To obtain a precursor fiber bundle used for producing carbon fibers, hardly generating fiber breakage and fuzz, enabling the supply of tows in an easily handleable form in a production process, and improving operation stability by controlling the dynamic frictional coefficient between the fibers and a metal and the crimp rate of the fiber bundle to prescribed ranges, respectively.
This precursor fiber bundle used for producing carbon fibers has a dynamic friction coefficient of 0.1-0.3 between the fibers and a metal, a crimp rate of 8-13 mountains/25 mm and preferably further a total fineness of 300,000-1,500,000 denier, and can be divided into small tows each having a total fineness of 50,000-250,000 denier. A silicone oil is preferably adhered to the fiber bundle in an amount of 0.2-2 wt.%, preferably 0.4-1.5 wt.%.
SHINDO MASAKATSU
ADACHI YASUO
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