Monocomponent Nonwoven Web with Bimodal Fibers for Shaped Filtration
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Solution Overview
Problem
Existing methods for manufacturing shaped filtration articles like molded respirators and pleated furnace filters often compromise web or article properties due to the use of multicomponent fibers and additional bonding materials, limiting recyclability and filtration performance.
Innovation Solution
A monocomponent nonwoven web is created using a single extruder and meltblowing die, comprising a bimodal mass fraction/fiber size mixture of intermingled continuous microfibers and larger size fibers of the same polymeric composition, which are formed through a process involving larger and smaller size orifices to produce fibers with improved stiffness and filtration capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If multicomponent fibers are used to manufacture shaped filtration articles, then the web can be formed into three-dimensional shapes, but the recyclability is limited and additional bonding materials are required
Solution Approach 1:
The die cavity is divided into multiple zones with different orifice sizes (first size, second size, and third size orifices) to produce fibers of different diameters. This segmentation allows the web to be formed into three-dimensional shapes through fiber length and diameter variation without requiring multicomponent fibers or bonding materials, maintaining recyclability.
Solution Approach 2:
The invention changes the parameter of orifice size within the die cavity to produce fibers with different diameters. By varying the orifice size parameter across different zones, the process creates a bimodal fiber distribution that enables three-dimensional shaping while using only a single polymer material, thus preserving recyclability.
2Shape
If multicomponent fibers are used, then shaped articles can be manufactured, but the extent to which charge may be placed on the web is limited
Solution Approach 1:
The invention uses a single polymer material fed through the entire die cavity, creating a homogeneous web composition. This homogeneity allows the entire web to be uniformly chargeable without the limitations imposed by multicomponent fiber structures, maximizing charge capacity while still achieving three-dimensional shaping through orifice size variation.
3Shape
If extraneous bonding material is added to a filtration web, then shaped articles can be formed, but the web basis weight increases and recyclability is lost
Solution Approach 1:
The invention extracts the need for extraneous bonding materials by using a single polymer system with varied orifice sizes. The different fiber diameters and lengths produced by the segmented die cavity enable three-dimensional shaping through the fiber structure itself, eliminating the need for additional bonding materials and maintaining the original web basis weight.
4Adaptability or versatility
If two extruders are used to feed different polymers, then bicomponent fibers can be produced, but cost and complexity increase
Solution Approach 1:
The die cavity is designed to perform multiple functions within a single polymer feed system. By incorporating zones with different orifice sizes (first, second, and third size orifices) in the same die cavity, the system produces fibers with different diameters and lengths from a single polymer, eliminating the need for multiple extruders while maintaining compositional versatility.
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 provides high-performance shaped filtration articles with excellent stiffness, filtration efficiency, and recyclability, while maintaining low pressure drop and high particle depth loading capacity, without the need for additional bonding materials.
Implementation Method 1
a process for forming a monocomponent nonwoven web comprising flowing fiber-forming material through a die cavity having larger size orifices and at least five times as many smaller size orifices to form filaments, using air or other fluid to attenuate the filaments into fibers
Data Source
AI summary
A porous monocomponent nonwoven web contains a bimodal mass fraction/fiber size mixture of intermingled continuous microfibers and larger size fibers of the same polymeric composition. There are at least five times as many microfibers as larger size fibers, and a histogram of the mass fraction of fibers vs. fiber size exhibits a larger size fiber mode greater than 10 μm. The web may be made by flowing fiber-forming material through a die cavity having larger size orifices and at least five times as many smaller size orifices to form filaments, attenuating the filaments into fibers and collecting the attenuated fibers to form the nonwoven web. The web is especially well suited to the manufacture of self-supporting three dimensional articles such as molded cup-shaped respirators and pleated air filters.