Waterborne coating composition comprising an epoxy-amine system and an aromatic carboxylic acid as a curing catalyst

Abstract

The present invention relates to an aqueous coating composition, preferably an aqueous sanding surfacer or primer-surfacer, comprising an aqueous epoxy resin dispersion (A), an aqueous amine-functional resin dispersion (B) and an aromatic carboxylic acid (C). The aqueous dispersion (B) comprises at least one specific di- and / or polyfunctional monomeric amine (A1) and at least one resin component (RC), the resin component (RC) comprising at least one specific polyfunctional organic amine (A2). The present invention also relates to a kit comprising a base varnish comprising an aqueous epoxy resin dispersion (A) and a curing component comprising an aqueous amine-functional resin dispersion (B) and an aromatic carboxylic acid (C). The present invention also relates to a method for preparing a coating on a substrate and a coated substrate obtained by the method. The cured coating formed from the composition exhibits good adhesion to the substrate under humid conditions, high intercoat adhesion and blister stability, without negatively affecting the excellent sanding properties and good stone chipping properties.

Description

[0001] The present invention relates to an aqueous coating composition, preferably an aqueous sanding surfacer or primer-surfacer, comprising an aqueous epoxy resin dispersion (A), an aqueous amine-functional resin dispersion (B), and an aromatic carboxylic acid (C). The aqueous dispersion (B) comprises at least one specific di- and / or polyfunctional monomeric amine (A1) and at least one resin component (RC), the resin component (RC) comprising at least one specific polyfunctional organic amine (A2). The present invention also relates to a kit comprising a base varnish comprising an aqueous epoxy resin dispersion (A) and a curing component comprising an aqueous amine-functional resin dispersion (B) and an aromatic carboxylic acid (C). The present invention also relates to a method for producing a coating on a substrate and a coated substrate obtained by the method. The cured coating formed from the composition exhibits good adhesion to the substrate under humid conditions, high intercoat adhesion, and blister stability, without negatively affecting the excellent sanding properties and good stone chipping properties. Existing technology

[0002] In the automotive recoating sector, repairing defects in the original coating may involve mechanically sanding or grinding away the defect, or completely stripping the entire part or vehicle of the original coating. This sanding or grinding process often results in the exposure of bare metal. Prior to applying the final topcoat material, a separate primer system is often recommended. The sanded areas of exposed bare metal are first covered with a corrosion-inhibiting primer, i.e., a primer formulated with corrosion-inhibiting pigments that also bonds to the bare metal and the organic coating. The next step involves applying what is known in the art as a sandable primer-surfacer. Finally, a basecoat / clearcoat system or topcoat is applied to complete the repair.

[0003] As environmental protection requirements become increasingly stringent, water-based primers and primer-surfacers for coating objects are becoming increasingly important. Their performance must be comparable to conventional systems (i.e., systems containing solvents). In cold-cure coating compositions, water-dilutable epoxy resin systems cured with amine-containing curing agents are gaining increasing importance. These two-component (2K) systems offer excellent properties, such as good drying properties and good adhesion to most substrates, as well as good metal corrosion protection.

[0004] To accelerate the curing time of these systems, thereby improving the efficiency of the recoating process, it is known to add curing catalysts such as tertiary amines, Lewis acids (e.g., BF3), or weak proton donors (e.g., phenols and carboxylic acids) to these systems. A commonly used curing catalyst for epoxy-amine systems is a phenol containing dendritic tertiary amine groups (i.e., tris-2,4,6-dimethylaminomethylphenol), available under the trade name Ancamine K54. However, the use of this catalyst in waterborne epoxy-amine systems can result in reduced intercoat adhesion and increased blistering of coatings prepared from such systems under humid conditions.

[0005] Other compounds known to accelerate the reaction between epoxy resins and amine-functional curing agents are aromatic carboxylic acids, such as benzoic acid and salicylic acid. For example, WO 2009 / 016162 A1 discloses a water-based amine-epoxy resin system containing salicylic acid. This system comprises an epoxy resin A and a water-soluble or water-dispersible amine-functional curing agent B, which comprises the reaction product of an amine B1 having at least one primary and / or at least one secondary amino group, an adduct B2 of a polyalkylene ether polyol B21 and an epoxide component B22, and an aromatic compound B3 (preferably salicylic acid). The use of this epoxy resin system can improve corrosion resistance. However, coatings obtained from this system also exhibit reduced intercoat adhesion and blister stability under humid conditions, as well as reduced stone chip resistance.

[0006] However, sufficient intercoat adhesion and high blister stability under wet conditions as well as sufficient stone chip resistance are very important in repainting procedures in order to ensure a constant aesthetically high-quality appearance of the painted surface under the conditions encountered during normal use of the repainted vehicle.

[0007] Therefore, there is a need for aqueous coating compositions, particularly in vehicle recoating, which exhibit fast cure times at low cure temperatures, preferably 80°C or lower. Cured coatings prepared from such compositions should exhibit good adhesion to the substrate, good intercoat adhesion, and high blister stability, especially under humid conditions. In addition, the cured coatings should exhibit excellent corrosion resistance and sand abrasion resistance, as well as adequate stone chip resistance. Finally, the cured coatings should result in a high-quality appearance when combined with other coatings, such as pigmented basecoats and / or clearcoats.

[0008] Purpose

[0009] The object of the present invention is therefore to provide an aqueous coating composition which cures rapidly at low curing temperatures, preferably 80° C. or lower, and which results in a cured coating having good adhesion to the substrate, good intercoat adhesion and high blister stability, especially under humid conditions, without negatively affecting the excellent sanding, corrosion and stone chip resistance of the coating. Furthermore, the application of further coatings, such as a pigmented basecoat and / or a clearcoat, should result in a multilayer coating having a high-quality appearance.

[0010] Technical Solutions

[0011] The above objects are achieved by the subject matter claimed in the claims and by preferred embodiments of this subject matter described in the following description.

[0012] Therefore, a first subject of the present invention is an aqueous coating composition comprising:

[0013] a) an aqueous dispersion (A) of at least one epoxy resin (ER1), said epoxy resin (ER) having on average at least one epoxy group per molecule,

[0014] b) at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5%, and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, and

[0015] c) at least one aromatic compound (C) having at least one carboxylic acid group,

[0016] in:

[0017] The resin component (RC) comprises at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, wherein the at least one polyfunctional organic amine (A2) comprises a reaction product of:

[0018] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0019] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and

[0020] (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups, and R is a

[0021] An organic group containing at least one polyoxyalkylene unit and no other X groups.

[0022] The coating composition described above is also referred to below as the coating composition of the invention and is therefore the subject matter of the present invention. Preferred embodiments of the coating composition of the invention emerge from the following description and the dependent claims.

[0023] In view of the prior art, the object underlying the present invention was surprisingly and unforeseeable to those skilled in the art that it could be achieved by using aromatic carboxylic acids as curing catalysts in combination with specific aqueous dispersions (B) as crosslinkers in aqueous epoxy resin-based coating systems. These systems exhibit fast curing times at low temperatures, preferably 80°C or lower, and are therefore very suitable for automotive recoating. The cured coatings obtained from these systems exhibit excellent adhesion to the substrate under wet conditions, as well as excellent intercoat adhesion and blister stability, without negatively affecting the excellent sanding resistance and good stone chip resistance. Furthermore, the combination of the aforementioned curing catalyst and aqueous dispersion (B) allows for significantly improved crosshatch adhesion and blister stability under wet conditions compared to aqueous epoxy systems containing different amino-functional curing agents or aqueous epoxy systems containing aqueous dispersion (B) and the curing catalyst Ancamine K54.

[0024] Another subject of the present invention is a kit comprising two separate components A) and B):

[0025] A) at least one aqueous base varnish comprising an aqueous dispersion (A) of at least one epoxy resin (ER1),

[0026] The epoxy resin (ER) has at least one epoxy group per molecule on average; and

[0027] B) at least one aqueous hardener component comprising:

[0028] at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5%, and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, said resin component (RC) comprising at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, said at least one polyfunctional organic amine (A2) comprising the reaction product of:

[0029] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0030] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and

[0031] (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups and R is an organic radical comprising at least one polyoxyalkylene unit and containing no other X groups; and

[0032] - at least one aromatic compound (C) having at least one carboxylic acid group.

[0033] Another subject of the present invention is a method for producing at least one coating on a substrate, comprising the following steps:

[0034] (i) applying the aqueous coating composition of the present invention or the coating composition prepared from the kit of parts of the present invention to a substrate;

[0035] (ii) forming a coating film from the coating composition applied in step (i);

[0036] (iii) curing the coating film formed in step (ii);

[0037] (iv) optionally sanding the cured coating obtained in step (iii); and

[0038] (v) optionally applying at least one further coating layer and curing said coating layer.

[0039] A final subject of the present invention is a coated substrate produced by the process according to the invention.

[0040] Detailed description

[0041] The measurement methods used to determine certain characteristic variables in the context of the present invention can be found in the Examples. Unless explicitly stated otherwise, these measurement methods should be used to determine the corresponding characteristic variables. If an official standard is cited in the context of the present invention without specifying any official validity period, the reference implicitly refers to the version of the standard in effect on the filing date, or, if no version was in effect at that time, to the most recent valid version.

[0042] All film thicknesses reported in the context of the present invention are to be understood as dry film thicknesses. Therefore, they are in each case the thickness of the cured film. Therefore, if a coating is reported as being applied at a certain film thickness, this means that the coating was applied in such a way that, after curing, the stated film thickness is achieved.

[0043] All temperatures stated in the context of the present invention are to be understood as the temperature of the room in which the substrate or coated substrate is located. This does not therefore mean that the substrate itself needs to have the temperature in question.

[0044] The term "resin or resin component" is understood to mean a product containing organic constituents, i.e., organic reaction products, oligomers and / or polymers, and, if appropriate, monomers, such as the resin component (RC). Resins have a more or less broad molar mass distribution and are generally used as binders in coating compositions. Therefore, after curing, they form at least part of the polymer network of the coating present.

[0045] In accordance with the relevant DIN EN ISO 4618:2007-03, the term "binder" or "binder component" in this document refers to the non-volatile components of a coating, excluding pigments and fillers. In this case, the specific binder component is the epoxy resin (ER1) or other coating additives. However, for the sake of clarity, the term "binder" is primarily used for the components responsible for film formation and does not include curing agents or crosslinkers.

