Porous PVDF Film Crystallinity and Surface Area for Chemical Resistance
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Solution Overview
Problem
Conventional porous PVDF films face challenges with low chemical resistance and water permeability, leading to membrane obstruction and deterioration during filtration processes, especially when exposed to washing chemicals, which limits their long-term use in applications requiring high water quality.
Innovation Solution
A porous PVDF film with a specific structure characterized by a degree of crystallization between 50% and 90% and a specific surface area of 300 to 1000 square meters per gram, incorporating polyethylene glycol for enhanced hydrophilicity and chemical resistance, and a hollow fiber membrane structure for improved strength and filtration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PVDF resin is used as polymer component of porous films, then processability is improved compared to other fluorine-based polymers, but chemical resistance to base deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of a porous PVDF film layer and a porous support layer. The PVDF film provides the required processability and filtration function, while the support layer provides mechanical strength and chemical resistance to base, creating a composite material system that combines the advantages of both materials.
2Ease of manufacture
If conventional polymers are used for membrane modules, then processability is good, but water permeability decreases due to membrane obstruction
Solution Approach 1:
The patent employs a porous PVDF film with controlled pore structure formed by phase separation method. The porous structure provides high water permeability while the PVDF material maintains good processability. The pores allow water to pass through efficiently, preventing the membrane obstruction problem that occurs with conventional non-porous or less porous membranes.
3Ease of operation
If chemical agents are used to remove accumulated organic matter, then chemical obstruction is eliminated, but membrane deterioration occurs
Solution Approach 1:
The patent converts the harmful effect of chemical agents on the membrane by using a PVDF material that has inherent resistance to chemical degradation. The membrane is designed to withstand exposure to chemical cleaning agents, transforming the situation where chemicals cause damage into one where the same chemicals can effectively clean the membrane without causing deterioration.
4Ease of manufacture
If PVDF resin is used in dry-wet method, then processability is limited by inferior solubility, but water permeability and durability cannot be achieved
Solution Approach 1:
The patent changes the manufacturing method from dry-wet method to phase separation method. This parameter change in the production process allows PVDF resin to form a porous structure with appropriate pore diameter and distribution, achieving both high water permeability and durability despite PVDF's limited solubility characteristics.
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 film exhibits high water permeability and chemical resistance, allowing for extended use without significant strength loss when exposed to washing chemicals, and can be produced stably and economically, making it suitable for various filtration applications, including those involving alkaline solutions.
Implementation Method 1
the film exhibits high water permeability
Implementation Method 2
Filtration processes are widely used in industrial fields
Data Source
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AI summary
The present invention provides a PVDF porous film, which has high water permeability and high chemical resistance to washing chemicals and the like that has been difficult to realize with conventional polymer porous films, and which can be used over a prolonged period of time; and a method of producing the same and the like. Namely, the present invention provides a porous film in which the degree of crystallization of the PVDF resin is 50% or more but not more than 90%, and the product of the degree of crystallization of the PVDF resin and the specific surface area of the film is 300 (% · m2/g) or more but not more than 2000 (% · m2/g). In addition, the present invention provides a method for producing a porous film comprising: producing a porous film having a PVDF resin as a main component thereof by extruding, from a molding nozzle, a film-forming solution which at least comprises a hydrophobic polymer component having a PVDF resin as a main component thereof, a hydrophilic polymer component and a common solvent for both the hydrophobic and hydrophilic polymer components, and solidifying the film-forming solution in a solution having water as a main component thereof, wherein polyethylene glycol having a weight average molecular weight of 20,000 or more but not more than 150,000 is used as the hydrophilic polymer component.