Low temperature curable multilayer coating system with excellent appearance

Abstract

The invention relates to a multi-layer coating system which is present on a substrate, comprising at least three layers L1 to L3, the layer L1 being obtainable from a primer coating composition which in turn is obtainable from a primer coating system comprising at least two components A) and B) which are separated from one another, component A) comprising in particular at least one component a2), and component B) comprising in particular at least one component a3), the component is at least one (meth) acrylic polymer which has been modified with at least one chlorinated polyolefin, the polymer containing functional groups reactive to NCO-groups, the layer L2 being obtained from a base coating composition, and the layer L3 being obtained from a clear coating composition, the invention further relates to a method for producing a multilayer coating system using the primer coating system, and to a kit comprising at least the primer coating system and a clear coating composition or clear coating system, separated from each other.

Description

[0001] The present invention relates to a multilayer coating system present on a substrate, the substrate comprising at least three layers L1 to L3, layer L1 being obtained from a specific primer coating composition, layer L2 being obtained from a base coating composition, and layer L3 being obtained from a clear coating composition, a method for preparing a multilayer coating system using the specific primer coating composition, and a kit of parts, the kit of parts comprising at least a primer coating system and a clear coating composition suitable for preparing the specific primer coating composition or a clear coating system suitable for preparing a clear coating composition, separated from each other. Background Art

[0002] In a typical automotive coating process, multiple layers are usually applied to the surface of a suitable substrate in the form of a multilayer coating system. Specifically, in the case of using a plastic or fiber-reinforced plastic substrate, at least a primer, at least one base coat and a top coat, particularly a clear coat as the outermost layer, are applied in this order. At least the base coat and the top coat are usually applied using wet-on-wet application today. Afterwards, the coated substrate is passed through an oven at a temperature where at least the base coat and the top coat, such as a clear coat, are simultaneously cured with, for example, a 2C1B process. In some cases, the primer coating is also cured with, for example, a 3C1B process at this stage together with the base coat and the top coat, particularly the clear coat.

[0003] As the demand for fuel-efficient vehicles increases, there is a great interest in using lightweight materials for automotive parts, in particular for exterior body parts. For this reason, it is particularly desirable to use the above-mentioned reinforced plastics and in particular carbon fiber reinforced plastic (CFRP) substrates as substrates for producing multilayer coating systems on their surfaces, since they are lightweight substrates.

[0004] In addition to this general advantage of using such lightweight substrates, there are usually considerable necessary requirements that must be achieved and / or met by the individual layers present in the multilayer coating systems on these substrates used in the automotive industry, but also on other substrates, as well as by the multilayer coating systems themselves, due to regulations, but also due to quality standards set by the automotive industry. Therefore, the multilayer coating must exhibit or show a number of desirable features to at least a sufficient degree in order to meet these requirements. In particular, the exterior body parts of automobiles must have an excellent paint finish, which is generally referred to as "Class A appearance" in the automotive industry.

[0005] When conventional multilayer coating systems are applied on top of fiber-reinforced substrates such as CFRP substrates, in particular, undesirable inhomogeneities of the corresponding coated substrate, i.e. paint defects, are often observed after the baking step once the coated substrate has cooled. Such inhomogeneities can propagate to the top layer of the multilayer coating system applied on the substrate such as the CFRP substrate and can then destroy the paint finish. Such undesirable defects are known as print-through effects. Print-through is mainly due to the relatively low glass transition temperature (T g ) and differences in the coefficients of thermal expansion (CTE) between the plastic substrate and the reinforcing fibers (usually glass fibers and / or carbon fibers) present therein. However, the observed undesirable surface inhomogeneities may not only be the result of the above-mentioned print-through effects of the (fiber-reinforced) plastic substrate used, but may also or even alternatively occur as a result of undesirable print-through effects at the interfaces between coating layers of a multilayer coating system also used on substrates of different kinds.

[0006] There is therefore a need to provide new multilayer coating systems on substrates, in particular on plastic substrates including reinforced plastic substrates such as CFRP, which do not show any undesirable print-through effects or at least show less print-through effects than is observed with conventional multilayer coating systems, i.e. show an excellent paint finish (“Class A appearance”), but at the same time also do not show any disadvantages as far as other relevant properties of the multilayer coating system are concerned, such as in particular packaging stability.

[0007] question

[0008] It is therefore an underlying object of the present invention to provide a multilayer coating system on substrates, in particular on plastic substrates including reinforced plastic substrates such as CFRP, which does not show any undesired print-through effects or at least shows less print-through effects than is observed for conventional multilayer coating systems and, therefore, exhibits an excellent paint finish (“Class A appearance”), but at the same time also does not exhibit any disadvantages as far as other relevant (critical) properties of the multilayer coating system are concerned, such as in particular packaging stability.

[0009] plan

[0010] This object has been solved by the subject matter of the claims of the present application and by its preferred embodiments disclosed in the present description, ie by the subject matter described herein.

[0011] A first subject of the invention is a multilayer coating system which is present on an optionally precoated substrate and comprises at least three coating layers L1, L2 and L3 which are different from one another, namely

[0012] a first coating layer L1 applied to at least a portion of the optionally precoated substrate, said layer L1 being obtainable from a primer coating composition which in turn is obtainable from a primer coating system comprising at least two components A) and B) and optionally at least one further component C), said components being different from one another and being separate from one another,

[0013] wherein component A) comprises at least component a2) and optionally at least component a1), which are different from one another, namely

[0014] optionally at least one organic solvent a1), and

[0015] at least one polymer a2) which contains functional groups which are reactive toward NCO groups, wherein the polymer a2) is a (meth)acrylic polymer which has been modified with at least one chlorinated polyolefin,

[0016] The component B) comprises at least two components b2) and optionally at least one component b1), which are different from one another, namely

[0017] optionally at least one organic solvent b1), and

[0018] at least one organic component b2) which carries on average two or more NCO groups, and

[0019] wherein the optional component C) is a reducing agent component and comprises at least one organic solvent c1),

[0020] a second coating layer L2 applied on this first coating layer L1, said layer L2 being obtainable from a basecoat composition, and

[0021] a third coating L3 applied on this second coating L2, said layer L3 being obtainable from a clear coating composition,

[0022] Preferably, the layer L3 is obtainable from a 2K clearcoat composition which in turn is obtainable from a clearcoat system comprising at least two components D) and E) and optionally at least one further component F), which components are different from one another and are separated from one another,

[0023] wherein component D) comprises at least component d2) and optionally at least component d1), which are different from one another, namely

[0024] optionally at least one organic solvent d1), and

[0025] at least one OH-functional (meth)acrylic polymer d2),

[0026] wherein component E) comprises at least component e2) and optionally at least component e1), which are different from one another, namely

[0027] optionally at least one organic solvent e1), and

[0028] at least one organic component e2) which carries on average two or more NCO groups, wherein at least some of these NCO groups have been reacted with at least one organosilane before the component e2) is incorporated into component E), and

[0029] The optional component F) is a reducing agent component and comprises at least one organic solvent f1).

[0030] Another subject of the present invention is the use of a multilayer coating system as defined above and below, comprising at least three coating layers L1, L2 and L3 that are different from one another, for application on a substrate selected from metal and plastic substrates, preferably selected from plastic substrates, more preferably selected from fiber-reinforced plastic substrates, even more preferably selected from carbon fiber-reinforced plastic substrates.

[0031] Another subject of the present invention is a method for producing a multilayer coating system on at least one surface of an optionally precoated substrate, the method comprising at least steps 1) to 3) and optionally 4), namely

[0032] 1) applying a first coating composition at least partially to at least one surface of an optionally pre-coated substrate and forming a first coating film on said surface,

[0033] wherein the first coating composition is a primer coating composition used in the present invention as defined above and below,

[0034] 2) applying at least one base coating composition as at least one second coating composition onto the first coating film present on the substrate obtained after step 1), preferably before curing the first coating film, and forming a second coating film preferably adjacent to the first coating film, and

[0035] 3) applying a clear coating composition as a third coating composition onto the second coating film present on the substrate obtained after step 2), preferably before curing the second coating film and forming a third coating film, which is preferably adjacent to the second coating film and is preferably the outermost coating film of the formed multi-layer coating system, wherein the third coating composition is preferably a clear coating composition used in the present invention as defined above and below,

[0036] 4) optionally co-curing the first, second and third coating films to obtain a multi-layer coating system comprising cured first, second and third coatings, preferably at a temperature of not more than 80° C., more preferably not more than 70° C., still more preferably not more than 60° C., even more preferably not more than 55° C., in particular, when a plastic substrate or a fiber-reinforced plastic substrate is used as the optionally pre-coated substrate.

[0037] Another subject of the invention is a kit of parts comprising at least

[0038] The primer coating system used in the present invention as defined above and below comprises at least two components A) and B) and optionally at least one further component C) and

[0039] The clearcoat composition, preferably a 1K clearcoat composition, or a 2K clearcoat system suitable for preparing the clearcoat composition, preferably comprises at least two components D) and E) as defined below and above and optionally at least one further component F).

[0040] It has been found, particularly surprisingly, that for the multi-layer coating system according to the invention present on substrates, in particular on plastic substrates such as TPO (thermoplastic polyolefins) and (carbon) fiber-reinforced plastic substrates (including carbon fiber-reinforced polyamides), excellent paint finishes (“Class A appearance”) with in particular LW (long wave) values ​​≤ 10 and short wave (SW) values ​​≤ 20 are achieved. In addition, it has been found, further surprisingly, that this effect can also be observed for a wide variety of other substrates, such as metal substrates, and also independently of the nature of the basecoat material (solvent-borne and water-based basecoat) used as an intermediate coating (basecoat) for producing the multi-layer coating system.

[0041] It has been found that the above advantages are particularly observed when the multi-layer coating system of the invention is prepared in a 3C1B process in which the primer, basecoat and clearcoat films are cured simultaneously. This process has the additional advantages of lower processing times and only a single baking step, which is economically and ecologically advantageous.

[0042] Furthermore, it has been found that the multilayer coating system can be obtained by curing (baking) at low temperatures of as low as 50° C., which is energy efficient and eco-friendly and is particularly advantageous when the substrate used is a plastic substrate, in particular a carbon fiber reinforced plastic substrate.

[0043] Furthermore, it has been found, particularly surprisingly, that when (i) a commercial (modified) 1K primer coating formulation is used in comparison instead of the primer coating composition used according to the invention (see comparative examples CE1 and CE5 disclosed in the experimental part), (ii) a comparative 2K primer coating formulation not containing component a2) is used instead of the primer coating composition used according to the invention (see comparative example CE2 disclosed in the experimental part), and (iii) a different comparative 2K clearcoat formulation is used instead of the primer coating composition used according to the invention (see comparative examples CE3 and CE4 disclosed in the experimental part), in the presence of a multilayer coating system on the substrate, the above-mentioned excellent paint finish is not achieved together with the achievement of other desired related properties. In each of CE2, CE3, CE4 and CE5, SW values ​​were observed that were too high to meet the "Class A requirements" with regard to appearance. CE2 and CE4 also showed too high LW values. In the case of CE1, the "Class A requirements" were met, but CE1 showed (similarly to each of CE2 to CE5) poor other required related properties, namely poor tape adhesion after humidity exposure, insufficient steam jet, and insufficient thermal shock properties.

[0044] It has also been found that the primer coating film prepared according to the invention obtained from the primer coating composition used according to the invention has the ability to at least partially cure the primer coating film applied on top of the primer coating film even at temperatures as low as 50° C. due to the migration of isocyanates from the primer coating film into the primer coating film, especially when the primer coating composition used contains an excess of component b2) having an average of two or more NCO groups, so that when the component migrates into the above-mentioned primer coating film applied on top of the primer coating film obtained from the primer coating composition, at least partial curing of the primer coating film is achieved when the film contains at least one preferably polymeric component (which contains functional groups reactive with the NCO groups of component b2)). DETAILED DESCRIPTION

[0045] In the sense of the present invention, the term "comprising", for example in relation to a basecoat composition, a clearcoat composition, or one of the components of a basecoat or clearcoat system, preferably has the meaning of "consisting of". For example, with respect to a basecoat composition, a clearcoat composition, or one of the components of a basecoat or clearcoat system, in addition to all the mandatory ingredients present therein, one or more further optional ingredients as defined below may also be included therein. In each case, all ingredients may be present in their preferred embodiments, as defined below.

[0046] The proportions and amounts of any ingredients given below in wt.-% (weight %) present in each coating composition, such as the basecoat composition or the clearcoat composition, add up to 100 wt.-%, in each case based on the total weight of the respective coating composition. The same applies to each component of the coating system, such as component A) or B) of the basecoat system or components D) and E) of the clearcoat system: The proportions and amounts of any ingredients given below in wt.-% (weight %) present in one of these components add up to 100 wt.-%, in each case based on the total weight of the respective component.

[0047] Multi-layer coating system

[0048] Layers L1, L2, L3 and substrate

[0049] A first subject matter of the present invention is a multilayer coating system which is present on an optionally precoated substrate and comprises at least three coating layers L1 , L2 and L3 which differ from one another.

[0050] Preferably, at least three coating layers L1, L2 and L3 are positioned adjacent to each other. Preferably, the third coating layer L3 is the outermost coating layer of the multilayer coating system.

[0051] Preferably, the multi-layer coating system is obtained by the method for preparing a multi-layer coating system of the present invention, which will be described in detail below.

[0052] Each of the layers L1, L2 and L3 represents a cured coating film. The first layer L1 is obtainable from a first coating film, the second layer L2 is obtainable from a second coating film, and the third layer L3 is obtainable from a third coating film. The first coating film is a primer coating film, the second coating film is a base coating film, and the third coating film is a clear coating film. The term "primer" is known to those skilled in the art. In the case of a metal substrate, the primer is typically applied after the substrate already has a cured electrodeposition coating. In this case, the cured electrodeposition coating film is present below the primer coating film and is preferably adjacent to the primer coating film. This is an example of a pre-coated substrate. In the case of a non-metallic substrate (such as a plastic substrate including a fiber-reinforced plastic substrate), the primer coating film typically represents the first coating film applied to its surface. The term "base coating" is also known to those skilled in the art, and is used, for example, in Lexikon, paints and printing inks, Georg Thieme Verlag, 1998, 10th edition, page 57. Thus, basecoats are particularly used for coloring automotive paints and general industrial paints in order to provide coloring and / or optical effects by using basecoats as intermediate coating compositions. This is usually applied to metal or plastic substrates, optionally pre-coated in each case. In order to protect the basecoat film, in particular from environmental influences, at least one additional clearcoat film is applied thereto. The term "clearcoat (clearcoat / clearcoat / clear coating)" is also known to those skilled in the art and refers to the transparent outermost layer of a multilayer coating structure applied to a substrate.

[0053] Preferably, the cured primer film (layer L1) obtained after step 4) of the method for preparing a multilayer coating system of the present invention has been carried out has a dry film thickness in the range of 10 to 35 μm. Preferably, the cured basecoat film (layer L2) obtained after step 4) of the method for preparing a multilayer coating system of the present invention has been carried out has a dry film thickness in the range of 12 to 35 μm. Preferably, the cured clearcoat film (layer L3) obtained after step 4) of the method for preparing a multilayer coating system of the present invention has been carried out has a dry film thickness in the range of 30 to 60 μm.

[0054] The substrate may be a car body or a part thereof. The substrate may be a metal substrate, but plastic substrates such as polymer substrates and fiber-reinforced plastic substrates may also be used.