[0046] The water-based coating composition of the present invention:

[0047] Coating composition of the present invention is an aqueous coating composition. The term "aqueous" relevant to coating composition is known in principle. This means that the coating composition contains a significant proportion of water as a solvent. It should be understood that aqueous systems can also contain at least a relatively small amount of organic solvents, for example as a cosolvent with an emulsifier function to stabilize a specific composition, such as a resin, a pigment or an additive. In the context of the present invention, "aqueous" is preferably understood to mean that the composition has at least 40 % by weight, preferably at least 50 % by weight, even more preferably at least 60 % by weight of the water ratio, in each case based on the total amount of the solvent (i.e. water and organic solvent) present. Preferably, the ratio of water is again 50-99 % by weight, especially 60-98 % by weight, in each case based on the total amount of the solvent present.

[0048] The above definition of “aqueous” also applies to the aqueous dispersions (A) and (B) described below, ie the dispersions have a water proportion of 50 to 99% by weight, in particular 60 to 98% by weight, based on the total amount of solvent present.

[0049] Aqueous dispersion (A) of epoxy resin (ER1):

[0050] The first mandatory component of the aqueous coating composition of the present invention is an aqueous dispersion (A) of an epoxy resin (ER1). The term "aqueous dispersion" is well known to those skilled in the art and is preferably understood to mean a dispersion comprising at least 40% by weight of water, based on the total amount of solvent present in the dispersion.

[0051] Epoxy resins are known as polycondensation resins that contain, on average, more than one epoxy group. For example, these resins can be prepared by condensing bisphenol A or bisphenol F with epichlorohydrin and have, on average, two epoxy groups. These compounds contain hydroxyl groups along the chain and epoxy groups at the ends. The crosslinking capacity via the epoxy groups depends on the chain length, decreasing with increasing chain length / molar mass.

[0052] Suitable epoxy resins (ER1) are selected from glycidyl ethers of diols or phenols, novolac resins, diglycidyl esters of carboxylic acids or mixtures thereof, preferably glycidyl ethers of phenols, more preferably glycidyl ethers of bisphenol A. Therefore, preferred epoxy resins (ER1) do not contain any bisphenol F, since the presence of bisphenol F in the epoxy resin (ER1) can negatively affect the sandability of the cured coating prepared from the coating composition of the present invention.

[0053] Preferably, the at least one epoxy resin (ER1) has a specific epoxy equivalent weight (EEW) and viscosity. According to a first embodiment, the epoxy resin (ER1) preferably has an epoxy equivalent weight (EEW) of 100-400 g / eq, more preferably 120-300 g / eq, even more preferably 150-250 g / eq, and very preferably 185-210 g / eq, as determined according to ASTM D1652-11 (2019).

[0054] Furthermore, the epoxy resin (ER1) of this first embodiment preferably has a viscosity at 25° C. of 1,000-20,000 mPa*s, more preferably 1,500-15,000 mPa*s, very preferably 2,500-9,500 mPa*s, as determined according to ASTM D2196-18.

[0055] According to an alternative embodiment, the epoxy resin (ER1) preferably has an epoxy equivalent weight (EEW), determined according to VLN 305, of 250-700 g / eq, more preferably 300-600 g / eq, even more preferably 350-550 g / eq, very preferably 380-520 g / eq.

[0056] Furthermore, the epoxy resin (ER1) of this alternative embodiment preferably has a -1 The kinematic viscosity is preferably 100-3,000 mPa*s, more preferably 150-2,500 mPa*s, even more preferably 200-2,000 mPa*s, very preferably 250-1,400 mPa*s, as determined according to DIN EN ISO 3219: 1994-10.

[0057] The use of the above-mentioned epoxy resin (ER1) leads to good optical and mechanical properties and high adhesion of the coatings prepared from the coating composition of the present invention. In addition, the epoxy resin (ER1) allows for stable dispersion of pigments and / or fillers without irreversible thickening or curing during dispersion.

[0058] The at least one dispersion (A) of epoxy resin (ER1) is preferably present in a total amount of 5 to 50% by weight, more preferably 10 to 40% by weight, even more preferably 15 to 30% by weight, very preferably 18 to 25% by weight, in each case based on the total weight of the aqueous coating composition.

[0059] The total amount of epoxy resin (ER1) in the aqueous coating composition is suitably 1 to 30% by weight, preferably 5 to 25% by weight, more preferably 8 to 20% by weight, very preferably 10 to 15% by weight, in each case based on the total weight of the aqueous coating composition.

[0060] Aqueous dispersion (B):

[0061] The second mandatory component of the aqueous coating composition of the present invention is an aqueous dispersion (B) which contains at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5%, and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol.

[0062] Di- and / or polyfunctional monomeric primary and / or secondary amines (A1):

[0063] Di- and / or polyfunctional monomeric primary and / or secondary amines (A1) are understood to mean low molecular weight compounds, i.e. compounds having a molecular weight of less than 500 g / mol, preferably less than 250 g / mol, having a discrete number of amino groups per molecule, which is constant for each molecule.

[0064] The at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) preferably comprises at least 65 mol %, preferably at least 75 mol %, more preferably at least 90 mol %, and very preferably 100 mol % of an amine composed of amino and hydrocarbon groups. Consequently, other functional groups, such as hydroxyl, carboxyl, or nitrile groups, are present only in small amounts or not at all. This low content of other functional groups (preferably the absence of other functional groups) results in improved sanding properties of the cured coatings obtained from the coating compositions of the present invention.

[0065] The proportion of the corresponding amine (A1) is based on the total amount of the aqueous dispersion (B) and is determined by the amount of amine (A1) introduced into the dispersion (B) during its preparation. When commercially available products are used, the proportion of the amine (A1) can be determined by known analytical methods, for example by gas chromatography (GC) or mass spectrometry (MS).

[0066] Examples of suitable amines (A1) are the monomeric aliphatic, aromatic and araliphatic (mixed aliphatic-aromatic) amines known in principle to the person skilled in the art. Examples of such amines include ethylenediamine, propylene-1,2-diamine, propylene-1,3-diamine, butane-1,4-diamine, octane-1,8-diamine, 1,3-diaminopentane, hexamethylenediamine, 2-methylpentamethylenediamine, neopentyldiamine, cyclohexanediamine, 2,2,4-(2,4,4-)trimethylhexamethylenediamine, 3,5-isophoronediamine, bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, bis(hexamethylenediamine), N,N-5-dimethylaminodipropylenetriamine, laurylpropylenediamine, 1,2- and 1,3-(m-)-xylenediamine, and 1,4-bis(aminomethyl)benzene. Other amines include aminoethylethanolamine or heterocyclic polyamines such as aminoethylpiperazine and bis(aminopropyl)piperazine.

[0067] Preference is given to difunctional monomeric primary and / or secondary amines. Particular preference is given to difunctional monomeric primary amines, very preferably isophoronediamine and / or m-xylylenediamine. Particularly preferably, aqueous dispersion (B) comprises at least two difunctional monomeric primary amines, namely isophoronediamine and m-xylylenediamine.

[0068] The proportion of the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), preferably isophoronediamine and / or meta-xylylenediamine, in the aqueous dispersion (B) is from 1 to 4.5% by weight, preferably from 1.5 to 4% by weight, based on the total weight of the aqueous dispersion (B).

[0069] Resin component (RC):

[0070] The resin component (RC) contains at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups. Unlike the monomeric amines (A1) already described, these are adducts or reaction products with a polymeric character and a specific number of amino groups per molecule (which can only be described as an average value).

[0071] The resin component (RC) preferably has an NH equivalent weight of 160 to 350 g / mol, preferably 170 to 250 g / mol (for determination method, see Examples).

[0072] The at least one polyfunctional organic amine (A2) comprises the reaction product of:

[0073] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0074] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A3), and

[0075] (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups, and R is a

[0076] An organic group containing at least one polyoxyalkylene unit and no other X groups.

[0077] Preferably, in the present invention, the resin component (RC) contains, in addition to the polyfunctional organic amine (A2), at least one polyfunctional organic amine (A3) having primary and / or secondary amino groups, wherein the polyfunctional organic amine (A3) is a reaction product of:

[0078] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0079] and

[0080] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1).

[0081] Therefore, polyfunctional organic amine (A3) is different from polyfunctional amine (A2) because different starting materials are used to prepare the polyfunctional organic amine. The term "reaction product" in the sense of the present invention is understood to mean the compound obtained by reacting the listed compounds with each other. This means that the reaction product cannot contain other components that are not explicitly listed in the reaction product.

[0082] Particularly preferably, the resin component (RC) consists of at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups and at least one polyfunctional organic amine (A3) having primary and / or secondary amino groups.

[0083] The at least one di- and / or multifunctional epoxy resin (ER2) used to prepare the multifunctional organic amine (A2) and the multifunctional amine (A3) has an average epoxy equivalent weight (EEW) of less than 400 g / eq. It has been found that a correspondingly lower average epoxy equivalent weight and therefore a higher epoxy functionality of the component leads to better sanding properties in the surfacer layer finally produced. More preferably, the average epoxy equivalent weight is less than 350 g / mol, preferably less than 300 g / mol, more preferably less than 250 g / mol, and very preferably 160-200 g / mol, determined according to DIN EN ISO 3001:2019-08. The average epoxy equivalent weight can be obtained by determining the epoxy equivalent weights of all epoxy compounds used and weighting their mass proportion in the total weight of the epoxy compounds. In the case of commercial products (in which the epoxy compounds may already be covalently bonded), the average epoxy equivalent weight can be determined by analyzing the product, for example by gas chromatography (GC) or mass spectrometry (MS).

[0084] Preferably, the at least one di- and / or polyfunctional epoxy resin (ER2) has on average 1 to 5 epoxy functional groups, preferably 1 to 4 epoxy functional groups, more preferably 1 to 3 epoxy functional groups, very preferably 2 epoxy functional groups, since such epoxy resins are readily commercially available.

[0085] Suitable epoxy resins (ER2) may be saturated or unsaturated, aliphatic and mixed aliphatic-aromatic compounds which optionally contain hydroxyl groups, for example selected from glycidyl ethers of diols or phenols, novolac resins, diglycidyl esters of carboxylic acids or mixtures thereof. Among the phenols, resorcinol, hydroquinone, 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A), isomer mixtures of dihydroxydiphenylmethane (bisphenol F), tetrabromobisphenol A, 4,4'-dihydroxydiphenylcyclohexane, 2,2-bis-(4-hydroxy-3-methylphenyl)-propane, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxybenzophenone, 1,1-bis-(4-hydroxyphenyl)-ethane, 2, 2-bis-[4-(2'-hydroxypropoxy)-phenyl]-propane, 1,1-bis-(4-hydroxyphenyl)-isobutane, 2,2-bis(4-hydroxy-3-tert-butylphenyl)-propane, bis-(2-hydroxynaphthyl)-methane, 1,5-dihydroxynaphthalene, tris-(4-hydroxyphenyl)-methane, bis-(4-hydroxyphenyl)ether, bis-(4-hydroxyphenyl)sulfone and halogenation and hydration products of the aforementioned compounds. Diepoxyalkanes prepared by epoxidation of dienes can also be used.

