Abstract: A pitch which affords a carbon fiber having a high strength and a high elastic modulus is obtained by treating a pitch containing 5 to 35 wt. % of an optically anisotropic region with an oxidizing gas, followed by hydrogenation treatment if required.

Abstract: A process for the production of carbon fibers which comprises using a specific optically isotropic pitch having a reflectivity of 9.0-11.0% as the material for the carbon fibers.

Abstract: A process for the production of high performance carbon fibers which comprises using as the starting material a specific pitch having the lowest reflectivity in the range of 8.5-9.3% and the highest reflectivity in the range of 11.8-12.5%.

Abstract: A process for the production of carbon fibers comprising heat treating a starting material, melt spinning the resulting precursor pitch, infusibilizing the pitch fibers and carbonizing or graphitizing the infusibilized pitch fibers, characterized in that the starting pitch is obtained by heat treating coal tar and/or coal liquefaction pitch at a specific temperature and a specific hydrogen pressure or by mixing coal tar and/or coal liquefaction tar with at least one nucleus-hydrogenated hydrocarbon of 2-3 rings in a specific mixing ratio and then heat treating the resulting mixture at a specific temperature and a specific pressure. In one embodiment, this invention relates to the starting pitch and carbon fibers obtained by said process.

Abstract: A starting pitch for carbon fibers, obtained by mixing (1) a heavy fraction oil boiling at not lower than 200.degree. C. obtained at the time of steam cracking of petroleum with (2) wax and then heat treating the resulting mixture at a specified temperature and pressure thereby to obtain the starting pitch, the thus obtained starting pitch being heat treated to produce a precursor pitch which is melt spun, infusibilized, carbonized or graphitized to obtain the carbon fibers.

Abstract: A starting pitch for carbon fibers, obtained by (A) mixing (1) a heavy fraction oil boiling at not lower than 200.degree. C. obtained at the time of steam cracking of petroleum with (2) a hydrogenated oil selected from aromatic hydrocarbons of 2-10 rings in which the nuclei have been hydrogenated and specific fractions boiling at 160.degree.-650.degree. C. and containing such nuclei-hydrogenated hydrocarbons and then (B) heat treating the resulting mixed oil at 370.degree.-480.degree. C. and 2-50 Kg/cm.sup.2.G to obtain the starting pitch for carbon fibers.

Abstract: A starting pitch for carbon fibers, produced by heat treating at 400.degree.-500.degree. C. under a hydrogen pressure of at least 20 Kg/cm.sup.2.G (1) a heavy fraction oil boiling at not lower than 200.degree. C. obtained at the time of fluidized catalytic cracking of petroleum or (3) a mixture of the heavy fraction oil (1) with (2) a heavy fraction oil boiling at not lower than 200.degree. C. obtained at the time of steam cracking of petroleum, the pitch so produced being heat treated to make precursor pitch therein, melt spun, infusibilized and carbonized or further graphitized to obtain the carbon fibers.