GB720380A - Improvements in the manufacture of filamentary material from copolymers of acrylonitrile and vinylidene chloride - Google Patents

Abstract

Artificial filaments are obtained by extruding an acetone solution of an acetone-soluble copolymer of acrylonitrile and vinylidene chloride into a coagulating bath of which at least 83 per cent by weight consists of one or more hydrocarbons. Single filaments, multifilament twisted and untwisted yarns, tow, bristles and like filamentary material may be obtained. The filaments are preferably subjected to stretching so as to increase the tensile strength, and they may also be heated first under tension and then while free to shrink so as to improve the extensibility and dimensional stability. The coagulating bath preferably comprises an aliphatic hydrocarbon, but an aromatic hydrocarbon such as benzene, toluene, xylene or solvent naphtha may be used. Hydrocarbons of boiling points above 120 DEG C. are suitable but mixtures of aliphatic hydrocarbons boiling within the range 150-300 DEG C., e.g. commercial kerosene, are preferred. The hydrocarbons may contain up to 20 per cent of their weight of a solvent or swelling agent for the polymer. The copolymer preferably contains 20-50 per cent by weight of acrylonitrile. It may be obtained by the methods described in Specification 643,198. The copolymer may be used in solution in pure acetone or in acetone containing a small proportion of water or methyl, ethyl or isopropyl alcohol. The concentration of the copolymer in the spinning solution may be 15-32 per cent. and the temperature of extrusion may be room temperature or higher, e.g. 60-85 DEG C. The coagulating bath may be at room or higher temperature, e.g. up to 90 DEG C., and it may be quiescent or may move in the same or opposite direction to that of the filaments. The filaments may be elongated during their travel through the bath, and on leaving the bath may be washed with petrol, ether or other volatile liquid until free from the coagulating liquid. The filaments may be stretched at temperatures of 120-210 DEG C. while or immediately after passing over heated surfaces, or through hot air or hot liquids. Following the stretching the filaments may be set by heating them at 150-190 DEG C. while under tension and may then be heated while under little or no tension. To avoid darkening of the filaments as a result of the heat treatment, a stabilizer may be incorporated in the copolymer which is used in preparing the spinning solution. The proportion of stabilizer may be 0.1-2 per cent of the weight of the polymer. Numerous stabilizers are specified, e.g. lead orthosilicate, phthalate, and stearate, zinc stearate, dibutyl tin laurate, calcium stearate, cadmium 2-ethyl-hexoate, barium stearate, epoxy-propyl ethers of bis-phenols, endo - methylene tetra - hydrophthalic acid, maleic acid, butyrolactone, 2,3,5-trichloro-21-hydroxybenzophenone and phenyl salicylate. Specifications 674,323 and 709,995 also are referred to.