Waterborne amine hardener with improved corrosion protection

Abstract

The present invention relates to a waterborne amine hardener composition (H) comprising a) an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P), wherein the adduct (PAd) is substantially free of epoxy groups and has an acid value of at least 10 mgKOH / g; b) a polyamine (A); and c) water; the molar ratio between the epoxy groups from the epoxy resin (E) and the acidic hydrogen atoms from the phosphorus-derived acids (P) being between 0.2 and 0.95, and the molar ratio between the acidic hydrogen atoms comprised in the adduct (PAd) and the basic nitrogen atoms from the polyamine (A) being between 0.02 and 0.90. The present invention also relates to the process for the preparation of a waterborne amine hardener composition (H) and to the use thereof for coating a substrate. It also relates to waterborne two-pack and three-pack coating compositions.

Description

[0001] WATERBORNE AMINE HARDENER WITH IMPROVED CORROSION

[0002] PROTECTION

[0003] FIELD OF THE INVENTION

[0004] The present invention generally relates to a waterborne amine hardener composition as well as a waterborne two-pack coating composition comprising an epoxy resin dispersion component and a hardener component, wherein the hardener component comprises said waterborne amine hardener composition. The invention further relates to a waterborne three-pack coating composition comprising in a first component an epoxy resin dispersion, in a second component a hardener comprising a polyamine, and in a third component an adduct of an epoxy resin and phosphorus-derived acids. Further the invention relates to a process for the preparation of said waterborne amine hardener composition. The invention further relates to the use of said waterborne amine hardener composition, or to the use of said waterborne two-pack coating composition, or to the use of said waterborne three-pack coating composition, for coating a substrate to protect the substrate from corrosion. The invention further relates to a substrate coated with said waterborne two-pack coating composition, or coated with said waterborne three-pack coating composition.

[0005] BACKGROUND OF THE INVENTION

[0006] Most metals, with the exception of noble metals, are provided with coating films when exposed to ambient conditions to prevent, or at least retard, corrosion. Application of a coating film onto a metal surface provides a barrier between the metal substrate and a damaging environment if there is sufficient adhesion of the coating film to the metal substrate, and if the permeability of the coating film for oxygen and water is low. Among coating films, paints in liquid form or powder form play an important role. An aspect which has to be considered when selecting a coating material is avoiding of constituents in the coating composition that can react with the metal surface, and thus possibly damage the metal substrate, for example chloride ions which may provide a seed for future corrosive attack. Many organic polymers are suitable for forming coating films on a metal surface. It is desired that these films have a sufficient hardness, sufficient adhesion as pointed out supra, and also sufficient elasticity to enable the coating film to follow possible deformations of the coated metal items.

[0007] Epoxy resins are one of the most-used materials in the formulation of corrosionprotection paints. Waterborne two-pack epoxy paints based on epoxy resins and hardeners therefor are preferred as they do not need organic solvents and therefore have a low VOC, and combine high molar mass resins with a high mass fraction of solids with low viscosity, due to their dispersion form.

[0008] WO 2022 / 201890 describes an epoxy resin composition containing an epoxy resin having an average epoxy equivalent of 160 g / eq or less, an amine curing agent and a phosphate compound having a molecular weight of 250 or less. The phosphate compound is not chemically incorporated into the crosslinked structure itself, but is contained within the network formed by the crosslinked structure and this state is maintained even after curing. Thereby, the elastic modulus of the obtained cured epoxy resin is increased.

[0009] US Patent No. 8,148,451 relates to aqueous, epoxy phosphate ester resin coatings having low volatile organic compounds (VOC) and to a process for their preparation and usage which provides better water dispersion stability and superior film forming properties. The epoxy phosphate ester resins are neutralized with monofunctional amine (i.e. AMP-95 from the Dow Chemical Co.) in order to obtain emulsions in water. These resin emulsions have been mixed with melamine resins, flow control resin and solvents, spray applied over untreated cold roll steel and cured for 2’@325F.

[0010] US Patent Application No. US 2004 / 0077801 relates to adducts of epoxy resins and phosphorus-derived acids and to a process for their preparation. The adducts have an acid number of from about 10 to about 70 mg / g and the acid groups remaining on the resin are at least partly converted to the salt form by addition of a neutralizing agent (i.e. dimethylethanolamine) in order to be dispersed in water. These materials were applied to cold-rolled metal sheet and cured either for 30 min at 160°C or for 48 hours at room temperature. Corrosion protection properties have been demonstrated in a salt spray test.

[0011] Japanese Patent Application JPH08143643 describes curing agents for epoxy resins containing as active ingredients organic polyamines addition modified with a phosphorus-containing epoxy compound having an unreacted epoxy group in the molecule. The application teaches that if the ratio of the phosphorus-containing epoxy compound is less than 0.01 (i.e. less than 0.01 phosphorus-containing epoxy with respect to one active hydrogen of organic polyamines), the effect of phosphoric acid addition is difficult to be exhibited. In fact, a phosphorus-containing epoxy compound with a specific epoxy equivalent (i.e. between 230 and 1360) has been added to meta- xylylenediamine to form a curing agent. The resulting curing agents were mixed with different types of epoxy resins, applied to steel plates and cured at room temperature for one week. Corrosion protection properties have been demonstrated in a salt spray test.

[0012] Despite the inherent corrosion resistance of epoxy-amine systems, the ever-increasing environmental challenges and harsh operating conditions have necessitated the development of more robust and durable coating solutions. Existing epoxy-amine systems have demonstrated satisfactory performance in standard neutral salt spray (NSS) tests, which simulate typical corrosive environments. However, when subjected to more aggressive testing methods, such as the acetic acid salt spray (AASS) test, these systems often exhibit performance failures within a relatively short period, especially on substrates like sandblasted aluminum.

[0013] The limitations of current epoxy-amine systems in providing long-term corrosion protection under severe conditions have prompted researchers and industry professionals to explore novel approaches to enhance the performance of these coatings. Improving the corrosion resistance of epoxy-amine systems while maintaining their desirable properties, such as adhesion and mechanical strength, remains a significant challenge in the field.

[0014] As the demand for high-performance coatings continues to grow across various industries, including transportation, infrastructure, and marine applications, there is a pressing need for innovative solutions that can address the shortcomings of existing epoxy-amine systems. The development of advanced curing agents and formulations that can withstand harsh environments and provide extended corrosion protection is crucial for meeting the evolving requirements of end-users and ensuring the longevity of coated structures.

[0015] Hence there remains a need in the art for paints with a low VOC content that can be cured at ambient temperature and that provide an improved protection against corrosion.

[0016] AIM OF THE INVENTION

[0017] It is accordingly an object of the invention, to provide a waterborne amine hardener that is useful in formulations of waterborne two-pack coating compositions for protecting metal substrates from corrosion. It is further an object of the invention to provide a waterborne amine hardener that improves the corrosion protection of paints for substrates, preferably metal substrates like aluminum, against acidic corrosive environments. Another object of the invention is to provide a waterborne amine hardener for two-pack coating compositions that have a low VOC content and that can be cured at ambient temperatures. A further object of the invention is to provide coatings with a good degree of drying, good adhesion to metal and high mechanical resistance. It is another object of the invention that the versatility of the waterborne amine hardener allows it to be used not only as a primer system in the field of railway, but anywhere corrosion protection directly on metal is required. A further object of the invention is to provide two-pack coating compositions or three-pack coating compositions that have a low VOC content, that can be cured at ambient temperatures, and when applied to metal substrates, show a good degree of drying, good adhesion, high mechanical resistance and that efficiently protect the metal substrates against acidic corrosive environments.

