CN117881753A

CN117881753A - Laser radar reflective multilayer coating with high flop index

Info

Publication number: CN117881753A
Application number: CN202280058685.8A
Authority: CN
Inventors: M·卡亚尔卡特; R·贾纳; Q·张; Z·P·佐尔尼; D·H·坎贝尔
Original assignee: BASF Coatings GmbH
Current assignee: BASF Coatings GmbH
Priority date: 2021-08-30
Filing date: 2022-08-30
Publication date: 2024-04-12

Abstract

The present invention relates to a multilayer coating system which is present on an optionally precoated substrate and comprises at least three mutually different coatings L1, L2 and L3, the first layer L1 being applied on an optionally precoated substrate, the second layer L2 being applied on L1 and the third top coating L3 being applied on L2, wherein layer L1 is formed from a primer coating composition and layer L2 is formed from a primer coating composition which is different from the primer coating composition, wherein the primer coating composition is free or essentially free of metallic effect pigments, but in particular comprises a pigment mixture P-C which comprises at least two pigments, namely at least one organic black or inorganic black pigment P-C1 which is not a carbon black pigment and which is transparent or essentially transparent or which is reflective to NIR radiation and at least one inorganic white pigment P-C2 which is reflective or essentially reflective to NIR radiation, and wherein the primer coating composition comprises at least one metallic effect pigment B-C1 in particular, and wherein the metallic effect of the kit is also present in an amount which increases the reflectance of a kit of metallic effect pigment B-C in excess of any of the kit and the kit is also present in the amount of the kit of measuring the reflectance of metallic effect of 0.

Description

Laser radar reflective multilayer coating with high flop index

Background

Recent advances have been made in technologies related to automatically driving vehicles and vehicles having ADAS (advanced driver assistance system). The ADAS-equipped vehicle can reduce driving pressure, reduce accident number, and improve fuel economy. ADAS is highly dependent on remote sensing technology, either optical or electromagnetic, to determine position and velocity.

LiDAR (LiDAR) is a remote sensing technology that can be deployed within such vehicles as a primary source of object identification. By illuminating the surrounding environment with laser light (typically 905nm or 1550 nm), the lidar draws the distance to objects in its path in real time by measuring the reflection with a sensor, and can be collocated with software to react safely to objects in its vicinity. For example, if the object is too close to the vehicle, the software may react to avoid collision with the object. Since lidar utilizes near infrared light (near IR light or NIR light) as its illumination source, the technology must overcome several challenges. Although many light-colored objects are relatively easy to reflect this type of light, especially dark and transparent objects absorb or transmit light, thereby reducing resolution and leading to the potential situation that the lidar cannot adequately view the object and that a vehicle equipped with such a system cannot avoid the object.

In addition to the lidar instrument itself, one of the important factors for measurement accuracy is the surface of the illuminated object. In the case of automobiles and other vehicles, the surface is typically covered with a multi-layer coating, which plays an important role in determining the laser radar reflectivity. The ability of an object to reflect light depends on its volume and its surface characteristics and itself exhibits specular or diffuse reflection. Specular reflection of light occurs when incident light from a light source in a single direction is reflected to a single exit direction at an angle opposite to the plane of the incident wave perpendicular to the reflective surface. Diffuse reflection occurs when incident light from a single direction of a light source is reflected at multiple angles. Theoretically, automotive lidar technology can utilize both specular and diffuse reflection, but in practice this is much more difficult. By specular reflection, most of the brightness is observed at an angle opposite to the angle of incidence. Thus, for a moving vehicle with a detector at the light source, this may be problematic if the angle of incidence is far from the series of light source and detector. This is the case when the angle of incidence is 45 degrees or more from a plane perpendicular to the reflective surface. In contrast, diffuse reflection exhibits equivalent brightness from all directions, which can alleviate such concerns and allow detection at all angles.

Nevertheless, most of the current coatings are applied to substrates such as car bodies to improve durability and aesthetics, but often do not impart sufficient functionality in reflecting near infrared light to achieve greater visibility of lidar technology.

In OEMs, the coatings on the vehicle body and its components are typically, in the following order from the substrate: a conversion coating, an electrodeposition coating (such as a cathodic electrodeposition layer), a primer layer (sometimes also referred to as a filler layer), at least one basecoat layer, and a clearcoat layer on top of the basecoat layer as a topcoat. Thus, a typical OEM multi-layer coating includes a primer, at least one basecoat, and a clearcoat layer. The varnish layer is a visually transparent layer and is generally transparent to IR radiation as well. US 8,679,617B2 discloses a solar reflective coating system comprising, inter alia, a first coating and a second coating present below the first coating. The second layer includes a visible absorbing infrared transparent pigment and a flake metal or metal alloy infrared reflecting pigment. However, the use of such flake-like metal or metal alloy pigments (i.e. metallic effect pigments) in the second layer is disadvantageous, because, due to its presence, it leads to an undesirably high angle dependence in lidar applications: the lidar reflectivity of such coatings at an angle of incidence of 45 ° is typically below 9% or even much lower, such as below 5%.

In recent years, methods have been developed to improve the lidar reflectivity of multilayer coatings, particularly those applied to vehicles. In the first method, the NIR-reflective pigment is contained in the primer layer. NIR light passes through the non-NIR-absorbing (NIR-transparent) protective varnish layer and is reflected by the NIR-reflecting pigment in the primer layer. However, the primer layer is typically a layer that determines the color and/or effect characteristics of the multilayer automotive coating. Thus, the basecoat typically contains organic pigments and effect pigments, such as metallic flakes. However, these flake pigments are transparent in the Near Infrared (NIR) region. Thus, in a second, different process, NIR light passes through the non-NIR protective varnish layer and also the primer layer containing non-NIR tinting pigments and/or effect pigments, but must then be reflected by the primer layer. Due to the transparency of the above pigments in the basecoat at the NIR, the NIR reflectance of the primer plays a key role in determining the reflectance of such systems. While clear primers are typically NIR reflective, dark primers, including those containing carbon black as described above, are typically NIR absorbing. However, the use of carbon black results in undesirable heat accumulation.

Furthermore, problems may occur in particular when metallic effect pigments are included in the basecoat to provide a multilayer coating with the so-called luminance flop effect (flop effect), in particular if the luminance flop effect is provided in the form of a silver-metallic multilayer coating. The term "luminance flop" (or flop as used herein) refers to the difference between the amount or hue of light reflected from a metal coating surface at different angles. The flop depends inter alia on the size and distribution of the effect pigment particles in the coating, the particle shape and orientation. The range of flop effects can be expressed by the so-called flop index, which is a measure of the change in reflectivity of a metallic coating containing a platelet-shaped pigment when rotated over a range of viewing angles. A flop index of 0 indicates a solid color, whereas a very high flop may even result in a flop index higher than 15. In general, larger platelet-shaped particles are better reflectors, resulting in higher flop index and brightness, while smaller particles show less flop because the amount of light scattered at the edges increases as a non-directional reflection. For coarser metallic pigments, individual particles become more pronounced, resulting in graininess or texture. Thus, while the most desirable flake metallic pigments are typically highly reflective and the coatings obtained by using such pigments typically have a high flop index, they also have very high specular reflectivity and thus low reflectivity in the non-specular angular range, which adversely affects the lidar reflectivity of vehicles that are not directly in front of the light source/detector system, but rather are at an angle thereto or in the vicinity of the lane.

Thus, the coatings obtained by using coating compositions containing conventional metallic pigments show a rather high flop index of 9 and above, whereas their lidar reflectivity at an angle of incidence of 45 ° is typically lower than 9% or even much lower, such as lower than 5%. In general, the higher the flop, the lower the lidar reflectivity.

Accordingly, there is a need to provide a multilayer coating system for the automotive industry that is capable of maintaining brightness flop at about the same level as conventional metal coatings, particularly silver-metal coatings, while exhibiting improved visibility of lidar detection, i.e., high lidar reflectivity, and excellent appearance, particularly the color effect provided by primer layers comprising such multilayer coating systems.

Problem(s)

It is therefore an object of the present invention to provide a multilayer coating system for the automotive industry which is capable of maintaining brightness flop at about the same level as conventional metal coatings, in particular silver-metal coatings, which at the same time exhibits improved visibility of lidar detection, i.e. high lidar reflectivity, and excellent appearance, in particular including the color effect provided by the primer layer of such a multilayer coating system.

