| 摘要 |
<p>Filaments, films and like shaped structures are obtained by wet-spinning a solution in nitric acid of an acrylonitrile polymer or copolymer containing at least 80 per cent of acrylonitrile in the polymer molecule, the coagulating bath consisting essentially of water and nitric acid and the temperature of the coagulating bath being so regulated that the filaments or other structures are of a matt white appearance. The concentration of the nitric acid solution in which the polymer is dissolved to form the spinning solution is preferably 46-68 per cent by weight, and the concentration of nitric acid in the coagulating bath may be 1-40 per cent by weight, the temperature being betweenn 15 DEG and 70 DEG C. The filaments or other products obtained have a fine regular porous structure. They may be subjected to stretching to improve the tensile strength. In an example, polyacrylonitrile of molecular weight about 60,000 and one per cent of urea, based on the weight of the polymer, are dissolved at 20 DEG C. in nitric acid of 59 per cent concentration to form a solution containing about 12 per cent of the polymer. The solution is filtered and stored at 10-15 DEG C. It is then extruded into a coagulating bath consisting of 10 per cent nitric acid, the temperature of the bath being maintained at 35-40 DEG C. The filaments obtained are washed with water and passed through a hot aqueous bath containing phosphoric acid, polyvinyl alcohol and glycerol, in which the main proportion of the absorbed water is removed from the filaments and the swollen condition is removed. The filaments are dried and then stretched while passing between a heated roller and a collecting bobbin. The filaments obtained have a dull lustre and snow-white colour. Instead of polyacrylonitrile, the polymer used may be a copolymer of acrylonitrile and methacrylamide, methacrylonitrile, dimethylaminoethyl methacrylate, vinyl pyridine, or vinylimidazole. If desired, the washed filaments may be treated with hot water at 70 DEG C. or above to remove the greater part of the absorbed water or they may be passed over a surface which is heated to 70-100 DEG C. The stretching or part of the stretching may be carried out in hot water or in water containing a very small proportion of a strong acid. The stretched filaments may be treated with a finishing solution containing a lubricant and a small proportion of a strong acid.</p> |
