Filter Media Adhesive Bonding for HEPA Stiffness and Air Resistance
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Solution Overview
Problem
Current filter media technologies face limitations in achieving high strength, air resistance, efficiency, and dust holding capacity, particularly in HEPA and ULPA applications, where improvements in physical and performance characteristics are needed.
Innovation Solution
A filter media comprising multiple layers with fine fibers and a solvent-based adhesive resin, where the adhesive is applied in a low amount and has a low glass transition temperature, enhancing bond strength and stiffness while maintaining low air resistance, achieved through a solvent-based spinning process and lamination techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is added to bond layers, then bond strength and stiffness are improved, but air resistance increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the glass transition temperature of the adhesive resin to be below the processing temperature but above ambient temperature, and by optimizing the adhesive content to 1-10 gsm. This allows the adhesive to provide sufficient bond strength while minimizing its impact on air resistance through controlled physical properties and dosage.
Solution Approach 2:
The patent uses composite materials by combining the adhesive resin with solvent-based spinning process and lamination techniques to create a multi-layer filter media structure. The adhesive is integrated with fiber layers having different diameters (including less than 1 micron fibers) to achieve both bonding and filtration performance.
2Strength
If adhesive content is increased to improve bond strength, then bond strength increases, but air resistance increases more significantly
Solution Approach 1:
The patent applies partial action by using a limited, optimized amount of adhesive (1-10 gsm) rather than excessive adhesive content. This partial application is sufficient to achieve the required bond strength (≥150 g/in²) while avoiding the negative impact of excessive adhesive on air resistance and stiffness.
3Strength
If glass transition temperature of adhesive is lowered to improve bonding at lower temperatures, then bond strength improves, but adhesive becomes more viscous and harder to apply
Solution Approach 1:
The patent applies parameter changes by setting the glass transition temperature within a specific range (below processing temperature but above ambient temperature). This parameter optimization allows the adhesive to remain applicably viscous during manufacturing while providing sufficient bond strength at operating temperatures.
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 solution results in a filter media with improved stiffness, bond strength, and gamma value, along with reduced air resistance increase after IPA vapor discharge, effectively addressing the limitations of existing technologies in HEPA and ULPA applications.
Implementation Method 1
an adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive
Implementation Method 2
spraying a composition comprising a solvent-based adhesive resin and a cross-linking agent onto a first layer to form an adhesive-coated first layer
Implementation Method 3
spraying a composition comprising a solvent-based adhesive resin and a cross-linking agent onto a first layer
Data Source
AI summary
Articles and methods involving filter media are generally provided. In certain embodiments, the filter media includes at least a first layer, a second layer, and an adhesive resin positioned between the first layer and the second layer. In some embodiments, the first layer may be a pre-filter layer or a support layer. The second layer may, for example, comprise fibers formed by a solution spinning process and/or may comprise fine fibers. In some embodiments, the adhesive resin may be present in a relatively low amount and/or may have a low glass transition temperature. The filter media as a whole may have one or more advantageous properties, including one or more of a high stiffness, a high bond strength between the first layer and the second layer, a high gamma, and/or a low increase in air resistance after being subjected to an IPA vapor discharge. The filter media may be, for example, a HEPA filter and/or an ULPA filter.