TACD Polyester Polyols for Scratch-Resistant 2K PUR Coatings
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Solution Overview
Problem
Existing 2K PUR clearcoats face challenges in achieving improved scratch resistance while maintaining high chemical resistance, particularly against solvents and tree resin.
Innovation Solution
The use of TACD-based polyester polyols combined with silane group-containing polyisocyanates in coating compositions, which includes a polyol component, a crosslinker component with isocyanate and silane groups, and optional catalysts and additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TMCD-based polyester polyols are used to improve solvent and chemical resistance, then chemical resistance is improved, but scratch resistance deteriorates significantly
Solution Approach 1:
The patent modifies the glass transition temperature parameter of the polyester polyol by changing the cyclobutane diol structure from tetramethyl (TMCD) to tetraalkyl (TACD) with longer alkyl chains. This parameter change reduces the glass transition temperature from above room temperature to below room temperature, thereby improving scratch resistance while maintaining chemical resistance through the inherent molecular structure of the TACD-based polyester.
Solution Approach 2:
The patent creates a composite coating system by combining TACD-based polyester polyols with specific polyisocyanate crosslinkers and silane modifiers. This composite approach allows the coating to simultaneously achieve improved scratch resistance (from the lower Tg polyester) and maintained chemical resistance (from the crosslinked network and silane groups), resolving the contradiction between these two properties.
2Reliability
If polyester polyols with high glass transition temperature are used to improve chemical resistance, then chemical resistance is improved, but scratch resistance deteriorates
Solution Approach 1:
The patent directly addresses this contradiction by changing the glass transition temperature parameter from high (above room temperature) to low (below room temperature) through structural modification of the cyclobutane diol component. The TACD structure with longer alkyl chains (C2-C8) reduces molecular packing efficiency and intermolecular forces, lowering Tg and improving scratch resistance while the polyester backbone maintains chemical 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
This approach results in coatings with significantly improved scratch resistance and maintained chemical resistance, outperforming similar coatings without silane group-containing polyisocyanates.
Implementation Method 1
at least one crosslinker component having free and/or blocked isocyanate groups which is obtained by reaction of at least one polyisocyanate with at least one amino-functional alkoxysilane
Implementation Method 2
reaction of at least one polyisocyanate with at least one amino-functional alkoxysilane
Implementation Method 3
two-component polyurethane (2K PUR) clearcoats
Data Source
AI summary
The invention relates to coating agents containing A) at least one polyol component, B) at least one crosslinking component which is obtained by reacting at least one polyisocyanate with at least one amino functional alkoxy silane and which comprises free and/or blocked isocyanate groups, optionally (C) at least one catalyst for crosslinking silane groups, and D) optionally additional auxiliary agents and additives. The invention is characterized in that the polyol component A) comprises at least one polyester polyol A1) that has been produced using a 2,2,4,4-tetraalkylcyclobutane-1,3-diol (TACD) of the general formula (I), in which independently of one another the groups R1, R2, R3, and R4 represent linear or branched alkyl groups with up to 8 carbon atoms. The invention additionally relates to the use of the coating agents and to substrates which are coated with the coating agents according to the invention.