Aqueous compositions comprising (METH)acrylic polymer suitable for permanent coating applications

Abstract

The present invention relates to an aqueous coating composition comprising at least one of Zr, Ti and Hf cations a1), at least one complexing agent a2) suitable for complexing a1), at least one polymer P as a3), which is obtainable from a polymerization of at least one (meth)acrylic monomer in the presence of at least one block copolymer BC, and said BC as a4), wherein BC contains at least two blocks B1 and B2, B1 comprising structural units SU1, wherein at least a part of SU1 contains at least one phosphorous containing moiety, and B2 comprising structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, a concentrate for producing the aqueous coating composition by dilution with water, a method for coating an optionally pre-coated metallic substrate, which makes use of said aqueous coating composition, to a coated substrate obtainable by said method, and to several uses related to the aqueous coating composition and / or at least one of its ingredients.

Description

[0001] Aqueous compositions comprising (meth)acrylic polymer suitable for permanent coating applications

[0002] The present invention relates to an aqueous coating composition, a concentrate for producing the aqueous coating composition by dilution with water, a method for coating an optionally pre-coated metallic substrate, which makes use of said aqueous coating composition, to a coated substrate obtainable by said method, and to several uses related to the aqueous coating composition and / or at least one of its ingredients.

[0003] Background of the invention

[0004] Metal substrates made, e.g., from aluminum, an aluminum alloy, steel, and / or a steel alloy, are nowadays typically generally subjected to an anti-corrosive and / or adhesion-promoting chemical pretreatment method for all sorts of different applications. Examples of such a chemical pretreatment is a pretreatment method, in which a coating is formed directly onto a surface of the metal (direct-to-metal applications), e.g., via the organic dip coating technology or the permanent coating (PC) technology.

[0005] By the organic dip coating technology coating films of around 20 to 25 pm dry film thicknesses are formed on the surface of the metal substrate used. Coating compositions suitable to be used in this kind of technology are known in the prior art. Often, (meth)acrylic polymers, in particular (meth)acrylic copolymers, are used as polymeric binder constituents in such coating compositions. For example, WO 2021 / 008860 A1 discloses an aqueous autophoretically depositable composition comprising inter alia fluoride ions, and at least one organic binder component dispersed in the aqueous phase, wherein said binder component comprises a co-polymerizate obtainable from a water-dispersible, polymerizable (meth)acry lie acid compound and at least one acrylated mono- or diphosphate ester compound. In particular for ecological reasons the use of fluoride ions is, however, undesired. The use of autophoretic deposition processes is, however, often disadvantageous in terms of an only insufficient corrosion protection, when autophoretically depositable compositions such as the ones disclosed in WO 2021 / 008860 A1 are applied onto metal surfaces.

[0006] By the permanent coating (PC) technology metallic surfaces such as galvanized surfaces of substrates are treated with suitable coating formulations in order to provide a thin permanent coating (PC) layer for corrosion protection, anti-fingerprint properties, water resistance and / or other properties such as paint adhesion on the surfaces of the substrates. Such permanent coating layers are usually transparent layers applied in a dry film thickness of about 0.1 to <2.0 pm. In particular on steel surfaces such as surfaces made of galvanized steel, the coating formulation applied is typically acidic and contains, besides water, a polymer dispersion for film-forming abilities and inorganic constituents such as in particular metal-fluoride complexes. A polymer dispersion alone is usually not sufficient to ensure a sufficient corrosion protection in each case. Therefore, aforementioned inorganic constituents are usually further added to fulfill in particular the industry's requirement of corrosion protection as these may react with the metallic surface to form a protective permanent (conversion) coating layer on the surface. The combination of the aforementioned inorganic constituents with the polymer dispersion usually yields a uniform thin film covering the metallic surface homogeneously. For example, WO 2012 / 032102 A1 relates to a method for coating metallic surfaces with an aqueous composition in order to provide a PC layer, wherein the composition inter alia contains at least one phosphate such as zinc phosphate, at least one titanium and / or zirconium compound such as at least one complex fluoride thereof, at least one complexing agent, and cations of aluminum, chromium (III), and / or zinc.

[0007] Typically, coating formulations, which are fluoride containing, are used in PC technology applications, such as disclosed in WO 2012 / 032102 A1 , in particular in order to provide sufficient corrosion resistance. The source of fluoride is often derived from a complex fluoride such as FhTiFe and / or FkZrFe. However, as mentioned above in particular for ecological reasons the use of fluoride ions is undesired. In addition, the formulations disclosed therein require comparably high amounts of zinc cations and / or silanes, which is undesired both from an ecological and an economic perspective. Further, the use of silanes, which are often additionally present in such formulations, leads to an increased VOC content due to alcohols being formed as side products of the silane hydrolysis / condensation taking place. In addition, the conventional formulations disclosed in the prior art offer not always a sufficient corrosion protection and / or water resistance and / or adhesion to the substrate and / or to further layers applied thereon, and, further, are not always suitable to provide permanent coating (PC) layers, in particular when applied in comparably thin dry film thicknesses such as thicknesses of about only 1 .0 m or lower.

[0008] It is further known that the use of certain polymers such as poly(meth)acrylates in compositions suitable for use in direct-to-metal applications may enhance the bonding to the metal surface and thus improve corrosion protection, in particular when phosphorous containing moieties such as phosphonic acid groups are present in the polymer. However, such aqueous poly(meth)acrylate dispersions, in particular aqueous phosphorous containing poly(meth)acrylate dispersions, have to be stabilized to be suitable for use in water or aqueous media by use of, e.g., sulfate or sulfo-groups containing emulsifiers and / or carboxylic acid-based emulsifiers. The use of such emulsifiers is, however, not desired, since often undesired migration of these kinds of emulsifiers to the metal surfaces may occur when using the aqueous poly(meth)acrylate dispersions in direct-to-metal applications such as PC applications, and, further, defects of the resulting films such as conversion coating films may be observed, particularly under corrosion conditions. Poly(meth)acrylates, in particular phosphorous containing poly(meth)acrylates, which do not have to be stabilized in water or aqueous media are known as well, but such polymers are usually water-soluble as such and bear only or at least mostly water-soluble monomeric units obtainable from using corresponding water-soluble monomers. Such water-soluble poly(meth)acrylates, however, are usually not suitable to provide sufficient adhesion and / or corrosion protection when incorporated in aqueous compositions intended to be used in direct-to-metal applications such as PC applications. Furthermore, such water- soluble poly(meth)acrylates often not even have an ability to form a closed film on the metal surfaces, let alone a closed PC layer.

[0009] Thus, there is a need to provide aqueous coating compositions, which are suitable to be used in permanent coating (PC) technology applications and can be applied in thin layers in dry film thicknesses of <2.0 pm on surfaces of metal substrates such as substrates made of galvanized steel and / or galvalume, which are furthermore suitable to be formulated as compositions that are free or essentially free of fluoride anions without any negative impact on corrosion protection and substrate adhesion compared to conventionally used fluoride anions containing compositions, and which allow to make use of polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder, that can be prepared and used within the compositions without having to use conventional emulsifiers such as sulfate and / or phosphate containing and / or carboxylic acid-based emulsifiers for stabilization of the polymers, although the polymers as such are not or are essentially not soluble in water, again without any negative impact on corrosion protection and substrate adhesion compared to compositions, that contain conventional polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder.

[0010] Problem

[0011] It has been therefore an objective underlying the present invention to provide aqueous coating compositions, which are suitable to be used in permanent coating (PC) technology applications and can be applied in thin layers in dry film thicknesses of <2.0 pm on surfaces of metal substrates such as substrates made of galvanized steel and / or galvalume, which are furthermore suitable to be formulated as compositions that are free or essentially free of fluoride anions without any negative impact on corrosion protection and substrate adhesion compared to conventionally used fluoride anions containing compositions, and which allow to make use of polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder, that can be prepared and used within the compositions without having to use conventional emulsifiers such as sulfate or sulfo-groups and / or phosphate containing and / or carboxylic acid-based emulsifiers for stabilization of the polymers, although the polymers as such are not or are essentially not soluble in water, again without any negative impact on corrosion protection and substrate adhesion compared to compositions, that contain conventional polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder.

[0012] Solution

[0013] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. by the subject matter described herein.

[0014] A first subject-matter of the present invention is an aqueous coating composition comprising, besides water, at least constituents a1), a2), a3, and a4), which are different from one of another, namely at least one of zirconium, titanium, and hafnium cations as constituent a1), at least one complexing agent as constituent a2), which is suitable to complex constituent a1), at least one polymer P as constituent a3), which is obtainable from a polymerization of at least one (meth)acrylic monomer in the presence of at least one block copolymer BC, and at least one block copolymer BC as constituent a4), in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the at least one polymer P has taken place, wherein said block copolymer BC contains at least two blocks B1 and B2, which are different from one another, the first block B1 comprising structural units SU1 , wherein at least a part of these structural units SU1 contains at least one phosphorous containing moiety, and the second block B2 comprising structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, which is identical to or different from the at least one (meth)acrylic monomer used for preparing the at least one polymer P, preferably wherein block B2 contains only monomeric units derived from at least one nonfunctionalized (meth)acrylic monomer and no other monomeric units besides said monomeric units.

[0015] A further subject-matter of the present invention is a concentrate for producing the aqueous coating composition according to one or more of the preceding claims by diluting the concentrate with water and optionally by adjusting the pH value.

[0016] A further subject-matter of the present invention is a use of the aqueous coating composition according to the present invention for corrosion protection of metallic substrates, preferably after having applied the aqueous coating composition at least in portion onto a surface of an optionally pre-coated metallic substrate to form a coating film at least in portion on said surface, and / or a use of the at least one inventively used block copolymer BC as defined hereinbefore and hereinafter for stabilizing at least one inventively used polymer P as defined hereinbefore and hereinafter in an aqueous coating composition according to the present invention, and / or a use of the at least one inventively used block copolymer BC as defined hereinbefore and hereinafter for improving and / or for establishing compatibility between at least one inventively used polymer P as defined hereinbefore and hereinafter and any inorganic constituents being present as well in an aqueous coating composition, preferably in an aqueous coating composition according to the present invention.

[0017] A further subject-matter of the present invention is a method of coating of an optionally pre-coated metallic substrate comprising at least a step 1) and optionally also a step 2), namely

[0018] 1) applying the aqueous coating composition according to the present invention at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface, and

[0019] 2) optionally curing or drying the coating film obtained after step 1) to give a cured or dried coating layer, wherein the obtained cured or dried coating layer preferably has a dry film thickness below 2.0 pm. A further subject-matter of the present invention is a substrate, which is a coated substrate being obtainable by the inventive coating method.

[0020] It has been surprisingly found that the inventive aqueous coating composition is suitable for use in direct-to-metal applications and particularly suitable to be used in permanent coating (PC) technology applications and can be applied in thin layers in dry film thicknesses of <2.0 pm or even <1 .0 pm on surfaces of metal substrates.

[0021] Further, it has been in particular surprisingly found that the inventive aqueous coating composition, after having been applied to a metal surface, is able to lead at least to the same, but preferably to an improved, substrate adhesion and adhesion to any layers applied on top, as conventionally used aqueous coating compositions, in particular due to the presence of the block copolymer BC therein and its phosphorous containing moiety within block B1 , which allows to be anchored to the metallic surface, and, further, is able to lead at least to the same, but preferably to an improved corrosion protection compared to conventional aqueous coating compositions, again in particular due to the presence of the block copolymer BC therein and its phosphorous containing moiety within block B1 , which allows to be anchored to the metallic surface.

[0022] Moreover, it has been surprisingly found that the inventive aqueous coating composition is suitable to be formulated as composition that is free or essentially free of fluoride anions without any negative impact on corrosion protection and substrate adhesion once applied to a metal surface of a substrate compared to conventionally used containing compositions that contain fluoride anions.

[0023] In addition, it has been surprisingly found that the inventive aqueous coating composition allows to make use of polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder such as of polymer P, that can be prepared and used within the compositions without having to use conventional emulsifiers such as sulfate and / or phosphate containing and / or carboxylic acid-based and / or amine-based emulsifiers for stabilization of the polymers in the aqueous medium of the composition, despite the fact that the polymers as such are not or are essentially not soluble in water, without any negative impact on corrosion protection and substrate adhesion once applied to a metal surface of a substrate compared to compositions that contain conventional polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder. It has been in particular found in this context that no external emulsifiers / surfactants are needed for stabilization of said polymer P in the aqueous medium of the composition due to the fact that the use and presence of the block copolymer BC in the inventive composition provides an excellent stability of polymer P in water, and that the water and thus rinsing resistance can be improved for this reason as well, since the block copolymers BC only have a very low or even no mobility to the surface, in contrast to conventionally used emulsifiers.

[0024] Moreover, it has been found that that the inventive aqueous coating composition exhibits a high storage stability over time. Finally, it has been found that polymers prepared from at least one kind of (meth)acrylic monomers as polymeric binder such as polymer P, when stabilized via block copolymer BC, have a high compatibility with the other constituents of the inventive aqueous coating composition and that no undesired precipitation of any of the constituents is observed.

[0025] Detailed description of the invention

[0026] The term "comprising” in the sense of the present invention, in connection for example with the aqueous coating composition, preferably has the meaning of "consisting of”. With regard, e.g., to said composition referred to hereinbefore, it is possible - in addition to all mandatory constituents present therein - for one or more of the further optional constituents identified hereinafter to be also included therein. All constituents may in each case be present in their preferred embodiments as identified below.

[0027] The proportions and amounts in wt.-% (% by weight) of any of the constituents given hereinafter, which are present in each of the compositions such as the aqueous coating composition add up to 100 wt.-%, based in each case on the total weight of the respective composition.

