Coating systems with increased jetness and improved color

Abstract

The present invention relates to a method for producing a multilayer coating system on a substrate, comprising the steps of applying a basecoat composition containing at least one organic black pigment to the substrate and forming a first coating film (1) thereon, optionally subsequently applying a second basecoat composition and forming a second coating film (2) adjoining the first coating film, and applying a colored topcoat composition to the first coating film (3a) without carrying out optional step (2) or applying a clearcoat composition to the second coating film in the case of carrying out optional step (2), wherein neither the second basecoat nor the topcoat or clearcoat composition comprises any black pigment, and wherein the second basecoat composition - in the case of carrying out steps (1), (2) and (3b) - or the topcoat composition - in the case of carrying out steps (1) and (3a) - comprises at least one non-black colored pigment having a volume average particle size of <1000 nm incorporated therein in the form of a pigment paste in an amount in the range of 0.01-7.50% by weight, based on its total solids content, as well as a multilayer coating system and a coated substrate obtainable therefrom.

Description

[0001] The present invention relates to a method for producing a multilayer coating system on a substrate, comprising the steps of applying a basecoat composition containing at least one organic black pigment to the substrate and forming a first coating film (1) thereon, optionally subsequently applying a second basecoat composition and forming a second coating film (2) adjoining the first coating film, and applying a colored topcoat composition to the first coating film (3a) without carrying out optional step (2) or applying a clearcoat composition to the second coating film in the case of carrying out optional step (2), wherein neither the second basecoat nor the topcoat or clearcoat composition comprises any black pigment, and wherein the second basecoat composition - in the case of carrying out steps (1), (2) and (3b) - or the topcoat composition - in the case of carrying out steps (1) and (3a) - comprises at least one non-black colored pigment having a volume average particle size of <1000 nm incorporated therein in the form of a pigment paste in an amount in the range of 0.01 to 7.50% by weight, based on its total solids content, as well as a multilayer coating system and a coated substrate obtainable therefrom. Background of the Invention

[0003] Especially in automotive coatings, dark colors such as black are desirable for aesthetic purposes. However, dark coatings tend to absorb near-infrared radiation because they often rely on the use of pigments that absorb near-infrared (NIR) radiation in addition to visible radiation, such as carbon black. Heat is a result of absorbing near-infrared radiation, and dark coatings are therefore prone to significant temperature increases. Attempts have been made to replace carbon black with organic black pigments, such as perylene pigments, to reduce heat generation. However, a problem associated with this is that the jetness of black achieved using such systems is generally lower than that achieved with carbon black, which is undesirable.

[0004] JP 2014-210856 A discloses a coating composition comprising a black pigment that reflects and / or transmits infrared (IR) radiation and a transparent blue pigment, combined in a single composition having a low lightness L*. The coating composition is used to apply a basecoat film to a substrate. A clearcoat composition is then applied thereon. JP 2014-210856 A aims to provide a coating having both a black color and heat-insulating properties.

[0005] Similarly, WO 2012 / 170230 A1 (US 2012 / 0308724 A1) relates to a coating composition comprising at least two visibly absorbing, infrared-transparent pigments combined in a single composition for producing a coating having a jetness of at least 240. This includes a blend of a non-black pigment with an IR-transparent black pigment in a basecoat to increase the jetness of the resulting coating. WO 2012 / 170230 A1 is directed to providing a coating that is deep black and transparent to IR radiation.

[0006] US 2008 / 0187708 A1 also relates to a dark-colored coating system comprising a first layer containing an IR-reflecting pigment and a dark-colored second layer, the latter being substantially transparent to IR radiation and comprising a tinting agent containing nanoparticle pigments, in particular a blend thereof. US 2008 / 0187708 A1 aims to provide a coating having a dark color and minimal absorption of radiation in the near-infrared spectrum.

[0007] WO 2013 / 037928 A1 discloses a coating formed on a substrate, comprising, inter alia, organic and / or inorganic pigments, such as NIR-transparent pigments, and a dye having a transmittance of at least 75% in the range of 700-2500 nm. WO 2013 / 037928 A1 is directed to providing a coating having high brightness and improved jetness and chromaticity properties. However, the use of the dyes disclosed in WO 2013 / 037928 A1 generally results in poor durability, and any color improvement achieved is generally diminished upon exposure to UV light.

[0008] While the use of pigment blends in basecoats, such as those disclosed in WO 2012 / 170230 A1 and US 2008 / 0187708 A1, can positively influence jetness values, the jetness of the resulting coatings is not always sufficient and, in particular, remains below that achieved with corresponding carbon black-containing coatings. Furthermore, the visual appearance of these basecoats is not always adequate and, in particular, remains inferior to that of carbon black-containing basecoats upon visual inspection. Specifically, prior art coatings often exhibit an undesirable brownish / reddish undertone. Furthermore, the brightness of the coatings is often still too high.

[0009] Therefore, there is a need to provide coatings and coating systems which exhibit an improved blackness compared to the coatings and coating systems known in the prior art. At the same time, these coatings and coating systems should have an excellent visual appearance, an improved color and in particular should not exhibit an undesirable brownish / reddish undertone.

[0010] question

[0011] The object of the present invention was therefore to provide coatings and coating systems which exhibit an improved degree of blackness compared to the coatings and coating systems known from the prior art and at the same time have an excellent visual appearance, have an improved color and in particular do not exhibit any undesirable brownish / reddish undertones.

[0012] Solution

[0013] This object is solved by the subject matter of the present application claims and its preferred embodiments disclosed in the present description, ie the subject matter described herein.

[0014] A first subject of the present invention is a method for producing a multilayer coating system on an optionally precoated substrate, comprising at least steps (1) and (3a) or at least steps (1), (2) and (3b), namely:

[0015] (1) applying a colored base coating composition to an optionally pre-coated substrate and forming a first coating film on the optionally pre-coated substrate, wherein the base coating composition comprises at least one black organic pigment,

[0016] (2) optionally applying a second colored base coating composition different from the base coating composition applied in step (1) to the first coating film existing on the substrate obtained after step (1) and forming a second coating film adjacent to the first coating film, and

[0017] (3a) applying a coating composition different from the composition applied in step (1) and in optional step (2) to the first coating film existing on the substrate obtained after step (1) without carrying out optional step (2) and forming a second coating film adjacent to the first coating film, wherein the coating composition is a colored topcoat composition, or

[0018] (3b) applying a coating composition different from the compositions applied in step (1) and in optional step (2) to the second coating film existing on the substrate obtained after step (2) while carrying out optional step (2) and forming a third coating film adjacent to the second coating film, wherein the coating composition is a clear coating composition,

[0019] wherein the second coating film obtained after step (3a) or the third coating film obtained after step (3b) is the outermost film of the formed multi-layer coating system,

[0020] Characterized in that neither the second basecoat composition applied in optional step (2) nor the coating composition applied in step (3a) or (3b) comprises any black pigments and that in addition—in the case of carrying out steps (1), (2) and (3b)—the second basecoat composition or—in the case of carrying out steps (1) and (3a)—the topcoat composition comprises at least one non-black coloring pigment with a volume average particle size of <1000 nm in an amount in the range of 0.01 to 7.50% by weight, in each case based on the total solids content of the respective composition, wherein the at least one non-black coloring pigment is in each case incorporated into the respective composition in the form of a pigment paste.

[0021] A further subject matter of the present invention is a multilayer coating system on an optionally precoated substrate, characterized in that it is obtainable by the process according to the invention.

[0022] The present invention further provides a coated substrate obtainable by the process according to the invention.

[0023] The present invention further provides for the use of a pigmented coating composition which does not comprise any black pigments and comprises at least one non-black pigmented pigment having a volume average particle size of <1000 nm in an amount in the range of 0.01 to 7.50% by weight, based on the total binder solids content of the coating composition, wherein the at least one non-black pigmented pigment is incorporated into the coating composition in the form of a pigment paste.

[0024] As a second basecoat composition in step (2) of the method for preparing a multi-layer coating system on an optionally precoated substrate as defined in the method of the present invention or as a topcoat composition in step (3a), the blackness (Mc) of the multi-layer coating system obtained after curing is increased to an extent that the blackness (Mc) exceeds the blackness (My) of the cured multi-layer coating system.

[0025] In particular, it has been surprisingly found that an excellent blackness (Mc) can be achieved by the method according to the invention and the multi-layer coating system according to the invention. This is particularly useful in the case of IR-reflecting black pigments, since currently available pigments and the resulting conventional coatings are not as black as standard carbon black pigments, the use of which is undesirable.

[0026] It was particularly surprising to find that by coloring the clearcoat composition used in the 2C1B process to form a topcoat composition with the non-black colored pigments used in the present invention or by coloring the second basecoat composition in the 3C1B process which does not contain any black pigment with the non-black colored pigments used in the present invention, wavelengths of light can be absorbed which would otherwise be reflected by the black pigments present in the (first) basecoat used in both the 2C1B and 3C1B processes, which in turn would lead to undesirable color properties.

[0027] In particular, it was surprisingly found that not only the overall blackness (Mc) of the multi-layer coating according to the invention can be improved, but also to such an extent that the blackness (Mc) value of the coating exceeds the black value (My), so that due to the positive value of the background color dM > 0 (dM = Mc-My), no light red / brown background color is achieved, but a background color of a different color, for example a blue or light blue or green or light green or purple or light purple background color, depending on the type of the at least one non-black coloring pigment used.

[0028] Surprisingly, the use of a clearcoat colored with the non-black pigments used in the present invention and / or a correspondingly colored second basecoat provides a rapid and unique method to increase the jetness (Mc) of black pigments, particularly solid black pigments, by increasing the absorption of target wavelengths in the visible spectrum. This strategy enables higher percent absorption of all wavelengths in the visible spectrum, resulting in deeper blacks. These deeper blacks are different from the prior art methods for coloring the basecoat, such as the 2C1B method disclosed in WO 2012 / 170230 A1.

[0029] Surprisingly, it has been found that the incorporation of non-black coloring pigments used in the present invention into a coating film present on top of an organic black pigment-containing basecoat layer can significantly improve both the black color (My) and the degree of blackness (Mc) to at least equal or, in particular, exceed that of carbon black. At the same time, a significant reduction in heat generation can be observed, which is not possible with basecoats containing carbon black.

[0030] In particular, it has further surprisingly been found that the lightness (L*) and especially the b* color value of the multilayer coatings according to the invention can be improved, ie minimized / shifted towards zero or below zero.

[0031] The present invention discloses that the present invention can improve the visual effect of blackness by the pigment blend that comprises black pigment and black base coating.Especially find that as disclosed in WO 2012 / 170230 A1, extra pigment is added in the black base coating, promptly in single base coating, use the pigment blend that comprises black pigment to improve blackness and do not obtain acceptable result.Although can increase blackness value in some cases, fully improve the visual effect of blackness.Yet surprisingly, when to form the used topcoat composition in the 2C1B method to be applied to on the black base coating film with non-black coloring pigment colored this clear coating composition used by the present invention and / or by to be applied to on the black base coating film with non-black coloring pigment colored second base coating composition in the 3C1B method that does not contain any black pigment, can significantly improve this visual effect.This will be described in detail in the test section and for example be summarized in the 6th. item of the test section.

[0032] In particular, it was surprisingly found that by pigmenting the clearcoat composition used in the 2C1B process with the pigments used according to the invention to form a topcoat composition or by pigmenting the second basecoat composition in the 3C1B process which does not contain any black pigment with the pigments used according to the invention, not only the blackness of the entire coating is increased and not only to the extent that the blackness value exceeds the black value, but also the color depth is simultaneously reduced, which is desirable (compared to coating systems containing a first black basecoat and having an unpigmented clearcoat or no midcoat, i.e. no second basecoat), contrary to what was intended to be achieved according to WO 2013 / 037928 A1. Detailed Description of the Invention

[0034] The term "comprising" in the sense of the present invention, for example with respect to the coating composition used in the method of the present invention, preferably has the meaning of "consisting of". For example, for the second basecoat composition or the topcoat coating composition, in addition to all the essential components present therein, one or more further components indicated below and optionally included therein may also be included therein. All components may in each case be present in their preferred embodiments as shown below.

