Waterborne crosslinker composition

Abstract

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(CO)R or CH2-OR, 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. ##STR00001##

Claims

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: ##STR00041## whereby R.sub.1, R.sub.2, R.sub.3 and R.sub.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(CO)R or CH2-OR, 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(CO)R or CH2-OR , 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: ##STR00042## wherein n is the number of repeat units and is an integer from 1 to 50, X is O or NH, R.sub.7 and R.sub.8 are independently H or CH.sub.3 in each repeating unit, R.sub.9 is an aliphatic hydrocarbon group, and R.sub.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: ##STR00043## 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.

Description

EXAMPLE 1

(1) A round bottom flask equipped with a condensor was placed under a N.sub.2 atmosphere and charged with ethylene imine (50.0 gram), n-butyl glycidyl ether (108.0 gram) and K.sub.2CO.sub.3 (5.00 gram) and heated to 40 C. in 30 min, after which the mixture was stirred for 48 h at T=40 C. After filtration the excess of El was removed in vacuo, followed by further purification via vacuum distillation, resulting in a colorless low viscous liquid.

(2) 17.2 grams of the resulting material (1-(aziridin-1-yl)-3-butoxypropan-2-ol) was charged to a reaction flask equipped with a thermometer, together with 150 grams of dimethylformamide. The mixture was stirred with a mechanical upper stirrer under a nitrogen atmosphere and heated to 50 C. A solution of 20.0 grams of Desmodur N 3600 in 75 grams of dimethylformamide was then added to a feeding vessel. Then, 0.02 grams of bismuth neodecanoate was added to the reaction flask and the solution in the feeding vessel was then added dropwise in 30 minutes to the reaction flask, while keeping the reaction temperature constant at 50 C. After completion of the feed, the temperature was increased to 80 C. Samples were taken at regular intervals and the reaction progress was monitored using a Bruker Alpha FT-IR spectrometer until no change in NCO-stretch at 2200-2300 cm.sup.1 was observed. Subsequently, 0.64 grams of 1-butanol were added to the mixture, followed by further reaction to complete disappearance of aforementioned NCO-stretch peak. Evaporation of the solvent in vacuo yielded a yellowish highly viscous liquid.

(3) The calculated theoretical molecular weight of the main component was 1023.69 Da, chemical structure is shown below.

(4) ##STR00032##

(5) Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=1046.69 Da; Obs. [M+Na+]=1046.72 Da.

(6) The following components with a mass below 580 Da were determined by LC-MS and quantified:

(7) ##STR00033##
was present in the composition at 0.48 wt. % and

(8) ##STR00034##
was present at less than 0.01 wt. %.
Genotoxicity Test

(9) 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 Composition 1 1.1 1.1 1.0 1.0 1.0 0.9 1.1 1.1 1.2 1.0 1.1 1.1

(10) The genotoxicity test results show that the crosslinker composition of example 1 is non-genotoxic.

(11) Subsequently, 10 grams of the viscous liquid obtained in the previous step was mixed with 5 grams of acetone and incubated at 50 C. until a homogeneous solution was obtained. To this solution was added 0.03 grams of triethylamine (TEA) and then 2 grams of molten Maxemul 7101 dispersant. The resulting mixture was stirred for 5 minutes at room temperature using an IKA T25 Digital Ultra-Turrax mixer with S 25 N-18G head at 2,000 rpm. Then, stirring was increased to 10,000 rpm and 10 grams of demineralized water, brought to pH 11 using triethylamine, was added gradually to the mixture over 15 minutes. During this addition process, the mixer was moved around the reaction vessel continuously. After completion of the addition, the resulting dispersion was stirred at 5,000 rpm for 10 more minutes, and the pH of the dispersion was set to 11 with TEA.

(12) Functional performance and stability of the crosslinker dispersion were assessed using spot tests on coating surfaces, based on procedures from the DIN 68861-1 standard, and viscosity measurements using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm unless mentioned otherwise). For these tests, the crosslinker dispersion was stored in an oven at 50 C. for 4 weeks. Every week, the viscosity of the crosslinker dispersion was determined. Additionally, every week, 1.0 grams of the aged crosslinker dispersion was mixed with 10.5 grams of Polymer P1 under continuous stirring, and the resulting mixture was further stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 m wire rod applicators (Test 1). For reference, films were also cast from the same composition lacking the crosslinker dispersion (Test Blank). The films were dried for 1 hour at 25 C., then annealed at 50 C. for 16 hours. Subsequently, a piece of cotton wool was soaked in 1:1 EtOH: demineralized water and placed on the film for 1 hour. After removal of the EtOH and 60 minutes recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no damage visible):

(13) Performance and Stability Test

(14) TABLE-US-00002 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size 1 (nm) 191 222 224 216 212 Viscosity 1 (mPa .Math. s) 477 490 450 684 738 Test 1 3 3 3 3 3 Test Blank 1 1 1 1 1

(15) Performance of the synthesized compound as a crosslinker was further assessed using spot tests on coating surfaces with different binder systems.