[0055] Suitable as metal substrates for use according to the present invention are all substrates commonly used and known by technicians. The substrate used according to the present invention is preferably a metal substrate, more preferably selected from the group consisting of steel, preferably selected from the steel, aluminum and magnesium of 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 (for example, Galvalume, Galvannealed or Galfan) and aluminized steel, and also Zn / Mg alloy and Zn / Ni alloy. Particularly suitable substrates are parts of the body of the car for production or the entire body of the car. The metal substrate may have been pretreated with at least one metal phosphate such as zinc phosphate and / or pretreated with at least one oxalate. This pretreatment using phosphating or oxalating is usually carried out after the substrate is cleaned and before the substrate is coated by electrodeposition, which is particularly a pretreatment step commonly used in the automotive industry. The metal substrate may further include a cured electrodeposition coating as a precoat.

[0056] Preferably, thermoplastic polymers are used as plastic substrates. Suitable polymers are poly(meth)acrylates (including poly(methyl)acrylate, poly(butyl)acrylate), polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyesters (including polycarbonate and polyvinyl acetate), polyamides, polyolefins (such as polyethylene, polypropylene, polystyrene and also polybutadiene), polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymer (A-EPDM), ASA (acrylonitrile-styrene-acrylate copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), polyetherimide, phenolic resin, urea resin, melamine resin, alkyd resin, epoxy resin, polyurethane (including TPU), polyetherketone, polyphenylene sulfide, polyether, polyvinyl alcohol, and mixtures thereof. Polycarbonate and poly(meth)acrylate are particularly preferred.

[0057] In addition, and most preferably, a fiber-reinforced plastic substrate is used. Glass and / or carbon fiber can be particularly used for reinforcement, most preferably carbon fiber. An example of a suitable carbon fiber-reinforced plastic substrate is a carbon fiber-reinforced polyamide substrate. As outlined above, most preferably, the substrate is a plastic substrate, more preferably a fiber-reinforced plastic substrate, more preferably a carbon fiber-reinforced plastic substrate.

[0058] Primer coating composition

[0059] A first coating L1 is applied to at least a portion of the optionally precoated substrate, said layer L1 being obtainable from a primer coating composition which in turn is obtainable from a primer coating system comprising at least two components A) and B) and optionally at least one further component C), said components being different from one another and being separate from one another. The preparation of the primer coating composition can be carried out using customary and known preparation and mixing methods and mixing units, or using conventional dissolvers and / or stirrers.

[0060] Preferably, the primer coating composition is a solvent-borne, i.e. a coating composition based on an organic solvent, preferably due to the presence of components a1) and b1) and optionally c1). For the purposes of the present invention, the term "solvent-borne" in relation to the coating composition is preferably understood to mean an organic solvent as mentioned above, as solvent and / or as diluent, as the main component of all solvents and / or diluents present therein, preferably in an amount of at least 35 wt.-%, based on the total weight of the coating composition. Thus, preferably, the coating composition is not water-based, i.e. not an aqueous coating composition.

[0061] The primer coating composition preferably comprises an organic solvent fraction of at most 75 wt.-%, more preferably at most 70 wt.-%, even more preferably at most 65 wt.-%, still more preferably at most 60 wt.-%, in each case based on the total weight of the coating composition. All customary organic solvents known to the person skilled in the art can be used as organic solvent, i.e. as components a1) and b1) and optionally c1). The term "organic solvent" is known to the person skilled in the art, in particular from Council Directive 1999 / 13 / EC of 11 March 1999. Examples of organic solvents that can be used have already been mentioned above in conjunction with components a1) and b1) and c1). Preferably, the primer coating composition comprises an organic solvent fraction in the range of 30 to 70 wt.-%, based on the total weight of the coating composition.

[0062] Preferably, the primer coating composition has a total solids content of >25 wt.-%, more preferably >30 wt.-%, even more preferably >35 wt.-%, in each case based on the total weight of the coating composition.

[0063] The total solids content of the primer coating composition is preferably in the range of >20 to 60 wt.-%, more preferably >25 to 55 wt.-%, even more preferably >30 to 50 wt.-%, yet more preferably >30 to 45 wt.-%, in each case based on the total weight of the coating composition. The total solids content, in other words the non-volatile fraction, is determined according to the method described below.

[0064] Preferably, the primer coating composition is obtainable by mixing components A) and B) in a weight ratio (component A) / component B)) in the range of 25:1 to 1:1. More preferably, the mixing is carried out in a weight ratio in the range of 20:1 to 1.1:1, even more preferably in a weight ratio in the range of 17.5:1 to 2:1, in particular in a weight ratio in the range of 15:1 to 3:1.

[0065] Preferably, the primer coating composition contains an excess of component b2), which carries on average two or more NCO groups, so that when said component migrates into the intermediate coating film, preferably into the primer coating film applied on top of the primer coating film obtained from the primer coating composition on the substrate, at least partial curing of the intermediate coating film is achieved when said intermediate coating film contains at least one, preferably polymeric component, which contains functional groups reactive toward NCO groups. In this context, the term "excess" preferably means a molar or mass excess, more preferably a mass excess.

[0066] The term "excess ingredient b2)" preferably means that after mixing, ingredient b2) originating from component "B" is still present in the resulting primer coating composition in an amount of 5 to 20 wt.-%, preferably 7.5 to 15 wt.-%, more preferably 10 to 12.5 wt.-%, based in each case on the total weight of ingredient b2) originally present in said component B), which, due to the use of an overstoichiometric amount of ingredient b), is not used for crosslinking with related ingredients, such as ingredient a2) of component A). Thus, when applied on top of the primer coating film obtainable by applying the primer coating material composition to the surface of the substrate, the subsequently applied primer coating film can also be at least partially cured by NCO migration.

[0067] Primer coating system

[0068] The primer coating system for preparing the primer coating composition is a two-(2K-) or multi-component coating system. In this context, separate from each other means that the components A) and B) and optionally C) of the coating system can be stored separately until they are mixed with each other in order to prepare the primer coating composition. In the case where the coating system is a two-component coating system, it preferably consists of components A) and B). When mixing at least two components A) and B) and applying the resulting composition to the surface of the substrate, preferably at least by the reaction of the functional groups of at least one component a2) such as OH-groups with the isocyanate groups of at least one component b2) to form a polyurethane or polyurethane-based coating film.

[0069] Preferably, components A) and B) and optionally also component C) of the coating system contain no or essentially no water. The same applies to the coating compositions obtainable therefrom. In the sense of the present invention, the term "free of water" preferably means that no water is present at all. In the sense of the present invention, the term "essentially free of water" preferably means that essentially no water is present. This means that at least no water is intentionally added to any of the components A) and B) and optionally C) used in the present invention and to the coating compositions obtainable therefrom. However, it cannot be excluded that residual residues of water formed during the preparation of any of the ingredients used to prepare the components A) and B) and optionally (C) used in the present invention are present therein. Preferably, the amount of any water present in each of components A) and B) and optionally C) is less than 1 wt.-%, more preferably less than 0.5 wt.-%, even more preferably less than 0.1 wt.-%, still more preferably less than 0.05 wt.-%, yet more preferably less than 0.01 wt.-%, in particular less than 0.005 wt.-% or less than 0.001 wt.-%, in each case based on the total weight of components A) or B) or optionally C). Preferably, components A) and B) and also optional component C) of the coating system are solvent-borne, i.e. based on organic solvents. Thus, preferably, the coating system is not water-based, i.e. not an aqueous coating system.

[0070] Component A)

[0071] Component A) comprises at least component a2) and optionally at least one component a1), which are different from one another, but may additionally comprise further optional components such as components a3), a4), a4a), a5), a6), a7), a8), a9) and / or a10). All components present are different from one another.

[0072] Preferably, component A) of the primer coating system has a total solids content of >20 wt.-%, preferably >25 wt.-%, more preferably >30 wt.-%, even more preferably >45 wt.-%, based on the total weight of component (A). The total solids content of component A) of the primer coating system is preferably in the range of >20 to 60 wt.-%, more preferably 25 to 50 wt.-%, even more preferably 30 to 45 wt.-%, in each case based on the total weight of component A). The total solids content, in other words the non-volatile fraction, is determined according to the method described below.

[0073] Optional ingredient a1)

[0074] Optional component a1) is at least one organic solvent. Examples of such organic solvents include heterocyclic, aliphatic or aromatic hydrocarbons, monohydric or polyhydric alcohols, in particular methanol and / or ethanol, ethers, esters, ketones and amides, for example N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, toluene, xylene, butanol, ethylene glycol and butanediol and also their acetates, butyl diglycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone, or mixtures thereof. Component A) may contain more than one organic solvent a1).

[0075] Preferably, the amount of optional ingredient a1) in component (A) is in the range from 0 to 80 wt.-% or 10 to 80 wt.-%, more preferably 25 to 75 wt.-%, even more preferably 40 to 70 wt.-%, in each case based on the total weight of component A).

[0076] Ingredient a2)

[0077] Component a2) is at least one (meth) acrylic polymer, which has been modified with at least one chlorinated polyolefin, and which contains functional groups such as OH-groups, thiol groups, carbamate groups, COOH-groups and / or amino groups that are reactive to NCO-groups. Preferably, component a2) is an OH-functional polymer. Component a2) such as an OH-functional polymer preferably acts as a film-forming adhesive. For the purposes of the present invention, the term "adhesive" is understood as a non-volatile component of the coating composition according to DIN EN ISO 4618 (German version, date: March 2007), which is responsible for film formation. Therefore, the pigments and / or fillers contained therein are not included under the term "adhesive". Preferably, component a2) represents the main adhesive. As the main adhesive in the sense of the present invention, the adhesive component is preferably mentioned, when there are no other adhesive components in the coating composition or the components used for its preparation, the adhesive component is present in a higher proportion based on the total weight of the coating composition or the components.

[0078] The term "polymer" is known to the person skilled in the art and for the purposes of the present invention encompasses addition polymers and polymerizates as well as condensation polymers. The term "polymer" includes both homopolymers and copolymers.

[0079] If component a2) is at least one OH-functional polymer, it preferably contains on average two or more OH groups.

[0080] Preferably, component a2) is at least one OH-functional (meth)acrylic polymer which has been modified with at least one chlorinated polyolefin. "Modification" preferably means that the chlorinated polyolefin is covalently linked to the (meth)acrylic polymer. The chlorinated polyolefin may be linked to the backbone (main chain) of the (meth)acrylic polymer and / or to at least one of its side chains. Examples of such polymers are CL-408.

[0081] Preferably, component A) of the primer coating system comprises at least one ingredient a2) in an amount in the range from 5.0 to 50.0 wt.-%, more preferably from 10.0 to 45.0 wt.-%, even more preferably from 15.0 to 40.0 wt.-%, yet more preferably from 17.5 to 35.0 wt.-%, in each case based on the total weight of component A).

[0082] Optional catalyst components a3), a4) and / or a4a)

[0083] Optionally, at least one of the catalyst components a3), a4) and a4a) may be present in component A) of the primer coating system.

[0084] The at least one catalyst a3) which is optionally present is suitable for crosslinking NCO groups and is preferably selected from organotin catalysts. Preferably, the at least one catalyst a3) is suitable for crosslinking NCO groups of constituent b2) of component B).

[0085] Preferably, component A) of the primer coating system comprises at least one catalyst a3) in an amount in the range from 0.001 to 1.00 wt.-%, more preferably from 0.002 to 0.80 wt.-%, even more preferably from 0.003 to 0.60 wt.-%, still more preferably from 0.004 to 0.40 wt.-%, yet more preferably from 0.005 to 0.20 wt.-%, most preferably from 0.007 to 0.15 wt.-%, in each case based on the total weight of component A).

[0086] The catalyst a3) is preferably selected from organometallic catalysts and more preferably from organotin catalysts. Examples of organotin catalysts are DOTL (dioctyltin dilaurate) and DBTL (dibutyltin dilaurate). DOTL is particularly preferred.

[0087] At least one optionally present catalyst a4) is selected from phosphorus-containing organic components which are not terminated by any amine and are preferably suitable for crosslinking Si-containing functional groups, in particular in component b3) of component B), if present.

[0088] Preferably, component A) of the primer coating system comprises at least one catalyst a4) in an amount in the range from 0.01 to 1.0 wt.-%, more preferably from 0.02 to 0.8 wt.-%, even more preferably from 0.03 to 0.6 wt.-%, still more preferably from 0.04 to 0.5 wt.-%, yet more preferably from 0.05 to 0.4 wt.-%, in each case based on the total weight of component A).

[0089] In particular, at least one catalyst a4), which is a phosphorus-containing catalyst, is a catalyst which does not contain any nitrogen. It is possible to use more than one, for example two different catalysts as catalyst a4).

[0090] Examples of suitable phosphorus-containing catalysts used as catalyst a4) are substituted phosphonic acid diesters and diphosphonic acid diesters, preferably selected from the group consisting of acyclic phosphonic acid diesters, cyclic phosphonic acid diesters, acyclic diphosphonic acid diesters and cyclic diphosphonic acid diesters. However, more particularly, used as at least one catalyst a4) are substituted phosphoric acid monoesters and phosphoric acid diesters, preferably selected from the group consisting of acyclic phosphoric acid diesters and monoesters and cyclic phosphoric acid diesters and monoesters. All these esters cannot exist in the form of amine adducts, because the catalyst a4) is not blocked by any amine.

[0091] Preferably, at least 2-ethylhexyl acid phosphate is used as at least one catalyst a4). The term "2-ethylhexyl acid phosphate" includes both monoethylhexyl acid phosphate and diethylhexyl acid phosphate.

[0092] Catalyst a4) is a phosphorus-containing organic component which is not blocked by at least one amine and can be and is preferably used in combination with at least one phosphorus-containing organic component as at least one catalyst a4a) which is blocked by at least one amine, i.e. it is also nitrogen-containing. However, it is also possible to use only catalyst a4a) and to have it present in component A), without also using catalyst a4).

[0093] Preferably, component A) of the primer coating system comprises at least one optionally present catalyst a4a) in an amount in the range from 0.05 to 2.0 wt.-%, more preferably from 0.06 to 1.8 wt.-%, even more preferably from 0.07 to 1.6 wt.-%, still more preferably from 0.08 to 1.4 wt.-%, yet more preferably from 0.09 to 1.2 wt.-%, particularly preferably from 0.10 to 1.0 wt.-%, in each case based on the total weight of component A).

[0094] Preferably, the amount of catalyst a4a) (if present) exceeds the amount of catalyst a4). Preferably, the relative weight ratio of catalysts a4) and a4a) to each other in component A) is in the range of 0.1 to 1.0 to 0.9:1.0, more preferably 0.2 to 1.0 to 0.8 to 1.0, even more preferably 0.3 to 1.0 to 0.7 to 1.0.

[0095] Preferably, at least one catalyst a4) such as 2-ethylhexyl acid phosphate is present in an amount ranging from 0.01 to 0.4 wt.-%, and at least one catalyst a4a) is present in an amount ranging from 0.05 to 1.0 wt.-%.

[0096] Preferably, at least one catalyst a4a) is selected from phosphorus-containing organic components, more preferably selected from acyclic phosphoric acid diesters, acyclic phosphoric acid monoesters, cyclic phosphoric acid diesters and cyclic phosphoric acid monoesters, wherein each of the above phosphoric acid diesters and monoesters is present in the form of an adduct with at least one amine (i.e., blocked with at least one amine), preferably at least one tertiary amine.

[0097] Optional ingredient a5) - condensation product

[0098] Optionally and preferably, component A) of the primer coating system further comprises at least one component a5) different from any of the components a1) to a4) and a4a), which is a condensation product, which in turn is obtainable by reacting at least (i) at least one organosilane with at least one hydrolyzable group with (ii) at least one silicon dioxide. The condensation product a5) is also referred to herein as a "condensate".

[0099] Preferably, the molar ratio of the at least one organosilane and the at least one silicon dioxide used to prepare the condensation product a5) to one another is in the range from 10:1 to 1:1, more preferably from 8:1 to 1:1, even more preferably from 6:1 to 1:1, yet more preferably from 4:1 to 1:1, still more preferably from 4:1 to 1.1:1, yet more preferably from 4:1 to 1.5:1, most preferably from 4:1 to 2:1.

