The present invention relates to a pigmented aqueous coating composition comprising at least one aqueous polyurethane dispersion, at least one phospholipid, at least one defoamer and at least one thickening agent. The aqueous coating composition results in peelable coatings having good optical properties and which can be removed residue free from the substrate without damaging the underlaying substrate. Moreover, the invention relates to a peelable coating system comprising a first coating layer being prepared from the inventive aqueous coating composition and a second coating layer being prepared from a clearcoat or tinted clearcoat composition. The present invention moreover relates to a method for forming a peelable coating system onto at least part of a surface of a substrate and a coated substrate prepared according to the inventive method. Finally, the present invention relates to the use of the inventive aqueous coating composition to form a peelable coating layer on at least part of the surface of a substrate.

State of the art

There is a need in the automotive market to personalize the automotive in terms of color and/or pattern, for example by temporarily changing the color and/or temporarily painting a personalized pattern onto the automobile, without damaging the original finish (e.g. original multilayer coating being present on the surface of the automobile).

It is known in the state of the art to temporarily color or pattern an automobile without damaging the original finish using colored plastic films, such as colored foils. However, glue and pulling force may be needed during attachment of the plastic film to the automobile surface since the plastic film is planar, while the automobile has a three- dimensional structure. Moreover, debonding and upwarping of the plastic film may occur at the edges of the automobile body due to the shrinkage tendency of the plastic film, thus damaging the overall appearance of the temporarily changed automobile surface. In addition, the attached plastic films are difficult to peel from the automobile surface and residual glue remaining on the automobile surface after peeling is hard to remove without damaging the original finish of the automobile. Finally, the plastic films are not available in all colors commonly used in the automotive industry, thus restricting the number of available colors usable for personalization of the automobile.

Therefore, efforts have been made to design peelable coatings that can replace the use of colored plastic films to temporarily change the appearance of automobiles.

U.S. Pat. No. 6,458,441 B1 discloses a single-layer peelable coating material consisting of a solvent-free aqueous anionic polyurethane-polyurea dispersion. The coating formed from the peelable coating material has the advantages of good ductility, and high tensile strength, is easy to peel off, and can be fitted on any cambered surface. Meanwhile, the coating also has the disadvantage of poor adhesion on the surface of products, and is easy to fall off.

In order to solve the problem of easily falling off of the peelable coating, US2014087070A1 discloses a multilayer peelable coating system comprising a primer layer formed of a heat activated adhesive, and a cover layer on the surface of the primer layer formed from an aqueous polymer system. Since the activation temperature required for the heat activated adhesive greatly exceeds the operation temperature of the automobile industry, the above multilayer peelable coating system is not suitable for use in the automobile industry.

US2012276381 A1 discloses a multilayer peelable coating system comprising a primer layer formed of an acrylic resin system, and a cover layer on the surface of the primer layer formed from an aqueous polyurethane system. However, the cover layer formed from the aqueous polyurethane system has low hardness, and thus cannot meet the polishability requirement on automobile coatings.

WO2019147519A1 discloses low volatile organic compound (VOC) peelable coatings made without the inclusion of exempt solvents that resist fuel staining, resist scratching and may be applied and cured in a shorter time than coatings made with exempt solvents. However, the aqueous coating compositions cannot be tinted with high amounts of pigments because the resulting pigmented coating compositions are non- homogenous and have a low storage stability, thus resulting in pigmented peelable coatings not fulfilling the optical quality required in the automotive sector. Thus, there still remains a need to provide aqueous peelable coatings and peelable coating systems having a high quality optical appearance, sufficient mechanical stability, sufficient adhesion to the original finish and which are suitable for substrates of various materials and shapes.

Object

Accordingly, an object of the present invention is to provide pigmented aqueous coating compositions resulting in peelable coating layers having a sufficient adhesion to the original finish to guarantee a sufficient life-time of the peelable coating layers while remaining peelable from the original finish, in particular by hand(s), without damaging the original finish and without leaving excess amounts of residues on the original finish. Moreover, the peelable coating layers should be overcoatable with commercially available coating materials, such as clearcoat or tinted clearcoat materials, without a negative influence on the peeling behavior of the resulting peelable coating systems. The resulting peelable coating systems should have a high quality optical appearance and sufficient mechanical stability to prevent damage of the peelable coating system from environmental influences, such as humidity, stone chipping, washing, etc., during the life-time of the peelable coating system on the automobile.

Technical solution

The objects described above are achieved by the subject matter claimed in the claims and also by the preferred embodiments of that subject matter that are described in the description hereinafter.

A first subject of the present invention is therefore an aqueous coating composition comprising

(a) at least one aqueous polyurethane dispersion (PUD),

(b) at least one phospholipid,

(c) at least one defoamer,

(d) at least one thickening agent, and

(e) at least one pigment, wherein the dried aqueous coating composition forms a peelable coating on at least part of a surface of a substrate, said peelable coating adhering to the surface without the use of a separate adhesive coating layer. The inventive aqueous coating composition can therefore also be regarded as peelable aqueous coating composition.

The above-specified aqueous coating composition is hereinafter also referred to as aqueous coating composition of the invention and accordingly is a subject of the present invention. Preferred embodiments of the peelable coating system of the invention are apparent from the description hereinafter and also from the dependent claims.

In light of the prior art it was surprising and unforeseeable for the skilled worker that the objects on which the invention is based could be achieved by a pigmented aqueous coating composition comprising an aqueous polyurethane dispersion (PUD), at least one phospholipid, at least one defoamer and at least one thickening agent. The at least one phospholipid increase the elasticity of the peelable coating layer formed from the inventive aqueous coating composition such that large pieces of the formed coating layer can be peeled by hand. The peelable coating layers can be used as basecoat layers because high amounts of pigments necessary for the required opacity can be incorporated into the coating composition without a negative influence on the homogeneity and storage stability of the coating compositions as well as a negative influence on the orientation of effect pigments in the resulting peelable coating layer. This allows to prepare pigmented peelable coating layers having a high optical quality in high dry film thicknesses which are required for peelable coating systems. The peelable coating layers have a sufficient durability, such as mechanical stability, weatherability, on the original finish (i.e. the original multilayer coating present on the substrate) while they can still be easily removed substantially residue free by applying force, such as by pulling on the coating layer with the hands, without damaging the original finish. The peelable coating layers can be overcoated with commonly used coating materials, such as clearcoat or tinted clearcoat materials, without a negative influence on the mechanical and optical properties or the peeling behavior of the resulting peelable coating system. The resulting peelable coating systems have a sufficient mechanical stability during their lifetime, such that the optical appearance is not damaged by environmental influences, such as humidity, car washing and stone chipping. This avoids early removal of the damaged peelable coating system and thus higher costs associated with the early removal and reattachment of a new peelable coating system.

A further subject of the present invention is a peelable coating system comprising

(a) a first coating layer (CL-1 ) being prepared by applying the aqueous coating composition according to the invention to at least part of a surface of a substrate (S); and

(b) a tinted clearcoat and/or a clearcoat layer (CL-2) being prepared by applying a tinted clearcoat and/or a clearcoat composition (C-2) to the first coating layer (CL-1 ); wherein the first coating layer (CL-1 ) and the second coating layer (CL-2) form a peelable coating, wherein an adhesive strength between the first coating layer (CL-1 ) and the second coating layer (CL-2) is greater than an adhesive strength between the first coating layer (CL-1 ) and the surface of the substrate (S).

Yet a further subject of the present invention is a method for forming a peelable coating system onto at least part of a surface of a substrate, said method comprising

(i) applying the aqueous coating composition (C-1 ) according to the invention to at least part of a surface of the substrate to form a first coating film (CF-1 ),

(ii) drying the formed first coating film (CF-1 ) to form a first coating layer (CL-1 ),

(iii) applying a tinted clearcoat and/or a clearcoat composition (C-2) on at least part of the first coating layer (CL-2) to form a tinted clearcoat and/or a clearcoat film (CF-2), and

(iv) jointly curing the first coating layer (CL-1 ) and the tinted clearcoat and/or the clearcoat film (CF-2) to form the peelable coating system, wherein the first coating layer (CL-1 ) and the tinted clearcoat and/or the clearcoat layer (CL-2) form a peelable coating, wherein an adhesive strength between the first coating layer (CL-1 ) and the clearcoat or tinted clearcoat layer (CL-2) is greater than an adhesive strength between the first coating layer (CL-1 ) and the surface of the substrate (S).

A further subject of the present invention is a coated substrate obtained by the inventive method. A final subject of the present invention is the use of the aqueous coating composition according to the invention to form a peelable coating layer on at least part of the surface of a substrate

Detailed description

Definitions:

First of all, a number of terms used in the context of the present invention will be explained.

The grammatical articles “a”, “an”, and “the”, as used herein, are intended to include “at least one” or “one or more”, unless otherwise indicated, even if “at least one” or “one or more” is expressly used in certain instances. Thus, these articles are used in this specification to refer to one or more than one (i.e., to “at least one”) of the grammatical objects of the article. By way of example, and without limitation, “a component” means one or more components, and thus, possibly, more than one component is contemplated and may be employed or used in an implementation of the described embodiments. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.

As used herein, the term "adhesive coating layer" refers to a coating layer which is designed to improve the adhesion between the substrate optionally comprising an original finish (i.e. a cured multilayer coating) and the coating layers applied on top of the adhesive coating layer. Such coating layers are typically denoted as primer coating layers.

As used herein, the term "polymer" encompasses prepolymers, oligomers and both homopolymers and copolymers; the prefix "poly" in this context referring to two or more.

As used herein, the term “polyol” refers to compounds comprising at least two free hydroxy groups. Polyols include polymers comprising pendant and terminal hydroxy groups. The term "coating composition" refers to a mixture of chemical components that will cure and form a coating when applied to a substrate.

As used herein, the term “substrate” is not particularly limited and includes any substrate that is desired to be coated with a peelable coating. The substrate exemplified in the examples is an exterior surface of a vehicle. The term “vehicle” means automobiles, vans, trucks, motorcycles, buses, heavy trucks, trailers, road paving machinery, tractors, bulldozers, cranes, combines, graders, locomotives, rail cars, snow mobiles, all-terrain vehicles, wagons, buggies, bicycles, watercraft, and aircraft.

As used herein, the term "dispersion" refers to a composition comprising a discontinuous phase distributed throughout a continuous phase and includes, for example, colloids, emulsions, suspensions, sols, solutions (i.e., molecular or ionic dispersions), and the like. The term "waterborne dispersion" or "aqueous dispersion" refers to compositions comprising particles or solutes distributed throughout liquid water. Waterborne dispersions and aqueous dispersions may also include one or more co-solvents in addition to the particles or solutes and water, however the principal solvent, i.e. the main solvent, being water.

