EMULGATORFREIES, HITZEHÄRTBARES ÜBERZUGSMITTEL, DESSEN HERSTELLUNG UND VERWENDUNG

摘要

Emulsifier-free heat-curable coating composition in the form of an aqueous emulsion, process for its preparation, and its use. The coating composition contains: A) from 30 to 80% by weight of one or more polyester oligomer polyacrylates which are dilutable in water after neutralisation with bases and are obtainable by free-radical polymerisation of from 50 to 95% by weight of one or more esters of unsaturated carboxylic acids, having hydrophobic and hydrophilic components, where a) the hydrophobic components are based on monomeric esters of unsaturated carboxylic acids having secondary OH groups which may be present as a mixture with comonomers which are free of OH groups, and b) the hydrophilic components are based on monomeric esters of unsaturated carboxylic acids having primary OH groups and on monomeric esters of unsaturated carboxylic acids having COOH groups, which may be present as a mixture with comonomers which are free of OH groups, the numerical ratio of the primary to the secondary OH groups in the copolymer, which groups derive from components b) and a), being from 1:1.5 to 1:2.5, in from 5 to 50% by weight of one or more hydroxy-functional polyester oligomers which is or are obtainable by polycondensation of one or more diols and/or polyols with one or more dicarboxylic acids and/or derivatives thereof, having a calculated molecular weight of from 200 to 1000, a hydroxyl number of from 100 to 600 and an acid number of from 0 to 15, the monomers a) and b) being employed in quantities such that the polyester oligomer polyacrylate has a hydroxyl number of from 100 to 390 and an acid number of from 16 to 50, and the percentages by weight being based in each case on the solids content and adding up to give 100% by weight, and B) from 70 to 20% by weight of one or more blocked polyisocyanates and/or one or more melamine resins, at least one of the melamine resins being a hexamethoxymethylmelamine resin, the percentage by weight of components A) and B) relating in each case to the mass of the solids in the resins and adding up to 100% by weight, and the ratio of OH groups of component A) to the blocked NCO groups of component B) being from 0.5:1 to 2:1; and water and, if desired, one or more organic solvents, pigments, fillers, catalysts and/or additives auxiliaries which are conventional in coatings.