Method for coating a substrate having metallic and plastic parts

Abstract

The present invention relates to a method for coating a substrate with an aqueous primer coating material, comprising the steps of providing a substrate which comprises at least two parts, one part of the substrate being a metal having a pre-coated metal surface area and one part of the substrate being a plastic material comprising one or more organic polymers and having a non-coated surface area comprising the one or more organic polymers, the one or more organic polymers consisting of carbon, hydrogen and optionally halogen atoms, or the one or more organic polymers containing carbonyl groups; and subsequently applying an aqueous primer coating material onto the at least two surface areas to form a primer coating layer, the aqueous primer coating material containing 10 to 75 wt.-%, based on total binder solids, of one or more polymeric resins A, each of which possesses a hydroxyl value of 0 to 10 mg KOH / g; at least partially neutralized acid groups; and a polymeric backbone consisting of hydrocarbon groups, if the part of the substrate being a plastic material comprises an organic polymer according to b1, or an organic polymer according to b2, if the carbonyl groups are part of amide moieties; or comprising carbonyl groups, if the part of the substrate being a plastic material comprises an organic polymer according to b2. The invention further relates to a thus coated substrate and the use of the aqueous primer coating material in coating substrates comprising the afore-mentioned two parts.

Description

[0001] METHOD FOR COATING A SUBSTRATE HAVING METALLIC AND PLASTIC PARTS

[0002] The present invention relates to a method for coating a substrate with an aqueous primer coating material, the substrate comprising a precoated metal part and a non-coated plastic material part. The invention further relates to thus coated substrates and the use of an aqueous primer coating material for coating substrates comprising a precoated metal part and a noncoated plastic material part.

[0003] TECHNOLOGICAL BACKGROUND

[0004] Particularly in the OEM (original equipment manufacturer) vehicle coating industry there are several challenges to be overcome in the coating process. Typically, any coating process starts with the selection of suitable substrates.

[0005] In vehicle coating many parts to be coated are metallic parts having metallic surfaces which are susceptible to corrosion. To increase the corrosion resistance of such parts, as for example vehicle bodies, the bare metallic substrates are thoroughly cleaned and conversion coated, such as zinc-phosphated, to obtain a first corrosion protection layer. Subsequently, it is common practice that an electrodeposition coating material is applied, preferably by cathodic electrodeposition coating, to obtain a second corrosion protection layer. To obtain a full multilayer architecture, the thus electrodeposition coated metallic substrates are coated with one or more primer coating layers, one or more basecoat layers and finally one or more clearcoat layers. Primer coating materials customized for adherence on electrocoating layers typically comprise, as the main resins, hydroxy group containing resins and do often not adhere well on plastic surfaces, particularly untreated plastic surfaces.

[0006] Other vehicle parts are made of plastic materials, containing one or more organic polymers. For such materials corrosion resistance is no problem, thus they do not comprise layers like the above-mentioned corrosion protection layers. Typically, coating starts with one or more primer coating layers, followed by one or more basecoat layers and finally one or more clearcoat layers. However, there are other challenges to be overcome with plastic substrates, predominantly related to the adhesion of the first or only primer coating layer on the plastic substrate. To increase the adhesion of the primer coating layer, the OEM vehicle industry makes use of physical surface treatment steps, such as flame treatment and / or plasma treatment, and coating the plastic material first with an adhesion promotor or a special adhesion promoting primer. Consequently, it is common practice in OEM coating that different primer coating materials are used on the metallic parts and on the plastic parts, both typically requiring different application and curing conditions. Since primer coating materials are also most often pigmented and thus color-imparting it is a further challenge to obtain primer formulations for metallic and plastic parts having virtually the same color, since even though further coating layers such as base coat layers are also color-imparting, some coloristic effects originating from the primer coating layer will impact the color of subsequent layers. If the metallic and plastic parts of the substrate should show have the same coloristic appearance after completion of the multilayer coating process, it would be of big advantage, if the same primer coating material could be used on the to be coated metallic parts and the plastic parts of a substrate.

[0007] This would also have the advantage that those parts of the substrate can be pre-assembled and coated with the very same primer coating material in a single step in one and the same coating line under the same conditions, allowing an improved throughput compared to the use of two separate coating lines for metallic and plastic parts.

[0008] Furthermore, from the view point of environmental aspects, the universal primer coating material to be used in the method for coating a substrate should be water-based. A waterbased primer composition solely for plastic material is, e.g., disclosed in CN 111117380 A.

[0009] In US 6,887,524 two-pack primer coating materials for use on metal parts as well as plastic parts are disclosed, which cure at temperatures below 100 °C.

[0010] Thus, there is a need for a method for coating a substrate with an aqueous universal primer coating material which adheres well on plastic substrates, even those which have not been flame- and / or plasma-treated or precoated with adhesion promoting primers, but also adheres well on electrocoated metallic substrates. Further, coating on the same line, in a single step under the same conditions does not only guarantee a higher throughput, it also provides for a more uniform appearance and appearance harmony as well as improved color on all parts of the substrate, metallic and plastic, if applied in a full hiding layer thickness. To achieve these aims, it was necessary to consider the different kind of plastic materials that might be used in OEM coating processes, particularly their surface energies, which typically differ from those of electrocoated metal substrates and their thermal stabilities at curing temperatures of the primer coating and / or multilayer coating. Thus, a general concept had to be developed allowing to tailor the universal primer coating material for application on electrocoated metal surfaces, such as electrocoated steel surfaces, and having excellent adhesion on different specific plastic surfaces.

[0011] SUMMARY

[0012] The above problems were overcome and the aims achieved by providing a method for coating a substrate with an aqueous primer coating material, comprising the following steps: i. providing a substrate which comprises at least two parts, a. one part of the substrate being a metal having a pre-coated metal surface area and b. one part of the substrate being a plastic material comprising one or more organic polymers and having a non-coated surface area comprising the one or more organic polymers, b1. the one or more organic polymers consisting of carbon, hydrogen and optionally halogen atoms, or b2. the one or more organic polymers containing carbonyl groups; and ii. applying an aqueous primer coating material onto the at least two surface areas to form a primer coating layer, the aqueous primer coating material containing 15 to 75 wt.-%, based on total binder solids, of one or more polymeric resins A, each of which possesses a. a hydroxyl value of 0 to 10 mg KOH / g, b. at least partially neutralized acid groups; and c. a polymeric backbone c1 . consisting of hydrocarbon groups, if the part of the substrate being a plastic material comprises an organic polymer according to b1 , or an organic polymer according to b2, if the carbonyl groups are part of amide moieties, or c2. comprising carbonyl groups, if the part of the substrate being a plastic material comprises an organic polymer according to b2.

[0013] This method and its preferred embodiment are hereinafter denoted as “method of the invention,” or “method according to the invention.”

