Thermoplastic Polyurethane Hot Melt Adhesive Viscosity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hot melt adhesives based on thermoplastic polyurethane copolymers face challenges with high viscosity and low thermal stability, making them difficult to process and apply, and they often contain hazardous free isocyanate monomers, which require expensive processing equipment and protective packaging.
Innovation Solution
A thermoplastic polyurethane copolymer with a specific NCO:OH ratio of less than 0.95:1 and viscosity between 1,000 to 100,000 mPas at 160°C, providing improved thermal stability and allowing for application in standard equipment without high heat and shear, and being essentially free of reactive functional groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the viscosity of the adhesive is increased to improve bond strength, then the strength of the bond formed is improved, but the application process becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the NCO:OH ratio (0.5:1 to 0.85:1) and molecular weight (5,000 to 20,000 g/mol) of the TPU adhesive. These parameter adjustments optimize the balance between viscosity and bond strength, enabling the adhesive to flow easily during application while forming strong bonds after solidification.
2Ease of operation
If the temperature is increased to reduce viscosity for easier application, then the ease of application is improved, but the stability of the polymer is reduced during the application
Solution Approach 1:
The patent uses parameter changes by selecting specific TPU molecular weights (5,000 to 20,000 g/mol) and NCO:OH ratios (0.5:1 to 0.85:1) that enable the adhesive to maintain adequate viscosity at lower application temperatures, thereby preserving polymer stability while still allowing for easy application.
3Reliability
If reactive polyurethane hot melt adhesives are used to achieve versatile adhesion and temperature resistance, then the adhesion performance is improved, but expensive packaging and processing equipment are required
Solution Approach 1:
The patent extracts the reactive isocyanate groups from the TPU adhesive formulation, creating a non-reactive thermoplastic polyurethane system. This eliminates the need for moisture-curing mechanisms, expensive protective packaging, and specialized processing equipment, while the patent compensates for the loss of reactive adhesion through optimized TPU composition and parameters.
4Reliability
If reactive polyurethane hot melt adhesives are used to achieve high adhesion, then the adhesion performance is improved, but free isocyanate monomers cause health issues
Solution Approach 1:
The patent removes free isocyanate monomers from the adhesive system by using a TPU formulation with controlled NCO:OH ratio (0.5:1 to 0.85:1), which ensures complete reaction of isocyanate groups during polymerization. This extraction of harmful monomers eliminates respiratory sensitization risks while maintaining adhesion performance through optimized TPU composition.
5Strength
If the number average molecular weight of TPU is increased to achieve good mechanical properties, then the mechanical properties are improved, but the viscosity becomes very high making processing difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight within the range of 5,000 to 20,000 g/mol. This optimization ensures the TPU has sufficient mechanical strength while maintaining manageable viscosity for easy processing and application, avoiding the extreme viscosity associated with higher molecular weights.
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 facilitates easier processing and application of the adhesive, extends its usable time, and reduces health risks associated with isocyanate monomers, while maintaining high adhesion and cohesion properties.
Implementation Method 1
hot melt adhesives composition based on thermally stable thermoplastic polyurethane copolymers (TPU)... behaviour during melting, application and the adhesion after solidification
Data Source
AI summary
A hot melt adhesive composition comprising a thermoplastic polyurethane copolymer, wherein the thermoplastic polyurethane copolymer comprises a reaction product of at least one polyester polyol; and at least one polyisocyanate; wherein the molar ratio of the NCO groups of the polyisocyanate to the OH groups of the polyester polyol is less than 0.95:1; wherein the viscosity of the thermoplastic polyurethane copolymer is 1,000 to 100,000 mPas at 160°C; wherein the thermoplastic polyurethane copolymer is thermally stable; and wherein the thermal stability is defined as a viscosity change of less than ± 10 % compared to the initial viscosity of the thermoplastic polyurethane copolymer after 6 hours at 160 °C.