| 摘要 |
Powder coating compositions are disclosed which comprise a blend of coreactable, thermosettable copolymers each of which have at least two different functional groups. Ordinarily, these polymers will be qualitatively difunctional, although they may contain more than two different functional groups, and quantitatively polyfunctional. At least one of the copolymers has epoxy functionality as one of its two or more different functionalities. Thus, in the preferred embodiments, the first copolymer of the blend has epoxy functionality and a second functionality selected from amide functionality, anhydride 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 also is crosslinkable with the first copolymer through at least two different types of functional groups on the second copolymer and may be (a) anhydride functional and carboxy functional, (b) carboxy functional and amide functional, (c) carboxy functional and hydroxy functional, (d) epoxy functional and amide functional or (e) epoxy functional and anhydride functional. The second copolymer is advantageously employed in an amount such that its functionality of greatest concentration provides about 0.3 to about 1.2 functional groups per functional group on the first copolymer and the functionality of lesser concentration provides about 0.1 to about 0.4 functional groups per functional group on the first copolymer. |
