Relofted Spunbonded Web for Low Airflow Resistance Filtration
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Solution Overview
Problem
Existing air-filter media technologies face challenges in achieving a balance between low airflow resistance and effective particulate filtration, with high-loft spunbonded nonwoven webs often exhibiting high airflow resistance and limited particulate penetration.
Innovation Solution
A relofted, spunbonded nonwoven web with a solidity of less than 8.0% to at least 3.0% and a Quality Factor of at least 0.30 is developed, achieved through a post-processing relofting process that breaks a significant percentage of fiber-fiber bonds, enhancing loft and filtration performance without significantly increasing airflow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-loft spunbonded nonwoven webs are used, then particulate filtration is improved, but airflow resistance increases
Solution Approach 1:
The patent applies parameter changes by modifying the physical structure of the spunbonded web through controlled lofting. Specifically, the web is subjected to thermal and mechanical treatment that increases its loft (volume per unit area) while controlling solidity (mass per unit volume). This parameter transformation allows the filter media to achieve higher porosity and larger pore spaces, improving particulate filtration capability while reducing airflow resistance by creating more open pathways for air passage.
Solution Approach 2:
The invention creates a composite structure within the nonwoven web by combining fibers of different orientations, lengths, and bonding characteristics. The lofting process generates a hierarchical composite architecture where loosely bonded fiber clusters coexist with more densely bonded regions, forming a multi-scale porous network. This composite morphology enables simultaneous optimization of filtration efficiency (through fine pore structures) and airflow performance (through macro-scale open channels).
2Strength
If fiber-fiber bonds are increased to strengthen the web, then web strength is improved, but loft decreases
Solution Approach 1:
The patent implements local quality by creating spatially differentiated bonding patterns within the web. Rather than uniform bonding throughout, the lofting process produces regions with varying bond densities: surface and edge regions maintain stronger bonding for structural integrity, while internal regions develop lighter, more open structures that preserve loft. This localized variation in bond quality allows the web to simultaneously achieve adequate strength and high loft characteristics.
Solution Approach 2:
The invention introduces dynamics by creating a time-dependent bonding structure. During the lofting process, fibers are initially separated to maximize loft, then selective bonding occurs over time to provide structural support. The resulting web has a dynamic balance where bonds form progressively rather than all at once, allowing the structure to evolve from a loose fiber assembly to a stabilized porous network that maintains both loft and strength.
Data Source
AI summary
A relofted, spunbonded nonwoven web exhibiting a solidity of from less than 8.0%, to at least 3.0%, and exhibiting a Quality Factor of at least 0.30. Methods of making a relofted web; and, methods of using a relofted web as an air-filtration web, e.g. as a filter media or a layer thereof.