Method for preparing color-clear composite coatings having resistance to acid etching
AssigneePPG Industries, Inc.
InventorsDebra L. Singer, Shanti Swarup, Michael A. Mayo
Life of this patent
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Abstract
A color-plus-clear coating system is disclosed. A pigmented or colored basecoat is first applied to a substrate followed by the application of a transparent topcoat to the basecoat. The transparent topcoat composition is a crosslinkable composition comprising (1) a material containing a plurality of carbamate and/or urea functional groups and (2) an aminoplast crosslinking agent. The topcoat composition provides a composite coating with improved acid etch resistance, making the composite coating particularly useful as an automotive topcoat.
Claims22
A method for applying a composite coating to a substrate which comprises applying to the substrate a colored film-forming composition to form a base coat and applying to said base coat a clear film-forming composition to form a transparent top coat over the base coat characterized in that the clear film-forming composition comprises (1 ) a polymer or oligomer containing a plurality of terminal or pendant groups of the structure:
- ##STR3## Where X is -N or ##STR4## and R is H or alkyl of 1--6 carbon atoms or R is bonded to X and forms part of a 5 or 6 membered ring;
- and (2) an aminoplast crosslinking agent containing methylol and/or methylol ether groups;
- said clear film-forming composition being crosslinkable through reaction of said pendant or terminal groups with said methylol and/or methylol ether groups;
- said clear film-forming composition being further characterized as having a calculated hydroxyl value less than 50 based on solid weight of said clear film-forming composition, excluding any hydroxyl functionality associated with N-methylol groups so as to result in a crosslinked coating which has urethane and/or urea crosslinks arising from said reaction of pendant or terminal groups with said methylol and/or methylol either groups.
A method for applying a composite coating to a substrate which comprises applying to the substrate a colored film-forming composition to form a base coat and applying to said base coat a clear film-forming composition to form a transparent top coat over the base coat characterized in that the clear film-forming composition comprises (1) a polymer or oligomer containing a plurality of terminal or pendant urea groups of the structure:
- ##STR6## where X is ##STR7## and R is H or alkyl of 1-6 carbon atoms or R is bonded to X and forms part of a 5 or 6 membered ring;
- and (2) an aminoplast crosslinking agent containing methylol and/or methylol ether groups;said clear film-forming composition being crosslinkable through reaction of said pendant or terminal groups with said methylol and/or methylol ether groups;
- said clear film-forming composition being further characterized as having a calculated hydroxyl value less than 50 based on solid weight of said clear film-forming composition, excluding any hydroxyl functionality associated with N-methylol groups so as to result in a crosslinked coating which has urea crosslinks arising from said reaction of pendant or terminal groups with said methylol and/or methylol ether groups.
Dependencies are inferred from the claim text.