Method for continuous production of multi-coated substrates

Abstract

The present invention relates to a method for the continuous production of multi-coated substrates, wherein the method is defined by sequentially producing a base coat and a clear coat on separate substrates, and wherein the curing of the clear coat is characterized by an average annual energy consumption value Ec of up to 1.5 kWh per square meter of multi-coated substrate.

Description

[0001] This invention relates to a method for the continuous production of multi-coated substrates, wherein a plurality of substrates to be coated are provided, and then a base coat is sequentially produced on these substrates, followed by a clear coat being sequentially produced on the substrates coated with the base coat. Finally, the method includes a curing step for the clear coat. Background Technology

[0002] Multi-coat paint systems on metal or plastic substrates, such as those used in the automotive industry, are known. Typically, viewed from the metal substrate outwards, such multi-coat paint systems comprise an electrocoating layer, a layer applied directly to the electrocoating layer and often referred to as a primer-topcoat layer, at least one coating containing colored pigments and / or effect pigments and often referred to as a base coat, and a clear coat.

[0003] The basic composition and function of these layers and the coating compositions required to form them (i.e., electrocoating materials (so-called primer-topcoat), coating compositions containing colored pigments and / or effect pigments and referred to as basecoat materials, and clearcoat materials) are known. For example, electrocoating applied by electrophoresis is primarily used to protect the substrate from corrosion. So-called primer-topcoat is primarily used to protect against mechanical stress (e.g., stone chips) and additionally to smooth out inhomogeneities in the substrate. The next coating (referred to as the basecoat) is primarily responsible for producing aesthetic properties (such as color and / or effects (such as chromatic aberration)), while the subsequent clearcoat is specifically used to impart scratch resistance and gloss to the multi-coat paint system.

[0004] These multi-coat paint systems are typically produced by first applying or depositing an electrocoating, particularly a cathodic electrocoating, onto a metallic substrate (e.g., a car body) via electrophoresis. Prior to electrocoating deposition, the metallic substrate may be pretreated in various ways; for example, known conversion coatings, such as phosphate coatings, particularly zinc phosphate coatings, may be applied. The electrocoating deposition process is typically carried out in a suitable electrocoating bath. After application, the coated substrate is removed from the bath, optionally rinsed, and air-dried and / or intermediate-dried, and finally cured. The target coating thickness is approximately 15 to 25 micrometers. Subsequently, a so-called primer-topcoat is applied directly to the cured electrocoating, optionally air-dried and / or intermediate-dried, and then cured. To enable the cured primer-topcoat to perform the aforementioned tasks, the target coating thickness is, for example, 25 to 45 micrometers. Subsequently, a so-called base coat containing colored pigments and / or effect pigments is applied directly to the cured primer-topcoat, optionally air-dried and / or intermediate-dried, and a clear coat is applied directly to the resulting base coat without separate curing. Subsequently, the primer and the clear coat, which have optionally been pre-dried and / or intermediate-dried, are co-cured (wet-on-wet method). While the cured primer generally has a relatively low coating thickness of, for example, 10 to 20 micrometers, the target coating thickness of the cured clear coat is, for example, 30 to 60 micrometers, in order to achieve the described performance characteristics. The primer-topcoat, primer, and clear coat can be applied, for example, by application methods known to those skilled in the art, such as pneumatic and / or electrostatic spraying. Nowadays, at least for environmental reasons, primer-topcoats and primers are increasingly used in the form of water-based coating materials.

[0005] This type of multi-coat paint system and the method for producing it are described, for example, in DE 199 48 004 A1, page 17, line 37 to page 19, line 22, or in DE 100 43 405 C1, column 3, paragraph

[0018] and column 8, paragraphs

[0052] to 9, paragraphs

[0057] together with column 6, paragraphs

[0039] to 8, paragraphs

[0050] .

[0006] It is also known (particularly in the automotive industry) that a separate curing step is omitted for coating compositions (referred to in the context of the above methods) that are directly applied to the curing electrocoating layer. In the technical field, this uncured coating film is often referred to as a base coat (and no longer as a base coat), or as a first base coat in contrast to a second base coat applied thereon. There are even attempts to completely omit this coating film (in which case a so-called base coat is produced directly on the electrocoating layer, over which a clear coat is applied without a separate curing step, meaning that a separate curing step is ultimately also omitted). Therefore, instead of a separate curing step and an additional final curing step, only a final curing step exists after all coating films applied to the electrocoating layer. Clearly, these attempts seek improved economics and, more specifically, improved sustainable coating methods. Such methods are also called "integrated methods."

[0007] However, a final curing step is unavoidable in any case, where at least the final clear coating is cured. Typically, during this curing step, previously applied layers (such as primers) are then cured in the same way, i.e., a co-curing process is achieved.

[0008] The final curing step is one that takes into account significant energy consumption. For example, curing processes via heating in an oven, and therefore thermally induced curing, obviously require considerable energy to heat the oven and the substrate / coating. It is known that the thermal curing of transparent coatings typically requires temperatures, for example, well above 120°C, for a duration of, for example, at least 20 minutes.

[0009] While existing technologies recognize this energy consumption and demonstrate methods to combat it, most of these methods are geared towards laboratory scale and do not focus on industrial-scale coating processes and methods in industrial equipment, i.e., industrial-scale continuous coating processes. More specifically, they do not focus on the specific factors influencing energy consumption in such industrial-scale processes.

[0010] question

[0011] Therefore, the problem solved by this invention is to find a method for the continuous production of multi-coated substrates, which is particularly advantageous for the final curing step (i.e., the curing step in which the produced clear coating (and, if applicable, additional layers) is cured) under industrial-scale conditions. Thus, during the continuous final curing steps, the resulting multi-coated substrate and therefore the multi-coated paint system on the substrate should be producible only with relatively low and therefore advantageous energy consumption, thereby contributing to a more sustainable coating method. However, the properties of the resulting coating should meet the high standards of industry, particularly the automotive industry.

[0012] Technical solutions

[0013] It has been found that the aforementioned problem is solved by a novel method for the continuous production of multi-coated substrates, wherein the method includes

[0014] (1) Provide multiple substrates to be coated

[0015] (2) A primer is produced by sequentially applying an aqueous primer composition to each of these substrates, wherein the aqueous primer material comprises at least one aqueous dispersion of at least one polyacrylate and at least one aqueous dispersion of at least one polyurethane. (3) By sequentially applying the transparent coating composition to each substrate coated according to step (2) to produce a transparent coating, a multi-coated substrate is produced. (4) Curing the transparent coating produced according to step (3), Step (4) is characterized by an average annual energy consumption value Ec of up to 1.5 kWh per square meter of multi-coated substrate. The annual average energy consumption value Ec is calculated as follows:

[0016] in

[0017] - e1 reflects the energy loss due to the exhaust gas from the oven and is determined as

[0018] in Reflecting the average density of air, Reflects the average specific heat capacity of air 293 K reflects the average room temperature / ambient temperature outside the oven. a = Year-based average exhaust volume flow rate from this oven [ ] b = Operating time from this oven / year [ ] c1 = Area of ​​multi-coated substrates processed in this oven per year [ ] T1 = Average oven temperature [K] during operation, based on the year. - e2 reflects the energy loss from the oven via surface transfer and is determined to be

[0019] in This is a correction factor that takes into account the insulation and heat transfer efficiency of a standard oven. d = Total surface area of ​​the oven (including the ground) ] - e3 reflects the energy consumption used to heat the multi-coated substrate for thermosetting and is determined to be...

