Clearcoat composition containing branched polyester in amounts as a flow promoter and leveling agent

Abstract

The present invention relates to a clear coat coating material composition comprising an OH-functional (meth)acrylic copolymer (A1), a branched OH-functional polyester (A2) in an amount ranging from 1.0 wt. % to 15.0 wt. % based on the total solids content of the coating material composition, obtainable by carrying out steps (a), (b) and (c), and at least one crosslinker (B1) which is different from both components (A1) and (A2) and which contains a crosslinkable functional group capable of crosslinking with an OH-functional group; a method for coating a substrate, which comprises applying the clear coat coating material composition of the present invention to an optionally pre-painted substrate; a coated substrate obtainable by the method of the present invention; and a method for using the branched OH-functional polyester (A2) as a flow promoter and / or leveling agent in a clear coat coating material for spray-applying the clear coat coating material onto an optionally pre-painted substrate.

Description

[Technical Field]

[0001] The present invention relates to a clear coat coating material composition comprising an OH-functional (meth)acrylic copolymer (A1), a branched OH-functional polyester (A2) obtainable by carrying out steps (a), (b) and (c), which is present in an amount ranging from 1.0 wt. % to 15.0 wt. %, relative to the total solids content of the coating material composition, and at least one crosslinker (B1) which is different from both components (A1) and (A2) and which contains a crosslinkable functional group capable of crosslinking with at least an OH functional group; to a method for coating a substrate, which comprises applying the clear coat coating material composition of the present invention to an optionally prepainted substrate; to coated substrates obtainable by the method of the present invention; and to a method for using the branched OH-functional polyester (A2) as a flow promoter and / or leveling agent in a clear coat coating material for spray application of said clear coat coating material onto an optionally prepainted substrate. [Background technology]

[0002] In the automotive industry, it is desirable and necessary, particularly for environmental reasons, to reduce as much as possible the VOC content, i.e., the content of volatile organic compounds, particularly organic solvents, present in coating material compositions used to paint substrates suitable for use in the automotive industry, such as automobile parts. Such a reduction in VOC content can be achieved, for example, by using aqueous (water-based) coating material compositions rather than solvent-based (solvent-based) coating material compositions. Alternatively, a reduction in VOC content can be achieved by increasing the solids content, i.e., the nonvolatile content, especially when the coating material composition is solvent-based, which is still the case for most commercially available clear coat compositions.

[0003] However, although increasing the solid content naturally leads to automatically reducing the VOC content, this approach has limitations, because the organic solvent present in the solvent-based coating material composition plays an important role in the sprayability of the coating composition during their spray application, since the solvent is important for achieving sufficient spray viscosity.When the amount of solvent is too small, sprayability difficulties occur.Furthermore, when there is not enough solvent available to promote polymer flow and achieve sufficient leveling of the coating on the substrate, the resulting coating may exhibit a deteriorated and inferior appearance.In other words, although it is desirable to reduce the VOC content as much as possible, there is a limit to how much solvent can actually be removed from the system used.

[0004] Furthermore, when using coating compositions, such as solvent-based coating compositions, in OEM applications, but also particularly in refinish applications, it is important to consider the different environmental conditions that may exist in a country such as the United States, depending on the geographic region, where even within a single country, there may be a relatively humid climate, such as Maryland, a significantly less humid climate, such as California, and, of course, humidity conditions between these two states in various other states. The existing climate, particularly humidity, as well as temperature, may have an effect on the spray method, especially when applying a solvent-based coating composition via spray application. For example, a deteriorated or poor appearance of the resulting coating may be observed in areas with higher humidity than California. In particular, coatings may suffer from dieback problems under such significantly higher humidity conditions. Dieback is a term used to describe a defect in the coating appearance that appears after the initial cure of the coating has been achieved. It resembles pinching or fine wrinkles in the formed coating film and is the result of uneven adaptation of stresses in the coating caused by continued shrinkage in the film during the final crosslinking phase after the initial cure is complete. If the mobility of the polymers present in the film is too suppressed before the final crosslinking of the coating is achieved, dieback defects will appear. Dieback defects in particular lead to poor, i.e., low DOI (distinctiveness of image) values. Higher humidity can lead to a faster decrease in polymer mobility in the film, thereby causing dieback to appear in the film.

[0005] Although it is known to incorporate conventional polyesters into coating material compositions to improve the aforementioned flow and leveling properties, these polyesters can only be used at relatively low solids levels in the coating material composition to maintain the desired and sufficient spray viscosity. Moreover, these conventional polyesters are often hydrolytically unstable, which makes them particularly disadvantageous when used in top coats, such as clear coats, as the outermost layer of a multilayer structure for durability reasons.

[0006] Unconventional polyesters are disclosed in WO 2016 / 008655 A1, which relates to coating compositions containing hyperbranched or dendritic polyols to improve the flexibility of coatings made from these compositions. Specifically, the coatings exhibit excellent stone chip resistance due to their improved flexibility. To achieve the desired flexibility / stone chip resistance, the coating composition must contain a relatively high amount of the aforementioned polyol, from about 5% to about 60% by weight, based on the total amount of film-forming materials contained in the coating composition.

[0007] Therefore, there is a need for a clearcoat coating material composition that can be applied with a high solids content, but that still exhibits excellent sprayability when used in spray applications without further increasing VOC content, from which a cured clear coating on a pre-painted substrate can be obtained, and that has excellent appearance with minimized or even non-existent dieback, even when spray application is carried out at relatively high temperatures, e.g., >85°F (>29.4°C), and relatively high relative humidity (RH), e.g., 65% RH, or even >85% RH. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] WO2016 / 008655 A1 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, the underlying object of the present invention is to provide a clearcoat coating material composition that can be applied with a high solids content, yet when used in spray application, exhibits excellent sprayability without the need to further increase the VOC content, from which a cured clear coating on a prepainted substrate can be obtained, and has an excellent appearance in terms of minimized or even non-existent dieback, even when the spray application is carried out at relatively high temperatures, for example, >85°F (>29.4°C), and relatively high relative humidity (RH), for example, 65% RH or even >85% RH. [Means for solving the problem]

[0010] This object has been solved by the subject matter of the claims of the present application and by the preferred embodiments thereof disclosed herein, i.e. by the subject matter described herein.

[0011] The first subject of the present invention is (A1) at least one OH-functional (meth)acrylic copolymer as component (A1), (A2) Steps (a), (b) and (c), i.e. (a) reacting at least one polyol containing at least three OH groups with at least one aliphatic dicarboxylic acid having 6 to 36 carbon atoms and / or its anhydride and / or its ester to form an OH-functional first intermediate product; (b) reacting the first intermediate product from step (a) with at least one cyclic carboxylic acid anhydride to form a carboxylic acid functional second intermediate product; and (c) reacting the second intermediate product from step (b) with at least one epoxide-functional compound having one epoxide group to form a branched OH-functional polyester. and at least one branched OH-functional polyester as component (A2), which can be obtained by carrying out (B1) at least one crosslinking agent as component (B1), which is different from both components (A1) and (A2) and contains crosslinkable functional groups that can be crosslinked with OH functional groups; Including, A clearcoat coating material composition comprising: the at least one branched OH-functional polyester (A2) is present in the clear coat coating material composition in an amount ranging from 1.0 wt.-% to 15.0 wt.-%, based on the total solids content of the coating material composition; A clearcoat coating material composition.

[0012] A further subject of the present invention is a method for coating a substrate, comprising at least one step of applying to an optionally pre-coated substrate a clear coat coating material composition of the present invention to form at least one coating on the optionally pre-coated substrate, and at least one further step of curing said at least one coating to obtain at least one cured coating layer on the substrate.

[0013] A further subject of the present invention is a coated substrate obtainable by the process according to the invention.

[0014] A further subject of the present invention is the use of at least one branched OH-functional polyester (A2) as defined above and further defined hereinafter as a flow promoter and / or leveling agent in a clear coat coating material for spray application of said clear coat coating material onto an optionally pre-painted substrate.

[0015] It has been surprisingly found that the clearcoat coating material composition of the present invention can be applied in the form of a composition with a high solids content, yet still exhibits excellent sprayability when used in spray application without the need to further increase its VOC content by adding more organic solvents. In contrast, it has been found that the VOC content can be effectively reduced, particularly by using a branched OH-functional polyester present as component (A2). It has been particularly surprising that the excellent sprayability of the clearcoat coating material composition of the present invention when used in spray application, particularly the excellent, enhanced flow in spray application, and the achieved good leveling properties, are due to the presence of the branched OH-functional polyester present as component (A2) in the clearcoat coating material composition of the present invention, because these effects were not observed when using a clearcoat coating material composition that does not contain the branched OH-functional polyester, which does not require the use of more organic solvents.

[0016] It has been further surprisingly found that clear coatings on previously painted substrates can be obtained from the clearcoat coating material compositions of the present invention by utilizing spray application, where the coating has excellent appearance in terms of minimized or even non-existent dieback, even when the spray application is carried out in an environment with a relatively high temperature, e.g., >85°F (>29.4°C), and a relatively high relative humidity (RH), e.g., 65% RH or even >85% RH. In particular, it has been found that the coatings obtained from the coating material compositions of the present invention have excellent DOI values. It has been particularly surprising to find that this is achieved due to the presence of the branched OH-functional polyester present as component (A2) in the clearcoat coating material compositions of the present invention, since this effect has not been observed when using clearcoat coating material compositions that do not contain said branched OH-functional polyester. It has further been found that in the clear coat coating material composition of the present invention, both the branched OH-functional polyester present as component (A2) and the at least one OH-functional (meth)acrylic copolymer present as component (A1) retain sufficient mobility throughout the entire crosslinking process of film curing to avoid dieback, thereby demonstrating the desired flow and leveling properties.

