Hafnocene Catalyst Composition for High-Temperature Ethylene Copolymerization
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Solution Overview
Problem
Existing metallocene catalyst systems for ethylene copolymerization lack an optimal balance of solubility, productivity, comonomer incorporation ability, and molecular weight capability, particularly at high temperatures, failing to produce polymers with desired properties such as low density and high melt index.
Innovation Solution
A new catalyst system comprising a metallocene complex with specific ligand configurations and a boron-containing cocatalyst is used for ethylene copolymerization in a high temperature solution process, enhancing solubility, productivity, and comonomer incorporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional metallocene catalyst systems are used for ethylene copolymerization at high temperatures, then productivity is improved, but the balance of solubility, comonomer incorporation ability, and molecular weight capability deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the catalyst structure (using hafnocene instead of conventional metallocene, adding specific ligand substitutions) and process conditions (high temperature solution polymerization at 80-150°C) to achieve a new balance of properties. The specific parameter changes include using Hf-based catalysts with R1R2C(Ph) bridges and C1-C10 alkyl substituents on Cp ligands, which fundamentally alter the catalyst's performance characteristics to simultaneously improve productivity while maintaining solubility, comonomer incorporation, and molecular weight capability.
2Productivity
If high temperature solution polymerization is used to improve productivity, then production efficiency is improved, but polymer properties such as low density and high melt index become difficult to achieve
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system (using hafnocene with specific ligand configurations) to enable precise control of polymer properties at high temperatures. The Hf-based catalyst with R1R2C(Ph) bridges and specific substituents allows the polymerization to proceed at 80-150°C while achieving densities down to 0.850 g/cm³ and melt indices below 0.3 g/10 min, which would normally require lower temperature processing.
3Adaptability or versatility
If catalyst structure is modified to improve solubility, then solubility is improved, but productivity and molecular weight capability may deteriorate
Solution Approach 1:
The patent applies local quality by making specific localized modifications to the catalyst structure: adding C1-C10 alkyl substituents (methyl, ethyl, propyl, butyl groups) at specific positions on the Cp ligands and using R1R2C(Ph) bridges. These localized structural changes improve solubility in hydrocarbon solvents while the overall catalyst architecture (Hf center, fluorenyl ligand) maintains high productivity and molecular weight capability.
4Productivity
If conventional catalyst systems are used to achieve high molecular weight, then molecular weight capability is improved, but comonomer incorporation ability and solubility deteriorate
Solution Approach 1:
The patent creates a composite catalyst structure combining multiple elements: hafnocene center, fluorenyl ligand with 2,7-di-tert-butyl substitution, R1R2C(Ph) bridge, and additional C1-C10 alkyl substituents on Cp ligands. This composite structure achieves synergistic effects where the Hf center provides high molecular weight capability, the fluorenyml and bridge provide structural stability, and the alkyl substituents provide solubility and comonomer incorporation ability.
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 new catalyst system achieves improved polymer properties with balanced solubility, productivity, and comonomer incorporation, producing ethylene copolymers with densities down to 0.850 g/cm³ and melt indices below 0.3 g/10 min, suitable for various end-use applications.
Implementation Method 1
a new catalyst system comprising a metallocene complex with specific ligand configurations and a boron-containing cocatalyst is used for ethylene copolymerization
Data Source
Figure 1~2
Figure 3
AI summary
Catalyst system for producing ethylene copolymers in a high temperature solution process, the catalyst system comprising (i) a metallocene complex of formula (I), M is Hf or a mixture with Zr, provided that more than 50% by moles of the complex of Formula I has M = Hf, X is a sigma ligand, R are the same or different from each other and can be saturated linear or branched C1-C10 alkyl, C5-C10 aryl, C6-C20 alkylaryl or C6-C20 arylalkyl groups, which can optionally contain up to 2 heteroatoms or silicon atoms, R1 is a C6-C20-aryl, which can be unsubstituted or substituted by one or up to 5 linear or branched C1- C10 alkyl group(s), R2 is a saturated linear or cyclic C3 - C20 alkyl group or a branched CR3R4R5 group, wherein R3 is hydrogen or an C1 - C20 alkyl group and R4 and R5 are the same or are different and can be an C1 - C20 alkyl group and (ii) a boron containing cocatalyst