3 Wet Coating Methods for Preparing Multilayer Coating Systems

Abstract

The present invention relates to a method for preparing a multi-layer coating system on a substrate, which comprises at least the steps of applying a first primer coating composition to a substrate (step (1)), applying a second base coating composition to the first coating film formed in step (1) to form a second coating film before curing the first coating film (step (2)), applying a third clear coating composition to the second coating film formed in step (2) to form a third coating film before curing the second coating film (step (3)), and curing the first, second, and third coating films together (step (4)). A multi-layer coating system on a substrate, obtainable by the method of the present invention and the use of an amino resin (AR) as a migratory crosslinking agent, wherein one or two of the first, second and third coating compositions comprise at least one amino resin (AR) as a crosslinking agent prior to their use in steps (1), (2) and / or (3), and at least one remaining coating composition(s) of these coating compositions does not comprise any crosslinking agent but comprises at least one crosslinking catalyst (CLC1) prior to their use in steps (1), (2) and / or (3).

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a multilayer coating system on a substrate, comprising at least the steps of: (1) applying a first primer coating composition to a substrate; (2) applying a second base coating composition to the first coating film formed in step (1) before curing the first coating film to form a second coating film; (3) applying a third clear coating composition to the second coating film obtained in step (2) before curing the second coating film to form a third coating film; and (4) curing the first, second, and third coating films together, wherein steps (1), (2), and / or (3) The present invention relates to a method for preparing a multilayer coating system in which, prior to its use in step (1), (2), and / or (3), one or two of the first, second, and third coating compositions contain at least one amino resin (AR) as a crosslinking agent, and prior to its use in step (1), (2), and / or (3), at least one remaining coating composition (or more) of these coating compositions contains no crosslinking agent but contains at least one crosslinking catalyst (CLC1), a multilayer coating system on a substrate obtained by the present invention, and a method for using the amino resin (AR) as a mobile crosslinking agent. [Background technology]

[0002] In typical automotive painting methods, at least four layers are applied to a suitable metal substrate surface: electrodeposition coating (e-coat), primer, base coat, and clear coat. The e-coat and primer layers are generally applied to the substrate surface and cured. Then, the base coat formulation is applied with a solvent, and the solvent is flashed off in a high-temperature process. After the base coat has been properly prepared, the clear coat is applied. Finally, the painted substrate surface is passed through an oven at over 140°C to cure the base coat and clear coat.

[0003] While this conventional method is appropriate and widely used in the automotive industry, there is significant room for improvement. Firstly, reducing the energy, materials, or time required for manufacturing these coatings would yield substantial economic benefits due to their large-scale use. Automakers, in particular, would benefit from reducing the number and duration of high-temperature processes. Furthermore, lowering the temperatures at which these processes are carried out would also be beneficial. Additionally, there is a desire to develop "lightweight" vehicles. One way to significantly reduce vehicle weight is to replace heavy metal parts with lightweight plastic parts. However, many lightweight plastic substrate materials physically deform at curing temperatures above 130°C, posing a challenge to using lightweight plastics in conventional methods. Therefore, lowering the curing temperatures of the base coat and clear coat would allow for the use of plastics and other heat-sensitive substrates necessary for vehicle weight reduction. Furthermore, it is beneficial to use a one-component system that remains stable for extended periods without decomposition or premature curing, such as a two-component system where one component contains a curable resin / polymer and the other contains a crosslinking agent for the curable resin.

[0004] WO2018 / 019685A1 describes a low-temperature curing composite coating comprising a substrate and two coating layers on which solvent-based paint compositions are applied. Each composition comprises an OH-functional resin, a crosslinking agent, and a catalyst. The catalyst present in the first solvent-based basecoat composition catalyzes the crosslinking reaction of components present in the second solvent-based clearcoat composition, and the catalyst present in the second composition catalyzes the crosslinking reaction of components present in the first composition. Crosslinking occurs only after the migration of each catalyst to each adjacent layer has occurred. WO2018 / 019686A1 relates to a similar low-temperature curing composite coating comprising a substrate and two coating layers on which it is applied. However, in this case, the solvent-based paint composition as the second composition is applied only to one of the coating layers, i.e., the clearcoat layer, and the water-based paint composition as the first composition is applied to the other coating layer, i.e., the basecoat layer. Similarly, US2019 / 031910A1 also relates to a low-temperature curing composite coating comprising a substrate and two coating layers applied thereon. The first and second coating compositions described in WO2018 / 019685A1, WO2018 / 01968A1, and US2019 / 031910A1 each require the presence of both a crosslinking agent and a catalyst.

[0005] WO2019 / 020324A1 describes a double coating on a substrate comprising a first layer prepared from a polar composition having a nonpolar catalyst and a second layer prepared from a nonpolar composition having a polar catalyst. The polar and nonpolar compositions described in WO2019 / 020324A1 require the presence of both a crosslinking agent and a catalyst.

[0006] Therefore, there is a need for further and improved methods for providing multilayer coatings on substrates used in the automotive industry, which exhibit good mechanical and optical properties while enabling reductions in energy, materials, and curing time. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] WO2018 / 019685A1 [Patent Document 2] WO2018 / 019686A1 [Patent Document 3] US2019 / 031910A1 [Patent Document 4] WO2019 / 020324A1 [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, the fundamental objective of the present invention is to provide further and improved methods for providing multilayer coatings on substrates used in the automotive industry, in particular a method that can reduce materials, curing time and temperature, while the resulting multilayer coated substrate exhibits good mechanical and optical properties. [Means for solving the problem]

[0009] This objective is achieved by the subject matter of the claims of this application and by the preferred embodiments thereof described herein, i.e., by the subject matter of the invention described herein. [Modes for carrying out the invention]

[0010] The first object of the present invention is at least steps (1), (2), (3), and (4), (1) Applying a first coating composition to a pre-coated substrate, forming a first coating film on the pre-coated substrate, wherein the first coating film is a primer coating film, (2) Apply the second coating 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 film is a base coating film. (3) Apply the third coating composition to the second coating film present on the substrate obtained after step (2) before curing the second coating film, thereby forming a third coating film adjacent to the second coating film, wherein the third coating film is a clear coating film. (4) The first, second, and third coating films are cured together, and the cured third coating film is the outermost layer of the formed multilayer coating system, step A method for preparing a multilayer coating system on a substrate, comprising: The first, second, and third coating compositions are all different from each other, the first coating composition comprises at least one polymer (P1) having a crosslinkable functional group, the second coating composition comprises at least one polymer (P2) having a crosslinkable functional group, and the third coating product comprises at least one polymer (P3) having a crosslinkable functional group. Prior to use in step (1), (2), and / or (3), one or two of the first, second, and third coating compositions further comprises, independently of each other, at least one amino resin (AR) as a crosslinking agent having crosslinkable functional groups that can crosslink with both the crosslinkable functional groups of polymer (P1), polymer (P2), and polymer (P3); prior to use in step (1), (2), and / or (3), at least one remaining coating composition of these coating compositions contains no crosslinking agent, but independently of each other, comprises at least one crosslinking catalyst (CLC1) suitable for catalyzing the crosslinking reaction between the functional groups of the amino resin (AR) and both the functional groups of polymer (P1), polymer (P2), and polymer (P3); This is a method for preparing a multilayer coating system.

[0011] A further subject of the present invention is a multilayer coating system on a substrate obtained by the method of the present invention.

[0012] A further subject of the present invention is a method of using an amino resin (AR) having a crosslinkable functional group, wherein the amino resin (AR) is present in one or two of the first, second, and third coating compositions, each coating composition being different from the other, the first coating composition comprising at least one polymer (P1) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR), the second coating composition comprising at least one polymer (P2) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR), the third coating composition comprising at least one polymer (P3) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR), and at least one coating composition selected from the first, second, and third coating compositions is not present with the amino resin (AR) and does not contain any crosslinking agent, but comprises at least one crosslinking catalyst (CLC1) suitable for catalyzing the crosslinking reaction between the functional group of the amino resin (AR) and the functional groups of both polymer (P1), polymer (P2), and polymer (P3). The method involves applying a third coating composition to a coating obtained from a second coating composition before curing the second coating, and then transferring the amino resin from one or two coatings obtained from one or more coatings selected from the first, second, and third coating compositions containing an amino resin to at least one coating obtained from the remaining coating composition of at least one of these three coating compositions, thereby forming a third coating adjacent to the second coating, wherein the second coating is obtained by applying the second coating composition to a first coating obtained from the first coating composition before curing the first coating, and the second coating is adjacent to the first coating and preferably for subsequent crosslinking with both crosslinkable functional groups of polymer (P1), polymer (P2), and polymer (P3), catalyzed by at least a crosslinking catalyst (CLC1). This describes the usage of amino resin (AR).

