| 摘要 |
<p>An optically anisotropic pitch of at least 80% optically anisotropic phase and a softening point of not more than 320 DEG C is obtained by (a) pyrolitically polycondensing preferably at 380 to 460 DEG C, a pitch-like starting material comprising compounds consisting of carbon and hydrogen and having a boiling point of 540 DEG C or higher and substantially free from quinoline insolubles, said pitch-like material containing a first component soluble in n-heptane, and a second component insoluble in n-heptane and soluble in benzene, the aromatic carbon fraction of each component being at least 0.7, the number average molecular weight of each fraction being not more than 2000, and preferably less than 1,500 and the maximum molecular weight of each fraction being not more than 10,000, the content of the pyrolytically polycondensed pitch-like material having an optically anisotropic phase of between 20 and 70%; (b) thereafter maintaining said pitch-like material at a temperature in the range 350 to 400 DEG C to deposit a portion rich in the optically anisotropic phase having a higher specific gravity; (c) separating this portion from a portion rich in an optically isotropic phase having a lower specific gravity; (d) subjecting the separated portion to a heat treatment, if necessary, to achieve desired anisotropic phase content and softening point. </p> |