[0020] in

[0021] f = Year-based average specific heat capacity of the treated substrate [ ]

[0022] g = Mass of uncoated substrate treated in this oven per year [kg]

[0023] - e4 reflects the energy consumption of the photochemical radiation used for photocuring and is determined to be... = Number of photochemical radiation sources of type x = Electrical power [Wh] of type x photochemical radiation source = Year-based average operating time of x-type photochemical radiation sources [h] (Where x reflects the number of different types of photochemical radiation sources applied) c2 = Area of ​​multi-coated substrates treated in the curing chamber per year [ ].

[0024] The method of the present invention allows for the continuous production of multi-coated substrates, which is particularly advantageous for the final curing step (i.e., the curing step in which the produced clear coating (and, if applicable, additional layers) is cured) under industrial-scale conditions. Therefore, the resulting multi-coated substrates and thus the multi-coated paint systems on the substrates are thus producible with relatively low and therefore advantageous energy consumption during the continuous final curing steps. Furthermore, the properties of the resulting coatings meet the high standards of industry, particularly the automotive industry. Detailed Implementation

[0025] First, some of the terminology used in this invention will be clarified.

[0026] The application of a coating composition to a substrate, or the production of a coating film (also referred to as a layer) on a substrate, should be understood as follows. The corresponding coating composition is applied in such a manner that the coating film produced therefrom is disposed on the substrate but does not necessarily need to be in direct contact with the substrate. For example, other layers may also be disposed between the coating film and the substrate. For example, in stage (2), the primer layer produced on the substrate does not necessarily need to be in direct contact with the substrate, but electrocoating and / or primer layers and / or conversion coatings (such as zinc phosphate coatings) as described below may also be disposed between the substrate and the primer layer.

[0027] The same principle applies to applying coating composition (b) to a coating film (A) produced by means of another coating composition (a). The coating film (B) does not necessarily need to be in contact with the coating film (A), but only needs to be placed above it, that is, on the side of the coating film (A) facing away from the substrate.

[0028] In contrast, applying the coating composition directly to the substrate or producing a coating film directly on the substrate should be understood as follows: The corresponding coating composition is applied in such a way that the coating film produced therefrom is arranged on the substrate and in direct contact with the substrate. Therefore, more specifically, no other layer is arranged between the coating film and the substrate. Of course, this also applies to applying the coating composition (b) directly to a coating film (A) produced by means of another coating composition (a). In this case, the two coating films are in direct contact, i.e., arranged directly above and below each other. More specifically, there is no other layer between coating films (A) and (B).

[0029] In the context of this invention, “flashing off,” “intermediately drying,” and “curing” should be understood to have meanings familiar to those skilled in the art in relation to methods for producing multi-coat paint systems.

[0030] Therefore, the term "air drying" should be understood in principle as referring to the vaporization of organic solvents and / or water in the coating composition applied during the production of the paint system, typically at room temperature (e.g., 15°C to 35°C) or for a period of time, such as 0.5 to 30 minutes. During the air drying operation, the organic solvents and / or water present in the applied coating composition are vaporized. Since the coating composition is still free-flowing, at least immediately after application and at the start of the air drying operation, it can be run during the air drying operation. This is because the coating composition applied, at least by spraying, is typically in droplet form and not applied at a uniform thickness. However, due to the presence of organic solvents and / or water, it is free-flowing and can therefore form a uniform, smooth coating film through running. Simultaneously, the organic solvents and / or water gradually vaporize, resulting in a relatively smooth coating film after the air drying stage, containing less water and / or solvent compared to the applied coating composition. However, after the air drying operation, the coating film is still not in a ready-to-use state. For example, it is no longer free-flowing, but remains soft and / or sticky, and in some cases only partially dried. More specifically, the coating film is still not cured as described below.

[0031] Therefore, intermediate drying should also be understood as meaning that the organic solvents and / or water in the coating composition applied in the production of the paint system are typically vaporized at a temperature elevated relative to room temperature (e.g., 40°C to 80°C) or allowed to vaporize for a period of time, for example, 1 to 60 minutes. Also in intermediate drying operations, the applied coating composition will thus lose a certain proportion of organic solvents and / or water. For a particular coating composition, it is generally the case that intermediate drying is carried out at, for example, higher temperatures and / or for a longer period of time compared to air drying, such that a higher proportion of organic solvents and / or water escapes from the applied coating film compared to air drying. However, intermediate drying does not yield a cured coating film as described below. A typical sequence of air drying and intermediate drying operations would involve, for example, allowing the coating film applied at ambient temperature to air dry for 5 minutes, and then intermediate drying it at 80°C for 10 minutes. However, conclusive definitions of these two terms are neither necessary nor intended. For clarity only, these terms are used to describe the variable and sequential adjustment of the coating film prior to the curing operation described below, wherein—depending on the coating composition, vaporization temperature, and vaporization time—a higher or lower proportion of organic solvents and / or water present in the coating composition may vaporize. It may be, depending on the circumstances, even in this early stage, that the proportion of polymers present as binders in the coating composition may be crosslinked or cyclic to each other.

[0032] Therefore, the curing of a coating film should be understood as meaning the transformation of such a film into a ready-to-use state, that is, a state in which the substrate with the corresponding coating film (or multiple coatings) can be transported, stored, and used as intended. More specifically, the cured coating film is no longer soft or sticky, but has been tempered into a solid coating film that does not undergo any further advantageous changes in its properties, such as hardness or adhesion to the substrate, even upon further exposure to the curing conditions described below.

[0033] As is well known, coating compositions can, in principle, be physically and / or chemically cured depending on the presence of their components, such as adhesives and crosslinking agents. In the case of chemical curing, thermochemical curing and photochemical (photochemical) curing are options. If it is thermochemically curable, the coating composition can be self-crosslinked and / or externally crosslinked. In the context of this invention, the statement that a coating composition is self-crosslinked and / or externally crosslinked should be understood to mean that the coating composition contains a polymer as an adhesive and optionally a crosslinking agent, which can be crosslinked with each other accordingly. The underlying mechanisms and the adhesives and crosslinking agents available are known.

[0034] In the context of this invention, "physically curable" or the term "physically curable" means the formation of a cured coating film by releasing a solvent from a polymer solution or polymer dispersion, wherein curing is achieved by the mutual cyclication of polymer chains.

[0035] In the context of this invention, "thermochemically curable" or the term "thermochemically curable" means the crosslinking of a paint film (forming a cured coating film) initiated by the chemical reaction of reactive functional groups, which can be activated by thermal energy. This can involve the reaction of different, complementary functional groups with each other (complementary functional groups) and / or the formation of a cured layer based on reactions of self-reactive groups (i.e., functional groups that react with groups of the same kind). Examples of suitable complementary reactive functional groups and self-reactive functional groups are known, for example, from page 7, line 28 to page 9, line 24 of German patent application DE 199 30 665 A1.

[0036] This crosslinking can be self-crosslinking and / or external crosslinking. For example, self-crosslinking exists if complementary reactive functional groups are already present in the organic polymer (e.g., polyester, polyurethane, or poly(meth)acrylate) used as an adhesive. External crosslinking exists, for example, when a (first) organic polymer containing a specific functional group (e.g., hydroxyl group) reacts with a crosslinking agent known per se (e.g., polyisocyanate and / or melamine resin). Thus, the crosslinking agent contains reactive functional groups complementary to those present in the (first) organic polymer used as an adhesive.

[0037] Especially in the case of external crosslinking, there are known single-component and multi-component systems, especially two-component systems.

