Gradient Spherical Separation Membrane for Clogging Resistance
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Solution Overview
Problem
Conventional methods for producing separation membranes, such as wet solution and melt-extraction methods, face challenges in achieving a balance between mechanical strength, water permeation performance, and resistance to clogging, with issues like insufficient mechanical strength, poor reproducibility, and high production costs.
Innovation Solution
A separation membrane with a spherical structure layer formed of a thermoplastic resin, where specific diameter ratios and temperature gradient processing techniques are used to achieve high mechanical strength and continuous water permeation performance, reducing clogging and filtration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If wet solution method is used to produce separation membrane, then asymmetric three-dimensional network structure containing macro-voids is formed, but mechanical strength becomes insufficient
Solution Approach 1:
The invention creates a gradient structure where the spherical structure diameter varies through the membrane thickness. The surface layer has larger spherical structures (D1) for high permeability, while the inner layer has smaller spherical structures (D3) for high strength. This local variation in structure quality resolves the contradiction between forming an open network structure and maintaining mechanical strength.
2Ease of manufacture
If conventional production methods are used, then production conditions are difficult to control, but reproducibility becomes poor
Solution Approach 1:
The invention specifies precise parameter ranges for spherical structure diameters (D1, D2, D3) and their relationships (D1>D2, D1/D3 ratios). By controlling these geometric parameters and the gradient distribution through the membrane thickness, the method achieves both ease of manufacture and high reproducibility of membrane performance.
3Productivity
If membrane has high water permeation performance, then same desalination amount can be realized with smaller membrane area, but equipment cost increases
Solution Approach 1:
The invention uses a spherical structure layer with controlled porosity and pore size distribution. The surface layer has larger pores (D1) for high initial permeability, while the inner layer has smaller pores (D3) for maintaining strength and preventing clogging. This porous structure design achieves high water permeation performance while maintaining mechanical integrity, reducing the need for frequent replacement and lowering overall equipment cost.
4Reliability
If separation membrane is resistant to clogging, then high water permeation performance can be continuously maintained, but cleaning frequency and power consumption increase
Solution Approach 1:
The invention designs the membrane structure in advance with a gradient spherical structure that prevents clogging before it occurs. The surface layer's larger spherical structures (D1) allow easy passage of particles, while the inner layer's smaller structures (D3) provide fine filtration. This preliminary structural design maintains continuous high permeability without requiring frequent high-power cleaning operations.
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 membrane maintains high water permeation performance and mechanical strength while minimizing clogging, achieving a balance between filtration resistance and strength/elongation properties.
Implementation Method 1
solidifying the polyvinylidene fluoride-based resin solution by solid-liquid thermally induced phase separation in a cooling bath
Implementation Method 2
imparting a temperature gradient in a separation membrane thickness direction to the polyvinylidene fluoride-based resin solution
Data Source
AI summary
An object of the present invention is to provide a separation membrane having high mechanical strength and being less likely to cause clogging and capable of continuously maintaining high water permeation performance. The present invention relates to a separation membrane characterized in that the average diameter D1 of a spherical structure in a region within 10 μm from a first surface in a separation membrane having a spherical structure layer formed of a thermoplastic resin and the average diameter D2 of a spherical structure in a region of 10 μm to 20 μm from a second surface satisfy the relational expression of D1>D2 and the average diameter D1 and the average diameter D3 of a spherical structure in a third region satisfy the relational expression of 1.10<D1/D3<4.00.