Fluorinated Copolymer Ion Exchange Membrane Impurity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ion exchange membranes used in alkali chloride electrolysis are prone to performance deterioration due to impurity deposition, leading to decreased current efficiency and increased operational costs, particularly from calcium and strontium impurities in aqueous alkali chloride solutions.
Innovation Solution
A fluorinated copolymer with a carboxylic acid type functional group is developed, where the proportion of low molecular weight components is controlled to minimize impurity interaction, achieved through a specific extraction method and molecular weight distribution optimization, resulting in an ion exchange membrane with enhanced durability and current efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fluorinated copolymer with carboxylic acid type functional groups is used to develop high current efficiency, then current efficiency is improved, but the membrane becomes susceptible to impurity deposition causing performance deterioration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight distribution of the fluorinated copolymer. Specifically, it limits the proportion of low molecular weight components (log M = 2.0 to 3.5) to 10 mass% or less per 100 mass% of total soluble components. This parameter control eliminates harmful low molecular weight fractions that cause impurity deposition, while maintaining high current efficiency through optimized functional group content and distribution.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous molecular weight distribution within the copolymer structure. It maintains high molecular weight components for structural integrity and impurity resistance, while incorporating controlled amounts of intermediate molecular weight components for optimal ion transport. This local differentiation of molecular weight zones allows simultaneous achievement of high current efficiency and impurity resistance.
2Ease of manufacture
If the proportion of low molecular weight components in the fluorinated copolymer is increased, then ease of manufacture is improved, but membrane durability against impurity deposition deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing an upper limit of 10 mass% for low molecular weight components (log M = 2.0 to 3.5) in the soluble content. This parameter constraint prevents excessive low molecular weight content that would cause impurity deposition, while allowing sufficient content to maintain manufacturing ease and polymer processability. The balanced parameter range optimizes both manufacturability and durability.
3Productivity
If an ion exchange membrane operates in an aqueous alkali chloride solution with impurities, then productivity is maintained, but chemical damage occurs due to calcium or strontium deposition
Solution Approach 1:
The patent applies the blessing in disguise principle by converting the potential harm of low molecular weight components into a benefit. Instead of completely eliminating all low molecular weight components (which would affect processability), it selectively removes the harmful fraction (log M = 2.0 to 3.5) while retaining beneficial intermediate components. This selective removal transforms the problem of low molecular weight content into an opportunity to optimize both performance and manufacturability.
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 optimized fluorinated copolymer-based ion exchange membrane effectively suppresses the decrease in current efficiency caused by impurities, reducing operational costs and extending membrane lifespan by maintaining high current efficiency even in the presence of calcium and strontium ions.
Implementation Method 1
a membrane made of a fluorinated copolymer having carboxylic acid type functional groups or sulfonic acid type functional groups
Implementation Method 2
deposition of impurities such as calcium or strontium in the ion exchange membrane
Data Source
AI summary
To provide a fluorinated copolymer which is capable of providing an ion exchange membrane having little adverse effect due to impurities in an alkali chloride aqueous solution on electrolysis of the alkali chloride aqueous solution. To use a fluorinated copolymer of a fluorinated monomer having a carboxylic acid type functional group with a fluorinated olefin, wherein the proportion of components having a common logarithm (log M) of a molecular weight M being from 2.0 to 3.5 is at most 10 mass % per 100 mass % of components having a common logarithm (log M) of a molecular weight M being at least 2.0, contained in a CClF2CF2CClFH soluble content.