Crosslinkable Composition with Polyurea Rheological Agent
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Solution Overview
Problem
Existing clearcoat compositions struggle to achieve a balance between sag resistance, leveling, and appearance, particularly in high solids or low VOC formulations, while maintaining properties like hardness, chemical resistance, flexibility, and durability, especially when applied to vertically oriented surfaces.
Innovation Solution
A crosslinkable composition using specific polyol components, including polyester and (meth)acrylic polyols, with controlled molecular weights and glass transition temperatures, combined with a polyurea rheological agent, to enhance leveling and sag resistance, and improve mechanical and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the solid content of the formulation is increased to decrease shrinkage, then the shrinkage is reduced and appearance is improved, but the viscosity increases making spray application difficult
Solution Approach 1:
The patent uses polyols with specifically controlled molecular weights (Mn: 600-1500, Mw: 1000-3000) and glass transition temperatures (Tg: -80 to 0°C) to adjust the formulation parameters. This allows achieving high solid content (50-95 wt%) while maintaining appropriate viscosity for spray application, resolving the contradiction between appearance quality and spray applicability
Solution Approach 2:
The patent employs composite polyol systems combining polyester polyols and (meth)acrylic polyols in specific ratios (15-85 wt% and 85-15 wt% respectively). This composite approach enables tuning of both viscosity and shrinkage properties simultaneously, allowing high solid content formulations to remain sprayable while reducing shrinkage for improved appearance
2Quantity of substance
If the molecular weight of the binder is reduced to increase solid content, then the solid content is increased, but the binder Tg decreases affecting coating performance
Solution Approach 1:
The patent precisely controls polyol parameters including molecular weight (Mn: 600-1500, Mw: 1000-3000) and glass transition temperature (Tg: -80 to 0°C). By adjusting these parameters within specific ranges and using composite polyol systems, the formulation achieves high solid content while maintaining adequate binder Tg through the synergistic effect of different polyol components, thus preserving coating performance
3Stability of the object's composition
If rheological agents are added to control sagging, then sag resistance is improved, but the balance between sagging and leveling is difficult to achieve
Solution Approach 1:
The patent incorporates polyurea rheological agents with specifically controlled particle size distributions (D10: 3-8 μm, D50: 8-15 μm, D90: 15-30 μm) and uses them in optimized quantities (0.1-5 wt%). This precise parameter control allows the formulation to achieve adequate sag resistance while maintaining good leveling, as the fine particle size provides subtle rheological modification without excessive thickening
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 provides improved leveling and appearance, excellent sag resistance, and well-balanced properties such as hardness, chemical resistance, and durability, suitable for high solids or low VOC applications, with reduced shrinkage and substrate roughness hiding capabilities.
Implementation Method 1
a crosslinkable composition with improved appearance and lower VOC comprising a polyol having free hydroxyl groups that can react with a crosslinker
Implementation Method 2
a polyurea rheological agent... to aid finding the balance between sagging and leveling
Data Source
AI summary
The present invention relates to a polyol component comprising a1) a polyol having a weight averaged molecular weight Mw of from 1,000 to 4,000 Dalton, a number averaged molecular weight Mn of from 600 to 2,500 Dalton, an OH value between 80 and 300 mg KOH / g of resin and a glass transition temperature Tg of from -10 to 90 °C, and a2) between 0.1 and 10 % by weight of polyurea product as rheological agent, as well as it use in a crosslinkable composition especially suitable for clear coat applications.