[0100] Preferably, the at least one condensation product a5) is present in component A) in an amount within the range of 1.0 to 25.0 wt.-%, more preferably 2.0 to 20.0 wt.-%, even more preferably 3.0 to 17.5 wt.-%, yet more preferably 4.0 to 15.0 wt.-%, still more preferably 5.0 to 14.0 wt.-%, even more preferably 6.0 to 13.0 wt.-%, most preferably 7.0 to 12.0 wt.-%, in each case based on the total weight of component A).

[0101] Preferably, the condensation product a5) has an average particle size in the range of 10 to 100 nm, more preferably 15 to 80 nm, even more preferably 20 to 70 nm, yet more preferably 25 to 60 nm, still more preferably 30 to 50, most preferably 35 to 45 nm, in each case measured by DLS (dynamic light scattering). The DLS method used is described below in the 'Methods' section. Preferably, the average particle size is measured at a high shear viscosity of 5 to 15 cP by using a CAP 2000 viscometer.

[0102] The term "silicon dioxide" used in this context is a term that is clear to the person skilled in the art and refers to SiO2. Preferably, the at least one silicon dioxide used is used in the form of an alkaline or acidic, preferably alkaline aqueous dispersion of preferably colloidal silicon dioxide particles. Preferably, the silicon dioxide particles have an average particle size of silicon dioxide in the range of 5 to about 300 nm, more preferably 5 to 200 nm, even more preferably 7.5 to 100 nm, still more preferably 7.5 to 50 nm, most preferably 10 to 30 nm. The average particle size is measured by DLS. The DLS method used is described below in the 'Methods' section and is the same method that is also used to determine the average particle size of the condensation product a5).

[0103] As outlined above, both acidic and basic colloidal silica dispersions may be used. However, colloidal silica dispersions having a low base content are preferred.

[0104] Commercially available silica products that can be used include, for example (Sigma Aldrich), (Nissan Chemical), (AkzoNobel), Colloidal silica (Nalco Chemical Company) and (Akzo Nobel) products. Particularly preferred colloidal silicon dioxide products that can be used include 1034A(Nalco Chemical Company), O40, Snowtex ST-033 and OL-40 (Nissan Chemical Co., Ltd.), AS40 and HS 40 (Sigma-Aldrich), Levasil 200 / 30 and 200S / 30 (now Levasil CS30-516P) (Akzo Nobel) and A205 (Cabot Corporation), etc.

[0105] The at least one organosilane carrying at least one hydrolyzable group may optionally comprise and preferably comprises at least one non-hydrolyzable group, which is preferably an organic (preferably aliphatic) residue having 1 to 10 carbon atoms, optionally further comprising at least one functional group.

[0106] Preferably, the at least one organosilane carrying at least one hydrolyzable group is a monosilane and has at least two, particularly preferably at least three, hydrolyzable groups X, and / or is at least one bis(silane) which preferably has at least four, particularly preferably six, hydrolyzable groups X. However, it is also possible to use monosilanes having four hydrolyzable groups X, i.e. monosilanes which do not contain any non-hydrolyzable residues, such as tetramethoxysilane and / or tetraethoxysilane.

[0107] Preferably, the at least one organosilane having at least one hydrolyzable group is an organosilane having the general formula (1) and / or (2):

[0108] Si(X) 4-y (R) y ,

[0109] (1)

[0110] Si(X) 3-z (T) z -(RA)-Si(X) 3-z (T) z

[0111] (2)

[0112] In the case of general formula (1)

[0113] X is each independently a hydrolyzable group, preferably each independently selected from OC 1-4 alkyl,

[0114] The parameter y is 0 or an integer in the range of 1 to 3, preferably at least 1, preferably exactly 1, and

[0115] R is a non-hydrolyzable organic residue, preferably an aliphatic residue, which preferably has 1 to 10 carbon atoms, wherein at least one of the residues R optionally contains at least one functional group,

[0116] And in the case of general formula (2)

[0117] X in each case independently of one another represents a hydrolyzable group and is preferably in each case independently of one another selected from OC 1-4 -alkyl,

[0118] RA represents a divalent non-hydrolyzable organic residue, preferably an aliphatic residue, which preferably has 1 to 10 carbon atoms and which preferably contains no functional groups,

[0119] The parameter z is in each case 0 or an integer in the range from 1 to 3, preferably in each case 0 or 1, more preferably in each case 1, and

[0120] T is a non-hydrolyzable organic residue, preferably an aliphatic residue, which preferably has 1 to 10 carbon atoms, which is different from the residue RA, and which optionally comprises at least one functional group.

[0121] Examples of suitable functional groups are in particular thiol groups, amino groups, epoxy groups, in particular glycidyloxy, epoxycyclohexyl and / or epoxycyclohexylethyl groups, OH groups protected by suitable protective groups, (meth)acrylate groups, vinyl groups, allyl groups, (meth)acryloyloxy groups, episulfide groups, urea groups, thiourea groups, ether groups, thioether groups, sulfide groups, in particular disulfide, trisulfide, tetrasulfide, pentasulfide, hexasulfide and / or polysulfide groups, xanthate groups, trithiocarbonate groups, dithiocarbonate groups, isocyanurate groups, and / or -Si(OR)3 groups, where R3 is an aliphatic residue which preferably has 1 to 10 carbon atoms.

[0122] Examples of suitable organosilanes bearing at least one non-hydrolyzable group are, for example, (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, (3-glycidyloxypropyl)triethoxysilane, bis(2-ethyl)- triethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, and / or propyltriethoxysilane.

[0123] Preferably, the condensation reaction of at least one organosilane carrying at least one hydrolyzable group with at least one silicon dioxide takes place in an aqueous medium and is preferably catalyzed by at least one preferably organic acid.

[0124] Preferably, at least one silica is added to at least one organosilane in the presence of water, preferably 0.5-2.0 moles of water, based on the molar amount of at least one organosilane, and in the presence of preferably catalytic amounts of at least one acid, more preferably at least one organic acid such as acetic acid. The addition is preferably carried out at a temperature between 0°C and 10°C. After stirring the resulting mixture, preferably at room temperature (18°C to 23°C) for 10 to 18 hours, preferably a further catalytic amount of at least one acid, more preferably at least one organic acid such as acetic acid and at least one ammonium salt such as tetrabutylammonium acetate (TBAA) is added as a further catalyst. Then, the resulting mixture is preferably stirred for 1 to 10 hours. Preferably, the pH value of the mixture is maintained at pH 3 to 6. Then, the resulting mixture is preferably diluted with at least one water-miscible organic solvent such as isopropanol (IPA), for example in a 1:1 weight ratio.

[0125] The preparation of exemplary condensation products a5) prepared from methyltrimethoxysilane (MTMS) as organosilane is outlined in the following scheme:

[0126]

[0127] Preferably, the at least one condensation product a5) is present in the primer coating composition in an amount in the range of 1.0 to 25.0 wt.-%, more preferably 2.0 to 20.0 wt.-%, even more preferably 3.0 to 17.5 wt.-%, yet more preferably 4.0 to 15.0 wt.-%, still more preferably 5.0 to 14.0 wt.-%, even more preferably 6.0 to 13.0 wt.-%, most preferably 7.0 to 12.0 wt.-%, based on the total weight of the primer coating composition.

[0128] Additional Ingredients

[0129] Component A) of the primer coating system may optionally contain one or more additional ingredients such as one or more of the ingredients a6) to a10), which are different from each other, from each of the ingredients a1) to a3), and from each of the optional ingredients a4), a4a) and a5). Preferably, component A) of the primer coating system contains at least one, preferably at least two, more preferably at least three ingredients a6) to a8).

[0130] Preferably, component A) of the primer coating system comprises

[0131] at least one epoxy resin as constituent a6), preferably in an amount in the range from 0.5 to 15.0 wt.-%, more preferably from 1.0 to 10.0 wt.-%, even more preferably from 1.5 to 7.5 wt.-%, still more preferably from 2.0 to 5.5 wt.-%, in each case based on the total weight of component A),

[0132] and / or

[0133] at least one chlorinated polyolefin as constituent a7), preferably in an amount in the range from 5.0 to 35 wt.-%, more preferably from 6.0 to 30.0 wt.-%, even more preferably from 7.0 to 25.0 wt.-%, still more preferably from 8.0 to 20 wt.-%, in each case based on the total weight of component A),

[0134] and / or

[0135] At least one pigment and / or filler as constituent a8), preferably in an amount in the range from 5.0 to 30 wt.-%, more preferably from 6.0 to 25.0 wt.-%, even more preferably from 7.0 to 20.0 wt.-%, still more preferably from 8.0 to 15 wt.-%, in each case based on the total weight of component A).

[0136] The term "pigment" is known to the skilled person, for example from DIN 55943 (date: October 2001). "Pigment" in the sense of the present invention preferably refers to components in the form of powders or flakes, which are substantially, preferably completely insoluble in the medium surrounding them, such as, for example, in one of the coating compositions used according to the invention. Pigments are preferably colorants and / or substances which can be used as pigments due to their magnetic, electric and / or electromagnetic properties. Pigments differ from "fillers" preferably in their refractive index, the refractive index of pigments being ≥1.7. The term "filler" is known to the skilled person, for example from DIN 55943 (date: October 2001). Pigments can be inorganic or organic.

[0137] The component A) of the primer coating system may optionally comprise one or more other ingredients such as in addition to one or more components a6) to a8) or as a substitute thereof. Depending on the desired application, component A) may contain one or more conventional additives. For example, it may comprise at least one additive selected from the group consisting of reactive diluents, light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, plasticizers, initiators for free radical polymerization, adhesion promoters, flow control agents, film-forming aids, flame retardants, corrosion inhibitors, desiccants, biocides, thickeners, and / or matting agents. They may be used in a known and conventional ratio. Preferably, their content is 0.01 to 20.0 wt.-%, more preferably 0.05 to 15.0 wt.-%, particularly preferably 0.1 to 10.0 wt.-%, even more preferably 0.1 to 7.5 wt.-%, in particular 0.1 to 5.0 wt.-%, and most preferably 0.1 to 2.5 wt.-%, based on the total weight of the coating composition obtained by mixing components A) and B) and optionally C), in each case based on the total weight of the coating composition.

[0138] In particular, component A) of the primer coating system optionally comprises at least one leveling agent and / or dispersant (wetting agent) as additive as component a9). Preferably, a9) is a (meth)acrylate polymer which contains at least one ether segment (preferably in a side chain) and / or at least one siloxane unit (preferably also in a side chain). Preferably, component a9) is present in component A) - in particular when at least one optional component a5) is also present - in an amount in the range of 0.10 to 5.0 wt.-%, more preferably 0.50 to 4.0 wt.-%, even more preferably 0.80 to 3.5 wt.-%, in each case based on the total weight of component A).

[0139] Component A) of the primer coating system may optionally comprise further polymer components other than a2), such as any type of polymer having functional groups reactive toward NCO groups, which may be used as component a10). Examples are (meth)acrylic polymers (other than a2), in particular (meth)acrylic polymers which have not been modified with at least one chlorinated polyolefin, polyesters, polyurethanes, polyureas and polyethers and mixtures thereof.

[0140] Component B)

[0141] Component B) comprises at least one component b2) and optionally at least one component b1), which are different from one another, but may additionally comprise further optional components which are each different from one another.

[0142] Preferably, component B) does not contain any condensates a5), ie the condensates a5) are present, if any, only in component A) of the primer coating system.

[0143] Preferably, component B) of the primer coating system has a total solids content of >40 wt.-%, more preferably >45 wt.-%, even more preferably >50 wt.-%, yet more preferably >55 wt.-%, in each case based on the total weight of component B). The total solids content of component B) of the primer coating system is preferably in the range from 45 to 100 wt.-%, more preferably from 50 to <100 wt.-%, even more preferably from 55 to <100 wt.-%, in each case based on the total weight of component B). The total solids content, in other words the non-volatile fraction, is determined according to the method described below.

[0144] Optional ingredient b1)

[0145] Optional ingredient b1) is at least one organic solvent. Examples of such organic solvents include those mentioned above for ingredient a1). Component B) may contain more than one organic solvent b1). The at least one organic solvent b1) may be the same as or different from the at least one organic solvent a1). If more than one organic solvent is used as a1) and / or b1), it may be that a1) and b1) are partly the same and partly different.

[0146] Preferably, the amount of ingredient b1) in component B) is in the range from 0 or 5 to 50 wt.-%, more preferably from 10 to 40 wt.-%, even more preferably from 15 to 35 wt.-%, in each case based on the total weight of component B).

[0147] Ingredient b2)

[0148] Component b2) is an organic component which carries on average two or more NCO groups. Preferably, component b2) carries on average more than two NCO groups.

[0149] Preferably, at least one organic component b2) present in component B) has an aliphatic or alicyclic structure and / or a parent structure derived from an aliphatic or alicyclic polyisocyanate by trimerization, dimerization, urethane formation, biuret formation, uretdione formation and / or allophanate formation. The trimers of IPDI (isophorone diisocyanate) and / or HDI (hexamethylene diisocyanate), i.e. isocyanurates, are particularly preferred.

[0150] Suitable aliphatic polyisocyanates are preferably substituted or unsubstituted aliphatic polyisocyanates, such as tetramethylene 1,4-diisocyanate, hexamethylene 1,6-diisocyanate, 2,2,4-trimethylhexane 1,6-diisocyanate, ethylene diisocyanate, dodecane 1,12-diisocyanate and mixtures of the above-mentioned polyisocyanates. Suitable polyisocyanate parent structures can be polyisocyanate prepolymers with urethane structural units, which are obtained by the reaction of polyols with stoichiometric excess of the above-mentioned aliphatic polyisocyanates. Particularly preferred polyisocyanate parent structures are hexamethylene diisocyanate and / or its biuret dimer and / or allophanate dimer and / or isocyanurate trimer and / or its uretdione, as well as mixtures of the polyisocyanate parent structures. Particularly preferred polyisocyanate parent structures are hexamethylene diisocyanate and / or its isocyanurate trimer, optionally with its uretdione.

[0151] Suitable cycloaliphatic polyisocyanates are preferably substituted or unsubstituted cycloaliphatic polyisocyanates, such as isophorone diisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene 2,4-diisocyanate, hexahydrotoluene 2,6-diisocyanate, hexahydrophenylene 1,3-diisocyanate, hexahydrophenylene 1,4-diisocyanate, perhydrodiphenylmethane 2,4′-diisocyanate and 4,4′-methylenedicyclohexyl diisocyanate and mixtures of the abovementioned polyisocyanates. Suitable polyisocyanate parent structures can be polyisocyanates derived from alicyclic polyisocyanates by trimerization, dimerization, carbamate formation, biuret formation, uretdione formation and / or allophanate formation, more particularly biuret dimer and / or allophanate dimer and / or isocyanurate trimer. The polyisocyanate parent structure can be a polyisocyanate prepolymer with carbamate structural units, which is obtained by the reaction of polyols with a stoichiometric excess of the above-mentioned alicyclic polyisocyanates. Particularly preferred alicyclic polyisocyanates are isophorone diisocyanate and 4,4'-methylene dicyclohexyl diisocyanate and / or its biuret dimer and / or its allophanate dimer and / or its isocyanurate trimer.

[0152] Preferably, component b2) does not contain any silane-modified NCO groups, ie none of its NCO groups preferably react with any silanes. Preferably, component B) itself does not contain any NCO-group-containing components which carry any silane-modified NCO groups.

[0153] Optional ingredient b3)

[0154] Optionally, component B) of the primer coating system contains at least one optional component b3). The optional component b3) is an organosilane component which is different from each of the components b1) and b2) and carries at least one hydrolyzable group X and preferably also at least one non-hydrolyzable organic residue R and / or T. The optional component b3) is also different from each of the components a1) to a3) of component A). Preferably, the component b3) is used as an adhesion promoter.

