AZIRIDINE FUNCTIONAL COMPOUND

Abstract

The present application relates to aziridine functional compounds with reduced genotoxicity and good crosslinking efficiency, for use in the preparation of, for example, coatings.

##STR00001##

Claims

1. An aziridine compound having: a) one or two of the following structural units A: ##STR00054## wherein R.sub.1 is H; R.sub.2 and R.sub.4 are independently chosen from H or an aliphatic hydrocarbon group containing from 1 to 4 carbon atoms; R.sub.3 is an aliphatic hydrocarbon group containing from 1 to 4 carbon atoms; 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″═H, an aliphatic hydrocarbon group containing from 5 to 14 carbon atoms, a cycloaliphatic hydrocarbon group containing from 5 to 12 carbon atoms, an aromatic hydrocarbon group containing from 6 to 12 carbon atoms, CH2—O—(C═O)—R′″, CH.sub.2—O—R″″, or CH.sub.2—(OCR′″″HCR′″″H).sub.n—OR″″″, whereby R″′ is an aliphatic hydrocarbon group containing from 4 to 14 carbon atoms and R″″ is an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms or an aromatic hydrocarbon group containing from 6 to 12 carbon atoms, n being from 1 to 35, R″″′ independently being H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms and R″″″ being an aliphatic hydrocarbon group containing from 1 to 4 carbon atoms, (1) R′ and R″ form together a saturated cycloaliphatic hydrocarbon group containing from 5 to 8 carbon atoms, R.sub.11 is H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, m is an integer from 1 to 6; b) one structural unit B: ##STR00055## wherein p+q is an integer from 0 to 4; r is an integer from 0 to 2; X is NH or O or NR, wherein R contains at most 36 carbon atoms and optionally contains one or more heteroatoms in the chain; R.sub.5 and R.sub.6 are independently containing from 4 to 13 carbon atoms; R.sub.7 is a divalent group; and c) optionally one structural unit C: ##STR00056## wherein Z is NH or O or NR wherein R contains at most 36 carbon atoms and optionally contains one or more heteroatoms in the chain; R.sub.8 is a monovalent group; and d) structural formula A-B-A or structural formula A-B-C; e) a molecular weight higher than 600 Daltons and at most 5000 Daltons; with the proviso that f) the mathematical sum of the molar mass of starting diisocyanate providing carbodiimide functionality in the structural unit B+the molar mass of structural unit A+the molar mass of structural unit A is higher than 600 Daltons; and g) in case structural unit C is present, the mathematical sum of the molar mass of starting diisocyanate providing the carbodiimide functionality in the structural unit B+the molar mass of structural unit A+the molar mass of structural unit C is higher than 600 Daltons.

2. The aziridine compound according to claim 1, wherein R.sub.1 is H, R.sub.2 is H, R.sub.3 is CH.sub.3 and R.sub.4 is H.

3. The aziridine compound according to claim 1, wherein Ru is H or methyl.

4. The aziridine compound according to claim 1, wherein m is 1.

5. The aziridine compound according to claim 1, wherein p+q is an integer from 0 to 2.

6. The aziridine compound according to claim 1, wherein r is 0 or 1.

7. The aziridine compound according to claim 1, wherein R.sub.5 and R.sub.6 are the hydrocarbon residue from a diisocyanate used to form the carbodiimide functionalities present in structural unit B and R.sub.5═R.sub.6.

8. The aziridine compound according to claim 1, X is O and Z is NH or O.

9. The aziridine compound according to claim 1, wherein R.sub.7 is a polyether with an average molecular weight of from 194 to 1300 Daltons and contains more than 80 wt. % ethoxylated groups.

10. The aziridine compound according to claim 1, wherein R.sub.8 is a polyether with an average molecular weight of from 500 to 1500 Daltons and contains more than 80 wt. % ethoxylated groups.

11. The aziridine compound according to claim 1, wherein the mathematical sum of the molar mass of starting diisocyanate providing carbodiimide functionality in the structural unit B+the molar mass of structural unit A+the molar mass of structural unit A is higher than 615 Daltons, and, in case structural unit C is present (i.e. the aziridine compound is according to structural formula A-B-C), the mathematical sum of the molar mass of starting diisocyanate providing carbodiimide functionality in the structural unit B+the molar mass of structural unit A+the molar mass of structural unit C is higher than 615 Daltons.

