Powder coating compositions

Claim 1

A powder coating composition comprising resinous polyhydroxy compounds as film-forming agents cross-linking agents and the conventional additives, such as levelling agents and optionally pigments, characterised by a bisazlactone as a cross-linking agent having the general formula (I): ##STR2## wherein R 1 and R 2 are selected from the group consisting of hydrogen, alkyl having 1 to 8 carbon atoms, cycloalkyl having from 4 to 16 carbon atoms or aryl having from 6 to 16 carbon atoms, wherein only one of R 1 and R 2 may be hydrogen, or wherein R 1 and R 2 together with the C in 4-position form a cycloaliphatic ring having from 4 to 12 carbon atoms; wherein R 3 is selected from the group consisting of alkylene having from 2 to 6 carbon atoms or arylene having from 6 to 16 carbon atoms, as the cross-linking agent, and a blocked acid as the activator; wherein said resinous polyhydroxy compounds are selected from the group consisting of (a) polyesters of glycols and terephthalic acid modified with triols and having a hydroxyl number of about 95 and (b) copolymers of styrene and unsaturated mono- or dicarboxylic esters having B-hydroxyalkyl groups and a hydroxyl number of about 100; wherein the said coating composition is composed of from 65 to 98 percent by weight of binder, from 0 to 35 percent by weight of pigments, and from 0 to 2 percent by weight of levelling agents and other additives and wherein the said binder is composed of from 83 to 93 percent by weight of said resinous polyhydroxy compounds based on the weight of the binder, from 5 to 15 percent by weight of the said bisazalactone and from 0.25 to 2 percent of the said activator.