section 28, to a hot fluid, e.g. steam or non-solvents (in relation to the filament material) such as ethylene glycol, diethylene glycol, ethylene glycol monoethyl ether, glycerol, propylene glycol. Tow then receives the aqueous fluid treatment at a temperature of 155 DEG to 205 DEG F. in a device 60 which may be spray means or a bath in which the tow, guided by rollers, is repeatedly immersed. Tow 76, continuously crimped in a "nip-rolls and stuffer-box" apparatus and discharged on to a conveyer 80 is cooled in a J-box 84. If water is the coolant, it is removed from the tow, as by a squeeze roll, and the tow is dried or stapled, dried and opened. If dry tow is to be freed of residual shrinkage, it may be first wetted with water, e.g. by a spray, trough, tube or wiper (not shown) to facilitate subsequent handling.