Ion Exchange Membrane Production via Alkaline Hydrolysis
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Solution Overview
Problem
Conventional ion exchange membranes used in alkali chloride electrolysis experience decreased current efficiency with increasing alkali hydroxide concentration, leading to inadequate alkali resistance, resulting in higher electric power consumption, frequent membrane replacement, and reduced chlorine quality due to increased oxygen concentration.
Innovation Solution
A production method for ion exchange membranes involving a fluorinated polymer with carboxylic acid type functional groups on the cathode side and sulfonic acid type functional groups on the anode side, utilizing an alkaline aqueous solution with specific concentrations of alkali metal hydroxide and water-soluble organic solvents, and incorporating inorganic particles and a binder for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ion exchange membranes are used in alkali chloride electrolysis, then the membrane structure is simple and easy to manufacture, but the current efficiency decreases as alkali hydroxide concentration increases, resulting in inadequate alkali resistance
Solution Approach 1:
The ion exchange membrane is divided into multiple functional layers: a cathode-side layer containing fluorinated polymer with carboxylic acid type functional groups, an anode-side layer containing fluorinated polymer with sulfonic acid type functional groups, and optionally an intermediate layer. This segmentation allows each layer to perform specific functions, with the carboxylic acid layer providing high alkali resistance and the sulfonic acid layer providing high proton conductivity, thereby resolving the contradiction between reliability and structural complexity.
Solution Approach 2:
The membrane uses composite material structure combining different fluorinated polymers with specific functional groups. The cathode-side layer uses fluorinated polymer containing carboxylic acid groups (such as poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether-co-methyl acrylate)) while the anode-side layer uses fluorinated polymer with sulfonic acid groups. This composite structure achieves both high alkali resistance and high current efficiency, resolving the technical contradiction.
2Productivity
If the concentration of alkali hydroxide is increased to improve production output, then productivity increases, but current efficiency decreases and electric power consumption increases
Solution Approach 1:
The invention changes the chemical parameters of the membrane by introducing fluorinated polymers with specific functional groups (carboxylic acid on cathode side, sulfonic acid on anode side) and controlling their proportions (carboxylic acid type: 10-20 mol%, sulfonic acid type: 15-25 mol%). This parameter optimization allows the membrane to maintain high current efficiency even at high alkali hydroxide concentrations, enabling increased productivity without proportional increase in power consumption.
3Reliability
If the proportion of functional groups in the fluorinated polymer is optimized to improve current efficiency, then manufacturing precision requirements increase
Solution Approach 1:
The invention performs preliminary action by pre-synthesizing fluorinated polymers with predetermined functional group proportions through controlled polymerization. The monomer composition is carefully selected and controlled during polymerization to achieve the desired functional group ratios (carboxylic acid: 10-20 mol%, sulfonic acid: 15-25 mol%). This preliminary preparation reduces the need for complex post-processing adjustments and simplifies the manufacturing process while ensuring consistent 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 method produces ion exchange membranes with high current efficiency and alkali resistance, reducing electric power consumption, extending membrane lifespan, and maintaining chlorine quality by optimizing the concentration of functional groups and water content within the membrane layers.
Implementation Method 1
an ion exchange membrane having a layer made of a fluorinated polymer having carboxylic acid type functional groups on the cathode side and having a layer made of a fluorinated polymer having sulfonic acid type functional groups on the anode side
Implementation Method 2
subjecting the groups convertible to carboxylic acid type functional groups to hydrolysis treatment to convert them to carboxylic acid type functional groups, and at the same time, subjecting the groups convertible to sulfonic acid type functional groups to hydrolysis treatment to convert them to sulfonic acid type functional groups
Implementation Method 3
In alkali chloride electrolysis to produce an alkali hydroxide and chlorine by electrolyzing an aqueous solution of an alkali chloride
Data Source
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AI summary
To provide a method whereby it is possible to efficiently produce an ion exchange membrane for alkali chloride electrolysis, which has high current efficiency and high alkali resistance at the time of electrolyzing an alkali chloride. This is a method for producing an ion exchange membrane 1 for alkali chloride electrolysis, having a layer (C) 12 containing a fluorinated polymer (A) having carboxylic acid type functional groups, by immersing an ion exchange membrane precursor film having a precursor layer (C') containing a fluorinated polymer (A') having groups convertible to carboxylic acid type functional groups, in an aqueous alkaline solution comprising an alkali metal hydroxide, a water-soluble organic solvent and water, and subjecting the groups convertible to carboxylic acid type functional groups to hydrolysis treatment to convert them to carboxylic acid type functional groups, wherein the concentration of the water-soluble organic solvent is from1 to 60 mass% in the alkaline aqueous solution (100 mass%); the proportion of structural units having carboxylic acid type functional groups in the fluorinated polymer (A) is from 14.00 to 14.50 mol%; and the resistivity in the layer (C) 12 is from 3.0×103 to 25.0×103 Ω·cm.