[0014] Further subject matter of the present invention is a coated substrate obtained by the method according to the invention, preferably a multilayer coated substrate obtained by the method according to the invention. The thus coated substrate and its preferred embodiments are herein denoted as “coated substrate of the invention,” or “coated substrate according to the invention.”

[0015] Yet another subject matter of the present invention is the use of the aqueous primer coating composition as in this specification to coat a substrate which comprises at least two parts as described in this specification in vehicle coating, particularly automotive coating.

[0016] This use and its preferred embodiments are hereinafter denoted as “use of the invention,” or “use according to the invention.”

[0017] DETAILED DESCRIPTION

[0018] In the following, the method according to the invention will be further described by preferred features and embodiments.

[0019] Method of the Invention

[0020] Step / .

[0021] In the first step of the invention a substrate is provide which comprises at least two parts, one part of the substrate being a metal having a pre-coated metal surface area, and one part of the substrate being a plastic material comprising one or more organic polymers and having a noncoated surface area comprising the one or more organic polymers.

[0022] A substrate comprising two parts as defined above is preferable a pre-assembled part, at least one part being a metal having a pre-coated metal surface area, and one part of the substrate being a plastic material comprising one or more organic polymers and having a non-coated surface area comprising the one or more organic polymers.

[0023] Metal Part of the Substrate

[0024] The part comprising the pre-coated metal surface is a metal part, the term “metal” including “alloys,” the metal being preferably selected from the group consisting of bare steel, hot dip or electro galvanized steel, cold rolled steel, aluminum, and magnesium, or any alloys of the afore-mentioned. These metal parts of the substrate are not used as such in the present invention, but precoated.

[0025] As pre-coating layer, at least one of a chemical pre-treatment layer, such as a conversion coating layer and an electrocoat layer is applied to the metal part before being used in the method according to the invention, more preferred at least an electrocoat layer is formed on the surface of the metal part, and even more preferred first a chemical pre-treatment layer, such as a conversion coating layer is formed on the surface of the metal part, followed by the formation of an electrocoating layer. Thus, it is particularly preferred that the pre-coated metal surface area comprises a chemical pre-treatment layer, such as conversion coating layer and thereon an electrodeposition coating layer.

[0026] The term “chemical pre-treatment” is used in accordance with EN ISO 4618:2006 (E / F / D) (term: 2.41 “chemical pre-treatment,” which stands for any chemical process applied to a surface priorto the application of a coating material). According to this standard, e.g., treatments like chromating and phosphating, which belong to conversion treatment, belong to the chemical pre-treatment and thus are to be distinguished from coating steps, wherein coating materials, i.e., coating compositions such electrodeposition coating materials, or other coating materials are applied.

[0027] Electrodeposition coating layers are formed by using electrodeposition coating materials, which are aqueous coating compositions being applied by dip coating, i.e., dipping the preferably chemically pre-treated metallic substrate into the electrically conductive, aqueous electrodeposition coating composition and applying a direct voltage between the substrate and a counter electrode. The electrodeposition coating composition is an anodic or cathodic electrodeposition coating composition, preferably a cathodic electrodeposition coating composition. Cathodic electrodeposition coating compositions are preferably selected from epoxy type and poly(meth)acrylate-type electrodeposition coating compositions. They are applied according to the coating manufacturers specifications.

[0028] The part of the substrate being a metal having a pre-coated metal surface area, is thus preferably an electrodeposition coat pre-coated metal surface area, the electrodeposition coating layer being a cured layer.

[0029] Suitable examples of metal parts of a substrate are, substrates of any shape, e.g., vehicle bodies, particularly motor vehicle bodies, such as automotive bodies, bodies of trucks and tractors, and parts thereof, such as hoods, doors, fenders, bumpers and trims. Plastic material part of the Substrate

[0030] The plastic material part of the substrate may roughly be categorized as being a plastic material comprising at least one of a polar or non-polar organic polymer. The plastic material part does comprise an organic polymer, or blend of organic polymers, and optionally at least one of pigments and fillers and additives. Thus, the term “plastic material part” comprises polymers, polymer blends as well as the afore-mentioned further blended with ingredients such as pigments, fillers and additives.

[0031] Suitable non-polar organic polymers comprised in the plastic part are so-called thermoplastic polyolefin elastomers (TPO).

[0032] Suitable polar organic polymers comprised in the plastic part contain carbonyl groups, which are preferably present in urethane moieties, carbonate moieties, but also amide moieties. Most suitable organic polymers are polycarbonates (PC) and polyamides

[0033] Unlike in prior art methods, the plastic parts used in the present invention are non-coated. They do not comprise a coating before carrying out step ii., such as an adhesion promotor or an adhesion promoting primer, and they are preferably not even flame-treated or plasma-treated. The method of the present invention does not require such treatments and coatings and thus reduces the efforts in coating such substrates.

[0034] Suitable examples of plastic material parts of a substrate are, e.g., bumpers, trims, spoilers, liftgates, hoods, gas caps and mirror housings.

[0035] Step ii.

[0036] In step ii. the aqueous primer coating material is applied the onto the at least two surface areas to form a primer coating layer.

[0037] Aqueous primer coating material

[0038] The aqueous primer coating material is preferably a one-component (1 K) primer coating material. The term “primer” as used herein is sometimes also denoted “primer surfacer” or “surfacer” in literature. Thus, a “primer coating material” is the same as a “primer surfacer material” or a “surfacer material.”

[0039] A “one-pack coating material” - as defined in the textbook “Rdmpp Lexikon Lacke und Druckfarben”, Thieme, 1998 - is a coating composition, which, contrary to the below described two-pack coating materials are produced and supplied in a way that they contain the base resins and the curing agents in one composition without premature reaction between the ingredients. Reaction is preferably caused either by heating / baking or reaction with air moisture. This definition is valid for all one-pack coating materials as described herein, irrespective of whether it is a primer coating material, a basecoat coating material or a clearcoat coating material.

[0040] In contrast thereto, a “two-pack coating material” - as defined in the textbook “Rdmpp Lexikon Lacke und Druckfarben”, Thieme, 1998 - is a material where curing is affected by mixing two components (a master batch “Stammlack” and a curing agent “Harter”) in a specified mixing ratio. The components themselves are not coating compositions, since they are not apt to film formation or do not form durable films. This definition is valid for all two-pack coating materials as described herein, irrespective of whether it is a primer coating material, a basecoat coating material or a clearcoat coating material.

[0041] The term “aqueous” as used herein implies that water is part of the volatile ingredients of the coating material. Another term for “aqueous” is “waterborne”, when used in combination with coating materials. Preferably the amount of water, based on the volatile ingredients of the coating material is at least 30 wt.-% more preferred at least 40 wt.-% and most preferred at least 50 wt.-%. Herein below the determination of the non-volatile part of coating materials, i.e. , the total solids content is described. The volatile part and the non-volatile part add up to 100 wt.-% of the coating material.