[0018] SUMMARY OF THE INVENTION

[0019] The first aspect of the present invention relates to a waterborne amine hardener composition (H) comprising: a) an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P), wherein the adduct (PAd) is substantially free of epoxy groups and has an acid value of at least 10 mgKOH / g, preferably an acid value comprised between 50 and 180 mgKOH / g; b) a polyamine (A); and c) water; the molar ratio between the epoxy groups from the epoxy resin (E) and the acidic hydrogen atoms from the phosphorus-derived acids (P) being between 0.2 and 0.95, preferably between 0.4 and 0.8, and the molar ratio between the acidic hydrogen atoms comprised in the adduct (PAd) and the basic nitrogen atoms from the polyamine (A) being between 0.02 and 0.90.

[0020] The present invention also relates, in a second aspect, to a waterborne two-pack coating composition comprising a) an epoxy component comprising an epoxy resin dispersion (ED), and b) a hardener component comprising the waterborne amine hardener composition (H) according to any embodiment of the first aspect, the amount of the waterborne amine hardener composition (H) being such that the weight percentage of the adduct (PAd) is between 0.25 and 10.0, based on the total solids content of the waterborne two-pack coating composition being 100 %.

[0021] Alternative to the second aspect, the present invention also relates in a third aspect to a waterborne three-pack coating composition comprising a) an epoxy component comprising an epoxy resin dispersion (ED), b) a hardener component comprising a polyamine (A), and c) a third component comprising an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P) according to any embodiment of the first aspect, wherein the weight percentage of the adduct (PAd) is between 0.25 and 10.0, based on the total solids content of the waterborne three-pack coating composition being 100 %.

[0022] In a fourth aspect, the present invention relates to a process for the preparation of a waterborne amine hardener composition (H) according to any embodiment of the first aspect, the process comprising the steps of: i) providing in a first vessel a phosphorus-derived acid (P) at a temperature between 50 and 120°C, ii) adding thereto an epoxy resin (E) having an epoxy equivalent weight of 100 to 1500 g / Eq, iii) maintaining a reaction temperature of between 50 and 120°C for at least 30 minutes, iv) mixing the reaction product obtained in step iii) with a polyamine (A) at a temperature between 20 and 70°C, preferably between 30 and 60°C, to form the waterborne amine hardener composition (H).

[0023] The present invention also relates, in a fifth aspect, to a use of the waterborne amine hardener composition (H) according to any embodiment of the first aspect, or of the waterborne two-pack coating composition according to any embodiment of the second aspect, or of the waterborne three-pack coating composition according to any embodiment of the third aspect, for coating a substrate, preferably a base metal substrate and more preferably an aluminum substrate, to protect the substrate from corrosion. The present invention also relates, in a sixth aspect, to a substrate, preferably a metal substrate, more preferably an aluminum substrate, coated with the waterborne two- pack coating composition according to any embodiment of the second aspect, or with the waterborne three-pack coating composition according to any embodiment of the third aspect.

[0024] Advantageous aspects of the invention are set out in the appended independent and dependent claims and are further discussed in the description below. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

[0025] The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying examples, which illustrate the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be described with respect to particular embodiments and with reference to certain experiments, however, the experiments and examples described are only schematic and are non-limiting.

[0028] The following terms are provided to aid in the understanding of the invention.

[0029] “Volatile organic compound (VOC)” is meant to designate in the present invention a compound having at 293.15 K a vapour pressure of 0.01 kPa or more. The VOC content of a composition accordingly is the total weight percentage of volatile organic compounds (VOC) comprised in such composition.

[0030] “Solids content” of a composition is meant to designate in the present invention the amount of non-volatile material that remains after the removal of solvents or volatile compound(s). The solids content is determined by gravimetric measurement, i.e. according to DIN 55671 (foil method) at 125°C for 10 min.

[0031] “Waterborne compositions” is meant to designate in the present invention compositions containing a substantial amount of water (preferably more than 50 weight-% of water based on the total volatile compound(s)) in the total volatile compound(s). The water in such waterborne compositions can originate form true solutions or form part of the continuous phase of waterborne emulsions or dispersions. "Base metal substrate" is meant to designate in the present invention to a substrate made from a metal that is not a noble metal. Examples of base metal substrates include steel and aluminum.

[0032] The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the technical teaching of the invention.

[0033] The first aspect of the present invention relates to a waterborne amine hardener composition (H) comprising: a) an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P), wherein the adduct (PAd) is substantially free of epoxy groups and has an acid value (based on solids content of adduct (Pad)) of at least 10 mgKOH / g, preferably an acid value comprised between 50 and 180 mgKOH / g, more preferably an acid value comprised between 80 and 150 mgKOH / g; b) a polyamine (A); and c) water.

[0034] The molar ratio between the epoxy groups from the epoxy resin (E) and the acidic hydrogen atoms from the phosphorus-derived acids (P) is between 0.2 and 0.95, preferably between 0.4 and 0.8.

[0035] The molar ratio between the acidic hydrogen atoms comprised in the adduct (PAd) and the basic nitrogen atoms from the polyamine (A) is between 0.02 and 0.90, preferably between 0.02 and 0.7, more preferably between 0.02 and 0.33, most preferably between 0.02 and 0.29.

[0036] It is surprisingly found that, due to the presence of the adduct (PAd) in the waterborne amine hardener composition (H) the anti-corrosion effect of paints based thereon is significantly improved. This effect is particularly pronounced if the paint is applied to aluminum substrates. Particularly the corrosion resistance tested in an Acetic Acid Salt Spray Test is improved. The technical effect can either be achieved if the paint is based on a two-pack coating composition comprising the waterborne amine hardener composition (H) in the hardener component or if the paint is based on a three-pack coating composition with the polyamine (A) and the adduct (PAd) comprised in different components and mixed just before application of the paint. It is especially surprising that such an improvement of anti-corrosion performance can be achieved while other important coating parameters like drying time, adhesion and mechanical resistance are maintained.

[0037] Alternatively and preferred, where possible, the waterborne amine hardener composition (H) is obtained from renewable feedstock or from recycled monomers. Preferably, the waterborne amine hardener composition (H) is obtained from renewable feedstock and has in total a bio-based carbon content of more than 20% by weight of total carbon content of the waterborne amine hardener composition (H), the bio-based carbon content being determined using the ASTM D6866-20 standard.

[0038] In the context of the present description, “renewable feedstock” refers to natural resources which will replenish to replace the portion depleted by usage and consumption, either through natural reproduction or other recurring processes (in a finite amount of time in a human time scale).

[0039] “Substantially free of epoxy groups” in the context of the present invention means that the specific epoxide group content (based on solids content of adduct (Pad)) preferably is not more than 100 mmol / kg, more preferably not more than 50 mmol / kg, and most preferably not more than 20 mmol / kg.

[0040] “Phosphorus-derived acids (P)” in the context of the present invention means acids that comprise phosphorus atoms bonded to oxygen atoms.

[0041] “Acidic hydrogen atoms comprised in the adduct (PAd)” means hydrogen atoms, which are attached directly or via an oxygen atom to a phosphorus atom of the adduct (Pad). “Acidic hydrogen atoms from the phosphorus-derived acids (P)” means hydrogen atoms, which are attached directly or via an oxygen atom to a phosphorus atom of the phosphorus-derived acids (P).

[0042] “Basic nitrogen atoms from the polyamine (A)” means the nitrogen atom comprised in primary, secondary, or tertiary amino groups of the polyamine (A). In contrast, the nitrogen atom of an amide, urethane, or urea group is not regarded as a basic nitrogen atom in the context of the present invention.

