Fluorine-Containing Aliphatic Polyamide Coating for Antifouling Membranes
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Solution Overview
Problem
Current composite semipermeable membranes suffer from insufficient antifouling properties, with performance and water permeability decreasing upon contact with acids or acidic solutions, and existing coatings either fail to inhibit fouling effectively or reduce water permeability.
Innovation Solution
A composite semipermeable membrane with a separation functional layer comprising a crosslinked aromatic polyamide and a fluorine-containing aliphatic polyamide coating, where the fluorine content and nitrogen-to-oxygen ratio are optimized to enhance antifouling properties and maintain high water permeability, even after exposure to acids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer including poly(vinyl alcohol) or poly(alkylene oxide) is formed to mitigate fouling substance adhesion, then antifouling properties are improved, but water permeability decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fluorine content (0.1-5.0 at%) and nitrogen-to-oxygen ratio (0.8-1.3) in the coating layer. These parameter optimizations enable the coating to provide antifouling properties while maintaining high water permeability, resolving the contradiction between fouling resistance and water transport efficiency
Solution Approach 2:
The patent uses composite materials by forming a coating layer that contains both fluorine atoms (for antifouling) and nitrogen/oxygen atoms (for hydrophilicity and water permeability). This composite approach combines the benefits of different elements to achieve both antifouling properties and high water permeability simultaneously
2Reliability
If the separation functional layer is coated with poly(vinyl alcohol) to neutralize charge state, then fouling is inhibited, but membrane performance is reduced by acid cleaning
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by incorporating fluorine atoms and optimizing the nitrogen-to-oxygen ratio. This composition modification provides fouling inhibition through hydrophilicity while enhancing acid resistance, preventing membrane performance degradation during acid cleaning operations
Solution Approach 2:
The patent replaces the vulnerable poly(vinyl alcohol) coating with a more chemically stable fluorine-containing coating. This new coating maintains its antifouling function through chemical stability rather than charge neutralization, making it resistant to degradation by acid cleaning and extending membrane service life
3Reliability
If a coating layer is formed to inhibit fouling, then antifouling properties are improved, but the effect is insufficient without optimal fluorine content control
Solution Approach 1:
The patent applies parameter changes by establishing specific ranges for fluorine content (0.1-5.0 at%) and nitrogen-to-oxygen ratio (0.8-1.3). These parameter specifications enable consistent manufacturing of coating layers with optimal antifouling properties, balancing fouling resistance with water permeability and chemical stability
Solution Approach 2:
The patent uses X-ray photoelectron spectrometry to measure and control the fluorine content and nitrogen-to-oxygen ratio in the coating layer. This analytical feedback mechanism ensures precise control of coating composition, enabling reproducible antifouling performance while maintaining manufacturing feasibility
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 stable antifouling performance and high water permeability, with improved resistance to fouling substances and chemical cleaning, ensuring long-term operational stability.
Implementation Method 1
a coating layer existing on the first layer and including an aliphatic polyamide including a fluorine atom
Implementation Method 2
the composite semipermeable membrane has a proportion of the number of fluorine atoms to the total number of atoms of all elements of 0.5% or more and 8% or less
Implementation Method 3
a separation functional layer disposed on the porous support layer, in which the separation functional layer includes a first layer including a crosslinked aromatic polyamide
Implementation Method 4
a composite semipermeable membrane obtained by coating a microporous support membrane with a separation functional layer constituted of a crosslinked polyamide obtained by a polycondensation reaction
Implementation Method 5
a first layer including a crosslinked aromatic polyamide that is a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride
Implementation Method 6
exhibiting stable antifouling properties before and after contact with an acid
Implementation Method 7
has a ratio (N/O ratio) of the number of nitrogen atoms to the number of oxygen atoms of 0.8 or more and 1.3 or less
Implementation Method 8
the composite semipermeable membrane has high water permeability and antifouling properties
Data Source
AI summary
The present invention relates to a composite semipermeable membrane including: a substrate; a porous support layer disposed on the substrate; and a separation functional layer disposed on the porous support layer, in which the separation functional layer includes: a first layer including a crosslinked aromatic polyamide; and a coating layer existing on the first layer and including an aliphatic polyamide including a fluorine atom, and the composite semipermeable membrane has a proportion of the number of fluorine atoms to the total number of atoms of all elements of 0.5% or more and 8% or less, and has a ratio (N/O ratio) of the number of nitrogen atoms to the number of oxygen atoms of 0.8 or more and 1.3 or less.