Copolymer, polymer composition, and crosslinked polymer

Abstract

A copolymer having a structural unit derived from a conjugated diene compound and a structural unit derived from an α-olefin having 3 to 8 carbon atoms, wherein the copolymer has a melting point within a temperature range of 0 to 10° C. and has a fusion enthalpy of 5 J/g or more as measured on a differential scanning calorimeter under the following conditions. Conditions: (1) cooling from 200° C. to −150° C. at a rate of 10° C./min; (2) retaining at −150° C. for 1 minute; and (3) heating from −150° C. to 200° C. at a rate of 20° C./min.

The invention claimed is: 
     
       1. A copolymer, comprising a structural unit derived from a conjugated diene compound and a structural unit derived from an α-olefin having 3 to 8 carbon atoms,
 wherein the copolymer is an alternating copolymer of the structural unit derived from the conjugated diene compound and the structural unit derived from the α-olefin copolymer, and 
 wherein the copolymer has a melting point within a temperature range of 0 to 10° C. and has a fusion enthalpy of 5 J/g or more as measured on a differential scanning calorimeter under the following conditions: 
 Conditions: 
 (1) cooling from 200° C. to −150° C. at a rate of 10° C./min; 
 (2) retaining at −150° C. for 1 minute; and 
 (3) heating from −150° C. to 200° C. at a rate of 20° C./min. 
 
     
     
       2. A polymer composition, comprising the copolymer according to  claim 1  and a crosslinking agent. 
     
     
       3. A crosslinked polymer obtained by crosslinking the polymer composition according to  claim 2 . 
     
     
       4. The copolymer according to  claim 1 , wherein the copolymer has a melting point within a temperature range of 0 to 8° C. 
     
     
       5. The copolymer according to  claim 1 , wherein the copolymer has a melting point within a temperature range of 1 to 7° C. 
     
     
       6. The copolymer according to  claim 1 , wherein the copolymer has a fusion enthalpy of 10 J/g or more. 
     
     
       7. The copolymer according to  claim 1 , wherein the copolymer has a fusion enthalpy of 15 J/g or more. 
     
     
       8. The copolymer according to  claim 1 , wherein the copolymer optionally comprises a structural unit derived from a monomer other than the conjugated diene compound or the α-olefin having 3 to 8 carbon atoms, an amount of the monomer being 10 weight % or less with respect to a total amount of monomers used in a polymerization of the copolymer. 
     
     
       9. The copolymer according to  claim 1 , wherein the copolymer optionally comprises a structural unit derived from a monomer other than the conjugated diene compound or the α-olefin having 3 to 8 carbon atoms, an amount of the monomer being 5 weight % or less with respect to a total amount of monomers used in a polymerization of the copolymer. 
     
     
       10. The copolymer according to  claim 1 , wherein the copolymer optionally comprises a structural unit derived from a monomer other than the conjugated diene compound or the α-olefin having 3 to 8 carbon atoms, an amount of the monomer being 1 weight % or less with respect to a total amount of monomers used in a polymerization of the copolymer.