WATER-BASED CROSSLINK COMPOSITION.

Abstract

The present invention relates to a multiaziridine crosslinking composition, characterized in that the composition is an aqueous dispersion having a pH ranging from 9 to 14 and comprising a multiaziridine compound in dispersed form, wherein such multiaziridine compound has: a. from 2 to 6 of the following structural units A: (see Formula) (A) wherein R1, R2, R3 and R4 are H m is 1, R' and R'' are in accordance with (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'''', wherein 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'' together form a saturated cycloaliphatic hydrocarbon group containing from 5 to 8 carbon atoms; b.one or more linking chains where each of these linking chains links two of the structural units A; and c. a molecular weight in the range of 600 to 10000 Daltons.

Description

WATER-BASED CROSSLINK COMPOSITION The present invention relates to multiaziridine crosslinking compositions which can be used for crosslinking polymers with carboxylic acid functional groups dissolved and / or dispersed in an aqueous medium. Coatings provide protection, aesthetic appeal, and new functionalities to a wide range of substrates with enormous industrial and domestic relevance. In this context, the need for coatings with enhanced resistances, such as stain and solvent resistance, improved mechanical properties, and enhanced adhesive strength, is constantly growing. One or more of these properties can be enhanced through crosslinking. For many years, numerous crosslinking mechanisms have been studied for polymeric binders and water-based latex polymer dispersions. The most useful are isocyanate crosslinking of hydroxyl-functional polymers, carbodiimide crosslinking of carboxylic acid-functional polymers, melamine crosslinking, epoxy crosslinking, and aziridine crosslinking of carboxylic acid-functional polymers. Water-based binders are generally colloidally stabilized by carboxylic acid groups, and the coating properties can be improved by using carbodiimide or aziridine crosslinkers, as these react with the polymer's carboxylic acid fractions to form a crosslinked network. Of the prior art crosslinkers mentioned above, aziridine crosslinkers are the most versatile for room-temperature curing of polymers with the carboxylic acid functional group. Traditional crosslinking strategies generally involve the use of low molecular weight reactive organic molecules, sometimes dissolved in volatile organic solvents to reduce viscosity. This facilitates the precise dosage and mixing of the crosslinker into the polymer composition to be crosslinked. Good miscibility of the crosslinker with the polymer composition is important for both the final properties (poor miscibility tends to result in inefficient crosslinking) and the material's effectiveness and user convenience. However, the use of volatile organic solvents to reduce viscosity is undesirable because it increases VOC (volatile organic compound) levels. Furthermore, the presence of solvents in the crosslinking composition would limit the formulation latitude of the coating composition formulator and is therefore undesirable.Therefore, supplying multiaziridine crosslinkers in water would be beneficial. At the same time, it is necessary to maintain the crosslinker's performance, in terms of crosslinking efficiency and storage stability, to ensure its continued commercial viability in a variety of polymer resins. However, prior art multiaziridine crosslinkers lack stability in aqueous media. For example, CX-100 (trimethylolpropane Tris(2-methyl-1-aziridinpropionate), CAS No. 64265-57-2) and XAMA-7 (pentaerythritol tris[3-(1-aziridinyl)propionate], CAS No. 57116-45-7) provide a very efficient reaction with carboxylic acids, but these crosslinkers are unstable in water and therefore have a limited stability period in water. This is described, for example, in US-A-5133997. Furthermore, these polyaziridines have an unfavorable genotoxic profile. The objective of the present invention is to provide multiaziridine crosslinkers which can be supplied and stored in water with a longer stability period, while maintaining sufficient reactivity towards polymers with the carboxylic acid functional group. This objective was surprisingly achieved by providing a multiaziridine crosslinking composition, characterized in that the composition is an aqueous dispersion having a pH ranging from 9 to 14 and comprising a multiaziridine compound in dispersed form, wherein such multiaziridine compound has: a. 2 to 6 of the following structural units A: QPRQnn / zznz / E / YiAiR4R3 (A) where Ri, R2, R3 and FU are H m is 1, R' and R" are in accordance with (1) or (2): (1) R'= H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, and R”= an alkyl group containing 1 to 4 carbon atoms, CH2-O-(C=O)-R”' or CH2-OR””, where R'' is an alkyl group containing 4 to 12 carbon atoms and R”” is an alkyl group containing 1 to 14 carbon atoms, (2) R' and R” together form a saturated cycloaliphatic hydrocarbon group containing 5 to 8 carbon atoms; b. one or more linking chains where each of these linking chains links two of the structural units A; and c. a molecular weight in the range of 600 to 10000 Daltons. Surprisingly, the aqueous crosslinking composition of the present invention has been found to have long-term storage stability while simultaneously maintaining good crosslinking efficacy towards polymers with the carboxylic acid functional group, particularly in aqueous dispersions of polymers with the carboxylic acid functional group. The compositions according to the invention exhibit an effective reaction with carboxylic acid groups at room temperature. The aqueous nature of the compositions of the invention also makes them easy to use; their aqueous nature provides good compatibility with water-based binders and thus good mixing and low scale formation during formulation. Furthermore, these compositions generally have low viscosities, resulting in easy handling and accurate dosing.The stability in prolonged storage in water, combined with a more favorable risk profile, allows coating manufacturers and applicators to easily and safely store and use the crosslinking composition in 2K two-component coating systems, where the binder and crosslinker are mixed shortly before application. US-A-3523750 describes a process for modifying protein substrates, such as wool, with a multiaziridine compound. US-A-5258481 describes water-dispersible multifunctional crosslinking agents, which are oligomeric materials containing carbodiimide functional groups and reactive functional groups other than the carbodiimide functional group. US-A-5241001 discloses multiaziridine compounds obtained by reacting 1-(2-hydroxyethyl)-ethyleneimine with a polyisocyanate. For all upper and / or lower limits of any interval provided herein, the limit value is included in the provided interval, unless specifically stated otherwise. Thus, when it says from “x” to “y”, it means that it includes “x” and “y” and also all intermediate values. The term coating composition, as used herein, encompasses, but is not limited to, paint, coating, varnish, adhesive, and ink compositions. The term aliphatic hydrocarbon group refers to an optionally branched alkyl, alkenyl, or alkynyl group. The term cycloaliphatic hydrocarbon group refers to a cycloalkyl or cycloalkenyl group optionally substituted with at least one aliphatic hydrocarbon group. The term aromatic hydrocarbon group refers to a benzene ring optionally substituted with at least one aliphatic hydrocarbon group. These optional aliphatic hydrocarbon group substituents are preferably alkyl groups. Examples of cycloaliphatic hydrocarbon groups with seven carbon atoms are cycloheptyl and cyclohexyl substituted with methyl. An example of an aromatic hydrocarbon group with seven carbon atoms is a methyl-substituted phenyl group.Examples of aromatic hydrocarbon groups with 8 carbon atoms are xylyl and ethyl-substituted phenyl. An aziridinyl group has the following structural formula: ^r / X-R3 R4 Multiaziridine compound While the structural A units present in the multiaziridine compound may independently have different R' and / or R, the structural A units present in the multiaziridine compound are preferably identical to each other. Preferably, R' is H and R is an alkyl group containing 1 to 4 carbon atoms, CH2-O-(C=O)-R or CH2-OR, where R' is an alkyl group containing 3 to 12 carbon atoms, preferably 4 to 12 carbon atoms, such as neopentyl or neodecyl. Most preferably, R' is a branched Cg alkyl group. R””” is an alkyl group containing 1 to 14 carbon atoms, preferably 1 to 12 carbon atoms. Examples, not limited to R, include ethyl, butyl, and 2-ethylhexyl. The multiaziridine compound containing 2 to 6 of the A structural units, preferably 2 to 4 of the A structural units, more preferably 2 to 3 A structural units. The multiaziridine compound comprises one or more linking chains, each linking chain linking two of the structural units A. The linking chains in the multiaziridine compound preferably consist of 4 to 300 atoms, more preferably 5 to 250, more preferably 6 to 100 atoms, and most preferably 6 to 20 atoms. The atoms in the linking chains are preferably C and optionally N, O, S, and / or P, or preferably C and optionally N and / or O. The linking chains are preferably a set of covalently connected atoms consisting of i) carbon atoms, ii) carbon and nitrogen atoms, or iii) carbon, oxygen, and nitrogen atoms. A linking chain is defined as the shortest chain of consecutive atoms that links two structural units A. The following drawings show examples of multiaziridine compounds and the linking chains between two structural units A. QPRQnn / zznz / E / YiAi ρρβοηη / ζζηζ / Ε / γίΛΐ Any two structural units A present in the multiaziridine compound are linked by a bonding chain as defined herein. Therefore, each structural unit A present in the multiaziridine compound is linked to each of the other structural units A via a bonding chain as defined herein. If the multiaziridine compound has two structural units A, the compound has one such bonding chain linking these two structural units. In the case of a multiaziridine compound having three structural units A, the multiaziridine compound has three linking chains, where each of the three linking chains links one structural unit A to another structural unit A, i.e., a first structural unit A is linked to a second structural unit A, through a linking chain and the first and second structural units A are both independently linked to a third structural unit A, through their respective linking chains. The following drawings show an example of a multiaziridine compound that has three A structural units, the three linking chains so that each of the three linking chains links two A structural units. ρρβοηη / ζζηζ / Ε / γίΛΐ Multiaziridine compounds with more than two A structural units have a number of linkage chains according to the following equation: LC = {(AN-1) × AN} / 2, where LC = is the number of linkage chains and AN = the number of structural units A in the multiaziridine compound. So, for example, if there are 5 structural units A in the multiaziridine compound, AN = 5; which means there are {(5-1) × 5} / 2 = 10 linkage chains. The molecular weight of the multiaziridine compound according to the invention is preferably from 600 to 5000 Daltons. The molecular weight of the multiaziridine compound according to the invention is preferably at most 3800 Daltons, more preferably at most 3600 Daltons, more preferably at most 3000 Daltons, more preferably at most 2300 Daltons, and even more preferably at most 1600 Daltons. The molecular weight of the multiaziridine compound according to the invention is preferably at least 700 Daltons, more preferably at least 800 Daltons, even more preferably at least 840 Daltons, and most preferably at least 1000 Daltons. As used herein, the molecular weight of the multiaziridine compound is the calculated molecular weight. The calculated molecular weight is obtained by summing the atomic masses of all the atoms present in the structural formula of the multiaziridine compound.If the multiaziridine compound is present in a composition comprising more than one multiaziridine compound according to the invention, for example, when one or more of the starting materials for preparing the multiaziridine compound is a mixture, the molecular weight calculation can be performed for each compound individually present in the composition. The molecular weight of the multiaziridine compound according to the invention can be measured using MALDI-TOF mass spectrometry, as described in the experimental section below. The multiaziridine compound preferably comprises one or more connecting groups, wherein each of these connecting groups connects two of the structural units A and wherein each of these connecting groups consists of at least one functional group selected from the group consisting of an aliphatic hydrocarbon functional group (preferably containing 1 to 8 carbon atoms), a cycloaliphatic hydrocarbon functional group (preferably containing 4 to 10 carbon atoms), an aromatic hydrocarbon functional group (preferably containing 6 to 12 carbon atoms), an isocyanurate functional group, an iminooxadiazindione functional group, an ether functional group, an ester functional group, an amide functional group, a carbonate functional group, a urethane functional group, a urea functional group, a biuret functional group, an allophanate functional group, a urethdione functional group, and any combination thereof.More preferably, the connecting groups are an array of consecutive functional groups whereby each functional group is selected from the group consisting of aliphatic hydrocarbon functional group (preferably containing 1 to 8 carbon atoms), cycloaliphatic hydrocarbon functional group (preferably containing 4 to 10 carbon atoms), aromatic hydrocarbon functional group (preferably containing 6 to 12 carbon atoms), isocyanurate functional group, iminooxadiazindione functional group, ether functional group, ester functional group, amide functional group, carbonate functional group, urethane functional group, urea functional group, biuret functional group, allophanate functional group, and urethdione functional group. The term aliphatic hydrocarbon functional group refers to optionally branched alkyl, alkenyl, and alkynyl groups. While the optional branches of the carbon atoms are part of the connecting group, they are not part of the linking chain. The term cycloaliphatic hydrocarbon functional group refers to cycloalkyl and cycloalkenyl groups optionally substituted with at least one aliphatic hydrocarbon functional group. While the optional substituents of the functional groups of QPRQnn / zznz / E / YiAi aliphatic hydrocarbons are part of the connecting group, not part of the linking chain. These optional aliphatic hydrocarbon functional group substituents are preferably alkyl groups. The term aromatic hydrocarbon group refers to a benzene ring optionally substituted with at least one aliphatic hydrocarbon group. While the optional substituents of the aliphatic hydrocarbon functional groups are part of the connecting group, they are not part of the linking chain. The substituents of the optional aliphatic hydrocarbon functional group are preferably alkyl groups. o / N “ N \ O ' N ' O An isocyanurate functional group is defined as — YNyNy An iminooxadiazindione functional group is defined as 0o or / NNN\ H H A Bluret functional group is defined as — oo / NN “ O u An allophanate functional group is defined as. - either vN A urethdione functional group is defined as... QQAQnn / ZZΖ / Β / YILI The following drawing shows in bold a connecting group for an example of a multiaziridine compound as defined herein. In this example, the connecting group linking two of the structural units A consists of the array of the following consecutive functional groups: functional group 1 of an aliphatic hydrocarbon (a linear C6H12), functional group 2 of an isocyanurate (a cyclic C3N3O3), and functional group 3 of an aliphatic hydrocarbon (a linear CeHi2). ορβοηη / ζζηζ / Ε / γίΛΐ The following drawing shows in bold a connecting group for the following example of a multiaziridine compound as defined herein. In this example, the connecting group linking the two structural units A consists of the array of the following consecutive functional groups: functional group 1 of an aliphatic hydrocarbon (a linear CeHi2), functional group 2 of an isocyanurate (a cyclic C3N3O3), and functional group 3 of an aliphatic hydrocarbon (a linear CeHi2). Any of the two structural units A present in the multiaziridine compound as defined herein are preferably connected via a connecting group as defined herein. Accordingly, each structural unit A present in the multiaziridine compound is preferably connected to each of the other structural units A with a connecting group as defined herein. If the multiaziridine compound has two structural units A, the multiaziridine compound has such a connecting group connecting these two structural units. If the multiaziridine compound