Electret Filter Media with Charged Fiber and Open Support Layer
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Solution Overview
Problem
Current filter media for air filtration lack improvements in physical and performance characteristics such as strength, air resistance, efficiency, and dust holding capacity, necessitating enhanced filtration solutions.
Innovation Solution
The development of filter media comprising an open support layer and a charged fiber layer, where the charged fiber layer is mechanically attached to the open support layer, utilizing polymers with different dielectric constants to enhance filtration efficiency and stability, and incorporating a coarse support layer to maintain a waved configuration and separate peaks and troughs, thereby improving air permeability and dust holding capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filter media uses traditional homogeneous fiber structure, then manufacturing is simple, but filtration efficiency and dust holding capacity are insufficient
Solution Approach 1:
The filter media employs a composite structure consisting of a charged fiber layer (containing acrylic and polypropylene fibers) bonded to an open support layer (mesh or scrim). This composite design combines the electrostatic filtration capabilities of charged fibers with the structural support and air permeability of the open support layer, achieving both high filtration efficiency and adequate mechanical strength without excessive complexity
Solution Approach 2:
The patent applies different properties to different regions and layers of the filter media. The charged fiber layer provides high filtration efficiency through electrostatic attraction and fine fiber capture mechanisms, while the open support layer provides mechanical support and maintains air permeability. This local differentiation of functions resolves the contradiction between filtration performance and structural requirements
2Reliability
If filter media increases fiber density to improve filtration efficiency, then dust holding capacity increases, but air resistance increases
Solution Approach 1:
The open support layer is designed with high porosity (open area content of at least 80%, preferably at least 90%) and high air permeability (at least 1000 CFM, preferably at least 5000 CFM). This porous structure allows air to flow through the filter media with low resistance while the charged fiber layer captures particles through electrostatic attraction, maintaining both high filtration efficiency and low air resistance
Solution Approach 2:
The open support layer acts as an intermediary between the charged fiber layer and the surrounding environment. It provides a scaffold that holds the charged fibers in a distributed configuration, preventing fiber clumping that would increase air resistance, while allowing air to pass through to the charged fibers for particle capture
3Reliability
If filter media uses fine fibers to improve filtration efficiency, then particle capture increases, but mechanical strength decreases
Solution Approach 1:
The filter media combines fine charged fibers (1-20 microns, preferably 3-15 microns) with a mesh or scrim support structure having much larger dimensions (e.g., 500-2000 microns). The fine charged fibers provide high filtration efficiency through their small diameter and electrostatic properties, while the mesh support provides the mechanical strength and structural integrity that fine fibers alone cannot provide
Solution Approach 2:
The filter media is segmented into two distinct functional layers: the charged fiber layer for filtration and the open support layer for structural support. This segmentation allows each layer to be optimized for its specific function without compromise - fine fibers can be used in the charged layer for high efficiency while the support layer provides the necessary mechanical strength
4Reliability
If filter media uses charged fiber layer alone, then filtration efficiency is high, but structural stability decreases
Solution Approach 1:
The charged fiber layer is bonded to an open support layer (mesh or scrim) to form a composite structure. The open support layer provides the structural framework that maintains the physical integrity and dimensional stability of the filter media, while the charged fiber layer maintains its filtration functionality. The bond between layers ensures they work together as a unified structure with both high filtration efficiency and structural stability
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 proposed filter media design achieves stable filtration efficiency over its lifetime with increased normalized gamma, low pressure drop, and high dust holding capacity, making it suitable for various air filtration applications.
Implementation Method 1
a charged fiber layer mechanically attached to the open support layer... the charged fiber layer comprises a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer, wherein the first polymer is acrylic
Implementation Method 2
the open support layer is a mesh having an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM
Data Source
AI summary
Filter media, such as electret-containing filtration media for filtering gas streams (e.g., air), are described herein. In some embodiments, the filter media may be designed to have desirable properties such as stable filtration efficiency over the lifetime of the filter media, increased normalized gamma, relatively low pressure drop (i.e. resistance), and/or relatively low basis weight. In certain embodiments, the filter media may be a composite of two or more types of fiber layers where each layer may be designed to enhance its function without substantially negatively impacting the performance of another layer of the media. For example, one layer of the media may be designed to have a relatively low basis weight and/or a relatively high air permeability, and another layer of the media may be designed to have stable filtration efficiency and/or a relatively high efficiency throughout the filter media's lifetime. The filter media described herein may be particularly well-suited for applications that involve filtering gas streams (e.g., face masks, cabin air filtration, vacuum filtration, room filtration, furnace filtration, respirator equipment, residential or industrial HVAC filtration, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, medical equipment), though the media may also be used in other applications.