[0043] The adduct (PAd) is the reaction product of an epoxy resin (E) and phosphorus-derived acids (P). The reaction resulting in the adduct (PAd) is a ring-opening reaction of the epoxide groups comprised in the epoxy resin (E) with the phosphorus-derived acids (P). The ratio between epoxy resin (E) and phosphorus-derived acids (P) is chosen such that there is a molar excess of acidic hydrogen atoms from the phosphorusderived acids (P) over the epoxy groups from the epoxy resin (E). As a matter of fact, the adduct (PAd) has a certain acid value, which can be determined by titration according to DIN EN ISO 2114 and is expressed by the unit mgKOH / g. From the acid value in mgKOH / g the skilled person is capable of determining the amount of substance of acid hydrogen atoms in mol / g by dividing the acid value by 56,100.

[0044] Due to its acid value, the adduct (PAd) forms an ammonium salt with the basic nitrogen atoms from the polyamine (A). The skilled person knows about the hydrophilicity of ammonium salts and would normally avoid the presence of such hydrophilic compounds in a coating that should protect a metal substrate from corrosion. It is therefore counterintuitive and surprising that the waterborne amine hardener composition (H) according to the present invention actually improves the corrosion performance of waterborne two-pack coating compositions.

[0045] The adduct (Pad) is comprised in the waterborne amine hardener composition (H) preferably in a weight percentage of from 5 to 50, more preferably from 10 to 40, most preferably from 15 to 35, based on the total weight of adduct (PAd) and polyamine (A) being 100 %.

[0046] The polyamine (A) is comprised in the waterborne amine hardener composition (H) preferably in a weight percentage of from 50 to 95, more preferably from 55 to 90, most preferably from 60 to 85, based on the total weight of adduct (PAd) and polyamine (A) being 100 %.

[0047] The waterborne amine hardener composition (H) further comprises water. The weight percentage of water comprised in the waterborne amine hardener composition (H) preferably is from 10 to 80, more preferably from 20 to 70, most preferably from 35 to 65, based on the total weight of the waterborne amine hardener composition (H) being 100 %.

[0048] Preferably the waterborne amine hardener composition (H) further comprises an organic solvent. The organic solvent is preferably selected from the group consisting of alcohols, ketones, esters, glycols, glycol ethers, glycol esters, and mixtures thereof. The weight percentage of organic solvent comprised in the waterborne amine hardener composition (H) preferably is less than 15, more preferably less than 10, and most preferably less than 5, based on the total weight of the waterborne amine hardener composition (H) being 100 %. The phosphorus-derived acids (P) are preferably selected from the group consisting of inorganic acidic phosphorus compounds (P1), organic phosphonic acids (P2), and mixtures thereof. Each of the inorganic acidic phosphorus compounds (P1) or organic phosphonic acids (P2) preferably have at least two acidic hydrogen atoms, which are attached directly or via an oxygen atom to a phosphorus atom. The inorganic phosphorus-derived acids (P1) are preferably selected from the group consisting of orthophosphoric acid (also known as phosphoric acid or phosphoric (V) acid) H3PO4, diphosphoric acid H4P2O7, triphosphoric acid H5P3O10, phosphorous acid H3PO3, diphosphorous acid H4P2O5, hypophosphorous acid H3PO2, higher homologs of phosphoric, phosphorous or hypophosphorous acid, and mixtures thereof. Particularly suitable are orthophosphoric acid, mixtures of dimers and higher oligomers of orthophosphoric acid, phosphorous acid, and higher oligomers thereof. More preferred are inorganic phosphorus-derived acids (P1) selected from the group consisting of orthophosphoric acid, dimers and higher oligomers of orthophosphoric acid, and mixtures thereof. The organic phosphonic acids (P2) preferably are alkanephosphonic acids R1-POSH3, aromatic phosphonic acids R2-POsH3, and the corresponding phosphonous acids R1-PO2H2 and R2-PO2H2 , R1being a linear, branched, or cyclic alkyl radical having 1 to 20 carbon atoms, and R2being a substituted or unsubstituted aromatic radical having 6 to 20 carbon atoms. Methanephosphonic acid and benzenephosphonic acid are particularly preferred.

[0049] The phosphorus-derived acids (P) are reacted with the epoxy resin (E) such that the resulting Adduct (PAd) comprises a certain amount of acidic hydrogen atoms. Specifically, the Adduct (PAd) of epoxy resin (E) and phosphorus-derived acids (P) has an acid value of at least 10 mgKOH / g, preferably between 50 and 180 mgKOH / g, more preferably between 80 and 150 mgKOH / g, based on solids content of the Adduct (PAd)

[0050] The weight percentage of phosphorus comprised in the adduct (PAd) preferably is from 1 .0 to 10.0, more preferably from 3.0 to 9.0, most preferably from 4.0 to 8.0, based on solids content of the Adduct (PAd). “Weight percentage of phosphorus” in the context of the present invention means the total weight fraction of phosphorus atoms based on solids content of the Adduct (PAd).

[0051] The epoxy resin (E) is a compound comprising at least one epoxy group, preferably a diepoxide compound or a polyepoxide compound, which are obtainable conventionally by reacting epichlorohydrin with aromatic or (cyclo)aliphatic compounds having two or more hydroxyl groups per molecule (Taffy process), or which can be obtained by reacting diepoxides or polyepoxides with said aromatic or (cyclo)aliphatic compounds having two or more hydroxyl groups per molecule (advancement reaction). Preference is given to epoxy resins based on aromatic dihydroxy compounds (such as bisphenol A, bisphenol F, dihydroxydiphenyl sulfone, hydroquinone, resorcinol, 1 ,4bis [2-(4- hydroxyphenyl)-2-propyl]benzene), or aliphatic dihydroxy compounds (such as hexane-1 ,6-diol, butane-1 ,4diol, cyclohexane dimethanol), or oligo-propylene and polypropylene glycol having mean degrees of polymerization of between 3 and 40. Preferably, the epoxy resin (E) has an epoxy equivalent weight of 100 to 1500 g / Eq, more preferably from 150 to 1000 g / Eq, most preferably from 150 to 500 g / Eq. Particular preference is given to epoxy resins based on bisphenol A, bisphenol F, and / or mixtures thereof.

[0052] The epoxy resin (E) is preferably obtained from petrochemical feedstock.

[0053] Alternatively and preferred, where possible, the epoxy resin (E) is obtained from renewable feedstock. Particularly preferred renewable feedstocks are those extracted from wood biomass, like lignin and tannins, as well as cashew nut shell liquid (CNSL) which is a source for phenolic derivatives such as for example anarcadic acid, cardanol, cardol, and 2-methyl cardol. Also preferred are feedstocks from lignocellulosic biomass such as cellulose and hemi-cellulose which are further depolymerized and dehydrated into 5-hydroxymethyl-2-furfural and then further derivatized to for example 2,5- furandicarboxylic acid or2,5-furandimethanol. Other preferred feedstocks are terpenes and terpenoids such as limonene and carvacrol as well as other phenolic compounds like eugenol, ferulic and sinapic acid. Other renewable feedstocks for epoxy based resins are rosin acids (and their mono- and diglycidyl ethers), isosorbide (and its diglycidyl ether), as well as oligo- or polyglycerols (and their glycidyl ethers). Epoxide groups may also be introduced into the epoxy resin (E) by epichlorohydrin derived in part or fully from (bio-)renewable glycerin. The exact amounts of bio-based carbon in these epoxy resins can be determined by the method described in ASTM D6866-20, wherein carbons resulting from contemporary biomass-based inputs are distinguished from those derived from fossil-based inputs, the bio-based carbon content being reported as the fraction of total organic carbon content (TOC). Other standardized methods to determine the fraction of renewable carbon are ISO 16620-2 and CEN 16640. Another alternative method for reducing the carbon footprint of the epoxy resin (E) is to use recycled monomers for the preparation thereof. Polymers, such as poly(bisphenol A carbonate), can be depolymerized to yield monomers (i.e. bisphenol A), which can then be further used to prepare the epoxy resin (E) of the present invention.

