The invention relates to preparation of silica-rich rubber compositions by
a sequence of sequential mixing steps conducted in internal rubber
mixer(s) with individual maximum temperature limitations. The mixing
steps are comprised of at least two non-productive mixing steps followed
by a productive mixing step. The non-productive mixing steps themselves
are comprised of at least one preliminary non-productive mixing step
followed by a final non-productive mixing step. Elastomer, silica and
coupling agent are added in at least one of said preliminary
non-productive mixing steps to the exclusion of said final non-productive
mixing step and said productive mixing step. Sulfur and sulfur
vulcanization accelerator(s) are added in said productive mixing step to
the exclusion of said non-productive mixing steps. The preliminary
non-productive mixing step(s) are individually conducted to a maximum
mixing temperature in a range of from about 150.degree. C. to about
180.degree. followed by the final non-productive mixing step to a reduced
maximum mixing temperature in a range of from about 90.degree. C. to
about 130.degree. C. The maximum mixing temperature of said final
non-productive mixing step is at least 20.degree. C. lower than the
maximum temperature for said preliminary non-productive mixing stage(s).
The productive mixing step is conducted to a maximum temperature in a
range of from about 90.degree. C. to about 120.degree. C. The rubber
composition is removed from its respective internal rubber mixer and
cooled to below 40.degree. C. between said mixing steps. The invention is
further intended to relate to a rubber composition prepared by such
mixing process and to a tire having at least one component comprised of
such rubber composition.