Porous PTFE Filter Medium for Low Pressure Loss and High Dust Holding
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Solution Overview
Problem
Medium-efficiency particulate air filters face challenges with high pressure loss and low dust holding capacity, especially when exposed to liquid droplets, and existing porous polytetrafluoroethylene films do not meet the required high collection efficiency and dust holding capacity standards.
Innovation Solution
A filter medium comprising a porous polytetrafluoroethylene film with a modified copolymer structure, supported by a non-woven fabric, which achieves high collection efficiency, low pressure loss, and enhanced dust holding capacity through specific manufacturing processes that include stretching and lamination techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass fiber is used as base material to achieve predetermined collection efficiency, then collection efficiency is improved, but pressure loss becomes higher
Solution Approach 1:
The patent employs porous polytetrafluoroethylene film as the filter medium, utilizing its inherent porous structure to achieve both high collection efficiency and low pressure loss. The porous nature allows air to pass through easily while the pore structure captures particles effectively, resolving the contradiction between filtration performance and pressure loss.
Solution Approach 2:
The patent modifies the porous PTFE film by controlling its thickness within a specific range (5-20 μm) and adjusting pore diameter and porosity parameters. By optimizing these physical parameters, the film achieves high collection efficiency for 0.3 μm particles while maintaining low pressure loss, thereby resolving the technical contradiction.
2Loss of energy
If porous polytetrafluoroethylene film thickness is reduced to achieve low pressure loss, then pressure loss is improved, but film strength becomes lower
Solution Approach 1:
The patent specifies a precise thickness range of 5-20 μm for the porous PTFE film. This parameter optimization ensures the film is thin enough to minimize pressure loss while remaining strong enough to maintain structural integrity. The controlled thickness prevents the film from being too weak despite its reduced dimension.
3Loss of energy
If conventional porous polytetrafluoroethylene film is used to achieve low pressure loss, then pressure loss is improved, but dust holding capacity becomes lower when liquid droplets flow into the film
Solution Approach 1:
The patent utilizes the specific porous structure of PTFE film with optimized pore diameter and porosity to achieve both low pressure loss and high dust holding capacity. The porous structure allows liquid droplets to pass through without clogging the film, maintaining dust holding capacity while keeping pressure loss low.
Solution Approach 2:
By optimizing pore diameter within 2-10 μm and porosity within 80-95%, the patent creates a porous structure that balances low pressure loss with high dust holding capacity. This parameter optimization ensures the film can handle liquid droplets effectively while maintaining filtration performance.
Data Source
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AI summary
To provide a filter medium equipped with a porous film whose collection efficiency is high, whose pressure loss is low, and whose dust holding capacity is high. A filter medium includes: a porous film that comprises polytetrafluoroethylene, has an average pore diameter of 2.5 µm or more, and has a porosity of 95% or more; and a support material that supports the porous film. In the filter medium, pressure loss when air is passed through the filter medium at a velocity of 5.3 cm/sec is less than 100 Pa, the collection efficiency of NaCl particles when air including NaCl particles with a particle diameter of 0.3 µm is passed through the filter medium at a velocity of 5.3 cm/sec is 95% or more, and the PF value obtained by the equation PF = {-log[(100-collection efficiency (%))/100]/pressure loss (Pa)} × 1000 is 30 or more. The dust holding capacity of polyalphaolefin particles when air including polyalphaolefin particles with a count median diameter of 0.25 µ3m is continuously passed through the filter medium at a velocity of 5.3 cm/sec and pressure loss reaches 300 Pa is 15 g/m2 or more.