Polyimide Separation Membrane Composition for Swelling Resistance
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Solution Overview
Problem
Conventional separation membranes made of polyimide experience a significant decrease in water separation performance over time, particularly when used with liquid mixtures containing moderate alcohol concentrations (20 wt % to 80 wt %).
Innovation Solution
A separation membrane comprising a polyimide with specific structural units represented by formulas (1) and (2), featuring a linking group A1 with a solubility parameter greater than 5.0 (cal/cm3)1/2 and a tetravalent organic group A2 with an arylene group, enhances water penetration and reduces performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polyimide separation membrane is used to suppress swelling with water, then the membrane stability is improved, but the water separation performance decreases
Solution Approach 1:
The invention changes the chemical structure parameters of the polyimide by introducing specific structural units with defined solubility parameters and molecular configurations. This modifies the membrane's interaction with water and alcohol molecules, enabling it to maintain both stability and separation performance by optimizing the balance between hydrophilicity and structural rigidity
Solution Approach 2:
The invention creates a composite polyimide structure by combining multiple structural units (represented by formulas (1) and (2)) with different functional characteristics. This composite approach allows the membrane to simultaneously achieve swelling resistance from one unit type and enhanced water separation from another, resolving the contradiction between stability and performance
2Reliability
If conventional polyimide separation membranes are used initially, then high water separation performance is achieved, but the performance greatly decreases through long-term use
Solution Approach 1:
The invention applies beforehand cushioning by designing a polyimide structure that preemptively compensates for performance degradation. The specific structural units are selected to resist the mechanisms of aging and swelling that cause performance loss over time, thereby cushioning against future deterioration and maintaining consistent separation performance throughout the membrane's service life
Solution Approach 2:
The invention modifies key structural parameters of the polyimide (solubility parameter, molecular weight, structural unit composition) to enhance long-term durability. These parameter changes make the membrane more resistant to chemical degradation, physical swelling, and performance衰减 over time, thereby extending effective service life while maintaining separation 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 membrane maintains high separation performance over long-term use by facilitating water permeation and minimizing swelling, thereby maintaining effective separation of water from alcohol-water mixtures.
Implementation Method 1
A pervaporation method and a vapor permeation method have been developed as methods for separating water from a liquid mixture containing an alcohol and water
Implementation Method 2
the separation membrane including a polyimide can be used for the pervaporation method
Data Source
AI summary
The present invention provides a separation membrane suitable for separating water from a liquid mixture containing an alcohol and water, the separation membrane being capable of reducing a decrease in separation performance regardless of long-term use.A separation membrane 10 of the present invention includes a polyimide having a structural unit X represented by the following formula (1) and a structural unit Y represented by following formula (2).A1 is a linking group including no arylene group in a main chain and having a solubility parameter, in accordance with a Fedors method, of more than 5.0 (cal/cm3)1/2. A2 is a tetravalent organic group including an arylene group.