Branched conjugated diene copolymer, rubber composition and pneumatic tire
The present invention relates to a branched conjugated diene copolymer which is useful for preparing a rubber composition, having high uniformity of a temperature dependence curve of a viscoelasticity tan δ, for a tire, a rubber composition comprising the copolymer, and a pneumatic tire produced using the rubber composition for a tire. The branched conjugated diene copolymer is composed of monomer components comprising a branched conjugated diene compound represented by a general formula (1): wherein R 1 represents an aliphatic hydrocarbon group having 6 to 11 carbon atoms, and an aromatic vinyl compound represented by a general formula (2): wherein R 2 represents an aromatic hydrocarbon group having 6 to 10 carbon atoms, and R 5 represents a hydrogen atom or the like, and a copolymerization ratio (m) of the aromatic vinyl compound (2) is 45% by mass or more.
1. A branched conjugated diene copolymer composed of monomer components comprising a branched conjugated diene compound represented by a general formula (1):
wherein R 1 represents an aliphatic hydrocarbon group having 6 to 11 carbon atoms, and an aromatic vinyl compound represented by a general formula (2):
wherein R 2 represents an aromatic hydrocarbon group having 6 to 10 carbon atoms, and R 5 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms,
wherein a copolymerization ratio (m) of the aromatic vinyl compound (2) is 45% to 60% by mass, and
wherein the branched conjugated diene copolymer has a weight-average molecular weight 500000 or more.
2. The branched conjugated diene copolymer of claim 1 , having a glass transition temperature of −25° C. or more.
3. The branched conjugated diene copolymer of claim 1 , having a glass transition temperature of −10° C. or more.
4. The branched conjugated diene copolymer of claim 1 , wherein a copolymerization ratio (l) of the branched conjugated diene compound (1) is from 1 to 54% by mass.
5. The branched conjugated diene copolymer of claim 1 , wherein the branched conjugated diene compound (1) is at least one of myrcene and farnesene.
6. The branched conjugated diene copolymer of claim 1 , wherein the aromatic vinyl compound (2) is at least one selected from the group consisting of styrene, α-methylstyrene, α-vinylnaphthalene and β-vinylnaphthalene.
7. A rubber composition comprising the branched conjugated diene copolymer of claim 1 as a rubber component, in which a half width at half maximum of a viscoelasticity tan δ is 40 or less, where the half width at half maximum=(Higher temperature at half height of tan δ peak)−(Tan δ peak temperature).
8. A pneumatic tire produced using the rubber composition of claim 7 .
9. A pneumatic tire comprising the rubber composition of claim 7 .
10. A branched conjugated diene copolymer, obtained by copolymerizing:
a branched conjugated diene compound represented by a general formula (1):
wherein R 1 represents an aliphatic hydrocarbon group having 6 to 11 carbon atoms, and an aromatic vinyl compound represented by a general formula (2):
wherein R 2 represents an aromatic hydrocarbon group having 6 to 10 carbon atoms, and R 5 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms,
wherein a copolymerization ratio of the aromatic vinyl compound is 45% to 60% by mass, and
wherein the branched conjugated diene copolymer has a weight-average molecular weight of 500000 or more.
11. The branched conjugated diene copolymer of claim 10 , having a glass transition temperature of −25° C. or more.
12. The branched conjugated diene copolymer of claim 10 , having a glass transition temperature of −10° C. or more.
13. The branched conjugated diene copolymer of claim 10 , wherein a copolymerization ratio of the branched conjugated diene compound is from 1 to 54% by mass.
14. The branched conjugated diene copolymer of claim 10 , wherein the branched conjugated diene compound is at least one of myrcene and farnesene.
15. The branched conjugated diene copolymer of claim 10 , wherein the aromatic vinyl compound is at least one selected from the group consisting of styrene, α-methylstyrene, α-vinylnaphthalene and β-vinylnaphthalene.
16. A rubber composition comprising the branched conjugated diene copolymer of claim 10 as a rubber component, in which a half width at half maximum of a viscoelasticity tan δ is 40 or less, where the half width at half maximum=(Higher temperature at half height of tan δ peak)−(Tan δ peak temperature).
17. A pneumatic tire comprising the rubber composition of claim 16 .