Polyimide composition and preparation method of separation membrane
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Solution Overview
Problem
Conventional membrane separation processes using PTFE, ceramic, or glass fiber membranes are limited by poor processability and are primarily suited for microfiltration, lacking effective resistance to high-polarity solvents for applications in pervaporation (PV) and vapor permeation (VP).
Innovation Solution
A polyimide composition comprising a dissolvable polyimide, a crosslinking agent, and a solvent is used to create a separation membrane with good processability and resistance to high-polarity solvents, achieved through a crosslinking process and dry phase inversion, allowing the membrane to be coated on a substrate and used in PV and VP processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTFE, ceramic, or glass fiber membranes are used for separation, then resistance to high-polarity solvents is improved, but processability deteriorates
Solution Approach 1:
The patent uses polyimide as a composite material that combines the solvent resistance of traditional materials with improved processability. The polyimide membrane incorporates specific chemical structures (aromatic groups, imide rings) that provide both chemical stability against high-polarity solvents and flexibility in manufacturing processes.
Solution Approach 2:
The patent modifies the chemical parameters of the membrane material by selecting specific polyimide compositions with controlled molecular weight, aromatic content, and imide ring structure. These parameter changes enable the material to maintain solvent resistance while achieving better processability through standard membrane fabrication techniques.
2Reliability
If PTFE, ceramic, or glass fiber membranes are used for separation, then resistance to high-polarity solvents is improved, but application scope deteriorates
Solution Approach 1:
The polyimide membrane is designed with multi-functionality to serve various separation applications including microfiltration, ultrafiltration, and reverse osmosis. The material's chemical stability allows it to function across different operating conditions and solvent types, making it universally applicable beyond the limitations of traditional materials.
Solution Approach 2:
By adjusting the polyimide composition parameters such as molecular weight distribution, crosslinking density, and pore structure, the membrane can be optimized for different separation mechanisms and applications, expanding its versatility while maintaining solvent resistance.
3Productivity
If conventional membrane materials are used, then microfiltration capability is achieved, but pervaporation and vapor permeation applicability deteriorates
Solution Approach 1:
The patent optimizes polyimide parameters including glass transition temperature, free volume, and chain flexibility to enable effective pervaporation and vapor permeation. These parameter adjustments allow the membrane to maintain microfiltration performance while gaining the molecular-level separation capability needed for PV and VP applications.
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 resulting separation membrane exhibits excellent stability against high-polarity solvents, porosity, and processability, making it suitable for efficient operation in pervaporation and vapor permeation applications.
Implementation Method 1
a crosslinking process is performed on the polyimide composition
Implementation Method 2
A dry phase inversion process is performed on the polyimide membrane
Data Source
AI summary
A preparation method of separation membrane is provided. First, a polyimide composition including a dissolvable polyimide, a crosslinking agent, and a solvent is provided. The dissolvable polyimide is represented by formula 1:wherein B is a tetravalent organic group derived from a tetracarboxylic dianhydride containing aromatic group, A is a divalent organic group derived from a diamine containing aromatic group, A′ is a divalent organic group derived from a diamine containing aromatic group and carboxylic acid group, and 0.1≤X≤0.9. The crosslinking agent is an aziridine crosslinking agent, an isocyanate crosslinking agent, an epoxy crosslinking agent, a diamine crosslinking agent, or a triamine crosslinking agent. A crosslinking process is performed on the polyimide composition. The polyimide composition which has been subjected to the crosslinking process is coated on a substrate to form a polyimide membrane. A dry phase inversion process is performed on the polyimide membrane.