As used herein, the term “aqueous polyurethane dispersion” means a dispersion of polyurethane particles in a continuous phase comprising water. As used herein, the term “polyurethane” refers to any polymer or oligomer comprising urethane (i.e., carbamate) groups, urea groups, or both. Thus, the term “polyurethane” as used herein refers collectively to polyurethanes, polyureas, and polymers containing both urethane and urea groups, unless otherwise indicated.

“Binder” in the context of the present invention and in accordance with DIN EN ISO 4618:2007-03 is the nonvolatile component of a coating composition, without pigments and fillers. Hereinafter, however, the expression is used principally in relation to particular physically and/or thermally curable polymers, examples being polyurethanes, polyesters, polyethers, polyureas, polyacrylates, polysiloxanes and/or copolymers of the stated polymers. The nonvolatile fraction may be determined according to DIN EN ISO 3251 : 2018-07 at 130°C for 60 min using a starting weight of 1.0 g.

“Drying” of an applied coating composition refers to the evaporation of solvents from the applied coating composition. Drying can be performed at ambient temperature or by use of elevated temperatures. However, the drying does not result in a coating film being ready for use, i.e. a cured coating film as described below, because the coating film is still soft or tacky after drying. Accordingly, “curing” of a coating film refers to the conversion of such a film into the ready-to-use state, i.e. into a state in which the substrate provided with the respective coating film can be transported, stored and used as intended. More particularly, a cured coating film is no longer soft or tacky, but has been conditioned as a solid coating film which does not undergo any further significant change in its properties, such as hardness or adhesion to the substrate, even under further exposure to curing conditions. Curing can be performed at higher temperatures and/or for longer times than used for drying of the coating composition.

The measurement methods to be employed in the context of the present invention for determining certain characteristic variables can be found in the Examples section. Unless explicitly indicated otherwise, these measurement methods are to be employed for determining the respective characteristic variable. Where reference is made in the context of the present invention to an official standard without any indication of the official period of validity, the reference is implicitly to that version of the standard that is valid on the filing date, or, in the absence of any valid version at that point in time, to the last valid version.

All film thicknesses reported in the context of the present invention should be understood as dry film thicknesses. It is therefore the thickness of the cured film in each case. Hence, where it is reported that a coating material is applied at a particular film thickness, this means that the coating material is applied in such a way as to result in the stated film thickness after curing.

All temperatures elucidated in the context of the present invention should be understood as the temperature of the room in which the substrate or the coated substrate is located. It does not mean, therefore, that the substrate itself is required to have the temperature in question.

Inventive aqueous coatinq composition:

The aqueous coating composition according to the invention comprises at least one aqueous polyurethane dispersion (PUD), at least one phospholipid, at least one defoamer, at least one thickening agent, and at least one pigment. After applying the pigmented aqueous coating composition on at least part of a surface of a substrate and drying the applied aqueous coating composition, a peelable coating is formed. This formed peelable coating adheres to the surface without the use of a separate adhesive coating layer, i.e. a separate adhesive layer is not necessary to achieve sufficient adhesion of the peelable coating to the surface of the substrate. In contrast, the adhesive strength between the peelable coating and the surface of the substrate is high enough such that the peelable coating remains on the surface even under mechanical stress resulting, for example, from bending, stone chipping, etc., but low enough such that the peelable coating can be removed mechanically, for example by pulling on the peelable coating with the hands.

Aqueous polyurethane dispersion (PUD):

As first mandatory ingredient (a), the aqueous coating composition contains an aqueous polyurethane dispersion (PUD). According to a preferred embodiment, the aqueous polyurethane dispersion (PUD) comprises the reaction product of:

(i) a polyisocyanate;

(ii) a polymeric polyol having a number average molecular weight of 400 to 8,000 g/mol;

(iii) a compound comprising at least one isocyanate-reactive group and an anionic group or potentially anionic group;

(iv) water;

(v) a mono functional polyalkylene ether;

(vi) a polyol having a number average molecular weight of less than < 400 g/mol, and

(vii) a polyamine or amino alcohol having a number average molecular weight of 32 to 400 g/mol. Polyisocyanate (i):

Suitable polyisocyanates (i) include, but are not limited to, aromatic, araliphatic, aliphatic and cycloaliphatic polyisocyanates, such as, for example, 1 ,4-butylene diisocyanate, 1 ,6-hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), isophorone diisocyanate (IPDI), 2,2,4- and 2,4,4-trimethyl-hexamethylene diisocyanate, the isomeric bis- (4,4'-isocyanatocyclohexyl)methanes or mixtures thereof of any desired isomer content, 1 ,4-cyclohexylene diisocyanate, 1 ,4-phenylene diisocyanate, 2,4- and/or 2,6-toluene diisocyanate or hydrogenated 2,4- and/or 2,6- toluene diisocyanate, 1 ,5-naphthalene diisocyanate, 2,4'- and 4,4'-diphenylmethane diisocyanate, 1 ,3- and 1 ,4-bis-(2-isocyanato-prop-2-yl)-benzene (TMXDI), 1 ,3- bis(isocyanato-methyl)benzene (XDI), (S)-alkyl 2,6-diisocyanato-hexanoates or (L)- alkyl 2,6-diisocyanatohexanoates and mixtures of the aforementioned polyisocyanates.

Polyisocyanates having a functionality > 2 can also be used if desired. Such polyisocyanates include modified diisocyanates having a uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazine-dione and/or oxadiazinetrione structure, as well as unmodified polyisocyanates having more than 2 NCO groups per molecule, for example 4-isocyanatomethyl-1 ,8-octane diisocyanate (nonane triisocyanate) or triphenylmethane- 4,4',4"-triisocyanate. In some embodiments of the present invention, polyisocyanates or polyisocyanate mixtures containing only aliphatically and/or cycloaliphatically bonded isocyanate groups are used that have a mean functionality of from 2 to 4, such as 2 to 2.6 or 2 to 2.4.

Polymeric polyol (ii):

Suitable polymeric polyols (ii) have a number average molecular weight M _n of 400 to 6,000 g/mol, preferably of 500 to 3,000 g/mol, more preferably of 1 ,000 to 3,000 g/mol, very preferably 1 ,500 to 3,000 g/mol. As will be appreciated, the M _n of the polymeric polyol can be calculated from the hydroxyl number according to methods known in the state of the art. In certain embodiments, the polymeric polyol (ii) has a hydroxyl number of 20 to 400 mg KOH/g solids, preferably of 20 to 300 mg KOH/g solids, more preferably of 20 to 200 mg KOH/g solids, very preferably of 20 to 100 mg KOH/g solids, as determined according to DIN 53240-2:2007-11. In certain embodiments, the polymeric polyol (ii) has a hydroxyl functionality of 1 .5 to 6, such as 1 .8 to 3 or 1 .9 to

2.1.

Exemplary polymeric polyols (ii) include, for example, polyester polyols, polyacrylate polyols, polyurethane polyols, polycarbonate polyols, polyether polyols, polyester polyacrylate polyols, polyurethane polyacrylate polyols, polyurethane polyester polyols, polyurethane polyether polyols, polyurethane polycarbonate polyols, polyester polycarbonate polyols, phenol/formaldehyde resins, on their own or in mixtures.

Suitable polyether polyols include, for example, the polyaddition products of the styrene oxides, of ethylene oxide, propylene oxide, tetrahydrofuran, butylene oxide, epichlorohydrin, as well as their mixed-addition and graft products, as well as the polyether polyols obtained by condensation of polyhydric alcohols or mixtures thereof and those obtained by alkoxylation of polyhydric alcohols, amines and amino alcohols. Suitable polyether polyols often have a hydroxyl functionality of 1 .5 to 6.0, such as 1 .8 to 3.0, a hydroxyl number of 20 to 700 mg KOH/g solid, such as 20 to 100, 20 to 50 or, in some cases 20 to 40 mg KOH/g solid, and/or a M _n of 400 to 4,000 g/mol, such as 100 to 4,000 or 1 ,000 to 3,000 g/mol.

Exemplary polyester polyols are the polycondensation products of di- as well as optionally tri- and tetra-ols and di- as well as optionally tri- and tetra-carboxyl ic acids or hydroxycarboxylic acids or lactones. Instead of the free polycarboxylic acids it is also possible to use the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols to prepare the polyesters. Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, further 1 ,2- propanediol, 1 ,3-propanediol, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,6-hexanediol and isomers, 1 ,8-octanediol, neopentyl glycol, 1 ,4-bishydroxymethyl- cyclohexane, 2- methyl-1 ,3-propanediol, 2,2,4-trimethyl-1 ,3-pentanediol, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, tetrabromobisphenol A, lactone-modified diols, or hydroxypivalic acid neopentyl glycol ester. In order to achieve a functionality > 2, polyols having a functionality of 3 can optionally be used proportionately, for example trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxyethyl isocyanurate. Suitable dicarboxylic acids are, for example, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydro-phthalic acid, cyclohexane-dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid, 3,3- diethylglutaric acid, and/or 2,2-dimethylsuccinic acid. Anhydrides of those acids can likewise be used, where they exist. Thus, for the purposes of the present invention, anhydrides are included in the expression “acid”. Monocarboxylic acids, such as benzoic acid and hexanecarboxylic acid, can also be used, provided that the mean functionality of the polyol is > 2. Saturated aliphatic or aromatic acids can be used, such as adipic acid or isophthalic acid. Trimellitic acid is a polycarboxylic acid which can also optionally be used. Hydroxycarboxylic acids which can be used as reactants in the preparation of a polyester polyol having terminal hydroxyl groups are, for example, hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and the like. Suitable lactones are, for example, e- caprolactone, butyrolactone and their homologues.

In certain embodiments of the present invention, polymer polyol (ii) comprises or, in some cases, consists essentially of or consists of a polyester diol that is a reaction product of butanediol and one or more of neopentyl glycol, hexanediol, ethylene glycol, and diethylene glycol with adipic acid and one or more of phthalic acid and isophthalic acid, such as polyester polyols that are a reaction product of at least one of butanediol, neopentyl glycol, and hexanediol with at least one of adipic acid and phthalic acid. Suitable polyester polyols, such as the foregoing polyester diols, often have a hydroxyl functionality of 1.5 to 6.0, such as 1.8 to 3.0, a hydroxyl number of 20 to 700 mg KOH/gram solid, such as 20 to 100, 20 to 80 or, in some cases 40 to 80 mg KOH/g solid, and/or a M _n of 500 to 3,000 g/mol, such as 600 to 2,500 g/mol.

