Thermoplastic elastomer composition

1. A thermoplastic elastomer composition obtained by dynamically heating a polymer composition in the presence of a crosslinking agent, the polymer composition comprising an α-olefin thermoplastic resin (A), and an oil-extended ethylene copolymer (B),

wherein B comprises:

an ethylene copolymer having a limiting viscosity [η] measured at 135° C. in a decalin solvent of 5.5 to 9.0 dl/g, and a ratio, Mw/Mn, of weight average molecular weight, Mw, to number average molecular weight, Mn, of 3 or less; and

50 to 150 parts by mass of a first mineral oil-based softener based on 100 parts by mass of the ethylene copolymer, the content of the oil-extended ethylene copolymer (B) is 30 mass % or more based on the total amount, 100 mass %, of a polymer component comprising the α-olefin thermoplastic resin (A) and the oil-extended ethylene copolymer (B),

wherein the ethylene copolymer is an ethylene-α-olefin-nonconjugated polyene copolymer.

2. The thermoplastic elastomer composition according to claim 1 , wherein the mass ratio, (A)/(B), of the α-olefin thermoplastic resin (A) to the oil-extended ethylene copolymer (B) comprised in the polymer component is 5/95 to 70/30.

3. The thermoplastic elastomer composition according to claim 1 , wherein the polymer composition further comprises (C) a second mineral oil-based softener.

4. The thermoplastic elastomer composition according to claim 1 , wherein the oil-extended ethylene copolymer (B) is obtained by removing a solvent from a mixture that comprises the ethylene copolymer, the first mineral oil-based softener, and a solvent.

5. The thermoplastic elastomer composition according to claim 1 , wherein the α-olefin thermoplastic resin (A) comprises (a1) an α-olefin crystalline thermoplastic resin and (a2) an α-olefin amorphous thermoplastic resin.

6. The thermoplastic elastomer composition according to claim 5 , wherein the polymer composition comprises:

2 to 50 mass % of the α-olefin crystalline thermoplastic resin (a1);

2 to 10 mass % of the α-olefin amorphous thermoplastic resin (a2); and

40 to 95 mass % of the oil-extended ethylene copolymer (B), based on 100 mass % of the α-olefin crystalline thermoplastic resin (a1), the α-olefin amorphous thermoplastic resin (a2), and the oil-extended ethylene copolymer (B) in total, and

the α-olefin amorphous thermoplastic resin (a2) comprises at least one repeating unit selected from the group consisting of a repeating unit derived from ethylene, a repeating unit derived from propylene, and a repeating unit derived from 1-butene.

7. The thermoplastic elastomer composition according to claim 5 , wherein the α-olefin crystalline thermoplastic resin (a1) has an elution volume at 80° C. of 30 mass % or less and a melting point of 155° C. or less.

8. The thermoplastic elastomer composition according to claim 5 , wherein the polymer composition comprises 5 to 400 parts by mass of the second mineral oil-based softener (C), based on 100 parts by mass of the α-olefin crystalline thermoplastic resin (a1), the α-olefin amorphous thermoplastic resin (a2), and the oil-extended ethylene copolymer (B) in total.

9. The thermoplastic elastomer composition according to claim 2 , wherein the polymer composition further comprises (C) a second mineral oil-based softener.

10. The thermoplastic elastomer composition according to claim 1 , wherein the polymer composition further comprises (C) a second mineral oil-based softener.

11. The thermoplastic elastomer composition according to claim 2 , wherein the oil-extended ethylene copolymer (B) is obtained by removing a solvent from a mixture that comprises the ethylene copolymer, the first mineral oil-based softener, and a solvent.

12. The thermoplastic elastomer composition according to claim 1 , wherein the oil-extended ethylene copolymer (B) is obtained by removing a solvent from a mixture that comprises the ethylene copolymer, the first mineral oil-based softener, and a solvent.

13. The thermoplastic elastomer composition according to claim 3 , wherein the oil-extended ethylene copolymer (B) is obtained by removing a solvent from a mixture that comprises the ethylene copolymer, the first mineral oil-based softener, and a solvent.

14. The thermoplastic elastomer composition according to claim 9 , wherein the oil-extended ethylene copolymer (B) is obtained by removing a solvent from a mixture that comprises the ethylene copolymer, the first mineral oil-based softener, and a solvent.

15. The thermoplastic elastomer composition according to claim 10 , wherein the oil-extended ethylene copolymer (B) is obtained by removing a solvent from a mixture that comprises the ethylene copolymer, the first mineral oil-based softener, and a solvent.

16. The thermoplastic elastomer composition according to claim 1 , wherein said ethylene copolymer is prepared by gas-phase polymerization in the presence of a Ziegler-Natta catalyst and hydrogen gas is used in an amount of 0.01 to 20 ppm, as a molecular weight modifier.

17. The thermoplastic elastomer composition according to claim 1 , wherein said ethylene copolymer is prepared by gas-phase polymerization in the presence of hydrogen gas in an amount of 0.01 to 20 ppm, as a molecular weight modifier.

18. The thermoplastic elastomer composition according to claim 1 , wherein said ethylene copolymer is prepared by gas-phase polymerization in the presence of hydrogen gas as a molecular weight modifier.