[0042] Polymeric resin A

[0043] The aqueous primer coating material contains 10 to 75 wt.-%, preferably 15 to 65 wt.-% and even more preferred 25 to 55 wt.-%, based on total binder solids, one or more polymeric resins A as described herein above and below. If it is referred to the total binder solids herein, it is meant the binder solids according to EN ISO 4618:2006 (E / F / D) which defines binders as being the non-volatile part of the coating material without pigments and fillers. The total binder solids are determined by first determining the total solids content. The total solids content is determined by drying a sample of the coating material (approx. 1 g) for 30 min at a temperature of 110 °C. The non-volatile part is expressed in weight percent and equals the solids content. The difference to 100 wt.-% is the volatile content. T o obtain the total binder content, the weighed-in amounts of pigments and fillers used in the coating material in weight percent of the coating material is subtracted from the total solids content in weight percent. The determination of the binder content and total solids content applies herein to any coating material, but also to ingredients of coating materials before their incorporation into the respective coating material.

[0044] The polymeric resin A have in common that they possess a hydroxyl value of 0 to 10 mg KOH / g, further preferred a hydroxyl value of 0 to 5 mg KOH / g, more preferred 0 to 3 mg KOH / g or 0 to 2 mg KOH / g. It is particularly preferred that the polymeric resins A have a hydroxyl value of 0 to 1 mg KOH / g. The hydroxyl values being determined according to ASTM Standard Test Method E222-23 “Standard Test Methods for Hydroxyl Groups Using Acetic Anhydride Acetylation.”

[0045] The polymeric resins A preferably have a weight-average molecular weight Mwin the range from 10,000 to 300,000 g / mol, more preferred in the range from 20,000 to 200,000 g / mol, even more preferred 30,000 to 150,000 g / mol and most preferred in the range from 50,000 to 120,000 g / mol as determined by gel permeation chromatography and described in more detail in the experimental section of the present invention.

[0046] The polymeric resin A further comprises at least partially neutralized acid groups. The acid groups are preferably selected from carboxylic acid groups and / or carbonic acid groups, carboxylic acid groups being more preferred. The term “at least partially neutralized acid groups” relates to the polymeric resin A as a substance, comprising acid groups. Some of the acid groups present in the polymeric resin may remain in protonated form, while others might be neutralized by one or more bases, such as alkali hydroxides or amines, preferably amines. The at least partial neutralization helps to dissolve or disperse the polymeric resin A in the aqueous medium.

[0047] The polymeric resins A have a polymeric backbone, the polymeric backbone being the main chain of the polymeric resin. As to IUPAC, “Glossary of basic terms in polymer science” in Pure and Applied Chemistry 68, 2287-2311 , the backbone is that linear chain to which all other chains, long or short or both, may be regarded as being pendant. Where two or more chains could equally be considered to be the main chain, that one is selected which leads to the simplest representation of the molecule. According to the afore-mentioned IIIPAC article so- called pendant groups or side-groups are offshoots (neither oligomeric nor polymeric) from a chain. Thus, they are - as used herein - not parts of the chain, but just offshoots. Consequently, a chlorinated copolymer of an olefin and a maleic acid has a polymeric backbone which is a hydrocarbon, while the chlorine atoms and carboxylic acid groups are considered not to belong to the polymeric backbone, but are regarded as side-groups or pendant groups hereinafter.

[0048] The selection of a suitable polymeric resin A to be used in the method according to the invention depends on the part of the substrate being the plastic material comprising an organic polymer on the respective surface area. Without wanting to be bound by theory, it is neither the hydroxyl value, preferably being as low as possible, most preferred being zero, nor the presence of at least partially neutralized acid groups in the polymeric resin A alone making the resin suitable for a specific plastic material comprising an organic polymer on the respective surface area of the substrate. It rather seem to be dispersive interactions and diffusive interactions at the interface of substrate to aqueous primer coating layer, which, in combination with the other requirements, play a crucial role for the good adhesion properties.

[0049] If the organic polymers on the part of the substrate being the plastic material are rather nonpolar polymers, such as polymers consisting of carbon, hydrogen and optionally halogen atoms, it is preferred that the polymeric resin A is obtained by polymerization of ethylenically unsaturated monomers, which lead to the formation of a backbone consisting of hydrocarbon groups. Most preferred such polymers are selected from the group consisting of copolymers formed by polymerization of olefins and ethylenically unsaturated dicarboxylic acid anhydrides, wherein as olefins also halogenated olefins can be used. In the final polymeric resin A the dicarboxylic acid anhydrides are hydrolyzed in form of acid groups, which again are at least partially neutralized. Such polymeric resins A are also suitable if the organic polymers on the part of the substrate being the plastic material are polyamides, thus comprising amide groups.

[0050] Examples of suitable resins A for plastic materials comprising one or more organic polymers, wherein the one or more organic polymers consisting of carbon, hydrogen and optionally halogen atoms are selected from copolymers containing or consisting of polymerized olefin groups, which are optionally partially halogenated, and possess maleic anhydride groups as pendant groups, which are hydrolyzed and at least partially neutralized before use. Suitable resins of the afore-mentioned type are, e.g., commercially available under the tradenames Hardlen NZ-1015, Hardlen EW-5303, Hardlen NZ-1004 (all from Toyobo), CP 310W, CP 347W, CP 349W (all from Eastman) and Superchlon S-4625.

[0051] If the organic polymers on the part of the substrate being the plastic material are rather polar polymers, such as polymers containing carbonyl groups, it is preferred that the polymeric resin A also contains carbonyl groups as part of the polymeric backbone. Such carbonyl groups (C=O) in the polymeric backbone are preferably selected from urethane groups, such as NH-(C=0)-0 groups, carbonic acid group, such as 0-(C=0)-0 groups and amide groups, such as -(C=O)-NH- groups.

[0052] A preferred example of such polymeric resin A is, e.g., the reaction product of an aliphatic polyisocyanate and a polycarbonate polyol. Such resin contains urethane groups as well as carbonic acid groups, wherein part of the latter groups might be neutralized.

[0053] Polymeric hydroxy functional Binders B

[0054] The aqueous primer coating material preferably further contains one or more polymeric hydroxy functional resins B, differing from polymeric resins A. Suitable polymeric hydroxy functional binders are in principle all polymeric polyhydroxy-functional binders which comprise at least two hydroxyl groups and preferably being selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and poly(meth)acrylate polyols and / or copolymers of the stated polymers. With particular preference the at least one polymeric hydroxy functional resin B is selected from the group consisting of polyurethane polyols, polyester polyols, poly(meth)acrylate polyols and / or copolymers of the stated polymers. The terms “(meth)acrylate” or “(meth)acrylic” stand for both, acrylate and methacrylate, and for both acrylic and methacrylic. Preferably, any of the afore-mentioned polymeric hydroxy functional binders B further contain carboxyl groups, preferably at least partially neutralized.