Exemplary polycarbonate polyols are obtainable by reaction of carbonic acid derivatives, for example diphenyl carbonate, dimethyl carbonate or phosgene, with diols. Suitable diols include the diols mentioned earlier with respect to the preparation of polyester polyols. In some cases, the diol component contains from 40 wt.% to 100 wt.% 1 ,6-hexanediol and/or hexanediol derivatives, often containing ether or ester groups in addition to terminal OH groups, for example products which are obtained by reaction of one mole of hexanediol with at least one mole, preferably from one to two moles, of e-caprolactone or by etherification of hexanediol with itself to form di- or trihexylene glycol. Polyether polycarbonate polyols can also be used.

Compound comprising at least one isocyanate-reactive group and an anionic group or potentially anionic group (iii):

Exemplary such compounds are those which contain, for example, carboxylate, sulfonate, phosphonate groups or groups which can be converted into the above- mentioned groups by salt formation (potentially anionic groups), and which can be incorporated into the polyisocyanate by isocyanate-reactive groups, such as hydroxyl or amine groups, that are present.

Suitable anionic or potentially anionic compounds are, for example, mono- and di- hydroxycarboxylic acids, mono- and di-aminocarboxylic acids, mono- and di- hydroxysulfonic acids, mono- and di-aminosulfonic acids as well as mono- and di- hydroxyphosphonic acids or mono- and di-aminophosphonic acids and their salts, such as dimethylol-propionic acid, dimethylolbutyric acid, hydroxypivalic acid, N-(2- amino-ethyl)-[3-alanine, 2-(2-amino-ethylamino)-ethanesulfonic acid, ethylene- diamine-propyl- or -butyl-sulfonic acid, 1 ,2- or 1 ,3-propylenediamine-3-ethylsulfonic acid, malic acid, citric acid, glycolic acid, lactic acid or mixtures thereof. In certain embodiments, the anionic or potentially anionic compounds have at least one of carboxy, carboxylate, and sulfonate groups and/or have a functionality of from 1.9 to 2.1 , such as the salts of 2-(2-aminoethyl-amino)ethanesulfonic acid.

In certain embodiments, component (iii) is used in an amount of at least 0.1 wt.%, such as at least 1 %, or at least 3wt.% and/or no more than 10wt.%, such as no more than 7wt.%, based on the total weight of compounds (i) to (vii).

Mono functional polyalkylene ether (v):

Component (v) is a mono functional polyalkylene ether that contains at least one, in some cases one, hydroxy or amino group. In some embodiments, component (v) comprises compounds of the general formula (I)

H— Y— X— Y— R (I) in which R is a monovalent hydrocarbon radical having 1 to 12 carbon atoms, such as an unsubstituted alkyl radical having 1 to 4 carbon atoms;

X is a polyalkylene oxide chain having 5 to 90, such as 20 to 70 chain members, which may comprise at least 40%, such as at least 65%, ethylene oxide units and which in addition to ethylene oxide units may comprise propylene oxide, butylene oxide and/or styrene oxide units; and

Y and Y' are each independently oxygen or -NR'- in which R' is H or R as defined above.

Mono functional polyalkylene ethers suitable for use as component (v) may, in some cases, contain 7 to 55 ethylene oxide units per molecule, and can be obtained by alkoxylation of suitable starter molecules, such as, for example, saturated monoalcohols, such as methanol, ethanol, n- propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n- decanol, n-dodecanol, n- tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methyl-cyclohexanols or hydroxymethyl-cyclohexane, 3-ethyl-3-hydroxy- methyloxetan or tetrahydrofurfuryl alcohol; diethylene glycol monoalkyl ethers, such as, for example, diethylene glycol monobutyl ether; unsaturated alcohols, such as allyl alcohol, 1 ,1 -dimethyl-allyl alcohol or oleic alcohol; aromatic alcohols, such as phenol, the isomeric cresols or methoxyphenols; araliphatic alcohols, such as benzyl alcohol, anis alcohol or cinnamic alcohol; secondary monoamines, such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutyl-amine, bis-(2-ethylhexyl)- amine, N-methyl- and N-ethyl-cyclohexylamine or dicyclohexylamine; as well as heterocyclic secondary amines, such as morpholine, pyrrolidine, piperidine or 1 H- pyrazole, including mixtures of two or more of any of the foregoing.

Alkylene oxides suitable for the alkoxylation reaction include, for example, ethylene oxide and propylene oxide, which can be used in the alkoxylation reaction in any desired sequence or alternatively in admixture. In some embodiments, component (v) comprises a copolymer of ethylene oxide with propylene oxide that contains ethylene oxide in an amount of at least 40 wt.% to 90 wt.%, preferably of 50 wt.% to 90 wt.%, more preferably of 60 wt.% to 90 wt.%, very preferably of 65 wt.% to 80 wt.%, based in each case on the total weight of ethylene oxide and propylene oxide. In certain embodiments, the M _n of such a copolymer is 300 g/mol to 6,000 g/mol, such as 500 g/mol to 4,000 g/mol, such as 1 ,000 g/mol to 3,000 g/mol.

In certain embodiments, component (v) is used in an amount of 1 wt.% to 30wt.%, preferably of 5 wt.% 30 wt.%, very preferably of 10 wt.% to 20 wt.%, based in each case on the total weight of compounds (i) to (vii).

Polyol having a number average molecular weight of less than < 400 grams/mol (vi): Examples of such polyols include, without limitation, the diols mentioned earlier with respect to the preparation of polyester polyols. In some cases, the polyol (vi) has up to 20 carbon atoms, such as is the case with, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,3- butylene glycol, cyclohexanediol, 1 ,4-cyclohexanedimethanol, 1 ,6-hexanediol, neopentyl glycol, hydroquinone dihydroxyethyl ether, bisphenol A (2,2-bis(4- hydroxyphenyl)propane), hydrogenated bisphenol A, (2,2-bis(4- hydroxycyclohexyl)propane), trimethylolpropane, glycerol, pentaerythritol and also any desired mixtures of two or more thereof. Also suitable are ester diols of the specified molecular weight range such as a-hydroxybutyl-s-hydroxy-caproic acid ester, o- hydroxyhexyl-y-hydroxybutyric acid ester, [3-hydroxy-ethyl adipate or bis(|3- hydroxyethyl) terephthalate.

In certain embodiments, component (vi) is used in an amount of 1 wt.% to 20 wt.%, preferably of 2 wt.% to 10 wt.%, very preferably of 3 wt.% to 5 wt.%, based in each case on the total weight of compounds (i) to (vii).

Polyamine (vii):

Component (vii) is used for chain extension and includes di- or polyamines as well as hydrazides, for example ethylenediamine, 1 ,2- and 1 ,3-diaminopropane, 1 ,4- diaminobutane, 1 ,6-diaminohexane, isophorone- diamine, isomer mixture of 2,2,4- and 2,4,4-trimethyl-hexamethylene-diamine, 2-methylpentamethylenediamine, diethylenetriamine, 1 ,3- and 1 ,4-xylylenediamine, a,a,a',a'-tetramethyl-l,3- and -1 ,4- xylylenediamine and 4,4-diaminodicyclohexylmethane, dimethylethylenediamine, hydrazine or adipic acid dihydrazide. Also suitable for use are compounds which contain active hydrogen of different reactivity towards NCO groups, such as compounds which contain, in addition to a primary amino group, also secondary amino groups or, in addition to an amino group (primary or secondary), also OH groups. Examples thereof are primary/secondary amines, such as 3-am ino-1 -methyl- am inopropane, 3-am ino-1 -ethylam inopropane, 3-am ino-1 -cyclohexylam inopropane, 3-amino-1 -methylaminobutane, also alkanolamines such as N-aminoethylethanol- amine, ethanolamine, 3-aminopropanol or neopentanolamine.

In certain embodiments, component (vii) is used in an amount of 1 wt.% to 10 wt.%, preferably of 3 wt.% to 8 wt.%, very preferably of 5 wt.% by to 7 wt.%, based in each case on the total weight of compounds (i) to (vii).

Preparation of the aqueous polyurethane dispersion (PUD):

Any of a variety of processes can be used to prepare the aqueous polyurethane dispersion (PUD), such as the prepolymer mixing method, acetone method or melt dispersing method, each of which will be understood by a person skilled in the art of making aqueous polyurethane dispersions. For example, in some embodiments, the aqueous polyurethane dispersions of the present invention may be produced by the acetone method, such as is described, for example, US 2007/0167565 A1 .

Properties of the aqueous polyurethane dispersion (PUD):

In certain embodiments, the resin solids content of the aqueous polyurethane dispersion (PUD) is 20 wt.% to 65 wt.%, preferably 25 wt.% to 50 wt.%, very preferably 30 wt.% to 45 wt.%, based in each case on the total weight of the aqueous polyurethane dispersion (PUD). The solid content can be determined, for example, according to DIN EN ISO 3251 :2008-06.

Amount of aqueous polyurethane dispersion (PUD):

The aqueous coating composition preferably comprises the aqueous polyurethane dispersion (PUD) in a total amount of 20 to 90 wt.%, more preferably of 40 to 85 wt.%, even more preferably of 50 to 80 wt.%, very preferably of 65 to 75 wt.%, based in each case on the total weight of the coating composition.

Use of the aqueous polyurethane dispersion (PUD) in combination with the further mandatory components mentioned below in the aqueous coating composition results, upon drying of the applied coating composition, in a peelable coating film which - on the one hand - has a sufficient adhesion to the substrate and - on the other hand - can be peeled residue-free from the substrate without damaging the underlying substrate.

Phospholipid (b):

As second mandatory component (b), the inventive aqueous coating composition comprises at least one phospholipid. With particular preference, the at least one phospholipid is selected from lecithins, in particular from soy lecithin. Soy lecithin (also known as L-a-phosphatidylcholine) contains predominantly C and Cis fatty acid side chains covalently attached to the C-1 and C-2 carbons of the glycerol backbone of the lecithin molecule. The C fatty acids are commonly saturated while the Cis fatty acids are commonly unsaturated and comprise one or more double bonds.

Suitable total amounts of the at least one phospholipid, preferably the at least one soy lecithin, include 0.1 wt.% to 5 wt.%, preferably 0.3 wt.% to 4 wt.%, more preferably 0.5 wt.% to 3 wt.%, very preferably 0.6 wt.% to 2 wt.%, based in each case on the total weight of the aqueous coating composition.

Use of a least one phospholipid, in particular soy lecithin, results in an increased elasticity of the peelable coating, thus allowing to remove large parts of the coating in one piece and therefore rendering removal of the peelable coating fast and efficient.