[0035] The proportions and amounts of any ingredients given below that are present in the respective coating composition in % by weight (wt %) add up to 100 wt %, based in each case on the total weight of the respective composition.

[0036] The coating compositions used in steps (1), (2), (3a) and (3b) may contain, depending on the desired application, in addition to the additional ingredients described in more detail below, one or more customary additives. For example, the coating compositions may, independently of one another, comprise at least one additive selected from the group consisting of reactive diluents, light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, plasticizers, free radical polymerization initiators, adhesion promoters, flow control agents, film-forming aids, sag control agents (SCAs), flame retardants, corrosion inhibitors, driers, thickeners, biocides and / or matting agents. These may be used in known and customary proportions. Preferably, their content is 0.01-20.0% by weight, more preferably 0.05-15.0% by weight, particularly preferably 0.1-10.0% by weight, most preferably 0.1-7.5% by weight, in particular 0.1-5.0% by weight, and most preferably 0.1-2.5% by weight, based on the total weight of the coating composition.

[0037] Method of the present invention

[0038] The method of the present invention is a method for producing a multilayer coating system on an optionally precoated substrate, comprising at least steps (1) and (3a) or at least steps (1), (2) and (3b).

[0039] Preferably all of these steps are performed via spraying.

[0040] The first and second coating films or the first, second and third coating films formed on the optionally precoated substrate by performing at least steps (1) and (3a) or at least steps (1), (2) and (3b) are preferably uncured coating films at this stage. Therefore, the coating composition applied in each of these steps is preferably applied wet-on-wet.

[0041] The method according to the invention is particularly suitable for coating automobile bodies or parts thereof, including corresponding metal substrates, but also plastic substrates such as polymer substrates. Therefore, preferred substrates are automobile bodies or parts thereof.

[0042] Suitable metal substrates for use according to the invention are all substrates commonly used and known to the skilled worker. The substrates used according to the invention are preferably metal substrates, more preferably selected from steel, preferably steel selected from bare steel, cold-rolled steel (CRS), hot-rolled steel, galvanized steel, such as hot-dip galvanized steel (HDG), alloyed galvanized steel (e.g., Galvalume, Galvannealed, or Galfan), and aluminized steel, aluminum and magnesium, as well as Zn / Mg alloys and Zn / Ni alloys. Particularly suitable substrates are vehicle body parts or complete production vehicles.

[0043] Preferably, thermoplastic polymers are used as plastic substrates. Suitable polymers are poly(meth)acrylates, including polymethyl(meth)acrylate, polybutyl(meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyesters, including polycarbonate and polyvinyl acetate, polyamides, polyolefins such as polyethylene, polypropylene, polystyrene and also polybutadiene, polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymer (A-EPDM), ASA (acrylonitrile-styrene-acrylate copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), polyetherimide, phenolic resins, urea resins, melamine resins, alkyd resins, epoxy resins, polyurethanes, including TPU, polyetherketone, polyphenylene sulfide, polyethers, polyvinyl alcohol and mixtures thereof. Particularly preferred are polycarbonate and poly(meth)acrylate.

[0044] The substrate used according to the invention is preferably a metal substrate pretreated with at least one metal phosphate, such as zinc phosphate, and / or with at least one oxalate. Such a pretreatment by phosphating—usually carried out after the substrate has been cleaned and before the substrate is coated by electrodeposition—is a customary pretreatment step, in particular, in the automotive industry.

[0045] As mentioned above, the substrate used can be a pre-coated substrate, i.e. a substrate with at least one cured coating film. The substrate used in step (1) can be pre-coated with a cured electrodeposition coating. The substrate can, for example, additionally or alternatively be provided with at least one cured or uncured primer coating as at least one additional pre-coating layer. The term "primer" is known to those skilled in the art. The primer is usually applied after the substrate has been provided with a cured electrodeposition coating. In the case where a cured primer coating film is also present, the cured electrodeposition coating film is present below and preferably adjacent to the cured primer coating film. The curing of the primer can be carried out at a temperature in the range of 40-140°C and can in particular include a "low temperature baking" step at a temperature in the range of 80-100°C. As mentioned above, substrates provided with an uncured primer coating film can also be used, in particular substrates such as metal substrates with a cured electrodeposition coating film, on which the uncured primer coating film is present. Therefore, the method of the present invention may include an additional step to be carried out before step (1), according to which the primer composition is applied to an optionally pre-coated substrate and a primer coating film is formed on the optionally pre-coated substrate. Step (1) of the method of the present invention is then preferably carried out before curing of the primer coating film, optionally and preferably after a drying period, such as a drying period of 1 to 20 minutes, preferably at a temperature not exceeding 40° C., such as at a temperature in the range of 18 to 30° C.

[0046] The basecoat compositions applied in step (1) and optional step (2) are each preferably aqueous, i.e., waterborne coating compositions, while the coating compositions applied in step (3a) or (3b) are preferably non-aqueous, i.e., solventborne (organic solvent-based). However, as described in more detail below, the basecoat compositions applied in step (1) and optional step (2) may alternatively be solventborne basecoat compositions. Similarly, the coating compositions applied in step (3a) or (3b) may also be aqueous. Preferably, the basecoat compositions applied in step (1) and optional step (2) are 1K (single component) or 2K (two component) compositions, more preferably 1K compositions. Preferably, the coating compositions applied in step (3a) or (3b) are 1K or 2K compositions, more preferably 2K compositions.

[0047] The term "solvent-based" or "non-aqueous" is preferably understood for the purposes of the present invention to mean that an organic solvent as solvent and / or diluent is present as the main component of all solvents and / or diluents present in the coating composition applied in step (3a) or (3b) - if these are solvent-based - or in any of the basecoat compositions - if at least one of these is solvent-based - and preferably also in any pigment slurry used to prepare said composition, preferably in an amount of at least 35% by weight, based on the total weight of the coating composition. The coating composition applied in step (3a) or (3b) preferably comprises a proportion of organic solvent of at least 40% by weight, more preferably at least 45% by weight, very preferably at least 50% by weight, in each case based on the total weight of the coating composition. All conventional organic solvents known to those skilled in the art can be used as organic solvents. The term "organic solvent" is known to those skilled in the art, in particular from Council Directive 1999 / 13 / EC of 11 March 1999. The example of such organic solvent comprises heterocycle, aliphatic or aromatic hydrocarbon, monovalent or polyhydric alcohol, especially methanol and / or ethanol, ethers, esters, ketones and amides, for example N-Methyl pyrrolidone, N-ethyl pyrrolidone, dimethyl formamide, toluene, dimethylbenzene, butanol, ethylene glycol and butyl glycol and also its acetic acid ester, diethylene glycol butyl ether, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone or its mixture.The coating composition that uses in step (3a) or (3b) preferably does not contain or does not contain water substantially.In the case that not only the coating composition that uses in step (3a) or (3b) but also one of the undercoat compositions that uses in step (1) and optional step (2) or both are solvent-based, above content also applies to these undercoat compositions.

[0048] The term "aqueous" or "aqueous" is preferably understood for the purposes of the present invention to mean that water is present as the main component of all solvents and / or diluents present in the basecoat compositions applied in step (1) and optionally in step (2), and preferably also in any pigment slurry used to prepare said compositions, preferably in an amount of at least 35% by weight, based on the total weight of the coating composition, in the case where one or both of these basecoat compositions are aqueous. In this case, the above basecoat compositions each preferably comprise a water proportion of at least 40% by weight, more preferably at least 45% by weight, very preferably at least 50% by weight, in each case based on the total weight of the coating composition. The proportion of organic solvents is preferably <20% by weight, more preferably in the range of 0 to <20% by weight, very preferably in the range of 0.5-20% by weight or 0.5-17.5% by weight or 0.5-15% by weight or 0.5-10% by weight, in each case based on the total weight of the coating composition. In the case where one or both of the coating compositions applied in step (3a) or (3b) are also aqueous, the above also applies to these coating compositions.

[0049] Step (1) and the first primer composition

[0050] According to step (1), a colored basecoat composition is applied to an optionally precoated substrate to form a first coating film on the optionally precoated substrate, wherein the basecoat composition comprises at least one organic black pigment. The basecoat composition used in step (1) of the method of the present invention is hereinafter also referred to as the "first basecoat composition". The basecoat composition used in step (1) can be solvent-based (non-aqueous) or aqueous.

[0051] Preferably, the method of the present invention further comprises a step (1a) performed after step (1) and before the optional step (2). In the step (1a), the first coating film obtained after step (1) is dried before the application of the second basecoat composition in the optional step (2) or before the application of the topcoat composition in step (3a), preferably for a period of 1 to 20 minutes, more preferably 2 to 15 minutes, and especially 5 to 10 minutes. Preferably, step (1a) is performed at a temperature not exceeding 40° C., more preferably at a temperature in the range of 18 to 30° C.

[0052] The term "air drying" in the sense of the present invention preferably means drying, wherein at least some and / or some amount of solvent (water and / or organic solvent) evaporates from the coating film before application of the next coating composition and / or curing. Air drying does not involve curing.

[0053] The term "pigment" is known to the skilled person, for example, from DIN 55943 (dated October 2001). "Pigment" in the sense of the present invention preferably refers to components in the form of powder or flakes that are essentially insoluble, preferably completely insoluble, in the medium surrounding them, such as one of the coating compositions used according to the invention. Pigments are preferably colorants and / or substances that can act as pigments due to their magnetic, electric and / or electromagnetic properties. Pigments preferably differ from "fillers" in their refractive index, which for pigments is ≥1.7. The term "filler" is known to the skilled person, for example, from DIN 55943 (dated October 2001).

[0054] The at least one black pigment present in the first basecoat composition is an organic black pigment, more preferably at least one IR transparent organic black pigment, especially at least one perylene and / or azomethine pigment. Most preferably, black pigments No. 31 and 32 (PB31 and PB32), especially PB32. Such pigments are commercially available. Examples are Black L0086. Another example of a suitable organic black pigment is Azo Black A-1103 (Dainichiseika Chemicals).

[0055] Preferably, the basecoat composition used in step (1) of the process of the present invention does not contain any other black pigments, such as black inorganic pigments, besides the at least one organic black pigment. In particular, the basecoat composition used in step (1) of the process of the present invention does not contain any carbon black pigments.

[0056] Preferably the at least one organic black pigment present in the first basecoat composition has a volume average particle size in the range of 10 nm to <1000 nm, preferably 25-800 nm, more preferably 30-600 nm, especially 40 nm to <500 nm, most preferably 50-300 nm.

[0057] Preferably the at least one organic black pigment present in the first basecoat composition has a Z average particle size in the range of 10 nm to <1000 nm, preferably 25-800 nm, more preferably 30-600 nm, especially 40 nm to <500 nm, most preferably 50-300 nm.

[0058] Preferably, the at least one organic black pigment present in the first basecoat composition has a number base median primary particle size (d N,50％ ). Term base median particle size (d N,50％) are parameters known to those skilled in the art. The characteristic variable marked with a lowercase "d" is the percentile (50%) of the cumulative distribution curve, where the 50% percentile corresponds to the median. The exponent "N" relates to the base distribution.

[0059] The volume average particle size, Z average particle size and number base median primary particle size were determined by DLS according to the methods described in the 'Methods' section below.