[0155] Preferably, the at least one organosilane component b3) is a monosilane and has at least two, particularly preferably at least three, hydrolyzable groups X and / or is at least one bis(silane) which preferably has at least four, particularly preferably six, hydrolyzable groups X.

[0156] Preferably, at least one organosilane b3) is an organosilane of the general formula (I) and / or (II)

[0157] Si(X) 4-y (R) y,

[0158] (I)

[0159] Si(X) 3-z (T) z -(RA)-Si(X) 3-z (T) z

[0160] (II)

[0161] Wherein in the case of general formula (I)

[0162] X is each independently a hydrolyzable group, preferably each independently selected from OC 1-4 alkyl,

[0163] The parameter y is an integer in the range 1 to 3, but is at least 1, preferably exactly 1, and

[0164] R is a non-hydrolyzable organic residue, preferably an aliphatic residue, which preferably has 1 to 10 carbon atoms, wherein at least one of the residues R optionally contains at least one functional group,

[0165] And wherein in the case of general formula (II)

[0166] X in each case independently of one another represents a hydrolyzable group and is preferably in each case independently of one another selected from OC 1-4 -alkyl,

[0167] RA represents a divalent non-hydrolyzable organic residue, preferably an aliphatic residue, which preferably has 1 to 10 carbon atoms and which preferably contains no functional groups,

[0168] The parameter z is in each case an integer in the range from 0 to 3, preferably in each case 0, and

[0169] T is a non-hydrolyzable organic residue, preferably an aliphatic residue, which preferably has 1 to 10 carbon atoms, which is different from the residue RA, and which optionally comprises at least one functional group.

[0170] Examples of suitable functional groups are, in particular, thiol groups, amino groups, epoxy groups.

[0171] Examples of suitable organosilanes are, for example, (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)triethoxysilane, bis(2-ethyltrimethoxysilyl)amine, bis(3-propyltrimethoxysilyl)amine, bis(4-butyltrimethoxysilyl)amine, bis(2-ethyltriethoxysilyl)amine, bis(3-propyltriethoxysilyl)amine and / or bis(4-butyltriethoxysilyl)amine.

[0172] Optional component C)

[0173] Optional component C) is a reducing agent component and comprises at least one organic solvent c1). Component C) is used to dilute the coating composition to be prepared and for this reason comprises at least one organic solvent c1) and preferably consists of at least one organic solvent c1). Examples of such organic solvents include those mentioned above for components a1) and b1). Component C) may comprise more than one organic solvent c1). At least one organic solvent c1) may be the same or different from at least one organic solvent a1) and / or b1). If more than one organic solvent is used as a1) and / or b1) and / or c1), it may be that a1) and / or b1) and / or c1) are partly the same and partly different.

[0174] Layer L2 and base coating composition

[0175] A second coating layer L2 is applied on the first coating layer L1 , said layer L2 being obtainable from a basecoat composition (intermediate coating composition).

[0176] Any type of basecoat composition can be used, for example 1K or 2K basecoat compositions, preferably 1K compositions, which can be solventborne or aqueous and can contain coloring and / or effect pigments. Preferably, the basecoat composition comprises at least one film-forming binder, preferably at least one polymer, more preferably at least one polymer having functional groups reactive toward NCO groups. Optionally, the basecoat composition can comprise at least one crosslinker, preferably selected from melamine formaldehyde resins and / or preferably blocked polyisocyanates, in particular in the case where at least the film-forming binder is an externally crosslinked polymer.

[0177] Layer L3, clear coating composition and clear coating system

[0178] A third coating layer L3 is applied on the second coating layer L2, said layer L3 being obtainable from a clear coating composition.

[0179] Any type of clearcoat composition can be used, for example 1K or 2K clearcoat compositions, preferably 2K clearcoat compositions, i.e. clearcoat compositions which in turn are obtainable from a clearcoat system suitable for the preparation of a clearcoat composition, the system preferably comprising at least two components, such as components D) and E) as defined below and optionally at least one further component F), also defined below. Preferably, a solvent-borne clearcoat composition is used. Preferably, the clearcoat composition comprises at least one film-forming binder, preferably at least one polymer, more preferably at least one polymer, which has functional groups reactive toward NCO groups. Optionally, the clearcoat composition can comprise at least one crosslinker, preferably selected from melamine formaldehyde resins and / or preferably blocked polyisocyanates, in particular in the case where at least the film-forming binder is an externally crosslinked polymer. However, in particular in the case where the clearcoat composition is obtainable from a clearcoat system, the at least one crosslinker can also be a polyisocyanate having free NCO groups.

[0180] Preferably, the clear coating composition for preparing layer L3 is obtained by a clear coating system such as a 2K-clear coating system comprising at least two components D) and E) and optionally at least one additional component F), which are different from each other and separated from each other. The clear coating system is a two-(2K-) or multi-component coating system. In this context, separated from each other means that the components D) and E) and optionally F) of the coating system can be stored separately until they are mixed with each other to prepare a primer coating composition. In the case where the coating system is a two-component coating system, it is preferably composed of components D) and E). When mixing at least two components D) and E) and applying the resulting composition to the surface of the substrate, it is preferably formed by at least the reaction of the OH-groups of at least one component d2) with the isocyanate groups of at least one component e2) and optionally e3) to form a polyurethane or polyurethane-based coating film. These components will be defined below.

[0181] The preparation of the clearcoat composition can be carried out using customary and known preparation methods and mixing methods and mixing units, or using conventional dissolvers and / or stirrers.

[0182] Preferably, the clearcoat composition is solventborne, ie a coating composition based on an organic solvent. The term "solventborne" has been defined above and applies here as well.

[0183] The clearcoat composition preferably comprises an organic solvent fraction of at most 65 wt.-%, more preferably at most 60 wt.-%, even more preferably at most 55 wt.-%, still more preferably at most 50 wt.-%, yet more preferably at most 48 wt.-%, in particular at most 45 wt.-% or at most 40 wt.-% or at most 35 wt.-% or at most 30 wt.-%, in each case based on the total weight of the coating composition. All conventional organic solvents known to the person skilled in the art can be used as organic solvents, for example the solvents which have been defined above as components a1) and b1) and optionally c1). Examples of organic solvents which can be used have already been mentioned above in conjunction with components a1) and b1) and c1).

[0184] Preferably, the clearcoat composition has a total solids content of >35 wt.-%, more preferably >40 wt.-%, even more preferably >45 wt.-%, yet more preferably >50 wt.-%, in each case based on the total weight of the coating composition.

[0185] The total solids content of the clearcoat composition is preferably in the range of >35 to 75 wt.-%, more preferably >40 to 70 wt.-%, even more preferably >45 to 65 wt.-%, yet more preferably >48 to 60 wt.-%, in each case based on the total weight of the coating composition. The total solids content, in other words the non-volatile fraction, is determined according to the method described below.

[0186] Preferably, the clear coating composition is obtainable by mixing components D) and E) in a weight ratio (component D) / component E)) in the range of 4:1 to 1:2. More preferably, the mixing is carried out in a weight ratio in the range of 3:1 to 1:1, even more preferably in a weight ratio in the range of 2:1 to 1:1, in particular in a weight ratio in the range of 1:1.

[0187] Preferably, components D) and E) and optionally also component F) of the coating system are free or essentially free of water. The same applies to the coating compositions obtainable therefrom. In the sense of the present invention, the term "free of water" preferably means that water is not present at all. In the sense of the present invention, the term "essentially free of water" preferably means that water is essentially absent. This means that at least no water is intentionally added to any of the components D) and E) and optionally F) used in the present invention and to the coating compositions obtainable therefrom. However, it cannot be excluded that residual residues of water formed during the preparation of any of the ingredients for the preparation of components D) and E) and optionally F) used in the present invention are present therein. Preferably, the amount of any water present in each of components D) and E) and optionally F) is less than 1 wt.-%, more preferably less than 0.5 wt.-%, even more preferably less than 0.1 wt.-%, still more preferably less than 0.05 wt.-%, yet more preferably less than 0.01 wt.-%, in particular less than 0.005 wt.-% or less than 0.001 wt.-%, in each case based on the total weight of components D) or E) or optionally F). Preferably, components D) and E) and also optional component F) of the coating system are solvent-borne, i.e. based on organic solvents. Thus, preferably, the coating system is not water-based, i.e. not an aqueous coating system.

[0188] Preferably, both components D) and E) and optionally F) of the clearcoat system are clear, i.e. transparent. Of course, preferably, the clearcoat composition obtainable therefrom is also clear, i.e. transparent. In particular, none of the components D) and E) and optionally F) of the coating system contains any pigments and / or fillers, in particular any color- and / or effect-imparting pigments and / or fillers. Of course, the same preferably also applies to the clearcoat composition.

[0189] Component D)

[0190] Component D) preferably comprises at least constituent d2) and optionally at least one constituent d1), which are different from one another, but may additionally comprise further optional constituents such as d3), d4) and / or d5), which are different from one another and also from d1) and d2).

[0191] Preferably, component D) of the clearcoat system has a total solids content of >30 wt.-%, preferably >35 wt.-%, more preferably >40 wt.-%, even more preferably >45 wt.-%, based on the total weight of component D). The total solids content of component D) of the coating system is preferably in the range of >35 to 60 wt.-%, more preferably 40 to 55.0 wt.-%, in each case based on the total weight of component D). The total solids content, in other words the non-volatile fraction, is determined according to the method described below.

[0192] Optional ingredient d1)

[0193] Optional ingredient d1) is at least one organic solvent. Examples of such organic solvents include those mentioned above for ingredients a1) and b1) and c1). Component D) may contain more than one organic solvent d1). The at least one organic solvent d1) may be the same or different from the at least one organic solvent a1) and / or b1) and / or c1). If more than one organic solvent is used as a1) and / or b1) and / or c1) and / or d1), a1) and b1) and / or c1) and / or d1) may be partly the same and partly different.

[0194] Ingredient d2) and optionally ingredient d3)

[0195] Ingredient d2) is at least one OH-functional (meth)acrylic polymer. Optional ingredient d3) is also at least one OH-functional (meth)acrylic polymer, which is different from d2, however. Preferably, both d2) and d3) are present in component D). The at least one OH-functional (meth)acrylic polymer d3) has a glass transition temperature (T g ) is lower than the glass transition temperature (T g ). The amount of component d2) in component D) exceeds the amount of component d3), that is, the component D) has a higher T g The (meth)acrylic polymer d2) (higher than the (meth)acrylic polymer d3)) is present in component D) in an amount higher than the (meth)acrylic polymer d3) (if d3) is present). It has been found that the use of d2) and d3) in this way leads in particular to improved packaging stability of the clear coatings produced by preparing component D). T was measured according to the method disclosed in the 'Methods' section g .

[0196] Preferably, the at least one OH-functional (meth)acrylic polymer d2) present in component D) of the clearcoat system has a glass transition temperature (Tg) in the range of +10°C to +75°C, preferably +15°C to +70°C, more preferably +20°C to +65°C, still more preferably +25°C to +60°C, even more preferably +30°C to +55°C, most preferably +35°C or +40°C to +50°C. g ).

[0197] Preferably, the at least one OH-functional (meth)acrylic polymer d3) optionally present in component D) of the clearcoat system has a glass transition temperature (Tg) in the range of -70°C to <+10°C, preferably -60°C to +5°C, more preferably -50°C to 0°C, still more preferably -45°C to 0°C, even more preferably -40°C to 0°C, yet more preferably -35°C or -30°C to -5°C, most preferably -25°C or -5°C. g ).

[0198] The OH-functional (meth) acrylic polymers d2) and d3) preferably each contain on average two or more OH groups. Preferably, each of the OH-functional (meth) acrylic polymers d2) and d3) has an OH value of 30 to 400 mg KOH / g, more particularly between 100 and 300 KOH / g.

[0199] Preferably, each of the components d2) and d3) has a weight average molecular weight M preferably between 800 and 100 000 g / mol, more particularly between 1000 and 75 000 g / mol, measured by gel permeation chromatography (GPC) against polystyrene standards. w .

[0200] The term (meth)acrylic polymer comprises in each case both homopolymers and copolymers, but preferably means copolymers.

[0201] The term "(meth)acryloyl" or "(meth)acrylate" or "(meth)acrylic" in the context of the present invention includes in each case the meaning "methacryloyl" and / or "acryloyl", "methacrylic" and / or "acrylic" or "methacrylate" and / or "acrylate". Thus, a "(meth)acrylic copolymer" may generally be formed from only "acrylic monomers", only "methacrylic monomers" or "acrylic and methacrylic monomers". However, polymerizable monomers other than acrylic and / or methacrylic monomers (e.g. styrene, etc.) may also be contained in the "(meth)acrylic copolymer". In other words, the (meth)acrylic polymer may consist exclusively of acrylic and / or methacrylic monomer units, but this is not mandatory. The notation "(meth)acrylate polymer or copolymer" or "(meth)acrylic polymer or copolymer" is intended to mean that the polymer / copolymer (polymer backbone / main chain) is mainly (i.e. preferably more than 50% or more than 75% of the monomer units used) formed from monomers having (meth)acrylate groups. In the preparation of (meth)acrylic copolymers, preferably more than 50% or 75% of the monomers thus have (meth)acrylate groups. However, the use of further monomers as comonomers such as copolymerizable vinyl monomers (eg styrene) for their preparation is not excluded.

[0202] In order to introduce OH-functionality, hydroxyl-containing monomers can be used, including hydroxyalkyl esters of acrylic acid or methacrylic acid. Non-limiting examples of hydroxyl-functional monomers include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, propylene glycol mono (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, pentaerythritol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, reaction products of these with ε-caprolactone, and other hydroxyalkyl (meth) acrylates with branched or linear alkyl groups up to about 10 carbons and mixtures of these, wherein the term "(meth) acrylate" indicates either or both of methacrylate and acrylate. Generally, it is preferred that at least about 5% by weight of hydroxyl-functional monomers be included in the polymer. Hydroxyl groups on vinyl polymers such as acrylic polymers can be produced by other means, such as ring-opening of glycidyl groups (e.g., glycidyl methacrylate from copolymerization) by organic acids or amines.

[0203] Hydroxyl functional groups can also be introduced through thiol compounds, including but not limited to 3-mercapto-1-propanol, 3-mercapto-2-butanol, 11-mercapto-1-undecanol, 1-mercapto-2-propanol, 2-mercaptoethanol, 6-mercapto-1-hexanol, 2-mercaptobenzyl alcohol, 3-mercapto-1,2-propylene glycol, 4-mercapto-1-butanol and combinations thereof. Any of these methods can be used to prepare useful hydroxyl-functional (meth) acrylic polymers.

[0204] Examples of suitable comonomers that may be used include, but are not limited to, α,β-ethylenically unsaturated monocarboxylic acids containing 3 to 5 carbon atoms, such as acrylic acid, methacrylic acid and crotonic acid and alkyl and cycloalkyl esters, nitriles and amides of acrylic acid, methacrylic acid and crotonic acid; α,β-ethylenically unsaturated dicarboxylic acids containing 4 to 6 carbon atoms and anhydrides, monoesters and diesters of these acids; vinyl esters, vinyl ethers, vinyl ketones and aromatic or heterocyclic aliphatic vinyl compounds. Representative examples of suitable esters of acrylic acid, methacrylic acid, and crotonic acid include, but are not limited to, esters derived from reactions with saturated fatty alcohols containing from 1 to 20 carbon atoms, such as the methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, hexyl, 2-ethylhexyl, dodecyl, 3,3,5-trimethylhexyl, stearyl, lauryl, cyclohexyl, alkyl-substituted cyclohexyl esters, alkanol-substituted cyclohexyl esters, such as 2-tert-butyl and 4-tert-butyl cyclohexyl, 4-cyclohexyl-1-butyl ester, and the like. esters, 2-tert-butyl cyclohexyl ester, 4-tert-butyl cyclohexyl ester, 3,3,5,5,-tetramethylcyclohexyl ester, tetrahydrofurfuryl ester and isobornyl ester; unsaturated dialkanoic acids and anhydrides, such as fumaric acid, maleic acid, itaconic acid and anhydrides and monoesters and diesters thereof with alcohols (such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol and tert-butanol), such as maleic anhydride, dimethyl maleate and monohexyl maleate; vinyl acetate, vinyl propionate, vinyl ethyl ether and vinyl ethyl ketone; styrene, α-methylstyrene, vinyltoluene, 2-vinylpyrrolidone and p-tert-butylstyrene.

