| abstract |
Powder coating compositions are disclosed which comprise a blend of coreactable, thermosettable copolymers one of which has at least two different functional groups while the other is qualitatively monofunctional and quantitatively polyfunctional. Ordinarily, the polymer having at least two different functional groups, will be quantitatively polyfunctional and qualitatively difunctional although it may contain more than two different functional groups. In the preferred embodiments, the first or difunctional copolymer of the blend has either (1) epoxy functionality and amide functionality, (2) epoxy functionality and hydroxy functionality, (3) carboxy functionality and amide functionality, or (4) carboxy functionality and hydroxy functionality and is crosslinkable with the second copolymer through at least two different types of functional groups on the first copolymer. The second copolymer has only one type of functionality that is crosslinkable with the functional groups on the first copolymer and may be termed the monofunctional copolymer although it is quantitatively polyfunctional. The second copolymer may have as its functionality (1) anhydride functionality, (2) carboxy functionality or (3) epoxy functionality. The second copolymer is advantageously employed in an amount such that it provides about 0.4 to about 1.4, preferably about 0.8 to about 1.1, functional groups per functional group on the first copolymer. |