[0055] The one or more polymeric hydroxy functional resins B can be self-crosslinking, thus not requiring a further crosslinking agent C as described herein after, or might crosslink, i.e. , react with a crosslinking agent C. If one or more crosslinking agents C are required to cure the primer coating material, the one or more polymeric hydroxy functional resins B are denoted as externally crosslinking in contrast to a self-crosslinking polymeric hydroxy functional resin B. In principle it is possible to employ mixtures of self-crosslinking and externally crosslinking polymeric hydroxy functional resins B in the primer coating material. Particularly preferred is the use of polyester polyols, since polyester polyols typically contain not only hydroxyl, but also carboxyl groups, whereas in case of an external crosslinking, both types of groups may react with, e.g., aminoplast resins. Furthermore, the carboxyl groups, if at least partially neutralized, allow an improved dispersibility in the aqueous primer coating material. Further carboxyl groups can be introduced into polyester polyols by addition of carboxylic acid anhydrides, partial esterification of hydroxyl groups using polycarboxylic acids or diene addition of unsaturated carboxylic acids.

[0056] Polyurethane polyols are preferably prepared from hydroxyl-bearing soft segments (polyesters, polyethers), diisocyanates and hydroxycarboxylic acid, which later forms the ionic carrier group, and so-called chain extenders, which are primary or secondary polyamines or polyols. Molecules of different sizes can be prepared depending on the molar ratios. If polyols are used in a certain excess, relatively low-molecular weight polyurethanes are obtained, which are doped with terminal hydroxyl groups that can participate in crosslinking reactions with aminoplast resins. In the same way, the free isocyanate groups of the prepolymer can be reacted with capping agents before the so-called chain extension. One may obtain - albeit only small proportions - of blocked isocyanate groups for crosslinking with hydroxyl groups.

[0057] Most preferred the polymeric hydroxy functional resins B are selected from polyester polyols and polyurethane polyols.

[0058] The polymeric hydroxy functional binders B preferably possess a hydroxyl number in the range from 1 to 200 mg KOH / g, more preferably from 5 to 180 mg KOH / g and even mor preferred from more than 10 to 150 mg KOH / g, such as 11 to 150 mg KOH / g. The OH number can be calculated. The hydroxyl values being determined according to ASTM Standard Test Method E222-23 “Standard Test Methods for Hydroxyl Groups Using Acetic Anhydride Acetylation.”

[0059] The polymeric hydroxy functional binders B preferably have a weight-average molecular weight in the range from 2,000 to 200,000 g / mol, more preferred in the range from 5,000 to 150,000 g / mol, even more preferred 8,000 to 120,000 g / mol and most preferred in the range from 10,000 to 100,000 g / mol as determined by gel permeation chromatography and described in more detail in the experimental section of the present invention. Based on total binder solids, the aqueous primer coating material the polymeric hydroxy functional binders B are contained in an amount in the range from 5 to 40 wt.-%, preferably 8 to 40 wt.-%, more preferably 10 to 35 wt.-%.

[0060] If the polymeric hydroxy functional binders B are comprised in the aqueous primer coating material, the weight ratio of polymeric resins A to the hydroxy functional binders B is in the range from 6:1 to 0.5:1. More preferred in the range from 5.5:1 to 1 :1 , and even more preferred in the range from 5: 1 to 1 : 1 .

[0061] Crosslinking agents C

[0062] The aqueous primer coating material is preferably a one-component (1 K) primer coating material. Amongst self-crosslinking and externally crosslinking 1 K primer coating materials the externally crosslinking primer coating materials are further preferred.

[0063] In the aqueous primer coating material preferably aminoplast resins (also denoted as amino resins in literature) are employed as external crosslinking agents C. These resins particularly include urea, melamine, and benzoguanamine (or glycoluril) resins. The aminoplast resins preferably contain methylol groups and / or ether groups, which can react with the hydroxyl groups, and, if present, the carboxyl groups of the polymeric hydroxy functional binders B.

[0064] Further, it is possible to employ as external crosslinkers C, as an alternative or in addition to the aminoplast resins, so-called blocked polyisocyanates. Blocked polyisocyanates, such as malonic ester blocked polyisocyanates and / or dimethyl pyrazol blocked polyisocyanates. The polyisocyanates are preferably aliphatic polyisocyanates, preferably based on aliphatic diisocyanates, such as hexamethylenediisocyanate and / or isophoronediisocyanate. The polyisocyanates preferably oligomers of diisocyanates, such as isocyanaurate trimers, allophanates, biurets and uretdions of the diisocyanates, preferably of aliphatic diisocyanates.

[0065] Based on total binder solids, the aqueous primer coating material the crosslinking agents C are contained in an amount in the range from 20 to 50 wt.-%, preferably 25 to 45 wt.-%, more preferably 30 to 40 wt.-%. The above ranges apply irrespective, if only aminoplast resins, or only blocked polyisocyanates, or mixtures of both are used. Preferably, only aminoplast resins are used as crosslinkers C. Coatings Additives D

[0066] The aqueous primer coating material preferably further contains typical coating additives D as for examples light stabilizers, UV absorbers, thickeners, surface active agents, catalysts, such as those suitable to catalyze a crosslinking reaction, flame-retardants, defoaming and deaerating additives, electrical conductivity regulators, soluble dyes, wetting and dispersing agents, corrosion inhibitors, rheology modifiers, such as thickener (also denoted as thickening agents). Examples of such thickeners are inorganic thickeners, examples being metal silicates such as phyllosilicates, and organic thickeners. Further typical additives for coatings are, e.g., described in “Additives for Coatings,” J. Bieleman, Wiley-VCH, reprint 2001 , pp. 248-253.

[0067] Based on total binder solids of the aqueous primer coating material the coatings additives D are contained in an amount in the range from 1 to 8 wt.-%, preferably 2 to 7 wt.-%, more preferably 2.5 to 6 wt.-%.

[0068] Pigments and / or Fillers E

[0069] The aqueous primer coating material preferably further contains one or more pigments and / or fillers E.

[0070] The term “pigment” is known to the skilled person, from DIN 55943 (date: October 2001), for example. A “pigment” in the sense of the present invention refers preferably to constituents in powder or flake form which are substantially, preferably entirely, insoluble in the application medium surrounding them. They are preferably colorants and / or substances which can be used as pigment on account of their magnetic, electrical and / or electromagnetic properties. Pigments differ from “fillers” preferably in their refractive index, which for pigments is at least 1.7.