12. The aziridine compound according to claim 1, wherein the aziridine compound has a molecular weight of at most 3000 Daltons, and the molecular weight of the compound is at least 700 Daltons.

13. The compound according to claim 1, wherein the aziridine compound has an aziridine equivalent weight (molecular weight of the aziridine compound divided by number of aziridinyl functionalities present in the compound) of at least 350, more preferably at least 400 and even more preferably at least 450 Daltons and preferably at most 5000, more preferably at most 3000, even more preferably at most 2500 Daltons and most preferably at most 2000 Daltons.

14. The aziridine compound according to claim 1, wherein the structural unit A is obtained by reacting at least a monoepoxide compound with an aziridine with the following structural formula: ##STR00057## whereby R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are defined as in claim 1.

15. The aziridine compound according to claim 14, wherein the monoepoxide compound is selected from the group consisting of n-butylglycidylether (CAS number 2426-08-6), 2-ethylhexylglycidylether (CAS number 2461-15-6), glycidyl neodecanoate (CAS number 26761-45-5) and any mixture thereof.

16. A process for preparing the aziridine compound according to claim 1, wherein the aziridine compound is obtained by reacting a compound with the following structural formula (D) (providing structural unit A) ##STR00058## wherein R′, R″, R.sub.11, m, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are as claimed above, and diisocyanate with formula O═C═N—R.sub.10—N═C═O (E), wherein R.sub.10 is R.sub.5 or R.sub.6 as claimed above, and optionally diol, diamine and/or hydroxylamine with formula HX—R.sub.7—XH (F), wherein X and R.sub.7 is as claimed above (providing structural unit B), and, in case the compound has structural formula A-B-C, compound G HZ—R.sub.8 (G), wherein Z and R.sub.8 are as claimed above (providing structural unit C).

17. The process according to claim 16, wherein the diisocyanate is isophorone diisocyanate IPDI, 4,4′-dicyclohexyl methane diisocyanate H12MDI and/or tetramethylxylene diisocyanate TMXDI (all isomers).

18. A crosslinker composition comprising at least one aziridine compound according to claim 1 and comprising at most 1 wt. % of aziridinyl group functional molecules having a molar mass of lower than 600 Daltons.

19. The crosslinker composition according to claim 18, wherein the composition is an aqueous dispersion comprising particles of the aziridine compound or of the aziridine compound obtained with the process.

Description

COMPARATIVE EXAMPLE 1

[0234] Comparative Example 1 is CX-100, trimethylolpropane tris(2-methyl-1-aziridinepropionate). Chemical structure is shown below.

##STR00026##

Genotoxicity Test Results:

[0235]

TABLE-US-00001 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Comp. Ex. 1 1.2 1.5 2.0 1.4 2.0 3.2 1.7 2.3 2.1 3.0 4.3 3.4
The genotoxicity test results show that the crosslinker of Comp. Ex. 1 is genotoxic.

COMPARATIVE EXAMPLE 2

(Example 5 EP0507407B1)

[0236] Under a nitrogen atmosphere, 21.3 g (0.354 mole) of 1-propanol was added over a period of 6 hours to 78.7 g Isophorone diisocyanate (IPDI) and 0.01 g tin 2-ethyl hexanoate at 20-25° C., while stirring. After standing overnight, 196.3 g (0.883 mole) IPDI, 74.1 g (0.0628 mole) Tegomer D3403 and 2.4 g 3-Methyl-1-phenyl-2-phospholene-1-oxide were added. The mixture was heated while stirring to 150° C. The mixture was kept at 150° C. until NCO content was 7.0 wt %. Mixture was cooled to 80° C. and 333g methoxypropyl acetate was added. A solution of isocyanate functional polycarbodiimide was obtained with a solid content of 50.6 wt % and an NCO content of 7.0 wt % on solids.

[0237] To 100g of this isocyanate functional polycarbodiimide was added 7.0 g 1-(2-hydroxyethyl)ethyleneimine (0.08 mole). One drop of dibutyltin dilaurate was added. The mixture was heated to 80° C. while stirring. The mixture was kept at 80° C. for 1 hour. FTIR showed a small remaining isocyanate signal, which disappeared after a few days. The solution was further diluted with 8.0 g methoxypropyl acetate, resulting in a yellow solution with a solid content of 50.4 wt %. This aziridine functional carbodiimide contains 3.2 meq acid reactive groups (i.e aziridine and carbodiimide functionality) per gram solids.

