RUBBER COMPOSITION AND PNEUMATIC TIRE

摘要

A rubber composition includes a rubber component including oil-extended butadiene rubber and/or styrene-butadiene rubber, an inorganic reinforcement agent having nitrogen adsorption specific surface area of 10 to 60 m2/g, and silica and/or carbon black. The oil-extended rubber has cis content of 95 mol % or greater, vinyl content of 1.2 mol % or less and weight-average molecular weight of 530,000 or greater and is synthesized with rare-earth catalyst. The styrene-butadiene rubber has bound styrene content of 10 to 60 mass % and weight-average molecular weight of 800,000 or greater. The reinforcement agent has formula, mM.xSiOy.zH2O, where M represents one or more metals selected from Al, Mg, Ti, Ca, Zr, oxide of the metal thereof and hydroxide of the metal thereof, m represents whole number of 1 to 5, x represents whole number of to 10, y represents whole number of 2 to 5, and z represents whole number of 0 to 10.

主权项

1. A rubber composition, comprising:
a rubber component comprising at least one of an oil-extended butadiene rubber and a styrene-butadiene rubber; an inorganic reinforcement agent having a nitrogen adsorption specific surface area in a range of 10 to 60 m2/g; and at least one of silica having a nitrogen adsorption specific surface area of 100 m2/g or greater and carbon black having a nitrogen adsorption specific surface area of 100 m2/g or greater, wherein the oil-extended butadiene rubber has a cis content of 95 mol % or greater, a vinyl content of 1.2 mol % or less and a weight-average molecular weight of 530,000 or greater and is synthesized with a rare-earth element-based catalyst, the styrene-butadiene rubber has a bound styrene content in a range of 10 to 60 mass % and a weight-average molecular weight of 800,000 or greater, the at least one of the oil-extended butadiene rubber and the styrene-butadiene rubber has a total content in a range of 10 to 100 mass % of the rubber component, the inorganic reinforcement agent has a content in a range of 1 to 70 parts by mass based on 100 parts by mass of the rubber component, the at least one of the silica and the carbon black has a total content of at least 50 parts by mass based on 100 parts by mass of the rubber component, and the inorganic reinforcement agent has formula, mM.xSiOy.zH2O, where M represents at least one metal selected from the group consisting of Al, Mg, Ti, Ca, Zr, an oxide of the metal thereof and a hydroxide of the metal thereof, m represents a whole number of from 1 to 5, x represents a whole number of from 0 to 10, y represents a whole number of from 2 to 5, and z represents a whole number of from 0 to 10.