[0038] In a one-component system, the components to be crosslinked (e.g., the organic polymer as a binder and the crosslinking agent) coexist, i.e., exist within a single component. A prerequisite for this is that the components to be crosslinked react with each other only at relatively high temperatures, such as above 100°C, i.e., enter the curing reaction. Otherwise, the components to be crosslinked must be stored separately and mixed only shortly before application to the substrate to avoid premature, at least partial, thermochemical curing (see two-component systems). An example of a combination is a combination of hydroxyl-functionalized polyesters and / or polyurethanes with melamine resins and / or end-capped polyisocyanates as crosslinking agents.

[0039] In a two-component system, the components to be crosslinked (e.g., the organic polymer as a binder and the crosslinking agent) exist individually in at least two components, which are combined only shortly before application. This form is chosen when the components to be crosslinked react with each other even at ambient temperature or at a slightly elevated temperature, such as 40°C to 90°C. An example of such a combination is a combination of hydroxyl-functionalized polyesters and / or polyurethanes and / or poly(meth)acrylates with free polyisocyanates as crosslinking agents.

[0040] It is also possible that the organic polymer used as an adhesive has both self-crosslinking functional groups and external crosslinking functional groups, and is then combined with a crosslinking agent.

[0041] In the context of this invention, "actinochemically curable" or the term "actinochemical curing" should be understood to mean that curing is possible using photochemical radiation (i.e., electromagnetic radiation, such as near-infrared (NIR) and UV radiation, especially UV radiation) and particulate radiation (such as electron beams). Curing by UV radiation is typically initiated by free radical or cationic photoinitiators. A typical photocurable functional group is the carbon-carbon double bond, which is typically initiated using free radical photoinitiators. Therefore, photocuring is also based on chemical crosslinking.

[0042] Of course, physical curing, i.e., the mutual ring formation of polymer chains, can always occur during the curing of coating compositions described as chemically curable. However, in this case, the coating composition is described as chemically curable.

[0043] Similarly, the coating composition can be chemically curable via both thermochemical and photochemical mechanisms. Such a composition can be named a dual-curing coating composition.

[0044] From the above, it can be concluded that curing is caused by different mechanisms depending on the properties of the coating composition and the components present therein. These mechanisms, of course, require different curing conditions, and more specifically, different curing temperatures, curing radiation, and curing times.

[0045] In the case of a purely physically curable coating composition, curing is preferably achieved over a period of 2 to 48 hours at a temperature between 15°C and 90°C. Therefore, in this case, the difference between curing and air-drying and / or intermediate drying operations may only lie in adjusting the duration of the coating film. Furthermore, the distinction between air-drying and intermediate drying is meaningless. For example, a coating film produced by applying a physically curable coating composition at 15°C to 35°C for a period of, for example, 0.5 to 30 minutes, can be first air-dried or intermediate-dried, and then held at 50°C for a period of 5 hours.

[0046] In principle, the thermochemical curing of a single-component system is preferably carried out at a temperature of 100°C to 250°C, preferably 100°C to 180°C, for a period of 5 to 60 minutes, preferably 10 to 45 minutes, because these conditions are generally necessary for the conversion of the coating film into a cured coating film through a chemical crosslinking reaction. Therefore, any air-drying and / or intermediate drying stages prior to curing are carried out at lower temperatures and / or for shorter periods. In this case, for example, air-drying can be achieved at 15°C to 35°C for a period of, for example, 0.5 to 30 minutes, and / or intermediate drying can be achieved at, for example, at 40°C to 90°C for a period of, for example, 1 to 60 minutes.

[0047] In principle, the thermochemical curing of the two-component system is carried out at a temperature, for example, 15°C to 100°C, preferably 40°C to 100°C, for a duration of 5 to 80 minutes, preferably 10 to 50 minutes. Therefore, any air-drying and / or intermediate drying stages prior to curing are carried out at lower temperatures and / or for shorter periods. In this case, for example, it is no longer meaningful to distinguish between the terms "air-drying" and "intermediate drying." Any air-drying and / or intermediate drying stages prior to curing can, for example, be carried out at 15°C to 35°C for a duration of, for example, 0.5 to 30 minutes, but at least at a lower temperature and / or for a shorter period than the subsequent curing. This, of course, does not preclude curing of the two-component system at higher temperatures.

[0048] Unless otherwise stated, all temperatures illustrated in the context of this invention should be understood as the temperature of the chamber in which the coated substrate is located. Therefore, it does not mean that the substrate itself must have a specific temperature.

[0049] If an official standard is mentioned in the context of this invention without specifying an official expiry date, it implies the standard version that was valid on the application date, or, if no valid version existed on that date, the last valid version.

[0050] The method of the present invention

[0051] In the method of the present invention, a multi-coat paint system is continuously formed on a substrate to produce a multi-coat substrate (i.e., a substrate coated with a multi-coat paint system). In the first step (also referred to as “stage”) (1) of the method of the present invention, a plurality of substrates to be coated are provided.

[0052] In general and quite obviously, "multiple" means more than one. However, more specifically, the term is understood to refer to a large number of types or objects or subjects (it is neither necessary nor desirable to explicitly define an exact number). Furthermore, in the context of this invention, it is necessary to consider implementing a continuous method, thereby also being partially defined by the year-based energy consumption value (see details below). It is also quite obvious and consistent with the understanding of those skilled in the art, a continuous method means a method in which at least one particular step is performed in a plurality and sequentially (i.e., successively and temporarily one after another). What is apparent from the year-based values ​​described below, and therefore implicit in the claims, is that a continuous method for at least one year is contemplated. Therefore, it is also not intended to limit the general understanding of those skilled in the art regarding precise numbers; "multiple" and "continuous" should be understood in such a way that a large number of substrates are processed one after another in the manner more specifically defined in the claims and the following description.

[0053] Of course, this continuous method is typically carried out continuously (in a way that the substrate is treated sequentially in a timely and uniform manner). However, this does not preclude the possibility that the method and series may be interrupted from time to time and then resumed. The reasons may be planned / scheduled or unplanned actions, such as maintenance, replenishment, repair, or change of the coating material to be applied. In general, as is also apparent from the following value Ec (which is an annual-based value), the method of the present invention is carried out for at least one year (including possible interruptions as defined above). Furthermore, as is apparent from the above, the method of the present invention is preferably carried out continuously.

[0054] Available metal substrates generally include those comprising or composed of the following: for example, iron, aluminum, copper, zinc, magnesium and their alloys, as well as steel in various forms and compositions. Iron and steel substrates are preferred, such as those typically used in the automotive industry. The substrates can be in any form, meaning they can be, for example, simple sheets or complex components, such as, more particularly and preferably, automobile bodies and their parts.

[0055] Prior to stage (2) of the method of the present invention, the metal substrate may be pretreated in a manner known per se (i.e., for example, cleaning and / or providing a known conversion coating). Pretreatment can also be performed by applying a conversion coating, particularly by phosphating and / or chromating, preferably phosphating. Preferably, the metal substrate is at least treated with a conversion coating, particularly preferably by zinc phosphate treatment and then phosphated. Furthermore, the metal substrate is typically coated with an electrocoating material prior to step (2), i.e., a cured electrocoating is produced on the metal substrate by electrophoretically applying the electrocoating material to the substrate and subsequently curing the electrocoating material. Finally, it can be mentioned that a typical primer layer may also be produced on the substrate prior to step (2), i.e., a primer composition may be applied and then cured.

[0056] Available plastic substrates are conventional plastics, examples of which are polystyrene (PS), polyvinyl chloride (PVC), polyurethane (PU), glass fiber reinforced unsaturated polyester, polymethyl methacrylate (PMMA), polyphenylene sulfide (PPS), polyoxymethylene (POM), polyphenylene ether (PPE), polyphenylene ether (PPO), polyurea, polybutadiene, terephthalate (PBT), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), and polyolefins such as polypropylene (PP). Alternatively, the substrate may comprise a variety of the aforementioned plastics, in other words, a mixture of these plastics. For example, polypropylene (PP) modified with ethylene-propylene-diene copolymer (EPDM) (PP / EPDM blends) may be mentioned.

