Coating Composition Scratch Resistance Sandability Balance
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Solution Overview
Problem
Current non-aqueous coating compositions for automotive painting lack improved scratch resistance, sandability, polishability, and weather stability while also being brittle and requiring stress crack prevention in thick layers.
Innovation Solution
The development of non-aqueous coating compositions containing polyhydroxyl groups, cycloaliphatic and acyclic polyisocyanates with specific structural units, and a catalyst for silane crosslinking, which are thermally curable and optimized for high binder content and structural unit ratios to enhance mechanical and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If non-aqueous coating compositions contain polyisocyanate with silane groups and catalyst for crosslinking, then scratch resistance is improved, but sandability and polishability deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully controlling the NCO-OH ratio (0.8-1.5) and the proportion of structural units (I) and (II) (each 10-50 mol%) to achieve optimal balance between crosslinking density and coating flexibility. This resolves the contradiction by adjusting chemical parameters to simultaneously improve scratch resistance while maintaining sandability and polishability
Solution Approach 2:
The patent uses composite materials by combining cycloaliphatic polyisocyanate (B1) and acyclic aliphatic polyisocyanate (B2) with specific structural units, along with polyhydroxyl group-containing compounds and silane crosslinking agents. This composite approach creates a network that provides both high scratch resistance and good sandability/polishability
2Reliability
If coating compositions use high binder content for durability, then weather resistance is improved, but brittleness increases and stress crack resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the NCO-OH ratio to 0.8-1.5 and controlling the molecular structure through specific structural units (I) and (II), which enables the coating to achieve high crosslinking density for weather resistance while maintaining flexibility to prevent stress cracks and brittleness
Solution Approach 2:
The patent applies local quality by creating different functional regions within the coating network through the combination of cycloaliphatic and acyclic polyisocyanates with silane groups, where certain regions provide crosslinking for weather resistance while other regions maintain flexibility to prevent cracking
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 coatings exhibit high scratch resistance, retention of gloss after scratching, good sandability and polishability, and high acid resistance, allowing for thick layer application without stress cracks, while being environmentally friendly and easy to reproduce.
Implementation Method 1
the scratch resistance of coatings based on polyurethanes can be improved if one uses coating materials which contain a binder containing hydroxyl groups, a crosslinker containing isocyanate groups and a metal catalyst for the OH/NCO reaction
Implementation Method 2
at least one catalyst (D) for crosslinking the silane groups
Data Source
AI summary
The invention relates to non-aqueous coating agent compositions containing: (A) at least one polyhydroxyl group-containing compound; (B1) at least one polyisocyanate group-containing compound (B1) having free or blocked isocyanate groups and a cycloaliphatic polyisocyanate body, and/or a polyisocyanate derived from said compound (B1); (B2) at least one polyisocyanate group-containing compound (B2) having free or blocked isocyanate groups and an acyclic, aliphatic polyisocyanate body, and/or a polyisocyanate derived from said compound (B2); and (D) at least one catalyst for crosslinking silane groups. Component (B1) and/or component (B2) contain/s at least one structural unit -NR-(X-SiR"x(OR')3-x) (I) and/or at least one structural unit -N(X-SiR"x(OR')3-x)n(X'-SiR"y(OR')3-y)m (II), compound (B1) is used at such an quantity that the percentage of binder(s) in compound (B1) amounts to 5 to 45% by weight in relation to the sum of binder percentages in compounds (B1) and (B2), and the mixture of components (B1) and (B2) contains both structural units (I) and structural units (II). The invention further relates to multistage coating methods and the use of the coating agent compositions.