To obtain a flameproof fiber which has a small low flameproof fiber ratio, a small amount dissolved in formic acid and is uniformly flameproofed.
In a method for producing the flameproof fiber by flameproofing an acrylic fiber provided with a finishing oil, the finishing oil comprises an emulsifying agent and base oil. The emulsifying agent is a single component of a 8-18C alkyl group-containing polyoxyethylene alkyl ether having 1-20 addition molar number of ethylene oxide and the base oil is an amino-modified silicone to give the flameproof fiber which has ≤1.5% low flameproof fiber content in the flameproof fiber, ≤12% dissolution amount in formic acid and 1.350-1.365 specific gravity. The flameproof fiber is carbonized to produce a carbon fiber having high quality and high strength.
YOSHIKAWA HIDEKAZU
MATSUKI TOSHITSUGU
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