METHOD FOR PRODUCING ULTRAFINE CARBON FIBER

PROBLEM TO BE SOLVED: To provide a method for producing an ultrafine carbon fiber having good characteristic, and simpler as compared to a conventional one.SOLUTION: A method for producing an ultrafine carbon fiber includes: (1) a step of molding, in a molten state, a composition formed from a thermoplastic resin and 1-150 pts.mass of mesophase pitch based on 100 pts.mass of the thermoplastic resin so as to fiberize the mesophase pitch and obtain a resin composite fiber; (2) a stabilization step of contacting a nitrogen oxide in a gas-phase state with the resin composite fiber in a reaction system in which gas containing the nitrogen oxide flows at a flow speed of 0.010-10.0 m/s so as to obtain a resin composite stabilized fiber; and (4) a carbonizing and baking step of heating, and carbonizing or graphitizing the stabilized fiber in the resin composite stabilized fiber under inert atmosphere to obtain an ultrafine carbon fiber.SELECTED DRAWING: None 【課題】従来と比較してより簡便に良好な特性の極細炭素繊維の製造方法を提供することである。【解決手段】（１）熱可塑性樹脂と、前記熱可塑性樹脂１００質量部に対して１〜１５０質量部のメソフェーズピッチと、からなる組成物を溶融状態で成形することにより前記メソフェーズピッチを繊維化して樹脂複合繊維を得る工程と、（２）気相状態の窒素酸化物を含むガスが流通速度０．０１０〜１０．０ｍ／ｓで流通する反応系内で、前記樹脂複合繊維に前記窒素酸化物を接触させて樹脂複合安定化繊維を得る安定化工程と、（４）前記樹脂複合安定化繊維中の安定化繊維を不活性雰囲気下で加熱して炭素化乃至黒鉛化し、極細炭素繊維を得る炭化焼成工程と、を含む方法により極細炭素繊維を製造する。【選択図】なし