[0238] Smallest intrinsically formed aziridine functional byproduct compound is the reaction product of 1-(2-hydroxyethyl)ethyleneimine/IPDI/1-propanol and has a calculated molar mass of 369.26 and this structure is illustrated below:

##STR00027##

Another intrinsically formed aziridine functional byproduct compound is the reaction product of 1-(2-hydroxyethyl)ethyleneimine/IPDI/1-(2-hydroxyethyl)ethyleneimine having a calculated molar mass of 396.27 and this structure is illustrated below:

##STR00028##

The chemical representation of the aziridine functional carbodiimide can be illustrated as:

##STR00029##

in which a, b and c indicates repeating units.

[0239] This generalized structure was confirmed by MALDI-TOF-MS, an example is shown below:

##STR00030##

Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=2043.34 Da; Obs. [M+Na+]=2043.32 Da.

Genotoxicity Test Results:

[0240]

TABLE-US-00002 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Comp. Ex. 2 1.3 1.5 1.6 1.2 1.9 1.9 1.2 1.4 1.5 2.0 2.0 1.8
The genotoxicity test results demonstrate that the crosslinker of comparative example 2 is genotoxic.

EXAMPLE 1

[0241] Under a nitrogen atmosphere a mixture of 46.7 g (0.210 mole) of Isophorone diisocyanate (IPDI), 25.3 g (0.0214 mole) Tegomer D3403 and 0.02 g Bismuth Neodecanoate was heated to 65° C. while stirring. After 1 hour of reacting at 65° C., 0.47 g 3-methyl-1-phenyl-2-phospholene-1-oxide was added to the mixture. The mixture was heated while stirring to 150° C. The mixture was kept at 150° C. until NCO content was 8.6 wt %. Mixture was cooled to 80° C. and 60.4g methoxypropyl acetate was added and stirred to homogeneous. 30 g Cardura E-10/propylene imine adduct (0.105 mole) and 1 drop of dibutyltin dilaurate were added to the reaction mixture. The mixture was kept while stirring at 65° C. for 5 hours. FTIR showed a no isocyanate signal. 30 g methoxypropyl acetate was added. A yellow solution with a solid content of 50.0 wt % was obtained. The reaction product is a mixture which contains a range of compounds having a structure according to claim 1.

[0242] This aziridine functional carbodiimide contains 1.2 meq per gram solids aziridine groups and 1.2 meq per gram solids carbodiimide groups resulting in a total of 2.4 meq acid reactive groups (i.e aziridine and carbodiimide functionality) per gram solids. The aziridine functional compound with the smallest (calculated) molar mass is the reaction product of propylene imine-CarduraE10/IPDI/CarduraE10-propylene imine having a molar mass 792.6.

[0243] The structure of the smallest intrinsically formed aziridine functional byproduct compound is illustrated as:

##STR00031##

[0244] The calculated molecular weights of the theoretical main components was confirmed with Maldi-TOF-MS and are shown below with their structures:

##STR00032##

Calcd. [M+Na+]=993.73 Da; Obs. [M+Na+]=993.68 Da.

[0245] ##STR00033##

Calcd. [M+Na+]=1171.88 Da; Obs. [M+Na+]=1171.89 Da.

[0246] ##STR00034##

Calcd. [M+Na+]=2334.60 Da; Obs. [M+Na+]=2334.60 Da.

[0247] The following component with a mass below 600 Da was determined by LC-MS and quantified:

##STR00035##

was present in the composition at 0.81 wt %.

Genotoxicity Test Results:

[0248]

TABLE-US-00003 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Example 1 1.1 1.2 1.3 1.2 1.3 1.2 1.1 1.2 1.3 1.2 1.4 1.2
All values in this table show a negative induction level of the biomarkers of lower than a 1.5-fold induction at 10, 25 and 50% cytotoxicity in the absence and presence of rat S9 liver extract-based metabolizing systems and demonstrate that the crosslinker of example 1 is non-genotoxic.

