METHOD FOR PRODUCING ACRYLIC CARBON FIBER PRECURSOR FIBER

PROBLEM TO BE SOLVED: To provide a method for producing acrylic carbon fiber precursor fiber at a relatively low cost, which is capable of reducing filament-filament sticking trouble under good drawability. SOLUTION: The method for producing acrylic carbon fiber precursor fiber includes the following process: Using a multistep washing tank including at least three washing tanks, unwashed coagulated filament yarn is washed by successively bringing it into the at least three washing tanks, and concurrently drawn by a factor of 1.2 or greater in the multistep washing tank using drive rollers installed at the entrance side of the first-step washing tank and the exit side of the final-step washing tank respectively. In this process, the washing water temperatures in the first-step washing tank, an intermediate-step washing tank and the final-step washing tank are set at 50 to 65°C, 68 to 90°C and 95 to 99°C, respectively, and prior to bringing the coagulated filament yarn into the final-step washing tank, the solvent concentration of the coagulated filament yarn is set to be 0.5 mass% or lower. COPYRIGHT: (C)2008,JPO&INPIT