| 摘要 |
Gelled polyacrylonitrile filamentary material which has been formed by wet-spinning a solution of the polymer in a concentrated aqueous solution of an alkali-metal thiocyanate into a dilute aqueous solution of an alkali-metal thiocyanate maintained at a temperature not exceeding 10 DEG C., or not exceeding 40 DEG C. if a water-miscible alcohol is a component of the spinning solution, or of the coagularing bath, or both, which filamentary material contains water and an alkali-metal thiocyanate, the latter being present in such a proportion that the ratio of the proportion of alkali metal thiocyanate in the filaments to that of acrylonitrile polymer in the filaments is 0.5 to 2.0, both constituents being reckoned as dry, is stretched at -2 DEG to 40 DEG C. to between 1.5 and 4 times its original length, the thiocyanate is extracted from the stretched filamentary material with water or other solvent for the thiocyanate, and the filamentary material is stretched a second time to between 1.5 and 10 times its once-stretched length, the total stretch being three to fifteen times the length of the filamentary material immediately before the first stretch, and the second stretch being effected at 70-110 DEG C. while the material is in contact with water or steam. The material is then dried, either with or without previous rinsing with water. The coagulating bath is preferably maintained at or below 0 DEG C., e.g. at -9 DEG to -0.5 DEG C., and may contain at least 4%, e.g. 5 to 15%, by weight of a water-miscible alcohol such as methyl, ethyl, propyl, isopropyl, n-butyl, sec.-butyl or tert.-butyl alcohol. The polymer should contain at least 35% of polyacrylonitrile, the balance, if any, being derived from other polymerizable vinyl compounds, a number of which are specified. In an example, a spinning solution containing 12.5% of a copolymer of 95% of acrylonitrile and 5% of methyl acrylate, 43.75% of sodium thiocyanate and 43.75% of water is spun into a 10% aqueous solution of sodium thiocyanate at -2 DEG C. to form a gelled thread which contains 1.1 times as much sodium thiocyanate as copolymer. The thread is stretched in air at 5 DEG C. to 3.63 times its original length, washed with water to remove substantially all the sodium thiocyanate, hot-stretched in water at 98 DEG C. to 10.89 times its original length, and dried on a set of rolls. |
