Crosslinked Polyimide Gas Separation Membrane
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Solution Overview
Problem
Existing gas separation membranes face challenges in achieving high gas permeability, separation selectivity, and mechanical strength, particularly under high pressure and high carbon dioxide concentration conditions, where plasticization leads to decreased separation selectivity and membrane durability.
Innovation Solution
A composite membrane is developed with a gas-permeable supporting layer and a gas separating layer containing crosslinked polyimide resin, where the crosslinked sites are optimized to maintain high gas permeability and separation selectivity, achieved by introducing a radically crosslinkable functional group and adjusting the crosslinking ratio, allowing for mild crosslinking conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single raw material is processed into an asymmetric membrane with a thin skin layer, then gas permeability is improved, but it is difficult to simultaneously achieve high separation selectivity and mechanical strength
Solution Approach 1:
The membrane is divided into two functional layers: a porous supporting layer that provides mechanical strength and a thin gas-separating layer that provides high gas permeability and separation selectivity. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The invention uses a composite membrane structure combining a porous supporting layer (made from materials like polyethylene terephthalate or polypropylene) with a gas-separating layer (made from crosslinked polyimide resin). This composite structure integrates the advantages of both materials to achieve simultaneous high permeability, selectivity, and mechanical strength.
2Reliability
If crosslinked structure is introduced into the polymer compound to suppress plasticization, then separation selectivity is improved, but high temperature or very long time is required for crosslinking
Solution Approach 1:
The invention changes the crosslinking parameters by using a photopolymerization initiator that enables crosslinking at low temperature (room temperature or slightly elevated) and short time (minutes to hours) through UV irradiation. This replaces conventional high-temperature/long-time thermal crosslinking methods.
Solution Approach 2:
The invention replaces thermal energy (heat) with electromagnetic energy (UV light) as the activation source for crosslinking. This substitution allows crosslinking to proceed under milder conditions with faster reaction kinetics, significantly reducing processing time and energy consumption.
3Duration of action of stationary object
If crosslinked structure is introduced to improve mechanical strength and suppress plasticization, then membrane durability is improved, but gas permeability may decrease due to reduced chain mobility
Solution Approach 1:
The crosslinked structure is localized specifically in the gas-separating layer where it is needed to suppress plasticization and improve durability, while the porous supporting layer remains uncrosslinked to maintain its mechanical support function and gas transport pathways. This local application minimizes the negative impact on overall gas permeability.
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 composite membrane achieves excellent gas permeability, high separation selectivity, and improved mechanical strength, enabling efficient separation of gases like carbon dioxide and methane while maintaining durability under varying conditions.
Implementation Method 1
allowing reaction of the crosslinkable functional group by irradiating the coating liquid with active radiation
Implementation Method 2
a desired gas component can be separated by allowing selective permeation by means of a membrane constituted of a specific polymer compound
Data Source
AI summary
A gas separation composite membrane, containing a gas-permeable supporting layer and a gas separating layer containing a crosslinked polyimide resin over the gas-permeable supporting layer, in which the crosslinked polyimide resin is formed by a polyimide compound being crosslinked by a radically crosslinkable functional group thereof, and a ratio [η] of a crosslinked site to an imide group of the polyimide compound (the number of crosslinked sites/the number of imide groups) in the crosslinked polyimide resin is 0.0001 or more and 0.45 or less; a method of producing the same; and a gas separating module, a gas separation apparatus and a gas separation method using the same.