One-component flexible etch resistant clearcoat
The present invention provides one-component compositions which comprise one or more hydroxyl functional acrylic resin having a glass transition temperature (Tg) of from −100° C. to −10° C. and one or more dialkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker, such as the isocyanurate of isophorone diisocyanate (IPDI), and flexible, environmental etch resistant coatings made therefrom. The acrylic resins comprise the polymerized reaction product of one or more flexibility conferring monomers, e.g. butyl acrylate, and provide the coating with its flexibility. The one or more dialkyl dicarboxylic acid ester endcapped polyisocyanate and the hydroxyl groups in the one or more acrylic resins react to cure at lower temperatures than current one-component blocked isocyanate coatings. Alternatively, one-component coating compositions consists essentially of one or more rigid hydroxyl functional acrylic resin and one or more dialkyl dicarboxylic acid ester endcapped aliphatic polyisocyanates. The present invention provides coated, environmental etch resistant exterior automotive plastic parts, such as bumpers, fascia, body trim and body molding.
1 . A coating composition comprising one or more hydroxyl functional acrylic resin chosen from flexible acrylic resin having a glass transition temperature (Tg) of from −100° C. to −10° C. and rigid acrylic resin having a glass transition temperature (Tg) of from 20° C. to 70° C., and
one or more di(alkoxy)alkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker,
wherein when the said one or more hydroxyl functional acrylic resin is rigid acrylic resin, the said one or more di(alkoxy)alkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker comprises aliphatic polyisocyanate.
2 . A coating composition as claimed in claim 1 , comprising:
from 5 to 50 wt. %, based on total resin solids, of the said one or more hydroxyl functional acrylic resin having a glass transition temperature (Tg) of from −100° C. to −10° C.,
from 5 to 35 wt. %, based on total resin solids, of the said one or more one or more dialkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker resin, and
from 0 to 15 wt. %, based on total resin solids of aminoplast resin.
3 . A coating composition as claimed in claim 2 , wherein the said one or more dialkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker comprises one or more dialkyl dicarboxylic acid ester endcapped oligomer, trimer, biuret or isocyanurate of an alicyclic or aromatic isocyanate.
4 . A coating composition as claimed in claim 1 , wherein the said hydroxyl functional acrylic resin comprises the copolymerization product of hydroxyl group containing monomers chosen from one or more of 4-hydroxybutyl (meth)acrylate, propylene glycol (meth)acrylate, pentanediol (meth)acrylate, hexylene glycol (meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol (meth)acrylate, dipropylene glycol (meth)acrylate, N-propanol (meth)acrylamide, N-butanol (meth)acrylamide, and polyether (meth)acrylate.
5 . A coating composition as claimed in claim 1 , wherein each of the said one or more endcapped polyisocyanate contains from 3 to 8 reactive endcapped isocyanate groups.
6 . A coating composition as claimed in claim 1 , wherein the said hydroxyl functional acrylic resin comprises the copolymerization product of flexibility conferring monomers chosen from one or more of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl acrylate, lauryl (meth)acrylate, polyurethane di(meth)acrylates, polyether di(meth)acrylates, polyester di(meth)acrylates, di(meth)acrylates of oligocaprolactone, and combinations thereof.
7 . A coating composition as claimed in claim 1 , wherein the said Tg of the said hydroxyl functional acrylic resin is −20° C. or less.
8 . A coating composition as claimed in any one of claims 1 to 7 , wherein the said one or more di(alkoxy)alkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker consists essentially of one or more dialkyl dicarboxylic acid ester endcapped polyisocyanate crosslinker.
9 . An environmental etch -resistant, flexible, one-component clearcoat produced from a coating composition as claimed in any one of claims 1 to 7 .
10 . A substrate coated with the coating composition of any one of claims 1 to 7 .