High-elongation meta-aramid fiber, preparation method and apparatus

A preparation method of a high-elongation meta-aramid fiber, comprising the steps of:

• S1:
• adding isophthaloyl chloride to a first m-phenylenediamine solution and reacting at a stirring speed of 20-30 r/min to obtain a first reaction liquid, and then adjusting the pH of the first reaction liquid to 6.5-7.5 to obtain a first slurry, wherein the molar ratio of isophthaloyl chloride to m-phenylenediamine in the first m-phenylenediamine solution is (0.95-1.05):1;
• adding a first part of isophthaloyl chloride to a second m-phenylenediamine solution and performing a first reaction at a stirring speed of 25-35 r/min to obtain a second reaction liquid;
• adjusting the pH of the second reaction liquid to 6.8-8 and then filtering insoluble matter to obtain a pre-polymerized slurry;
• adding an initiator and a second part of isophthaloyl chloride to the pre-polymerized slurry at a stirring speed of 25-35 r/min to perform a second reaction so as to obtain a third reaction liquid;
• adjusting the pH of the third reaction liquid to 7-8 to obtain a second slurry, wherein the mass ratio of the first part of isophthaloyl chloride to the second part of isophthaloyl chloride is (85.7-96):(4-14.3), and the molar ratio of the total amount of the first part of isophthaloyl chloride and the second part of isophthaloyl chloride to the m-phenylenediamine in the second m-phenylenediamine solution is (1-1.1):1;
• S2:
• uniformly mixing the first slurry and the second slurry at a mass ratio of (3-7):(1-3) to obtain a mixed slurry;
• and
• S3:
• de-foaming the mixed slurry to obtain a spinning solution and producing the high-elongation meta-aramid fiber from the spinning solution through a wet spinning process,
• wherein in S3, the spinning solution is firstly coagulated to obtain a primary fiber, and the primary fiber is sequentially subjected to stretching, water washing at 50-60° C., drying at 125-135° C., and heat-treating at 310-325° C. to obtain a shaped fiber, and the shaped fiber is oiled and curl formed to obtain the high-elongation meta-aramid fiber;
• the coagulation bath used for coagulation is an aqueous solution of N,N′-dimethylformamide having a N,N′-dimethylformamide concentration of 56%-60% at a temperature of 9-11° C., and the stretching ratio is 0.8-1.1.