[0013] Surprisingly, it has been found that in the method of the present invention, it is not necessary to incorporate a crosslinking agent into each coating composition used and applied in the method of the present invention. Rather, it is only necessary to incorporate at least one amino resin (AR) into one or two, preferably only one, of the three coating compositions used. Surprisingly, the amino resin (AR) can be partially transferred from (i) the first coating film to the second and third coating films, or (ii) the second coating film to the first and third coating films, or (iii) particularly from the third coating film to the first and second coating films after all the coating films have been applied by the wet-on-wet-on-wet (3W or 3-wet) method of the present invention. Similarly, since at least one coating composition containing no amino resin (AR) contains at least one crosslinking catalyst (CLC1), the crosslinking catalyst (CLC1) can also be transferred from the coating film obtained from the coating composition in which it was contained to other coating films after all the coating films have been applied by the wet-on-wet-on-wet method of the present invention. Thus, by the method of the present invention, once all the coating films are applied wet-on-wet, it is possible to transfer both the amino resin (AR) and the crosslinking catalyst (CLC1) originally contained in separate coating films. In particular, it is surprising that this is also possible for the 3-wet (wet-on-wet-on-wet) coating method.

[0014] Surprisingly, it has been found that by the method of the present invention, the curing step of curing all the applied coating films together is carried out at a temperature of less than 110°C, particularly less than 100°C, for a relatively short time of less than 30 minutes, and even less than 25 minutes. It is surprising that by using a coating composition containing no crosslinking agent, effective curing of all the coating films applied at such a low temperature can be achieved even though at least one of the coating films is applied. It is particularly surprising that sufficient transfer of the amino resin (AR) occurs to enable effective curing at such a temperature. In particular, it is surprising that this is also possible for the 3-wet (wet-on-wet-on-wet) coating method.

[0015] In the context of the present invention, for example, with respect to each paint composition used in the present invention, the term "comprising" preferably has the meaning of "consisting of". With respect to each paint composition used in the present invention, in addition to the essential components present therein, one or more additional components that are specifically identified below and are optionally included in each paint composition used in the present invention can be included therein. All of these components may be present in their preferred embodiments as specifically identified below in each case.

[0016] In relation to the amino resin (AR), crosslinking catalyst (CLC1) and (CLC2) present in any of the paint compositions used in the context of the present invention, the term "prior to its use or prior to their use" in a specific step of the method of the present invention preferably means that a specific component, namely (AR) or (CLC1) or (CLC2), is present as a component in each paint composition prior to using each paint composition in a specific step of the method of the present invention and also means that it (still) exists or still exists when any of these paint compositions are applied in any of the specific steps. However, any of these components can move from the paint film obtained by applying each paint composition to a further paint film applied thereon and / or a paint film already present below.

[0017] The method of the present invention The method of the present invention is a method for preparing and providing a multi-layer coating system on a substrate, including at least steps (1), (2), (3) and (4). However, the method may further include any additional optional steps.

[0018] Step (1) of the method In step (1) of the present invention, a first coating composition is applied to an optionally pre-coated substrate to form a first coating film on the optionally pre-coated substrate. The first coating film is a primer coating film. Therefore, the first coating composition is a primer coating composition. The term "primer" is known to those skilled in the art. Primers are usually applied after an electrodeposited curing coating layer has been applied to the substrate. In this case, the electrodeposited curing coating film is located beneath the primer coating film, preferably adjacent to the primer coating film.

[0019] The first coating film formed on a pre-coated substrate is an uncured coating film at this stage.

[0020] The method of the present invention is particularly suitable for painting the body or parts of an automobile vehicle, including not only metal substrates but also plastic substrates. Therefore, preferred substrates are automobile bodies or parts thereof.

[0021] The metal substrates used in the present invention are all commonly used and known to those skilled in the art. The substrates used in the present invention are preferably metal substrates, more preferably selected from the group consisting of steel, and more preferably steel selected from the group consisting of bare steel, cold-rolled steel (CRS), hot-rolled steel, galvanized steel such as hot-dip galvanized steel (HDG), alloy galvanized steel (e.g., Galvalume, hot-dip galvanized or Galfan, etc.), aluminum-plated steel, aluminum and magnesium, and furthermore, Zn / Mg alloys and Zn / Ni alloys. Particularly suitable substrates are parts or complete car bodies for the manufacture of automobiles.

[0022] The substrate used in the present invention is preferably a substrate pre-treated with at least one metal phosphate, such as zinc phosphate. This type of pre-treatment by phosphate treatment, which is usually performed after the substrate has been washed and before the substrate is electrodeposited, is a pre-treatment step that is commonly used, particularly in the automotive industry.

[0023] As described above, a pre-coated substrate, i.e., a substrate having at least one cured coating, may be used. The substrate used in step (1) may be pre-coated with an electrodeposition-cured coating layer.

[0024] Any step (1a) of this method Preferably, the method of the present invention further includes step (1a), which is performed after step (1) and before step (2). In step (1a), the first coating obtained after step (1) is flashed off for preferably 1 to 20 minutes, more preferably 1.5 to 15 minutes, particularly 2 to 10 minutes, and most preferably 3 to 6 minutes, before the application of the second coating composition in step (2). Preferably, step (1a) is performed at a temperature not exceeding 40°C, more preferably in the range of 18 to 30°C.

[0025] In the context of this invention, the term "flashing off" means drying in which at least a portion of the solvent and / or water evaporates from the coating film (i.e., from the formed coating layer) before the following coating composition is applied and / or cured. No curing occurs by flash-off.

[0026] Step (2) of this method In step (2) of the present invention, before curing the first coating film, the second coating composition is applied to the first coating film present on the substrate obtained after step (1), thereby forming the second coating film adjacent to the first coating film. In this way, both the first and second coating compositions are applied in a wet-on-wet manner.

[0027] The second coating is the base coating. Therefore, the second coating composition is the base coating composition. The term "base coat" is known to those skilled in the art and is defined, for example, in Roempp Lexikon, Paints and Printing Inks, Georg Thieme Verlag, 1998, 10th edition, page 57. Therefore, base coats are used in the coloring of automotive and general industrial coatings in order to produce coloring and / or optical effects by using a base coat as an intermediate coating composition. It is generally applied to a metal or plastic substrate, and in the case of a metal substrate, it is applied to a primer layer applied on an electrodeposited coating layer applied to the metal substrate, or in the case of refinishing, it is applied to an existing coating that also functions as a substrate. At least one clear coat film is additionally applied, especially to protect the base coat film from environmental impacts. The terms "clear coat," "clearcoat," or "clear coating" (clear paint, clear coating film) are also known to those skilled in the art and correspond to the transparent outermost layer of a multilayer coating structure applied to a substrate.

[0028] Any step (2a) of this method Preferably, the method of the present invention further includes step (2a), which is performed after step (2) and before step (3). In step (2a), the second coating obtained after step (2) is flashed off for preferably 1 to 20 minutes, more preferably 1.5 to 15 minutes, particularly 2 to 10 minutes, and most preferably 3 to 6 minutes, before the third coating composition is applied in step (3). Preferably, step (2a) is performed at a temperature not exceeding 40°C, more preferably in the range of 18 to 30°C.

[0029] Step (3) of this method In step (3) of the present invention, before curing the second coating film, the third coating composition is applied to the second coating film present on the substrate obtained after step (2), forming a third coating film adjacent to the second coating film. Thus, both the second and third coating compositions are applied wet-on-wet. The third coating film is a clear coating film. Therefore, the third coating composition is a clear coating composition. The term "clearcoat" is known to those skilled in the art.

[0030] Any step (3a) of this method Preferably, the method of the present invention further includes step (3a), which is performed after step (3) and before step (4). In step (3a), the third coating obtained after step (3) is flashed off for preferably 1 to 20 minutes, more preferably 3 to 12 minutes, and particularly 5 to 10 minutes, before performing the curing step (4). Preferably, step (3a) is performed at a temperature not exceeding 40°C, more preferably in the range of 18 to 30°C.

[0031] Preferably, steps (1a), (2a), and (3a) are all performed. Preferably, the flash-off time used in step (3a) exceeds the flash-off times used in each of steps (1a) and (2a).

[0032] Step (4) of this method In step (4) of the present invention, the first, second, and third coating films are cured together, that is, cured as a whole at the same time. The cured third coating film corresponds to the outermost layer of the multilayer coating system formed after step (4).

[0033] Each cured coating film corresponds to a coating layer. Therefore, after step (4), the first, second, and third coating layers are formed on an optionally pre-coated substrate, and the third layer becomes the outermost layer of the formed multilayer coating system.

[0034] Preferably, step (4) is carried out for 5 to 45 minutes, preferably 10 to 35 minutes, at a substrate temperature of less than 110°C, preferably less than 105°C, particularly in the range of 80 to 105°C or 80 to 100°C. The substrate temperature is measured with a thermocouple.