[0060] Depending on whether the basecoat composition used in step (1) is solvent-borne (non-aqueous) or aqueous, an aqueous or non-aqueous pigment slurry comprising the at least one organic black pigment is used to prepare the first basecoat composition.

[0061] Preferably, the pigment paste containing the at least one organic black pigment used to prepare the first basecoat composition has a turbidity of <15%, preferably <10%, more preferably <7.5%.

[0062] The term "turbidity" is known to those skilled in the art. Turbidity is a measure of transparency as defined by ASTM D 1003. The method for measuring the turbidity of the pigment slurries used according to the invention (and comparative use) is described in the 'Methods' section below.

[0063] The volume average particle size, Z average particle size and number base median primary particle size as well as the turbidity can be adjusted / reduced by subjecting the organic black pigment in the form of a pigment slurry to grinding conditions in a mill. This grinding method is described in more detail below with respect to the non-black colored pigments used in the present invention and can also be used for organic black pigments and pigment slurries containing said pigments.

[0064] Preferably, the at least one organic black pigment is the only pigment in the basecoat composition used in step (1) of the method of the present invention. However, the basecoat composition used in step (1) may alternatively comprise at least one other pigment different from the at least one organic black pigment present therein, preferably excluding inorganic black pigments such as carbon black. The at least one other pigment may be different from the specific at least one non-black coloring pigment used in the present invention present in the second basecoat composition or the non-aqueous topcoat composition, but does not necessarily have to be so. Examples of such other pigments are coloring pigments including white pigments and effect pigments.

[0065] The at least one organic black pigment is preferably present in the basecoat composition used in step (1) of the process of the invention in an amount, expressed in wt. %, which is higher than the amount, expressed in wt. % of any other pigment contained therein, in each case based on the total solids content of the first basecoat composition.

[0066] Preferably, the total amount of pigment present in the first basecoat composition is at most 40 wt%, more preferably at most 35 wt%, based on the total solids content of the first basecoat composition.

[0067] The at least one organic black pigment is preferably present in the first basecoat composition in an amount within the range of 5 to 30% by weight, more preferably 6.0 to 25.0% by weight, even more preferably 7.5 to 20% by weight and in particular 8.0 to 16% by weight, in each case based on the total solids content of the first basecoat composition.

[0068] Preferably, the total solids content of the first basecoat composition is in the range of 10-65% by weight, more preferably 15-60% by weight, even more preferably 20-50% by weight and in particular 25-45% by weight, in each case based on the total weight of the first basecoat composition.

[0069] The first basecoat composition preferably comprises, in addition to the at least one organic black pigment, at least one binder, more preferably at least one polymer (a1) as binder.

[0070] For the purposes of the present invention, the term "binder" is understood to mean the non-volatile constituents of a coating composition that are responsible for film formation, in accordance with DIN EN ISO 4618 (German version, dated March 2007). This term includes crosslinkers and additives, if these represent non-volatile constituents. Therefore, pigments and / or fillers contained therein are not included under the term "binder." Preferably, the at least one polymer (a1) is the main binder of the coating composition. When no other binder components are present in the coating composition, the binder component present in the greater proportion, based on the total weight of the coating composition, is preferably referred to as the main binder in the present invention.

[0071] The term "polymer" is known to the person skilled in the art and for the purposes of the present invention includes polyadducts and polymers as well as condensation polymers. The term "polymer" includes both homopolymers and copolymers.

[0072] The at least one polymer used as component (a1) may be self-crosslinking or non-self-crosslinking. Suitable polymers that can be used are known, for example, from EP 0 228 003 A1, DE 44 38 504 A1, EP 0 593 454 B1, DE 199 48 004 A1, EP 0 787 159 B1, DE 40 09 858 A1, DE 44 37 535 A1, WO 92 / 15405 A1 and WO 2005 / 021168 A1.

[0073] The at least one polymer used as component (a1) is preferably selected from polyurethanes, polyureas, polyesters, polyamides, polyethers, poly(meth)acrylates and / or copolymers of structural units of said polymers, in particular polyurethane-poly(meth)acrylates and / or polyurethane polyureas. The at least one polymer used as component (a1) is particularly preferably selected from polyurethanes, polyesters, poly(meth)acrylates and / or copolymers of structural units of said polymers. The term "(meth)acryloyl" or "(meth)acrylate" in the context of the present invention includes in each case the meaning "methacrylic acid" and / or "acrylic acid" or "methacrylate" and / or "acrylate".

[0074] Preferred polyurethanes are described, for example, in German patent application DE 199 48 004 A1, page 4, line 19 to page 11, line 29 (polyurethane prepolymer B1), in European patent application EP 0 228 003 A1, page 3, line 24 to page 5, line 40, in European patent application EP 0 634 431 A1, page 3, line 38 to page 8, line 9 and in international patent application WO 92 / 15405, page 2, line 35 to page 10, line 32.

[0075] Preferred polyesters are described, for example, in DE 4009858 A1, column 6, line 53 to column 7, line 61, and column 10, line 24 to column 13, line 3, or in WO 2014 / 033135 A2, page 2, line 24 to page 7, line 10, and page 28, line 13 to page 29, line 13. Also preferred are polyesters having a dendritic or star structure, such as those described in WO 2008 / 148555 A1. These can be used not only in clearcoats but also, in particular, in aqueous basecoats.

[0076] Preferred polyurethane-poly(meth)acrylate copolymers (eg (meth)acrylated polyurethanes)) and their preparation are described, for example, in WO 91 / 15528 A1, page 3, line 21 to page 20, line 33 and DE 4437535 A1, page 2, line 27 to page 6, line 22.

[0077] Preferred poly(meth)acrylates are those that can be prepared by multistage free-radical emulsion polymerization of ethylenically unsaturated monomers in water and / or organic solvents. For example, seed-core-shell polymers (SCS polymers) are particularly preferred. Such polymers or aqueous dispersions containing such polymers are known, for example, from WO 2016 / 116299 A1. Particularly preferred seed-core-shell polymers are polymers which can be prepared by the continuous free-radical emulsion polymerization of three preferably different monomer mixtures (A1), (B1) and (C1) of ethylenically unsaturated monomers in water, preferably those having an average particle size of 100 to 500 nm, wherein mixture (A1) contains at least 50% by weight of monomers having a solubility in water of less than 0.5 g / l at 25° C. and the polymer prepared from mixture (A1) has a glass transition temperature of 10 to 65° C., mixture (B1) contains at least one polyunsaturated monomer and the polymer prepared from mixture (B1) has a glass transition temperature of −35° C. to 15° C., and the polymer prepared from mixture (C1) has a glass transition temperature of −50° C. to 15° C., and wherein i. mixture (A1) is polymerized first, ii. mixture (B1) is then polymerized in the presence of the polymer formed under i., and iii. mixture (C1) is subsequently polymerized in the presence of the polymer formed under ii. All three mixtures are preferably different from one another.

[0078] Preferred polyurethane-polyurea copolymers are polyurethane-polyurea particles, preferably those having a Z-average particle size of 40 to 2000 nm, each of which contains, in reacted form, at least one polyurethane prepolymer containing isocyanate groups (containing anionic groups and / or groups that can be converted into anionic groups) and at least one polyamine containing two primary amino groups and one or two secondary amino groups. Such copolymers are preferably used in the form of aqueous dispersions. Such polymers can, in principle, be prepared, for example, by conventional polyaddition reactions of polyisocyanates with polyols and polyamines.

[0079] The polymer used as component (a1) preferably has reactive functional groups capable of undergoing a crosslinking reaction. Any common crosslinkable reactive functional groups known to those skilled in the art may be present. The polymer used as component (a1) preferably has at least one reactive functional group selected from primary amino groups, secondary amino groups, hydroxyl groups, thiol groups, carboxyl groups and carbamate groups. The polymer used as component (a1) preferably has a functional hydroxyl group.

[0080] Preferably the polymers used as component (a1) are hydroxy-functional and more preferably have an OH number in the range of 15 to 400 mg KOH / g, more preferably 20 to 250 mg KOH / g.

[0081] The polymers used as component (a1) are particularly preferably hydroxy-functional polyurethane-poly(meth)acrylate copolymers, hydroxy-functional polyesters and / or hydroxy-functional polyurethane-polyurea copolymers.

[0082] In addition, the first basecoat composition may contain at least one typical crosslinking agent known per se. Crosslinking agents are to be included among the film-forming non-volatile components of the coating composition and therefore fall within the general definition of "binder". Therefore, crosslinking agents should be included under component (a1).

[0083] If a crosslinking agent is present, it is preferably at least one aminoplast resin and / or at least one blocked or free polyisocyanate, preferably an aminoplast resin. Among the aminoplast resins, melamine resins such as melamine-formaldehyde resins are particularly preferred.

[0084] Optional step (2) and second primer composition

[0085] According to optional step (2), a second colored basecoat composition different from the first basecoat composition is applied to the first coating film present on the substrate obtained after step (1) and forms a second coating film adjacent to the first coating film. The second colored basecoat composition does not contain any black pigment. The basecoat composition used in optional step (2) of the method of the present invention is also referred to as "second basecoat composition" below. The basecoat composition used in optional step (2) can be solvent-based (non-aqueous) or aqueous.

[0086] If optional step (2) is carried out - and of course also the preceding step (1) and the subsequent step (3b), the second basecoat composition comprises at least one non-black colored pigment having a volume average particle size of <1000 nm in an amount in the range of 0.01-7.50 wt. %, based on the total solids content of the second basecoat composition, wherein the at least one non-black colored pigment is incorporated into the second basecoat composition in the form of a pigment slurry.

[0087] Depending on whether the basecoat composition used in step (1) is solvent-borne (non-aqueous) or aqueous, an aqueous or non-aqueous pigment slurry containing the at least one non-black colored pigment may be used to prepare the second basecoat composition.

[0088] The optional step (2) is preferably performed before curing the first coating film obtained after the step (1).

[0089] Preferably, the method of the present invention further comprises step (2a), which is performed after optional step (2) and before step (3b). In step (2a), the second coating film obtained after step (2) is dried before applying the clear coating composition in step (3b), preferably for a period of 1 to 20 minutes, more preferably 2 to 15 minutes, and especially 5 to 10 minutes. Preferably, step (2a) is performed at a temperature not exceeding 40°C, more preferably at a temperature in the range of 18 to 30°C.

[0090] Preferably, the at least one non-black colored pigment is the only pigment in the basecoat composition used in step (2) of the method of the present invention. However, the basecoat composition used in step (2) may alternatively contain at least one other pigment different from the at least one non-black colored pigment present therein. Examples of such other pigments are other colored pigments including white pigments and effect pigments.

[0091] The at least one non-black colored pigment is preferably present in the basecoat composition used in step (2) of the process of the invention in an amount, expressed in wt. %, that is higher than the amount, expressed in wt. % of any other pigment contained therein, in each case based on the total solids content of the second basecoat composition.

[0092] Preferably the total amount of pigment present in the second basecoat composition is at most 20 wt%, more preferably at most 10 wt%, based on the total solids content of the first basecoat composition.

[0093] The at least one non-black colored pigment is preferably present in the second basecoat composition in an amount within the range of 0.01-5.00 wt. %, more preferably 0.10-5.00 wt. %, even more preferably 0.10-3.50 wt. %, in particular 0.10-2.50 wt. %, most preferably 0.20-2.00 wt. %, in each case based on the total solids content of the second basecoat composition.

[0094] Preferably, the total solids content of the second basecoat composition is in the range of 10-65 wt. %, more preferably 15-60 wt. %, even more preferably 20-50 wt. %, in particular 25-45 wt. %, in each case based on the total weight of the second basecoat composition.

[0095] The second basecoat composition preferably comprises at least one binder, more preferably at least one polymer (b1) as a binder in addition to the at least one non-black colored pigment. The same binder including the crosslinking agent described above for component (a1) can also be used as component (b1).