has three structural units A, the multiaziridine compound has three such connecting groups, each of the three connecting groups connecting one structural unit A to another structural unit A. The following diagram shows, for an example of a multiaziridine compound having three structural units A, the three connecting groups such that each of the three connecting groups connects two structural units A. A connecting group consists of the array of the following consecutive functional groups: functional group 1 of aliphatic hydrocarbon (a linear CeHi2), isocyanurate 2 (a cyclic C3N3O3) and functional group 3 of aliphatic hydrocarbon (a linear CeHi2) connecting the structural units A which are labeled A1 and A2.For the connection between structural units A which are labeled A1 and A3, the connecting group consists of the matrix of the following consecutive functional groups: functional group 1 of aliphatic hydrocarbon (a linear CeHi2), isocyanurate 2 (a cyclic C3N3O3) and functional group 4 of aliphatic hydrocarbon (a linear CeHi2), while for the connection between structural units A which are labeled A2 and A3, the connecting group consists of the matrix of the following consecutive functional groups: functional group 3 of aliphatic hydrocarbon (a linear CeHi2), isocyanurate 2 (a cyclic C3N3O3) and functional group 4 of aliphatic hydrocarbon (a linear CeHi?). Preferably, the connecting groups consist of at least one functional group selected from the group consisting of an aliphatic hydrocarbon functional group (preferably containing 1 to 8 carbon atoms), a cycloaliphatic hydrocarbon functional group (preferably containing 4 to 10 carbon atoms), an aromatic hydrocarbon functional group (preferably containing 6 to 12 carbon atoms), an isocyanurate functional group, an iminooxadiazindione functional group, a urethane functional group, a urea functional group, a biuret functional group, and any combination thereof. The connecting groups preferably contain an isocyanurate functional group, an iminooxadiazindione functional group, a biuret functional group, an allophanate functional group, or a urethdione functional group. More preferably, the connecting groups contain an isocyanurate functional group or an iminooxadiazindione functional group.For clarity, the multiaziridine compound can be obtained from the reaction product of one or more suitable compounds B as defined later in this document and a hybrid isocyanurate such as, for example, an HDI / IPDI isocyanurate, resulting in a multiaziridine compound with a connecting group consisting of the array of the following consecutive functional groups: a linear CeHi2 (i.e., an aliphatic hydrocarbon functional group with 6 carbon atoms), an isocyanurate functional group (a cyclic C3N3O3), and (i.e., a cycloaliphatic hydrocarbon functional group with 9 carbon atoms and an aliphatic hydrocarbon functional group with 1 carbon atom).Even more preferably, the connecting groups consist of the following functional groups: at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and in addition an isocyanurate functional group or an iminooxadiazindione functional group. In connecting groups, one or more substituents may be present as dangling groups on the connecting group, as shown in bold, for example, in the following multiaziridine compound. These dangling groups are not part of the connecting groups. ορβοηη / ζζηζ / Ε / γίΛΐ Hir7 The pendant group preferably contains Rs, wherein X, Ry, Re, n' and Rio are as described below. In one embodiment of the invention, the multiaziridine compound comprises one or more connecting groups wherein each of these connecting groups connects two of the structural units A, wherein the connecting groups consist of (i) at least two aliphatic hydrocarbon functional groups or at least two cycloaliphatic hydrocarbon functional groups and (ii) an isocyanurate functional group or an iminooxadiazindione functional group, and wherein a pendant group is present in a connecting group, the pendant group having the following structural formula: or r7HUnn' is the number of repeating units and is an integer from 1 to 50, preferably from 2 to 30, more preferably from 5 to 20. X is O or NH, preferably X is O, Ry and Re are independently H or CH3 in each repeating unit, Rg is an aliphatic hydrocarbon group, preferably containing 1 to 8 carbon atoms, or a cycloaliphatic hydrocarbon group, preferably containing 4 to 10 carbon atoms, and Rio contains at most 20 carbon atoms and is an aliphatic, cycloaliphatic, or aromatic hydrocarbon group, or a combination thereof. In a preferred embodiment, R₁ and Re are H. In another more preferred embodiment, one of Ry and R₂ is H, and the other Ry or R₂ is CH₃. R₁₀ is preferably an aliphatic hydrocarbon group containing 1 to 20 carbon atoms (preferably CH₃), a cycloaliphatic hydrocarbon group containing 5 to 20 carbon atoms, or an aromatic hydrocarbon group containing 6 to 20 carbon atoms. The presence of the pendant group results in a decrease in the viscosity of the multiaziridine compound and, therefore, greater ease of dispersion in the aqueous medium. In this embodiment, the multiaziridine compound preferably contains structural units A.In this embodiment, the connecting group preferably consists of the array of the following consecutive functional groups: a first cycloaliphatic hydrocarbon functional group, an isocyanurate functional group or an aminooxadiazindione functional group and a second cycloaliphatic hydrocarbon functional group and Rg is a cycloaliphatic hydrocarbon group, so that the first and second cycloaliphatic hydrocarbon functional group and Rg are identical, more preferably the connecting group consists of the array of the following consecutive functional groups: a first aliphatic hydrocarbon functional group, an isocyanurate functional group or an aminooxadiazindione functional group and a second aliphatic hydrocarbon functional group and Rg is an aliphatic hydrocarbon group, so that the first and second aliphatic hydrocarbon functional group and Rg are identical. In a preferred embodiment of the invention, the connecting groups present in the multiaziridine compound as defined herein consist of the following functionalities: (i) at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and (ii) optionally at least one aromatic hydrocarbon functional group and (iii) optionally an isocyanurate functional group or an aminooxadiazindione functional group or an allophanate functional group or a urethdione functional group. Preferably, the connecting groups present in the multiaziridine compound of the invention consist of the following functionalities: (i) at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and (iii) optionally at least one aromatic hydrocarbon functional group and (iii) optionally an isocyanurate functional group or an aminooxadiazindione functional group.A very suitable way to obtain such a multiaziridine compound is to react compound B with the following structural formula:. R' r2*3 r4 Where R-ι, R2, R3, R4, R', and R” and their preferred groups as defined above, with an aliphatic polyisocyanate. The term aliphatic polyisocyanate refers to compounds in which all isocyanate groups are directly bonded to aliphatic or cycloaliphatic hydrocarbon groups, regardless of whether aromatic hydrocarbon groups are also present. The aliphatic polyisocyanate may be a mixture of aliphatic polyisocyanates. Compounds based on aliphatic polyisocyanates have a lower tendency to yellow over time compared to a similar compound based on aromatic polyisocyanates. The term aromatic polyisocyanate refers to ορβοηη / ζζηζ / Ε / γίΛΐ compounds in which all isocyanate groups are directly attached to benzene or naphthalene groups, regardless of whether aliphatic or cycloaliphatic groups are also present. The preferred polyisocyanates with aliphatic reactivity are pentamethylene 1,5-diisocyanate (PDI), hexamethylene 1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (H12MDI), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, tetramethylxylene diisocyanate (TMXDI) (all isomers) and higher molecular weight variants such as their isocyanurates, allophanates or iminooxadiazidiones.In this embodiment, the connecting groups preferably consist of the array of the following consecutive functional groups: aliphatic hydrocarbon functional group, aromatic hydrocarbon functional group and aliphatic hydrocarbon functional group (e.g., when TMXDI is used to prepare the multiaziridine compound) or the connecting groups consist of the array of the following consecutive functional groups: cycloaliphatic hydrocarbon functional group, aliphatic hydrocarbon functional group and cycloaliphatic hydrocarbon functional group (e.g., when H12MDI is used to prepare the multiaziridine compound) or, more preferably, the connecting groups consist of the array of the following consecutive functional groups: aliphatic hydrocarbon functional group, isocyanurate functional group or iminooxadiazindione functional group and aliphatic hydrocarbon functional group.Most preferably, in this embodiment, the connecting group consists of the array of the following consecutive functional groups: aliphatic hydrocarbon functional group, isocyanurate functional group, and aliphatic hydrocarbon functional group (e.g., when using hexamethylene 1,6-diisocyanate isocyanurate and / or pentamethylene 1,5-diisocyanate to prepare the multiaziridine compound). Preferably the number of consecutive C atoms and, optionally, O atoms between the N atom of the urethane group in one structural unit A and the next N atom which is present in the linking chain or which is the N atom of the urethane group of another structural unit A is at most 9, as shown, for example, in the following multiaziridine compound having 2 structural units A. QPRQnn / zznz / E / YiAi QPRQnn / zznz / E / YiAi The multiaziridine compound preferably contains at least 5 wt%, more preferably at least 5.5 wt%, more preferably at least 6 wt%, more preferably at least 9 wt%, more preferably at least 12 wt%, and preferably less than 25 wt%, preferably less than 20 wt% of urethane linkages. The multiaziridine compound preferably has an aziridine equivalent weight (molecular weight of the multiaziridine compound divided by the number of aziridinyl groups present in the multiaziridine compound) of at least 200, more preferably at least 230, and even more preferably at least 260 Daltons, and preferably at most 2500, more preferably at least 1000, and even more preferably at most 500 Daltons. The multiaziridine compound is preferably obtained by reacting at least one polyisocyanate and a compound B as defined above with the following structural formula: R4 Therefore, the molar ratio between compound B and the polyisocyanate is 2:6, more preferably 2:4, and even more preferably 2:3, where m, R', R, Ri, R2, R3, and R4 are as defined above. The reaction of the polyisocyanate with compound B can be carried out by contacting equivalent amounts of the polyisocyanate with compound B at a temperature in the range of 0 to 110 °C, more suitablely 20 °C to 110 °C, more suitablely 40 °C to 95 °C, and even more suitablely 60 to 85 °C, in the presence of, for example, a tin catalyst such as dibutyltin dilaureate or a bismuth catalyst such as bismuth neodecanoate. A solvent such as dimethylformamide (DMF), acetone, and / or methyl ethyl ketone can be used. The polyisocyanate contains at least 2 isocyanate groups, preferably at least 2.5 isocyanate groups on average, and more preferably at least 2.8 isocyanate groups on average.Polyisocyanate mixtures can also be used as starting materials. The preferred polyisocyanates are those with aliphatic reactivity. The term "aliphatic reactive polyisocyanate" refers to compounds in which all isocyanate groups are directly bonded to aliphatic or cycloaliphatic hydrocarbon groups, regardless of whether aromatic hydrocarbon groups are also present. An aliphatic reactive polyisocyanate can be a mixture of polyisocyanates with aliphatic reactivity.The preferred polyisocyanates with aliphatic reactivity are pentamethylene 1,5-diisocyanate (PDI), hexamethylene 1,6-diisocyanate (HDI), isophorone diisocyanate (I PDI), dicyclohexylmethane 4,4'-diisocyanate (H12MDI), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, p-tetramethylxylene diisocyanate (p-TMXDI) and its meta-isomer, and higher molecular weight variants such as, for example, its isocyanurates or iminooxadiazindiones or allophanates or urethdiones. The most preferred polyisocyanates with aliphatic reactivity are dichlorohexylmethane 4,4'-diisocyanate (H12MDI), m-TMXDI, hexamethylene 1,6-diisocyanate isocyanurate, iminooxadiazindione, allophanate, or urethione, and pentamethylene 1,5-diisocyanate isocyanurate. A suitable HDI containing an iminooxadiazindione trimer is Desmodur® N3900, available from Covestro. A suitable HDI containing allophanate is Desmodur® XP2860, also available from Covestro.A suitable HDI containing urethdione is Desmodur® N3400, which can be obtained from Covestro. Suitable HDI-based isocyanurate trimers can be obtained, for example, from Covestro (Desmodur® N3600), Vencorex (Tolonate™ HDT LV), Asahi Kasei (Duranate™ TPA-100), Evonik (Vestanat® HT2500 / LV), and Tosoh (Corónate® HXR LV). Methods for preparing compound (B) and its derivatives are known in the art. For example, the synthesis of 1-(2-methylaziridin-1-yl)propan-2-ol is described by S. Lesniak, M. Rachwalski, S. Jarzynski, and E. Obijalska in Tetrahedron Asymm. 2013, 24, 1336–1340. The synthesis of 1 -(aziridin-1 yl)propan-2-ol is described by A. Baklien, Μ. V. Leeding, J. Kolm Aust. J. Chem. 1968, 21, 1557-1570. The multiaziridine compound can also be obtained by reacting at least one compound B with a polyisocyanate as defined above and a polyol and / or a polyamine. The multiaziridine compound can also be obtained by reacting the polyisocyanate as defined above with a polyol and / or a polyamine and then reacting the resulting compound with compound B. The multiaziridine compound can also be obtained by reacting compound B with the polyisocyanate and then reacting the resulting compound with a polyol and / or a polyamine. The multiaziridine compound can also be obtained by reacting at least one compound B with an isocyanate-terminating polyurethane and / or a urea polyurethane. The (urea) isocyanate-terminating polyurethane is obtained by reacting at least one polyol and / or polyamine with at least one polyisocyanate. The preferred polyisocyanates are those described above.The polyol is preferably selected from the group consisting of polyether polyols, polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyvinyl polyols, polysiloxane polyols, and any mixture thereof. More preferably, the polyol is selected from the group consisting of polyether polyols and any mixture thereof. The preferred polyether polyols are polytetrahydrofuran, polyethylene oxide, polypropylene oxide, or any mixture thereof. The most preferred polyether polyol is poly(propylene glycol).The amount of polyoxyethylene (-O-CH2-CH2)X, polyoxypropylene (-O-CHCH3-CH2-)xo (-O-CH2-CH2-CH2)xy / or polytetrahydrofuran (-O-CH2-CH2-CH2-CH2)x groups in the multiaziridine compound is preferably at least 6 wt%, more preferably at least 10 wt% and preferably less than 45 wt%, more preferably less than 40 wt% and most preferably less than 35 wt%, with respect to the multiaziridine compound. x represents an average number of moles of added oxyethylene, oxypropylene, tetrahydrofuran, and x is preferably an integer from 5 to 20. The polyamine is preferably selected from the group consisting of polyether polyamines, polyester polyamines, polythioether polyamines, polycarbonate polyamines, polyacetal polyamines, polyvinyl polyamines, polysiloxane polyamines, and any mixture thereof. More preferably, the polyamine is selected from the group consisting of polyether polyamines and any mixture thereof.The preferred polyether polyamines are Jeffamine® D-230, Jeffamine® D-400, and Jeffamine® D-2000. The use of a polyol is preferred over the use of a polyamine. An example of such a multiaziridine compound is shown below. οοβοηη / ζζηζ / Ε / γίΛΐ Compound B is preferably obtained by reacting at least one non-functional monoepoxide compound with ethylene oxide. The non-functional monoepoxide can be a mixture of different non-functional monoepoxides. Examples, but not limited to, of non-functional monoepoxides include ethylene oxide, propylene oxide, ethyl 2-oxirane, n-butylglycidyl ether, 2-ethylhexylglycidyl ether, phenylglycidyl ether, 4-tert-butylphenyl 2,3-epoxypropyl ether (= t-butylphenylglycidyl ether), cresolglycidyl ether (ortho or para), and glycidyl neodecanoate. The OH nonfunctional monoepoxide is preferably selected from the group consisting of ethylene oxide (CAS No. 75-21-8), propylene oxide (CAS No. 75-56-9), ethyl 2-oxirane (CAS No. 106-88-7), n-butylglycidyl ether (CAS No. 2426-08-6), 2-ethylhexylglycidyl ether (CAS No. 2461-15-6), glycidyl neodecanoate (CAS No. 26761-45-5) and any mixture thereof.More preferably, the OH non-functional monoepoxide is selected from the group consisting of propylene oxide (CAS No. 75-56-9), ethyl 