Defoamer (c):

As third mandatory component (c), the inventive aqueous coating composition comprises at least one defoamer. Suitable defoamers used herein comprise at least an oil selected from silicon oils and/or mineral oils, preferably mineral oils, most preferred mineral oils from the group of hydrogenated naphthenic mineral oils.

The defoamer further contains hydrophobic solid particles, preferably from the group consisting of hydrophobic ureas or hydrophobic silicas, most preferred from the group of hydrophobic silicas. Hydrophobic silicas are preferably selected from the group of fumed and precipitated silicas which are surface-treated with organosilanes. The defoamer may further contain oxyalkylated compounds.

Most preferred the defoamer comprises at least a mineral oil selected from hydrogenated naphthenic mineral oils, hydrophobic silica and at least one oxyalkylated compound. Use of a defoamer comprising the aforementioned compounds does not have a negative influence on the optical properties of the resulting peelable coating, such as the gloss, and does not result in the formation of specks or bits upon preparation and/or storage of the inventive coating composition.

The at least one defoamer is preferably present in a total amount of 0.01 wt.% to 2 wt.%, preferably 0.02 wt.% to 1 wt.%, more preferably 0.04 wt.% to 0.5 wt.%, very preferably 0.06 wt.% to 0.2 wt.%, based in each case on the total weight of the coating composition.

Thickening agent (d):

As fourth mandatory component (d), the inventive coating composition comprises at least one thickening agent (d). Suitable thickening agents are selected from inorganic thickening agents, organic thickening agents and mixtures thereof. Inorganic thickening agents may be selected from phyllosilicates, in particular from lithium aluminum magnesium silicate. Lithium aluminum magnesium silicate is commercially available under the tradename Laponite® RD from Byk Chemie GmbH. Organic thickening agents may include (meth)acrylic acid-(meth)acrylate copolymer thickeners, polyurethane thickeners, polyamide thickeners or a mixture thereof A particular preferred organic thickening agent is selected from associative polyurethane thickeners. Such associative polyurethane thickeners are commercially available under the tradename Rheovis® PU 1250 from BASF SE.

With preference, a mixture of at least one organic and at least one inorganic thickening agent is present in the inventive coating composition. With particular preference, a mixture of lithium aluminum magnesium silicate and an associative polyurethane thickener is used as thickening agent (d).

In case a mixture of inorganic and organic thickening agents is used, it may be beneficial if a weight ratio of the at least one organic thickening agent to the at least one inorganic thickening agent of 5:1 to 1 :5, preferably of 4:1 to 1 :1 , very preferably of 3:1 to 1 :1 is used.

Use of a mixture of an inorganic thickening agent, such as lithium aluminum magnesium silicate, and an organic thickening agent, such as an associative polyurethane thickener, preferably in the aforementioned weight ratios, results in inventive coating compositions having an improved resistance to sagging and an improved effect particle orientation as compared to the use of other thickening agents known in the state of the art or the sole use of inorganic or organic thickening agents.

The at least one thickening agent, in particular the aforementioned mixture of organic and inorganic thickening agents, is preferably present a total amount of 0.01 wt.% to 3 wt.%, more preferably of 0.05 wt.% to 2 wt.%, even more preferably of 0.1 wt.% to 1.5 wt.%, very preferably 0.3 wt.% to 1 wt.%, based in each case on the total weight of the coating composition. Use of the thickening agent(s) in the aforementioned total amounts allows to obtain a spray viscosity which is sufficiently low to apply the inventive coating composition to the substrate by spraying methods but is, at the same time, sufficiently high to prevent sagging of the coating composition after application to the substrate.

Pigment (f):

The inventive aqueous coating compositions are pigmented aqueous coating compositions and therefore comprise at least one pigment. The at least one pigment can be a color pigment and/or an effect pigment. The term “color pigment” or “coloring pigment” refers to pigments producing an optical effect based on selective light absorption in conjunction with light scattering. Examples of color pigments include inorganic and organic color pigments. The term “inorganic color pigment” refers to natural and synthetically produced pigments based on inorganic compounds and includes white pigments, inorganic colored pigments and black pigments. The term “organic color pigment” refers to coloring agents which are practically insoluble in the application medium and includes azo pigments and polycyclic pigments, i.e. organic non-azo pigments characterized by at least one aromatic and/or heteroaromatic ring system. In contrast, the term “effect pigment” or “visual effect pigment” refers to pigments producing an optical effect, such as a color or lightness effect, based primarily on light reflection, in particular on angle dependent light reflection. Examples of effect pigments include luster pigments, such as metal effect pigments, pearlescent pigments and interference pigments, flaky graphene, flaky iron oxide and micronized titanium dioxide.

Suitable color pigments include monoazopigments, such as C.l. Pigment Brown 25, C.l. Pigment Orange 5, 36 and 67, C.l. Pigment Orange 5, 36 and 67, C.l. Pigment Red 3, 48:2, 48:3, 48:4, 52:2, 63, 112 and 170, and C.l. Pigment Yellow 3, 74, 151 and 183; disazopigments, such as C.l. Pigment Red 144, 166:214 and 242 C.l. Pigment Red 144, 166:214 and 242, 15 and also C.l. Pigment Yellow 83; anthraquinone pigments, such as C.l. Pigment Yellow 147 and 177, and also C.l. Pigment Violet 31 ; benzimidazole pigments, such as C.l. Pigment Orange 64; quinacridone pigments, such as C.l. Pigment Orange 48 and 49, C.l. Pigment Red 122, 202 and 206, and C.l. Pigment Violet 19; quinophthalone pigments, such as C.l. Pigment Yellow 138; diketopyrrolopyrrole pigments, such as C.l. Pigment Orange 71 and 73, and C.l. Pigment Red 254, 255, 264 and 270; dioxazine pigments, such as C.l. Pigment Violet 23 and 37; indanthrone pigments, such as C.l. Pigment Blue 60; isoindoline pigments, such as C.l. Pigment Yellow 139 and 185; isoindolinone pigments, such as C.l. Pigment Orange 61 and also C.l. Pigment Yellow 109 and 110; metal complex pigments, such as C.l. Pigment Yellow 153; perinone pigments, such as C.l. Pigment Orange 43; perylene pigments, such as C.l. Pigment Black 32, C.l. Pigment Red 149, 178 and 179 and C.l. Pigment Violet 29; phthalocyanine pigments, such as C.l. Pigment Violet 29, C.l. Pigment Blue 15, 15:1 , 15:2, 15:3, 15:4, 15:6 and 16, and C.l. Pigment Green 7 and 36; aniline black, 30 such as C.l. Pigment Black 1 ; azomethine pigments; white pigments, such as titanium dioxide (C.l. Pigment White 6), zinc white, pigmentary zinc oxide, zinc sulfide, lithopone; black pigments, such as black iron oxide (C.l. Pigment Black 11 ), iron manganese black, spinell black (C.l. Pigment Black 27), carbon black (C.l. Pigment Black 7); chromatic pigments, such as ultramarine green, ultramarine blue, manganese blue, ultramarine violet, manganese violet, red iron oxide (C.l. Pigment Red 101 ), molybdate red (C.l. Pigment Red 104), ultramarine red, brown iron oxide, mixed brown, spinell phases and corundum phases (C.l. Pigment Brown 24, 29 and 31 ), yellow iron oxide (C.l. Pigment Yellow 42), bismuth vanadate (C.l. Pigment Yellow 184); silicon dioxide; ground quartz; aluminum oxide; aluminum hydroxide; natural micas; natural and precipitated chalk; barium sulfate; and mixtures thereof.

Suitable effect pigments include platelet-shaped metallic effect pigments such as platelet-shaped aluminum pigments, gold bronzes, oxidized bronzes and/or 30 iron oxide-aluminum pigments, pearlescent pigments and/or metal oxide-mica pigments and/or other effect pigments such as platelet-shaped graphite, platelet-shaped iron oxide, multilayer effect pigments composed of PVD films and/or liquid crystal polymer pigments and mixtures thereof.

The pigments may be incorporated into the aqueous coating composition by use of organic or aqueous, preferably aqueous, pigment pastes. The term “pigment paste” refers to preparations of pigments or pigment mixtures in carrier materials in which the pigments are present in a higher concentration than in the inventive coating composition. Suitable carrier materials include binders or binder mixtures, such as further binders B described later on. The binders or binder mixtures may be dissolved or dispersed in organic solvents and/or water and the binder solution or dispersion may contain wetting agents and sometimes other additives. The carrier material should resemble or be compatible with the solvents present in the inventive coating composition Use of such pigment pastes allows to tint the aqueous coating composition in the desired color and thus allows to produce personalized peelable coatings which can be adapted to the desired color, for example by mixing the available pigment pastes in a defined mixing ratio.

Preferred aqueous coating compositions according to the invention comprise a pigment to binder ratio of at least 0.03, preferably of 0.04 to 0.15, very preferably of 0.05 to 0.08. The aforementioned pigment to binder ratio allows to obtain an opaque peelable coating, i.e. the underlying substrate and or any underlying colored coating layers is/are not visible through the peelable coating formed from the inventive aqueous coating composition. This ensures a high optical quality of the peelable coating due to the high hiding power and allows to apply the inventive aqueous coating composition on colored substrates without any negative influence on the overall optical appearance of the resulting peelable coating. Further ingredients:

The inventive coating composition is an aqueous coating composition in order to meet the current low overall solvent emission requirements. The expression "aqueous coating composition" is known to the skilled person. It refers fundamentally to a coating composition which is not based exclusively on organic solvents. Indeed, any such coating composition based on organic solvents contains exclusively organic solvents and no water for dissolving and/or dispersing the components, or is a coating composition for which no water is added explicitly during its production, water entering the composition instead only in the form of contaminant, atmospheric moisture and/or solvent for any specific additives employed. Such a composition, in contrast to an aqueous coating composition, would be referred to as being solvent borne or "based on organic solvents". "Aqueous" in the context of the present invention should be understood preferably to mean that the coating composition comprises a water fraction of at least 20 wt.%, preferably 40 wt.% to 85 wt.%, more preferably of 50 wt.% to 80 wt.%, very preferably of 55 wt.% to 70 wt.%, based in each case on the total weight of the coating composition. The water fraction in turn is preferably 40 to 100 wt.%, more particularly 60 to 100 wt.%, very preferably 90 to 98 wt.%, based in each case on the total amount of the solvents present.

