Thermoplastic elastomer composition and process for manufacturing the same

1. A thermoplastic elastomer composition which comprises a branched olefin copolymer comprising: a main chain of an ethylene/α-olefin copolymer; and a side chain derived from a crystalline propylene polymer containing a vinyl group at one end, wherein the content of α-olefin in the main chain is 70 mol % or less, the composition has an elongation at break of 500% or higher, and has an elastic recovery rate of 70% or more when recovering from an extension to 300% elongation.

2. The thermoplastic elastomer composition according to claim 1 , wherein the crystalline propylene polymer has an isotactic pentad ratio of 0.80 or higher.

3. The thermoplastic elastomer composition according to claim 1 , wherein the crystalline propylene polymer has a syndiotactic pentad ratio of 0.60 or higher.

4. The thermoplastic elastomer composition according to claim 1 , wherein the crystalline propylene polymer has a number-average molecular weight of 50,000 or less.

5. The thermoplastic elastomer composition according to claim 1 , which has a glass transition point of −30° C. or lower.

6. The thermoplastic elastomer composition according to claim 1 , which has a density of 0.880 g/ml or less.

7. The thermoplastic elastomer composition according to claim 1 , wherein

A) the crystalline propylene polymer has an isotactic pentad ratio of 0.80 or higher;

B) the crystalline propylene polymer has a number-average molecular weight of 50,000 or less;

C) the thermoplastic elastomer composition has a glass transition point of −30° C. or lower; and

D) the thermoplastic elastomer composition has a density of 0.880 g/ml or less.

8. The thermoplastic elastomer composition according to claim 7 , wherein the crystalline propylene polymer has an isotactic pentad ratio of 0.90 or higher.

9. The thermoplastic elastomer composition according to claim 1 , wherein

A) the crystalline propylene polymer has a syndiotactic pentad ratio of 0.60 or higher;

B) the crystalline propylene polymer has a number-average molecular weight of 50,000 or less;

C) the thermoplastic elastomer composition has a glass transition point of −30° C. or lower; and

D) the thermoplastic elastomer composition has a density of 0.880 g/ml or less.

10. The thermoplastic elastomer composition according to claim 9 , wherein the crystalline propylene polymer has a syndiotactic pentad ratio of 0.70 or higher.

11. The thermoplastic elastomer composition according to claim 1 , wherein the total content of the crystalline propylene polymer and component(s) derived from the crystalline propylene polymer, is 30% by weight or less in the thermoplastic elastomer composition.

12. A process for manufacturing a thermoplastic elastomer composition comprising a branched olefin copolymer comprising: a main chain of an ethylene/α-olefin copolymer; and a side chain derived from a crystalline propylene polymer containing a vinyl group at one end and having a number-average molecular weight of 50,000 or less, wherein the process comprises: mixing components (a) to (c) below; and coordination polymerizing the components (a) to (c) below in the presence of a transition metal catalyst so that the main chain may have the α-olefin (c) content of 5 to 70 mol %,

(a) a crystalline propylene polymer containing a vinyl group at one end, and having an isotactic pentad ratio of 0.80 or higher and a number-average molecular weight of 50,000 or less,

(b) ethylene, and

(c) at least one kind of α-olefin having 3 to 20 carbon atoms.

13. A process for manufacturing a thermoplastic elastomer composition comprising a branched olefin copolymer comprising: a main chain of an ethylene/α-olefin copolymer; and a side chain derived from a crystalline propylene polymer containing a vinyl group at one end and having a number-average molecular weight of 50,000 or less, wherein the process comprises: mixing components (a) to (c) below; and coordination polymerizing the components (a) to (c) below in the presence of a transition metal catalyst so that the main chain may have the α-olefin (c) content of 5 to 70 mol %,

(a) a crystalline propylene polymer containing a vinyl group at one end, and having a syndiotactic pentad ratio of 0.60 or higher and a number-average molecular weight of 50,000 or less,

(b) ethylene, and

(c) at least one kind of α-olefin having 3 to 20 carbon atoms.

14. The process for manufacturing a thermoplastic elastomer composition according to claim 12 , wherein the transition metal catalyst is a complex represented by general formula (VIII):

wherein R 9 is a hydrocarbon group having 1 to 30 carbon atoms, T 1 is a divalent group having 1 to 30 atoms excluding a hydrogen atom, R 10 is a heteroaryl group having 5 to 20 carbon atoms and having a Lewis base functionality, which may have a substituent, M 1 is a metal of Group 4 in the periodic table, X 1 is an anionic, neutral or dianionic ligand group, x′ is an integer of 0 to 5 denoting the number of X 1 groups, R 10 and M 1 may bind to each other to form a ring, and the solid lines, broken lines and arrow in the formula represent a bond, an arbitrary bond and a coordinate bond, respectively.

15. The process for manufacturing a thermoplastic elastomer composition according to claim 12 , wherein the mixing step is carried out so that the content of the component (a) is 30% by weight or less based on the total content of the components (a) to (c).

16. The process for manufacturing a thermoplastic elastomer composition according to claim 12 , wherein the polymerization is carried out so that the total amount of the crystalline propylene polymer and component(s) derived from the crystalline propylene polymer, is 30% by weight or less in the thermoplastic elastomer composition.

17. A thermoplastic elastomer composition manufactured by the method according to claim 12 .