Unstretched Polyethylene Ion-Exchange Membrane for Brine Concentration
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Solution Overview
Problem
Ion-exchange membranes with porous stretched sheets lack practical strength and exhibit low concentration properties during electrodialysis, failing to achieve high brine concentration due to high membrane resistance per unit thickness.
Innovation Solution
An ion-exchange membrane using an unstretched porous polyethylene sheet with fine pores filled with ion-exchange resin, offering improved mechanical strength and concentration properties by maintaining a high tensile elongation and adjustable thickness, which reduces membrane resistance and enhances brine concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous stretched polyethylene sheet is used as the base sheet, then the membrane resistance per unit thickness is reduced, but the mechanical strength and concentration property deteriorate
Solution Approach 1:
The patent inverts the conventional approach by using an unstretched porous polyethylene sheet instead of a stretched sheet. This inversion resolves the contradiction because the unstretched sheet maintains high tensile elongation (not less than 450% in both MD and TD directions) while achieving low membrane resistance per unit thickness, thereby improving concentration property without sacrificing mechanical strength
2Reliability
If the base sheet thickness is reduced to lower membrane resistance, then the concentration property is improved, but the mechanical strength deteriorates
Solution Approach 1:
The patent changes the key parameter of tensile elongation by using an unstretched porous polyethylene sheet with tensile elongation of not less than 450% in both machine direction and transverse direction. This parameter change allows the membrane to maintain high mechanical strength even at reduced thickness (10 to 300 μm), thereby improving concentration property without compromising strength
3Reliability
If a porous base sheet is used to reduce membrane resistance, then the concentration property is improved, but the shape stability deteriorates due to swelling
Solution Approach 1:
The patent creates a composite structure by filling the pores of the unstretched porous polyethylene sheet with ion-exchange resin. This composite material approach resolves the contradiction because the polyethylene base sheet with high tensile elongation provides dimensional stability that prevents excessive swelling, while the ion-exchange resin fills the pores to maintain low membrane resistance, achieving both high concentration property and shape stability
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 unstretched polyethylene sheet-based ion-exchange membrane achieves significantly improved concentration properties, allowing for higher brine concentration with lower membrane resistance, and provides enhanced mechanical strength and shape stability, preventing liquid leakage and swelling.
Implementation Method 1
Ion-exchange membranes have been industrially used in many fields as electrolytic membranes for conducting the electrodialysis
Implementation Method 2
a porous sheet in which fine pores are piercing
Data Source
AI summary
An ion-exchange membrane including a porous unstretched polyethylene sheet in which fine pores are piercing, the pores being filled with an ion-exchange resin.The ion-exchange membrane exhibits excellent concentration property.