Aqueous Curable Film-Forming Composition Catalyst Stabilization
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Solution Overview
Problem
Aqueous polyisocyanate-cured coating systems face challenges with catalyst instability and short pot life, leading to inconsistent performance and adhesion issues due to rapid viscosity increase, which affects the coating's ability to meet specification requirements for adhesion, chemical resistance, and appearance across different substrate areas.
Innovation Solution
Incorporating a catalytic organic compound comprising iron and/or tin, combined with a beta-diketone, into the aqueous curable film-forming composition to stabilize the catalyst and extend pot life while allowing for accelerated curing upon application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If metal complex catalysts are added to accelerate curing, then cure time is reduced, but catalyst instability and insolubility occur in aqueous medium
Solution Approach 1:
The patent uses a water-soluble organic metal complex catalyst as an intermediary substance that bridges the need for rapid curing while maintaining stability in aqueous medium. The organic ligands in the complex catalyst enable solubility and stability in water while preserving catalytic activity for accelerating the curing reaction between polyisocyanate and hydroxyl groups.
Solution Approach 2:
The patent changes the chemical parameters of the catalyst by using organic metal complexes with specific ligand structures that are water-soluble. This parameter change allows the catalyst to function effectively in aqueous environments without precipitating or degrading, thus maintaining both stability and catalytic efficiency.
2Productivity
If active catalyst is added to accelerate curing, then cure rate increases, but viscosity increases too quickly affecting spray application
Solution Approach 1:
The patent employs a water-soluble organic metal complex catalyst that provides dynamic control over the curing process. The catalyst maintains moderate catalytic activity during storage and mixing, allowing consistent spray application, then accelerates curing after application. This dynamic behavior resolves the contradiction between fast curing and ease of application.
3Loss of time
If catalyst is added to accelerate curing, then cure speed increases, but pot life becomes too short causing performance inconsistency
Solution Approach 1:
The water-soluble organic metal complex catalyst acts as an intermediary that moderates the curing reaction rate. It provides sufficient catalytic activity to achieve acceptable cure speeds while maintaining stability in the aqueous medium, thereby extending pot life and ensuring consistent performance across different substrate areas.
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 solution achieves a stable pot life with rapid curing, ensuring consistent performance and adhesion across substrate areas, as demonstrated by the examples showing extended MEK double rub resistance and controlled viscosity changes.
Implementation Method 1
addition of volatile chelating agents to the formulation can stabilize and inhibit the catalyst in the waterborne paint
Implementation Method 2
Certain metal complex compounds catalyze the reaction between active hydrogen compounds or water and isocyanate-containing compounds to produce polyurethane polymers
Implementation Method 3
the reaction between active hydrogen compounds or water and isocyanate-containing compounds to produce polyurethane polymers
Data Source
AI summary
The present invention is directed to an aqueous curable film-forming composition comprising: (a) a film-forming component comprising an aliphatic di- or higher functional polyisocyanate; and (b) a catalyst additive comprising: (i) a catalytic organic compound comprising iron and/or tin; and (ii) a beta-diketone. The present invention is further directed to a method of controlling the rate of cure of an aqueous curable film-forming composition. The method comprises adding to the aqueous curable film-forming composition the catalyst additive described above; the aqueous curable film-forming composition comprises a film-forming component comprising an aliphatic di- or higher functional polyisocyanate. The present invention is additionally directed to a coated article comprising a cured coating layer applied on at least one surface of a substrate to form a coated substrate; wherein the cured coating layer is deposited from the aqueous curable film-forming composition described above.