[0205] (Meth) acrylic polymers can be prepared using conventional techniques, such as by heating the monomers in the presence of a polymerization initiator and optionally a chain transfer agent. The polymerization can be carried out, for example, in solution. Typical initiators are organic peroxides such as dialkyl peroxides such as di-tert-butyl peroxide, peroxyesters such as tert-butyl peroxy 2-ethylhexanoate and tert-butyl peracetate, peroxydicarbonates, diacyl peroxides, hydroperoxides such as tert-butyl hydroperoxide and peroxyketals; azo compounds such as 2,2′azobis(2-methylbutyronitrile) and 1,1′-azobis(cyclohexanecarbonitrile); and combinations of these. Typical chain transfer agents are mercaptans such as octyl mercaptan, n- or tert-dodecyl mercaptan; halogenated compounds, thiosalicylic acid, thioglycolic acid, mercaptoethanol and other mercaptans already mentioned, as well as dimeric alpha-methylstyrene.

[0206] The polymerization reaction is usually carried out at a temperature of about 20°C to about 200°C. The reaction can be conveniently carried out at a temperature at which the solvent or solvent mixture is refluxed, although a temperature below reflux can be maintained under appropriate control. The initiator should be selected to match the temperature at which the reaction is carried out so that the half-life of the initiator at this temperature should preferably not exceed about thirty minutes. Additional details of general addition polymerization and the polymerization of a mixture including (meth) acrylate monomers are readily available in the polymer field. Usually the solvent or solvent mixture is heated to the reaction temperature, and the monomer and initiator are added at a controlled rate over a period of time (usually between 2 and 6 hours). During this time, a chain transfer agent or another solvent may also be fed at a controlled rate. The temperature of the mixture is then maintained for a period of time to complete the reaction. Alternatively, another initiator may be added to ensure complete conversion.

[0207] Ingredient d2) is preferably present in component D) in an amount in the range of 5.0 wt.-% to 85.0 wt.-%, based on the total weight of component (D). More preferably, ingredient d2) is present in component D) in an amount in the range of 10.0 wt.-% to 80.0 wt.-%, yet more preferably 15.0 wt.-% to 75.0 wt.-%, in each case based on the total weight of component D).

[0208] The optionally present ingredient d3) is preferably present in component D) in an amount in the range of 5.0 wt.-% to 85.0 wt.-%, based on the total weight of component (D). More preferably, ingredient d3) is present in component D) in an amount in the range of 10.0 wt.-% to 80.0 wt.-%, yet more preferably 15.0 wt.-% to 75.0 wt.-%, in each case based on the total weight of component D).

[0209] Optional ingredient d4)

[0210] An optional ingredient d4) is at least one catalyst d4) which is preferably suitable for crosslinking NCO groups and which is preferably selected from organotin catalysts. The catalyst d4) can be identical to or different from the catalyst a3). Preferably, the catalysts d4) and a3) are identical.

[0211] In addition to the catalyst d4), component D) may contain at least one further organometallic catalyst, such as, for example, an organobismuth catalyst. Preferably, however, if such at least one further organometallic catalyst, such as an organobismuth catalyst, is additionally present in component D), its amount is less than the amount of catalyst d4). More preferably, however, component D) does not contain any other organometallic catalyst in addition to the catalyst d4), and in particular does not contain any organobismuth catalyst.

[0212] Preferably, at least one catalyst d4) suitable for crosslinking the NCO groups of constituent e2) of component E), in particular, is present in component D) of the clearcoat system in an amount in the range from 0.001 to 3.00 wt.-%, preferably from 0.01 to 2.50 wt.-%, more preferably from 0.05 to 2.00 wt.-%, even more preferably from 0.10 to 1.50 wt.-%, yet more preferably from 0.20 to 1.25 wt.-%, most preferably from 0.30 to 1.00 wt.-%, based on the total weight of component D).

[0213] The catalyst d4) is preferably selected from organotin catalysts. Examples of organotin catalysts are DOTL (dioctyltin dilaurate) and DBTL (dibutyltin dilaurate). DOTL is particularly preferred.

[0214] Optional ingredient d5)

[0215] Preferably, component D) of the clearcoat system further comprises at least one catalyst d5), which is preferably suitable for crosslinking of Si-containing functional groups, the catalyst d5) being different from each of the components d1) to d4). The catalyst d5) may be the same as or different from the catalysts a4) and a4a).

[0216] Preferably, the at least one catalyst d5) is suitable for crosslinking the Si-containing functional groups present in constituent e2) of component E).

[0217] Preferably, component D) of the clearcoat system comprises at least one catalyst d5) in an amount in the range of 0.01 to 6.00 wt.-%, preferably 0.10 to 5.50 wt.-%, more preferably 0.40 to 5.00 wt.-%, still more preferably 0.70 to 4.50 wt.-%, yet more preferably 1.00 to 4.00 wt.-%, most preferably 1.10 to 3.75 wt.-%, based on the total weight of component D).

[0218] Preferably, at least one catalyst d5) is a phosphorus-containing catalyst and / or a phosphorus-containing and nitrogen-containing catalyst. It is possible to use more than one, for example two different catalysts as catalyst d5).

[0219] Examples of suitable phosphorus-containing catalysts are substituted phosphonic acid diesters and diphosphonic acid diesters, preferably selected from the group consisting of acyclic phosphonic acid diesters, cyclic phosphonic acid diesters, acyclic diphosphonic acid diesters and cyclic diphosphonic acid diesters. More particularly, however, substituted phosphoric acid monoesters and diesters, preferably selected from the group consisting of acyclic phosphoric acid diesters and monoesters and cyclic phosphoric acid diesters and monoesters, which in each case may be amine adducts, for example amine adducts of phosphoric acid monoesters and diesters, are used as at least one catalyst d5).

[0220] Examples of such amine adducts are the corresponding amine-terminated phosphates and, among them, more particularly, amine-terminated ethylhexyl phosphate and amine-terminated phenyl phosphate, very preferably amine-terminated bis(2-ethylhexyl) phosphate. Examples of amines with which the phosphates are terminated are in particular tertiary amines, examples being dicyclic amines such as, for example, diazabicyclooctane (DABCO), diazabicyclononene (DBN), diazabicycloundecene (DBU), dimethyldodecylamine or triethylamine. Particularly preferred for the termination of the phosphates is the use of tertiary amines, which ensure a high activity of the catalyst under curing conditions. Certain amine-terminated phosphoric acid catalysts are also commercially available (e.g., Nacure types from King Industries, such as 4167).

[0221] Preferably, at least one catalyst d5) is selected from phosphorus-containing organic components, more preferably selected from acyclic phosphoric acid diesters, acyclic phosphoric acid monoesters, cyclic phosphoric acid diesters and cyclic phosphoric acid monoesters, wherein each of the above-mentioned phosphoric acid diesters and monoesters can optionally be present in the form of an adduct with at least one amine (i.e., blocked with at least one amine), however, it is preferably not blocked by any amine, preferably at least one tertiary amine, even more preferably, at least two catalysts are present as at least one catalyst d5), these catalysts are both selected from acyclic phosphoric acid diesters, acyclic phosphoric acid monoesters, cyclic phosphoric acid diesters and cyclic phosphoric acid monoesters, but wherein at least one of these at least two catalysts is present in the form of its amine adduct and the other of these at least two catalysts is not present in the form of an amine adduct (i.e., in unblocked form).

[0222] Preferably, at least two catalysts d5) are present, one catalyst not present in any form of an amine adduct such as 2-ethylhexyl acid phosphate, preferably in an amount in the range of 0.05 to 3.5 wt.-%, more preferably 0.10 to 3.0 wt.-%, still more preferably 0.50 to 2.0 wt.-% or to 1.5 wt.-%, and one catalyst present in the form of an amine adduct, preferably in an amount in the range of 1.0 to 4.0 wt.-%, more preferably 1.0 to 3.0 wt.-%. Preferably, the amount of catalyst present in the form of an amine adduct exceeds the amount of catalyst not present in the form of an amine adduct.

[0223] Preferably, at least 2-ethylhexyl acid phosphate is used as at least one catalyst d5), in particular as at least one catalyst d5), which is not present in the form of an amine adduct, i.e. not in any amine-terminated form. The term "2-ethylhexyl acid phosphate" includes both monoethylhexyl acid phosphate and diethylhexyl acid phosphate.

[0224] Additional Ingredients

[0225] Component D) may optionally comprise one or more additional ingredients. Depending on the desired application, component D) may contain one or more conventional additives. For example, it may comprise at least one additive selected from the group consisting of reactive diluents, light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, plasticizers, initiators for free radical polymerization, adhesion promoters, flow control agents, film-forming aids, flame retardants, corrosion inhibitors, desiccants, biocides, thickeners, wetting agents, leveling agents and / or matting agents. They may be used in known and conventional ratios. Preferably, their content is 0.01 to 20.0 wt.-%, more preferably 0.05 to 15.0 wt.-%, particularly preferably 0.1 to 10.0 wt.-%, even more preferably 0.1 to 7.5 wt.-%, in particular 0.1 to 5.0 wt.-%, and most preferably 0.1 to 2.5 wt.-%, based on the total weight of the coating composition obtained by mixing components D) and E) and optionally F), in each case based on the total weight of the coating composition.

[0226] Component D) may further contain one or more additional (meth) acrylic polymers different from both d2) and d3), which may also be OH-functional, but not necessarily. Component D) may contain one or more additional film-forming polymers suitable as adhesive components, such as polyesters and / or polyurethanes. Suitable polyesters are described, for example, in EP-A-0994 117 and EP-A-1 273 640. Polyurethane polyols are preferably prepared by reaction of polyester polyol prepolymers with suitable di- and / or polyisocyanates and are described, for example, in EP-A-1 273 640.

[0227] Component E)

[0228] Component E) preferably comprises at least two constituents e2) and optionally at least constituent e1), which are different from one another, but may additionally comprise further optional constituents which are also different from one another and from e1) and e2).

[0229] Preferably, component E) of the clearcoat system has a total solids content of >40 wt.-%, more preferably >45 wt.-%, even more preferably >50 wt.-%, yet more preferably >55 wt.-%, in each case based on the total weight of component E). The total solids content of component E) of the clearcoat system is preferably in the range from 45 to 100 wt.-%, more preferably from 50 to <100 wt.-%, even more preferably from 55 to <100 wt.-%, in each case based on the total weight of component E). The total solids content, in other words the non-volatile fraction, is determined according to the method described below.

[0230] Optional ingredient e1)

[0231] Optional ingredient e1) is at least one organic solvent. Examples of such organic solvents include those mentioned above for ingredients a1) and b1) and c1) and d1. Component E) may contain more than one organic solvent e1). At least one organic solvent e1) may be the same or different from at least one organic solvent a1) and / or b1) and / or c1) and / or d1). If more than one organic solvent is used as a1) and / or b1) and / or c1) and / or d1) and / or e1), a1) and b1) and / or c1) and / or d1) and / or e1) may be partly the same and partly different.

[0232] Ingredient e2)

[0233] Component e2) is an organic component which carries on average two or more NCO groups, wherein preferably at least some of the NCO groups have been reacted with at least one organosilane before component e2) is incorporated into component E).

[0234] Examples of component e2) are disclosed, for example, in WO 2009 / 077181 A1, WO 2010 / 139375 A1, WO 2010 / 063332 A1, WO 2014 / 086530 A1 and WO 2014 / 086529 A1. Component e2) may be identical to or different from component b2). In particular, e2) is different from b2) when e2) has undergone at least partial silanization as outlined above.

[0235] Preferably, at least one component e2) of component E) of the clearcoat system carries at least one structural unit of the formula (I)

[0236] -NR-(X-SiR” x (OR') 3-x )(I),

[0237] and / or, preferably and, at least one structural unit having formula (II)

[0238] -N(X-SiR” x (OR') 3-x ) n (X'-SiR" y (OR') 3-y ) m (II)

[0239] in:

[0240] R = hydrogen, alkyl, cycloalkyl, aryl or aralkyl, the carbon chain may be replaced by non-adjacent oxygen, sulfur or NR a Group interruption, where R a =alkyl, cycloalkyl, aryl or aralkyl,

[0241] Each R' = independently hydrogen, alkyl or cycloalkyl, the carbon chain may be replaced by non-adjacent oxygen, sulfur or NR a The group is interrupted, preferably wherein each R'=ethyl and / or methyl,

[0242] each X, X' = independently of one another a linear and / or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, preferably wherein each X, X' = an alkylene radical having 1 to 4 carbon atoms,

[0243] Each R" = independently alkyl, cycloalkyl, aryl or aralkyl, the carbon chain may be replaced by non-adjacent oxygen, sulfur or NR a The radical is interrupted, preferably where each R"=alkyl, more particularly having 1 to 6 C atoms,

[0244] n=parameter 0 to 2, m=parameter 0 to 2, m+n=2, and x, y=parameter 0 to 2.

[0245] The corresponding preferred alkoxy groups (OR') may be identical or different, but what is decisive for the structure of these groups is the extent to which they influence the reactivity of the hydrolyzable silane groups. Preferably R' is an alkyl group, more particularly having 1 to 6 carbon atoms. Particularly preferred are groups R' which increase the reactivity of the silane groups, i.e. represent good leaving groups. Therefore, methoxy groups are preferred relative to ethoxy groups, which in turn are preferred relative to propoxy groups. Therefore, it is particularly preferred that R'=ethyl and / or methyl, more particularly methyl. In addition, the reactivity of the organofunctional silanes may also be significantly affected by the length of the spacer X, X' between the silane functional group and the organofunctional group for reacting with the component to be modified. Examples that can be mentioned include "α" silanes, which are available from Wacker and in which there is a methylene group between the Si atom and the functional group instead of the propylene group present in the case of "γ" silanes.

[0246] In component e2), preferably between 10 and 80 mol %, preferably between 15 and 70 mol %, more preferably between 20 and 50 mol % and even more preferably between 25 and 40 mol % of the isocyanate groups initially present have reacted with at least one organosilane, preferably to form structural units (I) and / or (II), more preferably to form structural units (I) and (II).

[0247] Furthermore, preference is given to components e2) in which the total amount of structural units (I) is between 3 and 90 mol-%, more preferably between 5 and 70 mol-%, in each case based on the total amount of structural units (I) plus (II), and the total amount of structural units (II) is between 97 and 10 mol-%, more preferably between 95 and 30 mol-%, in each case based on the total amount of structural units (I) plus (II).

[0248] At least one organic component e2) having on average two or more NCO groups, which before the reaction with the at least one silane serves as the parent structure of the component e2), before the reaction with the at least one silane, represents at this stage a di- and / or polyisocyanate. Preferably, the at least one di- and / or polyisocyanate is an aromatic, aliphatic, alicyclic and / or heterocyclic di- and / or polyisocyanate, in particular aliphatic and acyclic.

[0249] At least one organic component e2) preferably has a cycloaliphatic parent structure and / or a parent structure derived from a cycloaliphatic polyisocyanate by trimerization, dimerization, urethane formation, biuret formation, uretdione formation and / or allophanate formation, wherein component e2) has at least one structural unit of formula (I) and / or (II). Alternatively or additionally, at least one organic component e2) preferably has an acyclic aliphatic parent structure and / or a parent structure derived from an acyclic aliphatic polyisocyanate by trimerization, dimerization, urethane formation, biuret formation, uretdione formation and / or allophanate formation, wherein component e2) has at least one structural unit of formula (I) and / or (II).

