Multilayer Elastomeric Film Low Tear Propagation
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Solution Overview
Problem
Elastomeric laminates used in disposable absorbent products often lose elasticity, integrity, and fail aesthetic and processing tests due to issues like delamination and shifting during ultrasonic bonding, which complicates their use in consumer products.
Innovation Solution
Multilayer thermoplastic films with a polymeric composition of 55-95% non-hydrogenated styrenic block copolymers or olefinic block copolymers in the inner layer and 20-85% polypropylene in the outer layers, combined with strategic ultrasonic bonding and pre-activation, to create laminates with enhanced strength, softness, and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If elastomeric laminates are used to provide snug fit and conformability, then comfort and fit are improved, but integrity and elasticity are lost under sustained use
Solution Approach 1:
The elastomeric laminate is divided into multiple layers with distinct functions: an inner elastomeric layer providing conformability and comfort, and an outer nonwoven layer providing structural integrity and durability. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The invention uses a composite structure combining elastomeric material with nonwoven material to achieve both conformability and integrity. The composite laminate leverages the elastic properties of the inner layer and the structural strength of the outer layer to resolve the contradiction between comfort and durability.
2Strength
If ultrasonic bonding is used to bond laminates, then bonding strength is improved, but lateral shifting and web instability occur during processing
Solution Approach 1:
The elastomeric layer is pre-activated through stretching and heat treatment before lamination to stabilize its dimensions and reduce lateral shifting during ultrasonic bonding. This preliminary action prepares the material to maintain positional accuracy while still achieving strong bonding.
Solution Approach 2:
The invention modifies processing parameters including temperature, stretching ratio, and bonding pressure to optimize both bonding strength and positioning accuracy. By carefully controlling these parameters, the process achieves strong bonds without excessive lateral shifting or web instability.
3Ease of operation
If elastomeric materials are stretched during lamination, then fit and conformability are improved, but web shifting and processing difficulties increase
Solution Approach 1:
The elastomeric material is pre-stretched and heat-set before final lamination to establish stable dimensions. This preliminary deformation allows the material to achieve good fit while reducing subsequent web shifting during the actual lamination process.
Solution Approach 2:
Heat treatment is applied to the elastomeric layer to stabilize its molecular structure and reduce thermal expansion during processing. This thermal stabilization allows the material to maintain its stretched configuration without excessive web shifting, improving both fit and processability.
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 results in elastomeric films and laminates that maintain integrity and aesthetic properties, exhibit low tear propagation, and are suitable for consumer products, while minimizing processing difficulties such as lateral shifting during lamination.
Implementation Method 1
the laminate is made by a process comprising the step of bonding the film to the laminate by means of ultrasonic bonding
Data Source
AI summary
Multilayer thermoplastic films, and laminates and articles comprising the films, wherein the film comprises at least one inner layer and at least two outer layers, wherein the inner layer comprises a polymeric composition comprising from about 55% to about 95% of one or more non-hydrogenated styrenic block copolymers, olefinic block copolymers, or combinations thereof; and each outer layer comprises at least 20% polypropylene and has a thickness of from about 5% to about 15% of the total film thickness, and further wherein the film has a constant force tear propagation of about 20% or less.