Solution scheme

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

The first subject of the invention is a multilayer coating system which is present on an optionally precoated substrate and comprises at least three mutually different coatings L1, L2 and L3, i.e

A first coating L1 applied over at least a portion of the optionally pre-coated substrate,

a second coating layer L2 applied on the first coating layer L1, and

a third top coat L3 applied over the second coat L2,

wherein the first coating layer L1 is formed of a primer coating composition, and the second coating layer L2 is formed of a primer coating composition different from the primer coating composition,

it is characterized in that the method comprises the steps of,

the primer coating composition comprises at least one film-forming polymer P-A1 as at least one component P-A and, in the case where P-A1 is externally crosslinkable, at least one crosslinker P-A2, water and/or one or more organic solvents as component P-B and is free or substantially free of metallic effect pigments, but comprises at least one component P-C as a pigment mixture comprising at least two pigments which are different from one another, namely at least one organic black or inorganic black pigment P-C1 (which is not a carbon black pigment and which is transparent or substantially transparent or which is reflective or substantially reflective to NIR radiation) and at least one inorganic white pigment P-C2 (which is reflective or substantially reflective to NIR radiation),

Wherein pigment P-C1 is present in the primer coating composition in an amount ranging from 0.1 to 20.0wt. -% based on the total weight of the primer coating composition and pigment P-C2 is present in the primer coating composition in an amount ranging from 0.2 to 40.0wt. -% based on the total weight of the primer coating composition and is characterized in that,

the basecoat composition comprises at least one film-forming polymer B-A1 as at least one component B-ase:Sub>A and, in the case where B-A1 is externally crosslinkable, at least one crosslinker B-ase:Sub>A 2, water and/or one or more organic solvents as component B-B, and at least one effect pigment B-C1, preferably ase:Sub>A platy pearlescent pigment or an interference pigment, wherein the amount of the at least one pigment B-C1 in the basecoat composition exceeds the amount of any aluminum metal effect pigment B-C2 optionally also present therein.

A further subject matter of the invention is a process for preparing the multilayer coating system according to the invention, which comprises at least steps (1), (2), (3) and (4), i.e.

(1) Applying a primer coating composition to at least a portion of the optionally pre-coated substrate and forming a first coating film on at least a portion of the optionally pre-coated substrate,

(2) Applying a primer coating composition different from the primer coating composition applied in step (1) to the first coating film present on the substrate obtained after step (1), and forming a second coating film preferably adjacent to the first coating film,

(3) Applying a coating composition different from the composition applied in steps (1) and (2) to the second coating film present on the substrate obtained after step (2) and forming a third coating film preferably adjacent to the second coating film, wherein said coating composition is preferably a varnish layer composition, and

(4) Co-curing at least the second and third coating films applied in steps (2) and (3) and optionally also said first coating film, before performing step (2), in the case where the first coating film applied in step (1) is uncured, to obtain a multilayer coating system comprising at least the first, second and third coatings L1, L2 and L3.

A further subject matter of the invention is a kit of parts comprising, as part (A), a primer coating composition as defined above and below in spatially separated form, which can be used for preparing a first coating L1 of a multilayer coating system as defined above and below, and

The basecoat composition as defined hereinabove and hereinbelow is used as part (B) for the preparation of a second coating L2 of a multilayer coating system as defined hereinabove and hereinbelow, and

the varnish layer composition as defined above and below is optionally used as part (C) for the preparation of a third coating L3 of a multilayer coating system as defined above and below.

Further subjects of the invention are the use of the kit to improve, in particular to improve, preferably improve at least 10%, in particular at least 15%, the laser radar reflectance of a multilayer coating system, preferably a multilayer coating system as defined above and below, measured at an angle of incidence of 45 °, in particular to improve to 8, preferably 9, more preferably 10, even more preferably 12, the flop index of a multilayer coating system, more preferably a multilayer coating system as defined above and below.

It has surprisingly been found that the multilayer coating system of the invention is capable of maintaining a brightness flop-in particular caused by at least one, preferably platelet-shaped pearlescent pigment or interference pigment B-C1 and optionally further aluminum metal effect pigments present in the basecoat L2-at about the same level as conventional metal coatings, in particular silver-metal coatings, but wherein the multilayer coating system of the invention at the same time also exhibits improved visibility for lidar detection, i.e. a high lidar reflectivity-in particular due to its primer layer L1-and excellent appearance, in particular including the color effect provided by the primer layer of the multilayer coating system.

In particular, it has been found that the multilayer coating systems of the present invention provide high flop index and high non-specular lidar reflectivity, particularly for a variety of different silver hues, i.e., allow for the additional presence of suitable opaque aluminum metallic effect pigments in the basecoat without compromising the lidar reflectivity of the multilayer coating system. Such aluminum effect pigments are used to provide suitable and desirable silver hues, unique colors, and sparkling effects. Thus, by making the multilayer coating system of the present invention (particularly OEM), different silver hues can be more flexibly designed without compromising lidar reflectivity (particularly at 45 ° angles).

It has surprisingly been found that the multilayer coating system of the invention has both a high IR reflectivity and a high NIR reflectivity, and thus a high lidar reflectivity, in particular due to the presence of the primer layer L1. In particular, it has been found that for the multilayer coating system of the present invention, a lidar reflectivity of at least 10%, preferably at least 15%, measured at an angle of incidence (AOI) of 45 ° can be obtained. The primer layer L1 itself exhibits a lidar reflectivity of at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, still more preferably at least 60%, yet more preferably at least 65%, in particular at least 70%, measured at an angle of incidence (AOI) of 0 °. Lidar reflectivity is measured according to the method disclosed in the methods section. It has been found, particularly unexpectedly, that at the same time, particularly due to the presence of the basecoat layer L2 and the pigments present therein, the multilayer coating system of the present invention has a flop index of ≡8, preferably ≡9, more preferably ≡10, even more preferably ≡12.

It has further been found that the multilayer coating of the present invention is capable of preventing any undesired heat build-up from any of its components present in any of its layers, such as carbon black, particularly when used in the automotive industry as part of a multilayer coating system, since it is not necessary or essentially not necessary to use carbon black to provide any layer, in particular the primer layer L1. In particular, the primer coating composition used to prepare L1 is free or substantially free of any carbon black pigment. Instead, the primer coating composition used to prepare L1 is instead prepared using other suitable organic or inorganic black pigments, in particular perylene pigments, such asblack L0086。

Detailed Description

The term "comprising" in connection with, for example, a primer coating composition and/or a basecoat composition in the sense of the present invention preferably has the meaning of "consisting of. For example, with respect to the primer coating composition and/or the basecoat composition, in addition to all mandatory components present therein, one or more additional optional components identified below may also be included therein. In each case, all components may be present in their preferred embodiments, as determined below.

The proportions and amounts in wt.% (wt.%) of any of the components given below in each coating composition (e.g. primer coating composition and/or basecoat composition) total up to 100 wt.%, based in each case on the total weight of the coating composition (e.g. primer coating composition and/or basecoat composition).

As used herein, the term "near IR" or "near infrared radiation or light" or "NIR" refers to electromagnetic radiation in the near infrared range of the electromagnetic spectrum. Such near IR electromagnetic radiation may have a wavelength from 800nm to 2500nm, such as from 850nm to 2000nm or such as from 900nm to 1600 nm. In particular, the NIR light used has a wavelength of from 880nm to 930nm, with 905nm being the central wavelength. Near IR electromagnetic radiation sources useful in the present invention to generate NIR light include, but are not limited to, light Emitting Diodes (LEDs), laser diodes, or any light source capable of emitting electromagnetic radiation having wavelengths from 800nm to 2500nm (in the near IR range). The near IR electromagnetic radiation source may be used in a lidar system. Lidar systems may utilize lasers to produce electromagnetic radiation having wavelengths from 900nm to 1600 nm.

Preferably, the multilayer coating system of the present invention is capable of reflecting NIR light, preferably having a wavelength from 800 to 2500 nm. In particular, the first coating L1 is capable of reflecting NIR light, preferably having a wavelength from 800 to 2500 nm.