[0250] Most preferably, at least one organic component e2) has an acyclic aliphatic parent structure and / or a parent structure derived from an acyclic aliphatic polyisocyanate by trimerization, dimerization, urethane formation, biuret formation, uretdione formation and / or allophanate formation, wherein component e2) has at least one structural unit of formula (I) and / or (II). Trimers, i.e. isocyanurates, are particularly preferred.

[0251] The acyclic aliphatic polyisocyanates serving as parent structures are preferably substituted or unsubstituted aliphatic polyisocyanates known per se. Examples are tetramethylene 1,4-diisocyanate, hexamethylene 1,6-diisocyanate, 2,2,4-trimethylhexane 1,6-diisocyanate, ethylene diisocyanate, dodecane 1,12-diisocyanate and mixtures of the aforementioned polyisocyanates.

[0252] In addition, preferred polyisocyanate matrix structures are polyisocyanates derived from this acyclic aliphatic polyisocyanate by trimerization, dimerization, carbamate formation, biuret formation, uretdione formation and / or allophanate formation, more particularly biuret dimer and / or allophanate dimer and / or isocyanurate trimer. The polyisocyanate matrix structure can also be a polyisocyanate prepolymer with carbamate structural units, which is obtained by the reaction of polyols with stoichiometric excess of the above-mentioned acyclic aliphatic polyisocyanates. This polyisocyanate prepolymer is described in, for example, US-A-4,598,131. Particularly preferred polyisocyanate matrix structures are hexamethylene diisocyanate and / or its biuret dimer and / or allophanate dimer and / or isocyanurate trimer and / or its uretdione, and also a mixture of the polyisocyanate matrix structures. Particularly preferred polyisocyanate precursors are hexamethylene diisocyanate and / or its isocyanurate trimer, optionally together with its uretdione.

[0253] The cycloaliphatic polyisocyanates used as parent structures are preferably substituted or unsubstituted cycloaliphatic polyisocyanates known per se. Examples of preferred polyisocyanates are isophorone diisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene 2,4-diisocyanate, hexahydrotoluene 2,6-diisocyanate, hexahydrophenylene 1,3-diisocyanate, hexahydrophenylene 1,4-diisocyanate, perhydrodiphenylmethane 2,4′-diisocyanate, 4,4′-methylenedicyclohexyl diisocyanate (e.g., Benzene 2,4′-diisocyanate from Bayer AG), cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, cyclohexane 2,4′ ... W) and a mixture of the above-mentioned polyisocyanates. In addition, preferred polyisocyanate matrix structures are polyisocyanates derived from this alicyclic polyisocyanate by trimerization, dimerization, carbamate formation, biuret formation, uretdione formation and / or allophanate formation, more particularly biuret dimer and / or allophanate dimer and / or isocyanurate trimer. The polyisocyanate matrix structure can be a polyisocyanate prepolymer with carbamate structural units, which is obtained by the reaction of polyols with stoichiometric excess of the above-mentioned alicyclic polyisocyanates. This polyisocyanate prepolymer is described in, for example, US-A-4,598,131. Particularly preferred alicyclic polyisocyanates are isophorone diisocyanate and 4,4'-methylene dicyclohexyl diisocyanate and / or its biuret dimer and / or its allophanate dimer and / or its isocyanurate trimer.

[0254] The at least one silane for reaction with the at least one organic component e2) carrying on average two or more NCO groups, before e2) is incorporated into component E), is preferably

[0255] At least one compound having formula (Ia)

[0256] H-NR-(X-SiR” x (OR') 3-x )(Ia),

[0257] and / or at least one compound having formula (IIa)

[0258] HN(X-SiR” x (OR') 3-x ) n (X'-SiR" y (OR') 3-y ) m (IIa),

[0259] wherein the substituents have the definitions given above, including the preferred definitions.

[0260] Preferred compounds (Ia) are aminoalkyltrialkoxysilanes, such as preferably 2-aminoethyltrimethoxysilane, 2-aminoethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyltriethoxysilane. Particularly preferred compounds (Ia) are N-(2-(trimethoxysilyl)ethyl)alkylamine, N-(3-(trimethoxysilyl)propyl)alkylamine, N-(4-(trimethoxysilyl)butyl)alkylamine, N-(2-(triethoxysilyl)ethyl)alkylamine, N-(3-(triethoxysilyl)propyl)alkylamine and / or N-(4-(triethoxysilyl)butyl)alkylamine. Particularly preferred is N-(3-(trimethoxysilyl)propyl)butylamine. Aminosilanes of this type are available, for example, from Degussa under the trade name or from OSI Corporation under the trade name Available.

[0261] Preferred compounds (IIa) are bis(2-ethyltrimethoxysilyl)amine, bis(3-propyltrimethoxysilyl)amine, bis(4-butyltrimethoxysilyl)amine, bis(2-ethyltriethoxysilyl)amine, bis(3-propyltriethoxysilyl)amine and / or bis(4-butyltriethoxysilyl)amine. Particularly preferred is bis(3-propyltrimethoxysilyl)amine. Aminosilanes of these types are available, for example, from Degussa under the trade name or from OSI Corporation under the trade name Available.

[0262] Optional Ingredients e3)

[0263] The optionally present component e3) is an organic component which has on average two or more NCO groups, which is different from e2). In particular, when the component e2) has on average two or more NCO groups, at least some of these NCO groups have been reacted with at least one organosilane before the component e2) is incorporated into component E), the optionally present component e3) does not contain any silane-modified NCO groups.

[0264] The optionally present component e3) can be identical to or different from the component b2). Preferably, the component e3) carries on average more than two NCO groups.

[0265] Preferably, at least one organic component e3) optionally present in component E) has an aliphatic or alicyclic structure and / or a parent structure derived from an aliphatic or alicyclic polyisocyanate by trimerization, dimerization, urethane formation, biuret formation, uretdione formation and / or allophanate formation. The trimers of IPDI (isophorone diisocyanate) and / or HDI (hexamethylene diisocyanate), i.e. isocyanurates, are particularly preferred.

[0266] Suitable aliphatic polyisocyanates are preferably substituted or unsubstituted aliphatic polyisocyanates, such as tetramethylene 1,4-diisocyanate, hexamethylene 1,6-diisocyanate, 2,2,4-trimethylhexane 1,6-diisocyanate, ethylene diisocyanate, dodecane 1,12-diisocyanate and mixtures of the above-mentioned polyisocyanates. Suitable polyisocyanate parent structures can be polyisocyanate prepolymers with urethane structural units, which are obtained by the reaction of polyols with stoichiometric excess of the above-mentioned aliphatic polyisocyanates. Particularly preferred polyisocyanate parent structures are hexamethylene diisocyanate and / or its biuret dimer and / or allophanate dimer and / or isocyanurate trimer and / or its uretdione, as well as mixtures of the polyisocyanate parent structures. Particularly preferred polyisocyanate parent structures are hexamethylene diisocyanate and / or its isocyanurate trimer, optionally with its uretdione.

[0267] Suitable cycloaliphatic polyisocyanates are preferably substituted or unsubstituted cycloaliphatic polyisocyanates, such as isophorone diisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene 2,4-diisocyanate, hexahydrotoluene 2,6-diisocyanate, hexahydrophenylene 1,3-diisocyanate, hexahydrophenylene 1,4-diisocyanate, perhydrodiphenylmethane 2,4′-diisocyanate and 4,4′-methylenedicyclohexyl diisocyanate and mixtures of the abovementioned polyisocyanates. Suitable polyisocyanate parent structures can be polyisocyanates derived from alicyclic polyisocyanates by trimerization, dimerization, carbamate formation, biuret formation, uretdione formation and / or allophanate formation, more particularly biuret dimer and / or allophanate dimer and / or isocyanurate trimer. The polyisocyanate parent structure can be a polyisocyanate prepolymer with carbamate structural units, which is obtained by the reaction of polyols with a stoichiometric excess of the above-mentioned alicyclic polyisocyanates. Particularly preferred alicyclic polyisocyanates are isophorone diisocyanate and 4,4'-methylene dicyclohexyl diisocyanate and / or its biuret dimer and / or its allophanate dimer and / or its isocyanurate trimer.

[0268] Optional component F)

[0269] Optional component F) is a reducing agent component and comprises at least one organic solvent f1). Component F) is used to dilute the coating composition to be prepared and for this reason comprises at least one organic solvent f1) and preferably consists of at least one organic solvent f1). Examples of such organic solvents include those mentioned above with respect to components a1) and b1) and c1) and d1) and e1). Component F) may comprise more than one organic solvent f1). At least one organic solvent f1) may be the same or different from at least one organic solvent a1) and / or b1) and / or c1) and / or d1) and / or e1). If more than one organic solvent is used as a1) and / or b1) and / or c1) and / or d1) and / or e1) and / or f1), then a1) and / or b1) and / or c1) and / or d1) and / or e1) and / or f1) may be partly the same and partly different.

[0270] use

[0271] Another subject of the present invention is the use of a multilayer coating system as defined above and below, comprising at least three coating layers L1, L2 and L3 that are different from one another, for application on a substrate selected from metal and plastic substrates, preferably selected from plastic substrates, more preferably selected from fiber-reinforced plastic substrates, even more preferably selected from carbon fiber-reinforced plastic substrates.

[0272] All preferred embodiments described above in conjunction with the multi-layer coating system of the invention and in each case preferred embodiments thereof are also preferred embodiments of the above-mentioned use.

[0273] Method for preparing a multi-layer coating system

[0274] Another subject of the present invention is a method for producing a multilayer coating system on at least one surface of an optionally precoated substrate, the method comprising at least steps 1) to 3) and optionally 4). Preferably, this method is used for producing the multilayer coating system of the invention.

[0275] All preferred embodiments described above in conjunction with the inventive multi-layer coating system and the inventive use and in each case preferred embodiments thereof are also preferred embodiments of the above-described method for producing a multi-layer coating system.

[0276] The method comprises at least steps (1), (2), (3) and optionally (4). However, the method may comprise further additional optional steps.

[0277] Preferably, each of steps 1) to 3) is performed via spray application.

[0278] The first, second and third coating films formed on the optionally pre-coated substrate by performing steps 1), 2) and 3) are preferably each an uncured coating film at this stage. Therefore, preferably, the first, second and third coating compositions are all applied wet-on-wet.

[0279] Step 1)

[0280] Step 1) involves at least partially applying a first coating composition to at least one surface of an optionally pre-coated substrate and forming a first coating film on the surface, wherein the first coating composition is a primer coating composition used in the present invention.

[0281] Preferably, the method of the present invention further comprises a step 1a), which is performed after step 1) and before step 2). In said step 1a), before applying the second coating composition in step 2), the first coating film obtained after step 1) is flashed, preferably for a period of 1 to 20 minutes, more preferably for a period of 1.5 to 15 minutes, still more preferably for a period of 2 to 12 minutes, still more preferably for a period of 5 to 11 minutes, most preferably for a period of 8 to 10 minutes. Preferably, step 1a) is performed at a temperature not exceeding 40°C, more preferably at a temperature in the range of 18°C ​​to 30°C.

[0282] In the sense of the present invention, the term "flash" means drying, wherein at least some of the solvent and / or water evaporates from the coating film (ie from the formed primer coating) before any curing takes place. Curing does not take place by flashing.

[0283] Step 2)

[0284] Step 2) involves applying at least one base coating composition as at least one second coating composition onto the first coating film present on the substrate obtained after step 1), preferably before curing the first coating film, and forming a second coating film preferably adjacent to the first coating film.

[0285] Preferably, the method further comprises a step 2a), which is performed after step 2) and before step 3). In said step 2a), before applying the third coating composition in step 3), the second coating film obtained after step 2) is flashed, preferably for a period of 1 to 20 minutes, more preferably for a period of 1.5 to 15 minutes, still more preferably for a period of 2 to 12 minutes, still more preferably for a period of 5 to 11 minutes, most preferably for a period of 8 to 10 minutes. Preferably, step 2a) is performed at a temperature not exceeding 40°C, more preferably at a temperature in the range of 18°C ​​to 30°C.

[0286] Step 3)

[0287] Step 3) involves applying the clear coating composition as a third coating composition onto the second coating film present on the substrate obtained after step 2), preferably before curing the second coating film and forming a third coating film, which is preferably adjacent to the second coating film and is preferably the outermost coating film of the formed multi-layer coating system.

[0288] Preferably, the method further comprises step 3a), which is performed after step 3) and before step 4). In said step 3a), before performing the curing step 4), the third coating film obtained after step 3) is flashed, preferably for a period of 1 to 20 minutes, more preferably for a period of 3 to 15 minutes, and especially for a period of 7 to 12 minutes. Preferably, step 3a) is performed at a temperature not exceeding 40° C., more preferably at a temperature in the range of 18° C. to 30° C.

[0289] Step 4)

[0290] In optional step 4), the first, second and third coating films are cured together, ie cured simultaneously. Preferably, step 4) is performed. The cured third coating film preferably represents the outermost layer of the formed multilayer coating system obtained after step 4).

[0291] Each resulting cured coating film represents a coating. Thus, after performing step 4), the first, second and third coatings are formed on the optionally pre-coated substrate, wherein the third layer is preferably the outermost layer of the formed multilayer coating system. The first layer L1 is obtainable from the first coating film, the second layer L2 is obtainable from the second coating film, and the third layer L3 is obtainable from the third coating film.

[0292] Preferably, step 4) is carried out at a temperature in the range of 30° C. to 180° C., more preferably in the range of 35° C. to 170° C., even more preferably in the range of 40° C. to 140° C., still more preferably in the range of 40° C. to 130° C., in each case preferably for a period of 5 to 45 minutes, more preferably for a period of 10 to 40 minutes, in particular for a period of 12.5 to 35 minutes, most preferably for a period of 15 to 30 minutes. Most preferably, in particular when using plastic substrates or fiber-reinforced plastic substrates, step 4) is carried out at a temperature of not more than 80° C., preferably not more than 70° C., more preferably not more than 60° C., even more preferably not more than 55° C. The temperature is in each case the substrate temperature, which is preferably measured with a thermocouple.

[0293] Preferably, the cured primer film (layer L1) obtained after step 4) has been carried out has a dry film thickness in the range of 10 to 35 μm. Preferably, the cured basecoat film (layer L2) obtained after step 4) has been carried out has a dry film thickness in the range of 12 to 35 μm. Preferably, the cured topcoat, in particular clearcoat film (layer L3) obtained after step 4) has been carried out has a dry film thickness in the range of 30 to 60 μm.

[0294] Complete kit

[0295] Another subject of the invention is a kit of parts comprising at least

[0296] The primer coating system used in the present invention as defined above and below comprises at least two components A) and B) and optionally at least one further component C) and

[0297] The clearcoat composition, preferably a 1K clearcoat composition, or a 2K clearcoat system suitable for preparing the clearcoat composition, preferably comprises at least two components D) and E) as defined below and optionally at least one further component F).

[0298] The kit may optionally further comprise a basecoat composition or a basecoat coating system for providing a basecoat composition, but preferably consists of a basecoat coating system used in the present invention and a clearcoat composition or a clearcoat system suitable for preparing a clearcoat composition.

[0299] All preferred embodiments described above in conjunction with the multi-layer coating system of the invention and the above-mentioned uses and methods for producing the multi-layer coating system as well as preferred embodiments thereof in each case are also preferred embodiments of the above-mentioned kit of parts.

[0300] method

[0301] 1. Humidity exposure

[0302] Humidity exposure was determined according to the high humidity test (96 h) according to GMW 14729 (4th edition, August 2020).

