Abstract: Polymer-type fibers longitudinally shrinkable by calcination and other carbon fibers are mixed and mechanically compressed and integrated by a needle punch, and the polymer-type fibers are then shrunk when calcined. Thus, there is obtained high bulk density carbon fiber felt having average bulk density of 0.1 g/cm.sup.3 or more without the carbon fiber felt impregnated with, resin and compressingly molded. The density of carbon fiber felt may change in the thickness direction thereof. The high bulk density carbon fiber felt may be used as a thermal insulator for a high-temperature furnace, a heat-resisting cushioning material, and a material for the electrode of a secondary battery.

Abstract: Polymer-type fibers longitudinally shrinkable by calcination and other carbon fibers are mixed and mechanically compressed and integrated by a needle punch, and the polymer-type fibers are then shrunk when calcined. Thus, there is obtained high bulk density carbon fiber felt having average bulk density of 0.1 g/cm.sup.3 or more without the carbon fiber felt impregnated with resin and compressingly molded. The present invention also provides high bulk density carbon fiber felt of which bulk density is changed in the thickness direction thereof. The high bulk density carbon fiber felt may be used as a thermal insulator for a high-temperature furnace, a heat-resisting cushioning material, and a material for the electrode of a secondary battery.