Furan-Based Curing Agents for Low VOC Epoxy Resins
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Solution Overview
Problem
Commercial epoxy formulations using amine curing agents often suffer from 'amine blushing' or 'water spotting' due to carbamatization, especially at low temperatures, and rely on benzyl alcohol, which is a volatile organic compound (VOC), making them environmentally undesirable and affecting mechanical properties.
Innovation Solution
The use of furan-based curing agents and their adducts, which are derived from renewable resources, allows for low VOC or VOC-free epoxy formulations with improved curing speed and surface properties at low temperatures, eliminating the need for benzyl alcohol and reducing amine blushing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If primary amine curing agents are used for epoxy resins, then good curing performance is achieved, but amine blushing and water spotting occur due to carbamatization
Solution Approach 1:
The patent extracts the problematic primary amino groups from the curing agent structure and replaces them with secondary amino groups in the furan-based curing agent. This extraction of the harmful functional group while retaining the curing capability resolves the amine blushing issue while maintaining epoxy curing performance.
Solution Approach 2:
The patent changes the chemical parameter of the curing agent from primary amine to secondary amine structure. This parameter change in the functional group type eliminates carbamatization while preserving the essential curing function, thereby preventing amine blushing and water spotting.
2Object-affected harmful factors
If secondary amine polyamines are used as curing agents to avoid carbamatization, then amine blushing is reduced, but these polyamines are difficult to obtain and very expensive
Solution Approach 1:
The patent employs a furan-based curing agent that is inexpensive and readily available, replacing expensive and difficult-to-obtain secondary amine polyamines. The furan-based agent achieves the same amine blushing prevention effect while being economically viable for commercial applications.
Solution Approach 2:
The patent creates a composite molecular structure combining furan rings with secondary amine groups, resulting in a curing agent that exhibits both the desired chemical properties (resistance to carbamatization) and favorable economic properties (low cost and easy availability).
3Object-affected harmful factors
If epoxy-amine adducts are used as curing agents to avoid carbamatization, then amine blushing is reduced, but these adducts have high viscosity requiring dilution by solvents
Solution Approach 1:
The patent introduces furan rings into the curing agent structure, which provides local aromatic character and structural rigidity. This local quality enhancement maintains low viscosity while preserving the secondary amine functionality that prevents carbamatization, eliminating the need for solvent dilution.
4Ease of operation
If benzyl alcohol is added to epoxy formulations to improve physical properties and appearance, then workability is improved, but VOC emissions increase and mechanical properties are negatively impacted
Solution Approach 1:
The patent extracts and eliminates benzyl alcohol from the epoxy formulation by using a furan-based curing agent that provides inherent low viscosity and excellent workability. This removal of the VOC-containing additive achieves both environmental compliance and maintains operational ease.
5Adaptability or versatility
If curing is carried out at low temperatures, then application flexibility is improved, but curing speed is reduced allowing more time for carbamatization side reactions
Solution Approach 1:
The patent employs a composite molecular structure with furan rings and secondary amine groups that creates favorable steric and electronic effects. This composite structure maintains high reactivity at low temperatures, enabling fast curing even at 5°C while preventing carbamatization, thus achieving both application flexibility and productivity.
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 furan-based curing agents provide fast curing speed and glossy, defect-free surfaces even at low temperatures, matching the hardness of standard systems without benzyl alcohol and outperforming systems with benzyl alcohol in terms of amine blushing resistance.
Implementation Method 1
epoxy formulations comprising furan-based curing agents
Implementation Method 2
secondary amines are as much not subject to carbamatization
Data Source
AI summary
The invention relates to a room temperature or low temperature curable epoxy formulation comprising a) an epoxy component comprising at least one epoxy resin and b) a hardener component comprising at least one compound of formula (I) wherein X is a divalent hydrocarbon group, which optionally contains one or more heteroatoms, and n is 0, 1, 2 or 3, preferably 0 or 1, and/or at least one epoxy-amine adduct, which is a reaction product of the compound of formula (I) and an epoxy compound selected from at least one of a monoepoxide and a polyepoxide, as a curing agent. The compounds of formula (I) and the epoxy-amine adduct are suitable as curing agents for epoxy formulations which provide good surface properties and good cure speed, even at low temperature curing. In particular, amine blushing can be avoided or reduced to a large extent, when these curing agents are used. A particular advantage is that the respective epoxy formulations can be formulated as a low VOC epoxy formulation or even as an essentially VOC-free epoxy formulation.