Group 4 Metal Catalyst for Low Molecular Weight Olefin Polymerization
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Solution Overview
Problem
Current Group 4 metal complexes based on donor ligands face challenges in producing polymers with high molecular weight and tacticity at high temperatures, leading to increased viscosity and reduced polymer quality, and require excessive hydrogen as a chain transfer agent, which increases costs and complexity.
Innovation Solution
A catalyst composition comprising specific Group 4 metal donor ligand complexes, capable of operating at high temperatures, that reduces polymer molecular weight and maintains high tacticity without excessive hydrogen, using a catalyst composition including Group 4 metal complexes with anionic ligands like chloro, methyl, or benzyl, and activating cocatalysts to achieve efficient polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If higher polymerization temperatures are employed to decrease viscosity of the reaction mixture, then polymer viscosity is reduced, but polymer tacticity or crystallinity is reduced
Solution Approach 1:
The patent modifies the catalyst system parameters by introducing specific Group 4 metal complexes with heteroaryl donor ligands and modifying the ligand environment around the metal center. This allows the catalyst to maintain high activity and produce high molecular weight polymers with high tacticity even at elevated temperatures (100-200°C), resolving the contradiction between temperature increase and tacticity maintenance
Solution Approach 2:
The patent creates a composite catalyst system combining Group 4 metal complexes with specific heteroaryl donor ligands and cocatalysts. This composite catalyst architecture enables simultaneous control of polymerization rate, molecular weight, and tacticity at high temperatures, allowing the process to achieve both low viscosity (through high temperature) and high tacticity (through catalyst control)
2Quantity of substance
If chain transfer agent such as hydrogen is added to produce lower molecular weight polymers, then polymer molecular weight is reduced, but process complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for external chain transfer agents like hydrogen from the polymerization process. By designing the catalyst system with specific Group 4 metal complexes and heteroaryl ligands that inherently control chain growth and termination, the process achieves low molecular weight polymers without adding hydrogen, thereby reducing process complexity and cost
Solution Approach 2:
The catalyst system is designed to be self-regulating for molecular weight control. The Group 4 metal complex with heteroaryl donor ligands provides inherent chain transfer capability through the catalyst itself rather than requiring external hydrogen addition. This self-service approach allows molecular weight control without additional reagents, simplifying the process
3Quantity of substance
If standard chain transfer agents are used to control molecular weight, then polymer molecular weight is controlled, but solubility of chain transfer agent decreases at higher reaction temperatures
Solution Approach 1:
The patent changes the fundamental parameter of how chain transfer is achieved by using a catalyst-based mechanism rather than relying on solubility-dependent chain transfer agents. The Group 4 metal complex with heteroaryl ligands provides temperature-independent chain transfer control through its catalytic mechanism, eliminating the solubility limitation that plagues conventional hydrogen-based approaches at elevated temperatures
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 solution enables the production of polymers with improved melt flow properties and reduced molecular weight distribution, maintaining high isotacticity and crystallinity, suitable for applications in fibers, films, and adhesives, while minimizing hydrogen usage.
Implementation Method 1
A catalyst composition comprising specific Group 4 metal donor ligand complexes, capable of operating at high temperatures, that reduces polymer molecular weight and maintains high tacticity without excessive hydrogen
Implementation Method 2
Group 4 metal complexes based on donor ligands have published... metal complexes based on polyvalent metal-centered, heteroaryl donor ligands
Data Source
AI summary
Group 4 metal complexes comprising a polyvalent, heteroaryl donor ligand and their use as components of olefin polymerization catalysts, especially suited for preparing propylene copolymer products having high isotacticity and low molecular weight, are disclosed.