| abstract |
A rubber composition comprising 100 parts by weight of a natural rubber and/or a diene synthetic rubber, 15 to 85 parts by weight of silica, and 1 to 15 % by weight, based on the amount of silica, of a dispersion improver; and another rubber composition comprising 100 parts by weight of a natural rubber and/or a diene synthetic rubber, 20 to 60 parts by weight of silica, 30 to 80 parts by weight of a carbon black having a cetyltrimethylammonium bromide adsorption (CTAB) of not less than 120 m2/g and dibutyl phthalate absorption (DBP) of not less than 120 ml/100 g, and 3 to 15 % by weight, based on the amount of silica, of a dispersion improver, the total amount of silica and carbon black being 50 to 120 parts by weight. A particular nitrogen-containing carbonyl compound or silicone oil is used as the dispersion improver. |