(16) Waterborne acrylic binder A1 was synthesized as follows.

(17) 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 N.sub.2 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 (209.3 grams), n-butyl acrylate (453.56 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.

(18) For further spot tests, additional crosslinker dispersion, synthesized as described earlier, was stored in an oven at 50 C. for 4 weeks. Every week, 2.0 grams of the aged crosslinker dispersion was mixed with 10.5 grams of waterborne acrylic binder A1 under continuous stirring, and the resulting mixture was further stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 m wire rod applicators (Test 1-A1). For reference, a film was also cast from the same composition lacking the crosslinker dispersion (Blank-A1). The films were dried for 1 hour at 25 C., then annealed at 50 C. for 16 hours. Subsequently, a piece of cotton wool was soaked in 1:1 EtOH: demineralized water and placed on the film for 1 hour. After removal of the EtOH and 60 minutes recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no damage visible):

(19) TABLE-US-00003 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Test 1-A1 3 3 3 3 3 Blank-A1 1 1 1 1 1

COMPARATIVE EXAMPLE C1

(20) For Comparative Example 1, crosslinker CX-100-trimethylolpropane tris(2-methyl-1-aziridinepropionate)-was used:

(21) ##STR00035##
Genotoxicity Test

(22) 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 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

(23) The genotoxicity test results demonstrate that the crosslinker composition of Example C1 is genotoxic.

(24) Of this crosslinker, 7.5 grams was mixed with 3.75 grams of acetone and incubated at 50 C. until a homogeneous solution was obtained. To this solution was added 0.03 grams of triethylamine and then 0.75 grams of molten Atlas G-5000 dispersant. The resulting mixture was stirred for 5 minutes at room temperature using an IKA T25 Digital Ultra-Turrax mixer with S 25 N-18G head at 2,000 rpm. Then, stirring was increased to 10,000 rpm and 7.5 grams of demineralized water, brought to pH 11 using triethylamine (TEA), was added gradually to the mixture over 15 minutes. During this addition process, the mixer was moved around the reaction vessel continuously. After completion of the addition, the resulting mixture was stirred at 5,000 rpm for 10 more minutes, and the pH of the mixture was set to 11.

(25) Functional performance and stability of the crosslinker mixture were assessed using spot tests on coating surfaces, based on procedures from the DIN 68861-1 standard, and viscosity measurements using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm unless mentioned otherwise). For these tests, the crosslinker mixture was stored in an oven at 50 C. for 4 weeks. Every week, the viscosity of the crosslinker mixture was determined. Additionally, every week, 0.8 grams of the aged crosslinker mixture was mixed with 21 grams of Polymer P1 under continuous stirring, and the resulting coating composition was further stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 m wire rod applicators (Test C1). For reference, films were also cast from the same composition lacking the crosslinker mixture (Test Blank). The films were dried for 1 hour at 25 C., then annealed at 50 C. for 16 hours. Subsequently, a piece of cotton wool was soaked in 1:1 EtOH: demineralized water and placed on the film for 1 hour. After removal of the EtOH and 60 minutes recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no damage visible):

(26) Performance and Stability Test

(27) TABLE-US-00005 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C1 (nm) N/A * * * * Viscosity C1 (mPa .Math. s) 10 * * * * Test C1 5 * * * * Test Blank 1 1 1 1 1 *Crosslinker mixture gelled during first week of storage

COMPARATIVE EXAMPLE C2

(28) As example C1, where during the water addition step 7.5 grams of demineralized water, brought to pH 9 with TEA, was used instead of the demineralized water brought to pH 11, and the resulting mixture was set to pH 9 with TEA.

(29) Performance and Stability Test

(30) TABLE-US-00006 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C2 (nm) N/A * * * * Viscosity C2 (mPa .Math. s) 10 * * * * Test C2 5 * * * * Test Blank 1 1 1 1 1 *Crosslinker mixture gelled during first week of storage

COMPARATIVE EXAMPLE C3

(31) As example C1, where during the water addition step 7.5 grams of demineralized water, brought to pH 8 with TEA, was used instead of the demineralized water brought to pH 11, and the resulting mixture was set to pH 8 with TEA.

