Process for producing alpha-olefin/aromatic vinyl copolymer

The invention provides a method for producing &agr;-olefin-aromatic vinyl compound copolymers of high quality at high productivity. The method for producing an &agr;-olefin-aromatic vinyl compound copolymer including copolymerizing an &agr;-olefin and an aromatic vinyl compound in the presence of a copolymerization catalyst formed of a transition metal compound component (A) and a co-catalyst component (B) wherein the component (A) employs a transition metal compound having two cross-linking groups wherein at least one of the cross-linking groups is a cross-linking group exclusively formed of a carbon-carbon bond.

EXAMPLE 1 Into an autoclave (internal volume of 1.6 L) equipped with a catalyst-introduction pipe, toluene (180 mL), styrene (200 mL), and a solution (1.0 M, 1.0 mL) of triisobutylaluminum in toluene serving as catalyst component (C) were sequentially charged. The temperature was elevated to 50° C. Subsequently, ethylene was introduced into the autoclave until the partial pressure thereof reached 0.3 MPa. A solution of (2,2′-isopropylidene)(1,1′-dimethylsilylene)bis(indenyl)zirconium dichloride (10.0 &mgr;mol), serving as catalyst component (A), dissolved in toluene (20 mL) and methylaluminoxane (10.0 mmol) serving as catalyst component (B) were mixed, and the resultant mixture was introduced through the catalyst-introduction pipe. Since the internal pressure of the autoclave decreased as the progress of co-polymerization of ethylene and styrene, ethylene was continuously introduced such that the partial pressure thereof could be maintained at 0.3 MPa, during which co-polymerization was performed over one hour. Thereafter, the co-polymerization was terminated by adding methanol. A large amount of methanol was added to the reaction product, and the mixture was subjected to filtration, to thereby separate a solid. The separated solid was dried at 60° C. for four hours under reduced pressure, to thereby yield 92.0 g (catalyst activity with respect to co-polymerization&equals;101 kg/g-Zr/hr) of ethylene-styrene copolymer. 1 H-NMR measurement of the thus-obtained copolymer revealed that the styrene residue-derived structural unit content of the copolymer was 5.5 mol %. 13 C-NMR measurement confirmed that the copolymer included ethylene-styrene chain structure. 
 EXAMPLE 2 The procedure of Example 1 was repeated, except that hydrogen serving as a chain-transfer agent of component (D) was introduced at a partial pressure of 0.03 MPa together with ethylene serving as a raw material. Thus, 104.3 g (catalyst activity with respect to co-polymerization&equals;114 kg/g-Zr/hr) of ethylene-styrene copolymer was obtained. 
 EXAMPLE 3 The procedure of Example 1 was repeated, except that a 1M solution (1.0 mL) of dimethylanilinium tetrakis(pentafluorophenyl)borate in toluene was used instead of methylaluminoxane employed as a co-catalyst of component (B) used in Example 1, to thereby yield 41.7 g (catalyst activity with respect to co-polymerization&equals;46 kg/g-Zr/hr) of ethylene-styrene copolymer. 1H-NMR measurement of the thus-obtained copolymer revealed that the styrene residue-derived structural unit content of the copolymer was 8 mol %. 13 C-NMR measurement confirmed that the copolymer included ethylene-styrene chain structure. 
 EXAMPLE 4 The procedure of Example 2 was repeated, except that (1,2′-ethylene)(1′,2-ethylene)bis(3-normalbutylindenyl)zirconium dichloride (10.0 &mgr;mol) was used instead of catalyst component (A) employed in Example 2; hydrogen serving as a chain-transfer agent of component (D) was introduced at a partial pressure of 0.03 MPa; and the polymerization time was controlled to three minutes, to thereby yield 23.6 g (catalyst activity with respect to co-polymerization &equals;517 kg/g-Zr/hr) of ethylene-styrene copolymer. 1 H-NMR measurement of the thus-obtained copolymer revealed that the styrene residue-derived structural unit content of the copolymer was 1.5 mol %. 13 C-NMR measurement confirmed that the copolymer included ethylene-styrene chain structure. 
 EXAMPLE 5 The procedure of Example 1 was repeated, except that (1,2′-ethylene)(1′,2-ethylene)bis(3-trimethylsilylmethylindenyl)zirconium dichloride (10.0 &mgr;mol) was used instead of catalyst component (A) employed in Example 1; propylene was used as a raw material instead of ethylene; hydrogen serving as a chain-transfer agent of component (D) was introduced at a partial pressure of 0.03 MPa; and the polymerization time was controlled to 30 minutes, to thereby yield 19.8 g (catalyst activity with respect to co-polymerization&equals;145 kg/g-Zr/hr) of propylene-styrene copolymer. GPC-FT/IR measurement revealed that the thus-produced copolymer had a mass average molecular weight of 14,500 (as reduced to polystyrene) and a molecular weight distribution of 1.8. 