[0303] 2. Tape Adhesion

[0304] Tape adhesion was determined according to the Tape Adhesion Test of GMW 14829 (4th edition, June 2017) (Method A described therein).

[0305] 3. Appearance

[0306] The appearance is determined by measuring the LW (long wave) and short wave (SW) values ​​of the coating via a BYK wave scanner 2. To meet the criteria for "Class A appearance", the coating should preferably have an LW value of ≤10 and a SW value of ≤20.

[0307] 4. High pressure water jet resistance

[0308] To assess the resistance of the coatings to high-pressure water jets (steam jets), the method according to VW PV 1503B was used.

[0309] 5. Scratch resistance

[0310] Dry scratch resistance was determined using an Atlas M38BB Electric Crockmeter (10 cycles with 9 micron paper). A 2” x 2” sheet of 9 micron 3M 281Q WETODRY TM The polishing paper is fixed to the cylindrical acrylic finger of the movable arm of the abrasion tester. The coated 4" x 12" steel test plate is fixed under the movable arm with a magnet. After ensuring that the abrasive is smooth to the surface of the plate, ten back and forth (or double rub) cycles are performed. After sliding the plate to an untested area, the same steps are repeated a second time on the same plate with a new piece of 3M paper. After the test is completed, the 20° gloss of the tested area and the untested area of ​​the plate is measured using a micro-TRI-gloss gloss meter from BYK. The percent gloss retention (%GR) is calculated by taking the average of the gloss of the two tested areas and dividing it by the gloss of the untested area.

[0311] 6. Thermal shock

[0312] Thermal shock is determined according to the test of GMW 15919 (3rd edition, March 2019).

[0313] 7. Packaging stability

[0314] According to DIN EN ISO 3678:1995-04, the packaging stability is determined using the indentation test for the resistance to indentation. The round test weight is made of metal 500g (diameter 5cm / height 3cm). Each sample piece (the size of the test specimen: about 6×6cm) comes from the ASP consumer for packaging commonly used packaging materials (thin paper / packaging bag / packaging tissue) and is packaged with coated plastic parts. After the oven to be used is dried, the test plate is immediately placed in a standard climate control room (23°C / 50%RH (relative air humidity)) and the corresponding test points are determined. After a waiting time of 10-15 minutes, the first test point is filled with the first sample of the packaging medium and the test weight is immediately loaded. The other samples of the corresponding packaging medium are taken out from the furnace after an aging time of 1h, 2h, 4h and 24h and placed on the marked points on the test plate and also loaded with other test weights. Take out the samples of the test weights and packaging medium 24 hours after the start of each load test.

[0315] Rating criteria:

[0316]

[0317] 8. Glass transition temperature

[0318] The glass transition temperature is measured by DSC measurement in accordance with DIN EN ISO 11357-2 (2019-03).

[0319] 9. Dynamic Light Scattering (DLS)

[0320] The average particle size of the optional component a5) (and the silica starting material used) is determined by the dynamic light scattering (DLS) method according to ISO 21501-4 standard. The measurement is carried out using a Beckman coulter instrument (model: Delsa Nano C particle analyzer; software: Delsa Nano 2.31). Before the examination, a sample solution of about 0.01% is prepared in filtered distilled water.

[0321] Examples

[0322] The following examples further illustrate the present invention but should not be construed as limiting its scope. 'Pbw' means parts by weight. If not otherwise defined, 'parts' means 'parts by weight'.

[0323] 1. Preparation of 2K primer coating systems and coating material compositions obtainable therefrom

[0324] 1.1 The "A" component of the 2K primer coating systems IPC1 and IPC2 used according to the invention and the comparative 2K primer coating system CPC1 was prepared by mixing the ingredients listed in Table 1.1 in this order.

[0325] Table 1.1: “A” - Components

[0326]

[0327]

[0328] Pigment paste P1 contains 60 wt.-% of titanium dioxide pigment and further comprises an alkyl resin. Pigment paste P2 contains 6 wt.-% of carbon black pigment and further comprises an alkyl resin. Pigment paste P3 contains 10 wt.-% of organic blue pigment and further comprises an alkyl resin. Pigment paste P4 contains 47 wt.-% of inorganic yellow pigment and further comprises an alkyl resin. 4167 is a commercially available amine neutralized phosphate catalyst. TIB 216 is a liquid tin catalyst based on dioctyltin compounds. BYK 3565 is a commercially available surfactant additive. AS1 and AS2 are both commercially available aromatic solvent mixtures, which differ from each other. NMP is N-methylpyrrolidone. CPO is a commercially available chlorinated polyolefin solution (solids content 19.8 wt.-%). ACL is CL-408, a commercially available solvent-based acrylic resin, which is OH-functional and has been modified with chlorinated polypropylene (solids content 44.0 to 46 wt.-%). The epoxy resin is the reaction product of bisphenol A and DGEBA, bisphenol A diglycidyl ether, and has an epoxy equivalent weight of 465 to 500.

[0329] The silica-silane condensate used was MTMS-silica condensate and was prepared by reacting methyltrimethoxysilane (MTMS) with a commercially available nanosilica dispersion ( To prepare the silica-silane condensate, MTMS (0.45 mol) was mixed with acetic acid (1.45 wt.-%) and the mixture was cooled to 0° C. Then, water (9.7 wt.-%, 0.54 mol) and AS-40 (24.5 wt.-%, 0.97 mol, of which 0.16 mol thereof correspond to silica and the remainder to water also present in this product). The molar ratio of MTMS to silica is therefore 0.45:0.16, i.e. about 2.8. The resulting mixture is then stirred at room temperature for 12 to 16 h. Then, acetic acid and TBAA (tetrabutylammonium acetate) are added as catalysts (3.13 wt.-% acetic acid and 0.17 wt.-% TBAA), and the mixture is stirred for 2 to 3 h, keeping the pH at 5.1. The resulting mixture (solids content 43 wt.-%) is then diluted with isopropanol (1:1 by weight) and then used in this form as silica-silane condensate for the preparation of the "A" component of IPC2.

[0330] 1.2 The "B" component for the 2K primer coating systems IPC1, IPC2 and CPC1 is prepared by mixing the ingredients listed in Table 1.2 in this order.

[0331] Table 1.2: “B” - Components

[0332]

[0333] N3600 is a commercially available aliphatic polyisocyanate (HDI trimer). 1189 is N-(3-(trimethoxysilyl)propyl)butylamine. 1124 is bis(trimethoxysilylpropyl)amine.

[0334] 1.3 The primer coating material composition is prepared by mixing the "A" component of the primer coating system IPC1 with the "B" component in a weight ratio of 12.89:1 ("A" to "B") to each other or in the case of the primer coating system CPC1 in a weight ratio of 12.89:1 ("A" to "B") to each other or in the case of the primer coating system IPC2 in a weight ratio of 14.44:1 ("A" to "B") to each other.

[0335] The mixing ratio is calculated and selected such that an excess of about 10 to 12 wt.-% of polyisocyanate from component "B" is still present in the resulting composition, so that when applied on top of the primer coating film, the subsequently applied basecoat film also cures by NCO migration, which is obtained by applying the primer coating material composition to the surface of the substrate.

[0336] 2. Preparation of 2K clearcoat systems and clearcoat material compositions obtainable therefrom

[0337] 2.1 The "A"-component of the 2K clearcoat system ICC1 was prepared by mixing the ingredients listed in Table 2.1 in this order.

[0338] Table 2.1: “A”-components of ICC1

[0339]

[0340] Catalyst 1 is a commercially available catalyst, namely TIB 216 (DOTL), which is a liquid tin catalyst based on dioctyltin compounds. Additive 1 is a commercially available liquid hydroxyphenyl-triazine (HPT) UV absorber. Additive 2 is a commercially available liquid hindered amine light stabilizer. Additive 3 is a commercially available silicone-containing surface additive. Additive 4 is a commercially available defoamer. 4167 has been described above. AS3 is a commercially available aromatic solvent mixture that is different from AS1 and AS2 identified above. Acrylic Resin 1 is a 2-hydroxyethyl acrylate having a T of -15°C prepared from n-butyl methacrylate, styrene, 4-hydroxybutyl acrylate and 2-hydroxyethyl acrylate. g A solution of an OH-functional (meth) acrylic resin (solid content: 65 wt %). Acrylic resin 2 is prepared from 3-hydroxypropyl methacrylate, 2-ethylhexyl (meth)acrylate and cyclohexyl (meth)acrylate and has a T of +34°C. g Dispersion of an OH-functional (meth)acrylic resin (solids content: 67.5 wt.-%). Acrylic resin 3 is prepared from n-butyl methacrylate, styrene, cyclohexyl methacrylate, 2-hydroxypropyl methacrylate and 2-hydroxyethyl methacrylate and has a T of +46°C. g Dispersion of an OH-functional (meth)acrylic resin of (solids content: 60.0 wt.-%).

[0341] 2.2 The "B" component of the 2K clearcoat system ICC1 is a polyisocyanate. The polyisocyanate (product N3600 as starting material) before its use / as component "B" by using two different organosilanes (i.e. 1189 and 1124) silanization. N3600 is a commercially available aliphatic polyisocyanate (HDI trimer). 1189 is N-(3-(trimethoxysilyl)propyl)butylamine. 1124 is bis(trimethoxysilylpropyl)amine. The "B" component is commercially available ( "B" component of the repair paint).

[0342] 2.3 Clearcoat Material The composition was prepared by mixing the "A" component and the "B" component of the clearcoat system ICC1 in a weight ratio of 1:1 ("A" to "B") to each other.

[0343] 3. Preparation of multilayer coating systems

[0344] 3.1 A number of multilayer coating systems were obtained by using the above-described basecoat and clearcoat material compositions and by using in each case one of the different basecoat (midcoat) material compositions, as will be outlined below.

[0345] 3.2 Multilayer coating system comprising a primer layer obtained from IPC1 or IPC2, a basecoat layer and a clearcoat layer obtained from ICC1 (all according to the invention)

[0346] Carbon fiber (C-fiber) reinforced plastic substrate is used as substrate, i.e. product XA3418, which is a carbon fiber reinforced polyamide. The primer coating material composition obtained by the primer coating system IPC1 or IPC2 prepared as described in Item 1.3 is applied to the surface of the substrate to form a primer film and flashed for 10 minutes under ambient conditions (room temperature). Then one of the base coating material compositions SBBC1 to SBBC4 (each solvent-based) or WBBC1 to WBBC4 (each water-based) is sprayed on the primer film to form a base coating film and flashed for 10 minutes under ambient conditions (room temperature). In the case of a water-based base coating material composition (WBBC), an additional flash is performed at an elevated temperature of 140°F (60°C) for 5 minutes. Then, a clear coating material composition obtained by the clear coating system ICC1 prepared as described in Item 2.3 is applied to the base coating film and flashed for 10 minutes under ambient conditions (room temperature), and then all films are baked simultaneously at a substrate temperature of 122°F (50°C) for 30 minutes.

[0347] The dry film thickness of each primer layer obtained after curing each primer film is in the range of 0.5 to 1 mil (12.7 μm to 25.4 μm). The dry film thickness of each basecoat layer obtained after curing each basecoat layer film is in the range of 0.6 to 1 mil (15.24 μm to 25.4 μm), and the dry film thickness of each clearcoat layer obtained after curing each clearcoat layer film is in the range of 1.9 to 2.1 mil (48.26 μm to 53.34 μm).

[0348] SBBC1 to SBBC4 are different colored base coating material compositions of high solid solvent type. The following commercial products were used:

[0349] SBBC1: Shadow Black

[0350] SBBC2: Ingot Silver

[0351] SBBC3: Oxford White

[0352] SBBC4: Hot Pepper Red.

[0353] Before application, the spray viscosity of SBBC2 to SBBC4 was adjusted to about 35 cP using a suitable solvent such as n-butyl acetate. Before application, the spray viscosity of SBBC1 was adjusted to about 55 cP using a suitable solvent such as n-butyl acetate.

[0354] WBBC1 to WBBC4 are high solids differently colored water-based basecoat material compositions. The following commercial products were used:

[0355] WBBC1: Exterior Black

[0356] WBBC2: Switchblade Silver

[0357] WBBC3: Abalone White

[0358] WBBC4: Caught Red Handed.

[0359] Prior to application, the spray viscosity of WBBC1 to SBBC4 was adjusted to approximately 90 to 95 cP.

[0360] 3.3 Further multi-layer coating system comprising a primer layer obtained from IPC1, a basecoat layer and a clearcoat layer obtained from ICC1 (all according to the invention)

[0361] Using the same type of coating material composition, another multilayer coating system was prepared in the same manner as described in item 3.2. The only difference was that In addition to XA3418, three other different substrates were used, namely the following substrates S1 to S4, which are:

[0362] S1: Steel (CG 800)

[0363] S2: XA3418 (from the series described in item 3.2)

[0364] S3: Polypropylene, reinforced with carbon fibers (20 wt.-%) (CB201SY)

[0365] S4: TPO (thermoplastic olefin).

[0366] 3.4 Comparative Experiment

[0367] 3.4.1 Another multi-layer coating system was prepared in the same manner as described in item 3.2 using SBBC1 as a basecoat and comprising a clearcoat obtained from ICC1. However, instead of IPC1, a commercial internally crosslinked 1K primer coating material composition, Med Gray AdPro, was used which did not contain any polyisocyanate and also did not contain ACL ( CL-408, a commercially available solvent-based acrylic resin modified with chlorinated polypropylene, wherein the modified resin is OH-functional). In contrast, the commercial 1K primer coating material composition used contained an epoxy resin and an alkyd resin. This multi-layer coating system is referred to as comparative example CE1.

[0368] 3.4.2 Another multi-coat system was prepared in the same manner as described in item 3.2, using SBBC1 as basecoat and comprising a clearcoat obtained from ICC1. However, instead of IPC1, a comparative 2K primer coating system CPC1 was used. This multi-coat system is referred to as comparative example CE2.

[0369] 3.4.3 Another multi-layer coating system was prepared in the same manner as described in item 3.2 using SBBC1 as basecoat and comprising a clearcoat obtained from ICC1. However, instead of IPC1, a commercial 2K clearcoat product was used. 905 was used as the primer coating material composition. This multi-layer coating system is referred to as comparative example CE3.

[0370] 3.4.4 Another multi-layer coating system was prepared in the same manner as described in item 3.2, using SBBC1 as basecoat and comprising a clearcoat obtained from ICC1. However, instead of IPC1, a commercially available 2K clearcoat system (Refinish Coat) was used. ) as the primer coating material composition. This multi-layer coating system is referred to as comparative example CE4.

[0371] 3.4.5 Another multi-layer coating system was prepared in the same manner as described in item 3.2 using SBBC1 as the basecoat. However, for the preparation of the clearcoat, a commercial 2K clearcoat product was used instead of ICC1. 905. Furthermore, for the preparation of the primer layer, the commercial 1K primer Med Gray AdPro was used instead of IPC1. Furthermore, a baking temperature of 80° C. (instead of 50° C.) was used. This multilayer coating system is referred to as comparative example CE5.

[0372] 3.4.6 Another multi-coat system was prepared in the same manner as described in item 3.2 using SBBC1 as basecoat. For the preparation of the basecoat, IPC1 was used. However, for the preparation of the clearcoat, ICC1 was not used. Instead, three different clearcoat systems were used, each of which comprised the "A" component of the clearcoat system ICC1, but each contained a different "B" component. In each case, the different "B" components did not contain any silanized polyisocyanates, but only non-silanized polyisocyanates. In the case of the multi-coat system prepared according to comparative example CE6, only ICC1 was used. N3600 was used as the "B" component of the clear coating system used. In the case of the multilayer coating system prepared according to comparative example CE7, a commercially available clear coating system was used. In the case of the multi-layer coating system prepared according to Comparative Example CE8, a commercially available clear coating system was used. The "B" component.

