Hydrophilic sheet and process for producing the same
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Solution Overview
Problem
Conventional methods for processing polytetrafluoroethylene (PTFE) fibers face challenges such as difficulty in processing due to lack of flowability, inability to form direct bonds, and limited adhesion, which restricts the production of high-performance filters with enhanced filtering performance for gas and liquid filtration.
Innovation Solution
A hydrophilic sheet is created by applying hydrophilization treatment to a fluororesin sheet comprising PTFE fibers, where secondary fibers with smaller diameters are generated through stress application during heating, crosslinking with primary fibers without forming knots, and coated with a hydrophilic compound to improve filtering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PTFE is processed using conventional methods (press-forming, sintering, extrusion), then the material can be formed into products, but the processing difficulty remains high due to lack of flowability and inability to bond directly
Solution Approach 1:
The patent introduces a specific fluororesin composition containing PTFE particles, PFA particles, and a liquid lubricant as an intermediary system that enables both processing and bonding. The liquid lubricant acts as a temporary mediator that facilitates forming, then solidifies to enable heat fusion bonding, resolving the contradiction between processing ease and bonding capability
Solution Approach 2:
The patent changes the physical state parameters of the fluororesin mixture by controlling temperature and pressure during processing. By heating to specific temperature ranges and applying controlled pressure, the material transitions between states that enable forming and bonding, overcoming the conventional processing limitations
2Length of moving object
If PTFE fibers are made ultrafine using electrospinning, then fiber diameter is reduced to nanoscale, but the minimum fiber diameter is limited to about 500 nm
Solution Approach 1:
The patent replaces the electrospinning mechanical system with a thermal-mechanical processing system. By using heat and pressure to form and process the fluororesin fibers, the method achieves fiber diameters below 500 nm that are not attainable through electrospinning, while maintaining precise diameter control through parameter optimization
3Temperature
If PTFE is heated to 327°C or higher to achieve non-crystalline state for processing, then flowability is improved, but the material still exhibits no flowability for conventional processing methods
Solution Approach 1:
The patent creates a composite fluororesin system combining PTFE particles, PFA particles, and liquid lubricant. This composite structure enables processing at lower temperatures than conventional PTFE alone, as the liquid lubricant facilitates forming at temperatures below the PTFE melting point, while the PFA component provides necessary flowability
4Manufacturing precision
If hydrophilization treatment is applied to fluororesin sheet, then filtering performance is improved, but the water repellency property of PTFE is reduced
Solution Approach 1:
The patent applies hydrophilization treatment selectively to the surface of the fluororesin sheet while maintaining the bulk PTFE properties. This local modification enables improved filtering performance at the surface level while preserving the water repellency and other beneficial PTFE properties in the bulk material
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 hydrophilic sheet exhibits improved filtering performance for both gas and liquid filtration, maintaining the properties of PTFE such as water repellency and heat resistance, with enhanced strength and stability due to the integration of primary and secondary fibers, achieving isotropic or anisotropic physical properties depending on fiber orientation.
Implementation Method 1
secondary fibers with smaller diameters are generated through stress application during heating
Implementation Method 2
coated with a hydrophilic compound to improve filtering performance
Data Source
AI summary
Provided is a hydrophilic fluororesin sheet having significantly improved properties such as filtering performance which includes primary fibers and secondary fibers having a smaller fiber diameter than a fiber diameter of the primary fibers, the secondary fibers crosslinking in each of the primary fibers and/or crosslinking between different primary fibers in such a manner that no knots are formed at crosslinking points, the primary fibers and the secondary fibers including fluororesin fibers including polytetrafluoroethylene [PTFE], wherein a surface of the sheet to which hydrophilization treatment has been applied.