GB743761A - Improvements in or relating to method of producing fibers, threads, yarns, tows and the like - Google Patents

Abstract

<PICT:0743761/IV(a)/1> <PICT:0743761/IV(a)/2> Acrylonitrile polymer fibres are produced by extruding into a coagulating liquid comprising water and 10-50 per cent by weight of ethylene carbonate, a spinning solution comprising ethylene carbonate, water in an amount of 2.5-18.5 per cent by weight, and a polymer of acrylonitrile containing in the polymer molecule at least 80 per cent by weight of acrylonitrile. The resulting fibre is withdrawn from the coagulating liquid and stretched in the presence of an aqueous liquid maintained at a temperature above 80 DEG C. and comprising water and ethylene carbonate at a lower concentration than in the coagulating liquid. The stretched fibre is withdrawn from the hot-stretching liquid and subjected to an intermediate wash treatment with an aqueous liquid comprising water and ethylene carbonate at a concentration lower than in the coagulating liquid but greater than in the hot-stretching liquid, this intermediate wash liquid being prepared by incorporating at least a portion of the effluent resulting from the hot-stretching treatment. At least a portion of the effluent from the intermediate wash treatment is used for fortifying the coagulating liquid. The intermediately washed fibre is given a subsequent-wash treatment with an aqueous liquid which is substantially free from ethylene carbonate, and at least a portion of the effluent from this treatment is incorporated into the liquid used in the hot-stretching treatment. Preferably the processes of filament formation, hot-stretching, intermediate washing, and subsequent washing, are carried out in a continuous manner of operation. The fibres may be in the form of continuous filaments, threads, yarns, or tows. At any stage after the hot-stretching, the fibres or tows may be cut into staple lengths. The acrylonitrile polymer may be a simple polymer of acrylonitrile or it may be a copolymer of acrylonitrile with another polymerizable compound, particularly another vinyl compound. As shown in Fig. 1, spinning solution is extruded through spinneret 11 into a coagulating liquid 12 comprising ethylene carbonate and water, and the freshly formed multifilament yarn 15 is conducted to and around rollers 18, 19 between which it is stretched. The yarn passes to a trough 26 containing a hot dilute aqueous solution of ethylene carbonate, maintained above 80 DEG C. by means of heating coils 27, and is stretched as it passes therethrough on its way to the thread storage and advancing drums 30, 31, which have a peripheral speed greater than roller 19. The hot-stretched yarn 15 is subjected to the intermediate-wash treatment as it is advanced along drums 30, 31, which are partly immersed in a dilute aqueous solution of ethylene carbonate in trough 33, the temperature being maintained at 40-60 DEG C. The washed yarn passes to drums 36, 37, and is subjected to the subsequent-washing treatment by a stream of water from tube 34 as it is advanced in helical turns along the drums. The yarn passes around internally-heated drying drums 41, 42, and is then collected on the bobbin 45 of the captwister 44. The effluent 38 is passed along tube 40 so as to maintain the hot-stretch bath 25 at the desired low concentration of ethylene carbonate. The effluent from trough 26 is passed along pipe 29 to the intermediate-wash trough 33 and the effluent from trough 33, considerably enriched in ethylene carbonate but still more dilute than the coagulating liquid, is passed along pipe 16 to the trough 13 to assist in maintaining the coagulating liquid at the desired concentration. Effluent from trough 13 is passed along pipe 46 to a solvent recovery system 47. As shown in Fig. 2, spinning solution is extruded through one or more multi-holed spinnerets 51 into the coagulating liquid 53 in trough 54. The resulting high-denier yarn or tow 55, flattened into the form of a ribbon, is stretched by the roller systems 59, 60, and then hot-stretched as it passes through the liquid 65 in trough 66. The stretched yarn or tow is subjected to the intermediate washing as it passes through the liquid in troughs 72, 76, 80, 85, 89, and 93, the liquid flowing from trough to trough in counter-direction to that of the yarn. The subsequent washing treatment is carried out as the yarn travels through troughs 99, 103, and 107, and drying is effected as it travels over drums 108. Water 114 is supplied to the last wash-trough 107. The effluent 96 is passed through a heat-exchanger 95 and then fed into the hot-stretch trough 66. The hot effluent 94 is cooled in the heat-exchanger 95 and is then fed into trough 93. The effluent 81 may be directed entirely to the trough 80, or part of it may be passed via the valve 67 and pipe-line 57 to the trough 54. Effluent from trough 72 is passed through line 69 and valve 67 to line 57 and trough 54. It may also be diverted directly to the solvent recovery system 112 when desired. The effluent from the coagulating liquid 53 is sent to the recovery system 112 through lines 58 and 110. Specification 716,081 is referred to.