Homogeneous Catalyst System for High-Temperature Ethylene Polymerization
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Solution Overview
Problem
Existing catalyst systems for producing ethylene homopolymers or copolymers with α-olefins face challenges in achieving high molecular weights and stability at high temperatures, particularly in solution polymerization, with poor compatibility with paraffin hydrocarbon solvents and reduced activity above 140°C.
Innovation Solution
A homogeneous catalyst system featuring a cyclopentadiene derivative and electron donating substituent crosslinked through a silyl derivative substituted with cyclohexyl, bonded to a Group IV transition metal, combined with an aluminum or boron compound cocatalyst, providing thermal stability and compatibility with paraffin hydrocarbon solvents for high-temperature solution polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional Ziegler-Natta catalyst system is used, then polymerization activity is high, but molecular weight distribution is wide and composition distribution is non-uniform
Solution Approach 1:
The patent changes the fundamental parameter of catalyst structure from heterogeneous Ziegler-Natta to homogeneous metallocene/constrained geometry catalyst, maintaining high activity while achieving uniform product distribution through single-site mechanism
Solution Approach 2:
The patent employs composite catalyst systems combining metallocene compounds with specific ligands (amido, alkoxo, aryloxo) and cocatalysts (methylaluminoxane, boron compounds) to achieve both high activity and precise control over polymer properties
2Manufacturing precision
If metallocene catalyst system is used, then molecular weight distribution is narrow and composition distribution is uniform, but high molecular weight polymers cannot be obtained and stability decreases at high temperatures
Solution Approach 1:
The patent modifies the ligand structure parameters, introducing bulky substituents (tert-butyl, adamantyl) and electron-donating groups to enhance thermal stability while preserving the single-site homogeneous catalyst characteristics for uniform polymer distribution
Solution Approach 2:
The patent creates composite catalyst systems with constrained geometry catalysts featuring amido and alkoxo ligands that work synergistically to provide both thermal stability and uniform polymerization activity at high temperatures
3Productivity
If constrained geometry catalyst with amide group is used, then high molecular weight polymers can be produced with good reactivity, but stability decreases drastically at high temperatures and compatibility with paraffin hydrocarbon solvent is poor
Solution Approach 1:
The patent optimizes the amide ligand parameters by introducing bulky hydrophobic substituents (tert-butyl, adamantyl) that enhance both thermal stability and compatibility with paraffin hydrocarbon solvents while maintaining high molecular weight polymer production capability
Solution Approach 2:
The patent applies local quality modification by placing electron-donating and hydrophobic groups at specific positions on the amide ligand, creating regions of high electron density and hydrophobic character that simultaneously improve stability and solvent compatibility
4Temperature
If solution polymerization is conducted at high temperatures of 140°C or more, then polymerization activity is drastically decreased and β-dehydrogenation mainly occurs
Solution Approach 1:
The patent changes the catalyst's thermal stability parameter through ligand design, enabling the catalyst to maintain high activity at elevated temperatures (140-200°C) by preventing decomposition and suppressing β-dehydrogenation through enhanced metal-ligand bond strength
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 enables the production of high molecular weight ethylene polymers with controlled molecular weight distribution and density, maintaining stability and activity at temperatures up to 250°C, facilitating commercial application.
Implementation Method 1
a homogeneous catalyst system featuring a cyclopentadiene derivative and electron donating substituent crosslinked through a silyl derivative substituted with cyclohexyl, bonded to a Group IV transition metal, combined with an aluminum or boron compound cocatalyst
Data Source
AI summary
Disclosed is a homogeneous catalyst system for producing an ethylene homopolymer or an ethylene copolymer with α-olefin. Specifically, this invention pertains to a transition metal catalyst which has stability under high temperature solution polymerization at 120˜250° C., in which a cyclopentadiene derivative and an electron donating substituent, both of which are bonded to a Group IV transition metal acting as a central metal, are crosslinked through a silyl derivative substituted with a cyclohexyl, to a catalyst system including such a transition metal catalyst and an aluminoxane cocatalyst or a boron compound cocatalyst, and to a method of producing an ethylene homopolymer or an ethylene copolymer with α-olefin, having high molecular weight, using the catalyst system under conditions of high-temperature solution polymerization. The catalyst according to this invention has excellent thermal stability and compatibility with a paraffin hydrocarbon solvent and thus is effective in the production of an ethylene homopolymer or an ethylene copolymer with α-olefin having various properties in commercial polymerization processes.