[0017] Furthermore, it has been surprisingly found that the branched OH-functional polyesters present as component (A2), especially when used in combination with at least one OH-functional (meth)acrylic copolymer also present in the clearcoat coating material composition of the present invention, are hydrolytically stable to a greater extent than conventional polyesters, which is advantageous as far as the durability of the resulting coating is concerned, since the applied clearcoat derived from the clearcoat coating material composition of the present invention represents the outermost layer of a multi-layer coating system. This is particularly advantageous for use in the automotive industry, which operates in regions where the climate is fairly humid, e.g., relative humidity (RH) >65%, or even >85%, for at least a good part of the year, when the clearcoat is applied to an automobile part or body as part of a multi-layer structure.

[0018] Furthermore, it has been surprisingly discovered that high cured crosslink densities in clearcoats derived from the clearcoat coating material compositions of the present invention can be achieved without introducing brittleness, despite the use of branched OH-functional polyesters. DETAILED DESCRIPTION OF THE INVENTION

[0019] The term "comprises" in the sense of the present invention, for example in relation to the coating material composition of the present invention, preferably has the meaning of "consists of." In the context of the coating material composition of the present invention, in addition to the essential components present therein, one or more of the further components defined hereinafter and optionally included in the coating material composition of the present invention can be included therein. All these components can be present in their preferred embodiments, which are in each case defined below.

[0020] Clearcoat Coating Material Composition and Optional Components (A3) The clear coat coating material composition of the present invention comprises at least one OH-functional (meth)acrylic copolymer as component (A1), at least one branched OH-functional polyester as component (A2), and at least one crosslinker as component (B1).

[0021] The coating material composition of the present invention is particularly useful in the fields of automotive OEM finishing and also automotive refinishing, where technical and aesthetic qualities are particularly demanding.

[0022] The proportions and amounts in wt.-% (% by mass) of all components present in the respective coating material composition according to the invention add up to 100 wt.-% in each case, relative to the total mass of the coating material composition.

[0023] The terms "clear coat," "clearcoat," or "clear coating" are known to those skilled in the art and refer to a substantially transparent or transparent outermost layer of a multi-layer paint construction applied to a substrate.

[0024] Preferably, the clear coat coating material composition of the present invention does not contain more than 5 wt.-% of pigments and / or fillers, because otherwise the transparency or desired transparency of the clear coat coating layer produced from the composition may be affected. More preferably, the clear coat coating material composition of the present invention does not contain any pigments and / or fillers, and in particular does not contain any effect pigments.

[0025] The term "pigment" is known to those skilled in the art, for example from DIN 55943 (dated October 2001). "Pigments" in the sense of the present invention preferably refer to components in powder or flake form that are substantially, preferably completely, insoluble in the medium that surrounds them, for example, one of the coating material compositions used in the present invention. Pigments are preferably coloring substances and / or substances that can be used as pigments because of their magnetic, electric, and / or electromagnetic properties. Pigments preferably differ from "fillers" in their refractive index, which is ≧1.7. The term "filler" is known to those skilled in the art, for example from DIN 55943 (dated October 2001). "Fillers" for the purposes of the present invention are preferably components that are substantially, preferably completely, insoluble in the application medium, for example, one of the coating material compositions used in the present invention, specifically components used to increase the volume. "Fillers" in the sense of the present invention preferably differ from "pigments" in their refractive index, with the refractive index of the filler being <1.7. Examples of suitable fillers include kaolin, dolomite, calcite, chalk, calcium sulfate, barium sulfate, graphite, silicates such as magnesium silicate, in particular corresponding phyllosilicates such as hectorite, bentonite, montmorillonite, talc and / or mica, silica, in particular fumed silica, hydroxides such as aluminum hydroxide or magnesium hydroxide, or organic fillers such as textile fibers, cellulose fibers, polyethylene fibers or polymer powders; for further details, see Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, 250 ff., "Fillers". Examples of suitable pigments are inorganic and organic color pigments.Examples of suitable inorganic color pigments are white pigments, such as zinc white, zinc sulfide or lithophon; black pigments, such as carbon black, iron manganese black or spinel black; color pigments, such as chromium oxide hydrate green, cobalt green or ultramarine green, cobalt blue, ultramarine blue or manganese blue, ultramarine violet or cobalt violet and manganese violet, red iron oxide, cadmium sulfoselenide, molybdate red or ultramarine red; brown iron oxide, mixed brown, spinel phase and corundum phase or chrome orange; or yellow iron oxide, nickel titanium yellow, chromium yellow, cadmium sulfide, cadmium zinc sulfide, chrome yellow or bismuth vanadate.Other inorganic color pigments are silicon dioxide, aluminum oxide, aluminum oxide hydrate, especially boehmite, titanium dioxide, zirconium oxide, cerium oxide, and mixtures thereof. Examples of suitable organic colored pigments are monoazo pigments, disazo pigments, anthraquinone pigments, benzimidazole pigments, quinoacridone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, indanthrone pigments, isoindoline pigments, isoindolinone pigments, azomethine pigments, thioindigo pigments, metal complex pigments, perinone pigments, perylene pigments, phthalocyanine pigments or aniline black.

[0026] Preferably, the coating material composition of the present invention is a one-component (1K) coating material composition, or a two-component (2K) coating material composition obtained by mixing at least one component (A) containing at least components (A1) and (A2) with at least one component (B) containing at least component (B1) before mixing with component (A) that has been stored separately from component (A), and optionally with an additional diluent component (C) containing at least one organic solvent (A3). More preferably, the coating material composition of the present invention is a two-component (2K) coating material composition obtained by mixing at least one component (A) containing at least components (A1) and (A2) with at least one component (B) containing at least component (B1) before mixing with component (A) that has been stored separately from component (A), and optionally with an additional diluent component (C) containing at least one organic solvent (A3).

[0027] Preferably, the coating material composition of the present invention is a solvent-based, i.e., organic solvent(s)-based, coating material composition, and further comprises at least one organic solvent as component (A3). Thus, preferably, the coating material composition of the present invention is not solvent-based, i.e., is an aqueous coating material composition.

[0028] The term "solvent system" in the context of the coating material composition of the present invention is preferably understood for the purposes of the present invention to mean that organic solvent(s) are present as solvent and / or diluent, respectively, in the coating material composition of the present invention as the main constituent of all solvents and / or diluents, which are preferably present in an amount of at least 35 wt.-% relative to the total mass of the coating material composition of the present invention. Water may additionally be present in a smaller proportion, preferably present in an amount of <20 wt.-%, more preferably <10 wt.-%.

[0029] The coating material composition of the present invention, when the composition is solvent-based, preferably comprises at least 40 wt. %, more preferably at least 45 wt. %, and most preferably at least 50 wt. % of an organic solvent(s) fraction, in each case relative to the total weight of the coating material composition. All conventional organic solvents known to those skilled in the art can be used as organic solvents. The term "organic solvent" is particularly known to those skilled in the art from Council Directive 1999 / 13 / EC of March 11, 1999. Examples of such organic solvents include heterocyclic, aliphatic, or aromatic hydrocarbons, monoalcohols or polyalcohols, especially methanol and / or ethanol, ethers, esters, ketones, and amides, such as N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, toluene, xylene, butanol, ethyl glycol, and butyl glycol, and also their acetates, butyl diglycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone, or mixtures thereof.

[0030] The coating material composition of the present invention preferably comprises, when the composition is solvent-based, a water fraction of <20 wt. %, more preferably a water fraction in the range of 0 to <20 wt. %, very preferably 0.5 to 20 wt. %, or up to 17.5 wt. %, or up to 15 wt. %, or up to 10 wt. %, in each case relative to the total weight of the coating material composition.

[0031] Preferably, the coating material composition of the present invention has a total solids content that is >30 wt.-%, preferably >33 wt.-%, relative to the total weight of the coating material composition.

[0032] The total solids content of the coating material composition of the present invention is preferably in the range of >30 to 50 wt.-%, more preferably >33 to 45 wt.-%, in each case based on the total mass of the coating material composition. The total solids content, i.e. the non-volatile fraction, is determined according to the method described hereinafter.

[0033] OH-functional (meth)acrylic copolymer as component (A1) and optionally further film-forming resin as component (A5). Component (A1) functions as a film-forming binder. For the purposes of the present invention, the term "binder" is understood to mean a non-volatile component of the coating material composition that influences film formation in accordance with DIN EN ISO 4618 (German edition, date: March 2007). Therefore, the pigments and / or fillers contained therein are not included in the term "binder". Preferably, at least one (meth)acrylic copolymer is the main binder of the coating material composition. A binder component is referred to as the main binder in the sense of the present invention when there are no other binder components in the composition that are present in a higher proportion relative to the total weight of the coating material composition.