[0071] The concept of pigments encompasses color pigments (the terms “color-imparting pigment” and “color pigment” are interchangeable) and effect pigments. Effect pigments are preferably those pigments which impart optical effect or both color and optical effect, more particularly optical effect. The terms “optical effect and color pigment,” “optical effect pigment,” and “effect pigment” are therefore interchangeable. Examples of preferred effect pigments are flakelike metallic effect pigments such as lamellar aluminum pigments, gold bronzes, oxidized bronzes and / or iron-oxide-aluminum pigments, pearlescent pigments such as pearl essence, basic lead carbonate, bismuth oxychloride and / or metal oxide-mica pigments and / or other effect pigments such as lamellar graphite, lamellar iron oxide, multilayer effect pigments composed of PVD films and / or liquid-crystal polymer pigments.

[0072] In principle the use of effect pigments is possible. Since, however, the coating is a primer coating material, the incorporation of effect pigments is not preferable. Preferably, therefore, the primer coating material contains no effect pigments.

[0073] Employed with preference as pigments therefore, are color pigments. As color pigment it is possible to use organic and / or inorganic pigments. The color pigment is preferably an inorganic color pigment. Particularly preferred color pigments used are white pigments, chromatic pigments and / or black pigments. Examples of white pigments are titanium dioxide, zinc white, zinc sulfide, and lithopone. Examples of black pigments are carbon black, iron manganese black, and spinel black. Examples of chromatic pigments are chromium oxide, chromium oxide hydrate green, cobalt green, ultramarine green, cobalt blue, ultramarine blue, manganese blue, ultramarine violet, cobalt and manganese violet, red iron oxide, cadmium sulfoselenide, molybdate red and ultramarine red, brown iron oxide, mixed brown, spinel phases and corundum phases, and chromium orange, yellow iron oxide, nickel titanium yellow, chromium titanium yellow, cadmium sulfide, cadmium zinc sulfide, chromium yellow, and bismuth vanadate. Examples of suitable organic color-imparting pigments are monoazo pigments, disazo pigments, anthraquinone pigments, benzimidazole pigments, quinacridone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, indanthrone pigments, isoindoline pigments, isoindolinone pigments, azomethine pigments, thioindigo pigments, metal complex pigments, perinone pigments, perylene pigments, phthalocyanine pigments or aniline black.

[0074] Based on the total weight of the aqueous primer coating material the pigments and / or fillers E are contained in an amount in the range from 5 to 40 wt.-%, preferably 10 to 35 wt.-%, more preferably 15 to 30 wt.-%.

[0075] Organic Solvents F

[0076] The aqueous primer coating material preferably further contains one or more solvents F selected from the group consisting of water soluble and / or water-dispersible organic solvents, like alcohols, such as 2-ethylhexanol; glycol ethers such as ethylene glycol monobutyl ether, diethylene glycol butyl ether and dipropylene glycol methyl ether; glycol ether esters such as propylene glycol monomethyl ether acetate, ethylene glycol butyl ether acetate, 3-methoxy n- butyl acetate; and lactams, such as N-methyl pyrrolidone (NMP); and mixtures thereof.

[0077] Based on the total weight of the aqueous primer coating material the organic solvents F are contained in an amount in the range from 5 to 25 wt.-%, preferably 8 to 20 wt.-%, more preferably 10 to 17 wt.-%.

[0078] The aqueous primer coating material is preferably applied to the substrate by any of the customary application methods. Representative examples of the application methods include, but are not limited to, spraying, knife coating, spreading, pouring dipping, impregnating, trickling or rolling. With respect to such application, the substrate to be coated may itself be at rest, with the application unit or equipment being moved. Alternatively, the substrate to be coated, more particularly a coil, may be moved, with the application unit being at rest relative to the substrate or being moved appropriately. Preferable application methods are air spraying, airless spraying, high speed rotation, electrostatic spray application, alone or in conjunction with hot spray application such as hot air spraying.

[0079] Step Hi.

[0080] To obtain a multilayer coating as typically used in OEM vehicle coating, particularly OEM automotive coating, step ii. is followed by steps iii. and iv. , i.e., applying one or more basecoat coating materials onto the primer coating layer to form one or more basecoat coating layers and subsequently applying one or more clearcoat coating material, before finally curing all of the layers applied in steps ii., iii., and iv.

[0081] Before applying the one or more basecoat coating materials subsequent to step ii. the primer coating layer is at least partially dried (i.e., flashed), preferably at a temperature in the range from 15 °C to 35 °C, more preferably 20 °C to 30 °C. Curing the primer coating layer is preferably to be avoided at this stage.

[0082] The terms “basecoat coating material” (i.e., “basecoat material”) and, respectively, “basecoat film” are known to the skilled person and are used preferably as a designation for a color- and / or effect-imparting intermediate coating in general industrial finishing, especially automotive (OEM) finishing. Basecoat coating materials which can be used are commercial basecoat coating materials, such as solvent-based or aqueous basecoats, with aqueous basecoat coating materials being preferred. The basecoat coating material is preferably selected from 1 K basecoat coating materials (also denoted as “one-component basecoat coating material” or “one-pack basecoat coating material”) and 2K basecoat coating materials (also denoted as “two-component basecoat coating materials” or “two-pack basecoat coating materials”).

[0083] Preferred basecoat coating materials in the context of the present invention are those which comprise, as binders, polymers curable physically, thermally, or both thermally and with actinic radiation.

[0084] In the context of the present invention, the term “physical curing” means the formation of a film through loss of solvent from polymer solutions or polymer dispersions. Typically, no crosslinking agents are necessary for this curing.

[0085] In the context of the present invention, the term “thermal curing” means the heat-initiated crosslinking of a coating film, with either a separate crosslinking agent or else self-crosslinking binders being employed in the parent coating material. The crosslinking agent contains reactive functional groups which are complementary to the reactive functional groups present in the binders. This is commonly referred to by those in the art as external crosslinking. Where the complementary reactive functional groups or autoreactive functional groups - that is, groups which react with groups of the same kind - are already present in the binder molecules, the binders present are self-crosslinking. Examples of suitable complementary reactive functional groups and autoreactive functional groups are known from German patent application DE 199 30 665 A1 , page 7 line 28 to page 9 line 24.

[0086] For the purposes of the present invention, actinic radiation means electromagnetic radiation such as near infrared (NIR), UV radiation, more particularly UV radiation, and particulate radiation such as electron radiation. Curing by UV radiation is commonly initiated by radical or cationic photoinitiators. Where thermal curing and curing with actinic light are employed in unison, the term “dual cure” is also used.

[0087] In the present invention preference is given both to basecoat coating materials which are curable physically and to those which are curable thermally. In the case of basecoat coating materials which are curable thermally, there is of course always also a proportion of physical curing. For reasons not least of ease of comprehension, however, these coating materials are referred to as thermally curable.

[0088] Preferred thermally curing basecoat coating materials are those which comprise as binder at least one of a polyurethane resin, polyurethane-poly(meth)acrylate resin, a polyester resin and a poly(meth)acrylate resin, and as crosslinking agent, possessing the complementary reactive groups, an aminoplast resin or a blocked or nonblocked polyisocyanate, preferably an aminoplast resin. Among the aminoplast resins, melamine resins are preferred.

