Coating composition based on a hydroxyl-containing addition polymer and an amino resin crosslinking agent, agent and containing acid catalysts having hydroxy groups

A process for the preparation of a coating composition comprising

• A) 50 to 90% by weight of one or more hydroxyl-containing addition polymers, prepared by copolymerization of ethylenically unsaturated monomers which are in part hydroxyalkyl esters of .alpha.,.beta.-ethylenically unsaturated carboxylic acids and
• B) 10 to 50% by weight of one or more melamineformaldehyde crosslinking agents
• the sum of the proportions by weight of A and B being 100% by weight, and suitable auxiliaries and additives, optionally pigments, optionally fillers, organic solvent and an acid catalyst, wherein the acid catalyst comprises:
• 1) a sulfo- or sulfono-succinic diester which contains at least one hydroxyl group and corresponds to the following formulae (I) or (II):
• ##STR5## in which:
• R.sup.1 =a linear or branched alkyl or alkoxyalkyl radical having 2 to 12 carbon atoms and, if desired, up to 3 hydroxyl groups
• Z=H or NH.sub.n R.sub.4-n
• with
• n=0-4 and
• R=alkyl, hydroxyalkyl, aryl or hydroxyaryl, where R may be identical or different, or an aliphatic or aromatic N-heterocycle
• and/or
• 2) a sulfo- or sulfonic-succinic polyester which contains at least one hydroxyl group, and mixing components A and B with the catalyst and processing the mixture to form a coating composition.

A method of automobile repair finishing, comprising applying to the substrate a coating composition comprising

• A) 50 to 90% by weight of one or more hydroxyl-containing addition polymers, prepared by copolymerization of ethylenically unsaturated monomers which are in pat hydroxyalkyl esters of .alpha.,.beta.-ethylenically unsaturated carboxylic acids and
• B) 10 to 50% by weight of one or more melamineformaldehyde crosslinking agents
• the sum of the proportions by weight of A and B being 100% by weight, and suitable auxiliaries and additives, optionally pigments, optionally fillers, organic solvent and an acid catalyst, wherein the acid catalyst used comprises
• 1) a sulfo- or sulfono-succinic diester which contains at least one hydroxyl group and corresponds to the following formulae (I) or (II):
• ##STR6## in which:
• R.sup.1 =a linear or branched alkyl or alkoxyalkyl radical having 2 to 12 carbon atoms and having 1, 2 or 3 hydroxyl groups
• R.sup.2 =a linear or branched alkyl or alkoxyalkyl radical having 2 to 12 carbon atoms and, if desired, up to 3 hydroxyl groups
• Z=H or NH.sub.n R.sub.4-n
• with
• n=0-4 and
• R=alkyl, hydroxyalkyl, aryl or hydroxyaryl, where R may be identical or different, or an aliphatic or aromatic N-heterocycle
• and/or
• 2) a succinic polyester sulfonic acid and/or succinic polyester sulfonium salt in each case containing at least one hydroxyl group.

A method of coating a substrate comprising applying to the substrate a stoving paint comprising

• A) 50 to 90% by weight of one or more hydroxyl-containing addition polymers, prepared by copolymerization of ethylenically unsaturated monomers which are in part hydroxyalkyl esters of .alpha.,.beta.-ethylenically unsaturated carboxylic acids and
• B) 10 to 50% by weight of one or more melamineformaldehyde crosslinking agents
• the sum of the proportions by weight of A and B being 100% by weight, and suitable auxiliaries and additives, optionally pigments, optionally fillers, organic solvent and an acid catalyst, wherein the acid catalyst used comprises:
• 1) a sulfo- or sulfonio-succinic diester which contains at least one hydroxyl group and corresponds to the following formulae (I) or (II):
• ##STR7## in which:
• R.sup.1 =a linear or branched alkyl or alkoxyalkyl radical having 2 to 12 carbon atoms and having 1, 2 or 3 hydroxyl groups
• R.sup.2 =a linear or branched alkyl or alkoxyalkyl radical having 2 to 12 carbon atoms and, if desired, up to 3 hydroxyl groups
• Z=H or NH.sub.n R.sub.4-n
• with
• n=0-4 and
• R=alkyl, hydroxyalkyl, aryl or hydroxyaryl, where R may be identical or different, or an aliphatic or aromatic N-heterocycle
• and/or
• 2) a succinic polyester sulfonic acid and/or succinic polyester sulfonium salt in each case containing at least one hydroxyl group.