Acid functional polyester resins and lower temperature curable powder coating compositions comprising them

摘要

Linear, carboxylic acid functional polyester resins obtainable by reaction of: (a) at least one aromatic and/or cycloaliphatic dicarboxylic acid compound A, comprising two aromatic and/or secondary aliphatic carboxyl groups in the 1,2-position, or anhydride thereof; (b) at least one hydroxyl monocarboxylic acid B1, comprising two aliphatic hydroxyl groups, which groups each independently may be primary or secondary hydroxyl groups and wherein the carboxylic acid group is a tertiary carboxyl group, mixed with a cycloaliphatic diol B2 in an amount of at least 5 wt%, relative to the weight of B1 and B2 together; (c) optionally an aliphatic dicarboxylic acid C, comprising an alkylene group having from 3 to 8 carbon atoms and having two terminal aliphatic carboxyl groups; and (d) optionally an aromatic monocarboxylic acid D, the molar ratio of the compounds A:B1+B2:C:D being X:Y+X+Z1:Y:Z2, wherein X ranges from 1 to 8, Y ranges from 0 to 8, Z1 ranges from -3 to 3 and Z2 ranges from 0 to 2, until essentially all the hydroxyl groups as initially present in the reaction mixture have been reacted, and powder coating compositions containing an epoxy resin and said linear, carboxylic acid functional polyester resin, and a process for their preparation.