Solvent-Free Polyurethane Composition Using Dimethylpyrazole Blocking
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Solution Overview
Problem
Existing polyurethane compositions for coating flexible substrates require solvents for dilution due to high viscosity and contain oximes, which have unpleasant odors and toxicity concerns, leading to stability and regulatory issues, and result in inferior physical and mechanical properties.
Innovation Solution
A solvent-free thermosetting polyurethane composition using prepolymers with isocyanate groups blocked by dimethylpyrazole, combined with a polysiloxane-based prepolymer and a chain extender, which eliminates the need for solvents and reduces oxime content, while incorporating flame retardant additives for enhanced elasticity and breathability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oximes are used to block isocyanate groups in prepolymers, then long-term stability of the polyurethane composition is improved, but unpleasant odors and toxicity concerns worsen
Solution Approach 1:
The patent changes the chemical parameter of the blocking agent from traditional oximes to dimethylpyrazole. This substitution maintains the stability function while eliminating the harmful odor and toxicity characteristics of oximes, directly resolving the contradiction between reliability and harmful factors.
2Reliability
If prepolymers with blocked isocyanate groups are used, then stability is improved, but high viscosity requires dilution with solvents which worsens environmental and health issues
Solution Approach 1:
The patent changes the blocking agent parameter to dimethylpyrazole, which has different viscosity characteristics compared to traditional oximes. This allows the prepolymer to achieve suitable working viscosity without requiring solvent dilution, thereby maintaining stability while eliminating harmful solvent use.
3Reliability
If products with free isocyanates are used to avoid solvents and oximes, then stability issues are avoided, but physical and mechanical features of the final polymer deteriorate
Solution Approach 1:
The patent uses dimethylpyrazole as a blocking agent that allows the prepolymer to remain stable during storage while maintaining appropriate viscosity. After application, the blocked isocyanate groups react with the polyamine to form crosslinked polyurethane structures with excellent physical and mechanical properties, thus achieving both stability and strength.
4Reliability
If oximes are used for stability, then composition stability is improved, but regulatory compliance worsens due to prohibition in some European countries
Solution Approach 1:
The patent substitutes dimethylpyrazole for traditional oximes as the blocking agent. This chemical parameter change maintains the necessary composition stability while ensuring compliance with European regulations that prohibit or restrict certain oximes, thereby improving regulatory adaptability.
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 composition achieves excellent physical and mechanical properties, breathability, and flame retardancy without solvent use or unpleasant odors, making it suitable for various applications like sports clothing and furniture, while complying with regulatory standards.
Implementation Method 1
a prepolymer A having a molecular weight in the range between 5000 and 12000 terminated with blocked isocyanate groups, said prepolymer being obtained by reaction of a diisocyanate with a polyhydroxy compound
Implementation Method 2
a prepolymer B terminated with blocked isocyanate groups, obtained by reaction of an aliphatic diisocyanate with a polysiloxane compound
Data Source
AI summary
The present invention relates to a polyurethane composition for coating flexible supports, comprising a prepolymer A obtained by a reaction of a diisocyanate with a polyhydroxy compound and a prepolymer B containing blocked isocyanate groups, said prepolymer B being obtained by reaction of an aliphatic diisocyanate with a polysiloxane compound; wherein said prepolymer A and/or said prepolymer B comprise isocyanate groups blocked with a dimethylpyrazole