Abstract

Two‐stage mixing when applied to blends of Chlorobutyl Rubber (C1‐IIR), Natural Rubber (NR), and Polybutadiene Rubber (BR), can produce tread compounds exhibiting a combination of very low hysteresis, good wet skid resistance, and good abrasion resistance. In the first stage, about half the raw rubber, including all C1‐IIR and BR, is mixed with most of the carbon black to form a very high carbon black stock. In the second stage, the first‐stage stock is diluted with the remaining NR. Curatives, etc., are added on the mill. Tests on radial tires for automobiles confirm the advantages of the two‐stage mixed tri‐rubber blend tread compounds.