Electrically conductive carbon black prepn

The carbon black comprises aggregates of open structure, with mean dia. 1500-2000 A.U. and density -.14-0.25 g/cc, each aggregate comprising on average 100-200 particles of dia. 200-250 A.U., evenly distributed. The coefft. of roughness is 1.5-2.5 and the ash content 0.5 wt. % (max.). The C black is prepd. by pyrolysis of a hydrocarbon feedstock and then further thermal decompsn. of the prods., the pyrolysis zone comprising the feedstock stream and 3 concentric reagent streams surrounding it. The C black is useful in conductive polymers, which have increased conductivity (e.g. specific resistance of a standard compsn. based on 100 pts.wt. natural rubber and 50 pts.wt. black is 0.1 ohm.m), increased ageing resistance and reduced cost. The black yield is 40-45% (5-10% higher than in existing processes). (First major country equivalent to CS8106936-A)