Electret Web Composition for Single-Step Corona Charging
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Solution Overview
Problem
There is a need for electret webs with improved properties that can be easily charged through various mechanisms such as tribocharging, corona discharge, or hydrocharging, and that exhibit enhanced filtration performance without requiring additional charging methods.
Innovation Solution
The development of electret webs comprising a blend of a thermoplastic resin and a charge-enhancing additive, specifically fused aromatic urea or thiourea, which can be synergistically enhanced with hindered amine light stabilizer compounds, allowing for efficient charging and improved filtration capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electret webs are used without charge-enhancing additives, then the charging process requires multiple methods (tribocharging, corona discharge, hydrocharging), but the charging efficiency and filtration performance are limited
Solution Approach 1:
The patent modifies the chemical composition parameters of the electret web by incorporating fused aromatic urea or thiourea compounds at concentrations of 0.01-10% by weight. This compositional parameter change enables the material to achieve enhanced charging efficiency and filtration performance through a single corona discharge process, eliminating the need for multiple charging methods while improving reliability
Solution Approach 2:
The patent creates a composite material system by combining thermoplastic polymers (such as polypropylene, polyester, or polyacrylonitrile) with fused aromatic urea or thiourea charge-enhancing additives. This composite structure synergistically combines the structural properties of the polymer matrix with the charge-enhancing properties of the fused aromatic compounds, enabling effective filtration performance with simplified charging processes
2Ease of operation
If multiple charging methods are applied to electret webs, then charging can be achieved, but the process time and manufacturing complexity increase
Solution Approach 1:
By changing the chemical composition to include fused aromatic urea or thiourea compounds, the material's charge acceptance properties are fundamentally altered. This enables the electret web to achieve sufficient charging through a single corona discharge process, reducing both the number of operational steps and the total charging time while improving ease of operation
Solution Approach 2:
The charge-enhancing additives are incorporated into the electret web during the manufacturing process, before the charging step. This preliminary incorporation of functional additives ensures that the material is pre-prepared to accept and retain electrical charge efficiently, eliminating the need for subsequent multiple charging operations and reducing overall process time
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 electret webs demonstrate enhanced charging efficiency and filtration performance, with the ability to be charged by DC corona discharge alone, and maintain effective filtration properties even after aging, as evidenced by increased Quality Factor values and penetration ratios.
Implementation Method 1
An electret is a dielectric material that exhibits a quasi-permanent electrical charge. Electrets are useful in a variety of devices including, e.g. cling films, air filters, filtering facepieces, and respirators
Implementation Method 2
charging the fibers after the web is formed, by means of a corona discharge or imparting a charge to the fiber mat by means of carding and/or needle tacking (tribocharging)
Implementation Method 3
charging the fibers after the web is formed, by means of a corona discharge
Implementation Method 4
a method in which jets of water or a stream of water droplets impinge on a non-woven web at a pressure sufficient to provide filtration enhancing electret charge has also been described (hydrocharging)
Data Source
AI summary
Electret webs include a thermoplastic resin and a charge-enhancing additive. The charge-enhancing additive is a fused aromatic thiourea, a fused aromatic urea compound, or a combination thereof. The change-enhancing additive may also include a hindered amine light stabilizer compound. The electret webs may be a non-woven fibrous web or a film. The electret webs are suitable for use as filter media.