[0034] The terms "(meth)acrylic" or "(meth)acrylate" or "(meth)acrylic" include the meanings of "methacrylic" and / or "acrylic", "methacrylic" and / or "acrylic", or "methacrylate" and / or "acrylate", respectively, in the context of the present invention. Therefore, a "(meth)acrylic copolymer" in general can be formed from "acrylic monomers" only, "methacrylic monomers" only, or "acrylic and methacrylic monomers". However, polymerizable monomers other than acrylic and / or methacrylic monomers, such as styrene, can also be contained in a "(meth)acrylic copolymer". In other words, a (meth)acrylic polymer can be, but does not have to be, composed of only acrylic monomer units and / or methacrylic monomer units. The notation "(meth)acrylate polymer or copolymer" or "(meth)acrylic polymer or copolymer" is intended to mean that the polymer / copolymer (polymer backbone / main chain) is predominantly formed, i.e., preferably more than 50% or more than 75% of the monomer units used are formed from monomers having (meth)acrylate groups. In the production of (meth)acrylic copolymers, preferably more than 50% or more than 75% of the monomers therefore have (meth)acrylate groups. However, the use of additional monomers as comonomers, such as copolymerizable vinyl monomers, for example, the use of styrene for its production, is not excluded.

[0035] The (meth)acrylic copolymer (A1) is OH-functional. Hydroxyl-containing monomers include hydroxyalkyl esters of acrylic acid or methacrylic acid that can be used to prepare (A1). Non-limiting examples of hydroxyl-functional monomers include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, propylene glycol mono(meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, pentaerythritol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, their reaction products with epsilon-caprolactone, and other hydroxyalkyl (meth)acrylates having branched or linear alkyl groups of up to about 10 carbons, and mixtures thereof, where the term "(meth)acrylate" refers to either or both of the methacrylate ester and the acrylate ester. Generally, at least about 5% by weight of hydroxyl-functional monomers are included in the polymer. Hydroxyl groups on vinyl polymers, such as acrylic polymers, can be generated by other means, for example, by ring-opening of the glycidyl group from copolymerized glycidyl methacrylate with an organic acid or amine.

[0036] Hydroxyl functionality may also be introduced through thio-alcohol compounds, including, but not limited to, 3-mercapto-1-propanol, 3-mercapto-2-butanol, 11-mercapto-1-undecanol, 1-mercapto-2-propanol, 2-mercaptoethanol, 6-mercapto-1-hexanol, 2-mercaptobenzyl alcohol, 3-mercapto-1,2-propanediol, 4-mercapto-1-butanol, and combinations thereof. Any of these methods can be used to prepare useful hydroxyl-functional acrylic polymers.

[0037] Examples of suitable comonomers that can be used include, but are not limited to, α,β-ethylenically unsaturated monocarboxylic acids containing 3 to 5 carbon atoms, such as acrylic acid, methacrylic acid, and crotonic acid, and alkyl and cycloalkyl esters, nitriles, and amides of acrylic acid, methacrylic acid, and crotonic acid; α,β-ethylenically unsaturated dicarboxylic acids and anhydrides containing 4 to 6 carbon atoms, monoesters and diesters of these acids; vinyl esters, vinyl ethers, vinyl ketones, and aromatic or heterocyclic aliphatic vinyl compounds. Representative examples of suitable esters of acrylic acid, methacrylic acid and crotonic acid are esters from the reaction with saturated aliphatic alcohols containing 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, hexyl, 2-ethylhexyl, dodecyl, 3,3,5-trimethylhexyl, stearyl, lauryl, cyclohexyl, alkyl-substituted cyclohexyl, alkanol-substituted cyclohexyl, such as 2-tert-butyl and 4-tert-butylcyclohexyl, 4-cyclohexyl-1-butyl, 2-tert-butylcyclohexyl, 4-tert-butylcyclohexyl, 3,3,5,5-tetramethylcyclohexyl, tetrahydrofurfuryl. , and isobornyl acrylate, isobornyl methacrylate, and isobornyl crotonate; unsaturated dialkanonic acids and anhydrides, such as fumaric acid, maleic acid, itaconic acid and anhydride, and their mono- and diesters with alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and tert-butanol, such as maleic anhydride, maleic acid dimethyl ester, and maleic acid monohexyl ester; vinyl acetate, vinyl propionate, vinyl ethyl ether, and vinyl ethyl ketone; styrene, a-methylstyrene, vinyltoluene, 2-vinylpyrrolidone, and p-tert-butylstyrene.

[0038] The (meth)acrylic polymer (A1) can be prepared by conventional techniques, for example, by heating the monomers in the presence of a polymerization initiator and, optionally, a chain transfer agent. The polymerization can be carried out, for example, in solution. Typical initiators include organic peroxides, such as dialkyl peroxides, for example, di-t-butyl peroxide, peroxyesters, for example, t-butylperoxy 2-ethylhexanoate and t-butyl peracetate, peroxydicarbonates, diacyl peroxides, hydroperoxides, for example, t-butyl hydroperoxide and peroxyketals; azo compounds, for example, 2,2'-azobis(2-methylbutanenitrile) and 1,1'-azobis(cyclohexanecarbonitrile); and combinations thereof. Typical chain transfer agents are mercaptans, such as octyl mercaptan, n- or tert-dodecyl mercaptan; hydrogenated compounds, thiosalicylic acid, mercaptoacetic acid, mercaptoethanol, and other thiol alcohols already mentioned, as well as dimeric alpha-methylstyrene.

[0039] The polymerization reaction is typically carried out at a temperature of about 20°C to about 200°C. The reaction can conveniently be carried out at the temperature at which the solvent or solvent mixture refluxes, although with proper adjustments, temperatures below reflux can be maintained. The initiator should be selected to match the temperature at which the reaction will be carried out, so that its half-life at that temperature should preferably be about 30 minutes or less. Further details on addition polymerization are generally available in the polymer art, and further details on the polymerization of mixtures containing (meth)acrylate monomers are readily available in the polymer art. The solvent or solvent mixture is typically heated to the reaction temperature, and the monomer and initiator(s) are added at a controlled rate over a period typically between 2 and 6 hours. A chain transfer agent or additional solvent may be added at a controlled rate during this time. The temperature of the mixture is then maintained for a period to complete the reaction. Optionally, additional initiator may be added to ensure complete conversion.

[0040] The at least one (meth)acrylic polymer (A1) is preferably present in the clearcoat coating material composition in an amount ranging from 5.0 wt. % to 85.0 wt. %, based on the total solids content of the coating material composition. More preferably, the at least one (meth)acrylic polymer (A1) is present in the clearcoat coating material composition in an amount ranging from 10.0 wt. % to 80.0 wt. %, even more preferably from 15.0 wt. % to 75.0 wt. %, even more preferably from 20.0 wt. % to 70.0 wt. %, still more preferably from 25.0 to 65.0 wt. %, and most preferably from 30.0 to 60.0 wt. %, in each case based on the total solids content of the coating material composition.

[0041] In addition to at least one (meth)acrylic copolymer, the coating material composition of the present invention may also contain at least one further polymer as component (A5), which also functions as a binder and is different from both (A1) and (A2), but also different from (B1). The term "polymer" is known to those skilled in the art and, for the purposes of the present invention, includes polyadducts and polymers as well as polycondensates. The term "polymer" includes both homopolymers and copolymers.

[0042] Such optional component (A5) can preferably crosslink with the crosslinkable functional groups of the crosslinking agent (B1) and contain crosslinkable groups for this purpose. The crosslinkable groups may also be OH groups, as in the case of (A1), but may also be different therefrom, i.e., selected from the group consisting of primary amino groups, secondary amino groups, thiol groups, carboxyl groups and carbamate groups. Preferably, the optionally present component (A5) has functional hydroxyl groups (OH groups) and / or carbamate groups, in particular hydroxyl groups.

[0043] Optional component (A5) may be, for example, a carbamate-functional (meth)acrylic copolymer, which may additionally contain OH groups. Similarly, for example, polyethers, polyurethanes, natural oil-based polyols, such as those available under the trade name Polycin® from Vertellus Specialties Inc., Indianapolis, Ind., e.g., castor oil-based polyols, may be used as component (A5).

[0044] Branched OH-functional polyesters as component (A2) The at least one branched OH-functional polyester (A2) is present in the clearcoat coating material composition in an amount ranging from 1.0 wt.-% to 15.0 wt.-%, based on the total solids content of the coating material composition. Preferably, the at least one branched OH-functional polyester (A2) is present in the clearcoat coating material composition in an amount ranging from 1.1 wt.-% to 13.5 wt.-%, more preferably from 1.5 wt.-% to 12.5 wt.-%, even more preferably from 2.0 wt.-% to 12.0 wt.-%, still more preferably from 3.0 to 11.5 wt.-%, and most preferably from 4.0 to 10.5 wt.-%, in each case based on the total solids content of the coating material composition.

[0045] Preferably, the at least one branched OH-functional polyester (A2) is a polyester polyol. Preferably, the at least one branched OH-functional polyester (A2) has more than two OH groups.

[0046] Preferably, the at least one branched OH-functional polyester (A2) additionally comprises carboxylic acid groups. Preferably, the at least one branched OH-functional polyester (A2) has an acid number of less than 20 mg KOH / g of polyester solids, more preferably an acid number of 3 to 15 mg KOH / g of polyester solids, even more preferably an acid number in the range of 5 to 12 mg KOH / g of polyester solids.

[0047] Preferably, the at least one branched OH-functional polyester (A2) has an OH number in the range of 100 to 145 mg KOH / g of polyester solids, more preferably in the range of 115 to 130 mg KOH / g of polyester solids.

[0048] Suitable polyesters for use as component (A2) in the coating material composition of the present invention are disclosed, for example, in WO2016 / 008655 A1.