[0089] Coatings additives D, pigments E and / or fillers E, and organic solvents F, all as described for the aqueous primer coating composition, can also be contained in the basecoat coating material, preferably the aqueous basecoat coating material. However, different from the primer coating materials, effect pigments are preferably contained in the basecoat coating material.

[0090] The basecoat coating material is preferably applied to the not (yet fully) cured primer coating layer by any of the methods described for step ii. with the same preferences.

[0091] After step iii. the one or more basecoat coating layers preferably are at least partially dried (flashed), preferably at a temperature in the range from 50 °C to 80 °C, more preferably 55 °C to 75 °C. Curing, particularly fully curing the basecoat coating layer(s) is to be avoided at this stage.

[0092] Step iv.

[0093] On the not yet (fully) cured basecoat coating material one or more clearcoat coating materials are applied to form one or more clearcoat coating layers.

[0094] A clearcoat coating material, as is known, is a coating material which, following application and curing, forms a transparent coating (the clearcoat) having protective and / or decorative properties. Protective properties mean, for example, scratch resistance and weathering resistance, more particularly UV resistance. An example of what is understood as a decorative property is good gloss. The clearcoat materials to be used are the clearcoat materials customarily used in the field of the finishing of plastics, and their selection and use are known to the skilled person (in this regard, see also Rdmpp-Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, N.Y., 1998, page 325).

[0095] Any conventional clearcoat coating materials, such as liquid or solid clearcoat coating materials can be applied. Preferably, the clearcoat coating material is a liquid clearcoat coating material selected from the groups of 1 K solvent-borne clearcoat coating materials, 2K clearcoat coating materials and 1 K aqueous clearcoat coating materials. However, powder clearcoat coating materials may also be used. Amongst the one-component (1 K) clearcoat coating materials those are preferred which comprise one or more poly(meth)acrylic polyols and one or more aminoplast crosslinking agents, the latter one preferably being selected from the group of melamine resins, more preferably alkoxylated melamine resins. Preferably such systems are cured for 12 to 20 min at 130 °C to 150 °C.

[0096] Another group of one-component (1 K) clearcoat coating materials are so-called acrylic aminoplast silane clearcoat coating materials, which comprise one or more poly(meth)acrylic polyols additionally comprising hydrolysable silane groups, which will hydrolyze during the baking step to form silanol groups. The silanol groups condensate to build an additional crosslinking via siloxane structures. The further comprised one or more aminoplast crosslinking agents, the latter one preferably being selected from the group of melamine resins, more preferably alkoxylated melamine resins react with the hydroxy groups at the one or more poly(meth)acrylic polyols.

[0097] Yet another group of one-component (1 K) clearcoat coating materials comprises one or more primary carbamate functional polymers and one or more aminoplast crosslinking agents, the latter one preferably being selected from the group of melamine resins, more preferably alkoxylated melamine resins.

[0098] A further group of one-component (1 K) clearcoat coating materials comprises one or more hydroxy functional polymers, preferably one or more poly(meth)acrylic polyols and one or more blocked polyisocyanates, such as malonic ester blocked polyisocyanates and / or dimethyl pyrazol blocked polyisocyanates. The polyisocyanates are preferably aliphatic polyisocyanates, preferably based on aliphatic diisocyanates, such as hexamethylenediisocyanate and / or isophoronediisocyanate. The polyisocyanates preferably oligomers of diisocyanates, such as isocyanaurate trimers, allophanates, biurets and uretdions of the diisocyanates, preferably of aliphatic diisocyanates.

[0099] A further group of clearcoat coating material systems are so-called epoxy acid clearcoat coating systems, which comprise one or more poly(meth)acrylates comprising glycidyl groups and one or more polycarboxylic acid. In the curing reaction of both beta-hydroxy polyesters are formed. These systems can be formulated as one-component (1 K) or two-component (2K) systems.

[0100] A typical two-component clearcoat coating material, comprises one or more polymeric polyols, preferably selected from polyurethane polyols, polyester polyols and poly(meth)acrylate polyols and one or more polyisocyanates. The polyisocyanates are preferably aliphatic polyisocyanates, preferably based on aliphatic diisocyanates, such as hexamethylenediisocyanate and / or isophoronediisocyanate. The polyisocyanates preferably oligomers of diisocyanates, such as isocyanaurate trimers, allophanates, biurets and uretdions of the diisocyanates, preferably of aliphatic diisocyanates.

[0101] It is also possible to use one-component (1 K) aqueous clearcoat coating materials. Those clearcoat coating materials preferably comprise one or more polyester-poly(meth)acrylate polyols, and one or more blocked polyisocyanates and / or aminoplast resins, preferably melamine resins, most preferred alkoxylated melamin resins.

[0102] The general techniques for applying the clearcoat coating materials are in line with those described earlier on above for step ii. with the same preferences. The clearcoat coating material is preferably applied to the not (yet fully) cured basecoat coating layer. The clearcoat material is applied in the customary and known film thicknesses, as for example in wet film thicknesses of 50 to 250 micrometers, preferably of 100 to 180 micrometers. The resultant dry film thicknesses after curing are then, for example, in the range from 15 to 80 micrometers, more particularly 25 to 50 micrometers.

[0103] Afterwards the layers obtained in steps ii., iii. and iv. are cured jointly in step v. at a temperature depending on the chemistry of the coating materials forming the layers, but generally being in the range of from 120 °C to 160 °C, more preferably 130 °C to 150 °C.

[0104] Dry Film Thicknesses

[0105] The dry film thicknesses are determined by ISO 2808:2019 Method 7C.

[0106] The dry film thickness of the primer coating layer is preferably in the range from 5 to 20 pm, more preferably in the range from 8 to 16 pm, and most preferably in the range from 10 to 14 pm.

[0107] The dry film thickness of the basecoat coating layer(s) is preferably in the range from 7 to 25 pm, more preferably in the range from 10 to 20 pm, and most preferably in the range from 12 to 18 pm. The application of a plurality of basecoat layers is possible, however, a wet-on-wet application of the same basecoat is rather understood herein as the application of one basecoat coating material in several spray passes. Only if different basecoats are applied, it would be considered as an application of a plurality of basecoat coating materials. The term “dry film thickness” as used herein is the total dry film thickness of all basecoat coating layers, irrespective of the number of basecoat coating layers. The same applies likewise to the dry film thickness of the clearcoat coating layer(s).

[0108] The dry film thickness of the clearcoat coating layer(s) is preferably in the range from 35 to 70 pm, more preferably in the range from 40 to 65 pm, and most preferably in the range from 45 to 60 pm.

