Ion Exchange Membrane Production for Alkali Chloride Electrolysis
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Solution Overview
Problem
Conventional ion exchange membranes for alkali chloride electrolysis exhibit significant variations in current efficiency and inadequate alkali resistance, leading to increased electric power consumption, frequent membrane replacement, and decreased chlorine quality due to high oxygen concentration in the produced chlorine.
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, using an alkaline aqueous solution with specific concentrations of water-soluble organic solvent and alkali metal hydroxide, and incorporating inorganic particles and a binder on the outermost layers to enhance stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ion exchange membrane production method is used, then production cost is reduced, but current efficiency varies significantly and alkali resistance is inadequate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration of carboxylic acid type functional groups (13.25-14.35 mol%) and sulfonic acid type functional groups (13.10-30.50 mol%) in the fluorinated polymer layers. This specific parameter control ensures stable current efficiency and high alkali resistance while maintaining manufacturability through defined hydrolysis conditions (temperature 40-80°C, specific alkaline solution composition).
Solution Approach 2:
The patent uses composite materials by combining fluorinated polymers with specific functional groups in a multi-layer structure. The ion exchange membrane consists of a cathode-side layer with carboxylic acid type functional groups and an anode-side layer with sulfonic acid type functional groups, both based on fluorinated polymers. This composite structure provides both stability and manufacturability.
2Reliability
If ion exchange membrane with high alkali resistance is produced, then current efficiency is improved, but production process becomes more complex
Solution Approach 1:
The patent applies local quality by creating different functional layers at different locations of the membrane. The cathode-side layer contains carboxylic acid type functional groups (13.25-14.35 mol%) while the anode-side layer contains sulfonic acid type functional groups (13.10-30.50 mol%). This local differentiation provides high alkali resistance where needed while maintaining overall structural simplicity.
3Use of energy by moving object
If current efficiency is increased, then electric power consumption is reduced, but membrane manufacturing difficulty increases
Solution Approach 1:
The patent achieves high current efficiency (reducing electric power consumption) through parameter changes in the functional group concentrations: carboxylic acid type groups at 13.25-14.35 mol% and sulfonic acid type groups at 13.10-30.50 mol%. These parameters are controlled during hydrolysis treatment of the precursor film under specific conditions (temperature 40-80°C, alkaline solution with controlled composition), balancing performance with manufacturing ease.
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 results in ion exchange membranes with high current efficiency, minimal variation in current efficiency, and improved alkali resistance, reducing electric power consumption and extending membrane lifespan while maintaining chlorine quality.
Implementation Method 1
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 2
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, is used as a diaphragm
Data Source
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AI summary
To provide a production method whereby an ion exchange membrane for alkali chloride electrolysis can be obtained which has high current efficiency, little variation in current efficiency and high alkaline resistance. This is a method for producing an ion exchange membrane 1 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 converting the groups convertible to carboxylic acid type functional groups to carboxylic acid functional groups, wherein the concentration of the water-soluble organic solvent is from 1 to 60 mass% in the aqueous alkaline solution (100 mass%); the temperature of the aqueous alkaline solution is at least 40°C and less than 80°C; and the proportion of structural units having carboxylic acid type functional groups in the fluorinated polymer (A) is from 13.0 to 14.50 mol% in all structural units (100 mol%) in the fluorinated polymer (A).