2-oxirane (CAS No. 106-88-7), n-butylglycidyl ether (CAS No. 2426-08-6), 2-ethylhexylglycidyl ether (CAS No. 2461-15-6), glycidyl neodecanoate (CAS No. 26761-45-5), and any mixture thereof. The multiaziridine compound is preferably obtained in a process comprising at least the following steps (i) and (ii): (i) Reacting the ethylene tin with at least one non-OH functional monoepoxide compound to obtain compound B, and (ii) reacting compound B with a polyisocyanate. Step (i) can be carried out, for example, by contacting one equivalent of the epoxide compound with one equivalent of the aziridine at a temperature in the range of 20°C to 110°C, more suitablely from 40°C to 95°C, or even more suitablely from 60°C to 85°C at atmospheric pressure. The reaction (step (i)) of the adduct (compound B) obtained in step (i) with the polyisocyanate can be carried out, for example, by contacting equivalent amounts of the polyisocyanate with the adduct at a temperature in the range of 20°C to 110°C, more suitablely from 40°C to 95°C at atmospheric pressure, in the presence, for example, of a tin catalyst such as, for example, dibutyltin dilaureate. Examples of preferred multiaziridine compounds present in the crosslinking composition of the invention are ορβοηη / ζζηζ / Ε / γίΛΐ ρρβοηη / ζζηζ / Ε / γίΛΐ ρρβρηη / ζζηζ / Ε / γίΛΐ In a preferred embodiment of the invention, the multiaziridine compound present in dispersed form in the aqueous dispersion of the invention has a. 2 to 6 structural units according to structural formula A R4R3 (A) Where Ri, R2, R3, R4, R' and R” and their preferred shares as defined above, b. one or more linking chains wherein each of these linking chains links two of the structural units A; whereby the one or more linking chains are preferably as defined above, and c. a molecular weight of 840 to 5000 Daltons, preferably a molecular weight of at least 1000 Daltons and preferably a molecular weight at most 3800 Daltons, more preferably at most 3600 Daltons, more preferably at most 3000 Daltons, more preferably at most 2300 Daltons, even more preferably at most 1600 Daltons. Surprisingly, such multiaziridine compounds were found to have reduced genotoxicity compared to the widely used trimethylolpropane tris(2-methyl-1-aziridinopropionate). Multiaziridine compounds exhibit only weakly positive induced genotoxicity or even no genotoxicity at all, meaning they show a level of genotoxicity comparable to that of naturally occurring substances. Consequently, multiaziridine compounds with reduced genotoxicity, compared to trimethylolpropane tris(2-methyl-1-aziridinopropionate), have a more favorable risk profile than trimethylolpropane tris(2-methyl-1-aziridinopropionate), significantly reducing the safety, health, and environmental risks associated with their use. This results in a reduction and eventual elimination of the operational and administrative burden of handling these genotoxic multiaziridine compounds.The multiaziridine compound preferably comprises one or more connecting groups wherein each of the connecting groups connects two of the structural units A and whereby the connecting groups and their preferred ones were defined above. In this embodiment, the amount of aziridinyl functional group molecules (also referred to as aziridine functional group molecules) present in the multiaziridine crosslinking composition according to the invention, having a molecular weight of less than 250 Daltons, more preferably less than 350 Daltons, even more preferably less than 450 Daltons, even more preferably less than 550 Daltons, and even more preferably less than 580 Daltons, is preferably less than 5% by weight, more preferably less than 4% by weight, more preferably less than 3% by weight, more preferably less than 2% by weight, more preferably less than 1% by weight, more preferably less than 0.5% by weight, and more preferably less than 0.1 wt% and more preferably 0 wt%, relative to the total weight of the multiaziridine crosslinking composition, whereby the molecular weight is determined using LC-MS as described in the experimental section below. Such aziridine functional group molecules can be obtained as byproducts during the preparation of the multiaziridine compound as defined herein. The average number of aziridinyl groups per aziridinyl-containing molecule in the composition is preferably at least 1.8, more preferably at least 2, more preferably at least 2.2, and preferably less than 10, more preferably less than 6, and most preferably less than 4. Most preferably, the average number of aziridinyl groups per aziridinyl-containing molecule in the composition is 2.2 to 3. pH of the aqueous dispersion The pH of the aqueous dispersion is at least 9. To further extend the stability period of the aqueous dispersion of the invention, it is beneficial for the pH to be at least 9.5. The pH of the aqueous dispersion is at most 14, preferably at most 13, more preferably at most 12, and even more preferably at most 11.5, as this allows for a reduction in the amount of base present in the aqueous dispersion of the invention while still maintaining a sufficiently long stability period. Most preferably, the pH of the aqueous dispersion should be in the range of 9.5 to 11.5. The aqueous dispersion preferably comprises ammonia, a secondary amine, a QPRQnn / zznz / E / YiAi tertiary amine, L1OH, NaOH and / or KOH to adjust the pH to the desired value. The preferred amines are ammonia, secondary amines and / or tertiary amines. Examples of such secondary amines are, but are not limited to, diisopropylamine, di-sec-butylamine and di-t-butylamine. The most preferred amines are tertiary amines. Examples of such tertiary amines are, but are not limited to, n-ethylmorpholine, n-methylpiperidine, η,η-dimethylbutylamine, dimethylisopropylamine, dimethylpropylamine, dimethylethylamine, triethylamine, dimethylbenzylamine, n,n-dimethylethanolamine, 2-(diethylamino)ethanol, η,η-dimethylisopropanolamine, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-(dimethylamino)ethanol, 2-[2-(dimethylamino)ethoxy]ethanol. The preferred tertiary amines are n-ethylmorpholine, n-methylpiperidine, η,η-dimethylbutylamine, dimethylisopropylamine, dimethylpropylamine, dimethylethylamine, triethylamine, and / or dimethylbenzylamine. Triethylamine is the most preferred. The amount of water in the aqueous dispersion is preferably at least 15% by weight, more preferably at least 20% by weight, more preferably at least 30% by weight, and even more preferably at least 40% by weight, relative to the total weight of the aqueous dispersion. The amount of water in the aqueous dispersion is preferably at most 95% by weight, more preferably at most 90% by weight, more preferably at most 80% by weight, more preferably at most 70% by weight, more preferably at most 65% by weight, more preferably at most 60% by weight, and even more preferably at most 55% by weight, and even more preferably at most 48% by weight, relative to the total weight of the aqueous dispersion. The multiaziridine compound as defined herein is present in the aqueous dispersion in an amount preferably of at least 5% by weight, more preferably at least 10% by weight, more preferably at least 15% by weight, more preferably at least 20% by weight, even more preferably at least 25% by weight, even more preferably at least 30% by weight, even more preferably at least 35% by weight, relative to the total weight of the aqueous dispersion. The multiaziridine compound as defined herein is present in the aqueous dispersion in an amount preferably not exceeding 70% by weight, preferably not exceeding 65% by weight, more preferably not exceeding 60% by weight, even more preferably not exceeding 55% by weight, relative to the total weight of the aqueous dispersion. Preferably at least 70 wt%, more preferably at least 85 wt%, and most preferably at least 95 wt% of the multiaziridine compound as defined herein is present in the multiaziridine crosslinking composition in the dispersed form. Accordingly, the multiaziridine crosslinking composition of the invention comprises particles comprising a multiaziridine compound as defined herein. Such particles preferably have an average hydrodynamic diameter based on scattering intensity of 30 to 650 nanometers, preferably 50 to 500 nanometers, more preferably 70 to 350 nm, and even more preferably 120 to 275 nm. The average hydrodynamic diameter based on scattering intensity of such particles can be controlled in various ways.For example, the average hydrodynamic diameter based on the dispersion intensity of such particles can be controlled during the preparation of an aqueous dispersion of the invention by using different types of dispersants, and / or different amounts of dispersant(s), and / or by applying different shear stresses, and / or by applying different temperatures. For example, the average hydrodynamic diameter based on the dispersion intensity of the particles is inversely dependent on the amount of dispersant used in the preparation of an aqueous dispersion of the invention; for example, the average hydrodynamic diameter based on the dispersion intensity of the particles decreases as the amount of a dispersant increases.For example, the average hydrodynamic diameter based on particle dispersion intensity is inversely dependent on the shear stress applied during the preparation of an aqueous dispersion of the invention; for example, the average hydrodynamic diameter based on particle dispersion intensity decreases as the shear stress increases. Exemplary dispersants include, but are not limited to, ATLAS™ G-5000, ATLAS™ G-5002L-LQ, and Maxemul™ 7101 supplied by Croda. The solids content of the aqueous dispersion is preferably at least 5%, more preferably at least 10% by weight, even more preferably at least 20% by weight, even more preferably at least 30% by weight, and even more preferably at least 35% by weight. The solids content of the aqueous dispersion is preferably at most 70% by weight, preferably at most 65% by weight, and most preferably at most 55% by weight. The solids content of the aqueous dispersion is most preferably in the range of 35 to 55% by weight. The multiaziridine compound as defined above is typically obtained in a composition in which, along with the multiaziridine compound, the remaining starting materials, byproducts, and / or the solvent used in the preparation of the multiaziridine compounds may be present. The composition may contain only one multiaziridine compound as defined above, but it may also contain more than one. Mixtures of multiaziridine compounds are obtained, for example, when a mixture of polyisocyanates is used as the starting material.The aqueous dispersion of the invention can be obtained by dispersing the multiaziridine compound in water and adjusting the pH of the aqueous dispersion to the desired value, or by dispersing the multiaziridine compound in a mixture of water and at least one base, the mixture having a pH such that an aqueous dispersion with the desired pH value is obtained, or by adding a mixture of water and base to the multiaziridine compound. Dispersal of the multiaziridine compound in water or in a mixture of water and at least one base can be carried out using well-known techniques in the field. Solvents and / or high shear may be used to aid in the dispersion of the multiaziridine compound. The aqueous dispersion may further comprise an organic solvent in an amount not exceeding 35% by weight, preferably not exceeding 30%, for example, 25%, 20%, 12%, 10%, 8%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.2%, or 0.1% by weight, relative to the total weight of the aqueous dispersion. The organic solvent may be added optionally before, during, and / or after the synthesis of the multiaziridine(s). An organic solvent may be used to aid in the dispersion of the multiaziridine compound in water. If desired, the organic solvent may be subsequently removed from the crosslinking composition by reduced pressure and / or elevated temperatures.Common organic solvents include glycols, ethers, alcohols, cyclic carbonates, pyrrolidones, dimethylformamide, dimethyl sulfoxide, n-formylmorpholine, dimethylacetamide, and ketones. Preferred solvents include glycols, ethers, alcohols, cyclic carbonates, and ketones. Preferably, the dispersion of the multiaziridine compound is carried out in the presence of a dispersant. Accordingly, the aqueous dispersion of the invention preferably comprises a dispersant. In the context of the present invention, a dispersant is a substance that promotes the formation and colloidal stabilization of a dispersion. In the present invention, such a dispersant is preferably a species that is not covalently bonded to the multiaziridine compound and / or such a dispersant is a separate molecular component that is a surfactant. Examples of species non-covalently bonded to the multiaziridine compound are amphiphilic compounds containing urethane and / or urea, such as HEUR thickeners. More preferably, such a dispersant is at least one separate molecular component that is a surfactant. The preferred separate molecular surfactant components are: (i) multiaziridine compounds as defined above containing functional groups such as sultanate, sulfate, phosphate and / or phosphonate functional groups, preferably sultanate and / or phosphonate groups, more preferably sultanate groups, and / or (ii) a polymer having preferably a number-average molecular weight measured by MALDI-ToF-MS as described below of at least 2000 Daltons, more preferably at least 2500 Daltons, more preferably at least 3000 Daltons, more preferably at least 3500 Daltons, more preferably at least 4000 Daltons, and preferably at most 1000000 Daltons. The most preferred separate surfactant molecular components are polymers having a number-average molecular weight, measured by MALDI-ToF-MS, as described below, of at least 2000 Daltons, more preferably at least 2500 Daltons, more preferably at least 3000 Daltons, more preferably at least 3500 Daltons, more preferably at least 4000 Daltons, and preferably at most 1,000,000 Daltons, more preferably at most 100,000 Daltons, and even more preferably at most 10,000 Daltons. The preferred polymers are polyethers, more preferably polyether copolymers, even more preferably polyether block copolymers, even more preferably poly(alkylene oxide) block copolymers, and even more preferably poly(ethylene oxide)-propylene oxide block copolymers.Examples, but not limited to, of preferred separated molecular surfactant dispersants include Atlas™ G-5000 from Croda, Maxemul™ 7107 from Croda, and / or Pluronic® P84 from BASF. The amount of separated molecular surfactant component is generally in the range of 0.1 to 20 wt%, preferably at least 0.5 wt%, more preferably at least 1 wt%, even more preferably at least 2 wt%, and even more preferably at least 3 wt% based on the total weight of the aqueous dispersion. Multiaziridine compounds as defined in (i) containing functional groups such as sulfonate, sulfate, phosphate, and / or phosphonate functional groups, preferably containing sulfonate functional groups, are preferably obtained by reacting part of the isocyanate groups of the polyisocyanates used to prepare the multiaziridine compound with an ionic structural component having a hydroxy or amine functional group (preferably neutralized with an inorganic base). Examples of ionic structural components with a hydroxy or amine functional group include 2-(cyclohexylamino)ethanesulfonic acid, 3-(cyclohexylamino)propanesulfonic acid, methyltaurine, taurine, and Tegomer® DS-3404. Preferably, sulfonic acid salts are used as the ionic structural unit with a hydroxy or amine functional group. The crosslinking effectiveness of a crosslinking agent can be estimated by evaluating the defined and determined chemical resistance as described below. The storage stability of an aqueous dispersion according to the invention can be evaluated by storing the aqueous dispersion at a particularly elevated temperature, for example 50 °C, and evaluating the change in viscosity, defined and determined as described below, of the stored aqueous dispersion and / or evaluating the change in chemical resistance, defined and determined as described below, in particular the resistance to ethanol, of the stored aqueous dispersion. QPRQnn / zznz / E / YiAi The aqueous dispersion of the present invention preferably has a storage stability of at least 2 weeks, more preferably at least 3 weeks, and even more preferably at least 4 weeks at 50°C. Stable in storage for at least x week(s) at 50°C (i) the final viscosity of the aqueous dispersion is at most 50 times greater than the initial viscosity, preferably at most 45 times greater than the initial viscosity, more preferably at most 40 times greater than the initial viscosity, more preferably at most 35 times greater than the initial viscosity, more preferably at most 30 times greater than the initial viscosity, more preferably at most 25 times greater than the initial viscosity, more preferably at most 20 times greater than the initial viscosity, more preferably at most 15 times greater than the initial viscosity,More