[0109] Coated Substrate of the Invention

[0110] A further object of the invention is a coated substrate obtainable by the method according to the present invention. Any preferred features and embodiments disclosed in relation to the method of the invention also apply to the coated substrate of the invention.

[0111] Use of the Aqueous primer coating composition of the invention

[0112] Yet another object of the invention is the use of the aqueous primer coating composition as defined above in coating a substrate which comprises at least two parts as defined above, in vehicle coating, preferably automotive OEM coating.

[0113] Any preferred features and embodiments disclosed in relation to the method of the invention also apply to the coated substrate of the invention.

[0114] In the following the invention will be further exemplified by working examples. EXPERIMENTAL SECTION

[0115] Determination of Parameters and Testing Methods

[0116] Number-average molecular weight Mnand weight-average molecular weight Mw

[0117] The molecular weights were determined by gel permeation chromatography (GPC). To determine polymer molecular weights by GPC, fully dissolved molecules of the polymer sample were fractionated on a porous column stationary phase. A 0.1 mol / l acetic acid solution in tetra hydrofuran (THF) was used as the eluent solvent. The stationary phase was a combination of Waters Styragel HR 5, HR 4, HR 3, and HR 2 columns. Five milligrams of sample were added to 1.5 mL of eluent solvent and filtered through a 0.5 pm filter. After filtering, 100 pl of the polymer sample solution was injected into the column at a flow rate of 1 .0 ml / min. Separation took place according to the size of the polymer coils which form in the eluent solvent. Small molecules diffused into the pores of the column material more frequently and are therefore retarded more than large molecules. Thus, large molecules were eluted earlier than small molecules. The molecular weight distribution, the averages and the polydispersity Mw / Mnof the polymer samples were calculated with the aid of chromatography software utilizing a calibration curve generated with the EasyValid validation kit which includes a series of unbranched-polystyrene standards of varied molecular weights available from Polymer Standards Service.

[0118] Initial crosshatch adhesion

[0119] The initial crosshatch adhesion was determined in accordance with ISO 2409 (Paints and Varnishes - Cross-Cut Test).

[0120] Post-humidity crosshatch adhesion

[0121] The post-humidity crosshatch adhesion was determined in accordance with ISO 6270-2 (Paints and Varnishes - Determination of Resistance to Humidity - Part 2: Condensation (InCabinet Exposure with Heated Water Reservoir)) and ISO 2409 (Paints and Varnishes - Cross-Cut Test). Steamjet adhesion

[0122] The steamjet adhesion was determined in accordance with ISO 16925 (Paints and Varnishes - Determination of the Resistance of Coatings to Pressure Water-Jetting, Method B). Numeric ratings of 0-5 correspond to the degree of delamination (0 being no delamination and 5 being severe delamination). Letter classifications are given according to the appearance and characteristics of the areas of delamination (a: delamination along the scribe, b: circular zones of delamination, c: delamination perpendicular to the scribe).

[0123] Windshield bonding adhesion

[0124] To evaluate the windshield bonding adhesion, two urethane beads (BetaSeal 15709) were first applied to the surface of the coated panels (cold rolled steel) using a cordless, electric caulking gun. The urethane beads were then allowed to cure in a climate-controlled environment comprised of 65% humidity at 23 °C for 5 days. At this time, the coated substrate was removed and one urethane bead was cross-cut with a razor blade while pulling against the urethane bead with constant pressure to determine if separation occurs from the substrate (adhesive failure) or from within the bead (cohesive failure). The urethane bead was then inspected to determine the percentage of sealant adhesive splitting from the coating vs. sealant cohesive splitting of the sealant. A “pass” was considered >95 % cohesive failure (CF) of the sealant.

[0125] Following this, the panel was subjected to a high humidity environment in accordance with (ISO 6270-2 Determination of Resistance to Humidity - Part 2: Condensation (In-Cabinet Exposure with Heated Water Reservoir)) for 14 days. The panel received 24 hours of reacclimatization then the same urethane bead cutting and evaluation procedure was used.

[0126] Preparation of coated substrates

[0127] Cold rolled steel panels

[0128] Cold rolled steel test panels measuring 10 cm x 30 cm were used as a substrate. The panels were pretreated with Bondrite® 958 zinc phosphate chemical pre-treatment and rinsed with Parcolene® 90 post-rinse, both available from Henkel. The panels were electrocoated with an 18 to 20 pm layer of BASF Cathoguard® 800 electrocoat and baked for 20 minutes at 177 °C. The panels were sprayed with 13 pm to 18 pm layer of the comparative primer C1 , or inventive primers E1 and E2 (primer compositions are shown in Table 1).

[0129] After coating with the respective primer coating material, the panels received a 5-minute ambient flash. Subsequently, the panels were coated to form a layer having a 10 pm to 15 pm dry layer thickness with BASF E278KU105, a black waterborne basecoat applied to the panel in two coats. After coating with the basecoat, the panels received a 5-minute ambient flash and a 6-minute heated flash at 60 °C. Subsequently, a solvent borne two-component clearcoat coating material was applied to form a layer having a dry layer thickness of 46 to 51 pm applied (applied in two coats). After the clearcoat was applied the panels received a 10-minute ambient flash and a 20-minute bake at a temperature of 141 °C.

[0130] Plastic panels

[0131] For coating plastic panels according to the inventive method, the plastics panels were used untreated and uncoated (as received) following the same coatings procedure with primer, basecoat, and clearcoat as described above. For plastics coated using comparative primer C1 , the plastic panels were first coated with a 2.5 to 5 pm layer of BASF U339AW073, a waterborne adhesion promoter. As the polar plastic material, polycarbonate was used in the examples, and as the non-polar plastic material, thermoplastic polyolefin was used in the examples.

[0132] Plastic panels were coated alongside metal panels and then submitted for testing.

[0133] Table 1 provides the primer compositions that were prepared and applied to the substrates.

[0134] Table 1

[0135] Results

[0136] Initial crosshatch adhesion, post-humidity crosshatch adhesion, steamjet adhesion, and windshield bonding adhesion

[0137] The coated substrates of Example 1 were evaluated for initial crosshatch adhesion, posthumidity crosshatch adhesion, steamjet adhesion, and windshield bonding adhesion. The test results are shown in Table 2.

[0138] Table 2 summarizes the test results of the initial crosshatch adhesion, steamjet resistance, windshield bonding adhesion, and post-humidity crosshatch adhesion of the coated substrates from Example 1 .

[0139] Table 2 non-polar plastics material = thermoplastic polyolefin (TPO) polar plastics material = polycarbonate (PC)1with adhesion promotor2n.d. = not determined3n.a. = not applicable

[0140] 4values are percentages of cohesive failure

[0141] As indicated, the primer coating materials of the present disclosure are suitable for promoting the adhesion over both metallic and plastic substrates. Primer E1 in multilayer coating MLC- E1 is suitable for promoting adhesion over metallic and polar plastic substrates and primer E2 in multilayer coating MLC-E2 is suitable for promoting adhesion over metallic and non-polar plastic substrates. Unexpectedly, the primer compositions of the present invention are suitable for improving the adhesion of metallic and non-metallic coated substrates while utilizing a large percentage of non-functional resin components in the formulation. This is even achieved on plastics material with was neither flame-treated or plasma treated or even pre-coated with an adhesion promoter or adhesion promoting primer, but used fully untreated, as obtained.

