Cation-Exchange Membrane Water Content Control for Curling Prevention

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Solution Overview

Problem

Existing ion-exchange membranes for electrolysis face challenges in reducing power consumption and preventing curling, which affects their handling and installation in electrolyzers, due to issues with water content and ion-exchange group distribution between sulfonic acid and carboxylic acid layers.

Innovation Solution

A cation-exchange membrane with a specific configuration, including layers with repeating units of sulfonic acid and carboxylic acid-type ion-exchange groups, where the water content of the sulfonic acid layer is controlled between 26% and 35%, and the mass proportion of repeating units is optimized to suppress curling and achieve low electrolysis voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the number of ion-exchange groups in the sulfonic acid layer is increased to reduce electrolysis voltage, then power consumption is reduced, but water content increases and the membrane curls

Engineering Contradiction:

Improveelectrolysis voltageVSAvoidmembrane curling

Core Design Contradiction:

Use of energy by moving objectVSShape

Solution Approach 1:

The patent applies parameter changes by precisely controlling the water content of the sulfonic acid layer within 26-35% and the mass proportion of repeating units (A) within 53-70%. These parameter optimizations allow the membrane to achieve low electrolysis voltage while preventing curling during production and handling.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The membrane employs a composite structure with two distinct layers: a sulfonic acid layer containing repeating units (A) and (S), and a carboxylic acid layer containing fluorine-containing polymer with carboxylic acid-type ion-exchange groups. This composite structure enables the sulfonic acid layer to provide low electrolysis voltage while the overall membrane composition prevents excessive water content and curling.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the equivalent weight is lowered to increase ion-exchange groups, then electrolysis voltage decreases, but water content increases and TFE ratio decreases

Engineering Contradiction:

Improveelectrolysis voltageVSAvoidwater content

Core Design Contradiction:

Use of energy by moving objectVSQuantity of substance

Solution Approach 1:

The patent optimizes the equivalent weight parameters by controlling the mass proportion of repeating units (A) to be 53-70% and water content to be 26-35%. This parameter optimization achieves low electrolysis voltage while maintaining appropriate water content and TFE ratio.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The membrane structure distributes different functions to different layers: the sulfonic acid layer with controlled composition provides low electrolysis voltage through optimized ion-exchange group density, while the carboxylic acid layer contributes to overall membrane stability and water content management, creating local quality differentiation.

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If the TFE ratio in the polymer is lowered to increase ion-exchange groups, then electrolysis voltage decreases, but membrane rigidity is lost

Engineering Contradiction:

Improveelectrolysis voltageVSAvoidmembrane rigidity

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The patent maintains membrane rigidity by controlling the mass proportion of repeating units (A) to be 53-70%, which ensures sufficient TFE ratio is maintained in the polymer structure. This parameter control allows the membrane to achieve low electrolysis voltage while preserving the rigidity needed to prevent curling.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The composite structure combines the sulfonic acid layer with the carboxylic acid layer, where the carboxylic acid layer containing fluorine-containing polymer provides structural support and rigidity, compensating for any rigidity loss in the sulfonic acid layer while maintaining overall low electrolysis voltage.

Inventive Principle:

Principle #40Composite materials

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 effectively reduces power consumption and prevents curling, enabling more efficient energy use and stable membrane installation in electrolyzers, contributing to energy savings in chloro-alkali electrolysis.

Implementation Method 1

Ion-exchange membranes typically have a structure in which a layer containing sulfonic acid (sulfonic acid layer) and a layer containing carboxylic acid (carboxylic acid layer) are laminated

Methodology Applied

Scientific EffectIon exchange: Ion Exchange

Data Source

PatentUS12053770B2Cation-exchange membrane, electrolyzer, and method for producing cation-exchange membrane

Publication Date: 2024.08.06 ASAHI KASEI KOGYO KABUSHIKI KAISHA

AI summary

A cation-exchange membrane includes layer (I) containing repeating units (A) each represented by formula (1) and repeating units (S) each containing a sulfonic acid-type ion-exchange group, wherein the mass proportion of repeating units (A) based on the total mass proportion of repeating units (A) and repeating units (S) being 100% by mass is 53% by mass or more and 70% by mass or less; and layer (II) containing a fluorine-containing polymer containing a carboxylic acid-type ion-exchange group and disposed on layer (I), wherein the water content of layer (I) is 26% or more and 35% or less:CF2—CF2 (1)