Polyurethane-based polymer comprising n-vinylpyrrolidone-based moieties

Abstract

The present invention relates to a polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties, wherein the amount of polyurethane in the polyurethane-based polymer is greater than 10 wt.-% (based on the total weight of the polyurethane-based polymer) and wherein the electrophoretic mobility of the polymer in aqueous dispersion is not less than −4.0 (µm / s) / (V / cm) in the pH range from 3.0 to 10.0.

Description

[0001] Polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties

[0002] The present invention relates to a polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties and a method to produce the polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties. The invention also relates to an aqueous pigmented composition containing the polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties, a coating layer formed thereof and thus also a coated substrate. Moreover, the invention relates to the use of a coating composition comprising the polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties in automotive coating and a method of making a multilayer coating, wherein at least one coating layer is formed from a coating composition comprising the polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties.

[0003] BACKGROUND

[0004] The coating process of automobiles includes the application of several different paint layers each having specific properties. The multi-coat paint system includes a base coat layer that is applied first and may comprise pigments. After a short flash-off time without a baking step (wet-on-wet process), the base coat layer is coated with a clear coat layer. Subsequently, base coat layer and clear coat layer are baked together. New strategies are developed to improve the coating composition as the requirements of the paint systems such as weather resistance or scratch resistance in the industry like the automobile sector are immense.

[0005] In general, aqueous base coat compositions can contain binders that are either stabilized by Coulomb forces meaning electrostatic forces (generally via anionic groups)or via uncharged (i.e. non-ionic) water-soluble polymer chains, namely water- soluble polyether moieties. The stabilization of binders via electrostatic forces is based on the DLVO theory or Debye-Huckel theory. In contrast, the uncharged polymer chains stabilize the binder with osmotic pressure. The range of both stabilization forces is very different and varies depending on the hydrophilic group or chain length of the uncharged polymer. In general, the range of electrostatic interactions is larger than the osmotic interactions that result from the uncharged polymer chains (Steven Abbott, PhD, FRCS, TCNF Ltd., Ipswich, UK Visiting Professor, University Leeds, UK, “Surfactant Science Principles & Practice”). The range of electrostatic interactions is about 50 nm, while the range of uncharged polymers is about 5 nm. Formulations with high solids are of interest for industrial applications, which are influenced by the range of the interactions. Higher solids can be achieved in case of lower interactions ranges, which is an advantage of uncharged polymer chains for the preparation of aqueous base coat compositions.

[0006] Furthermore, it is of outstanding interest in the industrial application that coating compositions are robust and exhibit long-life stability. Electrostatically stabilized interactions, more specifically their ionic strength in aqueous dispersions, exhibit a large dependence on the pH value or salinity. The dependence can be observed in time-dependent effects such as resalting or aging. In contrast, steric stabilization by uncharged polymers exhibits a higher tolerance towards electrolytes in addition to a higher ability to stabilize larger particles and produce dispersions with a high solid content.

[0007] Another disadvantage of electrostatically stabilized interactions is their stabilization effect on foam in contrast to the uncharged polymer chains due to their larger range of the corresponding interactions (Steven Abott, PhD, FRCS, TCNF Ltd., Ipswich, UK Visiting Professor, University Leeds, UK, “Surfactant Science Principles & Practice”).

[0008] In virtue of the aforementioned features, uncharged polymer chains have advantages in aqueous base coat compositions. However, another important feature of coating compositions is the weather resistance. High quality coatings are required for the coating of aircrafts, rail vehicles, ships or automobiles and require a minimum standard with regard to weathering resistance, more particular with respect to their stability against UV-light irradiation, photo-oxidation and humidity. Especially aqueous basecoat compositions containing polymers stabilized by water-soluble glycols or glycol ethers (i.e. polyether moieties) known from the state of the art do not fulfill these requirements. Polyurethane dispersions are favorable in aqueous base coat compositions as they exhibit the aforementioned stability criteria (Goldschmidt, Streitberger, Basics of Coating Technology, 2nd, revised Edition, 2007, page 99-101 ).

[0009] Alternative aqueous, uncharged copolymers that do not contain water-soluble glycols (polyether moieties) are described in the literature. Hydrophilic coating compositions containing polyvinylpyrrolidone (PVP) are used to coat surfaces, especially for medical applications (WO 98 / 58990, WO 2013 / 109930 A1 ).

[0010] EP2283087 B1 describes cathodic electrodeposition paints with copolymers of polyvinylpyrrolidone and other polymers, which are based on vinyl-functional comonomers. Moreover, copolymers of polyvinylpyrrolidone are used in pigment preparations (EP0902061 A2). However, all these applications lack the combination of polyurethane with specific amounts of polyvinylpyrrolidone.

[0011] It was the aim of the present invention to improve the quality of the basecoat layer and provide new options to form a multilayer coating that fulfills the quality requirements of the industry. Therefore, it was aimed to prepare binder polymers and respective aqueous coating compositions that comprise such binder polymers, whereby the polymers mainly or even exclusively rely on non-ionic stabilization in the aqueous composition, but at the same time making it possible to produce coating layers exhibiting a high weathering resistance (i.e. resistance to e.g. UV-light irradiation, photo-oxidation and humidity) and long-life durability.

[0012] SUMMARY

[0013] The object has been solved by the subject-matter of the present application as well as by the preferred embodiments thereof disclosed in this specification.

[0014] A first subject-matter of the present invention is a polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties, wherein the amount of polyurethane in the polyurethane-based polymer is greater than 10 wt.-% (based on the total weight of the polyurethane-based polymer) and wherein the electrophoretic mobility of the polymer is not less than -4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0 in aqueous dispersion.

[0015] The above defined polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties may also be called polymer according to the present invention or inventive polymer.

[0016] A further subject-matter of the present invention is a pigmented composition selected from preferably thermally curable coating compositions and pigment pastes comprising at least one polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties, wherein the electrophoretic mobility of the polymer is not less than -4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0 in aqueous dispersion.

[0017] Another subject-matter of the present invention is a coating layer formed as a monolayer coating or at least one layer as part of a multilayer coating, wherein at least one coating layer is formed from an above-defined pigmented coating composition. Finally, a correspondingly coated substrate also is a subject-matter of the present invention.

[0018] A further object of the present invention is the use of a pigmented composition comprising at least one above-defined polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties) for producing an automotive coating.

[0019] Yet another subject-matter of the present invention is a method of making a multilayer coating, comprising the steps of a) optionally applying a filler coating composition on a substrate to obtain a filler layer, b) applying a base coat composition on top of the layer obtained in step a) or directly on a substrate to form a base coat layer, c) applying a clear coat composition on top of the base coat layer to form a clear coat layer, and d) simultaneously curing of the filler layer, base coat layer and clear coat layer or individually curing of one or more layers obtained in steps a) to c) before the subsequent coating layer is applied, wherein at least one coating composition of steps a) or b) comprises an abovedefined pigmented coating composition.

[0020] Preferred embodiments of the polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties and the coating composition of the invention are apparent from the description hereinafter and also from the dependent claims.

[0021] DETAILED DESCRIPTION

[0022] Definitions

[0023] The expression "aqueous coating composition" is known to the skilled person. It refers to a coating composition, wherein the solvent part of the coating composition is essentially based on water. "Aqueous" in the context of the present invention is therefore to be understood to mean that the coating composition comprises preferably a water fraction of at least 40 wt.-%, more preferably at least 50 wt.-%, even more preferably at least 60 wt.-%, based in each case on the total amount of the solvents present (that is, water and organic solvents). The same principle applies for aqueous dispersions in general, for example an aqueous dispersion of an inventive polymer.

[0024] The term “aliphatic” is used according to the IIIPAC definition thereby including all acyclic or cyclic, saturated or unsaturated carbon compounds, excluding aromatic compounds.

[0025] The term “(meth)acrylic” encompasses acrylic and methacrylic.

[0026] The term “thermally curable coating composition” describes coating compositions where crosslinking is typically achieved by self-crosslinking of preferably polymeric species or crosslinking of polymers carrying functional groups with so-called crosslinking agents carrying functional groups, which react with the functional groups of the before-mentioned polymers, thus forming a cured, i.e., crosslinked coating.

[0027] The term “polymer” describes components, which are composed of multiple individual molecules, whereby these individual molecules comprise monomeric entities and at least partly differ in terms of degree of polymerization, molar mass and chain length (i.e. number of monomeric entities). The monomeric entities (i.e. the entities originating from monomers applied for production of the polymers) may be the same or different. For versatile polymers it is an inherent feature that at least two different monomeric entities are comprised (for example, a polyurethane moiety at least comprises one type of isocyanate-based entity and one type of alcohol-based entity). Also, depending on educts and production process, a polymer may consist of individual molecules comprising only one type of polymerized monomeric entities (for example polyurethane moieties). Likewise, it is possible that a polymer comprises different types of individual molecules, for example a first type comprising a first type of polymerized monomeric entities (e.g. polyurethane moieties) and a second type comprising a second type of polymerized monomeric entities (e.g. polyvinylpyrrolidone moieties). It is also possible that a polymer contains individual molecules comprising, in one molecule, different types of polymerized monomeric entities, for example both polyurethane and polyvinylpyrrolidone moieties. A class of such latter polymers are, for example, graft polymers. Of course, a polymer may also contain both individual molecules of only one type of polymerized monomeric entities and molecules comprising different types of such polymerized monomeric entities (a situation which often already occurs for statistical reasons during production).

[0028] As is known to the person skilled in the art, a polymer may not only be formed by directly reacting monomers in just one reaction step, but the procedure my involve versatile steps and / or in a final step pre-produced polymers or macromonomers may be applied as reactants. For example, within production of polyurethanes, often hydroxy-functional polyesters are applied as reactants. However, of course these polyesters likewise go back to monomers and thus contains respective monomeric entities. Therefore, the final polymer again is composed of multiple individual molecules, whereby these molecules comprise monomeric entities. This aspect is explicitly meant to be embraced when referring to polymers within the scope of the present invention.

[0029] As known and for the reasons as described above, a polymer does not have a specific molecular weight like a monomeric component, but always an average molecular weight (representing the different individual molecules as described above).

[0030] Polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties

[0031] The polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties, quite obviously, comprises polyurethane moieties (as it is polyurethane-based) and also moieties consisting of or comprising N-vinylpyrrolidone (i.e. all or part of the monomeric entities of the moieties originate from N-vinylpyrrolidone). Polyvinylpyrrolidone moieties, for example, consist of polymerized monomeric entities solely originating from N-vinylpyrrolidone.