[0086] Particularly preferred epoxy resins (ER2) are glycidyl ethers of phenols, very preferably glycidyl ethers of bisphenol A. Therefore, it is particularly preferred that the epoxy resin (ER2) does not contain any bisphenol F. It has been found that the absence of bisphenol F in the epoxy resin leads to increased sandability of the cured coatings produced from the coating composition of the invention.

[0087] The at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) used for preparing the polyfunctional organic amine (A2) and the polyfunctional amine (A3) corresponds to the amine (A1) described previously for the aqueous dispersion (B).

[0088] In the preparation of the polyfunctional organic amine (A2), at least one specific compound XR is used. Preferably, only one compound XR is used.

[0089] The X group is a group known to those skilled in the art, such as a primary or secondary amino group, a hydroxyl group, a carboxylic acid group or a thiol group. It is crucial that the compound XR has exactly one X group. Otherwise, the sand-abrasive property of the cured coating obtained by the coating composition of the present invention would be adversely affected. The preferred X group is an amino group, and among these groups, a primary amino group is preferred. In addition to the good reactivity of the amino group with the epoxy group, the primary amine also has two NH equivalents and therefore has a connection site with the epoxide. In this way, the compound XR can be introduced into the side chain position of the multifunctional organic amine (A2). The presence of the amino group, preferably the primary amino group, causes the sand-abrasive property of the cured coating obtained by the coating composition of the present invention to be improved.

[0090] The R group is an organic group containing polyoxyalkylene units, particularly preferably polyethylene or polypropylene units or mixed polyethylene / polypropylene units.

[0091] Preferably, the organic R group is composed of polyoxyalkylene units in addition to any molecular units resulting from synthesis. For simplicity, this R group is also referred to as polyoxyalkylene. Molecular units resulting from synthesis are, for example, organic groups of molecules used to initiate the formation of the polyoxyalkylene chain, such as initiator alcohols for initiating the polymerization of ethylene oxide and / or propylene oxide.

[0092] Particularly preferred compounds XR are selected from polyoxyalkylene monoprimary amines. Such compounds can be synthesized or are commercially available, for example, under the trade name "Jeffamine" from Huntsman Corporation.

[0093] The weight average molecular weight of compound XR can vary within wide limits, for example 800-2200 g / mol (determined by size exclusion chromatography coupled to light scattering).

[0094] Particularly preferably, the at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups consists of a reaction product of components (i), (ii) and (iii). Therefore, the polyfunctional organic amine (A2) does not contain any other compounds besides the above reaction products.

[0095] Dispersion (B) preferably has a solids content of 25 to 45% by weight, based on the total weight of the dispersion and determined in accordance with DIN EN ISO 3251:2018-07.

[0096] The aqueous dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) and the resin component (RC) can be prepared, for example, by a two-step process, which will be described in detail below.

[0097] Step (1):

[0098] In a first step (1), an amino-functional resin mixture (I) is prepared by reacting an epoxy-functional resin mixture (Ia) with a component (Ib) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1).

[0099] The epoxy-functional resin mixture (Ia) is prepared by reacting at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol with at least one compound XR. To this end, the epoxy groups of the epoxy resin (ER2) are used in a molar stoichiometric excess relative to the reactive units X of the compound XR. The number of reactive units X means the number of potential attachment sites in the compound XR for each epoxy group. For example, for hydroxyl or secondary amino groups, there is one reactive unit per X group. For primary amino groups, there are two reactive units (two NH functions). Preferably, the molar ratio of the epoxy groups of the epoxy resin (ER2) to the epoxy-reactive units of the X groups of the component XR is 10-1.1, more preferably 5-1.5, and particularly preferably 3.5-1.8. The amount of epoxy groups in the epoxy resin (ER2) can be obtained or appropriately adjusted by determining the epoxy equivalent weight. For example, the amount of reactive units in the X group can be determined by determining the amine number, OH number or acid number (DIN 53176: 2002-11, DIN 53240-3: 2016-03, DIN EN ISO 2114 correction 1: 2006-11).

[0100] The epoxy-functional resin mixture (Ia) preferably has an epoxy equivalent weight of 500 to 1500 g / mol, more preferably 600 to 1200 g / mol.

[0101] The component (Ib) that reacts with the epoxy-functional resin mixture (Ia) comprises at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1). Preferably, component (Ib) consists of at least one such amine (A1).

[0102] Examples of suitable epoxy resins (ER2), compounds XR and amines (A1) have already been described above and apply accordingly.

[0103] Resin mixture (I) is an amino-functional resin mixture. Therefore, relative to epoxy-functional resin mixture (Ia), the NH equivalent of compound (Ib) must be used in molar excess. In particular, the NH equivalent of resin mixture (I) is 50-140g / mol, preferably 70-130g / mol (determination method see embodiment part). In addition, resin mixture (I) comprises 17.5-40 wt %, preferably 25-35 wt % ratio of di- and / or polyfunctional monomer primary amine and / or secondary amine (A1), i.e. component (Ib). Those skilled in the art can adjust these two standards by appropriately selecting the molar amount of the two components and knowing that there is the quantitative conversion of epoxy group and NH functional group under conditions and reaction scheme known per se. Preferably, after its preparation, resin mixture (I) is dispersed in water, in this case, it is an aqueous dispersion.

[0104] The resin mixture (I) itself can be prepared as described above and is thus obtained in an aqueous dispersion. Aqueous dispersions of the resin mixture (I) are likewise commercially available (eg Beckopox VEH 2849w / 80WA (from Allnex)).

[0105] Step (2):

[0106] In the second step (2), aqueous dispersion (B) is obtained by reacting component (IIa) comprising an amino-functional resin mixture (I) with component (IIb) comprising at least one di- and / or polyfunctional organic epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol, preferably less than 350 g / mol, and more preferably less than 250 g / mol. If necessary, the organic solvent used during the preparation of aqueous dispersion (B) can be removed. Since resin component (RC) is amine-functional, a molar excess of the NH equivalent of component (IIa) is used relative to the epoxy groups of component (IIb).

[0107] It is preferred to use the direct reaction product obtained from step (1) as component (IIa) because the resin mixture (I) is obtained as an aqueous dispersion after step (1) and can therefore be used directly in step (2) carried out in aqueous phase. Before carrying out step (2), a solvent or additive (e.g., an emulsifier) ​​may be added to the reaction product.

[0108] Besides the amino-functional resin mixture (I), component (IIa) preferably does not comprise any further compounds which are reactive with component (IIb).

[0109] Component (IIb) preferably consists of at least one, preferably exactly one, di- and / or polyfunctional organic epoxy resin (ER2) having an epoxy equivalent weight that satisfies the above-mentioned prerequisites. Examples of suitable epoxy compounds are those already mentioned above as components.

[0110] The above method also allows the use of existing commercial products (e.g. Beckopox VEH 2849w / 80WA mentioned above). Therefore, the aqueous dispersion (B) can be easily obtained by simply modifying the commercial product with a suitable epoxide (because, except for this last reaction, all further reaction processes are already carried out in the production of the commercial product).

[0111] However, the aqueous dispersion (B) can also be obtained by a one-step process in which all starting materials are reacted together by adjusting the stoichiometric ratio of amine and epoxide. It is also possible to first react the epoxy resin (ER2) with the compound XR and further react the resulting product with other epoxides and the monomeric amine (A1).

[0112] The resin component (RC) is preferably present in a total amount of 10 to 30% by weight, preferably 15 to 25% by weight, based in each case on the solids content of the aqueous coating composition.

[0113] Aromatic compound (C) having at least one carboxylic acid group:

[0114] The third mandatory component of the aqueous coating composition of the present invention is an aromatic compound (C) having at least one carboxylic acid group. Aromatic compound refers to a compound having at least one aromatic structure in the molecule. The carboxylic acid group can be connected to the aromatic structure directly or via a linking group. Preferably, the carboxylic acid group is directly connected to the aromatic structure.

[0115] Preferred compounds (C) further comprise at least one hydroxyl group. It has been found that the presence of said at least one hydroxyl group improves the acceleration of the crosslinking reaction compared to aromatic compounds not having any hydroxyl groups.

[0116] Particularly preferred are resorcinol, salicylic acid, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid (β-dihydroxybenzoic acid), 2,5-dihydroxybenzoic acid (gentisic acid), 2,6-dihydroxybenzoic acid (γ-dihydroxybenzoic acid), 3,4-dihydroxybenzoic acid (protocatechuic acid), 3,5-dihydroxybenzoic acid (α-dihydroxybenzoic acid), 3,4,5-trihydroxybenzoic acid (gallic acid), 2-hydroxy-3-naphthoic acid, 2-hydroxy-6-naphthoic acid, and alkyl derivatives thereof, such as 2-hydroxy-3-, -4- and -5-methyl-benzoic acid (cresol acid), and mixtures thereof. Particular preference is given to using salicylic acid as compound (C).

[0117] The at least one aromatic compound (C) is preferably present in a total amount of 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, even more preferably 0.3 to 1% by weight, very preferably 0.4 to 0.7% by weight, in each case based on the total weight of the aqueous coating composition.

[0118] Other optional ingredients of the waterborne coating composition:

[0119] Water-based coating composition of the present invention preferably comprises at least one pigment and / or filler, and promptly water-based coating composition of the present invention preferably produces color coating.Preferred pigment is black and / or white pigment.Therefore, described coating composition preferably comprises at least one black pigment or at least one white pigment, or at least one white pigment and a kind of black pigment.This means that coating composition of the present invention preferably has black, white or (various grades) gray.Described composition can also comprise other pigments.

[0120] Preferred black pigments are typical organic and inorganic, especially inorganic, black pigments, which are commercially available in powder form. Particular mention should be made of pigment black (carbon black), iron oxide (Fe 3 O 4 ) pigments, such as typical synthetic iron oxides (for example, commercially available under the Bayferrox trade name from Lanxess), and mixed oxide pigments such as manganese black or spinel black. Very particular preference is given to pigment black (carbon black) and iron oxide pigments.

[0121] Preferred white pigments are typical inorganic white pigments, such as titanium dioxide (eg the rutile pigments known under the Kronos trade name from Kronos), zinc oxide 15, zinc sulfide or antimony trioxide. Very particular preference is given to titanium dioxide, especially in its rutile modification.

[0122] Further preferred pigments are those known to those skilled in the art as "anticorrosion pigments." Zinc phosphate is particularly preferred here. Although zinc phosphate is white, due to its anticorrosion effect it is not classified as a white pigment, but rather as an anticorrosion pigment.

[0123] The proportion of pigments is preferably from 15 to 25% by weight, very preferably 20% by weight, in each case based on the solids content of the coating composition.