[0057] The plastic substrate can be a simple plastic sheet. However, as a substrate, it can also be a vehicle body made of plastic, or specific vehicle parts, as well as vehicle components and accessories for installation in or on a vehicle, for both interior and exterior vehicle areas.

[0058] The substrate can be pretreated in a conventional manner. Suitable pretreatments include surface activation pretreatments such as flame treatment, plasma treatment, and corona discharge, with flame treatment being particularly important.

[0059] As an alternative to or supplement to the described surface activation pretreatment, the substrate may be provided with an adhesion primer and / or primer-surface coating that are known in principle. The corresponding coating compositions are known and can be applied, for example, directly to a substrate that may have undergone surface activation pretreatment, and then these coating compositions can be cured.

[0060] In stage (2) of the method of the present invention, the primer coating on each substrate is produced by sequentially applying an aqueous primer coating composition to the substrate. As already explained above, “sequentially” means that individual substrates (which may be the same or different) are processed one after another as defined, i.e., coated by applying the aqueous primer coating composition. This continuous application is preferably carried out within an industrial coating production line. It is also preferred that the substrate to be coated is moved and conveyed to the coating position by common means (e.g., a skid). The coating process can then be carried out, for example, as a coating in progress (i.e., continuous movement of the substrate through a coating station (especially a robotic coating station)) or as a stop-and-go process (i.e., keeping the substrate in a fixed position, then coating it, and then moving it in the production line).

[0061] The aspects of "continuous production" and / or "serial production" are quite obviously relevant in many aspects of the invention. The terms and their meanings have been fully set forth above and will not be discussed further in any and all of the following descriptions. However, it will be apparent that the basic principles apply throughout the scope of the invention.

[0062] Since the method of the present invention is (partly) a continuous process / method defined by a year-based value, it is obvious that it is not possible to use only one single and specific type of primer composition throughout the entire duration of the method. It is quite apparent that, within a continuous process, the primer can be changed from time to time (e.g., to achieve different colors). There is no limitation on the number or variation of the specific primer compositions to be applied, provided that all applied primers meet the criteria for primers as defined for the embodiments (e.g., the criteria of claim 1). Therefore, the statement of "aqueous primer composition" in claim 1 does not mean that only "one type" of primer composition must be applied throughout the entire duration of the method, but should be understood as defining the application of one primer composition to a single substrate in step (2) (thereby allowing another primer composition to be applied to another single substrate).

[0063] Therefore, the primer coating is applied to the substrate after production. It is quite obvious that the exact basis of the primer coating depends on the substrate and any coating and / or treatment steps performed on the substrate prior to step (2). For example, the primer coating material (also referred to as the composition) may be applied directly to the cured electroplated coating.

[0064] The aqueous primer material contains at least one aqueous dispersion of at least one polyacrylate and at least one aqueous dispersion of at least one polyurethane, wherein the polyurethane comprises at least one cyclic polyisocyanate component. Furthermore, it is quite evident that the primer contains at least one pigment.

[0065] The base coat material can be applied by methods known to those skilled in the art for applying liquid coating compositions, such as by dipping, bar coating, spraying, roller coating, etc.

[0066] Preferred methods include spray application, such as compressed air spraying (pneumatic application), airless spraying, high-speed rotation, electrostatic spraying (ESTA), optionally combined with thermal spraying (e.g., hot air spraying).

[0067] After application, the applied primer material or corresponding primer is preferably allowed to air dry, for example, at 15°C to 35°C for a period of time, for example, 0.5 to 30 minutes, and / or intermediately dried and / or cured at a temperature preferably 40°C to 100°C for a period of time, for example, 1 to 60 minutes. It is preferred to first air dry at 15°C to 35°C for a period of time, and then intermediately dry and / or (partially) cure at 40°C to 100°C for a period of time, for example, 1 to 60 minutes.

[0068] In stage (2) and between stage (2) and stage (3), the base coat is preferably not exposed to temperatures above 100°C for a period of time longer than 1 min, and is particularly preferably not exposed to temperatures above 100°C at all.

[0069] The application of the base coat material is achieved in such a way that a coating thickness of, for example, 5 to 40 micrometers, preferably 6 to 35 micrometers, and especially preferably 7 to 30 micrometers, is achieved after curing in stage (4).

[0070] The waterborne primer material contains at least one waterborne dispersion of at least one polyacrylate and at least one waterborne dispersion of at least one polyurethane, wherein the polyurethane contains at least one cyclic polyisocyanate component.

[0071] It is quite obvious to those skilled in the art that the above-described aqueous dispersions and the corresponding polymers (i.e., polyacrylates and polyurethanes) contained therein are detailed, optional, and exemplary. Furthermore, the production of such polymers and the corresponding aqueous dispersions is known. For example, it is known that polyurethanes are prepared using polyisocyanates. Therefore, the statement "polyurethane contains at least one cyclic polyisocyanate component" is clearly understood in such a way that this polyisocyanate is used as a raw material / separate in the production of polyurethane. In other words: of course, polyurethane containing polyisocyanates means that the polyisocyanates are contained in their reactive form (i.e., if appropriate, primarily reacting with hydroxyl and also amino groups).

[0072] Preferably, the polyurethane contains a cyclic polyisocyanate, more preferably a cyclic diisocyanate. A particularly preferred cyclic polyisocyanate is isophorone diisocyanate.

[0073] The aqueous primer composition preferably has a VOC (volatile organic compound content) of no more than 300 g / l, more preferably no more than 250 g / l, even more preferably no more than 200 g / l, and in particularly preferred embodiments no more than 150 g / l (measured according to DIN EN ISO 11890-2 (December 2020)).

[0074] The base coat material used according to the invention and the corresponding stage (2) comprises at least one pigment. These should be understood to mean colored pigments and / or visual effect pigments known per se. More preferably, it includes visual effect pigments.

[0075] Such colored pigments and effect pigments are known to those skilled in the art and described, for example, in Römpp-Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, pp. 176 and 451. The terms “coloring pigment” and “color pigment” are used interchangeably, just as the terms “visual effect pigment” and “effect pigment” are used interchangeably.

[0076] Preferred effect pigments include, for example, flake-like metallic effect pigments such as layered aluminum pigments, gold bronze, bronze oxide, and / or iron oxide-aluminum pigments; pearlescent pigments such as pearl essence, basic lead carbonate, bismuth chloride and / or metal oxide-mica pigments; and / or other effect pigments such as layered graphite, layered iron oxide; multilayer effect pigments composed of PVD films; and / or liquid crystal polymer pigments. Layered metallic effect pigments, especially layered aluminum pigments, are particularly preferred.

[0077] Typical colored pigments include inorganic colored pigments, such as white pigments, such as titanium dioxide, zinc white, zinc sulfide or zinc barium white; black pigments, such as carbon black, iron manganese black or spinel black; colored pigments, such as chromium oxide, hydrated chromium oxide green, cobalt green or ultramarine green, cobalt blue, ultramarine blue or manganese blue, ultramarine violet or cobalt violet and manganese violet, iron oxide red, cadmium sulfide selenide, molybdenum chrome red or ultramarine red; iron oxide brown, mixed brown, spinel phase and corundum phase or chrome orange; or iron oxide yellow, nickel titanium yellow, chrome titanium yellow, cadmium sulfide, zinc cadmium sulfide, chrome yellow or bismuth vanadate.

