Nonwoven Sheet Elastic Stretchability via Combined Activation and Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional nonwoven sheets used in the hygiene industry, such as baby diapers, lack sufficient elastic stretchability, particularly in machine direction, and existing methods to enhance elasticity often result in discomfort or increased material thickness.
Innovation Solution
A method involving concurrent activation and bonding of precursor sheets using rollers with meshing ribs and grooves, allowing for significant pre-stretching and embossing of bonding points along the crests of these features to create elastically stretchable nonwoven sheets that can stretch beyond 150% of their original dimension without compromising structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elastic films are included between layers of nonwoven material, then elastic performance is improved, but air permeability deteriorates leading to wearer discomfort
Solution Approach 1:
The patent merges the functions of elastic film and nonwoven layers into a single integrated nonwoven sheet with through-width elastic fibers. This eliminates the need for separate elastic film layers while maintaining elastic performance and preserving air permeability, thereby resolving the contradiction between elastic performance and wearer comfort.
Solution Approach 2:
The patent creates a composite nonwoven material combining elastic fibers with carrier fibers in a single web structure. This composite approach provides the elastic properties traditionally achieved with elastic films while maintaining the breathability and comfort of nonwoven materials, thus resolving the contradiction.
2Strength
If elastic strands are included into the sheets, then elasticity is improved, but localized elastic force and strand breakage occur
Solution Approach 1:
The patent segments the elastic function into multiple discrete elastic fibers distributed throughout the entire width of the nonwoven sheet. This segmentation prevents localized stress concentration that would occur with single elastic strands, eliminating the risk of strand breakage while providing uniform elasticity across the sheet.
Solution Approach 2:
The patent applies elastic fibers locally at multiple points across the sheet width rather than using continuous strands. Each elastic fiber provides localized elastic response, and the distribution of many such fibers creates uniform overall elasticity without the weaknesses of continuous strands, resolving the reliability issue.
3Length of moving object
If nonwoven materials are pleated upon lamination, then extensibility is improved, but material thickness and production complexity increase
Solution Approach 1:
The patent incorporates elastic fibers that provide dynamic extensibility to the nonwoven sheet without requiring static pleated structures. The elastic fibers allow the material to stretch and recover dynamically, achieving the required extensibility while maintaining a flat, thin profile that avoids the thickness and complexity of pleated designs.
4Stability of the object's composition
If bonding is applied to carrier layers before activation, then structural integrity is improved, but pre-stretch capability deteriorates
Solution Approach 1:
The patent applies preliminary bonding to specific regions of the carrier layers before the activation/stretching process. This selective preliminary bonding provides enough structural integrity to handle the material during processing while leaving sufficient unbonded areas that allow the material to be pre-stretched to the required extent, resolving the contradiction between integrity and stretch capability.
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 method enables nonwoven sheets to achieve high elastic stretchability in both machine and cross-machine directions, meeting industry requirements while maintaining comfort and reducing material thickness, thus addressing the limitations of traditional approaches.
Implementation Method 1
the activating comprises passing the precursor sheet between a pair of activation rollers having a plurality of meshing ribs and grooves arranged in parallel on their collaborating surfaces, thereby stretching the precursor sheet in a direction perpendicular to the orientation of the ribs and grooves
Implementation Method 2
the bonding comprises an embossing of bonding points into the precursor sheet while it is stretched, the embossing being effected by embossing projections that are arranged along the crests of the ribs and/or grooves on the activation roller surfaces
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for manufacturing nonwoven sheets that includes a step of combined activation and bonding. The invention further relates to an application of this method to the making of elastically stretchable nonwoven laminate sheets, sheets produced by such method, and to uses for such sheets.