[0035] First, second, and third coating compositions, and first, second, and third coating films obtained therefrom. The first, second, and third coating compositions are all different from each other. The first coating composition comprises at least one polymer (P1) having a crosslinkable functional group, the second coating composition comprises at least one polymer (P2) having a crosslinkable functional group, and the third coating composition comprises at least one polymer (P3) having a crosslinkable functional group.

[0036] One or two of the first, second, and third coating compositions, i.e., strictly one or strictly two, preferably only one, independently contain at least one amino resin (AR) as a crosslinking agent before use in steps (1), (2), and / or (3), and at least one of the remaining coating compositions of these coating compositions before use in steps (1), (2), and / or (3), does not contain any crosslinking agent but independently contains at least one crosslinking catalyst (CLC1) before use in steps (1), (2), and / or (3). The at least one amino resin (AR) has functional groups that can crosslink with the crosslinkable functional groups of both polymers (P1), (P2), and (P3). Thus, it is clear that the amino resin (AR) is distinct from each of the polymers (P1), (P2), and (P3). At least one crosslinking catalyst (CLC1) is suitable for catalyzing crosslinking reactions between the functional groups of the amino resin (AR) and the functional groups of both polymers (P1), polymer (P2), and polymer (P3).

[0037] In the sense of the present invention, the term “free of any crosslinking agents” preferably means that no crosslinking agents are present in each coating composition before use in the method of the present invention. This means that no such crosslinking agents are intentionally added to any of the coating compositions used in the present invention. However, it cannot be denied that any residues of such crosslinking agents used to prepare, for example, some components present in the composition may still be present. Therefore, preferably, the amount of any crosslinking agents present in a “free of any crosslinking agents” coating composition is less than 1.0% by mass, or less than 0.5% by mass, most preferably less than 0.1% by mass, or less than 0.05% by mass, or less than 0.01% by mass, based on the total mass of the coating composition.

[0038] Preferably, one or two (or more) coating compositions selected from the first, second, and third coating compositions each independently contain at least one amino resin (AR) as a crosslinking agent before use in step (1), (2), and / or (3), and either contain no crosslinking catalyst at all before use in step (1), (2), and / or (3), or independently contain at least one crosslinking catalyst (CLC2) that is identical or different in amount to at least one crosslinking catalyst (CLC1) based on the total mass of each coating composition before use in step (1), (2), and / or (3), wherein the amount of crosslinking catalyst (CLC2) is lower than the amount of at least one crosslinking catalyst (CLC1) present in the at least one coating composition selected from the first, second, and third coating compositions that does not contain a crosslinking agent, based on the total mass of the coating composition before use in step (1), (2), and / or (3).

[0039] Preferably, the second and / or third coating composition independently comprises, before use in step (2) and / or (3), at least one amino resin (AR) as a crosslinking agent, and optionally, at least one crosslinking catalyst (CLC2) which is the same as or different from at least one crosslinking catalyst (CLC1), and the first and / or second coating composition (provided that, in the case of the second coating composition, it does not contain at least one amino resin (AR) as a crosslinking agent) independently comprises at least one crosslinking catalyst (CLC1) before use in step (1) and / or (2).

[0040] In particular, only the third coating composition contains, before its use in step (3), at least one amino resin (AR) as a crosslinking agent, and optionally at least one crosslinking catalyst (CLC2) that is the same as or different from at least one crosslinking catalyst (CLC1); the first and / or second, preferably the first or second coating composition, independently contain at least one crosslinking catalyst (CLC1) before its use in step (1) and / or (2), preferably before its use in step (1) or (2); or only the second coating composition contains, before its use in step (2), at least one amino resin (AR) as a crosslinking agent, and optionally at least one crosslinking catalyst (CLC2) that is the same as or different from at least one crosslinking catalyst (CLC1); the first and / or third, preferably the first or third coating composition, independently contain at least one crosslinking catalyst (CLC1) before its use in step (1) and / or (3), preferably before its use in step (1) or (3).

[0041] However, most preferably, only the third coating composition contains, before its use in step (3), at least one amino resin (AR) as a crosslinking agent, and optionally, at least one crosslinking catalyst (CLC2) which is the same as or different from at least one crosslinking catalyst (CLC1), while the first and / or second, preferably the first or second coating composition, independently contain at least one crosslinking catalyst (CLC1) before its use in step (1) and / or (2), preferably before its use in step (1) or (2).

[0042] If at least one crosslinking catalyst (CLC2) is present in one or two (or more) coating compositions selected from the first, second, and third coating compositions, and contains at least one amino resin (AR) as a crosslinking agent before its use in step (1), (2), and / or (3), then the relative mass ratio of at least one crosslinking catalyst (CLC1) present in at least one coating composition selected from the first, second, and third coating compositions that does not contain any crosslinking agent before its use in step (1), (2), and / or (3), to the at least one crosslinking catalyst (CLC2), is at least 5:1, more preferably at least 4:1, and even more preferably at least 3:1, based on the total mass of each coating composition.

[0043] Preferably, the first paint composition is a 1K (1 component) 1K paint composition. Preferably, the second paint composition is a 1K (1 component) paint composition. Preferably, the third paint composition is a 1K (1 component) paint composition.

[0044] Preferably, the first paint composition is a solvent-type, i.e., organic solvent (multiple types are possible) system, or water-based, i.e., aqueous, more preferably a solvent-type paint composition; the second paint composition is a solvent-type or water-based paint composition; and the third paint composition is a solvent-type paint composition.

[0045] In relation to any of the coating compositions used in the present invention, the terms "aqueous" or "water-based" are understood to mean, preferably for the purposes of the present invention, that water is present as a solvent and / or diluent, as the main component of all solvents and / or diluents present in each coating composition used in the present invention, preferably in an amount of at least 35% by mass, based on the total mass of the electrodeposition coating composition of the present invention. Organic solvents may be further present in a smaller proportion, preferably less than 20% by mass.

[0046] Each paint composition used in the present invention preferably contains, if the composition is water-based, at least 40% by mass, more preferably at least 45% by mass, very preferably at least 50% by mass, and more particularly at least 55% by mass of water, based on the total mass of the paint composition.

[0047] Each paint composition used in the present invention preferably contains, based on the total mass of the paint composition, a fraction of an organic solvent in the range of less than 20% by mass, more preferably 0 to less than 20% by mass, very preferably 0.5 to 20% by mass, or up to 17.5% by mass, or up to 15% by mass, or up to 10% by mass, when the composition is water-based. As the organic solvent, all conventional organic solvents known to those skilled in the art may be used. The term "organic solvent" is known to those skilled in the art, in particular by Council Directive 1999 / 13 / EC of 11 March 1999. Examples of such organic solvents include heterocyclic, aliphatic, or aromatic hydrocarbons, monohydric or polyhydric alcohols, particularly methanol and / or ethanol, ethers, esters, ketones, and amides, such as N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, toluene, xylene, butanol, ethyl glycol, and butyl glycol, as well as their acetates, butyl diglycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone, or mixtures thereof.

[0048] In relation to any of the coating compositions used in the present invention, the term “solvent-type” is understood to mean that, for the purposes of the present invention, an organic solvent(s) as a solvent and / or diluent is preferably present in an amount of at least 35% by mass, based on the total mass of the electrodeposition coating composition of the present invention, as the main component of all solvents and / or diluents present in each coating composition used in the present invention. Water may be further present in a smaller proportion, preferably less than 20% by mass.

[0049] Each paint composition used in the present invention preferably contains, based on the total mass of the paint composition, at least 40% by mass, more preferably at least 45% by mass, very preferably at least 50% by mass, and more particularly at least 55% by mass of an organic solvent (multiple types may be included), when the composition is solvent-type. Examples of such organic solvents include heterocyclic, aliphatic, or aromatic hydrocarbons, monohydric or polyhydric alcohols, particularly methanol and / or ethanol, ethers, esters, ketones, and amides, such as N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, toluene, xylene, butanol, ethyl glycol, and butyl glycol, as well as their acetates, butyl diglycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone, or mixtures thereof.

[0050] Each paint composition used in the present invention preferably contains, when the composition is solvent-based, a water fraction in the range of less than 20% by mass, more preferably 0 to less than 20% by mass, very preferably 0.5 to 20% by mass, or up to 17.5% by mass, or up to 15% by mass, or up to 10% by mass, based on the total mass of the paint composition.

[0051] The solid content of each coating composition used in the present invention is, independently of each other, preferably in the range of 5 to 45% by mass, more preferably 5 to 40% by mass, very preferably 7.5 to 40% by mass, even more particularly 7.5 to 35% by mass, and most preferably 10 to 35% by mass or 15 to 30% by mass, based on the total mass of the coating composition. The solid content, in other words, the non-volatile fraction, is determined by the method described later.

[0052] Each paint composition used in the present invention can be used as an OEM coating composition or for refinishing purposes, and is preferably used for OEM purposes.