EXAMPLE 2

[0249] Under a nitrogen atmosphere a mixture of 25.0 g (0.102 mole) of m-Tetramethylxylylene diisocyanate (TMXDI), 25.0 g (0.095 mole) Dicyclohexylmethane-4,4′-diisocyanate (H12MDI), 21.42 g (0.0182 mole) Tegomer D3403 and 0.02 g Bismuth Neodecanoate was heated to 65° C. while stirring. After 1 hour of reacting at 65° C., 0.50 g 3-methyl-1-phenyl-2-phospholene-1-oxide was added to the mixture. The mixture was heated while stirring to 150° C. The mixture was kept at 150° C. until NCO content was 7.2 wt %. Mixture was cooled to 80° C. and 65.8 g methoxypropyl acetate was added and stirred to homogeneous. 19.2 g Butylglycidylether/propylene imine adduct (0.103 mole) and 1 drop of dibutyltin dilaurate were added to the reaction mixture. The mixture was kept while stirring at 65° C. for 5 hours. FTIR showed a no isocyanate signal. 19.1 g methoxypropyl acetate was added. A yellow solution with a solid content of 50.0 wt % was obtained. The reaction product is a mixture which contains a range of compounds having a structure according to claim 1.

[0250] This aziridine functional carbodiimide contains 1.2 meq per gram solids aziridine groups and 1.4 meq per gram solids carbodiimide groups resulting in a total of 2.6 meq acid reactive groups (i.e aziridine and carbodiimide functionality) per gram solids. The aziridine functional compound with the smallest (calculated) molar mass is the reaction product of butylglycidylether-propylene imine/TMXDI/butylglycidylether-propylene imine having a molar mass of 618.44.

[0251] The structure of the smallest intrinsically formed aziridine functional byproduct compound is illustrated as:

##STR00036##

The calculated molecular weights of the theoretical main components was confirmed with Maldi-TOF-MS and are shown below with their structures:

##STR00037##

Calcd. [M+Na+]=841.56 Da; Obs. [M+Na+]=841.55 Da.

[0252] ##STR00038##

Calcd. [M+Na+]=859.60 Da; Obs. [M+Na+]=859.66 Da.

[0253] ##STR00039##

Calcd. [M+Na+]=877.65 Da; Obs. [M+Na+]=877.70 Da.

[0254] ##STR00040##

Calcd. [M+Na+]=1550.90 Da; Obs. [M+Na+]=1550.92 Da.

[0255] The following component with a mass below 600 Da was determined by LC-MS and quantified:

##STR00041##

was present in the composition at less than 0.01 wt %.

Genotoxicity Test

[0256]

TABLE-US-00004 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Example 2 1.1 1.5 1.7 1.2 1.3 1.3 1.2 1.5 1.7 1.2 1.3 1.3
All values in this table snow a negative induction level ot the biomarkers ot lower than a 2.0-fold induction at 10, 25 and 50% cytotoxicity in the absence and presence of rat S9 liver extract-based metabolizing systems and demonstrate that the crosslinker of example 2 shows weakly positive induction of genotoxicity.

EXAMPLE 3

[0257] Under a nitrogen atmosphere a mixture of 58.0 g (0.221 mole) Dicyclohexylmethane-4,4′-diisocyanate (H12MDI) and 0.58 g 3-methyl-1-phenyl-2-phospholene-1-oxide was heated while stirring to 150° C. The mixture was kept at 150° C. until NCO content was 16.4 wt %. Mixture was cooled to 80° C. and 53.04 g methoxypropyl acetate was added and stirred to homogeneous. 27.35 g Butylglycidylether/propylene imine adduct (0.146 mole) and 1 drop of dibutyltin dilaurate were added to the reaction mixture. The mixture was kept while stirring at 65° C. for 1 hour. 21.43 g (0.0286 mole) Poly(ethylene glycol) methyl ether average Mn 750 (MPEG 750) and a drop of dibutyltin dilaurate were added to the reaction mixture. The mixture was kept while stirring at 65° C. for 5 hours. FTIR showed a no isocyanate signal. 48.8 g methoxypropyl acetate was added. A yellow solution with a solid content of 50.0 wt % was obtained.

[0258] The reaction product is a mixture which contains a range of compounds having a structure according to claim 1.

[0259] This aziridine functional carbodiimide contains 1.4 meq per gram solids aziridine groups and 1.2 meq per gram solids carbodiimide groups resulting in a total of 2.6 meq acid reactive groups (i.e aziridine and carbodiimide functionality) per gram solids. The aziridine functional compound with the smallest (calculated) molar mass is the reaction product of butylglycidylether-propylene imine/H12MDI/butylglycidylether-propylene imine having a molar mass of 636.48

[0260] The structure of the smallest intrinsically formed aziridine functional byproduct compound is illustrated as:

##STR00042##

The calculated molecular weights of the theoretical main components was confirmed with Maldi-TOF-MS and are shown below with their structures:

##STR00043##

Calcd. [M+Na+]=877.65 Da; Obs. [M+Na+]=877.64 Da.

