The influence of the type of quinoline insolubles on the quality of coal tar binder pitch

Seven pitches containing three types of quinoline insolubles, QI, were produced from a single coke oven coal tar. The tar was centrifuged into QI-rich and QI-lean fractions. A blend of the two fractions yielded a typical graphite electrode binder pitch. The QI content of the pitch derived from the QI-lean tar was increased through the addition of natural QI concentrate, or QI as a furnace carbon black, or QI as mesophase by means of heat treatment. The pitches were evaluated as binders by measuring the flexural strength of 19 mm diameter graphite electrodes. The results show that the typical electrode pitch is superior, and that increasing the QI content of the QI-lean material did not upgrade it. The results also show that the flexural strength of the derived graphite is not simply related to the coking value of a binder.