[0049] At least one branched OH-functional polyester as component (A2) is prepared by the steps (a), (b) and (c), i.e. (a) reacting at least one polyol containing at least three OH groups with at least one aliphatic dicarboxylic acid having 6 to 36 carbon atoms and / or its anhydride and / or its ester to form an OH-functional first intermediate product; (b) reacting the first intermediate product from step (a) with at least one cyclic carboxylic acid anhydride to form a carboxylic acid functional second intermediate product; (c) reacting the second intermediate product from step (b) with at least one epoxide-functional compound having one epoxide group to form a branched OH-functional polyester; can be obtained by carrying out

[0050] Preparation of component (A2) - step (a) The aliphatic dicarboxylic acids and / or anhydrides and / or esters thereof having 6 to 36 carbon atoms may be linear, branched or cyclic, whereby the cyclic dicarboxylic acids most preferably contain an acyclic segment of at least about 6 carbon atoms.

[0051] Non-limiting examples of suitable dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid (brassylic acid), dodecanedioic acid, traumatic acid, hexadecanedioic acid (thapsic acid), octadecanedioic acid, tetradecanedioic acid, and dimeric fatty acids having 36 carbon atoms. In various embodiments, α,ω-dicarboxylic acids and dimeric fatty acids having 36 carbon atoms are preferred. It is known that dimeric fatty acids having 36 carbon atoms can have multiple isomers. Dimeric fatty acids are commercially available, for example, from BASF under the trade name EMPOL®, from Arizona Chemical under the trade name UNIDYME™, from Croda International Plc under the trade name Pripol™, and from Emery Oleochemicals under the trade name EMERY® Dimer Acids. In the production of dimeric fatty acids, it is generally inevitable to obtain a product that still contains small amounts of monomeric fatty acids, as well as trimer fatty acids and higher fatty acids. Preferred dimeric fatty acids are those that contain only minimal amounts of monomeric fatty acids and trimer or higher fatty acids.

[0052] Anhydrides and / or esters of dicarboxylic acids having 6 to 36 carbon atoms include their monoesters or diesters with aliphatic alcohols having 1 to 4 carbon atoms, preferably methyl esters and ethyl esters, as well as anhydrides. The term "anhydride" includes intramolecular anhydrides and intermolecular anhydrides. Examples of intermolecular anhydrides include anhydrides formed by condensation reaction of two carboxyl groups of the aforementioned dicarboxylic acid molecules and an anhydride of the aforementioned dicarboxylic acid with an inorganic acid such as hydrochloric acid.

[0053] An aliphatic dicarboxylic acid having 6 to 36 carbon atoms is reacted with a polyol containing at least three hydroxyl groups, which may be primary, secondary, and / or tertiary.

[0054] The polyol may be selected from the group consisting of triols, triol dimers, tetrols, tetrol dimers, tetrol trimers, and sugar alcohols. Non-limiting examples of suitable polyols having three or more hydroxyl groups include glycerol, trimethylolmethane, trimethylolethane, trimethylolpropane, 2,2,3-trimethylolbutane-1,4-diol, 1,2,4-butanetriol, 1,2,6-hexanetriol, tris(hydroxymethyl)aminomethane, tris(hydroxyethyl)amine, tris(hydroxypropyl)amine, erythritol, pentaerythritol, diglycerol, higher condensates of triglycerol or glycerol, di(trimethylolpropane), di(pentaerythritol), tri(pentaerythritol), pentaerythritol ethoxylate, pentaerythritol, glycerol ... tolpropoxylate, trishydroxymethylisocyanurate, tris(hydroxyethyl)isocyanurate (THEIC), tris(hydroxypropyl)isocyanurate, inositol, or sugars such as glucose, fructose or sucrose, for example sugar alcohols such as xylitol, sorbitol, mannitol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol) isomalt, polyetherols with a functionality of three or more, for example alcohols with a functionality of three, which react with ethylene oxide, propylene oxide and / or butylene oxide.

[0055] Preferably, the first polyol in step (a) is at least one of the group consisting of erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolethane, trimethylolpropane, trimethylolbutane, glycerol, ditrimethylolethane, ditrimethylolpropane, pentaerythritol ethoxylate and pentaerythritol propoxylate.

[0056] Preferably, in step (a) of preparing at least one branched OH-functional polyester as component (A2), the ratio of moles of polyol to moles of dicarboxylic acid and / or its anhydride and / or its ester is 2.0 to 2.2 moles, more preferably 2.0 to 2.07 moles of polyol per mole of dicarboxylic acid and / or its anhydride and / or its ester. Particularly preferably, on average one hydroxyl group of each polyol molecule is reacted with a dicarboxylic acid in step (a).

[0057] The esterification step (a) can be carried out by known standard methods. For example, this reaction is conventionally carried out at temperatures between about 60°C and about 280°C, if desired, in the presence of a suitable esterification catalyst. Typical catalysts for esterification polymerization include protonic acids and Lewis acids, such as sulfuric acid, para-toluenesulfonic acid, sulfates and hydrogen sulfates, such as sodium hydrogen sulfate, phosphoric acid, phosphonic acid, hypophosphorous acid, titanium alkoxides, and dialkyltin oxides, such as dibutyltin oxide, dibutyltin dilaurate, and lithium octoate, under reflux with a small amount of a suitable solvent as a tunable agent, such as an aromatic hydrocarbon, such as xylene, or a (cyclo)aliphatic hydrocarbon, such as cyclohexane. Non-limiting specific examples for polyesters include tin octoate or dibutyltin oxide. The acidic inorganic catalyst, organometallic catalyst, or organic catalyst can be used in an amount of 0.1% to 10% by weight, preferably 0.2% to 2% by weight, based on the total weight of the reactants. It may be desirable to carry out step (a) of the reaction without a catalyst in order to avoid or minimize side reactions during subsequent steps.

[0058] The esterification in step (a) may be carried out in bulk or in the presence of a solvent that is unreactive toward the reactants. Such a solvent is preferably an aprotic solvent. Non-limiting examples of suitable solvents include hydrocarbons, such as paraffins or aromatics. In some embodiments, it may be preferable to use n-heptane, cyclohexane, toluene, ortho-xylene, meta-xylene, para-xylene, a xylene isomer mixture, ethylbenzene, chlorobenzene, and ortho- and meta-dichlorobenzene. Other solvents that can be used in the absence of an acidic catalyst include ethers, such as dioxane tetrahydrofuran, and ketones, such as methyl ethyl ketone and methyl isobutyl ketone. A solvent can be used to assist in removing by-products of the esterification reaction by azeotropic distillation.

[0059] The amount of solvent that can be used can be at least 0.1% by weight, or at least 1% by weight, or at least 5% by weight, based on the weight of the starting reactants. Higher amounts of solvent can be used, but it is preferable to keep the concentration of the reactants high enough to allow the reaction to be carried out in a commercially viable length of time. Examples of ranges of solvent that can be utilized are 0.1% to about 20% by weight, or about 1% to about 15% by weight, or about 5% to about 10% by weight, in each case based on the weight of the starting reactants.

[0060] The reaction may be carried out in the presence of a water scavenger, such as molecular sieves, particularly molecular sieves 4 Å, MgSO 4 and Na 2 SO 4 .

[0061] The reaction of step (a) is preferably carried out at a temperature of 60°C to 250°C, more preferably at a temperature of 100°C to 240°C. Even more preferably, the reaction of step (a) is carried out at a temperature of 150°C to 235°C. The reaction time depends on known factors, including the temperature and concentration of the reactants, and the presence and identity of a catalyst, if any. Typical reaction times can be from about 1 to about 20 hours.

[0062] To minimize the final volatile organic content, as much of the solvent used to azeotrope the by-products from step (a) can be removed after completion of the step (a) reaction, as much as practical. Small amounts of solvent, selected for their potential in the final resin, can be used throughout the remainder of the synthesis, e.g., as a flush following the addition of reagents. Solvents that can react with active hydrogen-containing compounds, such as anhydrides or epoxides, e.g., hydroxy-functional solvents (e.g., monoethers of alcohols and glycols), are preferably avoided during both step (a) and subsequent reaction steps. After step (a), the reaction temperature is preferably kept below temperatures at which condensation-type esterification reactions can occur, e.g., below 150°C, to minimize the chance of condensation-type esterification reactions, which would have undesirable effects on molecular weight and structure after this stage of the synthesis. For example, further esterification could produce undesired branching or undesirably increased molecular weight. The temperature after step (a) and before carrying out step (b) may be kept below 145°C, preferably below 140°C, or even below 135°C, or below 130°C, depending on whether a catalyst is used during step (a) and depending on the nature of any catalyst used.

[0063] Production of component (A2) - step (b) The cyclic carboxylic acid anhydride reacts with at least one of the hydroxyl groups of the hydroxyl-functional first intermediate product to form a second intermediate composition having at least one carboxyl group. Preferably, the cyclic carboxylic acid anhydride reacts with all or substantially all of the hydroxyl groups of the first intermediate product to form the second intermediate product. The cyclic carboxylic acid anhydride reacted in step (b) can be either an aromatic cyclic anhydride or an aliphatic cyclic anhydride.