The aqueous coating composition may comprise, apart from polyurethane present in the aqueous polyurethane dispersion (PUD) described earlier, at least one further binder B which is different from the polyurethane present in the PUD. Suitable binders include (i) poly(meth)acrylates, more particularly hydroxy-functional and/or carboxylate-functional and/or amine-functional poly(meth)acrylates, (ii) polyurethanes, more particularly hydroxy-functional and/or carboxylate-functional and/or amine- functional polyurethanes, (iii) polyesters, more particularly polyester polyols and polycarbonate polyols, (iv) polyethers, more particularly polyether polyols, (v) copolymers of the stated polymers, and (vi) mixtures thereof, preferably from hydroxyfunctional poly(meth)acrylates, hydroxy-functional polyurethanes, hydroxy-functional polyesters, hydroxy-functional polyethers and copolymers of said polymers. If pigment paste(s) is/are used to tint the aqueous coating compositions, the least one further binder B may be present in the carrier of said pigment paste(s). The at least one further binder B may be present in a total amount of 0 wt.% to 25 wt.%, preferably of 5 wt.% to 20 wt.%, very preferably of 10 wt.% to 15 wt.%, based in each case on the total weight of the coating composition.

The compositions of the present invention may be mixed and combined with conventional auxiliaries and additives, selected from the group of dyes, matting agents, flow control additives, wetting additives, slip additives, nanoparticles, light stabilizing particles, anti-yellowing additives and mixtures thereof. Such auxiliaries and additives may be present in a total amount of 0.1 to 20 wt.%, more preferably 0.5 to 10 wt.%, very preferably 0.1 to 5 wt.%, based in each case on the total weight of the aqueous coating composition.

Properties of the peelable coating:

The peelable coating formed from the inventive aqueous coating composition is preferably removable over a temperature range of at least 0°C to 30°C. The wide temperature range allows to remove the peelable coating under conditions commonly present inside a vehicle refinish shop, thus rendering the use of highly defined conditions during removal of the peelable coating superfluous and allowing easy efficient removal of the peelable coating.

The peelable coating is very preferably mechanically peeled by hand. Thus, the adhesion of the peelable coating is, on the one hand, sufficiently high to provide sufficient mechanical properties and weatherability, but, on the other hand, sufficiently low to allow removal of the peelable coating by hand. This guarantees easy and efficient removal of the peelable coating at the end of its service period and renders the use of machines or specialized tools superfluous.

The peelable coating formed form the inventive aqueous coating composition is preferably not a foamed peelable coating, i.e. the coating layer resulting from applying the inventive aqueous coating composition onto a substrate and drying said coating composition does not in a coating layer comprising structures of gas-filled cells, which are bounded by cell webs. Thus, the resulting coating does not comprise any trapped pockets of gas which are resulting, for example, from the use of a propellant. The peelable coating of the invention has a good overall visual appearance irrespective of the pigments being present in the inventive aqueous coating composition. The use of commercially available pigment pastes for tinting the aqueous coating composition allows to prepare peelable coatings in all colors currently available in the vehicle sector and also allows to prepare customized colored peelable coatings by mixing the available tinting pastes in pre-defined ratios. Despite the good peelabilty, the peelable coating shows sufficient mechanical stability against environmental influences, e.g. bending, stone chipping, etc., and sufficient weatherability.

Inventive peelable coating system:

The inventive peelable coating system comprises a first coating layer (CL-1 ) on at least part of a surface of a substrate (S); and a tinted clearcoat and/or a clearcoat layer (CL-2) on top of the first coating layer (CL-1 ). The first coating layer (CL-1 ) and the tinted clearcoat and/or clearcoat layer (CL-2) form a peelable coating, wherein an adhesive strength between the first coating layer (CL-1 ) and the second coating layer (CL-2) is greater than an adhesive strength between the first coating layer (CL-1 ) and the surface of the substrate (S).

Substrate (S):

Suitable substrates (S) include metallic substrates optionally coated with at least one cured coating layer, plastic substrates optionally coated with at least one cured coating layer, substrates comprising metallic and plastic components and optionally coated with at least one cured coating layer, preferably from metallic substrates coated with at least one cured coating layer, in particular from metallic substrates coated with a cured multilayer coating. Metallic substrate may be selected from the group comprising or consisting of iron, aluminum, copper, zinc, magnesium and alloys thereof as well as steel.

Coated and uncoated metal substrates can be pretreated in a manner known per se, i.e. , for example, cleaned and/or provided with known conversion coatings. Cleaning can be performed mechanically, for example by means of wiping, grinding and/or polishing, and/or chemically by means of etching methods, such as surface etching in acid or alkali baths using, for example, hydrochloric acid or sulfuric acid, or by cleaning with organic solvents or aqueous detergents. Pretreatment by application of conversion coatings, especially by means of phosphation and/or chromation, preferably phosphation, may likewise take place. Preferably, the metallic substrates are at least conversion-coated, especially phosphated, preferably by a zinc phosphation.

Metal substrates being coated with a cured electrocoat are produced by electrophoretic application of an electrocoat material to the substrate and subsequent curing of the applied electrocoat material. The electrocoat material may be a cathodic or anodic electrocoat material, preferably a cathodic electrocoat material. Electrocoat materials are aqueous coating materials comprising anionic or cationic polymers as binders. These polymers contain functional groups which are potentially anionic, i.e. can be converted to anionic groups, for example carboxylic acid groups, or functional groups which are potentially cationic, i.e. can be converted to cationic groups, for example amino groups. The conversion to charged groups is generally achieved by the use of appropriate neutralizing agents (organic amines (anionic), organic carboxylic acids such as formic acid (cationic). The electrocoat materials generally comprise typical anticorrosion pigments. The cathodic electrocoat materials preferred in the context of the invention comprise preferably cationic polymers as binders, especially hydroxyfunctional polyether amines, which preferably have aromatic structural units. These polymers are especially used in combination with blocked polyisocyanates known per se. The application of the electrocoating material proceeds by electrophoresis. For this purpose, the metallic workpiece to be coated is first dipped into a dip bath containing the coating material, and an electrical DC field is applied between the metallic workpiece and a counterelectrode. The workpiece thus functions as an electrode; the nonvolatile constituents of the electrocoat material migrate, because of the described charge of the polymers used as binders, through the electrical field to the substrate and are deposited on the substrate, forming an electrocoat film. For example, in the case of a cathodic electrocoat, the substrate is thus connected as the cathode, and the hydroxide ions which form there through water electrolysis neutralize the cationic binder, such that it is deposited on the substrate and forms an electrocoat layer. After the electrolytic application of the electrocoat material, the coated substrate is removed from the bath, optionally rinsed off with, for example, water-based rinse solutions, then optionally flashed off and/or intermediately dried, and finally cured. The dry film thickness of the cured electrocoat is, for example, 10 to 40 micrometers, preferably 15 to 25 micrometers. Metal substrates being coated with a cured filler layer are produced by applying a filler coating composition to the substrate, optionally flashing off and/or intermediately drying said applied composition and finally curing said composition. Suitable filler coating compositions are known in the state of the art. The dry film thickness of the cured filler layer is, for example, 10 to 40 micrometers, preferably 25 to 30 micrometers.

Metal substrates being coated with a cured basecoat and clearcoat or tinted clearcoat layer are produced by applying a basecoat coating composition to the substrate, optionally flashing off and/or intermediately drying said applied composition, applying a clearcoat composition wet-on-wet on the uncured basecoat film and finally jointly curing the basecoat and the clearcoat film. Suitable basecoat and clearcoat or tinted clearcoat coating compositions are known in the state of the art. The cured multilayer coating preferably comprises at least one pigmented coating layer (e.g. basecoat layer) and optionally at least one clearcoat and/or tinted clearcoat layer.

Preferred plastic substrates are basically substrates comprising or consisting of (i) polar plastics, such as polycarbonate, polyamide, polystyrene, styrene copolymers, polyesters, polyphenylene oxides and blends of these plastics, (ii) synthetic resins such as polyurethane RIM, SMC, BMC and (iii) polyolefin substrates of the polyethylene and polypropylene type with a high rubber content, such as PP-EPDM, and surface-activated polyolefin substrates. The plastics may furthermore be fiber- reinforced, in particular using carbon fibers and/or metal fibers.

Preferable substrates according to the method of the present invention are (i) vehicles, including but not limited to automobiles, trucks, agricultural machines, ships, airplanes, motorcycles, etc., as well as parts of such vehicles; (ii) furniture surfaces, such as kitchen surfaces; (iii) everyday items, such as sportswear, helmets, etc..

First coating layer (CL-1):

The first coating layer (CL-1 ) is obtained by applying the inventive coating composition to at least part of the surface of the substrate (S) and drying the applied coating composition as described later on. Second coating layer (CL-2):

The second coating layer (CL-2) of the inventive peelable coating system is formed on the first coating layer (CL-1 ) by applying a tinted clearcoat and/or clearcoat composition to at least part of the first coating layer (CL-1 ). The term “tinted clearcoat composition” refers to coating compositions which, when applied to a substrate, are neither completely transparent and colorless as a clear coating nor completely opaque as the peelable coating resulting from the inventive aqueous coating composition. A tinted clear coating is therefore transparent and colored or semi-transparent and colored. The color can be achieved by adding at least one color and/or effect pigment previously described in a total amount of 0.1 to 10 wt.-%, preferably 1 to 4 wt.-%, based on the total weight of the tinted clearcoat composition.

The clearcoat composition may in principle be any transparent coating composition known to the person skilled in the art in this context. This includes aqueous or solvent borne transparent coating compositions as well as powder clearcoat materials. Suitable clearcoat materials are water-borne, solvent-borne and powder clearcoat materials, such as, for example, described in DE 34 12 534, DE 36 09 519, DE 37 31 652, and DE 38 23 005.

The tinted clearcoat and/or clearcoat composition may be formulated either as one- component or two-component or multicomponent coating compositions. In case of one-component coating compositions, crosslinking reactions during storage need to be avoided, for example by using blocked crosslinking agents which are only reactive at higher temperatures. Two-component coating compositions comprise the reactive components, i.e. binder and crosslinker, in separate containers. The components of containers 1 and 2 are then mixed prior to use, preferably shortly before application of the mixed coating composition to the substrate. In addition, powder slurry clearcoat materials are also suitable.

Preference is given to the use of solvent-based multi-component clearcoat and/or tinted clearcoat compositions.

In a preferred embodiment, the peelable coating system of the invention consists of two coating layers, namely a pigmented peelable base and a tinted clearcoat layer or a clearcoat layer. In another preferred embodiment, the peelable coating system consists of three coating layers, namely a pigmented peelable base, a tinted clearcoat layer and a clearcoat layer. The pigmented peelable base renders the use of a colorless peelable base, which has to be overcoated with a pigmented coating composition to result in a pigmented peelable coating superfluous, thus reducing the amount of material and time necessary to prepare the inventive peelable coating system. The inventive coating system shows sufficient mechanical stability and weatherability to allow an average presence on a vehicle of 6 month without getting damaged by environmental influences occurring during the use. Despite the absence of a further peelable base, the inventive coating system is peelable by hand residue- free without damaging the underlying coating layer(s)/substrate after being present on the vehicle for 6 month.

