Alkane-Soluble Non-Metallocene Precatalysts for Olefin Polymerization
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Solution Overview
Problem
The existing catalyst systems for olefin polymerization face challenges with transition complexity and stability, particularly with insoluble non-metallocene precatalysts like HN5Zr dibenzyl, which are unstable and require cooling, and result in bimodal polyethylene compositions with high gel content and limited flexibility in molecular weight ratios.
Innovation Solution
A new compound with silicon-free organic solubilizing groups is introduced, providing increased solubility in alkanes and improved catalyst light-off, allowing for a more stable and flexible catalyst system that can be used in both parts of the combining-the-parts feed method, enabling better control over bimodal polyethylene compositions and reducing gel content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If insoluble non-metallocene precatalysts are used, then higher molecular weight polyethylene component is produced, but gel content increases and stability decreases
Solution Approach 1:
The patent modifies the chemical structure of the precatalyst by introducing silicon-free organic solubilizing groups (such as alkyl, aryl, or alkylaryl groups) attached to the ligand framework. This structural parameter change increases solubility in alkanes while maintaining the catalyst's ability to produce high molecular weight polyethylene, thereby resolving the contradiction between molecular weight production and catalyst stability/solubility
Solution Approach 2:
The invention creates a composite catalyst system combining the non-metallocene precatalyst with metallocene precatalyst in a bimodal system. The non-metallocene component (with solubilizing groups) produces HMW polyethylene while the metallocene component produces LMW polyethylene. This composite approach allows the system to achieve both high molecular weight production and improved stability through the solubilizing groups, while also enabling control over gel content through the bimodal composition
2Quantity of substance
If insoluble non-metallocene precatalysts are used, then higher molecular weight polyethylene component is produced, but gel content increases
Solution Approach 1:
By changing the solubility parameter of the precatalyst through addition of silicon-free organic solubilizing groups, the catalyst remains better dispersed in the reaction medium. This improved dispersion prevents localized aggregation that leads to gel formation, while still enabling the production of high molecular weight polyethylene. The solubilizing groups modify the interaction between catalyst and solvent, reducing harmful gel byproducts
Solution Approach 2:
The bimodal catalyst system combines HMW-producing non-metallocene precatalyst with LMW-producing metallocene precatalyst. The LMW component acts as a modifier that reduces the harmful gel content generated by the HMW component, while the solubilizing groups on the non-metallocene precatalyst further reduce gel formation. This composite approach allows production of HMW polyethylene with controlled, reduced gel content
3Reliability
If cooling is applied to stabilize insoluble non-metallocene precatalysts, then stability improves, but operational complexity increases
Solution Approach 1:
The invention changes the thermal parameter of the precatalyst by introducing organic solubilizing groups that stabilize the catalyst structure at higher temperatures. These groups modify the electronic and steric environment around the metal center, increasing thermal stability and eliminating the need for cooling. The precatalyst becomes inherently stable under standard polymerization conditions without requiring temperature control infrastructure
Solution Approach 2:
The patent removes the requirement for cooling infrastructure by extracting the instability problem through molecular design. Instead of managing thermal instability through external cooling, the solution is embedded in the molecular structure itself through the addition of stabilizing solubilizing groups. This eliminates the harmful factor (instability) at its source rather than managing it through complex cooling systems
4Adaptability or versatility
If combining-the-parts feed method is used, then flexibility in polymerization rate is improved, but transition complexity increases
Solution Approach 1:
The patent modifies the chemical parameter of the precatalyst by adding silicon-free organic solubilizing groups, which improves solubility and creates a more uniform catalyst system. This uniformity simplifies transitions between different polymerization conditions and catalyst formulations, reducing the complexity associated with the combining-the-parts feed method while maintaining its flexibility for rate control
Data Source
AI summary
A compound of formula (1) as drawn herein, wherein M is a Group 4 metal and each R independently is a silicon-free organic solubilizing group. A method of synthesizing the compound (1). A solution of compound (1) in alkane solvent. A catalyst system comprising or made from compound (1) and an activator. A method of polymerizing an olefin monomer with the catalyst system.