Porous PTFE Membrane Reducing Mass Per Unit Area
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Solution Overview
Problem
Conventional methods for producing porous polytetrafluoroethylene (PTFE) membranes struggle to achieve a high PF value while maintaining low mass per unit area, leading to increased material costs and weight, as they often compromise collection efficiency or pressure loss.
Innovation Solution
A novel production method involving extrusion into a sheet form using a flat die, followed by sequential stretching and sintering, which reduces fibril diameter and increases node density, resulting in a membrane with a PF value of 36 or more and a mass per unit area of 0.90 g/m2 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the porous PTFE membrane is increased to increase the PF value, then the PF value improves, but the mass per unit area increases significantly
Solution Approach 1:
The invention changes the physical and chemical parameters of the PTFE membrane structure, specifically controlling the pore size distribution, fibril diameter, and node density to achieve high PF values without increasing mass per unit area. The membrane structure is optimized at the micro-scale to maximize performance while minimizing material usage.
Solution Approach 2:
The invention utilizes a specifically designed porous structure with controlled pore sizes and distributions to achieve high filtration performance. The porous structure is optimized to provide sufficient collection efficiency while maintaining low mass per unit area, resolving the contradiction between PF value and material quantity.
2Manufacturing precision
If conventional production methods are used to increase PF value, then pressure loss and collection efficiency balance improves, but material cost and weight increase
Solution Approach 1:
The invention optimizes multiple parameters simultaneously including pore size distribution, fibril diameter, and node density to achieve high PF values with minimal mass per unit area, thereby reducing membrane weight while maintaining performance.
Solution Approach 2:
The invention creates local variations in the membrane structure with different pore sizes and fibril densities in different regions to optimize both filtration performance and material efficiency, achieving high PF values without uniform increases in mass throughout the membrane.
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
This method enhances the PF value of porous PTFE membranes while maintaining low mass per unit area, reducing material costs and weight, and achieves a balance between collection efficiency and pressure loss, suitable for air filter media applications.
Implementation Method 1
Porous PTFE membranes are generally produced as follows. A mixture obtained by mixing a PTFE fine powder and a liquid lubricant serving as an extrusion aid is extrusion-molded, and the resulting molded body is rolled to form a PTFE sheet. The liquid lubricant is removed from the PTFE sheet, and then the resulting PTFE sheet, from which the liquid lubricant has been removed, is stretched to make the sheet porous.
Data Source
AI summary
Provided is a porous polytetrafluoroethylene (PTFE) membrane having a PF value of 36 or more and a mass per unit area of 0.90 g/m2 or less. The PF value is determined by the following equation: PF value={−log(PT (%)/100)/(PL(Pa)/9.8)}×100. PT (permeability) is determined by PT (%)=100−CE (%), CE (collection efficiency) is determined by a value measured using dioctyl phthalate particles with a particle diameter of 0.10 μm to 0.20 μm under a condition of a permeate flow rate of 5.3 cm/sec, and PL (pressure loss) is determined by a value measured under a condition of a permeate flow rate of 5.3 cm/sec. This porous PTFE membrane is suitable for air filter media.