preferably, at most 10 times the initial viscosity, and most preferably at most 5 times the initial viscosity, and / or (i) the chemical resistance, defined and determined as described below, of the aqueous dispersion decreases by at most 3 points, preferably by at most 2 points, and even more preferably by at most 1 point. Preferably, stable in storage for at least x week(s) at 50 °C means that after the dispersion has been stored for x weeks at 50 °C (i) the final viscosity of the aqueous dispersion is at most 50 times the initial viscosity, preferably at most 45 times the initial viscosity, more preferably at most 40 times the initial viscosity, more preferably at most 35 times the initial viscosity, more preferably at most 30 times the initial viscosity,more preferably not more than 25 times the initial viscosity, more preferably not more than 20 times the initial viscosity, more preferably not more than 15 times the initial viscosity, more preferably not more than 10 times the initial viscosity, and most preferably not more than 5 times the initial viscosity, and (i) the chemical resistance, defined and determined as described below, of the aqueous dispersion decreases by a maximum of 3 points, preferably by a maximum of 2 points, and even more preferably by a maximum of 1 point. The initial viscosity of an aqueous dispersion means the viscosity (defined and determined as described below) of the aqueous dispersion immediately after its preparation and just before the aqueous dispersion is stored at 50 °C. The final viscosity of an aqueous dispersion means the viscosity (defined and determined as described below) of the aqueous dispersion after the aqueous dispersion has been stored for x weeks at 50 °C. The present invention further relates to a process for preparing the multiaziridine crosslinking composition according to the invention, wherein the process comprises dispersing the multiaziridine compound as defined herein in water to obtain an aqueous dispersion and adjusting the pH of the aqueous dispersion to the desired value, or preferably wherein the process comprises dispersing the multiaziridine compound as defined herein in a mixture of water and at least one base, the mixture having a pH such that an aqueous dispersion with the desired pH value is obtained. In a preferred embodiment of the invention, the dispersant is a separate surfactant polymer having a number-average molecular weight of at least 2000 Daltons (i). In this preferred embodiment, the process for preparing the multiaziridine crosslinking composition according to the invention preferably comprises A) Optionally, but preferably, mix the multiaziridine compound as defined above in an organic solvent, B) mixing the multiaziridine compound as defined above or the solution obtained in step A) with a dispersant as described above to obtain a composition comprising the multiaziridine compound and the dispersant, C) mixing water and base or mixing in basic aqueous medium in such a composition comprising the multiaziridine compound and the dispersant, to obtain a dispersion D) Optionally, but preferably, evaporate the organic solvent from such dispersion to obtain another dispersion, and optionally mix water or additional basic aqueous medium into such additional dispersion, to obtain the aqueous dispersion of the present invention. Step C) is preferably performed using a high shear dispersion equipment. The present invention further relates to the use of the multiaziridine crosslinking composition according to the invention for crosslinking a polymer with a dissolved and / or dispersed carboxylic acid functional group, preferably dispersed, in water, wherein the amounts of aziridinyl groups and carboxylic acid groups are chosen such that the stoichiometric (SA) amount of aziridinyl groups relative to carboxylic acid groups is from 0.1 to 2.0, more preferably from 0.2 to 1.5, even more preferably from 0.25 to 0.95, most preferably from 0.3 to 0.8. The polymer with a carboxylic acid functional group contains carboxylic acid groups and / or carboxylate groups which are preferably free from a covalent bond that blocks these groups from chemically reacting with the aziridine fraction present in the multiaziridine compound.As used herein, the number of carboxylic acid groups present in the polymer with a carboxylic acid functional group is the sum of the number of protonated and deprotonated carboxylic acid groups present in the polymer to be crosslinked, i.e., in the polymer with a carboxylic acid functional group. Thus, the number of carboxylic acid groups present in the polymer with a carboxylic acid functional group is the sum of the number of carboxylate groups and carboxylic acid groups present in the polymer with a carboxylic acid functional group. The polymer to be crosslinked preferably comprises carboxylate groups which are at least partially neutralized with a base. Preferably, at least part of the base is a volatile base. Preferably, at least some of the carboxylic acid groups present in the polymer with a carboxylic acid functional group to be crosslinked are deprotonated to obtain carboxylate groups.Deprotonation is carried out by neutralizing the polymer with a carboxylic acid functional group using a base. Examples of suitable bases include ammonia, secondary amines, tertiary amines, LiOH, NaOH, and / or KOH. Examples of secondary and tertiary amines are described above. Tertiary amines are the preferred bases. The preferred tertiary amines are those described above. The most preferred is triethylamine. To avoid an unwanted premature crosslinking reaction between the crosslinking agent and the polymer to be crosslinked during storage of the multiaziridine crosslinking composition, it is known that the multiaziridine crosslinking composition should preferably not be mixed with the polymer to be crosslinked during storage. The reason is that the crosslinking reaction between the crosslinking agent and the polymer to be crosslinked can begin immediately after mixing the crosslinking agent and the polymer to be crosslinked. Therefore, it is preferred that the multiaziridine crosslinking composition of the invention not contain the polymer(s) to be crosslinked.The present invention therefore also relates to a two-component coating system comprising a first component and a second component which are separate and distinct from each other, wherein the first component comprises a polymer with a carboxylic acid functional group dissolved and / or dispersed, preferably dispersed, in an aqueous medium and the second component comprises the multiaziridine crosslinking composition of the present invention, wherein the first and second components are stored separately, since the crosslinking reaction between the crosslinking agent and the polymer to be crosslinked can be initiated immediately after mixing the crosslinking agent with the aqueous composition of the polymer to be crosslinked.As used herein, a coating composition refers to the composition comprising the polymer(s) to be crosslinked, the polymer(s) being dissolved and / or dispersed, preferably dispersed, in water, and further comprising the multiaziridine crosslinking composition of the present invention. The present invention also relates to a coating composition obtained by mixing the first and second components of the two-component system just before applying the coating composition, wherein the coating composition QPRQnn / zznz / E / YiAi comprises aziridinyl Q groups and carboxylic acid groups in an amount such that the stoichiometric amount (SA) of the aziridinyl Q groups in the carboxylic acid groups is preferably from 0.1 to 2.0, more preferably from 0.2 to 1.5, even more preferably from 0.25 to 0.95, and most preferably from 0.3 to 0.8.The present invention further relates to a substrate having a coating obtained (i) by applying a coating composition as described above to a substrate and (ii) by drying the coating composition through evaporation of the volatile components. The drying of the coating composition is preferably carried out at a temperature below 160°C, preferably below 90°C, more preferably below 50°C, and most preferably at room temperature. The coating composition according to the invention can be applied to any type of substrate, such as, for example, wood, leather, concrete, textiles, plastic, vinyl flooring, glass, metal, ceramics, paper, wood-plastic composites, and fiberglass-reinforced materials.The dry coating thickness on the substrate is preferably 1 to 200 micrometers, more preferably 5 to 150 micrometers, and most preferably 15 to 90 micrometers. If the coating composition is an ink composition, the dry ink thickness is preferably 0.005 to 35 micrometers, more preferably 0.05 to 25 micrometers, and most preferably 4 to 15 micrometers. Non-limited examples of crosslinkable carboxylic acid functional group polymers are vinyl polymers such as styrene-acrylics, (meth)acrylic copolymers, vinyl acetate (co)polymers such as, for example, vinyl acetate-ethylene vinyl chloride polymers, polyurethanes, polycondensates such as polyesters, polyamides, polycarbonates, and hybrids of any of these polymers where at least one of the two polymers has a carboxylic acid functionality. The polymer with a carboxylic acid functional group is preferably selected from the group consisting of polyesters, polycarbonates, polyamides, vinyl polymers, polyacrylates, polymethacrylates, poly(acrylate-co-methacrylate), polyurethanes, poly(urethane-co-acrylate), poly(urethane-co-methacrylate), poly(urethane-co-acrylate-co-methacrylate), polyureas, and mixtures thereof. In one embodiment of the invention, the preferred crosslinkable polymers with a carboxylic acid functional group are selected from the group consisting of vinyl polymers, polyacrylates, polymethacrylates, poly(acrylate-co-methacrylate), and mixtures thereof. Preferably, a vinyl polymer is understood to be a polymer comprising reacted residues of styrene and acrylates and / or methacrylates.In another embodiment, the polymer with carboxylic acid functional group is selected from the group consisting of polyurethanes, poly(urethane-co-acrylate), poly(urethane-co-methacrylate), poly(urethane-co-acrylate-co-methacrylate). QPRQnn / zznz / E / YiAi polyureas and mixtures thereof. The acid value of the polymer with the carboxylic acid functional group is preferably 2 to 135 mg KOH / g of the polymer with the carboxylic acid functional group, more preferably 3 to 70 mg KOH / g of the polymer with the carboxylic acid functional group, even more preferably 10 to 50 mg KOH / g of the polymer with the carboxylic acid functional group, and even more preferably 15 to 50 mg KOH / g of the polymer with the carboxylic acid functional group. In cases where high crosslinking density is required, the acid value of the polymer with the carboxylic acid functional group is preferably 50 to 200 mg KOH / g of the polymer with the carboxylic acid functional group.As used herein, the acid number of the polymer(s) with a carboxylic acid functional group is calculated according to the formula AV = ((total molar amount of carboxylic acid components included in the polymer(s) with a carboxylic acid functional group per gram of the total amount of components included in the polymer(s) with a carboxylic acid functional group) * 56.1 * 1000) and is reported as mg KOH / gram of the polymer(s) with a carboxylic acid functional group. The acid number of the polymer(s) with a carboxylic acid functional group can therefore be controlled by the molar amount of carboxylic acid components used to prepare the polymer(s) with a carboxylic acid functional group. If the acid number cannot be correctly calculated, it is determined according to ASTM D1639-90(1996)e1. The ratio of the average molecular weight in Mn number of the polymer with a carboxylic acid functional group to the acid number of the polymer with a carboxylic acid functional group is preferably at least 150, more preferably at least 300, even more preferably at least 600, even more preferably at least 1000, even more preferably at least 5000, and most preferably at least 15000. As used herein, the average molecular weight in Mn number of the polymer with a carboxylic acid functional group is determined by size exclusion chromatography with MEK-MPN. The invention is further defined by the series of exemplary embodiments listed below. Any of the embodiments, aspects, and preferred features or ranges as disclosed in this application may be combined in any combination, unless otherwise stated herein or if it is not technically obvious to a person skilled in the art. [1] A multiaziridine crosslinking composition, wherein the composition is an aqueous dispersion having a pH range of 8 to 14 and comprising a multiaziridine compound in dispersed form, wherein such multiaziridine compound has: QPAonn / zznz / E / YiAi a. 2 to 6 of the following structural units A: OR5 R' ρρβρηη / ζζηζ / Ε / γίΛΐ IX'1V R sRl NR?mX R4 R3 (A) where Ri, R2, R3 and R4 are H, m is 1, R' and R" are in accordance with (1) or (2): (1) R'= H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, R” - an alkyl group containing 1 to 4 carbon atoms, CH2-O-(C=O)-R”' or CH2-OR””, wherein R'' is an alkyl group containing 3 to 12 carbon atoms and R”” is an alkyl group containing 1 to 14 carbon atoms, (2) R' and R” together form a saturated cycloaliphatic hydrocarbon group containing 5 to 8 carbon atoms, t is 0, Rses H or CH3, XesOy Yes NH; b. one or more linking chains where each of these linking chains links two of the structural units A; and c. a molecular weight in the range of 500 to 10000 Daltons. [2] The multiaziridine crosslinking composition of modality [1], wherein the linking chains consist of 4 to 300 atoms, more preferably 5 to 250 and most preferably 6 to 100 atoms and the linking chains are a set of covalently connected atoms whose set of atoms consists of i) carbon atoms, i) carbon and nitrogen atoms, oi) carbon, oxygen and nitrogen atoms. [3] The multiaziridine crosslinking composition of any of the forms [1] to [2], wherein the multiaziridine compound contains 2 to 3 structural units A. [4] The multiaziridine crosslinking composition of any of the forms [1] to [3], wherein R' is H and R” = an alkyl group containing 1 to 4 carbon atoms, CH2O-(C=O) -R'” or CH2-OR””, wherein R'” is an alkyl group containing 3 to 12 carbon atoms and R”” is an alkyl group containing 1 to 14 carbon atoms. [5] The multiaziridine crosslinking composition of any of embodiments [1] to [4], wherein the multiaziridine compound comprises one or more connecting groups, each of these connecting groups connecting two of the structural units A, the connecting groups consisting of at least one functional group selected from the group consisting of an aliphatic hydrocarbon functional group (preferably containing 1 to 8 carbon atoms), a cycloaliphatic hydrocarbon functional group (preferably containing 4 to 10 carbon atoms), an aromatic hydrocarbon functional group (preferably containing 6 to 12 carbon atoms), an isocyanurate functional group, an iminooxadiazindione functional group, an ether functional group, an ester functional group, an amide functional group, a carbonate functional group, a urethane functional group, a urea functional group, a biuret functional group, or an allophanate functional group.urethdione functional group and any combination thereof. [6] The multiaziridine crosslinking composition of modality [5], wherein the connecting groups consist of at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and optionally at least one aromatic hydrocarbon functional group and optionally an isocyanurate functional group or an iminooxadiazindione functional group. [7] The multiaziridine crosslinking composition of modality [5], wherein the connecting groups consist of at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and an isocyanurate functional group or an iminooxadiazindione functional group. [8] The multiaziridine crosslinking composition of any of embodiments [1] to [4], wherein the multiaziridine compound comprises one or more connecting groups, each of these connecting groups connecting two of the structural units A, wherein the connecting groups consist of (i) at least two aliphatic hydrocarbon functional groups and (ii) an isocyanurate functional group or an iminooxadiazindione functional group and wherein a pendant group is present in a connecting group, wherein the pendant group has the following structural formula: or r7HUnn' is the number of repeating units and is an integer from 1 to 50, preferably from 2 to 30, more preferably from 5 to 20. X is O or NH, preferably X is O, R? and Rs are independently H or CH3 in each repeating unit, Rg is an aliphatic hydrocarbon group that preferably contains 1 to 8 carbon atoms, and Rio preferably is an aliphatic hydrocarbon group containing from 1 to 20 atoms QPRQnn / zznz / E / YiAi QPRQnn / zznz / E / YiAi R' R2*3 r4 wherein the molar ratio between compound B and the polyisocyanate is 2 to 6, more preferably 2 to 4 and most preferably 2 to 3, and wherein m, R', R" R·,, R2, R3 and R4 are as defined in any of the above embodiments.

