Coating Agent Scratch Resistance via Silane Adducts
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Solution Overview
Problem
Aliphatic polyurethane coatings lack sufficient scratch resistance, particularly in automotive clear coats, which require enhanced durability against acidic environmental influences and have limitations in solids content and solvent usage.
Innovation Solution
A coating agent comprising aliphatic or cycloaliphatic polyisocyanate with NCO functionality of at least 2, combined with a hydroxyl-containing binder and an adduct of isocyanato-trialkyloxysilane and polyhydric alcohol, along with a catalyst, to achieve high scratch and chemical resistance while maximizing solids content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyisocyanate crosslinkers partially derivatized with secondary aminosilanes are used to improve scratch resistance, then scratch resistance is improved, but the molecular weight of crosslinking components increases resulting in higher viscosity and lower solids content
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking agent by using isocyanato-trialkoxysilane adducts with polyhydric alcohols instead of conventional secondary aminosilane-modified polyisocyanates. This parameter change results in lower molecular weight crosslinking components that provide the same scratch resistance improvement while maintaining lower viscosity and higher solids content in the coating formulation
Solution Approach 2:
The patent employs a composite crosslinking approach by combining isocyanato-trialkoxysilane with polyhydric alcohols to create adducts that integrate multiple functional groups (isocyanate, alkoxy, and hydroxyl groups) into a single molecular structure. This composite material strategy enables simultaneous achievement of scratch resistance, controlled reactivity, and optimized solids content
2Strength
If conventional 2K PUR coatings are used, then chemical resistance is provided, but scratch resistance is insufficient
Solution Approach 1:
The patent merges the scratch resistance enhancement function with the chemical resistance function by incorporating isocyanato-trialkoxysilane adducts that can simultaneously form strong crosslinked networks (providing scratch resistance) and maintain the polyurethane coating's inherent chemical resistance properties. The dual-functional crosslinking mechanism combines silane-based crosslinking with isocyanate-hydroxyl reactions to achieve both performance requirements
3Strength
If crosslinkers with high molecular weight are used to achieve scratch resistance, then scratch resistance is improved, but viscosity increases and application becomes more difficult
Solution Approach 1:
The patent optimizes the molecular weight parameter of the crosslinking agent by selecting polyhydric alcohols with appropriate molecular weights and structures that, when reacted with isocyanato-trialkoxysilane, produce crosslinking components with lower molecular weights than conventional aminosilane-modified polyisocyanates. This parameter optimization reduces viscosity while maintaining crosslinking efficiency and scratch 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 agent provides enhanced scratch and chemical resistance, improved durability, and increased solids content, surpassing the limitations of conventional 2K PUR paints in terms of mechanical and chemical performance.
Implementation Method 1
at least one adduct of an isocyanato-trialkoxysilane and a polyhydric alcohol, wherein more than 90, preferably more than 95, most preferably more than 99 percent of the hydroxy groups of the polyhydric alcohol are reacted with the isocyanato-trialkoxysilane
Implementation Method 2
an adduct of an isocyanato-trialkoxysilane and a polyhydric alcohol
Implementation Method 3
at least one adduct of an isocyanato-trialkoxysilane and a polyhydric alcohol
Implementation Method 4
at least one catalyst selected from the group comprising Lewis acids, phosphoric acid or phosphorous acid and their esters, blocked or unblocked sulfonic acids, sulfuric acid, carboxylic acids with a melting point > 60 °C and tetraalkylammonium carboxylates
Data Source
AI summary
The present invention relates to a coating agent, comprising at least one aliphatic or alicyclic polyisocyanate, which has an NCO functionality of at least 2, preferably 2.8 to 6, optionally at least one binder, preferably a hydroxyl-group-bearing binder, at least one adduct of an isocyanatotrialkoxysilane and a multivalent alcohol, wherein more than 90, preferably more than 95, most preferably more than 99 percent of the hydroxy groups of the multivalent alcohol are converted by reaction with the isocyanatotrialkoxysilane and less than 0.1 wt% of the isocyanate groups from the isocyanatotrialkoxysilane are reactive in the adduct, at least one catalyst selected from the group that comprises Lewis acids, phosphoric acid or phosphonic acid and esters thereof, blocked or unblocked sulfonic acids, sulfuric acid, carboxylic acids having a melting point > 60 °C, and tetraalkylammonium carboxylates, optionally at least one auxiliary agent, preferably at least one additional cross-linking agent, and/or additive, and optionally organic solvents, and to a method comprising providing the coating agent, applying the coating agent to a surface, and curing the coating agent, to a coating that can be obtained by curing the coating agent, and to a use of the coating agent to coat a metal, glass, plastic, or wood surface.