[0028] Aqueous coating composition

[0029] The aqueous coating composition comprises, besides water, at least constituents a1), a2), a3, and a4), which are different from one of another.

[0030] The aqueous coating composition is suitable to be used in permanent coating applications. This technique is known by a person skilled in the art.

[0031] Preferably, the aqueous coating composition is an aqueous acidic coating composition, which more preferably has a pH value in a range of from 0.1 to <7.0, still more preferably of from 0.5 to 6.5, even more preferably of from 1.0 to 6.0, yet more preferably of from 1.5 to 5.5, still more preferably of from 2.0 to 5.0. The pH value can be in particular adjusted by using a suitable pH adjusting constituent, in particular sodium and / or potassium hydroxide and / or sodium and / or potassium and / or ammonium carbonate for alkaline adjustment, or can be in particular adjusted in case acidic adjustment is needed by at least one inorganic acid such as phosphoric and / or sulfuric and / or boric acid and / or nitric acid and / or by at least one organic acid such as methyl sulfonic acid. Preferably, at least one of phosphoric acid, sulfuric acid and nitric acid is used.

[0032] The aqueous coating composition preferably is a dispersion or solution.

[0033] The aqueous coating composition is preferably free or essentially free of any chromium ions such as Cr(VI) cations and / or Cr(lll) cations, more preferably is free of chromium ions or comprises a maximum amount of chromium ions of <10 mg / L, calculated as metal, and / or is free or essentially free of any nickel ions such as Ni(ll) cations and / or Ni(lll) cations, more preferably is free of nickel ions or comprises a maximum amount of nickel ions of <10 mg / L, calculated as metal. "Essentially free” in this context means in each case that at least on purpose none of the aforementioned constituents is added, but it may not be ruled out that any residues of any of the constituents may be present as impurities and / or may be present in amounts being naturally present in water.

[0034] The term "aqueous” with respect to the aqueous coating composition in the sense of the present invention preferably means that the composition is a composition containing at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% in particular at least 80 wt.-%, of water, based on its total content of organic and inorganic solvents including water. Thus, the aqueous composition may contain at least one organic solvent besides water - however, in an amount lower than the amount of water present.

[0035] Preferably, the aqueous coating composition contains at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% in particular at least 80 wt.-%, of water, in each case based on its total weight.

[0036] Preferably, the amount of organic solvent(s) present in the aqueous coating composition does not exceed 5 wt.-%, yet more preferably does not exceed 2.5 wt.-%, even more preferably is lower than 2.0 wt.-%, most preferably is at most 1 .0 wt.-% or at most 0.5 wt.-% or at most 0.2 wt.-%, in each case based on the total weight of the composition.

[0037] Preferably, the aqueous coating composition has a solid content in a range of from 5.0 to 50.0 wt.-%, more preferably of from 7.5 to 40.0 wt.-%, even more preferably of from 10.0 to 35.0 wt.-%, still more preferably of from 12.5 to 30.0 wt.-%, even more preferably of from 15.0 to 25.0 wt.-%. The solid content is determined according to the method disclosed in the 'method' section.

[0038] Preferably, the aqueous coating composition does not comprise any sulfate and / or phosphate containing constituents such as sulfate and / or phosphate containing emulsifiers and / or surfactants. Preferably, the aqueous coating composition does not comprise any emulsifiers and / or surfactants except of non-ionic surfactants such as alkylene oxide units containing polymers including copolymers and particularly alkylene oxide units containing block copolymers, and despite any emulsifiers and / or surfactants being subsumable under the definition of the mandatory constituents of the aqueous coating composition. More preferably, however, the aqueous coating composition does not comprise any emulsifiers and / or surfactants at all, despite any emulsifiers and / or surfactants being subsumable under the definition of the mandatory constituents of the aqueous coating composition.

[0039] The aqueous coating composition is preferably free or essentially free of any complex fluorides. Preferably, the aqueous coating composition is free or essentially free of free fluoride anions. Most preferably, the aqueous coating composition is free or essentially free of fluoride anions both being present in the form as complex fluorides and as free fluorides. "Essentially free” in this context means in each case that at least on purpose none of the aforementioned constituents is added, but it may not be ruled out that any residues of any of the constituents may be present as impurities and / or may be present in amounts being naturally present in water. Preferably, the maximum amount of free fluoride anions and / or complex fluorides anions is 10 mg / L, more preferably is 7.5 mg / L, still more preferably is 5 mg / L, calculated in each case as fluorine.

[0040] Constituent a1)

[0041] At least one of zirconium, titanium, and hafnium cations is present as constituent a1) in the aqueous coating composition. Preferably, at least one of zirconium and titanium cations, more preferably titanium cations, are present as constituent a1).

[0042] Preferably, the aqueous coating composition comprises the at least one of zirconium, titanium, and hafnium cations as constituent a1) in an amount in a range of from 5 to 50 000 mg / L, more preferably of from 7.5 to 40 000 mg / L, even more preferably of from 10 to 30 000 mg / L, still more preferably of from 12.5 to 20 000 mg / L, yet more preferably of from 15 to 10 000 mg / L, even more preferably of from 20 to 8 000 mg / L, still more preferably of from 25 to 6 000 mg / L, most preferably of from 50 to 3 000 mg / L, in each case calculated as metal.

[0043] The content of constituent a1) can be monitored and determined by the means of ICP-OES (optical emission spectroscopy with inductively coupled plasma). Said method is described hereinafter in the 'method' section.

[0044] The use of titanium cations is particularly preferred when the surface of the substrate used for PC application is at least partially made of at least one kind of steel such as HDG and / or of at least one kind of steel being coated at least in portion with at least one kind of zinc-aluminum-magnesium alloy (ZM). The use of zirconium cations is particularly preferred when the surface of the substrate used for PC application is at least partially made of at least one kind of aluminum and / or of at least one kind of steel being coated at least in portion with at least one kind of zinc-aluminum alloy such as Galvalume®.

[0045] Preferably, a precursor metal compound is used to generate constituent a1). Preferably, the precursor metal compound is water-soluble. Solubility is determined at a temperature of 20°C and atmospheric pressure (1.013 bar).

[0046] Notwithstanding the preferred definitions of constituent a2) as defined hereinafter and, further, the fact that the aqueous coating composition preferably is free or essentially free of complex and / or free fluoride anions, suitable zirconium, titanium, and / or hafnium compounds for use as precursor compounds are the complex fluorides of these metals. The term "complex fluoride” includes the single and multiple protonated forms as well as the deprotonated forms. It is also possible to use mixtures of such complex fluorides. Complex fluorides in the sense of the present invention are preferably complexes of metal cations such as zirconium, titanium and / or hafnium cations formed with fluoride ions in the composition, e.g., by coordination of fluoride anions to zirconium, titanium, and / or hafnium cations in the presence of water. In case complex fluorides of at least one of zirconium, titanium and / or hafnium cations have been used as precursor compounds, the aqueous composition further comprises fluoride anions as optional constituent. However, preferably the complex fluorides of zirconium, titanium and / or hafnium are not used as precursor compounds.

[0047] Zirconium cations can optionally be added in form of zirconyl compounds as, e.g., zirconyl nitrate, zirconyl acetate, zirconyl acetonyl acetate, zirconium carbonate and / or zirconium nitrate, the latter one being particularly preferred, in particular when the aqueous composition is acidic. The same similarly applies to titanium and hafnium cations: here the respective titanium and / or hafnium compounds are optionally used.

[0048] However, preferably constituent a1) is used in a complexed form thereof with the aid of the at least one complexing agent a2). Preferably, a complexed form of a1) by means of a2) is prepared first and then included into the composition.

[0049] Constituent a2)

[0050] At least one complexing agent is present as constituent a2), which is suitable to complex constituent a1).

[0051] Preferably, the at least one complexing agent a2), which is suitable to complex constituent a1), is selected from organic compounds bearing at least one kind of functional groups, which are able to coordinate to constituent a1) in water, more preferably is selected from organic compounds bearing at least one kind of functional groups selected from OH-groups, carboxylic acid groups, salts and / or derivatives such as esters thereof, and mixtures thereof, more preferably is selected from organic compounds bearing both at least one OH-group and at least one carboxylic acid group, a salts and / or a derivatives such as an ester thereof. Examples of suitable complexing agents a2), which bear both at least one OH-group and at least one carboxylic acid group are lactic acid, citric acid, and galactaric acid. Citric acid is particularly preferred.

[0052] Complexing agent a2) may be an organic compound, which is suitable to form at least one organic metalate with constituent a1), wherein the metal of the metalate is selected from Ti, Zr and Hf, more preferably from Ti and Zr. Hence, most preferably, the metalate corresponds to a titanate and / or zirconate in this case.

[0053] Preferably, complexing agent a2) comprises at least one organic group, that is suitable to form at least one organic metalate with constituent a1). Preferably, the organic group(s) are bonded to constituent a1), more preferably to titanium and / or zirconium via divalent oxygen atoms. Preferably, constituent a2) comprises at least one alkoxide groups, wherein each alkoxide group preferably represents a -O-Ci-Cs group, more preferably a -O-C3-C8 group. Even more preferably, each alkoxide group has 3 to 6, still more preferably 3 to 4 carbon atoms. Examples of alkoxide groups are n-butyl alkoxides, n-propyl alkoxides, isopropyl alkoxides. Exemplary metalates such as titanates and / or zirconates formed by constituents a1) and a2) are tetra-n-butyl zirconate (available under the trade name Tyzor® NBZ), tetra-n-propyl titanate (available under the trade name Tyzor® TPT by Dorf Ketal) and titanium acetyl acetonate (available under the trade names Tyzor® AA 75, Tyzor® AA 65 and Tyzor® AA 105 by Dorf Ketal). More preferably, complexing agent a2) is selected from organic compounds comprising an organic group, which comprises both at least one OH-group and at least one carboxylic acid group, such as citric acid. Citrates of a1) can be, e.g., prepared by reacting a suitable alkoxide of a1) such as titanium tetra-isopropylate and / or zirconium tetra-isopropylate with citric acid, e.g., in a molar ratio of about 1 :1. Formed isopropanol may be distilled of afterwards.

[0054] Further, suitable metal halogenides (with the metal being selected from Ti, Zr and Hf) can react with suitable organic compounds, which comprise at least one OH-group under hydrogen halide cleavage to build the desired complex.

[0055] Preferred suitable complexing agents for use as constituent a2) are selected from glycolic acid, lactic acid, 2- hydroxybutanoic acid, leucic acid, glyceric acid, malic acid, citric acid, tartaric acid, fumaric acid, maleic acid, mandelic acid, quinic acid, aromatic hydroxy carboxylic acids such as, e.g., salicylic acid and other hydroxy carboxylic acids as well as keto acids, glycerin, oxalic acid aspartic acid, and asparagine, nitrogen-containing complexing agents such as N,N,N',N'-tetrakis(2-hydroxyethyl)ethylene-diamine and / or N,N,N',N'-tetrakis(2- hydroxypropyl)-ethylenediamine and mixtures thereof. Nitrogen-containing complexing agents are, e.g., described in WO 2008 / 155568 A1 and WO 2008 / 155569 A1.

[0056] Preferably, the molar ratio of complexing agent a2) to constituent a1) is in a range of from 0.5 to 1.0 to 8.0 to 1.0, more preferably of from 0.5 to 1 .0 to 6.0 to 1 .0, even more preferably of from 1 .0 to 1 .0 to 3.0 to 1 .0.

[0057] Preferably, the aqueous composition comprises the at least one complexing agent present as constituent a2) in an amount of from 0.25 to 3.0 wt.-%, more preferably of from 0.5 to 2.5 wt.-%, based on the total weight of the composition.

[0058] Constituents a3) and a4)

[0059] At least one polymer P is present as constituent a3) in the aqueous coating composition, which polymer P is obtainable from a polymerization of at least one (meth)acrylic monomer in the presence of at least one block copolymer BC. Said at least one block copolymer BC, in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the at least one polymer P has taken place, is also present in the aqueous coating composition, i.e., as constituent a4).

[0060] Preferably, an aqueous dispersion of at least one polymer P and at least one block copolymer BC is prepared first and then incorporated into the aqueous coating composition.

[0061] Block copolymer BC

[0062] Block copolymer BC contains at least two blocks B1 and B2, which are different from one another. The block copolymer BC may comprise one or more further blocks, each of which are different from one another and also different from both blocks B1 and B2. However, preferably, the block copolymer BC is composed of the two blocks B1 and B2 and does not contain any further blocks. Hence, preferably the block copolymer BC is a diblock copolymer, more preferably a linear diblock copolymer. Preferably, each of block B1 and B2 comprises or is composed of monomeric units, which comprise side chains.

[0063] A person skilled in the art is aware of the term "block copolymer”. Block copolymers are copolymers obtained by adding at least two different ethy lenically unsaturated monomers, two different mixtures of ethy lenical ly unsaturated monomers or by adding an ethylenically unsaturated monomer and a mixture of ethylenically unsaturated monomers at different times in the practice of a controlled polymerization, wherein an ethylenically unsaturated monomer or a mixture of ethylenically unsaturated monomers is initially charged at the start of the reaction. At the time of adding the further ethylenically unsaturated monomer or the mixture of ethylenically unsaturated monomers or adding ethylenically unsaturated monomers in multiple installments, the ethylenically unsaturated monomers added at the start of the polymerization can be already completely reacted, or still be partly non-polymerized. As a result of such a polymerization, block copolymers may have at least one transition in their structural units along the polymer chain (polymer backbone), said transition marking the boundary between the individual blocks. Suitable block copolymer structures are e.g. AB diblock copolymers, ABA triblock copolymers or ABC triblock copolymers. Block copolymers, which are preferably used according to the present invention, are AB diblock copolymers.

