Polyurethane resins, processes for their preparation, and their use in water-dilutable coating compositions

Process for the preparation of polyurethane resins, comprising reacting

• a) at least one compound having two hydroxyl groups,
• b) optionally at least one compound which is different from the compound (a) and has at least one, and less than three hydroxyl and/or amino groups,
• c) at least one di- and/or polyisocyanate,
• d) at least one compound which has two groups which are reactive toward isocyanate groups and at least one group capable of forming anions, where the group capable of forming ions is neutralized before or after the incorporation of component (d) into the polyurethane molecule, and
• e) at least one compound having at least 3 hydroxyl and/or amino groups, where components (a), (b), (c) and (d) are initially reacted to form an intermediate which contains terminal isocyanate groups wherein component (a) comprises a compound selected from the group consisting of
• a.sub.1) at least one diol of the formula (I) ##STR12## wherein R.sub.1 and R.sub.2 are identical or different radicals selected from the group consisting of alkyl radicals having 1 to 18 carbon atoms, aryl radicals, and cycloaliphatic radicals, with the proviso that R.sub.1 and/or R.sub.2 may not be methyl,
• a.sub.2) at least one diol of the formula (II) ##STR13## in which R.sub.3, R.sub.4, R.sub.6 and R.sub.7 are each identical or different radicals and R.sub.3, R.sub.4, R.sub.6 and R.sub.7 are selected from the group consisting of alkyl radicals having 1 to 6 carbon atoms, cycloalkyl radicals and aryl radicals, and R.sub.5 is a radical selected from the group consisting of alkyl radicals having 1 to 6 carbon atoms, aryl radicals, and unsaturated alkyl radicals having 1 to 6 carbon atoms, and n is either 0 or 1, and mixtures of (a1) and (a2).

Water-dilutable polyurethane resin comprising the reaction product of

• a) at least one compound having two hydroxyl groups,
• b) optionally at least one compound which is different from the compound (a) and has at least 1, and less than 3 hydroxyl and/or amino groups,
• c) at least one di- and/or polyisocyanate,
• d) at least one compound which has two groups which are reactive toward isocyanate groups and at least one group capable of forming anions, wherein the anionic group is neutralized before or after the incorporation of component (d) into the polyurethane molecule, and
• e) optionally at least one compound having at least 3 hydroxyl and/or amino groups, where components (a), (b), (c) and (d) are reacted to form an intermediate which contains terminal isocyanate groups and wherein component (a) comprises 2,5-dimethyl-2,5-hexanediol.