Cationic Electrodeposition Coating with Hydrolysis-Resistant Catalyst
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Solution Overview
Problem
Bismuth compounds in cationic electrodeposition coating compositions hydrolyze over time, losing catalytic activity, while organic amine catalysts like cyclic guanidine have high solubility in water and poor electrodeposition efficiency, leading to inadequate corrosion resistance and appearance in cured films.
Innovation Solution
A cationic electrodeposition coating composition comprising an amine-modified epoxy resin, a blocked polyisocyanate curing agent, and a coordination polymer catalyst with specific metal ions and organic ligands, which enhances stability and catalytic activity, ensuring uniform deposition and improved corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bismuth compound is used as catalyst, then initial catalytic activity is high, but catalytic activity is lost over time due to hydrolysis
Solution Approach 1:
The patent introduces an organic ligand as an intermediary substance that coordinates with the metal ion to form a coordination polymer catalyst. This coordination structure acts as a mediator that protects the metal ion from hydrolysis while maintaining its catalytic function, thereby extending the catalyst's effective period and improving reliability.
2Quantity of substance
If organic amine catalyst is used, then solubility in water is high, but electrodeposition efficiency is poor
Solution Approach 1:
The patent creates a composite catalyst system by combining metal ions with organic ligands to form a coordination polymer. This composite structure integrates the benefits of both components: the metal ion provides catalytic activity while the organic ligand framework controls solubility and enhances electrodeposition efficiency, overcoming the limitations of using organic amine catalysts alone.
3Stability of the object's composition
If catalyst stability is improved, then hydrolysis resistance increases, but catalytic activity may be reduced
Solution Approach 1:
The patent optimizes the coordination parameters between metal ions and organic ligands, including the choice of specific ligand structures and metal-to-ligand ratios. By adjusting these parameters, the coordination polymer achieves an optimal balance where the metal ion remains sufficiently accessible for catalysis while being protected by the coordination structure against hydrolysis, thus maintaining both stability and activity.
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 results in a cured electrodeposition coating film with excellent corrosion resistance and appearance by maintaining high catalytic activity and reducing solubility, achieving dense and smooth film curing.
Implementation Method 1
a coordination polymer catalyst (C) having a metal complex containing a metal ion (C1) and an organic ligand (C2) as a constituent unit
Implementation Method 2
forming an uncured electrodeposition coating film by immersing an article to be coated in the cationic electrodeposition coating composition and performing electrodeposition coating
Implementation Method 3
cationic electrodeposition coating composition
Data Source
AI summary
A cationic electrodeposition coating composition including :an amine-modified epoxy resin (A); a blocked polyisocyanate curing agent (B); and a coordination polymer catalyst (C) having a metal complex containing a metal ion (C1) and an organic ligand (C2) as a constituent unit, wherein the metal ion (C1) includes an ion of at least one metal element selected from the group consisting of Bi, Zn, Zr, Cs, and lanthanoid, and the organic ligand (C2) includes at least one selected from the group consisting of amine compounds represented by general formulas (1) to (5).