Spunbond Nonwoven Composite Fibers for Pleating and Electret Uniformity
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Solution Overview
Problem
Existing filter media face challenges in achieving high performance due to insufficient liquid retention of functional agents, non-uniform electret performance, and increased production costs and time in laminated nonwoven fabrics.
Innovation Solution
A spun-bonded nonwoven fabric composed of composite fibers with specific resin combinations, featuring micro bonding areas and controlled fiber diameters and distances, which allows for improved pleating, air permeability, and reduced basis weight, enabling one-step production with electret nonwoven fabrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a long-fiber nonwoven fabric is used for the aggregate layer to improve pleating processability and shape retention, then liquid retention of functional agents becomes insufficient
Solution Approach 1:
The patent employs composite fibers comprising a polyester-based resin and a polyolefin-based resin with specific melting point differences (20°C or more). This composite structure creates micro bonding areas at fiber contact points that provide both structural integrity for pleating and sufficient surface area for liquid retention of functional agents, thus resolving the contradiction between shape retention and liquid retention capability.
Solution Approach 2:
The invention creates localized micro bonding areas at fiber contact points through controlled melting of the lower-melting-point polyolefin resin. These micro bonding areas (5-100 μm in length) provide localized adhesion for shape retention while the overall fiber structure maintains porosity and surface area for functional agent retention, achieving both requirements through spatially differentiated properties.
2Quantity of substance
If a conical nozzle is used for spraying water in electret processing to improve water application, then uniform electret performance across the transverse direction becomes difficult to achieve
Solution Approach 1:
The patent addresses the asymmetric discharge pattern of conical nozzles (which naturally creates mountain-shaped distribution) by adjusting the nonwoven fabric properties - specifically using composite fibers with controlled micro bonding areas and specific center-to-center distances. This compensates for the asymmetric spray pattern, ensuring uniform electret performance across the transverse direction despite the inherently asymmetric water application method.
3Reliability
If laminated nonwoven fabric is used as filter medium to achieve high performance, then production cost and production time increase
Solution Approach 1:
The patent merges the aggregate layer and filter medium layer into a single integrated spun-bonded nonwoven fabric structure. By using composite fibers with dual functionality - providing both structural support through micro bonding areas and filtration capability through controlled porosity and fiber arrangement - the invention eliminates the need for separate lamination processes, thereby reducing production steps, cost, and time while maintaining high filter performance.
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 a filter medium with enhanced pleating processability, shape retention, and uniform electret performance while reducing production costs and environmental impact.
Implementation Method 1
a thermoplastic resin P2 having a melting point lower by 20°C or more than the melting point of the polyester-based resin P1, in which at least a part of a surface of the composite fibers is the thermoplastic resin P2, and at least some of contact points between fibers of the composite fibers have a micro bonding area
Implementation Method 2
the spun-bonded nonwoven fabric includes composite fibers containing, as constituent components, a polyester-based resin P1, and a thermoplastic resin P2 having a melting point lower by 20°C or more than the melting point of the polyester-based resin P1
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
To provide a spun-bonded nonwoven fabric which is excellent in pleating processability and shape retention, excellent in air permeability, and suitable for imparting functionality, there is provided a spun-bonded nonwoven fabric including composite fibers containing, as constituent components, a polyester-based resin P1, and a thermoplastic resin P2 having a melting point lower by 20°C or more than the melting point of the polyester-based resin P1, in which at least a part of a surface of the composite fibers is the thermoplastic resin P2, at least some of the contact points between fibers of the composite fibers have a micro bonding area having a length of 5 µm or more and 100 µm or less in a fiber axis direction, an average single-fiber diameter of the composite fibers is 15.0 µm or more and 40.0 µm or less, and an average center-to-center distance between nearest neighbor fibers in a cross section in a transverse direction of the spun-bonded nonwoven fabric is 50 µm or less.