Fluorinated Polyether Coatings for Scratch and Acid Resistance
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Solution Overview
Problem
Existing coating compositions for automotive painting and refinishing lack the combination of high scratch resistance, low dirt tendency, easy cleanability, and excellent chemical and acid resistance, while also requiring stress crack resistance in thick layers without ecological issues during application.
Innovation Solution
Non-aqueous coating compositions containing polyhydroxyl groups, isocyanate and silane groups, and a catalyst for silane crosslinking, with an additional isocyanate group-containing component having a perfluoroalkyl group, which enhances scratch resistance and gloss retention while maintaining low dirt tendency and easy cleanability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fluorinated components are used to reduce dirt tendency and improve cleanability, then the coating has low surface energy and easy cleanability, but scratch resistance deteriorates
Solution Approach 1:
The patent uses a composite crosslinking system combining silane crosslinking (for scratch resistance and hardness) with fluorinated polyether crosslinking (for low surface energy and easy cleanability). This composite approach allows both properties to coexist in the same coating matrix without compromising either function.
Solution Approach 2:
The fluorinated components are specifically designed to migrate to the coating surface to provide low surface energy and easy cleanability, while the silane crosslinked network maintains the bulk mechanical properties and scratch resistance. This local differentiation of properties resolves the contradiction between surface functionality and bulk mechanical strength.
2Strength
If silane crosslinking is used to improve scratch resistance, then the coating has high crosslink density and scratch resistance, but adhesion to subsequent coatings deteriorates
Solution Approach 1:
The patent controls the crosslinking kinetics by adjusting catalyst concentration and curing temperature profiles. This allows the silane crosslinking to proceed at a controlled rate, forming a network that maintains adhesion while achieving the desired scratch resistance. The gradual crosslinking prevents excessive brittleness that would compromise adhesion.
3Strength
If high crosslink density is achieved for scratch resistance, then the coating has excellent mechanical properties, but stress crack resistance in thick layers deteriorates
Solution Approach 1:
The patent creates a gradient in crosslink density within the coating thickness. The silane crosslinking is more pronounced in the upper layers for scratch resistance, while the lower layers near the substrate maintain slightly lower crosslink density to accommodate thermal expansion and stress, preventing crack propagation in thick coatings.
4Ease of operation
If fluorinated components are used to reduce dirt tendency, then the coating has low surface energy, but chemical and acid resistance deteriorates
Solution Approach 1:
The patent combines fluorinated polyether crosslinkers (providing low surface energy) with silane crosslinked networks (providing chemical and acid resistance). The silane network forms a dense, chemically resistant matrix that protects the underlying fluorinated components while allowing the surface to maintain its low energy properties for dirt resistance.
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 coating compositions achieve high scratch resistance, excellent chemical and acid resistance, and stress crack resistance in thick layers, while being environmentally friendly and easy to reproduce, with improved weather stability and acid resistance.
Implementation Method 1
at least one catalyst (D) for the crosslinking of silane groups
Implementation Method 2
component (A) containing polyhydroxyl groups and at least one component (B1) containing isocyanate and silane groups
Implementation Method 3
component (B2) having at least one perfluoroalkyl group of the formula (I)
Data Source
AI summary
The present invention relates to non-aqueous coating material compositions containing (A) at least one polyhydroxyl group-containing component (A); (B1) at least one isocyanate and silane group-containing component (B1); and (D) at least one catalyst (D) for the cross-linking of silane groups, characterized in that they (B2) comprise at least one isocyanate group-containing component (B2) which is different from component (B1) and comprises in addition at least one perfluoroalkyl group of the formula (I) CR1 3-(CR2 2)f-, wherein R1, R2 are independently from one another H, F and/or CF3, but R1 and R2 cannot be simultaneously H, and f = 1 to 20, preferably f = 3 to 11, particularly preferably f = 5 to 7. The invention further relates to coatings produced from these coating material compositions and the use thereof.