Bridged Metallocene Catalysts for Stable Multimodal Polymerization
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Solution Overview
Problem
Existing metallocene catalysts struggle to maintain stability and performance across different reaction conditions in multi-stage polymerization processes, particularly in producing multimodal polymers with varying molecular weights and comonomer concentrations, while achieving high catalyst activity and controlled polymer architecture.
Innovation Solution
Development of bridged bis-cyclopentadienyl type metallocene complexes with heterocyclic substituents, such as furanyl moieties, which are supported on a carrier, offering enhanced stability, higher activity, and improved comonomer incorporation capabilities, allowing for the production of multimodal polymers with controlled molecular weights and morphologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metallocene catalysts are used in multi-stage polymerization, then catalyst stability is improved, but catalyst activity and comonomer incorporation capability deteriorate
Solution Approach 1:
The patent modifies the catalyst system by changing the metallocene complex parameters (using bridged bis-cyclopentadienyl structures with heterocyclic substituents like furanyl moieties) and support characteristics to achieve both high stability and high activity. This allows the catalyst to maintain performance across different reaction conditions in multi-stage processes while producing multimodal polymers with controlled molecular weights and high comonomer incorporation.
Solution Approach 2:
The invention employs composite catalyst systems combining metallocene complexes with specific supports (such as silica or alumina) to create a synergistic effect. The support provides stability and mechanical strength while the metallocene complex provides catalytic activity and comonomer incorporation capability, resolving the contradiction between stability and activity.
2Manufacturing precision
If single site catalysts are used to produce controlled polymer structures, then polymer architecture control is improved, but catalyst stability under different reaction conditions deteriorates
Solution Approach 1:
The patent modifies the metallocene complex structure (using bridged bis-cyclopentadienyl type complexes with heterocyclic substituents) to enhance kinetic stability while preserving single-site catalysis characteristics. This allows the catalyst to maintain controlled polymer architecture production across varying reaction conditions including slurry and gas phase polymerizations.
Solution Approach 2:
The support material acts as an intermediary that stabilizes the metallocene complex under different reaction conditions. The support provides a stable framework that maintains the catalytic site's integrity while allowing the metallocene complex to produce controlled polymer structures across multiple stages and different polymerization modes.
3Productivity
If catalyst activity is increased in gas phase, then productivity is improved, but comonomer incorporation capability deteriorates
Solution Approach 1:
The patent optimizes the metallocene complex parameters (bridged bis-cyclopentadienyl structure with heterocyclic substituents) to achieve a favorable balance between gas phase activity and comonomer incorporation. The specific molecular structure and support characteristics allow the catalyst to maintain high activity in gas phase while preserving the ability to incorporate comonomers effectively, enabling production of multimodal polymers with controlled composition.
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 metallocene complexes demonstrate higher activity, better comonomer incorporation, and stable kinetic profiles in both slurry and gas phases, enabling the production of polymers with desired properties, including high molecular weight capability and good powder morphology.
Implementation Method 1
The invention concerns certain novel metallocene complexes and catalysts made therefrom... a process for the preparation of an olefin polymer, such as a polyethylene or polypropylene polymer, especially a polyethylene polymer, using said metallocene catalyst
Data Source
AI summary
A racemic metallocene complex of formula (I′) wherein each X is a sigma donor ligand; L is a carbon, silicon or germanium based divalent bridge in which one or two backbone atoms link the ligands; M is Ti, Zr or Hf; each Het is independently a monocyclic or multicyclic heteroaromatic or heterocyclic group containing at least one heteroatom selected from O, N or S; each R1 is the same or different and is a linear C1-10 alkyl group, or linear C1-10 alkoxy, each n is 0 to 3; each R2 is the same or different and is a —Si(RaRbRc) group; Ra is C1-10 alkyl or phenyl group optionally substituted by 1 to 3 C1-6 alkyl groups; Rb is C1-10 alkyl or phenyl group optionally substituted by 1 to 3 C1-6 alkyl groups; Rc is a phenyl group optionally substituted by 1 to 3 C1-6 alkyl groups; and each p is 1 to 3.