Multimodal Polyethylene Catalyst for Stable Multi-Stage Polymerization
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Solution Overview
Problem
Existing metallocene catalysts struggle to produce multimodal polyethylene polymers effectively in multi-stage polymerization processes due to challenges in maintaining stability, activity, and molecular weight control across different reaction conditions, particularly in slurry and gas phases.
Innovation Solution
The use of bridged bis-cyclopentadienyl type metallocene complexes with heterocyclic substituents, such as furanyl moieties, supported on a carrier, which exhibit high activity and comonomer incorporation capabilities, allowing for the production of multimodal polyethylene polymers with controlled molecular weights in both slurry and gas phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional metallocene catalysts are used in multi-stage polymerization, then catalyst stability is improved, but molecular weight control and activity across different phases deteriorates
Solution Approach 1:
The patent modifies the catalyst structure by changing parameters such as introducing heterocyclic substituents (furanyl moieties) on the cyclopentadienyl rings and using bridged bis-cyclopentadienyl configurations. These structural parameter changes enable the catalyst to maintain stability while achieving high activity in both slurry and gas phase polymerizations, resolving the contradiction between stability and productivity.
Solution Approach 2:
The invention creates a composite catalyst system combining metallocene complexes with heterocyclic substituents and bridged structures. This composite approach allows the catalyst to exhibit both stability (from the metallocene core) and enhanced activity (from the heterocyclic and bridged modifications), simultaneously satisfying both requirements.
2Manufacturing precision
If single site catalysts are used to produce controlled polymer structures, then manufacturing precision is improved, but adaptability to multi-stage processes deteriorates
Solution Approach 1:
The patent designs metallocene catalysts with universal functionality by incorporating heterocyclic substituents and bridged structures that enable the same catalyst system to operate effectively in multiple polymerization stages and phases. The catalyst maintains precise polymer structure control while adapting to different reaction conditions, achieving both manufacturing precision and process adaptability.
Solution Approach 2:
By adjusting catalyst structure parameters (heterocyclic substituents, bridged configurations), the invention creates a single-site catalyst that can adapt to multi-stage processes. The parameter changes enable the catalyst to maintain its single-site characteristics for precise control while gaining the versatility needed for multi-stage operation.
3Productivity
If catalyst activity is increased in gas phase, then productivity is improved, but stability in slurry phase deteriorates
Solution Approach 1:
The patent employs parameter changes by introducing heterocyclic substituents and bridged structures that differentially enhance catalyst properties. These structural modifications increase gas phase activity while maintaining slurry phase stability, resolving the contradiction between productivity and stability across different phases.
Solution Approach 2:
The invention applies local quality by having different parts of the catalyst structure serve different functions: the metallocene core provides stability in slurry phase, while the heterocyclic substituents and bridged structures enhance gas phase activity. This localized functional differentiation resolves the phase-specific performance contradiction.
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
These catalysts provide stable kinetic profiles in slurry phase and enhanced activity in gas phase, enabling the production of multimodal polyethylene polymers with high molecular weight and comonomer incorporation, addressing the limitations of previous catalysts in multi-stage processes.
Implementation Method 1
polymerising ethylene and optionally at least one C4-10 alpha olefin comonomer in a first stage in the presence of a metallocene catalyst
Data Source
AI summary
The invention provides a process for the preparation of a multimodal ethylene polymer in a multistage process in the presence of a catalyst comprising a complex of formula (Ix) wherein each X is a sigma donor ligand; each Het is independently a monocyclic or multicyclic heteroaromatic or heterocyclic group containing at least one heteroatom selected from O, N or S; 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 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 C1-10 alkyl group, C1-10 alkoxy group or —Si(R)3 group; each R is the same or different and is C1-10 alkyl or phenyl group optionally substituted by 1 to 3 C1-6 alkyl groups; and each p is 0 to 3.