Patent ID: 6916888

Claim:
A vulcanized rubber composition comprising a vulcanizable rubber, a reinforcing filler, and a sulfur compound having the formula (I): —(S x R 1 ) n — (I) wherein R 1 represents an organic group, x is an average number of 3 to 5, and n is an integer of 1 to 100, wherein a ratio (VM/VD) is not more than 0.4, in which: a value VM is obtained from the degree of change before and after toluene swelling of the vulcanized rubber composition treated in a lithium aluminum hydride saturated tetrahydrofural/toluene (ratio by volume 1/1) mixed solution using the formula (A): VM = - 1 Vs · [ ln ⁡ ( 1 - vr M ) + vr M + μ ⁣ · vr M 2 vr M 1 / 3 - vr M / 2 ] ⁢ ⁢ wherein ⁢ ⁢ vr M = 1 - ϕ X M - ϕ ( A ) wherein X M is the degree of change before and after toluene swelling (volume after toluene swelling/volume before toluene swelling) after treatment in a lithium aluminum hydride saturated tetrahydrofuran/toluene (ratio by volume 1/1) mixed solution, φ is the volume percentage of the reinforcing filler in the rubber composition, V s is the molecular volume of toluene, μ is the rubber •toluene interaction coefficient, and vr M is the volume percentage of rubber in the swelled rubber after treatment in a lithium aluminum hydride saturated tetrahydrofuran/toluene (ratio by volume 1/1) mixed solution) and a value VD is obtained from the degree of change before and after toluene swelling of the vulcanized rubber composition treated in a propane-2-thiol (0.4 mol/l)/piperidine (0.4 mol/l) added tetrahydrofuran/toluene (ratio by volume 1/1) mixed solution using the formula (B): VD = ⁢ - 1 Vs · [ ln ⁡ ( 1 - vr D + M ) + vr D + M + μ · vr D + M 2 vr D + M 1 / 3 - vr D + M / 2 - ⁢ ln ⁡ ( 1 - vr M ) + vr M ) + μ · vr M 2 vr M 1 / 3 - vr M / 2 ] ⁢ ⁢ wherein ⁢ vr D + M = 1 - ϕ x D + M - ϕ ( B ) wherein X D+M is the degree of change before and after toluene swelling (volume after toluene swelling/volume before toluene swelling) after treatment in a propane-2-thiol (0.4 mol/l)/piperidine (0.4 mol/l) added tetrahydrofuran/toluene (ratio by volume 1/1) mixed solution vr D+M is the volume percentage of rubber in the swelled rubber after treatment in a propane-2-thiol (0.4 mol/l)/piperidine (0.4 mol/l) added tetrahydrofuran/toluene (ratio by volume 1/1) mixed solution; and wherein at least one vulcanization accelerator selected from the group consisting of a thiazole base, sulfenamide base, thiuram base, and dithio acid salt base accelerators is compounded into 0.5 to 5 parts by weight of the polysulfide polymer so as to give a ratio by weight of the vulcanization accelerator and the polysufide polymer of 0.3 to 4.