Asymmetric ANSA-Metallocene Catalyst for Broad Polyolefin Distribution
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Solution Overview
Problem
There is a need for new catalyst systems that utilize a single catalyst compound to produce polyolefins with a broad and/or bimodal molecular weight distribution, which is challenging with existing technologies that often require dual catalyst systems or specific stereoisomers.
Innovation Solution
The development of asymmetric ansa-metallocene catalyst compounds, represented by Formula (I), which include a group 4 metal, a branched alkyl group, and specific substituents, used in conjunction with an activator to achieve polymerization processes that produce polyolefins with desired molecular weight distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dual catalyst system is used to produce polyethylene with broad molecular weight distribution, then the molecular weight distribution is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple catalytic functions into a single metallocene catalyst compound that can produce broad molecular weight distribution polymers. The asymmetric metallocene structure with specific substituents enables the catalyst to perform both high and low molecular weight polymerization activities simultaneously, eliminating the need for dual catalyst systems while achieving the desired broad molecular weight distribution.
Solution Approach 2:
The patent employs asymmetric metallocene catalyst compounds with specific chiral configurations and substituted indenyl groups. The asymmetric structure creates different steric environments that facilitate diverse polymerization pathways, enabling the single catalyst to produce polymers with broad molecular weight distribution without requiring multiple catalyst components.
2Device complexity
If a single catalyst compound is used to simplify the catalyst system, then the device complexity is reduced, but the ability to produce broad molecular weight distribution polymers is worsened
Solution Approach 1:
The patent modifies the structural parameters of the metallocene catalyst by introducing specific substituents at defined positions on the indenyl rings. These parameter changes in the catalyst structure (substituent types, positions, and configurations) enable the single catalyst compound to achieve broad molecular weight distribution polymerization capability that was previously only attainable with dual catalyst systems.
3Manufacturing precision
If stereorigid metallocene compounds with specific stereoisomers are used to achieve broad molecular weight distribution, then the molecular weight distribution is improved, but the ease of manufacture is worsened
Solution Approach 1:
The patent utilizes asymmetric metallocene structures with defined stereoisomers that can be synthesized through established asymmetric synthesis methodologies. The specific asymmetric configuration of the metallocene catalyst enables broad molecular weight distribution polymerization while maintaining reasonable synthetic accessibility through conventional organometallic synthesis techniques.
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 catalyst system effectively produces polyolefins with broad and/or bimodal molecular weight distributions, improving processability and toughness, and allows for the production of linear low density polyethylene with uniform comonomer distribution and high molecular weight characteristics.
Implementation Method 1
Catalysts for olefin polymerization typically have transition metals. For example, some catalysts are ansa-metallocenes, i.e., 'bridged' metallocenes, which can be activated by alumoxane or an activator containing a non-coordinating anion.
Data Source
AI summary
The present disclosure relates to asymmetric ansa-metallocene catalyst compounds that include at least one indenyl ligand substituted at the 3-position with a C3-C40 α-branched alkyl, such as 1-methylethyl, 1-methylpropyl, 1-methylbutyl, 1-ethylbutyl, 1,3-dimethylbutyl, 1-methyl-1-ethylbutyl, 1,1-diethylbutyl, 1-propylpentyl, and the like. Catalyst systems prepared with the catalyst compounds, polymerization methods using such catalyst systems, and polyolefins made using the polymerization methods are also described.