Carbodiimide Crosslinker Composition for Stable Low-Temperature Curing
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Solution Overview
Problem
Existing carbodiimide-based aqueous resin cross-linking agents suffer from storage stability issues during long-term storage and reduced reaction activity at low temperatures, leading to thickening or gelation, and require high temperatures for effective curing.
Innovation Solution
A carbodiimide composition comprising a water-soluble modified polycarbodiimide (A) and a water-insoluble polycarbodiimide (B), with specific modification rates and ratios to form an association structure that maintains stability during storage and allows low-temperature curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a carbodiimide-based aqueous resin cross-linking agent is used to consume carboxylic acid at low temperature, then low-temperature curability is improved, but storage stability deteriorates due to thickening or gelation during long-term storage
Solution Approach 1:
The invention divides the cross-linking agent into two distinct components: a water-soluble modified polycarbodiimide (A) with reduced reactivity and a water-insoluble polycarbodiimide (B) with high reactivity. This segmentation allows component (A) to provide storage stability while component (B) enables low-temperature curability, resolving the contradiction between storage stability and low-temperature reactivity.
Solution Approach 2:
The invention modifies the polycarbodiimide by changing its solubility parameter and reactivity parameters. Component (A) is modified to be water-soluble with reduced reactivity toward carboxylic acid, while component (B) remains water-insoluble with high reactivity. This parameter change allows the system to maintain stability during storage and activate curing only when needed.
2Stability of the object's composition
If the carbodiimide is modified with a reactive group to improve storage stability, then storage stability is improved, but reaction activity at low temperature is reduced
Solution Approach 1:
The invention segments the modified carbodiimide into two components with different modification rates. Component (A) has a high modification rate (5-100%) providing storage stability, while component (B) has a low modification rate (0-70%) preserving low-temperature curability. This segmentation resolves the contradiction between storage stability and low-temperature reactivity.
Solution Approach 2:
The invention creates a composite system combining two types of polycarbodiimides with different properties. The water-soluble modified polycarbodiimide (A) and water-insoluble polycarbodiimide (B) work synergistically, with (A) providing storage stability and (B) providing curing activity, achieving both storage stability and low-temperature curability simultaneously.
3Stability of the object's composition
If a modified carbodiimide-based aqueous resin cross-linking agent is used to prevent thickening during storage, then storage stability is improved, but the modifying agent dissociates only at high temperature (100°C or higher)
Solution Approach 1:
The invention changes the dissociation temperature parameter by selecting specific modifying agents and controlling modification rates. The water-soluble modified polycarbodiimide (A) is designed to remain stable during storage but become reactive at lower curing temperatures (80°C) through the presence of unmodified polycarbodiimide (B), achieving both storage stability and low-temperature curability.
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 excellent storage stability and low-temperature curability, resulting in a cured resin product with improved water resistance and appearance.
Implementation Method 1
a water-soluble modified polycarbodiimide (A) and a water-insoluble polycarbodiimide (B)
Implementation Method 2
form an association structure that maintains stability during storage
Implementation Method 3
the carbodiimide group can react with the carboxylic acid in the aqueous resin
Data Source
AI summary
The present invention provides a carbodiimide composition containing a water-soluble modified polycarbodiimide (A) and a water-insoluble polycarbodiimide (B), a curing agent composition using the same, a coating composition, and a resin cured product.