Thin Film Composite Membrane Preparation via Integrated Crosslinking
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Solution Overview
Problem
Existing methods for preparing thin film composite (TFC) membranes by interfacial polymerization are time-consuming and lack sufficient resistance to organic solvents, limiting their application in organic solvent nanofiltration due to the instability of support membranes and multiple processing steps.
Innovation Solution
A simplified method where polyfunctional monomers are introduced during membrane solidification in the coagulation bath, allowing for simultaneous crosslinking and impregnation, followed by interfacial polymerization with a water-immiscible solvent solution to form a solvent-resistant TFC membrane with a crosslinked polyimide support and a polyamide top layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional interfacial polymerization method is used to prepare TFC membranes, then the membrane formation process is completed, but the process is time-consuming and requires multiple separate steps (support membrane preparation, crosslinking, and impregnation)
Solution Approach 1:
The patent combines multiple separate steps (support membrane preparation, crosslinking, and impregnation) into a single integrated process. The polyfunctional monomer serves dual purposes: it acts as both the support membrane forming agent and the crosslinking agent, eliminating the need for separate crosslinking and impregnation steps. This merging of functions directly resolves the technical contradiction by improving productivity while reducing process complexity.
Solution Approach 2:
The polyfunctional monomer exhibits multi-functionality by simultaneously performing multiple roles: it forms the support membrane structure, provides crosslinking functionality for stability, and serves as the impregnation agent for the active layer. This universal agent approach eliminates the need for multiple specialized reagents and steps, thereby improving preparation efficiency and simplifying the overall process.
2Reliability
If conventional TFC membranes are used, then membrane separation function is provided, but the support membranes lack sufficient resistance to organic solvents
Solution Approach 1:
The patent creates a composite membrane structure where a polyfunctional monomer-based crosslinked support membrane is combined with an active layer formed from reactive monomers. The crosslinked support provides enhanced mechanical strength and chemical stability (solvent resistance), while the active layer provides separation functionality. This composite approach resolves the contradiction by achieving high solvent resistance without significantly complicating the manufacturing process.
Solution Approach 2:
The patent modifies the chemical structure and properties of the support membrane by introducing crosslinking through polyfunctional monomers. This parameter change (from linear to crosslinked structure) dramatically improves solvent resistance and membrane stability. The crosslinked network structure prevents polymer chain dissolution in organic solvents while maintaining porosity for separation, thus achieving high reliability without excessive manufacturing complexity.
3Manufacturing precision
If multiple separate steps are used for membrane preparation, then each step can be optimized independently, but the overall preparation time increases
Solution Approach 1:
The patent incorporates the crosslinking functionality into the support membrane formation step itself, rather than performing crosslinking as a subsequent separate operation. The polyfunctional monomer is pre-loaded into the support membrane structure during formation, so that crosslinking occurs concurrently with membrane formation. This preliminary action eliminates idle time between steps while maintaining adequate control over each functional aspect.
Solution Approach 2:
The patent establishes a continuous process where support membrane formation, crosslinking, and impregnation occur in an uninterrupted sequence within a single operational framework. The reactive groups are continuously available for crosslinking as the membrane forms, and the impregnation follows immediately without intermediate processing. This continuity eliminates downtime and transfer operations, significantly reducing total preparation time while maintaining process control through the unified nature of the continuous operation.
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 results in TFC membranes with enhanced resistance to organic solvents, improving their stability and filtration performance, enabling broader applications in organic solvent nanofiltration while reducing the complexity and time of the membrane preparation process.
Implementation Method 1
contacting the solidified and impregnated support obtained in step (ii) with a water-immiscible solvent solution comprising a polyfunctional monomer for interfacial polymerization, whereby said latter monomer interfacially polymerises with at least one of the polyfunctional monomers impregnated in the support to form a thin film layer
Implementation Method 2
immersing said casted first polymer solution into a coagulation medium to solidify the first polymer
Data Source
AI summary
The present invention relates to improved methods for the preparation of thin film composite membranes by interfacial polymerization, preferably (organic) solvent resistant thin film composite membranes. More in particular the method of the present invention allows for the preparation of thin film composite membranes wherein a thin film is deposited on a porous crosslinked support. Said method comprises the one step solidification, impregnation and crosslinking of the porous support through phase inversion by immersion of the cast membrane polymer film in an (aqueous) solvent comprising a polyfunctional monomers.