Positively Charged Membrane Production Using Sulfolane Solvent
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Solution Overview
Problem
Current methods for producing positively charged membranes are inefficient, requiring multiple steps and additional post-treatments, which affect pore size and increase production costs, and have not successfully achieved durable, single-step production of such membranes using engineering plastics and polycations due to solubility issues with standard solvents.
Innovation Solution
The use of 2,3,4,5-tetrahydrothiophene-1,1-dioxide as a solvent, which dissolves polycations and polyarylethers, allowing for a one-step blending process that produces positively charged membranes with a stable and homogenous structure without the need for additional additives or post-treatments, by mixing the solvent with aprotic solvents to reduce the critical mixing temperature and achieve a clear, stable dope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard solvents (e.g., NMP, DMF) are used to produce membranes, then the membrane formation process is straightforward, but polycations cannot be dissolved and positively charged membranes cannot be produced
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by selecting 2,3,4,5-tetrahydrothiophene-1,1-dioxide (sulfolane) instead of standard solvents like NMP or DMF. This parameter change enables the dissolution of polycations while maintaining compatibility with polyarylethers, allowing the formation of positively charged membranes through a single-step process.
2Reliability
If multiple-step procedures with coating or chemical grafting are used to produce positively charged membranes, then the membranes can be positively charged, but the production cost increases and the pore size is negatively affected
Solution Approach 1:
The patent merges the membrane formation process with the charging process into a single step. By incorporating polycations directly into the polymer solution before membrane formation, the positively charged membrane is produced in one operation, eliminating separate coating or grafting steps and their associated complexity and cost.
Solution Approach 2:
The patent performs preliminary action by pre-mixing polycations with the polymer solution before membrane formation. This ensures the polycations are already integrated into the membrane matrix during the phase separation process, rather than requiring post-formation modification.
3Adaptability or versatility
If fugitive additives are used to improve membrane properties, then additional characteristics can be achieved, but the additives must be removed in an additional costly step
Solution Approach 1:
The patent uses the polycations as intrinsic components of the membrane rather than fugitive additives. The polycations perform multiple functions (providing positive charge, influencing phase separation, contributing to membrane structure) and remain as permanent, beneficial components of the membrane, eliminating the need for removal steps.
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
This method enables the production of durable, positively charged membranes with a desired sponge structure and optimal pore size, eliminating the need for pore-forming additives and post-treatments, thereby reducing production costs and improving membrane quality.
Implementation Method 1
The use of 2,3,4,5-tetrahydrothiophene-1,1-dioxide as a solvent, which dissolves polycations and polyarylethers, allowing for a one-step blending process
Implementation Method 2
In the coagulation process the membranes are formed by phase separation of the polymer solution. Phase separation can be induced by cooling said mixture or exposing the mixture to a non-solvent. The latter method is known as non-solvent induced phase separation (NIPS).
Implementation Method 3
In NIPS, the polymer solution is immersed in a non-solvent bath (coagulation bath), where the exchange of solvent and non-solvent takes place. The solvent migrates from the polymer solution into the coagulation bath, while the non-solvent follows the reverse path, leading finally to the formation of the membrane.
Data Source
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AI summary
The present invention relates to a method for the production of a positively charged membrane. Furthermore the present invention relates to a positively charged membrane obtainable by the methods of present invention and the use of these positively charged membranes.