Powder coating of semicrystalline and amorphous polyesters with crosslinker

Thermosetting powder compositions comprising a binder a mixture of polyesters containing carboxyl groups and of a crosslinking agent having functional groups capable of reacting with the carboxyl groups, wherein the polyesters comprise:

• (a) from 5 to 45 parts by weight, calculated on the total of polyesters, of a semicrystalline polyester containing carboxyl groups, which comprises, with respect to the total amount of alcohols, of from 85 to 100 mol % of 1,4-cyclohexanediol and of from 0 to 15 mol % of at least one other aliphatic and/or cycloaliphatic polyol and, with respect to the total amount of acids, of from 85 to 100 mol % of a straight-chain saturated di-carboxylic aliphatic acid having from 4 to 14 carbon atoms and of from 0 to 15 mol % of at least one other aliphatic and/or cycloaliphatic and/or aromatic polycarboxylic acid, this semicrystalline polyester having an acid number of from 10 to 70 mg of KOH/g, a number average molecular weight of from 1600 to 17000 and a melting temperature of from 60 to 140° C. and a glass transition temperature ranging from −50 to 50° C.;
• and
• (b) from 95 to 55 parts by weight, calculated on the total of polyesters, of an amorphous polyester containing carboxyl groups, which comprises, with respect to the total amount of acids, of from 70 to 100 mol % of isophthalic acid and of from 0 to 30 mol % of at least one other aliphatic and/or cycloaliphatic and/or aromatic polycarboxylic acid and, with respect to the total amount of alcohols, of from 70 to 100 mol % of neopentyl glycol and/or of 2-butyl-2-ethyl-1,3-propanediol and of from 0 to 30 mol % of at least other aliphatic and/or cycloaliphatic polyol, this amorphous polyester having an acid number of from 15 to 100 mg of KOH/g and a number average molecular weight of from 1100 to 11500.