The term "pigments" is known to the skilled worker, for example from DIN 55943 (date: 10. 2001). "pigment" in the sense of the present invention preferably means a component in the form of a powder or flake which is substantially, preferably completely, insoluble in the medium surrounding them, for example in one of the coating compositions. Pigments are preferably colorants and/or substances which can be used as pigments due to their magnetic, electrical and/or electromagnetic properties. Pigments differ from "fillers" such as barium sulfate by their refractive index, preferably not less than 1.7. The term "filler" is known to the person skilled in the art, for example from DIN 55943 (date: 10. 2001). Pigments may be inorganic or organic.

Each of the coating compositions used in steps (1), (2) and (3) of the process of the invention and/or for preparing the coatings L1, L2 and L3 of the multilayer coating system of the invention may contain-in addition to the components outlined in more detail below-one or more customary additives, depending on the desired application. For example, each coating composition may comprise, independently of the other, at least one additive selected from the group consisting of reactive diluents, catalysts, light stabilizers, antioxidants, deaerators, emulsifiers, slip additives, polymerization inhibitors, plasticizers, free radical polymerization initiators, adhesion promoters, flow control agents, film forming aids, sag Control Agents (SCAs), flame retardants, corrosion inhibitors, drying agents, thickeners, biocides and/or matting agents. They may be used in known and conventional proportions. Preferably, their content is 0.01 to 20.0wt. -%, more preferably 0.05 to 15.0wt. -%, particularly preferably 0.1 to 10.0% by weight, most preferably from 0.1 to 7.5% by weight, especially from 0.1 to 5.0% by weight and most preferably from 0.1 to 2.5% by weight, based on the total weight of each coating composition.

Multilayer coating system

The first subject of the invention is a multilayer coating system which is present on an optionally precoated substrate and comprises at least three mutually different coatings L1, L2 and L3. Preferably, at least the second coating L2 and the third coating L3 are positioned adjacent to each other. More preferably, the first and second coatings L1 and L2 are also positioned adjacent to each other.

Preferably, the primer coating composition used to form the first coating layer L1 and the basecoat coating composition used to form the second coating layer L2 are both free or substantially free of any carbon black. Preferably, the top coat composition used to form the third coating layer L3 is also free or substantially free of any carbon black. By "substantially free" is meant that no carbon black pigments are intentionally added, and preferably, their amount (if present) is less than 0.1wt. -%, in particular less than 0.01wt. -%, most preferably less than 0.001wt. -%, based on the total weight of the corresponding coating composition.

Preferably, the multilayer coating system has a lidar reflectance of at least 10%, more preferably at least 15%, measured at an angle of incidence of 0 °, and a flop index of ≡8, more preferably ≡9, even more preferably ≡10, yet more preferably ≡12.

Each of the coating compositions used in the process of the present invention, in particular in each of the steps (1) to (3) to be described below and/or for the preparation of the multilayer coating system, may be aqueous or organic solvent-based (solvent-based, non-aqueous). Preferably, the top coat, preferably varnish layer, composition is organic solvent based (solvent-based, non-aqueous). Preferably, the primer coating composition is aqueous or solvent-borne, more preferably aqueous. Preferably, the primer coating composition is aqueous or solvent-borne, more preferably aqueous.

For the purposes of the present invention, the term "solvent-based" or "non-aqueous" is preferably understood to mean that the organic solvent as solvent and/or diluent is present as the main component of all solvents and/or diluents present in the respective coating composition, for example in the primer coating composition if the respective coating composition is solvent-based. Preferably, the organic solvent is present in an amount of at least 35wt. -%, based on the total weight of the coating composition. The solvent-borne coating composition preferably comprises at least 40wt. -%, more preferably at least 45wt. -%, very preferably at least 50wt. -% of organic solvent fraction, based in each case on the total weight of the coating composition. All conventional organic solvents known to those skilled in the art can be used as the organic solvent. The term "organic solvent" is known to the person skilled in the art, in particular from the European Union directive 1999/13/EC at 11, 3, 1999. Examples of such organic solvents include heterocyclic, aliphatic, or aromatic hydrocarbons, mono-or polyhydric alcohols, especially methanol and/or ethanol, ethers, esters, ketones and amides, such as N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, toluene, xylene, butanol, ethylene glycol and butylene glycol and also acetates thereof, butyldiglycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone or mixtures thereof. The solvent coating composition is preferably free or substantially free of water. In this context, the term "substantially" preferably means that no water is intentionally added in the preparation of the coating composition.

For the purposes of the present invention, the term "aqueous" or "aqueous" is preferably understood to mean that water is present as the main component of all solvents and/or diluents present in the aqueous coating composition, such as in the primer coating composition. Preferably, water is present in an amount of at least 35wt. -%, based on the total weight of the coating composition. The aqueous coating composition preferably comprises at least 40wt. -%, more preferably at least 45wt. -%, very preferably at least 50wt. -% of water fraction, based in each case on the total weight of the coating composition. The organic solvent fraction is preferably <20wt. -%, more preferably in the range from 0 to <20wt. -%, very preferably in the range from 0.5 to 20wt. -% or to 17.5wt. -% or to 15wt. -% or to 10wt. -%, based in each case on the total weight of the coating composition.

The multilayer coating system of the invention is particularly suitable as a coating for automotive bodies or parts thereof, including corresponding metal substrates, but also plastic substrates, such as polymer substrates. Thus, the preferred substrate is an automotive body or part thereof.

Suitable as metal substrates for use according to the invention are all substrates which are generally used and known to the skilled worker. The substrate used according to the invention is preferably a metal substrate, more preferably a steel selected from the group consisting of steel, preferably steel selected from the group consisting of bare steel, cold Rolled Steel (CRS), hot rolled steel, galvanized steel (such as hot dip galvanized steel (HDG)), alloy galvanized steel (e.g. Galvalume, galvannealed or Galfan) and aluminized steel, aluminum and magnesium, and also Zn/Mg alloys and Zn/Ni alloys. Particularly suitable substrates are parts of vehicle bodies for production or the entire body of a motor vehicle.

Preferably, thermoplastic polymers are used as plastic substrates. Suitable polymers are poly (meth) acrylates (including poly (meth) methyl acrylate, poly (butyl (meth) acrylate), polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyesters (including polycarbonates 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), polyetherimides, phenolic resins, urea-formaldehyde resins, melamine resins, alkyd resins, epoxy resins, polyurethanes (including TPU), polyetherketones, polyphenylene sulfide, polyethers, polyvinyl alcohol and mixtures thereof. Polycarbonates and poly (meth) acrylates are particularly preferred.

The substrate used according to the invention is preferably a metal substrate pretreated with at least one metal phosphate such as zinc phosphate and/or pretreated with at least one oxalate. Such pretreatment with phosphating is usually carried out after the substrate has been cleaned and before the substrate has been electrodeposited, which is a pretreatment step commonly used in the automotive industry in particular.

First layer L1 and primer coating composition

A first coating L1 of a multilayer coating system is applied over at least a portion of an optionally pre-coated substrate. The first coating layer L1 is formed of a primer coating composition.

The term "primer" or "primer coating composition" is known to those skilled in the art. The primer is typically applied after the substrate has had a cured electrodeposited coating. The cured electrodeposited coating film is present beneath and preferably adjacent to the cured primer coating film. Thus, the primer coating composition can be applied to an optionally pre-coated substrate and a primer coating film formed on the optionally pre-coated substrate. The primer coating film may then be subjected to an optional curing step prior to application of any additional coating composition.

The primer coating composition may be aqueous or organic solvent-based (solvent-borne, non-aqueous). Preferably, it is aqueous.

The primer coating composition is free or substantially free of any metallic effect pigments, in particular free or substantially free of any aluminum pigments. Preferably, the primer coating composition is free or substantially free of any effect pigments at all. The terms "effect pigment" and "metallic effect pigment" are described in more detail below. In this context, "substantially free" preferably means that no metal effect pigments or effect pigments are intentionally added, and preferably, their amount (if present) is less than 0.1wt. -%, in particular less than 0.01wt. -%, most preferably less than 0.001wt. -%, based on the total weight of the primer coating composition.

The primer coating composition comprises at least one film-forming polymer P-A1 as at least one component P-A and, in the case where P-A1 is externally crosslinkable, at least one crosslinker P-A2, water and/or one or more organic solvents as component P-B, and at least one component P-C as a pigment mixture comprising at least two pigments which are different from one another, namely at least one organic black or inorganic black pigment P-C1 (which is not a carbon black pigment and which is transparent or substantially transparent or which is reflective or substantially reflective to NIR radiation) and at least one inorganic white pigment P-C2 (which is reflective or substantially reflective to NIR radiation).

