Acrylonitrile-based fiber bundle manufacturing method

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, then allowing the spinning dope solution to run downward into a coagulation bath liquid stored in a coagulation bath to form coagulated fibers, turning the coagulated fibers upward on a direction changing guide part located in the coagulation bath liquid below the spinneret, and pulling them out of the coagulation bath liquid, wherein the requirements 1) to 3) given below are met:

• 1) the axis direction of the direction changing guide part is perpendicular to both the traveling direction of the coagulated fibers moving from the surface of the coagulation bath liquid toward the direction changing guide part and the take-up direction of the coagulated fibers moving from the direction changing guide part and exiting out of the coagulation bath liquid,
• 2) the traveling region of the coagulated fibers ranging from the surface of the coagulating bath liquid to the direction changing guide part includes two or more fiber-existing regions containing coagulated fibers that exist continuously in the traveling direction of the coagulated fibers, and at least one fiber-free region free of coagulated fibers, which are continuously absent in the traveling direction of the coagulated fibers, wherein each fiber-free region is located between two fiber-existing regions, and
• 3) for at least one of the fiber-free regions, the width thereof measured at the surface of the coagulation bath liquid in the axis direction of the direction changing guide part is at least four times the shortest distance between discharge holes in the spinneret.