Modified PTFE Fine Powder for Paste Extrusion and Hose Strength
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Solution Overview
Problem
The use of fluorinated emulsifiers with low bioaccumulation properties in polytetrafluoroethylene (PTFE) production leads to deteriorated moldability and mechanical properties of molded articles, and the feasibility of producing modified PTFE fine powder at general polymerization pressures is unclear.
Innovation Solution
A modified PTFE fine powder is produced by copolymerizing tetrafluoroethylene with perfluoroalkyl vinyl ether and perfluoroalkylethylene in the presence of a fluorinated emulsifier, such as ammonium salts of fluorinated carboxylic acids, at pressures between 1.0 to 2.5 MPa, resulting in a powder with specific particle size and specific gravity ranges, enhancing moldability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fluorinated emulsifier with low bioaccumulation property is used instead of APFO, then environmental compatibility is improved, but moldability and mechanical properties of molded articles deteriorate
Solution Approach 1:
The invention changes the chemical structure parameters of the emulsifier by specifying fluorinated carboxylic acids with 4-7 carbon atoms and requiring at least one etheric oxygen atom in the carbon chain. This parameter modification allows the emulsifier to maintain effective surfactant properties for good moldability while having shorter carbon chains that reduce bioaccumulation, thus resolving the contradiction between environmental compatibility and manufacturing ease.
Solution Approach 2:
The invention introduces specific local structural features (etheric oxygen atoms) at particular positions in the emulsifier molecule (in the carbon chain between the carboxylic acid group and the terminal fluorinated group). This local quality enhancement provides sufficient surfactant activity for good moldability while the overall shorter chain length reduces bioaccumulation potential.
2Object-affected harmful factors
If a fluorinated emulsifier with low bioaccumulation property is used instead of APFO, then environmental compatibility is improved, but mechanical properties of molded articles deteriorate
Solution Approach 1:
The invention modifies the emulsifier structure by limiting the carbon chain length to 4-7 atoms and mandating the presence of etheric oxygen atoms, which creates a balance between surfactant effectiveness (for proper particle formation) and reduced persistence in the environment. This parameter optimization ensures that the resulting PTFE particles have appropriate characteristics for both environmental safety and mechanical strength.
Solution Approach 2:
The invention creates a composite functional structure in the emulsifier molecule, combining a fluorinated carboxylic acid head group with etheric oxygen-containing chains. This composite structure provides multiple functional capabilities: surfactant activity for particle formation, controlled solubility, and reduced bioaccumulation, while ensuring the PTFE particles maintain good mechanical properties after molding.
3Ease of manufacture
If copolymerization with comonomers is performed to improve moldability and mechanical properties, then paste extrusion moldability and article strength are improved, but production complexity increases
Solution Approach 1:
The invention optimizes the comonomer content parameters to very small ranges (0.01-0.5 mass% for perfluoroalkylethylene and 0.0001-0.05 mass% for perfluoroalkyl vinyl ether). These precise parameter specifications ensure sufficient moldability improvement while keeping the comonomer amounts so small that they do not significantly complicate the production process or require major equipment modifications.
Solution Approach 2:
The invention applies partial action by using trace amounts of comonomers rather than large quantities. This partial incorporation is sufficient to improve paste extrusion moldability and mechanical properties without requiring complete process redesign or excessive complexity in the production system.
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 modified PTFE fine powder exhibits excellent moldability and mechanical properties, including improved pressure resistance, while maintaining a low bioaccumulation profile and suitable for producing tubes or hoses with enhanced performance.
Implementation Method 1
copolymerizing tetrafluoroethylene with perfluoroalkyl vinyl ether and perfluoroalkylethylene in the presence of a fluorinated emulsifier
Implementation Method 2
emulsion polymerization method in which polymerization is carried out with an emulsifier in an aqueous medium
Data Source
AI summary
To provide a modified polytetrafluoroethylene which is excellent in the moldability by paste extrusion and the mechanical property of the molded article. A modified polytetrafluoroethylene fine powder which is a fine powder of a non-melt-moldable modified polytetrafluoroethylene, characterized in that the modified polytetrafluoroethylene comprises units derived from tetrafluoroethylene, units derived from a perfluoroalkyl vinyl ether represented by CF2═CFO—CnF2n+1 (wherein n is an integer of from 1 to 6), and units derived from a perfluoroalkylethylene represented by CH2═CH—CmF2m+1 (wherein m is an integer of from 3 to 6), and that the content of the units derived from the perfluoroalkyl vinyl ether is from 0.1 to 0.25 mass % and the content of the units derived from a perfluoroalkylethylene is from 0.001 to 0.1 mass %, based on all monomer units in the modified polytetrafluoroethylene.