[0078] The proportion of pigment is preferably in the range of 1.0% to 40.0% by weight, preferably 2.0% to 20.0% by weight, and more preferably 5.0% to 15.0% by weight, in each case based on the total weight of the water-based primer material.

[0079] The waterborne primer material preferably further comprises at least one polymer, particularly at least one polyester, in addition to the polymers in the dispersion described above. Furthermore, the primer material may contain at least one typical crosslinking agent known per se, such as amino plastic resins or polyisocyanates. Additionally, the waterborne primer material may contain at least one additive. Examples of such additives include salts that can be thermally decomposed with no or substantially no residue; resins that act as binders that are physically, thermally, and / or photochemically irradiable and are different from the polymers already mentioned; additional crosslinking agents; organic solvents; reactive diluents; transparent pigments; fillers; dyes soluble in the molecular dispersion; nanoparticles; light stabilizers; antioxidants; degassing agents; emulsifiers; slip additives; polymerization inhibitors; free radical polymerization initiators; adhesion promoters; flow control agents; film-forming aids; sag control agents (SCA); flame retardants; corrosion inhibitors; waxes; desiccants; biocides; and matting agents.

[0080] The solids content of the primer material can vary depending on the requirements of individual cases. The solids content is primarily guided by the viscosity required for application, more specifically, spray application, and can therefore be adjusted by a technician, optionally with the aid of several exploratory tests, based on his or her general technical knowledge. The solids content of the primer material is preferably 5% to 70% by weight, more preferably 8% to 60% by weight, and most preferably 12% to 55% by weight. Solids content (non-volatile fraction) refers to the weight fraction retained as a residue upon evaporation under specified conditions. In this specification, the solids content is determined according to DIN EN ISO 3251. This is accomplished by evaporating the primer material at 130°C for 60 minutes.

[0081] The primer material is water-based. In this context, the term "aqueous" is known to those skilled in the art. The phrase generally refers to a primer material that is not solely based on organic solvents, i.e., it does not merely contain organic-based solvents as its solvent, but rather includes a significant fraction of water as a solvent. For the purposes of this invention, "aqueous" should preferably be understood to mean that the coating composition in question, more particularly the primer material, has a water content of at least 40%, preferably at least 45%, and very preferably at least 50% by weight, based on the total amount of solvents present (i.e., water and organic solvents). More preferably, the water content is 40% to 95% by weight, more particularly 45% to 90%, and very preferably 50% to 85% by weight, based on the total amount of solvents present.

[0082] The base coating material used according to the present invention can be produced using conventional and known mixing components and mixing techniques for producing base coating materials.

[0083] After stage (2) of the invention and before stage (3), additional layers, particularly additional base coats, may of course be produced. In this case, it is quite obvious that the transparent coating produced in step (3) is therefore not produced directly on the base coat of stage (2). Such additional base coats may be optional in the case of an integration process, for example, as mentioned in the introduction. In this case, the base coat material may be the same or different.

[0084] In a preferred embodiment of the invention, after stage (2) and before stage (3), in stage (2a), the sequential production of the second base coat is carried out by sequentially applying the aqueous base coat composition directly onto the substrate coated with the base coat produced according to step (2). Therefore, the aqueous base coat compositions of stage (2) and stage (2a) are different from each other. Preferably, the base coat composition of stage (2) has a higher pigment content than the base coat composition of stage (2a).

[0085] In stage (3) of the method of the present invention, a transparent coating material is sequentially applied to the base coat of step (2) and thus to the substrate coated with the base coat produced in step (2). Thus, a transparent coating is produced sequentially.

[0086] In this context, the transparent coating material can, in principle, be any transparent coating composition known to those skilled in the art. This includes aqueous or solvent-based transparent coating compositions, which can be formulated as one-component, two-component, or multi-component coating compositions. Solvent-based transparent coating materials are preferred.

[0087] Similarly, as explained for the base coat composition of stage (2), more than one single and specific type of clear coat composition must be used throughout the duration of the method. The same principles outlined above for the base coat composition of stage (2) apply to stage (3) and the clear coat composition.

[0088] The transparent coating material used can be, in particular, thermochemically and / or photochemically curable. Thermochemically curable transparent coating materials are preferably two-component transparent coating materials. Furthermore, the transparent coating material can be a dual-curing transparent coating material. In any case, it is important that the transparent coating material is adapted to correspond to step (4) of the present invention, i.e., the curing of the transparent coating material does not exceed a certain level of the average annual energy consumption value Ec as defined below.

[0089] In a preferred embodiment, the transparent coating material is a photochemically curable transparent coating material, and more particularly a UV-curable transparent coating material. Such preferred transparent coating materials may particularly comprise olefinically unsaturated urethane-acrylate oligomers. These oligomers are then crosslinked under UV exposure, resulting in the formation of a cured coating film.

[0090] In another preferred embodiment, the transparent coating material is a thermocurable two-component transparent coating material containing hydroxyl-functional polymers, particularly hydroxyl-functional acrylates and free polyisocyanates as crosslinking agents.

[0091] In another preferred embodiment, the transparent coating material has dual curing characteristics, meaning that the components of the preferred photochemically curable transparent coating material and the two-component transparent coating material are both part of the transparent coating material.

[0092] The transparent coating composition preferably has a VOC (volatile organic compound content) of no more than 500 g / l, more preferably no more than 400 g / l, even more preferably no more than 350 g / l, and in particularly preferred embodiments no more than 300 g / l (measured according to DIN EN ISO 11890-2 (December 2020)).

[0093] The transparent coating material is applied by methods known to those skilled in the art for applying the liquid coating composition, such as dipping, bar coating, spraying, roller coating, etc. Spraying application methods, such as compressed air spraying (pneumatic application) and electrostatic spraying (ESTA), are preferred.

[0094] After application, the transparent coating material or the corresponding transparent coating is preferably air-dried or intermediate-dried at 15°C to 35°C for a period of 0.5 to 30 minutes. The application of the transparent coating material is carried out in such a way that the transparent coating has a coating thickness of, for example, 15 to 80 micrometers, preferably 20 to 65 micrometers, and particularly preferably 25 to 60 micrometers after curing in stage (4).

[0095] Preferably, the transparent coating material is the last coating material applied in the method of the present invention. Therefore, the transparent coating is the uppermost layer in all multi-coat paint systems.

[0096] In stage (4) of the method of the present invention, the curing of the transparent coating occurs. As outlined in the introduction, curing should be understood as meaning the transformation of the corresponding film into a ready-to-use state, that is, a state in which the substrate provided with the corresponding coated film (or multiple coatings) can be transported, stored and used as intended.

[0097] Similarly, as outlined above, the method of the present invention is a continuous method, meaning that the sequentially coated substrates are then introduced into a curing zone (e.g., an oven or photochemical radiation and thus a curing chamber). As the substrates are preferably moved and conveyed through a production line setup (e.g., on corresponding skids), typically more than one coated substrate is introduced in parallel into the curing zone and moved through it. Again, as outlined above, the movement can be at a constant or varying speed, meaning that each coated substrate is exposed to curing conditions within the curing zone for a certain and adjustable duration.

[0098] Therefore, the curing step (4) is carried out in a curing chamber (or curing area / curing compartment) (i.e., an oven or curing chamber for photocuring). Of course, it is also possible to achieve both functions in one curing chamber (or curing area / curing compartment), namely the functions of an oven and a curing chamber for photocuring. However, it is clear that thermocuring requires the function of an oven, while photocuring requires the function of a photocuring chamber. For clarity, these functions, and therefore the terms (oven, curing chamber), are used in the definitions of summation e1 to e4 as defined below.

[0099] Furthermore, as is clearly understood from this specification, step (4) involves thermosetting or photocuring or both.

