Porous Asymmetric Membrane Surface Modification via Phase Inversion
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Solution Overview
Problem
Current methods for producing porous asymmetric membranes face challenges in delivering polymer additives to the selective surface without causing incompatibility or solubility issues, affecting filtration properties and permeation flux.
Innovation Solution
A method involving dissolving hydrophobic polymers like poly(phenylene ether) in water-miscible polar aprotic solvents, followed by phase-inversion with a non-solvent composition containing a polymer additive, ensures the additive is selectively incorporated into the membrane surface, improving filtration properties and reducing extraction during coagulation and end-use applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polymer additives are added to the dope solution to obtain desired pore size and pore distribution, then the selective surface properties are improved, but the polymer additive can be incompatible with the membrane-forming polymer or insoluble in the dope solution
Solution Approach 1:
The patent uses a water-miscible polar aprotic solvent as an intermediary medium that is compatible with both the hydrophobic polymer and the polymer additive. This solvent acts as a bridge, allowing the additive to be delivered to the selective surface without direct incompatibility issues between the additive and the polymer matrix, thus resolving the contradiction between achieving desired pore properties and maintaining system compatibility
Solution Approach 2:
The patent changes the solvent parameter from traditional organic solvents to water-miscible polar aprotic solvents, which fundamentally alters the solubility and compatibility characteristics of the system. This parameter change enables the polymer additive to remain soluble and compatible while still achieving the desired pore size and distribution in the selective surface
2Manufacturing precision
If significant amounts of polymer additive are used to achieve optimal membrane properties, then the filtration performance is improved, but significant amounts of the polymer additive can remain trapped in the interior of the hollow fiber annular section
Solution Approach 1:
The patent extracts or removes the polymer additive from the dope solution before membrane formation, and instead introduces it during the phase inversion step. This prevents the additive from being trapped in the bulk polymer matrix during coagulation, allowing it to be selectively incorporated only in the selective surface layer, thus avoiding waste while achieving optimal membrane properties
Solution Approach 2:
The patent prepares the polymer additive solution in advance in a separate non-solvent composition, and then introduces it during the phase inversion process. This preliminary preparation ensures that the additive is available in the correct form and concentration to be selectively incorporated into the selective surface without being wasted in the bulk membrane structure
3Manufacturing precision
If polymer additive is added to improve selectivity, then the filtration properties are enhanced, but it can adversely affect permeation flux
Solution Approach 1:
The patent applies the polymer additive locally only to the selective surface layer of the membrane, rather than throughout the entire membrane structure. This localized application enhances selectivity at the surface where it is most needed for filtration, while minimizing its impact on the bulk membrane structure that governs permeation flux, thus resolving the contradiction between selectivity and productivity
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 approach enhances surface pore size, pore density, water contact angle, and molecular weight cut-off, resulting in membranes with improved filtration performance and reduced waste, suitable for various separation processes.
Implementation Method 1
phase-inverting the membrane-forming composition in a first non-solvent composition comprising a non-solvent comprising water, a water-miscible polar aprotic solvent, or a combination comprising at least one of the foregoing, and a polymer additive dissolved in the first non-solvent composition, to form the porous asymmetric membrane
Data Source
AI summary
An method of making a porous asymmetric membrane involves dissolving a poly(phenylene ether), poly(phenylene ether) copolymer, polyethersulfone, polysulfone, polyphenylsulfone, polyimide, polyetherimide, polyvinylidene fluoride, or a combination thereof in a water-miscible polar aprotic solvent to provide a membrane-forming composition; and phase-inverting the membrane-forming composition in a first non-solvent composition composed of water, a water-miscible polar aprotic solvent, or a mixture thereof, and a polymer additive dissolved in the first non-solvent composition. The method can be a method of making a hollow fiber by coextrusion through a spinneret having an annulus and a bore, including coextruding the membrane-forming composition through the annulus, and the first non-solvent composition through the bore, into a second non-solvent composition composed of water, a water-miscible polar aprotic solvent, or a mixture thereof to form the hollow fiber.