What has been said about the inventive coating composition applies mutatis mutandis with respect to further preferred embodiments of the inventive peelable coating system.

Inventive method:

The inventive method for forming a peelable coating system onto at least part of a surface of a substrate involves the application of at least two coating compositions (C-1 ), and (C-2) consecutively over the substrate in the manner described below. The peelable coating system is formed at least from the first coating layer (CL-1 ) and the second coating layer (CL-2) and an adhesive strength between the first coating layer (CL-1 ) and the second coating layer (CL-2) is greater than an adhesive strength between the first coating layer (CL-1 ) and the surface of the substrate (S).

The at least two different coating compositions that are used in the method of the present invention include: the first coating composition (C-1 ) to provide a peelable pigmented base and a tinted clearcoat and/or a clearcoat composition (C-2) to provide protection of the peelable pigmented base and/or further visual effects.

Step (i):

In step (i) of the inventive method, the inventive aqueous coating composition (C-1 ) is applied to at least part of a surface of the substrate to form a first coating film (CF-1 ). The coating composition (C-1 ) can be applied by methods known to those skilled in the art for application of liquid coating compositions, for example by dipping, bar coating, spraying, rolling or the like. Preference is given to employing spray application methods, for example compressed air spraying (pneumatic application), airless spraying, high-speed rotation, electrostatic spray application (ESTA), optionally in association with hot-spray application, for example hot-air spraying. Most preferably, the basecoat material(s) is/are applied by means of compressed air spraying or electrostatic spray application (ESTA).

The application of the coating composition (C-1 ) is preferably performed in such a way that the first coating layer (CL-1 ), after the drying in step (ii), has a dry film thickness of 40 to 200 pm, preferably of 45 to 120 pm, very preferably of 50 to 100 pm. A dry film thickness of at least 40 pm is necessary to be able to peel the obtained coating system mechanically by hands. Lower film thicknesses result in coating systems which cannot be mechanically peeled by hands such that large parts of the coating film are removed at once due to the low film thickness of the coating system.

In order to achieve the aforementioned film thickness, it may be beneficial if step (i) is repeated at least once, preferably at least twice, very preferably at least four times. In case step (i) is repeated at least once, the term “coating film” refers to the multilayer film obtained after the last repetition of step (i). In this regard, it may be preferably to dry the coating composition (C-1 ) applied in the first run of step (i) at 15 to 30 °C, preferably at 18 to 25 °C, for 2 to 10 minutes prior to repeating step (i). Drying of the applied coating composition (C-1 ) prior to repeating step (i) results in an adhesion promoting layer for the following coating films produced by repeating step (i). It may be beneficial in terms of visual appearance to at least partially dry the coating film obtained after the third time prior to repeating step (i) for the fourth times because this results in a better effect formation in case effect pigments are present in the coating composition (C-1 ).

Step (ii):

In step (ii) of the inventive method, the first coating film (CF-1 ) formed in step (i) is dried to form a first coating layer (CL-1 ). Drying of the first coating film (CF-1 ) may be performed at 15 to 30°C, preferably at 18 to 25°C, for 2 to 10 minutes. The coating film (CF-1 ) is not cured in step (ii), i.e. it is preferably not exposed to temperatures of more than 40 °C for a period of longer than 1 min, and especially preferably are not exposed to temperatures of more than 40 °C at all.

Step (Hi):

In step (iii) of the inventive method, a tinted clearcoat and/or clearcoat composition (C-2) is applied on at least part of the first coating layer (CL-1 ) to form a tinted clearcoat and/or clearcoat film (CF-2).

Application of the tinted clearcoat and/or the clearcoat composition (C-2) can be performed using the methods previously described in relation to step (i). In case a tinted clearcoat and a clearcoat composition are applied, it may be beneficial to dry the applied tinted clearcoat composition as previously described in relation to step (ii) prior to application of the clearcoat composition.

The application of the tinted clearcoat and/or the clearcoat composition (C-2) is preferably performed in such a way that the second coating layer (CL-2), after the joint curing in step (iv), has a dry film thickness of 30 to 70 pm. In case a tinted clearcoat and a clearcoat composition are applied, the dry film thickness refers to the dry film thickness of the tinted clearcoat and the clearcoat layer.

Step (iv):

In step (iv) of the inventive method, the first coating layer (CL-1 ) and the tinted clearcoat and/or the clearcoat film (CF-2) is/are jointly cured to form the peelable coating system.

Joint curing in step (v) is preferably performed at 15 to 30°C, preferably at 18 to 25°C, for a duration of 0.5 days to 5 days. What has been said about the inventive coating composition and the inventive peelable coating system applies mutatis mutandis with respect to further preferred embodiments of the inventive peelable coating system.

Inventive coated substrate:

After the end of the method of the invention, the result is a coated object of the invention.

The coated object of the present invention has a good overall visual appearance irrespective of the pigmented coating composition used to prepare the coated substrate. Despite the good mechanical properties including the good adhesion to the underlying substrate as well as the good interlayer adhesion, the peelable coating system can be removed form the coated object without any residues and without damaging the underlying object.

What has been said about the inventive coating composition, the inventive peelable coating system and the inventive method applies mutatis mutandis with respect to further preferred embodiments of the inventive coated substrates.

Inventive use:

A further subject matter of the invention is the use of an inventive aqueous coating composition to form a peelable coating layer on at least part of the surface of a substrate.

What has been said about the inventive coating composition, the inventive peelable coating system and the inventive method applies mutatis mutandis with respect to further preferred embodiments of the inventive use.

The invention is described in particular by the following embodiments:

1 . An aqueous coating composition comprising

(a) at least one aqueous polyurethane dispersion (PUD),

(b) at least one phospholipid,

(c) at least one defoamer,

(d) at least one thickening agent, and (e) at least one pigment, wherein the dried aqueous coating composition forms a peelable coating on at least part of a surface of a substrate, said peelable coating adhering to the surface without the use of a separate adhesive coating layer. The aqueous coating composition according to clause 1 , wherein the at least one aqueous polyurethane dispersion (PUD) comprises the reaction product of:

(i) a polyisocyanate;

(ii) a polymeric polyol having a number average molecular weight of 400 to 8,000 g/mol;

(iii) a compound comprising at least one isocyanate-reactive group and an anionic group or potentially anionic group;

(iv) water;

(v) a mono functional polyalkylene ether;

(vi) a polyol having a number average molecular weight of less than < 400 g/mol, and

(vii) a polyamine or amino alcohol having a number average molecular weight of 32 to 400 g/mol. The aqueous coating composition according to clause 2, wherein the polyisocyanate (i) is selected from the group consisting of 1 ,4-butylene diisocyanate, 1 ,6-hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), isophorone diisocyanate (IPDI), 2,2,4- and 2,4,4-trimethyl- hexamethylene diisocyanate, isomeric bis-(4,4'- isocyanatocyclohexyl)methanes or mixtures thereof of any desired isomer content, 1 ,4-cyclohexylene diisocyanate,

1.4-phenylene diisocyanate, 2,4- and 2,6-toluene diisocyanate or hydrogenated

2.4- and 2,6-toluene diisocyanate, 1 ,5-naphthalene diisocyanate, 2,4'- and 4,4'- diphenylmethane diisocyanate, 1 ,3- and 1 ,4-bis-(2-isocyanato-prop-2-yl)-benzene (TMXDI), 1 ,3-bis(isocyanato-methyl)benzene (XDI), (S)-alkyl 2,6- diisocyanatohexanoates or (L)-alkyl 2,6-diisocyanatohexanoates and mixtures thereof. The aqueous coating composition according to clause 2 or 3, wherein the polymeric polyol (ii) has a number average molecular weight M _n of 400 to 6,000 g/mol, preferably of 500 to 3000 g/mol, more preferably of 1 ,000 to 3,000 g/mol, very preferably 1 ,500 to 3,000 g/mol. The aqueous coating composition according to any one of clauses 2 to 4, wherein the polymeric polyol (ii) has a hydroxyl number of 20 to 400 mg KOH/g solids, preferably of 20 to 300 mg KOH/g solids, more preferably of 20 to 200 mg KOH/g solids, very preferably of 20 to 100 mg KOH/g solids, as determined according to DIN 53240-2:2007-11 . The aqueous coating composition according to any one of clauses 2 to 5, wherein the polymeric polyol (ii) has a hydroxyl functionality of 1 .5 to 6, such as 1 .8 to 3 or 1.9 to 2.1. The aqueous coating composition according to any one of clauses 2 to 6, wherein the polymeric polyol (ii) is selected from the group consisting of polyester polyols, polyacrylate polyols, polyurethane polyols, polycarbonate polyols, polyether polyols, polyester polyacrylate polyols, polyurethane polyacrylate polyols, polyurethane polyester polyols, polyurethane polyether polyols, polyurethane polycarbonate polyols, polyester polycarbonate polyols, phenol/formaldehyde resins or mixtures thereof. The aqueous coating composition according to any one of clauses 2 to 7, wherein compound (iii) is selected from the group consisting of mono- and di- hydroxycarboxylic acids, mono- and di-aminocarboxylic acids, mono- and di- hydroxysulfonic acids, mono- and di-aminosulfonic acids as well as mono- and di- hydroxyphosphonic acids or mono- and di- aminophosphonic acids and their salts, such as dimethylol-propionic acid, dimethylolbutyric acid, hydroxypivalic acid, N- (2-amino-ethyl)-[3-alanine, 2- (2-amino-ethylamino)-ethanesulfonic acid, ethylene- diamine-propyl- or -butyl-sulfonic acid, 1 ,2- or 1 ,3-propylenediamine-3- ethylsulfonic acid, malic acid, citric acid, glycolic acid, lactic acid or mixtures thereof. The aqueous coating composition according to any one of clauses 2 to 8, wherein the anionic group comprises at least one of carboxy, carboxylate, and sulfonate group. 10. The aqueous coating composition according to any one of clauses 2 to 9, wherein compound (iii) has a functionality of 1 .9 to 2.1 .

11 . The aqueous coating composition according to any one of clauses 2 to 10, wherein compound (iii) is used in an amount of at least 0.1 wt.%, preferably 1 wt.% to 10 wt.%, very preferably 3 wt.% to 7 wt.%, based in each case on the total weight of reactants used to make the polyurethane.