[0064] The at least one block copolymer BC preferably contains a polymer main chain as backbone and the at least two blocks B1 and B2 being different from one another, wherein part of the backbone is a part of block B1 and another part of the backbone is part of block B2.

[0065] Preferably, the at least one block copolymer BC is bound, more preferably bound in a non-covalently manner, to at least part of the polymer P, more preferably to at least part of the surface of polymer P, by means of at least part of its block B2.

[0066] Preferably, the at least one block copolymer BC, in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the polymer P has taken place, is bound to at least part of the polymer P, more preferably to at least part of the surface of polymer P, even more preferably to at least part of the surface of a polymeric core formed by the at least one polymer P by means of at least part of its block B2, still more preferably via at least one kind of physical interactions. Examples of such physical interactions are van der Waals interactions and any hydrophobic interactions, e.g., hydrophobic effects, by which at least part of block B2 of the block copolymer is bound to the polymer P. Preferably, the at least one block copolymer BC is non-covalently bound to at least part of the surface of the polymeric core by means of at least part of its block B2. Preferably, each block B2 of each block copolymer BC bound to at least part of the surface of the polymeric core faces the surface of the polymeric core.

[0067] Block copolymer BC is preferably an amphiphilic block copolymer. The first block B1 is preferably a hydrophilic block, e.g., an ionic block, in particular a block, which is more hydrophilic than the second block B2, and which preferably allows a stabilization of the block copolymer in water or in an aqueous medium. The second block B2 is preferably a hydrophobic block, e.g., a lipophilic block, in particular a block, which is more hydrophobic than the first block B1 , and allows to be bound to at least part the surface of the polymer P.

[0068] Preferably, the number average molecular weight of the block copolymer BC is in a range of from 500 to 10 000 g / mol, more preferably of from 600 to 8 000 g / mol, even more preferably of from 800 to 6 000 g / mol. The number average molecular weight is determined according to the method disclosed in the ‘methods' section.

[0069] Preferably, the block copolymer BC is obtainable by a controlled radical polymerization technique. Examples thereof are ATRP (atom transfer radical polymerization) and RAFT (reversible addition-fragmentation chain-transfer polymerization). The RAFT polymerization technique is known to a person skilled in the art, e.g., from WO 2022 / 228846 A1. The ATRP polymerization technique is also known to a person skilled in the art. For preparation of the block copolymer BC preferably at least one suitable chain transfer agent is used, at least when the block copolymer is prepared via RAFT, more preferably at least one chain transfer agent suitable for RAFT polymerization. In case of ATRP polymerization preferably an agent such as a copper halide is used. Examples of suitable chain transfer agents are dithioesters, thiocarbamates, xanthates, thiols, such as dodecyl mercaptan, secondary alcohols, and halocarbons, such as carbon tetrachloride.

[0070] In particular in case the block copolymer is obtainable by ATRP for preparing the first block B1 , preferably at least one monomer is used, which is able to be used to generate precursor monomeric units forming a block B1 a of the block copolymer, wherein at least part of the moieties defining block B1 a, in particular at least part of the side chains of block B1 a, are able to be subjected to chemical transformation after preparation of the block copolymer, which results in phosphorous containing moieties, in particular within or as the side chain, and which thus allow the block B1 defined hereinbefore and hereinafter to be formed. For example, glycidyl (meth)acrylate can be used a monomer for generating a precursor block B1 a, which then, after formation of the block copolymer including the second block B2, is subjected to a treatment with a suitable phosphorous containing agent such as phosphoric acid, phosphonic acid, and / or any derivatives thereof, which leads, upon epoxide ring-opening, to formation of, e.g., phosphonic acids group in the side chain of block B1 a and hence to the formation of block B1 as defined hereinbefore and hereinafter.

[0071] When the block copolymer BC is prepared via ATRP polymerization, the monomers used are preferably polymerized via an oil in water emulsion polymerization. Advantages of the ATRP technique are that ATRP allows for precise control over the polymer chain growth by utilizing a reversible transfer process. In ATRP, the polymerization reaction typically involves a transition metal catalyst, such as copper, and a halogen-containing initiator. The reaction proceeds preferably through a series of steps of

[0072] A) Initiation: The halogen-containing initiator, often a bromide or chloride, reacts with the transition metal catalyst to generate an active species known as an "initiator radical" or "activator complex." B) Activation and Propagation: The initiator radical reacts with a monomer, abstracting a hydrogen atom from its carbon-carbon double bond, which generates a carbon-centered radical. This carbon-centered radical then reacts with a monomer, incorporating it into the growing polymer chain.

[0073] C) Reversible Transfer: The transition metal catalyst facilitates the reversible transfer of the active radical species back to the initiator radical or activator complex. This transfer process allows for control over the polymerization kinetics and molecular weight distribution.

[0074] D) Termination: The polymerization can be terminated by various mechanisms, including radical-radical coupling or reaction with a terminating agent. This termination process helps control the polymer chain length and molecular weight.

[0075] By manipulating the monomer feed and reaction conditions, different monomers can be incorporated into the polymer chain, resulting in tailored material properties. ATRP allows for the incorporation of various functional groups into the polymer structure. By using functional monomers or post-polymerization modification techniques, specific functionalities can be introduced, expanding the range of potential applications. ATRP can be performed under a broad range of reaction conditions, making it compatible with various solvents, temperatures, and monomer types. This compatibility enables the synthesis of polymers with different properties and architectures.

[0076] When the block copolymer BC is prepared via RAFT polymerization, which is preferred, the monomers used are preferably polymerized via an oil in water emulsion polymerization. Preferably, the RAFT polymerization method includes at least steps 1 a) and 2a) or 1 b) and 2b), namely

[0077] 1a) polymerizing at least one (meth)acrylic monomer in at least one non-aqueous solvent, more preferably with the aid of at least one chain transfer agent such as a RAFT chain transfer agent, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer to be formed, and

[0078] 2a) using the intermediate product IP1 obtainable after step 1 a) as a macroinitiator for polymerizing at least one monomer, which contains at least one phosphorous containing moiety, in the presence of said intermediate product IP1 , to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such, or

[0079] 1 b) polymerizing at least one monomer, which contains at least one phosphorous containing moiety, in water, in an aqueous solvent mixture or in an aqueous solvent mixture or in at least one non-aqueous solvent, more preferably with the aid of at least one chain transfer agent such as a RAFT chain transfer agent, to form polymerized structural units SU1 corresponding to the first block B1 of the block copolymer to be formed, and

[0080] 2b) using the intermediate product IP2 obtainable after step 1 b) as a macroinitiator for polymerizing at least one (meth)acrylic monomer, in the presence of said intermediate product IP2, to form polymerized structural units SU2 corresponding to the second block B2 of the block copolymer BC and to form the block copolymer BC containing at least blocks B1 and B2 as such. Optionally, the block copolymer BC obtained after step 2a) or 2b) is subjected to a purification, preferably in order to remove any excess monomers.

[0081] In case steps 1 a) and 2a) are performed, the second hydrophobic block B2 is synthesized first, followed by synthesis of the first hydrophilic block B1. Preferably, step 1a) is performed in at least one alcohol. An example of a suitable alcohol is ethanol. Preferably, step 2a) is performed by adding at least one non-aqueous solvent such as at least one alcohol and / or water together with the at least one monomer, which contains at least one phosphorous containing moiety to IP1. In case steps 1 b) and 2b) are performed, the first hydrophilic block B1 is synthesized first, followed by synthesis of the second hydrophobic block B2. Preferably, step 1 b) is performed in water, in an aqueous solvent mixture, which contains, besides water at least one alcohol, or in at least one nonaqueous solvent, which is at least one alcohol. An example of a suitable alcohol is ethanol. Preferably, step 2b) is performed by adding at least one non-aqueous solvent such as at least one alcohol together with the least one (meth)acrylic monomer to IP2.

[0082] Preferably, the at least one chain transfer agent (CTA) is at least one agent suitable for RAFT polymerization and is thus also referred to as RAFT agent.

[0083] Preferably, the RAFT agent used for preparing polymer the block copolymer is a compound, which comprises at least one thiocarbonylthio group -S(C=S)-. Thus, for example, it may be a compound which comprises at least one xanthate group (bearing -SC=S-O- functions), for example one or two xanthates. Typically, the RAFT agent is a non-polymeric compound bearing a group that ensures control of the radical polymerization, especially a thiocarbonylthio group -S(C=S)-. Advantageously, the RAFT agent is selected from compounds bearing a xanthate -S(C=S)O-, trithiocarbonate, dithiocarbamate or dithiocarbazate function, for example compounds bearing an 0- ethyl xanthate function of formula -S(C=S)OCH2CH3. Xanthates prove to be very particularly advantageous, in particular those bearing an O-ethyl xanthate -S(C=S)OCH2CH3 function, such as O-ethyl S-(1- (methoxycarbonyl)ethyl) xanthate (CH3CH(CO2CH3))S(C=S)OEt.

[0084] Preferably, the at least one block copolymer BC is present in the aqueous coating composition in an amount in a range from 0.1 wt.-% to 10.0 wt.-%, more preferably of from 0.5 wt.-% to 7.5 or to 5.0 wt.-%, even more preferably of from 1 .0 wt.-% to 2.5 or to 2.0 wt.-%, based in each case on the total weight of the sum of polymer P and block copolymer BC.

[0085] Preferably, the at least one block copolymer BC is present in the aqueous coating composition in an amount in a range of from 0.05 wt.-% to 5.0 wt.-%, more preferably of from 0.07 to 3.5 wt.-%, yet more preferably of from 0.10 to 3.0 or to 2.0 wt.-%, based in each case on the total weight of the aqueous coating composition. Block B1

[0086] The first block B1 comprises structural units SU1 , wherein at least a part of these structural units SU1 contains at least one phosphorous containing moiety.

[0087] The at least one phosphorous containing moiety preferably is (I) part of the side chains of the structural units SU1 and is, within each structural unit SU1 , separated from the main chain of the block copolymer BC by at least one carbon atom, or, preferably (II) represents the side chains of the structural units SU1 and is, within each structural unit SU1 , directly bound to the main chain of the block copolymer BC, preferably by means of a P-C-single bond. Most preferably, the at least one phosphorous containing moiety represents the side chains of the structural units SU1 and is, within each structural unit SU1 , directly bound to the main chain of the block copolymer BC, in particular by means of a P-C-single bond, preferably when the structural unit SU1 is a polymerized vinyl phosphonic acid unit.

[0088] Preferably, the at least one phosphorous containing moiety of at least a part of the structural units SU1 of the first block B1 of the block copolymer BC is part of a functional group being present within a side chain in each structural SU1 , which contains the at least one phosphorous containing moiety, or represents a functional group being present as side chain in each structural SU1 , more preferably represents a functional group being present as side chain in each structural SU1.

[0089] Preferably, the number average molecular weight of the first block B1 of the block copolymer BC is in a range of from 200 to 4 000 g / mol, more preferably of from 300 to 3 000 g / mol, even more preferably of from 400 to 2 000 g / mol. The number average molecular weight is determined according to the method disclosed in the ‘methods' section.

[0090] Preferably, the amount of the first block B1 of the block copolymer BC is in a range of from 70.0 to 30.0 wt.-%, more preferably of from 65.0 to 35.0 wt.-%, even more preferably of from 60.0 to 40.0 wt.-%, based on the total weight of the block copolymer BC.

[0091] If the amount of the first block B1 is too high, e.g. exceeds 70 or 65.0 wt.-%, based on the total weight of the block copolymer BC, the water solubility of the block copolymer may be too high to be effectively usable as an emulsifier and / or surfactant for stabilizing the polymer P in water or in an aqueous medium, and this may lead to an undesired destabilization of the dispersion of polymer P in water or an aqueous medium.

[0092] Preferably, the at least one phosphorous containing moiety of at least a part of the structural units SU1 of the first block B1 of the block copolymer BC is selected from phosphonic acid groups, phosphonic acid ester groups (at least partially esterified phosphonic acid groups), at least partially esterified phosphoric acid groups, and salts of each of these groups such as for example phosphonates or phosphates, more preferably is selected from phosphonic acid groups and salts thereof, even more preferably is selected from phosphonic acid groups. The phosphonate ester groups and phosphate ester groups can in each case be completely or only partially esterified groups. For example, a phosphate ester group includes both a phosphate monoester group and also a phosphate diester group and also a phosphate tri-ester group. It is clear to those skilled in the art that a completely esterified phosphonic acid group or a completely esterified phosphoric acid group cannot be present in the form of a salt. Suitable alcohols for the partial or complete esterification of the phosphonate ester groups and phosphate ester groups are preferably Ci-s aliphatic alcohols, particularly preferably Ci-s alkyl alcohols such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, and tert-butanol.

[0093] If only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, the remaining part preferably comprises at least one functional group per structural unit SU1 not containing the at least one phosphorous containing moiety, which is preferably selected from OH- groups and carboxyl groups, more preferably is selected from carboxyl groups, e.g., by using (meth)acrylic acid as additional monomer(s) for preparing the first block B1 , or is selected from OH-groups, e.g., by using poly(ethylene glycol)(meth)acry late (PEGMA) as additional monomer for preparing the first block B1.

[0094] Preferably, each structural unit SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, more preferably such that the first block B1 of the block copolymer BC is a poly(vinyl phosphonic acid), or in that only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety and the remaining part of the structural units SU1 of the first block B1 of the block copolymer BC contains at least one carboxylic acid group or a salt thereof, more preferably such that the first block B1 of the block copolymer BC is poly (vinyl phosphonic acid-co- (meth)acrylic acid).