[0064] Preferably, the cyclic carboxylic acid anhydride is maleic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, succinic anhydride, trimellitic anhydride, methyltetrahydrophthalic anhydride, adipic anhydride, glutaric anhydride, malonic anhydride, itaconic anhydride, 5-methyl-5-nobornene dicarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, isatoic anhydride, diphenic anhydride, substituted anhydrides, particularly including lower alkyl substituted anhydrides. anhydrides such as butylsuccinic anhydride, hexylsuccinic anhydride, octylsuccinic anhydride, butylmaleic anhydride, pentylmaleic anhydride, hexylmaleic anhydride, octylmaleic anhydride, butylglutaric anhydride, hexylglutaric anhydride, heptylglutaric anhydride, octylglutaric anhydride, alkylcyclohexanedicarboxylic anhydrides, and alkylphthalic anhydrides such as 4-n-butylphthalic anhydride, hexylphthalic anhydride, and octylphthalic anhydride.

[0065] Even more preferably, the carboxylic acid anhydride comprises or is hexahydrophthalic anhydride.

[0066] The reaction of step (b) provides a second intermediate product having a carboxylic acid group for each molecule of cyclic carboxylic acid anhydride reacted with the hydroxyl-functional first intermediate product of step (a). Preferably, the equivalent ratio of cyclic carboxylic acid anhydride to the first intermediate product is 0.8 to 1.0 equivalents per equivalent of hydroxyl group, more preferably 0.85 to 1.0 equivalents, and most preferably 0.9 to 1.0 equivalents of anhydride group per equivalent of hydroxyl group. Particularly preferably, one molecule or substantially one molecule of hexahydrophthalic anhydride reacts with each hydroxyl group of the first intermediate product to form the second intermediate product. Most preferably, substantially all of the hydroxyl groups of the hydroxyl-functional first intermediate product react with the carboxylic acid anhydride to provide an ester of the hydroxyl group and the carboxylic acid group from the ring-opening of the cyclic anhydride.

[0067] Preferably, in step (b) of preparing at least one branched OH-functional polyester as component (A2), the equivalent ratio of hydroxyl groups of the first intermediate product to anhydride groups of the cyclic carboxylic acid anhydride is 1.0 to 1.25 equivalents of hydroxyl groups per carboxylic acid anhydride group.

[0068] The anhydride ring-opening reaction of step (b) is exothermic. The reaction temperature can be controlled, e.g., not to exceed about 150°C, by dividing the addition of the carboxylic acid anhydride reactant into two or more addition portions. For example, the first addition portion can be about one-third to about one-half of the carboxylic acid anhydride, and the second portion can be the balance of the carboxylic acid anhydride reacted in step (b). The temperature of the reaction mixture can be allowed to cool to about 90°C to 95°C before each addition portion. After the first addition portion is added, the reaction mixture can be heated to about 110°C to 115°C or higher, resulting in an exotherm that can allow the temperature of the reaction mixture to rise, but not exceed a target maximum, e.g., 150°C. After the exotherm, the reaction mixture can be cooled to about 90°C to 95°C for the addition of the second anhydride. Similarly, after the addition of the second anhydride is complete, the reaction mixture may be heated to about 110°C to 115°C or higher, after which the reaction exotherm (and additional heating, if necessary) is used to bring the temperature of the reaction mixture up to, for example, about 135°C to about 145°C, or about 140°C to about 145°C, where the reaction mixture is held to allow the reaction to go to completion. Again, the batch should preferably not exceed 150°C.

[0069] Production of component (A2) - step (c) In the third step (c), preferably at least two up to all of the carboxylic acid groups of the second intermediate product are reacted with an epoxide-functional compound having one epoxide group (i.e., a monoepoxide compound) to form a hyperbranched polyester polyol.

[0070] Monoepoxide compounds are well known in the art and have the general formula: [ka] wherein R1, R2, R3, and R4 are each independently hydrogen or an organic group, with the proviso that at least one of R1-R4 is other than hydrogen and may be unsaturated or contain a heteroatom, or two of R1-R4 may form a cyclic ring, which may be unsaturated or contain a heteroatom. It can be characterized by:

[0071] Particularly preferred monoepoxides of the above formula are those in which R=CH—O—(C=O) n -R a (wherein n is 0 or 1, and R a is a branched or straight-chain, saturated or unsaturated hydrocarbon residue having 1 to 30, preferably 1 to 20, more preferably 1 to 16, most preferably 4 to 14, or even more preferably 6 to 12 or 8 to 10 carbon atoms), and R2 = R3 = R4 = H. When n = 1, the formula represents a glycidyl ester, and when n = 0, the formula represents a glycidyl ether.

[0072] For example, the epoxide-functional compound may be an epoxy ester, particularly a glycidyl ester. Glycidyl esters can be prepared by reacting a monofunctional carboxylic acid with an epihalohydrin (e.g., epichlorohydrin) under conditions well known in the art. Examples of glycidyl esters are glycidyl acetate, glycidyl propionate, glycidyl methylmaleate, glycidyl stearate, glycidyl benzoate, and glycidyl oleate. Among useful glycidyl esters are those having alkyl groups containing 7 to 17 carbon atoms. Particularly preferred glycidyl esters are glycidyl esters of saturated tertiary monocarboxylic acids containing 9 to 11 carbon atoms. Preferably, the monofunctional carboxylic acid used to produce the glycidyl ester is a neoalkanoic acid, such as, without limitation, neodecanoic acid or neononanoic acid. Glycidyl esters of neoacids are commercially available, for example, under the trade name Cardura® from Momentive Specialty Chemicals, Inc., Columbus, Ohio.

[0073] Another useful class of monoepoxides are glycidyl ethers. Glycidyl ethers can be prepared by reacting a monofunctional alcohol (e.g., n-butanol, propanol, 2-ethylhexanol, dodecanol, phenol, cresol, cyclohexanol, or benzyl alcohol) with an epihalohydrin (e.g., epichlorohydrin). Useful glycidyl ethers include methyl glycidyl ether, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, pentyl glycidyl ether, hexyl glycidyl ether, heptyl glycidyl ether, octyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, undecyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, pentadecyl glycidyl ether, and hexadecyl glycidyl ether. , heptadecyl glycidyl ether, octadecyl glycidyl ether, nonadecyl glycidyl ether, eicosyl glycidyl ether, beneicosyl glycidyl ether, docosyl glycidyl ether, tricosyl glycidyl ether, tetracosyl glycidyl ether, pentacosyl glycidyl ether, decenyl glycidyl ether, undecenyl glycidyl ether, tetradecenyl glycidyl ether, hexadecenyl glycidyl ether, heptadecenyl glycidyl ether, octadecenyl glycidyl ether, nonadecenyl glycidyl ether, eicosenyl glycidyl ether, beneicosenyl glycidyl ether, docosenyl glycidyl ether, tricosenyl glycidyl ether, tetracosenyl glycidyl ether and pentacosenyl glycidyl ether.

[0074] In step (c), the equivalent ratio of carboxylic acid groups of the second intermediate product to epoxide groups of the epoxide-functional compound is 1.0 to 2.5 equivalents, or 1.0 to 2.0 equivalents, or 1.0 to 1.5 equivalents, or 1.0 to 1.3 equivalents, or 1.0 to 1.1 equivalents of carboxylic acid per equivalent of epoxide groups. The preferred range of equivalents of carboxylic acid groups to epoxide groups varies, depending on whether the embodiment is for a solvent-based or water-based coating composition.

[0075] Preferably, all or substantially all of the carboxyl groups of the second intermediate product are reacted with a monoepoxide compound.

[0076] Crosslinking agent as component (B1) The crosslinking agent as component (B1) is different from both components (A1) and (A2) and contains crosslinkable functional groups capable of crosslinking at least with OH functional groups. Preferably, the crosslinkable functional groups of the crosslinking agent are suitable for crosslinking at least with the OH groups of component (A1) and, optionally, also with the OH groups of component (A2).

[0077] Suitable crosslinkers (B1) are aminoplast crosslinkers having active methylol, methylalkoxy, or butylalkoxy groups, polyisocyanate crosslinkers, which may have blocked or unblocked (free) isocyanate groups, polyanhydride and polyepoxide functional crosslinkers or curing agents, which may be reactive with the hydroxyls of (A1) and with the hydroxyl and / or carboxylic acid groups of (A2).

[0078] Aminoplasts or amino resins are known to those skilled in the art. Aminoplasts are obtained by reacting activated nitrogen with a low molecular weight aldehyde, optionally followed by further reaction with an alcohol (preferably a monoalcohol having 1 to 4 carbon atoms, such as methanol, isopropanol, n-butanol, isobutanol, etc.) to form an ether group. Preferred examples of activated nitrogen include activated amines such as melamine, benzoguanamine, cyclohexylcarboguanamine, and acetoguanamine; ureas, including urea itself, thiourea, ethyleneurea, dihydroxyethyleneurea, and guanylurea; glycoluril; amides such as dicyandiamide; and carbamate-functional compounds having at least one primary carbamate group or at least two secondary carbamate groups. The activated nitrogen is reacted with a low molecular weight aldehyde. The aldehyde can be selected from formaldehyde, acetaldehyde, crotonaldehyde, benzaldehyde, or other aldehydes used to prepare aminoplast resins, but formaldehyde and acetaldehyde are preferred, with formaldehyde and acetaldehyde being particularly preferred. The active nitrogen group can be at least partially alkylolated with the aldehyde, or can be fully alkylolated; preferably, the active nitrogen group is fully alkylolated. The reaction can be catalyzed by an acid.

