Anticrater Agent for Electrocoating Surface Finish
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Solution Overview
Problem
Cathodic electrocoating compositions often result in cratered finishes, which negatively impact the adhesion of subsequent coating layers, particularly when cured without NOx presence.
Innovation Solution
Incorporation of a non-water reducible anticrater agent, specifically a polyesterurethane formed from a monomer mixture of cyclic aliphatic carboxylic acid anhydride, monofunctional epoxy compound, monofunctional alcohol, and diisocyanate, into the electrocoating composition to reduce craters and enhance smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional anticrater agents are used in electrocoating compositions, then craters are reduced, but adhesion of subsequent coating layers is adversely affected
Solution Approach 1:
The patent changes the chemical parameters of the anticrater agent by using a non-water soluble polyesterurethane with specific molecular structure (containing cyclic aliphatic carboxylic acid anhydride, monofunctional epoxy compound, monofunctional alcohol, and diisocyanate) instead of conventional water-soluble anticrater agents. This parameter change allows the agent to reduce craters while maintaining adhesion of subsequent coatings, as the non-water soluble nature prevents it from interfering with the bonding of later coating layers.
2Manufacturing precision
If conventional anticrater agents are used, then crater formation is reduced, but the electrocoating composition requires NOx presence for proper curing
Solution Approach 1:
The patent extracts the NOx dependency from the curing process by using a non-water soluble anticrater agent that does not require NOx presence for proper curing. The polyesterurethane-based anticrater agent allows the electrocoating composition to be cured in indirect gas or electric ovens without NOx, simplifying the curing process requirements while maintaining surface smoothness.
3Strength
If non-water soluble anticrater agents are used, then adhesion of subsequent coatings is maintained, but crater reduction effectiveness may be compromised
Solution Approach 1:
The patent uses a composite material approach by formulating a polyesterurethane anticrater agent that combines multiple functional groups (cyclic aliphatic carboxylic acid anhydride, monofunctional epoxy compound, monofunctional alcohol, and diisocyanate) within a single non-water soluble molecule. This composite structure provides both the crater reduction capability and the adhesion maintenance property, as the specific molecular composition allows it to function effectively as an anticrater agent while remaining compatible with subsequent coating layers.
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 non-water reducible anticrater agent significantly reduces crater formation and improves the smoothness of the electrocoated film without adversely affecting the adhesion of subsequent coatings.
Implementation Method 1
The electrocoating of primers to substrates is widely used in the automotive industry. In this process, a conductive article, such as an automobile body or an automobile part, is immersed in a bath comprising an aqueous emulsion of film forming polymer and acts as an electrode in the electrocoating process. An electric current is passed between the article and a counter-electrode in electrical contact with the aqueous emulsion, until a desired coating is deposited on the article.
Implementation Method 2
The coating on the article can then be cured, typically in an oven, at sufficient temperature to produce a crosslinked finish on the article.
Implementation Method 3
These polymers are blended with a crosslinking agent and then neutralized with an acid to form a water emulsion. The resulting coated article is removed from the bath after a period of time and is rinsed with deionized water. The coating on the article can then be cured, typically in an oven, at sufficient temperature to produce a crosslinked finish on the article.
Data Source
AI summary
The present disclosure relates to an improved electrocoating coating composition wherein the improvement is the addition of a non-water reducible anticrater agent. The non-water reducible anticrater agent is a polyesterurethane that is the reaction product of an aliphatic carboxylic acid anhydride, a monofunctional epoxy compound, a monofunctional alcohol and a diisocyanate and/or a polyisocyanate. The improved electrocoating composition provides cured coatings that have fewer craters and have a smooth surface when compared to coatings utilizing other anticrater additives.