Silane Adduct Coating for Scratch Resistance and Weather Stability
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Solution Overview
Problem
Current coating agents for automotive painting face challenges in achieving high micropenetration hardness, dry scratch resistance, and weather stability while avoiding the formation of undesirable Si-O-C and Si-N-C network points, which affect the chemical resistance and processing difficulties of clear coats.
Innovation Solution
The development of coating agents containing an adduct with silane functionality, a catalyst for crosslinking, and a film-forming material, along with aprotic solvents, where the adduct is produced through an addition reaction involving a silane with hydrolysable groups and a compound with surface-active residues, enhancing scratch resistance and weather stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If coating agents contain adducts with alkoxysilane functionality to achieve high scratch resistance, then micropenetration hardness and dry scratch resistance are improved, but weather stability deteriorates and crack formation increases at layer thicknesses above 40 μm
Solution Approach 1:
The invention changes the chemical composition parameters by using specific adducts with silane functionality (containing at least one alkoxy group and at least one other hydrolyzable group) and controls their content within 1-30% by weight based on non-volatile components. This parameter optimization allows achieving high scratch resistance while maintaining weather stability and preventing crack formation in thicker layers.
Solution Approach 2:
The invention creates a composite coating system combining multiple components: adducts with silane functionality, catalysts for crosslinking, film-forming materials with reactive functional groups, and aprotic solvents. This composite approach synergistically improves scratch resistance through silane crosslinking while maintaining overall coating reliability and weather resistance.
2Strength
If coating agents contain adducts with alkoxysilane functionality to improve scratch resistance, then micropenetration hardness is increased, but the formation of undesirable Si-O-C and Si-N-C network points increases, affecting chemical resistance
Solution Approach 1:
The invention optimizes the chemical structure parameters of the adducts by specifying they must contain at least one alkoxy group and at least one other hydrolyzable group (such as oxo, carboxy, or amino groups). This structural parameter control promotes the formation of desirable Si-O-Si networks while minimizing harmful Si-O-C and Si-N-C network points, thereby maintaining chemical resistance.
Solution Approach 2:
The invention creates local quality differences in the coating network by promoting Si-O-Si crosslinking structures in specific regions while avoiding the formation of harmful network points. The controlled hydrolysis and condensation of silane groups lead to localized formation of stable silica-like networks that provide hardness without compromising chemical resistance.
3Illumination intensity
If the proportion of coating agent in reaction products with isocyanatoalkyltrialkoxysilane is increased to improve gloss, then hardness and resistance to solvents decrease
Solution Approach 1:
The invention changes the formulation parameters by using adducts with silane functionality containing specific ratios of alkoxy groups to other hydrolyzable groups, and controls the content within 1-30% by weight. This parameter optimization enables achieving high gloss through proper surface formation while maintaining high hardness and solvent resistance through adequate silane crosslinking density.
Solution Approach 2:
The invention creates a composite system where adducts with silane functionality work synergistically with film-forming materials containing reactive functional groups. This composite approach allows the coating to achieve both high gloss (through proper surface morphology) and high hardness (through silane crosslinking), resolving the trade-off present in previous single-component systems.
4Strength
If coating agents use silane oligomers to improve adhesion to aluminum substrates, then adhesion is enhanced, but the coating requires additional catalysts and processing steps
Solution Approach 1:
The invention makes the adducts with silane functionality multi-functional: they provide adhesion promotion to aluminum substrates through silane chemistry, contribute to scratch resistance through crosslinking, and participate in the overall film formation. This universality reduces the need for separate adhesion promoters and simplifies the overall formulation and processing.
Solution Approach 2:
The invention merges the adhesion promotion function with the crosslinking and film-forming functions into a single integrated component system. The adducts with silane functionality serve multiple purposes simultaneously, eliminating the need for separate adhesion promoters and reducing processing complexity despite the presence of catalysts for crosslinking.
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 resulting coatings exhibit improved micro-penetration hardness, dry scratch resistance, and weather stability, meeting automotive painting requirements with reduced formation of undesirable network points, and are cost-effective with minimal toxicological or ecological concerns.
Implementation Method 1
coating agents containing (i) at least one adduct (A) with silane functionality, (ii) at least one catalyst (C) for the crosslinking of the silane groups
Implementation Method 2
the adduct (A) can be produced by an addition reaction of (a) at least one silane (S1) which has at least one functional group G' and at least one hydrolysable group
Implementation Method 3
the compound (O) which has at least one complementary functional group G'' and at least one surface-active residue, the surface-active residue being selected from the group of hydrocarbon residues, fluorinated hydrocarbon residues, fatty acid residues and optionally substituted siloxane residues
Implementation Method 4
wherein the compound (O) has a surface tension that is at least 1 mN/m lower than the silane (S1)
Data Source
AI summary
The invention relates to coating agents containing a film-forming material comprising at least one reactive functional group G´´´, a catalyst for cross-linking the silane groups, aprotic solvents, and at least one addition compound with silane functionality, that can be produced by an addition reaction of (a) at least one silane (S1) comprising at least one functional group G´ reactive with the complementary functional groups G´´ of the compound (O), and (b) at least one compound (O) comprising at least one complementary functional group G´´ and at least one surface-active radical. The invention also relates to multilayer lacquers having a transparent coating produced from said coating agents, and to methods for producing said multilayer lacquers and the use thereof. The invention further relates to the use of a mixture of the addition compound with silane functionality and the catalyst for cross-linking the silane groups in methods for improving the hardness and/or the scratch resistance of coatings.