[0053] The mass percentage (wt.-%, % by weight) and amount of all components present in each coating composition used in the present invention are, in each case, based on the total mass of each coating composition, totaling 100% by mass.

[0054] Polymers (P1), (P2), and (P3) The first coating composition contains at least one polymer (P1) having a crosslinkable functional group. The second coating composition contains at least one polymer (P2) having a crosslinkable functional group. The third coating composition contains at least one polymer (P3) having a crosslinkable functional group.

[0055] Polymers (P1), (P2), and (P3) may be the same or different from each other. Each of these polymers is different from the amino resin (AR).

[0056] Polymers (P1), (P2), and (P3) function as film-forming binders. For the purposes of this invention, the term "binder" is understood, according to DIN EN ISO 4618 (German version, dated March 2007), to be a non-volatile component of the paint composition that is involved in film formation. Therefore, pigments and / or fillers contained herein are not included in the term "binder." Preferably, at least one polymer is the main binder of each paint composition. As the main binder in the sense of this invention, preferably, the binder component refers to the binder component that is present in a higher proportion based on the total mass of the paint composition when no other binder components are present in the paint composition.

[0057] The term "polymer" is known to those skilled in the art and, for the purposes of this invention, includes polyadditives and polymers, as well as polycondensates. The term "polymer" includes both homopolymers and copolymers.

[0058] Each polymer (P1), (P2), and (P3) has a crosslinkable functional group that can crosslink with the crosslinkable functional group of the amino resin (AR), i.e., a crosslinkable functional group that enables a crosslinking reaction with the crosslinkable functional group of the amino resin (AR). The crosslinkable functional groups of polymers (P1), (P2), and (P3) may be the same or different from each other. Any general crosslinkable functional group known to those skilled in the art may exist. The crosslinkable functional groups of each polymer (P1), (P2), and (P3) are independently selected from the group consisting of primary amino groups, secondary amino groups, hydroxyl groups, thiol groups, carboxyl groups, and carbamate groups. Preferably, each polymer (P1), (P2), and (P3) has a functional hydroxyl group (OH- group) and / or a carbamate group, particularly a hydroxyl group.

[0059] Each polymer (P1), (P2), and (P3) is preferably independently selected from the group consisting of polyurethane, polyurea, polyester, polyamide, polyether, poly(meth)acrylate, and / or copolymers of the structural units of the polymers, particularly polyurethane-poly(meth)acrylate and / or polyurethane-polyurea, and hybrid polymers thereof. In particular, each polymer (P1), (P2), and (P3) is preferably independently selected from the group consisting of polyurethane, polyester, poly(meth)acrylate, and / or copolymers of the structural units of the polymers. In the context of the present invention, the terms "(meth)acrylic" or "(meth)acrylate" include, in each case, the meanings of "methacrylic" and / or "acrylic" or "methacrylate" and / or "acrylate".

[0060] Preferred polyurethanes are described, for example, in German Patent Application DE19948004A1, page 4, line 19 to page 11, line 29 (polyurethane prepolymer B1), European Patent Application EP0228003A1, page 3, line 24 to page 5, line 40, European Patent Application EP0634431A1, page 3, line 38 to page 8, line 9, and International Patent Application WO92 / 15405, page 2, line 35 to page 10, line 32.

[0061] Preferred polyesters are described, for example, in DE4009858A1, column 6, line 53 to column 7, line 61 and column 10, line 24 to column 13, line 3, or in WO2014 / 033135A2, page 2, line 24 to page 7, line 10 and page 28, line 13 to page 29, line 13. Similarly preferred polyesters are those having a dendritic structure, such as those described in WO2008 / 148555A1. These can be used not only in clear coats but also in certain aqueous base coats.

[0062] Preferred polyurethane-poly(meth)acrylate copolymers (e.g., (meth)acrylic polyurethanes) and their preparations are described, for example, in WO91 / 15528A1, page 3, line 21 to page 20, line 33, and DE4437535A1, page 2, line 27 to page 6, line 22.

[0063] Preferred poly(meth)acrylates can be prepared by multi-step free-radical emulsion polymerization of olefinic unsaturated monomers in water and / or organic solvents. Seed-core-shell polymers (SCS polymers) are particularly preferred, for example. Such polymers or aqueous dispersants containing such polymers are known, for example, from WO2016 / 116299A1. A particularly preferred seed-core-shell polymer is a polymer, preferably having an average particle size of 100 to 500 nm, which can be prepared by the sequential free-radical emulsion polymerization of three preferably different monomer mixtures (A1), (B1), and (C1) of olefinic unsaturated monomers in water, wherein mixture (A1) contains at least 50% by mass of monomers having a solubility in water of less than 0.5 g / l at 25°C, the polymer prepared from mixture (A1) has a glass transition temperature of 10 to 65°C, mixture (B1) contains at least one polyvalent unsaturated monomer, the polymer prepared from mixture (B1) has a glass transition temperature of -35 to 15°C, and the polymer prepared from mixture (C1) has a glass transition temperature of -50 to 15°C, i. first mixture (A1) is polymerized, ii. then mixture (B1) is polymerized in the presence of the polymer formed in i., and iii. then mixture (C1) is polymerized in the presence of the polymer formed in ii. It is preferable that all three mixtures are different from each other.

[0064] Preferred polyurethane-polyurea copolymers are polyurethane-polyurea particles, preferably having an average particle size of 40 to 2000 nm, where each reacted polyurethane-polyurea particle comprises a polyurethane prepolymer containing at least one isocyanate group containing an anionic group and / or a group that can be converted to anionic groups, and at least one polyamine containing two primary amino groups and one or two secondary amino groups. Preferably, such copolymers are used in the form of aqueous dispersants. Such polymers can, in principle, be prepared, for example, by conventional polyaddition of polyisocyanates with polyols and polyamines.

[0065] In particular, each polymer (P1) and (P2) is hydroxyl-functional and more preferably has an OH value in the range of 15 to 200 mg KOH / g, more preferably 20 to 150 mg KOH / g. Most preferred are the corresponding hydroxyl-functional polyurethane-poly(meth)acrylate copolymer, hydroxyl-functional polyester, hydroxyl-poly(meth)acrylate copolymer, and / or hydroxyl-functional polyurethane-polyurea copolymer.

[0066] Preferably, at least one polymer (P1) is present in the first paint composition in an amount ranging from 10 to 50% by mass, more preferably 12 to 45% by mass, based on the total mass of the paint composition.

[0067] Preferably, at least one polymer (P2) is present in the second coating composition in an amount ranging from 10 to 50% by mass, more preferably 12 to 45% by mass, based on the total mass of the coating composition.

[0068] Preferably, at least one polymer (P3) is present in the third coating composition in an amount ranging from 10 to 50% by mass, more preferably 12 to 45% by mass, based on the total mass of the coating composition.

[0069] Amino resin (AR) Preferably, at least one amino resin (AR) used as a crosslinking agent in either the first or second coating composition is an aminoplast resin, more preferably a melamine resin, even more preferably a melamine-formaldehyde resin, and particularly a hexamethoxymethylmelamine-formaldehyde resin. Aminoplast resins generally use a condensation product of formaldehyde and an amino group and / or amide group supported substance such as melamine, urea, and / or benzoguanamine as a material.

[0070] At least one amino resin (AR) contains a crosslinkable functional group which is reactive with both crosslinkable functional groups of polymers (P1), (P2), and (P3), such as OH- groups, when catalyzed by at least one crosslinking catalyst (CLC1).

[0071] Suitable aldehydes for preparing a suitable melamine-formaldehyde resin include those that yield C1-C8 groups bonded to nitrogen atoms retained from the triazene ring of melamine, where these C1-C8 alcohol groups substitute for nitrogen-bonded hydrogen atoms. Specific examples of suitable aldehydes include, but are not limited to, formaldehyde, acetaldehyde, propaldehyde, butyraldehyde, and combinations thereof. Formaldehyde is particularly preferred. Preferably, the at least one melamine resin used as the amino resin (AR) is a formaldehyde resin, more preferably a monomer melamine formaldehyde resin, and even more preferably a hexamethoxyalkyl melamine formaldehyde resin, and in particular a hexamethoxyalkyl melamine formaldehyde resin selected from the group consisting of hexamethoxymethyl melamine formaldehyde resin, hexamethoxybutyl melamine formaldehyde resin, hexamethoxy(methyl and butyl) melamine formaldehyde resin, and mixtures thereof.

