PURPOSE: To lower the softening point and improve the homogeneity of a mesophase pitch and the mechanical strengths of a final pitch-based carbon fiber, by conducting finishing heat treatment of a mesophase pitch obtd. in the step of separating a mesophase pitch and then hydrogenating the heat-treated pitch to a slight extent.
CONSTITUTION: A carbonaceous raw material (e.g., bottom oil obtd. by catalytic cracking of petroleum) which has optionally undergone preliminary treatments, such as filtration or solvent extraction, is heat-treated at 380-460°C to effect thermal cracking polycondensation for mesophase formation, thereby obtaining a pitch having a softening point of 260°C or below and a mesophase content of 20-80%, which comprises a mesophase most or substantially the whole of which is in the form of a sphere having a diameter not larger than 500μm. Subsequently, this pitch is separated into a mesophase pitch and non-mesophase components by centrifugation, etc. The mesophase pitch is heat-treated for finishing at 330-430°C for 0.1-24hr. and then hydrogenated to a slight extent at 250-400°C and 1-200atm. Thus, a mesophase pitch having a mesophase content of 95% or higher and a softening point of 250-300°C is obtd.
NAITO TSUTOMU
MIURA MASARU
KOMINE KIKUJI
