Non-crosslinked Transition Metal Catalyst for Ethylene Polymerization
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Solution Overview
Problem
Existing catalyst systems for ethylene polymerization, such as Ziegler-Natta and metallocene, face challenges in producing high molecular weight polymers with uniform molecular weight distribution and compositional uniformity, especially under high-temperature solution polymerization conditions, and are limited by environmental and safety concerns with certain phosphinimine compounds.
Innovation Solution
A non-crosslinked transition metal catalyst composition featuring a cyclopentadiene derivative and phenyl oxide ligands substituted with C1-C20 hydrocarbon groups, combined with an aluminoxane or boron cocatalyst, enables efficient polymerization of ethylene and α-olefins at elevated temperatures, producing high molecular weight polymers with narrow molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metallocene catalyst system is used, then molecular weight distribution becomes narrower and compositional distribution becomes more uniform, but high molecular weight polymers cannot be obtained especially at high temperature
Solution Approach 1:
The patent changes the chemical structure parameters of the catalyst ligands by introducing phenyl oxide ligands with specific substituents (alkyl, aryl, alkoxy groups at ortho positions) to the metallocene framework. This structural modification allows the catalyst to maintain homogeneous active sites for narrow molecular weight distribution while enabling high molecular weight polymer production through altered steric and electronic properties that reduce beta-hydrogen elimination at high temperatures
Solution Approach 2:
The patent creates a composite catalyst system combining metallocene core structure with phenyl oxide ligand components. This composite structure integrates the homogeneous catalysis benefits of metallocenes with the high molecular weight capabilities of constrained geometry catalysts, achieving both narrow molecular weight distribution and high molecular weight in the produced polymers
2Strength
If geometrically constrained non-metallocene catalyst system is used, then high molecular weight polymers can be prepared, but yield of ring forming reaction is very low making it inappropriate for commercial application
Solution Approach 1:
The patent extracts the beneficial high molecular weight capability from geometrically constrained catalysts by incorporating phenyl oxide ligands with ortho substituents that create appropriate steric constraints without requiring complex ring-forming reactions. This approach achieves high molecular weight polymer production through simplified catalyst synthesis with high yields, making the system suitable for commercial application
Solution Approach 2:
The patent employs readily available phenyl oxide ligands with simple ortho substituents that can be synthesized through straightforward, high-yield reactions. These catalyst components are easier and more economical to produce than complex geometrically constrained catalysts, enabling cost-effective commercial-scale polymer production while maintaining high molecular weight output
3Productivity
If phosphinimine compound catalyst is used, then superior ethylene transition ratio is achieved during copolymerization at high temperature, but specific phosphine compounds required are harmful to environment and humans
Solution Approach 1:
The patent replaces harmful phosphinimine compounds with phenyl oxide ligands featuring ortho substituents that create similar steric and electronic environments. This substitution eliminates environmental and safety hazards while preserving the high ethylene transition ratio and copolymerization performance at elevated temperatures, converting a harmful catalyst system into a safe one
4Productivity
If Ziegler-Natta catalyst system is used, then good efficiency of ethylene polymerization is achieved, but molecular weight distribution becomes broad due to heterogeneous catalytic active sites
Solution Approach 1:
The patent transforms the heterogeneous Ziegler-Natta catalyst system into a homogeneous metallocene-based system with phenyl oxide ligands. This fundamental parameter change in catalyst structure creates uniform single-site active centers, eliminating the broad molecular weight distribution problem while maintaining high polymerization efficiency through the well-defined catalytic mechanism
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The catalyst system achieves high catalytic activity and efficient production of ethylene homopolymers and copolymers with controlled molecular weights and compositions, suitable for commercial-scale production with environmentally friendly materials.
Implementation Method 1
transition metal complex having a cyclopentadiene derivative and at least one phenyl oxide ligand substituted at the 2-position of phenyl with a C 1 -C 20 hydrocarbon group, around a group IV transition metal, with no crosslinkage between the ligands and a cocatalyst selected from the group consisting of an aluminoxane and a boron compound
Data Source
Figure 1
AI summary
The present invention relates to a transition metal complex useful as a transition metal catalyst in the preparation of an ethylene homopolymer or a copolymer of ethylene and an a-olefin, a catalyst composition comprising the same and a process of preparing an ethylene homopolymer or a copolymer of ethylene and an a-olefin using the same. More particularly, it relates to a transition metal complex having a cyclopentadiene derivative and at least one phenyl oxide ligand substituted at the 2 -position of phenyl with, for example, a silyl group having a C1-C30 hydrocarbon group or a C1-C2O hydrocarbon group, around a group IV transition metal, with no crosslinkage between the ligands, a catalyst composition comprising the transition metal complex and a cocatalyst selected from the group consisting of an aluminoxane and a boron compound, and a process for preparing an ethylene homopolymer or a copolymer of ethylene and an a- olefin using the same.