Process for preparation of pitch for producing carbon fiber

Claim 1

A process for preparing a pitch suitable for use in producing carbon fibers comprising: filtering at a temperature of 250° to 300° C. a heavy petroleum pitch, containing 20 to 45% by weight of compounds insoluble in benzene and having a softening point of 150° to 200° C., to remove fractions non-liquefying or infusible at a temperature higher than 250° to 300° C. therefrom using more than one filter net of meshes finer than 200 mesh at a rate of 0.5 to 2 g/min/cm 2 , introducing the thus filtered pitch at a temperature of 250° to 300° C. in the form of laminar flow of 1 to 30 mm in thickness into a vessel at a reduced pressure of 300 to 500 mm Hg of an inert gas to remove volatile fractions and bubbles from said filtered pitch in the laminar flow, thereby obtaining a treated pitch containing substantially no bubbles and no components non-liquefying or infusible at a temperature of 250° to 300° C., containing less than 5% by weight of low-molecular weight fractions boiling at a temperature lower than 500° C.