| 摘要 |
PURPOSE:To obtain a carbon fiber having high tensile strength and usable for concrete reinforcement, by melt-spinning an optically isotropic pitch, infusibilizing in an oxidizing atmosphere under a specific condition and thermally carbonizing and graphitizing the infusibilized fiber in an inert atmosphere. CONSTITUTION:An optically isotropic pitch is spun under melting, infusibilized by heating in an oxidizing atmosphere and carbonized and graphitized by heating in an inert atmosphere. In the above process, the maximum temperature of the infusibilization heat-treatment is 300-340 deg.C and the maximum temperature of infusibilization heat-treatment and the retaining period (R) at the maximum temperature are selected to satisfy the formula I (when R becomes <0, R=0 is assumed as the shortest time) when the oxidizing gas for infusibilization is air, or the maximum temperature of the infusibilization heat-treatment is 240-300 deg.C and the maximum temperature of infusibilization heat-treatment and the retaining period (R') at the maximum temperature are selected to satisfy the formula II (when R' becomes, <0, R'=0 is assumed as the shortest time) when the oxidizing gas for infusibilization is oxygen.
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