Half-Sandwich Chromium Catalyst for Polyethylene Barrier Films
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Solution Overview
Problem
Polyethylene films exhibit permeability to moisture and gases such as oxygen and carbon dioxide, limiting their barrier properties, which is undesirable for applications like food packaging.
Innovation Solution
A catalyst system comprising a half-sandwich chromium complex, an activator support, and an optional cocatalyst is used to produce polymer resins with improved barrier properties, specifically polyethylene homopolymers that can be formed into films with enhanced moisture vapor transmission rate resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyethylene films are used, then they provide basic packaging functionality with good stiffness and ductility, but they exhibit high permeability to moisture and gases resulting in poor barrier properties
Solution Approach 1:
The patent employs parameter changes by utilizing a specific chromium-based catalyst system with particular ligand structures (Cp*Cr(Cl)2(Ln)) and activator combinations to produce polyethylene with modified molecular characteristics. This catalytic approach generates polymers with enhanced crystallinity and reduced permeability, directly addressing the barrier property deficiency while maintaining the inherent mechanical advantages of PE
2Reliability
If polyethylene films are used for packaging applications, then they offer cost-effectiveness and mechanical strength, but their permeability to moisture and gases limits their suitability for applications requiring improved barrier properties
Solution Approach 1:
By changing the catalytic parameters and polymerization conditions using the disclosed chromium complex system, the patent produces polyethylene with tailored molecular weight distributions and enhanced crystalline structures. These parameter modifications result in films with superior barrier properties, expanding the adaptability of PE for food packaging applications where moisture and gas resistance are critical
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 enhances the barrier properties of polyethylene films, reducing moisture vapor transmission rates and improving their suitability for food packaging applications.
Implementation Method 1
a catalyst system comprising a half-sandwich chromium complex, an activator support and an optional cocatalyst
Data Source
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AI summary
A catalyst system comprising a half-sandwich chromium complex, an activator support and an optional cocatalyst. A compound of formula Cp'Cr(C1)2(Ln), where Cp' is ?5- C5H4CH2CH2CH=CH2 and Ln is pyridine, THF or diethylether. A compound of formula Cp"Cr(C1)2(Ln), where Cp" is ?5-C5H4C(Me)2CH2CH2CH=CH2 and Ln is pyridine, THF or diethylether.