Nonwoven Web Bonding Protrusions for Loft and Strength
Solution Overview
Problem
Current methods for enhancing the softness and loft of nonwoven web materials face challenges in achieving a balance between improving tactile and visual perceptions while maintaining mechanical properties and controlling costs, often resulting in decreased tensile strength and increased production costs.
Innovation Solution
A process involving a batt of heat-bondable fibers is fed through a nip between rollers with spaced bonding protrusions and recessed areas, where the bonding protrusions have a convex shape with an aspect ratio of at least 2.5 and an asymmetric or tilted orientation, forming thermally fused bonds to create a nonwoven web with enhanced loft and softness without compromising tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the total bond area is limited to increase loose fibers for softness and loft, then softness and loft are improved, but tensile strength is significantly reduced
Solution Approach 1:
The bonding protrusions are designed with non-uniform geometry, featuring a convex shape with a specific aspect ratio (length/width ≥ 2.5) and asymmetric or tilted orientation. This creates localized variations in bond strength and distribution, allowing certain areas to provide structural support while other areas maintain loft and softness through reduced bonding.
Solution Approach 2:
The bonding protrusions exhibit asymmetric geometry with an aspect ratio of at least 2.5 and are oriented at specific angles relative to the machine direction. This asymmetric configuration creates directional bonding patterns that enhance tensile strength in critical directions while preserving loft in other directions, resolving the contradiction between strength and softness.
2Strength
If elongated bonding points are used to increase tensile strength, then strength is improved, but softness and loft are compromised
Solution Approach 1:
The bonding protrusions are designed with moderate dimensions and spacing that provide sufficient bonding for tensile strength without excessive bonding area. The aspect ratio of at least 2.5 allows for effective stress distribution with reduced total bond area, maintaining both strength and softness by applying just enough bonding action where needed.
3Reliability
If rectangular bonding points with longer side in CD direction are used, then abrasion resistance is improved, but softness is reduced
Solution Approach 1:
The bonding protrusions feature asymmetric geometry with tilted or angled orientations relative to the machine direction, rather than aligned rectangular shapes. This asymmetric configuration provides abrasion resistance through directional bonding while the tilted orientation creates a more open structure that preserves softness and loft compared to straight-aligned rectangular bonds.
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 process effectively enhances the softness and loft of nonwoven webs, improving their tactile and visual attributes while maintaining or improving tensile strength, thus addressing the challenges of cost and mechanical property preservation.
Implementation Method 1
bonding the batt in the nip by contacting the web with the bonding protrusions of the first surface and the second surface thereby forming consolidating bonds comprising thermally fused fibers
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
The present invention relates to a process of forming a soft bulky nonwoven web from a batt using thermobonding and to a soft bulky nonwoven web with a bond impression pattern and shape. The process comprises several steps including feeding a batt to a nip between first and second surface of first and second roller, where at least the first of the surfaces comprises spaced apart bonding protrusions surrounded by recessed areas. The bonding protrusions and the bond impression shape in the web exhibit a ratio of the greatest measurable width to the greatest measurable length of at least 1:2.5 and the perimeters thereof comprise a convex portion. The bonding protrusions are symmetric and/or have a certain angle to the machine direction.