[0100] As outlined above, in step (4), the curing of the transparent coating occurs. This should be understood in a way that at least the transparent coating is cured. Therefore, it is possible that, in addition to the transparent coating, other layers, particularly the undercoat from step (2), are cured. However, this is not necessarily the case, but depends on the exact curing conditions, for example, in step (4), and also on the properties and chemical composition of the undercoat material and the layers. Furthermore, it is certainly possible, of course, that the undercoat is cured at least partially at an earlier stage in the method and therefore before step (4).

[0101] In and after stage (4), it is preferable that the coating and therefore the multi-coated substrate are not exposed to temperatures greater than 115°C for a period of time greater than 1 minute, and particularly preferably not exposed to temperatures greater than 115°C at all. More preferably, it is preferable that the coating and therefore the multi-coated substrate are not exposed to temperatures greater than 105°C for a period of time greater than 1 minute, and particularly preferably not exposed to temperatures greater than 105°C at all. Even more preferably, it is preferable that the coating and therefore the multi-coated substrate are not exposed to temperatures greater than 80°C for a period of time greater than 1 minute, and particularly preferably not exposed to temperatures greater than 80°C at all. Most preferably, it is preferable that the coating and therefore the multi-coated substrate are not exposed to temperatures greater than 60°C for a period of time greater than 1 minute, and particularly preferably not exposed to temperatures greater than 60°C at all.

[0102] Necessary, the curing step (4) is carried out in such a manner as follows: based on the average energy consumption value per square meter of multi-coated substrate Ec, which is at most and therefore does not exceed 1.5 kWh / m². 2 Preferably, the energy consumption value Ec does not exceed 1.25 kWh / m³. 2 Or 1.0 kWh / m 2 Or 0.9 kWh / m 2 Or 0.8 kWh / m 2 or 0.7 kWh / m 2 or 0.6 kWh / m 2 or 0.5 kWh / m 2 or 0.4 kWh / m 2 or 0.3 kWh / m 2 or 0.2 kWh / m 2 Or 0.1 kWh / m 2 .

[0103] As is evident from the above, the value Ec refers to one square meter of multi-coated substrate, i.e., a multi-coated substrate produced by the method of the present invention. Therefore, the substrate is coated with at least both a base coat and a clear coat (i.e., portions of the substrate, for example, not coated with a clear coat, are not considered in this calculation).

[0104] According to the definition, the average energy consumption value Ec / m² for multi-coated substrates based on the year is calculated as follows:

[0105] in

[0106] - e1 reflects the energy loss due to the exhaust gas from the oven and is determined as

[0107] in Reflecting the average density of air, Reflects the average specific heat capacity of air 293 K reflects the average room temperature / ambient temperature outside the oven. a = Year-based average exhaust volume flow rate from this oven [ ] b = Operating time from this oven / year [ ] c1 = Area of ​​multi-coated substrates processed in this oven per year [ ] T1 = Average oven temperature [K] during operation, based on the year. - e2 reflects the energy loss from the oven via surface transfer and is determined to be

[0108] in This is a correction factor that takes into account the insulation and heat transfer efficiency of a standard oven. d = Total surface area of ​​the oven (including the ground) calculated as a cuboid. ] - e3 reflects the energy consumption used to heat the multi-coated substrate for thermosetting and is determined to be...

[0109] in

[0110] f = Year-based average specific heat capacity of the treated substrate [ ]

[0111] g = Mass of uncoated substrate treated in this oven per year [kg]

[0112] - e4 reflects the energy consumption of the photochemical radiation used for photocuring and is determined to be... = Number of photochemical radiation sources of type x = Electrical power [kW] of type x photochemical radiation source = Year-based average operating time of x-type photochemical radiation sources [h] (Where x reflects the number of different types of photochemical radiation sources applied) c2 = Area of ​​multi-coated substrates treated in the curing chamber per year [ ].

[0113] As can be observed from the sum of the four individual influencing factors in the above formula, the value Ec reflects the energy consumption per square meter of coated substrate for treatment for curing (i.e., heating in an oven and / or exposure to photochemical radiation), and furthermore, a year-based average is considered (to produce a representative value). The value Ec is clearly intended to reflect and therefore specifically describe the curing process in industrial equipment, and not necessarily a laboratory-scale value. In general, the present invention focuses precisely on this industrial-scale method and the conditions of such a method (see also the explanation of "multiple" and "continuous" above). Therefore, it is preferred that the method of the present invention (also referred to as the method) is an industrial-scale method carried out in industrial equipment.

[0114] The first summation and influence factor e1 reflect the energy loss from the oven exhaust. It is quite understandable that ovens used for heating multi-coated substrates and thus curing at least the transparent coating of the multi-coated substrate require an effective exhaust system, as the curing process results in the evaporation of solvent / water and possibly additional chemical compounds generated by chemical transformations during chemical curing. It is quite understandable that the foregoing is particularly important in industrial-scale settings. Of course, removing this evaporation via exhaust inevitably involves significant heat and therefore energy loss. Factor e1 describes this energy loss, calculated by taking into account a representative and therefore meaningful average of the air density, the average specific heat capacity of air, and the average room temperature / ambient temperature outside the oven. The average exhaust volume a for the year is obtained from the documentation and monitoring of the corresponding setup curves of the oven. This also applies to the average oven temperature T1 for the year and the oven operating time / year b for the oven's operation period. Specifically, "operation time" and "operation period" reflect the active operation of the oven and therefore the time during which the heating scheme runs, i.e., the time during which the oven actually consumes energy. For example, the passive cooling time (where no active heating occurs and therefore no energy consumption of the oven occurs, such as cooling for preparation for maintenance) is not part of the operating time. Furthermore, the area / year c1 of multi-coated substrates treated in the oven is obtained from documentation and monitoring of the relevant equipment settings. Quite clearly, parameter c1 still refers to the operating time, i.e., the area treated in the oven under oven operation.

[0115] It is obvious that, in the absence of heating in the oven during step (4) of the method of the present invention, the energy loss e1 from the exhaust gas from the oven is zero by definition (because T1 is set to 293 K by definition). For example, this could be the case for a pure photocuring step (4).

[0116] In the case of at least one thermosetting step (4), the energy loss e1 from the exhaust gas from the oven is preferably no greater than 0.6 kWh / m. 2 More preferably not greater than 0.5 kWh / m 2 Or even more preferably no more than 0.4 kWh / m 2 And particularly preferably not greater than 0.3 kWh / m 2 Preferably, e1 is no greater than 0.25 kWh / m³. 2 Or even no more than 0.2 kWh / m 2 In another preferred embodiment, i.e., in which step (4) is purely photochemical, it is quite obvious that the factor e1 will even be 0 kWh / m. 2 .

[0117] For example, in a standard oven used for thermosetting in an industrial-scale setup, it would be expected to have approximately 15,000 [ The average exhaust volume flow rate from the oven based on the year. Set the oven's operating time / year to 6100 [ The area / year of multi-coated substrates to be processed in the oven is set at 10,500,000. (250,000 cars, with a multi-coated substrate surface area of ​​42 m²) 2 Furthermore, setting the average oven temperature during operation based on the year to 110°C will result in an energy loss of e1 = 0.28 kWh / m³ from the oven exhaust. 2 For example, variations in the year-based average exhaust volume flow rate from the oven, or the oven's operating time per year, or the area per year of multi-coated substrates treated in the oven, may certainly deviate, but are fully taken into account in the calculation of e1.

