Copolymer, rubber composition, crosslinked rubber composition, and tire
Provided is a block copolymer of a conjugated diene compound and a non-conjugated olefin, a rubber composition including the block copolymer, a crosslinked rubber obtained by crosslinking the rubber composition, and a tire using the rubber composition or the crosslinked rubber composition. The copolymer of the present invention is a block copolymer of a conjugated diene compound and a non-conjugated olefin, the copolymer having a peak area in a temperature range in a range of 70° C. to 110° C. that accounts for at least 60% of a peak area in a range of 40° C. to 140° C. and a peak area in a range of 110° C. to 140° C. that accounts for 20% or less of a peak area in a range of 40° C. to 140° C., the peak areas being measured by the differential scanning calorimetry (DSC) according to JIS K 7121-1987.
1. A copolymer of a conjugated diene compound and a non-conjugated olefin, wherein the copolymer is a block copolymer having a peak area in a range of 70° C. to 110° C. that accounts for at least 60% of a peak area in a range of 40° C. to 140° C. and a peak area in a range of 110° C. to 140° C. that accounts for 20% or less of a peak area in a range of 40° C. to 140° C., the peak areas being measured by the differential scanning calorimetry (DSC) according to JIS K 7121-1987.
2. The copolymer according to claim 1 , wherein the conjugated diene compound unit has a cis-1,4 bond content of at least 80%.
3. The copolymer according to claim 1 , wherein the non-conjugated olefin is contained over 0 mol % to 40 mol % or less.
4. The copolymer according to claim 1 , wherein the block copolymer has any one of the structures of (A-B)x, A-(B-A)x and B-(A-B)x,
where A represents a block sequence including monomer units of the non-conjugated olefin, B represents a block sequence including monomer units of the conjugated diene compound, and x represents an integer of at least 1.
5. The copolymer according to claim 1 , comprising a copolymer having a polystyrene-equivalent average-weight molecular weight of 10,000 to 10,000,000.
6. The copolymer according to claim 1 , comprising a copolymer having a molecular weight distribution (Mw/Mn) of 10 or less.
7. The copolymer according to claim 1 , wherein the non-conjugated olefin is an acyclic olefin.
8. The copolymer according to claim 1 , wherein the non-conjugated olefin has 2 to 10 carbon atoms.
9. The copolymer of according to claim 7 , wherein the non-conjugated olefin is at least one selected from a group consisting of ethylene, propylene, and 1-butene.
10. The copolymer according to claim 9 , wherein the non-conjugated olefin is ethylene.
11. The copolymer according to claim 1 , wherein the conjugated diene compound is at least one selected from a group consisting of 1,3-butadiene and isoprene.
12. A rubber composition comprising the copolymer according to claim 1 .
13. The rubber composition according to claim 12 , comprising, with respect to 100 parts by mass of the rubber component, a reinforcing filler by 5 parts by mass to 200 parts by mass and a crosslinking agent by 0.1 parts by mass to 20 parts by mass.
14. A crosslinked rubber composition obtained by crosslinking the rubber composition according to claim 12 .
15. A tire manufactured by using the rubber composition according to claim 12 .