[0072] Aldehydes and melamines typically react in a stoichiometric ratio of 5.4:1 to 6:1, preferably 5.7:1 to 6:1, and more preferably 5.9:1 to 6:1. In other words, the reactive sites in melamine, i.e., the imino groups, can react partially or completely as a result of the reaction between the aldehyde and melamine. Theoretically, if the ratio of aldehyde to melamine is 5.4:1, then after the reaction between the aldehyde and melamine, and before further reactions such as the reaction with alcohol in subsequent etherification, the content of alkylol groups in the resulting product should be approximately 90%, based on the total number of reactive sites present in the melamine before the reaction. Similarly, based on the total number of reactive sites present in the melamine before any further reactions, such as reactions with alcohols, a 5.7:1 aldehyde-to-melamine ratio should result in approximately 95% alkylol group content, a 5.9:1 aldehyde-to-melamine ratio should result in approximately 99% alkylol group content, and a 6:1 aldehyde-to-melamine ratio should result in approximately 100% alkylol group content. After the reaction of the aldehyde with melamine, the reactive sites from unreacted melamine remain in the resulting product as imino groups.

[0073] Preferably, the melamine resin used as the amino resin (AR) has an imino group content of 10% or less (corresponding to an aldehyde-to-melamine ratio of about 5.4:1), more preferably less than 5% (corresponding to an aldehyde-to-melamine ratio of about 5.7:1), even more preferably less than 3%, and even more preferably less than 1% (corresponding to an aldehyde-to-melamine ratio of about 5.9:1), based on the total number of reactive sites present in the melamine before the reaction. If there are any remaining groups in the melamine resin, they are preferably alkoxyalkyl groups.

[0074] The melamine resin used as the amino resin (AR) preferably contains alkylol groups, more preferably methylol groups and / or other alkylol groups such as butyrol groups. The preferred butyrol group is the n-butylol group. Methylol groups or mixtures of methylol and butyrol groups are also possible. The most preferred is the methylol group.

[0075] At least some of the alkylol groups present in the melamine resin used as an amino resin (AR) can be alkylated by further reaction with at least one alcohol to produce nitrogen-bonded alkoxyalkyl groups. In particular, the hydroxyl groups in the nitrogen-bonded alkylol groups can be reacted with the alcohol by an etherification reaction to produce nitrogen-bonded alkoxyalkyl groups. These alkoxyalkyl groups can be used in crosslinking reactions with both crosslinkable functional groups of the polymer (P1), (P2), and (P3), such as OH- and / or carbamate groups. The remaining imino groups present in the melamine resin used as an amino resin (AR) after the aldehyde / melamine reaction do not react with the alcohol used for alkylation. Some of the remaining imino groups may be reacted with hydroxyl groups in other melamine-derived nitrogen-bonded alkylol groups to form crosslinking units. However, most of the remaining imino groups remain unreacted.

[0076] As described above, the alkylol groups of melamine resin used as an amino resin (AR) may be partially alkylated. "Partially alkylated" means that under reaction conditions that result in incomplete alkylation of the alkylol groups, a sufficiently small amount of alcohol reacts with the melamine resin to leave some of the alkylol groups in the melamine resin. When a melamine resin is partially alkylated, it is typically alkylated with an amount of alcohol sufficient to leave some of the alkylol groups present in the aminoplast, in each case, at least about 7%, more preferably about 10% to about 50%, and even more preferably about 15% to about 40%, based on the total number of reactive sites present in the melamine before the reaction. Typically, the melamine resin is partially alkylated to obtain about 40% to about 93% alkoxyalkyl groups, more preferably about 50% to about 90%, and even more preferably about 60% to about 75%, based on the total number of reactive sites present in the melamine before the reaction. Therefore, when partially alkylated, the melamine resin is typically alkylated with at least one alcohol in a stoichiometric ratio of hydroxyl groups in the alcohol to alkylol groups in the melamine resin of about 0.5:1.0 to about 0.93:1.0, more preferably about 0.60:1.0 to about 0.9:1.0, and even more preferably about 0.6:1 to about 0.85:1.0.

[0077] Preferably, at least some, more preferably only, of the alkylol groups, such as the methylol groups of the melamine resin are etherified by reaction with at least one alcohol. For this purpose, any monohydric alcohol can be used, including methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, t-butanol, pentanol, hexanol, heptanol, as well as benzyl alcohol and other aromatic alcohols, cyclic alcohols such as cyclohexanol, glycol monoethers, and halogen-substituted or otherwise substituted alcohols such as 3-chloropropanol and butoxyethanol. In particular, melamine resins used as amino resins (ARs) partially contain methanol and / or butanol, most preferably methanol and / or n-butanol.

[0078] Preferably, the melamine resin used as the amino resin (AR) is a melamine aldehyde resin, particularly a melamine formaldehyde resin, having alkylol groups, preferably methylol groups and / or butyrol groups, as crosslinkable functional groups in an amount of at least 90%, based on the total number of reactive sites present in melamine before reaction with the aldehyde, and preferably having an imino group content of 10% or less, more preferably 5% or less, even more preferably 3% or less, and particularly 1% or less, based on the total number of reactive sites present in melamine before reaction with the aldehyde.

[0079] At least one methylol group (-CH2OH) and / or general formula -CH2OR 1 at least one alkoxymethyl group (R 1Melamine formaldehyde resins containing alkyl chains having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and combinations thereof, are particularly preferred as melamine resins. Most preferred are hexamethoxymethyl melamine (HMMM) and / or hexamethoxybutyl melamine (HMBM), with (HMMM) being particularly preferred. Melamine resins containing a combination of methoxybutyl and methoxymethyl groups are also suitable as melamine resins.

[0080] The alkylol groups and alkoxyalkyl groups (e.g., the CH2OCH3 ether group of HMMM) of melamine resin are particularly reactive with the OH- and / or carbamate groups of polymers (P1), (P2), and (P3), such as OH-functional and / or carbamate-functional polymers, when catalyzed by at least one crosslinking catalyst (CLC1), such as a strong acid catalyst such as a non-blocked sulfonic acid used as a crosslinking catalyst (CLC1).

[0081] Preferably, at least one amino resin (AR) used as a crosslinking agent has a maximum number average molecular weight of 1500 g / mol. Preferably, at least one amino resin (AR) used as a crosslinking agent has a number average molecular weight in the range of 200 to 1500 g / mol, more preferably 250 to 1000 g / mol, and particularly 300 to 700 g / mol. The number average molecular weight is determined by the method described in the "Method" section.

[0082] Preferably, at least one amino resin (AR) is present in one or two, preferably one, of the first, second, and third coating compositions, in an amount ranging from 10 to 40% by mass, more preferably 12 to 35% by mass, based on the total mass of each coating composition.

[0083] Crosslinking catalysts (CLC1) and (CLC2) Preferably, at least one crosslinking catalyst (CLC1) is present in at least one of the first, second, and third coating compositions in an amount ranging from 5 to 40% by mass, more preferably 7.5 to 35% by mass, based on the total solids content of each coating composition.

[0084] The crosslinking catalysts (CLC1) and (CLC2) may be the same or they may be different from each other.

[0085] Preferably, at least one crosslinking catalyst (CLC1) is a sulfonic acid such as an unblocked sulfonic acid. If at least one crosslinking catalyst (CLC2) is present, it is also preferable that it be a sulfonic acid such as an unblocked sulfonic acid.

[0086] Crosslinking catalyst (CLC1), preferably crosslinking catalyst (CLC2), is also suitable for catalyzing crosslinking reactions between functional groups of amino resins (AR), such as alkylols and alkoxymethyl groups, and functional groups of these polymers, such as OH groups of both polymers (P1), polymer (P2), and polymer (P3).

[0087] Examples of non-blocked sulfonic acids include p-toluenesulfonic acid (pTSA), methanesulfonic acid (MSA), dodecylbenzenesulfonic acid (DDBSA), dinonylnaphthalenedisulfonic acid (DNNDSA), and mixtures thereof. DDBSA is particularly preferred as both a crosslinking catalyst (CLC1) and a crosslinking catalyst (CLC2).

[0088] If at least one crosslinking catalyst (CLC2) is present in one or two of the first, second, and third coating compositions, which further contain at least one amino resin (AR), then in each case, based on the total solids content of each coating composition, it is present in an amount ranging from 1 to 10% by mass, more preferably 1.5 to 5% by mass.

[0089] Any further components of the paint composition Preferably, the first paint composition contains at least one pigment and / or filler. Preferably, the second paint composition contains at least one pigment and / or filler. Preferably, the third paint composition contains no pigment.

[0090] The term "pigment" is known to those skilled in the art, for example, from DIN 55943 (dated October 2001). In the sense of the present invention, "pigment" preferably refers to a component in the form of a powder or flake that is substantially, preferably completely, insoluble in the surrounding medium, such as in one of the coating compositions used in the present invention. A pigment is preferably a colorant and / or a substance that can be used as a pigment due to its magnetic, electrical, and / or electromagnetic properties. A pigment is preferably different from a "filler" in its refractive index, which for a pigment is ≥1.7. The term "filler" is known to those skilled in the art, for example, from DIN 55943 (dated October 2001). For the purposes of the present invention, a "filler" is preferably a component that is substantially, preferably completely, insoluble in the application medium, such as in one of the coating compositions used in the present invention, and is used particularly to increase volume. In the sense of the present invention, "filler" preferably differs from "pigment" in its refractive index, with the filler having a refractive index of <1.7.

