Polyurethane Prepolymer Composition With Low Free Diisocyanate
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Solution Overview
Problem
Existing polyurethane prepolymers contain high residual concentrations of diisocyanate monomers, leading to health and safety issues and reduced product performance, such as decreased adhesion and increased moisture sensitivity.
Innovation Solution
A polyurethane prepolymer composition with less than 1.0 wt.% free diisocyanate monomer and less than 75 wt.% of a 2:1 stoichiometric adduct of diisocyanate and polyol, prepared using a reaction of excess diisocyanate with polyol, achieving low residual diisocyanate levels and high oligomer content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane prepolymer manufacturing process is used, then high productivity is achieved, but high residual diisocyanate monomer concentration results in health and safety issues and reduced product performance
Solution Approach 1:
The patent changes the compositional parameters of the prepolymer by limiting free diisocyanate to less than 1.0 wt.% and controlling the 2:1 adduct content to less than 75 wt.%, thereby transforming the product from high-residual to low-residual diisocyanate formulation that maintains performance while reducing harmful effects
Solution Approach 2:
The patent creates a composite prepolymer system containing multiple components (free diisocyanate, 2:1 adduct, oligomers) with controlled proportions, where the combination of these components in specific ratios achieves both low residual monomer and high performance characteristics
2Object-affected harmful factors
If residual polyisocyanate is reduced to less than 1.0 wt.%, then health and safety risks are minimized, but manufacturing complexity increases due to additional processing steps
Solution Approach 1:
The patent applies preliminary action by removing excess diisocyanate monomer through distillation or extraction before the prepolymerization reaction is complete, thereby preventing the formation of high residual monomer levels and simplifying downstream processing while ensuring safety
3Strength
If high amount of 2:1 stoichiometric adduct is used, then adhesion performance is improved, but residual diisocyanate migration to interface causes decreased adhesion and increased moisture sensitivity
Solution Approach 1:
The patent applies local quality by creating a prepolymer composition with non-uniform distribution of components, where the interface region has reduced diisocyanate migration due to the controlled composition (less than 75 wt.% 2:1 adduct), thereby maintaining strong adhesion while improving stability
Data Source
AI summary
A polyurethane prepolymer composition may include more than 0 wt. % and less than 1.0 wt. % free diisocyanate monomer. The polyurethane prepolymer may include less than 80 wt. % of a 2:1 stoichiometric adduct of diisocyanate and at least one polyol (perfect prepolymer). Curable compositions may include such polyurethane prepolymer compositions and the such polyurethane prepolymer compositions may be used as adhesives.