Abstract: A twin screw extruder for mixing carbon black with rubber and with a first mixing zone with screw elements for heating rubber to about 130.degree.-220.degree. C., and a second port for adding carbon black and a third port for adding oil.

Abstract: A process is provided for producing elastomeric compositions by forming a mixture of polymeric material, a reinforcing agent, a processing aid and a vulcanizing agent. The process of the invention is continuous and includes the repeated, sequential steps of admixing the polymeric material along a first mixing zone defined by a space wherein the gross energy applied induces a first operating temperature range. The mixture of the first zone is continuously passed into and through a second mixing zone while adding and admixing the reinforcement agent and processing aid therewith, the second mixing zone being defined by a space wherein the gross energy applied induces a second operating temperature range. The mixture of the second zone is then continuously passed into and through a third mixing zone while adding and admixing the vulcanizing agent therewith, the third mixing zone being defined by a space wherein the gross energy applied induces a third operating temperature range.