 EXAMPLE 6 Into an autoclave (internal volume of 1.6 L) equipped with a catalyst-introduction pipe, toluene (180 mL), styrene (200 mL), 1-octene (20 mL) serving as a comonomer, and a solution (1.0 M, 1.0 mL) of triisobutylaluminum in toluene serving as catalyst component (C) were sequentially charged. The temperature was elevated to 50° C. Subsequently, ethylene was introduced into the autoclave until the partial pressure thereof reached 0.3 MPa. A solution of (2,2′-isopropylidene)(1,1′-dimethylsilylene)bis(indenyl)zirconium dichloride (10.0 &mgr;mol), serving as catalyst component (A), dissolved in toluene (20 mL) and methylaluminoxane (10 mmol) serving as catalyst component (B) were mixed, and the resultant mixture was introduced through the catalyst-introduction pipe. Since the internal pressure of the autoclave decreased as the progress of co-polymerization of ethylene and styrene, ethylene was continuously introduced such that the partial pressure thereof could be maintained at 0.3 MPa, during which co-polymerization was performed over one hour. Thereafter, the co-polymerization was terminated by adding methanol. A large amount of methanol was added to the reaction product, and the mixture was subjected to filtration, to thereby separate a solid. The separated solid was dried at 60° C. for four hours under reduced pressure, to thereby yield 92.3 g (catalyst activity with respect to co-polymerization&equals;101 kg/g-Zr/hr) of ethylene-styrene-octene copolymer. 1 H-NMR measurement of the thus-obtained copolymer revealed that the styrene residue-derived structural unit content of the copolymer was 4 mol % and the octene residue-derived structural unit content of the copolymer was 12 mol %. 13 C-NMR measurement confirmed that the copolymer included ethylene-styrene-ethylene chain structure and ethylene-octene-ethylene chain structure. 
 EXAMPLE 7 Into an autoclave (internal volume of 1.6 L) equipped with a catalyst-introduction pipe, toluene (180 mL), styrene (200 mL), and a solution (1.0 M, 1.0 mL) of triisobutylaluminum in toluene serving as catalyst component (C) were sequentially charged. The temperature was elevated to 50° C. Subsequently, into this autoclave, hydrogen serving as a chain-transfer agent of component (D) was introduced at a partial pressure of 0.05 MPa and propylene was introduced such that the partial pressure thereof attained 0.5 MPa. A solution of (1,2′-ethylene)(1′,2-ethylene)bis(3-normalbutylindenyl)zirconium dichloride (10.0 &mgr;mol), serving as catalyst component (A), dissolved in toluene (20 mL) and methylaluminoxane (10.0 mmol) serving as catalyst component (B) were introduced into the autoclave. Since the internal pressure of the autoclave decreased as the progress of co-polymerization of propylene and styrene, propylene was continuously introduced such that the partial pressure thereof could be maintained at 0.5 MPa, during which co-polymerization was performed over five minutes. Thereafter, the co-polymerization was terminated by adding methanol. A large amount of methanol was added to the reaction product, and the mixture was subjected to filtration, to thereby separate a solid. The separated solid was dried at 60° C. for four hours under reduced pressure, to thereby yield 33.4 g (catalyst activity with respect to co-polymerization&equals;879 kg/g-Zr/hr) of propylene-styrene copolymer. GPC-FT/IR measurement revealed that the thus-produced copolymer had a mass average molecular weight of 16,800 (as reduced to polystyrene) and a molecular weight distribution of 2.0. 
 COMPARATIVE EXAMPLE 1 The procedure of Example 1 was repeated, except that a known transition metal compound catalyst component, bis(dimethylsilylene)bis(cyclopentadienyl)zirconium dichloride (10.0 pmol), was used instead of catalyst component (A) used in Example 1, to thereby yield 10.5 g (catalyst activity with respect to co-polymerization &equals;22 kg/g-Zr/hr) of ethylene-styrene copolymer. GPC-FT/IR measurement revealed that the thus-produced copolymer had a mass average molecular weight of 16,400 (as reduced to polystyrene) and a molecular weight distribution of 2.0. 1 H-NMR measurement of the thus-obtained copolymer revealed that the styrene residue-derived structural unit content of the copolymer was 38 mol %. 13 C-NMR measurement confirmed that the copolymer included an ethylene-styrene chain structure. 
 INDUSTRIAL APPLICABILITY According to the method of the present invention, high catalyst activity with respect to co-polymerization of &agr;-olefin, an aromatic vinyl compound, and an optional cyclic olefin or diene can be attained; the amount of aluminoxane or a boron compound serving as a co-catalyst can be reduced; and the amount of the catalyst remaining in the produced copolymer can be reduced. Thus, olefin-aromatic vinyl compound copolymers of high quality can be produced at high productivity.