[0032] Polyurethanes (and respective moieties) are well known in the art. For preparing such polyurethanes it is possible to employ the aliphatic, cycloaliphatic, aliphatic- cycloaliphatic, aromatic, aliphatic-aromatic and / or cycloaliphatic-aromatic polyisocyanates that are known to the skilled person. Diisocyanates are used with preference. Mention may be made, by way of example, of the following diisocyanates:

[0033] 1.3- or 1 ,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 4,4'- or 2,4'- diphenylmethane diisocyanate, 1 ,4- or 1 ,5-naphthylene diisocyanate, diisocyanatodiphenyl ether, trimethylene diisocyanate, tetramethylene diisocyanate, ethylethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1 -methyltrimethylene diisocyanate, pentamethylene diisocyanate, 1 ,3-cyclopentylene diisocyanate, hexamethylene diisocyanate, cyclohexylene diisocyanate, 1 ,2-cyclohexylene diisocyanate, octamethylene diisocyanate, trimethylhexane diisocyanate, tetramethylhexane diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, isophorone diisocyanate (IPDI), 2- isocyanatopropylcyclohexyl isocyanate, dicyclohexylmethane 2,4'-diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, 1 ,4- or 1 ,3-bis(isocyanatomethyl)cyclohexane,

[0034] 1.4- or 1 ,3- or 1 ,2-diisocyanatocyclohexane, 2,4- or 2,6-diisocyanato-1 - methylcyclohexane, 1 -isocyanatomethyl-5-isocyanato-1 ,3,3-trimethylcyclohexane, 2,3-bis(8-isocyanatooctyl)-4-octyl-5-hexylcyclohexene, tetramethylxylylene diisocyanates (TMXDI) such as m-tetramethylxylylene diisocyanate, or mixtures of these polyisocyanates. Also possible, of course, is the use of different dimers and trimers of the stated diisocyanates, such as uretdiones and isocyanurates. Polyisocyanates of higher isocyanate functionality may also be used. Examples thereof are tris(4-isocyanatophenyl)methane, 1 ,3,4-triisocyanatobenzene, 2,4,6- triisocyanatotoluene, 1 ,3,5-tris(6-isocyanatohexylbiuret), bis(2,5-diisocyanato-4- methylphenyl)methane. The functionality may optionally be lowered by reaction with monoalcohols and / or secondary amines. Preference, however, is given to using diisocyanates, more particularly to using aliphatic diisocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate, 2,4- or 2, 6-diisocyanato-1 -methylcyclohexane, and m- tetramethylxylylene diisocyanate (m-TMXDI). An isocyanate is termed aliphatic when the isocyanate groups are attached to aliphatic groups; in other words, when there is no aromatic carbon present in alpha position to an isocyanate group.

[0035] Generally, polyurethanes are prepared by reacting the stated polyisocyanates with polyols, more particularly diols. Examples of polyols are the generally known monomeric polyols, polyester, polycarbonates, polyether, polydiene, polyene, poly(meth)acrylate and / or polysiloxane polyols, more particularly diols. Mixtures of polyols are likewise possible.

[0036] Preferred examples of suitable polyols are saturated or olefinically unsaturated polyester polyols. Polyols used more particularly are polyester polyols having a number-average molecular weight of 400 to 5000 g / mol (for measurement method, see Example section). Such polyester polyols, preferably polyester diols, may be prepared in a known way by reaction of corresponding polycarboxylic acids, preferably dicarboxylic acids, and / or their anhydrides with corresponding polyols, preferably diols, by esterification. It is of course optionally possible in addition, even proportionally, to use monocarboxylic acids and / or monoalcohols for the preparation. The polyester diols are preferably saturated, more particularly saturated and linear. Examples of corresponding polyols for preparing polyester polyols, preferably polyester diols, are ethylene glycol, 1 ,2- or 1 ,3-propanediol, 1 ,2-, 1 ,3-, or 1 ,4- butanediol, 1 ,2-, 1 ,3-, 1 ,4-, or 1 ,5-pentanediol, 2,2-dimethyl-1 ,3-propanediol (neopentylglycol), 2-methyl-2,4-pentanediol, 1 ,2-, 1 ,3-, 1 ,4-, 1 ,5-, or 1 ,6-hexanediol, trimethylpentanediol, 1 ,2-, 1 ,3-, or 1 ,4-cyclohexanediol, 1 ,2-, 1 ,3-, or 1 ,4- cyclohexanedimethanol, bifunctional alcohols which are alpha-, omega- or alpha-, beta-dihydroxyalkanes from eight to twenty-five carbon atoms, particularly 1 ,2- octanediol, 1 ,8-octanediol, 1 ,2-decanediol, 1 ,10-decanediol, 1 ,2-dodecanediol, 1 ,12- dodecanediol, 1 ,13-tridecanediol, 1 ,2-octadecanediol, 1 ,18-octadecanediol, 1 ,2- heneicosanediol, 1 ,21 -heneicosanediol and 1 ,25-pentacosanediol. Furthermore examples of corresponding polyols for preparing polyester polyols, preferably polyester diols, are polyols based on the hydrogenation products of methylesters of polycarboxylic acids which are derived from dimeric and trimeric fatty acids, for example, the dimer fatty C36 diol after hydrogenation of the methylester of saturated dimeric C36 fatty acid (Pripol® 2033; from Croda) More examples of corresponding polyols for preparing polyester polyols, preferably polyester diols, are ether Oder cyclic ether alcohols like, diethylene glycol, triethylene glycol, tetraethylene glycol, 2,5- bis(hydroxymethyl)furane, 2,5-bis(hydroxymethyl)terahydrofurane, as well as carbohydate-based cyclic etheralcohols such as isosorbide, isomannide, and isoidide, and ester alcohols like 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2- dimethylpropionate (neopentyl glycol mono(hydroxypivalate)).

[0037] Polyhydroxy-polyesters which are derived from polyhydroxyalkyl acids, like poly 2- hydroxyethanoic acid (polyglycolic acid) or polyhydoxypropionic acid, its other name is poly(lactic acid) (polylactides), and polyhydroxyalkyl acids with higher number of carbon atoms can also be used. The direct method is based on the direct polycondensation of hydroxycarboxylic acids as alpha, beta, gamma or omega- hydroxylic acids. Due to the presence of a hydroxyl group and carbonyl group, examples of corresponding hydroxycarboxylic acids are 2-hydroxyethanoic acid (glycolic acid), 2-hydroxypropionic acid, 3-hydroxypropionic acid (lactic acid), 3- hydroxy-2-methylpropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 3- hydroxypentanoic acid, 5-hydroxypentanoic acid up to 12-hydroxydodecanoic acid (sabinic acid) or 13-hydroxytridecanoic acid. It is also possible and prefered to form polyester diols based on polyhydroxyalkyl acids by ring-opening polymerization of cyclic oligomers, prefered dimers, of the corresponding hydroxycarboxylic acids, for example dilactides from corresponding lactic acid to form the best-known biodegradable polymer poly(lactic acid)

[0038] The term polyester diol is also to be understood as meaning polylactone diols, obtained by reaction of a lactone with polyol as an initiator that has active hydrogen-containing groups; illustrative of which is ethylene glycol, diethylene glycol, propanediols, 1 ,4- butanediol, 1 ,5-pentandiol or 1 ,6-hexanediol, and generated by ring opening polymerization. Lactones which can be used for the synthesis of the polyester polyols are butyrolactone, valerolactone, methylvalerolactone, caprolactone, methylcaprolactone, and 2-oxocanone (enantholactone). The preferred lactone polyols are known as polycaprolactone polyols.

[0039] Further examples of suitable polyols are polycarbonate polyols, more particularly polycarbonate diols. These polycarbonate polyols can be prepared by reaction of polyols, such as 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 2-methylpentane- 1 ,3-diol, neopentylglycol, 1 ,6-hexanediol, 2,2,4-trimethylpentane-1 ,3-diol, 2-butyl-3- ethylpropan-1 ,3-diol, trimethylolpropane or pentaerythritol, 1 ,4- bishydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane, diethylene glycol, triethylene glycol or tetraethylene glycol, with di-carbonates, such as dimethyl, diethyl or diphenyl carbonate, or phosgene.

[0040] Further oligomeric or polymeric hydroxy-functional compounds are polydiene or polyene, and there are at least two, preferably terminal, hydroxyl groups per molecule. Particularly preferred are dihydroxy compounds based on polybutadiene, polyisoprene or polyolefin, like polyethylene (hydrogenated polybutadiene) and polybutadiene, polyisoprene or polyolefin block copolymers with polystyrene.

[0041] Examples of polyether polyols here include polyols of polyoxyethylene, polyoxypropylene polyoxybutylene, mixed and block copolymers of these, in blocks or randomly distributed along the polymer chain, and, polyoxytetramethylene (polytetrahydrofurane, for example PolyTHF 2000 from BASF SE) containing terminal OH groups, also simply known as glycols.

[0042] Further possibilities for use in preparing polyurethanes are polyamines such as diamines and / or amino alcohols. Examples of diamines include hydrazine, alkyl- or cycloalkyldiamines such as propylene diamine and 1 -amino-3-aminomethyl-3,5,5- trimethylcyclohexane, and examples of amino alcohols include ethanolamine or diethanolamine. Accordingly, and in line with the general understanding of the person skilled in the art, the general term “polyurethane” also embraces polyureapolyurethanes, i.e. polymers including, besides polyurethane bonds, also polyurea bonds and respective polyurea character.

[0043] Of course, it is also possible to apply polyols having more than two hydroxyl groups like three hydroxyl groups, for example trimethylolpropane.

[0044] In one embodiment the inventive polymer is obtainable by polymerizing N- vinylpyrrolidone or a monomer mixture comprising N-vinylpyrrolidone in the presence of a polyurethane. As is known to the person skilled in the art, such polymerization is conducted as chain polymerization, in particular radical chain polymerization. To facilitate a covalent binding between polyurethane (polyurethane moieties) and N- vinylpyrrolidone-based moieties, the polyurethane preferably comprises olefinically unsaturated groups. However, it is not necessarily required that the polyurethane comprises such unsaturated groups. The polymer, however, may also be gained by polymerizing N-vinylpyrrolidone or a monomer mixture comprising N-vinylpyrrolidone in the presence of a polyurethane without such unsaturated groups, as this also results in an inseparable entanglement between both species, thus leading to one polymer comprising both polyurethane-based moieties and polyvinylpyrrolidone-based moieties. Also, as is known, under standard reaction conditions for polymerization, often rearrangement I side reactions will occur for statical reasons, thus promoting covalent binding between the different types of moieties also without any unsaturated groups in the polyurethane. Still, it is preferred that the polyurethane comprises such unsaturated groups. These may be introduced by means of polyols, in particular diols, containing one or more ethylenically unsaturated groups. The polyols, in particular diols containing one or more ethylenically unsaturated groups can be monomeric diols or polymeric diols. The preferred diols being ethylenically unsaturated comprise preferably at least one allyl group, vinyl group, acryl group or methacryl group, preferably the diols being ethylenically unsaturated comprise at least one allyl group. Preferably the one or more ethylenically unsaturated groups are present in a monomeric diol. Preferred ethylenically unsaturated monomeric diols are trimethylolpropane monoallyl ether and pentaerythritol-diallylether, most preferably trimethylolpropane monoallyl ether.

