A METHOD FOR MANUFACTURING ACRYLONITRILE POLYMER FILAMENTS

摘要

1,247,222. Making acrylonitrile polymer filaments. MITSUBISHI RAYON CO. Ltd. 30 Dec., 1968, No. 61782/68. Heading B5B. Acrylonitrile polymer solutions are wet spun or dry spun to form filaments which are stretched, in hot water, washed either before, during or after the stretching operation and dried in a state having a moisture regain higher than 15% while they are relaxed in a humid stream of air or other gas maintained at a dew point within the range of from 45‹ to 100‹ C. and a dry bulb temperature within the range 130‹ to 180‹ C., whereby voids within the filaments which formed during the spinning step are caused to collapse, the period of the drying operation being long enough to allow this collapse to occur. The heat shrinkage of the filaments during the relaxation and drying step may be 15 to 30%. If the filaments are formed by wet spinning the moisture regain of the gaseous medium in the relaxing and drying zone may be higher than 50%. The stretched filaments may be subjected to a pre-shrinkage treatment before supplying them to the relaxation and drying zone. The total shrinkage of the filaments after the relaxation and drying step may be 18 to 35%. The filaments may be mechanically crimped prior to the relaxation and drying treatment. The solvent content of the filaments before the relaxation and drying treatment is preferably below 3À0% by weight and more preferably below 1À5% by weight. In a set of examples furnished the spinning solution contains 20À5% by weight of the polymer and is prepared by dissolving a copolymer of 95% by weight of acrylonitrile and 5% of vinyl acetate in dimethyl formamide. The solution is wet spun into an aqueous coagulating bath containing 40% by weight of DMF and maintained at 30‹ C. The filaments thereby formed are washed and stretched in water at 100‹ C. at a stretch ratio of 5À0 and then oiled. The moisture regain of the oiled filaments in a swollen gel condition is adjusted to 120%. The relaxation and drying treatment of the filaments is effected in air maintained (in different examples) at 140‹ and 160‹ C., the dew point of the air ranging from 59‹ to 100‹ C., the treatment being applied for 10 minutes. The filaments shrink about 19 to 28% during the treatment. In a different example a similar spinning solution is dry spun in to air maintained at 220‹ C., the taken-up filaments thereby formed containing about 9% by weight of the solvent. The filaments are then treated in a manner similar to that employed in the previous examples.