[0124] The fillers preferably present are all inorganic and organic fillers known and familiar to the person skilled in the art, preferably inorganic fillers. Thus, fillers include in particular substances known to the person skilled in the art, which are used, for example, in particulate or powder form to achieve the specific physical properties of the coating composition and are insoluble in the corresponding application medium. These include in particular carbonates such as calcium carbonate or barium carbonate, sulfates such as calcium sulfate and barium sulfate, silicates and phyllosilicates such as talc, pyrophyllite, mica, kaolin, precipitated calcium silicate, aluminum silicate, calcium / aluminum silicate, sodium / aluminum silicate and mullite, silicon dioxide such as quartz, cristobalite, precipitated silicon dioxide or in particular fumed silicon dioxide, available, for example, under the Aerosil trade name (Evonik), metal oxides and hydroxides, for example aluminum hydroxide and magnesium hydroxide.

[0125] The proportion of fillers is preferably from 30 to 50% by weight, in particular from 30 to 40% by weight, in each case based on the solids content of the coating composition.

[0126] Furthermore, the coating composition may also contain at least one additive. Examples of such additives include light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, tackifiers, leveling agents, film-forming aids, thickeners, sag control agents (SCAs), or corrosion inhibitors. These are used in customary and known amounts. The same applies to the possible use of organic solvents, which are used in amounts that do not alter the aqueous properties of the coating composition.

[0127] Properties of waterborne coating compositions

[0128] In order to ensure rapid and complete crosslinking under curing conditions, the aqueous coating composition preferably comprises a specific molar ratio of NH groups of the resin compound (RC) to epoxy groups of the epoxy resin (ER1). Thus, the molar ratio of NH groups of the resin compound (RC) to epoxy groups of the epoxy resin (ER1) is preferably from 0.74:1 to 0.95:1, preferably 0.9:1.

[0129] The solids content of the 2K coating composition can vary depending on the requirements of the specific case, but is preferably 70-85% by weight, based on the total weight of the aqueous coating composition and determined in accordance with DIN EN ISO 3251:2018-07. The solids content is primarily determined by the viscosity required for application, more particularly for spray application, and can therefore be adjusted by a person skilled in the art based on his or her general technical knowledge (optionally with the aid of a small amount of exploratory testing).

[0130] The coating compositions can be prepared using customary and known mixing methods and mixing units for preparing coating compositions, such as stirred tanks, stirred mills, bead mills, extruders, kneaders, Ultraturrax, inline dissolvers, static mixers, toothed ring dispersers, expansion nozzles and / or microfluidizers.

[0131] The coating composition of the present invention has excellent applicability as a surfacer and / or primer-surfacer. Therefore, the coating composition of the present invention is preferably a surfacer or primer-surfacer. The functions, configurations and application areas of surfacers and primer-surfacers are in principle known to those skilled in the art and have distinguishing characteristics in this respect. Surfacers are usually applied as an intermediate layer (applied to a previously cured electrophoretic coating) in automotive OEM finishing, cured separately, and then overcoated with a basecoat and a clearcoat. Primer-surfacers are particularly used in the automotive recoating sector, where they are used to fill local damaged areas in the initial paint system and to obtain suitable adhesion on the substrate and to ensure corrosion protection.

[0132] The complete packaging of the present invention:

[0133] In order to prevent the epoxy resin (ER1) from reacting with the components of the aqueous dispersion (B), the coating composition of the present invention is preferably formulated as a multi-component, more preferably a two-component coating composition. In a multi-component composition, the compounds of the coating composition are contained in separate containers, and the coating composition is prepared by mixing the contents of the containers, preferably shortly before applying the prepared coating composition to the substrate.

[0134] The present invention therefore also relates to a kit comprising the two separate components A) and B):

[0135] A) at least one aqueous base varnish comprising an aqueous dispersion (A) of at least one epoxy resin (ER1), said epoxy resin (ER) having on average at least one epoxy group per molecule; and

[0136] B) at least one aqueous hardener component comprising:

[0137] at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5%, and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, said resin component (RC) comprising at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, said at least one polyfunctional organic amine (A2) comprising the reaction product of:

[0138] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0139] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and

[0140] (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups and R is an organic radical comprising at least one polyoxyalkylene unit and containing no other X groups; and

[0141] - at least one aromatic compound (C) having at least one carboxylic acid group.

[0142] The kit of parts according to the invention thus comprises at least two components A) and B), preferably consists of exactly these two components A) and B). It is also possible in the present invention that further compounds such as solvents or additives may be present as separate components and may serve to adjust the viscosity of the coating composition obtained after mixing components a) and B).

[0143] In the kit of parts according to the invention, the base clearcoat (component A) and the hardener component (component B), as defined below, are prepared and stored separately and mixed only shortly before application to the substrate. The processing time or pot life (i.e., the time during which the coating composition obtained by mixing components A) and B) can be processed and applied at room temperature (15-25°C, in particular 20°C)) depends on the compounds present in the base clearcoat and hardener components. In the context of the present invention, the processing time of the coating composition obtained by mixing components A) and B) is preferably at least 2 minutes to 60 minutes, more preferably at least 5 minutes to 60 minutes. A particular advantage of this two-component coating composition is that it can be cured at temperatures below 100°C, making it suitable for recoating applications.

[0144] It is also known that, in addition to the epoxy resin (ER1) serving as the binder and the solvent, the base clearcoat component A) typically contains all or most of the other functional components of the composition, such as pigments, fillers, and additives, while the hardener component B) contains, in addition to the solvent and any additives, only the compounds used for crosslinking. The terms "base clearcoat component" and "hardener component" in the context of multi-component coating compositions are known to those skilled in the art and also have essential characterizing and therefore distinguishable characteristics within the scope of a particular configuration. In the context of the present invention, it is particularly preferred that the base clearcoat component A) contains pigments and fillers, preferably all of the pigments and fillers in the coating composition obtained after mixing components A) and B). It is also preferred that, in addition to the at least one epoxy resin (ER1), the base clearcoat component A) contains no other epoxy resins, i.e., the epoxy resin (ER1) accounts for at least 90% by weight, preferably at least 95% by weight, of the binder component of the base clearcoat A. The binder component is determined by subtracting the pigment and filler proportions from the solids (non-volatiles) of the dispersion. After mixing the two main components A) and B), the epoxy groups can react with the NH functions of the polyamine components present in the hardener component B), thereby forming a network structure and in this way accelerating the curing of the coating produced from the coating composition.

[0145] Furthermore, the base clearcoat material A) is preferably in the form of an aqueous dispersion.

[0146] In principle, it is known that pigments and fillers are used in coating compositions in the form of dispersions. This means that the preparation of the coating composition includes a step in which the pigment or filler is dispersed with a resin and a common solvent such as water in a grinder or dissolver under high shear forces. Here, the resin has a dispersing or emulsifying effect and only promotes the stabilization of the pigment or filler. In order to further assist dispersion, other additives can of course also be used. It is also possible that the preparation of the dispersion includes adding all the paint ingredients to be introduced into the base varnish A) so that the base varnish A) ultimately consists of a dispersion. Therefore, a dispersion is a mixture that at least (but not necessarily exclusively) contains the resin and the pigment and / or filler in a dispersed form.

[0147] The fact that the base clearcoat material A) preferably comprises a dispersion or consists of a dispersion therefore means that either the dispersion is prepared as described above and then, in the absence of further coating components, is completed to prepare the base clearcoat material A) (e.g. using standard stirring equipment), or, in the case of a dispersion, all the constituents of the base clearcoat material A) are introduced into the dispersion process, with the dispersion thus constituting the base clearcoat material A). Since the dispersion is preferably aqueous, water is preferably used in the actual dispersion process.

[0148] With regard to the preferred aqueous dispersion (A) comprising at least one epoxy resin (ER1), the aqueous dispersion (B), the compound (C), pigments and / or fillers and further additives and compounds which may be present in components A) and / or B) of the kit of parts according to the invention, reference is made to the description of said components of the coating composition according to the invention.

[0149] What was stated with regard to the coating composition according to the invention applies mutatis mutandis to further preferred embodiments of the kit according to the invention.

[0150] The method of the present invention:

[0151] The present invention further provides a method for preparing a coating on a substrate, wherein the coating composition of the present invention is applied to the substrate, formed into a coating film, and then cured. The cured coating may be sanded and coated with another coating. It should be understood that in the context of the present method using the coating composition, the above-mentioned specific and preferred embodiments of the coating composition also apply.

[0152] Step (i):

[0153] In step (i) of the inventive method, the aqueous coating composition of the present invention or the coating composition prepared by the kit of parts of the present invention is applied to a substrate. In the sense of the present invention, applying the composition to a substrate is not limited to applying it directly to a metal substrate. On the contrary, at least one other layer may be present between the metal substrate and the layer formed by the composition. This is the case, for example, when the coating composition is used as a surfacer in OEM finishing. This is because, in this case, at least one electrophoretic coating layer is present between the surfacer layer and the metal substrate. In other words, the substrate to which the inventive composition is applied is therefore a metal substrate coated with an electrophoretic coating layer.

[0154] The composition can be applied to the substrate by methods known in the art, for example by spraying, knife coating, painting, pouring, dipping, immersing, dripping or rolling. Preference is given to using the spraying method.

[0155] The substrates used are, for example, metal substrates, preferably substrates used in the automotive industry (vehicle construction). Advantageously, unalloyed and alloyed steels and / or iron, zinc and aluminum substrates and corresponding alloys are used. In addition, the coating composition can also be applied to plastic substrates and substrates with metal and plastic parts. In addition, the composition can also be applied to old paint, for example multilayer coatings with defects. Step (ii):

[0156] After the coating composition is applied to the substrate, a polymer film is formed therefrom. This film formation is preferably accomplished by drying and / or flash evaporation of the applied composition. In the context of the present invention, drying and flash evaporation refer to the evaporation of organic solvents and / or water, whereby the paint dries but does not yet cure, more particularly, does not yet form a fully crosslinked coating film.

[0157] Drying and / or flashing of the applied coating composition is preferably carried out at 15-25° C. for 1-60 minutes.

[0158] Step (iii):

[0159] In step (iii) of the method according to the invention, the coating film formed in step (ii) is cured by known methods. Curing refers to methods known to those skilled in the art, in other words, the conversion of the coating composition applied as a film to the substrate into a ready-to-use state, and thus, in other words, the conversion of the substrate provided with the coating into a state in which it can be put into its intended use. Regarding the problem also related to recoating and addressed in the context of the present invention, namely, obtaining good sandability, specifically sandability and subsequent overcoatability, are of course criteria for the intended use. Curing is influenced, in particular, by the chemical reaction of the reactive functional groups of the epoxy resin (ER1) and the compounds of the aqueous dispersion (B). Due to these crosslinking reactions and the parallel evaporation of any organic solvent and / or water present, a coating film is formed—that is, a cured coating (cured coating) is produced. Activation of the reaction can be carried out with the aid of thermal energy, although in the case of the present invention there is the aforementioned advantage that high temperatures are not required.

