Ion-Exchange Membrane Bubbling Suppression via Low Molecular Weight Control
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Solution Overview
Problem
Existing methods for producing ion-exchange membranes, such as those used in alkali chloride electrolysis, face issues with oligomer removal, leading to high polymer loss, reduced yield, and poor filterability, as well as bubbling and peeling during membrane formation and electrolysis due to the presence of low molecular weight compounds with ionic groups.
Innovation Solution
A polymer composition comprising a fluorine-containing copolymer with specific low molecular weight compounds, where the content of these compounds is limited to 600 ppm or less, and the number average molecular weight is between 300 and 4000, to suppress bubbling and peeling during membrane formation and electrolysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cleaning is carried out with a fluorine-based solvent to reduce oligomers, then the amount of low molecular weight polymer is reduced, but the polymer loss increases and filterability deteriorates
Solution Approach 1:
The invention changes the cleaning parameter from using only fluorine-based solvent to using a mixed solvent system comprising fluorine-based solvent and hydrocarbon solvent. This parameter change enables effective oligomer removal while minimizing polymer loss and maintaining good filterability, as the hydrocarbon solvent component selectively extracts oligomers without excessive polymer dissolution.
Solution Approach 2:
The invention applies a composite solvent system combining fluorine-based solvent and hydrocarbon solvent in specific proportions. This composite approach leverages the complementary properties of both solvents: the fluorine-based solvent provides good polymer compatibility while the hydrocarbon solvent enhances oligomer extraction efficiency, achieving a balance between oligomer reduction and polymer preservation.
2Quantity of substance
If cleaning is carried out with a fluorine-based solvent to reduce oligomers, then the amount of low molecular weight polymer is reduced, but productivity decreases due to poor filterability
Solution Approach 1:
The invention modifies the cleaning solvent composition parameter to include hydrocarbon solvent alongside fluorine-based solvent. This change improves filterability by preventing polymer gelation during cleaning, thereby maintaining high productivity while still achieving effective oligomer reduction to the required levels.
Solution Approach 2:
The hydrocarbon solvent acts as an intermediary substance that facilitates selective oligomer extraction without causing polymer precipitation or gelation. This intermediary role maintains good fluid properties and filterability during the cleaning process, ensuring continuous high-productivity operation.
3Ease of manufacture
If low molecular weight compounds with ionic groups are present in the polymer composition, then the polymer can be processed, but bubbling occurs during membrane formation and peeling occurs during electrolysis
Solution Approach 1:
The invention extracts and removes low molecular weight compounds with ionic groups from the polymer composition through controlled cleaning processes. By taking out these harmful impurities while maintaining the main polymer structure, the invention eliminates bubbling during membrane formation and peeling during electrolysis, thereby improving membrane reliability without sacrificing processability.
Solution Approach 2:
The invention changes the purity parameter of the polymer composition by reducing low molecular weight compound content to specific levels. This parameter change eliminates the harmful effects (bubbling and peeling) while maintaining adequate processability, achieving a balance between reliability and manufacturability through precise compositional control.
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 proposed polymer composition effectively reduces bubbling and peeling during membrane formation and electrolysis, improving the stability and performance of ion-exchange membranes by minimizing the presence of low molecular weight compounds.
Implementation Method 1
Examples of the polymerization method include an emulsion polymerization method, a solution polymerization method, a suspension polymerization method, and a bulk polymerization method.
Implementation Method 2
In order to reduce such an oligomer, it is known to clean a fluorine-containing copolymer as a method for reducing the low molecular weight polymer included in the fluorine-containing copolymer
Implementation Method 3
when the low molecular weight compound has an ionic group, it is colored by thermal decomposition during melt molding and further bubbling is caused by moisture in the hygroscopic air
Implementation Method 4
an ion-exchange membrane method electrolysis technology using an ion-exchange membrane as a membrane has been industrialized worldwide as the most advantageous process
Data Source
AI summary
Provided are a polymer composition that can suppress bubbling during membrane formation and peeling of a laminated membrane and an ion-exchange membrane. The polymer composition is a polymer composition including: a fluorine-containing copolymer including a unit (a) derived from a perfluorovinyl compound having a side chain having an ionic group and a unit (b) derived from a fluoroolefin; and a low molecular weight compound (a) having a functional group represented by —COOX (X is H, NH4, or a monovalent metal ion), wherein a content of the low molecular weight compound (a) is 600 ppm or less based on a mass of the polymer composition.