[0096] Step (3a) and colored topcoat composition

[0097] According to optional step (3a), a topcoat coating composition is applied to the first coating film present on the substrate obtained after step (1) without carrying out optional step (2) and forms a second coating film adjacent to the first coating film, wherein the topcoat coating composition is a colored topcoat composition, and wherein the second coating film obtained after step (3a) is the outermost film of the multilayer coating system formed. The topcoat coating composition does not contain any black pigment. The topcoat composition used in step (3a) can be solvent-based (non-aqueous) or aqueous, preferably solvent-based.

[0098] In the case of carrying out step (3a), step (2) is not carried out. In this case, the colored topcoat composition comprises at least one non-black colored pigment having a volume average particle size of <1000 nm in an amount in the range of 0.01-7.50 wt. %, based on the total solids content of the topcoat coating composition, wherein the at least one non-black colored pigment is incorporated into the topcoat coating composition in the form of a pigment paste.

[0099] Preferably, a non-aqueous pigment paste comprising the at least one non-black colored pigment is used to prepare the topcoat composition if the topcoat composition is solvent-based. Equally, preferably, an aqueous pigment paste comprising the at least one non-black colored pigment is used to prepare the topcoat composition if the topcoat composition is aqueous.

[0100] It is preferred that step (3a) is performed before curing the first coating film obtained after step (1).

[0101] Preferably, the at least one non-black coloring pigment is the only pigment in the topcoat composition used in step (3a) of the inventive method. However, the topcoat composition used in step (3a) may alternatively comprise at least one other pigment different from the at least one non-black coloring pigment present therein. Examples of such other pigments are other coloring pigments including white pigments and / or effect pigments. However, preferably, no effect pigments are present.

[0102] The at least one non-black colored pigment is preferably present in the topcoat composition used in step (3) of the process of the invention in an amount, expressed in wt. %, that is higher than the amount, expressed in wt. % of any other pigment contained therein, in each case based on the total solids content of the topcoat composition.

[0103] Preferably the total amount of pigment present in the topcoat composition is at most 30 wt%, more preferably at most 20 wt%, based on the total solids content of the topcoat composition.

[0104] The at least one non-black colored pigment is preferably present in the topcoat composition in an amount within the range of 0.01 to 5.00 wt. %, more preferably 0.01 to 3.50 wt. %, even more preferably 0.01 to 2.50 wt. %, in particular 0.02 to 1.50 wt. %, most preferably 0.03 to 1.00 wt. %, in each case based on the total solids content of the topcoat composition.

[0105] Preferably, the total solids content of the topcoat composition is in the range from 10 to 65% by weight, more preferably from 15 to 60% by weight, even more preferably from 20 to 50% by weight and in particular from 25 to 45% by weight, in each case based on the total weight of the topcoat composition.

[0106] The topcoat composition preferably comprises, in addition to the at least one non-black colored pigment, at least one binder, more preferably at least one polymer (c1) as a binder. The same binder including the crosslinking agent described above for components (a1) and (b1) can also be used as component (c1).

[0107] Step (3b) and clear coating composition

[0108] According to optional step (3b), another coating composition is applied to the second coating film present on the substrate obtained after step (2) while carrying out optional step (2) and a third coating film is formed adjacent to the second coating film, wherein the coating composition is a clearcoat composition, and wherein the third coating film obtained after step (3b) is the outermost film of the formed multi-layer coating system. The clearcoat coating composition does not contain any black pigment. The clearcoat composition used in step (3b) can be solvent-based (non-aqueous) or aqueous, preferably solvent-based.

[0109] The clearcoat composition can be unpigmented, i.e., it can contain not only no black pigment, but no pigment at all. However, the clearcoat composition can alternatively contain color and / or effect pigments—in the case of color pigments other than black pigments, preferably color pigments in an amount that does not interfere with the desired transparency of the clearcoat once cured. For example, the clearcoat composition can contain up to 7.5% by weight, preferably up to 5.0% by weight, more preferably up to 2.5% by weight, and still more preferably up to 1.5% by weight of at least one color pigment, in each case based on the total solids content of the clearcoat composition.

[0110] It is preferred that step (3b) is performed before curing the second coating film obtained after step (2).

[0111] Preferably, the total solids content of the clearcoat composition is in the range of 10-65% by weight, more preferably 15-60% by weight, even more preferably 20-50% by weight and in particular 25-45% by weight, in each case based on the total weight of the clearcoat composition.

[0112] The clearcoat composition preferably comprises at least one binder, more preferably at least one polymer (c1) as the binder.The same binders including the crosslinking agents described above for components (a1) and (b1) can also be used as component (c1).

[0113] The clearcoat or topcoat composition applied in step (3a) or (3b)

[0114] The clearcoat or topcoat coating composition may comprise at least one binder, more preferably at least one polymer (c1) as a binder. Since the clearcoat or topcoat coating composition is preferably a 2K composition, it preferably comprises at least one polymer (c1) having on average two or more OH groups and / or amino groups and / or urethane groups, more preferably OH groups, and at least one further polymer and at least one polyisocyanate having free NCO groups as a crosslinker.

[0115] Preferably, the at least one preferably OH-functional polymer (c1) has a weight average molecular weight M w Preferably, it is between 800 and 100 000 g / mol, more particularly between 1000 and 75 000 g / mol, measured against polystyrene standards by means of gel permeation chromatography (GPC).

[0116] Particularly preferred components (c1) are selected from polyesters, polyurethanes, poly(meth)acrylates and mixtures thereof. As stated above, these terms in each case include both homopolymers and copolymers.

[0117] Suitable polyesters are described, for example, in EP-A-0 994 117 and EP-A-1 273 640. Polyurethane polyols are preferably prepared by reaction of polyester polyol prepolymers with suitable di- and / or polyisocyanates and are described, for example, in EP-A-1 273 640. Preferably, the at least one OH-functional polymer (c1) is at least one OH-functional (meth)acrylic copolymer and / or at least one OH-functional polyester, preferably at least one OH-functional (meth)acrylic copolymer.

[0118] Preferably, the at least one OH-functional polymer (c1) has an OH number of 30 to 400 mg KOH / g, more particularly 100 to 300 mg KOH / g. The glass transition temperature of the polymer, measured by DSC according to DIN EN ISO 11357-2 (2019-03), is preferably from -150°C to 100°C, more preferably from -120°C to 80°C.

[0119] Suitable cross-linking agent is an organic component with two or more NCO groups on average.Preferably, at least one organic component as cross-linking agent has alicyclic structure and / or forms a parent structure derived from alicyclic polyisocyanates by trimerization, dimerization, urethane formation, biuret formation, diazepine dione formation and / or allophanate formation.Alternately or additionally, at least one organic component as cross-linking agent preferably has acyclic aliphatic structure and / or forms a parent structure derived from acyclic aliphatic polyisocyanates by trimerization, dimerization, urethane formation, biuret formation, diazepine dione formation and / or allophanate formation.Acyclic aliphatic polyisocyanates-optionally used as parent structure-preferably substitution known per se or unsubstituted aliphatic polyisocyanates. Examples are tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate, ethylene diisocyanate, dodecane-1,12-diisocyanate and mixtures of the aforementioned polyisocyanates. The cycloaliphatic polyisocyanates, which are optionally used as parent structures, are preferably substituted or unsubstituted cycloaliphatic polyisocyanates known per se. Examples of preferred polyisocyanates are isophorone diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrobenzene-1,3-diisocyanate, hexahydrobenzene-1,4-diisocyanate, perhydrodiphenylmethane-2,4′-diisocyanate, 4,4′-methylenedicyclohexyl diisocyanate (e.g., cyclopentane from Bayer AG), W) and mixtures of the above polyisocyanates.

[0120] Non-black colored pigments present in a second basecoat or topcoat composition and pigment slurries containing said pigments

[0121] The non-black colored organic pigments used in the present invention are further described below.

[0122] Preferably, the at least one non-black colored pigment present in the second basecoat composition or the topcoat composition is a blue and / or green and / or violet and / or red pigment, more preferably a blue and / or green and / or violet pigment, still more preferably a blue and / or green pigment, especially a blue pigment. Preferably, it is the only colored pigment present in the second basecoat or the topcoat composition, even more preferably the only pigment present in the second basecoat or the topcoat composition.

[0123] The at least one non-black colored pigment present in the second basecoat composition or the topcoat composition can be an inorganic or organic pigment such as an inorganic or organic blue pigment. Suitable inorganic blue pigments are commercially available, such as Blue 550. However, it is preferably an organic pigment, especially an organic blue pigment. Preferably, the at least one non-black pigment used in the present invention is a phthalocyanine pigment. Most preferably, the blue pigments numbered 15:1, 15:2, 15:3, 15:4 and 15:6, especially 15:1 (PB15:1, PB15:2, PB15:3, PB15:4 and PB15:6) are suitable. Suitable organic blue pigments are also commercially available. Examples are Blue 15:1-248-4806 and Blue 15:1-248-4816.

[0124] Preferably the at least one non-black colored organic pigment present in the second basecoat composition or the topcoat composition has a volume average particle size in the range of 10 nm to <950 nm, preferably 25-900 nm, more preferably 30-850 nm, especially 40 nm to <800 nm.

[0125] Preferably the at least one non-black colored organic pigment present in the second basecoat composition or the topcoat composition has a Z-average particle size in the range of 10-750 nm, preferably 25-500 nm, more preferably 30-350 nm, especially 40-300 nm.

[0126] Preferably, the at least one non-black colored organic pigment present in the second basecoat composition or the topcoat composition has a number basis median primary particle size (d ) in the range of 10-700 nm, preferably 25-500 nm, more preferably 30-400 nm, especially 50-350 nm. N,50％ ). Term base median particle size (d N,50％ ) are parameters known to those skilled in the art. The characteristic variable marked with a lowercase "d" is the percentile (50%) of the cumulative distribution curve, where the 50% percentile corresponds to the median. The exponent "N" relates to the base distribution.

[0127] The volume average particle size, Z average particle size and number base median primary particle size were determined by DLS according to the methods described in the 'Methods' section below.

[0128] The pigment slurry comprising the at least one non-black coloring pigment is used to prepare the second base coat or topcoat composition. When the second base coat composition is aqueous and the topcoat coating composition is non-aqueous, the pigment slurries used for the two compositions can be different from each other. When the two compositions are all non-aqueous, they can also be identical. The pigment slurry preferably contains at least one dispersant and / or grinding resin to disperse / grind the pigment in each case. The at least one non-black coloring pigment used in the present invention present in the pigment slurry is preferably ground with a mill to reduce its volume average particle size to <1000nm. Preferably, grinding is also performed to achieve the above-mentioned preferred range of Z average particle size and number base median primary particle size. Preferably, grinding is also performed to achieve following turbidity values. Grinding is preferably performed by using a grinding bead with a diameter of 0.5mm or less such as 0.4 and / or 0.3mm. When it is desired to reduce at least one of the volume average particle size, the Z average particle size and the number base median primary particle size and the turbidity of the at least one black pigment present in the first basecoat composition before incorporating it into the first basecoat composition, the same grinding conditions can also be used in the case of preparing a pigment slurry of the black pigment. Particularly suitable grinding conditions are clear from the examples.

[0129] The pigment slurry containing the at least one non-black colored pigment preferably used to prepare the second basecoat composition or the topcoat composition has a turbidity of <20%, preferably <15%, more preferably <10%, in particular <7.5%, and most preferably ≤5%. The term "turbidity" is known to those skilled in the art. Turbidity is a measure of transparency as defined in ASTM D 1003. The method for measuring the turbidity of the pigment slurries used in the present invention (and comparative use) is described below in the 'Methods' section.

