PREPARATION OF ISOTROPIC PITCH PRECURSORS FOR GENERAL-PURPOSE CARBON-FIBERS (GPCF) BY AIR BLOWING .3. AIR BLOWING OF ISOTROPIC NAPHTHALENE AND HYDROGENATED COAL-TAR PITCHES WITH ADDITION OF 1,8-DINITRONAPHTHALENE

Isotropic naphthalene and hydrogenated coal tar pitches with a lower s oftening point were air blown at 330-degrees-C with or without additio n of 1,8-dinitronaphthalene (DNN) in order to prepare a fully isotropi c pitch with a higher softening point. The softening point of the naph thalene and hydrogenated coal tar pitches could be raised to approxima tely 240-degrees-C and 275-degrees-C, respectively, by air or nitrogen blowing with 5 to 15 wt% DNN, while the softening point of naphthalen e pitch was only raised to 200 approximately 210-degrees-C by air blow ing without DNN. To retain the isotropic texture of naphthalene pitch, the reaction conditions, including amounts of additive, blowing tempe ratures, soak times at the blowing temperature, as well as blowing atm ospheres need to be controlled. Air blowing at the high temperature of 330-degrees-C promoted the dehydrogenation and aromatization through a significant reduction of aliphatic or naphthenic hydrogens. Thermal decomposition of DNN during blowing treatment created NO2 or NO which may initiate oxidation or radical reactions, accelerating the condensa tion of naphthalene and hydrogenated coal tar pitches.