Process for producing carbon fibers from mesophase pitch

Claim 1

In a process for producing a high-modulus, high-strength carbon fiber which comprises spinning a carbonaceous fiber from a nonthixotropic carbonaceous mesophase pitch which under quiescent conditions forms a homogeneous bulk mesophase having large coalesced domains, thermosetting the fiber so produced by heating the fiber in an oxygen-containing atmosphere for a time sufficient to render it infusible, and carbonizing the thermoset fiber by heating it in an inert atmosphere, the improvement which comprises spinning the carbonaceous fiber from a mesophase pitch which has been prepared while passing an inert gas through the pitch during formation of the mesophase at a rate of at least 0.5 scfh. per pound of pitch while heating the pitch in an inert atmosphere at a temperature of from 350°C. to 450°C. for a time sufficient to produce a mesophase content of from 40 per cent by weight to 90 per cent by weight.