Preferably, the first coating L1 formed from the primer coating composition and applied on at least a portion of the optionally pre-coated substrate has a brightness value L of no more than 40, preferably no more than 38, more preferably no more than 35, even more preferably no more than 30 at 45 ° according to the CIELAB system and/or has a lidar reflectivity of at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, still more preferably at least 60%, still more preferably at least 65%, in particular at least 70%, measured at an angle of incidence of 0 °.

Preferably, the first coating layer L1 is obtained by applying a primer coating composition and curing the resulting primer coating film to obtain the first coating layer L1. Preferably, curing is carried out at about 140 ℃ for 25 minutes.

Preferably, the brightness value L at 45 ° according to the CIELAB system is expected to not exceed 40 to ensure that the primer coating color is dark. Preferably, a brightness value L of not more than 40 at 45 ° according to the CIELAB system is achieved by incorporating at least two pigments P-C1 and P-C2 into the primer coating composition in the amounts given above.

Components P-A1 and P-A2

The at least one film-forming polymer P-A1 acts as a binder. For the purposes of the present invention, the term "binder" is understood to mean the non-volatile component of the coating composition, which is responsible for film formation, in accordance with DIN EN ISO 4618 (German version, date: 3 month 2007). The term includes cross-linking agents such as cross-linking agent P-A2 and additives (if they represent non-volatile components). Thus, the pigments and/or fillers contained therein are not contained under the term "binder". Preferably, the at least one polymer P-A1 is the primary binder of the coating composition. As the main binder of the present invention, when there is no other binder component in the coating composition, it is preferable to mention that the binder component is present in a higher proportion based on the total weight of the coating composition.

The term "polymer" is known to those skilled in the art and, for the purposes of the present invention, includes addition polymers and polymerization products as well as condensation polymers. The term "polymer" includes both homopolymers and copolymers.

The at least one polymer used as component P-A1 may be self-crosslinking or non-self-crosslinking. Suitable polymers which can be used are known, for example, from EP 0 228,003 A1, DE 44,504 A1, EP 0,593,454 B1, DE 199,004 A1, EP 0,787,159 B1, DE 40,09,858 A1, DE 44,37,535 A1, WO 92/15405 A1 and WO 2005/021168 A1.

The at least one polymer used as component P-A1 is preferably selected from the group consisting of polyurethanes, polyureas, polyesters, polyamides, polyethers, poly (meth) acrylates and/or copolymers of structural units of the polymers, in particular polyurethane-poly (meth) acrylates and/or polyurethane polyureas. The at least one polymer used as component P-A1 is particularly preferably selected from the group consisting of polyurethanes, polyesters, poly (meth) acrylates and/or copolymers of structural units of the polymers. In the context of the present invention, the term "(meth) acryl" or "(meth) acrylate" includes in each case the meaning "methacrylic acid" and/or "acrylic acid" or "methacrylate" and/or "acrylate".

Preferred polyurethanes are described, for example, in German patent application DE 199 004A1, page 4, line 19 to page 11, line 29 (polyurethane prepolymer B1), european patent application EP 0 228 003A1, page 3, line 24 to page 5, line 40, european patent application EP 0 634 A1, page 3, line 38 to page 8, line 9 and International patent application WO 92/15405, page 2, line 35 to page 10, line 32.

Preferred polyethers are described, for example, in WO 2017/097642 A1 and WO 2017/121683 A1.

Preferred polyesters are described, for example, in DE 4009858 A1, column 6, lines 53 to 7, line 61 and column 10, line 24 to column 13, line 3 or WO 2014/033135 A2, page 2, line 24 to page 7, line 10 and page 28, line 13 to page 29, line 13. Also preferred polyesters are polyesters having a dendritic or star structure, as described for example in WO 2008/148555 A1.

Preferred polyurethane-poly (meth) acrylate copolymers (e.g., (meth) acrylated polyurethanes) and their preparation are described, for example, in WO 91/15528A1, page 3, line 21 to page 20, line 33 and DE 4437535 A1, page 2, line 27 to page 6, line 22.

Preferred (meth) acrylic copolymers are OH-functional. Hydroxyl-containing monomers include hydroxyalkyl esters of acrylic or methacrylic acid, which can be used to prepare the copolymer. Non-limiting examples of hydroxy-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 epsilon-caprolactone, and other hydroxyalkyl (meth) acrylates having branched or straight chain alkyl groups up to about 10 carbons, and mixtures of these. Hydroxyl groups on vinyl polymers such as (meth) acrylic polymers can be produced by other means, for example by ring opening of glycidyl groups (e.g. from copolymerized glycidyl methacrylate) by organic acids or amines. Hydroxyl functionality may also be introduced by thio alcohol compounds including, but not limited to, 3-mercapto-1-propanol, 3-mercapto-2-butanol, 11-mercapto-1-undecanol, 1-mercapto-2-propanol, 2-mercaptoethanol, 6-mercapto-1-hexanol, 2-mercaptobenzyl alcohol, 3-mercapto-1, 2-propanediol, 4-mercapto-1-butanol, and combinations of these. Any of these methods can be used to prepare useful hydroxy-functional (meth) acrylic polymers. Examples of suitable comonomers that may be used include, but are not limited to, alpha, beta-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; alpha, beta-ethylenically unsaturated dicarboxylic acids having 4 to 6 carbon atoms, 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 from reaction with saturated aliphatic alcohols containing 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, hexyl, 2-ethylhexyl, dodecyl, 3, 5-trimethylhexyl, stearyl, lauryl, cyclohexyl, alkyl substituted cyclohexyl, alkanol substituted cyclohexyl esters, such as 2-t-butyl and 4-t-butylcyclohexyl, 4-cyclohexyl-1-butyl, 2-t-butylcyclohexyl, 4-t-butylcyclohexyl, 3,5, -tetramethylcyclohexyl, tetrahydrofurfuryl and isobornyl esters; unsaturated dicarboxylic acids and anhydrides such as fumaric acid, maleic acid, itaconic acid and anhydride 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, a-methylstyrene, vinyltoluene, 2-vinylpyrrolidone and p-tert-butylstyrene. The (meth) acrylic copolymer may be prepared using conventional techniques, such as by heating the monomers in the presence of a polymerization initiator and optionally a chain transfer agent.

Suitable poly (meth) acrylates are also those which can be prepared by multistage free-radical emulsion polymerization of ethylenically unsaturated monomers in water and/or organic solvents. Examples of seed-core-shell polymers (SCS polymers) obtained in this way are disclosed in WO 2016/116299 A1.

Preferred polyurethane-polyurea copolymers are those of polyurethane-polyurea particles, preferably having a Z-average particle size of 40 to 2000nm, each in a reactive form, containing at least one polyurethane prepolymer containing isocyanate groups, which polyurethane prepolymer contains anions and/or groups which can be converted into anionic groups and at least one polyamine containing two primary amino groups and one or two secondary amino groups. Preferably, such copolymers are used in the form of aqueous dispersions. Such polymers can in principle be prepared by conventional polyaddition of, for example, polyisocyanates with polyols and polyamines.

The polymers used as component P-A1 preferably have reactive functional groups which are capable of undergoing crosslinking reactions. Any common crosslinkable reactive functional group known to those skilled in the art may be present. Preferably, the polymer used as component P-A1 has at least one functional reactive group selected from the group consisting of primary amino groups, secondary amino groups, hydroxyl groups, thiol groups, carboxyl groups and urethane groups. Preferably, the polymers used as component P-A1 have functional hydroxyl and/or carbamate groups.

Preferably, the polymer used as component P-A1 is hydroxy-functional and more preferably has an OH number in the range of 15 to 400mg KOH/g, more preferably from 20 to 250mg KOH/g.

The polymers used as component P-A1 are particularly preferably hydroxy-functional polyurethane-poly (meth) acrylate copolymers, hydroxy-functional polyesters and/or hydroxy-functional polyurethane-polyurea copolymers.

In addition, the primer coating composition may contain at least one typical crosslinker P-A2 known per se. The crosslinker is included in the film-forming nonvolatile components of the coating composition and thus falls within the general definition of "binder".

