Phosphoric Esters in Basecoats for Overbaked Clearcoat Adhesion
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Solution Overview
Problem
The intercoat adhesion between a basecoat and an overbaked clearcoat material containing boron compounds is exceptionally poor, leading to potential delamination under mechanical stress, such as stonechip exposure, in multicoat paint systems.
Innovation Solution
Incorporating phosphoric acid and/or its monoesters or diesters into the basecoat material at concentrations of 0.1 to 5 wt% improves the adhesion to overbaked clearcoats, with specific advantages seen at 0.3 to 1.5 wt%, enhancing the stonechip resistance of the paint system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clearcoat material is overbaked (exceeded baking time and/or temperature), then the curing process is completed, but the intercoat adhesion to subsequent basecoat materials becomes extraordinarily poor
Solution Approach 1:
Phosphoric acid and/or phosphoric esters are introduced as intermediary substances in the basecoat material that chemically interact with the overbaked clearcoat surface containing boron compounds. These intermediaries form bridging bonds between the clearcoat and the basecoat, enabling adhesion despite the overbaking condition that would otherwise prevent bonding.
Solution Approach 2:
The invention changes the chemical composition parameters of the basecoat material by incorporating phosphoric acid and/or phosphoric esters at specific concentrations (0.1 to 5 wt%). This parameter change enables the basecoat to chemically interact with the overbaked clearcoat surface, transforming the adhesion mechanism from physical to chemical bonding.
2Strength
If phosphoric acid and/or phosphoric esters are added to improve intercoat adhesion, then adhesion is enhanced, but the complexity of the basecoat formulation increases
Solution Approach 1:
The invention optimizes the concentration range of phosphoric acid and/or phosphoric esters to 0.1 to 5 wt%, with particular advantage at 0.3 to 1.5 wt%. This parameter optimization ensures effective adhesion promotion while minimizing formulation complexity and avoiding excessive chemical additions.
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 use of phosphoric acid and/or phosphoric esters significantly enhances the cross-cut resistance and intercoat adhesion, preventing delamination and improving the overall stonechip resistance of the paint finish.
Implementation Method 1
the addition to the basecoat material of phosphoric acid and/or phosphoric esters... improves the adhesion of these coating materials on overbaked clearcoat materials which comprise boron compounds
Data Source
AI summary
The invention relates to the use of phosphoric acid and/or of monoesters and/or diesters of phosphoric acid in aqueous basecoat materials for improving adhesion of these coating materials to overbaked clearcoat materials which comprise boron compounds.