[0045] In case the polyurethanes shall include ionic groups, in particular anionic groups (and groups which can be converted into anionic groups, respectively, the latter also called potentially ionic groups), these may be chosen from carboxylic, sulfonic and / or phosphonic acid groups, especially carboxylic acid groups. The introduction of such groups is known to increase the dispersibility in water. To introduce the stated groups, it is possible, during the preparation of the polyurethanes to use starting compounds which as well as groups for reaction in the preparation of urethane bonds, preferably hydroxyl groups, further comprise the abovementioned groups, carboxylic acid groups for example. In this way the groups in question are introduced into the prepolymer.

[0046] Corresponding compounds contemplated for introducing the for example carboxylic acid groups are polyether polyols and / or polyester polyols, provided they contain carboxyl groups and low molecular weight compounds which have at least one carboxylic acid group and at least one functional group reactive toward isocyanate groups, preferably hydroxyl groups. In the context of the present invention, the expression "low molecular weight compound", as opposed to higher molecular weight compounds should be understood to mean those to which a discrete molecular weight can be assigned, as preferably monomeric compounds. A low molecular weight compound is thus, more particularly, not a polymer, since the latter are always a mixture of molecules and have to be described using mean molecular weights. Preferably, the term "low molecular weight compound" is understood to mean that the corresponding compounds have a molecular weight of less than 300 g / mol. Compounds to be named in this context are, for example, monocarboxylic acids containing two hydroxyl groups, as for example dihydroxypropionic acid, dihydroxysuccinic acid, and dihydroxybenzoic acid. Very particular compounds are alpha, alpha-dimethylolalkanoic acids such as 2,2-dimethylolacetic acid, 2,2- dimethylolpropionic acid, 2,2-dimethylolbutyric acid and 2,2-dimethylolpentanoic acid, especially 2,2-dimethylolpropionic acid.

[0047] Respective polyurethanes may be prepared by known and established methods in bulk or solution, especially preferably by reaction of the starting compounds in organic solvents, such as preferably methyl ethyl ketone, at temperatures of, for example, 60 to 120°C, and optionally with use of catalysts typical for polyurethane preparation. Such catalysts are known to those skilled in the art, one example being dibutyltin laurate. It is directly apparent that the solvents ought to be selected in such a way that they do not enter into any unwanted reactions with the functional groups of the starting compounds, in other words being inert toward these groups to the effect that they do not hinder the reaction of these functional groups. The preparation is preferably actually carried out in organic solvents.

[0048] As described above, it is of decisive advantage that the inventive polymers may achieve decent water dispersibility by means of mainly or even exclusively non-ionic stabilization, meaning that the known drawbacks in connection with ionic stabilization as outlined in the introductory part may be avoided or at least set to a minimum. Also as described above, this goal is reached by making it possible, at the same time, to provide for aqueous coating composition comprising the inventive polymer which leads to coating layers exhibiting a high weathering resistance and long-life durability.

[0049] Accordingly, the amounts of ionic groups in the polyurethane I polyurethane moieties as part of the inventive polymer are comparably low or such ionic groups are even completely avoided. Quantitative figures defining this principle in a more detailed manner are specifically described further below by means of the electrophoretic mobility of the inventive polymer being essential within the context of the present invention. Likewise, the amounts of water-soluble polyether groups (also called segments or moieties) in the polyurethane I polyurethane moieties as part of the inventive polymer preferably are comparably low or such polyether groups are even completely avoided. Quantitative figures defining this principle in a more detailed manner and in form of preferred embodiments are described further below by means of the amount of such polyether groups in the inventive polymer.

[0050] As mentioned above, in one embodiment the inventive polymer is obtainable by polymerizing N-vinylpyrrolidone or a monomer mixture consisting of N-vinylpyrrolidone and at least one further ethylenically unsaturated monomer in the presence of the at least one polyurethane and / or polyurea-polyurethane. Thereby, the preferably present ethylenically unsaturated groups in the polyurethane are reacted with N- vinylpyrrolidone to attach one or more homopolyvinylpyrrolidone (PVP) chain(s) and / or N-vinylpyrrolidone and at least one further ethylenically unsaturated monomer to attach one or more polyvinylpyrrolidone-copolymer chain(s) to the polyurethane prepolymer and / or rearrangement / side reactions will lead to such attachment and / or entanglement of the forming N-vinylpyrrolidone-based moieties with the polyurethane (moieties) occurs. Ultimately, this procedure leads to an inventive polymer.

[0051] In case at least one further ethylenically unsaturated monomer is applied, these monomers preferably are selected from the group consisting of cyclic, linear or branched alkyl (meth)acrylates, hydroxyalkyl esters of (meth)acrylic acid, (meth)acrylic acid and / or vinylaromatic hydrocarbons. Preferably, the further ethylenically unsaturated monomers are monoethylenically unsaturated.

[0052] Particularly suitable cyclic, linear or branched alkyl (meth)acrylates are cyclohexyl (meth)acrylates and alkyl (meth)acrylates having up to 20 carbon atoms.

[0053] Particularly suitable hydroxyalkyl esters of (meth)acrylic acid are hydroxyalkyl esters of (meth)acrylic acid in which the hydroxyalkyl group contains up to 6 carbon atoms, preferably 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3- hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. Particularly suitable vinylaromatic hydrocarbons are styrene, a-alkylstyrenes, vinyltoluene, (meth)acrylamide and (meth)acrylonitrile.

[0054] Again, as already described above in the context of the polyurethane, the amounts of ionic groups in the inventive polymer preferably are comparably low or such ionic groups are even completely avoided, meaning that the amount of, for example, (meth)acrylic acid as further ethylenically unsaturated monomer is correspondingly low or set to zero, respectively. Again, it is referred to below for quantitative figures defining this principle in a more detailed manner by means of the electrophoretic mobility of the inventive polymer.

[0055] The polymerization of N-vinylpyrrolidone or a monomer mixture consisting of N- vinylpyrrolidone and at least one further ethylenically unsaturated monomer preferably is a radical polymerization. To initiate this radical polymerization an organic peroxide can be used. Examples of organic peroxides are diacetyl peroxide, dibenzoyl peroxide, tertiary butyl peroxy pivalate and tert, butyl peroxyethylhexanoate. Preferably tert, butyl peroxyethylhexanoate is used to start the radical polymerization. The radical starter produces a free radical at ethylenically unsaturated group(s), for example ethylenically unsaturated group(s) of the polyurethane and / or N-vinylpyrrolidone and / or the at least one further ethylenically unsaturated monomer. The main reaction will be the radical formation at these ethylenically unsaturated group(s). However, side reactions as the radical formation at a nitrogen atom within the polyurethane backbone may also occur. The free radical will then be the starting point of polymerization (chain propagation) of N-vinylpyrrolidone and optionally the at least one further ethylenically unsaturated monomer, finally leading to the respective N-vinylpyrrolidone-based moieties.

[0056] In case of applying both N-vinylpyrrolidone and at least one further ethylenically unsaturated monomer, the resulting N-vinylpyrrolidone-based moiety preferably comprises at least of >40 wt.-%, more preferably >50 wt.-%, even more preferably >60 wt.-%, in particular >70 wt.-%, most preferably >80 wt.-% of N-vinylpyrrolidone (determined by means of calculation based on the weight ratio of respective monomers applied for polymerization). Preferably, the amount of N-vinylpyrrolidone in the polyurethane-based polymer is at least 5 wt.-% (based on the total weight of the polyurethane-based polymer). Preferably, the amount is at least 7.5 wt.-% or at least 10 wt.-% or even at least 12.5 wt.-%. With particular preference, the amount is at least 15 wt.-% or at least 17.5 wt.- %. Preferred ranges are from 10 to 60 wt.-%, more preferably 12.5 to 50 wt.-% or even more preferably 15 to 40 wt.-%. The amount is determined by means of calculation based on the weight of respective monomers I educts applied for production of the polymer (i.e. polyurethane and N-vinylpyrrolidone I olefinically unsaturated monomers).

[0057] In one embodiment, the amount of polyurethane in the polyurethane-based polymer is greater than 10 wt.-% (based on the total weight of the polyurethane-based polymer). Preferably, the amount is at least 10.1 wt.-%, more preferably at least 11 wt.-% or at least 15 wt.-% like at least 20 wt.-% (in each case based on the total weight of the polyurethane-based polymer). Particularly, the amount is greater than 25 wt.-% like at least 25.1 wt.-% or at least 26 wt.-% or at least 30 wt.-% or at least 35 wt.-% or at least 40 wt.-% (in each case based on the total weight of the polyurethane-based polymer). Also, the amount of polyurethane in the polyurethane-based polymer is at most 95 wt.- %, preferably at most 90 wt.-% like at most 85 wt.-% or at most 80 wt.-% (in each case based on the total weight of the polyurethane-based polymer).

[0058] Explicit preferred ranges result from the above lower and upper limits. For example, preferred ranges are greater than 10 wt.-% to 95 wt.-% or 10.1 wt.-% to 95 wt.-% or greater than 25 wt.-% to 95 wt.-% or 25.1 wt.-% to 95 wt.-% or greater than 10 wt.-% to 90 wt.-% or 10.1 wt.-% to 90 wt.-% or greater than 25 wt.-% to 90 wt.-% or 25.1 wt.- % to 90 wt.-% or greater than 10 wt.-% to 85 wt.-% or 10.1 wt.-% to 85 wt.-% or greater than 25 wt.-% to 85 wt.-% or 25.1 wt.-% to 85 wt.-% (in each case based on the total weight of the polyurethane-based polymer). In one embodiment the inventive polymer is hydroxy-functional. This may be achieved by adjusting I selecting respective amounts and types of monomers I educts for production.

[0059] As evident from the above, after its production, the inventive polymer preferably is present in organic solvent. However, as pointed out above, the inventive polymer is very well dispersible and stable in aqueous media and consequently is preferably applied as aqueous dispersion in the aqueous pigmented composition according to the invention. Therefore, an aqueous dispersion comprising an inventive polymer also is a subject-matter according to the present invention. The inventive dispersion, obviously, preferably is prepared from an organic-based mixture by adding appropriate amounts of water and then optionally removing at least part of the organic solvents. Therefore, the inventive dispersion preferably is a secondary dispersion.

