GB1054927A - - Google Patents

Abstract

1,054,927. Treating polyacrylonitrile fibres. COURTAULDS Ltd. Nov. 12, 1963 [Nov. 13, 1962], No. 42804/62. Heading B5B. Neon dried polyacrylonitrile fibres containing at least 80% by weight of acrylonitrile units, particularly 90 to 95% by weight of acrylonitrile units, are impregnated with an aqueous solution of an N-cyanoalkyl amide, or an N,N-bis-cyanoalkyl amide, the impregnated fibres are dried under conditions allowing them to shrink and are then stretched. The fibres may be brought into contact with steam, e.g. with steam at a pressure of 5 to 30 p.s.i.g. The cyanoalkyl amide may be a formamide or an acetamide. The alkyl group substituted by the cyano-group may contain from 1 to 3 carbon atoms. The aqueous solution may contain 1À5 to 4% by weight of amide and the proportion of amide left on the fibre may be at least 2%, e.g. 3 to 6% by weight. The fibres may be dried at 90‹ C. under zero tension. They may be stretched after drying by 15 to 85%, e.g. 30 to 60%. The stretching may be carried out at an elevated temperature, e.g. 100‹ to 110‹ C. The acrylonitrile may have been copolymerized with styrene, methyl acrylate, itaconic acid, methallyl sulphonic acid and its salts, vinyl acetate or vinyl pyridine. In all the examples, the polyacrylonitrile filaments treated are a copolymer of acrylonitrile, methyl acrylate and itaconic acid in the proportions 93 : 6 : 1 by weight and have been produced by extruding a solution of the polymer in a concentrated aqueous solution of sodium thiocyanate into a weaker solution of the same salt. The filaments are washed but not dried prior to the treatment with the aqueous amide solution, which imparts a high '' potential shrinkage " to the filaments. This shrinkage is defined as the shrinkage undergone by the filament when it is subjected to conditions allowing it to shrink freely, e.g. contacting the filament with boiling water or steam, under low tension or without tension.