THERMOSET COATING COMPOSITION HAVING IMPROVED HARDNESS

The present invention provides for amino-crosslinkable coating formulations based on a mixture of a di or polyhydroxy functional polymeric component selected from the group consisting of diesters, polyesters, alkyd polymers, acrylic polymers and polycarbonate polymers, a methylol (alkoxymethyl) amino crosslinking agent and a bis-aromatic polyhydric phenol component having the structure of formula I: I. wherein X is selected from the group consisting of carbon to carbon covalent bond, oxygen, sulfur, -S-S-, -CO-, -SO-, -SO2- and a divalent organic radical having a molecular weight less than about 400, and wherein Y is independently selected from the group consisting of hydrogen, halogen, C1 to C4 alkyl and C1 to C4 alkoxy. The crosslinkable compositions of this invention may be used to prepare curable coating and paint formulations, and also may contain other ingredients such as a crosslinking catalyst, fillers, pigments and the like. When cured, the coatings of this invention exhibit improved hardness properties when compared with cured coatings which do not contain the aromatic polyhydric phenol additive. The presence of the additive also serves to eliminate the problem of coating softening when the coated substrate is baked for a prolonged period of time. These cured coatings also have good weatherability, good corrosion resistance and hydrolytic stability, enhanced oxidative and radiation stability, good solvent resistance and good adhesion properties.