Ester-Based Filter Membrane Saponification for Sterile Filtration
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Solution Overview
Problem
Filter modules with membranes made of cellulose acetate face challenges in achieving spontaneous wetting with water and maintaining fluid-tight connections to boundary members, leading to inadequate performance in sterile filtration due to material incompatibility and adverse effects from auxiliary substances or reinforcement methods.
Innovation Solution
The method of inline saponification, where the membrane surface is saponified only in regions not connected to the boundary member, allowing for hydrophilic surfaces without compromising the hydrophobic peripheral regions, ensuring fluid-tightness and mechanical stability while enabling spontaneous wetting and integrity testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the membrane surface is saponified to enable spontaneous wetting with water, then the membrane can undergo integrity testing, but the connection between the peripheral region of the membrane and the boundary member becomes inadequate due to material incompatibility
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different regions of the membrane. The peripheral region (connection zone) is kept in its original hydrophobic state to ensure compatibility with the hydrophobic boundary member and maintain fluid-tight connection, while the filtration area is saponified to become hydrophilic and enable spontaneous wetting for integrity testing. This spatial differentiation of properties resolves the contradiction between connection quality and test capability.
2Reliability
If auxiliary substances such as glycerin or surfactants are added to render the membrane surface hydrophilic, then spontaneous wetting is achieved, but the filtration properties are adversely affected and the filtrate may be contaminated
Solution Approach 1:
The patent employs parameter changes by modifying the chemical composition of the membrane surface through saponification. The ester groups in the membrane polymer are hydrolyzed to carboxylic acid groups, fundamentally changing the surface chemistry from hydrophobic to hydrophilic. This chemical transformation enables spontaneous wetting without introducing any auxiliary substances, thereby avoiding contamination of the filtrate and maintaining filtration performance.
3Duration of action of stationary object
If the membrane is completely dried before use, then storage stability is improved, but the membrane cannot spontaneously wet with water and must be discarded
Solution Approach 1:
The patent applies parameter changes by permanently modifying the surface chemistry of the membrane through saponification. The hydrophilic carboxylic acid groups created through saponification ensure that the membrane will spontaneously wet with water regardless of its storage history or degree of drying. This chemical modification makes the wetting capability independent of the membrane's hydration state, allowing the membrane to be stored dry for long periods while maintaining its ability to wet and undergo integrity testing when needed.
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
This approach allows for effective leakage testing and maintains the membrane's mechanical stability and filtration performance, reducing adsorption issues and ensuring compatibility with boundary members, thus enabling suitable use in sterile and other filtration techniques.
Implementation Method 1
During such saponification, the acetate groups present on the surface of the membrane are hydrolyzed, which means that the surface becomes cellulose while the bulk of the membrane remains cellulose acetate
Implementation Method 2
In order to do so, it is essential that the surface of the membrane spontaneously wets with water
Implementation Method 3
With low-melting thermoplastics such as polyolefins, e.g. polypropylene, being hydrophobic, the material of the membrane should be hydrophobic as well in order to achieve an adequate, i.e. fluid-tight, connection
Data Source
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AI summary
The present invention relates to a filter module comprising an ester-based membrane and at least one boundary member, wherein the peripheral region of the membrane is connected to the at least one boundary member, and wherein the surface of the membrane is saponified in the regions other than the peripheral region connected to the at least one boundary member. Further, the present invention relates to a method of producing such filter module and to the use of such filter module.