Waterborne Base Coat Resin Reduces Thread Formation in Rotary Atomization
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Solution Overview
Problem
The production of automotive OEM base coat/clear top coat multi-layer coatings using waterborne compositions faces issues with thread formation during electrostatically-assisted high speed rotary atomization, leading to productivity losses and equipment contamination, especially in industrial mass-production processes where substrates are coated in multiple colors.
Innovation Solution
A process involving a waterborne base coat composition with a polyurethane urea resin dispersion, produced through specific steps including reaction of polyols, polyisocyanates, and polyhydroxycarboxylic acids, followed by chain extension, which minimizes thread formation by forming a non-sticky, non-susceptible base coat layer to handling and reduces scrap in the coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If waterborne base coat compositions are applied by electrostatically-assisted high speed rotary atomization, then productivity is improved through efficient coating application, but thread formation occurs leading to equipment contamination and productivity losses
Solution Approach 1:
The patent modifies the chemical composition parameters of the waterborne base coat composition by incorporating specific resin systems, crosslinking agents, and functional additives in controlled proportions. This changes the physical and chemical properties of the coating material to reduce thread formation during electrostatically-assisted high speed rotary atomization while maintaining coating efficiency
Solution Approach 2:
The invention creates a composite coating system by combining waterborne base coat composition with clear top coat composition that have complementary properties. The base coat is formulated to be non-sticky and non-susceptible to handling, while the clear top coat provides protective properties, together resolving the thread formation issue while maintaining productivity
2Adaptability or versatility
If multiple colors are coated on substrates in industrial mass-production processes, then product versatility is improved, but thread formation and equipment contamination increase
Solution Approach 1:
The patent extracts and eliminates the problematic properties (stickiness and susceptibility to handling) from the base coat composition through careful formulation. By removing these detrimental characteristics while retaining the desired multi-color coating capability, the system reduces equipment contamination across color changes
Solution Approach 2:
The invention changes the rheological and chemical parameters of the base coat composition to achieve a non-sticky state that prevents thread formation during color changes. This parameter modification allows versatile multi-color coating operations without the equipment contamination that would otherwise occur
3Ease of operation
If base coat layers are made non-sticky and non-susceptible to handling, then ease of operation is improved, but coating composition complexity increases
Solution Approach 1:
The patent creates a composite coating system where the base coat and clear top coat have distinct but complementary functions. The base coat is optimized for non-sticky handling properties, while the clear top coat provides the protective and aesthetic functions, distributing the complexity across two coordinated materials rather than one complex formulation
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 process enhances productivity by minimizing thread and speck formation, ensuring a smooth, uniform coating appearance and reducing cleaning efforts, while allowing for safe handling of uncured base coat layers, thus improving industrial mass-production efficiency.
Implementation Method 1
The NCO-functional hydrophilic polyurethane prepolymer may be reacted with a NCO-reactive chain extender like, for example, a polyamine or a hydrazine derivative
Implementation Method 2
The acetone solution is converted into an aqueous dispersion by mixing with water
Implementation Method 3
spray-applying a waterborne base coat composition on said substrate by electrostatically-assisted high speed rotary atomization
Implementation Method 4
jointly curing the base coat and the clear top coat layers
Data Source
AI summary
A process for the production of an OEM base coat/clear top coat multi-layer coating wherein a waterborne base coat composition is spray-applied by electrostatically-assisted high speed rotary atomization, wherein the waterborne base coat composition comprises binder solids comprising about 20 to about 100 wt. % of an aqueously dispersed polyurethane urea resin with a carboxyl number of about 10 to 50 mg KOH/g.