Epoxy Resin Coating Composition Using Branched Thiol Curing Agent
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Solution Overview
Problem
Conventional epoxy resin coating compositions face challenges with storage stability and toxicity, particularly at low temperatures, due to the high reactivity of polythiol-based curing agents and the use of tin compounds, which are toxic.
Innovation Solution
A two-component curable epoxy resin coating composition is developed by mixing liquid (A) containing epoxy resin and a specific branched thiol-type curing agent with liquid (B) containing a curing assistant, where the thiol-type curing agent is an ester of polyhydric alcohol with thiol group-containing carboxylic acid, and an aprotic volatile solvent is used, improving storage stability and reducing toxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional polythiol-based curing agents are used to achieve low temperature curability, then curability at low temperature is improved, but storage stability deteriorates due to high reactivity between epoxy resin and polythiol
Solution Approach 1:
The curing agent is segmented into two separate components: liquid (A) containing the thiol-type curing agent and liquid (B) containing the curing assistant. This segmentation prevents premature reaction between the thiol group and epoxy resin during storage, while enabling low-temperature curability when the two liquids are mixed before application.
Solution Approach 2:
The curing assistant in liquid (B) acts as an intermediary that activates the thiol-type curing agent. The curing assistant mediates the reaction between the thiol group and epoxy resin, enabling low-temperature curing while the separated storage conditions maintain stability.
2Temperature
If conventional polythiol is added to liquid (B) containing curing assistant, then curability is improved, but storage stability worsens due to disulfide bond formation and skim generation
Solution Approach 1:
The formulation is segmented into liquid (A) containing the thiol-type curing agent and liquid (B) containing only the curing assistant. This prevents the thiol group from contacting the curing assistant during storage, eliminating disulfide bond formation and skim generation, while maintaining low-temperature curability through controlled mixing before application.
3Ease of operation
If two-component formulation is used to improve handling ease, then ease of operation is improved, but storage stability worsens due to reactivity between components
Solution Approach 1:
The two-component formulation is designed with liquid (A) containing the thiol-type curing agent and liquid (B) containing the curing assistant, separated to prevent reaction during storage. The segmentation maintains stability while providing ease of operation through simple mixing before application.
Solution Approach 2:
The physical state and chemical stability parameters are optimized by selecting specific compounds: the thiol-type curing agent with controlled reactivity and the curing assistant with appropriate basicity. This allows the two-component system to maintain stability during storage while achieving desired curability and handling ease.
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 exhibits excellent curability at low and ordinary temperatures with improved storage stability and reduced toxicity, offering a suitable pot life and enhanced workability by using a branched compound with a thiol group, which is easy to store and handle.
Implementation Method 1
A compound containing two or more thiol groups in one molecule reacts more readily to form a cured product by being mixed with epoxy resin
Implementation Method 2
liquid (A) containing epoxy resin, a specific thiol-type curing agent and an aprotic volatile solvent
Data Source
AI summary
The present invention relates to epoxy resin coating composition which comprises, at least, epoxy resin, a thiol-type curing agent and a curing assistant, being composed of two liquids of liquid (A) containing epoxy resin and a thiol-type curing agent and liquid (B) containing a curing assistant, which liquids are mixed just before using, wherein the thiol-type curing agent contains a branched compound containing a thiol group (P), which compound is an ester of polyhydric alcohol with thiol group-containing carboxylic acid represented by formula (1) HOCO(CH2)nCR1R2SH (1) (in the formula, R1 represents a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, R2 represents a linear or branched alkyl group having 1 to 10 carbon atoms, and n represents an integer of 1 to 4), which exhibits a suitable pot life, excellent curability particularly at low and ordinary temperature and low toxicity.