[0060] It is preferred that the aqueous dispersion of the inventive polymer has a solids content of 20 to 60 %, preferably, 25 to 50 %. Also, it is preferred that the amount of water in the aqueous dispersion is from 35 to 75 wt.-%, preferably from 45 to 70 wt.-%. Also, in a preferred embodiment, the sum of solids content and amount of water (both calculated as wt.-%) is at least 80 wt.-%, more preferably at least 90 wt.-% or even 95 wt.-%.

[0061] Without wanting to limit the scope of the present invention it may be said that the inventive polymer, in one specific embodiment, is obtainable by a) synthesizing an NCO-terminated polyurethane prepolymer by reacting one or more diisocyanates with one or more diols selected from the group consisting of monomeric diols and polymeric diols, b) reacting the terminal NCO groups of the NCO-terminated polyurethane prepolymer obtained in step a) with one or more saturated or ethylenically unsaturated monomer(s), the monomers comprising at least one NCO-reactive group selected from the group consisting of -OH groups, primary amino groups and secondary amino groups; wherein in step a) at least one of the diols contains an ethylenically unsaturated group and / or in step b) at least one monomer is an ethylenically unsaturated monomer; and subsequently c) reacting at least one ethylenically unsaturated group of the ethylenically unsaturated polyurethane prepolymer obtained in step b) with N- vinylpyrrolidone to attach one or more homopolyvinylpyrrolidone (PVP) chain(s), and / or reacting N-vinylpyrrolidone and at least one further ethylenically unsaturated monomer preferably selected from the group consisting of cyclic, linear or branched alkyl (meth)acrylates, hydroxyalkyl esters of (meth)acrylic acid, (meth)acrylic acid and / or vinylaromatic hydrocarbons to attach one or more polyvinylpyrrolidonecopolymer chain(s).

[0062] In step a), an NCO-terminated polyurethane prepolymer is synthesized by reacting one or more diisocyanates with one or more diols selected from the group consisting of monomeric diols and polymeric diols. The monomeric and / or polymeric diols can be saturated or ethylenically unsaturated, preferably at least one monomeric and / or polymeric diol is ethylenically unsaturated. The diols can be aromatic or aliphatic, more preferably aliphatic. The monomeric diols can be linear or branched.

[0063] Examples of suitable monomeric diols are ethylene glycol, neopentyl glycol, 1 ,2- propanediol, 1 ,4-butanediol, 1 ,3-butanediol, 1 ,5-pentanediol, 2,2,4-trimethyl-1 ,3- pentanediol, 1 ,6-hexanediol, 1 ,4-cyclohexanedimethanol, 1 ,2- cyclohexanedimethanol, 2,2-Bis(4-hydroxy-cyclohexyl)-propane, trimethylolpropane monoallyl ether and pentaerythritol-diallylether. Preferred monomeric diols are neopentyl glycol, 1 ,6-hexanediol and trimethylolpropane monoallyl ether.

[0064] Suitable polymeric diols are e.g., polyester diols, polyether diols, polycarbonate diols or linear polyether-polyester diols having preferably a number average molecular weight of 400 to 4000 g / mol, more preferably of 400 to 3000 g / mol as determined by vapor pressure osmometry. The polymeric diols can also contain one or more ethylenically unsaturated groups. Preferably the polymeric diol is a polyester diol. The polyester diol preferably has a number average molecular weight of 400 to 4000 g / mol, more preferably 400 to 3000 g / mol, even more preferably 450 to 2000 g / mol, most preferably 550 to 1500 g / mol as determined by vapor pressure osmometry. The hydroxyl number of the polyester diol is preferably 40 to 250 mg KOH I g solids, more preferably 50 to 200 mg KOH I g solids, most preferably 60 to 180 mg KOH / g solids. The acid number of the polyester diol is preferably 1 to 5 mg KOH I g solids, more preferably 2 to 4 mg KOH I g solids, most preferably 3 to 4 mg KOH I g solids.

[0065] Preferably at least one diol in step a) contains one or more ethylenically unsaturated groups. The diols containing one or more ethylenically unsaturated groups can be monomeric diols or polymeric diols. The diols being ethylenically unsaturated comprise preferably at least one allyl group, vinyl group, acryl group or methacryl group, preferably the diols being ethylenically unsaturated comprise at least one allyl group. Preferably the one or more ethylenically unsaturated groups are present in a monomeric diol. Preferred ethylenically unsaturated monomeric diols are trimethylolpropane monoallyl ether and pentaerythritol-diallylether, most preferably trimethylolpropane monoallyl ether.

[0066] The at least one diol is reacted with one or more diisocyanates to synthesize a polyurethane prepolymer. The diisocyanate is used in excess to ensure that the polyurethane prepolymer is an isocyanate terminated polyurethane prepolymer obtained in step a). The reaction mixture preferably has a temperature below 100°C.

[0067] In step b), the NCO-terminated polyurethane prepolymer obtainable in step a) is reacted with one or more saturated or ethylenically unsaturated monomer(s), the monomers comprising at least one NCO-reactive group selected from the group consisting of -OH groups, primary amino groups and secondary amino groups.

[0068] At least one of the diols in step a) contains an ethylenically unsaturated group and / or at least one monomer in step b) is an ethylenically unsaturated monomer to prepare a polyurethane prepolymer containing one or more ethylenically unsaturated group(s). The one or more saturated or ethylenically unsaturated monomer(s) react with the polyurethane prepolymer until the content of isocyanate is preferably below 1 .0 wt.-%, most preferably until free isocyanate groups can no longer be detected.

[0069] Preferably the monomer is a monoalcohol or polyol, more preferably a polyol. The polyol is preferably a trifunctional polyol, most preferably the polyol is trimethylolpropane.

[0070] Suitable monomers comprising a primary amino group or secondary amino group are primary or secondary amines comprising an alkyl or hydroxyalkyl residue. Preferably the monomer comprises a secondary amino group, more preferably the monomer is N-methylethanolamine, diethanolamine or di n-butyl amine.

[0071] Ethylenically unsaturated monomers can comprise one or more NCO-reactive groups, wherein the NCO-reactive group is selected from the group consisting of OH groups, primary amino groups and secondary amino groups. Preferably the ethylenically unsaturated monomers comprise one or more OH groups, most preferably only one OH group. Suitable ethylenically unsaturated monomers are hydroxy(meth)acrylates, preferably hydroxyalkyl (meth)acrylates, more preferably hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, most preferably 2-hydroxyethylmethacrylate.

[0072] In step c), the ethylenically unsaturated group(s) in the polyurethane prepolymer is / are reacted with N-vinylpyrrolidone to attach one or more homopolyvinylpyrrolidone (PVP) chain(s); and / or N-vinylpyrrolidone and at least one further ethylenically unsaturated monomer preferably selected from the group consisting of cyclic, linear or branched alkyl (meth)acrylates, hydroxyalkyl esters of (meth)acrylic acid, (meth)acrylic acid and / or vinylaromatic hydrocarbons to attach one or more polyvinylpyrrolidonecopolymer chain(s) to the polyurethane prepolymer. Suitable ethylenically unsaturated monomers as well as reaction conditions are already described above.

[0073] In aqueous dispersion, the inventive polymer preferably has an average particle size from 50 to 400 nm (volume average), more preferably 80 to 300 nm, most preferably 100 to 300 nm as being determined by measuring the hydrodynamic volume of the dispersion particles using photon correlation spectroscopy.

[0074] The acid number of the inventive polymer (based on solids content) is preferably 0 to 10 mg KOH I g solids, more preferably 0 to 7 mg KOH I g solids, even more preferably 0 to 5 mg KOH / g solids and most preferably 0 to 3 mg KOH / g.

[0075] As already stated above, the amount of water-soluble polyether moieties in the inventive polymer preferably are comparably low. Polyether moieties may generally be described by formula (I) wherein R is an aliphatic or aromatic radical and n depicts the number of monomeric entities within the polyether moiety, wherein R may be the same or may be different for all or part of the monomeric entities. As known, for non-ionic stabilization of polymers, as a standard, polyethylene glycol moieties (i.e. R = C2-alkylene radical) are employed.

[0076] Considering the objectives of the present invention as described above, it is preferred that the amount of polyethylene glycol moieties is not more than 5 wt.-% (based on the total weight of the inventive polymer). More preferably, the amount is not more than 2.5 wt.-% or even not more than 1 wt.-%. In a particularly preferred embodiment, the inventive polymer does not comprise any such moieties. The amount may be determined by means of calculation based on the weight of respective monomers I educts applied for production of the polymer.

[0077] Again, as already stated above, the amounts of ionic groups in the inventive polymer preferably are comparably low or such ionic groups are completely avoided. This, for example, also becomes evident from the above-defined preferred (low) acid number ranges. Of course, the amounts of ionic groups do not only depend on the chemical character of the groups themselves, but also on further conditions, in particular the pH of the media in which the respective polymer and thus groups are dispersed or dissolved in and also whether neutralizing agents are applied (which promote the transfer of potentially ionic groups into ionic groups). For example, a carboxylic acid group, itself a potentially ionic group and not being of ionic character, may dissociate into a carboxylate anion and a hydrogen cation. This, quite obviously, depends on the pH value or amount of neutralizing agent (base like organic amines). Similar principles apply for e.g. amino groups and ammonium ions (even if the vast majority of ionic stabilization for binder polymers for in particular aqueous base coat compositions is anionic, meaning that the present invention is lying focus on these, cationic stabilization may be mentioned here for the sake of completeness).

[0078] Also as known to the person skilled in the art, aqueous coating compositions have pH values ranging from, for example, 3 to 10, in particular 4 to 9 or 5 to 8.5 or 6 to 8, depending on field of application and chemical character / constituents.

[0079] Depending on the amount and type of ionic groups, components like polymers exhibit a specific electrophoretic mobility in aqueous media. For example, at pH values of above 7 carboxylic acid groups will predominantly be deprotonated and the thus present carboxylate groups will lead to a corresponding electrophoretic mobility. Higher amounts of carboxylate groups will lead to a correspondingly higher magnitude in electrophoretic mobility. On the other hand, at pH values of below 7 amino groups will partly or predominantly protonated and the thus present ammonium groups will lead to a respective electrophoretic mobility. Again, higher amounts of ammonium groups will lead to a correspondingly higher magnitude in electrophoretic mobility.

[0080] The inventive polymer exhibits an electrophoretic mobility of not less than -4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0 in aqueous dispersion (measurement method in the example section). Preferably, the electrophoretic mobility is not less than -3.5 (pm / s) / (V / cm) or even not less than -2.5 (pm / s) / (V / cm) and more particularly not less than -2.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0 in aqueous dispersion. The inventive polymer, preferably, exhibits an electrophoretic mobility from -4.0 to 4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0. Even more preferably, the electrophoretic mobility is from -3.5 to 3.5 (pm / s) / (V / cm) or even from -2.5 to 2.5 (pm / s) / (V / cm) and more particularly from (in each case in the pH range from 3.0 to 10.0 in aqueous dispersion). Accordingly, within the entire above-mentioned pH range the value I magnitude in electrophoretic mobility (and thus the amounts of ionic groups, in particular anionic groups, providing for such electrophoretic mobility) is within the defined ranges (and thus the amount of respective ionic groups is sufficiently low to provide for such electrophoretic mobility). Of course, it is not excluded that the electrophoretic mobility also is within the above-mentioned ranges at lower or higher pH values.

