| 摘要 |
In the manufacture of polyacrylonitrile fibres, a solution of polyacrylonitrile, or a copolymer thereof containing at least 80 per cent. by weight of acrylonitrile, in a mixture of ethylene carbonate and water, the water being present in an amount of 2.5-18.5 per cent. by weight of the solution, is extruded into a coagulating bath comprising ethylene carbonate and water, the ethylene carbonate concentration in the bath being 10-50 per cent. by weight. The spinning solution, which may contain small amounts of polyhydric alcohols, e.g. ethylene, propylene or dipropylene glycol, preferably has a temperature of 40 DEG -80 DEG C. or above, and the "cloud point" of the solution is preferably below 67 DEG C. The coagulating bath, which preferably has a temperature of 45 DEG -80 DEG C., may also contain small amounts of ethylene or dipropylene glycol, but ethylene carbonate and water preferably comprise at least 95 per cent. by weight of the bath. The ethylene carbonate concentration of the bath may be maintained by continuously withdrawing portions of the bath, and these portions may be subjected to flash-distillation to remove the water, the residuum being used as solvent in preparing the spinning solution. The fibres may be submitted to one or more stretching operations, e.g. an air-stretch followed by a hot water- or steam-stretch, and thereafter heat-treated in the relaxed condition, e.g. in hot water or steam. Examples are given. Copolymers of acrylonitrile with vinyl esters, ethers, and ketones; acrylic acid and its esters and amide; methacrylic acid and its esters, amide and nitrile; maleic, itaconic, fumaric and crotonic acids and their esters, amides and nitriles; allyl alcohol and its esters or ethers; styrene and nuclear substituted styrenes, e.g. chloro- and dichlorostyrene; halogenated monoethylenic compounds such as vinyl chloride, vinyl fluoride, vinylidene chloride, 1, 2-dichloropropene-1, 1,2-dichloro-propene-2, allyl chloride, methallyl chloride, 2-chloro-allyl-alcohol and 1-allyloxy-3-chloro-2-propanol; N-vinyl compounds such as N-vinyl-pyrrolidone, N-vinyl succinimide or N-vinyl carbazole; N-tertiary butyl acrylamide, N-tertiary octyl acrylamide; and 2-or 4-vinylpyridine may be employed. |
