PREPARATION OF MESOCARBON MICROBEADS BY DISPERSING MESOPHASE PITCH INISOTROPIC PITCHES

Mesocarbon microbeads of 1-10 mu m were prepared through dispersing th e synthetic mesophase pitches in synthetic isotropic pitches and succe ssive solvent extraction. The suitable ratio of mesophase pitch/isotro pic pitch, temperature and rapid agitation at dispersion were found to be key factors to obtain the high yields of tetrahydrofuran and pyrid ine insoluble microbeads which were 34 and 20 wt%, of the highest yiel d, respectively. In contrast, the combinations of coal tar derived mes ophase pitch/synthetic pitch or synthetic mesophase pitch/petroleum A2 40 pitch failed to disperse spheres of mesophase pitch in the isotropi c matrix, leaving bulk grains of mesophase pitch at the bottom of the matrix. The melt mesophase pitch of adequate viscosity is dispersed by the agitation into viscous droplets in the isotropic matrix, while th e droplets stay afloat because of their similar specific gravities. Th e lighter component in the droplet of the mesophase pitch was extracte d into the isotropic matrix while the mesophase pitch is melted, leavi ng spheres of smooth surface. Extraction by the solvent at a lower tem perature than the softening point leaves mesocarbon microbeads isolate d, removing the solvent soluble fraction. (C) 1997 Elsevier Science Lt d.