All conventional crosslinking agents can be used. This includes melamine resins, preferably melamine formaldehyde resins, more preferably melamine formaldehyde resins, blocked polyisocyanates, polyisocyanates having free (unblocked) isocyanate groups, crosslinkers having amino groups such as secondary amino groups and/or primary amino groups, and crosslinkers having epoxy groups and/or hydrazide groups, as well as crosslinkers having carbodiimide groups, provided that the functional groups of a particular crosslinker are suitable for reacting with the crosslinkable functional groups of the film-forming polymer used as binder in the crosslinking reaction. For example, a crosslinker having blocked or free isocyanate groups can be reacted with a film-forming polymer having crosslinkable OH-groups and/or amino groups at elevated temperature (in the case of 1K formulations) and at ambient temperature (in the case of 2K formulations).

If present, the crosslinker is preferably at least one aminoplast resin and/or at least one blocked or free polyisocyanate, preferably an aminoplast resin. Among the aminoplast resins, melamine resins such as melamine formaldehyde resins are particularly preferred. Preferably, the melamine formaldehyde resin, preferably the melamine formaldehyde resin, carries in each case at least one of imino groups, alkanol groups and etherified alkanol groups as functional groups, which are reactive towards the functional groups of the polymer P-A1. An example of an alkanol group is hydroxymethyl.

Component P-B

The primer coating composition comprises water and/or an organic solvent as one or more components P-B. This has been described above in connection with the terms "aqueous" and "solvent-based".

Component P-C

The pigment mixture P-C comprises at least two pigments which are different from one another, namely at least one organic black or inorganic black pigment P-C1 which is not a carbon black pigment and which is transparent or substantially transparent to NIR radiation or reflective or substantially reflective to NIR radiation; and at least one inorganic white pigment P-C2 which is reflective or substantially reflective to NIR-radiation. The term "NIR-radiation" has been defined above and particularly covers the wavelength region from 800nm to 2500nm, such as from 850 to 2000nm or such as from 900nm to 1600nm, most preferably at least from 880nm to 930nm, with 905nm being the central wavelength. Of course, the primer coating composition may comprise a pigment mixture P-C, which in turn comprises at least two pigments P-C1 (one transparent or substantially transparent to NIR-radiation and the other reflective or substantially reflective to NIR-radiation) and at least one pigment P-C2. Preferably, pigment P-C1 is transparent or substantially transparent to NIR-radiation. Since the primer coating composition is free or substantially free of any metallic effect pigment, it is clear that none of the pigments present therein (including the pigments in pigment mixture P-C) can be such metallic effect pigments.

Pigment P-C1 is transparent or substantially transparent or reflective or substantially reflective to NIR-radiation, while pigment P-C2 is necessarily reflective or substantially reflective to NIR-radiation. The term "substantially" in connection with the term "substantially transparent" preferably means that a major part of the wavelength region of the NIR radiation (preferably the region from 800nm to 2500nm, such as from 850 to 2000nm or such as from 900nm to 1600 nm), more preferably at least 80% or 90% or 95% of the wavelength region is transmitted by the corresponding pigment. The term "substantially" in connection with the term "substantially reflective" preferably means that 25 to <100% of the wavelength region of NIR radiation from 900nm to 1600nm is reflected by the corresponding pigment.

Pigment P-C1 is present in an amount ranging from 0.1 to 20.0wt. -%, preferably from 0.2 to 15.0wt. -%, more preferably from 0.5 to 12.0wt. -%, even more preferably from 1.0 to 10.0wt. -%, still more preferably from 1.5 to 8.5wt. -%, still more preferably from 2.0 to 7.0wt. -%, and pigment P-C2 is present in an amount ranging from 0.2 to 40.0wt. -%, preferably from 0.5 to 35.0wt. -%, more preferably from 1.0 to 30.0wt. -%, even more preferably from 2.0 to 25.0wt. -%, still more preferably from 4.0 to 20.0wt. -%, still more preferably from 5.0 to 18.0wt. -%, based on the total weight of the primer coating composition.

Preferably, the amount of pigment P-C2 in the primer coating composition exceeds the amount of pigment P-C1C 2 in the primer coating composition, preferably characterized in that the relative weight ratio of pigment P-C2 to P-C1 is in the range from 15:1 to 1.1:1, more preferably from 12:1 to 1.5:1, even more preferably from 10:1 to 2:1.

Preferably, the color of pigment P-C1 is characterized according to the CIELAB system at 45 °, wherein the L x value is less than 17, more preferably less than 15, and wherein the a and b x values are greater than-4 and less than 9, more preferably less than 6 and most preferably less than 4 and preferably greater than 0. Preferably, the color of pigment P-C2 is characterized according to the CIELAB system at 45 ° wherein L is greater than 85, preferably greater than 90, a is greater than-2 and less than 2, preferably less than 0, and b is less than 6 and preferably greater than 0, more preferably greater than 2 or 3.

Preferably, the method comprises the steps of,

the at least one black pigment P-C1 is a black pigment having a multi-tone color according to the CIELAB system at 45 ° with a value L x <17, a x-4 and <9, and b x-4 and <9, preferably wherein the at least one pigment P-C1 is selected from the group consisting of iron/chromium oxide compounds, manganese ferrite black oxides, calcium manganese titanium oxides, perylene pigments, azomethine pigments and mixtures thereof, in particular pigment numbers 31 and 32 (PBk 31 and PBk 32; ci name), more preferably from perylene pigments, azomethine pigments and mixtures thereof, most preferably from perylene pigments, and mixtures thereof, and

The at least one white pigment P-C2 is a white pigment having a multi-tone color according to the CIELAB system at 45 ° of L x 85, a x 2 and <2, and b x 0 and <6, preferably selected from the group consisting of titanium dioxide based or titanium dioxide containing pigments, more preferably selected from titanium/aluminum/silicon oxide based pigments and rod-shaped aluminum doped titanium dioxide pigments. The rod pigments preferably have a long dimension of 1 to 5, such as 2 to 4 μm and a Hart (hart) dimension of 0.2 to 0.6, such as 0.3 to 0.5 μm. Preferably, the rod-shaped pigment has an average D50 value, i.e. median particle size, in the range from 0.01 μm to 1 μm as determined by laser granulometry according to ISO 13320-1 (determined with a CILAS1064 instrument).

The term "multi-tone color" or "fully hidden multi-tone color" is used and understood the same as is commonly used and understood in colorimetry. "multicolor color" is defined as the color obtained by applying a coating containing the corresponding pigment to completely cover the black and white substrate (typically using a so-called "checkerboard" of partial black and partial white) over the layer thickness, with no black and white information transmitted. The corresponding layer thicknesses are obtained by repeatedly spraying the coating composition until the colorimetric data of the L, a and b color parts of the coated black and white portions of the substrate are respectively identical, thereby ensuring that no substrate color specific information confuses the pigment specific values. Further details are disclosed in the methods section of the present invention. Thus, the term "multi-tone color" may be used to determine whether a pigment is a black pigment or a white pigment in the sense of the term.

Commercially available pigments P-C2 are, for example, tipaque Black SG103 (from Shi hara) and from Basf (BASF)Black L0086. Commercially available white pigments P-C2 are selected, for example, from Altidis 550 and Altidis 800 (both from Vanator), tipaque PFR404 (from Shiyuan Co.), tipaque PFR404,R-906->2310。

The weight ratio [ (P-C1) + (P-C2) ]/[ (P-A1) + (P-A2) ] in the primer coating composition is preferably in the range from 0.005 to 1.2, more preferably in the range from 0.01 to 1.0 and most preferably in the range from 0.015 to 0.75.

Preferably, the primer coating composition further comprises at least one, preferably organic or inorganic, more preferably organic, coloring pigment P-C3, which is different from both pigments P-C1 and P-C2 and which is not a carbon black pigment, more preferably selected from blue, red and violet organic pigments.

Second layer L2 and primer composition

A second coating L2 of the multilayer coating system is applied over the first coating L1. The second coating layer L2 is formed of a primer coating composition different from the primer coating composition.

The term "primer" is known in the art and is used, for example, inLexikon, paints and printing inks [ paint and printing ink ] ]Georg Thieme Verlag,1998, 10 th edition, page 57. Accordingly, basecoats are particularly useful for automotive and general industrial paint tinting to provide tinting and/or optical effects by using the basecoat as a intercoat composition.

