Polyamide Hollow Fiber Membrane Phase Separation
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Solution Overview
Problem
Current porous filtration membranes, particularly those made from polyolefins and polyvinylidene fluorides, suffer from low water flow rates, fouling, and limited resistance to chemicals and organic solvents, while polyamide membranes face challenges in production due to solvent limitations and high costs, lacking high water permeability and controlled pore size.
Innovation Solution
A polyamide hollow fiber membrane is produced by dissolving a highly hydrophilic polyamide resin in a specific organic solvent at high temperature, followed by cooling to induce phase separation, resulting in a membrane with a water contact angle less than 80 degrees, high water permeability, and a 0.1-μm particle rejection percentage of not less than 90%, using solvents like sulfolane and polyethylene glycol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyolefin or polyvinylidene fluoride membranes are used, then chemical resistance is improved, but water flow rate decreases and fouling increases
Solution Approach 1:
The patent changes the chemical composition parameters by using polyamide resin instead of polyolefin or polyvinylidene fluoride, and adjusts the molecular weight and crystallinity parameters to achieve both chemical resistance and high water flow rate. The specific polyamide resin with controlled molecular weight and the phase separation process create a membrane structure that maintains chemical resistance while improving water permeability.
Solution Approach 2:
The patent creates a composite membrane structure by combining polyamide resin with specific additives and controlling the phase separation process to form a dual-layer structure with distinct pore distributions. This composite approach allows the membrane to simultaneously achieve chemical resistance from the polyamide base material and high water flow rate through the optimized pore structure.
2Productivity
If polyamide resin is used, then water flow rate is improved, but production difficulty increases due to solvent limitations
Solution Approach 1:
The patent changes the solvent selection parameter by using fluorinated solvents with specific boiling points and chemical properties that are soluble to polyamide resin. It also adjusts the temperature parameter during the phase separation process to control the membrane formation, thereby achieving high water flow rate while managing production complexity through controlled parameter changes.
Solution Approach 2:
The patent introduces a fluorinated solvent as an intermediary medium that facilitates the dissolution of polyamide resin and enables the phase separation process. This intermediary solvent allows the membrane to be formed with controlled pore structure and high water flow rate, while the solvent's specific properties help manage the production process complexity.
3Ease of manufacture
If conventional phase separation process is used, then manufacturing ease is improved, but pore size control precision deteriorates
Solution Approach 1:
The patent adjusts multiple parameters including the polyamide resin molecular weight, solvent type, temperature profile, and cooling rate to precisely control the phase separation process. By optimizing these parameters, the membrane achieves both ease of manufacture through a systematic process and high pore size control precision for effective filtration.
Solution Approach 2:
The patent performs preliminary actions by pre-dissolving the polyamide resin in the fluorinated solvent under controlled conditions before the phase separation process. This preliminary step ensures uniform distribution and controlled nucleation during subsequent cooling, enabling precise pore size control while maintaining manufacturing ease through a standardized preliminary procedure.
4Productivity
If hydrophilic resin is used, then water flow rate is improved, but membrane strength decreases
Solution Approach 1:
The patent changes the polyamide resin parameters including molecular weight, crystallinity, and composition ratio to achieve the optimal balance between hydrophilicity and strength. By controlling these parameters, the membrane maintains high water flow rate through adequate hydrophilicity while preserving sufficient mechanical strength for practical applications.
Solution Approach 2:
The patent creates a composite membrane structure where the polyamide base material provides both hydrophilicity and structural strength. The addition of specific additives and the controlled phase separation process create a dual-phase structure that maintains membrane integrity while providing high water flow rate through optimized pore distribution and hydrophilic pathways.
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 membrane is highly hydrophilic, resistant to fouling, and exhibits enhanced water permeability and particle rejection, suitable for applications in water treatment, pharmaceutical, and semiconductor industries.
Implementation Method 1
a homogeneous polymer solution prepared by dissolution of a polymer at a higher temperature is cooled to a temperature below a binodal curve (a boundary line between a first phase and a second phase) to induce the phase separation
Implementation Method 2
the polyamide resin is highly hydrophilic and highly resistant to chemicals
Data Source
AI summary
A hollow fiber membrane is produced through a thermally induced phase separation process by dissolving a highly hydrophilic polyamide resin in a high-boiling-point solvent such as an aprotic polar solvent at a temperature of not lower than 100° C. The hollow fiber membrane has a membrane surface having a water contact angle of not greater than 80 degrees, and has a water permeability of not less than 100 L/m2·atm·h and a 0.1-μm particle rejection percentage of not less than 90%.