Patent ID: 7473724

Claim:
A process of preparing a rubber composition which comprises the steps of: (A) blending, based upon parts by weight per 100 parts by weight rubber (phr): (1) 100 phr of at least one conjugated diene-based elastomer consisting essentially of: (a) from about 50 to about 100 phr of dry cis 1 ,4-polyisoprene rubber, and (b) from zero to about 50 phr of at least one additional conjugated diene-based elastomer selected from at least one of cis 1,4-polybutadiene rubber, styrene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene-isoprene rubber, isoprene-butadiene rubber and high vinyl-polybutadiene rubber having a vinyl 1,2- content in a range of from about 30 to about 80 percent, (2) from about 25 to about 120 phr of reinforcing filler comprised of: (a) from about 20 to about 115 phr of precipitated silica aggregates, and (b) from about 5 to about 70 phr of rubber reinforcing carbon black, and (B) thereafter adding and blending sulfur curative therewith; characterized in that said precipitated silica aggregates are treated with a modifier selected from a fatty alcohol and epoxidized soybean oil and their mixtures in the absence of and prior to said addition of said sulfur curative addition by pre-treating said precipitated silica aggregates with said modifier to form a pre-formed silica/modifier composite as a reaction product thereof and blending said pre-formed silica/modifier composite with said conjugated diene-based elastomer(s), followed by reacting said pre-formed silica/modifier composite with a coupling agent in situ within said conjugated diene-based elastomer(s) to form a silica/modifier/coupling agent composite thereof wherein said fatty alcohol is selected from at least one of 1 -octanol, 1 -decanol, 1 -dodecanol, 1 -tetradecanol, 1 -hexadecanol, 1 -octadecanol, 1 -eicosanol, 1 -docosanol, 1 -tetracosanol, 1-hexacosanol, or 1 -octacosanol, and their mixtures; wherein said coupling agent is selected from bis(ω-trialkoxysilylalkyl) polysulfide having an average of from about 2 to about 4 connecting sulfur atoms in its polysulfidic bridge, or ω-mercaptoalkyltrialkoxysilane, or ω-mercaptoalkyltrialkoxysilane having its mercapto moiety blocked from pre-reacting with hydroxyl groups contained on said precipitated silica aggregates prior to unblocking said blocked mercapto moiety.