The basecoat composition comprises at least one film-forming polymer B-A1 as at least one component B-ase:Sub>A and, in the case where B-A1 is externally crosslinkable, at least one crosslinker B-ase:Sub>A 2, water and/or one or more organic solvents as component B-B and at least one metallic effect pigment B-C1, which is preferably ase:Sub>A platy pearlescent pigment or an interference pigment, wherein the amount of the at least one pigment B-C1 in the basecoat composition exceeds the amount of any aluminum metallic effect pigment B-C2 optionally also present therein.

Components B-A1 and B-A2

The same components described above for P-A1 and P-A2 can also be used as components B-A1 and B-A2.

Component B-B

The primer coating composition comprises water and/or one or more organic solvents as component B-B. This has been described above in connection with the terms "aqueous" and "solvent-based".

Component B-C1

The at least one pearlescent pigment or interference pigment B-C1 is an effect pigment. The skilled person is familiar with the concept of effect pigments. For example, in Corresponding definitions are found in Lexikon, lacke und Druckfarben, georg Thieme Verlag,1998, 10 th edition, pages 176 and 471. General definition of pigments and their further details are specified in DIN 55943 (date: 10 in 2001). The effect pigment is preferably a pigment which imparts an optical effect or both a color and an optical effect, in particular an optical effect. Thus, the terms "optical effect and color pigment", "optical effect pigment" and "effect pigment" are preferably interchangeable. Pigment B-C1 may be used to achieve a high flop index, optionally in combination with at least one additional pigment B-C2.

Preferably, pigments B-C1 are present in the form of flakes, more preferably opaque flakes. Preferably, pigment B-C1 is selected from mica pigments coated with at least one metal oxide or semi-metal oxide, such as alumina and/or silica; glass pigments, such as glass flakes having a silvery reflective color; and metal oxide or semi-metal oxide flakes coated with another metal oxide or semi-metal oxide, such as silica flakes coated with titanium dioxide. Examples of commercially available pigments for use as pigments B-C1 are, for example Bright Silver1303Z-Ext (mica flakes coated with titanium dioxide and/or iron oxide),>9225Rutile Blue Pearl SW (mica flakes) and +.>9605Blue-Shade Silver SW (mica flake). Other examplesIs->Bright Silver 1303V and9602 and Colorstream T20-04 Lapis sun light. An example of a glass sheet with a silvery reflective colour is the product +.>CFX B001。/>

Preferably, pigment B-C1 has a D50 value, i.e. median particle size, in the range from 1 μm to 80 μm and even more preferably in the range from 5 μm to 35 μm as determined by laser granulometry according to ISO 13320-1 (determined with a CILAS1064 instrument).

Pearlescent pigments or interference pigments, such as B-C1, are different from metallic effect pigments, such as pigments B-C2.

The term "metallic effect Pigments" is according to EN ISO 18451-1:2019 (Pigments, dyes and extenders-Part 1, section 1, dyestuffs and extenders-terminalogy)]) And (3) using. They are defined as platelet-shaped pigments composed of metals such as aluminum. In the present invention, the term "consisting of metal" does not exclude surface modification of metallic effect pigments, such as the presence of further oxide layers, for example a silicon dioxide layer. The term "metal" as used in the term "metallic effect pigment" likewise includes metals and metal alloys. As described above, metallic effect pigments may be oriented in parallel and then show metallic luster due to light reflection by flakes. Typical metals and alloys used in metallic effect pigments are aluminum and its alloys. Most suitable and preferred as pigment B-C2 in the present invention are platelet-shaped aluminum effect pigments, which may be coated or uncoated and are preferably coated, especially in the case of preferred aluminum pigments for inhibiting their reaction with water in aqueous color paint compositions. Such inhibition may be achieved, for example, by: stabilization using an organic phosphorus; passivating the aluminum pigment with a conversion layer, for example, by chromizing; encapsulation with protective layers, e.g. polymer coatings or dioxygen Silicon oxide coating (Peter Wi beta ling, "Metallic Effect Pigments [ metallic effect pigment ]]", vincent z Network 2006, pages 85-89). Such aluminium effect pigments are for example under the trade nameHydroxal (stabilized),>hydrolux (chromized) and +.>Hydrolan (silica encapsulated) is commercially available from ECKART GmbH (Germany). Further modification of the pigment surface is also possible, for example by modification with nonpolar groups, such as alkyl groups, resulting in the so-called semi-floating effect. The metallic effect pigments B-C2, in particular aluminum effect pigments, may be coated with an oxide layer, such as a silica layer, which further helps to stabilize the pigments against mechanical impact and in particular improves the circulation line stability. In the present invention, silica-encapsulated aluminum metallic effect pigments are most preferred. Preferably, the amount of silica ranges from 3 to 15wt. -%, more preferably from 5 to 12wt. -% and most preferably from 6 to 10wt. -%, based on the sum of the amounts of aluminum and silica in such preferred aluminum effect pigments. However, the term "metallic effect pigment" includes such coated pigments, and the total weight of such coated metallic effect pigment is to be understood as the weight of the metallic effect pigment. Thus, the weight includes the coating material.

Preferably, pigment B-C2 (if present) is present in the form of flakes, more preferably in the form of opaque flakes. Preferably, pigment B-C2 has a D50 value, i.e. median particle size, in the range from 5 μm to 100 μm and even more preferably in the range from 15 μm to 30 μm as determined by laser granulometry according to ISO 13320-1 (determined with a CILAS1064 instrument).

Preferably, the relative weight ratio of the at least one, preferably platy pearlescent pigment or interference pigment B-C1 to any one or more aluminum metal effect pigments B-C2-if present in the basecoat composition-is in the range of from 15:1.0 to 1.1:1.0, preferably from 12:1.0 to 1.2:1.0.

Preferably, the basecoat composition additionally optionally comprises at least one, preferably platy pearlescent pigment or interference pigment B-C2, preferably in an amount ranging from 0 to 10wt. -% based on the total weight of the basecoat composition.

Preferably, the at least one, preferably platy pearlescent pigment or interference pigment B-C1 is present in the basecoat composition in an amount ranging from 1 to 50wt. -%, more preferably from 2 to 30wt. -%, based in each case on the total weight of the basecoat composition.

The weight ratio [ (B-C1) + (B-C2) ]/[ (B-A1) + (B-A2) ] in the primer coating composition is preferably in the range from 0.02 to 1.0, more preferably in the range from 0.05 to 0.5 and most preferably in the range from 0.1 to 0.35.

Preferably, the primer composition does not include any pigment, which is not a carbon black pigment or NIR radiation absorbing pigment. In addition to B-C1 and optionally B-C2, the basecoat composition may further comprise at least one additional pigment, such as at least one pigment that is transparent or substantially transparent to NIR radiation or reflective or substantially reflective to NIR radiation. The at least one additional pigment may be the same as or different from pigment P-C1 present in the primer coating composition. Preferably, the at least one further pigment is chosen from perylene pigments, azomethine pigments and mixtures thereof, in particular pigments No. 31 and No. 32 (PBk 31 and PBk 32; CI name). Preferably, the amount of pigment B-C1 present in the basecoat composition exceeds the amount of the at least one additional pigment.

Third coating L3 and Top coating composition

A third top coat L3 of the multilayer coating system is applied over the second coat L2.

Preferably, the third coating L3 is formed from a coating composition which is a clearcoat layer composition, preferably a solvent-based clearcoat layer composition, wherein the third coating L3 is the outermost coating layer of the multilayer coating system.

Preferably, at least the second and third coating layers L2, L3 are positioned adjacent to each other, preferably the first and second coating layers L1, L2 are also positioned adjacent to each other. However, at least layers L1 and L2 may not be positioned adjacent to each other. Conversely, a further coating L1a may be positioned between the first coating L1 and the second coating L2, wherein the further coating L1a is preferably formed from a coating composition comprising at least one organic black or inorganic black pigment, which is not a carbon black pigment and is transparent or substantially transparent to NIR radiation and may be the same or different pigment P-C1. The further coating composition is preferably different from all coating compositions used for forming layers L1, L2 and L3. It has been found that the flop index of the multilayer coating system can be further improved/increased when a further layer L1a is present between the layers L1 and L2.

