Water-vapor permeable composite
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Solution Overview
Problem
Existing methods for producing composite materials involving nonwoven layers and differently shaped materials, such as sewing, gluing, or hot welding, often result in damaged micro/nanostructures, leading to unsuitable properties like inadequate gas permeability or rigidity, especially when used in functional articles like clothing.
Innovation Solution
A process involving a nonwoven layer made of thermoplastic polyurethane with specific mesh sizes and a compatible porous membrane layer, where cold welding is used to create a positive connection between the layers, allowing for the preservation of desired properties like water resistance and breathability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional hot welding is used to join nonwoven layers, then bonding strength is improved, but the micro/nanostructures are destroyed leading to loss of gas permeability
Solution Approach 1:
The patent changes the welding temperature parameter from conventional high temperatures to below the melting point of the thermoplastic fibers. This allows the fibers to be joined through heat-induced softening and interdiffusion without reaching the melting point that would destroy the micro/nanostructures. The temperature is carefully controlled to maintain gas permeability while achieving sufficient bonding strength.
2Strength
If conventional hot welding is used to join nonwoven layers, then bonding strength is improved, but the layers cannot be welded due to material incompatibility or lack of thermoplasticity
Solution Approach 1:
The patent introduces a two-stage temperature approach: first heating below the melting point to activate thermoplasticity for welding, then optionally heating above the melting point if needed. This parameter change enables welding of materials that would otherwise be incompatible or non-thermoplastic at conventional welding temperatures.
Solution Approach 2:
The patent applies a preliminary heating step to activate the thermoplastic properties of the fibers before the actual welding process. This preliminary action prepares the material by softening it just enough to enable bonding, while avoiding the material degradation that would occur at higher temperatures.
3Strength
If sewing or gluing is used to join layers, then bonding is achieved, but the micro/nanostructures are damaged and desired properties are lost
Solution Approach 1:
The patent replaces mechanical joining methods (sewing with needles and threads, gluing with adhesives) with a thermal field-based welding process. This substitution eliminates the mechanical damage caused by needle punctures and adhesive application, preserving the integrity of the micro/nanostructures while achieving bonding through controlled thermal softening and fiber interdiffusion.
4Strength
If conventional welding temperatures are used, then bonding strength is improved, but the desired elongation at break is lost
Solution Approach 1:
The patent carefully controls the welding temperature parameter to remain below the melting point of the thermoplastic fibers. This temperature control allows sufficient thermal activation for bonding while preventing the excessive heat that would cause fiber fusion and loss of elongation capability. The temperature is optimized to balance bonding strength and flexibility.
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 composite material exhibits sufficient elongation at break, high water vapor permeability, and excellent water resistance, making it suitable for functional articles like clothing without compromising on breathability or durability.
Implementation Method 1
wherein due to the presence of solvent, the nonwoven layer (i) and/or the membrane layer (ii) are initially dissolved and subsequently the membrane layer (ii) hardens on the nonwoven layer (i) upon removal of the solvent
Implementation Method 2
subsequently the membrane layer (ii) hardens on the nonwoven layer (i) upon removal of the solvent
Data Source
AI summary
The invention relates to a composite material comprising a nonwoven layer (i) comprising fibres of a first thermoplastic elastomer having meshes with a mesh size in the range from 10 to 100 µm, determined by means of scanning electron microscopy; and a membrane layer (ii) comprising a second thermoplastic elastomer and having a layer thickness of less than 30 µm, determined by means of scanning electron microscopy, wherein the membrane is either free of pores (ii.1) or is porous and has pores having an average pore diameter of less than 2000 nm, determined by means of Hg porosimetry to DIN 66133 (ii.2); wherein the membrane (ii) is at least partly in direct contact with the fibres of the nonwoven layer (i), and at least partly covers the mesh openings of the nonwoven layer (i), and wherein the fibres of the first nonwoven layer (i) and the membrane (ii) are at least partly form-fittingly connected to one another in the contact region. The invention further relates to a process for producing such a composite material, and to a composite material obtained or obtainable by this process. The invention likewise relates to the use of such a composite material for the production of a functional article.