Oil-Repellent Stretched PTFE Filter Coating
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Solution Overview
Problem
Conventional gas-permeable filters with high crystallinity fluorine-containing polymers for oil repellency often significantly reduce gas permeability, particularly in stretched PTFE porous membranes with microporous structures.
Innovation Solution
A gas-permeable filter with a surface coated using an oil-repellent agent featuring a linear fluorine-containing hydrocarbon group, such as -R1 < C5F10CH2C4F9, which maintains gas permeability while providing sufficient oil repellency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluorine-containing polymer with high crystallinity (Rf group having eight or more carbon atoms) is used for oil-repellent treatment, then oil repellency is improved, but gas permeability is significantly reduced
Solution Approach 1:
The patent changes the chemical structure parameters of the fluorine-containing polymer by introducing branched perfluoroalkyl groups (specifically perfluoro-2-methyl-3-(heptafluoroisopropyl)propyl groups) instead of linear perfluoroalkyl groups. This structural parameter change reduces crystallinity while maintaining oil repellency through the fluorine atoms' inherent low surface energy properties, thereby resolving the contradiction between oil repellency and gas permeability
Solution Approach 2:
The patent uses a composite approach by combining fluorine-containing polymers with specific branched structures with stretched PTFE porous membranes. The composite material leverages the microporous structure of PTFE for gas permeability while the fluorine-containing polymer coating provides oil repellency, achieving both properties simultaneously
2Productivity
If a stretched PTFE porous membrane with microporous structure is used, then gas permeability is improved, but oil repellency is insufficient when contacting liquids with low surface tension
Solution Approach 1:
The patent applies preliminary oil-repellent treatment to the stretched PTFE porous membrane before use. By coating the membrane surface with fluorine-containing polymers having branched perfluoroalkyl groups, the membrane is pre-equipped with oil repellency properties, ensuring it can resist liquids with low surface tension while maintaining its inherent gas permeability
Solution Approach 2:
The patent applies oil-repellent properties locally to the surface of the stretched PTFE porous membrane through coating with fluorine-containing polymers. The bulk PTFE structure maintains high gas permeability, while the surface coating provides localized oil repellency, resolving the contradiction between these two properties
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 effectively provides practical oil repellency to stretched PTFE porous membranes without substantially reducing gas permeability, meeting requirements for both properties.
Implementation Method 1
a linear fluorine-containing hydrocarbon group, which has a specific structure and provides practical oil repellency
Implementation Method 2
a porous membrane having a surface coated with an oil-repellent agent
Implementation Method 3
stretched PTFE porous membranes with microporous structures
Data Source
AI summary
A gas-permeable filter provided with oil repellency is provided. The gas-permeable filter includes a porous membrane having a surface coated with an oil-repellent agent. The oil-repellent agent includes a linear fluorine-containing hydrocarbon group represented by -R1C5F10CH2C4F9 or -R2C6F13, and the porous membrane is a stretched polytetrafluoroethylene (PTFE) porous membrane. Here, R1 and R2 are each independently an alkylene group having 1 to 12 carbon atoms or a phenylene group. The gas-permeable filter is provided with oil repellency without significant reduction in gas permeability.