[0081] Accordingly, the inventive polymer may comprise in particular anionic (potentially anionic) groups, but the amount of these groups is rather low (expressed by, in particular, the electrophoretic mobility). Preferably, the inventive polymer, if at all, does comprise anionic (potentially anionic) groups as ionic (potentially ionic groups), in particular carboxylate I carboxy groups.

[0082] The polymer according to the invention preferably does not have an isoelectric point at a pH value of 3 or greater. Even more preferably, the polymer does not have any isoelectric point.

[0083] Use of the polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties according to the invention

[0084] The polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties according to the invention is suitable for multiple applications. For example, it can inter alia be used in many areas of coating, particularly in automotive coating.

[0085] Particularly, the polymer according to the invention can for example be used in an preferably aqueous pigmented composition selected from thermally curable coating compositions and pigment pastes. Thermally curable coating composition comprising the inventive polymerpreferably are filler coating compositions or a basecoat compositions, particularly for application in automotive coatings. The basecoat composition comprising the inventive polymer can be used to form a basecoat layer on an untreated or a pretreated substrate. Furthermore, the basecoat composition comprising the hydroxy-group containing polymer can be used to form one or more layers in a multilayer coating, preferably i on automotive bodies or parts thereof.

[0086] Coating composition comprising the inventive polymer

[0087] Another object of the present invention is a particularly thermally curable coating composition comprising at least one inventive polymer. The coating composition preferably is an aqueous coating composition.

[0088] The polymer may function as main binder polymer. The polymer according to the invention may also be used, for example, in pigment pastes as grinding resin.

[0089] The polymer may be used in any aqueous composition. Within these aqueous compositions, the inventive polymer preferably is applied in form of an aqueous dispersion as defined above.

[0090] The coating composition is preferably thermally curable. The thermally curably coating composition comprises besides the polymer according to the invention at least one additional binder and pigments, which preferably are applied in form of a pigment paste, whereby the paste preferably comprises an inventive polymer (or aqueous dispersion comprising the polymer).

[0091] The content of the polymer according to the invention with respect to the total weight of a coating composition preferably is 2 to 30 wt.-%, more preferably 2 to 20 wt.-%, most preferably 2 to 15 wt.-% based on the total weight of the coating composition (in case the polymer is applied as dispersion or solution in any solvent, the solids content of this dispersion or solution gives the actual amount of polymer applied). Besides the polymer according to the invention, other polymers can be used as a binder component such as poly(meth)acrylate polyols, polyester polyols, polyether polyols, polyether-polyester polyols and polyurethane polyols. The term “poly(meth)acrylate” refers to not only polyacrylates but also polymethacrylates, and also polymers which comprise both methacrylates and / or methacrylic acid and / or acrylates and / or acrylic acid. The beforementioned polymers preferably are hydroxyfunctional.

[0092] Preferably, at least one further binder is comprised for crosslinking with at least one of the above-mentioned binders. Suitable crosslinking agents are amino resins such as urea-formaldehyde resins or melamine-formaldehyde resins or polyisocyanates, which can be free or blocked polyisocyanates.

[0093] The isocyanates can be di- or polyisocyanates, which can be aromatic or aliphatic, more preferably aliphatic as aromatic components tend to cause yellowing. Aliphatic diisocyanates and aliphatic polyisocyanates are herein understood to be compounds having at least two free isocyanate groups in the molecule, that is, isocyanate groups which are not blocked at room temperature (25°C). Blocked isocyanates refer to reaction products of an isocyanate in which the isocyanate functionality has been reacted with a “blocking agent”. The blocking of the isocyanate occurs through a reaction of the isocyanate with a compound containing an active hydrogen. Suitable blocking agents are derivatives from oximes, lactams, phenols, active methylenes, pyrazoles, mercaptans, imidazoles, amines, imines, triazoles, hydroxyl amines, and aliphatic or cycloaliphatic alkyl monoalcohols. The blocked isocyanate component will not react at room temperature. The crosslinking reaction of blocked isocyanates with hydroxy-functional compounds will be achieved using elevated temperatures.

[0094] The coating composition may comprise at least one additive selected from the group consisting of reactive diluents, light stabilizers, antioxidants, defoamers, emulsifiers, slip additives, polymerization inhibitors, initiators for free-radical polymerizations, catalysts, adhesion promoters, film-forming auxiliaries, dispersants, levelling agents, rheology control agents, sag-control agents (SCA), flame retardants, corrosion inhibitors, siccatives, biocides, matting agents as well as dyes, which are colorants, which are soluble in the coating composition. Further examples of suitable coatings additives are e.g., described in the textbook “Lackadditive” (“Additives for Coatings” by Johan Bieleman, Wiley-VCH, Weinheim, 1998). The additives can be used in the known and customary amounts.

[0095] The coating composition according to the present invention may contain pigments, particularly if the coating composition is a basecoat composition or a filler composition. The terms "coloring pigment" and "color pigment" are interchangeable and include colored, black and white pigments. As a color pigment inorganic and organic pigments can be used.

[0096] Examples of white pigments are titanium dioxide, zinc white, zinc sulfide and lithopone. Examples of black pigments are carbon black, iron manganese black and spinel black. Examples of pigments with other colors are chromium oxide, chromium oxide hydrate green, cobalt green, ultramarine green, cobalt blue, ultramarine blue, manganese blue, ultramarine violet, cobalt and manganese violet, iron oxide red, cadmium sulfoselenide, molybdate red and ultramarine red, iron oxide brown, mixed brown, spinel and corundum phases and chromium orange, iron oxide yellow, nickel titanium yellow, chrome titanium yellow, cadmium sulfide, cadmium zinc sulfide, chrome yellow and bismuth vanadate.

[0097] Possible organic pigments are azo pigments, polycyclic pigments and anthraquinone pigments. Polycyclic pigments are preferably diketopyrrolo-pyrrole pigments.

[0098] Amongst the effect pigments, metal effect pigments such as aluminum pigments and / or pearlescent effect pigments may be comprised in the coating composition according to the invention.

[0099] The coating composition according to the present invention may contain fillers. The term "filler" (in respect to one constituent of a coating composition and not in respect of a coating composition as a whole) is known to the person skilled in the art, for example from DIN 55943 (date: October 2001 ). Examples of suitable fillers are kaolin, dolomite, calcite, chalk, calcium sulfate, barium sulfate, talc, silica, in particular pyrogenic silica, hydroxides such as aluminum hydroxide or magnesium hydroxide; in addition, reference is made to Rdmpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, pages 250 ff., "Fillers".

[0100] Preferably, the coating composition comprises at least one pigment, wherein the amount of pigment preferably is from 2 to 40 wt.-%. (based on the total weight of the coating composition).

[0101] In case the coating composition contains at least one filler, the amount of filler preferably is from 2 to 40 wt.-%.

[0102] In case a coating composition contains at least one pigment and at least one filler, the cumulative amount of pigment and filler preferably is from 5 to 60 wt.-%.

[0103] Pigments and fillers are typically employed in coating compositions in form of a pigment paste or a filler paste. It has been found that pigment I filler pastes comprising an inventive polymer are well suitable for coating composition applications. Specifically, such pigment pastes are of great stability and are very well applicable in coating compositions, in particular aqueous coating compositions. Such a pigment I filler paste also is a subject-matter of the present invention. Preferably, the inventive paste comprises an organic pigment.

[0104] To produce pigment I filler pastes, normally a polymer (grinding resin), for example an inventive polymer, is mixed with at least one additive and at least one pigment and optionally solvents. As known, the mixing process may include at least one grinding step.

[0105] Coating layer formed from a coating composition comprising an inventive polymer and a thus coated substrate.

[0106] The coating composition to form a coating layer is applied to a substrate by customary painting methods familiar to a person of ordinary skill in the art. Substrate materials are chosen from the group consisting of metals, plastics, wood, glass, mineral-based materials and composites of any of the aforementioned materials. It is possible to use untreated or pre-treated substrates, where the pre-treatment regularly depends on the chemical nature of the substrate.

[0107] The coating composition comprising the inventive polymer according to the invention is preferably applied by spraying, pneumatically and / or electrostatically. The coating composition is thermally curable, preferably at temperatures between 60°C to 180°C, depending on the reactivity of the crosslinking agent and the duration, most preferably 80°C to 160°C.

[0108] The invention further provides a substrate coated with a coating layer formed from a coating composition comprising the hydroxy-group containing polyurethane- polyvinylpyrrolidone polymer reaction product according to the invention.

[0109] Multilayer coating and multilayer-coated substrates

[0110] Another object of the present invention is a method of making a multilayer coating, comprising the steps of a) optionally applying a filler coating composition on a substrate to obtain a filler layer, b) applying a basecoat composition on top of the layer obtained in step a) or directly on a substrate to form a basecoat layer, c) applying a clear coat composition on top of the base coat layer to form a clear coat layer, and d) simultaneously curing of the filler layer, base coat layer and clear coat layer or individually curing of one or more layers obtained in steps a) to c) before the subsequent coating layer is applied or individually curing of all compositions obtained in steps a) to c), wherein at least one coating composition of steps a) and / or b) comprises an inventive polymer. The multilayer-coated substrate can be a pretreated or untreated substrate, which can be uncoated or precoated. The individual coating layers are applied by the customary painting methods familiar to a person of ordinary skill in the art. Preferably, a filler coating composition and / or basecoat composition comprises at least one inventive polymer. Most preferably, the basecoat composition in any case comprises an inventive polymer.

[0111] The application of the basecoat composition on the substrate to form a basecoat layer and the application of the clear coat composition on the base coat layer is preferably carried out by a wet-on-wet application, i.e. , an application where the preceding layer is not cured or not fully cured before the coating composition is applied. Thus, prior to the application of the clear coat composition, the base coat layer may be flashed off at room temperature (25°C) and / or alternatively, it may be dried at elevated temperatures.

[0112] The coating composition is thermally curable at elevated temperatures, preferably at temperatures between 60°C to 180°C, depending on the reactivity of the crosslinking agent and the duration, most preferably 80°C to 160°C. The coating composition is preferably cured for 15 min to 50 min, most preferably 20 min to 40 min.

