Patent ID: 8801985

Claim:
A production method of a carbon fiber precursor fiber bundle, characterized by comprising: a coagulation step of forming swollen yarn by extruding an organic solvent solution of an acrylonitrile-based polymer into an aqueous solution of dimethylacetamide from a spinning nozzle having a nozzle hole diameter of 45 μm or more and 75 μm or less and the number of holes of 50,000 or more at a coagulated yarn take-up speed/extrusion linear speed ratio of 0.8 or less; a wet heat drawing step of wet heat drawing the swollen yarn; an oiling agent imparting step of imparting a first oiling agent to the wet heat drawn yarn by guiding the heat wet drawn yarn into a first oil bath, and subsequently imparting a second oiling agent in a second oil bath after once squeezing the yarn by use of two or more guides; a small tow production step of obtaining a small tow by drying, densifying and secondarily drawing the yarn imparted with the first and second oiling agents so as to have a total drawing magnification of 5 or more and 10 or less; and an aggregate-of-tows production step of obtaining an aggregate of tows by feeding a plurality of the small tows so as to be in parallel and so that side ends of the small tows adjacent to each other are in contact with each other into an intermingling device that comprises a yarn channel having a flat rectangular section and a plurality of air jet holes which are disposed with a predetermined interval along the long side direction of the flat rectangle and which open into the yarn channel, and by jetting out air from the air jet holes to intermingle the adjacent small tows with each other.