1. Field of the Invention
The present invention relates to a novel dinuclear transition metal compound, a catalyst composition including the same, a method of preparing an olefin polymer, and an olefin polymer produced using the method, and more particularly, to a novel dinuclear transition metal compound which includes two complexes bridged each other in which transition metals including nickel are coordinated to a novel tetradentate ligand having salicylaldimine derivatives, a catalyst composition including the novel dinuclear transition metal compound and a cocatalyst, a method of preparing an olefin polymer, and an olefin polymer produced using the method.
2. Description of the Related Art
In general, a transition metal compound to which a salicylaldimine ligand is introduced is a transition metal compound where a Group 4 transition metal, such as titanium, zirconium, or hafnium, a transition metal, such as copper or zinc, or a Group 10 transition metal, such as nickel or palladium is coordinated with one or two salicylaldimine groups. Such transition metal compounds can be used for olefin polymerization, in particular, copolymerization of ethylene with a comonomer having a polar functional group.
For example, Fujita, T. of Mitsui Chemicals in 1999 found that in a case of a Group 4 transition metal, such as titanium, zirconium, or hafnium, by introducing a salicylaldimine ligand having various substituents to an amine, the obtained catalyst system was very active for polymerization of olefin, such as ethylene or propylene, which is disclosed in EP No. 0874005.
Meanwhile, it is known that a late transition metal, such as nickel or palladium, is highly active for polymerization of olefin and has low affinity with respect to functional groups so that it provides high activity in polymerization of polar monomers having a functional group.
For example, U.S. Pat. No. 6,576,779 B1 discloses that a nickel or palladium compound to which a salicylaldimine ligand is introduced is highly active for homopolymerization of olefin and copolymerization of olefin with a polar monomer.
However, since a conventional transition metal compound including a salicylaldimine ligand includes only one transition metal acting as active site per molecule, it was difficult to effectively prevent a decrease in catalyst activation due to a polar functional group.
Accordingly, there is a need to develop a novel transition metal compound including a salicylaldimine ligand which prevents a decrease in catalyst activation due to a polar functional group by overcoming the structural limitation of a conventional transition metal compound.