Multimodal Polymer Catalyst System for Molecular Weight Distribution Control
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Solution Overview
Problem
There is an ongoing need for improved catalyst systems to produce multimodal polyethylene resins with specific molecular weight distributions and processing characteristics, such as high zero shear viscosity and tensile natural draw ratio, to enhance the performance and applicability of polyolefins.
Innovation Solution
A polymer reactor-blend comprising a first component with a polydispersity index greater than 20 and a second component with a polydispersity index less than 20, using a catalyst composition that includes an imine (bis)phenolate compound and a metallocene complex, which is used to polymerize ethylene and 1-hexene, resulting in a polymer with tailored molecular weight distribution and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single catalyst system is used for polymerization, then the production process is simple, but the molecular weight distribution and processing characteristics cannot be optimized
Solution Approach 1:
The patent divides the catalyst system into multiple distinct catalyst compositions, each with specific ligand structures (e.g., compounds of formulas 1-4). Each catalyst component is designed to produce polymer with specific molecular weight characteristics, allowing precise control over the overall molecular weight distribution when combined.
Solution Approach 2:
The patent systematically varies key parameters of the catalyst ligands including substituents (R1-R6), bridging groups (E), and metal centers (M) to tune the polymerization activity and molecular weight distribution. By changing these chemical parameters, the catalyst produces polymers with tailored properties for specific applications.
2Strength
If polymer with high molecular weight is produced, then the mechanical strength is improved, but the processing characteristics deteriorate
Solution Approach 1:
The patent creates a multimodal molecular weight distribution where different portions of the polymer population have different molecular weights. The high molecular weight portion (from certain catalyst components) provides mechanical strength, while the low molecular weight portion (from other catalyst components) provides processability. Each catalyst component contributes specific local quality to the overall polymer properties.
Solution Approach 2:
The patent produces a composite polymer material with multimodal molecular weight distribution by combining products from multiple catalyst systems. This composite structure integrates the advantages of both high and low molecular weight polymers, achieving a balance between mechanical strength and processing characteristics that cannot be obtained from a single homogeneous polymer.
3Adaptability or versatility
If multimodal polymer resin is produced with multiple catalysts, then the performance and applicability are enhanced, but the catalyst system complexity increases
Solution Approach 1:
The patent designs catalyst ligands with universal features that can be systematically modified. The core ligand structure (e.g., compounds of formulas 1-4) serves as a universal platform that can be adapted to produce different polymer properties by changing substituents and bridging groups, allowing a single catalyst design approach to address multiple application requirements.
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 solution achieves polymers with desired molecular weight distribution and processing characteristics, including high zero shear viscosity and tensile natural draw ratio, thereby improving the performance and applicability of polyolefins for various applications.
Implementation Method 1
contacting ethylene monomer and 1-hexene with a catalyst composition comprising (i) an imine (bis) phenolate compound having Structure XIV wherein M is a Group 3 to Group 12 transition metal or lanthanide; R2 and R3 can each independently be hydrogen, a halogen, a hydrocarbyl group, or a substituted hydrocarbyl group and (ii) a metallocene complex under conditions suitable for the formation of a polymer
Data Source
AI summary
A polymer reactor-blend comprising at least a first component having a polydispersity index of greater than about 20 and is present in an amount of from about 1 wt. % to about 99 wt. % based on the total weight of the polymer and a second component having a polydispersity index of less than about 20 and is present in an amount of from about 1 wt. % to about 99 wt. % based on the total weight of the polymer wherein a molecular weight distribution of the second component lies within a molecular weight distribution of the first component.