[0091] Any conventional filler known to those skilled in the art may be used. Examples of suitable fillers include silicates such as kaolin, dolomite, calcite, chalk, calcium sulfate, barium sulfate, graphite, and magnesium silicate; silicas, particularly hectorite, bentonite, montmorillonite, talc and / or mica; silicas, particularly fumed silica; hydroxides, particularly aluminum hydroxide or magnesium hydroxide; or organic fillers such as textile fibers, cellulose fibers, polyethylene fibers or polymer powders. For further details, see Roempp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, pp. 250 et seq., “Fillers”.

[0092] Any conventional pigment known to those skilled in the art may be used. Examples of suitable pigments include inorganic coloring pigments and organic coloring pigments. Examples of suitable inorganic coloring pigments include white pigments such as zinc white, zinc sulfide, or lithopone; black pigments such as carbon black, iron manganese black, or spinel black; colored pigments such as chromium oxide, 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 selenide sulfide, molybdate red, or ultramarine red; brown iron oxide, mixed brown, spinel phase and corundum phase, or chromium orange, or yellow iron oxide, nickel titanium yellow, chromium titanium yellow, cadmium sulfide, cadmium zinc sulfide, chromium yellow, or bismuth vanadate. Further inorganic coloring pigments include silicon dioxide, aluminum oxide, aluminum oxide hydrate, especially boehmite, titanium dioxide, zirconium oxide, cerium oxide, and mixtures thereof. Suitable examples of organic coloring pigments include monoazo pigments, disazo pigments, anthraquinone pigments, benzimidazole pigments, quinoacridone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, indanthron pigments, isoindoline pigments, isoindolinone pigments, azomethine pigments, thioindigo pigments, metal complex pigments, perinone pigments, perylene pigments, phthalocyanine pigments, or aniline black.

[0093] If one or more pigments and / or fillers are present in any of the paint compositions, particularly in one of the first and second paint compositions, their proportion in the paint composition is preferably in the range of 1.0 to 40.0% by mass, more preferably 2.0 to 35.0% by mass, and particularly preferably 5.0 to 30.0% by mass, based on the total mass of the paint composition. In the case of the third paint composition, the amount is preferably less, and its proportion is particularly in the range of 0 to 6% by mass, based on the total mass of the paint composition.

[0094] Each coating composition used in the present invention may contain one or more commonly used additives depending on the desired application. For example, each coating composition may contain at least one additive selected from the group consisting of reactive diluents, light stabilizers, antioxidants, degassing agents, emulsifiers, lubricants, polymerization inhibitors, plasticizers, free radical polymerization initiators, adhesion promoters, flow control agents, film-forming aids, anti-sagging agents (SCAs), flame retardants, corrosion inhibitors, drying agents, biocides, and / or matting agents. These can be used in known and conventional proportions. Preferably, their content is 0.01 to 20.0% by mass, more preferably 0.05 to 15.0% by mass, particularly preferably 0.1 to 10.0% by mass, most preferably 0.1 to 7.5% by mass, particularly preferably 0.1 to 5.0% by mass, and most preferably 0.1 to 2.5% by mass, based on the total mass of the coating composition.

[0095] Each coating composition used in the present invention may optionally contain at least one thickening agent. Examples of such thickening agents include inorganic thickening agents, such as metal silicates such as sheet silicates, and organic thickening agents, such as poly(meth)acrylic acid thickening agents and / or (meth)acrylic acid (meth)acrylate copolymer thickening agents, polyurethane thickening agents, and polymeric waxes. Such organic thickening agents are incorporated into polymers (P1) and (P2) used as binders. The metal silicate is preferably selected from the group of smectites. The smectite is particularly preferably selected from the group of montmorillonite and hectorite. In particular, montmorillonite and hectorite are selected from the group consisting of aluminum-magnesium silicate and sodium-magnesium and sodium-magnesium fluorine-lithium phylrosilicate. These inorganic phylrosilicates are sold, for example, under the trademark Laponite®. Thickeners made from poly(meth)acrylic acid and (meth)acrylic acid (meth)acrylate copolymers are optionally crosslinked or neutralized with a suitable base. Examples of such thickeners include "alkaline swelling emulsions" (ASE) and their hydrophobic modified variants, "hydrophilic modified alkali swelling emulsions" (HASE). Preferably, these thickeners are anionic. Corresponding products such as Rheovis® AS 1130 are commercially available. Thickeners made from polyurethane (e.g., polyurethane-associating thickeners) are optionally crosslinked and / or neutralized with a suitable base. Corresponding products such as Rheovis® PU 1250 are commercially available. An example of a suitable polymer wax is an optionally modified polymer wax made from ethylene vinyl acetate copolymer. Corresponding products are commercially available, for example, under the name Aquatix® 8421.

[0096] If at least one thickening agent is present in any of the paint compositions, it is preferably present in an amount of at most 10% by mass, more preferably at most 7.5% by mass, most preferably at most 5% by mass, particularly at most 3% by mass, and most preferably less than 2% by mass, based on the total mass of the paint composition. The minimum amount of the thickening agent is preferably 0.1% by mass, based on the total mass of the paint composition, in each case.

[0097] The preparation of each paint composition may be carried out using conventional and known preparation and mixing methods and mixing units, or using conventional dissolving and / or stirring machines.

[0098] The multilayer coating system of the present invention A further subject of the present invention is a multilayer coating system on a substrate that can be obtained by the method of the present invention.

[0099] All preferred embodiments described herein in relation to the method of the present invention are also preferred embodiments with respect to the multilayer coating system of the present invention on the aforementioned substrate.

[0100] Method of use of the present invention A further subject of the present invention is a method for using an amino resin (AR) having a crosslinkable functional group, The amino resin (AR) is present in one or two of the first, second, and third coating compositions, and each coating composition is different from the others. The first coating composition comprises at least one polymer (P1) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR). The second coating composition comprises at least one polymer (P2) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR). The third coating composition comprises at least one polymer (P3) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR). At least one coating composition selected from the first, second, and third coating compositions does not contain the amino resin (AR) and does not contain any crosslinking agent, but comprises at least one crosslinking catalyst (CLC1) suitable for catalyzing the crosslinking reaction between the functional group of the amino resin (AR) and the functional groups of both polymers (P1), polymer (P2), and polymer (P3). The method involves applying a third coating composition to a coating obtained from a second coating composition before curing the second coating, and then transferring the amino resin from one or two coatings obtained from one or more coatings selected from the first, second, and third coating compositions containing an amino resin to at least one coating obtained from the remaining coating composition of at least one of these three coating compositions, thereby forming a third coating adjacent to the second coating, wherein the second coating is obtained by applying the second coating composition to a first coating obtained from the first coating composition before curing the first coating, and the second coating is adjacent to the first coating and is preferably catalyzed by at least a crosslinking catalyst (CLC1) for subsequent crosslinking by the crosslinkable functional groups of polymer (P1), polymer (P2), and polymer (P3).

[0101] All preferred embodiments described herein in relation to the method of the present invention and the multilayer coating system of the present invention on a substrate are also preferred embodiments with respect to the aforementioned use of the present invention.

[0102] method 1. Non-volatile fraction The non-volatile fraction (solid content or solid content ratio) is determined according to DIN EN ISO 3251 (date: June 2008). This involves weighing 1 g of the sample into a pre-dried aluminum dish, drying the dish with the sample in a drying oven at 130 °C for 60 minutes, cooling it in a desiccator, and weighing it again. The residue relative to the total amount of the sample used corresponds to the non-volatile fraction.

[0103] 2. Number average molecular weight (Mn) The average molecular weight (M w , M n , M p ) of the polymer is determined by fractionating a completely dissolved polymer sample on a porous column stationary phase. Tetrahydrofuran (THF) is used as the eluent. The stationary phase is a combination of Waters Styragel's HR5, HR4, HR3, and HR2 columns. 5 milligrams of the sample is added to 1.5 mL of the eluent and filtered through a 0.5 μm filter. After filtration, 100 μl of the polymer sample solution is injected into the column at a flow rate of 1.0 ml / min. Separation is performed based on the size of the polymer coils formed in the eluent. The molecular weight distribution, number average molecular weight M n , mass average molecular weight M w , and the molecular weight M of the highest peak p are calculated using chromatography software with a calibration curve created using a polymer standard verification kit containing a series of non-branched polystyrene standards with different molecular weights available from Polymer Standards Service. The polydispersity index (PDI) is determined by the formula M w / M n .

[0104] 3. MEK friction test The MEK friction test is carried out according to ASTM D5402.

