Method for producing carbon-fiber bundles

摘要

The invention provides a method for producing carbon fiber bundles excellent in productivity without impairing the quality in the process for producing carbon fibers. The method includes a flame-retarding step, a precarbonization step, and a carbonization step. When traveling pitches of the fiber bundles in the flame-retarding step, precarbonization step and carbonization step are represented by P1, P2 and P3, respectively, 0.8≦P2/P1≦1.0 and 0.4≦P3/P1≦0.8 are satisfied; when traveling pitches of the fiber bundles at the inlet and the outlet of a heat treatment section of a precarbonization furnace are represented by P11 and P12, respectively, 0.40≦(P12/P11)≦0.90 is satisfied; or when traveling pitches of the fiber bundles at the inlet and the outlet of a heat treatment section of a carbonization furnace are represented by P13 and P14, 0.40≦(P14/P13)≦0.90 is satisfied.

主权项

1. A method for producing carbon fiber bundles, comprising:
a flame-retarding step of converting a plurality of precursor fiber bundles into flame-retardant fiber bundles by heat treating the plurality of precursor fiber bundles in an oxidizing gas atmosphere at from 200 to 300° C. in a state that the plurality of precursor fiber bundles are lined up side by side in parallel to each other; a precarbonization step of converting the flame-retardant fiber bundles into precarbonization-treated fiber bundles by heat treating the flame-retardant fiber bundles in an inert gas atmosphere with the highest treatment temperature of from 500 to 800° C. in a state that the flame-retardant fiber bundles are lined up side by side in parallel to each other; and a carbonization step of converting the precarbonization-treated fiber bundles into carbon fiber bundles by heat treating the precarbonization-treated fiber bundles in an inert gas atmosphere with the highest treatment temperature of 1000° C. or higher in a state that the precarbonization-treated fiber bundles are lined up side by side in parallel to each other, wherein when a traveling pitch of the fiber bundles in the flame-retarding step is represented by P1, a traveling pitch of the fiber bundles in the precarbonization step is represented by P2, and a traveling pitch of the fiber bundles in the carbonization step is represented by P3, the following relations are satisfied:
0.8≦P2/P1≦1.00.4≦P3/P1≦0.8.