[0160] Curing is carried out at a temperature of, for example, 15-180° C., in particular 20-80° C., and most preferably 20-65° C. These preferred relatively low curing temperatures are due in particular to the fact that the coating composition is preferably formulated as a (2K) coating composition, in which case, in particular, only relatively low curing temperatures are required for thermal crosslinking. The duration of curing can vary significantly in the individual cases, for example, from 5 minutes to 16 hours, preferably 20-80 minutes. These preferred relatively short curing times are due in particular to the fact that the compositions of the invention require only relatively short curing times despite relatively low temperatures in order to still have sufficient hardness to allow the cured coating to be sanded. In this regard, very particularly preferred curing operations are carried out at 40-65° C. for 20-80 minutes.

[0161] Preferred layer thicknesses produced after curing in step (iii) are those customary in the automotive industry and range, for example, from 5 to 200 μm, preferably from 10 to 150 μm, more preferably from 30 to 80 μm.

[0162] Optional step (iv):

[0163] In the optional step (iv) of the method of the present invention, the cured coating obtained after step (iii) is sanded. This step is preferably carried out when another coating is applied on top of the cured coating formed in step (iii). Sanding can be carried out by methods well known in the art, for example by using suitable sandpaper and sanding equipment.

[0164] Optional step (v):

[0165] In optional step (v) of the method of the present invention, at least one further coating layer is applied and cured. This step may be performed after step (iii) or optional step (iv), preferably after optional step (IV). The at least one further coating layer is selected from a pigmented basecoat layer and / or a clearcoat layer.

[0166] The basecoat layer and / or the clearcoat layer can be obtained by applying commercially known waterborne or solventborne basecoat and / or topcoat compositions. In the case of applying further coating compositions, a multicoat paint system is formed.

[0167] As already mentioned above, the coating composition of the present invention can be used particularly advantageously as a primer-surfacer in the recoating sector, in particular in automotive recoating. Thus, in a particular embodiment of the present invention, the substrate is a fully painted metal substrate, in particular one painted with a multi-coat automotive paint system, wherein the corresponding multi-coat layer has local damage (defects). More particularly, these are automobile bodies or parts thereof with damage, such as stone chip damage, etc. Consequently, in the damaged areas, the original multi-coat layer has been at least partially stripped by external forces. The coating composition of the present invention is then used as a primer-surfacer to repair these damaged areas, i.e., to recoat. Generally speaking, in recoating operations, the damaged, initially coated substrate is cleaned and sanded before the primer is applied. This removes only any areas of insufficient adhesion and partial stripping of the initial coating layer and / or already formed corrosion products, as well as, in particular, locally exposed metal substrate. Thus, this is a complex substrate surface with a wide range of different interfaces. Here, one interface is the interface with the completely exposed metal substrate. Other interfaces and edges can be found in areas between the damaged, cleaned, and sanded areas, as well as in areas surrounding these areas with the intact initial paint system. At all these interfaces, one and the same coating composition must ensure adequate adhesion. The composition of the invention therefore offers great advantages, since excellent adhesion, corrosion resistance and sanding properties can be achieved even in this demanding area.

[0168] What was stated above with regard to the coating composition according to the invention and the kit according to the invention applies mutatis mutandis to further preferred embodiments of the method according to the invention.

[0169] The coated substrate of the present invention:

[0170] The result after step (iii) or optional step (v) of the process of the invention is a coated substrate.

[0171] What has been said above with respect to the coating composition according to the invention, the kit according to the invention and the process according to the invention applies mutatis mutandis to further preferred embodiments of the coated substrate according to the invention.

[0172] In particular, the present invention is described by the following embodiments:

[0173] Embodiment 1: A water-based coating composition comprising:

[0174] a) an aqueous dispersion (A) of at least one epoxy resin (ER1), said epoxy resin (ER) having on average at least one epoxy group per molecule,

[0175] b) at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5% and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, and

[0176] c) at least one aromatic compound (C) having at least one carboxylic acid group,

[0177] in:

[0178] The resin component (RC) comprises at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, wherein the at least one polyfunctional organic amine (A2) comprises a reaction product of:

[0179] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0180] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and

[0181] (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups and R is an organic radical comprising at least one polyoxyalkylene unit and containing no other X groups.

[0182] Embodiment 2: The aqueous coating composition according to Embodiment 1, wherein the epoxy resin (ER1) is selected from glycidyl ethers of diols or phenols, novolac resins, diglycidyl carboxylate or mixtures thereof, preferably glycidyl ethers of phenols, more preferably glycidyl ethers of bisphenol A.

[0183] Embodiment 3: The aqueous coating composition according to embodiment 1 or 2, wherein the epoxy resin (ER1) has an epoxy equivalent weight (EEW) of 100-400 g / eq, preferably 120-300 g / eq, more preferably 150-250 g / eq, and very preferably 185-210 g / eq, as determined according to ASTM D1652-11 (2019).

[0184] Embodiment 4: The aqueous coating composition according to any of the preceding embodiments, wherein the epoxy resin (ER1) has a viscosity at 25° C. of 1,000-20,000 mPa*s, preferably 1,500-15,000 mPa*s, very preferably 2,500-9,500 mPa*s, as measured according to ASTM D2196-18.

[0185] Embodiment 5: The aqueous coating composition according to embodiment 1 or 2, wherein the epoxy resin (ER1) has an epoxy equivalent weight (EEW) of 250-700 g / eq, preferably 300-600 g / eq, more preferably 350-550 g / eq, and very preferably 380-520 g / eq, as determined according to VLN 305.

[0186] Embodiment 6: The aqueous coating composition according to any one of embodiments 1, 2 or 5, wherein the epoxy resin (ER1) has a -1 The dynamic viscosity is 100-3,000 mPa*s, preferably 150-2,500 mPa*s, more preferably 200-2,000 mPa*s, very preferably 250-1,400 mPa*s, determined according to DIN EN ISO 3219:1994-10.

[0187] Embodiment 7: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one dispersion (A) of the epoxy resin (ER1) is present in a total amount of 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 15 to 30% by weight, very preferably 18 to 25% by weight, in each case based on the total weight of the aqueous coating composition.

[0188] Embodiment 8: The aqueous coating composition according to any of the preceding embodiments, wherein the epoxy resin (ER1) is present in a total amount of 1 to 30 wt %, preferably 5 to 25 wt %, more preferably 8 to 20 wt %, very preferably 10 to 15 wt %, in each case based on the total weight of the aqueous coating composition.

[0189] Embodiment 9: An aqueous coating composition according to any of the preceding embodiments, wherein the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) comprises at least 65 mol%, preferably at least 75 mol%, more preferably at least 90 mol%, and very preferably 100 mol% of amines consisting of amino groups and hydrocarbon groups.

[0190] Embodiment 10: An aqueous coating composition according to any of the preceding embodiments, wherein the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) is selected from difunctional monomeric primary and / or secondary amines, preferably difunctional monomeric primary amines, very preferably isophoronediamine and / or m-xylenediamine.

[0191] Embodiment 11: An aqueous coating composition according to any of the preceding embodiments, wherein in the aqueous dispersion (B), the proportion of the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), preferably isophoronediamine and / or meta-xylylenediamine, is 1-4.5% by weight, preferably 1.5-4% by weight, based on the total weight of the aqueous dispersion (B).

[0192] Embodiment 12: The aqueous coating composition according to any one of the preceding claims, wherein the resin component (RC) has an NH equivalent weight of 160-350 g / mol, preferably 170-250 g / mol.

[0193] Embodiment 13: The aqueous coating composition according to any one of the preceding embodiments, wherein the resin component (RC) further comprises at least one polyfunctional organic amine (A3) having primary and / or secondary amino groups, wherein the polyfunctional organic amine (A3) is a reaction product of:

[0194] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0195] and

[0196] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1).

[0197] Embodiment 14: The aqueous coating composition according to any one of the preceding embodiments, wherein the resin component (RC) consists of at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups and at least one polyfunctional organic amine (A3) having primary and / or secondary amino groups.

[0198] Embodiment 15: An aqueous coating composition according to any of the preceding embodiments, wherein the at least one di- and / or multifunctional epoxy resin (ER2) has an average epoxy equivalent weight of less than 350 g / mol, preferably less than 300 g / mol, more preferably less than 250 g / mol, even more preferably less than 200 g / mol, very more preferably 160-200 g / mol, as determined according to DIN EN ISO 3001:2019-08.

[0199] Embodiment 16: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one di- and / or multifunctional epoxy resin (ER2) has an average of 1 to 5 epoxy functional groups, preferably 1 to 4 epoxy functional groups, more preferably 1 to 3 epoxy functional groups, and very preferably 2 epoxy functional groups.

[0200] Embodiment 17: An aqueous coating composition according to any of the preceding embodiments, wherein the at least one di- and / or polyfunctional epoxy resin (ER2) is selected from glycidyl ethers of diols or phenols, novolac resins, diglycidyl esters of carboxylic acids or mixtures thereof, preferably glycidyl ethers of phenols, very preferably glycidyl ether of bisphenol A.

[0201] Embodiment 18: The aqueous coating composition according to any one of the preceding embodiments, wherein X in the at least one compound XR is selected from a primary or secondary amino group, a hydroxyl group, a carboxylic acid group, or a thiol group, preferably a primary amino group.

[0202] Embodiment 19: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one polyoxyalkylene unit in the organic group R in the at least one compound XR is selected from polyethylene units, polypropylene units and mixed polyethylene / polypropylene units.

[0203] Embodiment 20: The aqueous coating composition according to any of the preceding embodiments, wherein R in the at least one compound XR consists of polyoxyalkylene units.

[0204] Embodiment 21: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one compound XR is selected from polyoxyalkylene monoprimary amines.

[0205] Embodiment 22: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one compound XR has a weight average molecular weight Mw of 800 to 2,200 g / mol, as determined by GPC coupled light scattering.

[0206] Embodiment 23: The aqueous coating composition according to any one of the preceding embodiments, wherein the at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups is composed of the reaction product of components (i), (ii) and (iii).

[0207] Embodiment 24: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one dispersion (B) has a solids content of 25-45 wt %, based on the total weight of the dispersion, and measured according to DIN EN ISO 3251:2018-07.

[0208] Embodiment 25: The aqueous coating composition according to any of the preceding embodiments, wherein the resin component (RC) is present in a total amount of 10-30% by weight, preferably 15-25% by weight, based in each case on the solids content of the aqueous coating composition.

