Coextruded Multilayer Gas Separation Membrane
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Solution Overview
Problem
Current membrane technologies for fluid separation, such as gas separation and desalination, face challenges in achieving high selectivity and flux while being cost-effective, as they often require thin membranes that are prone to pinhole defects and rely on expensive and toxic organic solvents for processing.
Innovation Solution
A thin, coextruded multilayer film with axially oriented polymer layers, specifically using poly(ether block amide) and polypropylene with additives like CaCO3 or beta-nucleation agents, which can be processed solventlessly to achieve high CO2/O2 selectivity and flux, and can be heat-treated to enhance permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If membranes are made thinner to achieve high flux, then flux is improved, but the probability of pinhole defects increases
Solution Approach 1:
The membrane is divided into multiple alternating layers of different polymers (first polymer layers and second polymer layers) with distinct functions. The first polymer layers provide selectivity while the second polymer layers provide mechanical stability and pinhole prevention. This segmentation allows the membrane to achieve high flux through selective thinning of specific layers without compromising overall reliability.
Solution Approach 2:
Different regions of the membrane have different properties tailored to specific functions. The first polymer layers are designed with high selectivity characteristics, while the second polymer layers are designed with high mechanical strength and defect resistance. This local differentiation enables the thin membrane to maintain both high flux and low defect probability.
2Ease of manufacture
If conventional solvent-based processing is used, then membrane formation is achieved, but solvent costs and toxicity increase
Solution Approach 1:
The processing method changes from solvent-based to solventless melt extrusion. By changing the physical state parameters (temperature, viscosity) and eliminating the solvent component entirely, the process achieves membrane formation without the harmful factors associated with organic solvents, while maintaining manufacturing feasibility.
Solution Approach 2:
The harmful solvent component is completely extracted from the processing system. The invention uses only the polymer materials themselves, processed in the melt state, to form the membrane structure. This elimination of the solvent entirely removes the associated costs and toxicity issues.
3Reliability
If thin membranes are used to reduce pinhole defects, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The complex requirement of creating a thin, defect-free membrane is segmented into multiple layers with different thicknesses and functions. The second polymer layers can be thicker to provide mechanical integrity and pinhole prevention, while the first polymer layers are thinner to provide selectivity. This segmentation simplifies the manufacturing approach compared to attempting to make a single ultra-thin layer.
Solution Approach 2:
The membrane uses composite construction with alternating layers of different polymers. This composite structure combines the advantages of each material while mitigating their individual weaknesses, achieving high reliability without requiring the entire membrane to be extremely thin, thus simplifying manufacturing.
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 solution enables the production of membranes with high CO2/O2 selectivity and flux, reducing the risk of pinhole defects and solvent-related costs, while maintaining structural stability and chemical resistance, suitable for various fluid separation applications.
Implementation Method 1
The coextruded multilayer film is axially oriented to provide an axially oriented coextruded multilayer film
Implementation Method 2
heat-treated to enhance permeability
Implementation Method 3
Gas separation membranes can also be used to remove carbon dioxide and other impurities from natural gas
Data Source
AI summary
A method of fabricating a gas separation membrane includes providing a coextruded multilayer film that includes a first polymer layer formed of a first polymer material and a second polymer layer formed of a second polymer material, the first polymer material having a first gas permeability. The coextruded multilayer film is axially oriented such that the second polymer layer has a second gas permeability that is greater than the first gas permeability.