The impregnating-grade coal tar pitch is a special type of coal tar pitch, which has a low content (0-3 %) of quinoline insolubles (QI), besides having lower values of softening point (SP), toluene insolubles (TI), coking yield and specific gravity (SG), compared to those of the binder-grade coal tar pitch. It is used in large quantities to densify graphite electrodes, employed in steel and chemical industry. Besides this, it is also used in the development of advanced carbon products like high performance carbon fibre, needle coke, high-density high-strength graphite and carbon-carbon composites which has many potential applications. The commercially-available coal tars or tar pitches invariably contain the QI-particles (5-15%), which make them unsuitable for the impregnation purposes. The conventional methods involving filtration, solvent extraction and centrifugation for the reduction or total removal of these QI-particles from these materials are cumbersome and expensive. The present process of the producing the impregnating-grade coal tar pitch is very novel and involves the treatment of the commercial coal tar or coal tar pitch with special inexpensive / industrial solvents. The treatment results in the separation of the pitch-solvent mixture into two components - one major, which contains almost no QI, and the other minor, which is rich in QI. The minor component is reused in the process and the major component is heat-treated to recover the solvent and obtain the impregnating pitch. The characteristics of the pitch produced at NPL by the present process are as follows:-

Softening point 80-100*C Quinoline insolubles 0.0-3.0 % Toluene insolubles 16-24 % Coking value 42-46 % Specific gravity 1.26-1.28 Ash content 0.05 % (Max.)