Nonwoven Filter Sheet With Uniform Melt-Bonding
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Solution Overview
Problem
Existing nonwoven sheets for filters face challenges in maintaining flexural rigidity and formability while being thin, and they often suffer from deformation under load and poor long-term filterability due to uneven fiber bonding and voids between fibers.
Innovation Solution
A nonwoven sheet with a substrate layer of thermal adhesive fibers uniformly melt-bonded in the surface direction, combined with a higher-density surface layer, providing improved stiffness and formability without chemical binders, and a production process involving high-temperature water vapor for melt-bonding and heat-pressing to achieve a balanced density and bonding structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the nonwoven sheet is made thin to reduce weight and improve flexibility, then the sheet becomes easier to handle and install, but the flexural rigidity decreases and the sheet deforms easily under load
Solution Approach 1:
The nonwoven sheet uses a composite structure combining different fiber types (thermal adhesive fibers, base fibers, and optional surface layer fibers) with distinct functions. The thermal adhesive fibers provide bonding strength, the base fibers provide structural integrity, and the surface layer enhances filtration performance, achieving high flexural rigidity in a thin configuration without chemical binders
Solution Approach 2:
The patent applies local quality by creating a higher-density surface layer with different fiber composition than the bulk layer. The surface layer has increased concentration of filtration fibers and reduced adhesive fiber content compared to the uniform distribution in conventional sheets, optimizing both structural strength and filtration performance locally where needed
2Strength
If thermal adhesive fibers are added to bond fibers together, then the flexural rigidity and formability improve, but chemical binders and additives must be used which can release volatile organic compounds
Solution Approach 1:
The patent replaces the chemical bonding system (chemical binders and resins) with a physical/thermal bonding system using heat-meltable adhesive fibers. The thermal adhesive fibers melt and bond other fibers through heat application during the manufacturing process, eliminating the need for chemical binders that release volatile organic compounds while maintaining equivalent or superior bonding strength
Solution Approach 2:
The thermal adhesive fibers serve as a consumable bonding agent that is melted and consumed during the heat treatment process to create permanent bonds between structural fibers. This disposable approach using simple polyolefin fibers is more environmentally friendly than persistent chemical binders
3Quantity of substance
If the sheet is made thin to improve filterability, then the air-permeability increases, but the sheet lacks sufficient strength to maintain pleated form during long-term use
Solution Approach 1:
The composite fiber structure provides differential functionality: the high air-permeability is achieved through the thin overall structure and controlled void distribution, while the long-term form stability is provided by the thermal adhesive fibers that create a rigid bonded network maintaining the pleated configuration under operational conditions
Solution Approach 2:
The patent optimizes the thermal adhesive fiber content parameter (5-30% by weight) to achieve the right balance between flexibility for pleating and rigidity for maintaining form. The adhesive fiber content and bonding parameters are specifically tuned to provide sufficient structural support for long-term use while preserving the thin profile needed for high air-permeability
4Strength
If fibers are densely packed to increase strength, then the flexural rigidity improves, but the air-permeability decreases and filterability is compromised
Solution Approach 1:
The patent applies local quality by creating a non-uniform fiber distribution with a higher-density surface layer and a slightly lower-density bulk layer. This gradient structure provides sufficient overall strength and rigidity while maintaining adequate air-permeability pathways through the bulk structure, optimizing both mechanical and filtration properties
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 nonwoven sheet with enhanced flexural rigidity, formability, and long-term filterability, maintaining stability and efficiency even when pleated, while avoiding the use of chemical additives that could release volatile organic compounds.
Implementation Method 1
the thermal adhesive fibers are melt-bonded to bond other fibers
Implementation Method 2
heat-treating the mixture to bond the fibers
Implementation Method 3
heating a nonwoven web containing a thermal adhesive fiber to melt-bond the thermal adhesive fibers
Implementation Method 4
heat-pressing at least one side of the plate-like fiber aggregate nonwoven structural member
Data Source
Figure 1(a)~2
AI summary
A nonwoven sheet contains a substrate layer formed from a fiber aggregate nonwoven structural member; the fiber aggregate nonwoven structural member containing a thermal adhesive fiber; the thermal adhesive fibers are melt-bonded to fix the fibers of the member. The average thickness of the substrate layer is adjusted to not less than 0.2 mm to less than 1 mm, and the thermal adhesive fibers are substantially uniformly melt-bonded in a surface direction of the substrate layer. The sheet may have a surface layer over at least one side of the substrate layer, the surface layer may contain a fiber aggregate nonwoven structural member having an apparent density higher than the apparent density of the substrate layer. The surface layer may comprise a layer formed by heat-pressing or may be formed from a meltblown nonwoven fabric. The thermal adhesive fiber may be substantially uniformly melt-bonded in a thickness direction of the substrate layer. The thermal adhesive fiber may contain an ethylene-vinyl alcohol-series copolymer; the copolymer may form a continuous area of a surface of the fiber. The sheet has an improved flexural rigidity, less deformation under a load, and an excellent formability, in spite of a small thickness thereof.