Apertured Web Forming with Asymmetric Roller Teeth
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Solution Overview
Problem
Existing methods for creating apertures in films and nonwovens often produce slits due to molecular orientation, limiting the ability to form oval holes, which are preferred for improved fluid acquisition and aesthetics in disposable absorbent products.
Innovation Solution
A method using counter-rotating intermeshing rollers with teeth and grooves, where the orientation of the teeth relative to the molecular orientation is adjusted to produce apertures with minimal aspect ratios, allowing for the formation of oval-shaped holes by modifying the intermeshing process and potentially pre-straining the web to alter molecular orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If teeth on the roller are oriented in the machine direction to align with molecular orientation, then the aperture forming process is simple and efficient, but the apertures are produced as slits with high aspect ratios
Solution Approach 1:
The tooth cross-section is designed with asymmetric dimensions where the width dimension (transverse to machine direction) is greater than the length dimension (machine direction), creating an aspect ratio less than 1.0. This asymmetric tooth geometry produces oval-shaped apertures with minimal aspect ratios, transforming the conventional slit-like apertures into desired oval holes while maintaining manufacturing efficiency
Solution Approach 2:
The invention changes the dimensional parameters of the tooth cross-section by controlling the width dimension to be greater than the length dimension. This parameter modification ensures that the aperture formed has an aspect ratio less than 1.0, producing oval shapes rather than slits, while the tooth geometry itself remains simple and easy to manufacture
2Productivity
If teeth cross-sectional length is aligned in the machine direction to match extruded film molecular orientation, then the process is efficient, but apertures resemble slits rather than oval holes
Solution Approach 1:
The tooth cross-section employs asymmetric dimensions with width greater than length, creating an aspect ratio less than 1.0. This asymmetric design produces oval-shaped apertures with minimal aspect ratios, achieving precise oval hole formation rather than slit-like apertures, while maintaining high productivity through the simple and efficient intermeshing roller process
3Ease of manufacture
If conventional intermeshing rollers are used to form apertures, then the process is cost-effective and efficient, but the aperture shape is limited by tooth geometry and molecular orientation
Solution Approach 1:
The tooth cross-section is designed with asymmetric dimensions where width exceeds length, creating an aspect ratio less than 1.0. This asymmetric geometry enables the formation of oval-shaped apertures with minimal aspect ratios, significantly improving aperture shape variability and adaptability while maintaining the cost-effectiveness and efficiency of the conventional intermeshing roller process
Solution Approach 2:
By modifying the dimensional parameters of the tooth cross-section to have width greater than length, the invention achieves versatile aperture shape control. This parameter change allows the same intermeshing roller process to produce oval holes with minimal aspect ratios, enhancing adaptability for different applications while keeping the process cost-effective
Data Source
AI summary
A method for making apertures in a precursor web using a forming apparatus is described herein. The precursor web comprises a film layer and a nonwoven layer having molecular orientation and the forming apparatus comprises an arrangement of teeth. The forming apparatus heats and stretches the precursor web forming apertures therein.