[0130] Optional step (4)

[0131] As described above, it is preferred to perform optional step (2) before curing the first coating film obtained after step (1), perform step (3a) before curing the first coating film obtained after step (1), and perform step (3b) before curing the second coating film obtained after step (2).

[0132] Preferably, the method of the present invention further comprises a step (3c), which is performed after step (3a) or (3b) and before step (4). In step (3c), the third coating film obtained after step (3a) or (3b) is dried before the optional curing step (4), preferably for a period of 1-20 minutes, more preferably 2-15 minutes, and especially 5-10 minutes. Preferably, step (3c) is performed at a temperature not exceeding 40°C, more preferably at a temperature in the range of 18-30°C.

[0133] The method of the present invention may optionally include and preferably includes an additional step (4), namely:

[0134] (4) Joint curing, i.e., simultaneously curing all the coating films applied in steps (1) and (3a) or steps (1), (2) and (3b) to obtain a cured multi-layer coating system comprising at least a first and a second coating layer, wherein the second coating layer is the outermost layer of the formed multi-layer coating system, or a cured multi-layer coating system comprising at least a first, a second and a third coating layer, wherein the third coating layer is the outermost layer of the formed multi-layer coating system.

[0135] Each resulting cured coating film represents one coating layer.

[0136] Preferably, step (4) is carried out at a temperature of less than 150°C, preferably less than 130°C, especially at a temperature in the range of 15-110°C or 15-90°C, for a period of 5-45 minutes, preferably 20-45 minutes, especially 25-35 minutes.

[0137] Multi-layer coating system of the present invention

[0138] The present invention further provides a multilayer coating system on an optionally precoated substrate, which is obtainable by the process according to the invention.

[0139] All preferred embodiments described above with respect to the process according to the invention are also preferred embodiments with respect to the above-described coated substrate according to the invention.

[0140] Preferably, the multi-layer coating system of the present invention obtainable by the process of the present invention has, after curing, a blackness (Mc) of at least 250, preferably at least 270 and / or has a blackness (Mc) value that exceeds its blackness (My) value, preferably by at least 1%. Methods for measuring this blackness and blackness are described below in the 'Methods' section.

[0141] The terms "black" (My) and "blackness" (Mc) are known to those skilled in the art and are parameters by which the color quality of "black" can be quantified. Black (My) is a measure of the degree of blackness, is directly related to reflectivity, and is defined, for example, in DIN 55979 (04-1989). Black (My) can be quantified using the general formula My = 100*log(Yn / Y). Blackness (Mc) is a color-related black value developed by K. Lippok-Lohmer (K. Lippok-Lohmer, Farbe und Lack, 92, p. 1024 (1986) and is also mentioned in DIN 53235-1 (06-2005) and DIN 53235-2 (06-2005). Blackness (Mc) can be quantified by using the general formula Mc=100*[log(Xn / X)-log(Zn / Z)+log(Yn / Y)]. X, Y, Z are the CIE tristimulus values of the measured sample. Xn, Yn, Zn are the tristimulus values of the light source. The difference between Mc and My, i.e. Mc–My, is the background color (dM). If dM<0, the background color is brown / light red (My>Mc). If dM>0, black has a light blue background (My <Mc)。

[0142] Coated substrate of the present invention

[0143] The present invention further provides a coated substrate obtainable by the process according to the invention.

[0144] All preferred embodiments described above with respect to the method according to the invention and the multi-layer coating system according to the invention are also preferred embodiments with respect to the above-described coated substrate according to the invention.

[0145] Uses of the present invention

[0146] The present invention further provides for the use of a pigmented coating composition which does not comprise any black pigments and comprises at least one non-black pigmented pigment having a volume average particle size of <1000 nm in an amount in the range of 0.01 to 7.50% by weight, based on the total solids content of the coating composition, wherein the at least one non-black pigmented pigment is incorporated into the coating composition in the form of a pigment paste.

[0147] as a second basecoat composition in step (2) of the process according to the invention for producing a multilayer coating system on an optionally precoated substrate or as a topcoat composition in step (3a),

[0148] The blackness (Mc) of the multi-layer coating system obtained after curing is increased to an extent that the blackness (Mc) exceeds the blackness (My) of the cured multi-layer coating system, preferably by at least 1%.

[0149] All preferred embodiments described above with respect to the method according to the invention, the multi-layer coating system according to the invention and the coated substrate according to the invention are also preferred embodiments with respect to the above-described use according to the invention.

[0150] method

[0151] 1. Determination of non-volatile matter ratio

[0152] The amount of solids content (non-volatile matter, solid fraction) including the total solids content was determined via DIN EN ISO 3251:2019-09 at 110° C. for 60 minutes.

[0153] 2. Turbidity measurement

[0154] The pigment slurry to be subjected to turbidity measurement is diluted with deionized water (in the case of aqueous pigment slurry) or n-butyl acetate (in the case of solvent-based pigment slurry) to provide a suitable diluted sample, which is then used for the measurement. The measurement is carried out within 24 hours of grinding the pigment slurry. As a device for measuring turbidity, a Haze-gard I instrument that can be purchased from Byk-Gardner is used. The instrument is calibrated in a solution-based quartz cuvette flow sample holder using deionized water or n-butyl acetate as a reference standard. A 500 micron path length cuvette is used for the measurement. The measurement is carried out at a transmittance of 17.5% ± 1.0% at the wavelength of maximum absorbance. If the transmittance of the sample prepared after dilution is found to be too low, the sample is further diluted until a transmittance of 17.5% ± 1.0% is reached.

[0155] 3. Particle size characteristics

[0156] Different parameters of particle size were measured. All parameters were measured by DLS particle size measurement (dynamic light scattering measurement). DLS measurements were performed within 24 hours of grinding the pigment slurry. Z-average particle size, volume average particle size (V-average) and d N,50％ d N,10％ and d N,90％ Parameter.d N,50％ d N,10％ and d N,90％Parameters are measured using intensity weighting. Each parameter of each slurry is determined by four tests and the given value represents the average of these four tests. The pigment slurry to be subjected to particle size analysis is diluted with deionized water (in the case of aqueous pigment slurry) or n-butyl acetate (in the case of solvent-based pigment slurry) to provide a suitable diluted sample and subsequently analyzed. In the case of aqueous pigment slurry, each slurry is diluted into deionized water with a first dilution ratio of 1:100, and the solution is then further diluted to 1:50. Therefore, the total dilution ratio is 1:5000 (based on the original slurry in each case). In the case of solvent-based pigment slurry, each slurry is diluted into n-butyl acetate with a first dilution ratio of 1:100, and the solution is then further diluted to 1:50. Therefore, the total dilution ratio is 1:5000 (based on the original slurry in each case). Each sample is transferred to a glass cuvette (glass cuvette PCS1115) as a cuvette. The sample is then placed in a DLS measurement system. The Malvern Zetasizer Nano series was used as a DLS particle size analyzer, which was purchased from Malvern (model ZEN 1690). Each sample was allowed to equilibrate in the chamber for 2 minutes before starting the particle size analysis. Data were then collected.

[0157] 4. Measurement of color values (L*, a*, b*)

[0158] The L*a*b* color space or L*a*b* color model (i.e., CIELAB color model) is known to those skilled in the art. The L*a*b* color model is standardized, for example, in DIN EN ISO / CIE 11664-4:2020-03. The various perceived colors in the L*a*b* color space are described by specific color positions with coordinates {L*, a*, b*} in a three-dimensional coordinate system. The a* axis describes the green or red portion of the color, where negative values represent green and positive values represent red. The b* axis describes the blue or yellow portion of the color, where negative values represent blue and positive values represent yellow. Therefore, smaller numbers represent bluer colors. The L* axis is perpendicular to the plane and represents lightness (brightness). The L* axis has endpoints black (L=0) and white (L=100). Therefore, smaller values represent darker colors. The color values L*, a*, and b* of the coated substrate (after curing) are measured according to ASTM E 284-81a after its preparation including curing. These values were measured using an instrument BYK-mac i (BYK-Gardner). The analysis of the cured samples was carried out according to the color, sparkle and particle size measurements using the BYK-mac i spectrophotometer standard operating procedure. The fully cured sample to be analyzed was wiped with a microfiber cloth. The BYK-mac i instrument was then placed on the substrate surface and measured using a D65 light source at -15 °, 15 °, 25 °, 45 °, 75 ° and 110 ° angles, with CIELab settings used to record data for each angle. The measurements were carried out at least three different locations on a single plate, and these tests were averaged and recorded. The color values L*, a* and b* recorded below in the test section relate to an angle of 110 °.

[0159] 5. Measurement of blackness (Mc) and blackness (My)

[0160] After its preparation including curing, the blackness and black color of the coated substrate are measured. The black color (My) is a measure of the degree of blackness, which is directly related to the reflectance and is defined, for example, in DIN 55979 (04 - 1989). The black color (My) of a sample can be quantified using the general formula My = 100 * log(Yn / Y) by obtaining color data using a suitable spectrophotometer. The blackness (Mc) is a color-related black value developed by K. Lippok-Lohmer (K. Lippok-Lohmer, Farbe und Lack, 92, page 1024 (1986) and is also mentioned in DIN 53235-1 (06 - 2005) and DIN 53235-2 (06 - 2005). The blackness (Mc) can be quantified using the general formula Mc = 100 * [log(Xn / X) - log(Zn / Z) + log(Yn / Y)] by obtaining color data using a suitable spectrophotometer. X, Y, Z are the CIE tristimulus values of the measured sample. Xn, Yn, Zn are the tristimulus values of the light source. The light source used for this measurement is the D65 light source (simulating daylight CIE standard). The standard 2° standard observer normalizes the relative luminance, where Yn = 100 gives Xn = 95.047 and Zn = 108.883. They also record the supplementary 10° observer with Xn = 94.8110 and Zn = 107.304. These values are measured using the instrument BYK-mac i (BYK-Gardner). The analysis of the cured sample is carried out according to the color, gloss, and particle size measurement of the standard operating procedure of the BYK-mac i spectrophotometer. The fully cured sample to be analyzed is wiped with an ultra-fine fiber cloth. Then the BYK-mac i instrument is placed on the substrate surface and measurements are carried out at angles of -15°, 15°, 25°, 45°, 75°, and 110° using the D65 light source, and data are recorded using the CIELab setting for each angle. The My and Mc values recorded in the test section below relate to the measurement at an angle of 75°. The difference between Mc and My, i.e., Mc – My, is the undertone (dM). If dM < 0, the undertone is brown / light red (My > Mc). If dM > 0, the black exhibits an undertone of a different color (My < Mc), which depends on the non-black coloring pigment used. A neutral to blue and / or green undertone, especially a blue undertone, is particularly desired. Examples

[0161] The following examples further illustrate the invention but should not be construed as limiting its scope. 'Pbw' refers to parts by weight. Unless otherwise defined, 'parts' means 'parts by weight'.

[0162] 1. Preparation of pigment slurry

[0163] 1.1 Preparation of aqueous pigment slurries P1 - P7 and P2a

[0164] The pigment slurry shown in Table 1 was prepared from the ingredients and amounts shown in Table 1 by the following method:

[0165] Pigment paste P1

[0166] Black pigment paste P1 is made by Black L0086 is added into the stirred mixture of dispersant 1, propylene glycol n-butyl ether and deionized water and produced. The gained suspension is stirred using Cowles blade for 5 minutes. Use 20 % by weight dimethylethanolamine aqueous solution by pH adjustment to 8.1 (measured with Starter300pH portable pH meter (Ohaus Corporation, Parsippany, New Jersey, USA)). Then the suspension is transferred to a mixing tank and 0.9-1.1mmYTZ grinding media (Fox Industries) (medium: suspension in a 2:1 weight ratio) is added. Then the suspension is stirred 4 hours using LAU shaker (LAU disperser DAS 200-LAU GmbH). Use gravity filtration to separate 0.9-1.1mm YTZ media. The collected slurry is transferred to another mixing tank, injected with a 0.3-0.4mm YTZ grinding media at a 2:1 bead / slurry weight ratio and stirred 9 hours using LAU shaker (LAU disperser DAS 200-LAU GmbH). The resulting final pulp product was filtered to remove 0.3-0.4 mm media and used as pigment pulp P1 without further modification.