[0373] 4. Characterization of substrates coated with multi-layer coating systems

[0374] 4.1 In Tables 4.1a, 4.1b and 4.1c, a number of properties measured and / or determined according to the methods defined in the "Methods" section are summarized, which properties are obtained for the multilayer coating system present on the carbon fiber reinforced plastic substrate prepared as described in item 3.2 above.

[0375] Table 4.1a: Properties of a multi-layer coating system with a primer layer obtained from IPC1, a basecoat and a clearcoat obtained from ICC1

[0376]

[0377] Table 4.1b: Properties of a multilayer coating system having a primer layer obtained from IPC1, a basecoat and a clearcoat obtained from ICC1 (continued)

[0378]

[0379] Table 4.1c: Properties of a multi-layer coating system with a primer layer obtained from IPC2, a basecoat and a clearcoat obtained from ICC1

[0380]

[0381] 4.2 In addition, accelerated weathering studies were performed using the multi-layer coating systems on different substrates as described in item 3.3 according to SAE J2527 and ASTM 7869 methods. All multi-layer coating systems on all substrates passed the tests.

[0382] 4.3 In Table 4.2, a number of properties measured and / or determined according to the methods defined in the "Methods" section are summarized, which properties were obtained for the comparative multi-layer coating system CE1 prepared as described in Item 3.4.1 above, the comparative multi-layer coating system CE2 prepared as described in Item 3.4.2 above, the comparative multi-layer coating system CE3 prepared as described in Item 3.4.3 above, and the comparative multi-layer coating system CE4 prepared as described in Item 3.4.4 above.

[0383] Table 4.2: Properties of a multilayer coating system having a primer layer, a basecoat obtained from SBBC1 and a clearcoat obtained from ICC1 (comparison)

[0384]

[0385] Each of CE1 to CE4 exhibited poor tape adhesion, steam jet and thermal shock properties after humidity exposure. The "black stripes" that appeared when using the tape adhesion test indicated that the basecoat was insufficiently cured. In this regard, it has been found that using excess isocyanate in the clearcoat does not improve basecoat cure. In addition, each of CE2 to CE4 had too high a SW value to meet the A-level requirements for appearance.

[0386] 4.4 In Table 4.3, a number of properties measured and / or determined according to the methods defined in the "Methods" section are summarized, which were obtained for the comparative multilayer coating system CE5 prepared as described above in item 3.4.5.

[0387] Table 4.3: Basecoat with primer layer, obtained from SBBC1 and from Properties of multi-layer coating systems with clear coatings obtained with 905 (comparison)

[0388]

[0389] CE5 has too high LW and SW values ​​to meet the Class A requirements regarding appearance.

[0390] 4.5 In Table 4.5, the packaging stability data measured according to the method defined in the "Methods" section and rated according to the criteria defined therein are summarized, which data were obtained for a multilayer system according to the present invention having a primer layer obtained from IPC1, a basecoat obtained from SBBC1 and a clearcoat obtained from ICC1.

[0391] Table 4.5: Packaging stability

[0392]

[0393] 4.6 In Table 4.6, a number of properties measured and / or determined according to the methods defined in the "Methods" section are summarized, which properties were obtained for the comparative multilayer coating systems CE6, CE7 and CE8 prepared as described above in item 3.4.6.

[0394] Table 4.6: Characteristics of multilayer coating systems CE6, CE7 and CE8 (comparison)

[0395]

[0396] CE6 to CE8 had poor appearance and showed poor tape adhesion after humidity exposure (CE7 and CE8), steam spray and thermal shock properties (each of CE6 to CE8).

Claims

1. A multilayer coating system, which is present on an optionally pre-coated substrate and comprises at least three coating layers L1, L2 and L3 which are different from each other, namely a first coating layer L1 applied to at least a portion of the optionally precoated substrate, said layer L1 being obtainable from a primer coating composition which in turn is obtainable from a primer coating system comprising at least two components A) and B) and optionally at least one further component C), said components being different from one another and being separate from one another, wherein component A) comprises at least component a2) and optionally at least component a1), which are different from one another, namely optionally at least one organic solvent a1), and at least one polymer a2) which contains functional groups reactive toward NCO groups, wherein the polymer a2) is a (meth)acrylic polymer which has been modified with at least one chlorinated polyolefin, The component B) comprises at least two components b2) and optionally at least one component b1), which are different from one another, namely optionally at least one organic solvent b1), and at least one organic component b2) which carries on average two or more NCO groups, and wherein the optional component C) is a reducing agent component and comprises at least one organic solvent c1), a second coating layer L2 applied on this first coating layer L1, said layer L2 being obtainable from a basecoat composition, and a third coating L3 applied on this second coating L2, said layer L3 being obtainable from a clear coating composition, wherein the layer L3 is obtainable from a 2K clearcoat composition which in turn is obtainable from a clearcoat system comprising at least two components D) and E) and optionally at least one further component F), which components are different from one another and are separated from one another, wherein component D) comprises at least component d2) and optionally at least component d1), which are different from one another, namely optionally at least one organic solvent d1), and at least one OH-functional (meth)acrylic polymer d2), wherein component E) comprises at least component e2) and optionally at least component e1), which are different from one another, namely optionally at least one organic solvent e1), and at least one organic component e2) which carries on average two or more NCO groups, wherein at least some of these NCO groups have been reacted with at least one organosilane before the component e2) is incorporated into component E), and The optional component F) is a reducing agent component and comprises at least one organic solvent f1).

2. The multi-layer coating system according to claim 1, wherein: The at least three coating layers L1 , L2 and L3 are positioned adjacent to each other and / or wherein the third coating layer L3 is the outermost coating layer of the multilayer coating system.

3. The multi-layer coating system according to claim 1 or 2, wherein: The substrate is selected from metal and plastic substrates, preferably a plastic substrate, more preferably a fiber-reinforced plastic substrate, even more preferably a carbon fiber-reinforced plastic substrate.

4. The multilayer coating system according to one or more of the preceding claims, wherein: The multilayer coating system exhibits an LW (long wave) value of ≤10 and an SW (short wave) value of ≤20, which are determined by the method disclosed in the description.

5. The multilayer coating system according to one or more of the preceding claims, wherein: The polymer a2) is contained in component A) of the primer coating system in an amount in the range from 5.0 to 50.0 wt.-%, preferably 10.0 to 45.0 wt.-%, more preferably 15.0 to 40.0 wt.-%, still more preferably 17.5 to 35.0 wt.-%, based in each case on the total weight of component A).

6. The multilayer coating system according to one or more of the preceding claims, wherein: Component A) of the primer coating system further comprises at least one of components a3) and a4), preferably both components a3) and a4), which components are different from each other and from each of components a1) and a2), Component a3) is a catalyst a3) suitable for crosslinking the NCO groups of component b2) of component B), wherein component a3) is preferably selected from organotin catalysts and / or is preferably present in component A) of the primer coating system in an amount in the range of 0.001 to 1.00 wt.-%, preferably 0.002 to 0.80 wt.-%, more preferably 0.003 to 0.60 wt.-%, even more preferably 0.004 to 0.40 wt.-%, yet more preferably 0.005 to 0.20 wt.-%, most preferably 0.007 to 0.15 wt.-%, based on the total weight of component A), and Component a4) is a catalyst a4) selected from phosphorus-containing organic components, which are preferably not terminated by any amine, wherein the at least one catalyst a4) is preferably present in component A) of the primer coating system in an amount in the range of 0.01 to 2.5 wt.-%, more preferably 0.02 to 2.0 wt.-%, even more preferably 0.03 to 1.5 wt.-%, still more preferably 0.04 to 1.2 wt.-%, yet more preferably 0.05 to 1.0 wt.-%, based on the total weight of component A).

7. The multilayer coating system according to one or more of the preceding claims, wherein: Component A) of the primer coating system further comprises at least one component a5), which is different from any of the components a1) to a4) and is a condensation product, which in turn is obtainable by at least (i) reacting at least one organosilane carrying at least one hydrolyzable group with (ii) at least one silicon dioxide, wherein the molar ratio of the at least one organosilane and the at least one silicon dioxide used to prepare the condensation product a5) to each other is preferably in the range of 10:1 to 1:1, preferably 8:1 to 1:1, more preferably 6:1 to 1:1, even more preferably 4:1 to 1:1, still more preferably 4 :1 to 1.1:1, yet more preferably in the range of 4:1 to 1.5:1, most preferably in the range of 4:1 to 2:1, and / or wherein the at least one condensation product a5) is present in component A) in an amount in the range of 1.0 to 25.0 wt.-%, preferably 2.0 to 20.0 wt.-%, more preferably 3.0 to 17.5 wt.-%, yet more preferably 4.0 to 15.0 wt.-%, still more preferably 5.0 to 14.0 wt.-%, even more preferably 6.0 to 13.0 wt.-%, most preferably 7.0 to 12.0 wt.-%, based on the total weight of component A).

8. The multilayer coating system according to one or more of the preceding claims, wherein: Component A) of the primer coating system further comprises at least one leveling agent and / or dispersant as added component a9), which is different from each of the components a1) to a4), which is preferably a (meth)acrylate polymer, which preferably contains at least one ether segment, more preferably in the side chain, and / or which preferably contains at least one siloxane unit, more preferably also in the side chain, wherein component a9) is preferably present in component A) in a range of 0.10 to 5.0 wt.-%, more preferably 0.50 to 4.0 wt.-%, even more preferably 0.80 to 3.5 wt.-%, in each case based on the total weight of component A).

9. The multilayer coating system according to one or more of the preceding claims, wherein: Component D) of the clearcoat system comprises at least two OH-functional (meth)acrylic polymers d2) and d3) which are different from one another, wherein the amount of component d2) in component D) preferably exceeds the amount of component d3), wherein the at least one OH-functional (meth)acrylic polymer d3) has a glass transition temperature (T g ) is lower than the glass transition temperature (T g ), preferably wherein the at least one OH-functional (meth)acrylic polymer d2) has a glass transition temperature (Tg) in the range of +10°C to +75°C, preferably +15°C to +70°C, more preferably +20°C to +65°C, still more preferably +25°C to +60°C, even more preferably +30°C to +55°C, most preferably +35°C or +40°C to +50°C. g ), and preferably wherein the at least one OH-functional (meth)acrylic polymer d3) has a glass transition temperature (Tg) in the range of -70°C to <+10°C, preferably -60°C to +5°C, more preferably -50°C to 0°C, still more preferably -45°C to 0°C, even more preferably -40°C to 0°C, yet more preferably -35°C or -30°C to -5°C, most preferably -25°C or -5°C. g ).

10. The multilayer coating system according to one or more of the preceding claims, wherein: Component D) of the clearcoat system further comprises at least one of ingredients d4) and d5), preferably both ingredients d4) and d5), which ingredients are different from each other and from each of ingredients d1) to d3), Component d4) is at least one catalyst d4) suitable for crosslinking the NCO groups of component e2) of component E), which is preferably selected from organotin catalysts and is identical to or different from catalyst a3), wherein the catalyst d4) is preferably present in component D) of the clearcoat system in an amount in the range from 0.001 to 3.00 wt.-%, preferably 0.01 to 2.50 wt.-%, more preferably 0.05 to 2.00 wt.-%, even more preferably 0.10 to 1.50 wt.-%, yet more preferably 0.20 to 1.25 wt.-%, most preferably 0.30 to 1.00 wt.-%, based on the total weight of component D), Component d5) is at least one catalyst d5) selected from phosphorus-containing organic components, which are preferably not terminated by any amine and which is the same as or different from the catalyst a4), preferably in an amount in the range of 0.01 to 6.00 wt.-%, preferably 0.10 to 5.50 wt.-%, more preferably 0.40 to 5.00 wt.-%, still more preferably 0.70 to 4.50 wt.-%, yet more preferably 1.00 to 4.00 wt.-%, most preferably 1.10 to 3.75 wt.-%, based on the total weight of component D).

11. The multilayer coating system according to one or more of the preceding claims, wherein: At least one component e2) of component E) of the clearcoat system carries at least one structural unit of the formula (I) -NR-(X-SiR” x (OR') 3-x )(I), and / or, preferably and, at least one structural unit having formula (II) -N(X-SiR” x (OR') 3-x ) n (X'-SiR” y (OR') 3-y ) m (II), in: R = hydrogen, alkyl, cycloalkyl, aryl or aralkyl, the carbon chain may be replaced by non-adjacent oxygen, sulfur or NR a Group interruption, where R a =alkyl, cycloalkyl, aryl or aralkyl, Each R' = independently hydrogen, alkyl or cycloalkyl, the carbon chain may be replaced by non-adjacent oxygen, sulfur or NR a The group is interrupted, preferably wherein each R'=ethyl and / or methyl, each X, X' = independently of one another a linear and / or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, preferably wherein each X, X' = an alkylene radical having 1 to 4 carbon atoms, Each R" = independently alkyl, cycloalkyl, aryl or aralkyl, the carbon chain may be replaced by non-adjacent oxygen, sulfur or NR a The radical is interrupted, preferably where each R"=alkyl, more particularly having 1 to 6 C atoms, n=parameter 0 to 2, m=parameter 0 to 2, m+n=2, and x, y=parameter 0 to 2, and / or wherein between 10 and 80 mol-%, preferably between 15 and 70 mol-%, more preferably between 20 and 50 mol-% and even more preferably between 25 and 40 mol-% of the isocyanate groups initially present in the at least one component e2) have reacted with the at least one organosilane, preferably to form structural units (I) and / or (II), more preferably to form structural units (I) and (II), and / or wherein component E) further comprises at least one organic component e3) having on average two or more NCO groups, which is different from component e2) and does not contain any silane-modified NCO groups and which is identical to or different from component b2), wherein the at least one organic component e3) present in component E) preferably has an aliphatic or cycloaliphatic parent structure and / or a parent structure which is derived from an aliphatic or cycloaliphatic polyisocyanate by trimerization, dimerization, urethane formation, biuret formation, uretdione formation and / or allophanate formation.

12. Use of a multilayer coating system as defined in one or more of the preceding claims, comprising at least three coating layers L1, L2 and L3 which are different from one another, for application on a substrate selected from metal and plastic substrates, preferably selected from plastic substrates, more preferably selected from fiber-reinforced plastic substrates, even more preferably selected from carbon fiber-reinforced plastic substrates.

13. A method for preparing a multilayer coating system on at least one surface of an optionally pre-coated substrate, the method comprising at least steps 1) to 3) and optionally 4), namely 1) applying a first coating composition at least partially to at least one surface of an optionally pre-coated substrate and forming a first coating film on said surface, wherein the first coating composition is a primer coating composition as defined in claims 1 and 5 to 8, 2) applying at least one base coating composition as at least one second coating composition onto the first coating film present on the substrate obtained after step 1), preferably before curing the first coating film, and forming a second coating film preferably adjacent to the first coating film, and 3) applying a clear coating composition as a third coating composition onto the second coating film present on the substrate obtained after step 2), preferably before curing the second coating film and forming a third coating film, which is preferably adjacent to the second coating film and is preferably the outermost coating film of the formed multi-layer coating system, wherein the third coating composition is a clear coating composition as defined in claims 1 and 9 to 11, and 4) optionally co-curing the first, second and third coating films to obtain a multi-layer coating system comprising cured first, second and third coatings, preferably at a temperature of not more than 80° C., more preferably not more than 70° C., still more preferably not more than 60° C., even more preferably not more than 55° C., in particular, when a plastic substrate or a fiber-reinforced plastic substrate is used as the optionally pre-coated substrate.

14. The method according to claim 13, wherein: The multi-layer coating system obtained is a multi-layer coating system according to one or more of claims 1 to 11.

15. A kit comprising at least A primer coating system comprising at least two components A) and B) as defined in claims 1 and 5 to 8 and optionally at least one further component C), and 2K clearcoat systems suitable for producing clearcoat compositions comprising at least two components D) and E) as defined in claims 1 and 9 to 11 and optionally at least one further component F).

Images