Cyclic Urea Crosslinker Process for Low-Temperature Coatings
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Solution Overview
Problem
Industrial coatings based on amino resins, which use formaldehyde as crosslinkers, face issues such as formaldehyde emission and the need for high temperatures for curing, making them environmentally undesirable and energy-intensive. Additionally, existing processes for preparing etherified crosslinkers from cyclic ureas and multifunctional aldehydes are difficult to control and may result in gel-like products unsuitable for surface coatings.
Innovation Solution
A process involving the mixing of a multifunctional aldehyde with a cyclic urea in the presence of an alcohol, followed by adjustment of pH and further etherification under acidic conditions, to produce a partially etherified reaction product that can act as a crosslinker for coatings, allowing for ambient or heat-cured applications without gel formation and with improved stability and color retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amino resins with formaldehyde are used as crosslinkers, then crosslinking reaction occurs to form protective coating film, but formaldehyde is emitted during curing which is environmentally undesirable
Solution Approach 1:
The patent replaces harmful formaldehyde crosslinking with a beneficial alternative using cyclic urea and multifunctional aldehyde that does not emit harmful substances. The crosslinking mechanism is changed from formaldehyde-based to a different chemical pathway that achieves the same protective function without the harmful byproduct.
Solution Approach 2:
The patent changes the chemical parameters of the crosslinking system by substituting formaldehyde with cyclic urea and multifunctional aldehyde combinations. This parameter change transforms the crosslinking chemistry to eliminate formaldehyde emission while maintaining coating performance.
2Reliability
If amino resins are used as crosslinkers, then crosslinking reaction occurs to provide coating protection, but temperatures of at least 80 °C are required which is time-consuming and energy-consuming
Solution Approach 1:
The patent changes the thermal parameters of the crosslinking process by using a crosslinking system that operates at lower temperatures. The cyclic urea and multifunctional aldehyde combination enables crosslinking without requiring the high temperatures (≥80°C) needed for amino resin curing, thus reducing energy consumption.
3Reliability
If glyoxal is reacted with ethylene urea under acidic conditions to form crosslinker, then crosslinking capability is achieved, but gel-like solid product is formed which is unusable for surface coating applications
Solution Approach 1:
The patent introduces local quality control by carefully managing the reaction conditions at different stages. By controlling the local environment (pH, temperature, reagent addition rate) during the condensation reaction, the process prevents gel formation while maintaining crosslinking capability. The reaction is optimized to produce a usable liquid or soluble crosslinker rather than an insoluble gel.
Solution Approach 2:
The patent applies dynamic control to the reaction process by adjusting conditions during the reaction rather than using fixed conditions. The reaction parameters (temperature, pH, reagent addition) are dynamically adjusted to prevent gel formation while ensuring crosslinker formation, allowing the process to adapt and produce usable products.
4Reliability
If conventional multi-step reaction sequence is used to prepare etherified crosslinkers, then crosslinker formation is achieved, but the process is difficult to control and requires multiple steps
Solution Approach 1:
The patent merges multiple reaction steps into a single integrated process. By combining the condensation reaction, etherification, and crosslinker formation into one operation, the process eliminates the need for separate steps while maintaining control over the reaction. This integration simplifies the overall process and improves manufacturability.
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 process produces crosslinkers that enable coatings with good stability, resistance properties, and favorable appearance, capable of curing at ambient temperatures, reducing energy consumption and formaldehyde emission, and providing superior formulation stability compared to traditional amino-formaldehyde resin-based coatings.
Implementation Method 1
by performing the initial condensation reaction between glyoxal and ethylene urea in the presence of at least one alcohol
Implementation Method 2
leads to the preparation of at least partially etherified ethylene urea-glyoxal condensed resin
Implementation Method 3
the addition reaction is conducted in a pH range of more than 7.5 or in a pH range of from 4.5 to 7.5, and wherein after the addition reaction of step a), b) the pH is adjusted to at most 5.0
Implementation Method 4
In the so-called chemical drying, chemical reactions occur during film formation which lead to crosslinked macromolecules
Data Source
AI summary
This invention relates to a process to make a reaction product UA of at least one multifunctional aldehyde A with at least one cyclic urea U, by mixing the at least one multifunctional aldehyde A with the at least one cyclic urea U in the presence of at least one alcohol R1-OH, and optionally, at least one solvent that has no reactive groups which may react with aldehyde groups, -CO-NH- groups, or hydroxyl groups, to effect an addition reaction to obtain a solution of a product UA, where R1 is selected from the group consisting of linear, branched or cyclic alkyl groups having from one to twelve carbon atoms, to the reaction product obtained by this process, and to a method of use thereof as crosslinker for coating compositions.