[0167] Pigment paste P2a

[0168] The blue pigment paste P2a is prepared by Blue 15:1-248-4816 (Sun Chemical) is added to the stirred mixture of dispersant 1, propylene glycol n-butyl ether and deionized water to produce. The gained suspension is stirred for 5 minutes using a Cowles blade. The pH is adjusted to 8.1 (measured using a Starter 300pH portable pH meter (Ohaus Corporation, Parsippany, New Jersey, USA)) using a 20 wt % dimethylethanolamine aqueous solution. The suspension is then transferred to a mixing tank and a 0.3-0.4 mm YTZ grinding media (Fox Industries) is added in a 2:1 weight ratio (medium: suspension). The suspension is stirred for 10 hours using a LAU shaker (LAU disperser DAS 200-LAU GmbH). The gained slurry is separated by gravity filtration from the 0.3-0.4 mm YTZ media and is used as pigment slurry P2a without further modification.

[0169] Pigment paste P2b

[0170] Blue pigment paste P2b was produced by further modifying pigment paste P2a. 5.7 parts of dispersant 2 were diluted with 14.3 parts of deionized water while stirring. This resin solution was then slowly added to 80 parts of pigment paste P2a while stirring. The resulting paste was then used as pigment paste P2b without further modification.

[0171] Pigment paste P3

[0172] Blue pigment slurry P3 was prepared by adding dispersant 3 to a large mixing vessel and diluting the dispersant with deionized water, then adding the blue pigment in small aliquots. Blue 15: 1-248-4806 (Sun Chemical). The slurry was sheared until it was homogeneous and then further diluted with deionized water. The suspension was then transferred to an Eiger bead mill (EMI) containing 0.9-1.1 YTZ beads (Fox Industries) and processed to 275 Whr / kg. The resulting slurry was then used as pigment slurry P3 without further modification after removing the beads.

[0173] Pigment paste P4

[0174] Blue pigment paste P4 is made by Blue 15:1-248-4806 (Sun Chemical) was added to a stirred mixture of dispersant 4, propylene glycol n-butyl ether and deionized water. The resulting suspension was stirred for 5 minutes using a Cowles blade. The pH was adjusted to 8.1 (measured using a Starter 300pH portable pH meter (Ohaus Corporation, Parsippany, New Jersey, USA) using a 20 wt % aqueous solution of dimethylethanolamine. The suspension was then transferred to a mixing tank and 0.3-0.4 mm YTZ grinding media (Fox Industries) was added in a 2:1 weight ratio (medium:suspension). The suspension was stirred for 10 hours using a LAU shaker (LAU disperser DAS 200 - LAU GmbH). The resulting slurry was separated from the 0.3-0.4 mm YTZ media by gravity filtration. 5.7 parts of dispersant 2 were diluted with 14.3 parts of deionized water under agitation. The resin solution was then slowly added to 80 parts of the above resulting slurry under agitation. The resulting slurry after removal of the beads was then used without further modification as pigment slurry P4.

[0175] Pigment paste P5

[0176] Blue pigment paste P5 was produced by adding dispersant 5 to a large mixing vessel and diluting the dispersant with deionized water, followed by addition of wetting additives, polypropylene glycol and emulsifier. The blue pigment was then added in small aliquots. Blue 550 (Heubach). The slurry was sheared using a Cowles blade until uniform. The resulting slurry was then further diluted with deionized water, mixed thoroughly, and subsequently transferred to an Eiger bead mill (EMI) to be processed with 0.9-1.1 mm YTZ beads (Fox Industries) and ground to an energy of 300 Whr / kg at a weight ratio of 2:1 (media:slurry). After removing the beads, the resulting slurry was used as pigment slurry P5 without further modification.

[0177] Pigment paste P6

[0178] Yellow pigment paste P6 was prepared by adding dispersant 3, deionized water, propylene glycol n-propyl ether to a large mixing vessel, mixing thoroughly, and adjusting the pH to 8.1 (measured with a Starter 300 pH portable pH meter (Ohaus Corporation, Parsippany, New Jersey, USA)) using a 20 wt% aqueous solution of dimethylethanolamine. To this solution was added small aliquots with stirring. Yellow Y-5688 (Bayer) was added and mixed until homogeneous. The solution was then diluted with deionized water and the pH was adjusted to 8.1 (measured using a Starter 300 pH portable pH meter (Ohaus Corporation, Parsippany, New Jersey, USA)) using a 20 wt% aqueous solution of dimethylethanolamine. The pigment slurry was transferred to an Eiger bead mill (EMI) containing 0.9-1.0 mm YTZ beads (Fox Industries) at a media / slurry weight ratio of 2:1 and ground to an energy of 175 Whr / kg. After removing the beads, the resulting slurry was used as pigment slurry P6 without further modification.

[0179] Pigment paste P7

[0180] Yellow pigment paste P7 was produced by adding dispersant 3, deionized water, propylene glycol n-propyl ether and fumed silica to a large mixing vessel and mixing thoroughly. To this solution was added small aliquots under agitation. Yellow 3RLTN (BASF SE) was added and mixed until homogeneous. The mixture was then diluted with deionized water and transferred to an Eiger bead mill (EMI) containing 0.9-1.0 mm YTZ beads (Fox Industries) at a media / slurry weight ratio of 2:1 and ground to an energy of 190 Whr / kg. After removing the beads, the resulting slurry was used as pigment slurry P7 without further modification.

[0181] Dispersant 1 was composed of 42.5 wt% (meth)acrylic resin solids, 31.3 wt% ethylene glycol monobutyl ether, and 26.2 wt% deionized water.

[0182] Dispersant 2 consists of 27.0 wt% of polyurethane resin, 6.0 wt% of ethylene glycol monobutyl ether and 67.0 wt% of deionized water, and is adjusted with a small amount of dimethylethanolamine.

[0183] Dispersant 3 consisted of 35.5 wt% resin solids and 64.5 wt% solvent. The solvent content of this dispersant was as follows: 28.40 wt% propylene glycol n-propyl ether, 6.12 wt% methyl isoamyl ketone (MIAK), 28.45 wt% deionized water, and 1.53 wt% mineral spirits. The resin present in this dispersant was prepared as disclosed in Example 5 of U.S. Patent No. 5,270,399.

[0184] Dispersant 4 is composed of 61 wt% resin solids and 39 wt% solvent. The resin is a PEG-modified polyester-based star polymer.

[0185] Dispersant 5 consisted of 45.3 wt% (meth)acrylic resin solids and 54.6 wt% deionized water, adjusted with a small amount of dimethylethanolamine.

[0186] The wetting additive is a commercially available wetting additive. The emulsifier is a commercially available emulsifier. The polypropylene glycol used is also commercially available.

[0187] Table 1 - Pigment pastes P1, P2a, P2b and P3-P7

[0188]

[0189] As mentioned above, the black pigment 1 present in the pigment paste P1 is Black L0086. Pigment pastes P2a and P2b each contain blue pigment 1, the latter being Blue 15:1-248-4816. Pigment pastes P3 and P4 each contain blue pigment 2, the latter being Blue 15: 1-248-4806. The blue pigment 3 present in the pigment paste P5 is Blue 550. Yellow Pigment 1 is Yellow Y-5688. Yellow pigment 2 is Yellow 3RLTN.

[0190] After their preparation, including the grinding step, pigment slurries P1, P2a, P2b, and P3-P7 were analyzed by particle size analysis. Their turbidity was also measured. Both the turbidity measurement and the particle size characteristics measurements shown in Table 2 were performed according to the methods disclosed in the 'Methods' section. The measured values are shown in Table 2. No values were determined for pigment slurry P2a.

[0191] Table 2 - Turbidity and particle size characteristics of pigment slurries P1-P7

[0192]

[0193] 1.2 Preparation of solvent-based pigment pastes P8 and P9

[0194] The pigment slurry shown in Table 3 was prepared from the ingredients and amounts shown in Table 3 by the following method:

[0195] Pigment paste P8

[0196] Blue pigment paste P8 is made by 76500 (Lubrizol) and Solsperse (Lubrizol) in n-butyl acetate and then slowly add under thorough stirring Blue 248-4816 (Sun Chemical) is prepared until uniformity is achieved. The gained mixture is further diluted with n-butyl acetate, transferred to the Eiger bead mill (EMI) containing 0.9-1.1YTZ media (Fox Industries) and ground to 500Whr / kg (2: 1 media / mixture weight ratio). The gained slurry is separated and transferred to use the Eiger mill (EMI) containing 0.3-0.4mm YTZ media (Fox Industries) to carry out the second grinding step and be processed to 3000Whr / kg (2: 1 media / mixture weight ratio). After grinding is complete, the gained slurry is further diluted with n-butyl acetate, then used as pigment slurry P8 after removing beads without further modification.

[0197] Pigment paste P9

[0198] Blue pigment paste P9 is made by PX 4350 and MI 6745 was mixed in n-butyl acetate and then slowly added with thorough stirring. Blue L6600F is prepared until uniformity is achieved. The gained mixture is further diluted with n-butyl acetate, transferred to the Eiger bead mill (EMI) containing 0.9-1.1YTZ media (Fox Industries) and ground to 500Whr / kg (2:1 media / mixture weight ratio). The gained slurry is separated and transferred to use the Eiger mill (EMI) containing 0.3-0.4mm YTZ media (Fox Industries) to carry out the second grinding step and be processed to 3500Whr / kg (2:1 media / mixture weight ratio). After grinding is complete, the gained slurry is further diluted with n-butyl acetate, then used as pigment slurry P9 after removing beads without further modification.

[0199] The formulations of pigment pastes P8 and P9 are shown in Table 3.

[0200] Table 3 - Pigment pastes P8 and P9

[0201]

[0202] Pigment paste P8 contains blue pigment 1, which is Blue 15:1-248-4816.

[0203] Blue pigment 4 is Blue L6600F (15:6 blue pigment; BASF SE). 76500 is a commercially available dispersant (Lubrizol) and 5000s is a commercially available dispersing additive (Lubrizol). MI 6745 is a commercial dispersing additive (BASF SE) and PX 4350 is a commercially available dispersant (BASF SE).

[0204] Pigment slurries P8 and P9 were analyzed by particle size analysis after their preparation including the grinding step. Their turbidity was additionally measured. Both the turbidity measurement and the particle size characteristic measurement shown in Table 4 were performed according to the method disclosed in the 'Methods' section. The measured values are shown in Table 4.

[0205] Table 4 - Turbidity and particle size characteristics of pigment pastes P8 and P9

[0206] P8 P9 Turbidity 0.8 0.7 Volume average particle size [nm] 108.9 54.6 Z-average particle size [nm] 54.2 63.8 <![CDATA[d N,10％ [nm]]]> 32.8 44.4 <![CDATA[d N,50％ [nm]]]> 67.0 76.4 <![CDATA[d N,90％ [nm]]]> 140.0 133.0

[0207] 1.3 Preparation of additional aqueous pigment slurries P10-P12

[0208] Three additional pigment pastes containing commercially available black pigments were prepared. P10 and P11 both contained commercially available organic azomethine black pigments, namely A-1103 (Dainichiseika Chemicals). P12 contains commercially available inorganic black pigment, namely carbon black pigment 1300(Cabot).