[0209] Embodiment 26: The aqueous coating composition of any preceding Embodiment, wherein the at least one aromatic compound (C) further comprises at least one hydroxyl group.

[0210] Embodiment 27: An aqueous coating composition according to any of the preceding embodiments, wherein the at least one aromatic compound (C) is selected from resorcinol, salicylic acid, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, 2-hydroxy-3-naphthoic acid, 2-hydroxy-6-naphthoic acid, cresol acid and mixtures thereof, preferably salicylic acid.

[0211] Embodiment 28: The aqueous coating composition according to any of the preceding embodiments, wherein the at least one aromatic compound (C) is present in a total amount of 0.1-5 wt. %, preferably 0.2-3 wt. %, more preferably 0.3-1 wt. %, very preferably 0.4-0.7 wt. %, in each case based on the total weight of the aqueous coating composition.

[0212] Embodiment 29: The aqueous coating composition according to any one of the preceding embodiments, wherein the molar ratio of the NH groups of the resin compound (RC) to the epoxy groups of the epoxy resin (ER1) is 0.74:1 to 0.95:1, preferably 0.9:1.

[0213] Embodiment 30: The aqueous coating composition of any one of the preceding embodiments, wherein the coating composition further comprises at least one pigment and / or filler.

[0214] Embodiment 31: An aqueous coating composition according to Embodiment 30, wherein the at least one pigment is selected from (i) black pigments such as carbon black, iron oxide pigments, manganese black and spinel black, preferably carbon black and iron oxide pigments; (ii) white pigments such as titanium dioxide, zinc oxide, zinc sulfide and antimony trioxide, preferably titanium dioxide; and (iii) mixtures thereof.

[0215] Embodiment 32: An aqueous coating composition according to embodiment 30 or 31, wherein the at least one filler is selected from (i) carbonates, such as calcium carbonate or barium carbonate; (ii) sulfates, such as calcium sulfate and barium sulfate, (iii) silicates and layered silicates, such as talc, pyrophyllite, mica, kaolin, precipitated calcium silicate, aluminum silicate, calcium / aluminum silicate, sodium / aluminum silicate, and mullite; (iv) silica, such as quartz, cristobalite, precipitated silica, and fumed silica; (v) metal oxides and hydroxides, such as aluminum hydroxide and magnesium hydroxide; and (vi) mixtures thereof.

[0216] Embodiment 33: The aqueous coating composition according to any of Embodiments 30 to 32, wherein the at least one pigment, preferably the at least one white and / or black pigment, is present in a total amount of 15 to 20% by weight, preferably 20% by weight, based in each case on the solids content of the aqueous coating composition.

[0217] Embodiment 34: The aqueous coating composition according to any of Embodiments 30-33, wherein the at least one filler is present in a total amount of 30-50% by weight, preferably 30-40% by weight, based in each case on the solids content of the aqueous coating composition.

[0218] Embodiment 35: The aqueous coating composition of any preceding embodiment, wherein the coating composition further comprises at least one additive.

[0219] Embodiment 36: The aqueous coating composition of embodiment 35, wherein the at least one additive is selected from the group consisting of light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, tackifiers, leveling agents, film-forming aids, thickeners, sag control agents (SCAs), corrosion inhibitors, and mixtures thereof.

[0220] Embodiment 37: The aqueous coating composition of any one of the preceding embodiments, wherein the coating composition has a solids content of 70-85 wt %, based on the total weight of the aqueous coating composition, and measured according to DIN EN ISO 3251:2018-07.

[0221] Embodiment 38: The aqueous coating composition of any one of the preceding embodiments, wherein the coating composition is a surfacer or primer-surfacer.

[0222] Embodiment 39: A kit comprising two separate components A) and B):

[0223] A) at least one aqueous base varnish comprising an aqueous dispersion (A) of at least one epoxy resin (ER1), said epoxy resin (ER) having on average at least one epoxy group per molecule; and

[0224] B) at least one aqueous hardener component comprising:

[0225] at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5%, and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, said resin component (RC) comprising at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, said at least one polyfunctional organic amine (A2) comprising the reaction product of:

[0226] (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol,

[0227] (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and

[0228] (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups and R is an organic radical comprising at least one polyoxyalkylene unit and containing no other X groups; and

[0229] - at least one aromatic compound (C) having at least one carboxylic acid group.

[0230] Embodiment 40: A method of preparing at least one coating on a substrate, the method comprising the steps of:

[0231] i) applying the aqueous coating composition according to any one of embodiments 1 to 38 or the coating composition prepared from the kit according to embodiment 39 to a substrate;

[0232] ii) forming a coating film from the coating composition applied in step (i);

[0233] iii) curing the coating film formed in step (ii);

[0234] iv) optionally sanding the cured coating obtained in step (iii); and

[0235] v) optionally applying at least one further coating layer and curing said coating layer.

[0236] Embodiment 41: A method according to embodiment 40, wherein the substrate is selected from (i) metal substrates, such as unalloyed steel and alloy steel and / or iron, zinc and aluminum substrates and corresponding alloys; (ii) plastic substrates; (iii) substrates comprising metal and plastic parts; and (iv) metal substrates painted with multiple layers of coating and preferably having defects.

[0237] Embodiment 42: The method according to embodiment 40 or 41, wherein the film formation in step (ii) is performed by drying and / or flashing the applied coating composition at 15-25°C for 1-60 minutes.

[0238] Embodiment 43: The method according to any one of embodiments 40-42, wherein the curing in step (iii) is carried out at a temperature of 15-180°C, preferably 20-80°C, more preferably 20-65°C, and for a duration of 20 minutes to 16 hours, preferably 20-80 minutes.

[0239] Embodiment 44: The method according to any one of embodiments 40 to 43, wherein the dry film thickness of the cured coating obtained after step (iii) is 5 to 200 μm, preferably 10 to 150 μm, and very preferably 30 to 80 μm.

[0240] Embodiment 45: The method of any one of Embodiments 40-44, wherein the at least one additional coating layer applied and cured in step (v) is selected from a pigmented basecoat layer and / or a clearcoat layer.

[0241] Embodiment 46: The method according to any one of Embodiments 40-45, wherein the method is used to repair a multi-layer paint system having at least one defect site.

[0242] Embodiment 47: A coated substrate prepared by the method according to any one of Embodiments 40-46. Example

[0243] The present invention will now be explained in more detail using working examples, but the present invention is by no means limited to these working examples. In addition, unless otherwise indicated, the terms "parts", "%" and "ratio" in the examples represent "parts by mass", "mass %" and "mass ratio" respectively.

[0244] 1. Determination method:

[0245] 1.1 Solid content (solids, non-volatile matter)

[0246] Unless otherwise stated, the solids content (also referred to as solids fraction, solids content, non-volatile fraction) is determined in accordance with DIN EN ISO 3251:2018-07 at 130° C.; 60 minutes, starting weight 1.0 g.

[0247] 1.2 Proportion of Monomeric Amine (A1) in Aqueous Dispersion (B)

[0248] The proportion of the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in the aqueous dispersion (B) is determined by gas chromatography in accordance with DIN 51405:2004-01 and is as follows:

[0249] Weigh approximately 100-500 mg of the corresponding aqueous dispersion (B) (depending on the amine content) to an accuracy of 0.1 mg into a 5 ml snap-top vial on an analytical balance. Weigh approximately 5% ISTD diglyme to an accuracy of 0.1 mg into the sample. Dilute the sample with 5 ml of THF (if the sample is not soluble in THF, a suitable solvent must be found experimentally).

[0250] The samples prepared in this manner were analyzed on an Agilent 7890 gas chromatograph. Injection was performed using an autosampler. The samples were injected directly into the split injector of the gas chromatograph equipped with a flame ionization detector and separated on a column with a polar phase (polyethylene glycol; a 50 μm fused silica capillary column with a polyethylene glycol phase) and a non-polar phase (polydimethylsiloxane; a 50 μm fused silica capillary column with a polydimethylsiloxane phase). Evaluation was performed using the ISTD% method.

[0251] Gas chromatography conditions:

[0252] Oven program: 40°C (holding time 5 minutes) (3°C / minute) → 100°C (10°C / minute) → 230°C (holding time 5 minutes),

[0253] Carrier gas: hydrogen,

[0254] Separation column: Agilent Innowax: length 50m, membrane thickness 0.2μm, diameter 0.2mm, pressure 1.0 bar HP-1, length 50m, membrane thickness 0.33μm, diameter 0.2mm, pressure 1.3 bar,

[0255] Injector temperature: 250°C (lower if necessary),

[0256] Injection volume: 0.3 μL (manual injection 0.3-0.6 μL),

[0257] Detector: flame ionization detector,

[0258] Detector temperature: 275°C,

[0259] Split flow: 15mL / min

[0260] Amines (A1) are identified by their retention times on polar and nonpolar columns. For unknown components, GC / MS analysis is necessary.

[0261] An internal standard containing the detected amines was weighed to an accuracy of 0.1 mg, based on the approximate proportion in the sample on an analytical balance. The amine concentration in the entire calibration solution corresponded to the amine concentration in the prepared sample (the amine concentration was calculated using the GC analyzer program). The calibration solution was then analyzed under the same conditions as the sample, and the correction factor for each substance was determined.

[0262] The amine content in the sample was calculated by the ISTD% method with the aid of the GC analyzer program.

[0263] 1.3 Epoxy equivalent

[0264] The epoxy equivalent weight of the epoxy resin (ER1) was determined according to ASTM D1652-11 (2019), and the epoxy equivalent weight of the epoxy resin (ER2) was determined according to DIN EN ISO 3001: 2019-08.

[0265] 1.4 Ratio of resin component (RC) in aqueous dispersion (B)

[0266] The determination is carried out as described in point 1.1, except that the corresponding aqueous dispersion (B) is kept at 130° C. for 8 hours (instead of 60 minutes). This ensures that the amount of remaining non-volatile monomeric amine (A1) is negligibly small and the weight obtained corresponds to the proportion of the resin component (RC) present in the aqueous dispersion (B).

[0267] 1.5 NH equivalent

[0268] The NH equivalent weight of the resin component (RC) was determined according to the following two-step method:

[0269] Step 1:

[0270] First, the NH equivalent weight of the resin mixture (I) present in the aqueous dispersion was determined. To this end, the different mass ratios of primary and secondary amino groups (each as % nitrogen) in the aqueous dispersion were determined using the method for aliphatic amines according to DIN EN ISO 9702 (October 1998). The mass ratios obtained were then used to determine the molar amount of NH groups in 100 g of the aqueous dispersion using the following equation:

[0271] n(NH)=(m(N from primary amino groups) / (14 g / mol))*2+m(N from secondary amino groups) / 14 g / mol

[0272] In this equation, "m" represents the measured mass ratio of primary and secondary amino groups.

