Carbodihydrazide Crosslinkable Aqueous Coating Composition
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Solution Overview
Problem
Existing crosslinkable vinyl polymer coating compositions using polyhydrazides like adipic acid dihydrazide and succinic acid dihydrazide face issues with hydrolysis, leading to the formation of toxic hydrazine, which is undesirable, and require a two-pack system due to rapid curing reaction when using carbodihydrazide, resulting in poor workability and short pot life.
Innovation Solution
An aqueous coating composition comprising carbodihydrazide and carbonyl functional vinyl polymers with a specific molar ratio of hydrazide to carbonyl groups (0.1 to 0.95) and a molecular weight to acid value ratio greater than 400, allowing for a one-pack system with improved stability and reduced hydrazine formation, and incorporating reducing agents to minimize oxidation and extend shelf life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyhydrazides like adipic acid dihydrazide or succinic acid dihydrazide are used as crosslinkers, then adhesion and resistance level are improved, but toxic hydrazine is formed due to hydrolysis
Solution Approach 1:
The patent changes the chemical structure parameter of the polyhydrazide crosslinker from conventional adipic acid dihydrazide or succinic acid dihydrazide to carbodihydrazide, which has a different molecular structure that prevents hydrolysis and toxic hydrazine formation while maintaining crosslinking functionality
Solution Approach 2:
The patent converts the potential harm of hydrazine formation into a benefit by using carbodihydrazide, which not only eliminates toxic hydrazine formation but also provides superior performance characteristics including enhanced adhesion, chemical resistance, and durability
2Object-generated harmful factors
If carbodihydrazide is used as crosslinker, then toxic hydrazine formation is reduced, but rapid curing reaction occurs resulting in short pot life and poor workability
Solution Approach 1:
The patent adjusts the pH parameter of the coating composition to a basic range (pH 8-12), which slows down the curing reaction rate of carbodihydrazide, thereby extending pot life and improving workability while maintaining the advantage of reduced hydrazine formation
Solution Approach 2:
The patent creates a dynamic system where the curing reaction rate can be controlled by pH adjustments, allowing the composition to remain stable during storage and application (extended pot life) while still achieving effective crosslinking when needed
3Stability of the object's composition
If one-pack system is used with carbodihydrazide, then storage stability is improved, but rapid curing reaction reduces workability
Solution Approach 1:
The patent utilizes pH as a control parameter to stabilize the one-pack system containing carbodihydrazide, where the basic pH environment prevents premature curing during storage while allowing the composition to be applied and processed effectively
Solution Approach 2:
The patent prepares the coating composition in advance with all components including carbodihydrazide already mixed (one-pack system), and uses preliminary pH adjustment to prevent premature reaction, enabling stable storage before application
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 achieves a pot life of at least one year at 25°C, reducing toxic hydrazine formation and maintaining stability, while allowing for a one-pack system with improved workability and environmental safety.
Implementation Method 1
crosslinking agent which is carbodihydrazide... reacting with carbonyl groups
Implementation Method 2
crosslinking takes place rapidly at room temperature... crosslinking agent reactable with the crosslinker groups
Data Source
AI summary
The current invention relates to an one-pack aqueous coating composition comprising dispersed carbonyl functional vinyl polymer(s) particles, characterized in that the coating composition further comprises carbodihydrazide, whereby (i) the equivalent molar ratio of hydrazide groups to carbonyl groups is from 0.1 to 0.95, (ii) the ratio of number-average molecular weight of the carbonyl functional vinyl polymer(s) to acid value of the carbonyl functional vinyl polymer(s) is higher than 400, and (iii) the acid value of the carbonyl functional vinyl polymer(s) is from 2 to 100 mg KOH/gram carbonyl functional vinyl polymer.