[0261] ##STR00044##

Calcd. [M+Na+]=1294.86 Da; Obs. [M+Na+]=1294.88 Da.

[0262] ##STR00045##

Calcd. [M+Na+]=1513.04 Da; Obs. [M+Na+]=1513.08 Da.

[0263] ##STR00046##

Calcd. [M+Na+]=1731.22 Da; Obs. [M+Na+]=1731.23 Da.

[0264] The following component with a mass below 600 Da was determined by LC-MS and quantified:

##STR00047##

was present in the composition at less than 0.01 wt %.

Genotoxicity Test

[0265]

TABLE-US-00005 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Example 3 1.3 1.7 1.5 1.2 1.3 1.1 1.4 1.6 1.6 1.2 1.4 1.2
All values in this table show a negative induction level of the biomarkers of lower than a 2.0-fold induction at 10, 25 and 50% cytotoxicity in the absence and presence of rat S9 liver extract-based metabolizing systems and demonstrate that the crosslinker of example 3 shows weakly positive induction of genotoxicity.

EXAMPLE 4

[0266] Under a nitrogen atmosphere a mixture of 58.0 g (0.221 mole) Dicyclohexylmethane-4,4′-diisocyanate (H12MDI) and 0.58 g 3-methyl-1-phenyl-2-phospholene-1-oxide was heated while stirring to 150° C. The mixture was kept at 150° C. until NCO content was 16.4 wt %. Mixture was cooled to 80° C. and 53.04 g methoxypropyl acetate was added and stirred to homogeneous. 27.95 g Butylglycidylether/propylene imine adduct (0.149 mole) and 1 drop of dibutyltin dilaurate were added to the reaction mixture. The mixture was kept while stirring at 65° C. for 1 hour. 25.0 g (0.025 mole) Jeffamine® M-1000 (obtained from Huntsman) was added to the reaction mixture. The mixture was kept while stirring at 65° C. for 15 minutes. FTIR showed a no isocyanate signal. 53.0 g methoxypropyl acetate was added. A yellow solution with a solid content of 50.0 wt % was obtained.

[0267] The reaction product is a mixture which contains a range of compounds having a structure according to claim 1.

[0268] This aziridine functional carbodiimide contains 1.4 meq per gram solids aziridine groups and 1.1 meq per gram solids carbodiimide groups resulting in a total of 2.5 meq acid reactive groups (i.e aziridine and carbodiimide functionality) per gram solids. The aziridine functional compound with the smallest (calculated) molar mass is the reaction product of butylglycidylether-propylene imine/H12MDI/butylglycidylether-propylene imine having a molar mass of 636.48 of which the structure is illustrated in example 3.

[0269] The calculated molecular weights of the theoretical main components was confirmed with Maldi-TOF-MS and are shown below with their structures:

##STR00048##

Calcd. [M+Na+]=877.65 Da; Obs. [M+Na+]=877.65 Da.

[0270] ##STR00049##

Calcd. [M+Na+]=1762.17; Obs. [M+Na+]=1762.20 Da.

[0271] The following component with a mass below 600 Da was determined by LC-MS and quantified:

##STR00050##

was present in the composition at less than 0.01 wt %.

Genotoxicity Test

[0272]

TABLE-US-00006 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Example 4 1.2 1.6 1.4 1.1 1.3 1.2 1.3 1.6 1.6 1.1 1.4 1.3
The genotoxicity test results show that the crosslinker composition of Example 4 only has weakly positive induced genotoxicity

EXAMPLE 5

[0273] Under a nitrogen atmosphere a mixture of 80.4 g (0.306 mole) of Dicyclohexylmethane-4,4′-diisocyanate (H12MDI), 33.4 g (0.0668 mole) Poly(ethylene glycol) methyl ether average Mn 500 (MPEG 500) and 0.02 g Bismuth Neodecanoate was heated to 65° C. while stirring. After 1 hour of reacting at 65° C., 0.80 g 3-methyl-1-phenyl-2-phospholene-1-oxide was added to the mixture. The mixture was heated while stirring to 150° C. The mixture was kept at 150° C. until NCO content was 2.7 wt %. Mixture was cooled to 80° C. and 11.4 g Butylglycidylether/propylene imine adduct (0.061 mole) and 1 drop of dibutyltin dilaurate were added to the reaction mixture. The mixture was kept while stirring at 80° C. for 1 hour. 177.8 g water was slowly added to the mixture while stirring. Mixture was cooled to RT. 2.5 g of a 15wt % solids potassiumhydroxide solution was added. A slightly hazy low viscous dispersion with a solid content of 39.3 wt % was obtained.