12. The aqueous coating composition according to any one of clauses 2 to 11 , wherein the mono functional polyalkylene ether (v) contains at least one, preferably exactly one, hydroxy or amino group.

13. The aqueous coating composition according to any one of clauses 2 to 12, wherein the mono functional polyalkylene ether (v) contains 7 to 55 ethylene oxide units per molecule.

14. The aqueous coating composition according to any one of clauses 2 to 13, wherein the mono functional polyalkylene ether (v) comprises a copolymer of ethylene oxide with propylene oxide that contains ethylene oxide in an amount of 40 wt.% to 90 wt.%, preferably of 50 wt.% to 90 wt.%, more preferably of 60 wt.% to 90 wt.%, very preferably of 65 wt.% to 80 wt.%, based in each case on the total weight of ethylene oxide and propylene oxide.

15. The aqueous coating composition according to any one of clauses 2 to 14, wherein the mono functional polyalkylene ether (v) is used in a total amount of 1 wt.% to 30 wt.%, preferably of 5 wt.% 30 wt.%, very preferably of 10 wt.% to 20 wt.%, based in each case on the total weight of reactants used to make the polyurethane.

16. The aqueous coating composition according to any one of clauses 2 to 15, wherein the polyol (vi) is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,3- butylene glycol, cyclohexanediol, 1 ,4-cyclohexanedimethanol, 1 ,6-hexanediol, neopentyl glycol, hydroquinone dihydroxyethyl ether, bisphenol A (2,2-bis(4- hydroxyphenyl)propane), hydrogenated bisphenol A, (2,2-bis(4- hydroxycyclohexyl)propane), trimethylolpropane, glycerol, pentaerythritol hydroxybutyl-s-hydroxy-caproic acid ester, o-hydroxyhexyl-y-hydroxybutyric acid ester, [3-hydroxy-ethyl adipate or bis([3-hydroxyethyl) terephthalate and mixtures thereof.

17. The aqueous coating composition according to any one of clauses 2 to 16, wherein the polyol (vi) is used in a total amount of 1 wt.% to 20 wt.%, preferably of 2 wt.% to 10 wt.%, very preferably of 3 wt.% to 5 wt.%, based in each case on the total weight of reactants used to make the polyurethane.

18. The aqueous coating composition according to any one of clauses 2 to 17, wherein the polyamine (vii) is selected from the group consisting of ethylenediamine, 1 ,2- and 1 ,3-diaminopropane, 1 ,4-diaminobutane, 1 ,6-diaminohexane, isophoronediamine, isomer mixture of 2,2,4- and 2,4,4-trimethyl-hexamethylene-diamine, 2- methylpentamethylenediamine, diethylenetriamine, 1 ,3- and 1 ,4-xylylenediamine, a,a,a',a'-tetramethyl-l,3- and -1 ,4-xylylenediamine and 4,4- diaminodicyclohexylmethane, dimethylethylenediamine, hydrazine, adipic acid dihydrazide, 3-amino-1 -methyl-aminopropane, 3-amino-1 -ethylaminopropane, 3- am ino-1 -cyclohexylam inopropane, 3-am ino-1 -methylam inobutane, N- aminoethylethanol-amine, ethanolamine, 3-aminopropanol, neopentanolamine or mixtures thereof.

19. The aqueous coating composition according to any one of clauses 2 to 18, wherein the polyamine (vii) is used in a total amount of 1 wt.% to 10 wt.%, preferably of 3 wt.% to 8 wt.%, very preferably of 5 wt.% by to 7 wt.%, based in each case on the total weight of reactants used to make the polyurethane.

20. The aqueous coating composition according to any one of the preceding clauses, wherein the solids content of the aqueous polyurethane dispersion (PUD) is 20 wt.% to 65 wt.%, preferably 25 wt.% to 50 wt.%, very preferably 30 wt.% to 45 wt.%, based in each case on the total weight of the aqueous polyurethane dispersion (PUD).

21 . The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises the aqueous polyurethane dispersion (PUD) in a total amount of 20 to 90 wt.%, preferably of 40 to 85 wt.%, more preferably of 50 to 80 wt.%, very preferably of 65 to 75 wt.%, based in each case on the total weight of the coating composition. The aqueous coating composition according to any one of the preceding clauses, wherein the at least one phospholipid is selected from lecithins, in particular from soy lecithin. The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises the at least phospholipid, preferably the at least one soy lecithin, in a total amount of 0.1 wt.% to 5 wt.%, preferably 0.3 wt.% to 4 wt.%, more preferably 0.5 wt.% to 3 wt.%, very preferably 0.6 wt.% to 2 wt.%, based in each case on the total weight of the coating composition. The aqueous coating composition according to any one of the preceding clauses, wherein the at least one defoamer comprises (i) at least one oil, such as a silicon and/or mineral oil, in particular a mineral oil, such as hydrogenated naphthenic mineral oil; (ii) solid particles, such as hydrophobic silica; (iii) oxyalkylated compounds and (iv) mixtures thereof. The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises the at least one defoamer in a total amount of 0.01 wt.% to 2 wt.%, preferably 0.02 wt.% to 1 wt.%, more preferably 0.04 wt.% to 0.5 wt.%, very preferably 0.06 wt.% to 0.2 wt.%, based in each case on the total weight of the coating composition. The aqueous coating composition according to any one of the preceding clauses, wherein the at least one thickening agent is selected from inorganic thickening agents, organic thickening agents and mixtures thereof, in particular a mixture of at least one organic and at least one inorganic thickening agent. The aqueous coating composition according to clause 26, wherein the weight ratio of the at least one organic thickening agent to the at least one inorganic thickening agent is from 5:1 to 1 :5, preferably from 4:1 to 1 :1 , very preferably from 3:1 to 1 :1 . 28. The aqueous coating composition according to clause 26 or 27, wherein the inorganic thickening agent is selected from phyllosilicates, in particular from lithium aluminum magnesium silicate.

29. The aqueous coating composition according to any one of clauses 26 to 28, wherein the organic thickening agent is the group consisting of (meth)acrylic acid- (meth)acrylate copolymer thickeners, polyurethane thickeners, polyamide thickeners or a mixture thereof, in particular from associative polyurethane thickeners.

30. The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises the at least one thickening agent, in particular a mixture of organic and inorganic thickening agents, in a total amount of 0.01 wt.% to 3 wt.%, preferably of 0.05 wt.% to 2 wt.%, more preferably of 0.1 wt.% to 1.5 wt.%, very preferably 0.3 wt.% to 1 wt.%, based in each case on the total weight of the coating composition.

31 . The aqueous coating composition according to any one of the preceding clauses, wherein the at least one pigment is selected from color pigment(s) and/or effect pigment(s).

32. The aqueous coating composition according to clause 31 , wherein the color pigment(s) is/are selected from the group consisting of monoazopigments, such as C.l. Pigment Brown 25, C.l. Pigment Orange 5, 36 and 67, C.l. Pigment Orange 5, 36 and 67, C.l. Pigment Red 3, 48:2, 48:3, 48:4, 52:2, 63, 112 and 170, and C.l. Pigment Yellow 3, 74, 151 and 183; disazopigments, such as C.l. Pigment Red 144, 166:214 and 242 C.l. Pigment Red 144, 166:214 and 242, 15 and also C.l. Pigment Yellow 83; anthraquinone pigments, such as C.l. Pigment Yellow 147 and 177, and also C.l. Pigment Violet 31 ; benzimidazole pigments, such as C.l. Pigment Orange 64; quinacridone pigments, such as C.l. Pigment Orange 48 and 49, C.l. Pigment Red 122, 202 and 206, and C.l. Pigment Violet 19; quinophthalone pigments, such as C.l. Pigment Yellow 138; diketopyrrolopyrrole pigments, such as C.l. Pigment Orange 71 and 73, and C.l. Pigment Red 254, 255, 264 and 270; dioxazine pigments, such as C.l. Pigment Violet 23 and 37; indanthrone pigments, such as C.l. Pigment Blue 60; isoindoline pigments, such as C. I. Pigment Yellow 139 and 185; isoindolinone pigments, such as C. I. Pigment Orange 61 and also C.l. Pigment Yellow 109 and 110; metal complex pigments, such as C.l. Pigment Yellow 153; perinone pigments, such as C.l. Pigment Orange 43; perylene pigments, such as C.l. Pigment Black 32, C.l. Pigment Red 149, 178 and 179 and C.l. Pigment Violet 29; phthalocyanine pigments, such as C.l. Pigment Violet 29, C.l. Pigment Blue 15, 15:1 , 15:2, 15:3, 15:4, 15:6 and 16, and C.l. Pigment Green 7 and 36; aniline black, 30 such as C.l. Pigment Black 1 ; azomethine pigments; white pigments, such as titanium dioxide (C.l. Pigment White 6), zinc white, pigmentary zinc oxide, zinc sulfide, lithopone; black pigments, such as black iron oxide (C.l. Pigment Black 11 ), iron manganese black, spinell black (C.l. Pigment Black 27), carbon black (C.l. Pigment Black 7); chromatic pigments, such as ultramarine green, ultramarine blue, manganese blue, ultramarine violet, manganese violet, red iron oxide (C.l. Pigment Red 101 ), molybdate red (C.l. Pigment Red 104), ultramarine red, brown iron oxide, mixed brown, spinell phases and corundum phases (C.l. Pigment Brown 24, 29 and 31 ), yellow iron oxide (C.l. Pigment Yellow 42), bismuth vanadate (C.l. Pigment Yellow 184); silicon dioxide; ground quartz; aluminum oxide; aluminum hydroxide; natural micas; natural and precipitated chalk; barium sulfate; and mixtures thereof. The aqueous coating composition according to clause 31 or 32, wherein the effect pigment(s) is/are selected from platelet-shaped metallic effect pigments such as platelet-shaped aluminum pigments, gold bronzes, oxidized bronzes and/or 30 iron oxide-aluminum pigments, pearlescent pigments and/or metal oxide-mica pigments and/or other effect pigments such as platelet-shaped graphite, plateletshaped iron oxide, multilayer effect pigments composed of PVD films and/or liquid crystal polymer pigments and mixtures thereof. The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises a pigment to binder ratio of at least 0.03, preferably of 0.04 to 0.15, very preferably of 0.05 to 0.08. The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises a total amount of water of 40 wt.% to 100 wt.%, preferably of 60 wt.% to 100 wt.%, very preferably of 90 wt.% to 98 wt.%, based in each case on the total amount of solvents present in the aqueous coating composition.