[0273] Using the molar amount of NH groups and the mass of the sample (100 g), the NH equivalent weight of the sample (aqueous dispersion (B)) can be obtained, that is, the mass of the sample containing 1 mol of NH functional groups.

[0274] By determining the proportion of the resin mixture (I) in the sample, the NH equivalent weight of the resin mixture (I) can then be calculated using the following equation:

[0275] NH equivalent (resin mixture (I) = NH equivalent (sample) * ratio (resin mixture (I) in sample)

[0276] Step 2:

[0277] The NH equivalent weight of the resin component (RC) is then calculated from the previously determined NH equivalent weight of the resin mixture (I), the mass of the resin mixture used in step (B), the mass of component (IIb) used in step (B), and the molar amount of epoxy groups used in component (IIb) (determined by the mass of component (IIb) used and the epoxy equivalent weight). This assumes that the epoxy groups of component (IIb) react quantitatively with the NH functional groups of the resin mixture (I). The total mass of the resin component (RC) is obtained by adding the mass of the resin mixture (I) used and the mass of component (IIb) used.

[0278] 1.6 Determination of abrasiveness

[0279] The coated substrate prepared as described in point 3.1 below was stored at 20° C. for 20 minutes, and then 09560 black control powder (from 3M) was applied to the coated surface and dry sanded using an Excenter (FESTOOL LEX3), a 5 mm eccentric stroke and standard P400 sandpaper from RODIM until the black control powder was completely removed.

[0280] Determine abrasiveness by sandpaper evaluation as follows:

[0281] 0→No slagging (very good sanding performance)

[0282] 1→Minimal slagging (abrasiveness is still acceptable)

[0283] 2→Slagging, forming small "nodules" (poor sanding properties)

[0284] 3 → Severe slagging, forming "nodules" (spacers) (very poor sanding properties)

[0285] By using a black contrast powder, scumming of the paint on the sandpaper can be very easily identified. No scumming means that the sanded-off material is obtained as a fine dust and therefore does not scum the sandpaper and produce a difficult-to-remove residue on the coating surface.

[0286] 1.7 Determination of blistering after constant climate testing

[0287] The panels prepared as described in point 3.2 were stored in a conditioning chamber under CH test conditions according to DIN EN ISO 6270-2:2005-09 for a period of 10 days. Within 1 hour after removal from the conditioning chamber, the panels were then inspected for blistering according to DIN EN ISO 4628-2:2016-07.

[0288] The occurrence of foaming was evaluated by a combination of two values ​​as follows:

[0289] The amount of foaming was assessed by means of a quantitative number from 1 to 5, m1 indicating very little foaming and m5 indicating very much foaming.

[0290] The size of the bubbles is rated by a size number from 1 to 5, with g1 indicating very small bubbles and g5 indicating very large bubbles.

[0291] Thus, the designation m0g0 designates a paint system which exhibits no blistering after storage with condensed water, whereas the designation m1g1 designates a paint system which exhibits very few, small blistering events.

[0292] 1.8 Determination of adhesion by cross-hatch method after constant climate test

[0293] The panels prepared as described in point 3.2 were stored in a conditioning chamber under CH test conditions according to DIN EN ISO 6270-2:2005-09 for a period of 10 days. Within 1 hour after removal from the conditioning chamber, the crosshatch adhesion was determined according to DIN EN ISO 2409:2013-06 (rating GT 0 to GT 5; GT 0 = best score; GT 5 = worst score).

[0294] 1.9 Determination of stone impact resistance

[0295] Stone chip resistance was determined according to ISO 20567-1 (Determination of stone chip resistance of coatings — Part 1: Multiple impact test (ISO 20567-1:2017)) at 2 bar pressure and 2 x 500 g grit.

[0296] 1.10 Determination of dry film thickness

[0297] The dry film thickness was determined in accordance with DIN EN ISO 2808, May 2007, using a Dualscope MP40 from Fischer, probe ED10.

[0298] 2. Preparation of Aqueous Dispersion (B)

[0299] 2.1 Aqueous dispersion (B1) Preparation

[0300] The aqueous dispersion (B1) was prepared according to the following procedure:

[0301] 683.00 g of Beckopox VEH 2849W (an aqueous dispersion of resin mixture (I), wherein the resin mixture comprises 27.5% by weight of monomeric amines (isophoronediamine and xylenediamine) and 72.5% by weight of polyamines, and additionally has an NH equivalent weight of 108 g / mol) and 1663.77 g of demineralized water were combined in a reaction vessel, stirred continuously, and maintained at 95° C. for 1 hour. The mixture was subsequently cooled to 70° C., and a mixture of 163.44 g of a bisphenol A diglycidyl ether epoxy resin having an average epoxy equivalent weight of 186.5 g / mol, 39.46 g of a polyalkylene polyether epoxide based on polypropylene oxide and having an average epoxy resin equivalent weight of 395 g / mol, 81.96 g of ethoxypropanol, 81.47 g of methyl ethyl ketone, and 81.72 g of isobutanol was metered in continuously over 4 hours while stirring. The mixture was then maintained at 70° C. for a further 1 hour. The reaction product thus obtained was cooled to 45° C. At 25° C., the viscosity of the product was 150-250 mPa*s.

[0302] In a subsequent process step, the solvents isobutanol and methyl ethyl ketone were removed from the product by distillation under reduced pressure. The resulting aqueous dispersion (B1) had a residual content of isobutanol and methyl ethyl ketone of <0.5% (gas chromatography).

[0303] The content of monomeric amine (A1) in the aqueous dispersion was 2.4%, and the content of resin component (RC) was 31% by weight. The resin component additionally had an amine equivalent weight (NH equivalent) of 171 g / mol.

[0304] 2.2 Preparation of aqueous dispersion (B2)

[0305] 876.19 g of Beckopox VEH 2849W (an aqueous dispersion (I) of a resin mixture comprising 27.5 wt.% of monomeric amines (A1) (isophorone diamine and xylenediamine) and 72.5 wt.% of a polyfunctional organic amine (A2) having an NH equivalent weight of 108 g / mol) and 2132.20 g of (demineralized) water were combined in a reaction kettle, stirred continuously, and maintained at 95°C for 1 hour. Subsequently, a mixture of 233.41 g of a bisphenol A diglycidyl ether-based epoxy resin having an average epoxy equivalent weight of 186.5 g / mol, 117.30 g of ethoxypropanol, 117.30 g of methyl ethyl ketone, 117.30 g of isobutyl alcohol, and 58.21 g of salicylic acid was added continuously over 4 hours while stirring. The resulting dispersion was then cooled to 30°C while stirring.

[0306] In a subsequent process step, the process solvents ethoxypropanol, methyl ethyl ketone and isobutanol are removed from the dispersion by distillation under reduced pressure.

[0307] The aqueous dispersion contained 3% by weight of monomeric amine (A1) (1.5% by weight of m-xylylenediamine and 1.5% by weight of isophoronediamine), and 32% by weight of the resin component (RC) having an amine equivalent weight (NH equivalent) of 171 g / mol.

[0308] 3. Preparation of water-based coating composition

[0309] With respect to the formulation ingredients and their amounts, the following should be remembered: Any reference to a commercially available product refers precisely to that commercially available product, regardless of the particular primary name chosen for that ingredient.

[0310] The aqueous coating compositions (I1) and (I2) of the present invention and the comparative aqueous coating compositions (C1) and (C2) were prepared by mixing a base varnish (A) with a curing component (B), adding additional water and mixing thoroughly. The resulting coating compositions were applied to a substrate and cured within 1 hour of their preparation. The ingredients of the base varnish (A) and the curing component (B) are listed in Table 1 below.

[0311] Table 1: Ingredients used to prepare aqueous coating compositions I1, I2, C1 and C2 (amounts in wt%)

[0312]

[0313]

[0314] *The present invention

[0315] 1) Liquid bisphenol A-based epoxy resin aqueous emulsion, EEW=193-204g / eq (German Blue Cube),

[0316] 2) Polymeric nonionic dispersing additive, 50% solids (Allnex Belgium SA),

[0317] 3) Silicone-free polymer-based defoamer (Byk Chemie GmbH),

[0318] 4) Hydrated magnesium silicate, D 50 =1.8μm (Elementis),

[0319] 5) Rutile TiO2, inorganic zirconium and alumina coating, organic treatment (Huntsman),

[0320] 6) Powdered iron oxide black pigment (Lanxess AG),

[0321] 7) Precipitated barium sulfate, average particle size 1.7 μm (Solvay),

[0322] 8) Organically modified basic zinc orthophosphate hydrate (Heubach GmbH),

[0323] 9) Zinc 5-nitroisophthalate (Heubach GmbH),

[0324] 10) Polyether-modified polydimethylsiloxane (BYK Chemie GmbH),

[0325] 11) Contains 1.6% by weight of salicylic acid,

[0326] 12) Amine resin comprising an amine having at least one primary and / or at least one secondary amino group, an adduct of a polyalkylene ether polyol and an epoxide resin, and a reaction product of salicylic acid; NH equivalent weight: 138 g / mol, amount of salicylic acid based on solids content: 10-15 wt. % (Allnex Belgium SA),

[0327] 13) (Tris-2,4,6-dimethylaminomethylphenol) (Evonik Industries AG),

[0328] 14) The amount of curing catalyst salicylic acid or Ancamine K54.

[0329] 3. Preparation of coated substrates from coating compositions I1, I2, C1 and C2

[0330] 3.1 Preparation of Coated Substrates C-I1, C-I2, C-C1, and C-C2 for Sanding

[0331] The sandability was tested on the obtained coated substrates according to the following procedure:

[0332] Cold rolled steel sheets (60 cm x 50 cm) were used as substrates. These were pre-treated / cleaned as follows: cleaned with 360-4 Glasurit Metal Cleaner, sanded with P80 (gold) from Mirka, and cleaned again with 360-4 Glasurit to remove sanded dust. The air was vented for 15 minutes.

[0333] The corresponding coating compositions I1, I2, C1 and C2 were each stirred and applied to the substrate using a standard spray gun (e.g., SATA 100B F1.6 mm RP at 2.0 bar) in a thin continuous spraying operation, flashed off for 5 minutes, applied in a further full spraying operation, flashed off for 5 minutes, and then cured for 35 minutes at a temperature of 60° C. The dry film thickness in each case was 60-80 μm.

[0334] The resulting panels were stored at 23° C. for 20 minutes (cured at 60° C.) or 16 hours (cured at 23° C.) before the sanding properties were determined as described in point 1.6.