Preferably, the multilayer coating system can be obtained by a method according to which at least a primer composition for preparing the second coating L2 and a coating composition (which is preferably a varnish layer composition) for preparing the third coating L3 are co-cured to obtain the second coating L2 and the third coating L3 of the multilayer coating system. Preferably, the basecoat composition is applied into the already cured first coating L1 or onto the already cured coating L1a (if present). Alternatively, a multilayer coating system can also be obtained by the 3C 1B-method, wherein all coating compositions for forming the coatings L1, L2 and L3 are applied in a wet-on-wet manner. In the case of the further layer L1a, a multilayer coating system can also be obtained by the 4C1B method, in which all coating compositions for forming the coatings L1, L1a, L2 and L3 are applied in a wet-on-wet manner.

Method for producing a multilayer coating system

All the preferred embodiments described above in connection with the multilayer coating system of the invention and in each case with the preferred embodiments thereof are also preferred embodiments of the process for preparing the multilayer coating system of the invention.

The curing is preferably selected from chemical curing, such as chemical crosslinking, radiation curing, and/or physical drying (non-chemical curing), in each case at room temperature or at elevated temperature, more preferably from chemical curing, such as chemical crosslinking, and/or physical drying (non-chemical curing), in each case at room temperature or at elevated temperature. The curing temperature can vary from 80℃to 160 DEG C

The method may comprise a further optional step (1 a) carried out between steps (1) and (2), namely

(1a) Applying a coating composition different from the primer coating composition applied in step (1) to a first coating film present on the substrate obtained after step (1), and forming a further coating film preferably adjacent to the first coating film,

preferably, after step (1 a) an optional flash curing is performed to obtain a coating L1a present on the first coating L1, preferably adjacent to said coating L1, before step (2).

Kit of parts

All the preferred embodiments described above in connection with the multilayer coating system of the invention, the method for producing the multilayer coating system of the invention and in each case the preferred embodiments thereof are also preferred embodiments of the kit of parts of the invention.

Use of the same

Further subjects of the invention are the use of the kit to improve, in particular to improve, preferably improve at least 10%, in particular at least 15%, the laser radar reflectance of a multilayer coating system, preferably a multilayer coating system as defined above and below, measured at an angle of incidence of 0 °, in particular to improve to 8, preferably 9, more preferably 10, even more preferably 12, the flop index of a multilayer coating system, more preferably a multilayer coating system as defined above and below.

All the preferred embodiments described above in connection with the multilayer coating system of the invention, the method for producing the multilayer coating system of the invention, the kit of parts of the invention and in each case the preferred embodiments thereof are also preferred embodiments for the use of the invention.

The use of the invention may benefit from better infrared and lidar visibility, especially for automated systems such as autonomous vehicles and vehicles with ADAS.

Method

1.Determination of non-volatile fraction

The amount of solids content (non-volatile material, solids fraction) including the total solids content was determined by DIN EN ISO 3251:2019-09 at 110℃for 60 min.

2.Measurement of color values

Color space or color model L x a x b x (i.e., CIELAB color model) is known to those skilled in the art. The color model l.a.b.has been standardized, for example in DIN EN ISO/CIE 11664-4:2020-03. Each perceived color in the L x a x b x color space is described by a specific color location of coordinates { L x, a x, b x } in the three-dimensional coordinate system. The a-axis describes the green or red part of the color, where negative values represent green and positive values represent red. The b-axis describes the blue or yellow part of the color, where blue is negative and yellow is positive. Thus, a smaller number indicates a bluer color. The L axis is perpendicular to the plane and represents brightness (luminance). Color value L is determined according to ASTM E284-81 a. These values were measured according to ASTM D2244, E308, E1164 and E2194 using the instrument BYK-mac i (BYK-Gardner). Samples were analyzed according to color, sparkle and particle size measurements using a BYK-mac i spectrophotometer standard procedure. The sample to be analyzed was carefully wiped with a superfine fiber cloth. The BYK-mac i instrument was then placed on the substrate surface and measurements were made at angles of 15, 45, and 110 using a D65 light source, and the data for each angle was recorded. The measurements were made on a single panel in at least three different locations and the values tested were averaged and reported.

3.Determination of laser radar reflectivity

Lidar measurements were performed at different angles using a Velodyne VLP-16 instrument (905 nm), measuring a distance of 1m. The instrument was calibrated using Permaflect 10%, 50% and 80% calibration grids to provide 10%, 50% and 80% reflectivity at 0 ° AOI, respectively.

4.Determination of flop index

The flop index is calculated according to the following formula:

the L-values at different angles were measured according to the method described in the previous item 2.

5.Determination of the multicolor of pigments P-C1 and P-C2

"multi-tone color" is defined as the color obtained by applying a coating containing the corresponding pigment to completely cover the black and white substrate over the layer thickness (typically using a so-called "checkerboard" of partial black and partial white), with no black and white information transmitted (completely hidden). The coating compositions used to determine the multi-tone color for the purposes of the present invention are described in the following table. Pigment slurries were prepared by shaking for each pigment P-C1 or P-C2, or for each pigment P-C1 mixture or pigment P-C2 mixture. The components in each pigment slurry are: 30 parts by weight of the corresponding solid pigment (i.e., pigment P-C1 or pigment P-C2 or a mixture of pigments P-C1 or a mixture of pigments P-C2), 15 parts by weight of water, 2 parts by weight of butyl cellosolve, 39.2 parts by weight of polyurethane grinding resin, 4.8 parts by weight of Pluracol 1010 polyol and 9 parts by weight of Byk 184. Pigment slurry is incorporated into the coating composition such that the pigment volume concentration is about 20%. The corresponding layer thicknesses are obtained by repeatedly spraying the coating composition until the colorimetric data of the L, a and b color parts of the coated black and white portions of the substrate are respectively identical, thereby ensuring that no substrate color specific information confuses the pigment specific values. Typically, this is achieved at a coating thickness of about 20 μm. Table: coating composition for determining multi-tone color

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Examples

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

1.Preparation of primer coating composition

1.1 the primer coating composition P1I1 used in the present invention was prepared by mixing the components listed in table 1a in this order.

Table 1: P1I1 component

Component (A)	Quantity [ pbw]
		White pigment paste WP1	31.25
Adhesive dispersion BD1	37.01
		Deionized water	4.20
Crosslinker dispersion CD1	20.03
		Deionized water	8.96
2-ethylhexanol	2.04
		OS3	2.56
OS2	2.04
		N, N' -dimethylethanolamine	0.001
Ethylene glycol monobutyl ether	0.001
		Deionized water	6.72
Black pigment paste BP2	60.71
		White pigment paste WP1	24.86
Color pigment paste CP1	15.51
		Color pigment paste CP2	1.92

White pigment slurry WP1 has a solids content of 63wt. -% and contains 49wt. -% of commercial titanium dioxide white reflective pigment, based on the total weight of WP12310). The adhesive dispersion BD1 contains acrylic resin and has a solids content (resin solids) of 27wt. -%. The crosslinker dispersion CD1 contains crosslinker resin (++>203 And a polyester resin and has a total solids content (resin solids) of 55.54wt. -%. OS2 is used as->13 mixtures of commercially available organic solvents. OS3 is used as->Mixtures of commercially available organic solvents. Black pigment paste BP2 contains 18.5wt. -% of +_ based on its total weight >L0086, commercially available organic black pigment from Basoff, which is a non-carbon black pigment. BP2 further contains 21wt. -% of polyacrylic resin solids based on its total weight. Color pigment paste CP1 is a commercially available pigment paste containing a red pigment (++>Scarlet GO). CP1 contains in each case 25wt. -% of pigment and 22wt. -% of polyurethane resin, based on the total weight thereof. The color pigment paste CP2 contains a phthalocyanine blue pigment. CP2 contains 27.47wt. -% of pigment and 17wt. -% of polyacrylic resin, based in each case on the total weight thereof.

The primer P1I1 has a brightness L of about 25 at 45 °.

1.2 commercially available primer coating compositions for comparison use have been used as primer composition P1C1 (from Dolomite Gray of Basoff).

The primer P1C1 has a brightness L of about 65 at 45 °.

1.3 commercially available primer coating compositions for comparison use have been used as primer compositions P1C2 (Alaska Gray from Basoff).

The primer P1C2 has a brightness L of about 18 at 45 °.

