Low-VOC primer for plastic coating

Coating compositions for direct coating of plastic substrates, consisting of the following components:

• A) a hydroxy-functional binder component, consisting essentially of at least one branched hydroxy-functional polyester having a hydroxyl value of 50-300 mg KOH/g solid, a polydispersity Mw/Mn of <2 and a number average molecular weight (Mn) of 300 to 4000, having at least three branches, having at least one hydroxyl group on each of the at least three branches and wherein the polyester comprises reacted the following components:
• a) 20-50% by weight of at least one polycarboxylic acid anhydride selected from a group consisting of hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, phthalic anhydride, trimellitic anhydride and mixtures thereof,
• b) 2-30% by weight of at least one polyol having at least three hydroxyl groups selected from a group consisting of trimethylolpropane, trimethylolethane, ditrimethylolpropane, monopentaerythritol, dipentaerythritol and mixtures thereof and
• c) 30-80% by weight of at least one glycidyl ester of a saturated monocarboxylic acid branched in the alpha position, wherein the saturated monocarboxylic acid branched in the alpha position is selected from a group consisting of alpha-alkylalkane monocarboxylic acid having 7 to 13 carbon atoms in the acid molecule, alpha,alpha′-dialkylalkane monocarboxylic acids having 7 to 13 carbon atoms in the acid molecule, and mixtures thereof,
• wherein the % by weight of components a), b) and c) add up to 100% by weight,
• B) a crosslinking component for the hydroxyfunctional binder component A) that comprises at least one polyisocyanate crosslinking agent having free isocyanate groups,
• C) at least one adhesion promoting component comprising at least one chlorinated polyolefin and,
• D) organic solvents, organic pigments, inorganic pigments, fillers, extenders, leveling agents based on silicone oils, anticratering agents, antifoaming agents, catalysts, dispersing agents, thickeners, emulsifiers, or a combination thereof.