Si-Si Bridged Metallocene Catalysts for Polyolefin Composition Control
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Solution Overview
Problem
Current catalyst systems struggle to produce polyolefins with high molecular weight, high comonomer content, narrow polydispersity indices, and broad orthogonal composition distribution, which are essential for achieving balanced mechanical and processing properties.
Innovation Solution
Development of bridged metallocene catalyst compounds with -Si-Si- bridges, specifically hafnium-containing compounds with cyclopentadiene ligands and silyl neopentyl groups, used in polymerization processes to produce polyolefins with high productivity, molecular weight, and specific composition distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional metallocene catalysts are used, then narrow composition distribution is achieved, but high molecular weight and high comonomer content cannot be simultaneously obtained
Solution Approach 1:
The patent modifies the catalyst structure by introducing -Si-Si- bridges between cyclopentadiene ligands and incorporating silyl neopentyl groups. This structural parameter change fundamentally alters the catalyst's electronic and steric properties, enabling it to simultaneously achieve narrow composition distribution, high molecular weight, and high comonomer content - a combination previously unattainable with conventional metallocene catalysts.
2Strength
If high molecular weight polyolefins are produced, then desirable mechanical properties are achieved, but processing difficulty increases
Solution Approach 1:
The patent creates local quality variation through broad orthogonal composition distribution, where different molecular weight fractions have different comonomer contents. High molecular weight fractions provide mechanical strength while low molecular weight fractions with higher comonomer content improve processability. This local differentiation within the polymer composition resolves the contradiction between strength and ease of operation.
3Reliability
If broad orthogonal composition distribution is achieved, then improved physical properties are obtained, but catalyst complexity increases
Solution Approach 1:
The patent creates a composite catalyst structure combining cyclopentadiene ligands, -Si-Si- bridge units, and silyl neopentyl groups. This composite structure integrates multiple functional elements that work synergistically: the -Si-Si- bridges provide structural rigidity and control stereochemistry, while silyl neopentyl groups modulate electron density and steric environment. The result is a catalyst that produces broad orthogonal composition distribution with improved physical properties.
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 achieves high productivity and produces polyolefins with high molecular weight, high comonomer content, narrow polydispersity indices, and broad orthogonal composition distribution, enhancing mechanical and processing properties.
Implementation Method 1
The present invention provides bridged metallocene catalyst compounds comprising -Si-Si- bridges, catalyst systems comprising such compounds, and uses thereof
Data Source
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AI summary
The present disclosure provides bridged metallocene catalyst compounds comprising - Si-Si- bridges, catalyst systems comprising such compounds, and uses thereof. Catalyst compounds of the present disclosure can be hafnium-containing compounds having one or more cyclopentadiene ligand(s) substituted with one or more silyl neopentyl groups and linked with an Si-Si-containing bridge. In another class of embodiments, the present disclosure is directed to polymerization processes to produce polyolefin polymers from catalyst systems comprising one or more olefin polymerization catalysts, at least one activator, and an optional support.