Waterborne crosslinker composition
The present invention relates to a multi-aziridine crosslinker composition, including an aqueous dispersion having a pH ranging from 9 to 14 and including a multi-aziridine compound in dispersed form. The multi-aziridine compound has: a. from 2 to 6 of the following structural units A: (A) whereby R1, R2, R3 and R4 are H; m is 1, R′ and R″ are according to (1) or (2): (2) R′=H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, and R″=an alkyl group containing from 1 to 4 carbon atoms, CH2-O—(C═O)—R′″ or CH2-O—R″″, whereby R′″ is an alkyl group containing from 4 to 12 carbon atoms and R″″ is an alkyl group containing from 1 to 14 carbon atoms, (2) R′ and R″ form together a saturated cycloaliphatic hydrocarbon group containing from 5 to 8 carbon atoms.
1. A multi-aziridine crosslinker composition, wherein the multi-aziridine crosslinker composition is an aqueous dispersion having a pH ranging from 9 to 14 and comprises a multi-aziridine compound in dispersed form, wherein
said multi-aziridine compound has:
a. from 2 to 6 of the following structural units A:
whereby
R 1 , R 2 , R 3 and R 4 are H;
m is 1,
R′ and R″ are according to (1) or (2):
(1) R′=H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, and
R″=an alkyl group containing from 1 to 4 carbon atoms, CH2-O—(C═O)—R′″ or CH2-O—R″″, whereby R′″ is an alkyl group containing from 4 to 12 carbon atoms and R″″ is an alkyl group containing from 1 to 14 carbon atoms,
(2) R′ and R″ form together a saturated cycloaliphatic hydrocarbon group containing from 5 to 8 carbon atoms;
b. one or more linking chains wherein each one of these linking chains links two of the structural units A, whereby a linking chain is the shortest chain of consecutive atoms that links two structural units A; and
c. a molecular weight in the range from 600 to 10000 Daltons, wherein the molecular weight is determined using MALDI-TOF mass spectrometry.
2. The multi-aziridine crosslinker composition according to claim 1 , wherein the linking chains consist of from 4 to 300 atoms and the linking chains are a collection of atoms covalently connected which collection of atoms consists of i) carbon atoms, ii) carbon and nitrogen atoms, or iii) carbon, oxygen and nitrogen atoms.
3. The multi-aziridine crosslinker composition according to claim 1 , wherein the multi-aziridine compound contains 2 or 3 structural units A.
4. The multi-aziridine crosslinker composition according to claim 1 , wherein R′ is H and R″=an alkyl group containing from 1 to 4 carbon atoms, CH2-O—(C═O)—R″ or CH2-O—R″ “, whereby R” is an alkyl group containing from 4 to 12 carbon atoms and R″″ is an alkyl group containing from 1 to 14 carbon atoms.
5. The multi-aziridine crosslinker composition according to claim 1 , wherein the multi-aziridine compound comprises one or more connecting groups wherein each one of these connecting groups connects two of the structural units A, whereby the connecting groups consist of at least one functionality selected from the group consisting of aliphatic hydrocarbon functionality, cycloaliphatic hydrocarbon functionality, aromatic hydrocarbon functionality, isocyanurate functionality, iminooxadiazindione functionality, ether functionality, ester functionality, amide functionality, carbonate functionality, urethane functionality, urea functionality, biuret functionality, allophanate functionality, uretdione functionality and any combination thereof.
6. The multi-aziridine crosslinker composition according to claim 5 wherein the connecting groups consist of at least one aliphatic hydrocarbon functionality and/or at least one cycloaliphatic hydrocarbon functionality, and further optionally an isocyanurate functionality or an iminooxadiazindione functionality.
7. The multi-aziridine crosslinker composition according to claim 5 , wherein the connecting groups consist of at least one aliphatic hydrocarbon functionality and/or at least one cycloaliphatic hydrocarbon functionality, and further an isocyanurate functionality or an iminooxadiazindione functionality.