[0054] In yet another alternative, the epoxy resin (E) is obtained from petrochemical feedstock and / or renewable feedstock, and / or derived from recycled monomers.

[0055] In the context of the present description, “bio-based carbon content” refers to biocarbon content.

[0056] The polyamine (A) preferably comprises at least two amino groups per molecule and is characterized by a hydrogen equivalent weight (in the range) of from 30 to 1500 g / Eq, more preferable from 80 to 1000 g / Eq. The hydrogen equivalent weight of the polyamine (A) is determined as grams of polyamine (A) equivalent to 1 mol of active hydrogen linked to nitrogen and can be calculated by the skilled person by dividing the grams of polyamine (A) by the molar amount of active hydrogen linked to nitrogen (“active hydrogen” in the context of the invention refers to a hydrogen atom directly bond to a nitrogen atom in a primary or secondary amino group).

[0057] The polyamine (A) usually has primary, secondary, or tertiary amino groups that are capable to react with an epoxide group under formation of a beta-hydroxy amine structure or a betaine structure. The reactivity towards epoxide groups decreases from primary to secondary to tertiary amines. While it is possible to use multifunctional primary amines as curing agents for epoxide-functional compounds (primary amines, such as isophorone diamine or metaxylylene diamine, being the most efficient amines due to their higher reaction rate), their high vapour pressure and unfavourable smell, together with potential health hazard, has barred their use in applications where no sufficient ventilation is available. Moreover, lack of compatibility of monomeric amines with epoxy resins has limited their usefulness.

[0058] It is therefore preferred that the polyamine (A) is an amino-functional epoxy-amine adduct. Such amino-functional epoxy-amine adduct preferably is the reaction product of a compound comprising at least one, more preferably two or more primary amine groups (such as for example ethylene diamine, isophorone diamine, metaxylylene diamine, or diethylene triamine) with epoxide-functional compounds, preferably with epoxide-functional compounds, more preferably diepoxide or polyepoxide compounds, which are obtainable conventionally by reacting epichlorohydrin with aromatic or (cyclo)aliphatic compounds having two or more hydroxyl groups per molecule (Taffy process), or which are obtainable by reacting diepoxides or polyepoxides with said aromatic or (cyclo)aliphatic compounds having two or more hydroxyl groups per molecule (advancement reaction). Most preferably the amino-functional epoxy-amine adduct is the reaction product of a diamine with a bisphenol A based epoxy resin. Optionally, the amino-functional epoxy-amine adduct is further modified with a mono- epoxide-functional compound, such as for example cresyl glycidylether or 4-tert- butylphenyl glycidylether.

[0059] The polyamine (A) preferably comprises a hydrophilic modification in order to improve the compatibility with water.

[0060] In one preferred embodiment the polyamine (A) comprises moieties derived from polyethylene glycols, from polypropylene glycols, or from oxyethylene-oxypropylene copolymers, which are linked to the amine part by linking groups which may be derived from diepoxides (such as the diglycidyl ether of aliphatic dihydric or polyhydric alcohols, the diglycidyl ether of bisphenol A, the diglycidyl ether of bisphenol F, or the diglycidyl ether of bisphenol S, the diglycidyl esters of dicarboxylic or polycarboxylic acids), from di- or polyfunctional aziridines, from acid anhydrides (such as maleic or tetrahydrophthalic or phthalic anhydrides), from acid dichlorides (such as terephthalic or isophthalic dichloride), or from diisocyanates (such as toluylene diisocyanate or bis(4-isocyanatophenyl)-methane also known as MDI). Particularly preferred polyamine (A) comprises moieties derived from an adduct of polyethylene glycol and a bisphenol A based epoxy resin.

[0061] In another preferred embodiment the polyamine (A) is at least partially neutralized with an acid, such as for example formic acid, acetic acid, propionic acid, or lactic acid.

[0062] In still another preferred embodiment the polyamine (A) comprises moieties derived from polyethylene glycols, from polypropylene glycols, or from oxyethylene- oxypropylene copolymers, and is at least partially neutralized with an acid.

[0063] The polyamine (A) used in the present invention is preferably in the form of an aqueous dispersion. Aqueous dispersions of epoxy hardeners are known in the prior art and have for example been commercialized under the tradenames of BECKOCURE® EH 2260w / 41WA. Alternatively, the polyamine (A) is selected from the group consisting of polyalkyleneglycol polyamines, amidoamines, polyamides, Mannich bases, phenalkamines, phenalkamides, and mixtures thereof.

[0064] The polyamine (A) is preferably hydrophil ically modified, but can also be dispersed in water using surfactants which are preferably non-ionic surfactants.

[0065] The polyamine (A) can be obtained from petrochemical feedstock and / or renewable feedstock.

[0066] Any feature of the first aspect can be as correspondingly described in any of the other aspects of the invention.

[0067] The second aspect of the present invention relates to a waterborne two-pack coating composition comprising two separate components. The waterborne two-pack coating composition comprises a) an epoxy component comprising an epoxy resin dispersion (ED), and b) a hardener component comprising the waterborne amine hardener composition (H) according to any embodiment of the first aspect of the invention, the amount of the waterborne amine hardener composition (H) being such that the weight percentage of the adduct (PAd) is between 0.25 and 10.0, preferably between 0.5 and 8.0, more preferably between 1 .0 and 5.0, based on the total solids content of the waterborne two-pack coating composition being 100 % (the total solids content of the waterborne two-pack coating composition being determined according to DIN 55671 (foil method) at 125°C for 10 min).

[0068] “Two-pack coating compositions”, also known as 2K paint (or 2K paint compositions), in the current invention refer to a paint that consists of two separate components. The first component is the epoxy component (comprising the epoxy resin dispersion (ED)) and the second component is the hardener component. The two components are separated from each other and are mixed together just before application of the paint and they undergo a chemical reaction with each other after mixing. This reaction causes the paint to dry and harden into a tough, durable coating layer. Two-pack coating compositions can be cured at ambient temperature, preferably at temperatures between 10 and 40°C, more preferably between 15 and 35°C. Optionally, a post-curing procedure at elevated temperature, preferably at a temperature between 50 and 120°C, more preferably between 50 and 100°C, most preferably between 60 and 90°C, can be applied.

[0069] The waterborne two-pack coating composition of the invention comprises a hardener component which comprises the hardener composition (H) according to the first aspect of the invention. The hardener component can in addition also comprise hardeners different from hardener composition (H). Preferably, the hardener component comprises predominantly hardener composition (H). More preferably, the weight percentage of hardener composition (H) based on the total hardener component (excluding water and organic solvent) is more than 50, preferably more than 70, more preferably more than 90. Most preferably, no hardener different from hardener composition (H) is present in the hardener component (i.e., most preferably, the hardener component of the waterborne two-pack coating composition consists of hardener composition (H)).

[0070] Alternatively to the second aspect, the adduct (PAd) may be comprised in a separate component of a three-pack coating composition. Similar as with the two-pack coating composition, the three separate components of the three-pack coating composition are only mixed together just before application of the paint. Therefore, in a third aspect the invention also relates to a waterborne three-pack coating composition comprising a) an epoxy component comprising an epoxy resin dispersion (ED), b) a hardener component comprising a polyamine (A), and c) a third component comprising an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P) according to according to the first aspect of the invention, wherein the weight percentage of the adduct (PAd) is between 0.25 and 10.0, preferably between 0.5 and 8.0, more preferably between 1.0 and 5.0, based on the total solids content of the waterborne three-pack coating composition being 100 % (the total solids content of the waterborne three-pack coating composition being determined according to DIN 55671 (foil method) at 125°C for 10 min).

