Aqueous dispersions containing a mixture of copolymers and their use in binders

An aqueous solution or dispersion of a copolymer mixture A) comprising:

• I) a hydroxy-functional, hydrophobic, copolymer which is free of carboxyl groups and is polymerized from monomers comprising:
• Ia) 30 to 85% by weight of a (meth)acrylic acid ester having C1-C18 hydrocarbon radicals in the alcohol portion, an aromatic vinyl compound and/or a vinyl ester;
• and
• Ib) 5 to 45% by weight of hydroxy-functional monomers;
• II) a hydroxy- and carboxy-functional, hydrophilic-hydrophobic copolymer polymerized from monomers comprising:
• IIa) 4 to 20% by weight of a (meth)acrylic acid ester having C1-C18 hydrocarbon radicals in the alcohol portion, an aromatic vinyl compound and/or a vinyl ester;
• IIb) 4 to 15% by weight of a hydroxy-functional monomer;
• and
• IIc) 0.8 to 3.0% by weight of an acid-functional monomer;
• and
• III) optionally a hydroxy-functional hydrophobic copolymer polymerized from monomers comprising:
• IIIa) 0 to 16% by weight of a hydroxy- and/or non-functional (meth)acrylic acid ester or an aromatic vinyl compound;
• wherein
• i) the preceding percentages are based on the total weight of components I), II) and III;
• ii) the sum of Ia), Ib), IIa), IIb) IIc) and IIIa) is 100%, based on the weight of these components;
• iii) copolymer mixture A) has an acid number, based on solids, of 10 to 28 mg KOH/g substance;
• iv) the weight percent of monomer IIc) in the monomers used to polymerize copolymer II) is less than 25% by weight;
• v) the weight percent of hydroxy-functional monomer IIb) in the monomers used to polymerize copolymer II) is higher than the weight percent of hydroxy-functional monomer Ib) in the monomers used to polymerize copolymer I);
• and
• vi) the copolymer mixture is free of hydroxy-functional polyethers.