Low molecular weight mesophase pitch

A process for producing a single phase essentially completely anisotropic pitch consisting of essentially 100 percent mesophase and suitable for spinning into continuous filaments, said pitch having a number average molecular weight below 1000, a net pyridine insoluble content no greater than 60 percent by weight, a softening temperature no greater than 350.degree. C., and a viscosity no greater than 200 poises at 380.degree. C., which comprises passing an inert gas through an isotropic carbonaceous pitch while heating the pitch at a temperature of from about 380.degree. C. to about 430.degree. C. to produce mesophase and simultaneously agitating the pitch so as to produce a homogeneous emulsion of the mesophase produced and the remaining non-mesophase portion of the pitch, said inert gas being passed through the pitch at a rate sufficient to ensure essentially complete removal of the volatile low molecular weight components of the pitch which do not form mesophase at a rate sufficiently rapid to allow formation of said single phase essentially completely anisotropic pitch, said rate being at least 4.0 scfh. per pound of pitch, and said heating and agitation being continued until the pitch has been essentially completely converted to mesophase and the emulsion has been transformed into an essentially single phase system.

A continuous carbonaceous pitch fiber spun from a single phase essentially completely anisotropic pitch consisting of essentially 100 percent mesophase, said pitch having a number average molecular weight below 1000, a net pyridine insoluble content no greater than 60 percent by weight, a softening temperature no greater than 350.degree. C., and a viscosity no greater than 200 poises at 380.degree. C.

In a process for producing continuous carbon fiber which comprises spinning a carbonaceous fiber from a nonthixotropic carbonaceous pitch which under quiescent conditions forms a homogeneous bulk mesophase having large coalesced domains;

• heating the spun fiber in an oxygen-containing atmosphere for a time sufficient to render it infusible;
• and carbonizing the infusible fiber so produced by heating in an inert atmosphere;
• the improvement which comprises spinning the carbonaceous fiber from a single phase essentially completely anisotropic pitch consisting of essentially 100 percent mesophase, said pitch having a number of average molecular weight below 1000, a net pyridine insoluble content no greater than 60 percent by weight, a softening temperature no greater than 350.degree. C., and a viscosity no greater than 200 poises at 380.degree. C.