Uncrosslinked Polyimide Membrane for Gas Separation
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Solution Overview
Problem
Crosslinked hollow fiber membranes for gas separation experience a significant drop in permeance, making them less effective for separating gas mixtures like methane and carbon dioxide, and the crosslinking process is challenging on a commercial scale.
Innovation Solution
Development of uncrosslinked high molecular weight polyimide polymer membranes using a small amount of bulky diamine, which maintains selectivity and permeability without the need for crosslinking, allowing for the separation of gas mixtures like CO2 and CH4.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If crosslinked hollow fiber membranes are used for gas separation, then selectivity is improved, but permeance drops significantly
Solution Approach 1:
The patent removes the crosslinking step from the membrane fabrication process. By using uncrosslinked polyimide polymers with high molecular weight (Mw > 100,000), the invention extracts the harmful crosslinking reaction that causes permeance loss while retaining the beneficial selectivity properties through careful polymer selection and formulation.
Solution Approach 2:
The invention changes the molecular weight parameter of the polyimide polymer to be greater than 100,000, which fundamentally alters the membrane's performance characteristics. This parameter change allows the membrane to achieve both high selectivity and high permeance without requiring crosslinking, thereby resolving the trade-off between these two properties.
2Reliability
If crosslinking process is applied to hollow fiber membranes, then membrane stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent removes the crosslinking step from the manufacturing process. By utilizing uncrosslinked high molecular weight polyimide polymers, the invention eliminates the complex crosslinking reaction conditions, catalysts, and process control requirements while maintaining membrane stability through the inherent properties of the high Mw polymer.
Solution Approach 2:
The invention replaces the complex crosslinking process with a simpler, more direct fabrication approach using high molecular weight polyimide polymers. This substitution eliminates the need for additional chemicals, extended processing time, and complex equipment requirements associated with crosslinking, thereby reducing manufacturing complexity.
3Productivity
If uncrosslinked high molecular weight polyimide polymer is used, then permeance is improved, but molecular weight control becomes more challenging
Solution Approach 1:
The invention establishes a minimum molecular weight threshold (Mw > 100,000) for the polyimide polymer. By setting this parameter boundary, the patent ensures that the polymer achieves the necessary permeance performance while providing a clear specification that guides manufacturing control, thereby balancing performance improvement with manufacturability.
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 membranes exhibit high CO2 permeance and selectivity even at high pressures, enhancing their suitability for gas separation applications without the complexity of crosslinking, and are more commercially viable.
Implementation Method 1
Incorporating a small amount of bulky diamines into a high molecular weight polyimide polymer inhibits segmental motion and reduces chain mobility or flexibility
Implementation Method 2
Incorporating a small amount of bulky diamines into a high molecular weight polyimide polymer inhibits segmental motion and reduces chain mobility or flexibility, which increases the glass transition temperature and free volume
Implementation Method 3
These uncrosslinked, high molecular weight polyimide polymers are useful for polymer membranes with high permeance and good selectivity, which can be used for the separation of fluid mixtures
Data Source
AI summary
One method as described herein relates to making a membrane comprising an uncrosslinked high molecular weight polyimide polymer with a small amount of bulky diamine. Also as described herein is a hollow fiber polymer membrane comprising an uncrosslinked high molecular weight polyimide polymer with a small amount of bulky diamine. The polyimide polymers include monomers comprising dianhydride monomers, diamino monomers without carboxylic acid functional groups, and optionally diamino monomers with carboxylic acid functional groups, wherein 2 to 10 mole % of the diamino monomers are bulky diamino compounds and the ratio of diamino monomers with carboxylic acid functional groups to diamino monomers without carboxylic acid functional groups is 0 to 2:3. These uncrosslinked high molecular weight polyimide polymers with a small amount of bulky diamine are useful in forming polymer membranes with high permeance and good selectivity that are useful for the separation of fluid mixtures.