PROCESS FOR PREPARING PITCHES

摘要

Commercially attractive continuous processes for the preparation of mesophase pitches for manufacturing highperformance carbon fibers are disclosed. One feature resides in that conversion of a pitch into a mesophase pitch is conducted continuously by using a unique continuous dispersionheat-treating apparatus. The other feature resides in that the raw material for hydrogenation treatment which is a pretreatment preceeding to the final heat treatment for the production of a mesophase pitch, is prepared by using a heavy oil or pitch having substantially no BTX-insoluble material as the starting raw material, subjecting the raw material to a simple four-step treatment of (1) a continuous heat treatment in a tubular heater, (2) a distillation operation, (3) a BTXsolvent extraction and (4) a distillation operation; while recycling a soluble component obtained in the step (4) to the heat treatment of step (1) and recovering a BTX-solvent insoluble component formed in step (3) as the material for the hydrogenation treatment. This feature can provide a significant increase in the yield of a mesophase pitch. Furthermore, unexpectedly, the recycle of the soluble component into the heat treatment of step (1) is helpful to improve the characteristics of the ultimate products, i.e., carbon fibers or graphite fibers. Combination of the first and the second features, of course, can provide a better commercial success. In fact, the process of the present invention can provide a carbon fiber having a tensile strength of more than 300 kg/mm2 and a graphite fiber having a tensile strength of more than 400 kg/mm2 and a modulus of elasticity of more than 60 ton/mm2. Processes with minor modifications to the above are also disclosed.