[13] The multiaziridine crosslinking composition of modality

[12] , wherein the polyisocyanate is an aliphatic reactive polyisocyanate.

[14] The multiaziridine crosslinking composition of modality

[12] or

[13] , wherein compound B is obtained by reacting at least one OH-nonfunctional monoepoxide compound with an aziridine having the following structural formula: where R1, R2, R3 and R4 are as defined in any of the above modalities.

[15] The multiaziridine crosslinking composition of modality

[14] , wherein the OH-nonfunctional monoepoxide compound is selected from the group consisting of ethylene oxide, propylene oxide, ethyl 2-oxirane, n-butylglycidyl ether, 2-ethylhexylglycidyl ether, glycidyl neodecanoate, and any mixture thereof.

[16] The multiaziridine crosslinking composition of any of the forms

[12] to

[15] , wherein the multiaziridine compound is the reaction product of at least one compound (B), a polyisocyanate and alkoxy poly(propylene glycol) and / or poly(propylene glycol).

[17] The multiaziridine crosslinking composition of any of the embodiments [1] to

[16] , wherein the multiaziridine compound has a molecular weight of 600 to 5000 Daltons, more preferably the multiaziridine compound has a molecular weight of at least 800 Daltons, even more preferably at least 840 Daltons, even more preferably at least 1000 Daltons and preferably at most 3800 Daltons, more preferably at most 3600 Daltons, more preferably at most 3000 Daltons, more preferably at most 1600 Daltons, even more preferably at most 2300 Daltons, even more preferably at most 1600 Daltons.

[18] The multiaziridine crosslinking composition of any of embodiments [1] to

[17] , wherein the aqueous dispersion comprises molecules of aziridine functional groups having a molecular weight of less than 250 Daltons, more preferably less than 350 Daltons, even more preferably less than 450 Daltons, even more preferably less than 550 Daltons and even more preferably less than 580 Daltons in an amount less than 5% by weight, more preferably less than 4% by weight, more preferably less than 3% by weight, more preferably less than 2% by weight, more preferably less than 1% by weight, more preferably less than 0.5% by weight, more preferably less than 0.1% by weight and most preferably 0% by weight, with respect to the total weight of the aqueous dispersion, wherein the molecular weight is determined using LC-MS as described in the description.

[19] The multiaziridine crosslinking composition of any of the forms [1] to

[18] , wherein the pH of the aqueous dispersion is at least 9.5.

[20] The multiaziridine crosslinking composition of any of the forms [1] to

[19] , wherein the pH of the aqueous dispersion is at most 14, more preferably at most 13, even more preferably at most 12, even more preferably at most 11.5.

[21] The multiaziridine crosslinking composition of any of the forms [1] to

[20] , wherein the pH of the aqueous dispersion is in the range of 9.5 to 11.5.

[22] The multiaziridine crosslinking composition of any of embodiments [1] to

[21] , wherein the aqueous dispersion comprises ammonia, a secondary amine(s), a tertiary amine(s), LiOH, NaOH and / or KOH to adjust the pH to the desired value, preferably the aqueous dispersion comprises a tertiary amine selected from n-ethylmorpholine, n-methylpiperidine, η,η-dimethylbutylamine, dimethylisopropylamine, dimethylpropylamine, dimethylethylamine, triethylamine and / or dimethylbenzylamine, more preferably comprising triethylamine to adjust the pH to the desired value.

[23] The multiaziridine crosslinking composition of any of the forms [1] to

[22] , wherein the amount of water in the aqueous dispersion is at least 15% by weight, preferably at least 20% by weight, more preferably at least 30% by weight, even more preferably at least 40% by weight, with respect to the total weight of the aqueous dispersion.

[24] The multiaziridine crosslinking composition of any of the forms [1] to

[23] , wherein the amount of water in the aqueous dispersion is at most 95% by weight, preferably at most 90% by weight, more preferably at most 85% by weight, more preferably at most 80% by weight, even more preferably at most 70% by weight, even more preferably at most 60% by weight, with respect to the total weight of the aqueous dispersion.

[25] The multiaziridine crosslinking composition of any of the embodiments [1] to

[24] , wherein the amount of such multiaziridine compound in the aqueous dispersion is at least 5 wt%, preferably at least 10 wt%, more preferably at least 15 wt%, more preferably at least 20 wt%, even more preferably at least 25 wt%, even more preferably at least 30 wt%, even more preferably QPRQnn / zznz / E / YiAi at least 35% by weight, with respect to the total weight of the aqueous dispersion.

[26] The multiaziridine crosslinking composition of any of the forms [1] to

[25] , wherein the amount of such multiaziridine compound in the aqueous dispersion is at most 70% by weight, preferably at most 65% by weight, more preferably at most 60% by weight, even more preferably at most 55% by weight with respect to the total weight of the aqueous dispersion.

[27] The multiaziridine crosslinking composition of any of embodiments [1] to

[26] , wherein the aqueous dispersion further comprises an organic solvent in an amount of, at most 35% by weight, preferably at most 30, for example at most 25, for example at most 20, for example at most 12, for example at most 10, for example at most 8, for example at most 5, for example at most 4, for example at most 3, for example at most 2, for example at most 1, for example at most 0.5, for example at most 0.2, for example at most 0.1% by weight with respect to the total weight of the aqueous dispersion.

[28] The multiaziridine crosslinking composition of any of the forms [1] to

[27] , wherein the solids content of the aqueous dispersion is at least 5, preferably at least 10, even more preferably at least 20, even more preferably at least 30, even more preferably at least 35 and at most 70, more preferably at most 65 and even more preferably at most 55% by weight.

[29] The multiaziridine crosslinking composition of any of the forms [1] to

[28] wherein the particles have an average hydrodynamic diameter based on scattering intensity of 30 to 650 nanometers, preferably 50 to 500 nm, more preferably 70 to 350 nm, even more preferably 120 to 275 nm.

[30] The multiaziridine crosslinking composition of any of the forms [1] to

[29] , wherein the aqueous dispersion comprises a dispersant.

[31] The multiaziridine crosslinking composition of any of embodiments [1] to

[30] , wherein the aqueous dispersion comprises a separate molecular surfactant component as a dispersant in an amount ranging from 0.1 to 20% by weight, preferably at least 0.5, more preferably at least 1, even more preferably at least 2, even more preferably at least 3% by weight, with respect to the total weight of the aqueous dispersion.

[32] The multiaziridine crosslinking composition of embodiment

[32] , wherein the dispersant is a polymer having a number-average molecular weight of at least 2000 Daltons, more preferably at least 2500 Daltons, more preferably at least 3000 Daltons, more preferably at least 3500 Daltons, more preferably at least 4000 Daltons and preferably at most 1000000 Daltons, more preferably at most 100000, at most 10000 Daltons. ορβοηη / ζζηζ / Ε / γίΛΐ

[33] The multiaziridine crosslinking composition of any of the forms

[30] to

[32] wherein the dispersant is a polyether, more preferably polyether copolymers, even more preferably polyether block copolymers, even more preferably poly(alkylene oxide) block copolymers, even more preferably poly(ethylene oxide)-co-poly(propylene oxide) block copolymers.

[34] The multiaziridine crosslinking composition of any of the forms [1] to

[33] , wherein the aqueous dispersion has a storage stability of at least 2 weeks, more preferably at least 3 weeks and even more preferably at least 4 weeks at 50 °C.

[35] The multiaziridine crosslinking composition of any of embodiments [1] to

[34] , wherein the multiaziridine crosslinking composition is used to crosslink a dissolved and / or dispersed, preferably dispersed, carboxylic acid functional group polymer in an aqueous medium, wherein the carboxylic acid functional group polymer contains carboxylic acid groups and / or carboxylate groups.

[36] The multiaziridine crosslinking composition of any of the forms [1] to

[35] , wherein the multiaziridine crosslinking composition does not contain polymer to crosslink with the multiaziridine crosslinking composition.

[37] A process for preparing the multiaziridine crosslinking composition of any of the embodiments [1] to

[36] , wherein the process comprises dispersing the multiaziridine compound as defined in any of the above embodiments in water to obtain an aqueous dispersion and adjusting the pH of the aqueous dispersion to the desired value, or wherein the process comprises dispersing the multiaziridine compound as defined in any of the above embodiments in a mixture of water and at least one base, the mixture having a pH such that an aqueous dispersion with the desired pH value is obtained.

[38] The process of modality

[37] , wherein the process comprises mixing a basic aqueous medium in the multiaziridine compound as defined in any of the above modalities, wherein the pH of the basic aqueous medium is chosen so as to obtain an aqueous dispersion with the desired pH value.

[39] The process of modality

[37] , where the process comprises A) Optionally, but preferably, mix the multiaziridine compound as defined in any of the above embodiments in an organic solvent, B) mixing the multiaziridine compound as defined in any of the above embodiments or the solution obtained in step A) with a dispersant to obtain a composition comprising the multiaziridine compound and the dispersant, C) mixing water and base or mixing in a basic aqueous medium in such a composition comprising the multiaziridine compound and the dispersant, to obtain a dispersion ορβοηη / ζζηζ / E / γίΛΐ D) Optionally, but preferably, evaporate the organic solvent from such dispersion to obtain a further dispersion and, optionally, mix additional water or basic aqueous medium into such further dispersion, to obtain the aqueous dispersion of any of the forms [1] to

[36] .

[40] Use of the multiaziridine crosslinking composition of any of embodiments [1] to

[36] or obtained by the process according to any of embodiments

[37] to

[39] for crosslinking a polymer with a dissolved and / or dispersed carboxylic acid functional group, preferably dispersed, in an aqueous medium, wherein the amounts of aziridinyl groups and carboxylic acid groups are chosen such that the stoichiometric amount (SA) of aziridinyl groups with respect to carboxylic acid groups is from 0.1 to 2.0, more preferably from 0.2 to 1.5, even more preferably from 0.25 to 0.95, most preferably from 0.3 to 0.8.

[41] A two-component coating system comprising a first component and a second component, each of which is separate and distinct from each other, wherein the first component comprises a polymer with a carboxylic acid functional group dissolved and / or dispersed, preferably dispersed, in an aqueous medium, and the second component comprises the multiaziridine crosslinking composition of any of embodiments [1] to

[36] or obtained by the process according to any of embodiments

[37] to

[39] ,

[42] A substrate having a coating obtained by (i) applying a coating composition obtained by mixing the first and second component of the two-component coating system of embodiment

