ACRYLONITRILE-BASED FIBER BUNDLE MANUFACTURING METHOD

The object of the present invention is to provide a method for producing an acrylonitrile based fiber bundle by dry-jet wet spinning technique that serves to allow a high-grade, high-quality acrylonitrile based fiber bundle to be produced stably even if the traveling speed of the coagulated fibers is increased or the number of spinneret discharge holes is maximized in an attempt to enhance the production efficiency. To meet the object, the invention provides a production method for an acrylonitrile based fiber bundle characterized by first extruding a spinning dope solution through a plurality of discharge holes in a spinneret 1, then allowing the spinning dope solution to run downward into a coagulation bath liquid 12 stored in a coagulation bath 2 to form coagulated fibers 3, turning the coagulated fibers 3 upward on a direction changing guide part 4 located in the coagulation bath liquid 12 below the spinneret 1, and pulling them out of the coagulation bath liquid 12, wherein the requirements 1) to 3) given below are met: 1) the axis direction of the direction changing guide part 4 is perpendicular to both the traveling direction Da of the coagulated fibers 3 running from the surface 9 of the coagulation bath liquid toward the direction changing guide part 4 and the take-up direction Db of the coagulated fibers 3 running from the direction changing guide part 4 and exiting out of the coagulation bath 2, 2) the traveling region of the coagulated fibers 3 ranging from the surface 9 of the coagulating bath liquid to the direction changing guide part 4 includes two or more fiber-existing regions 24 containing coagulated fibers 3 that exist continuously in the traveling direction Da of the coagulated fibers 3, and at least one fiber-free region 23 free of coagulated fibers 3, which are continuously absent in the traveling direction Da of the coagulated fibers 3, wherein each fiber-free region 23 is located between two fiber-existing regions 24, and 3) for at least one of the fiber-free regions 23, the width thereof measured at the surface 9 of the coagulation bath liquid in the axis direction of the direction changing guide part 4 is at least four times the shortest distance between discharge holes in the spinneret 1.