[0079] Any alkylol group formed by the reaction of the activated nitrogen with the aldehyde may be partially or fully etherified with one or more monofunctional alcohols. Suitable examples of monofunctional alcohols include, but are not limited to, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, benzyl alcohol, and the like. Monofunctional alcohols having 1 to 4 carbon atoms and mixtures thereof are preferred. The aminoplast may be at least partially etherified, and in various embodiments, the aminoplast is fully etherified. For example, the aminoplast compound may have multiple methylol and / or etherified methylol, butyrol, or alkylol groups, which may be present in any combination and with unsubstituted nitrogen hydrogens. Examples of suitable curing agent compounds include, but are not limited to, melamine-formaldehyde resins, including monomeric or polymeric melamine resins, as well as partially or fully alkylated melamine resins, and urea resins (e.g., methylol ureas, such as urea-formaldehyde resins, and alkoxy ureas, such as butylated urea-formaldehyde resins). One non-limiting example of a fully etherified melamine-formaldehyde resin is hexamethoxymethyl melamine.

[0080] The alkylol groups can self-react to form oligomeric and polymeric aminoplast crosslinkers. Useful materials are characterized by their degree of polymerization. For melamine-formaldehyde resins, it is preferred to use resins having a number average molecular weight of less than about 2000, more preferably less than 1500, and even more preferably less than 1000.

[0081] Coating compositions containing aminoplast crosslinkers may further include a strong acid catalyst to enhance the curing reaction. Such catalysts are well known in the art and include, for example, para-toluenesulfonic acid, dinonylnaphthalenedisulfonic acid, dodecylbenzenesulfonic acid, phenyl acid phosphate, monobutyl maleate, butyl phosphate, and hydroxyester phosphate. Strong acid catalysts are often blocked, for example, with amines.

[0082] Particularly for refinishing applications, polyisocyanate crosslinkers are commonly used. Examples of suitable polyisocyanate crosslinkers include, but are not limited to, alkylene polyisocyanates such as hexamethylene diisocyanate, 4- and / or 2,4,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate), 2,4'- and / or 4,4'-diisocyanatodicyclohexylmethane, 3-isocyanato-methyl-3,5,5-trimethylcyclohexylisocyanate, aromatic polyisocyanates such as 2,4'- and / or 4,4'-diisocyanatodiphenylmethane, 2,4- and / or 2,6-diisocyanatotoluene, naphthylene diisocyanate, and mixtures of these polyisocyanates. Generally, polyisocyanates having three or more isocyanate groups are preferably used, and these may be derivatives or adducts of diisocyanates. Useful polyisocyanates can be obtained by reacting an excess amount of isocyanate with water, polyols (e.g., ethylene glycol, propylene glycol, 1,3-butylene glycol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, hexamethylene glycol, cyclohexanedimethanol, hydrogenated bisphenol A, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, glycerin, sorbitol, or pentaerythritol), or by reacting an isocyanate with itself to give an isocyanate. Examples include biuret group-containing polyisocyanates, isocyanurate group-containing polyisocyanates, urethane group-containing polyisocyanates, carbodiimide group-containing polyisocyanates, allophanate group-containing polyisocyanates and uretdione group-containing polyisocyanates.

[0083] Curing catalysts for the urethane reaction, such as tin catalysts, can be used in the coating compositions. Typical examples are tin and bismuth compounds, including, but not limited to, dibutyltin dilaurate, dibutyltin oxide, and bismuth octoate. When used, catalysts are typically present in amounts of about 0.05 to 2 weight percent tin, based on the weight of the total nonvolatile content.

[0084] Preferably, the at least one crosslinker present as component (B1) is a polyisocyanate having two or more NCO groups, which is preferably unblocked. In this case, the coating material composition of the invention is naturally a 2K coating material composition.

[0085] Further optional components The coating material composition of the present invention may contain one or more commonly used additives depending on the desired application. For example, the coating material composition may contain at least one additive selected from the group consisting of reactive diluents, light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, plasticizers, initiators for free radical polymerization, adhesion promoters, flow control agents, film-forming aids, sag control agents (SCAs), flame retardants, corrosion inhibitors, drying agents, biocides, thickeners, and / or matting agents. These additives may be used in known and customary proportions. Preferably, the content of these additives is 0.01 to 20.0 wt. %, more preferably 0.05 to 15.0 wt. %, particularly preferably 0.1 to 10.0 wt. %, most preferably 0.1 to 7.5 wt. %, particularly preferably 0.1 to 5.0 wt. %, and most preferably 0.1 to 2.5 wt. %, based on the total weight of the coating material composition.

[0086] The preparation of the coating material compositions can be carried out using customary, known production and mixing methods and mixing units or using conventional dissolvers and / or stirrers.

[0087] Methods of the Invention A further subject of the present invention is a method for coating a substrate, said method comprising at least one step of applying the clear coat coating material composition of the present invention to an optionally pre-painted substrate, preferably via spray application, to form at least one coating film on the optionally pre-painted substrate, and at least one further step of curing said at least one coating film to obtain at least one cured coating layer on said substrate.

[0088] The method can be used for automotive OEM finishes, but can also be used for automotive refinish applications.

[0089] All preferred embodiments described herein above in connection with the coating material composition of the present invention are also preferred embodiments with respect to the method of the present invention as described above.

[0090] Preferably, the method of the present invention comprises at least steps (1), (2) and (3), i.e. (1) applying a basecoat coating material composition onto an optionally pre-painted substrate to form a first coating film on the optionally pre-painted substrate; (2) applying a second coating material composition to the first coating film present on the substrate obtained after step (1) before curing the first coating film to form a second coating film adjacent to the first coating film, wherein the second coating material composition is the clear coat coating material composition of the present invention; (3) a step of curing the first and second coating films together, the cured second coating film being the outermost layer of the formed multi-layer coating system, to obtain the cured first and second coating layers; Including, A method for producing a multi-layer coating system, optionally on a pre-coated substrate.

[0091] Preferably, at least step (2), and more preferably also step (1), is carried out via spray application.

[0092] The first coating film formed on the optionally previously coated substrate is an uncured coating film at this stage, and therefore both the first coating material composition and the second coating material composition are applied wet-on-wet.

[0093] The method of the present invention is particularly suitable for painting automotive bodies or parts thereof, including respective metal substrates, but also plastic substrates, such as polymeric substrates. As a result, the preferred substrate is an automotive body or part thereof.

[0094] Suitable metal substrates for use according to the present invention are all substrates that are commonly used and known to those skilled in the art.The substrates used according to the present invention are preferably metal substrates, more preferably steel; preferably selected from the group consisting of bare steel, cold rolled steel (CRS), hot rolled steel, galvanized steel, for example hot dip galvanized steel (HDG), alloy galvanized steel (for example, Galvalume®, Galvannealed or Galfan) and aluminum-based plated steel, aluminum-magnesium alloy, and also Zn / Mg alloy and Zn / Ni alloy.Particularly suitable substrates are used for the manufacture of automobile body parts or complete car bodies.

[0095] Preferably, thermoplastic polymer is used as plastic substrate.Suitable polymer is poly(meth)acrylate, including polymethyl (meth)acrylate, polybutyl (meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyester, including polycarbonate and polyvinyl acetate, polyamide, polyolefin, such as polyethylene, polypropylene, polystyrene, and also polybutadiene, polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymer (A-EPDM), ASA (acrylonitrile-styrene-acrylic ester copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), polyetherimide, phenolic resin, urea resin, melamine resin, alkyd resin, epoxy resin, polyurethane, including TPU, polyether ketone, polyphenylene sulfide, polyether, polyvinyl alcohol, and their mixtures. Polycarbonates and poly(meth)acrylates are particularly preferred.

[0096] The substrates used according to the present invention are preferably metal substrates that have been pretreated with at least one metal phosphate, such as zinc phosphate. This type of pretreatment by means of phosphating, which usually occurs after the substrate has been cleaned and before the substrate is electrocoated, is a pretreatment step that is customary, especially in the automotive industry.

[0097] As summarized above, the substrate used may be a pre-painted substrate, i.e., a substrate bearing at least one cured coating. The substrate used in step (1) may be pre-painted with a cured electrodeposition coating layer. The substrate may also be provided with at least one cured primer coating, for example, as at least one additional precoat. The term "primer" is known to those skilled in the art. A primer is typically applied after the substrate is provided with a cured electrodeposition coating layer. If a cured primer coating is also present, the cured electrodeposition coating is present underneath, preferably adjacent to the cured primer coating.

[0098] Preferably, the method of the present invention further comprises step (1a), which is carried out after step (1) and before step (2). In step (1a), the first coating film obtained after step (1) is evaporated, preferably for 1 to 20 minutes, more preferably for 2 to 15 minutes, and particularly for 5 to 10 minutes, before applying the second coating material composition in step (2). Preferably, step (1a) is carried out at a temperature not exceeding 40°C, more preferably at a temperature within the range of 18 to 30°C.

[0099] The term "evaporation" in the sense of the present invention means dehydration, in which at least some of the solvent and / or water is evaporated from the coating (i.e., from the formed coating layer) before the next coating material composition is applied and / or before curing is carried out. Curing is not carried out by evaporation at all.

[0100] Preferably, the method of the present invention further comprises step (2a), which is carried out after step (2) and before step (3). In step (2a), the second coating obtained after step (2) is evaporated, preferably for 1 to 20 minutes, more preferably for 2 to 15 minutes, particularly for 5 to 10 minutes, before carrying out step (3) of curing. Preferably, step (2a) is carried out at a temperature not exceeding 40°C, more preferably at a temperature in the range of 18 to 30°C.