[0113] Additionally, provided by the invention is a substrate coated with a multilayer coating of the invention. Substrate materials are chosen from the group consisting of metals, plastic, wood, glass, mineral-based materials and composites of any of the aforementioned materials. It is possible to use untreated or pre-treated substrates, where the pre-treatment regularly depends on the chemical nature of the substrate. A pretreatment of a metallic substrate is a conversion coating layer like for example a layer produced by a zinc phosphating step. Preferred substrates are metals and plastics as customary used in the automotive industry. A particularly preferred substrate is a pretreated (i.e. conversion coated) metal substrate which additionally is coated with an electrocoat layer. The electrocoat layer, preferably, originates from a cationic electrodeposition coating and corresponding electrodeposition step. The coating composition of the invention is robust against the influence of salt and the coating layer formed by the coating composition of the invention does exhibit an only minor aging effect. This is combined with the unexpected excellent stability against photo-oxidation in contrast to other basecoat layers formed by non-ionically stabilized base coat compositions such as coating compositions based on glycols (polyether moieties), which are susceptible to photo-oxidation. The coating composition comprising the polymer according to the invention increases weather resistance of the coating layer formed thereof.

[0114] EXAMPLES

[0115] Methods

[0116] Solids content

[0117] Unless stated otherwise, the solids content was determined in accordance with DIN EN ISO 3251 at 130°C for 60 min with 1 .0 g weighed portion.

[0118] Content of isocyanate

[0119] The content of isocyanate (NCO content) was determined by adding an excess of 2% N,N-dibutylamine solution in xylene to a homogeneous solution of the specimen in acetone I N-ethylpyrrolidone (1 :1 Vol.-%) by potentiometric back titration of the amine excess with 0.1 N hydrochloric acid following DIN EN ISO 3251 , DIN EN ISO 11909 and DIN EN ISO 14886. The content of a polymer (solids content) in a solution is used to refer to the NCO content of the polymer with respect to the solids content.

[0120] Hydroxyl number

[0121] The hydroxyl number was determined following R.-P. Kruger, R. Gnauck and R. Algeier (Plaste und Kautschuk, 20, 274 (1982)) using acetic anhydride in the presence of 4-dimethylaminopyridine as a catalyst in a tetrahydrofuran (THF) I dimethylformamide (DMF) solution at room temperature. The residual excess of acetic anhydride after acetylation is completely hydrolyzed and acetic acid is potentiometric back titrated with alcoholic potassium hydroxide solution.

[0122] Acid number

[0123] The acid number was determined in accordance to DIN EN ISO 2114 in a homogenous solution of tetrahydrofuran (THF) I water (9 Vol. parts THF and 1 Vol. part distilled water) with ethanolic potassium hydroxide solution.

[0124] Number average molecular weight

[0125] The number average molecular weight (Mn) was determined using a vapor pressure osmometer type 10.00 (Knauer) with concentration series in toluene at 50°C with benzophenone as a calibration substance to determine the experimental calibration constant of the measuring device in accordance to E. Schroder, G. Muller, K.-F. Arndt, “Leitfaden der Polymercharakterisierung”, Akademie-Verlag, Berlin, S.47-54, 1982.

[0126] Solvent and monomer content

[0127] The content of organic solvents and monomers (residual monomers) in a mixture (for example an aqueous dispersion) was determined using gas chromatography (Agilent 7890A, 50m silica capillary column with polyethylene glycol phase or 50m silica capillary column with polydimethylsiloxane phase, carrier gas helium, split injector 250°C (for solvents) or 150°C (for vinyl monomers), oven temperature 40 to 220°C, flame ionization detector, detector temperature 275°C, internal standard n-propylene glycol). size

[0128] In the present application, the average particle size (volume average) of the particles of the polyurethane or polymer mixture of polyurethane in the aqueous dispersion is determined by measuring the hydrodynamic volume / hydrodynamic radius of the dispersion particles using photon correlation spectroscopy (PCS).

[0129] A “Malvern Nano S90” (Malvern Instruments) was used for the measurement at 25 ± 1 °C. The device covers a size range of 3 to 3000 nm and was equipped with a 4 mW He-Ne laser at 633 nm. The polymer dispersion was diluted with particle free, deionized water as a dispersing medium to measure the polymer dispersion in a 1 ml polystyrene cuvette at a suitable scattering intensity. The analysis was performed using a digital correlator using the evaluation software Zetasizer Vers. 6.32 (Malvern Instruments). The measurement was performed five times and repeated using a second, freshly prepared sample. The standard deviation of a 5-fold determination was <4%. The maximum deviation of the arithmetic mean of the volume average (V- average mean) of the five single measurements was ± 15%. The stated average particle size (volume average) is the arithmetic mean of the average particle size (volume average) of the individual preparations. Polystyrene standards with certified particle sizes between 50 and 3000 nm were used for the validation.

[0130] The solubility of polymers in tetrahydrofuran (THF) was determined at 23°C after drying the aqueous dispersion at 130°C and dissolving the dry residue in THF after 24 hours unless stated otherwise. A completely dissolved sample is characterized in the absence of any insoluble residues after filtration and that after evaporation of the solvent the balanced quantity of the polymer is equal to the initial weighted quantity of the polymer.

[0131] Determination of the electrophoretic mobility

[0132] The electrophoretic mobility (corresponding to the surface charge) in aqueous dispersion was determined using electrophoretic light scattering in a pH range of 3 to 10 at a temperature of 25°C using the Zetasizer Nano (Malvern). Thereby, a sample (i.e. a respective aqueous polymer dispersion) was diluted by 1 : 100 (based on weight) in 10 mmol / l KCI solution in water. The measurement was started at the pH which the respective sample had after this dilution in KCI. In case that this pH was in the abovedefined range of 3 to 10 (which was the case for all samples measured and shown within this example section), in a first set of experiments the pH was increased (by 0.1 M KOH), while in a second set of experiments the pH was correspondingly decreased (by 0.1 HCL), in each set of experiments until the limit values of the above-defined pH range had been reached. Thereby, the pH was varied in steps of approximately 0.5 - 1.5 units.

[0133] In case of any (potentially) ionic groups within the polymer, these groups were completely neutralized by common neutralizing agents before dilution in KCI solution (i.e. a molar amount of neutralizing groups in form of a neutralizing agent equaling the amount of (potentially) ionic groups within the polymer was added before measurement).

[0134] Negative values in electrophoretic mobility correlate with negative charge of the respective polymer (and vice versa).

[0135] Evaluation of coating layers formed from the coating compositions WOM (Weather-O-meter)Test

[0136] The coating layers were tested in the CAM180 test (according to DIN EN ISO 11341 Feb 98 and DIN EN ISO 4892-2 Nov 00) for their resistance to cracking in response to UV radiation and wet-dry cycles.

[0137] Condense water test

[0138] To simulate conditions in tropical regions as well as damp locations and test the robustness and lifetime of the coating composition, the condensing water test was performed according to DIN 50017 (Goldschmidt, Streitberger, Basics of Coating Technology, 2002, page 440).

[0139] Synthesis of aqueous polymer dispersions B1 to B9

[0140] The polymer dispersions B1 to B5, B8 and B9 were synthesized using inter alia the linear polyester polyol PES-1 or PES-2. Therefore, the compounds as indicated in Table 1 were reacted and polyester polyols with the indicated properties were obtained. The numbers given are in parts by weight.

[0141] Table 1

[0142] A reaction tube equipped with a stirrer, internal thermometer, reflux condenser, two feed vessels and an electric heater was used to prepare the respective polyurethane. Synthesis took place by dissolving the compounds indicated in Table 2 in the respective amount of methyl isobutyl ketone (Pll-1 ) or methyl ethyl ketone (Pll-2 to PU-9) under nitrogen.

[0143] The diisocyanate compound with the indicated isocyanate content was added at room temperature (23°C, Pll-2) or 45°C (Pll-1 , Pll-3 to PU-9) to the resulting solution while stirring. The reaction mixture was heated and kept at 105°C (PU-1 ) or 80 °C (PU-2 to PU-9) after the exothermic reaction had subsided until the indicated isocyanate content was reached and was constant. Trimethylolpropane (PU-1 to PU-4, PU-6, PU-7), diethanolamine (PU-5), di-n-butyl amine (PU-8) or 2-hydroxyethyl methacrylate and 30 min later trimethylolpropane (PU-9) were added and the resulting mixtures were kept at the respective temperature of 105°C (PU-1 ) or 80°C (PU-2 to PU-9) until free isocyanate groups could no longer be detected. 2,6-di-tert-butyl-4-methylphenol was added immediately after the complete consumption of isocyanate groups in mixture PU-9. The solids content (measured for 1 hour at 130°C) of the resulting polyurethane solution is indicated in Tables 2a and 2b.

[0144] Table 2a

[0145] Table 2b

[0146] The polyurethanes dissolved in organic solvent were reacted further to synthesize polyurethane-based polymers comprising N-vinylpyrrolidone-based moieties and respective aqueous dispersions. Also, aqueous dispersion of further polyurethane- based polymers (B1 , B2) were prepared as outlined below.

[0147] B1 -comparative example A mixture of 254.8 parts by weight n-butyl acrylate, 254.8 parts by weight methyl methacrylate, 60.9 parts by weight hydroxypropyl methacrylate and 47.6 parts by weight acrylic acid were added to the polyurethane solution Pll-1 evenly at a temperature of 105°C within 5 hours under normal pressure.

[0148] Simultaneously with the addition of the monomeric mixture, a solution of 18.5 parts by weight of tert.-butyl peroxyethylhexanoate in 190.6 parts by weight methyl isobutyl ketone was added within 5.5 hours. Afterwards, the resulting reaction mixture was stirred for additional 2 hours at 105°C until all monomers reacted.

[0149] Subsequently, the reaction was cooled down to 90°C and 36.4 parts by weight dimethylethanolamine and 1644 parts by weight deionized water were added while stirring.

[0150] Methyl isobutyl ketone of the resulting dispersion was removed by distillation under vacuum at 60°C while simultaneous solvent and water losses were compensated.

[0151] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0152] Butylglycol (236.2 parts by weight) was added to the polyurethane solution Pll-2 while cooling. The reaction mixture was drained at 60°C into 1627 parts by weight preheated deionized water (60°C) while stirring.

[0153] Methyl ethyl ketone of the resulting dispersion was removed by distillation under vacuum at 40°C while simultaneous solvent and water losses were compensated.

[0154] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0155] B3 -inventive example The polyurethane solution Pll-3 was diluted with 202.0 parts by weight of n-propanol and a mixture of 170.3 parts by weight of vinylpyrrolidone and 2.1 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 5 hours.

[0156] Simultaneously to the addition of the monomer mixture, a solution of 5.1 parts by weight of tert. -butyl peroxyethylhexanoate in 26.7 parts by weight methyl ethyl ketone was added within 5.5 hours. Afterwards, the resulting reaction mixture was stirred for additional 2 hours at 80°C until the N-vinylpyrrolidone had completely reacted.

