Solventborne Clearcoat Rheology Control
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Solution Overview
Problem
Existing solvent-based clearcoat coating compositions struggle to achieve a balance between flow and sagging, leading to uneven paint surfaces and reduced optical quality, while also being susceptible to changes in rheological properties under shear stress, which affects their application and durability in automotive painting.
Innovation Solution
A clearcoat coating composition containing OH-functional (meth)acrylate polymers, synthetic polyamide wax particles, a urea compound derived from a polyisocyanate and monoamine, and a crosslinking agent with reactive hydroxyl groups, which provides excellent leveling, gloss, and resistance to condensation, while maintaining stability under shear stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If larger amounts of rheology aids or rheology-controlling additives are added to improve flow properties and reduce runner formation, then the tendency for runners to form decreases, but the flow of the clear coat is impaired and application properties deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by introducing a specific crosslinking system with OH-functional (meth)acrylate (co)polymers and crosslinking agents. This chemical modification alters the rheological behavior and flow properties of the clear coat, enabling good leveling and runner formation resistance without adding conventional rheology aids that would impair application properties.
Solution Approach 2:
The patent creates a composite coating system combining OH-functional (meth)acrylate (co)polymers with specific crosslinking agents (isocyanates, carboxylic acids, or phenols). This composite approach produces synergistic effects where the crosslinked network structure provides both improved flow characteristics and maintained application properties, resolving the contradiction between runner resistance and ease of application.
2Object-generated harmful factors
If the layer thickness of the clear coats is reduced to avoid runner formation, then runner formation decreases, but essential application properties such as top coat level, leveling, gloss, image distinction and weather and UV resistance are severely impaired
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating crosslinking agents and OH-functional polymers, which change the curing behavior and film formation characteristics. This allows the clear coat to be applied at optimal thicknesses for optical quality while the crosslinked structure prevents runner formation during application.
Solution Approach 2:
The patent implements preliminary crosslinking preparation in the coating composition itself, where the crosslinking agents are pre-incorporated into the clear coat formulation. This preliminary action enables the coating to self-regulate during application, preventing runner formation before it occurs while maintaining the necessary thickness for optical quality and durability.
3Ease of manufacture
If conventional clearcoat compositions are used, then the coating can be applied, but the coating compositions are exposed to constant shear stress in circulation systems which leads to significant change in rheological properties and negatively influences application properties
Solution Approach 1:
The patent changes the rheological parameters of the coating composition through the crosslinking system. The crosslinked network structure provides shear thinning behavior that stabilizes viscosity under circulation conditions, maintaining consistent flow properties despite constant shear stress in the application system.
Solution Approach 2:
The patent implements a self-regulating rheological system where the crosslinked polymer network responds to shear stress by adjusting its structure. Under circulation conditions, the network adapts to maintain stable viscosity, providing feedback control of the rheological properties without external intervention.
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 achieves a superior balance of application properties, including reduced runner formation and enhanced optical quality, with improved stability and resistance to condensation, even after prolonged circulation in application systems.
Implementation Method 1
a crosslinking agent with reactive functional groups towards OH groups
Implementation Method 2
at least one type of synthetic polyamide wax particles, at least one urea compound as an addition product of a polyisocyanate and a monoamine
Data Source
AI summary
The present invention relates to a solventborne clearcoat coating composition comprising (A) an OH-functional (meth)acrylate (co)polymer component consisting of (A1) 30-99 weight %, based on the mass of the non-volatile fraction of the OH-functional (meth)acrylate (co)polymer component (A), of at least one OH-functional (meth)acrylate (co)polymer having an OH number of 60-200 mg KOH/g and a glass transition temperature (Tg) of 15°C to 100°C, (A2) 1-70 weight %, based on the mass of the non-volatile fraction of the OH-functional (meth)acrylate (co)polymer component (A), of at least one OH-functional (meth)acrylate (co)polymer having an OH number of 60-200 mg KOH/g and a glass transition temperature (Tg) of -100°C to -120°C, (B) a crosslinker component comprising at least one crosslinking agent having functional groups that are reactive with respect to OH groups, and also (C) 0.02-1.2 weight %, based on the mass of the non-volatile fraction of the OH-functional (meth)acrylate (co)polymer component (A), of at least one polyamide, (D) 0.04-2.9 weight %, based on the mass of the non-volatile fraction of the OH-functional (meth)acrylate (co)polymer component (A), of at least one urea compound which is an adduct of a polyisocyanate and methoxypropylamine. The present invention further relates to a method for producing the solventborne clearcoat coating composition, to the use of the solventborne clearcoat coating composition, and to a clearcoat system produced using the clearcoat coating composition.