GB1027018A - Acrylic composite fibres and production thereof - Google Patents

Abstract

1,027,018. Composite acrylic fibres. JAPAN EXLAN CO. Ltd. Oct. 14, 1964 [Oct. 14, 1963], No. 42005/64. Heading B5B. A composite acrylic fibre comprises at least two different acrylonitrile polymers having different thermal shrinkages and arranged in lamination along the length of the fibre and eccentrically in respect of the fibre axis, wherein the fibre possesses potential coil crimps which could be developed upon heating and exhibits a rate of shrinkage of 5 to 20% and a shrinkability of at least 30 mg./d. when immersed in hot water at 98‹ C. Acrylonitrile polymers are defined as containing at least 50% acrylonitrile, and ethenically unsaturated copolymerizable monomers which may be present include alkyl acrylates and methacrylates, acrylamide and methacrylamide, acrylic acid and methacrylic acid, vinyl acetate, vinyl chloride, vinyl pyridine, and methallyl sulphonic acid and its salts. Such a fibre may be made by extruding two or more dissimilar spinning solutions of different acrylonitrile polymers having different thermal shrinkages simultaneously through a spinning nozzle in a coagulating bath to form composite filaments, stretching the composite filaments for orientation, subjecting the filaments to a structure collapsing treatment, heat treating the filaments in a relaxed state, and further stretching the filaments. Initial stretching may be to 5 to 15 times the initial length and conducted at a temperature of 80-150‹ C., e.g. in hot air, steam or a liquid medium, e.g. hot water. Suitably the structure collapsing treatment is conducted by drying the fibres in a drying atmosphere until substantially all of the water has been evolved from the fibres. Relaxation may be conducted at 100-160‹ C. Final stretching may be to 1À05 to 125 times the initial length and may be conducted at 100- 260‹ C. In examples:-(1) a copolymer of 90% acrylonitrile and 10% methyl acrylate and a copolymer of 88% acrylonitrile and 12% methyl acrylate are separately dissolved in 50% aqueous sodium thiocyanate to prepare two spinning solutions which are extruded at equal rates through a suitable spinneret into 8% aqueous sodium thiocyanate. The tow is washed with water, stretched 8 times in boiling water, dried in a humid atmosphere to a moisture content of less than 3%, relaxed in boiling water for 10 mins., crimped, dried, and stretched 1À07-1À22 times at 120‹ C. (3) A copolymer of 90% acrylonitrile, 9À5% methyl acrylate, 0À5% sodium methallyl sulphonate, and a copolymer of 88% acrylonitrile, 11À5% methyl acrylate and 0À5% sodium methallyl sulphonate are separately dissolved in 50% aqueous sodium thiocyanate to prepare two spinning solutions which are extruded into 8% aqueous sodium thiocyanate. The tow is washed with water, stretched 8 times in boiling water, subjected to a structure collapsing treatment by drying or otherwise, relaxed in saturated water vapour at 110‹ C. for 10 mins., crimped, and dried.