[0095] Preferably, each structural unit SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, more preferably such that the first block B1 of the block copolymer BC is a poly(vinyl phosphonic acid), or in that only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety and the remaining part of the structural units SU1 of the first block B1 of the block copolymer BC contains at least one OH-group. Suitable monomers for generating said remaining part of the structural units SU1 of the first block B1 of the block copolymer BC are preferably OH-group(s) containing hydrophilic monomers, more preferably OH-group(s) containing non-ionic hydrophilic monomers. The hydrophilic character of such monomers is preferably achieved by the presence of alkylene oxide units such as ethylene and / or propylene oxide units in the chemical structure of the monomers.

[0096] For preparation of at least part of the first block B1 any suitable ethylenically unsaturated monomer can be used, which contains at least one phosphorous containing moiety. Preferably, at least one ethylenically unsaturated monomer, which contains at least one phosphorous containing moiety is used, wherein said at least one monomer can be a (meth)acrylic monomer as, e.g., in case 2-(meth)acryloyloxyethyl phosphate, 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, 10-(meth)acryloyloxydecyl dihydrogen phosphate, ethyl-2-[4- (dihydroxyphosphoryl)-2-oxabutyl] (meth)acrylate and 2,4,6-trimethylphenyl-2-[4-(dihydroxyphosphoryl)-2- oxabutyl] (meth)acrylate, and / or can be a non-(meth)acrylic monomer such as a vinyl monomer such as vinyl phosphonic acid, vinyl phosphonic acid in a form at least partially esterified with a Ci-s alkyl alcohol, vinyl phosphoric acid in a form at least partially esterified with a Ci-s alkyl alcohol, and mixtures thereof. Preferred monomers for generating the block B1 are vinyl phosphonic acid, vinyl phosphonic acid in a form at least partially esterified with a Ci-s alkyl alcohol, vinyl phosphoric acid in a form at least partially esterified with a Ci-s alkyl alcohol, 2- (meth)acryloyloxyethyl phosphate, 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, and mixtures thereof. Most preferred is vinyl phosphonic acid.

[0097] In case it is desired that the at least one phosphorous containing moiety of the first block B1 is to be part of the side chains of the structural units SU1 of the block copolymer BC once prepared, such that, within each structural unit SU1 , said moiety is separated from the main chain of the block copolymer BC by at least one carbon atom, preferably by at least two carbon atoms, it would not be possible to use vinyl phosphonic acid or derivatives thereof as suitable monomer for generating block B1 , since the phosphonic acid groups thereof as phosphorous containing moiety would be directly bound to the main chain of the block copolymer, the main chain being formed from polymerized vinyl units, and hence said moiety would not be separated from the main chain by at least one carbon atom. However, this is not preferred. Since it is rather preferred that the at least one phosphorous containing moiety of the first block B1 is to completely represent the side chains of the structural units SU1 of the block copolymer BC once prepared, such that, within each structural unit SU1, said moiety is directly bound to the main chain of the block copolymer BC, it is preferred to use at least one of vinyl phosphonic acid, vinyl phosphonic acid in a form at least partially esterified with a Ci-s alkyl alcohol, vinyl phosphoric acid in a form at least partially esterified with a Ci-s alkyl alcohol, more preferably to use vinyl phosphonic acid for generation of block B1.

[0098] It is also possible to introduce the phosphorous containing moiety afterwards in a polymer analogous reaction and to form block B1 in this manner from a suitable precursor block B1a. Preferably, in case of introducing said moiety after the polymerization has taken place, a monomer comprising a suitable moiety for later modification is used for polymerization to generate said precursor block B1a. Preferably, at least one monomer selected from the group consisting of preferably (meth)acrylic monomers having at least one epoxide group is used. Most preferred is glycidyl (meth)acrylate. For introducing the at least one phosphorous containing moiety a suitable phosphorous containing compound is used, preferably a compound having at least one phosphorous containing group, which can react with the epoxide moiety after ring opening of the epoxide group and form the at least one phosphorous containing moiety. Preferably, the phosphorous containing compound is selected from the groups consisting of phosphoric acid including polyphosphoric acid, P2O5, and phosphoryl chloride, as well as phosphonic acid and / or esters and / or derivatives thereof such as octyl phosphonic acid, and leads to formation of at least one phosphorous containing moiety selected from phosphonic acid groups and / or esters and / or salts thereof. However, this approach is not preferred. Preferably, block B1 of the block copolymer BC contains only monomeric units derivable from at least one suitable ethylenically unsaturated monomer, which contains at least one phosphorous containing moiety, or contains monomeric units derivable from at least one suitable ethylenically unsaturated monomer, which contains at least one phosphorous containing moiety, in an amount in a range of from 60 to 99 wt.-%, preferably of from 65 to 95 wt.-%, more preferably of from 70 to 90 wt.-%, and monomeric units different therefrom derivable from the at least one monomer containing at least one carboxyl group such as (meth)acrylic acid and / or from the at least one preferably hydrophilic monomer containing at least one OH-group such as PEGMA in an amount in a range of from 1 to 40 wt.-%, preferably of from 5 to 35 wt.-%, more preferably of from 10 to 30 wt.-%.

[0099] The sum of all monomers used for preparing the block B1 , of course, adds up to 100 wt.-% in each case.

[0100] Preferably, the amounts of monomeric units in wt.-% derivable from at least one ethylenically unsaturated monomer, which contains at least one phosphorous containing moiety, exceeds the amounts of any further monomeric units also present in block B1.

[0101] Block B2

[0102] The second block B2 of the block copolymer BC comprises structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, which is identical to or different from the at least one (meth)acrylic monomer used for preparing the at least one polymer P.

[0103] As suitable monomers for preparing the second block B2 of the block copolymer BC the same kind of monomer can be used as described hereinafter in connection with preparation of polymer P.

[0104] Preferably, at least one non-functionalized and preferably hydrophobic (meth)acrylic monomer is used as monomer ml for preparing the second block B2, more preferably at least one (meth)acrylic ester of an aliphatic C1-C30- monoalcohol. Preferably, block B2 contains only monomeric units mu1 derived from the at least one (meth)acrylic monomer ml and no other monomeric units besides monomeric units ml .

[0105] Preferably, the number average molecular weight of the second block B2 of the block copolymer BC is in a range of from 200 or 300 to 6 000 g / mol, more preferably of from 300 or 400 to 5 000 g / mol, even more preferably of from 400 or 500 to 4 000 or 3 000 g / mol. Preferably, the number average molecular weight of the second block B2 exceeds the number average molecular weight of the first block B1. The number average molecular weight is determined according to the method disclosed in the ‘methods' section. Preferably, the amount of the second block B2 of the block copolymer BC is in a range of from 30.0 wt.-% to 70.0 wt.-%, more preferably of from 35.0 wt.-% to 65.0 wt.-%, even more preferably of from 40.0 to 60.0 wt.-%, based on the total weight of the block copolymer BC.

[0106] Polymer P

[0107] The at least one polymer P is obtainable from a polymerization of at least one (meth)acrylic monomer, said polymerization taking place in the presence of the at least one block copolymer BC.

[0108] Preferably, the at least one polymer P is a (meth)acrylic homopolymer in case precisely one kind of (meth)acrylic monomers is used for its polymerization, or is a (meth)acrylic copolymer in case at least two kinds of (meth)acrylic monomers, which are different from one another, or at least one kind of (meth)acrylic monomers and at least one kind of further monomers are used for its polymerization, wherein said at least one kind of further monomers are ethy lenically unsaturated monomers, which are not (meth)acrylic monomers.

[0109] The term "(meth)acrylic” means "acrylic” and / or "methacrylic”. Similarly, "(meth)acrylate” means acrylate and / or methacrylate. The polymer P can be regarded as a "(meth)acrylic polymer”, since it is formed at least partially from "acrylic monomers” and / or "methacrylic monomers”, but it additionally may contain non-acrylic and / or nonmethacrylic monomeric units if other ethylenically unsaturated monomers such as vinyl monomers, e.g., styrene, are additionally used for its preparation. Preferably, the polymer P is formed from more than 20 wt.-%, even more preferably of from more than 25 wt.-%, still more preferably of more than 30 wt.-%, yet more preferably of more than 35 wt.-%, of (meth)acrylic monomers.

[0110] The polymerization performed for preparing the polymer P preferably is an emulsion polymerization.

[0111] Preferably, the aqueous coating composition comprises the at least one polymer P in form of a (meth)acrylic polymeric core, since the at least one polymer P is a (meth)acrylic polymer, more preferably a (meth)acrylic copolymer.

[0112] Preferably, the at least one polymer P is present in the aqueous coating composition in form of a polymeric core and wherein the at least one block copolymer BC is bound, preferably bound in a non-covalently manner, to at least part of the surface of said polymeric core by means of at least part of its block B2.

[0113] Preferably, the at least one polymer P is present in the aqueous coating composition in an amount in a range of from 90.0 wt.-% to 99.9 wt.-%, more preferably of from 95.0 wt.-% to 99.5 wt.-%, even more preferably of from 98.0 wt.-% to 99.0 %, based in each case on the total weight of the sum of polymer P and block copolymer BC. Preferably, the at least one polymer P is present in the aqueous coating composition in an amount in a range of from 5.0 wt.-% to 70.0 wt.-%, more preferably of from 7.5 to 65.0 wt.-%, even more preferably of from 10.0 to 60.0 wt.-%, based in each case on the total weight of the aqueous coating composition.

[0114] Preferably, the total amount of the sum of polymer P and block copolymer BC in the aqueous coating composition is in a range of from 5.0 wt.-% to 70.0 wt.-%, more preferably of from 7.5 to 65.0 wt.-%, even more preferably of from 10.0 to 60.0 wt.-%, based in each case on the total weight of the aqueous coating composition.

[0115] Preferably, polymer P represents a film-forming polymer, and, hence functions as polymeric binder.

[0116] Preferably, the amount of the at least one polymer P being present in the aqueous coating composition exceeds the amount of any further polymeric binder also present therein, which is different from polymer P. Polymer P hence preferably functions as the main binder in the aqueous coating composition.

[0117] Preferably, the at least one polymer P comprises at least one kind of functional groups, more preferably selected from functional groups, which are reactive towards isocyanate groups, even more preferably selected from OH- groups, amino groups, and thiol groups, still more preferably selected from OH-groups.

[0118] Preferably, the at least one (meth)acrylic monomer used for preparing polymer P is selected from nonfunctionalized, (meth)acrylic monomers, functionalized (meth)acrylic monomers, and mixtures thereof, more preferably is selected from (meth)acrylic esters of aliphatic Ci-Cao-monoalcohols, which optionally contain at least one functional group, said at least one functional group being preferably selected from hydroxyl groups, ether groups, carbonyl groups, amino groups, epoxide groups, carboxylic acid groups, and sulfur atoms containing functional groups such as thiol groups, thioether groups, thioester groups and / or thiocarboxylic acid groups, and mixtures thereof.

[0119] Preferably, at least one non-functionalized and preferably hydrophobic (meth)acrylic monomer is used as monomer ml for preparing polymer P, more preferably at least one (meth)acrylic ester of an aliphatic Ci-Cso-monoalcohol.

[0120] Examples of suitable monomers ml , i.e., of (meth)acrylic esters of aliphatic Ci-Cso-monoalcohols, which can be used, are methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate), i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3- propylheptyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate and / or isobornyl (meth)acrylate. Most preferred are methyl (meth)acrylate, ethyl (meth)acrylate, n- propyl (meth)acrylate), i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, lauryl (meth)acrylate, and / or 2-ethylhexyl (meth)acrylate. Preferably, at least one functionalized (meth)acrylic monomer is used as monomer m2 for preparing polymer P, in particular in combination with the at least one monomer ml , wherein monomer m2 is preferably at least one (meth)acrylic ester of a functionalized aliphatic Ci-Cso-monoalcohol.

[0121] Examples of suitable monomers m2, which can be used, are 2-hydroxyethy I acrylate, 2-hydroxyethy I methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3- phenoxy-2-hydroxypropyl (meth)acrylate, glycerol mono (meth)acrylate, acrylic acid, methacrylic acid, glycidyl (meth)acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl acrylate, N,N-dimethylaminopropyl methacrylate, 2-(N,N-diethylamino)ethyl (meth)acrylate, 2-(N,N- dimethylamino)ethyl (meth)acrylate, 3-dimethylaminoneopentyl (meth)acrylate, 2-N-morpholinoethyl (meth)acrylate, 2-(tert-butylamino)ethyl (meth)acrylate, and / or 2-diisopropylaminoethyl (meth)acrylate. Most preferred are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and / or 4-hydroxybutyl methacrylate.

[0122] Optionally, at least further (meth)acrylic monomer is used as monomer m3 for preparing polymer P, which preferably is selected from (meth)acryl amide, N-hydroxy ethyl (meth)acrylamide, N-lsopropyl acrylamide, N-(2- hydroxypropyl) (meth)acryl amide, N-[3-(N,N-dimethylamino)propyl] (meth)acrylamide, 2-(N,N-diethylamino)ethyl (meth)acrylamide, N-dodecylacrylamide and N-[2-(N,N-Dimethylamino)ethyl] (meth)acrylamide, and / or N,N- Dimethyl (meth)acrylamide.

