Polyurethane Coating Curing Speed and Water Resistance
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Solution Overview
Problem
Existing polyurethane-based coating systems do not set quickly and are not water-resistant, often resulting in coatings with poor tear or abrasion resistance and durability, especially when exposed to moisture, due to the isocyanate's affinity for water leading to air bubble formation.
Innovation Solution
A polyurethane composition comprising a reaction product of an isocyanate component with 2-30% NCO content, a polyol component with an equivalent weight of 1500-2500, an aromatic diamine, a moisture scavenger, and a catalyst, which reacts to form a water-resistant coating with superior mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing polyurethane-based coating systems are used, then the coating can be formed, but the coating does not set quickly and has poor water resistance
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane system by using specific isocyanate indices (20-50%) and equivalent weights (1500-2500), and by incorporating aromatic diamines and moisture scavengers. These parameter changes enable the coating to cure quickly while maintaining water resistance, resolving the contradiction between curing speed and water resistance.
2Ease of manufacture
If isocyanate component with high affinity for water is used, then the coating can be formed, but air bubbles form due to reaction with water
Solution Approach 1:
The patent applies preliminary anti-action by incorporating moisture scavengers into the polyol component before the coating is applied. These moisture scavengers preemptively remove water from the system, preventing the harmful reaction between isocyanate and water that would otherwise produce air bubbles and compromise coating quality.
Solution Approach 2:
The patent uses aromatic diamines as intermediaries that facilitate the reaction between isocyanate and polyol while the moisture scavenger acts as a mediator to remove water. This intermediary approach allows the coating to form properly without the adverse effects of water reaction, maintaining both ease of manufacture and coating quality.
3Adaptability or versatility
If polyurethane-based system is used on moisture-susceptible substrates, then coating can be applied, but the coating has poor durability due to hydrophilicity
Solution Approach 1:
The patent changes the hydrophilicity parameter of the polyurethane system by using specific isocyanate indices and incorporating moisture scavengers. This reduces the hydrophilic nature of the coating, allowing it to be applied to moisture-susceptible substrates like cardboard while maintaining long-term durability and resistance to moisture-related degradation.
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 cures quickly and provides coatings with enhanced tear and abrasion resistance and durability, even under ambient humidity, making it suitable for substrates susceptible to moisture absorption.
Implementation Method 1
a polyurethane composition comprising a reaction product of an isocyanate component comprising one or more aromatic isocyanates... and a polyol component comprising a polyol having an equivalent weight (EW) of about 1500-2500, an aromatic diamine
Implementation Method 2
a moisture scavenger... wherein the aromatic isocyanate has an isocyanate (NCO) content of about 2-30%... This may be because the isocyanate portion of the system has a stronger affinity for, or reacts faster with water than the polyol portion, to produce carbon dioxide
Data Source
AI summary
The present disclosure provides a polyurethane composition comprising a reaction product of an isocyanate component comprising one or more aromatic isocyanates, wherein the aromatic isocyanate has an isocyanate (NCO) content of about 2-30% NCO; and a polyol component comprising a polyol having an equivalent weight (EW) of about 1500-2500, an aromatic diamine, a moisture scavenger and a catalyst. A process for preparing the polyurethane composition and an article, coating or film comprising the polyurethane composition are also provided.