Asymmetric Polyethylene Filter Membrane Balancing Retention and Flow
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Solution Overview
Problem
Existing liquid-flowable polyethylene filter membranes face challenges in achieving high retention with minimal flow restriction, as reducing pore size for improved retention often leads to unacceptable decreases in flow rate, which is critical for industrial applications like semiconductor processing.
Innovation Solution
Development of a porous polyethylene filter membrane with an asymmetric pore structure, featuring smaller pores on one side for retention and larger pores on the other for support, manufactured through an extrusion melt-cast process using specific solvent blends and controlled phase separation, allowing for high retention and flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pore size is reduced to improve retention, then retention of contaminants is improved, but flow rate decreases
Solution Approach 1:
The membrane is designed with spatially varying pore sizes: smaller pores in the filtration layer (closest to feed) for high retention, and larger pores in the support layer for high flow rate. This local differentiation allows each region to optimize for its specific function, resolving the contradiction between retention and flow rate.
Solution Approach 2:
The membrane employs an asymmetric structure with distinct filtration and support layers having different pore size distributions and porosity. The filtration layer has smaller, more uniform pores for contaminant rejection, while the support layer has larger, more interconnected pores for fluid transport, creating an asymmetric pore structure that simultaneously achieves high retention and maintains flow rate.
2Reliability
If pore size is reduced to improve retention, then retention of contaminants is improved, but flow restriction increases
Solution Approach 1:
The membrane structure is differentiated into regions with distinct pore characteristics: the filtration layer has smaller pores for retention while the support layer has larger pores that minimize flow restriction. This local optimization allows the system to achieve high retention without proportionally increasing flow restriction.
Solution Approach 2:
The asymmetric design creates a pore size gradient from the filtration layer to the support layer. The larger pores in the support layer provide low-resistance flow paths that compensate for the flow restriction introduced by the smaller pores in the filtration layer, thereby maintaining overall system performance.
3Productivity
If porosity is increased to improve flow rate, then flow rate is improved, but retention decreases
Solution Approach 1:
The membrane assigns different porosity values to different layers: the filtration layer has lower porosity with smaller pores for high retention, while the support layer has higher porosity with larger pores for high flow rate. This local differentiation allows the system to achieve both high retention and high flow rate simultaneously.
Solution Approach 2:
The asymmetric pore structure creates a porosity gradient across the membrane thickness. The support layer's higher porosity compensates for the filtration layer's lower porosity, ensuring adequate flow rate while the filtration layer's smaller pores maintain high retention. The asymmetric design decouples the trade-off between porosity and performance.
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 asymmetric membrane achieves high retention of contaminants while maintaining sufficient flow rates, suitable for industrial processes, particularly in semiconductor manufacturing, by optimizing pore size and structure across the membrane's thickness.
Implementation Method 1
a first liquid-flowable porous polyethylene filter membrane that includes two opposed sides and a thickness between the two opposed sides, with pores throughout the thickness, and with the pores having an asymmetric pore structure
Implementation Method 2
manufactured through an extrusion melt-cast process using specific solvent blends and controlled phase separation
Data Source
AI summary
Described are liquid-flowable, porous polyethylene filter membranes that include two opposing sides and that have an asymmetric pore structure; filter components and filters that include this type of porous polyethylene filter membrane; methods of making the porous polyethylene filter membranes, filter components, and filters; and methods of using a porous polyethylene filter membrane, filter component, or filter, to filter a fluid such as a liquid chemical to remove unwanted material from the fluid.