[0118] The second summation and influence factor e2 reflect the energy loss from the oven via surface transfer. Similarly, it is quite understandable that an oven used for heating multi-coated substrates and thus curing at least the transparent coating of the multi-coated substrate will result in energy loss via its interface between the interior and exterior of the oven due to the temperature difference between the interior and exterior. While oven setups are typically insulated via, for example, walls / tops, such energy loss is, of course, unavoidable. Again, it is quite understandable that the foregoing aspects are particularly important in industrial-scale setups. Factor e2 describes this energy loss, and is thus calculated considering a representative and therefore meaningful correction factor that takes into account the insulation and heat transfer efficiency of a standard oven. The total surface area d of the oven (including the ground) represents the geometry of the oven as a cuboid. It is quite obvious that such an oven will always be constructed as a building block or unit that can generally be described as such a cuboid. However, to properly account for cavities, pipes, exhaust pipes, and other geometric deviations of the oven surface, a factor of 1.8 is considered in the calculation. Finally, representative values ​​are generated that appropriately represent the geometry of the interface between the interior and exterior. Parameters b and c1 have been described above, and the year-based average value e2 is also provided. Parameter T1 has also been described above.

[0119] Similarly, it is obvious that, in the absence of heating in the oven during step (4) of the method of the present invention, the energy loss value e2 is zero by definition (because T1 is set to 293 K by definition). For example, this could be the case for a pure photocuring step (4).

[0120] In the case of at least one thermosetting step (4), the energy loss e2 from the oven via surface transfer is preferably no greater than 0.4 kWh / m 2 More preferably, not greater than 0.3 kWh / m 2 Or even more preferably no more than 0.2 kWh / m 2 And particularly preferably not greater than 0.15 kWh / m 2 Preferably, e1 is no greater than 0.125 kWh / m³. 2 Or even no more than 0.1 kWh / m 2 In another preferred embodiment, i.e., in which step (4) is purely photochemical, it is quite evident that the factor e2 will even be 0 kWh / m. 2 .

[0121] For example, in a standard oven used for thermosetting in an industrial-scale setup, a capacity of approximately 3500 m³ would be expected. 2 The total area of ​​the oven surface (including the ground).

[0122] Similarly, set the oven's operating time / year to 6100 [ The area / year of multi-coated substrates to be processed in the oven is set at 10,500,000. (250,000 cars, with a multi-coated substrate surface area of ​​42 m²) 2 Furthermore, setting the average oven temperature during operation to 110°C based on the year will result in an energy loss e2 = 0.17 kWh / m² via surface transfer. 2 For example, variations in the total area of ​​the oven surface (including the ground), the oven's operating time per year, or the area per year of multi-coated substrates treated in the oven may certainly deviate, but are fully taken into account in the calculation of e2.

[0123] The third sum and influence factor e3 reflect the energy consumption of thermosetting, i.e., the energy invested in heating the multi-coated substrate in the oven to thermoset at least the produced clear coating. Obviously, heating the clear coating deposited on the substrate also requires heating the substrate itself (the total substrate, not just the multi-coated portion by the method of the present invention). The energy consumption is also calculated via temperature T1, however, corrected by factor 1.1 to account for the deviation between the substrate temperature and the oven temperature (i.e., the ambient temperature). Parameter f is the year-based average specific heat capacity of the substrate (uncoated) heated in the method of step (4). Obviously, different materials (such as different metals or plastics instead of metals) have varying specific heat capacities, which need to be taken into account based on the year-based average. Parameter f can be obtained from documentation and monitoring of the corresponding equipment settings (i.e., documentation of the type and amount of substrate applied by the equipment and therefore the method). The heat capacity and its year-based average are calculated based on the substrate itself (i.e., the substrate before any coating (such as pretreatment or primer) is applied) or also according to the undercoat in stage (2) or according to the clear coating in stage (3). Parameter g is the total mass / year of substrates (also uncoated) treated in the corresponding oven (total substrates, not just the portion multi-coated by the method of the present invention). Quite obviously, parameter g also refers to the operating time, i.e., the mass processed in the oven under oven conditions. Again, this parameter is available from the documentation of equipment settings and operation. Parameter c1 has been described above, and an average value e3 per square meter based on the year is provided.

[0124] Similarly, it is obvious here that, in the absence of heating in the oven during step (4) of the method of the present invention, the energy consumption e3 is zero by definition.

[0125] In the case of at least one thermosetting step (4), the energy consumption e3 is preferably not greater than 0.7 kWh / m 2More preferably not greater than 0.6 kWh / m 2 Or even more preferably no more than 0.5 kWh / m 2 And particularly preferably not greater than 0.4 kWh / m 2 Preferably, e1 is no greater than 0.3 kWh / m³. 2 Or even no more than 0.25 kWh / m 2 In another preferred embodiment, i.e., in which step (4) is purely photochemical, it is quite obvious that the factor e3 will even be 0 kWh / m³. 2 .

[0126] For example, in a standard oven used for thermosetting in an industrial-scale setup, a substrate (steel) of 0.475 [is expected to be present]. The average specific heat capacity based on the year and the mass / year of substrate (uncoated) treated in the oven at 307,500,000 kg (250,000 cars, each with a gross mass of 1230 kg) are also used. Similarly, the average oven temperature based on the year during operation will be set at 110°C, and the area / year of multi-coated substrates treated in the oven will be set at 10,500,000. This will result in an energy consumption of e3 = 0.38 kWh / m³. 2 For example, the year-based average specific heat capacity of the substrate treated in the oven or the variation in the mass / year of the substrate (uncoated) may certainly be biased, but these variations are fully accounted for in the calculation of e3.

[0127] The fourth and last summation and influence factor for the value Ec reflect the energy consumption of the photochemical radiation used for photocuring. Understandably, this energy consumption of the corresponding photochemical radiation source, preferably a UV lamp, positioned for irradiating a multi-coated substrate (i.e., positioned within an illumination / curing chamber), is calculated as the sum of the energy consumption contributions of all different types of radiation sources of x applied over the relevant time period (i.e., year). Similarly, to calculate the year-based average, the number of sources of a certain type, the electrical power of the corresponding type of radiation source, and the year-based average operating time of the corresponding type of radiation source need to be considered. This parameter is also available from documentation of equipment setup and operation. Parameter c2 is equivalent to parameter c1 already described above (i.e., the curing chamber, not the oven) and ultimately provides a year-based average value e4 / m².

[0128] It is obvious that, in the absence of photochemical radiation, this means that no photochemical curing occurs in step (4), and by definition, the energy consumption e4 of the method of the present invention is zero.

[0129] In the case of at least one photocuring step (4), the energy consumption e4 is preferably no greater than 0.25 kWh / m 2 More preferably not greater than 0.2 kWh / m 2 Or even more preferably no more than 0.175 kWh / m 2 And particularly preferably not greater than 0.15 kWh / m 2 Preferably, e1 is no greater than 0.125 kWh / m³. 2 Or even no more than 0.1 kWh / m 2 In another possible embodiment, i.e., in which step (4) is purely thermal, it is quite obvious that the factor e4 would even be 0 kWh / m. 2 .

[0130] For example, in a standard oven used for photocuring in an industrial-scale setup, it is expected to have 25 UV lamps as radiation sources, one type of which has an electrical power of 6 kW and a power rating of 5200 [ ]. The average operating time based on the year. Similarly, the area / year of multi-coated substrates to be treated in the curing chamber is set to 10,500,000. This will result in an energy consumption of e4 = 0.074 kWh / m³. 2 .

[0131] In a preferred embodiment, the curing step (4) is a thermosetting step, and the average energy consumption value Ec based on the year does not exceed 0.9 kWh / m 2 In another preferred embodiment, the curing step (4) is a photocuring step, and the average energy consumption value Ec based on the year does not exceed 0.2 kWh / m. 2 .

