| 摘要 |
The present invention is directed to a pneumatic tire having a rubber tread of a cap/base construction comprised of an outer rubber tread cap layer containing an outer running surface and an underlying rubber tread base layer, wherein said tread cap layer is comprised of a plurality of circumferential, longitudinal rubber tread cap zones of graduated physical properties, wherein said tread cap zones individually extend from said tread cap running surface radially inward to said tread base layer: wherein said tread cap zones are comprised of two primary tread cap zones and one central tread cap zone; wherein said central tread cap zone is positioned between said primary tread cap zones and spans at least 14 percent of the total running surface of the tread cap layer, wherein said primary tread cap zones are of substantially equal widths and collectively span at least 50 percent of the total running surface of the tread cap layer; wherein the central tread cap zone comprises a vulcanizable rubber composition comprising, based on 100 parts by weight of elastomer (phr), (A1) from about 60 to about 90 phr of an emulsion or solution polymerized styrene-butadiene rubber with a styrene content of from about 20 to about 40 percent by weight, and a Tg of from about−55° C. to about−20° C.; (A2) from about 40 to about 10 phr of a polybutadiene with a cis 1, 4 content of at least 90 percent, a number average molecular weight (Mn) of greater than 175,000 and a heterogeneity index (Mw/Mn) of less than 2.5; (A3) from about 50 to about 150 phr of silica; wherein the primary tread cap zones comprise a vulcanizable rubber composition comprising, based on 100 parts by weight of elastomer (phr), (B1) from about 60 to about 90 phr of a solution polymerized styrene-butadiene rubber functionalized with an alkoxysilane group and at least one functional group selected from the group consisting of primary amines and thiols; (B2) from about 40 to about 10 phr of polybutadiene having a microstructure comprised of about 96 to about 99 percent cis 1,4-isomeric units, about 0.1 to about 1 percent trans 1,4-isomeric units and from about 1 to about 3 percent vinyl 1,2-isomeric units; a number average molecular weight (Mn) in a range of from about 75,000 to about 150,000 and a heterogeneity index (Mw/Mn) in a range of from about 3/1 to about 5/1; and (B3) from about 50 to about 150 phr of silica.
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