Ansа-Metallocene Catalyst for High Molecular Weight Polyolefins
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Solution Overview
Problem
Existing metallocene catalysts are not suitable for producing polypropylene with high molecular weight and low melt index, leading to limitations in film applications requiring transparency and low volatility, and suffer from leaching issues during polymerization, affecting catalyst activity and particle formation.
Innovation Solution
A transition metal compound with an ansa-metallocene structure and specific cocatalyst composition, including aluminum and boron compounds, is used for polymerizing olefin monomers to achieve high molecular weight and low melt index polyolefins, minimizing fine particle production and enhancing catalyst activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing asymmetric structure metallocene catalyst is used, then catalyst activity is improved, but molecular weight decreases and melt index increases
Solution Approach 1:
The patent modifies the ligand structure parameters of the metallocene catalyst, specifically using a cyclopentadienyl-fluorenyl ligand system with specific substitution patterns (R1-R6 groups) to achieve optimal balance between activity and molecular weight control
Solution Approach 2:
The catalyst system combines metallocene compound with specific cocatalysts (aluminoxane or alkyl aluminum compound) to create a composite catalytic system that enhances both activity and molecular weight control capabilities
2Productivity
If existing asymmetric structure metallocene catalyst is used, then catalyst activity is improved, but melt index increases
Solution Approach 1:
The patent adjusts the steric and electronic parameters of the ligand structure to control the polymerization kinetics, achieving low melt index (≤30 g/10min) while maintaining high catalyst activity through optimized R1-R6 substituent groups
3Productivity
If existing asymmetric structure metallocene catalyst is used, then catalyst activity is improved, but leaching occurs during polymerization
Solution Approach 1:
The patent introduces aluminoxane or alkyl aluminum compound as intermediary substances that form stable complexes with the metallocene catalyst, preventing catalyst leaching while maintaining high activity during the polymerization process
4Productivity
If existing asymmetric structure metallocene catalyst is used, then catalyst activity is improved, but fine particle production increases
Solution Approach 1:
The cocatalyst system acts as a mediator that controls catalyst particle formation, reducing fine particle generation (≤0.5 wt%) while maintaining high catalyst activity through controlled polymerization kinetics
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 solution enables the production of polyolefins with excellent activity, high molecular weight, and low melt index, improving physical properties and reducing leaching-related issues, making it suitable for transparent film applications.
Implementation Method 1
a metallocene catalyst system, which is composed of a metallocene compound of a transition metal of group 4 in the periodic table, such as titanium, zirconium and hafnium and methylaluminoxane as a co-catalyst, is a homogeneous catalyst having a catalyst active site of a single species
Data Source
AI summary
Disclosed are a novel metallocene catalyst and a method for preparing a polyolefin having a high molecular weight and a low melt index by using the same. The present invention provides a transition metal compound represented by formula 1.