[0209] The pigment slurry shown in Table 4a was prepared from the ingredients and amounts shown in Table 4a by the following method:

[0210] Pigment paste P10

[0211] Black pigment paste P10 is made by Azo Black A-1103 (Dainichiseika Chemicals) is added to the stirred mixture of dispersant 1, propylene glycol n-butyl ether and deionized water to produce. The gained suspension is stirred for 5 minutes using a Cowles blade. The pH is adjusted to 8.1 (measured using a Starter 300 pH portable pH meter (Ohaus Corporation, Parsippany, New Jersey, USA)) using a 20 wt % dimethylethanolamine aqueous solution. The suspension is transferred to a mixing tank, and the 0.9-1.1 mm YTZ grinding media (Fox Industries) (medium: suspension) of a 2:1 weight ratio is added, and the suspension is stirred for 5 hours using a LAU shaker (LAU disperser DAS 200-LAU GmbH). Gravity filtration is used to separate the 0.9-1.1 mm YTZ media. The collected slurry was transferred to another mixing tank, injected with 0.3-0.4 mm YTZ grinding media at a 2:1 bead / slurry weight ratio and agitated for 12 hours using a LAU shaker (LAU disperser DAS 200 - LAU GmbH). The resulting final slurry was filtered to remove the 0.3-0.4 mm media and used as pigment slurry P10 without further modification.

[0212] Pigment paste P11

[0213] Black pigment paste P11 was prepared in the same manner as pigment paste P10, except that the milling step after the addition of 0.3-0.4 mm YTZ milling media was carried out for only 2 hours instead of 12 hours.

[0214] Pigment paste P12

[0215] Black pigment paste P12 was produced by adding dispersant 3, deionized water and propylene glycol n-propyl ether to a large mixing vessel, mixing thoroughly and then adjusting the pH to 8.1 using a 20 wt% aqueous solution of dimethylethanolamine. 1300 (Cabot) and mixed until homogeneity is achieved. The mixture is then diluted with deionized water and the pH is adjusted again in the same manner as described above for 8.1. The pigment slurry is transferred to an Eiger bead mill (EMI) containing 0.9-1.0 mm beads and ground to an energy of 180 Whr / kg.

[0216] Table 4a - Pigment pastes P10-P12

[0217]

[0218]

[0219] As mentioned above, the black pigment 2 present in pigment pastes P10 and P11 is A-1103 (Dainichiseika Chemicals). The black pigment 3 present in the pigment paste P12 is 1300 (Cabot). Dispersants 1 and 2 have been explained above.

[0220] The pigment slurries P10-P12 were analyzed by particle size analysis after their preparation including the grinding step. Their turbidity was additionally measured. Both the turbidity measurement and the particle size characteristic measurement shown in Table 4b were performed according to the method disclosed in the 'Methods' section. The measured values are shown in Table 4b.

[0221] Table 4b - Turbidity and particle size characteristics of pigment pastes P10, P11 and P12

[0222] P10 P11 P12 Turbidity 4.9 6.5 2.2 Volume average particle size [nm] 685.9 2116 96.0 Z-average particle size [nm] 145.3 165.7 127.9 <![CDATA[d N,10％ [nm]]]> 84 101 79.3 <![CDATA[d N,50％ [nm]]]> 176 189 140 <![CDATA[d N,90％ [nm]]]> 399 357 246

[0223] 2. Preparation of aqueous basecoat compositions

[0224] A number of aqueous basecoat compositions were prepared by using one of the aqueous pigment pastes P2a and P10 to P12. Aqueous basecoat compositions WBC2c and WBC10 to WBC12 were prepared by mixing the ingredients listed in Table 5a in a dissolver in the order given in said table with stirring.

[0225] A number of other aqueous basecoat compositions were prepared using one of the aqueous pigment slurries P1-P7. Aqueous basecoat compositions WBC1-WBC7 and MWBC0, MWBC2a-d, and MWBC4a-c were prepared by mixing the ingredients listed in Tables 5 and 6 below in a dissolver in the order given in the tables with stirring. Each composition in Table 6 was diluted with deionized water (approximately 25-75 parts by weight of deionized water) to a (spray) viscosity of 85.0 ± 5.0 P.

[0226] The resin blend mixture mentioned below was prepared as follows: (i) 3.72 parts Powder (BYK Chemie) was slowly added to 90.08 parts of deionized water and mixed under high shear with a Cowles blade for 45 minutes. 3.5 parts of P1010 Polyol (BASF). Once homogeneity is achieved, the contents are transferred from the mixing vessel to a storage container and rinsed with 2.7 parts of deionized water.

[0227] (ii) 16.7 parts of the solution described in (i) above were diluted with 8.8 parts of deionized water, and then 16.0 parts of polyurethane resin were added and mixed. (iii) 9.4 parts of (meth)acrylic polymer aqueous dispersion (containing 44 wt% resin solids, 54.7 wt% deionized water and 1.33 wt% dimethylethanolamine), 12.34 parts of 36.0 wt% A mixture of VTW 6462 / 36WA (Allnex) and 64.0 wt. % deionized water and 7.41 parts 327 (Allnex). (iv) The resulting resin blend was diluted with 3.3 parts of propylene glycol n-butyl ether, followed by the introduction of 0.94 parts of a commercially available additive. (v) 10.7 parts of a branched polyester dispersion containing 42.3% by weight of resin solids and 53.7% by weight of ethylene glycol monobutyl ether and 4.0% by weight of an aqueous solution containing dimethylethanolamine (20% by weight) were then added, followed by the addition of 2.3 parts of propylene glycol n-butyl ether. (vi) The pH of the resulting mixture was adjusted to 8.1 with an aqueous solution containing dimethylethanolamine (20% by weight), and the resulting product was used as a resin blend mixture.

[0228] The polyurethane referred to hereinafter is an aqueous mixture containing 27.0 wt% polyurethane resin solids, 0.3 wt% n-butanol, 3.9 wt% methyl propyl ketone, 4.0 wt% N-methylpyrrolidone and 64.8 wt% deionized water.

[0229] Table 5a - Waterborne basecoat compositions WBC2c and WBC10-WBC12

[0230]

[0231]

[0232] 3. Preparation of solvent-based topcoat composition

[0233] A number of solvent-based topcoat compositions were prepared using either of the solvent-based pigment pastes P8 and P9 or, in the case of SBCCO and TCO, no pigment paste was used. Each of these compositions was a 2K composition. Pigment paste P8 or P9 was first mixed with the "A" component, namely E10CG081 G, under stirring. The resulting mixture was then mixed with the "B" component, a polyisocyanate with free NCO groups (N52CG081). Both E10CG081 G and N52CG081 are commercially available (available as 2K4 is available from BASF Corporation, Coatings Division, USA). In this way, the solvent-borne topcoat compositions SBCC0, SBCC8a, SBCC8b, SBCC8c, SBCC8d, SBCC9a, SBCC9b, SBCC9c and SBCC9d are obtained as shown in Table 7. The pigment amounts indicated are in each case based on the total solids content of components "A" + "B".

[0234]

[0235] 4. Preparation of multilayer coating systems

[0236] 4.1 Multilayer coating systems obtained by using pigmented solventborne topcoat compositions in the 2C1B process

[0237] A corrugated steel sheet with a cured primer coating was used as the substrate. An aqueous basecoat WBC1, prepared using pigment paste P1 containing an organic black pigment, an aqueous basecoat WBC11, prepared using pigment paste P11 containing an organic black pigment, or an aqueous basecoat WBC12, prepared using pigment paste P12 containing an inorganic carbon black pigment, was sprayed onto the basecoat in an amount that resulted in a dry film thickness of 18-20 μm upon curing. After drying for up to 10 minutes at room temperature (23°C), one of the solvent-borne topcoat compositions SBCC0, SBCC8a, SBCC8b, SBCC8c, SBCC8d, SBCC9a, SBCC9b, SBCC9c, and SBCC9d was sprayed wet-on-wet onto the uncured basecoat film in an amount that resulted in a dry film thickness of 45-55 μm upon curing. The two applied coatings were then jointly cured at 130°C for 30 minutes.

[0238] 4.2 Multilayer coating systems obtained by the 3C1B process with a pigmented aqueous basecoat composition applied as a midcoat

[0239] A corrugated steel sheet with a cured primer coating was used as the substrate. An aqueous basecoat WBC1, prepared using a pigment paste P1 containing black pigment, was sprayed onto the basecoat as the first basecoat in an amount that resulted in a dry film thickness of 18-20 μm upon curing. After drying for up to 10 minutes at room temperature (23°C), one of the aqueous basecoat compositions MWBC0, MWBC2a, MWBC2b, MWBC2c, MWBC2d, MWBC4a, MWBC4b, and MWBC4c was sprayed wet-on-wet onto the uncured first basecoat film as the second basecoat in an amount that resulted in a dry film thickness of 9-11 μm upon curing. In an additional control experiment, no second basecoat was applied; i.e., the first basecoat represented the sole basecoat in the 2C1B control experiment. After drying for up to 10 minutes at room temperature (23° C.), the solvent-borne topcoat composition SBCC0 was sprayed wet-on-wet as a clearcoat onto the uncured basecoat film or, in the case of the control test, the first basecoat film, in each case, in an amount such that upon curing a dry film thickness of 45 to 55 μm was obtained. All three (or two) applied coating films were then jointly cured at 130° C. for 30 minutes.

[0240] 5. Properties of substrates coated with multi-layer coating systems

[0241] 5.1 Each substrate coated with an aqueous basecoat WBC1, WBC11, or WBC12 as described in 4.1 and subsequently coated with one of the solventborne topcoat compositions SBCC0, SBCC8a, SBCC8b, SBCC8c, SBCC8d, SBCC9a, SBCC9b, SBCC9c, and SBCC9d was investigated for its blackness (My) and jetness (Mc) values as well as its color values L*, a*, and b*. These values were measured according to the method disclosed in the "Methods" section. The measured values are shown in Tables 8a, 8b, and 8c. In addition, each coated substrate was visually inspected (by a human) and scored (score 1-6):

[0242] Rating 5 = no or essentially no improvement in color position when compared to the control (in this case SBCC0 was applied over WBC1, WBC11, or WBC12, SBCC0 did not contain any pigment and WBC1 and WBC11 each contained an organic black pigment and WBC12 contained an inorganic carbon black pigment);

[0243] Rating 6 = The coated substrate no longer appears black due to an overly strong base color; and

[0244] Rating 1-4 = improvement in color position when compared to the control, with '1' being the most significant improvement.

[0245] Table 8a - Color, Jet and Black Value of Substrates Coated with WBC1 and Subsequently with Solventborne Topcoat, Part I

[0246]

[0247] Table 8b - Color, Jet and Black Value of Substrates Coated with WBC1 and Subsequently Topcoated with Solventborne Topcoat, Part II

[0248]

[0249] Table 8c - Color, Jet and Black Value of Substrates Coated with WBC11 or WBC12 and Subsequently Topcoated with a Solventborne Topcoat

[0250]

[0251] 5.2 The black (My) and blackness (Mc) values as well as the color values L*, a* and b* of each substrate coated with an aqueous basecoat WBC1 as the first basecoat, followed by an aqueous basecoat composition MWBC0, MWBC2a, MWBC2b, MWBC2c, MWBC2d, MWBC4a, MWBC4b and MWBC4c as the second basecoat and then a solvent-based topcoat composition SBCC0 as the clearcoat were studied. These values were measured according to the method disclosed in the 'Methods' section. The measured values are shown in Tables 9a and 9b. In addition, each coated substrate was visually inspected (by a human) and scored (score 1-6):

[0252] Rating 5 = no or virtually no improvement in color position when compared to the control (in this case SBCC0 applied over MWBC0 applied over WBC1, neither SBCC0 nor MWBC0 containing any pigment and WBC1 containing an organic black pigment);

[0253] Rating 6 = The coated substrate no longer appears black due to an overly strong base color; and

[0254] Rating 1-4 = improvement in color position when compared to the control, with '1' being the most significant improvement.

