PREPARATION OF ISOTROPIC PITCH PRECURSORS FOR GENERAL-PURPOSE CARBON-FIBERS (GPCF) BY AIR BLOWING .1. PREPARATION OF SPINNABLE ISOTROPIC PITCH PRECURSOR FROM COAL-TAR BY AIR BLOWING

A Ql-free coal tar pitch with a softening point around 80-degrees-C wa s air blown in an autoclave at 330-degrees, 360-degrees, and 380-degre es-C, respectively, for various periods in order to prepare a pitch pr ecursor for GPCF. Air blowing markedly increased the softening point a nd contents of solvent insoluble fractions such as BI, QI, as well as atomic C/H ratio. The pitches blown at 360-degrees-C for 2 to 4 h show ed excellent spinnability into thin fibers of 12 to 14 mum in diameter at a wide range of 255-degrees to 330-degrees-C. Structural character ization by NMR, FT-IR, and elemental analysis on the blown pitches sho wed that distillation of lighter fractions, aromatization, and polymer ization of the remaining fractions due to oxidative dehydrogenation ra ised their softening points. Although all blown pitches stayed complet ely isotropic. further heat treatment at 380-degrees-C under N2 flow f or 14 to 21 h allowed generation of mesophase spheres in the isotropic matrix. After the carbonization at 600-degrees-C, all pitches showed anisotropic texture, suggesting that blown pitches maintain fusibility and reactivity to follow the growth and development of mesophase sphe res in the successive carbonization.