Aromatic vinyl compound-conjugated diene compound copolymer and method of producing the same as well as rubber composition and tire

1. An aromatic vinyl compound-conjugated diene compound copolymer obtained by an addition polymerization of an aromatic vinyl compound and a conjugated diene compound in the presence of a polymerization catalyst composition comprising at least one complex selected from the group consisting of a metallocene complex represented by the following general formula (I):

wherein M is a lanthanoid element, scandium or yttrium, Cp R is independently a non-substituted or substituted indenyl, R a to R f are independently an alkyl group having a carbon number of 1-3 or a hydrogen atom, L is a neutral Lewis base, and w is an integer of 0-3;

a metallocene complex represented by the following general formula (II):

wherein M is a lanthanoid element, scandium or yttrium, Cp R is independently a non-substituted or substituted indenyl, X′ is a hydrogen atom, a halogen atom, an alkoxide group, a thiolate group, an amide group, a silyl group or a hydrocarbon group having a carbon number of 1-20, L is a neutral Lewis base, and w is an integer of 0-3; and

a half metallocene complex represented by the following general formula (III):

wherein M is a lanthanoid element, scandium or yttrium, Cp R′ is a non-substituted or substituted cyclopentadienyl, indenyl or fluorenyl, X is a hydrogen atom, a halogen atom, an alkoxide group, a thiolate group, an amide group, a silyl group or a hydrocarbon group having a carbon number of 1-20, L is a neutral Lewis base, w is an integer of 0-3, and [B] − is a non-coordinate anion,

wherein a content of cis-1,4 bond in a conjugated diene compound portion is not less than 80%, and

a block quantity of the aromatic vinyl repeating unit portion as measured by NMR is not more than 13% based on the total amount of aromatic vinyl repeating units in the copolymer.

2. The aromatic vinyl compound-conjugated diene compound copolymer according to claim 1 , wherein a content of vinyl bond in the conjugated diene compound portion is not more than 10%.

3. The aromatic vinyl compound-conjugated diene compound copolymer according to claim 1 , wherein a block quantity of the aromatic vinyl repeating unit portion as measured by NMR is not more than 10% based on the total amount of aromatic vinyl repeating units in the copolymer.

4. The aromatic vinyl compound-conjugated diene compound copolymer according to claim 1 , wherein the copolymer has a melting point (Tm) as measured by DSC.

5. The aromatic vinyl compound-conjugated diene compound copolymer according to claim 1 , wherein the copolymer is styrene-butadiene copolymer.

6. An aromatic vinyl compound-conjugated diene compound copolymer obtained by polymerizing an aromatic vinyl compound and a conjugated diene compound, wherein a content of cis-1,4 bond in a conjugated diene compound portion is not less than 80%, and a content of vinyl bond in a conjugated diene compound portion is not more than 5%, and a block quantity of the aromatic vinyl repeating unit portion as measured by NMR is not more than 13% based on the total amount of aromatic vinyl repeating units in the copolymer, and a number average molecular weight converted polystyrene as measured by a gel permeation chromatography is not less than 80,000.

7. A rubber composition comprising the aromatic vinyl compound-conjugated diene compound copolymer as claimed in claim 1 as a rubber component.

8. A tire comprising the rubber composition as claimed in claim 7 in any tire member.

9. The tire according to claim 8 , wherein the tire member is a tread.