Patent ID: 7718728

Claim:
A rubber composition using a modified conjugated diene polymer, characterized by comprising (A) 100 parts by mass of a rubber component containing not less than 10% by mass of a conjugated diene polymer having a polymer chain with at least one functional group selected from the group consisting of a substituted amino group represented by the following formula (I): wherein R 1 is independently an alkyl, cycloalkyl or aralkyl group having a carbon number of 1-12, and a cyclic amino group represented by the following formula (II): wherein R 2 is an alkylene group having 3-16 methylene groups, a substituted alkylene group or an oxy- or N-alkylamino-alkylene group, wherein the conjugated diene polymer is formed by forming a solution of one or more anion-polymerizable monomers consisting essentially of 1,3-butadiene in a hydrocarbon solvent, and then polymerizing the monomers with (D) a lithioamine represented by a general formula of (AM)Li(Q) y , wherein y is 0 or 0.5 to 3, and Q is a soluble component selected from the group consisting of a hydrocarbon, an ether, an amine and a mixture thereof, and AM is the formula (I): wherein R 1 is the same as mentioned above, or the formula (II): wherein R 2 is the same as mentioned above; or a mixture of the item (D) and (E) an organic alkali metal compound selected from compounds represented by general formulae of R 4 M, R 5 OM, R 6 C(O)OM, R 7 R 8 NM and R 9 SO 3 M, wherein each of R 4 , R 5 , R 6 , R 7 , R 8 and R 9 is selected from the group consisting of alkyl, cycloalkyl, alkenyl and aryl groups having a carbon number of about 1 to about 12 and phenyl group and M is selected from the group consisting of Na, K, Rb and Cs, as a polymerization initiator in the presence of at least one selected from the group consisting of a hydrocarbon, an ether, an amine and a chelating agent; (B) not less than 20 parts by mass of carbon black; and (C) not more than 1.0 part by mass of a polycyclic aromatic compound (PCA), wherein the conjugated diene polymer is a copolymer of butadiene and an aromatic vinyl compound or a homopolymer of butadiene, and a content of the aromatic vinyl compound as a copolymer component is not more than 10% by mass.