[0101] In step (3) of the method of the present invention, the first and second coatings are cured together, i.e., simultaneously, with the cured second coating representing the outermost layer of the resulting multi-layer coating system obtained after step (3).

[0102] Each resulting cured coating represents a coating layer, and therefore, after carrying out step (3), a first and a second coating are formed on the optionally previously coated substrate, with the second layer being the outermost layer of the formed multi-layer coating system.

[0103] Preferably, step (3) is carried out at a temperature below 110°C, preferably below 105°C, specifically in the range of 15 to 75°C, or 15 to 65°C, for a period of 5 to 45 minutes, preferably 20 to 45 minutes, specifically 25 to 35 minutes.

[0104] The coated substrate of the present invention A further subject of the present invention is a coated substrate obtainable by the process according to the invention.

[0105] All preferred embodiments described hereinabove in relation to the coating material composition of the invention and the method of the invention are also preferred embodiments in relation to the coated substrate of the invention as described above.

[0106] Uses of the present invention A further subject of the present invention is the use of at least one branched OH-functional polyester (A2) as defined above and further defined hereinafter as a flow promoter and / or leveling agent in a clear coat coating material for spray application of said clear coat coating material onto an optionally pre-painted substrate.

[0107] Preferably, at least one branched OH-functional polyester is present in the application of the clearcoat coating material of the present invention.

[0108] All preferred embodiments described hereinabove in connection with the coating material composition of the invention, the method of the invention and the coated substrate of the invention are also preferred embodiments in connection with the aforementioned uses of the invention.

[0109] method 1. Nonvolatile Fraction The non-volatile fraction (solids or solid content) is determined in accordance with ASTM D-2369 (date: July 2010). This involves weighing 0.3 g of sample into a pre-dried aluminum dish, drying the dish with the sample in a drying cabinet at 110° C. for 60 minutes, cooling it in a desiccator, and then reweighing. The residue relative to the total amount of sample used corresponds to the non-volatile fraction.

[0110] 2. DOI and Appearance DOI (Distinctness of Image), an aspect of gloss characterized by the clarity of an object's image produced by reflection on a surface, is measured according to ASTM E 284-17. The highest and best rating is 10. When the measured DOI is ≦7 (at a 20° angle) due to the occurrence of dieback, the appearance is considered unacceptable. [Example]

[0111] The following examples further illustrate the present invention but are not to be construed as limiting the scope thereof.

[0112] 1. Production of branched polyester polyol used in the present invention Process (a) A reactor was charged with 12.01 parts by weight of trimethylolpropane, 6.30 parts by weight of adipic acid, and 1.13 parts by weight of mixed xylenes. The contents of the reactor were mixed and heated to 230°C. By-product water was removed as it formed, the temperature was maintained above 200°C for approximately 5 hours, then as much xylene as possible was removed and the reaction product (first intermediate product) was cooled to 90°C.

[0113] Process (b) Next, 8.39 parts by weight of molten hexahydrophthalic anhydride (60°C) and 4.52 parts by weight of ethyl 3-ethoxypropionate were added to the reactor. The contents of the reactor were stirred and heated to 115°C. After the exotherm peaked (keeping the temperature below 150°C), the contents of the reactor were heated to 136°C, then cooled again to 90°C, and an additional 16.78 parts by weight of molten hexahydrophthalic anhydride (60°C) was added, followed by a flash of 1.42 parts by weight of ethyl 3-ethoxypropionate. The contents of the reactor were stirred and heated to 115°C. After the exotherm peaked (keeping the temperature below 150°C), the contents of the reactor were heated to 145°C. The temperature was maintained at 145°C for 90 minutes, then cooled to 140°C. This formed a second intermediate.

[0114] Process (c) The temperature was maintained between 140°C and 148°C, and 37.40 parts by weight of Cardura™ E10-P was added over approximately 90 minutes, followed by a flash of 1.42 parts by weight of ethyl 3-ethoxypropionate. The reaction mixture was held at 145°C for 3 hours, then cooled and diluted with 5.32 parts by weight of Aromatic 100 and 5.31 parts by weight of n-butyl acetate. This resulted in a hyperbranched polyester polyol (PP) solution (80 wt.-% solids).

[0115] 2. Preparation of clear coat material coating composition 2.1 "A" Component for Making Comparative Example C1 The "A" component for making Comparative Example C1 was prepared by mixing the components listed in Table 2.1 in the order listed. "pbw" means parts by weight.

[0116] [Table 1]

[0117] Solus® 2300 is a commercially available cellulose-based product available from Eastman. The castor oil-based polyol has an OH number of 365 mg KOH / g and is commercially available. HALS is a commercially available hindered amine light stabilizer. The (meth)acrylic resin 1 dispersion has a solids content of about 50 wt.-% and a calculated T at about 75°C. g (Meth)acrylic Resin 2 is an organic solvent dispersion of an OH-functional (meth)acrylic resin having a solids content of about 69 wt.-%, a calculated T (glass transition temperature) of about 64°C, and a calculated hydroxyl equivalent weight of about 400 g solids / equivalent -OH. g and an organic solvent dispersion of an OH-functional (meth)acrylic resin having a calculated hydroxyl equivalent weight of about 449 g solids / equivalent -OH, the dispersion containing p-chlorobenzotrifluoride (PCBTF), the PCBTF being present in the dispersion in an amount of 42 wt.-% based on the total weight of all solvents present in the dispersion. (Meth)acrylic Resin 3 Dispersion has a solids content of about 43 wt.-%, a calculated T at about 74°C. g and an organic solvent dispersion of an OH-functional (meth)acrylic resin having a calculated hydroxyl equivalent weight of about 645 g solids / equivalent --OH.

[0118] 2.2 Component "A" for preparing Example I1 of the present invention The "A" component for preparing Inventive Example I1 was prepared by mixing the components listed in Table 2.1 in the order listed, followed by the addition of an additional 4.86 parts by weight of the branched polyester polyol solution described in Item 1.

[0119] 2.3 Clear Coat Painting Material Composition C1 (Comparative) The "A" component described above in Section 2.1 was mixed with a polyisocyanate curing agent as the "B" component using a mixing volume ratio of 2:1 ("A":"B"). A dispersion of HDI-based polyisocyanate curing agent (54-56 wt.-% solids content) was used as the curing agent "B" component. Thus, 95.14 parts by weight of the "A" component were mixed with 51.13 parts by weight of the "B" component. The resulting composition was then diluted up to 20 vol.-% with the aid of a diluent containing one or more organic solvents to a sprayable viscosity (14-18 mPa·s in a Ford #4 cup). The resulting Comparative Example C1 had a total solids content of 34-38 wt.-%.

[0120] 2.4 Clear Coat Painting Material Composition I1 (Invention) The "A" component described in Section 2.2 above was mixed with a polyisocyanate curing agent as the "B" component using a mixing volume ratio of 2:1 ("A":"B"). A dispersion of HDI-based polyisocyanate curing agent (54-56 wt.-% solids content) was used as the curing agent "B" component. Thus, 100 parts by weight of "A" component were mixed with 53.93 parts by weight of "B" component. The resulting composition was then diluted up to 20 vol.-% to a sprayable viscosity (14-18 mPa·s in a Ford #4 cup) using a diluent containing one or more organic solvents. The resulting inventive example I1 had a total solids content of 34-38 wt.-%. The amount of polyester (A2) present in the resulting coating material composition was 5.19 wt.-% based on the total content of the composition.

[0121] 2.5 "A" Component for Making Comparative Example C2 The "A" component for making Comparative Example C2 was prepared by mixing the components listed in Table 2.2 in the order listed. "pbw" means parts by weight.

[0122] [Table 2]

[0123] Solus® 2300 is a commercially available cellulose-based product available from Eastman. A solution containing Solus® 2300, used as one component, was prepared by adding 12.52 parts by weight of methyl acetate and 18.79 parts by weight of acetone to 47.10 parts by weight of PCBTF, mixing the solvents together with vigorous stirring, adding 18.59 parts by weight of Solus® 2300 with stirring, ensuring that the temperature of the mixture did not exceed 125°F (51.67°C), and adding 3.00 parts by weight of PCBTF. The mixture was ready for use once all components present therein were completely dissolved. (Meth)acrylic Resin 1 Dispersion, (Meth)acrylic Resin 2 Dispersion, and (Meth)acrylic Resin 3 Dispersion were the dispersions used in the preparation of the "A" component for preparing C1 and I1.

[0124] 2.6 "A" Component for Preparing Inventive Example I2 The "A" component for preparing Inventive Example I2 was made by mixing the components listed in Table 2.3 in the order listed, where "pbw" means parts by weight.

[0125] [Table 3]

[0126] The "A" component for preparing Inventive Example I2 corresponding to Table 2.3 corresponds to the "A" component for preparing Comparative Example C2 corresponding to Table 2.2, except that it additionally contains a hyperbranched polyester (6.01 parts by weight). The branched polyester polyol solution is that described in Item 1.

[0127] 2.7 Clear Coat Painting Material Composition C2 (Comparative) The "A" component described above in Section 2.5 was mixed with a polyisocyanate curing agent as the "B" component using a mixing volume ratio of 4:1 ("A":"B"). A dispersion of HDI-based polyisocyanate curing agent (54-56 wt.-% solids content) was used as the curing agent "B" component. Thus, 93.99 parts by weight of the "A" component was mixed with 25.27 parts by weight of the "B" component. The resulting composition was then diluted up to 15 vol.-% to a sprayable viscosity (14-18 mPa·s in a Ford #4 cup) using a diluent component containing one or more organic solvents. The resulting Comparative Example C2 had a total solids content of 34-38 wt.-%.

