Bisphenol Metal Complex Catalyst for Polyethylene Molecular Weight Control
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Solution Overview
Problem
There is a need for novel metal compounds exhibiting desired catalytic performance and olefin polymerization processes that can achieve high molecular weights and comonomer incorporation in polyethylene production.
Innovation Solution
A bisphenol metal complex-based catalyst system is developed, comprising a main catalyst and a cocatalyst, which enables homopolymerization of ethylene with molecular weights up to 200,000 and molecular weight distribution of 1.5 to 20, and copolymerization with comonomer content of 1-30 mol%, using a process that includes specific preparation methods for the bisphenol metal complexes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional single metal catalysts are used for olefin polymerization, then the catalytic activity is moderate, but the comonomer incorporation ability is limited
Solution Approach 1:
The patent employs a composite catalyst system consisting of a bisphenol metal complex (main catalyst) combined with a cocatalyst. This composite structure integrates the functions of both catalyst components, where the bisphenol metal complex provides high catalytic activity and the cocatalyst enhances comonomer incorporation ability, thereby resolving the contradiction between moderate activity and limited comonomer incorporation of single metal catalysts
Solution Approach 2:
The patent modifies the ligand structure of the metal catalyst by introducing bisphenol ligands with specific substituents (R1-R9 groups). By changing the steric and electronic parameters of the ligand environment, the catalyst achieves both high activity and improved comonomer incorporation capability simultaneously
2Productivity
If double zirconium metal catalysts are used for ethylene polymerization, then the ethyl grafting rate increases to 12%, but the molecular weight control becomes less precise
Solution Approach 1:
The patent introduces specific substituents (R3-R7 groups) at localized positions on the bisphenol ligand structure. These local structural modifications create specific steric environments around the metal center that control the grafting reactions, allowing high ethyl grafting rates while maintaining precise molecular weight control through localized steric effects
3Adaptability or versatility
If high comonomer content copolymers are produced, then the polymer versatility increases, but the molecular weight distribution broadens
Solution Approach 1:
The patent employs a dynamic catalyst system where the bisphenol metal complex maintains a stable yet adaptable coordination environment. The ligand structure allows for dynamic adjustment of the metal center's electronic and steric properties during polymerization, enabling the catalyst to accommodate varying comonomer concentrations while maintaining relatively narrow molecular weight distributions through consistent catalytic cycle kinetics
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 bisphenol metal complex catalyst system achieves high catalytic efficiency and comonomer incorporation, producing polyethylene with desired molecular weights and distributions, suitable for various polymerization processes including solution, slurry, and gas phase polymerization.
Implementation Method 1
a catalyst for olefin polymerization, which comprises a bisphenol metal complex-based main catalyst and a cocatalyst
Data Source
AI summary
Disclosed is a catalyst for olefin polymerization, comprising a main catalyst and a cocatalyst; the main catalyst is a bisphenol metal complex represented by formula I, and the cocatalyst comprises an organoaluminum compound; in formula I, R1, R1′, R2, R2′ are the same or different, and are each independently selected from hydrogen and a substituted or unsubstituted C1-C20 hydrocarbyl; R3-R7, R3′-R7′ are the same or different, and are each independently selected from hydrogen and a substituted or unsubstituted C1-C20 hydrocarbyl; R8 and R9 are the same or different, and are each independently selected from hydrogen or a substituted or unsubstituted C1-C20 hydrocarbyl; M and M′ are the same or different, and are selected from Group IV metals; and X is halogen;