Amine Curative Composition for Polyurethane Coatings
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Solution Overview
Problem
The use of 4,4'-methylenebis(2-chloroaniline) (MOCA) as a curing agent in polyurethane and polyurea coatings poses safety and health concerns due to its carcinogenic properties and is difficult to work with due to its crystalline nature, necessitating a safer alternative that maintains good physical and mechanical properties.
Innovation Solution
A coating composition comprising a bis-aromatic secondary diamine and a bis-aromatic primary diamine, with specific molar ratios and optional mono-aromatic primary diamine, combined with an isocyanate-terminated prepolymer, which provides a safer and more workable curing agent for polyurethane or polyurea coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If MOCA is used as a curing agent, then good physical and mechanical properties are achieved, but safety and health concerns arise due to carcinogenic properties
Solution Approach 1:
The patent changes the chemical structure parameters of the curing agent by replacing MOCA with a blend of aromatic diamines having different molecular structures (bis-aromatic secondary diamine with specific R1 and R2 groups, and bis-aromatic primary diamine). This structural modification eliminates carcinogenicity while maintaining the crosslinking reactivity and mechanical property enhancement needed for polyurethane coatings.
Solution Approach 2:
The patent uses a composite curing agent system consisting of multiple aromatic diamine components in specific ratios (60-90 mol% bis-aromatic secondary diamine and 10-40 mol% bis-aromatic primary diamine). This composite approach combines the beneficial properties of different diamine structures to achieve both safety and performance, replacing the single-component MOCA system.
2Strength
If MOCA is used as a curing agent, then good physical and mechanical properties are achieved, but ease of operation deteriorates due to crystalline nature and dissolution difficulty
Solution Approach 1:
The patent modifies the physical state parameters of the curing agent system by selecting aromatic diamines that are liquids or low-melting solids at room temperature, unlike highly crystalline MOCA. The selected diamines have appropriate viscosity and solubility characteristics that enable easy mixing and application, while their chemical structures provide the necessary reactivity for forming strong crosslinked networks.
3Object-affected harmful factors
If a safer alternative to MOCA is used, then health risks are eliminated, but maintaining good pot life and mechanical properties becomes challenging
Solution Approach 1:
The patent carefully adjusts the chemical composition parameters of the aromatic diamine blend, specifically the ratio of secondary to primary diamines and the types of substituent groups (R1 and R2), to control the reaction rate with isocyanate. This optimization ensures adequate pot life for application while achieving the required crosslink density for mechanical properties, all using non-carcinogenic aromatic diamines.
Solution Approach 2:
The patent employs a composite curing system with multiple aromatic diamine components that have different reactivities toward isocyanate. The bis-aromatic secondary diamine provides controlled reaction rate for good pot life, while the bis-aromatic primary diamine enhances crosslinking for mechanical properties. This synergistic combination maintains reliability without health risks.
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 solution offers a safer alternative with improved pot life and mechanical properties, such as tensile strength, tear resistance, and hardness, meeting or exceeding standards for waterproof coatings, while eliminating the health risks associated with MOCA.
Implementation Method 1
Two component (2K) polyurethane or polyurea coatings are typically prepared by in-situ mixing together and reacting of a curing agent with an isocyanate-terminated prepolymer
Data Source
AI summary
The present invention relates to a coating composition. More particularly the present invention relates to a coating composition comprising an amine curative composition comprising a bis-aromatic secondary diamine, a bis-aromatic primary diamine and optionally a mono-aromatic primary diamine.