A twin screw extruder for mixing carbon black with rubber and with a first mixing zone with screw elements for heating rubber to about 130-220 C., and a second port for adding carbon black and a third port for adding oil.The conversion of elastomeric compositions, and in particular elastomeric polymers such as rubber, into commercially significant materials has been a focal point of the rubber industry throughout its history. The earliest commercial process was largely based on a mixing process utilizing two-roll mills to modify the basic polymer's characteristics by adjusting the viscosity of the polymer as well as by incorporating enhancing ingredients such as reinforcing agents, modifying oils and curatives. Over the years, a wide variety of mixing processes and devices have evolved in the rubber industry. A thorough treatment of such development is set forth in an article entitled, "Development of Internal-Mixer Technology for the Rubber Industry" by James L. White, Rubber Chemistry and Technology, Volume 65, page 528, the contents of which are specifically incorporated herein by reference.

The elastomer mixing process is basically defined as combining the ingredients specified in an elastomeric recipe, on some schedule of addition, and under some regime of mastications for a certain period of time and/or temperature. Rubber elastomer mixing technology is focused principally upon controlling five principal features of the mixing process independent of the recipe specifics. One feature of concern is the uniform distribution of raw materials of the elastomer recipe throughout a single unit mass or volume. The second feature involves dispersive mixing which focuses on the intimate association of the elastomer ingredients in a physical sense, typically at a molecular level, which influence the mechanical characteristics of the final composition. The third feature involves viscosity modification while the fourth feature is concerned with chemical reactions of the ingredients. The final feature involves, of course, economic considerations which control capital utilization and manufacturing costs. These five factors are interrelated, often inversely, and they are sensitive to rate, volume, power, time and temperature limitations.

With the advent of the Banbury mixer, which is described in the above-referenced article, and its commercial adoption, the rubber industry was able to substantially increase uniformity of the process and productivity of manufacturing elastomeric compositions. The Banbury-type intensive mixer, and its many modifications and adaptations as indicated, still remains the primary processing device and process in the rubber industry throughout the world today.