Process for producing propylene/ethylene block copolymer and propylene/ethylene block copolymer

1. A process for producing a propylene-ethylene block copolymer in which propylene is copolymerized with ethylene in the presence of a catalyst system comprising a metallocene catalyst (1), a metallocene catalyst (2), a porous carrier (3), at least one aluminoxane (4) and/or compound (4) which can form an ionic complex by reacting with the metallocene catalysts described above and, optionally, an organic aluminum compound (5),

wherein the metallocene catalyst (1) is a monocross-linked metallocene catalyst, and the metallocene catalyst (2) is a dicross-linked metallocene catalyst, and

wherein the monocross-linked metallocene catalyst is a transition metal compound represented by general formula (I):

wherein E1 represents a bonding group which cross-links two conjugate five-membered ring ligands; R1 and R2 each represent a hydrocarbon group, a halogen atom, an alkoxy group, a silicon-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group or a boron-containing hydrocarbon group; R3 to R6 each represent hydrogen, a hydrocarbon group, a halogen atom, an alkoxy group, a silicon-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group or a boron-containing hydrocarbon group; M1 represents a transition metal of the IV to VI group in the periodic table; X1 and Y1 each represent a covalent bonding ligand; and X1 and Y1 may be combined with each other to form a ring structure; and the dicross-linked metallocene catalyst is a transition metal compound represented by general formula (II) or general formula (III):

wherein E2 and E3 independently represent a silylene group, an oligosilylene group, or a side chain lower alkyl or phenyl-substituted group thereof; R9 to R18 each represent hydrogen, a hydrocarbon group, a halogen atom, an alkoxy group, a silicon-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group or a boron-containing hydrocarbon group; R7, R8, R19 and R20 each represent a hydrocarbon group, a halogen atom, an alkoxy group, a silicon-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group or a boron-containing hydrocarbon group; M2 represents a transition metal of the IV to VI group in the periodic table; X2 and Y2 each represent a covalent bonding ligand; and X1 and Y1 may be combined with each other to form a ring structure.

2. The process for producing a propylene-ethylene block copolymer as described in claim 1 , wherein propylene is polymerized in a first step, and propylene and ethylene are random-copolymerized in a second step.

3. The process for producing the propylene-ethylene block copolymer as described in claim 2 , wherein the propylene-ethylene block copolymer satisfies the following requirement of:

(1) a triad chain fraction fEEE of [EEE]≦0.01 (mole %), (2) R1·R2≧0.5,

(3) its intrinsic viscosity [η]≧1.0 dl/g, and

(4) an intrinsic viscosity [η] of a xylene-soluble fraction ≧1.0 dl/g.

4. The method as claimed in claim 1 , wherein E2 and E3 independently represent a silylene, dimethylsilylene, methylphenylene, diphenylsilylene, disilylene, and tetramethyldisilylene group.

5. The method as claimed in claim 1 , wherein said catalyst system comprises at least one aluminoxane.

6. The method as claimed in claim 2 , wherein said catalyst system comprises at least one aluminoxane.

7. A propylene-ethylene block copolymer produced by the process as described in claim 1 .

8. The propylene-ethylene block copolymer as described in claim 7 , wherein an elastic modulus E is less than 330 (MPa), and an internal haze H is less than 55(%).

9. A propylene-ethylene block copolymer produced by the process as described in claim 2 .

10. The propylene-ethylene block copolymer as described in claim 9 , wherein an elastic modulus E is less than 330 (MPa), and an internal haze H is less than 55(%).

11. A process for producing a propylene-ethylene block copolymer in which propylene is copolymerized with ethylene in the presence of a catalyst system comprising a metallocene catalyst (1), a metallocene catalyst (2), a porous carrier (3), at least one aluminoxane (4) and/or compound (4) which can form an ionic complex by reacting with the metallocene catalysts described above and, optionally, an organic aluminum compound (5),

wherein the metallocene catalyst (1) is a monocross-linked metallocene catalyst, and the metallocene catalyst (2) is a dicross-linked metallocene catalyst, and

wherein the monocross-linked metallocene catalyst is dimethylsilylenebis(2-methylbenzoindenyl)zirconium dichloride or dimethylsilylenebis(2-methyl-4-phenylindenyl)zirconium dichloride, and the dicross-linked metallocene catalyst is (1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-trimethylsilylmethylindenyl)zirconium dichloride or (1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-n-butylindenyl)zirconium dichloride.

12. The process for producing a propylene-ethylene block copolymer as described in claim 11 , wherein propylene is polymerized in a first step, and propylene and ethylene are random-copolymerized in a second step.

13. The process for producing the propylene-ethylene block copolymer as described in claim 12 , wherein the propylene-ethylene block copolymer satisfies the following requirement of:

(1) a triad chain fraction fEEE of [EEE]≦0.1 (mole %), (2) R1·R2≧0.5,

(3) its intrinsic viscosity [η]≧1.0 dl/g, and

(4) an intrinsic viscosity [η] of a xylene-soluble fraction≧1.0 dl/g.

14. The method as claimed in claim 11 , wherein said catalyst system comprises at least one aluminoxane.

15. A propylene-ethylene block copolymer produced by the process as described in claim 11 .

16. The propylene-ethylene block copolymer as described in claim 15 , wherein an elastic modulus E is less than 330 (MPa), and an internal haze H is less than 55(%).

17. A propylene-ethylene block copolymer produced by the process as described in claim 12 .

18. The propylene-ethylene block copolymer as described in claim 17 , wherein an elastic modulus B is less than 330 (MPa), and an internal haze H is less than 55(%).