36. The aqueous coating composition according to any one of the preceding clauses, wherein the coating composition comprises a total amount of at least one further binder B being different from the polyurethane present in the aqueous polyurethane dispersion (PUD) of 0 wt.% to 25 wt.%, preferably of 5 wt.% to 20 wt.%, very preferably of 10 wt.% to 15 wt.%, based in each case on the total weight of the coating composition.

37. The aqueous coating composition according to any one of the preceding clauses, wherein the peelable coating is removable over a temperature range of at least 0°C to 30°C.

38. The aqueous coating composition according to any one of the preceding clauses, wherein the peelable coating is mechanically peeled by hand.

39. The aqueous coating composition according to any one of the preceding clauses, wherein the peelable coating is not a foamed peelable coating.

40. A peelable coating system comprising

(a) a first coating layer (CL-1 ) being prepared by applying an aqueous coating composition according to any one of clauses 1 to 38 to at least part of a surface of a substrate (S); and

(b) a tinted clearcoat and/or a clearcoat layer (CL-2) being prepared by applying a tinted clearcoat and/or a clearcoat composition (C-2) to the first coating layer (CL-1 ); wherein the first coating layer (CL-1 ) and the second coating layer (CL-2) form a peelable coating, wherein an adhesive strength between the first coating layer (CL- 1 ) and the second coating layer (CL-2) is greater than an adhesive strength between the first coating layer (CL-1 ) and the surface of the substrate (S).

41 . The peelable coating system according to clause 40, wherein the substrate (S) is selected from metallic substrates optionally coated with at least one cured coating layer, plastic substrates optionally coated with at least one cured coating layer, substrates comprising metallic and plastic components and optionally coated with at least one cured coating layer, preferably from metallic substrates coated with at least one cured coating layer, in particular from metallic substrates coated with a cured multilayer coating.

42. The peelable coating system according to clause 41 , wherein the metallic substrate is selected from the group comprising or consisting of iron, aluminum, copper, zinc, magnesium and alloys thereof as well as steel.

43. The peelable coating system according to clause 41 or 42, wherein the cured multilayer coating comprises at least one pigmented coating layer and optionally at least one clearcoat and/or tinted clearcoat layer.

44. The peelable coating system according to any one of the preceding system clauses, wherein the clearcoat and/or tinted clearcoat composition (C-2) is selected from solvent borne 1 -component or multi-component clearcoat and/or tinted clearcoat compositions, preferably from solvent borne multi-component clearcoat and/or tinted clearcoat compositions.

45. A method for forming a peelable coating system onto at least part of a surface of a substrate, said method comprising

(i) applying an aqueous coating composition (C-1 ) according to any one of clauses 1 to 39 to at least part of a surface of the substrate to form a first coating film (CF-1 ),

(ii) drying the formed first coating film (CF-1 ) to form a first coating layer (CL-1 ),

(iii) applying a tinted clearcoat and/or a clearcoat composition (C-2) on at least part of the first coating layer (CL-2) to form a tinted clearcoat and/or clearcoat film (CF-2), and

(iv) jointly curing the first coating layer (CL-1 ) and the tinted clearcoat and/or the clearcoat film (CF-2) to form the peelable coating system, wherein the first coating layer (CL-1 ) and the tinted clearcoat and/or clearcoat layer (CL-2) form a peelable coating, wherein an adhesive strength between the first coating layer (CL-1 ) and the clearcoat or tinted clearcoat layer (CL-2) is greater than an adhesive strength between the first coating layer (CL-1 ) and the surface of the substrate (S).

46. The method according to clause 45, wherein step (i) is repeated at least once, preferably at least twice, very preferably at least four times.

47. The method according to clause 46, wherein the coating composition applied in the first run of step (i) is dried at 15 to 30 °C, preferably at 18 to 25 °C, for 2 to 10 minutes prior to repeating step (i).

48. The method according to any one of the preceding method clauses, wherein the first coating film (CF-1 ) is dried at 15 to 30°C, preferably at 18 to 25°C, for 2 to 10 minutes.

49. The method according to any one of the preceding method clauses, wherein the first coating layer (CL-1 ) has a dry film thickness of 40 to 200 pm, preferably of 45 to 120 pm, very preferably of 50 to 100 pm.

50. The method according to any one of the preceding method clauses, wherein the joint curing in step (v) is performed at 15 to 30°C, preferably at 18 to 25°C, for a duration of 0.5 days to 5 days.

51 . The method according to any one of the preceding method clauses, wherein the second coating layer (CL-2) has a dry film thickness of 30 to 70 pm.

52. A coated substrate obtained by the method of any one of clauses 45 to 51 .

53. Use of an aqueous coating composition according to any one of clauses 1 to 39 to form a peelable coating layer on at least part of the surface of a substrate. Examples

The present invention will now be explained in greater detail through the use of working examples, but the present invention is in no way limited to these working examples. Moreover, the terms "parts", "%" and "ratio" in the examples denote "parts by mass", "mass %" and "mass ratio" respectively unless otherwise indicated.

1. Methods of determination:

1.1 Solids content (solids, non-volatile fraction)

Unless stated otherwise, the solids content (also called proportion of solids, solid-state content, proportion of non-volatiles) was determined to DIN EN ISO 3251 : 2018-07 at 130°C; 60 min, starting weight 1 .0 g.

1.2. Initial peelablity

The initial peelability of peelable coating systems was determined 11 days after their preparation as follows: if the respective peelable coating system could be completely peeled off from the surface of the substrate in the form of a film or a fragmented film, leaving no obvious marks of the coating on the substrate surface, then the coating was considered to have a good peelability, or otherwise the coating was considered to have a poor peelability.

1.3 Determination of optical properties of peelable coating systems

The optical properties of the peelable coating systems were determined visually.

2. Aqueous coating compositions

2.1 Preparation of pigment paste P

The pigment paste P used to prepare the aqueous coating composition was obtained by mixing the refinish tinting pastes commercially available from BASF Coatings GmbH in the amounts listed in Table 1 . Table 2: Ingredients used to prepare the pigment paste P

2.2 Preparation of pigmented aqueous coating compositions

The compounds listed in Table 2 were mixed in the stated order to obtain the respective aqueous coating composition.

Table 2: Ingredients used to prepare the aqueous coating compositions (C-1 ) and (C-2) (all amounts are given in wt.%, based in each case on the total weight of the respective first coating composition)

* inventive

¹⁾ aqueous polyurethane dispersion (PUD), solids content ~ 40%, available from Covestro LLC,

²⁾ 52wt.% of polyether modified polysiloxane, available from BYK-Chemie GmbH,

³⁾ blend of liquid hydrocarbons, hydrophobic silica, synthetic copolymers and nonionic emulsifiers, available from Munzing Chemie GmbH,

⁴⁾ available from Lubrizol,

⁵⁾ VOC-free silicone-containing defoamer, available from BYK-Chemie GmbH,

⁶⁾ prepared as described in point 2.1 ,

⁷⁾ Non-ionic rheology modifier, available from BASF Corporation

⁸⁾ contains 92.9 wt.% of water, 0.1 wt.% of Acticide MBR, 3 wt.% of Laponite RD and

3 wt.% of Pluriol P 900 C 3. Preparation of peelable coating systems

A commercial two-component clearcoat (ProGloss® FF99-0373, from BASF Coatings GmbH) was applied to coil sheets (60 x 32 cm) such that such that the film thickness of the obtained clearcoat layer after curing was 40 to 45 pm. The resulting clearcoat film was flashed at 18 to 23°C for 10 minutes and afterwards cured at 140°C for 20 minutes. The cured clearcoat film was then coated with the respective aqueous coating composition (C-1 ) or (C-2) via pneumatic spray application (spraying gun RP 5000, pressure: 2 bar) in four spraying passes such that the film thickness of the obtained pigmented coating layer after curing was 50 pm. After the first spraying pass, the resulting coating layer is blown dry to increase the adhesion of the coating layers produced in the following spraying passes. After the last spraying pass, the obtained coating film was dried at 18 to 23°C for 4 minutes. Afterwards, a commercially available three-component clearcoat composition (Glasurit® HS clearcoat fast drying VOC, 923- 610, from BASF Coatings GmbH) was applied such that the film thickness of the obtained clearcoat layer after curing was 40 to 45 pm. Afterwards, the obtained peelable coating systems were cured at 18 to 23°C for 3 days.

4. Results

4.1 . Initial peelabilitv

The results for the initial peelability are listed in Table 3 below.

Table 3: Results of initial peelablilty of peelable coating systems (MC-1 ), (MC-2)

* inventive, prepared using aqueous coating composition (C-2)

4.2 Optical properties

The comparative aqueous coating composition (C-1 ) is not homogenous and not storage stable. This results in a strongly disturbed alignment of the aluminum platelets in the comparative peelable coting system (MC-C) and therefore in unacceptable optical properties.

In contrast, inventive aqueous coating composition (C-2) is very homogeneous and storage stable. This results in a very uniform alignment and distribution of the aluminum platelets in the inventive peelable coating system (MC-I) and therefore in a very uniform visual appearance. The surface of the coating layer produced by applying the aqueous coating composition (C-2) on the cured clearcoat is very matt but this mattness can be reduced to result in acceptable optical properties by overcoating the coating layer with a commercially available clearcoat material. Moreover, the coating layer produced by applying the aqueous coating composition (C-2) on the cured clearcoat has a sufficient opacity, i.e. it hides the underlaying substrate such that it is no longer visible through the pigmented peelable coating layer. In conclusion, the inventive peelable coating system (MC-I) shows good optical properties.

5. Discussion of the results

Peelable coating systems comprising the pigmented coating layers show a good peeling behavior and can be fully removed from the underlying original finish without damaging the original finish by pulling on the intentionally damaged peelable coating system with the hand(s). The residue-free removal of the peelable coating system renders subsequent cleaning of the original finish superfluous, thus reducing the costs associated with the peelable coating and peelable coating system. Since the inventive coating composition can be tinted with effect as well as solid pigment pastes without negatively influencing the good optical properties of the resulting peelable coating system, the color of the peelable coating system can be adapted to the specific needs of the customer without the use of further colored coating layers within the peelable coating system.

In conclusion, peelable coating layers produced from the inventive aqueous coating compositions and inventive peelable coating systems comprising the peelable coating layers allow to temporarily customize or personalize a substrate, such as an automotive, in a high optical and mechanical quality without damaging the original finish. Moreover, the color of the peelable coating layer and peelable coating system can be freely adapted to the specific needs of the customer by tinting the aqueous coating composition with pigment pastes commercially available for refinish purposes. This allows to obtain the peelable coating system in all colors available in the refinish sector without the use of further colored coating layers, thus reducing the effort and costs associated with producing a peelable coating having the desired visual impression.