Metallocene Catalyst Ligand Design for Polyolefin Molecular Weight
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Solution Overview
Problem
Existing catalysts struggle to achieve high molecular weight ethylene-based polymers with high comonomer incorporation, particularly with sterically encumbered olefins, due to low reactivity and resulting sub-optimal mechanical properties.
Innovation Solution
A compound according to formula I, where each R1-R10 can be H or various organic moieties, Y is O or N—R11, and M is a group 3 or 4 transition metal, is used in a catalyst system for olefin polymerization, enhancing catalyst activity, comonomer incorporation, and molecular weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional catalysts are used for ethylene polymerization, then polymer production is achieved, but the molecular weight remains insufficient for high-demanding applications
Solution Approach 1:
The patent modifies the ligand structure parameters of the metallocene catalyst, specifically using bridged bicyclic ligands with controlled steric bulk and electronic properties to optimize both molecular weight and catalyst activity simultaneously
Solution Approach 2:
The catalyst system combines metallocene compound with specific bridged bicyclic ligands and aluminoxane activators to create a composite catalytic system that achieves superior performance compared to individual components
2Quantity of substance
If high concentrations of comonomer are used to improve incorporation, then comonomer content increases, but energy-intensive separation and recycling processes are required
Solution Approach 1:
The catalyst modifies the polymerization kinetics parameters to enhance comonomer reactivity ratio, enabling high comonomer incorporation at lower comonomer concentrations and reducing separation requirements
3Productivity
If conventional catalysts are used with sterically encumbered olefins, then polymerization occurs, but reactivity towards comonomers is low
Solution Approach 1:
The bridged bicyclic ligand creates a specific local geometry at the metal center that provides optimal steric environment for comonomer coordination and insertion, enhancing reactivity towards sterically encumbered olefins
Solution Approach 2:
The patent introduces a bridging dimension between the cyclopentadienyl rings, creating a three-dimensional rigid structure that controls the steric environment and enhances comonomer reactivity
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 catalyst activity, significant comonomer incorporation, and high molecular weight polymers, particularly with sterically hindered olefins, thereby addressing the limitations of existing catalysts.
Implementation Method 1
compounds that are suitable for use as single-site type catalyst for the production of polyolefins
Data Source
AI summary
The present invention relates to compounds according to formula I:wherein: each R1-R10 may individually be H, a halogen, an alkoxy moiety, a siloxy moiety, a nitrogen-containing moiety, an alkyl moiety, an aryl moiety, or an aralkyl moiety, wherein each R1-R10 comprises ≤10 carbon atoms, wherein each of R1-R10 may form a cyclic moiety with an adjacent R1-R10 moiety; Y is O or N—R11, wherein R11 is an alkyl, cycloalkyl, aryl or aralkyl moiety comprising 1-12 carbon atoms; M is a group 3 or 4 transition metal; X is a sigma-bonded ligand, or a diene; z is the number of ligands X that are bonded to M. Such compounds may be used in a catalyst system for olefin polymerisation.