[0123] Preferably, at least one further monomer is used as monomer m4 for preparing polymer P, in particular in combination with the at least one monomer ml and / or m2 and optionally m3, wherein monomer m4 is selected from ethylenically unsaturated monomers bearing precisely one ethylenically unsaturated group, which are not (meth)acrylic monomers, more preferably is selected from allyl alcohol, hydroxy styrene, styrene, hydroxyalkyl vinyl ethers such as hydroxy butyl vinyl ether, vinylbenzyl alcohol, vinyl mercapto alcohols such as vinyl mercaptoethanol, vinyl thiazoles, vinyl thiophenes, 2-vinylpyridine, 4-vinylpyridine, allyl amine, vinylimidazole, N- vinyl-pyrrolidone, vinyl acetate, N-vinylformamide, N,N-diethylamino styrene (all isomers) and N,N-diethylamino- alpha-methylstyrene (all isomers). Most preferred is styrene.

[0124] Optionally, at least one further monomer is used as monomer m5 for preparing polymer P, in particular in combination with the at least one monomer ml and / or m2 and optionally m3 and / or m4, wherein monomer m5 is selected from ethylenically unsaturated monomers bearing more than one ethylenically unsaturated group. Monomer m5 is preferably a monomer selected from vinylic and / or (meth)acrylic monomers. Preferably, it has at least two vinylic or at least two (meth)acrylic groups. Suitable difunctional monomers m5 are divinyl benzene (DVB), divinyl cyclohexane, diesters of diols with (meth)acrylic acid and diallyl and divinyl ethers of such diols as, e.g., ethanediol di(meth)acrylate, ethylene glycol dimethacrylate, 1 ,3-butylene glycol dimethacrylate, methallylmethacrylamide, allyl (meth)acrylate, 1 ,4-butanediol diacrylate (BDDA), 1 ,4-butanediol dimethacrylate, 1,5-pentanediol di(meth)acrylate, 1 ,6-hexandiol di(meth)acrylate, and methacrylic acid anhydride (MAA). Further suitable difunctionalized monomers m5 are PEG di(meth)acrylate, PPG di(meth)acrylate, polyglycerol di(meth)acrylates, polyurethane di(meth)acrylate resins and polyester di(meth)acrylates. Suitable polyfunctionalized monomers m5 are PEG bearing more than two (meth)acrylate groups, PPG bearing more than two (meth)acrylate groups, polyglycerols with more than two (meth)acrylate groups, polyurethanes with more than two (meth)acrylate groups and polyesters with more than two (meth)acrylate groups, polyesters of polyols with (meth)acrylic acid and the polyallyl and polyvinyl ethers of such polyols, trivinylbenzene, trivinylcyclohexane, trimethylolpropane tri(meth)acrylate, pentaerythritol tetraallyl ether and pentaerythritol tri(meth)acrylate.

[0125] Preferably, polymer P contains only monomeric units mu1 derived from the at least one (meth)acrylic monomer ml and no other monomeric units besides monomeric units ml, or contains monomeric units mu1 derived from the at least one (meth)acrylic monomer ml in an amount in a range of from 60 to 99 wt.-%, preferably of from 65 to 95 wt.-%, more preferably of from 70 to 90 wt.-%, and monomeric units mu2 derived from the at least one monomer m2 in an amount in a range of from 1 to 40 wt.-%, preferably of from 5 to 35 wt.-%, more preferably of from 10 to 30 wt.-%, or contains monomeric units mu1 derived from the at least one (meth)acrylic monomer ml in an amount in a range of from 40 to 99 wt.-%, preferably of from 50 to 95 wt.-%, more preferably of from 50 to 90 wt.-%, and monomeric units mu2 derived from the at least one monomer m2 in an amount in a range of from 1 to 60 wt.-%, preferably of from 5 to 50 wt.-%, more preferably of from 10 to 50 wt.-%, or contains monomeric units mu1 derived from the at least one (meth)acrylic monomer ml in an amount in a range of from 30 to 98 wt.-%, preferably of from 36 to 92 wt.-%, more preferably of from 44 to 86 wt.-%, monomeric units mu2 derived from the at least one monomer m2 in an amount in a range of from 1 to 35 wt.-%, preferably of from 4 to 32 wt.-%, more preferably of from 5 to 25 wt.-%, and monomeric units mu4 derived from the at least one monomer m4 in an amount in a range of from 1 to 50 wt.-%, preferably of from 2 to 45 wt.-%, more preferably of from 5 to 40 wt.-%.

[0126] The sum of all monomers used for preparing the polymer P, of course, adds up to 100 wt.-% in each case.

[0127] Preferably, the amounts of monomeric units mu1 in wt.-% exceeds the amounts of any monomeric units mu2 also present.

[0128] As outlined hereinbefore, preferably, an aqueous dispersion of at least one polymer P and at least one block copolymer BC is prepared first and then incorporated into the aqueous coating composition. Preferably, said aqueous dispersion is prepared in that the at least one (meth)acrylic monomer used for preparing the at least one polymer P is polymerized in the presence of the at least one block copolymer BC in water or an aqueous medium to form the aqueous dispersion of the at least one polymer P.

[0129] Preferably, the at least one block copolymer BC is used in an amount in a range of from 0.1 wt.-% to 9.0 wt.-%, more preferably of from 0.4 wt.-% to 4.0 wt.-%, even more preferably of from 1 .0 wt.-% to 2.0 % wt.-%, based in each case on the total weight of all monomers including the at least one (meth)acrylic monomer used for preparing the polymer P.

[0130] Preferably, the polymerization is an emulsion polymerization, more preferably an oil-in-water emulsion polymerization. The at least one (meth)acrylic monomer, which can be used as part of a monomer mixture for preparing polymer P, is preferably suitable to form an oil phase. Preferably, said oil phase is then emulsified, with the aid of the at least one block copolymer BC, into water or an aqueous medium as aqueous continuous phase, and the at least one (meth)acrylic monomer is then polymerized to form polymer P. Preferably, the first block B1 of the block copolymer BC is in the aqueous phase during and after polymerization, whereas the second block B2 of the block copolymer BC preferably is in the oil phase, said oil phase corresponding to the at least one (meth)acrylic monomer including a monomer mixture comprising said at least one (meth)acrylic monomer used for preparing polymer P during or before the polymerization and / or said oil phase corresponding to the at least one polymer P obtained in this manner after the polymerization.

[0131] Preferably, the polymerization is a free radical polymerization. Hence, preferably, one or more initiator compounds are used such as redox initiators and / or thermal initiators. Suitable thermal initiators are, e.g., dialkyl peroxides, hydroperoxides, peroxyesters, peroxyketals, diacylperoxides, peroxy(di)carbonates, persulphates and / or azo initiators. Redox initiators may include a reducing agent such as sodium sulfite, sulfur dioxide and an oxidizing compound such as ammonium persulphate or a suitable peroxide compound, such as tertiary butyl hydroperoxide.

[0132] Preferably, the polymerization is performed at a temperature in a range of from 5 to 100 °C, more preferably of from 40 to 95 °C.

[0133] Optional constituent a5) and optional constituent a6)

[0134] Preferably, the aqueous coating composition further comprises zinc cations as constituent a5). It has been found that the presence of zinc ions has a positive effect on the corrosion resistance.

[0135] Preferably, zinc cations are present in an amount in a range of from 5 to 5 000 mg / L, more preferably of from 7.5 to 2 500 mg / L, even more preferably of from 10 to 1 500 mg / L, still more preferably of from 12.5 to 1 000 mg / L, yet more preferably of from 15 to 500 mg / L, even more preferably of from 20 to 250 mg / L, in each case calculated as metal. Preferably, zinc cations as constituent a5) are present in combination with at least one complexing agent a6) in the composition, wherein a6) is suitable to complex constituent a5), and wherein a6) is preferably different from complexing agent a2), and wherein a6) is preferably selected from organic compounds bearing at least one kind of functional groups, which are able to coordinate to constituent a5) in water, more preferably is selected from organic compounds bearing at least one kind of functional groups selected from (i) carboxylic acids, salts thereof, derivatives, in particular esters, thereof, and mixtures thereof, (ii) sulfamic acids, (iii) phosphonic acid, phosphonates and derivatives of phosphonic acid such as esters thereof, (iv) polyols, in particular having two or more OH-groups, and (v) polyethyleneimines, and mixtures of (i) to (v). Carboxylic acids include polymeric carboxylic acids in each case and polyols include polymeric polyols in each case.

[0136] More preferably, the at least one complexing agent present as at least one constituent a6) is selected from (i) carboxylic acids, salts thereof, derivatives, in particular esters, thereof, and mixtures thereof, wherein the carboxylic acids include polymeric carboxylic acids in each case, and (iii) phosphonic acid, phosphonates and derivatives of phosphonic acid such as esters thereof, and mixtures thereof, even more preferably from iii) phosphonic acid, phosphonates and derivatives of phosphonic acid such as esters thereof, and mixtures thereof.

[0137] Exemplary suitable complexing agents a6) are HEDP (1-hydroxyethylidene-1,1-diphosphonic acid), EDTMP (ethylenediamine tetra(methylene phosphonic acid), aminotrimethylene phosphonic acid (ATMP), MGDA-Na3 (methylglycinediacetic acid trisodium salt), diethylene triamine penta(methylene phosphonic acid) (DTPMP), DTPA- Na5 (diethylenetriaminepentaacetic acid pentasodium salt), bishexamethylene triamine-penta(methylene phosphonic acid) (BHMTPMPA), trisodium N-(2-hydroxyethyl) ethylenediamine-N,N',N'-triacetate dihydrate (HEDTA), PBTC-Na4 (2-phosphonobutane-1 , 2, 4, -tricarboxylic acid tetrasodium salt), glutamic acid, N,N-diacetic tetrasodium salt (GLDA-Na4), glutamic acid, N,N-diacetic acid (GLDA), methyl glycine N, N-diacetic trisodium salt (MGDA-Naa), glucoheptonic sodium salt, diethylenetriaminepentaacetic acid (DTPA), dthylenediaminetetraacetic acid (EDTA), dthanoldiglycinic disodium salt (EDG-Na2), polyethyleneimines, amido sulfonic acid, and mixtures thereof. Most preferred are HEDP, EDTMP and ATMP.

[0138] Preferably, at least one suitable zinc containing precursor compound is used for generating zinc cations as constituent a5). Preferably, zinc oxide is used. Preferably, any kind of zinc phosphates are not used as precursor. More preferably, zinc oxide is reacted in water, prior to addition to the composition, in water with at least one suitable complexing agent a6) such as HEDP and / or ATMP, e.g., in a molar ratio of about 1 :1. Preferably, zinc oxide is used for the preparation of the aqueous coating composition such that the amount of zinc oxide used is in a range of from 0.1 to 2.0 wt.-%, more preferably of from 0.2 to 1 .5 wt.-%, even more preferably of from 0.3 to 1 .0 wt.-%, still more preferably of from 0.4 to 0.7 wt.-%, in each case based on the total weight of the composition.

[0139] Preferably, the aqueous composition comprises the at least one complexing agent present as constituent a6) in an amount of from 0.25 to 3.0 wt.-%, more preferably of from 0.5 to 2.5 wt.-%, based on the total weight of the composition. However, preferably constituent a5) is used in a complexed form thereof with the aid of the at least one complexing agent a6). Preferably, a complexed form of a5) by means of a6) is prepared first and then included into the composition. Preferably, complexing agent a6) is different from complexing agent a2).

[0140] Optional constituent a7)

[0141] At least one organosilane and / or at least one hydrolysis and / or condensation product is optionally present as constituent a7). Examples of hydrolysis and / or condensation products of organosilanes that can be formed in the presence of water are organosiloxanes and polyorganosiloxanes. The term "organo” in "organosilane” preferably means that at least one organic group is present, which is connected directly to a silicon atom via a carbon atom and can consequently not be subjected to hydrolysis.

[0142] Examples of suitable organosilanes are, e.g., aminoalkyltrialkoxysilanes, such as, preferably, 2- aminoethyltri methoxysilane, 2-aminoethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- aminopropyltriethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyltriethoxysilane, bis(2- ethyltrimethoxysilyljamine, bis(3-propyltrimethoxysilyl)amine, bis(4-butyltrimethoxysilyl)amine, bis(2- ethyltriethoxysilyljamine, bis(3-propyltriethoxysilyl)amine and / or bis(4-butyltriethoxysilyl)amine. Further examples of suitable organosilanes are 1 ,2-bis(triethoxysilyl)ethane, (3-mercaptopropyl)trimethoxysilane, (3- mercaptopropyljtriethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, (3-glycidyloxypropyl)triethoxysilane, and / or vinyltrimethoxysilane.

[0143] Preferably, at least one aminoalkyltrialkoxysilane and / or at least one hydrolysis and / or condensation product thereof is present as constituent a7).

[0144] Preferably, constituent a7) is present in the composition in such an amount that results in a content of Si in a range of from 1 or 5 to 500 mg / L, more preferably of from 7.5 to 250 mg / L, even more preferably of from 10 to 100 mg / L, still more preferably of from 20 to 80 mg / L, most preferably of from 25 to 50 mg / L, in each case calculated as elemental silicon. The amount of Si can be measured according to the method described in the ‘methods' section, i.e., by ICP-OES.

[0145] Further optional constituents

[0146] Optionally, the aqueous composition further comprises free and / or complex fluoride anions, e.g., in an amount in a range of from 0 or 1 mg / L to 500 mg / L, still more preferably of from 0 or 5 or 400 mg / L, yet more preferably of from 0 or 10 or 300 mg / L, even more preferably of from 0 or 15 to 200 mg / L, still more preferably of from 0 or 20 to 100 mg / L calculated in each case as fluorine. The free fluoride content is determined by means of a fluoride ion sensitive electrode according to the method disclosed in the ‘methods' section. These anions may be generated by adding water-soluble fluorine compounds, e.g., fluorides other than complex fluorides as well as hydrofluoric acid to the composition. However, as outlined hereinbefore, preferably no fluoride anions or essentially no fluoride anions of any kind are present.

