Tetrafluoroethylene Copolymer Emulsion Polymerization Without PFAS
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Solution Overview
Problem
Fluoropolymers with high TFE content often contain extractable perfluorinated alkanoic acids, which are poorly biodegradable and pose environmental concerns, despite efforts to avoid their use in production, as they can still be generated during polymerization without traditional fluorinated emulsifiers.
Innovation Solution
Development of tetrafluoroethylene copolymers with a high content of perfluorinated alkyl allyl ether comonomers, produced through aqueous emulsion polymerization without added perfluorinated alkanoic acid emulsifiers, followed by anion exchange treatment to minimize extractable perfluorinated alkanoic acids, resulting in polymers with improved mechanical properties and reduced environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fluorinated emulsifiers (perfluorinated alkanoic acids) are used in aqueous emulsion polymerization, then polymerization efficiency and emulsion stability are improved, but extractable perfluorinated alkanoic acids are generated in the polymer product, causing environmental harm due to poor biodegradability
Solution Approach 1:
The invention extracts and removes the harmful perfluorinated alkanoic acid emulsifiers from the polymerization system entirely. By using alternative non-fluorinated emulsifiers or emulsifier-free conditions, the source of the harmful substances is eliminated, preventing their incorporation into the polymer structure and subsequent extraction into the final product.
Solution Approach 2:
The invention employs biodegradable alternative emulsifiers that can be easily degraded and removed, replacing the persistent perfluorinated alkanoic acids. These alternative emulsifiers serve their function during polymerization but do not persist in the final product, effectively being 'disposable' in the sense that they are temporary and environmentally benign.
2Strength
If perfluorinated alkanoic acids are used as emulsifiers in high TFE content copolymers, then good mechanical properties and processability are achieved, but the polymers contain significant amounts of extractable perfluorinated alkanoic acids that are difficult to remove
Solution Approach 1:
The harmful perfluorinated alkanoic acid component is completely removed from the emulsifier system. The invention uses alternative emulsification mechanisms that do not rely on fluorinated compounds, thereby eliminating the source of extractable harmful substances while maintaining the necessary emulsion stability for producing high TFE content copolymers with good mechanical properties.
Solution Approach 2:
The invention introduces alternative emulsifiers (non-fluorinated or biodegradable fluorinated compounds) as intermediary substances that perform the emulsification function without introducing persistent harmful residues. These intermediary emulsifiers enable the polymerization process while being environmentally compatible and easily removable.
3Object-generated harmful factors
If methods are developed to remove emulsifiers from polymer dispersions, then extractable perfluorinated alkanoic acid content is reduced, but additional processing steps and complexity are introduced
Solution Approach 1:
The invention takes preliminary action by selecting emulsifiers that are inherently easy to remove or that do not require complex removal processes. By choosing biodegradable alternative emulsifiers from the beginning, the need for sophisticated post-polymerization treatment steps is minimized, as these emulsifiers can be removed through simple biological degradation or standard washing procedures.
Solution Approach 2:
The invention employs emulsifiers that are temporarily present during polymerization but are designed to be easily eliminated afterward. The alternative emulsifiers used are biodegradable and can be removed through simple processing, avoiding the need for complex removal technologies while still achieving low extractable contaminant levels in the final product.
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 resulting copolymers exhibit excellent mechanical properties, such as high melting points and melt flow indices, while being essentially free of extractable perfluorinated alkanoic acids, addressing the environmental concerns associated with their poor biodegradability.
Implementation Method 1
a melting point of from about 250 °C to about 326 °C
Implementation Method 2
copolymerizing tetrafluoroethylene, the one or more perfluoro alkyl allyl ethers and, optionally, the one or more copolymerizable optional comonomers through aqueous emulsion polymerization
Implementation Method 3
subjecting the reaction mixture to anion exchange treatment in the presence of one or more non-fluorinated emulsifier
Data Source
AI summary
Disclosed is a tetrafluoroethylene copolymer, methods of making the polymer, and articles comprising the polymer and methods of making the articles.