[0105] 4. Two-con hardness A Wolpert Wilson Tukon 2100 instrument was used to evaluate the Tukon microhardness of a painted substrate. The painted substrate was placed on the instrument's stage, under a Tukon indenter. The indenter had a pyramidal diamond tip and applied a 25g load to the surface of the painted substrate for 18±0.5 seconds. The instrument also included a microscope with a filer micrometer eyepiece. After the indentation was complete, the length of the indentation was measured using the microscope. The instrument calculates the Knoop hardness number (KHN) using the following formula.

[0106]

number

[0107] 5. Adhesive strength The adhesive strength is measured according to ASTM D3359.

[0108] 5. Chip resistors The chip resistance is measured using SAE J400.

[0109] 6.Layer thickness The dry layer thickness is determined using ASTM D4138 (Standard method for measuring dry film thickness of protective coating systems by destructive cross-sectional means).

[0110] Examples The following embodiments further illustrate the present invention, but should not be construed as limiting its scope.

[0111] 1. Primer used as the first paint composition 1.1 To use as a first paint composition, the components shown in Table 1.1 were mixed in this order to prepare a gray primer composition PC1. Primer composition PC1 does not contain any crosslinking agents, particularly amino resins, nor any crosslinking catalysts. The total solids content of PC1 is 59.8% by mass, based on its total mass.

[0112] [Table 1]

[0113] The branched polyester resin has an acid value of 30 mgKOH / g. This resin is used in the form of a dispersant with a solid content of 73% by mass.

[0114] Emulsion Microgel 1 is a branched acrylic microgel emulsion available from BASF Corp., with an acid value of 10 mg KOH / g. The solids content of this emulsion is 31% by mass.

[0115] Acrylic resin 1 is an ε-caprolactone-modified acrylic resin available from BASF Corp., having an OH number of 73 mg KOH / g and a mass-average molecular weight of 11,100 g / mol. This resin is used in the form of a dispersant having a solids content of 75% by mass.

[0116] 1.2 For use as a first paint composition, primer composition PC1 was mixed with different crosslinking catalysts to prepare numerous further primer compositions. A summary is shown in Table 1.2.

[0117] [Table 2]

[0118] As crosslinking catalyst C1, a commercially available sulfonic acid crosslinking catalyst, Naxcat® 1270 (dodecylbenzenesulfonic acid (DDBSA) in isopropyl alcohol), was used. As crosslinking catalyst C2, a solution of p-toluenesulfonic acid (pTSA) in n-butanol (17.8% by mass of pTSA) was used. As crosslinking catalyst C3, a solution of methanesulfonic acid (MSA) in n-butanol (10% by mass of MSA) was used.

[0119] 1.3 To use as a first coating composition, the components shown in Table 1.3 were mixed in this order to prepare a commonly used primer composition PC5. Primer composition PC5 contains two amino resins (Resimene® 755 and Resimene® 747) as crosslinking agents. PC5 also contains a crosslinking catalyst, namely a blocked sulfonic acid catalyst (amine-blocked decylbenzenesulfonic acid (DDBSA)).

[0120] [Table 3]

[0121] Emulsion microgel 1, acrylic resin 1, and branched polyester resin are as previously described for PC1.

[0122] 2. Base coat used as the second paint composition 2.1 The components shown in Table 2.1 were mixed in this order to prepare the black base coat composition BC1. BC1 does not contain any crosslinking agents, particularly amino resins, nor any crosslinking catalysts.

[0123] [Table 4]

[0124] Emulsion microgel 1 and acrylic resin 1 are as previously described for PC1.

[0125] Emulsion Microgel 2 is a branched acrylic microgel emulsion available from BASF Corp., with an acid value of 13.5 mg KOH / g. This emulsion has a solids content of 31.3% by mass.

[0126] 2.2 For use as a second coating composition, base coat composition BC1 was mixed with different crosslinking catalysts to prepare numerous further base coat compositions. A summary is shown in Table 2.2.

[0127] [Table 5]

[0128] As crosslinking catalyst C1, Naxcat® 1270, a commercially available sulfonic acid crosslinking catalyst (dodecylbenzenesulfonic acid (DDBSA) in isopropyl alcohol), was used. As crosslinking catalyst C2, a solution of p-toluenesulfonic acid (pTSA) in n-butanol (17.8% by mass of pTSA) was used. As crosslinking catalyst C3, a solution of methanesulfonic acid (MSA) in n-butanol (10% by mass of MSA) was used.

[0129] 2.3 For use as a second coating composition, the components shown in Table 2.3 were mixed in this order to prepare the relatively commonly used base coat composition BC5. BC5 contains two amino resins (Resimene® 755 and Resimene® 764) as crosslinking agents. BC5 also contains a crosslinking catalyst, namely a blocked sulfonic acid catalyst (amine-blocked decylbenzenesulfonic acid (DDBSA)).

[0130] [Table 6]

[0131] The acrylic resin 1 and emulsion microgel 1 are as previously described for PC1.

[0132] The polyester resin (star-shaped) is a branched aliphatic star-shaped polyester resin available from BASF Corp., having an OH number of 115 mg KOH / g and a mass-average molecular weight of 2000 g / mol. This resin is used in the form of a dispersant with a solids content of 80% by mass.

[0133] 3. Clear coat used as the third coating composition 3.1 Solvent-based clear coat composition CC1 Clear coat composition CC1 was prepared by mixing the substituents shown in Table 3.1 in this order. CC1 contains an amino resin (Resimene® 747) as a crosslinking agent. The total solids content of CC1 is 57.9% by mass, based on its total mass.

[0134] [Table 7]

[0135] The carbamate acrylic resin is available from BASF Corp., with an OH number of 0 mgKOH / g and a mass-average molecular weight of 4000 g / mol. The carbamate equivalent is 438 g / mol. This resin is used in the form of a dispersant with a solid content of 70% by mass.

[0136] C present in the resin blend 36 Dicarbamate consists of 2 mmol of methylcarbamate and 1 mmol of C 36 It is obtained from a diol and used in the form of a dispersant with a solid content of 60% by mass. The carbamate equivalent is 344 g / mol. The IPDI / HPC reactive intermediate present in the resin blend is obtained from 1 mol of IPDI trimer and 3 mol of hydroxypropyl carbamate and is used in the form of a dispersant with a solid content of 38.5% by mass. The carbamate equivalent is 374 g / mol. The total solid content of the resin blend used is 55% by mass.

[0137] As described above, the IPDI / HPC reactive intermediates present in CC1 are as explained in the resin blend section.

[0138] Acrylic resin 2 is available from BASF Corp. and is a GMA-acrylic resin, i.e., an epoxy resin with a mass-average molecular weight of 27,400 g / mol. The epoxy equivalent is 430 g / mol. This resin is used in the form of a dispersant with a solids content of 60% by mass.

[0139] The thermosetting acrylic resin is available from BASF Corp. and is an OH-functional acrylic resin with an OH number of 182 mg KOH / g and a mass-average molecular weight of 4600 g / mol. This resin is used in the form of a dispersant with a solids content of 67.5% by mass.

[0140] BYK(registered trademark)LP R 23429 is a rheological additive commercially available from BYK Chemie GmbH.

[0141] 3.2 (Relatively Common) Solvent-Based Clear Coat Composition CC2 Clear coat composition CC2 was prepared by mixing the components shown in Table 3.2 in this order. CC2 contains an amino resin (Resimene® 747) as a crosslinking agent. CC2 also contains two crosslinking catalysts, namely a blocked sulfonic acid catalyst (amine-blocked decylbenzenesulfonic acid (DDBSA)) and Naxcat® 1270.

[0142] [Table 8]

[0143] Carbamate acrylic resin, resin blend (50% by mass of C 36 The dicarbamate (50% by mass of IPDI / HPC reactive intermediate), IPDI / HPC reactive intermediate, acrylic resin 2, and thermosetting acrylic resin are as previously described for CC1.

[0144] 4. Preparation of multilayer coating system 4.1 Many multilayer coating systems were obtained using the primer, base coat, and clear coat compositions described above.

[0145] Multilayer coating systems IE1-IE3 containing a crosslinking catalyst-containing primer composition: Multilayer coating system IE1 was prepared using primer composition PC2, base coat composition BC1, and clear coat composition CC1. Multilayer coating system IE2 was prepared using primer composition PC3, base coat composition BC1, and clear coat composition CC1. Multilayer coating system IE3 was prepared using primer composition PC4, base coat composition BC1, and clear coat composition CC1.

[0146] Multilayer coating systems IE4-IE6 including a crosslinking catalyst-containing base coat composition: Multilayer coating system IE4 was prepared using primer composition PC1, base coat composition BC2, and clear coat composition CC1. Multilayer coating system IE5 was prepared using primer composition PC1, base coat composition BC3, and clear coat composition CC1. Multilayer coating system IE6 was prepared using primer composition PC1, base coat composition BC4, and clear coat composition CC1.