[0147] Optionally, the aqueous coating composition further comprises at least one kind of metal cations selected from the group of cations of metals of the 1stto 3rdsubgroup (copper, zinc and scandium groups) and 5thto 8thsubgroup (vanadium, manganese and iron groups) of the periodic table of the elements including the lanthanides as well as the 2ndmain group of the periodic table of the elements (alkaline earth metal group), lithium and bismuth and / or tin, except of zinc ions, which may be present as constituent a5). More preferably, the aqueous composition further optionally comprises at least one kind of metal cations selected from the group consisting of cations of cerium and other lanthanides, iron, calcium, copper, cobalt, magnesium, manganese, molybdenum, niobium, tantalum, yttrium, vanadium, lithium, bismuth, and tin, and mixtures thereof.

[0148] Optionally, the aqueous coating composition further comprises at least one pH-value adjusting constituent, preferably selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid, phosphoric acid, acetic acid, aqueous ammonia, sodium hydroxide and sodium carbonate, wherein methanesulfonic acid and sodium carbonate are preferred. Depending on the pH value of the aqueous composition, the above constituent can be present in their fully or partially deprotonated form or in protonated forms.

[0149] The aqueous coating composition may further comprise at least one of the following constituents: one or more waxes, one or more wetting agents and one or more defoamers and / or rheology additives.

[0150] Optionally, the aqueous coating composition may comprise at least one water-soluble polymer such as a water- soluble polymer different from polymer P (and also block copolymer BC) having at least one kind of functional groups selected from acid groups, hydroxyl groups, and mixtures thereof. Preferably, the at least one water-soluble polymer if present is a homopolymer or copolymer obtainable from polymerization of at least one kind of ethy lenically unsaturated monomers, wherein at least part of said monomers bear at least one kind of functional groups selected from acid groups, hydroxyl groups, and mixtures thereof, more preferably is a homopolymer or copolymer obtainable from polymerization of at least one kind of vinyl monomers and / or (meth)acry lie monomers, wherein at least part of said monomers bear at least one kind of functional groups selected from acid groups, hydroxyl groups, and mixtures thereof.

[0151] Concentrate

[0152] A further subject-matter of the present invention is a concentrate for producing the aqueous coating composition according to one or more of the preceding claims by diluting the concentrate with water and if applicable, i.e., optionally, by adjusting the pH value. All preferred embodiments described above herein in connection with the aqueous coating composition and preferred embodiments thereof are also preferred embodiments of the concentrate.

[0153] The concentrate used to produce the aqueous coating composition typically contains the constituents of the aqueous coating composition to be produced in the desired proportions, but at a higher concentration. Such concentrate is diluted with water to the desired concentrations of the constituents as disclosed hereinbefore to form aqueous coating composition. If necessary, the pH value of the composition may be adjusted after dilution as well as outlined hereinbefore. Of course, it is also possible to further add any of the optional constituents of the composition to the water used for dilution or to add any of the optional or some of the necessary constituents after diluting the concentrate with water. It is, however, preferred that the concentrate already contains all necessary constituents.

[0154] Preferably, the aqueous coating composition is obtainable from a concentrate by dilution with water, preferably with deionized water, such that the concentrate is present in the composition after dilution in an amount of from 5 to 60 g / L, more preferably 10 to 40 g / L, even more preferably of from 15 to 30 g / L, based on the total weight of the composition (obtained after dilution of the concentrate).

[0155] Preferably, the concentrate is diluted with water in a weight ratio of 1 :5000 to 1 :10, more preferably of 1 :1000 to 1 : 10, even more preferably of 1 :300 to 1 :10, still more preferably of 1 : 150 to 1 : 10, yet more preferably of 1 :50 to 1 : 10, even more preferably of 1 :20 to 1 :5, most preferably of 1 :10 or 1 :5 to 1 :2, to produce the aqueous coating composition.

[0156] Preferably, aqueous coating composition can be prepared from a concentrate by dilution of the concentrate with water.

[0157] Uses

[0158] A further subject-matter of the present invention is a use of the aqueous coating composition according to the present invention for corrosion protection of metallic substrates, preferably after having applied the aqueous coating composition at least in portion onto a surface of an optionally pre-coated metallic substrate to form a coating film at least in portion on said surface, and / or a use of the at least one inventively used block copolymer BC as defined hereinbefore and hereinafter for stabilizing at least one inventively used polymer P as defined as defined hereinbefore and hereinafter in an aqueous coating composition according to the present invention, and / or a use of the at least one inventively used block copolymer BC as defined hereinbefore and hereinafter for improving and / or for establishing compatibility between at least one inventively used polymer P as defined hereinbefore and hereinafter and any inorganic constituents being present as well in an aqueous coating composition, preferably in an aqueous coating composition according to the present invention. All preferred embodiments described above herein in connection with the aqueous coating composition and the concentrate and in each case preferred embodiments thereof are also preferred embodiments of the aforementioned uses.

[0159] Coating method

[0160] A further subject-matter of the present invention is a method of coating of an optionally pre-coated metallic substrate comprising at least a step 1) and optionally also a step 2), namely

[0161] 1) applying the aqueous coating composition according to the present invention at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface, and

[0162] 2) optionally curing or drying the coating film obtained after step 1) to give a cured or dried coating layer, wherein the obtained cured or dried coating layer preferably has a dry film thickness below 2.0 m, more preferably below 1.0 pm.

[0163] All preferred embodiments described above herein in connection with the aqueous coating composition and the concentrate and the aforementioned uses and in each case preferred embodiments thereof are also preferred embodiments of the inventive method.

[0164] Optional steps performed prior to step 1 )

[0165] Prior to step 1) step A-1) as defined hereinafter can optionally be performed:

[0166] Step A-1): optionally cleaning and subsequently rinsing the surface of the substrate.

[0167] Substrate

[0168] The metallic substrate used in step 1) contains at least one surface, preferably at least one metallic surface. The term "metallic surface” in the sense of the present invention preferably means that the surface of the substrate used is at least partially made of at least one metal, i.e., that at least one region of said surface is made of at least one metal and / or alloy thereof. Preferably, the overall surface of the substrate is made of at least one metal and / or alloy thereof, more preferably, the whole substrate is made of at least one metal and / or alloy thereof, i.e., the substrate consists of at least one metal and / or alloy thereof. If a substrate comprises areas of different metals, such substrate is herein denoted as "multi-metallic substrate” as a subclass of metallic substrates. Such multi-metallic substrates can be subjected to step 1) of the chemical pretreatment method and can be coated in the same treatment bath

[0169] The at least one metallic surface of the substrate may be optionally pre-coated, such as with at least one zinc phosphating coating layer. Preferably, however, it is not pre-coated. Preferably, the substrate used is an electrically conductive substrate, which is used customarily and known to the skilled person. The substrate can have all sorts of geometry and shape such as coils, foils and sheets as well as represent parts such as automotive parts including vehicle parts such as wheel parts. Particularly suitable substrates are coils, e.g., for use in the appliance and coating industry.

[0170] Preferably, the at least one surface of the substrate is at least partially made of at least one metal and / or alloy thereof, more preferably is made at least partially of at least one of steel, steel alloys, aluminum, aluminum alloys, zinc, zinc alloys including zinc magnesium alloys, and mixtures thereof, even more preferably is made at least partially of at least one of steel and steel alloys. Examples of steel and / or steel alloys are bare steel, cold rolled steel (CRS), hot rolled steel (HRS), galvanized steel (zinc plated steel) such as hot dip galvanized steel (HDG), electrolytically galvanized steel (EG), alloy galvanized steel and aluminized steel such as, for example, Galvalume®, Galvannealed® or Galfan®, as well as steel coated at least in portion with at least one kind of zinc- aluminum-magnesium alloy (ZM). Examples of aluminum alloys are aluminum magnesium alloys, aluminum magnesium silicon alloys, aluminum copper alloys, aluminum zinc alloys, and aluminum zinc copper alloys. Examples of zinc alloys are Zn / Mg alloys and Zn / Ni alloys as well as Zn / Mg / AI alloys.

[0171] Step 1)

[0172] In step 1) the aqueous coating composition according to the present invention is applied at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface. By performing step 1) a coating film is formed on the surface of the substrate, which has been in contact with the aqueous coating composition.

[0173] The coating film obtained after step 1) is preferably suitable to provide a permanent coating (PC) layer such as the coating layer obtained after performance of step 2).

[0174] The term "at least in portion” preferably means in this context, in accordance with the general understanding of said term, that in some cases it might be desired or sufficient to contact not the whole surface of the substrate with aqueous coating composition. If only part of the metallic surface is contacted with the respective composition, it is typically the same part for all steps of the method. However, generally, it is desired to contact the whole surface of the metallic substrate with the aqueous coating composition.

[0175] The "contacting” according to step 1) can be a spraying, a dipping (immersing) or a roll coating (rolling) step. The aqueous coating composition can also be applied by flooding the surface or even manually by wiping or brushing. Preferred is roll coating.

[0176] The treatment time, i.e. , the period of time the surface is contacted with the aqueous coating composition in step 1), is preferably from 1 seconds to 20 minutes, more preferably from 15 or 30 seconds to 10 minutes, and most preferably 20 seconds to 5 minutes, as for example 20 seconds to 3 minutes. However, when the contacting step 1) is performed via roll coating, which is preferred, the treatment time is defined by the speed of the roll applied.

[0177] The temperature of the aqueous coating composition used in step 1) is preferably of from 5 to 50 °C, more preferably of from 15 to 45 °C or to 40 °C and most preferably from 25 to 35 °C.

[0178] The aqueous coating composition can be used as a dip coat bath. However, it can also be applied by virtually any conventional coating procedure like, e.g., spray coating, roll coating, brushing, wiping etc. as outlined above in connection with step 1). Most preferred is roll coating.

[0179] Optional step 1a)

[0180] In optional step a) the film obtained after step 1) is rinsed at least once with water or with at least one aqueous rinsing composition ARC, which is different from the aqueous coating composition. The term "rinsing” preferably means, in accordance with the general understanding of this term, a removal excessive parts of the aqueous coating composition, which was contacted with the surface in the step directly preceding the optional rinsing step. Preferably, however, no rinsing step 1 a) and more preferably no rinsing at all is performed after contacting step 1) has been carried out.

[0181] Tap water and / or deionized water can be used for rinsing in optional step 1 a). As outlined hereinbefore, optional step 1 a) can be performed more than once. It is hence possible, e.g., to perform a rinsing in step 1 a) once with tap water followed by rinsing with deionized water or vice versa.

[0182] Optional step 2)

[0183] In optional step 2) the film obtained after step 1) or after optional step 1 a) is dried or cured to give a cured or dried coating layer.

[0184] The drying or curing step 2) may be preferably performed (if performed at all), e.g., at a temperature in the range of 15°C to 180°C, more preferably at a temperature in the range of 25°C to 150°C, in particular at a temperature in the range of 50°C to 130°C. Temperature is in each case the peak metal temperature (PMT). "Drying” in the sense of the present invention means physical drying by evaporation of in particular water originally present in the composition(s) used, whereas "curing” further includes a chemical reaction between at least two constituents originally present in the composition(s) and / or between at least one constituent originally present in the composition(s) and a suitable functional group present on the metallic surface or in the conversion film, e.g., due to the presence of polymer P including its block B1 in the aqueous coating composition. Once a film is dried, the resulting product can be regarded as a layer.

[0185] Preferably, the obtained cured or dried coating layer has a dry film thickness in a range of from 0.1 to <2.0 pm, more preferably of from 0.3 to 1 .9 pm, in particular of from 0.5 to 1 .7 pm, most preferably of from 0.7 to 1 .5 pm. Preferably, when optional step 2) has been performed, the substrate comprises a cured or dried coating layer obtained after step 2), which has a coating weight of Zr (if Zr cations have been used as a1 )), calculated as metal, in a range of from 10 to 300 mg / m2, more preferably of from 10 to 75 mg / m2, of Ti (if Ti cations have been used as a1 )), and of Si, calculated as element, (if constituent a7 has been used), in a range of from 1 to 20 mg / m2, more preferably of from 2 to 15 mg / m2, even more preferably of from 4 to 15 mg / m2, determined in each case via XRF measurements.

[0186] Optional step 3)

[0187] The method may comprise an additional step 3), namely applying at least one further coating composition to the coating film present on the surface of the substrate obtained after step 1) or to the coating layer present on the surface of the substrate obtained after optional step 2) to form a further coating film layer upon the surface. Said at least one further coating composition is different from the aqueous coating composition applied in step 1).

[0188] The coating composition used in optional step 3) preferably comprises at least one polymer being suitable as binder. Preferably, the coating composition used in step 3) is a powder coating composition and is applied after step 2). Any conventional powder coating composition may be used in such a step. Alternatively, the coating composition used in step 3) can be, e.g., an electro-depositable coating composition. However, most preferably, the coating composition used in step 3) is a powder coating composition and is applied after step 2).

[0189] Coated substrate

[0190] A further subject-matter of the present invention is a substrate, which is a coated substrate being obtainable by the inventive coating method. Preferably, said coated substrate is a part or component, which can be used in appliance industry applications and ca, e.g., be used for construction of computer housings.

[0191] All preferred embodiments described above herein in connection with the aqueous coating composition and the concentrate and the aforementioned uses and the method in each case preferred embodiments thereof are also preferred embodiments of the inventive coated substrate. METHODS

[0192] 1. Solid content

[0193] The solid content (non-volatile content) was determined via DIN EN ISO 3251 :2019-09 at 110 °C for 60 min.

