| abstract |
A rubber composition (COM) obtained by dissolving solution polymerized BR or SBR having a Tg of −100° C. to −40° C. in an organic solvent to form a starting rubber solution, by adding and mixing thereto silica or a mixture of carbon black and silica, silane coupling agent, and softening agent, followed by drying to obtain a master batch (MB) of the silica or carbon black/silica with rubber, adding thereto BR or SBR (R) having a Tg of at least 10° C. higher than the Tg of the starting rubber in the MB, and mixing in an internal mixer, wherein the ratio F MB /F COM of the concentration F MB of the silica or the mixture of carbon black and silica based upon the rubber in the MB and the concentration F COM of the silica or the mixture of carbon black and silica based upon the COM is 1.2 to 3.0. |