Semi-permeable Membrane Support Thickness Control
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Solution Overview
Problem
The issue of low adhesion between the raw water spacer and the semipermeable membrane in spiral modules results in reduced water permeability after modulation, which affects the performance of filtration membranes.
Innovation Solution
A semipermeable membrane support is developed using a wet nonwoven fabric with a specific combination of main synthetic fibers and binder fibers, where the thickness difference between measurement points is controlled between 1.0% to 5.0% to ensure proper adhesion and turbulence, utilizing hot-press processing with metal and elastic rolls to enhance adhesion and maintain high water permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermal fusion or ultrasonic fusion processing is used to bond the filtration membrane to the frame material, then adhesion between the membrane and support is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The invention applies preliminary action by pre-forming the nonwoven fabric support with controlled thickness distribution (thickness difference ≤5% and ≥10% at different positions) before membrane formation. This preliminary structural preparation ensures proper adhesion and turbulence generation without requiring complex post-processing bonding steps, thereby improving strength while avoiding increased process complexity
Solution Approach 2:
The invention changes physical parameters of the support structure, specifically controlling the thickness distribution of the nonwoven fabric (thickness difference between measurement points within 5% and 10% ranges). This parameter optimization enables effective adhesion and fluid turbulence without needing additional bonding processes, resolving the contradiction between strength improvement and process complexity
2Strength
If the thickness difference of the nonwoven fabric support is too large, then manufacturing simplicity is maintained, but adhesion to the semipermeable membrane and turbulence generation are insufficient
Solution Approach 1:
The invention optimizes the thickness parameter of the nonwoven fabric support by establishing specific ranges: thickness difference between first and second measurement positions is 5% or less, while thickness difference between third and fourth measurement positions is 10% or less. These controlled parameter changes ensure sufficient adhesion and turbulence generation while maintaining reasonable manufacturing precision
Solution Approach 2:
The invention applies local quality by differentiating thickness control requirements at different locations of the support. The first and second measurement positions (likely on the coating surface) require tighter control (≤5%), while the third and fourth positions (likely on the noncoating surface or edges) allow greater variation (≤10%). This localized quality approach balances adhesion requirements with manufacturing feasibility
3Strength
If hot-press processing is applied to increase density and strength, then mechanical strength is improved, but water permeability may be reduced
Solution Approach 1:
The invention changes the density parameter of the nonwoven fabric support to a specific range (0.03 g/cm³ or more and less than 0.10 g/cm³). This optimized density parameter provides sufficient mechanical strength while maintaining adequate porosity for water permeability, resolving the contradiction between strength improvement and productivity maintenance
Solution Approach 2:
The invention applies partial action by implementing hot-press processing with controlled parameters that provide just enough densification to achieve the target density range for sufficient strength, while avoiding excessive densification that would compromise water permeability. The processing is optimized to achieve the minimum necessary density without over-processing
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 solution achieves excellent adhesion between the raw water spacer and the semipermeable membrane, maintaining high water permeability and preventing the formation of spaces that reduce filtration efficiency, thereby ensuring consistent performance in spiral modules.
Implementation Method 1
hot-press processing is carried out on a sheet produced by a wet papermaking method
Data Source
Figure 1~2
AI summary
A semipermeable membrane support having a thickness difference between measurement thickness at 0.80 N/cm2 and measurement thickness at 1.27 N/cm2 of 1.0 to 5.0 % is excellent in adhesion to a semipermeable membrane and also adhesion between a raw water spacer and the semipermeable membrane and thereby can be expected to maintain high water permeability after modulation. A method of producing a semipermeable membrane support comprises the step of carrying out hot-press processing by using an elastic roll, which has(have) a hardness between a type A durometer hardness of 60 or more and a type D durometer hardness of 95 or less.