[0194] 2. pH pH measurements were done using the device "WTW pH 330 I” with the following pH electrode: "SI Analytics BlueLine 28 pH”. The calibration was done with three buffer solutions (traceable to SRM from NIST and PTB) with the following pH values: 4, 7, 10.

[0195] 3. Average particle size

[0196] The average particle size was determined by dynamic light scattering in accordance with DIN ISO 13321 (October 2004). In the context of the present invention, particle size refers to the measured average particle diameter (Z- average mean).

[0197] 4. Average molecular weight of polymers P and block copolymers BO

[0198] The number average molecular weight (Mn) was determined by means of gel permeation chromatography (GPC) in accordance with DIN 55672-1 (date: August 2007). Besides the number-average molecular weight, this method may also be used to determine the weight-average molecular weight (Mw) and also the polydispersity d (ratio of weight average molecular weight (Mw) to number-average molecular weight (Mn)). Tetrahydrofuran was used as eluent. The determination was made against polymethyl methacrylate standards. The column material consists of styrene-divinylbenzene copolymers.

[0199] 5. ICP-OES

[0200] The amounts of certain elements in a sample under analysis, such as of zirconium, titanium, hafnium etc., is determined using inductively coupled plasma atomic emission spectrometry (ICP-OES) according to DIN EN ISO 11885 (date: September 1 , 2009). A sample is subjected to thermal excitation in an argon plasma generated by a high-frequency field, and the light emitted due to electron transitions becomes visible as a spectral line of the corresponding wavelength and is analyzed using an optical system. There is a linear relation between the intensity of the light emitted and the concentration of the element in question. Prior to implementation, using known element standards (reference standards), the calibration measurements are carried out as a function of the particular sample under analysis. These calibrations can be used to determine concentrations of unknown solutions such as the concentration of the amount of titanium, zirconium, and hafnium.

[0201] 6. Free fluoride content determination

[0202] The free fluoride content was determined by means of a fluoride ion selective electrode. The electrode was calibrated using at least three master solutions with known fluoride concentrations. The calibration process resulted in the building of calibration curve. Then the fluoride content was determined by using of the curve. 7. Neutral salt spray (NSS) testing

[0203] The NSS test was used for determining the corrosion resistance of a coating on a substrate. In accordance with DIN EN ISO 9227:2017-07 the samples under analysis were positioned in a chamber in which there was continuous misting of a 5% strength sodium chloride salt solution at a temperature of 50 °C for a duration of 48, 72, and 96 or 144 hours with controlled pH. The spray mist deposited on the samples under analysis, covering them with a corrosive film of salt water. Each of the tests was performed three times and an average value was determined. The substrates were investigated with respect to formation of white rust. A coverage of the surface of an area <10 % of white rust is considered as good corrosion protection, whereas a coverage between 10 and 30 % is considered as being medium and a coverage of above 30% is considered as a fail.

[0204] 8. XRF (X-ray fluorescence spectroscopy)

[0205] XRF (X-ray fluorescence spectroscopy) was used for determining the coating weight in mg / m2of certain (tracer) element(s) such as Ti, Zr, Cu and / or Si in a layer such as the conversion layer resulting from applying the chemical pretreatment composition to a substrate. XRF analyses were performed on the following instruments: Panalytical Axios max or Malvern Panalytical Zetium. There was one calibration per substrate for the particular element required. The calibrations were based on the data of the ICP measurements (the surface of the panels used for calibration was detached and measured by ICP; ICP uses standards traceable to NIST). The samples were circular blanks with a diameter of 4 cm.

[0206] 9. Glass transition temperature

[0207] The glass transition temperature was measured by means of DSC measurements in accordance with DIN EN ISO 11357-2 (2019-03).

[0208] EXAMPLES

[0209] The following examples further illustrate the invention but are not to be construed as limiting its scope. Pbw means parts by weight and wt.-% means weight percents.

[0210] 1. Aqueous coating compositions

[0211] 1.1 A number of aqueous coating compositions according to the present invention or comparative aqueous coating compositions have been prepared from the constituents as listed in Table 1. C1 , C2 and C3 are each comparative compositions and 11 is an inventive composition

[0212] Table 1

[0213] A commercially available defoamer has been used. A commercially available glycol ether has been used. A commercially available silicone-based surface additive has been used. A commercially available wax dispersion has been used. A conventional and commercially available acrylic copolymer dispersion (Picassian® AC 055) has been used as acrylic copolymer dispersion. A conventional and commercially available polyurethane-polycarbonate dispersion (Alberdingk® CUD 4835) has been used as polyurethane-polycarbonate dispersion.

[0214] The preparation of aqueous precursors AP1 to AP4 will be described hereinafter in section 2. The preparation of aqueous polymer dispersions CAD1 (comparative) and AD1 as well as AD2 (inventive) will be described hereinafter in section 3.

[0215] 1.2 A number of further aqueous coating compositions according to the present invention or comparative aqueous coating compositions have been prepared from the constituents as listed in Table 2. C4 is a comparative composition and each of I2 and I3 is an inventive composition

[0216] Table 2

[0217] A commercially available defoamer has been used. A commercially available glycol ether has been used. A commercially available silicone-based surface additive has been used. A commercially available wax dispersion has been used. Tyzor® LA is a commercially available lactic acid chelated titanate. A conventional and commercially available acrylic copolymer dispersion (Picassian® AC 055) has been used as acrylic copolymer dispersion.

[0218] The preparation of aqueous precursors AP5 to AP7 will be described hereinafter in section 2.

[0219] The preparation of aqueous polymer dispersions CAD1 (comparative) and AD3 will be described hereinafter in section 3. 2. Aqueous precursors

[0220] A number of aqueous precursors have been prepared as intermediates, from which the aqueous coating compositions according to the present invention or comparative aqueous coating compositions have been prepared.

[0221] AP1 represents an aqueous precursor as intermediate, which had a solid content of 35.84 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organic titanate comprising titanium cations and an organic complexing agent for complexing said titanium cations, a commercially available organosilane, and deionized water, as well as inorganic acids in order to adjust the pH value of AP1 such that AP1 was acidic.

[0222] AP2 represents an aqueous precursor as intermediate, which had a solid content of 38.94 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organic titanate comprising titanium cations and an organic complexing agent for complexing said titanium cations, zirconium cations (added in the form of zirconium acetate), a commercially available organosilane, and deionized water, as well as inorganic acids and an organic acid in order to adjust the pH value of AP2 such that AP2 was acidic.

[0223] AP3 represents an aqueous precursor as intermediate, which had a solid content of 35.85 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organosilane, and deionized water, an aqueous ammonia solution, as well as an inorganic acid in order to adjust the pH value of AP3 such that AP3 was acidic (pH 2.6).

[0224] AP4 represents an aqueous precursor as intermediate, which had a solid content of 34.75 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organosilane, and deionized water, an aqueous ammonia solution, as well as an inorganic acid in order to adjust the pH value of AP4 such that AP4 was acidic (pH 2.4).

[0225] AP5 represents an aqueous precursor as intermediate, which had a solid content of 20.16 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organic titanate comprising titanium cations and an organic complexing agent for complexing said titanium cations (triethanolamine titanate), a commercially available organosilane, and deionized water, as well as inorganic acids and an organic acid in order to adjust the pH value of AP5 such that AP5 was acidic.

[0226] AP6 represents an aqueous precursor as intermediate, which had a solid content of 23.19 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organosilane, and deionized water, as well as inorganic acids and an organic acid in order to adjust the pH value of AP6 such that AP6 was acidic.

[0227] AP7 represents an aqueous precursor as intermediate, which had a solid content of 23.27 wt.-%, and contained zinc cations (added in the form of zinc oxide), HEDP as an organic complexing agent for said zinc cations, a commercially available organosilane, and deionized water, as well as an inorganic acid and an organic acid in order to adjust the pH value of AP7 such that AP7 was acidic.

[0228] 3. Synthesis of aqueous polymer dispersions AD1 , AD2 and CAD1

[0229] 3.1 Aqueous polymer dispersion CAD1 (comparative)

[0230] A 2-L stainless steel reactor equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet was charged with a mixture of water and Lutensit® AB-0 emulsifier, which is sulfosuccinate emulsifier. The mixture was heated to 80 °C and a solution of ammonium peroxodisulfate in water was added under stirring over the course of 50 min. 5 min later a monomer pre-emulsion feed consisting of water, Lutensit® AB-O, butyl acrylate and styrene was started over the course of 40 min. Polymerization was continued for 1 h. Water was then added to the dispersion and a second initiator feed of ammonium peroxodisulfate in water was added in parallel with the second monomer pre-emulsion feed consisting of water, Lutensit® AB-O, methyl methacrylate, butyl acrylate, allyl methacrylate and 1 ,6-hexamethylenedioldiacrylate over the course of 2 h. The reaction was then continued for 1 h before a third initiator feed of ammonium peroxodisulfate in water was added in parallel to the third monomer pre-emulsion feed consisting of water, Lutensit® AB-O, methacrylic acid, 2-hydroxyethylacrylate, butyl acrylate, Sipomer® PAM 100 (a commercially available phosphate ester of polyethylene glycol monomethacrylate) and methyl methacrylate over the course of 1 h. Polymerization was continued for 2 h before the resulting dispersion was cooled to room temperature. The resulting poly (meth)acrylate dispersion had a solid content of about 36 wt.-% and an average particle size of about 420 nm.

[0231] 3.2 Aqueous dispersions AD1 and AD3 (inventive)

[0232] A 2-L stainless steel reactor equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet was charged with a mixture of water and a block copolymer dispersion containing block copolymer BC1 to obtain a mixture 1. The preparation of block copolymer BC1 will be described hereinafter in section 4.1 An initiator feed consisting of ammonium peroxodisulfate in water was prepared. Part of the feed was added over a period of time to mixture 1. A monomer feed consisting of water, block copolymer dispersion containing BC1 , styrene, 2- hydroxyethylmethacrylate (HEMA), n-butylacrylate (n-BA) and methylmethacrylate (MMA) was shaken to form a pre-emulsion and continuously stirred. Part of the monomer feed was added to the mixture 1 over a certain period of time, starting sometime after the start of the initiator feed. The polymerization was continued for 30 min after the end of the feeds. The remaining initiator- and monomer feeds were then added simultaneously over the course of a certain period of time and the reaction was continued for another certain period of time before cooling to 40 °C. Each of the resulting poly(meth)acrylate dispersion was characterized by its solid content, average particle size, glass transition temperature Tg, and pH value.

[0233] 3.3 Aqueous dispersion AD2 (inventive)

[0234] A 2-L stainless steel reactor equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet was charged with a mixture of 460 g water and of the block copolymer dispersion containing BC2 to obtain a mixture 1. The preparation of block copolymer BC2 will be described hereinafter in section 4.2 An initiator feed consisting of 0.84 g ammonium peroxodisulfate in 93 g of water was prepared. 18.8 g of the feed were added over the course of 40 min to mixture 1. A monomer feed consisting of 142 g water, of block copolymer dispersion containing BC2, 104 g styrene, 30.7 g 2-hydroxyethylmethacrylate (HEMA), 184 g n-butylacrylate (n-BA) and 83 g methylmethacrylate (MMA) was shaken to form a pre-emulsion and continuously stirred. 30.6 g of the monomer feed were added to the mixture 1 over the course of 30 min, starting 5 min after the start of the initiator feed. The polymerization was continued for 30 min after the end of the feeds. The remaining initiator- and monomer feeds were then added simultaneously over the course of 3 h and the reaction was continued for another 2 h before cooling to 40 °C. The resulting poly(meth)acrylate dispersion had a solid content of around 34 wt.-% and an average particle size of about 330 nm.

[0235] 3.4 For preparation of AD1 to AD3, the amounts of monomers (styrene, HEMA, BA, and / or MMA) and / or the amount of block copolymer BC1 had been varied. The dispersions had a solid content between 30.0 and 40.0 wt.-%. The pH of the dispersions was between 1 .0 to 4.0.

[0236] AD1 had an average particle size of about 203 nm, a solid content of about 32.7 wt.-%, and a pH value of about 1.67. AD2 had an average particle size of about 479 nm, a solid content of about 28.8 wt.-%, and a pH value of about 1 .8. AD3 had an average particle size of about 360 nm, a solid content of 30.8 wt.-%, and a pH value of 4.63.

[0237] 4. Synthesis of block copolymers

[0238] 4.1 Block copolymer BC1 prepared via RAFT polymerization n-butyl acrylate (n-BA) was dissolved in ethanol in a 1-L three-necked flask equipped with a reflux condenser and a nitrogen inlet under an atmosphere of nitrogen. A solution of 2-mercaptopropionic acid methyl ester O-ethyl- dithiocarbonate in ethanol was added to the flask followed by a solution of 2,2-azobis(2-methylbutyronitile) in ethanol. The mixture was heated to about 75 °C for a certain period of time such as 4 h under stirring with a magnetic stir bar. Vinyl phosphonic acid (VPA) in ethanol was added to the solution followed by addition of 2,2- azobis(2-methylbutyronitrile) in ethanol. Stirring was continued at about 75 °C for a certain period of time such as 48 h. The synthesized block copolymer contained residual amounts of monomeric vinyl phosphonic acid, which were removed by precipitation from a suitable solvent to yield a solid block copolymer BC1. 4.2 Block copolymer BC2 prepared via ATRP polymerization

[0239] Step A: A 1 L four neck round bottom flask fitted with a nitrogen line, a condenser, an agitator, a heating mantle, and a thermocouple was charged with p-toluenesulfonyl chloride and 2-butanone. In a 20 mL sintered vial, tris(2- pyridyl-methyl)amine, anhydrous copper dichloride and ethanol were mixed and stirred to make a bluish green homogeneous solution of the catalyst, and the solution was added to the reaction flask. The mixture was heated under nitrogen blanket. When the temperature reached about 75 °C, 2,2'-azodi (2-methylbutyronitrile), dissolved in 2-butanone, was added to the flask at once. When the temperature increased to about 75 °C again, the monomer glycidyl methacrylate was fed to the reaction flask using a monomer pump. The feeding was done at 75 °C for a total of about 5 hours. After 2 hours a mixture of 2,2'-azodi(2-methylbutyronitrile) in 2-butanone was added in one portion. After the monomer feed was finished the temperature was held at about 75 °C for another 75 minutes.