[0274] The reaction product is a mixture which contains a range of compounds having a structure according to claim 1.

[0275] This aziridine functional carbodiimide contains 0.5 meq aziridine groups per gram solids and 2.1 meq carbodiimide groups per gram solids resulting in a total of 2.6 meq acid reactive groups (i.e aziridine and carbodiimide functionality) per gram solids. The aziridine functional compound with the smallest (calculated) molar mass is the reaction product of butylglycidylether-propylene imine/H12MDI/butylglycidylether propylene imine having a molar mass of 636.48 of which the structure is illustrated in example 3.

[0276] The calculated molecular weights of the theoretical main components was confirmed with Maldi-TOF-MS and are shown below with their structures:

##STR00051##

Calcd. [M+Na+]=877.65 Da; Obs. [M+Na+]=877.64 Da.

[0277] ##STR00052##

Calcd. [M+Na+]=1074.73 Da; Obs. [M+Na+]=1074.72 Da.

[0278] The following component with a mass below 600 Da was determined by LC-MS and auantified:

##STR00053##

was present in the composition at less than 0.01 wt %.

Genotoxicity Test

[0279]

TABLE-US-00007 Without S9 rat liver extract With S9 rat liver extract Bscl 2 Rtkn Bscl 2 Rtkn concentration 10 25 50 10 25 50 10 25 50 10 25 50 Example 5 1.3 1.5 1.4 0.8 0.8 0.7 1.4 1.4 1.4 1.0 0.9 0.7
The genotoxicity test results show that the crosslinker composition of Example 5 is non-genotoxic.

Test Results of the Crosslinkers

Synthesis of P1, a Waterborne Polyurethane

[0280] A one-liter flask (equipped with a thermometer and an overhead stirrer), was charged with 29.9 grams of dimethylol propionic acid, 282.1 grams of a polypropylene glycol with a calculated average molecular weight (M) of 2000 Da and an OH-value of 56±2 mg KOH/g polypropylene glycol), 166.5 grams of a polypropylene glycol with a calculated average molecular weight (M) of 1000 Da and an OH-value of 112±2 mg KOH/g polypropylene glycol, and 262.8 grams of isophorone diisocyanate (the average molecular weight of each of the polyols is calculated from its OH-value according to the equation: M=2*56100/[OH-value in mg KOH/g polypropylene glycol). The reaction mixture was placed under N.sub.2 atmosphere, heated to 50° C. and subsequently 0.07 g dibutyltin dilaurate were added to the reaction mixture. An exothermic reaction was observed; however proper care was taken in order for the reaction temperature not to exceed 97° C. The reaction was maintained at 95° C. for an hour. The NCO content of the resultant polyurethane P1′ was 7.00% on solids as determined according to the ISO 14896 Method A (year 2009) (theoretically 7.44%) and the acid value of the polyurethane P1′ was 16.1±1 mg KOH/g polyurethane P1′. The polyurethane P1′ was cooled down to 60° C. and 18.7 grams of triethylamine were added, and the resulting mixture was stirred for 30 minutes. Subsequently, an aqueous dispersion of the polyurethane P1′ (the aqueous dispersion of the polyurethane P1′ is further referred to as P1) was prepared as follows: the thus prepared mixture of the polyurethane P1′ and triethylamine was fed—at room temperature over a time period of 60 minutes—to a mixture of 1100 grams of demineralized water, 19.5 grams of nonylphenol ethoxylate (9 ethoxylate groups), and 4.0 grams of triethylamine. After the feed was completed, the mixture was stirred for additional 5 minutes, and subsequently 111.2 grams of hydrazine (16 wt % solution in water) were added to the mixture. The aqueous dispersion of the polyurethane P1′ thus prepared was stirred for an additional 1 h and P1 was obtained.

