Abstract: Urea derivatives of formula 1 for the hardening of hydroxyl group-containing polymers.

Abstract: A process is described for the production of 3-alkyl-3-hydroxymethyloxetanes of the general formula (1), ##STR1## in which R.sup.1 denotes a linear or branched C.sub.1 -C.sub.12 alkyl group, which process comprises reacting a trimethylolalkane of the general formula (2),(HO--CH.sub.2).sub.3 C--R.sup.1 (2)in which R.sup.1 is defined as above, with a dialkyl carbonate of the general formula (3),R.sup.2 --O--(C.dbd.O)--O--R.sup.2 (3)in which R.sup.2 denotes a linear or branched C.sub.1 -C.sub.4 alkyl group, in the presence of a basic catalyst, wherein in a first stage the reaction mixture is stirred for at least 6 hours with refluxing at a temperature of 90-120.degree. C., in a second stage the alcohol formed R.sub.2 OH is distilled off at the same temperature and in a third stage the product formed is decarboxylated and deoligomerised at a temperature of 125-150.degree. C. and the desired 3-alkyl-3-hydroxymethyloxetane is simultaneously distilled off.