[0335] 3.2 Preparation of coated substrates C-I1, C-I2, C-C1, and C-C2 for stone chip resistance and humidity testing

[0336] First, clean the substrate according to its material type, i.e., use Glasurit Sheet Metal Cleaner 360-4 for metal substrates, Glasurit Universal Cleaner for Plastics 541-30 for plastic parts, and Glasurit KH Remover for Silicone and Tar 541-5 for old painted parts or new factory-primed parts.

[0337] The substrates were then sanded according to their material type: steel with P80, galvanized steel with a sanding pad, aluminum with P150, and plastics and old painted or factory-primed parts with a sanding pad. The sanded dust was then removed using the aforementioned cleaners. After dry rubbing, the corresponding water-based primer-surfacer composition I1, I2, C1, or C2 was applied. To this end, two full coats were applied using a flow-cup spray gun (SATA BF 100RP 1.6, 2.0 bar) without an intermediate flash-off time, resulting in dry film thicknesses of 60 and 80 μm. After the second coat, the resulting primer-surfacer layer was cured at 60°C for 40 minutes.

[0338] After the coated substrate has cooled, the primer-surfacer layer is sanded. To this end, a black control (09560 Black Fa.3M) is applied to the coated surface and sanded using an eccentric sander (LEX3 from Festool) with a 5 mm stroke and P400 sandpaper (standard type from RODIM). The sanded surface is subsequently cleaned with Glasurit Cleaner 700-1, and the basecoat layer is then applied. To this end, a commercially available water-based basecoat composition (Glasurit 90-1250 Deep Black, from BASF Coatings GmbH) is applied using a spray gun (SATA5000 HVLP 1.3, 2.0 bar) in two topcoats and one effect coat, with a flash-off time of approximately 5 minutes, to a dry film thickness of 10-15 μm.

[0339] Subsequently, a commercial solvent-based clearcoat composition (Glasurit HS clearcoat High Gloss VOC 923-630, available from BASF Coatings GmbH) was applied in two coats using a spray gun (SATA 5000RP 1.3, 2.0 bar) with a flash time of 3 minutes and a dry film thickness of 50-60 μm. The applied basecoat and clearcoat were finally cured at 60° C. for 30 minutes.

[0340] The prepared panels were aged at 23°C for at least 10 days before being subjected to humidity testing and stone chip resistance testing.

[0341] 4. Results

[0342] Table 2 lists the sanding, blistering, crosshatch adhesion, and stone chip resistance results for the coated panels prepared as described above:

[0343] Table 2: Results of sanding, foaming, crosshatch adhesion and stone chip resistance (In the upper half of this table, only the differences in ingredients between the present invention and the comparative example are listed)

[0344]

[0345] 5. Discussion of Results

[0346] Coated panels prepared using the coating compositions (I1) and (I2) of the present invention exhibit excellent sanding properties and high stone chip resistance without negatively affecting the excellent blister stability and crosshatch adhesion of the multi-layer coatings prepared using the coating compositions of the present invention as a primer-surfacer mix. The excellent properties achieved are attributed to the combination of the aqueous dispersion (B) containing the specific resin component (RC) and salicylic acid as a curing catalyst. Surprisingly, comparable results are achieved if salicylic acid is not added as a separate compound during the preparation of the coating composition (coating composition I1), but is incorporated via the aqueous dispersion (B2) (coating composition I2). Since salicylic acid is known to catalyze reactions between epoxy groups and amino groups, the use of salicylic acid during the preparation of aqueous dispersion (B) allows for the efficient preparation of aqueous dispersion (A) without the use of other catalysts without negatively affecting the catalytic activity during the curing of the coating composition.

[0347] In contrast, the use of the known curing catalyst Ancamine K54 in combination with the aqueous dispersion (B) as a crosslinker (comparative coating composition C1) resulted in coated panels having significantly reduced blister stability and crosshatch adhesion under humid conditions compared to panels coated with the coating compositions (I1) or (I2) of the invention comprising salicylic acid as a curing catalyst.

[0348] The combined use of an aqueous dispersion of a curing agent without the specific resin component (RC) (Comparative coating composition C2) with salicylic acid as a curing catalyst also resulted in a significant decrease in blister stability, crosshatch adhesion, and stonechip resistance.

[0349] Therefore, only when the primer-surfacer comprises a combination of an aqueous dispersion (B) containing a specific resin component (RC) and salicylic acid as a curing catalyst can excellent sanding resistance and high stone chip resistance be achieved without negatively affecting the high blister stability and cross-hatch adhesion of the multi-layer coating.

Claims

1. A water-based coating composition comprising: a) an aqueous dispersion (A) of at least one epoxy resin (ER1) having on average at least one epoxy group per molecule, b) at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5% and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, and c) at least one aromatic compound (C) having at least one carboxylic acid group, in: The resin component (RC) comprises at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, wherein the at least one polyfunctional organic amine (A2) comprises a reaction product of: (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol, (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups and R is an organic radical comprising at least one polyoxyalkylene unit and containing no other X groups.

2. The aqueous coating composition according to claim 1, wherein the epoxy resin (ER1) is present in a total amount of 1 to 30% by weight, based in each case on the total weight of the aqueous coating component.

3. The aqueous coating composition according to claim 1, wherein the epoxy resin (ER1) is present in a total amount of 5 to 25% by weight, based in each case on the total weight of the aqueous coating component.

4. The aqueous coating composition according to claim 1, wherein the epoxy resin (ER1) is present in a total amount of 8 to 20% by weight, based in each case on the total weight of the aqueous coating component.

5. The aqueous coating composition according to claim 1, wherein the epoxy resin (ER1) is present in a total amount of 10 to 15% by weight, based in each case on the total weight of the aqueous coating component.

6. The aqueous coating composition according to any one of claims 1 to 5, wherein the at least one difunctional and / or polyfunctional monomeric primary and / or secondary amine (A1) comprises at least 65 mol% of amines consisting of amino groups and hydrocarbon groups.

7. The aqueous coating composition according to claim 6, wherein the at least one difunctional and / or polyfunctional monomeric primary and / or secondary amine (A1) comprises at least 75 mol% of amines consisting of amino groups and hydrocarbon groups.

8. The aqueous coating composition according to claim 6, wherein the at least one difunctional and / or polyfunctional monomeric primary and / or secondary amine (A1) comprises at least 90 mol% of amines consisting of amino groups and hydrocarbon groups.

9. The aqueous coating composition according to claim 6, wherein the at least one difunctional and / or polyfunctional monomeric primary and / or secondary amine (A1) comprises 100 mol% of an amine consisting of an amino group and a hydrocarbon group.

10. The aqueous coating composition according to any one of claims 1 to 5, wherein the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) is selected from difunctional monomeric primary and / or secondary amines.

11. The aqueous coating composition according to claim 10, wherein the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) is selected from isophoronediamine and / or m-xylylenediamine.

12. The aqueous coating composition according to any one of claims 1 to 5, wherein the proportion of the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in the aqueous dispersion is 1 to 4.5% by weight, based on the total weight of the aqueous dispersion (B).

13. The aqueous coating composition according to claim 12, wherein the proportion of the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in the aqueous dispersion is 1.5 to 4% by weight, based on the total weight of the aqueous dispersion (B).

14. The aqueous coating composition according to any one of claims 1 to 5, wherein the resin component (RC) has an NH equivalent weight of 160 to 350 g / mol.

15. The aqueous coating composition according to claim 14, wherein the resin component (RC) has an NH equivalent weight of 170 to 250 g / mol.

16. The aqueous coating composition according to any one of claims 1 to 5, wherein the at least one di- and / or polyfunctional epoxy resin (ER2) is selected from glycidyl ethers of diols or phenols, novolac resins, diglycidyl esters of carboxylic acids or mixtures thereof.

17. The aqueous coating composition according to claim 16, wherein the at least one di- and / or polyfunctional epoxy resin (ER2) is selected from glycidyl ethers of bisphenol A.

18. The aqueous coating composition according to any one of claims 1 to 5, wherein the at least one compound XR is selected from polyoxyalkylene monoprimary amines.

19. The aqueous coating composition according to any one of claims 1 to 5, wherein the resin component (RC) is present in a total amount of 10 to 30% by weight, based in each case on the solids content of the aqueous coating composition.

20. The aqueous coating composition according to claim 19, wherein the resin component (RC) is present in a total amount of 15 to 25% by weight, based in each case on the solids content of the aqueous coating composition.

21. The aqueous coating composition according to any one of claims 1 to 5, wherein the at least one aromatic compound (C) is selected from salicylic acid, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2-hydroxy-3-naphthoic acid, 3,4,5-trihydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, cresol acid, and mixtures thereof.

22. The aqueous coating composition according to claim 21, wherein the at least one aromatic compound (C) is selected from salicylic acid.

23. The aqueous coating composition according to any one of claims 1 to 5, wherein the at least one aromatic compound (C) is present in a total amount of 0.1 to 5% by weight, based in each case on the total weight of the aqueous coating composition.

24. The aqueous coating composition according to claim 23, wherein the at least one aromatic compound (C) is present in a total amount of 0.4 to 0.7% by weight, based in each case on the total weight of the aqueous coating composition.

25. The aqueous coating composition of any one of claims 1-5, wherein the coating composition is a surfacer or a primer-surfacer.

26. A kit comprising two separate components A) and B): A) at least one aqueous base varnish comprising an aqueous dispersion (A) of at least one epoxy resin (ER1), said epoxy resin (ER) having on average at least one epoxy group per molecule; and B) at least one aqueous hardener component comprising: at least one aqueous resin dispersion (B) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1) in a proportion by weight of 0.5 to 5%, and a resin component (RC) having an NH equivalent weight of 150 to 400 g / mol, said resin component (RC) comprising at least one polyfunctional organic amine (A2) having primary and / or secondary amino groups, said at least one polyfunctional organic amine (A2) comprising the reaction product of: (i) at least one di- and / or polyfunctional epoxy resin (ER2) having an average epoxy equivalent weight of less than 400 g / mol, (ii) at least one di- and / or polyfunctional monomeric primary and / or secondary amine (A1), and (iii) at least one compound XR, wherein X is a functional group reactive toward epoxy groups and R is an organic radical comprising at least one polyoxyalkylene unit and containing no other X groups; and - at least one aromatic compound (C) having at least one carboxylic acid group.

27. A method for preparing at least one coating on a substrate, said method comprising the steps of: i) applying the aqueous coating composition according to any one of claims 1 to 25 or the coating composition prepared from the kit according to claim 26 to a substrate; ii) forming a coating film from the coating composition applied in step (i); iii) curing the coating film formed in step (ii); iv) optionally sanding the cured coating obtained in step (iii); and v) optionally applying at least one further coating layer and curing said coating layer.

28. A coated substrate prepared by the method of claim 27.

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