Moisture-Curing Polyurethane Composition with Aldimine Hardening
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Solution Overview
Problem
Moisture-curing polyurethane compositions with low monomeric isophorone diisocyanate content suffer from surface tackiness and limited mechanical strength, particularly under outdoor weathering conditions, and pose health risks due to the toxicity of monomeric isophorone diisocyanate.
Innovation Solution
A moisture-curing polyurethane composition with a low content of monomeric isophorone diisocyanate, using an aldimine of formula (I) to form elastic materials with improved mechanical strength and reduced tackiness, suitable for outdoor applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If monomeric isophorone diisocyanate is removed from the isocyanate-functional polymer to reduce toxicity, then health safety is improved, but mechanical strength and surface tackiness deteriorate
Solution Approach 1:
The patent removes monomeric isophorone diisocyanate from the isocyanate-functional polymer through distillation to eliminate toxicity, then compensates for the resulting mechanical strength loss by adding oligomeric isophorone diisocyanate crosslinkers and specific aldimines as latent hardeners
Solution Approach 2:
The patent changes the molecular weight distribution of isocyanate compounds by replacing monomeric IPDI with oligomeric IPDI crosslinkers, thereby maintaining crosslinking density and mechanical strength while reducing toxicity from the monomeric form
2Strength
If oligomeric isophorone diisocyanate crosslinkers are added to compensate for mechanical strength, then mechanical strength is improved, but elongation and flexibility deteriorate due to stiffening
Solution Approach 1:
The patent optimizes the molecular weight and functionality of oligomeric IPDI crosslinkers to achieve sufficient mechanical strength while maintaining elongation above 200%, and controls the NCO content and aldimine ratio to balance crosslinking density with flexibility
Solution Approach 2:
The patent creates a composite curing system combining oligomeric IPDI crosslinkers with specific aldimines (N,N'-bis(2,2-dimethyl-3-(N-morpholino)propylidene)-4,4'-methylene-bis(cyclohexylamine)) to achieve synergistic effects that maintain both strength and elasticity
3Object-affected harmful factors
If isocyanate content is reduced to lower toxicity, then health safety is improved, but UV resistance and mechanical performance deteriorate
Solution Approach 1:
The patent uses isocyanate-functional polymers with controlled NCO content (1-10 wt%) and replaces monomeric IPDI with oligomeric IPDI, maintaining UV resistance through the isophorone diisocyanate-based polymer structure while reducing toxicity by eliminating monomeric IPDI through distillation
4Reliability
If aldimines are used as latent hardeners to improve curing properties, then bubble formation is prevented, but surface tackiness increases
Solution Approach 1:
The patent selects specific aldimines with controlled molecular weight and structure (N,N'-bis(2,2-dimethyl-3-(N-morpholino)propylidene)-4,4'-methylene-bis(cyclohexylamine)) and optimizes their content (0.1-10 wt%) to achieve complete curing with minimal surface tackiness while maintaining bubble formation prevention
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 fast curing with low surface tackiness, high mechanical strength, and durability under UV and water exposure, while maintaining low viscosity and shelf life stability, suitable for outdoor coatings and sealants.
Implementation Method 1
They react with isocyanate groups upon contact with moisture
Implementation Method 2
aldimines serve as so-called latent hardeners or blocked amines. They react with isocyanate groups
Implementation Method 3
good UV resistance... durability under UV and water exposure
Data Source
AI summary
The present invention describes a moisture-curing polyurethane composition comprising – at least one isocyanate-functional polymer with a content of monomeric isophorone diisocyanate of below 0.5 weight-%, obtained from the reaction of isophorone diisocyanate and at least one polyol, and – at least one aldimine of the formula (I). The composition has a low toxicity, a good shelf life stability and cures quickly to an elastic material of low surface tack and good mechanical properties, particularly in terms of high tensile strength and modulus of elasticity at high elongation. It enables coatings, sealants and adhesives with excellent stability under outdoor wheathering conditions and high UV load. The aldimine of the formula (I) allows to overcome the drawbacks caused by the removal of most of the monomeric isophorone diisocyanate in terms of cure speed, surface tackyness and final strength of such compositions. The inventive compositions are particularly suitable as elastic adhesives and/or sealants or elastic coatings, particularly for outdoor use such as on roofs, floors or ships.