Patent ID: 7294666

Claim:
A tire having a tread of a rubber composition which is prepared a process comprised of blending, based on 100 parts by weight (phr) of rubber: (A) 100 phr of elastomers consisting of (1) about 25 to about 75 phr of aqueous emulsion polymerization prepared terpolymer rubber comprised of repeat units derived from monomers consisting of: (a) about 49.5 to about 84.5 weight percent of 1,3-butadiene, (b) about 15 to about 50 weight percent of styrene, and (c) about 0.5 to about 5 weight percent of a co-monomer selected from at least one of the group consisting of hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate (HPMA isomer), 3-hydroxypropyl methacrylate (HPMA isomer), 3-phenoxy-2-hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyhexyl methacrylate and hydroxyoctyl methacrylate, and (2) from 25 to about 75 phr of at least one additional conjugated diene-based elastomer selected from the group consisting of homopolymers and copolymers of monomers selected from the group consisting of least one of isoprene and 1,3 butadiene and copolymers of monomers consisting of at least one of isoprene and 1,3-butadiene with styrene, (B) about 40 to about 120 phr reinforcing filler selected from at least one of carbon black and particulate synthetic amorphous silica; wherein said filler is comprised of (1) about 35 to about 90 phr of carbon black and about 5 to about 30 phr of said synthetic amorphous silica, or (2) about 5 to about 30 phr of carbon black and about 35 to about 90 phr of said synthetic amorphous silica, and (C) about 1 to about 7 phr of at least one silica coupling agent having a moiety reactive with hydroxyl groups on the surface of the said synthetic amorphous silica and an additional moiety interactive with the said elastomer(s); wherein said rubber composition is prepared by a process which comprises: (1) blending, in at least one mixing step in an internal mixer and in the absence of free sulfur, said terpolymer rubber, and additional diene-based elastomer(s) if used, together with said reinforcing filler(s) to include a portion of said synthetic amorphous silica, to a temperature in a range of about 140° C. to about 175° C.; (2) blending therewith in the same or subsequent mixing step in an internal rubber mixer and in the absence of free sulfur, said coupling agent and the remaining amount of said synthetic amorphous silica to a temperature in a range of about 140° C. to about 175° C., (3) subsequently blending free sulfur therewith in an internal rubber mixer to a temperature in a range of about 100° C. to about 125° C.