[41] to a substrate and (ii) drying the coating composition by evaporating volatile compounds. The present invention is now illustrated with reference to the following examples. Unless otherwise specified, all parts, percentages, and proportions are expressed by weight. Particle size measurement The average hydrodynamic diameter based on particle dispersion intensity was determined using a method derived from ISO 22412:2017 with a Malvern Zetasizer Nano S90 DLS instrument operated under the following configurations: as material, a polystyrene latex was defined with an Rl of 1.590 and an absorption of 0.10 in a continuous medium of demineralized water with a viscosity of 0.8812 cP (0.8812 mPa-s) and an Rl of 1.332 at 25 °C. The measurements were performed in DTS0012 disposable cuvettes, obtained from Malvern Instruments (Malvern, Worcestershire, UK). The measurements were taken under a backscatter angle of 173° as an average of 3 measurements after 120 seconds of balancing, consisting of 10–15 sub-runs, optimized by the machine itself. The laser focus point was at a fixed position of 4.65 cm and the data were analyzed using a general-purpose data fitting process.The samples were prepared by diluting 0.05 g (1 drop) of sample dispersion in approximately 5 mL of demineralized water. If the sample still appeared cloudy, it was further diluted with distilled water until it became almost clear. This method is suitable for determining particle sizes from 2 nm to 3 pm. pH measurement The pH of a sample is determined based on ISO 976:2013. Samples are measured at 23 °C using a Metrohm 691 potentiometer equipped with a combined glass electrode and PT-1000 temperature sensor. The potentiometer is calibrated using pH 7.00 and 9.21 buffer solutions before use. Determination of NCO The NCO content of a sample is determined based on ASTM D257219. In the procedure, the sample is reacted with an excess of n-dibutylamine. The excess n-dibutylamine is then back-titrated with standard 1N hydrochloric acid (HCl). The difference in titration volume between the sample and a blank is a measure of the isocyanate content in solids, according to the following formula: %NCOsolds = [(Vb - Vm) * N * 4.2] / (A * s / 100), where %NCOsolds is the isocyanate content in solids, Vb is the volume of HCl used in the blank, Vm is the volume of HCl used in the sample, N is the normality of the HCl solution, A is the weight of the sample in grams, and s is the sample solids content in %. Measurements are performed in duplicate using the potentiometric endpoint on a Metrohm 702SM Titrino titrator (which accepts the measurement if the difference between duplicates is < 0.1%nco). Determination of AVThe acid value (AV) of the solid material in a sample is determined based on ASTM D1639-90(1996)e1. In the procedure, the sample, dissolved in a suitable solvent, is titrated with an alcoholic solution of potassium hydroxide (KOH) of known concentration. The difference in the titration volume between the sample and a blank is the measure of the acid value of the solids, according to the following formula: AV = [(Vblank - Vsample) * Nkoh * 56.1] / (W * S / 100), where AV is the acid value of the solids in mg of KOH / g of solid material, Vblank is the volume of KOH solution used in the blank, Vsample is the volume of KOH solution used in the sample, Nkoh is the normality of the KOH solution, W is the weight of the sample in grams, and S is the solids content of the sample in %.Measurements are performed in duplicate using the potentiometric endpoint on a Metrohm 702SM Titrino titrator (which accepts the measurement if the difference between duplicates is < 0.1 mg KOH / g of solid material). ορβοηη / ζζηζ / Ε / γίΛΐ Chemical resistance The chemical resistance test was performed based on the DIN 68861-1:201101 standard. Unless otherwise stated, chemical resistance is tested as follows: The coating compositions consist of stoichiometric (SA) amounts of 0.9 of total carboxylic acid reactive functional groups (e.g., aziridine) compared to the carboxylic acid functional groups. The coating compositions are treated as described in the examples and then molded into a wet film 100 µm thick using a wire rod applicator. After molding, the films were dried for 1 hour at 25 °C, then reheated at 50 °C for 16 hours. Subsequently, a piece of cotton was soaked in 1:1 (by weight) ethane to demineralized water and placed on the film for 60 minutes (unless otherwise stated). After removing the cotton and allowing overnight recovery, the stains were scored according to the following ranges: 1. Complete degradation of the coating 2. Structural damage to the coating 3. Severe marking on the coating, visible from multiple directions 4. Light marking on the coating, visible from specific angles 5. No marking or change in brightness is observed Viscosity measurements: Apparent viscosity is determined according to ISO 2555:2018. The measurement is performed at 23°C on a Brookfield DVE-LV viscometer (single-cylinder geometry) at 60 rpm. The spindle is selected from S62, S63, or S64, using the spindle with the lowest number (i.e., the largest spindle) that produces a reading between 10% and 100% of torque. Size exclusion chromatography with NMP-MEK Molecular weight distribution was measured using an Alliance Separations Module (Waters e2695), which includes a pump, autoinjector, degasser, and column oven. The eluent was 80% n-methylpyrrolidone (NMP) / 20% methyl ethyl ketone (MEK) with the addition of 0.01 M lithium bromide. The injection volume was 150 µL. The flow rate was set at 1.0 mL / min. Three PL Mixed B columns (Polymer Laboratories) with a pre-column (5 µm PL) were applied at 70 °C. Detection was performed using a differential refractive index detector (Waters 2414) at 50 °C. Samples were dissolved in the eluent using a concentration of 5 mg of polymer per mL of solvent. Solubility is assessed using a laser pointer after 24 hours of stabilization at temperature QPRQnn / zznz / E / YiAi environment; if there is any visible dispersion, the samples are filtered first. The calculation was performed using eight polystyrene standards (Polymer Standard Services), ranging from 160 to 1,737,000 Daltons. The calculation was performed using Empower software (Waters) with a third-order calibration curve. The molar masses obtained are equivalent molar masses to polystyrene (Daltons). Tg measurement using DSC The glass transition temperature (Tg) of a polymer was measured by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min in a N2 atmosphere at a flow rate of 50 mL / min, in a TA Instruments Discovery DSC 250 apparatus according to the following method: a 5 ± 0.5 mg sample was weighed and placed in the DSC cell at a temperature between 20 and 25 °C. The sample was cooled to -120 °C and equilibrated at that temperature; after equilibration, the sample was heated from -120 °C to 160 °C at a heating rate of 5 °C / min; the sample was held at that temperature for 2 minutes and subsequently cooled to -120 °C at a cooling rate of 20 °C / min; once the sample reached -120 °C, the temperature was held for 5 minutes; Subsequently, the sample was heated from -120 °C to 220 °C at a heating rate of 5 °C / minute (thermogram A).The Tgse was measured from this last thermogram (thermogram A) as half the step width in the DSC signal (DSC thermogram, Heat Flux vs. Temperature) observed for a Tg. The processing of the DSC signal and the determination of the Tgse were performed using the TRIOS software package version 5.0 provided by TA Instruments. Analysis of the low molecular weight fraction by LC-MS LC system: Agilent 1290 Infinity II; Detector #1: Agilent 1290 Infinity II PDA; Detector #2: Agilent ¡Funnel 6550 Q-TOF-MS. The LC-MS analysis for the low molecular weight fraction was performed using the following procedure. A 100 mg / kg solution of material was prepared gravimetrically in methanol and stirred. 0.5 pL of this solution was injected into a UPLC system equipped with ESI-TOF-MS detection. The column used was a Waters HSS T3 C18, 100 x 2.1 mm, 1.8 pm, operating at 40 °C. The flow rate was 0.5 mL / min. The solvents used were 10 mM NH4CH3COO in water adjusted to pH 9.0 with NH3 (Eluent A), acetonitrile (B), and THF (C). Two binary gradients were applied from 80 / 20 A / B to 1 / 99 A / B over 10 minutes and from 1 / 99 A / B to 1 / 49 / 50 A / B / C over 5 minutes, after which the initial conditions (80 / 20 A / B) were applied. Assuming a linear MS response of all components across all response intervals and equal ionization efficiency for all components, the total ion current signals were integrated.In the case of coelution, the chromatograms of ions extracted from that particular species were integrated. QPAQnn / zznz / E / YiAi Division of the integrated signal of a particular low molecular weight peak between the total integrated sample signal yields the fraction of that low molecular weight species. MALDI-ToF-MS All MALDI-ToF-MS spectra were acquired using a Bruker Ultraflextreme MALDI-ToF mass spectrometer. The instrument is equipped with an Nd:YAG laser emitting at 1064 nm and a collision cell (not used for these samples). Spectra were acquired in positive ion mode using the reflectron, employing the highest resolution mode that provides accurate masses (range 60–7000 m / z). Cesium triiodide (range 0.3–3.5 kDa) was used for mass calibration (calibration method: Molecular Characterization of IAV, code MC-MS-05). The laser energy was set to 20%. Samples were dissolved in THF at approximately 50 mg / mL. The matrix used was: DCTB (trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile), CAS Number 300364-84-5. The matrix solution was prepared by dissolving 20 mg in 1 mL of THF. Sodium iodide (NaI, CAS No. 7681-82-5) was used as the salt; 10 mg were dissolved in 1 mL of THF with one drop of MeOH added. The sample:matrix:salt ratio was 10:200:10 (pL). After mixing, 0.5 pL was placed on a MALDI plate and allowed to air dry. The peaks measured in the MALDI spectrum are sodium adducts of multiaziridine compounds, and for the purposes of this report, the molecular weight (MW) of the multiaziridine compound is defined as MW = [M + MCation] Obs - MCation, where Obs . [M + MCation] Obs is the MALDI-TOF MS peak and MCation is the exact mass of the cation used to form the adduct (in this case, sodium with MCation = 23.0 Da). Multiaziridine compounds can be identified by comparing the MW with the exact molecular mass (i.e., the sum of the averaged non-isotopic atomic masses of its constituent atoms) of a theoretical structure, using a maximum deviation of 0.6 Da. Genotoxicity tests Genotoxicity was assessed using the ToxTracker® assay (Toxys, Leiden, The Netherlands). The ToxTracker assay is a panel of various validated green fluorescent protein (GFP)-based mouse embryonic stem (mES) reporter cell lines that can be used to identify the biological reactivity and potential carcinogenic properties of newly developed compounds in a single test. This methodology uses a two-step approach. In the first step, a dose range determination was performed using wild-type mES cells (strain B4418). Twenty different concentrations were tested for each compound, starting with 10 mM in DMSO as the highest concentration and nineteen consecutive two-fold dilutions. Subsequently, genotoxicity was assessed using specific genes linked to reporter genes for DNA damage detection; namely, the biomarkers Bscl2 (as explained in US9695481B2 and EP2616484B1) and Rtkn (Hendriks et al. Toxicol. Sci. 2015, 150, 190-203). Genotoxicity was assessed at 10, 25, and 50% cytotoxicity in the absence and presence of metabolizing systems based on rat S9 liver extract (rats induced with aroclor1254, Moltox, Boone, NC, USA). Independent cell lines were seeded in 96-well cell culture plates. Twenty-four hours after seeding, fresh ES cell medium containing the diluted test substance was added to the cells. For each compound tested, five concentrations were tested at two-fold dilutions. The highest concentration of the sample induced significant cytotoxicity (50–70%).In cases of negligible or low cytotoxicity, 10 mM or the maximum soluble concentration of the mixture is used as the maximum test concentration. Cytotoxicity is determined by cell count after 24 h of exposure using a Guava easyCyte 10HT flow cytometer (Millipore). GFP reporter induction was always compared to a vehicle control treatment. The DMSO concentration was similar in all wells for a given compound and never exceeded 1%. All compounds were tested in at least three completely independent, replicate experiments. A cisplatin-positive reference treatment (DNA damage) was included in all experiments. Metabolism was assessed by the addition of S9 liver extract. Cells were exposed to five concentrations of the test compound in the presence of S9 and the required cofactors (RegenSysA+B, Moltox, Boone, NC, USA) for 3 h. After washing, cells were incubated for 24 h in fresh ES cell medium. GFP reporter induction was determined after 24 h of exposure using a Guava easyCyte 10HT flow cytometer (Millipore). GFP expression was determined only in intact individual cells.The mean fluorescence of GFP and cell concentrations were measured in each well and used to assess cytotoxicity. Data were analyzed using ToxPlot software (Toxys, Leiden, The Netherlands). The reported induction levels are at compound concentrations that induce 10%, 25%, and 50% cytotoxicity after 3 h of exposure in the presence of rat S9 liver extract and 24 h of recovery, or alternatively, after 24 h of exposure without rat S9 liver extract. A positive induction level of the biomarkers is defined as equal to or greater than a 2-fold induction in at least one of 10, 25 and 50% cytotoxicity in the absence or presence of the rat liver extract S9 metabolizing system; a weakly positive induction as greater than a 1.5-fold induction and less than a 2-fold induction in at least one of 10, 25 and 50% cytotoxicity (but less than 2-fold in 10, 25 and 50% cytotoxicity) in the absence or presence of the rat liver extract S9 metabolizing system; and a negative level as less than or equal to a 1.5-fold induction in 10, 25 and 50% cytotoxicity in the absence and presence of rat liver extract S9-based metabolizing systems. Components and abbreviations used: Polytetrahydrofuran with an average Mn of 1000 Da (pTHF1000) was obtained from BASF, o-xylene (CAS No. 95-47-6) was obtained from Sigma-Aldrich. TDI (toluene diisocyanate, CAS No. 26471-62-5, Desmodur® T80, an 80 / 20 mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate) obtained from Covestro. 1-(2-hydroxyethyl)-ethyleneimine (CAS No. 1072-52-2) was obtained from Tokyo Chemical Industry Co., Ltd. Triton X-100 (Phoctylphenoxypolyethoxyethanol, CAS No. 9002-93-1) was obtained from SigmaAldrich. Tegomer® D3403 was obtained from Evonik. IPDI (5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane, Desmodur® I, isophorone diisocyanate, CAS No. 4098-71-9) was obtained from Covestro. 1-Methoxy-2-propanol acetate (propylene glycol methyl ether acetate, CAS No. 108-65-6) was obtained from Shell Chemicals. Dibutyltin dilaurate (CAS No. 77-58-7) was obtained from Sigma-Aldrich. 1-propanol (CAS No. 71-23-8) was obtained from Sigma-Aldrich. Tin 2-ethylhexanoate (CAS No. 301-10-0) was obtained from Sigma-Aldrich. Atlas™ G-5000 and Maxemul™ 7101 were obtained from Croda. Bismuth neodecanoate (CAS No. 34364-26-6) obtained from TIB Chemicals AG (Mannheim, Germany). Ethyleneimine (CAS No. 151-56-4) was obtained from Menadiona SL (Palafolls, Spain). Desmodur® N3600 was obtained from Covestro. Dimethylformamide (CAS No. 68-12-2) was obtained from Acros Organics (a division of Thermo Fisher Scientific). Di(propylene glycol) dimethyl ether (Proglyde™ DMM, CAS No. 111109-77-4) was obtained from Dow Inc. Trimethylolpropane Ths(2-methyl-1-aziridinepropionate), CAS No. 64265-57-2, CX-100 was obtained from DSM. Potassium carbonate (CAS No. 584-08-7) was obtained from Alfa Aesar (a division of Thermo Fisher Scientific). n-butylglycidyl ether (CAS No. 2426-08-6) was obtained from Alfa Aesar (a division of Thermo Fisher Scientific). Hydrazine (16% solution in water, CAS No. 302-01-2) was obtained from Honeywell. ρρβοηη / ζζηζ / Ε / γίΛΐ45 Dimethylolpropionic acid (DMPA, CAS No. 4767-03-7) was obtained from Perstop Polyols. Triethylamine (TEA, CAS No. 121-44-8) was obtained from Arkema Polypropylene glycol with a number average molecular weight of 1000 Da and with a number average molecular weight of 2000 Da was obtained from BASF. 3-methyl-1-phenyl-2-phospholene-1-oxide (CAS No. 707-61-9) was obtained from Sigma-Aldrich. Sodium lauryl sulfate (30% solution in water, CAS No. 73296-89-6) was obtained from BASF. Methyl methacrylate (CAS No. 80-62-6) was obtained from Lucite Int. n-Butyl acrylate (CAS No. 141-32-2) was obtained from Dow Chemical. Methacrylic acid (CAS No. 79-41-4) was obtained from Lucite Int. Ammonium persulfate (CAS No. 7727-54-0) was obtained from United Initiators. Ammonia (25% solution in water, CAS No. 1336-21-6) was obtained from Merck. 