Improvements in or relating to the production of synthetic fibres from polymers and copolymers of acrylonitrile

摘要

The process of the parent specification is modified in that the stretched polyacrylonitrile filaments are treated with a liquid composition containing an antistatic agent, then dried while travelling under tension in a helical path, and then passed in a continuous manner, while relaxed and free to contract linearly, through a heated zone maintained at a temperature within the range of 100-500 DEG C. at a rate such that the time of exposure of any point of the filaments is within the range of 0.01-5.0 seconds. The treated filaments have little or no residual shrinkage, and they have improved extensibility, rendering them suitable for weaving, knitting, and other textile operations. As shown in Fig. 1, polyacrylonitrile filaments are obtained by extruding a solution of the polymer through a heated spinning head and nozzle 14 into a cooled aqueous coagulating liquid 22 in the bath 24. The coagulating liquid may be water and it may be maintained at a temperature below 10 DEG C. by continuous circulation and cooling, or by adding ice or a freezing mixture to the water in the bath. The filaments are given an extended travel in the bath by passing them to and from submerged rollers 34, 36. The filaments pass from the bath to a stretching device. They are stretched by passing round roller 38, then in a straight line through a trough 42 containing hot water and then round roller 44 which has a greater peripheral speed than roller 38. They are collected on a bobbin 50. The wound bobbin 50 is placed in a trough 64, Fig. 2, containing an anti-static finishing composition, and filaments from the bobbin pass in helical turns round a pair of mutually inclined drying cylinders 70, 72. The dried filaments pass through a heating zone provided by a groove in a metal block 82, which is heated electrically, and thence to a godet 76, which has a lower peripheral speed than rollers 70, 72, so as to allow the filaments to contract during the heat treatment. Slippage of the filaments over godet 76 is prevented by means of the weighted pinch-roll 92. The filaments pass under tension from godet 76 to a ring-twister 86. If desired, the filaments may be passed continuously from the stretching device to the devices for applying the anti-static composition, to the drying, heat-treatment, and relaxing devices, and finally to a winding and twisting device. The apparatus described in Specification 695,536 may be used. Specifications 594,999, 672,775, 689,742 and 689,744 also are referred to.