[0071] The polyamine (A) comprised in the hardener component of the waterborne three-pack coating composition preferably comprises at least two amino groups per molecule and is characterized by a hydrogen equivalent weight of from 30 to 1500 g / Eq, more preferably from 80 to 1000 g / Eq. More preferably the polyamine (A) is selected from the group consisting of amino-functional epoxy-amine adducts, polyalkyleneglycol polyamines, amidoamines, polyamides, Mannich bases, phenalkamines, phenalkamides, and mixtures thereof. Most preferably the polyamine (A) is an aminofunctional epoxy-amine adduct which is the reaction product of primary amines with epoxide-functional compounds.

[0072] The adduct (PAd) comprised in the third component of the waterborne three-pack coating composition is the adduct (PAd) of an epoxy resin (E), the epoxy resin (E) preferably having an epoxy equivalent weight of 100 to 1500 g / Eq, and phosphorusderived acids (P), wherein the adduct (PAd) is substantially free of epoxy groups and has an acid value of at least 10 mgKOH / g, preferably an acid value comprised between 50 and 180 mgKOH / g, the molar ratio between the epoxy groups from the epoxy resin (E) and the acidic hydrogen atoms from the phosphorus-derived acids (P) being between 0.2 and 0.95, preferably between 0.4 and 0.8. The amount of adduct (PAd) comprised in the third component of the waterborne three-pack coating composition is preferably such that the molar ratio between the acidic hydrogen atoms comprised in the adduct (PAd) and the basic nitrogen atoms from the polyamine (A) is between 0.02 and 0.90, more preferably between 0.02 and 0.33. The phosphorus-derived acids (P) are preferably selected from the group consisting of inorganic acidic phosphorus compounds (P1), organic phosphonic acids (P2), and mixtures thereof, more preferably selected from inorganic acidic phosphorus compounds (P1) selected from the group consisting of orthophosphoric acid (H3PO4), diphosphoric acid (H4P2O7), triphosphoric acid (H5P3O10), phosphorous acid (H3PO3), diphosphorous acid (H4P2O5), hypophosphorous acid (H3PO2), higher homologs of orthophosphoric acid, higher homologs of phosphorous acid, higher homologs of hypophosphorous acid, and mixtures thereof.

[0073] The epoxy resin dispersions (ED) comprised in the epoxy component of the waterborne two-pack coating composition or the waterborne three-pack coating composition are well known and are for example commercially available under the tradenames of BECKOPOX® EP 384w / 53WAMP and BECKOPOX® EP 387w / 53WA. Preferred epoxy resins are hydrophilic modified epoxy resins, especially by introduction of non-ionic hydrophilic moieties. Introduction of the commonly used poly(oxyethylene)-blocks as hydrophilizing moiety is a difficult step, as strong acid catalysts, mostly Lewis acids (such as boron trifluoride, or complexes thereof with ethers or amines) have to be used, and the process is difficult to control. Such chemistry has been described in US 4,886,845A and US 4,987, 163A. Preferred epoxy resin dispersions (ED) are self-emulsified resin dispersions where the epoxy resin is modified by reaction with modifiers comprising oxyalkylene groups. Preferably these modifiers comprise of oligomeric or polymeric oxyethylene moieties as hydrophilic constituents, and functional groups that can take part in an advancement reaction between low molar mass polymeric epoxy resins or oligomeric epoxy resins (such as bisphenol A diglycidylether), and aromatic hydroxyl group-containing compounds (such as bisphenol A), or similar compounds usually used in the synthesis of epoxy resin paints. Examples of such aqueous dispersions of epoxy resins have for example been described in US 4,886,845A and US 4,987, 163A.

[0074] The epoxy resin dispersions (ED) can be obtained from petrochemical feedstock and / or renewable feedstock.

[0075] In a particularly preferred embodiment, the epoxy resin dispersion (ED) comprised in the epoxy component of the coating compositions is formulated as a mixture of at least two different types of epoxy resin dispersions and optional epoxy resin. This mixture comprises: a) a first epoxy resin dispersion comprising a modifier resin, wherein said modifier resin is the reaction product of a poly(oxyalkylene) glycol, preferably a poly(oxy-1 ,4-butylene) glycol, and a diisocyanate; b) a second epoxy resin dispersion which is substantially free of said modifier resin; and c) optionally a low molar mass polymeric epoxy resin or oligomeric epoxy resin (such as bisphenol A diglycidylether or liquid epoxy resin having an epoxy equivalent weight of 170 to 210 g / Eq).

[0076] A preferred example of the first type of epoxy resin dispersion, which contains the modifier resin, is described in Example 5.

[0077] A preferred example of the second type of epoxy resin dispersion, which is substantially free of the modifier resin, is described in Example 6. It is understood that this second type of dispersion may still contain hydrophilic moieties for emulsification, such as those derived from polyethylene glycol, as described in Step 2 of Example 5. The weight ratio of the first epoxy resin dispersion to the second epoxy resin dispersion can be varied, for example in a range from 10:90 to 90:10, based on the solids content of the respective dispersions. It has been advantageously found that formulating the epoxy resin dispersion (ED) from such a mixture allows for an optimal balance between the hardness development and the flexibility of the final cured coating. This tailored mechanical performance is achieved while still maintaining the excellent corrosion resistance performance, particularly in the demanding Acetic Acid Salt Spray (AASS) test.

[0078] The epoxy resin dispersions (ED) used in the present invention preferably has an epoxy equivalent weight of 100 to 1500, more preferably of 150 to 700. The epoxy equivalent weight of the epoxy resin is determined as the grams solids content of epoxy resin equivalent to 1 mol of epoxy groups.

[0079] The amount of epoxy resin dispersion (ED) comprised in the waterborne two-pack coating composition, or comprised in the waterborne three-pack coating composition, is preferably chosen such that the weight percentage of the solids content of epoxy resin dispersion (ED) amounts in the range of from 15 to 90, more preferably from 50 to 80, based on the total solids content of epoxy resin dispersion (ED) and hardener component being 100 %.

[0080] The skilled person is well aware of the requirement to add other ingredients to the (components of the) waterborne two-pack coating compositions, or to the (components of the) waterborne three-pack coating composition, in order to improve certain properties like appearance and durability (of the resulting coating layer after the coating composition (or paint) has been applied). The waterborne two-pack coating composition or the waterborne three-pack coating composition of the invention may therefore further comprise, in at least one of its components, one or more of (inorganic or organic) pigments, dyes, anti-corrosive pigments, fillers, pigment dispersion aids, emulsifiers, surfactants, pigment wetting agents, levelling agents, substrate wetting agents, flow modifiers, defoamers, antisettling agents, rheology modifiers, coalescing agents (or coalescents), hydrophobizing agents, biocides, antioxidants, radical inhibitors, adhesion promoters and UV absorbers. Not every ingredient will be compatible with all other ingredients of a particular component of the two-pack coating composition or the waterborne three-pack coating composition, therefore, the skilled person will make a judgement (and this is well within the practice of those skilled in the art) which of the components is most suitable to comprise a particular ingredient.

[0081] Coalescing agents (or coalescents) function as temporary plasticizers for the particles of polymer dispersions comprised in coating compositions and support the formation of polymeric films after application of the coating composition (or paint) to a substrate. The coalescing agent can be an organic solvent which is the same as or different from the organic solvent optionally present in the waterborne amine hardener composition (H).

[0082] The waterborne two-pack coating compositions and the waterborne three-pack coating compositions of the invention are particularly useful for (providing) anti-corrosion coating on metals. Formulation of such a coating composition is preferably carried out by preparation of a pigment slurry in a step A), where a first group of additives is added to deionised water, preferably comprising pigment dispersion aids, and defoamers, followed by a step B) where fillers, pigments, and optional anti-corrosive pigments, are added one after the other, again followed by a next step C) where further additives can be added (such as further defoamer, a solvent to lower the minimum film forming temperature, rheology modifiers, and substrate wetting additives). Step A) is preferably conducted in a mixer, step B) is preferably conducted in a bead mill to effectively homogenize the pigments which are solid constituents. Addition of the further additives or solvents in step C) is also conducted in the bead mill. In a next step D), the epoxy resin dispersion (ED) is added to obtain the epoxy component of the waterborne two- pack coating composition or the waterborne three-pack coating composition.

