Boron-Bridged Metallocene Catalysts for Polyolefin Control
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Solution Overview
Problem
Current catalyst systems for producing polyolefins, such as HDPE and LLDPE, face challenges in achieving a combination of flat comonomer distribution and low long chain branching, along with easy control of molecular weight distribution during polymerization.
Innovation Solution
The development of boron-bridged metallocene compounds with an alkenyl substituent, used in catalyst compositions that include these metallocene compounds, activators, and optional co-catalysts like organoaluminum compounds, to facilitate efficient polymerization of olefins and produce polymers with desired properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional catalyst systems are used for polymerization, then polymer production is achieved, but the comonomer distribution becomes uneven and long chain branching increases
Solution Approach 1:
The patent modifies the chemical structure of metallocene catalysts by introducing specific substituent groups (such as fluorenyl and cyclopentadienyl combinations with particular R1-R6 groups) to change the catalytic parameters. This structural modification enables better control over comonomer insertion behavior, achieving more uniform comonomer distribution and reduced long chain branching compared to conventional catalysts.
Solution Approach 2:
The invention employs composite catalyst systems combining metallocene compounds with specific ligand structures (formula I) and co-catalysts (MAO or organoboron compounds). This composite approach creates a synergistic effect where the specialized metallocene structure works with the activator system to achieve precise control over polymer microstructure, resolving the contradiction between production efficiency and structural control.
2Manufacturing precision
If conventional catalyst systems are used, then polymerization proceeds, but molecular weight distribution control becomes difficult
Solution Approach 1:
The patent utilizes specific parameter modifications in the metallocene structure (formula I), particularly the arrangement and type of substituent groups (R1-R6), to tune the catalytic activity and stereoselectivity. These parameter changes enable better molecular weight distribution control through enhanced control over propagation and termination rates, while maintaining manageable catalyst system complexity.
3Object-generated harmful factors
If catalyst systems aim to achieve low long chain branching, then polymer structure improves, but comonomer incorporation efficiency decreases
Solution Approach 1:
The invention optimizes the catalytic parameters by selecting specific metallocene structures with particular ligand combinations (Cp and fluorenyl groups with defined substituents). These parameter optimizations create a catalyst system that maintains high comonomer incorporation efficiency while simultaneously suppressing unwanted long chain branching, resolving the trade-off between productivity and polymer quality.
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 catalyst compositions enable the production of polyolefins with controlled molecular weight distribution and low long chain branching, achieving improved polymer properties suitable for various applications.
Implementation Method 1
boron-bridged metallocene compounds containing an alkenyl substituent, and to catalyst compositions employing such metallocene compounds. Catalyst compositions of the present invention that contain these boron-bridged metallocene compounds can be used to produce, for example, ethylene-based homopolymers and copolymers
Data Source
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AI summary
Disclosed herein are catalyst compositions containing boron-bridged, cyclopentadienyl-fluorenyl metallocene compounds with an alkenyl substituent. These catalyst compositions can be used for the polymerization of olefins. For example, ethylene copolymers produced using these catalyst compositions can be characterized by a combination of a flat or a conventional comonomer distribution and low levels of long chain branching.