1-Butanol (CAS No. 71-36-3) was obtained from Sigma-Aldrich. Acetone (CAS No. 67-64-1) was obtained from Acros Organics (a division of Thermo Fisher Scientific). Methyl ethyl ketone (CAS No. 78-93-3) was obtained from Sigma-Aldrich. Synthesis of P1, a water-based polyurethane In a one liter flask (equipped with a thermometer and a raised-head stirrer) were loaded 29.9 grams of dimethylolpropionic acid, 282.1 grams of polypropylene glycol with a calculated average molecular weight (M) of 2000 Da and an OH value of 56 ± 2 mg KOH / g of polypropylene glycol), 166.5 grams of polypropylene glycol with a calculated average molecular weight (M) of 1000 Da and an OH value of 112 ± 2 mg KOH / g of 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 of polypropylene glycol). The reaction mixture was placed under a nitrogen atmosphere, heated to 50 °C, and then 0.07 g of dibutyltin dilaurate was added to the reaction mixture. An exothermic reaction was observed; however, due care was taken to ensure that the reaction temperature did not exceed 97 °C.The reaction was maintained at 95 °C for one hour. The NCO content of the resulting P1' polyurethane was 7.00% solids, as determined according to the method described herein (theoretically 7.44%), and the acid value of the PT polyurethane was 16.1 ± 1 mg KOH / g of P1' polyurethane. The PT polyurethane was cooled to 60 °C, and 18.7 grams of triethylamine were added. The resulting mixture was stirred for 30 minutes. Subsequently, an aqueous dispersion of the PT polyurethane (also referred to as P1) was prepared as follows: the mixture of PT polyurethane and triethylamine prepared in this manner was added (at room temperature for 60 minutes) to 1100 grams of water. QPRQnn / zznz / E / YiAi demineralized, 19.5 grams of nonylphenol ethoxylate (9 ethoxylated groups) and 4.0 grams of triethylamine. Once the supply was complete, the mixture was stirred for a further 5 minutes and then 111.2 grams of hydrazine (16% wt% solution in water) were added to the mixture. The aqueous dispersion of polyurethane P1' prepared in this manner was stirred for a further 1 h and P1 was obtained. Example 1 A round-bottom flask fitted with a condenser was placed under an N2 atmosphere and charged with ethyleneimine (50.0 grams), n-butylglycidyl ether (108.0 grams) and K2CO3 (5.00 grams) and heated to 40 °C for 30 min, after which the mixture was stirred for 48 h at T= 40 °C. After filtration, the excess El was removed under vacuum, followed by further purification by vacuum distillation, resulting in a colorless, low-viscosity liquid. In a reaction flask equipped with a thermometer, 17.2 grams of the resulting material (1-(aziridin-1-yl)-3-butoxypropan-2-ol) were loaded along with 150 grams of dimethylformamide. The mixture was stirred with a mechanical 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 supply vessel. Next, 0.02 grams of bismuth neodecanoate was added to the reaction flask, and the solution from the supply vessel was added dropwise to the reaction flask over 30 minutes, maintaining a constant reaction temperature of 50 °C. After the supply was complete, the temperature was increased to 80 °C. Samples were taken at regular intervals and the progress of the reaction was monitored using a Bruker Alpha FT-IR spectrometer until no change in NCO elongation was observed at 2200-2300 cnr1.Subsequently, 0.64 grams of 1-butanol were added to the mixture, followed by further reaction until the complete disappearance of the aforementioned NCO elongation peak. Evaporation of the solvent under vacuum yielded a highly viscous, yellowish liquid. The calculated theoretical molecular weight of the main component was 1023.69 Da, the chemical structure is shown below. QPRQnn / zznz / E / YiAi ρρβοηη / ζζηζ / Ε / γίΛΐ The molecular weight was confirmed by Maldi-TOF-MS: [M + Na+] Calcd = 1046.69 Da; [M + Na+] Obs. = 1046.72 Da. The following components with a mass below 580 Da were determined by LC-MS and quantified: was present in the composition at 0.48% by weight and v was present in less than 0.01% by weight. Genotoxicity test Without rat liver extract S9 With rat liver extract S9 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 The results of the genotoxicity test show that the crosslinking composition of Example 1 is not genotoxic. Subsequently, 10 grams of the viscous liquid obtained in the previous step were mixed with 5 grams of acetone and incubated at 50 °C until a homogeneous solution was obtained. To this solution, 0.03 grams of triethylamine (TEA) were added, followed by 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 an S 25 N - 18G head at 2,000 rpm. The stirring speed was then increased to 10,000 rpm, and 10 grams of demineralized water, brought to pH 11 using triethylamine, were gradually added to the mixture over 15 minutes. During this addition process, the mixer was continuously moved around the reaction vessel. Upon completion of the addition, the resulting dispersion was stirred at 5,000 rpm for a further 10 minutes and the pH of the dispersion was adjusted to 11 with TEA. The functional performance and stability of the crosslinking dispersion were evaluated by spot testing on coating surfaces, based on the procedures in DIN 68861-1, and viscosity measurements were taken using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm, unless otherwise stated). For these tests, the crosslinking dispersion was stored in an oven at 50 °C for 4 weeks. The viscosity of the crosslinking dispersion was determined each week. In addition, each week, 1.0 gram of the aged crosslinking dispersion was mixed with 10.5 strands of P1 polymer under continuous stirring, and the resulting mixture was stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 µm wire rod applicators (Test 1). As a reference, films of the same composition lacking the crosslinking dispersion were also molded (Test Blank).The films were dried for 1 hour at 25 °C, then reheated to 50 °C for 16 hours. Subsequently, a piece of cotton was soaked in 1:1 EtOH:demineralized water and placed on the film for 1 hour. After removing the EtOH and 60 minutes of recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no visible damage): Performance and stability test ορβοηη / ζζηζ / E / γίΛΐ Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size 1 (nm) 191 222 224 216 212 Viscosity 1 477 490 450 684 738 (mPa.s) Test 1 3 3 3 3 3 Test blank 1 1 1 1 1 The performance of the synthesized compound as a crosslinking agent was further evaluated using spot tests on coating surfaces with different binder systems. The water-based acrylic binder A1 was synthesized as follows. A 2 L four-necked flask equipped with a thermometer and an up-head stirrer was charged with sodium lauryl sulfate (30% solids in water, 18.6 g solution) and demineralized water (711 g). The phase in the reactor was placed under a nitrogen atmosphere and heated to 82 °C. A mixture of demineralized water (112 g), sodium lauryl sulfate (30% solids in water, 37.2 g solution), methyl methacrylate (209.3 g), n-butyl acrylate (453.56 g), and methacrylic acid (34.88 g) was placed in a large-delivery funnel and emulsified with an up-head stirrer (monomer delivery). Ammonium persulfate (1.75 grams) was dissolved in demineralized water (89.61 grams) and placed in a small funnel for dispensing (starter feed). The ammonium persulfate (1.75 grams) was dissolved in demineralized water (10.5 grams), and this solution was added to the phase in the reactor.Immediately afterward, 5% by volume of the monomer supply was added to the phase in the reactor. The reaction mixture was then heated exothermically to 85 °C and maintained at 85 °C for 5 minutes. Following this, the remaining monomer and initiator supplies were added to the reaction mixture for 90 minutes, maintaining a temperature of 85 °C. Once these supplies were complete, the monomer supply funnel was rinsed with demineralized water (18.9 grams), and the reaction temperature was maintained at 85 °C for 45 minutes. The mixture was then cooled to room temperature and adjusted to pH 7.2 with ammonia solution (6.25 wt% in demineralized water), and brought to 40% solids with additional demineralized water. For further staining tests, an additional crosslinking dispersion, synthesized as described above, was stored in an oven at 50 °C for 4 weeks. Each week, 2.0 grams of the aged crosslinking dispersion was mixed with 10.5 grams of water-based acrylic binder A1 under continuous stirring, and the resulting mixture was stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 µm wire rod applicators (Test 1-A1). As a reference, film was also molded from the same composition but lacking the crosslinking dispersion (Blank-A1). The films were dried for 1 hour at 25 °C, then reheated at 50 °C for 16 hours. Subsequently, a piece of cotton was soaked in 1:1 EtOH:demineralized water and placed on the film for 1 hour.After removing the EtOH and 60 minutes of recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates that there is no visible damage):. QPRQnn / zznz / E / YiAi Sample Week Week Week Week Week Week 0 1 2 3 4 Test 1 -A1 3 3 3 3 3 Blank-A1 1 1 1 1 1 Comparative example C1 For comparative example 1, the trimethylolpropane crosslinking agent tris(2-methyl-1-aziridinpropionate) was used Genotoxicity test Without rat liver extract S9 With rat liver extract S9 Bscl 2 Concentration 10 25 50 —> Rtkn 10 Bscl 2 Rtkn 10 25 50 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 results of the genotoxicity test demonstrate that the crosslinking composition of Example C1 is genotoxic. 7.5 grams of this crosslinking agent were mixed with 3.75 grams of acetone and incubated at 50 °C until a homogeneous solution was obtained. To this solution, 0.03 grams of triethylamine were added, followed by 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 an S 25 N - 18G head at 2,000 rpm. Stirring was then increased to 10,000 rpm, and 7.5 grams of demineralized water, adjusted to pH 11 using triethylamine (TEA), were gradually added to the mixture over 15 minutes. During this addition process, the mixer was continuously moved around the reaction vessel. Upon completion of the addition, the resulting mixture was stirred at 5,000 rpm for a further 10 minutes and the pH of the mixture was adjusted to 11. The functional performance and stability of the crosslinking mixture were evaluated by spot testing on coating surfaces, based on the procedures in DIN 68861-1, and viscosity measurements were taken using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm, unless otherwise stated). For these tests, the crosslinking mixture was stored in an oven at 50 °C for four weeks. The viscosity of the crosslinking mixture was determined weekly. In addition, each week, 0.8 grams of the aged crosslinking mixture was mixed with 21 grams of P1 polymer under continuous stirring, and the resulting coating composition was stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 µm wire rod applicators (Test C1). As a reference, films of the same composition lacking the crosslinking mixture were also molded (Test Blank).The films were dried for 1 hour at 25 °C, then reheated to 50 °C for 16 hours. Subsequently, a piece of cotton was soaked in 1:1 EtOH:demineralized water and placed on the film for 1 hour. After removing the EtOH and 60 minutes of recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no visible damage): ορβοηη / ζζηζ / Ε / γίΛΐ Performance and stability test Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C1 (nm) N / A _* _* _* _* Viscosity C1 (mPa.s) 10 ★ _* _* _* Test C1 5 _* _* _* -* Test blank 1111 The crosslinking mixture gelled during the first week of storage 1 Comparative example C2 As in example C1, where during the water addition step 7.5 grams of demineralized water, brought to pH 9 with TEA, were used instead of demineralized water brought to pH 11 and the resulting mixture was adjusted to pH 9 with TEA. Performance and stability test. Sample Week 0 Week 1 Week 2 Week 3 Week 4 Particle size C2 N / A _* _* * _* (nm) Viscosity C2 (mPa.s) 10 _* _* ★ _* Test C2 5 _* _* ★ _* Test blank 1 1 1 1 1 The crosslinking mixture gelled during the first week of storage Comparative example C3 As in example C1, where during the water addition step 7.5 grams of demineralized water, brought to pH 8 with TEA, were used instead of demineralized water brought to pH 11 and the resulting mixture was adjusted to pH 8 with TEA. 52 Performance and Stability Test. Sample Week 0 Week 2 Week 3 Week 4 C3 Particle Size N / A (nm) C3 Viscosity (mPa.s) 20 C3 Test 5 Test Blank 11111 *The crosslinking mixture gelled during the first week of storage QPAonn / zznz / E / YiAi Comparative example C4 13.0 grams of 1-(2-hydroxyethyl)ethyleneimine and 175 grams of dimethylformamide were loaded into a reaction flask equipped with a thermometer. The mixture was stirred using a mechanical stirrer under a nitrogen atmosphere. The mixture was then heated to 50 °C, after which 0.03 grams of bismuth neodecanoate were added 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. Once the addition was complete, the reaction temperature was increased to 80 °C. Samples were taken at regular intervals, and the progress of the reaction was monitored using a Bruker Alpha FT-IR spectrometer until no further elongation of NCO was observed at 2200–2300 cm⁻¹. The solvent was removed under vacuum to obtain a clear, colorless, and highly viscous liquid. The calculated molecular weight of the theoretical main component was 765.47 Da, the chemical structure is shown below. The molecular weight was confirmed by Maldi-TOF-MS: [M + Na+] Calc. = 788.46 Da; [M + Na+] Obs. = 788.31 Da. Subsequently, 7.5 grams of the colorless liquid obtained in the previous step were mixed with 3.8 grams of acetone and incubated at 50 °C until a homogeneous solution was obtained. To this solution, 0.03 grams of triethylamine (TEA) were added, followed by 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 an S 25 N - 18G head at 2,000 rpm. The stirring speed was then increased to 10,000 rpm, and 7.5 grams of demineralized water, adjusted to pH 11 using triethylamine, were gradually added to the mixture over 15 minutes. During this addition process, the mixer was continuously moved around the reaction vessel. Upon completion of the addition, the resulting dispersion was stirred at 5,000 rpm for a further 10 minutes and the pH of the dispersion was adjusted to 11 with TEA.Within 4 hours of completing the preparation of this 1-(2-hydroxyethyl)ethyleneimine-based product, severe coagulation was observed. Therefore, stable dispersion was not achieved during storage. Comparative example C5 Under a nitrogen atmosphere, 21.3 grams of 1-propanol were added over a period of 6 hours to 78.7 grams of isophorone diisocyanate (IPDI) and 0.01 grams of tin 2-ethylhexanoate 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 maintained at 150 °C until the NCO content reached 7.0% by weight. The mixture was then cooled to 80 °C, and 333 grams of 1-methoxy-2-propyl acetate (MPA) were added. A polycarbodiimide solution with an isocyanate functional group was obtained with a solids content of 50.6% by weight and an NCO content of 7.0% by weight of solids. 7.0 grams of 1-(2-hydroxyethyl)ethyleneimine were added to 100 grams of this polycarbodiimide with an isocyanate functional group. One drop of dibutyltin dilaurate was added. The mixture was heated to 80 °C while stirring. The mixture was maintained at 80 °C for 1 hour. FTIR showed a small signal of residual isocyanate, which disappeared after a few days. The solution was further diluted with 8.0 grams of MPA, resulting in a yellow solution with a solids content of 50.4 wt%. This carbodiimide with an aziridine functional group contains 3.2 meq of acid-reactive groups (i.e., aziridine and carbodiimide functional groups) per gram of solids. The generalized structure of this carbodiimide is shown below. QPRQnn / zznz / E / YiAi in which a, b and c indicate repetition units. This generalized structure was confirmed by MALDI-TOF-MS, an example of which is shown below: QPRQnn / zznz / E / YiAi The molecular weight was confirmed by Maldi-TOF-MS: [M + Na+] Calc. = 2043.34 Da; [M + Na+] Obs. = 2043.32 Da. Genotoxicity test results Concentration —>· Without rat liver extract S9 With rat liver extract S9 Bscl 2 10 25 50 10 Rtkn 25 50 Bscl 2 10 25 50 10 Rtkn 25 50 Composition C5 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 results of the genotoxicity test demonstrate that the crosslinking composition of Example C5 is genotoxic. Subsequently, 25.0 grams of the yellow solution obtained in the previous step were stirred at room temperature using a 50 mm diameter three-bladed propeller stirrer at 500 rpm. Then, 25.0 grams of demineralized water were gradually added to the mixture over 15 minutes. Upon completion of the addition, the resulting dispersion was stirred at 500 rpm for an additional 5 minutes. The functional performance and stability of the crosslinking dispersion were evaluated by spot testing on coating surfaces, based on the procedures in DIN 68861-1, and viscosity measurements were taken using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm, unless otherwise stated). For these tests, the crosslinking dispersion was stored in an oven at 50 °C for 4 weeks. The viscosity of the crosslinking dispersion was determined weekly. In addition, each week, 5.1 grams of the aged crosslinking dispersion were mixed with 10.5 strands of P1 polymer under continuous stirring, and the resulting mixture was stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 µm wire rod applicators (Test C7). As a reference, films of the same composition lacking the crosslinking dispersion were also molded (Test Blank).The films were dried for 1 hour at 25 °C, then reheated to 50 °C for 16 hours. Subsequently, a piece of cotton was soaked in 1:1 EtOH:demineralized water and placed on the film for 1 hour. After removing the EtOH and allowing a few minutes of recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no visible damage): Performance and stability test. Sample Week 0 Week 1 Week 2 Week 3 Week 4 C5 Particle Size (nm) 76 _* _* _* _* C5 Viscosity (mPa.s) 812 ★ ★ ★ ★ C5 Test 4 _* _* ★ _* Test Blank 1 1 1 1 1 *The crosslinking mixture coagulated during the first week of storage Comparative example C8 A 1 L round-bottom flask equipped with a thermometer and a raised-head stirrer was placed under a nitrogen atmosphere and charged with 196.1 g of polytetrahydrofuran with an average Mn of 1000 Da (pTHF1000) and 200.0 g of o-xylene. The resulting mixture was cooled to -10 °C using ethanol and ice, after which a solution of 68.4 g of toluene diisocyanate (TDI) in 50.0 g of o-xylene was added. The mixture was allowed to become exothermic by bringing it to -1 °C, followed by a gradual increase to room temperature without further heating. The reaction continued to complete conversion (residual NCO of 3.2%), and 200 g of the resulting reaction mixture was transferred to a 500 mL round-bottom flask equipped with a thermometer and a raised-head stirrer under a nitrogen atmosphere. Then 14 were added to this mixture.Five grams of 1-(2-hydroxyethyl)ethyleneimine were heated for 60 minutes, maintaining room temperature using a water bath. The mixture was then stirred for 1 hour at 25 °C. Samples were taken at regular intervals, and the reaction progress was monitored using a Bruker Alpha FT-IR spectrometer until no further NCO elongation was observed at 2200–2300 cm⁻¹. The solids content was adjusted to 49% using additional o-xylene, resulting in a slightly cloudy, low-viscosity solution. The calculated molecular weights of the theoretical main components and their chemical structures are shown below: The molecular weight was confirmed by Maldi-TOF-MS: [M + Na+] Calc. = 1427.91 Da; [M + Na+] Obs. = 1428.02 Da. The molecular weight was confirmed by Maldi-TOF-MS: [M + Na+] Calc. = 371.17 Da; [M + Na+] Obs. = 371.21 Da. Subsequently, 18.0 grams of the low-viscosity solution obtained as described above were 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-blade propeller stirrer with a 50 mm diameter at 500 rpm. The stirring speed was then increased to 800 rpm, and 15.0 grams of demineralized water were gradually added to the mixture over 15 minutes. After the addition was complete, the resulting dispersion was stirred at 500 rpm for an additional 10 minutes. The functional performance and stability of the crosslinking dispersion were evaluated by spot testing on coating surfaces, based on the procedures in DIN 68861-1, and viscosity measurements were taken using a Brookfield DVE-LV viscometer (S62 spindle at 60 rpm, unless otherwise stated). For these tests, the crosslinking dispersion was stored in an oven at 50 °C for 4 weeks. The viscosity of the crosslinking dispersion was determined each week. In addition, each week, 2.8 grams of the aged crosslinking dispersion were mixed with 10.5 strands of P1 polymer under continuous stirring, and the resulting mixture was stirred for 30 minutes. This coating composition was filtered and applied to Leneta test cards using 100 µm wire rod applicators (Test C8). As a reference, films of the same composition lacking the crosslinking dispersion were also molded (Test Blank).The films were dried for 1 hour at 25 °C, then reheated to 50 °C for 16 hours. Subsequently, a piece of cotton was soaked in 1:1 EtOH:demineralized water and placed on the film for 1 hour. After removing the EtOH and 60 minutes of recovery, the following results were obtained (a score of 1 indicates complete degradation of the film, 5 indicates no visible damage): QPRQnn / zznz / E / YiAi Performance and stability test. Sample Week 0 Week 1 Week 2 Week 3 Week 4 C8 Particle Size (nm) 1387t 423t _* * _* C8 Viscosity (mPa.s) 4032 600 _* * _* C8 Test 3 3 _* ★ Test Blank 1 1 1 1 1 *The crosslinking mixture gelled during the second week of storage; a reliable particle size measurement could not be obtained for this sample.

