Process for the preparation of a reaction product of a cyclic urea and a multifunctional aldehyde
View Patent ↗This invention relates to a process to make a reaction product UA of at least one multifunctional aldehyde A with at least one cyclic urea U, by mixing the at least one multifunctional aldehyde A with the at least one cyclic urea U in the presence of at least one alcohol R 1 —OH, and optionally, at least one solvent that has no reactive groups which may react with aldehyde groups, —CO—NH— groups, or hydroxyl groups, to effect an addition reaction to obtain a solution of a product UA, where R 1 is selected from the group consisting of linear, branched or cyclic alkyl groups having from one to twelve carbon atoms, to the reaction product obtained by this process, and to a method of use thereof as crosslinker for coating compositions.
1. A process to make a reaction product UA of at least one multifunctional aldehyde A with at least one cyclic urea U, by
a) mixing the at least one multifunctional aldehyde A with the at least one cyclic urea U in the presence of at least one alcohol R 1 —OH to a temperature of between 35° C. and 50° C. to effect an addition reaction, optionally, in the presence of at least one solvent that has no reactive groups which may react with aldehyde groups, —CO—NH— groups, or hydroxyl groups,
to obtain a solution of a product UA, where R 1 is selected from the group consisting of linear, branched or cyclic alkyl groups having from one to twelve carbon atoms which may be interrupted by one or more of —O—, —NR″—, —S—, where R″ stands for H, or an alkyl group having from one to six carbon atoms, with the proviso that not two —O— or not two —S— atoms may be immediately adjacent, characterised in that the cyclic urea U is selected from the group consisting of ethylene urea, 1,3-propylene urea, 1,2-propylene urea, 1,4-butylene urea, and glycol uril,
wherein the addition reaction is conducted in a pH range of more than 7.5 or in a pH range of form 4.5 to 7.5, and
wherein, after the addition reaction of step a),
b) the pH is adjusted to at most 5.0
c) optionally, adding a further quantity of the said aliphatic alcohol R 1 —OH; and optionally, adding at least one solvent that has no reactive groups which react with aldehyde groups, —CO—NH— groups, or hydroxyl groups; and etherifying under acid conditions
d) adding a further aliphatic alcohol R 2 —OH which has at least one carbon atom in its molecule more that there is in R 1 —OH; optionally, adding at least one solvent that has no reactive groups which react with aldehyde groups, —CO—NH— groups, or hydroxyl groups; and etherifying under acid conditions.
2. The process of claim 1 , wherein the steps c), and/or d) may be repeated one or more times.
3. The process of claim 1 , wherein the ratio of the amount of substance n(-O—R 2 ) of alkoxy groups —O—R 2 to the amount of substance n(-O—R 1 ) of alkoxy groups —O—R 1 in the etherified product of the process of claim 1 is between 0.11 mol/mol and 20 mol/mol.
4. The process of claim 1 , wherein, after the addition reaction of step a),
b) the pH is adjusted to at most 5.0
c) adding a further quantity of the said aliphatic alcohol R 1 —OH; optionally, adding at least one solvent that has no reactive groups which react with aldehyde groups, amide groups, or hydroxyl groups; and etherifying under acid conditions
wherein step c) may be repeated one or more times.
5. The process of claim 1 characterised in that in step a), the amount of multifunctional aldehyde A added is between 20% and 80% of the stoichiometric amount needed, and that after step a), a further quantity of multifunctional aldehyde A is added and reacted with the reaction mixture formed in step a) wherein the total amount of multifunctional aldehyde A added is chosen such that the ratio of the amount of substance of aldehyde groups n(-CHO) in the multifunctional aldehyde A and the amount of substance of groups n(-CO—NH) in the cyclic urea U is from 0.2 mol/mol to 4 mol/mol.
6. The process of claim 1 characterised in that after an etherification step, at least a part of the unreacted alcohol and optionally, at least a part of the water present, and further optionally, at least a part of the at least one solvent that has no reactive groups which react with aldehyde groups, —CO—NH— groups, or hydroxyl groups, is removed by distillation.
7. The process of claim 6 wherein after an etherification step, at least a part of the unreacted alcohol and optionally, at least a part of the water present, and further optionally, at least a part of the at least one solvent that has no reactive groups which react with aldehyde groups, amide groups, or hydroxyl groups, is removed by azeotropic distillation wherein a solvent is added that is immiscible with water in a way that it forms a phase separate from an aqueous phase containing at least a part of the water separated by distillation, wherein the phase different from the aqueous phase is recycled to the distillation still or to the reactor.
8. The process of claim 1 characterised in that purified cyclic urea U is used.