(32) Performance and Stability Test

(33) TABLE-US-00007 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C3 (nm) N/A * * * * Viscosity C3 20 * * * * (mPa .Math. s) Test C3 5 * * * * Test Blank 1 1 1 1 1 *Crosslinker mixture gelled during first week of storage

COMPARATIVE EXAMPLE C4

(34) 13.0 grams of 1-(2-hydroxyethyl)ethyleneimine and 175 grams of dimethylformamide were charged to a reaction flask equipped with a thermometer. The mixture was stirred with a mechanical upper stirrer under a nitrogen atmosphere. The mixture was than heated to 50 C., whereafter 0.03 grams of bismuth neodecanoate was charged to the reaction flask. Subsequently, a solution of 30.0 grams of Desmodur N 3600 in 87.5 grams of dimethylformamide was added over 30 minutes. After completion of the feed, the reaction temperature was increased to 80 C. Samples were taken at regular intervals and the reaction progress was monitored using a Bruker Alpha FT-IR spectrometer until no NCO-stretch at 2200-2300 cm.sup.1 was observed. The solvent was removed in vacuo to obtain a clear, colorless highly viscous liquid. The calculated molecular weight of the theoretical main component was 765.47 Da, chemical structure is shown below.

(35) ##STR00036##

(36) Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=788.46 Da; Obs. [M+Na+]=788.31 Da.

(37) Subsequently, 7.5 grams of the colorless liquid obtained in the previous step was mixed with 3.8 grams of acetone and incubated at 50 C. until a homogeneous solution was obtained. To this solution was added 0.03 grams of triethylamine (TEA) and then 0.8 grams of molten Maxemul 7101 dispersant. The resulting mixture was stirred for 5 minutes at room temperature using an IKA T25 Digital Ultra-Turrax mixer with S 25 N-18G head at 2,000 rpm. Then, stirring was increased to 10,000 rpm and 7.5 grams of demineralized water, brought to pH 11 using triethylamine, was added gradually to the mixture over 15 minutes. During this addition process, the mixer was moved around the reaction vessel continuously. After completion of the addition, the resulting dispersion was stirred at 5,000 rpm for 10 more minutes, and the pH of the dispersion was set to 11 with TEA. Already within 4 hours after conclusion of this 1-(2-hydroxyethyl)ethyleneimine based preparation, severe coagulation was observed. Hence, a storage stable dispersion was not obtained.

COMPARATIVE EXAMPLE C5

(38) Under a nitrogen atmosphere, 21.3 grams of 1-propanol was added over a period of 6 hours to 78.7 grams of isophorone diisocyanate (IPDI) and 0.01 grams of tin 2-ethyl hexanoate at 20-25 C., while stirring. After standing overnight, 196.3 grams of IPDI, 74.1 grams of Tegomer D3403 and 2.4 grams of 3-Methyl-1-phenyl-2-phospholene-1-oxide were added. The mixture was heated to 150 C. while stirring. The mixture was kept at 150 C. until NCO content was 7.0 wt %. Mixture was cooled to 80 C. and 333 grams of 1-methoxy-2-propyl acetate (MPA) 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.

(39) To 100 grams of this isocyanate functional polycarbodiimide was added 7.0 grams of 1-(2-hydroxyethyl)ethyleneimine. 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 grams of MPA, 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. The generalized structure of this carbodiimide is depicted below.

(40) ##STR00037##
in which a, b and c indicates repeating units.

(41) This generalized structure was confirmed by MALDI-TOF-MS, an example is shown below:

(42) ##STR00038##

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

(44) Genotoxicity Test Results:

(45) TABLE-US-00008 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 Composition 1.3 1.5 1.6 1.2 1.9 1.9 1.2 1.4 1.5 2.0 2.0 1.8 C5

(46) The genotoxicity test results demonstrate that the crosslinker composition of Example C5 is genotoxic.

(47) Subsequently, 25.0 grams of the yellow solution obtained in the previous step was stirred for at room temperature using a three-bladed propeller stirrer with diameter 50 mm at 500 rpm. Then, 25.0 grams of demineralized water was added gradually to the mixture over 15 minutes. After completion of the addition, the resulting dispersion was stirred at 500 rpm for 5 more minutes.

