Control of Softening Point and Glass Transition Temperature of Coal Tar Pitch

Abstract

Influences of heavy fraction such as toluene insoluble (TI) and light fractions in pitch on the softening point and on the glass transition temperature were studied in order to control these properties. Influences of both fractions on coke yields were also studied. The relations among the softening point, the glass transition temperature, and the coke yield led to the following results.(1) The softening point and the glass transition temperature of the pitches from the same tar are independently controlled by changing the amounts of both light fraction and TI in pitch.(2) Since the coke yield is also influenced by the amounts of both light fraction and TI, a pitch with a fixed softening point and a glass transition temperature gives a fixed coke yield.(3) Contributions of the amounts of both light fractions and TI to the changes of softening point, glass transition temperature, and coke yield are different. To reduce the differences in the contributions, it is effective to decrease the amounts of light fraction for the control of glass transition temperature, to decrease the difference in both amounts of light fraction and TI for the control of softening point, and to decrease the difference in the amount of TI for the control of coke yield.