MD Stretch Laminate Cross-Directional Elasticity
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Solution Overview
Problem
Existing elastic laminate fabrication processes primarily achieve machine direction stretch with limited or no cross-direction stretch, resulting in costly and bulky elasticized features in disposable absorbent articles, which are expensive to produce and affect the product's fit and aesthetics.
Innovation Solution
A process that stretches the elastic film to at least 50% of its initial machine direction length and 20% of its initial cross direction length before lamination, combined with nonwoven fabric gathering, to create a laminate with both machine direction and cross-direction stretch, optimizing the tensile forces and recovery properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If elastic films are stretched only in machine direction with sequential rollers, then machine direction stretch is achieved, but cross-direction stretch is limited or nonexistent
Solution Approach 1:
The patent transitions from uniaxial (machine direction only) stretching to biaxial stretching by adding cross-direction stretching capability. This is achieved by modifying the roller arrangement to include cross-direction stretching zones, enabling the elastic film to stretch in both machine and cross directions simultaneously, thus resolving the limitation of no cross-direction stretch
2Ease of operation
If elasticized materials are used to provide fit and comfort, then wearer comfort is improved, but production cost increases due to expensive elastic materials and difficult processing
Solution Approach 1:
The patent changes the physical parameters of the elastic film during processing by implementing a controlled stretching regimen. The elastic film is stretched to specific elongation levels (50-100% in machine direction, 10-30% in cross direction) at controlled rates, which activates the elastic properties and creates permanent set. This allows standard elastic films to achieve functional elasticity without requiring expensive elastomeric materials like Lycra
3Ease of operation
If elastic strands are used to enhance fit and comfort, then wearer comfort is improved, but the side area becomes bulky
Solution Approach 1:
The patent replaces bulky elastic strands with thin elastic films that are stretched and laminated to the nonwoven substrate. The film, when stretched to appropriate elongation levels and properly laminated, provides the necessary elastic function without adding bulk, thereby maintaining a flat side panel appearance while still delivering fit and comfort benefits
4Length of moving object
If elastic films are stretched to high elongation levels, then machine direction stretch is improved, but the web narrows significantly
Solution Approach 1:
The patent compensates for cross-direction narrowing by intentionally stretching the film in the cross direction during the stretching process. By applying cross-direction stretching (10-30% elongation) simultaneously or sequentially with machine direction stretching, the final web width is maintained closer to original dimensions while achieving high machine direction elongation (50-100%), thus resolving the necking problem
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 resulting laminate achieves 20% cross-directional stretch with 50% recovery, enhancing the fit and reducing production costs by minimizing the need for expensive elastic materials and complex processing steps, while maintaining excellent tensile strength in both directions.
Implementation Method 1
The elastic film layer is stretched to at least about 50% of its initial machine direction length and to at least about 20% of its initial cross direction length prior to lamination... When the stretching tension is released, the elastic film returns to a length near its original length and draws the attached nonwoven layer back with it
Implementation Method 2
the stretched elastic film is laminated to a nonwoven fabric layer... at least one nonwoven fabric layer and at least one elastic film layer laminated to the nonwoven fabric layer
Data Source
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AI summary
The presently described technology provides a machine-direction stretch elastic laminate having in addition cross-direction stretch. The elastomeric laminate comprises an elastic film layer laminated to at least one nonwoven fabric layer and may be used in elasticized features of various articles, such as disposable absorbent articles. Methods for producing the elastic laminate are also described.