[0157] Subsequently, the reaction mixture was cooled to room temperature and 340.8 parts by weight ethanol and 1363 parts by weight deionized water were added while stirring. The solvents of the resulting dispersion were removed by distillation under vacuum at 40°C while simultaneous water loss was compensated.

[0158] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0159] The polyurethane solution Pll-4 was diluted with 2.1 parts by weight methyl ethyl ketone and 180.3 parts by weight of n-propanol. A mixture of 135.2 parts by weight N- vinylpyrrolidone and 142.2 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 2 h 30 min.

[0160] Simultaneously to the addition of the monomer mixture, a solution of 4.1 parts by weight of tert. -butyl peroxyethylhexanoate in 41 .7 parts by weight methyl ethyl ketone was added within 2h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2h at 80°C until the vinylpyrrolidone had completely reacted.

[0161] Subsequently, 283.7 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. A mixture of 1560 parts by weight deionized water and 269.8 parts by weight ethanol having a temperature of 60°C was added to the reaction mixture while stirring. The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated.

[0162] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0163] The polyurethane solution Pll-5 was diluted with 2.3 parts by weight methyl ethyl ketone and 195.4 parts by weight of n-propanol. A mixture of 146.5 parts by weight N- vinylpyrrolidone and 148.4 parts by weight methyl ethyl ketone was added evenly to reaction mixture at 80°C within 2 h 30 min.

[0164] Simultaneously to the addition of the monomer mixture, a solution of 4.4 parts by weight of tert. -butyl peroxyethylhexanoate in 39.6 parts by weight methyl ethyl ketone was added within 2 h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2 h at 80°C until the N-vinylpyrrolidone had completely reacted.

[0165] Subsequently, 318.8 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. A mixture of 1691 parts by weight deionized water having a temperature of 60°C was added to the reaction mixture while stirring.

[0166] The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated.

[0167] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0168] B6 — inventive example

[0169] The polyurethane solution Pll-6 was diluted with 184.4 parts by weight of n-propanol. A mixture of 153.7 parts by weight N-vinylpyrrolidone and 155.7 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 2 h 30 min. Simultaneously to the addition of the monomer mixture, a solution of 4.6 parts by weight of tert. -butyl peroxyethylhexanoate in 41 .5 parts by weight methyl ethyl ketone was added within 2 h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2 h at 80°C until the N-vinylpyrrolidone had completely reacted.

[0170] Subsequently, 289.5 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. A mixture of 1793 parts by weight deionized water having a temperature of 60°C was added to the reaction mixture while stirring.

[0171] The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated.

[0172] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0173] B7 - inventive example

[0174] The polyurethane solution Pll-7 was diluted with 184.4 parts by weight of n-propanol. A mixture of 153.7 parts by weight N-vinylpyrrolidoneand 155.7 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 2 h 30 min.

[0175] Simultaneously to the addition of the monomer mixture, a solution of 4.6 parts by weight of tert. -butyl peroxyethylhexanoate in 41 .5 parts by weight methyl ethyl ketone was added within 2 h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2 h at 80°C until N-vinylpyrrolidone had completely reacted.

[0176] Subsequently, 289.5 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. A mixture of 1793 parts by weight deionized water having a temperature of 60°C was added to the reaction mixture while stirring.

[0177] The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated. The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0178] B8- inventive example

[0179] The polyurethane solution Pll-8 was diluted with 188.8 parts by weight of n-propanol. A mixture of 130.2 parts by weight N-vinylpyrrolidone, 27.1 parts by weight 2- hydroxyethyl methacrylate and 159.4 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 2 h 30 min.

[0180] Simultaneously to the addition of the monomer mixture, a solution of 4.7 parts by weight of tert. -butyl peroxyethylhexanoate in 50.8 parts by weight methyl ethyl ketone was added within 2 h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2 h at 80°C until the vinyl monomers had completely reacted.

[0181] Subsequently, 288.1 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. A mixture of 1752 parts by weight deionized water having a temperature of 60°C was added to the reaction mixture while stirring.

[0182] The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated.

[0183] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0184] B9- inventive example

[0185] The polyurethane solution Pll-9 was diluted with 193.2 parts by weight of n-propanol. A mixture of 144.9 parts by weight N-vinylpyrrolidone and 144.9 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 2 h 30 min.

[0186] Simultaneously to the addition of the monomer mixture, a solution of 4.3 parts by weight of tert. -butyl peroxyethylhexanoate in 50.0 parts by weight methyl ethyl ketone was added within 2 h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2 h at 80°C until the N-vinylpyrrolidone had completely reacted.

[0187] Subsequently, 308.6 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. A mixture of 1711 parts by weight deionized water having a temperature of 60°C was added to the reaction mixture while stirring.

[0188] The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated.

[0189] The polymer solid isolated and dried at 130°C was completely soluble in tetrahydrofuran.

[0190] The produced polymer (also called binder) dispersions B1 to B9 were coagulate-free and exhibited the properties indicated in Tables 3a and 3b. The solids content and acid number were measured for 1 hour at 130°C. The pH value was measured at 23°C. The average particle size (volume average) was determined using photon correlation spectroscopy (PCS). All dispersions showed a unimodal particle size distribution. The calculated contents of moieties of poly(meth)acrylate, polyethylene oxide, polyvinylpyrrolidone or polyvinylpyrrolidone copolymer in the polymer are specified in Tables 3a and 3b.

[0191] Table 3a

[0192] Table 3b

[0193]

[0194] Using gas chromatography, the content of the solvents in the produced binders B1 to B9 was determined (Tables 4a and 4b). The content of the residual vinyl monomers in B1 , B3 to B9 was below 0.1 wt.-%.

[0195] Table 4a

[0196] Table 4b

[0197] Similar to the above-described synthesis of Pll-1 to Pll-9, 390.2 parts by weight (pbw) of PES-2, 23.1 pbw trimethylolpropane monoallyl ether, 4.6 pbw of dimethylol butanoic acid and 1.9 pbw of Dibutyltin dilaurate were dissolved in 260.3 pbw of methyl ethyl ketone under nitrogen. Then, 149.5 pbw of dicyclohexylmethane 4,4’-diisocyanate were added at 45°C under stirring. The mixture was heated and kept at 80°C until a stable isocyanate content of 1 .44 % was reached. Trimethylolpropane (37.8 pbw) was added and the resulting mixture was held at 80°C until no further isocyanate groups could be detected. The solids content (measured for 1 hour at 130°C) of the resulting polyurethane solution was 69.9 %.

[0198] The resulting solution was diluted with 207 parts by weight of n-propanol. A mixture of 82.8 parts by weight N-vinylpyrrolidone and 82.8 parts by weight methyl ethyl ketone was added evenly to the reaction mixture at 80°C within 2 h 30 min.

[0199] Simultaneously, a solution of 2.5 parts by weight of tert. -butyl peroxyethylhexanoate in 22.4 parts by weight methyl ethyl ketone was added within 2 h 40 min. Afterwards, the resulting reaction mixture was stirred for additional 2 h at 80°C until N-vinylpyrrolidone had completely reacted.

[0200] Subsequently, 460.2 parts by weight methyl ethyl ketone was added to the reaction mixture and the reaction mixture was cooled down to 60°C. Then, 4.4 parts by weight of dimethyl ethanolamine was added, followed by addition of 1770 parts by weight deionized water while stirring.

[0201] The solvents of the resulting dispersion were removed by distillation under vacuum at 50°C while simultaneous water loss was compensated.

[0202] The produced polymer (also called binder) dispersion B10 was coagulate-free and exhibited an solids content of 28 %, an acid number of 5.7 mg KOH / g and a pH of 8.7 8at 23°C). The dispersion had a unimodal particle size distribution (PCS, v-mean) of 75 nm; the residual organic solvent content was substantially zero (0.2 wt.-% of n- propanol, 0.0 wt.-% of methyl ethyl ketone).

[0203] Electrophoretic mobility

[0204] The results of the electrophoretic characterization of the polymers of dispersions B1 to B4 are demonstrated in the following Table 5.

[0205] For the sake of completeness, it shall be mentioned that binders B2, B3 and B4 did not show electrophoretic mobilities outside the range of -2.5 to 2.5 (pm / s) / (V / cm) in the entire pH range from 3.0 to 10.0 (also including below 3.3 and more than 9.7). The same is true for all of binders B5 to B9 (explicit data not shown). Also, binder B10 did not show any electrophoretic mobility outside the range of -3.5 to 3.5 (pm / s) / (V / cm) in the entire pH range from 3.0 to 10.0 (also including below 3.3 and more than 9.7). In contrast, the ionic binder B1 exhibits a significantly higher mobility in at least parts of the relevant pH range.

[0206] Synthesis of pigment pastes P1 and P1A (inventive)

[0207] Example P1 - Preparation of a red paste

[0208] A red paste was prepared with 35 parts by weight of a polyurethane dispersion prepared according to the binder dispersion A of WO 92 / 15405, 8.5 parts by weight Disperbyk 184 (commercially available from BYK Chemie (Altana)), 34.5 parts by weight Irgazin Red L 3663 HD (commercially available from BASF SE), 18 parts by weight fully desalinated water, 2 parts by weight propylene glycol ether and 2 parts by weight of a customary polyether (Pluriol® P900, BASF SE).

[0209] Example P1 A - Preparation of an inventive red paste

[0210] An inventive red paste was prepared with 47 parts by weight of the inventive polymer dispersion of example B4, 8.5 parts by weight Disperbyk 184 (commercially available from BYK Chemie (Altana)), 34.5 parts by weight Irgazin Red L3663 HD (commercially available from BASF SE), 6.0 parts by weight fully desalinated water, 2 parts by weight propylene glycol ether and 2 parts by weight of a customary polyether (Pluriol® P900, BASF SE).

[0211] An Aerosil® paste was prepared with 36 parts by weight of a polyurethane dispersion prepared according to the binder dispersion A of WO 92 / 15405, 39 parts by weight of fully desalinated water, 7 parts by weight of butylglycol, 7 parts by weight of Aerosil® R 972 (Evonik) and 1 part by weight of 15% aqueous ammonia solution.