Synthesis of A1, a Waterborne Acrylic Binder

[0281] A 2 L four-necked flask equipped with a thermometer and overhead stirrer was charged with sodium lauryl sulphate (30% solids in water, 18.6 grams of solution) and demineralized water (711 grams). The reactor phase was placed under N2 atmosphere and heated to 82° C. A mixture of demineralized water (112 grams), sodium lauryl sulphate (30% solids in water, 37.2 grams of solution), methyl methacrylate (174.41 grams), n-butyl acrylate (488.44 grams) and methacrylic acid (34.88 grams) was placed in a large feeding funnel and emulsified with an overhead stirrer (monomer feed). Ammonium persulphate (1.75 grams) was dissolved in demineralized water (89.61 grams) and placed in a small feeding funnel (initiator feed). Ammonium persulphate (1.75 grams) was dissolved in demineralized water (10.5 grams), and this solution was added to the reactor phase. Immediately afterwards, 5% by volume of the monomer feed was added to the reactor phase. The reaction mixture then exothermed to 85° C. and was kept at 85° C. for 5 minutes. Then, the residual monomer feed and the initiator feed were fed to the reaction mixture over 90 minutes, maintaining a temperature of 85° C. After completion of the feeds, the monomer feed funnel was rinsed with demineralized water (18.9 grams) and reaction temperature maintained at 85° C. for 45 minutes. Subsequently, the mixture was cooled to room temperature and brought to pH=7.2 with ammonia solution (6.25 wt. % in demineralized water), and brought to 40% solids with further demineralized water and A1 was obtained.

[0282] Both binders and the crosslinkers were combined in a stoichiometric ratio typically ranging from 0.25 to 1.0 stoichiometric amounts, this is the total amount of carboxylic acid reactive groups (i.e aziridine and carbodiimide functionality) versus the amount of carboxylic acid groups. The crosslinker was diluted 50/50 with water prior to adding to the binder. The effect of addition of the crosslinker is assessed by using spot tests on coating surfaces, based on procedures from the DIN 68861-1:2011 standard. The coating compositions were filtered and applied to Leneta test cards using 100 μm wire rod applicators. The films were then dried according to the conditions described below. Subsequently, a piece of cotton wool was soaked in 1:1 EtOH:demineralized water and placed on the film for 1 and 4 hours. Similarly, a water spot test was placed on the film for 16 hours. After removal of the cotton wool respectively spot liquid and 60 minutes recovery, the following results were obtained (a score of 0 indicates complete degradation of the film, 5 indicates no damage visible):

[0283] Test results after 1 day drying at 23±2° C. (stoichiometric amounts acid reactive groups crosslinker versus acid groups binder is 0.93):

TABLE-US-00008 Cross- EtOH EtOH Binder Cross- linker 50% 50% Water Binder amount linker amount Water (1 (4 (16 type (grams) type (grams) (grams) hr) hrs) hrs) P1 N/A No N/A 1 1 1 cross- linker P1 49.5 Compar- 0.8 4 4 4 ative Example 1 P1 46.2 Compar- 3.0 3.0 4 4 4 ative Example 2 P1 34.8 Example 1 3.0 3.0 4 4 4 P1 15.0 Example 2 1.2 1.2 4 3 5 P1 15.0 Example 3 1.2 1.2 4 3 4 P1 15.0 Example 4 1.2 1.2 4 3 4 P1 15.0 Example 5 1.5 1.5 4 3 4 A1 No 1 1 1 cross- linker A1 23.8 Compar- 0.8 4 4 4 ative Example 1 A1 22.9 Compar- 3.0 3.0 4 4 4 ative Example 2 A1 17.3 Example 1 3.0 3.0 4 4 4
Test results after 1 day drying at 23±2° C., overnight annealing at 80° C. and further drying for 1 day at 23±2° C. (stoichiometric amounts acid reactive groups crosslinker versus acid groups binder is 0.93):

TABLE-US-00009 Cross- EtOH EtOH Binder Cross- linker 50% 50% Water Binder amount linker amount Water (1 (4 (16 type (grams) type (grams) (grams) hr) hrs) hrs) P1 N/A No N/A 3 3 3 cross- linker P1 49.5 Compar- 0.8 4 4 4 ative Example 1 P1 46.2 Compar- 3.0 3.0 4 4 4 ative Example 2 P1 34.8 Example 1 3.0 3.0 4 4 4 A1 No 1 1 1 cross- linker A1 23.8 Compar- 0.8 4 4 4 ative Example 1 A1 22.9 Compar- 3.0 3.0 5 5 5 ative Example 2 A1 17.3 Example 1 3.0 3.0 5 5 5