[0083] In a last mixing step E), the hardener component (and in case of the waterborne three- pack coating composition, the third component comprising the adduct (PAd)) is then added to the first component before applying the coating composition to the substrate. The VOC content of the waterborne two-pack coating composition or of the waterborne three-pack coating composition, expressed in weight percentage (based on the total weight of the waterborne two-pack coating composition or of the waterborne three- pack coating composition) is preferably less than 20, more preferably less than 17, and most preferably less than 14.

[0084] In the waterborne two-pack coating compositions of the second aspect, or in the waterborne three-pack coating composition of the third aspect, the crosslinking ratio can be varied. “Crosslinking ratio” is meant to designate in the present invention the molar ratio between the active hydrogen comprised in the hardener component and the epoxy groups comprised in the epoxy component (the epoxy component being the component comprising the epoxy resin dispersion (ED)).

[0085] The two components of the waterborne two-pack coating compositions are preferably mixed in amounts to achieve a crosslinking ratio of between 50 and 95 %, more preferably between 60 and 85 %, most preferably between 60 and 75 %. The three components of the waterborne three-pack coating compositions are preferably mixed in amounts to achieve a crosslinking ratio of between 50 and 95 %, more preferably between 60 and 85 %, most preferably between 60 and 75 %.

[0086] Any feature of the second and the third aspect can be as correspondingly described in any of the other aspects of the invention.

[0087] The fourth aspect of the present invention relates to a process for the preparation of a waterborne amine hardener composition (H) according to any embodiment of the first aspect of the invention, the process comprising the steps of: i) providing in a first vessel a phosphorus-derived acid (P) at a temperature between 50 and 120°C, preferably between 50 and 100°C, more preferably between 60 and 90°C, optionally in the presence of an organic solvent, ii) adding thereto an epoxy resin (E) having an epoxy equivalent weight of 100 to 1500 g / Eq, preferably from 150 to 1000 g / Eq, more preferably from 150 to 500 g / Eq, preferably over a period of between 2 and 8 hours, more preferably over a period of between 3 and 6 hours, iii) maintaining a reaction temperature of between 50 and 120°C, preferably between 50 and 100°C, more preferably between 60 and 90°C, for at least 30 minutes, preferably between 1 and 8 hours, to form (or thereby forming) the adduct (PAd) according to the first aspect of the invention, iv) mixing the reaction product obtained in step iii) with a polyamine (A) at a temperature between 20 and 70°C, preferably between 30 and 60°C, to form (or thereby forming) the waterborne amine hardener composition (H) according to the first aspect of the invention.

[0088] Step iv) is preferably comprising the steps of: iv-1 ) providing in a second vessel a polyamine (A) at a temperature between 20 and 70°C, preferably between 30 and 60°C, and iv-2) adding thereto the reaction product obtained in step iii), to form (or thereby forming) the waterborne amine hardener composition (H) according to the first aspect of the invention.

[0089] Alternatively, step iv) can be carried out by providing the reaction product obtained in step iii) in a second vessel at a temperature between 20 and 70°C, preferably between 30 and 60°C, and adding the polyamine (A) thereto, to form (or thereby forming) the waterborne amine hardener composition (H) according to the first aspect of the invention.

[0090] Preferably, the epoxy resin (E) from step ii) is diluted in an organic solvent before adding. The organic solvent can be the same as or different from the optional organic solvent from step i), preferably it is the same organic solvent as the one from step i). Any feature of the fourth aspect can be as correspondingly described in any of the other aspects of the invention.

[0091] The fifth aspect of the present invention relates to a use of the waterborne amine hardener composition (H) according to any embodiment of the first aspect, or of the waterborne two-pack coating composition according to any embodiment of the second aspect, or of the waterborne three-pack coating composition according to any embodiment of the third aspect, for coating a substrate, preferably a base metal substrate and more preferably an aluminum substrate, to protect the substrate from corrosion.

[0092] Any feature of the fifth aspect can be as correspondingly described in any of the other aspects of the invention.

[0093] The sixth aspect of the present invention relates to a substrate or an article, preferably a metal substrate, more preferably an aluminum substrate, coated with the waterborne two-pack coating composition according to any embodiment of the second aspect, or with the waterborne three-pack coating composition according to any embodiment of the third aspect. Preferably, the substrate is a corrosion resistant metal substrate comprising the waterborne two-pack coating composition according to any embodiment of the second aspect, or comprising the waterborne three-pack coating composition according to any embodiment of the third aspect. Preferably, the article is a coated article comprising a substrate being at least partly coated with the waterborne two-pack coating composition according to any embodiment of the second aspect, or being at least partly coated with the waterborne three-pack coating composition according to any embodiment of the third aspect.

[0094] Any feature of the sixth aspect can be as correspondingly described in any of the other aspects of the invention. EXAMPLES

[0095] The following illustrative examples are merely meant to exemplify the present invention but are not intended to limit or otherwise define its scope.

[0096] In the specification, and also in the examples, the following parameters and test methods have been used to describe physicochemical properties of the compounds and substances: solids content according to DIN 55671 (foil method) at 125°C for 10 min acid value according to DIN EN ISO 2114 epoxy equivalent weight according to DIN EN ISO 3001 amine value according to DIN 16945 mass fraction of NCO groups was determined by titration: The sample was dissolved in acetone and mixed with an appropriate (excessive) amount of a 0.5 molar solution of diisobutylamine. The excessive diisobutylamine was titrated back with a 0.5 molar solution of hydrochloric acid. specific epoxy group content was determined by titration: The sample was dissolved in a solvent mix of propylene carbonate / acetic acid (4:1 ), mixed with an appropriate (excessive) amount of tetrabutylammonium iodide and titrated with a 0.1 molar solution of perchloric acid in anhydrous acetic acid. hydrogen equivalent weight was calculated by dividing the total weight of polyamine by the molar amount of active hydrogen linked to nitrogen. dynamic viscosity according to DIN EN ISO 3219 at a temperature of 23°C and a shear rate of 100 s-1

[0097] Drying degree (DIN 53150)

[0098] Natural salt spray test (DIN EN ISO 9227)

[0099] Humidity chamber test (DIN EN ISO 6270-2)

[0100] Acetic acid salt spray test (DIN EN ISO 9227)

[0101] Cross-cut test (DIN EN ISO 2409)

[0102] Impact test (ASTM D 2794-93) Example 1 : Solution of Adduct (PAd) of epoxy resin (E) and phosphorus-derived acids (P)

[0103] 36 parts by weight of orthophosphoric acid (75 % weight in water) were placed in a glass flask equipped with a thermometer, stirrer, and cooling tube together with 22 parts by weight of methyl ethyl ketone. The mixture was heated to 70°C and homogenized. 100 parts by weight of bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) diluted with 14 parts by weight of methyl ethyl ketone were added dropwise over 5 hours. After the addition the reaction mixture was hold at 70°C for 1 hour to obtain a pale yellow liquid with a solids content of 75 % and an acid value of 123 mg KOH / g (based on solids content). The weight percentage of phosphorus comprised in the adduct was 6.7 (based on solids content).

