Toray Industries, Inc.

Hiroyoshi Ikuta

Tomoki Tamura

Takeya Ohashi

A drawing method is provided which enables a pressurized steam drawing of an acrylonitrile-based fiber bundle used as the precursor fiber of the carbon fiber bundle. In particular, a drawing method is provided which realizes a high processability when this treatment is conducted at a high draw ratio and high speed. This invention is a method for producing an acrylonitrile-based fiber bundle which includes the steps of spinning a spinning solution containing an acrylonitrile-based copolymer, and subjecting the fiber bundle to a pressurized steam drawing in a pressurized steam drawing apparatus (A) having at least two zones which are a preheating zone on the fiber bundle inlet side and a heating zone on the fiber bundle exit side, the two zones being separated by a seal member. The preheating zone is in a pressurized steam atmosphere at 0.05 to 0.35 MPa, the heating zone is in a pressurized steam atmosphere at 0.45 to 0.70 MPa, temperature difference &#x394;T1 in the preheating zone of the steam drawing apparatus in the fiber bundle-moving direction defined in the specification is up to 5&#xb0; C., and temperature difference &#x394;T2 in the preheating zone of the steam drawing apparatus in the cross-sectional direction of the steam drawing apparatus defined in the specification is up to 5&#xb0; C.

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Tokyo, Japan

Hiroyoshi Ikuta