(48) Functional performance and stability of the crosslinker dispersion were assessed using spot tests on coating surfaces, based on procedures from the DIN 68861-1 standard, and viscosity measurements using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm unless mentioned otherwise). For these tests, the crosslinker dispersion was stored in an oven at 50 C. for 4 weeks. Every week, the viscosity of the crosslinker dispersion was determined. Additionally, every week, 5.1 grams of the aged crosslinker dispersion was mixed with 10.5 grams of Polymer P1 under continuous stirring, and the resulting mixture was further stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 m wire rod applicators (Test C7). For reference, films were also cast from the same composition lacking the crosslinker dispersion (Test Blank). The films were dried for 1 hour at 25 C., then annealed at 50 C. for 16 hours. Subsequently, a piece of cotton wool was soaked in 1:1 EtOH: demineralized water and placed on the film for 1 hour. After removal of the EtOH and 60 minutes recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no damage visible):

(49) Performance and Stability Test

(50) TABLE-US-00009 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C5 (nm) 76 * * * * Viscosity C5 (mPa .Math. s) 812 * * * * Test C5 4 * * * * Test Blank 1 1 1 1 1 *Crosslinker mixture coagulated during first week of storage

COMPARATIVE EXAMPLE C8

(51) A 1 L round bottom flask equipped with a thermometer and overhead stirrer was placed under a N.sub.2 atmosphere and charged with 196.1 grams of polytetrahydrofuran with an average Mn of 1000 Da (pTHF1000) and 200.0 grams of o-xylene. The resulting mixture was cooled to 10 C. using ethanol and ice, after which a solution of 68.4 grams of toluene diisocyanate (TDI) in 50.0 grams of o-xylene was added. The mixture was allowed to exotherm bringing the mixture to 1 C., followed by a gradual rise to room temperature without added heating. The reaction was continued to full conversion (residual NCO of 3.2%), and 200 grams of the resulting reaction mixture was transferred to a 500 mL round bottom flask equipped with a thermometer and overhead stirrer under a N.sub.2 atmosphere. To this mixture was then added 14.5 grams of 1-(2-hydroxyethyl)ethyleneimine over 60 minutes, maintaining room temperature using a water bath. The mixture was then stirred for 1 hour at 25 C. Then, samples were taken at regular intervals and the reaction progress was monitored using a Bruker Alpha FT-IR spectrometer until no NCO-stretch at 2200-2300 cm.sup.1 was observed. Solids was set to 49% using further o-xylene, resulting in a slightly turbid low-viscous solution.

(52) The calculated molecular weights of the theoretical main components and their chemical structures are shown below:

(53) ##STR00039##

(54) Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=1427.91 Da; Obs. [M+Na+]=1428.02 Da.

(55) ##STR00040##

(56) Molecular weight was confirmed by Maldi-TOF-MS: Calcd. [M+Na+]=371.17 Da; Obs. [M+Na+]=371.21 Da.

(57) Subsequently, 18.0 grams of the low-viscous solution obtained as described above was mixed with 1.5 grams of Triton X-100 and incubated at 50 C. until a homogeneous solution was obtained. The resulting mixture was stirred for 30 minutes at room temperature using a three-bladed propeller stirrer with diameter 50 mm at 500 rpm. Then, stirring was increased to 800 rpm and 15.0 grams of demineralized water was added gradually to the mixture over 15 minutes. After completion of the addition, the resulting dispersion was stirred at 500 rpm for 10 more minutes.

(58) Functional performance and stability of the crosslinker dispersion were assessed using spot tests on coating surfaces, based on procedures from the DIN 68861-1 standard, and viscosity measurements using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm unless mentioned otherwise). For these tests, the crosslinker dispersion was stored in an oven at 50 C. for 4 weeks. Every week, the viscosity of the crosslinker dispersion was determined. Additionally, every week, 2.8 grams of the aged crosslinker dispersion was mixed with 10.5 grams of Polymer P1 under continuous stirring, and the resulting mixture was further stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 m wire rod applicators (Test C8). For reference, films were also cast from the same composition lacking the crosslinker dispersion (Test Blank). The films were dried for 1 hour at 25 C., then annealed at 50 C. for 16 hours. Subsequently, a piece of cotton wool was soaked in 1:1 EtOH: demineralized water and placed on the film for 1 hour. After removal of the EtOH and 60 minutes recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no damage visible):

(59) Performance and Stability Test

(60) TABLE-US-00010 Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C8 (nm) 1387.sup. 423.sup. * * * Viscosity C8 (mPa .Math. s) 4032 600 * * * Test C8 3 3 * * * Test Blank 1 1 1 1 1 *Crosslinker mixture gelled during second week of storage .sup.A reliable particle size measurement could not be obtained for this sample