[0147] Multilayer coating system IE7 (comparison) The multilayer coating system IE7 was prepared using primer composition PC5, base coat composition BC5, and clear coat composition CC2.

[0148] 4.2 A 4-inch x 12-inch cold-rolled steel sheet test panel was used as the substrate. The panel was pre-treated with Bondrite® 958 zinc phosphate pre-treatment agent and rinsed with Parcolene® 90 post-rinse. Both are available from Henkel. A 0.7-0.8 mil layer of BASF's Cathoguard® 800 electrodeposition coating was electrodeposited onto the panel and baked at a substrate temperature of 350°F (176.7°C) for 20 minutes. One of PC2-PC5 was sprayed onto the panel and flashed at ambient temperature for 4 minutes. One of BC1-BC5 was sprayed onto the primed panel and flashed at ambient conditions for 4 minutes. Then, CC1 or CC2 was applied and flashed at ambient conditions for 10 minutes. After the CC flash, the panel was baked at 210°F (98.9°C) for 20 minutes.

[0149] The dry film thickness of each base coat after curing was 0.6 mil (15.24 μm), and the dry film thickness of each clear coat CC1 after curing was 1.8 mil (45.72 μm). The dry film thickness of each primer coat after curing was 0.8 mil (20.32 μm).

[0150] Before applying CC1 or CC2 to the substrate, it was diluted to 105 cP with n-butyl acetate.

[0151] 5. Characteristics of substrates coated with a multilayer coating system Table 5.1 summarizes many of the characteristics measured and / or determined by the methods defined in the "Methods" section.

[0152] [Table 9]

[0153] Regarding the multilayer coating system IE7, similar to IE1 to IE6, after preparation and firing at 210°F (98.9°C) for 20 minutes as described in item 4.2, the multilayer coating system IE7 present on the resulting panel was found to be sticky (not cured) and was not suitable for testing using the same protocol that was successful for IE1 to IE6. In contrast to IE7, all of IE1 to IE6 showed excellent curing (no stickiness) when fired at 210°F (98.9°C) for 20 minutes. In the case of IE7, sufficient curing was not obtained under these conditions.

Claims

1. At least steps (1), (2), (3), and (4), (1) Applying a first coating composition to a pre-coated substrate, forming a first coating film on the pre-coated substrate, wherein the first coating film is a primer coating film, (2) Apply the second coating 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 film is a base coating film. (3) Apply the third coating composition to the second coating film present on the substrate obtained after step (2) before curing the second coating film to form a third coating film adjacent to the second coating film, wherein the third coating film is a clear coating film. (4) The first, second, and third coating films are cured together, and the cured third coating film is the outermost layer of the formed multilayer coating system, step A method for preparing a multilayer coating system on a substrate, comprising: The first, second, and third coating compositions are all different from each other, the first coating composition comprises at least one polymer (P1) having a crosslinkable functional group, the second coating composition comprises at least one polymer (P2) having a crosslinkable functional group, and the third coating product comprises at least one polymer (P3) having a crosslinkable functional group. One or two of the first, second, and third paint compositions, Prior to use in step (1), (2) and / or (3), the mixture further comprises at least one amino resin (AR) as a crosslinking agent having a crosslinkable functional group that can crosslink with the crosslinkable functional groups of both polymer (P1), polymer (P2), and polymer (P3), independently of each other. Prior to use in steps (1), (2), and / or (3), at least one of the remaining paint compositions of these paint compositions does not contain any crosslinking agent, but independently of each other prior to use in steps (1), (2), and / or (3), it contains at least one crosslinking catalyst (CLC1) suitable for catalyzing the crosslinking reaction between the crosslinkable functional groups of the amino resin (AR) and the crosslinkable functional groups of both polymer (P1), polymer (P2), and polymer (P3). A method for preparing a multilayer coating system.

2. The process includes a further step (1a) and / or a further step (2a) and / or a further step (3a), where step (1a) is performed after step (1) and before step (2), step (2a) is performed after step (2) and before step (3), and step (3a) is performed after step (3) and before step (4), i.e., (1a) Before applying the second coating composition in step (2), the first coating obtained after step (1) is flashed off for 1 to 20 minutes, and / or (2a) Before applying the third coating composition in step (3), the step of flashing off the second coating obtained after step (2) for 1 to 20 minutes, and / or, (3a) Before performing the curing step (4), the third coating obtained after step (3) is flashed off for 1 to 20 minutes, The method according to claim 1, including the method described in claim 1.

3. The method according to claim 1 or 2, wherein, prior to use in step (1), (2), and / or (3), one or two of the first, second, and third paint compositions, each independently containing at least one amino resin (AR) as a crosslinking agent, either does not contain any crosslinking catalyst, or independently contains at least one crosslinking catalyst (CLC2), and the amount of the crosslinking catalyst (CLC2) is lower, based on the total mass of the paint compositions, than the amount of the at least one crosslinking catalyst (CLC1) present in the remaining paint composition of the first, second, and third paint compositions that does not contain any crosslinking agent, prior to use in step (1), (2), and / or (3).

4. The second and / or third coating composition independently comprises, before use in step (2) and / or (3), at least one amino resin (AR) as a crosslinking agent, and optionally at least one crosslinking catalyst (CLC2), and the first and / or second coating composition (in the case of the second coating composition, provided that it does not contain at least one amino resin (AR) as a crosslinking agent) independently comprises, before use in step (1) and / or (2), The method according to any one of claims 1 to 3.

5. The third coating composition alone contains at least one amino resin (AR) as a crosslinking agent and optionally at least one crosslinking catalyst (CLC2) before use in step (3), and the first and / or second coating compositions independently contain at least one crosslinking catalyst (CLC1) before use in step (1) and / or (2), or the second coating composition alone contains at least one amino resin (AR) as a crosslinking agent and optionally at least one crosslinking catalyst (CLC2) before use in step (2), and the first and / or third coating compositions independently contain at least one crosslinking catalyst (CLC1) before use in step (1) and / or (3). The method according to any one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein the first paint composition is a solvent-based or water-based paint composition, the second paint composition is a solvent-based or water-based paint composition, and the third paint composition is a solvent-based paint composition.

7. The method according to any one of claims 1 to 6, wherein at least one amino resin (AR) used as an existing crosslinking agent is an aminoplast resin.

8. The method according to any one of claims 1 to 7, wherein at least one amino resin (AR) used as a crosslinking agent has a number average molecular weight of 1500 g / mol or less.

9. The method according to any one of claims 1 to 8, wherein at least one amino resin (AR) is present in one or two of the first, second, and third paint compositions in an amount ranging from 10 to 40% by mass, based on the total mass of each paint composition, in each case.

10. The method according to any one of claims 1 to 9, wherein step (4) is performed at a temperature of less than 110°C for 5 to 45 minutes.

11. The method according to any one of claims 1 to 10, wherein at least one crosslinking catalyst (CLC1) is a non-blocked sulfonic acid.

12. The method according to any one of claims 1 to 11, wherein at least one crosslinking catalyst (CLC1) is present in at least one of the first, second, and third paint compositions in an amount ranging from 5 to 40% by mass, based on the total solid content of each paint composition, in each case.

13. The method according to any one of claims 1 to 12, wherein each polymer (P1) and (P2) has a hydroxyl group as a crosslinkable functional group.

14. A method for using an amino resin (AR) having a crosslinkable functional group, The amino resin (AR) is present in one or two of the first, second, and third coating compositions, and each coating composition is different from the others. The first coating composition comprises at least one polymer (P1) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR). The second coating composition comprises at least one polymer (P2) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR). The third coating composition comprises at least one polymer (P3) having a crosslinkable functional group that can be crosslinked with the crosslinkable functional group of the amino resin (AR). At least one coating composition selected from the first, second, and third coating compositions does not contain the amino resin (AR) and does not contain any crosslinking agent, but comprises at least one crosslinking catalyst (CLC1) suitable for catalyzing the crosslinking reaction between the crosslinkable functional group of the amino resin (AR) and the crosslinkable functional groups of both polymers (P1), polymer (P2), and polymer (P3). The method involves applying a third coating composition to a coating obtained from a second coating composition before curing the second coating, and then transferring the amino resin (AR) from one or two coatings obtained from one or more coatings selected from the first, second, and third coating compositions containing amino resin (AR) to at least one coating obtained from the remaining coating composition of at least one of these three coating compositions, thereby forming a third coating adjacent to the second coating, wherein the second coating is obtained by applying the second coating composition to a first coating obtained from the first coating composition before curing the first coating, and the second coating is adjacent to the first coating, Furthermore, this is for subsequent crosslinking with the crosslinkable functional groups of polymer (P1), polymer (P2), and polymer (P3). How to use amino resin (AR).

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