[0255] Table 9a - Color, Jet and Black Value of Substrates Coated with WBC1, Then with Another Aqueous Basecoat and Then with SBCCO, Part 1

[0256]

[0257] Table 9b - Color, Jet and Black Value of Substrates Coated with WBC1, Then with Another Aqueous Basecoat and Then with SBCC0, Part II

[0258]

[0259] 6. Comparative test data

[0260] In view of and in accordance with the disclosure of WO 2012 / 170230 A1, other comparative tests were conducted:

[0261] An aqueous basecoat composition containing a black pigment and another additional pigment is prepared by preparing a blend of basecoat composition WBC1 (containing pigment paste P1, which in turn contains an organic black pigment) or WBC10 and basecoat compositions WBC2a or WBC2c (containing pigment paste P2b or P2a), WBC3 (containing pigment paste P3), WBC4 (containing pigment paste P4), WBC5a and WBC5b (each containing pigment paste P5), and one of WBC6 and WBC7 (containing pigment pastes P6 or P7). In other words, a basecoat composition is prepared that contains both a black pigment (from P1) and another pigment (from P2b, P2a, P3, and P5-P7) in the same basecoat composition.

[0262] The ingredients listed in Tables 10-13, 13a, and 13b below were mixed in a dissolver in the order given in the tables with stirring to prepare the aqueous basecoat composition blends shown therein. Tables 10-12 represent the first run of experiments. Tables 13, 13a, and 13b represent the second run of experiments. In this manner, basecoat composition blends B1-B56 were obtained.

[0263] A number of additional aqueous basecoat compositions were prepared by using aqueous pigment paste P11 alone or together with pigment paste P2a.Aqueous basecoat compositions RWBC1 to RWBC5 were prepared by mixing the ingredients listed in Table 13c in a dissolver in the order given in said table with stirring.

[0264] These aqueous basecoat composition blends were then used to produce a multi-layer coating system using the 2C1B method according to WO 2012 / 170230 A1: Corrugated steel sheets with a cured basecoat were used as substrates. Aqueous basecoat WBC1 or WBC10, or one of the blends B1-B56, or one of RWBC1-RWBC5, was sprayed onto the basecoat as a basecoat in an amount that yielded a dry film thickness of 18-20 μm upon curing. After drying at room temperature (23°C) for up to 10 minutes, a solvent-borne topcoat composition BCC0 or TCO was sprayed wet-on-wet onto the uncured basecoat film as a clearcoat in an amount that yielded a dry film thickness of 45-55 μm upon curing. The two applied coating films were then jointly cured at 130°C for 30 minutes in each case.

[0265] Each coated substrate was then investigated for its blackness (My) and jetness (Mc) values, as well as its color values L*, a*, and b*. These values were measured according to the methods disclosed in the 'Methods' section. The measured values are shown in Tables 14-18. In addition, each coated substrate was visually inspected (by a human) and scored (scores 1-6).

[0266] Rating 5 = no or virtually no improvement in color position when compared to the control (in this case SBCC0 was applied to WBC1 or WBC10, SBCC0 did not contain any pigment and WBC1 contained a black organic pigment);

[0267] Rating 6 = The coated substrate no longer appears black due to an overly strong base color; and

[0268] Rating 1-4 = improvement in color position when compared to the control, with '1' being the most significant improvement.

[0269]

[0270]

[0271]

[0272]

[0273]

[0274]

[0275] It can be seen that the pigment blends present in the basecoat composition blends B1-B14 and B19-, B53-B56-, RWBC1-RWBC5 and as disclosed in WO 2012 / 170230 A1 can, in principle, increase the jetness (Mc); however, as can be seen in the first round of testing when comparing B9-B14, B19-B28, and B31-B36 with WBC1, this does not generally apply in all cases. For example, in the second round of testing, when comparing a coated substrate prepared using blend B52 with a coated substrate prepared using WBC1, an increased jetness (Mc=288.4 vs. Mc=247.3) was observed. However, the visual appearance (color) of this coating system was still inferior to that of a system prepared using a basecoat containing carbon black (not shown).

[0276] Furthermore, to prepare blend B52, an aqueous basecoat WBC4 was used, which contained a low-turbidity pigment paste P4, which in turn contained blue pigment 2. When the same paste P4 was used to prepare the midcoat layer, MWBC4b, to be used as an additional second aqueous basecoat composition in the 3C1B process, slightly better blackness values were observed compared to when blend B52 was used in the 2C1B process (Mc = 292.4 for the system obtained using MWBC4b, compared to Mc = 288.4 for B52). However, surprisingly, the visual appearance of the coating system obtained using MWBC4b was much better compared to the system obtained using B52, especially when using MWBC4b, because the b* values obtained using MWBC4b were more negative (score 2 vs. 5 and b* = -1.69 vs. b* = -0.57), which resulted in an overall more bluish impression. Furthermore, the dM (undertone) values were also better for the MWBC4b system, as the black (My) values were approximately the same in both cases.

[0277] Even greater increases in jetness and visual appearance are obtained by using a pigmented clearcoat in the 2C1B process (see item 5.1).

Claims

1. A method for preparing a multilayer coating system on an optionally precoated substrate, comprising at least steps (1) and (3a) or at least steps (1), (2) and (3b), namely: (1) applying a colored base coating composition to an optionally precoated substrate and forming a first coating film on the optionally precoated substrate, wherein the base coating composition contains at least one organic black pigment, (2) optionally applying a second colored base coating composition different from the base coating composition applied in step (1) to the first coating film existing on the substrate obtained after step (1) and forming a second coating film adjacent to the first coating film, and (3a) will be different from the conditions in step (1) and in optional step (2) if optional step (2) is not performed. a coating composition of the composition applied in step (1) is applied to the first coating film existing on the substrate obtained after step (1) and forms a second coating film adjacent to the first coating film, wherein the coating composition is a colored topcoat composition, or (3b) applying a coating composition different from the compositions applied in step (1) and in optional step (2) to the second coating film existing on the substrate obtained after step (2) while carrying out optional step (2) and forming a third coating film adjacent to the second coating film, wherein the coating composition is a clear coating composition, wherein the second coating film obtained after step (3a) or the third coating film obtained after step (3b) is the outermost film of the formed multi-layer coating system, It is characterized by Neither the second pigmented basecoat composition applied in optional step (2) nor the coating composition applied in step (3a) or (3b) comprises any black pigments and - in the case of carrying out steps (1), (2) and (3b) - the second pigmented basecoat composition or - in the case of carrying out steps (1) and (3a) - the topcoat composition comprises at least one non-black pigmented pigment having a volume average particle size of <1000 nm in an amount in the range from 0.01 to 7.50% by weight, in each case based on the total solids content of the respective composition, wherein the at least one non-black pigmented pigment is in each case incorporated into the respective composition in the form of a pigment paste.

2. The method according to claim 1, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition is a blue pigment.

3. The method according to claim 1, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition is an organic pigment.

4. The method according to claim 1, wherein The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition is an organic blue pigment.

5. The method according to claim 1, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition is the only colored pigment present in the second colored basecoat composition or the topcoat composition.

6. The method according to claim 1, characterized in that The pigment slurry containing the at least one non-black colored pigment used to prepare the second colored basecoat composition or the topcoat composition has a turbidity of <20%.

7. The method according to claim 2, characterized in that The pigment slurry containing the at least one non-black colored pigment used to prepare the second colored basecoat composition or the topcoat composition has a turbidity of <15%.

8. The method according to claim 5, characterized in that The pigment slurry containing the at least one non-black colored pigment used to prepare the second colored basecoat composition or the topcoat composition has a turbidity of <10%.

9. The method according to claim 1, wherein The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition has a volume average particle size in the range of 10 nm to <950 nm.

10. The method according to claim 9, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition has a volume average particle size in the range of 25-900 nm.

11. The method according to claim 8, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition has a volume average particle size in the range of 30-850 nm.

12. The method according to claim 1, wherein The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition has a Z-average particle size in the range of 10-750 nm.

13. The method according to claim 12, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition has a Z-average particle size in the range of 25-500 nm.

14. The method according to claim 11, characterized in that The at least one non-black colored pigment present in the second colored basecoat composition or the topcoat composition has a Z-average particle size in the range of 30-350 nm.

15. The method according to any one of claims 1 to 8, characterized in that The multilayer coating system obtained after curing has a blackness Mc of at least 250 and / or has a blackness Mc value that exceeds its blackness My value.

16. The method according to claim 15, characterized in that The multilayer coating system obtained after curing has a blackness Mc of at least 270 and / or has a blackness Mc value that exceeds its blackness My value by at least 1%.

17. The method according to any one of claims 1 to 8, characterized in that The at least one non-black colored pigment is present in the second colored basecoat composition or the topcoat composition in an amount within the range from 0.01 to 5.00% by weight, in each case based on the total solids content of the respective composition.

18. The method according to claim 17, characterized in that The at least one non-black colored pigment is present in the second colored basecoat composition or the topcoat composition in an amount within the range from 0.01 to 3.50% by weight, in each case based on the total solids content of the respective composition.

19. The method according to any one of claims 1 to 8, characterized in that The at least one non-black colored pigment is present in the second colored basecoat composition in an amount ranging from 0.10 to 5.00 weight percent based on the total solids content of the second colored basecoat composition or in the topcoat composition in an amount ranging from 0.01 to 2.50 weight percent based on the total solids content of the topcoat composition.

20. The method according to any one of claims 1 to 8, characterized in that The at least one organic black pigment present in the basecoat composition applied in step (1) is an IR transparent organic black pigment.

21. The method according to claim 20, characterized in that The IR transparent organic black pigment is at least one perylene and / or azomethine pigment.

22. The method according to any one of claims 1 to 8, characterized in that The total solids content of the second pigmented basecoat composition or of the topcoat composition is in each case in the range from 10 to 65% by weight, based in each case on the total weight of the respective composition.

23. The method according to claim 22, characterized in that The total solids content of the second pigmented basecoat composition or of the topcoat composition is in each case in the range from 25 to 45% by weight, based in each case on the total weight of the respective composition.

24. The method according to any one of claims 1 to 8, characterized in that Optionally, step (2) is performed before curing the first coating film obtained after step (1), step (3a) is performed before curing the first coating film obtained after step (1), and step (3b) is performed before curing the second coating film obtained after step (2).

25. The method of claim 24, wherein the method comprises at least one further step (4), namely: (4) jointly curing all the coating films applied in steps (1) and (3a) or steps (1), (2) and (3b), A cured multilayer coating system comprising at least a first and a second coating layer is obtained, wherein the second coating layer is the outermost layer of the formed multilayer coating system, or a cured multilayer coating system comprising at least a first, a second and a third coating layer, wherein the third coating layer is the outermost layer of the formed multilayer coating system.

26. A multi-layer coating system present on an optionally pre-coated substrate, characterized in that It is obtained by a process according to any one of claims 1-25.

27. A coated substrate obtainable by a process according to any one of claims 1 to 25.

28. Use of a colored coating composition, The colored coating composition does not contain any black pigment and contains at least one non-black colored pigment having a volume average particle size of less than 1000 nm in an amount in the range of 0.01-7.50 wt. % based on the total solid content of the coating composition, wherein the at least one non-black colored pigment having a volume average particle size of less than 1000 nm is incorporated into the coating composition in the form of a pigment paste, as a second pigmented basecoat composition in step (2) or as a topcoat composition in step (3a) of the process for producing a multilayer coating system on an optionally precoated substrate according to any one of claims 1 to 25, The blackness Mc of the resulting multi-layer coating system after curing is increased to an extent that the blackness Mc exceeds the blackness My of the cured multi-layer coating system.

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