Carboxy-functional polyester resin used in powder lacquer formulation is based on dicarboxylic acids and diols including pentan-1,5-diol, diethylene glycol and/or derivatives with alkyl side chains

摘要

Carboxy-functional polyester resin (I), is based on not more than 80 mole% isophthalic acid and not less than 20 mole% other aromatic, (cyclo)aliphatic dicarboxylic and/or dimerized fatty acid and not less than 50 mole% branched aliphatic (ester)diol and not more than 50 mole% linear and/or cycloaliphatic diol and includes pentan-1,5-diol, diethylene glycol and/or alkyl derivatives. Carboxy-functional polyester resin (I) has an acid number of 15-70 mg KOH/g and hydroxyl number at most 10 mg KOH/g and consists mainly of dicarboxylic acids and diols, optionally with small amounts of monomers with functionality at least 3 and/or monofunctional monomers. The novel features are that (I) has (1) a dicarboxylic acid component comprising not more than 80 mole% isophthalic acid and not less than 20 mole% other 8-16 carbon (C) aromatic, 4-22 C aliphatic and/or 8-16 C cycloaliphatic dicarboxylic acid(s) and/or dimerized fatty acid(s); (2) a diol component comprising not less than 50 mole% 4-12 C branched aliphatic diol(s), optionally containing an ester group, not more than 50 mole% 2-22 C linear aliphatic diol(s) and/or 6-16 C cycloaliphatic diol(s) and includes pentan-1,5-diol, diethylene glycol, derivative(s) with lateral alkyl substituent(s), e.g. 3-methylpentan-1,5-diol and dipropylene glycol, or a mixture of these, preferably in a total amount of 0.5-30 mole% with respect to all diols; and (3) a glass transition temperature, Tg, not less than 35 degreesC. Independent claims are also included for (a) powder lacquer formulations containing (I), an organic crosslinker that can react with the carboxyl groups of (I) to form a covalent bond and usual additives and optionally pigments and fillers; (b) articles coated with these powder lacquers; and (c) a process comprising thermosetting powder lacquer formulations based on (I) are produced by mixing (I) with beta-hydroxyalkylamide(s) or polyepoxide(s) and optionally other additives, then extrusion at 80-130 degreesC, granulation, milling and classification to a particle size less than 100 micro m.