[0212] Preparation of red aqueous coating compositions

[0213] The components listed in Table 7 as aqueous phase were added in the indicated order to an aqueous solution. Afterwards, the mixture was stirred for 10 min and a pH value of 8.4 was adjusted at 23°C using deionized water and N,N-dimethylethanolamine (BASF SE). Moreover, a spray viscosity of 135 mPas using a shear stress of 1000 s_1was adjusted with a rotation viscometer (RheolabQC from Anton Paar). In total six base coat compositions were prepared. Two comparative basecoat compositions (C1 and C3) were ionic, while comparative basecoat composition C2 was non-ionic. All inventive basecoat compositions (11 to I3) were non-ionic. Basecoat composition I2 comprised both inventive binders B3 and B4, which was present in the inventive red paste P1A. Table 7

[0214] Sum 100 100 100 100 100 100

[0215] The solids, pigment to binder ration (p / b) and volatile organic compounds (VOC) of the synthesized base coat compositions were determined: Table 8

[0216] Application of the coating compositions

[0217] A steel sheet (according to DIN EN ISO 28199-1 , point 8.1 , version A) with the dimensions of 57 cm x 20 cm was coated with a standard cathodically electrodepositable coating composition (CathoGuard® 800 OG, BASF Coatings GmbH). A commercially available filler of the company Hemmelrath (HR ALG 670173, medium gray) was applied with a layer thickness of 33 ± 5 pm. After 10 min flash-off time at room temperature, the paint was cured for 20 min at 160°C. Afterwards basecoat compositions C1 to C3 and 11 to I3 were applied electrostatically with a layer thickness of 22 ± 5 pm. After 5 min flash-off time, the paint was cured for 10 min at 80°C.

[0218] Subsequently a commercially available two component clearcoat composition (ProGloss, FF99-0364, BASF Coatings GmbH) with a layer thickness of 45 ± 5 pm was applied electrostatically. The paint was cured for 25 min at 140°C after a flash-off time of 5 min.

[0219] Testing of the basecoat layers

[0220] The coated panels of formulations C1 , C2 and 11 have been tested for 3000 h and 4800 h in a Weather-O-Meter®-Weathering equipment, „Weather-O-Meters“ commercially available from Atlas Material Testing Technology LLC (“WOM- Bewitterung following SAE J 2527-04”). Afterwards, they have been treated for 240 h in a condensing water test, (“SKK-Test”; according to DIN 50017). The adhesion of the panels, freshly, before the weathering test, directly after the WOM test and finally after WOM and condensing water test, was evaluated by employing a cross cut test according to DIN EN ISO 2409.

[0221] The coated steel sheets were tested regarding their weather resistance. The cross-cut results according to DIN EN ISO 2409 are displayed in Table 9.

[0222] Table 9

[0223] The cut was in each case between the filler and the basecoat layer. The results verify the susceptibility of glycols to photo-oxidation known from the literature and underline the better performance of the basecoat layer that was stabilized by N-Vinylpyrrolidon- based moieties.

[0224] Testing of the basecoat compositions

[0225] To highlight the advantages of the non-ionic resin in base coat compositions, the six basecoat compositions were tested regarding their resistance to saline solutions.

[0226] First, a saline solution was prepared of 50 g fully desalinated water and 15 g of commercially available sodium chloride. Then, 40 g of the respective basecoat compositions C1 to C3 or 11 to I3 were added to the saline solution under stirring. In the following, 0.5 g of saline chloride was added and stirred for 5 min before the homogeneity of the base coat compositions regarding their segregation or coagulation of the solids content was evaluated. The addition of saline chloride was repeated until in total 9 g of saline chloride was added.

[0227] The sensitivity was categorized into homogenous and stable (HG) if the base coat composition was homogenous and no segregation or coagulation of the dispersion was observed. Upon addition of the sodium chloride, segregation was observed for some base coat compositions, which was divided into the categories of slight segregation (S-SG) because it was still possible to homogenize the base coat composition or segregation (SG) when homogenization of the base coat composition was not possible any more. The results are summarized in Table 10.

[0228] Table 10

[0229] The results highlight that the basecoat compositions comprising non-ionic binders (C2,

[0230] 11 to I3) are more resistant to the saline solution as they were homogenous and stable until a high amount of potassium chloride was added. Inventive basecoat compositions

[0231] 12 and I3 were still homogenous even after the highest amount of potassium chloride was added. These results underline that the inventive base coat compositions 11 to I3 do not only exhibit an improved weather resistance (Table 9) but are additionally also more robust with respect to a change in the pH value or salinity than ionic base coat compositions (Table 10). This effect is unexpected as the influence of polyvinylpyrrolidone on the weather resistance of a coating composition was not known so far.

[0232] Employing mixtures of inventive polymers in a red aqueous coating composition The components listed in Table 11 as aqueous phase were added in the indicated order to an aqueous solution. Afterwards, the mixture was stirred for 10 min and a pH value of 8.4 was adjusted at 23°C using deionized water and N,N-dimethyl- ethanolamine (BASF SE). Moreover, a spray viscosity of 117 mPas using a shear stress of 1000 s_1was adjusted with a rotation viscometer (RheolabQC from Anton Paar). For the evaluation of the performance of a mixture of two different, non-ionic resins within a red base coat, two formulations have been investigated. One comparative base coat composition C4 was based on ionic binders, while another inventive base coat composition 14 was based on a mixture of non-ionic binders. Base coat composition 14 comprised both inventive binders B3 and B4 as free binder, not employed as a dispersing aid for the pigment(s). Thus, for these investigations, the standard, comparative red paste P1 , based on the ionic binder was employed.

[0233] Table 11

[0234] Sum 100 100

[0235] Application of the coating compositions

[0236] The application of basecoats C4 and I4 basically has been pursued following the same procedure as for C1 to C3 and 11 to I3. To investigate and judge about the appearance of the coated surfaces, directly after finishing all paint applications, a series of completely painted panels have been cured vertically, another sample series horizontally.

[0237] The resulting red paint films were evaluated for smoothness in terms of LW and SW and for gloss in terms of DOI (distinctness of image) by an orange peel meter (BYK 4840 wave scan dual, from BYK-Gardner GmbH), according to DIN EN ISO 2813. Respective measurement results for C4 and I4 are summarized in Table 12.

[0238] In addition to the appearance evaluation, the sag stability of the materials has been tested as well. For this purpose, a perforated steel plate with dimensions of 57 cm x 20 cm (according to DIN EN ISO 28199-1 , section 8.1 , version A), coated with a standard electrocoat material (CathoGuard® 800 from BASF Coatings GmbH), was prepared in analogy to DIN EN ISO 28199-1 , section 8.2 (version A). This was followed, in a method based on DIN EN ISO 28199-2, section 8.3, by electrostatic application of both base coat compositions, C4 and I4 in a single application in the form of a wedge with a target film thickness (film thickness of the dried material) in the range from 0 pm to 40 pm. After a flash-off time of 10 minutes at 18 to 23°C (run test) or without a prior flash-off time, the resulting waterborne basecoat film is dried in a forced air oven at 80°C for 5 minutes. To evaluate the sagging performance, the resulting steel plates have been flashed off and dried vertically. The determination of the sagging performance tendency was carried out according to DIN EN ISO 28199-3, section 4. As well as the film thickness at which a sag exceeding a length of 10 mm from the bottom edge of the perforation, a determination is made of the film thickness above which an initial tendency to run can be observed visually at a perforation. Respective results on sag performance of basecoats C4 and 14 are summarized in Table 13.

[0239] Table 12

[0240] Table 13 As shown in the above examples, a further advantage of the inventive polymers is that also different types of these polymers may be combined as demonstrated in the basecoat compositions I2 and I4, which comprise both inventive polymers B3 and B4. Thus, a high compatibility is observed for the polymers according to the invention, yielding in performance advantages of coating systems. In particular, this is proven by improved sag stability while maintaining excellent appearance performance.

[0241] The use of the inventive polymers in the coating composition improves the weather resistance and robustness against a change in pH value or salinity. Another advantage is of the polymers is their broad applicability, for example as main binder in coating compositions and / or as binder component in pigment pastes.

Claims

Claims1. Polyurethane-based polymer comprising N-vinylpyrrolidone-based moieties, wherein the amount of polyurethane in the polyurethane-based polymer is greater than 10 wt.-% (based on the total weight of the polyurethane-based polymer) and wherein the electrophoretic mobility of the polymer in aqueous dispersion is not less than -4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0.

2. Polymer according to claim 1 , wherein the polymer is obtainable by(a) providing at least one polyurethane(b) polymerizing N-vinylpyrrolidone or a monomer mixture consisting of N- vinylpyrrolidone and at least one further ethylenically unsaturated monomer in the presence of the at least one polyurethane and / or polyurea-polyurethane.

3. Polymer according to claim 2, wherein the polyurethane of step (a) is ethylenically unsaturated.

4. Polymer according to claim 2 or 3, wherein the polyurethane of step (a) comprises ethylenically unsaturated groups selected from vinyl groups, acryl groups, methacryl groups and allyl groups.

5. Polymer according to any of claims 1 to 4, wherein the amount of N-vinylpyrrolidone in the polyurethane-based polymer is at least 5 wt.-%, preferably at least 10 wt.-%, more preferably at least 15 wt.-% (based on the total weight of the polyurethane-based polymer).

6. Polymer according to any of claims 1 to 5, wherein the acid number of the polymer is 0 to 7 mg KOH / g.

7. Polymer according to any of claims 1 to 6, wherein the electrophoretic mobility of the polymer is from -4.0 to 4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0 in aqueous dispersion.

8. Polymer according to any of claims 1 to 7, wherein the amount of polyethylene glycol moieties is not more than 5 wt.-% ((based on the total weight of the polyurethane- based polymer).

9. Polymer according to any of claims 1 to 7, wherein the amount of polyethylene glycol moieties is not more than 2.5 wt.-% ((based on the total weight of the polyurethane- based polymer).

10. Polymer according to any of claims 1 to 9, wherein the amount of polyurethane in the polyurethane-based polymer is greater than 25 wt.-%, preferably at least 25.1 wt.- %, more preferably 25.1 wt.-% to 95 wt.-% (in each case based on the total weight of the polyurethane-based polymer).11 . Aqueous dispersion of a polymer according to any of claims 1 to 10.

12. Aqueous pigmented composition selected from coating compositions and pigment pastes comprising at least one polyurethane-based polymer comprising N- vinylpyrrolidone-based moieties, wherein the electrophoretic mobility of the polymer in aqueous dispersion is not less than -4.0 (pm / s) / (V / cm) in the pH range from 3.0 to 10.0.

13. Method of producing a multilayer coating, comprising the steps of a) optionally applying a filler coating composition on a substrate to obtain a filler layer, b) applying a basecoat composition on top of the layer obtained in step a) or directly on a substrate to form a basecoat layer, c) applying a clearcoat composition on top of the basecoat layer to form a clearcoat layer, and d) simultaneously curing of the filler layer, basecoat layer and clearcoat layer or individually curing of one or more layers obtained in steps a) to c) before the subsequent coating layer is applied,wherein at least one coating composition according to claim 12 is applied within the method and wherein this at least one coating composition is applied within step a) and / or step b), preferably within step b).

14. Method according to claim 13, wherein the substrate is a pretreated (i.e. conversion coated) metal substrate which additionally is coated with an electrocoat layer, wherein the electrocoat layer originates from a cationic electrodeposition coating and corresponding electrodeposition step.

15. Coated substrate produced by the method according to claim 13 or 14.