Elastic Laminate with Coextruded Film and Spot Welding
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Solution Overview
Problem
Current hygienic and sanitary products, such as diapers, fail to simultaneously achieve optimal elastic features, tensile strength, and softness, making them unsuitable for prolonged use and user comfort.
Innovation Solution
A method of producing an elastic laminate by coextruding a three-layer elastic film with different polymer materials and joining it with nonwoven webs through thermal binding and mechanical stretching, ensuring the film transitions from a melted to a solidified state for spot welding, followed by cooling and cross-directional stretching to enhance elasticity and strength while maintaining softness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer elastic film is used to achieve simplicity in structure, then manufacturing is easier, but the product cannot simultaneously achieve high elasticity, high tensile strength, and softness
Solution Approach 1:
The elastic film is divided into multiple layers with different functions: outer layers provide softness and comfort, while the inner layer provides elasticity and tensile strength. This segmentation allows each layer to optimize its specific function, resolving the contradiction between structural simplicity and performance consistency.
Solution Approach 2:
The patent uses composite materials by combining different polymer types in a multi-layer structure. The outer layers use soft polymers for comfort, while the inner layer uses elastic polymers for stretch and recovery. This composite approach enables simultaneous achievement of high elasticity, high tensile strength, and softness.
2Strength
If the elastic film is made thicker to increase tensile strength, then strength is improved, but softness and comfort are reduced
Solution Approach 1:
The film thickness is segmented across multiple layers with different functions. The outer layers are made thinner and softer for comfort, while the inner layer provides the necessary tensile strength through elastic materials. This segmentation resolves the contradiction between strength and softness by distributing thickness across functional layers.
Solution Approach 2:
Different regions of the film have different thicknesses and material properties tailored to their specific functions. The outer surfaces are optimized for softness with thinner, softer materials, while the inner region is optimized for strength with elastic materials. This local quality differentiation resolves the contradiction between tensile strength and softness.
3Adaptability or versatility
If the elastic film is stretched more to increase elasticity, then elasticity is improved, but tensile strength decreases
Solution Approach 1:
The elastic film is segmented into multiple layers with different stretch characteristics. The inner layer is designed for high elasticity with greater stretch capacity, while the outer layers maintain tensile strength and structural integrity. This segmentation allows the product to achieve both high elasticity and maintained tensile strength.
Solution Approach 2:
The patent uses composite materials with different mechanical properties in each layer. The inner elastic layer provides high stretch and recovery, while the outer layers provide tensile strength. This composite structure resolves the contradiction between elasticity and tensile strength by combining materials with complementary properties.
4Productivity
If spot welding is used to join nonwoven layers to elastic film, then manufacturing efficiency is improved, but the product softness is reduced
Solution Approach 1:
The welding is applied locally at specific points rather than across the entire surface. This localized spot welding provides sufficient mechanical attachment while leaving most of the surface area unwelded, thereby preserving the softness and comfort of the nonwoven layers. This resolves the contradiction between manufacturing efficiency and softness.
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 exhibits high elasticity, tensile strength, and increased softness, addressing the limitations of existing products by providing a durable and comfortable solution for hygienic and sanitary applications.
Implementation Method 1
a first web of elastic film with at least three layers is coextruded, comprising at least two different polymer materials
Implementation Method 2
to join, through spot welding in said calender, said second nonwoven webs with respective opposite outer layers of said first elastic film web
Implementation Method 3
to stretch mechanically said intermediate web according to a direction transverse to the same web
Data Source
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AI summary
Elastic laminate comprising - a polymer intermediate elastic film (F) formed by three coextruded layers (F1, F2, F1), wherein the outer layers (F1) are made of the same polymer material, and the inner layer (F2) is made of a different polymer material, - two nonwoven fabrics (T1, T2) joined, through spot or areas welding (Z), to the two opposite faces of said coextruded elastic film (F), and wherein • the ratio between MD elongation at break at 10N, and laminate thickness after the stretching step is lower than 8, and preferably lower than 7,5 and/or • the ratio in (N/50 mm)/(mm), between CD tensile strength and laminate thickness after the stretching step is lower than 79, and preferably lower than 78 and/or • the ratio in (g/m2/mm) between laminate weight and thickness after the stretching step is lower than 105, and more preferably lower than 100.