[0128] 2.8 Clear Coat Painting Material Composition I2 (Invention) The "A" component described in Section 2.6 above was mixed with a polyisocyanate curing agent as the "B" component using a mixing volume ratio of 4:1 ("A":"B"). A dispersion of HDI-based polyisocyanate curing agent (54-56 wt.-% solids content) was used as the curing agent "B" component. Thus, 100 parts by weight of "A" component were mixed with 27.01 parts by weight of "B" component. The resulting composition was then diluted up to 15 vol.-% to a sprayable viscosity (14-18 mPa·s in a Ford #4 cup) using a diluent containing one or more organic solvents. The resulting inventive example I2 had a solids content of 34-38 wt.-%. The amount of polyester (A2) present in the resulting coating material composition was 9.28 wt.-% based on the total solids content of the composition.

[0129] 3. Manufacturing of multi-layer coating systems 3.1 Multi-layer coating system MCC1 obtained using clear coat coating material composition C1 Substrates used were 30.48 × 40.64 centimeter (12 × 16 inch) steel panels bearing a cured primer coat, and a commercially available solvent-based system. A water-reducible basecoat material (BASF's 90-line waterborne metallic basecoat) was spray-applied onto the primer coat via a spraymation® machine. After evaporation for a maximum of 10 minutes at room temperature (23°C), comparative clearcoat coating material composition C1 was spray-applied wet-on-wet directly onto the uncured basecoat film after its preparation as described in Section 2.3 above. The coating process, including wet-on-wet application of the basecoat and clearcoat, was carried out at temperatures >90°F (>32.2°C) and >90% relative humidity (RH) to simulate relatively humid conditions. Both applied coatings were then cured together for 30 minutes at 60°C to obtain a substrate coated with multi-layer coating system MCC1.

[0130] 3.2 Multi-layer coating system MCI1 obtained using clear coat coating material composition I1 Substrates coated with the multilayer coating system MCI1 were obtained in the same manner as described above in section 3.1 for MCC1, with the exception that instead of the comparative clear coat coating composition C1, the clear coat coating composition I1 of the invention was used directly after its preparation as described above in section 2.4.

[0131] 3.3 Multi-layer coating system MCC2 obtained using clear coat coating material composition C2 Substrates coated with the multilayer coating system MCC2 were obtained in the same manner as described above in section 3.1 for MCC1, with the exception that instead of the comparative clear coat coating composition C1, the comparative clear coat coating composition C2 was used directly after its preparation as described above in section 2.7.

[0132] 3.4 Multi-layer coating system MCI2 obtained using clear coat coating material composition C2 Substrates coated with the multilayer coating system MCI2 were obtained in the same manner as described above in section 3.1 for MCC1, with the exception that instead of the comparative clear coat coating composition C1, the clear coat coating composition I2 of the invention was used directly after its preparation as described above in section 2.8.

[0133] 4. Properties of substrates coated with multi-layer coating systems Each substrate coated with one of the multi-layer coating systems MCC1, MCC2, MCI1, and MCI2 was rated for appearance (dieback) after cool down (immediately after coating) and again the next day, after 24 hours.

[0134] Dieback and DOI Dieback and also pinching was observed in the case of multi-coat systems MCC1 and MCC2, while no dieback and no pinching was observed in MCI1 and MCI2.

[0135] The DOI for MCC1 and MCC2 was <7, respectively, while the DOI measured for MCI1 and MCI2 was 8–9 in both cases.

[0136] These data show that the incorporation of the polyesters used in the present invention in dosage amounts into clearcoat coating compositions leads to improved appearance in that no dieback and no pinching was observed, even under hot and humid conditions. These data also show that the polyesters used in the present invention can be advantageously used as flow and leveling agents in clearcoat coating compositions.

Claims

1. (A1) at least one OH-functional (meth)acrylic copolymer as component (A1), (A2) Steps (a), (b) and (c), i.e. (a) reacting at least one polyol containing at least three OH groups with at least one aliphatic dicarboxylic acid having 6 to 36 carbon atoms and / or its anhydride and / or its ester to form an OH-functional first intermediate product; (b) reacting the first intermediate product from step (a) with at least one cyclic carboxylic acid anhydride to form a carboxylic acid functional second intermediate product; and (c) reacting the second intermediate product from step (b) with at least one epoxide-functional compound having one epoxide group to form a branched OH-functional polyester. obtained by carrying out at least one branched OH-functional polyester as component (A2); (B1) at least one crosslinking agent as component (B1), which is different from both components (A1) and (A2) and contains crosslinkable functional groups that can at least crosslink with OH functional groups; Including, A clearcoat coating material composition comprising: the at least one branched OH-functional polyester (A2) is present in the clearcoat coating material composition in an amount ranging from 1.0 wt.-% to 15.0 wt.-%, based on the total solids content of the coating material composition; A clearcoat coating material composition having a total solids content of >30-50 wt.-%, based on the total weight of the coating material composition.

2. 2. The clearcoat coating material composition of claim 1, wherein the at least one branched OH-functional polyester (A2) is present in the clearcoat coating material composition in an amount ranging from 1.0 wt.-% to 13.5 wt.-%, based on the total solids content of the coating material composition.

3. 3. The clear coat coating material composition according to claim 1, wherein the clear coat coating material composition is a one-component (1K) coating material composition or a two-component (2K) coating material composition, which is obtained by mixing at least one component (A) containing at least components (A1) and (A2) with at least one component (B) containing at least component (B1) and optionally further with an additional diluent component (C) containing at least one organic solvent (A3) before mixing with component (A) that has been stored separately from component (A), or which is obtained by mixing at least one component (A) containing at least components (A1) and (A2) with at least one component (B) containing at least component (B1) and optionally further with an additional diluent component (C) containing at least one organic solvent (A3) before mixing with component (A) that has been stored separately from component (A).

4. 4. The clear coat coating material composition according to claim 1, which is a solvent-based coating material composition and further comprises at least one organic solvent as component (A3).

5. 5. The clearcoat coating material composition according to claim 1, having a total solids content of >30 wt.-%, based on the total weight of the coating material composition.

6. 6. The clearcoat coating material composition according to claim 1, wherein the at least one branched OH-functional polyester (A2) is present in the clearcoat coating material composition in an amount ranging from 1.1 to 13.5 wt.-%, based in each case on the total solids content of the coating material composition.

7. 7. The clearcoat coating material composition of any one of claims 1 to 6, which does not contain more than 5 wt-% of pigments and / or fillers.

8. 8. The clearcoat coating material composition of any one of claims 1 to 7, which does not contain any effect pigments.

9. 9. The clearcoat coating material composition of claim 1, which is free of any pigments and / or fillers.

10. 10. The clearcoat coating material composition of claim 1, wherein the at least one crosslinker present as component (B1) is a polyisocyanate having two or more NCO groups.

11. 11. The clear coat coating material composition according to claim 1, wherein in step (a) of preparing at least one branched OH-functional polyester as component (A2), the ratio of moles of polyol to moles of dicarboxylic acid and / or its anhydride and / or its ester is 2.0 to 2.2 moles of polyol per mole of dicarboxylic acid and / or its anhydride and / or its ester.

12. 12. The clear coat coating material composition according to claim 1, wherein in step (b) of preparing at least one branched OH-functional polyester as component (A2), the equivalent ratio of hydroxyl groups of the first intermediate product to anhydride groups of the cyclic carboxylic acid anhydride is 1.0 to 1.25 equivalents of hydroxyl groups per carboxylic acid anhydride group.

13. 13. The clearcoat coating material composition of claim 1, wherein in step (c) of preparing the at least one branched OH-functional polyester as component (A2), the equivalent ratio of carboxylic acid groups of the second intermediate product to epoxide groups of the epoxide-functional compound is from 1.0 to 2.5 equivalents of carboxylic acid groups per equivalent of epoxide group.

14. 14. A method for coating a substrate, comprising at least one step of applying to an optionally pre-coated substrate at least one clear coat coating material composition according to any one of claims 1 to 13 to form at least one coating film on the optionally pre-coated substrate, and at least one further step of curing the at least one coating film to obtain at least one cured coating layer on the substrate.

15. At least steps (1), (2) and (3), i.e. (1) applying a base coat coating material composition onto an optionally pre-painted substrate to form a first coating film on the optionally pre-painted substrate; (2) applying a second coating material composition to the first coating film present on the substrate obtained after step (1) before curing the first coating film to form a second coating film adjacent to the first coating film, wherein the second coating material composition is the clear coat coating material composition according to any one of claims 1 to 14; (3) a step of curing the first and second coating films together, the cured second coating film being the outermost layer of the formed multi-layer coating system, to obtain the cured first and second coating layers; Including, 15. The method according to claim 14, wherein a multi-layer coating system is produced on an optionally pre-painted substrate.

16. 16. The method of claim 15, wherein at least step (2) is carried out via spray application.

17. A coated substrate obtainable by the method according to any one of claims 14 to 16.

18. 14. Use of at least one branched OH-functional polyester as component (A2) according to any one of claims 1 to 13 as a flow promoter and / or leveling agent in a clear coat coating material for spray application of said clear coat coating material onto an optionally previously painted substrate.

19. 19. The method of claim 18, wherein at least one branched OH-functional polyester is present in the application of the clearcoat coating material of any one of claims 1 to 13.

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