Thermally Treated Magnesium Chloride Procatalyst for Molecular Weight Control
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Solution Overview
Problem
Existing Ziegler-Natta catalysts for producing ethylene-based polymers, such as LLDPE, result in broad polydispersity and undesirably broad short chain branching distribution (SCBD), with limited molecular weight capability and high comonomer weight percent, limiting the production of differentiated polymers with increased weight average molecular weight (Mw) and high density fraction (HDF).
Innovation Solution
A heterogeneous Ziegler-Natta procatalyst system incorporating a thermally treated magnesium chloride component, combined with a titanium species and a chlorinating agent, enhances molecular weight capability and reduces comonomer content, allowing for the production of ethylene-based polymers with increased Mw and HDF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Ziegler-Natta catalysts are used for ethylene polymerization, then the polymerization process is effective and produces LLDPE, but the resulting resin has broad polydispersity and undesirably broad short chain branching distribution
Solution Approach 1:
The patent applies parameter changes by thermally treating the magnesium chloride support at elevated temperatures (100-500°C) to modify its surface properties and morphology. This thermal treatment alters the support's characteristics, enabling better control over polymer molecular weight and branching distribution while maintaining catalytic effectiveness
Solution Approach 2:
The patent employs composite materials by combining thermally treated magnesium chloride support with specific titanium species and electron-donating compounds. This composite catalyst system synergistically improves both the precision of polymer structure control and the versatility of molecular weight capability
2Quantity of substance
If conventional Ziegler-Natta catalysts are used, then the catalyst system is simple and effective, but the molecular weight capability is limited and comonomer weight percent is high
Solution Approach 1:
The patent applies preliminary action by pre-treating the magnesium chloride support with heat before introducing the titanium species and other catalyst components. This preliminary thermal treatment prepares the support surface to enhance subsequent catalyst formation, enabling improved molecular weight capability without significantly increasing overall system complexity
Solution Approach 2:
The patent uses electron-donating compounds as intermediaries that mediate between the titanium species and the polymerization process. These intermediaries modulate the catalyst's electronic properties, enabling better control over comonomer incorporation and molecular weight while maintaining reasonable system complexity
3Manufacturing precision
If conventional Ziegler-Natta catalysts are used to produce LLDPE, then the process is straightforward, but the short chain branching distribution is broad and comonomer content is high
Solution Approach 1:
The patent applies parameter changes by modifying the thermal treatment conditions of the magnesium chloride support (temperature, time, atmosphere) to optimize the catalyst's ability to control comonomer incorporation. These parameter adjustments enable narrower short chain branching distribution and reduced comonomer content in the resulting polymer
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 procatalyst system produces ethylene-based polymers with improved molecular weight, higher density fraction, and reduced comonomer content, enabling the production of polymers with tunable properties and narrower molecular weight distribution.
Implementation Method 1
thermally treating an untreated magnesium chloride slurry at a temperature of from 150 °C to 500 °C for at least 30 minutes
Implementation Method 2
at least one titanium species adsorbed onto the thermally treated magnesium chloride component
Data Source
AI summary
A heterogeneous procatalyst includes a titanium species, a magnesium chloride component, and a chlorinating agent having a structure A(C1)x(R1)3-x, where A is aluminum or boron, R1 is a (C1-C30) hydrocarbyl, and x is 1, 2, or 3. The magnesium chloride component may be thermally treated at a temperature greater than 100 C for at least 30 minutes before or after introduction of the chlorinating agent and titanium species to the heterogeneous procatalyst. The heterogeneous procatalyst having the thermally treated magnesium chloride exhibits improved average molecular weight capability. Processes for producing the heterogeneous procatalyst and processes for producing ethylene-based polymers utilizing the heterogeneous procatalyst are also disclosed.