Method for producing a precursor pitch for carbon fiber

Abstract

Precursor pitch to be used for formation of carbon fiber is produced by heating a coal tar soft or middle pitch at a temperature of 350.degree.-500.degree. C. at a first stage to form mesophase, extracting the thus treated pitch with a solvent, separating and removing the solvent insoluble portion including mesophase to obtain a pitch containing no free carbon and further at the second stage heat-treating the pitch containing no free carbon in an inert gas atmosphere under atmospheric pressure or a reduced pressure under the following condition 600-1.2 T.ltoreq..theta..ltoreq.1,800-3.6 T (provided that 350.ltoreq.T.ltoreq.500) wherein T(.degree.C.) is the temperature of the heat treatment and .theta. (min) is the time for which said temperature is held, to form bulk mesophase pitch containing 20-60% by weight of quinoline insoluble portion.

Dependencies are inferred from the claim text.