Benzylated Polyamine Epoxy Curing Agents
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Solution Overview
Problem
Epoxy resins cured with neat polyalkylene polyamines, such as those based on ethylenediamine homologues, tend to 'smoke' or 'fume' due to high amine vapor pressure, leading to surface defects like blush, carbamation, and exudate, which affect the appearance and intercoat adhesion of coatings, especially when applied at low temperatures.
Innovation Solution
The use of benzylated polyalkylene polyamine curing agents, derived from the reaction of benzaldehyde with polyalkylene polyamines, which have at least three nitrogen atoms and one benzyl group, improves compatibility with epoxy resins, reducing smoking, fuming, and the need for induction time, and results in a final product with low free amine levels, enhancing handling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If neat polyalkylene polyamines are used as curing agents for epoxy resins, then the curing process can proceed effectively, but the coatings exhibit surface defects such as blush, carbamation, and exudate due to high amine vapor pressure and smoking
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of the polyalkylene polyamine through benzylation. This chemical modification changes the physical and chemical parameters of the curing agent, specifically reducing amine vapor pressure and eliminating smoking while maintaining curing effectiveness. The benzylation process alters the molecular weight, volatility, and reactivity parameters of the amine to resolve the contradiction between effective curing and surface quality.
Solution Approach 2:
The patent creates a composite chemical structure by combining benzyl groups with polyalkylene polyamine chains. This composite approach integrates the reactive amine functionality needed for curing with the benzyl groups that reduce volatility and prevent surface defects. The resulting benzylated polyalkylene polyamine acts as a composite material that simultaneously provides effective curing and eliminates harmful smoking and surface defects.
2Ease of operation
If neat polyalkylene polyamines are used at low temperatures, then the coating can be applied, but the amine-epoxy incompatibility is exacerbated, extending setting time and increasing amine migration to the surface
Solution Approach 1:
The benzylation modification changes the reactivity parameters of the polyalkylene polyamine, making it more compatible with epoxy resins at low temperatures. This parameter change reduces the activation energy barrier for the curing reaction, allowing the coating to set properly at lower temperatures without excessive migration or extended setting times.
3Manufacturing precision
If induction time is extended to achieve high gloss and clarity in clear coats, then the coating appearance improves, but the process time and productivity are reduced
Solution Approach 1:
The benzylation of polyalkylene polyamine modifies the chemical parameters to improve compatibility with epoxy resins, resulting in a more homogeneous mixture that requires less or no induction time to achieve high gloss and clarity. This parameter change eliminates the need for extended waiting periods while maintaining excellent coating appearance.
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 benzylated polyalkylene polyamine curing agents provide improved compatibility with epoxy resins, reducing surface defects and the need for induction time, resulting in coatings with high gloss and clarity, and improved handling properties by eliminating smoking and fuming, and minimizing free amine presence.
Implementation Method 1
the reaction product of the reductive amination of a benzaldehyde compound with a polyalkylene polyamine having at least three nitrogen atoms
Implementation Method 2
When epoxy resins are cured with neat polyalkylene polyamines such as those based on the ethylenediamine (EDA) homologues, the mixtures will tend to 'smoke' or 'fume'. This describes the protonation of the amine with water or slight acidity present in the surrounding air. This phenomenon is due to the high amine vapor pressure.
Data Source
AI summary
The present invention provides curing agent compositions comprising benzylated polyalkylene polyamine compounds. Amine-epoxy compositions and articles produced from these amine-epoxy compositions are also disclosed.