Ion Exchange Membrane Strength Retention
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Solution Overview
Problem
Ion exchange membranes used in alkali chloride electrolysis, such as those described in Patent Literature 1, experience a significant decrease in strength before and after operation, limiting their ability to retain mechanical strength over a long period.
Innovation Solution
An ion exchange membrane with a specific structure comprising a layer S of fluorine-containing polymer with sulfonic acid groups, a layer C of fluorine-containing polymer with carboxylic acid groups, and reinforcing materials, where the average cross-sectional thickness and strength change ratio are optimized to maintain mechanical strength during and after electrolysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an ion exchange membrane with thin cross-sectional thickness is used to reduce electrolytic voltage, then productivity is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent employs a composite structure combining a fluorine-containing polymer matrix with embedded reinforcement yarn and sacrifice yarn. The reinforcement yarn (e.g., PTFE) provides mechanical strength while the sacrifice yarn (e.g., polyacrylonitrile) creates ion-permeable pores when dissolved, achieving both structural integrity and electrolyte penetration for reduced electrolytic voltage
Solution Approach 2:
The patent creates a porous structure by embedding sacrifice yarn that is subsequently dissolved to form continuous holes or pores within the membrane. This porous architecture allows efficient ion transport through the thin membrane structure, maintaining low electrolytic voltage while the reinforcement yarn preserves mechanical strength
2Productivity
If the membrane structure is optimized for low electrolytic voltage, then productivity is improved, but strength retention after electrolysis deteriorates
Solution Approach 1:
The composite structure of reinforcement yarn embedded in fluorine-containing polymer provides both the optimized thin structure for low electrolytic voltage and the mechanical robustness for long-term strength retention. The fluorine-containing polymer matrix offers chemical and heat resistance essential for maintaining reliability during extended electrolysis operations
Solution Approach 2:
The patent optimizes specific parameters including the cross-sectional thickness (20-75 μm), the ratio of reinforcement yarn to sacrifice yarn, and the ion exchange capacity of the fluorine-containing polymer. These parameter adjustments ensure both low electrolytic voltage during operation and adequate strength retention after prolonged electrolysis
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 ion exchange membrane retains strength over a long period, ensuring consistent performance in alkali chloride electrolysis by maintaining mechanical integrity during and after the electrolysis process.
Implementation Method 1
a layer S comprising a fluorine-containing polymer having a sulfonic acid group; a layer C comprising a fluorine-containing polymer having a carboxylic acid group
Implementation Method 2
alkali chloride electrolysis for producing chlorine and alkali hydroxide
Data Source
AI summary
An ion exchange membrane containing: a layer S containing a fluorine-containing polymer having a sulfonic acid group; a layer C containing a fluorine-containing polymer having a carboxylic acid group; and—a plurality of reinforcing materials functioning as at least one of reinforcement yarn and sacrifice yarn; wherein, when the ion exchange membrane is viewed from a top surface, an average cross-sectional thickness A of the ion exchange membrane measured in pure water for a region, is μm or more and 75 μm or less, and wherein a strength change ratio calculated from strength S2 of the ion exchange membrane measured after the ion exchange membrane is subjected to a predetermined electrolysis test and strength S1 of the ion exchange membrane measured before the ion exchange membrane is subjected to the electrolysis test, in terms of 100×S2/S1, is 85% or more and 120% or less.