FLAME-PROOFED FIBER BUNDLE, CARBON FIBER BUNDLE, AND PROCESSES FOR PRODUCING THESE

摘要

[Problem] To efficiently and inexpensively provide a flame-resistant fiber bundle having high performance and high quality and a carbon fiber bundle which is obtained using the flame-resistant fiber bundle. [Solution] A process for producing a flame-resistant fiber bundle, the process comprising a step in which a flame-resistant fiber bundle (1) having a single-fiber density Á F1 of 1.26 g/cm 3 to 1.36 g/cm 3 is brought into contact sequentially with a heater group having a surface temperature T H of 240°C to 400°C under the following conditions (A), (B), and (C) to obtain a flame-resistant fiber bundle (2) having a single-fiber density Á F2 of 1.33 g/cm 3 to 1.43 g/cm 3 : (A) the heater H n+1 with which the fiber bundle is brought into contact "n+1"-thly has a highter temperature than the heater H n with which the fiber bundle is brought into contact "n"-thly; (B) the total contact time between the fiber bundle and the heater group is 10 seconds to 360 seconds; and (C) the contact time between the fiber bundle and each heater is 2 seconds to 20 seconds. A flame-resistant fiber bundle configured by a single fiber group having a single-fiber fineness of 0.8 dTex to 5.0 dTex, wherein an average density of a single fiber is 1.33 g/cm 3 to 1.43 g/cm 3 , and a variation coefficient CV of the density in the fiber bundle is 0.2% or less.