Claims

57 NOVELTY OF THE INVENTION Having described the present invention as above, the following is considered novel and is therefore claimed as property: CLAIMS 1. A multiaziridine crosslinking composition, characterized in that the multiaziridine crosslinking composition is an aqueous dispersion having a pH ranging from 9 to 14 and comprising a multiaziridine compound in dispersed form, wherein such multiaziridine compound has: a.of 2 to 6 of the following structural units A: R4R3 where R1, R2, R3 and R4 are H; m is 1, R' and R” are in accordance with (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-OR””, wherein 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” together form a saturated cycloaliphatic hydrocarbon group containing from 5 to 8 carbon atoms; b. one or more linking chains wherein each of these linking chains links two of the structural units A; wherein a linking chain is the shortest chain of consecutive atoms linking two structural units A; and c.a molecular weight in the range of 600 to 10000 Daltons, wherein the molecular weight is determined using MALDI-TOF mass spectrometry as described in the description.

2. The multiaziridine crosslinking composition according to claim 1, characterized in that the linking chains consist of 4 to 300 atoms, more preferably 5 to 250 and most preferably 6 to 100 atoms and the linking chains are preferably an assembly of covalently connected atoms, said assembly of atoms consisting of i) carbon atoms, ii) carbon and nitrogen atoms or iii) carbon, oxygen and nitrogen atoms.

3. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the multiaziridine compound contains 2 or 3 structural units A.

4. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that R' is H and R” = an alkyl group containing 1 to 4 carbon atoms, CH2-O-(C=O)-R'' or CH2-OR””, wherein R'' is an alkyl group containing 4 to 12 carbon atoms and R”” is an alkyl group containing 1 to 14 carbon atoms.

5. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the multiaziridine compound comprises one or more connecting groups, wherein each of these connecting groups connects two of the structural units A, wherein the connecting groups consist of at least one functional group selected from the group consisting of an aliphatic hydrocarbon functional group (preferably containing 1 to 8 carbon atoms), a cycloaliphatic hydrocarbon functional group (preferably containing 4 to 10 carbon atoms), an aromatic hydrocarbon functional group (preferably containing 6 to 12 carbon atoms), an isocyanurate functional group, an iminooxadiazindione functional group, an ether functional group, an ester functional group, an amide functional group, a carbonate functional group, a urethane functional group, a urea functional group, a biuret functional group, or an allophanate functional group.urethdione functional group and any combination thereof.

6. The multiaziridine crosslinking composition according to claim 5, characterized in that the connecting groups consist of at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and additionally optionally an isocyanurate functional group or an iminooxadiazindione functional group.

7. The multiaziridine crosslinking composition according to claim 5 or 6, characterized in that the connecting groups consist of at least one aliphatic hydrocarbon functional group and / or at least one cycloaliphatic hydrocarbon functional group and furthermore an isocyanurate functional group or an iminooxadiazindione functional group.

8. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the multiaziridine compound comprises one or more connecting groups wherein each of these connecting groups connects two of the structural units A, wherein the connecting groups consist of (i) at least two aliphatic hydrocarbon functional groups and (ii) an isocyanurate functional group or an iminooxadiazindione functional group and wherein a pendant group is present in a connecting group, wherein the pendant group has the following structural formula: QPRQnn / zznz / E / YiAi ορβοηη / ζζηζ / E / γίΛΐ where: n' is the number of repeating units and is an integer from 1 to 50, preferably from 2 to 30, more preferably from 5 to 20.X is O or NH, preferably X is O, R? and Rs are independently H or CH3 in each repeating unit, R9 is an aliphatic hydrocarbon group, preferably containing 1 to 8 carbon atoms, and R10 is an aliphatic hydrocarbon group containing 1 to 20 carbon atoms (preferably CH3), a cycloaliphatic hydrocarbon group containing 5 to 20 carbon atoms or an aromatic hydrocarbon group containing 6 to 20 carbon atoms.

9. The multiaziridine crosslinking composition according to claim 8, characterized in that one of R7 and Rs is H and the other R7 or Rs is CH3.

10. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the number of consecutive C atoms and, optionally, O atoms between the N atom of the urethane group in one structural unit A and the next N atom which is present in the linking chain or which is in the N atom of the urethane group of another structural unit A is at most 9.

11. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the multiaziridine compound is obtained by reacting at least one polyisocyanate with aliphatic reactivity in which all the isocyanate groups are directly bonded to aliphatic or cycloaliphatic hydrocarbon groups, regardless of whether aromatic hydrocarbon groups are also present, and a compound B having the following structural formula: Whereas the molar ratio between compound B and the polyisocyanate is 2 to 6, more preferably 2 to 4 and most preferably 2 to 3, and wherein m, R', R", R1, R2, R3 and R4 are as defined in the preceding claims.

12. The multiaziridine crosslinking composition according to any of claims 8 to 11, characterized in that the multiaziridine compound is the reaction product of at least one compound (B), a polyisocyanate and alkoxy poly(propylene glycol) and / or poly(propylene glycol).

13. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the multiaziridine compound has a molecular weight of 600 to 5000 Daltons, more preferably the multiaziridine compound has a molecular weight of at least 800 Daltons, even more preferably at least 840 Daltons, even more preferably at least 1000 Daltons and preferably at most 3800 Daltons, more preferably at most 3600 Daltons, more preferably at most 3000 Daltons, more preferably at most 1600 Daltons, even more preferably at most 2300 Daltons, even more preferably at most 1600 Daltons.

14. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the aqueous dispersion comprises molecules with an aziridine functional group having a molecular weight of less than 580 Daltons in an amount of less than 5% by weight, with respect to the total weight of the aqueous dispersion, the molecular weight being determined using LC-MS as described in the description.

15. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the pH of the aqueous dispersion is at least 9.5 and preferably at most 13, more preferably at most 12.

16. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the amount of water in the aqueous dispersion is at least 15% by weight, preferably at least 20% by weight, more preferably at least 30% by weight, even more preferably at least 40% by weight and at most 95% by weight, preferably at most 90% by weight, more preferably at most 85% by weight, more preferably at most 80% by weight, even more preferably at most 70% by weight, even more preferably at most 60% by weight, with respect to the total weight of the aqueous dispersion.

17. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the amount of such multiaziridine compound in the aqueous dispersion is at least 5% by weight, preferably at least 10% by weight, more preferably at least 15% by weight, more preferably at least 20% by weight, even more preferably at least 25% by weight, even more preferably at least 30% by weight, even more preferably at least 35% by weight and at most 70% by weight, preferably at most 65% by weight, more preferably at most 60% by weight, even more preferably at most 55% by weight, with respect to the total weight of the aqueous dispersion.

18. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the solids content of the aqueous dispersion is at least 5, preferably at least 10, even more preferably at least 20, even more preferably at least 30, even more preferably at least 35 and at most 70, more preferably at most 65 and even more preferably at most 55% by weight.

19. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the multiaziridine crosslinking composition comprises particles comprising such multiaziridine compound, wherein such particles have a scattering intensity-averaged hydrodynamic diameter of 50 to 500 nanometers, more preferably 70 to 350 nm, even more preferably 120 to 275 nm, wherein the scattering intensity-averaged hydrodynamic diameter is determined as specified in the description.

20. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the aqueous dispersion comprises a dispersant.

21. The multiaziridine crosslinking composition according to any of the preceding claims, characterized in that the aqueous dispersion comprises a separate surfactant molecular component as a dispersant in an amount ranging from 0.1 to 20% by weight, with respect to the total weight of the aqueous dispersion.

22. The multiaziridine crosslinking composition according to claim 21, characterized in that the dispersant is a polymer having a number-average molecular weight of at least 2000 Daltons, more preferably at least 2500 Daltons, more preferably at least 3000 Daltons, more preferably at least 3500 Daltons, more preferably at least 4000 Daltons, and preferably at most 1000000 Daltons, and the polymer is a polyether, more preferably a polyether copolymer, even more preferably a polyether block copolymer, even more preferably a poly(alkylene oxide) block copolymer, even more preferably a poly(ethylene oxide)-poly(propylene oxide) block copolymer, wherein the number-average molecular weight is determined using MALDI-ToF mass spectrometry as described in the description.

23. Use of the multiaziridine crosslinking composition according to any of claims 1 to 22 for crosslinking a carboxylic acid functional group polymer dissolved and / or dispersed in an aqueous medium, wherein the carboxylic acid functional group polymer contains carboxylic acid groups and / or carboxylate groups and the amounts of aziridinyl groups and carboxylic acid and carboxylate groups are chosen such that the stoichiometric amount (SA) of aziridinyl groups in carboxylic acid and carboxylate groups is from 0.1 to 2.0, more preferably from 0.2 to 1.5, even more preferably from 0.25 to 0.95, most preferably from 0.3 to 0.

8.

24. A two-component coating system characterized in that it comprises a first component and a second component, each of which is separate and distinct from each other, and wherein the first component comprises a polymer with a carboxylic acid functional group dissolved and / or dispersed in an aqueous medium, wherein the polymer with a carboxylic acid functional group comprises carboxylic acid groups and / or carboxylate groups, and the second component comprises the multiaziridine crosslinking composition according to any one of claims 1 to 22.