Polyimide Separation Functional Layer for Acid Gas

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Solution Overview

Problem

There is a need for a new separation functional layer suitable for efficiently separating acid gases, such as carbon dioxide, from gas mixtures containing them.

Innovation Solution

The development of a separation functional layer made of polyimide P, which includes structural units derived from tetracarboxylic dianhydride and diamine, with at least one functional group selected from carboxyl, hydroxyl, thiol, or metal salts of these groups.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional polyimide resins are used for separation functional layers, then manufacturing is straightforward, but separation efficiency for acid gases is insufficient

Engineering Contradiction:

Improveseparation efficiencyVSAvoidmaterial complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The invention modifies the chemical structure of polyimide by incorporating functional groups (carboxyl, hydroxyl, thiol, or metal salts) into the polymer chain. These parameter changes in molecular structure enable enhanced interaction with acid gases through chemical mechanisms, significantly improving separation efficiency while maintaining compatibility with conventional coating processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates composite polyimide structures by combining conventional polyimide backbone with functional groups containing metal salts or reactive moieties. This composite approach integrates the mechanical stability of polyimide with the acid gas affinity of functional groups, achieving high separation efficiency without sacrificing ease of manufacture

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If separation functional layer is made more selective for acid gases, then separation factor improves, but permeation coefficient may be compromised

Engineering Contradiction:

Improveseparation factorVSAvoidpermeation coefficient

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The invention introduces functional groups at specific locations within the polyimide structure to create local zones of high acid gas affinity. These localized functional regions enhance separation factor by preferentially binding acid gases, while the bulk polyimide structure maintains adequate free volume and chain mobility to preserve permeation coefficient

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The functional groups act as intermediary sites that facilitate acid gas transport through the membrane. These intermediaries provide binding and release mechanisms that enhance selectivity while maintaining permeation pathways, effectively mediating between separation factor and permeation coefficient requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If functional groups are added to polyimide structure, then acid gas separation performance improves, but resistance to physical aging may deteriorate

Engineering Contradiction:

Improveseparation performanceVSAvoidresistance to physical aging

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The invention uses metal salts as templates or crosslinking agents that create stable structural networks within the polyimide. These metal salt structures act as stable copies or frameworks that maintain the polyimide chain arrangement, preventing physical aging while preserving the functional groups' acid gas separation capabilities

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The functional groups and metal salts are incorporated into the polyimide structure during manufacturing to pre-establish stable configurations. This preliminary structuring prevents subsequent physical aging by locking the polymer chains in stable arrangements before exposure to service conditions, thereby maintaining separation performance over time

Inventive Principle:

Principle #10Preliminary action

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 new separation functional layer effectively enhances the permeation coefficient and separation factor for acid gases, improving the efficiency of acid gas separation from gas mixtures while maintaining durability and resistance to physical aging.

Implementation Method 1

a membrane separation method has been developed as a method for separating an acid gas such as carbon dioxide from a gas mixture containing the acid gas

Methodology Applied

Scientific EffectPermeation: Permeation

Data Source

PatentUS20250041808A1Separation functional layer, separation membrane, and method for manufacturing separation functional layer

Publication Date: 2025.02.06 NITTO DENKO CORP

AI summary

The present invention provides a new separation functional layer suitable for separating an acid gas from a gas mixture containing the acid gas. A separation functional layer of the present invention includes polyimide. The polyimide includes a structural unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure, and a structural unit B1 derived from diamine. At least one of the structural unit A1 and the structural unit B1 has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, a thiol group, and metal salts of these groups.