TPU Non-Woven Fabrics Using Crosslinking Agents
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Solution Overview
Problem
High melt viscosity of thermoplastic polyurethane (TPU) polymers hinders the production of small-diameter fibers in non-woven fabrics, and existing additives that reduce viscosity often compromise the physical properties of the fibers.
Innovation Solution
The use of a crosslinking agent, added at 5 to 20 weight percent to the TPU polymer melt, reduces melt viscosity, allowing for the production of smaller diameter fibers and enhancing the tensile strength and elasticity of the non-woven fabric, which can then be further processed into membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the temperature of the TPU polymer melt is increased to reduce viscosity, then the melt becomes less viscous and easier to process, but the physical properties of the polymer deteriorate due to depolymerization
Solution Approach 1:
The patent changes the chemical composition parameter by introducing a crosslinking agent (polyisocyanate) to modify the polymer melt properties. This allows viscosity reduction through chemical crosslinking rather than thermal heating, thereby maintaining polymer integrity and physical properties while achieving improved processability
Solution Approach 2:
The crosslinking agent acts as an intermediary substance that mediates between the conflicting requirements of low viscosity and high strength. It chemically interacts with the TPU polymer chains to create a crosslinked structure that reduces melt viscosity while preserving or enhancing the physical properties of the resulting non-woven fabric
2Ease of manufacture
If additives such as plasticizers are used to reduce melt viscosity, then the polymer becomes easier to process into small fibers, but the physical properties of the fibers deteriorate
Solution Approach 1:
Instead of using plasticizer additives that compromise fiber strength, the patent changes the fundamental parameter of polymer chain interaction by introducing crosslinking. This creates a chemically modified system where the crosslinked network provides both low melt viscosity for easy spinning and high fiber strength through the crosslinked structure
Solution Approach 2:
The patent converts the typically harmful effect of high viscosity (which prevents small fiber formation) into a benefit by using crosslinking to create a unique melt behavior. The crosslinked structure allows the polymer to flow easily during processing while maintaining strength in the final product, effectively turning the viscosity problem into a solution
3Productivity
If the TPU polymer melt viscosity is reduced to allow smaller fiber diameters, then higher polymer throughput and greater attenuation are achieved, but existing methods compromise fiber strength
Solution Approach 1:
The patent changes the rheological parameters of the polymer melt through crosslinking, achieving low viscosity that enables high throughput and small fiber diameters. The crosslinked network structure allows the melt to flow readily during extrusion while the resulting fibers maintain high tensile strength due to the crosslinked morphology
Solution Approach 2:
The patent creates a composite system combining TPU polymer with crosslinking agents (polyisocyanates). This composite approach allows the material to exhibit both low melt viscosity for high productivity and high fiber strength, achieving properties that neither component alone could provide
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 crosslinking agent enables the production of high-strength, elastic non-woven fabrics with smaller fiber diameters, improving their tensile strength and set properties, while allowing for higher polymer throughput and finer fiber production, suitable for various applications including filtration and breathable garments.
Implementation Method 1
adding a crosslinking agent to the TPU polymer melt. The crosslinking agent reduces the melt viscosity of the TPU polymer melt allowing the fibers to exit the die at smaller diameters
Implementation Method 2
High velocity air is applied adjacent to the fibers, which elongate the fibers and cause them to deposit in a random alignment on a belt below the die
Implementation Method 3
the non-woven fabric is further melt processed to compact the fabric, such that the air passages in the fabric are reduced. The air passages can be reduced to an extent where a membrane is formed
Data Source
Figure 1
AI summary
Elastic non-woven fabrics are disclosed which are made in a melt blown process or a spun bond process. The fabric is made from a thermoplastic polyurethane polymer mixed with a crosslinking agent to give high strength elastic non-woven fabric. The crosslinking agent is added to the polymer melt prior to the melt passing through the die which forms the individual fibers. Further processing the non-woven is also disclosed.