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% by mass or more,
wherein the monomer components further comprise a conjugated diene compound represented by a general formula (3):
wherein R 3 and R 4 are the same or different, and each represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a halogen atom.
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 , having a weight-average molecular weight of more than 100000.
5. The branched conjugated diene copolymer of claim 1 , wherein a copolymerization ratio (1) of the branched conjugated diene compound (1) is from 1 to 54% by mass, a copolymerization ratio (m) of the aromatic vinyl compound (2) is from 45 to 99% by mass, and a copolymerization ratio (n) of the conjugated diene compound (3) is 54% by mass or less.
6. The branched conjugated diene copolymer of claim 1 , wherein the branched conjugated diene compound (1) is myrcene and/or farnesene.
7. The branched conjugated diene copolymer of claim 1 , wherein the aromatic vinyl compound (2) is one or more selected from the group consisting of styrene, α-methylstyrene, α-vinylnaphthalene and β-vinylnaphthalene.
8. The branched conjugated diene copolymer of claim 1 , wherein the conjugated diene compound (3) is 1,3-butadiene and/or isoprene.
9. 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)−(Tanδ peak temperature).
10. A pneumatic tire produced using the rubber composition of claim 9 .
11. The branched conjugated diene copolymer of claim 1 , wherein a copolymerization ratio (1) of the branched conjugated diene compound (1) is from 1 to 54% by mass, a copolymerization ratio (m) of the aromatic vinyl compound (2) is from 45 to 99% by mass, and a copolymerization ratio (n) of the conjugated diene compound (3) is in a range of 2 to 54% by mass.
12. The branched conjugated diene copolymer of claim 1 , wherein a copolymerization ratio (1) of the branched conjugated diene compound (1) is from 1 to 54% by mass, a copolymerization ratio (m) of the aromatic vinyl compound (2) is from 45 to 99% by mass, and a copolymerization ratio (n) of the conjugated diene compound (3) is 50% by mass or less.
13. A rubber composition, comprising:
a branched conjugated diene copolymer 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)−(Tanδ peak temperature),
wherein 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 an alkyl group having 1 to 3 carbon atoms,
wherein a copolymerization ratio (m) of the aromatic vinyl compound (2) is 45% by mass or more,
wherein the branched conjugated diene copolymer has glass transition temperature of −25° C. or more.
14. The rubber composition of claim 13 , wherein the branched conjugated diene copolymer has glass transition temperature of −25° C. or more.
15. The rubber composition of claim 13 , wherein the branched conjugated diene copolymer has a glass transition temperature of −10° C. or more.
16. The rubber composition of claim 13 , wherein the branched conjugated diene copolymer has a weight-average molecular weight of more than 100000.
17. The rubber composition of claim 13 , wherein a copolymerization ratio (1) of the branched conjugated diene compound (1) is from 1 to 54% by mass, and a copolymerization ratio (m) of the aromatic vinyl compound (2) is from 45 to 99% by mass.
18. The rubber composition of claim 13 , wherein the branched conjugated diene compound (1) is myrcene and/or farnesene.
19. The rubber composition of claim 13 , wherein the aromatic vinyl compound (2) is one or more selected from the group consisting of styrene, α-methylstyrene, α-vinylnaphthalene and β-vinylnaphthalene.
20. A pneumatic tire comprising the rubber composition of claim 13 .
21. A pneumatic tire comprising the rubber composition of claim 15 .