Porous Hollow Fiber Membrane Crystallization Control
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Solution Overview
Problem
Existing porous hollow fiber membranes used in water treatment face challenges with maintaining high water permeability, blocking performance, and chemical resistance over long periods, especially under repeated chemical cleaning.
Innovation Solution
A porous hollow fiber membrane made of a thermoplastic resin with specific crystallization onset temperature, enthalpy of crystal fusion, and degree of crystallinity, produced using the thermally induced phase separation (TIPS) method, which includes a multi-stage heat treatment step and the use of a polyvinylidene fluoride-based resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If chemical cleaning is performed to remove accumulated organic substances on the membrane surface, then cleaning performance is improved, but the polymer constituting the hollow fiber membrane is degraded
Solution Approach 1:
The patent changes the chemical parameters of the cleaning solution by specifying precise compositions (e.g., alkaline cleaners with controlled pH, enzymatic cleaners with specific enzyme types and concentrations) to optimize cleaning effectiveness while minimizing damage to the membrane polymer structure
Solution Approach 2:
The patent applies different cleaning solutions with varying strengths to different parts of the membrane system or uses staged cleaning approaches where milder solutions are applied first followed by stronger solutions only when necessary, thereby preserving membrane integrity while achieving thorough cleaning
2Strength
If the hollow fiber membrane is made stronger to withstand external pressure during filtration, then mechanical strength is improved, but chemical resistance may be compromised
Solution Approach 1:
The patent employs composite material structures combining different polymer components or integrating reinforcement layers with specific chemical resistance properties, thereby achieving both high mechanical strength and excellent chemical resistance simultaneously
Solution Approach 2:
The patent optimizes polymer composition parameters including molecular weight distribution, crosslinking density, and additive packages to enhance both mechanical strength and chemical resistance without compromising either property
3Productivity
If the membrane is designed for high water permeability to process large volumes of water, then filtration efficiency is improved, but blocking performance and structural stability may be reduced
Solution Approach 1:
The patent divides the membrane into multiple functional layers with different pore sizes and structures - a selective skin layer for blocking performance and a support layer for high permeability - thereby achieving both high water throughput and effective contaminant rejection
Solution Approach 2:
The patent utilizes controlled porous structures with optimized pore size distributions, porosity gradients, and interconnected pore networks to maximize water permeability while maintaining sufficient blocking performance through appropriate pore architecture
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 membrane achieves high water permeability, effective blocking performance, and enhanced chemical resistance, enabling continuous long-term operation without significant degradation.
Implementation Method 1
the thermally induced phase separation (TIPS) method, which includes a multi-stage heat treatment step
Implementation Method 2
a crystallization onset temperature is 140° C. or lower, and an enthalpy of crystal fusion at and below the crystallization onset temperature is 10 J/g or less
Data Source
AI summary
The present disclosure provides a porous hollow fiber membrane that exhibits blocking performance and water permeability performance suitable for filtration applications, as well as having excellent chemical resistance. In order to provide a solution to the above issue, the porous hollow fiber membrane of the present disclosure is made of a thermoplastic resin, wherein the crystallization onset temperature is 140° C. or lower, and the enthalpy of crystal fusion at and below the crystallization onset temperature is 10 J/g or less.