Process for producing wholly aromatic polyamide fibers

Claim 1

A process for producing wholly aromatic polyamide filaments having at least 75 mol% of the recurring units being derived from m-phenylene isophthalamide, said process comprising extruding a spinning solution of said wholly aromatic polyamide in an amide solvent having a polymer concentration of 15 to 30 % by weight and being free of inorganic salts through a spinneret into an aqueous coagulating bath containing a total concentration of calcium chloride, magnesium chloride, calcium nitrate and zinc chloride of at least 35% by weight of liquid and a concentration of calcium chloride of at least 20% by weight of liquid and having an amide solvent concentration of not more than 3% by weight of liquid to the vicinity of said spinneret, said amide solvent essentially consisting of N-methyl-2-pyrrolidone, taking-up the coagulated filaments from the lower portion to the upper portion of the coagulating bath, flowing the coagulating liquid in said bath at an average velocity from 0.04 to 0.1 times the velocity of filament take-up in the filament advancing direction, discharging the coagulating liquid having a specific gravity, measured at 60° C of at least 1.36 and an amide solvent concentration of not less than 4% by weight from said bath, extracting N-methyl-2-pyrrolidone from the discharged coagulating liquid with an organic solvent consisting essentially of methylene chloride, and recovering the N-methyl-2-pyrrolidene from the organic solvent.