[0240] Step B: At the end of step A, further 2-butanone was added at once. Temperature dropped slightly. When the temperature reached about 75 °C again, a mixture of 2,2'-azodi(2-methylbutyronitrile) in 2-butanone was added to the flask at once. The temperature dropped slightly, and it was allowed to reach to about 75 °C. At this point, a monomer mixture of n-butyl methacrylate (BMA), 2-hydroxyethylmethacrylate (HEMA) and butyl acrylate (BA) was fed at a constant rate over the course of about 4.5 h. A mixture of 2,2'-azodi(2-methylbutyronitrile) in 2-butanone was added and the polymerization was continued at about 75 °C for another 75 minutes. The monomer conversion reached >99% and was analyzed via NMR.

[0241] Step C: The resulting polymer solution from step B was mixed with a solution of phosphonic acid in 2-butanone in a 500 ml three necked flask equipped with a magnetic stirrer, a reflux condenser, a nitrogen inlet, and a thermometer. The mixture was heated to about 60 °C for 7 h before a mixture of diethanolamine in water was added. The 2-butanone was removed from the resulting mixture under reduced pressure to yield a block copolymer dispersion containing a block copolymer BC2 with approximately 16.5 wt.-% solid content.

[0242] 5. Coatings obtained from the aqueous coating compositions and properties thereof

[0243] 5.1 Each of the aqueous coating compositions described in section 1.1 hereinbefore was applied to the surface of a panel made of galvanized steel (HDG) at room temperature (23 °C) using a blade doctor or roll coater. The coated substrates were then dried at a peak metal temperature of 60 °C (oven temperature 210 °C) for about 10 s. The resulting permanent coatings had a dry layer film thickness of about 1.2 pm as measured by XRF using a tracer element. The coating weights were in a range of from 1.1 to 1.2 g / m2. The coated substrates obtained were then subjected to a NSS test as described in the ‘methods’ section. The results are displayed in Table 3. Table 3 nd = not determined

[0244] 5.2 Each of the aqueous coating compositions described in section 1.2 hereinbefore was applied to the surface of a panel made of galvanized steel (HDG) at room temperature (23 °C) using a blade doctor or roll coater. The coated substrates were then dried at a peak metal temperature of 60 °C (oven temperature 210 °C) for about 10 s. The resulting permanent coatings had a dry layer film thickness of about 1.2 pm as measured by XRF using a tracer element. The coating weights were in a range of from 1.1 to 1.2 g / m2. The coated substrates obtained were then subjected to a NSS test as described in the ‘methods' section. The results are displayed in Table 4.

[0245] Table 4 nd = not determined

Claims

CLAIMS1. An aqueous coating composition comprising, besides water, at least constituents a1), a2), a3, and a4), which are different from one of another, namely at least one of zirconium, titanium, and hafnium cations as constituent a1), at least one complexing agent as constituent a2), which is suitable to complex constituent a1), at least one polymer P as constituent a3), which is obtainable from a polymerization of at least one (meth)acrylic monomer in the presence of at least one block copolymer BC, and at least one block copolymer BC as constituent a4), in which presence the polymerization of the at least one (meth)acrylic monomer for preparing the at least one polymer P has taken place, wherein said block copolymer BC contains at least two blocks B1 and B2, which are different from one another, the first block B1 comprising structural units SU1 , wherein at least a part of these structural units SU1 contains at least one phosphorous containing moiety, and the second block B2 comprising structural units SU2, which are obtainable from a polymerization of at least one (meth)acrylic monomer, which is identical to or different from the at least one (meth)acrylic monomer used for preparing the at least one polymer P, wherein block B2 contains only monomeric units derived from at least one non-functionalized (meth)acrylic monomer and no other monomeric units besides said monomeric units.

2. The composition according to claim 1 , characterized in that it is an aqueous acidic coating composition, which preferably has a pH value in a range of from 0.1 to <7.0, more preferably of from 0.5 to 6.5, even more preferably of from 1 .0 to 6.0, yet more preferably of from 1 .5 to 5.5, still more preferably of from 2.0 or 5.0.

3. The composition according to claim 1 or 2, characterized in that at least one of zirconium and titanium cations, preferably titanium cations, are present as constituent a1), and / or in that the composition comprises the at least one of zirconium, titanium, and hafnium cations as constituent a1) in an amount in a range of from 5 to 50 000 mg / L, more preferably of from 7.5 to 40 000 mg / L, even more preferably of from 10 to 30 000 mg / L, still more preferably of from 12.5 to 20 000 mg / L, yet more preferably of from 15 to 10 000 mg / L, even more preferably of from 20 to 8 000 mg / L, still more preferably of from 25 to 6 000 mg / L, most preferably of from 50 to 3 000 mg / L, in each case calculated as metal.

4. The composition according to one or more of the preceding claims, characterized in that the at least one phosphorous containing moiety of at least a part of the structural units SU1 of the first block B1 of the block copolymer BC is part of a functional group being present, preferably within a or as a side chain, in each structural SU1 , which contains the at least one phosphorous containing moiety, wherein the at least one phosphorous containing moiety is preferably selected from phosphonic acid groups, phosphonic acid ester groups (at least partially esterified phosphonic acid groups), at least partially esterified phosphoric acid groups, and salts of each of these groups, more preferably is selected from phosphonic acid groups and salts thereof, and / or in that the at least one phosphorous containing moiety of the structural units SU1 is (I) part of the side chains of the structural units SU1 and is, within each structural unit SU1 , separated from the main chain of the block copolymer BC by at least one carbon atom, or, (II) represents the side chains of the structural units SU1 and is, within each structural unit SU1 , directly bound to the main chain of the block copolymer BC, preferably by means of a P-C-single bond, preferably represents the side chains of the structural units SU1 and is, within each structural unit SU1 , directly bound to the main chain of the block copolymer BC, more preferably by means of a P-C-single bond.

5. The composition according to one or more of the preceding claims, characterized in that each structural unit SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety, preferably such that the first block B1 of the block copolymer BC is a poly (vinyl phosphonic acid), or in that only a part of the structural units SU1 of the first block B1 of the block copolymer BC contains the at least one phosphorous containing moiety and the remaining part of the structural units SU1 of the first block B1 of the block copolymer BC contains at least one carboxylic acid group or a salt thereof, preferably such that the first block B1 of the block copolymer BC is a poly(vinyl phosphonic acid-co- (meth)acrylic acid), or in that the remaining part contains at least one OH-group, preferably when the remaining part of structural units SU1 of the first block B1 of the block copolymer BC is derivable from at least one OH-group(s) containing hydrophilic monomer.

6. The composition according to one or more of the preceding claims, characterized in that the number average molecular weight of the first block B1 of the block copolymer BC is in a range of from 200 to 4 000 g / mol, preferably of from 300 to 3 000 g / mol, more preferably of from 400 to 2 000 g / mol, and / or in that the number average molecular weight of the second block B2 of the block copolymer BC is in a range of from 200 or 300 to 6 000 g / mol, preferably of from 300 or 400 to 5 000 g / mol, more preferably of from 400 or 500 to 4 000 or 3 000 g / mol, wherein the number average molecular weight of the second block B2 preferably exceeds the number average molecular weight of the first block B1 , and / or in that the number average molecular weight of the block copolymer BC per se is in a range of from 500 to 10 000 g / mol, preferably of from 600 to 8 000 g / mol, more preferably of from 800 to 6 000 g / mol, and / or in that the amount of the first block B1 of the block copolymer BC is in a range of from 70.0 to 30.0 wt.-%, preferably of from 65.0 to 35.0 wt.-%, more preferably of from 60.0 to 40.0, based on the total weight of the block copolymer BC, and / or in that the amount of the second block B2 of the block copolymer BC is ina range of from 30.0 wt.-% to 70.0 wt.-%, more preferably of from 35.0 wt.-% to 65.0 wt.-%, even more preferably of from 40.0 to 60.0 wt.-%, based on the total weight of the block copolymer BC, and / or in that the block copolymer BC is composed of the two blocks B1 and B2 and does not contain any further blocks and / or in that the copolymer BC is bound, preferably bound in a non-covalently manner, to at least part of the polymer P by means of at least part of its block B2.

7. The composition according to one or more of the preceding claims, characterized in that the at least one polymer P is a (meth)acrylic homopolymer in case precisely one kind of (meth)acrylic monomers is used for the polymerization, or is a (meth)acrylic copolymer in case at least two kinds of (meth)acrylic monomers, which are different from one another, or at least one kind of (meth)acrylic monomers and at least one kind of further monomers is used for the polymerization, wherein said at least one kind of further monomers are ethy lenical ly unsaturated monomers, which are not (meth)acrylic monomers, and / or in that the at least one polymer P comprises at least one kind of functional groups, preferably selected from functional groups, which are reactive towards isocyanate groups, more preferably selected from OH- groups, amino groups, and thiol groups, even more preferably selected from OH-groups, and / or in that the at least one polymer P is present in the aqueous coating composition in form of a polymeric core and wherein the at least one block copolymer BC is bound, preferably bound in a non-covalently manner, to at least part of the surface of said polymeric core by means of at least part of its block B2.

8. The composition according to one or more of the preceding claims, characterized in that the at least one polymer P is present in the aqueous coating composition in an amount in a range of from 90.0 wt.-% to 99.9 wt.-%, preferably of from 95.0 wt.-% to 99.5 wt.-%, more preferably of from 98.0 wt.-% to 99.0 %, based on the total weight of the sum of polymer P and block copolymer BC, and / or in that the at least one block copolymer BC is present in the aqueous coating composition in an amount in a range of from 0.1 wt.-% to 10.0 wt.-%, preferably of from 0.5 wt.-% to 7.5 or to 5.0 wt.-%, more preferably of from 1 .0 wt.-% to 2.5 or to 2.0 wt.-%, based on the total weight of the sum of polymer P and block copolymer BC.

9. The composition according to one or more of the preceding claims, characterized in that it is free or essentially free of complex fluoride anions and of free fluoride anions.

10. The composition according to one or more of the preceding claims, characterized in that the at least one complexing agent a2), which is suitable to complex constituent a1), is selected from organic compounds bearing at least one kind of functional groups, which are able to coordinate to constituent a1) in water, preferably is selected from organic compounds bearing at least one kind of functional groups selected from OH-groups, carboxylic acid groups, salts and / or derivatives such as esters thereof, and mixtures thereof, more preferably is selected from organic compounds bearing at least one OH-group and at least one carboxylic acid group and / or salts and / or derivatives such as esters thereof.11 . The composition according to one or more of the preceding claims, characterized in that further comprises zinc cations as constituent a5), preferably in an amount in a range of from 5 to 5000 mg / L, more preferably of from 7.5 to 2 500 mg / L, even more preferably of from 10 to 1 500 mg / L, still more preferably of from 12.5 to 1 000 mg / L, yet more preferably of from 15 to 500 mg / L, even more preferably of from 20 to 250 mg / L, in each case calculated as metal, wherein the zinc cations as constituent a5) are preferably present in combination with at least one complexing agent a6), which is suitable to complex constituent a5), which is preferably different from complexing agent a2), and which is preferably selected from organic compounds bearing at least one kind of functional groups, which are able to coordinate to constituent a5) in water, more preferably is selected from organic compounds bearing at least one kind of functional groups selected from (I) carboxylic acids, salts thereof, derivatives, in particular esters, thereof, and mixtures thereof, (II) sulfamic acids, (ill) phosphonic acid, phosphonates and derivatives of phosphonic acid such as esters thereof, (iv) polyols, in particular having two or more OH-groups, and (v) polyethyleneimines, and mixtures of (I) to (v).

12. A concentrate for producing the aqueous coating composition according to one or more of the preceding claims by diluting the concentrate with water and optionally by adjusting the pH value.

13. A use of the aqueous coating composition according to one or more of claims 1 to 11 for corrosion protection of metallic substrates, preferably after having applied the aqueous coating composition at least in portion onto a surface of an optionally pre-coated metallic substrate to form a coating film at least in portion on said surface, and / or a use of the at least one block copolymer BC as defined in one or more of claims 1 and 4 to 6 for stabilizing at least one polymer P as defined in one or more of claims 1 , 7 and 8 in an aqueous coating composition as defined in one or more of claims 1 to 11 , and / or a use of the at least one block copolymer BC as defined in one or more of claims 1 and 4 to 6 for improving and / or for establishing compatibility between at least one polymer P as defined in one or more of claims 1 , 7 and 8 and any inorganic constituents being present as well in an aqueous coating composition, preferably in an aqueous coating composition as defined in one or more of claims 1 to 11.

14. A method of coating of an optionally pre-coated metallic substrate comprising at least a step 1) and optionally also a step 2), namely1) applying the aqueous coating composition according to one or more of claims 1 to 11 at least in portion onto at least one surface of at least one metallic substrate to form a coating film at least in portion onto said surface, and2) optionally curing or drying the coating film obtained after step 1) to give a cured or dried coating layer, wherein the obtained cured or dried coating layer preferably has a dry film thickness below 2.0 pm.

15. A substrate, which is a coated substrate being obtainable by the method according to claim 14.

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