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紀要論文

The 13C-NMR (Nuclear Magnetic Resonance) and ESR (Electron Spin Resonance) analyses were applied to four kinds of coal-tar pitches as raw material, and to the fractions of toluene insolublequinoline soluble (β-resin) and quinoline insoluble (QI) which were components of meso-carbon microbeads (MCMB) prepared from the heat-treatment of raw materials. It should be noted that QI had higher average molecular weight and more developed aromatic ring structure than β-resin, while QI and β-resin had almost the same aromaticity. Therefore, it was plausible that the change from raw material to β-resin was mainly caused by the increase of aromaticity, while the change from β-resin to QI was mainly caused by the development of aromatic ring structure. Furthermore, the content of bridged carbon locating between two aromatic rings was markedly reduced by the heat-treatment. It was found out that the yield and development of aromatic ring structure of MCMB were positively correlated with the average molecular weight and the content of bridged carbon of raw material as well.

The isotropic pitches as the materials for carbon fibers were prepared from various tars. The quality of the material pitches was evaluated by observing fiber continuity, infusibility in the processing and strength of the product fibers. The pitches were also characterized by means of elemental analysis, solvent fractionation analysis, NMR and ESR spectroscopies. It was confirmed that pitches with higher spin concentrations, larger aliphatic carbon amounts and higher mobilities show higher qualities. The desirable condition of the air-blowing reaction was found to be at lower temperature and pressure.

In order to investigate the roles of oxygen, heat and distillation in air-blowing reaction, the polymerization of a coal tar pitch in oxygen reaction, heat-treated reaction and distillation were studied by observing the molecular structures of the material pitches and product pitches with NMR and ESR measurements. It was found that the oxygen reaction was most effective to raise the softening point of the product pitches. This can be mainly ascribed to the polymerization with biphenyl-type bonding and the suppression of the pyrolysis of material in the reaction. On the other hand, the heattreated reaction without oxygen proceeded to the formation of larger peri-condensed aromatics which gave rise to anisotropy of pitches. The distillated pitch increased methylenic bonding between two aromatics in molecule which gave lower molecular orientation.