METHOD OF MANUFACTURING POLYOXADIAZOLE FIBER OR THREAD Russian patent published in 2003 - IPC

FIELD: polymer production. SUBSTANCE: invention relates to manufacturing polyoxadiazole fibers or threads useful in metallurgy, chemical industry, and other areas for providing various heat-resistant products. Spinning solution is prepared by heating hydrazine sulfate with arylenedicarboxylic acid in concentrated sulfuric acid containing free sulfuric anhydride, said arylenedicarboxylic acid being, in particular, terephthalic acid with 0.004-0.017% p-toluyl acid or mixture of terephthalic acid with 0.5 to 99% isophthalic acid with 0.04- 0.017% of mixture of p-toluyl acid with 0.5 to 99% m-toluyl acid. Heating is conducted gradually with intermediate formation of first 6.0-20% oligomer solution and then 5,0-14.18% oligomer solution followed by continuously or periodically performed polycondensation resulting in 3 to 14% solution of polymer in sulfuric acid. Solution is homogenized, filtered, and degassed. Spinning is carried out into sulfuric acid precipitation bath with density constituting 0.65-0.85 that of spinning solution at 30-70 C. Thread travels during 1 to 17 sec and is stretched 2-6-fold in sulfuric acid solution. Threads are then subjected to heat treatment at 270-520 C for 2 to 900 sec being additionally stretched by 0.1-2%. EFFECT: improved physicochemical characteristics and oxygen index. 6 cl, 1 tbl, 6 ex