Electret Web Additives for Simple Corona-Charged Filtration
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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 can maintain 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 substituted heterocyclic thiols, which can be easily charged by corona discharge alone, enhancing their filtration capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple charging methods are used to enhance filtration performance, then particle capture efficiency is improved, but device complexity and processing time increase
Solution Approach 1:
The patent applies preliminary action by incorporating charge-enhancing additives into the polymer composition before web formation. This pre-charging approach eliminates the need for subsequent complex charging processes, as the web is inherently capable of being charged by simple corona discharge alone, thereby reducing device complexity while maintaining filtration performance
Solution Approach 2:
The patent changes the chemical composition parameter by adding charge-enhancing additives (0.01-10% by weight) to the polymer matrix. This compositional modification enables the material to respond more effectively to simple corona charging, achieving high filtration performance without requiring multiple complex charging methods
2Productivity
If charge-enhancing additives are incorporated into polymer composition, then charging efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the charging enhancement function directly into the polymer composition by incorporating charge-enhancing additives during the extrusion process. This combination allows the additive and polymer to be processed together in a single extrusion step, improving charging efficiency without adding separate manufacturing steps
Solution Approach 2:
The charge-enhancing additives provide self-service by automatically enhancing the charging efficiency of the web through their inherent chemical properties. The additives (such as mercaptobenzimidazolate salts or thiourea compounds) naturally facilitate charge retention and corona discharge effectiveness, eliminating the need for additional charging equipment or complex processing
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 improved charging efficiency and filtration performance, particularly in aerosol capture, with the ability to maintain effective charge distribution and filtration properties across varying web thickness and solidity.
Implementation Method 1
a charge-enhancing additive comprising a substituted heterocyclic thiol
Implementation Method 2
electrets are effective in enhancing particle capture in aerosol filters
Implementation Method 3
charging the fibers after the web is formed, by means of a corona discharge
Implementation Method 4
imparting a charge to the fiber mat by means of carding and/or needle tacking (tribocharging)
Data Source
AI summary
Charged polymeric webs, such as electret webs, include a thermoplastic resin and a charge-enhancing additive. The additives are substituted heterocyclic thiols. The heterocyclic thiol has 2 nitrogen groups and a third group that may be an NH, N—NH2, O, or S group. The substituent group is an aromatic or heterocyclic aromatic group. The electret webs may be a non-woven fibrous web or a film. The electret webs are suitable for use as filter media.