| 摘要 |
Acrylonitrile polymer fibres having a negative birefringence and a shrinkability of at least 35% are produced by drying undrawn, solvent-free fibres of the polymer at 100 DEG -130 DEG C. to reduce their moisture content to below 10%, treating the dried fibres with an aqueous medium at 96 DEG -110 DEG C. for at least 15 seconds, and then drawing the fibres to 1,5-2,5 times their original length. The polymer may be polyacrylonitrile or a copolymer containing at least 70% of acrylonitrile and not more than 30% of one or more neutral mono-ethylenically unsaturated monomers copolymerizable with acrylonitrile, such as vinyl acetate, methyl vinyl ketone, methyl acrylate, methyl methacrylate, vinyl chloride, or vinylidene chloride. All or part of the neutral monomer may be replaced by up to about 10% of a cationic or anionic monomer, such as sodium styrene sulphonate or 2-vinylpyridine, to give improved dye receptivity. The aqueous medium is water, steam, or an aqueous solution or dispersion of a conventional textile-treating agent. The fibres may be dried between the treatment with an aqueous medium and the subsequent stretching operation. When stretching in an aqueous medium a temperature of about 70 DEG -80 DEG C. is preferred. When stretching in hot air, as between heated closely spaced plates, plate temperatures of 118 DEG -138 DEG C. may be used. "Solvent-free fibres" are defined as fibres containing not more than 3% of the spinning solvent and "undrawn fibres" are defined as fibres which have been given no substantial degree of permanent stretch. The fibres may be either dry- or wet-spun and are free from voids. Shrinkage of the final fibres may be effected by treating them with boiling water or dry heat, e.g. at 143 DEG C. In an example, a tow of fibres formed by dry-spinning a solution in dimethyl formamide of a terpolymer of 94% acrylonitrile, 5,7% methyl acrylate, and 0,3% sodium styrene sulphonate has its solvent content reduced to 1,4% (based on the dry fibre) by passage through a series of aqueous solutions of solvent of diminishing concentration, is dried at 127 DEG C. in air for 8 minutes to below 1% water content, is then boiled in water for 30 minutes and is finally given a 90% stretch while being passed between and in contact with two parallel flat plates heated to a surface temperature of 118 DEG C. The fibres may be used, blended with low shrinkage fibres, for the production of yarns for conversion into pile fabrics. Specification 586,881 is referred to.
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