8. The multi-aziridine crosslinker composition according to claim 1 , wherein the multi-aziridine compound comprises one or more connecting groups wherein each one of these connecting groups connects two of the structural units A, wherein the connecting groups consist of (i) at least two aliphatic hydrocarbon functionality and (ii) an isocyanurate functionality or an iminooxadiazindione functionality and wherein a pendant group is present on a connecting group, whereby the pendant group has the following structural formula:
wherein
n′ is the number of repeat units and is an integer from 1 to 50,
X is O or NH,
R 7 and R 8 are independently H or CH 3 in each repeating unit,
R 9 is an aliphatic hydrocarbon group, and
R 10 is an aliphatic hydrocarbon group containing from 1 to 20 carbon atoms, a cycloaliphatic hydrocarbon group containing from 5 to 20 carbon atoms or an aromatic hydrocarbon group containing from 6 to 20 carbon atoms.
9. The multi-aziridine crosslinker composition according to claim 1 , wherein the number of consecutive C atoms and optionally O atoms between the N atom of the urethane group in a structural unit A and the next N atom which is either present in the linking chain or which is the N atom of the urethane group of another structural unit A is at most 9.
10. The multi-aziridine crosslinker composition according to claim 1 , wherein the multi-aziridine compound is obtained by reacting at least a polyisocyanate with aliphatic reactivity in which all of the isocyanate groups are directly bonded to aliphatic or cycloaliphatic hydrocarbon groups, irrespective of whether aromatic hydrocarbon groups are also present, and a compound B with the following structural formula:
whereby the molar ratio of compound B to polyisocyanate is from 2 to 6.
11. The multi-aziridine crosslinker composition according to claim 1 , wherein the multi-aziridine compound has a molecular weight of from 600 to 5000 Daltons.
12. The multi-aziridine crosslinker composition according to claim 1 , wherein the aqueous dispersion comprises aziridine functional molecules having a molecular weight lower than 580 Daltons in an amount lower than 5 wt. %, on the total weight of the aqueous dispersion, whereby the molecular weight is determined using LC-MS.
13. The multi-aziridine crosslinker composition according to claim 1 , wherein the pH of the aqueous dispersion is at least 9.5.
14. The multi-aziridine crosslinker composition according to claim 1 , wherein the amount of water in the aqueous dispersion is at least 15 wt. % and at most 95 wt. %, on the total weight of the aqueous dispersion.
15. The multi-aziridine crosslinker composition according to claim 1 , wherein the amount of said multi-aziridine compound in the aqueous dispersion is at least 5 wt. % and at most 70 wt. %, on the total weight of the aqueous dispersion.
16. The multi-aziridine crosslinker composition according to claim 1 , wherein the solids content of the aqueous dispersion is at least 5 and at most 70 wt. %.
17. The multi-aziridine crosslinker composition according to claim 1 , wherein the multi-aziridine crosslinker composition comprises particles comprising said multi-aziridine compound, wherein said particles have a scatter intensity based average hydrodynamic diameter from 50 to 500 nanometer.
18. The multi-aziridine crosslinker composition according to claim 1 , wherein the aqueous dispersion comprises a dispersant.
19. A method for crosslinking a carboxylic acid functional polymer dissolved and/or dispersed in an aqueous medium, the method comprising providing the multi-aziridine crosslinking composition according to claim 1 , whereby the carboxylic acid functional polymer contains carboxylic acid groups and/or carboxylate groups and the amounts of aziridinyl groups and of carboxylic acid groups and carboxylate groups are chosen such that the stoichiometric amount of aziridinyl groups on carboxylic acid groups and carboxylate groups is from 0.1 to 2.0.
20. A two-component coating system comprising a first component and a second component each of which is separate and distinct from each other and characterized in that the first component comprises a carboxylic acid functional polymer dissolved and/or dispersed in an aqueous medium, whereby the carboxylic acid functional polymer comprises carboxylic acid groups and/or carboxylate groups and the second component comprises the multi-aziridine crosslinker composition according to claim 1 .