[0142] Table 3

[0143] 1Color data taken using a BYKmac-l multiangle spectrophotometer2Values measured at 45° angle

[0144] As indicated, the primer coating materials of the present disclosure allow for simultaneous coating of both substrates on a single paint-line. This ability to coat plastic and metal substrates on the same line, in a single step under the same conditions results in improved color harmony between substrates when applied in a full hiding layer thickness as evident in Table 3.

Claims

CLAIMS1. Method for coating a substrate with an aqueous primer coating material, comprising the following steps: i. providing a substrate which comprises at least two parts, a. one part of the substrate being a metal having a pre-coated metal surface area and b. one part of the substrate being a plastic material comprising one or more organic polymers and having a non-coated surface area comprising the one or more organic polymers, b1 . the one or more organic polymers consisting of carbon, hydrogen and optionally halogen atoms, or b2. the one or more organic polymers containing carbonyl groups; and ii. applying an aqueous primer coating material onto the at least two surface areas to form a primer coating layer, the aqueous primer coating material containing 15 to 75 wt.-%, based on total binder solids, of one or more polymeric resins A, each of which possesses a. a hydroxyl value of 0 to 10 mg KOH / g, b. at least partially neutralized acid groups; and c. a polymeric backbone c1. consisting of hydrocarbon groups, if the part of the substrate being a plastic material comprises an organic polymer according to b1 , or an organic polymer according to b2, if the carbonyl groups are part of amide moieties, or c2. comprising carbonyl groups, if the part of the substrate being a plastic material comprises an organic polymer according to b2.

2. Method for coating a substrate according to claim 1 , wherein the non-coated surface area comprising the one or more organic polymers is not flame-treated and not plasma- treated.

3. Method for coating a substrate according to claim 1 or 2, wherein the pre-coated metal surface area is a metal surface area which is pre-coated with a cured electrocoat layer and optionally a conversion coating layer underneath the cured electrocoat layer.

4. Method for coating a substrate according to any one or more of the preceding claims, wherein the b.1 one or more organic polymers consisting of carbon, hydrogen and optionally halogen are selected from polyolefins and halogenated polyolefins; and the b2. one or more organic polymers comprising carbonyl groups are selected from the group consisting of polycarbonates and polyamides.

5. Method for coating a substrate according to any one or more of the preceding claims, wherein the polymeric backbone of the one or more polymeric resins A comprised in the aqueous primer coating material c1 . is a polymeric backbone of an (unsaturated dicarboxylic acid) / (olefin) copolymer, and c2. is a polymeric backbone, wherein the carbonyl groups contained therein are present at least in one or more of the following moieties: urethane groups and carbonate groups.

6. Method for coating a substrate according to any one or more of the preceding claims, wherein the at least partially neutralized acid groups of the one or more polymeric resins comprised in the aqueous primer coating material are at least partially neutralized carboxylic acid groups and / or at least partially neutralized carbonic acid groups.

7. Method for coating a substrate according to any one or more of the preceding claims, wherein the aqueous primer coating material is a one-pack coating material.

8. Method for coating a substrate according to any one or more of the preceding claims, wherein the aqueous primer coating material further contains the following ingredients:B. one or more polymeric hydroxy functional binders B selected from polyurethane polyols, polyester polyols, polyether polyols, poly(meth)acrylate polyols and copolymers thereof;C. one or more crosslinking agents C selected from aminoplast resins and blocked polyisocyanates;D. one or more coatings additives D selected from light stabilizers, UV absorbers, thickeners, surface active agents, catalysts, such as those suitable to catalyze a crosslinking reaction, flame-retardants, defoaming and de-aerating additives, electrical conductivity regulators, soluble dyes, wetting and dispersing agents, corrosion inhibitors, and rheology modifiers;E. one or more pigments and / or fillers E from color pigments and effect pigments; andF. one or more organic solvents F selected from water soluble and / or water-dispersible organic solvents.

9. Method for coating a substrate according claim 8, wherein the amounts of ingredients in the aqueous primer coating material are in the following ranges:10 to 75 wt.-%, preferably 15 to 65 wt.-%, more preferably 25 to 55 wt.-% of A based on total binder solids;5 to 40 wt.-%, preferably 8 to 40 wt.-%, more preferably 10 to 35 wt.-% of B based on total binder solids;20 to 50 wt.-%, preferably 25 to 45 wt.-%, more preferably 30 to 40 wt.-% of C based on total binder solids;1 to 8 wt.-%, preferably 2 to 7 wt.-%, more preferably 2.5 to 6 wt.-% of D based on total binder solids;5 to 40 wt.-%, preferably 10 to 35 wt.-%, more preferably 15 to 30 wt.-% of E based on the total weight of the aqueous primer coating material, and5 to 25 wt.-%, preferably 8 to 20 wt.-%, more preferably 10 to 17 wt.-% of F, based on the total weight of the aqueous primer coating material.

10. Method for coating a substrate according claim 8 or 9, wherein the weight ratio of A to B is in the range from 6:1 to 0.5:1 preferably 5.5:1 to 1 :1 more preferably 5:1 to 1 :111 . Method for coating a substrate according to any one or more of the preceding claims, wherein step ii. is followed by iii. applying one or more basecoat coating materials onto the primer coating layer to form one or more basecoat coating layers, and iv. applying one or more clearcoat coating materials onto the one or more basecoat coating layers to form one or more clearcoat coating layers, and v. separately or jointly curing any of the layers formed in steps ii. to iv.

12. Method for coating a substrate according to claim 11 , wherein subsequent to step ii. the primer coating layer is at least partially dried, preferably at a temperature in the range from 15 °C to 35 °C, more preferably 20 °C to 30 °C, before step iii. is carried out; and subsequent to step iii. the one or more basecoat coating layers are at least partially dried, preferably at a temperature in the range from 50 °C to 80 °C, more preferably 55 °C to 75 °C, before step iv. is carried out; andsubsequent to step iv. the layers obtained in steps ii., iii. and iv. are cured jointly in step v. at a temperature in the range from 120 °C to 160 °C, more preferably 130 °C to 150 °C.

13. A coated substrate obtainable by a method according to any one or more of the preceding claims.

14. Use of the aqueous primer coating composition as defined in any one or more of the preceding claims in coating a substrate which comprises at least two parts as defined in any one or more of the preceding claims, in vehicle coating, preferably automotive OEM coating.

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