Mesophase pitch raw material used for preparing high-modulus high-thermal-conductivity carbon fiber, and preparation method thereof

The invention relates to a mesophase pitch raw mateiral for preparing high-modulus high-thermal-conductivity carbon fiber, and a preparation method thereof. With a polarizing microscope measuring method, a mesophase content of the mesophase pitch raw material is 100%. With a capillary rheometer measuring method, a softening point of the mesophase pitch raw material is 220-260 DEG C. With an X-ray diffraction measuring method, an aromatic hydrocarbon macromolecule average sheet piling thickness Lc of the mesophase pitch raw material is larger than 8nm. According to the invention, a naphthalene series compound such as methylnaphthalene is adopted as a raw material; hydrogen fluoride-boron trifluoride is adopted as a catalyst; and through controlling a catalyst dose, polymerization conditions and low-boiling-point product separation conditions, the mesophase pitch is prepared. Compared with prior arts, the mesophase pitch provided by the invention has excellent spinnability, such that spinning process controlling and operation are facilitated. The mesophase pitch has good molecular orientation, such that high-modulus high-thermal-conductivity carbon fiber with high orientation degree can be prepared under a relatively low graphitization temperature. Therefore, the production cost of high-performance carbon fiber is greatly reduced.