[0104] Example 2: Aqueous dispersion of a Polyamine (A)

[0105] 100 parts by weight of ethylene diamine were reacted with 44 parts by weight of a bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) and with 130 parts by weight of an emulsifier component, derived (with an acidic catalyst according to the process disclosed in example 1.15 of EP 0 272 595 A2) from polyethylene glycol (with an average molecular weight of 600 g / mol) and a bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq). The excess of diamine was distilled off. 350 parts of deionized water were added at 80°C. Then the reaction mixture was cooled to 70°C and 22 parts by weight of a reactive diluent based on 1 ,4-bis[(2,3- epoxypropoxy)methyl]cyclohexane and 6 parts of cresyl glycidylether were added. 4 parts by weight of propionic acid were added for neutralization. The resulting reaction product was in the form of an aqueous dispersion with 40.0 % by weight of polyamine (A) dispersed in water. The amine value of the aqueous dispersion was 100 mg KOH / g (based on total aqueous dispersion). The hydrogen equivalent weight of the polyamine (A) was 170 g / Eq.

[0106] Example 3: Aqueous composition of a Polyamine (A)

[0107] Step 1 : 40 parts by weight of polyethylene glycol (with an average molecular weight of 1000 g / mol) and 60 parts by weight of a bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) were reacted with an acidic catalyst according to the process disclosed in example 1.15 of EP 0 272 595 A2 and 5 parts by weight of deionized water were added. Step 2: In a second round neck flask, 27 parts by weight of metaxylylene diamine and 33 parts by weight of isophorone diamine were added together with 2 parts of water and homogenized. The component from step 1 was slowly added to the amine solution to allow the temperature to rise to 80°C. After full addition the reaction mixture was kept at 80°C for 1.5 hours. Afterwards the mixture was cooled to 60°C and 40 parts by weight of deionized water was added. The resulting reaction product comprised of 80.0 % by weight of polyamine (A) in water. The amine value of the reaction product was 230 mg KOH / g (based on total reaction product). The hydrogen equivalent weight of the polyamine (A) was 116 g / Eq. Example 4: Waterborne amine hardener compositions (H)

[0108] The reaction products from Examples 2 and 3 were heated to 40°C and mixed in amounts according to Table 1 with the solution of Adduct (PAd) from Example 1 . The mixtures were homogenized and cooled down. Table 1

[0109] ** molar ratio between the acidic hydrogen atoms comprised in the Adduct (PAd) and the basic nitrogen atoms from polyamine (A) Example 5: Epoxy resin dispersion (ED)

[0110] Step 1 (Preparation of a modifier resin): 1300 g of poly(oxy-1 ,4-butylene) glycol with a number average molar mass of 650 g / mol were heated to 80 °C, then 174 g of a commercial mixture of toluylene diisocyanate isomers were added under stirring. The reaction mixture was kept under these conditions until no more free isocyanate was detectable (mass fraction of NCO groups was less than 0.1 %). The reaction mixture was heated to 150 °C, then 296 g of phthalic anhydride were added. The reaction mixture was stirred at 150 °C until the acid number had reached 70 mg / g. 1770 g of pale yellow resin were isolated.

[0111] Step 2 (Preparation of emulsifier): 1500 g of a commercial polyethylene glycol with a number average molar mass Mn of 3000 g / mol and 185 g of a bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) were heated to 100 °C. Under stirring, 8 g of boron trifluoride - diethyl ether complex were added, as a solution in 1 ,4-dioxane. The temperature was raised to 130 °C and kept until the specific epoxy group content had reached a constant level. The ratio of the number of epoxy and hydroxyl groups was 1 :1 in this case, the final specific epoxy group content was 2.7 mmol / g.

[0112] Step 3 (modified aqueous epoxy resin dispersion): 1200 g of the resin of step 1 were heated in a flask to 125 °C. 1100 g of bisphenol A , 4380 g of bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) and 950 g of emulsifier of step 2 were added, together with 6 g of triphenyl phosphine catalyst. The temperature of the mixture rose to 150 °C due to the heat of reaction and was kept at this temperature until the specific content of epoxy groups had reached 2 mmol / g. The mixture was then cooled to 100 °C whereupon 628 g of methoxy propanol were added. The temperature was lowered further to 80 °C, and 5639 g of deionized water was added under careful stirring. The resulting epoxy resin dispersion had a solids content of 52.0 % and a dynamic viscosity of 890 mPa.s. The epoxy equivalent weight was 520 g / Eq (based on solids content).

[0113] Example 6: Epoxy resin dispersion (ED)

[0114] 92 g of the emulsifier from step 2 of Example 5, 97 g of bisphenol A and 248 g of bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) were heated in a flask to 130 °C, together with 0.5 g of triphenyl phosphine catalyst. The temperature of the mixture rose to 150 °C due to the heat of reaction and was kept at this temperature until the specific content of epoxy groups had reached 2 mmol / g. The mixture was then cooled to 140 °C whereupon 28 g of methoxy propanol were added. The temperature was lowered further to 65 °C and 328 g of deionized water was added under careful stirring. At a temperature of 40 °C 153 g of bisphenol A based epoxy resin (epoxy equivalent weight: 180 g / Eq) was added. After homogenization a dispersion was obtained. The resulting epoxy resin dispersion had a solids content of 60.0 % and a dynamic viscosity of 5,500 mPa.s. The epoxy equivalent weight was 350 g / Eq (based on solids content).

[0115] Example 7: Paint Formulations

[0116] A pigment slurry was prepared from the constituents as listed in Table 2. These materials were added in the sequence of the groups shown (i.e. first group A, then group B, and finally group C), and within the groups, in the sequence of the rows in the table).

[0117] The pigment slurry was prepared by mixing components of group A in the mentioned order of Table 2, adding the components of group B (in the mentioned order of Table 2) under slow stirring, and dispersing for 15 minutes in a bead mill until the desired grinding fineness (particle size below 10 pm) was reached, and then adding components of group C in the mentioned order of Table 2 under moderate stirring.

[0118] The pigment slurry of T able 2 was used to prepare the Paint 0 (comparative) and Paint 1 (according to the invention). First the slurry was mixed with the epoxy resin dispersion (ED) of examples 5 or 6, resulting in the Part A of the waterborne two-pack coating composition. Part B was provided separately and then mixed and homogenized with Part A as provided in Table 3 just before spray application. When necessary, the dynamic viscosity of the waterborne two-pack coating composition (Part A + Part B mixed with each other) was adjusted to 500 - 600 mPa.s by addition of water according to application requirements. Table 2

[0119] 1Talcum: highest chemical purity and talc content, 52% of the particle size <2 pm; Elementis UK Ltd c / o Elementis GmbH, Cologne

[0120] 2KRONOS® 2190: Al / Zr stabilised titanium dioxide pigment, relative scattering power according to DIN 53165: 103; oil absorption according to ASTM 767 / 5: 18 g / (100 g): Kronos

[0121] International Inc., Leverkusen

[0122] 3Bayferrox® 3920: micronised iron oxide yellow, Colour index 77492; Bayferrox® 306: iron oxide black, Colour Index 77499; LANXESS Deutschland GmbH, Kbln

[0123] 4EWO white baryte, brightness Ry 92, d50 3.5 pm; Sachtleben Minerals GmbH&Co. KG, Hausach

[0124] 5ADDITOL® VXW 6208: polymeric nonionic dispersing additive; ADDITOL® VXW 6393: mineral oil defoamer, silicon-free; ADDITOL® VXW 6388: polyurethane thickener; ADDITOL® VXW 6503 N: levelling and substrate wetting additive, polyether modified polysiloxane; Allnex

[0125] 6Plastorit® 0000: SiO2 with particle size < 50 p; Kremer Pigmente GmbH & Co. KG, Aichstetten7Zinc orthophosphate hydrate, organically modified; Heubach Table 3

[0126] * ratio between hydrogen equivalents of hardener and epoxy equivalents of epoxy resin dispersion The paints were applied at room temperature by airmix spray application onto cold rolled steel (Gardobond OC - CRS), sandblasted steel and sandblasted aluminum substrates, at a targeted dry film thickness (DFT) of 50 - 60pm on Gardobond OC - CRS and 70-90pm on sandblasted steel as well as sandblasted aluminum. The coated substrates were cured for 7 days at 23 °C and 50 % relative humidity.

