20 particularly preferably from 6 to 12 carbon atoms r 2 r 4 can be substituted by heteroatoms or ether groups r 3 r 5 either correspond to the above definition of the radicals r 2 r 4 including the preferred ranges or together form a bridging radical of the abovementioned type which preferably has from 4 to 20 particularly preferably from 4 to 12 carbon atoms and may be substituted by heteroatoms or functional groups and or be unsaturated preferred compounds of the formula ii are those in which r 1 and r 6 are independently of one another identical or different alkyl groups which are preferably selected from the group consisting of methyl ethyl propyl and butyl r 2 and r 4 are independently of one another h or identical or different alkyl groups selected from the group consisting of methyl ethyl propyl and butyl and r 3 and r 5 together form a 1 3 propylene 1 3 butylene 2 4 pentylene 1 4 butylene 1 4 pentylene 2 4 hexylene 1 2 cyclopentylene or 1 2 cyclohexylene bridge for the present purposes u201c propyl u201d and u201c butyl u201d in each case encompass all corresponding isomeric compounds examples of 3 4 diaminopyridines which can be used according to the invention are those of the formulae iii to xi below these can be used as catalyst for uretdione formation either individually in any mixtures with one another or in mixtures.