Ans-Metallocene Catalyst for High Molecular Weight Polyolefins
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Solution Overview
Problem
Existing metallocene catalysts face challenges in producing high molecular weight polyolefins with even comonomer composition distribution and desired properties, as they often form both racemate and meso diastereomers during the preparation process, leading to limitations in polymer properties like crystallinity and mechanical strength.
Innovation Solution
A novel ansa-metallocene compound with a specific structure, featuring two indenyl groups connected by a bridge group with a Lewis base functional group and a bulky aryl substituent, which maximizes catalyst activity and prevents meso-form formation, allowing for the production of polyolefins with enhanced molecular weight and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional metallocene catalysts are used for polyolefin preparation, then the catalyst shows acceptable activity, but the molecular weight of the resulting polyolefin is limited and cannot achieve high molecular weight
Solution Approach 1:
The patent modifies the chemical parameters of the metallocene catalyst by introducing a specific bridge group structure connecting two indenyl ligands, and by selecting particular substituents (R1-R6 groups) to optimize the electronic and steric environment around the metal center. These parameter changes enable the catalyst to produce high molecular weight polyolefins while maintaining stable activity
Solution Approach 2:
The catalyst employs a composite structure combining a transition metal center (zirconium or hafnium) with a specially designed organic ligand system featuring a bridge group and multiple substituent groups. This composite architecture provides both the necessary catalytic activity and the ability to generate high molecular weight polymers
2Strength
If conventional metallocene catalysts are used, then the preparation process is straightforward, but both racemate and meso diastereomers are formed simultaneously, leading to mixed polymer structures with reduced crystallinity and mechanical strength
Solution Approach 1:
The patent introduces asymmetry through the bridge group structure and chiral substituents on the indenyl ligands. This asymmetric design creates a chiral environment that favors the formation of one enantiomer over the other, enabling selective production of the racemate form which leads to isotactic polymers with high crystallinity and mechanical strength
Solution Approach 2:
The catalyst structure is pre-designed with steric hindrance elements and specific geometric constraints that prevent the formation of the meso diastereomer from the outset. The bridge group and substituent positions are arranged to create repulsive interactions that block the meso-form formation pathway before the reaction occurs
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 novel metallocene compound achieves higher catalytic activity and produces polyolefins with improved molecular weight, crystallinity, and mechanical strength, while minimizing the formation of undesirable meso-forms, thus overcoming the limitations of traditional catalysts.
Implementation Method 1
The present invention relates to a metallocene catalyst having novel structure for preparing a high molecular weight polyolefin
Data Source
AI summary
The present invention relates to a metallocene compound having novel structure which can provide various selectivity and activity to polyolefin copolymers, a preparation method thereof, and a preparation method of polyolefin using the metallocene compound.