[0132] After stage (4) of the method of the present invention, a multi-coat paint system is obtained on a substrate (i.e., a multi-coat substrate).

[0133] The present invention will be illustrated by examples below.

[0134] Example

[0135] Producing water-based primer compositions and solvent-based transparent coating compositions for the production of multi-coated metal substrates.

[0136] In other conventional components, the produced first aqueous primer composition contains an aqueous dispersion of polyacrylate and an aqueous dispersion of polyurethane. The polyurethane is synthesized using a cyclic diisocyanate. The first aqueous primer contains 40% as a pigment (in the form of a pigment paste). The mixture is prepared by heating at 23°C for 1000 s.-1 The individual components were mixed under shear load, and the primer composition was then adjusted to a pH of 8 and a spray viscosity of 100 mPas (from a Mettler-Toledo Rheomat RM 180 rotational viscometer) using deionized water and dimethylethanolamine for actual production.

[0137] In other conventional components, the produced second aqueous primer composition contains an aqueous dispersion of polyacrylate and an aqueous dispersion of polyurethane. The polyurethane is synthesized using a cyclic diisocyanate. The first aqueous primer contains 8% as a pigment (in the form of a pigment paste). The mixture is prepared by heating at 23°C for 1000 s. -1 The individual components were mixed under shear load, and the primer composition was then adjusted to a pH of 8 and a spray viscosity of 100 mPas (from a Mettler-Toledo Rheomat RM 180 rotational viscometer) using deionized water and dimethylethanolamine for actual production.

[0138] In other conventional components, the produced solvent-based clear coating composition contains a mixture of urethane acrylate resins. Actual production is carried out by mixing the individual components under stirring. The isocyanate-containing compound is added to the mixture prior to spray application.

[0139] Subsequently, multi-coated metal substrates are produced according to the following general procedures.

[0140] Provide a 10×20 cm cathode electrocoated steel sheet. Then, apply a first aqueous primer composition to a thickness of 18-23 micrometers (all specified thicknesses are related to the final cured thickness). Subsequently, allow the primer to air dry at room temperature for 5 minutes.

[0141] Next, a second water-based primer composition is applied to a thickness of 10-15 micrometers, allowed to air dry at room temperature for 5 minutes, and then cured in an air-circulating oven at 90°C for 10 minutes. Finally, a solvent-based clear coating composition is applied to the primer-coated substrate to a thickness of 35-40 micrometers. The resulting clear coating is allowed to air dry at room temperature for 5 minutes and then cured by UV radiation.

[0142] The method for continuous production of multi-coated substrates as claimed in claim 1 can be carried out using the coating compositions described above and combinations thereof, as similarly outlined. This method can achieve a flow rate of less than 0.1 kWh / m³. 2 The annual average energy consumption value Ec is calculated (e1 = e2 = e3 = 0; e4 is less than 0.1 kWh / m³).2 ).

[0143] The coating substrates were evaluated in terms of appearance and adhesion properties.

[0144] Appearance:

[0145] Adhesion: Before and after humidity exposure, GT (2 mm) = 0-1 (DIN EN ISO 6270-2). It passed the chemical resistance test conducted with a fluid containing NaOH and methanol.

[0146] Therefore, multi-coated substrates have shown good results in terms of coating properties in the automotive industry.

Claims

1. A method for continuous production of multi-coated substrates, wherein, The method includes (1) Provide multiple substrates to be coated. (2) A primer is produced by sequentially applying an aqueous primer composition to each of these substrates, wherein the aqueous primer composition comprises at least one aqueous dispersion of at least one polyacrylate and at least one aqueous dispersion of at least one polyurethane. (3) By sequentially applying the transparent coating composition to each substrate coated according to step (2) to produce a transparent coating, a multi-coated substrate is produced. (4) Curing the transparent coating produced according to step (3), Step (4) is characterized by an average annual energy consumption value Ec of up to 1.5 kWh per square meter of multi-coated substrate. The annual average energy consumption value Ec is calculated as follows: in - e1 reflects the energy loss due to the exhaust gas from the oven and is determined as in Reflecting the average density of air, Reflects the average specific heat capacity of air 293 K reflects the average room temperature / ambient temperature outside the oven. a = Year-based average exhaust volume flow rate from this oven [ ] b = Operating time from this oven / year [ ] c1 = Area of ​​multi-coated substrates processed in this oven per year [ ] T1 = Average oven temperature [K] during operation, based on the year. - e2 reflects the energy loss from the oven via surface transfer and is determined to be in This is a correction factor that takes into account the insulation and heat transfer efficiency of a standard oven. d = Total surface area of ​​the oven (including the ground) ] - e3 reflects the energy consumption used to heat the multi-coated substrate for thermosetting and is determined to be... in f = Year-based average specific heat capacity of the treated substrate [ ] g = Mass of uncoated substrate treated in this oven per year [kg] - e4 reflects the energy consumption of the photochemical radiation used for photocuring and is determined to be... = Number of photochemical radiation sources of type x = Electrical power [kW] of type x photochemical radiation source = Year-based average operating time of x-type photochemical radiation sources [h] (Where x reflects the number of different types of photochemical radiation sources applied) c2 = Area of ​​multi-coated substrates treated in the curing chamber per year [ ].

2. The method according to claim 1, wherein, The substrate is a car body or a part thereof, or both.

3. The method according to any one of claims 1 to 2, wherein, During stage (2) and between stage (2) and stage (4), the coating composition and layer, as well as the substrate, are not exposed to temperatures greater than 100°C.

4. The method according to any one of claims 1 to 3, wherein, In stage (4) and thereafter, the coating and therefore the multi-coated substrate are not exposed to temperatures greater than 115°C, preferably not greater than 105°C.

5. The method according to any one of claims 1 to 4, wherein, Any transparent coating composition used is a thermochemically curable two-component transparent coating composition and / or a photochemically curable transparent coating composition and / or a dual-curing transparent coating composition.

6. The method according to any one of claims 1 to 5, wherein, The transparent coating composition used is a photochemically curable transparent coating composition, preferably a UV-curable transparent coating composition.

7. The method according to any one of claims 1 to 6, wherein, The curing step (4) is a thermosetting step, and the average energy consumption value Ec based on the year does not exceed 0.9 kWh / m 2 Preferably 0.7 kWh / m 2 .

8. The method according to any one of claims 1 to 7, wherein, The transparent coating composition used contains an olefinically unsaturated urethane-acrylate oligomer.

9. The method according to any one of claims 1 to 8, wherein, The substrate is at least partially selected from metal substrates, wherein prior to stage (2), the metal substrate is pretreated by producing at least (i) a conversion coating and (ii) an electrocoating layer thereon.

10. The method according to claim 9, wherein, The substrate is selected from metal substrates.

11. The method according to any one of claims 1 to 9, wherein, The substrate is at least partially a plastic substrate.

12. The method according to any one of claims 1 to 11, wherein, The polyurethane contains at least one cyclic polyisocyanate component.

13. The method according to any one of claims 1 to 12, wherein, The aqueous primer composition of step (2) has a VOC (volatile organic compound content) of not more than 300 g / l, preferably not more than 250 g / l, more preferably not more than 200 g / l (measured according to DIN EN ISO 11890-2 (December 2020)).

14. The method according to any one of claims 1 to 13, wherein, The transparent coating composition has a VOC (volatile organic compound content) of no more than 500 g / l, preferably no more than 400 g / l, more preferably no more than 350 g / l (measured according to DIN ENISO 11890-2 (December 2020)).

15. The method according to any one of claims 1 to 6 or 8 to 14, wherein, The curing step (4) is a photocuring step, and the average energy consumption value Ec based on the year does not exceed 0.2 kWh / m. 2 .

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