Cross-Linked Polybenzimidazole Membranes for Organic Solvent Filtration
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Solution Overview
Problem
Existing membranes for ultrafiltration and nanofiltration are not suitable for use in organic solvents due to lack of solvent stability, leading to structural degradation and poor performance, and there is a need for membranes with tunable permeance and rejection properties.
Innovation Solution
A process for preparing asymmetric integrally skinned membranes using polybenzimidazole polymers, involving a cross-linking agent with electrophilic functional groups and a cross-link modification agent with nucleophilic functional groups to enhance stability and performance in organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polybenzimidazole membranes are cross-linked to improve solvent stability, then chemical resistance improves, but membrane brittleness increases dramatically
Solution Approach 1:
A flexible spacer molecule is introduced as an intermediary between the polybenzimidazole chains and the cross-linking agent. The spacer has the formula -[CH2]x- where x is 2-10, providing flexibility and preventing direct rigid cross-linking that causes brittleness. This mediator allows cross-linking for solvent stability while maintaining membrane flexibility through the flexible spacer chain.
2Ease of manufacture
If existing membranes are used for organic solvent filtration, then manufacturing simplicity is maintained, but membrane structural degradation occurs
Solution Approach 1:
The chemical composition parameters of the membrane are changed by incorporating polybenzimidazole polymer with specific structural features and using a flexible spacer cross-linking system. This changes the membrane's chemical resistance properties to withstand organic solvents while maintaining manufacturing feasibility through established cross-linking methodologies.
3Reliability
If membrane cross-linking is performed to enhance chemical resistance, then solvent stability improves, but manufacturing complexity increases
Solution Approach 1:
The flexible spacer is incorporated into the cross-linking agent structure before the cross-linking reaction takes place. This preliminary design of the cross-linking agent with built-in flexibility prevents brittleness from the start, eliminating the need for subsequent corrective treatments or complex multi-step processes to address brittleness after cross-linking.
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 improved solvent stability, higher permeance, and consistent performance in organic solvents, with tunable properties for enhanced separation efficiency.
Implementation Method 1
the cross-linking agent is at least difunctionalised and comprises an electrophilic functional group
Implementation Method 2
the cross-link modification agent is mono-functional and comprises a functional group capable of reacting with an electrophilic functional group on the cross-linking agent
Implementation Method 3
asymmetric integrally skinned membrane for the separation of at least one solute from a solution
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The present invention relates to a process for preparing an asymmetric integrally skinned membrane for the separation of at least one solute from a solution, comprising the steps of: (a) preparing a polybenzimidazole dope solution comprising: (i) a polybenzimidazole polymer, and (ii) a solvent system for said polybenzimidazole which is water miscible; (b) casting a film of said dope solution onto a support; (c) immersing the film cast on the support into a coagulating medium to form an asymmetric integrally skinned membrane; (d) treating the membrane from step (c) with a cross-linking agent; (e) treating the membrane from step (d) with a cross-link modification agent. Further aspects relate to an asymmetric integrally skinned membrane and uses thereof.