Porous Multi-Layer PTFE Filter for Ultrafine Particle Retention
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Solution Overview
Problem
Existing microfiltration filters struggle to retain ultrafine particles of less than 0.1 µm without compromising their surface integrity, leading to decreased filtration efficiency and increased risk of damage during production and use.
Innovation Solution
A porous multi-layer filter design featuring a laminated body of three sheets with biaxially stretched PTFE layers, where the protection layer and support layer have larger pores than the filtration layer, providing isotropic tensile strength and protecting the filtration layer from external damage while maintaining high flow rates and particle retention capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pore size of the filtration layer is decreased to ensure particle retention efficiency for fine particles, then the particle retention capability is improved, but the surface of the filtration layer becomes more vulnerable to damage during production, processing, or use
Solution Approach 1:
The invention uses a composite structure consisting of a filtration layer with fine pores (0.01 to 0.45 μm) sandwiched between two protection layers with larger pores. This composite material approach allows the filtration layer to maintain its fine pore structure for high particle retention while the protection layers provide mechanical strength and surface durability, resolving the contradiction between retention capability and surface strength
Solution Approach 2:
The filter is segmented into three distinct functional layers: a filtration layer for particle retention, and two protection layers for mechanical support. This segmentation allows each layer to be optimized independently - the filtration layer can have extremely fine pores without compromising overall filter strength, as the protection layers bear the mechanical load
2Device complexity
If a laminated body of two layers is used with a filtration membrane fixed on a support, then the structure is simplified, but the treatment rate decreases and the filtration surface remains exposed to damage
Solution Approach 1:
The invention transitions from a two-layer structure to a three-layer structure by adding a protection layer on the inflow side. This dimensional change in the filter architecture enables simultaneous achievement of high treatment rate (through the protection layer's larger pores) and enhanced surface protection, while maintaining relatively simple lamination processing
3Productivity
If the filtration layer is made thinner to increase flow rate, then the treatment rate is improved, but the filtration layer becomes more susceptible to damage and deformation
Solution Approach 1:
Different layers are assigned different pore sizes and thicknesses according to their specific functions. The protection layers have larger pores and provide mechanical strength, while the filtration layer has fine pores for particle retention. This local quality differentiation allows the filtration layer to be thin for high flow rate without compromising overall filter strength, as the protection layers provide the necessary structural support
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 multi-layer filter effectively retains ultrafine particles of less than 0.1 µm with increased strength and stability, preventing surface damage and ensuring high flow rates and filtration performance in sensitive applications like semiconductor and liquid crystal manufacturing and food/medicine fields.
Implementation Method 1
each of the porous stretched PTFE sheets serving as the protection layer, the filtration layer, and the support layer is a sheet biaxially stretched in longitudinal and transverse directions
Implementation Method 2
PTFE porous filters have characteristics inherent in PTFE... as well as characteristics possessed by porous bodies, such as flexibility, liquid permeability, particle collection efficiency
Data Source
Figure 1A~1B
Figure 2~3
AI summary
In a filter for microfiltration, a filtration layer is protected so as not to be damaged. A porous multi-layer filter, which is a laminated body of three porous stretched PTFE sheets that have been biaxially stretched in the longitudinal and transverse directions, includes a filtration layer as a middle layer, a protection layer stacked on one surface of the filtration layer on the liquid-to-be-treated inflow side, and a support layer stacked on another surface of the filtration layer, in which the one surface and the other surface of the filtration layer are fusion-bonded to the protection layer and the support layer at boundaries therebetween, pores of the protection layer and pores of the support layer three-dimensionally communicate with pores of the filtration layer, and the mean pore size of pores of the filtration layer is smaller than the mean pore size of pores of each of the protection layer and the support layer.