[0127] Anticorrosion Tests

[0128] The results of the Salt Spray Test (according to DIN EN ISO 9227, 1 mm scratch), Acetic Acid Salt Spray Test (according to DIN EN ISO 9227, 1 mm scratch), and Humidity Chamber Test (according to ISO 6270-2), conducted after 7 days at 23 °C and 50 % relative humidity storage, are presented in Table 4 and 5. The exposure time was 1000 hrs.

[0129] Table 4 Table 5

[0130] The results presented in Table 4 and 5 demonstrate the advantageous anti-corrosion properties of amine hardener compositions according to the invention compared to amine hardeners compositions according to the state of the art. Particularly surprising is the outstanding performance in corrosion protection of sandblasted aluminum substrates. A comparison of the anti-corrosion performance of the paints at same crosslinking ratio (Paint 0 compared with Paint 1 and Paint 3, Paint 5 compared with Paint 6) demonstrates the positive effect of Adduct (PAd), particularly for sandblasted aluminum. The comparison of Paint 1 with Paint 2 as well as Paint 3 with Paint 4 shows that the anti-corrosion performance on sandblasted aluminum can be improved by reducing the crosslinking ratio, even if the amount of Adduct (PAd) in the paint is reduced in parallel.

[0131] For the performance tests presented in Table 6 and 7 the coating compositions applied on cold rolled steel were used. It can be seen that the important paint parameters Drying degree, Cross-cut adhesion and Impact test were maintained or even improved as compared to the state of the art.

[0132] Table 6

[0133] Table 7

Claims

CLAIMS1 . A waterborne amine hardener composition (H) comprising: a) an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P), wherein the adduct (PAd) is substantially free of epoxy groups and has an acid value of at least 10 mgKOH / g, preferably an acid value comprised between 50 and 180 mgKOH / g; b) a polyamine (A); and c) water; the molar ratio between the epoxy groups from the epoxy resin (E) and the acidic hydrogen atoms from the phosphorus-derived acids (P) being between 0.2 and 0.95, preferably between 0.4 and 0.8, and the molar ratio between the acidic hydrogen atoms comprised in the adduct (PAd) and the basic nitrogen atoms from the polyamine (A) being between 0.02 and 0.90.

2. The waterborne amine hardener composition (H) according to claim 1 , wherein the weight percentage of the adduct (PAd) is from 5 to 50, and the weight percentage of the polyamine (A) is from 50 to 95, based on the total weight of adduct (PAd) and polyamine (A) being 100 %.

3. The waterborne amine hardener composition (H) according to claim 1 or 2, wherein the weight percentage of water is from 10 to 80, preferably from 20 to 70, more preferably from 35 to 65, based on the total weight of the waterborne amine hardener composition (H) being 100 %.

4. The waterborne amine hardener composition (H) according to any one of claims 1 to 3, wherein the waterborne amine hardener composition (H) further comprises an organic solvent.

5. The waterborne amine hardener composition (H) according to any one of claims 1 to 4, wherein the weight percentage of phosphorus comprised in the adduct (PAd) is from 1 .0 to 10.0.

6. The waterborne amine hardener composition (H) according to any one of claims 1 to 5, wherein the polyamine (A) comprises at least two amino groups per molecule and is characterized by a hydrogen equivalent weight of from 30 to 1500 g / Eq, more preferably from 80 to 1000 g / Eq.

7. The waterborne amine hardener composition (H) according to any one of claims 1 to 6, wherein the molar ratio between the acid groups comprised in the adduct (PAd) and the basic nitrogen atoms from the polyamine (A) is between 0.02 and 0.33.

8. The waterborne amine hardener composition (H) according to any one of claims 1 to 7, wherein the polyamine (A) is selected from the group consisting of aminofunctional epoxy-amine adducts, polyalkyleneglycol polyamines, amidoamines, polyamides, Mannich bases, phenalkamines, phenalkamides, and mixtures thereof.

9. The waterborne amine hardener composition (H) according to any one of claims 1 to 8, wherein the polyamine (A) is an amino-functional epoxy-amine adduct which is the reaction product of primary amines with epoxide-functional compounds.

10. The waterborne amine hardener composition (H) according to any one of claims 1 to 9, wherein the adduct (PAd) is the reaction product of at least one type of epoxy resin (E) having an epoxy equivalent weight of 100 to 1500 g / Eq with at least one phosphorus-derived acid (P).

11. The waterborne amine hardener composition (H) according to claim 10, wherein the at least one phosphorus-derived acid (P) is selected from the group consisting of inorganic acidic phosphorus compounds (P1), organic phosphonic acids (P2), and mixtures thereof.

12. The waterborne amine hardener composition (H) according to claim 11 , wherein the inorganic acidic phosphorus compounds (P1) are selected from the group consisting of orthophosphoric acid (H3PO4), diphosphoric acid (H4P2O7), triphosphoric acid (H5P3O10), phosphorous acid (H3PO3), diphosphorous acid (H4P2O5), hypophosphorous acid (H3PO2), higher homologs of orthophosphoric acid, higher homologs of phosphorous acid, higher homologs of hypophosphorous acid, and mixtures thereof.

13. A waterborne two-pack coating composition comprising: a) an epoxy component comprising an epoxy resin dispersion (ED), and b) a hardener component comprising the waterborne amine hardener composition (H) according to any one of claims 1 to 12, the amount of the waterborne amine hardener composition (H) being such that the weight percentage of the adduct (PAd) is between 0.25 and 10.0, based on the total solids content of the waterborne two-pack coating composition being 100 %.

14. A waterborne three-pack coating composition comprising: a) an epoxy component comprising an epoxy resin dispersion (ED), b) a hardener component comprising a polyamine (A), and c) a third component comprising an adduct (PAd) of an epoxy resin (E) and phosphorus-derived acids (P) according to any one of claims 1 , 7, or 10 to 12, wherein the weight percentage of the adduct (PAd) is between 0.25 and 10.0, based on the total solids content of the waterborne three-pack coating composition being 100 %.

15. The waterborne two-pack coating composition of claim 13 or the waterborne three- pack coating composition of claim 14, further comprising, in at least one of its components, one or more of pigments, dyes, anti-corrosive pigments, fillers, pigment dispersion aids, emulsifiers, surfactants, pigment wetting agents, levelling agents, substrate wetting agents, flow modifiers, defoamers, antisettling agents, rheology modifiers, coalescing agents, hydrophobizing agents, biocides, antioxidants, radical inhibitors, adhesion promoters and UV absorbers.

16. A process for the preparation of a waterborne amine hardener composition (H) according to any one of claims 1 to 12, the process comprising the steps of: i) providing in a first vessel a phosphorus-derived acid (P) at a temperature between 50 and 120°C, ii) adding thereto an epoxy resin (E) having an epoxy equivalent weight of 100 to 1500 g / Eq,iii) maintaining a reaction temperature of between 50 and 120°C for at least 30 minutes, iv) mixing the reaction product obtained in step iii) with a polyamine (A) at a temperature between 20 and 70°C, preferably between 30 and 60°C, to form the waterborne amine hardener composition (H).

17. Use of the waterborne amine hardener composition (H) according to any one of claims 1 to 12, or of the coating composition according to any one of claims 13 to 15, for coating a substrate, preferably a base metal substrate and more preferably an aluminum substrate, to protect the substrate from corrosion.

18. A substrate, preferably a metal substrate, more preferably an aluminum substrate, coated with the coating composition according to any one of claims 13 to 15.

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