2.Preparation of primer coating composition

2.1 the basecoat starting formulations shown in table 2 below were prepared by mixing the components listed in table 2 in this order.

TABLE 2 a-primer coating starting formulation

2.2 different kinds of pigments are added to the primer starting formulation in order to obtain a plurality of different primer compositions.

The following commercially available pigments were used:

pigment 1 (Pi 1):hydrolan 2153 (aluminum flake pigment)

Pigment 2 (Pi 2):bright Silver 1303Z-Ext (mica flakes coated with titanium dioxide and/or iron oxide)

Pigment 3 (Pi 3):hydrolan 9160 (aluminum flake pigment)

Pigment 4 (Pi 4):9225 Rutile Blue Pearl SW (mica flake)

Pigment 5 (Pi 5):hydrolan 2197 (aluminum flake pigment)

Pigment 6 (Pi 6):9605 Blue-Shade Silver SW (mica flake).

In this way a total of five different base coats (BC 1 to BC 5) were obtained. The pigment types present therein are summarized in table 2 b. P/B means pigment/binder resin ratio.

TABLE 2b bottom coating

3.Preparation of a multilayer coating System

On the pretreated steel sheet coated with the cathodic electrodeposition coating using the catoguard 800, a primer layer made of one of P1C1, P1C2 or P1I1 was formed and cured at about 140 ℃ for 25 minutes (about 20 to 23 μm dry film thickness). One of the primer compositions BC1, BC2, BC3, BC4 or BC5 was then applied to the cured primer film and flash-evaporated at about 60 ℃ for 7 minutes. The clearcoat composition is then applied to the flashed basecoat film. The two films were then co-cured at about 140 ℃ for 25 minutes (about 20 to 23 μm dry primer film thickness and about 50 μm dry varnish film thickness). Commercial varnish layer products (ProGloss/2K 4) were used. All compositions were applied by pneumatic spraying. The varnish layer is a transparent layer and is also transparent to IR radiation. The multilayer coating system (MLCS) obtained was then investigated. The properties shown in table 3 were measured as described in the 'methods' section above.

Table 3: comparison of lidar and flop indexes for different multilayer coating systems with different silver hues

Both CE1 and E1 have similar silver flop indices, but the multilayer coating system of E1 has much higher lidar reflectivity. The primers used in the systems in both examples were lidar active. Aluminum flake pigments (such as Pi1 present in BC 1) are an opaque metal whose reflection is completely independent of the primer system used. This can be seen from the silver color of one of CE2A and CE2B, wherein the primer BC3 used in both cases contains only a small amount (< 10wt. -%) of mica flakes (Pi 4). In the case of E2, it can be seen that the multilayer coating system made by using primer P1I1 and mica flake substrate coating BC4 not only provides high flop but also provides good lidar reflectivity. The conventional clear primer (P1C 1) may provide good lidar reflectivity but only poor color, while the conventional dark primer (P1C 2) may provide good flop index but only poor lidar reflectivity.

These results demonstrate that only the multilayer coating systems of the present invention made by using a non-opaque flake substrate coating such as BC2, BC4 or BC5 in combination with a dark primer such as P1I1 (L x 40) can provide a unique silvery color with not only a high flop index but also a high lidar reflectivity at non-specular angles.

Claims

1. A multilayer coating system which is present on an optionally precoated substrate and comprises at least three mutually different coatings L1, L2 and L3, i.e

a second coating layer L2 applied on the first coating layer L1, and

a third top coat L3 applied over the second coat L2,

it is characterized in that the method comprises the steps of,

the primer coating composition comprises at least one film-forming polymer P-A1 as at least one component P-A and, in the case where P-A1 is externally crosslinkable, at least one crosslinker P-A2, water and/or one or more organic solvents as component P-B and is free or substantially free of metallic effect pigments, but comprises at least one component P-C as a pigment mixture comprising at least two pigments which are different from one another, namely at least one organic black or inorganic black pigment P-C1 which is not a carbon black pigment and which is transparent or substantially transparent or which is reflective or substantially reflective to NIR radiation, and at least one inorganic white pigment P-C2 which is reflective or substantially reflective to NIR radiation,

the basecoat composition comprises at least one film-forming polymer B-A1 as at least one component B-ase:Sub>A and, in the case where B-A1 is externally crosslinkable, at least one crosslinker B-ase:Sub>A 2, water and/or one or more organic solvents as component B-B, and at least one effect pigment B-C1, which is ase:Sub>A pearlescent pigment or an interference pigment, wherein the amount of the at least one pigment B-C1 in the basecoat composition exceeds the amount of any aluminum metal effect pigment B-C2 optionally also present therein.

2. The multilayer coating system according to claim 1, characterized in that the first coating L1 formed from the primer coating composition and applied on at least a portion of the optionally pre-coated substrate has a brightness value L of no more than 40, preferably no more than 38, more preferably no more than 35, even more preferably no more than 30 at 45 ° and/or has a lidar reflectivity of at least 40%, preferably at least 45%, more preferably at least 50%, even more preferably at least 55%, still more preferably at least 60%, yet more preferably at least 65%, in particular at least 70%, measured at an angle of incidence of 0 °, according to the CIELAB system.

3. The multilayer coating system according to claim 1 or 2, characterized in that the amount of pigment P-C2 in the primer coating composition exceeds the amount of pigment P-C1C 2 in the primer coating composition, preferably characterized in that the relative weight ratio of pigment P-C2 to P-C1 is in the range from 15:1 to 1.1:1, more preferably from 12:1 to 1.5:1, even more preferably from 10:1 to 2:1.

4. The multilayer coating system according to one or more of the preceding claims, characterized in that,

the at least one black pigment P-C1 is a black pigment having a multi-tone color according to the CIELAB system at 45 ° of L x <17, a x-4 and <9, and b x-4 and <9, preferably characterized in that the at least one pigment P-C1 is selected from the group consisting of iron/chromium oxide compounds, manganese ferrite black oxides, calcium manganese titanium oxides, perylene pigments, azomethine pigments and mixtures thereof, more preferably from the group consisting of perylene pigments, azomethine pigments and mixtures thereof, most preferably from the group consisting of perylene pigments, and characterized in that,

the at least one white pigment P-C2 is a white pigment having a multi-tone color according to the CIELAB system at 45 ° of L x 85, a x 2 and <2, and b x 0 and <6, preferably selected from the group consisting of titanium dioxide based or titanium dioxide containing pigments, more preferably selected from titanium/aluminum/silicon oxide based pigments and rod-shaped aluminum doped titanium dioxide pigments.

5. The multilayer coating system according to one or more of the preceding claims, characterized in that the relative weight ratio of the at least one, preferably platy pearlescent pigment or interference pigment B-C1 to any one or more aluminum metal effect pigments B-C2-if present in the basecoat composition-is in the range from 15:1.0 to 1.1:1.0, preferably from 12:1.0 to 1.2:1.0.

6. The multilayer coating system according to one or more of the preceding claims, characterized in that the basecoat composition additionally comprises at least one, preferably platelet-shaped aluminum metal effect pigment B-C2, preferably in an amount in the range of from 1 to 10wt. -% based on the total weight of the basecoat composition.

7. The multilayer coating system according to one or more of the preceding claims, characterized in that the at least one, preferably platelet-shaped pearlescent pigment or interference pigment B-C1 is present in the basecoat composition in an amount ranging from 1 to 15wt. -%, based on the total weight of the basecoat composition.

8. The multilayer coating system according to one or more of the preceding claims, characterized in that the primer coating composition for forming the first coating L1 and the basecoat composition for forming the second coating L2 are each free or substantially free of any carbon black.

9. The multilayer coating system according to one or more of the preceding claims, characterized in that it has a lidar reflectivity of at least 10%, preferably at least 15%, measured at an angle of incidence of 45 °, and in that it has a flop index of ≡8, preferably ≡9, more preferably ≡10, even more preferably ≡12.

10. The multilayer coating system according to one or more of the preceding claims, characterized in that the third coating L3 is formed from a coating composition, which is a clearcoat layer composition, preferably a solvent-borne clearcoat layer composition, wherein the third coating L3 is the outermost coating of the multilayer coating system.

11. The multilayer coating system according to one or more of the preceding claims, characterized in that at least the second coating L2 and the third coating L3 are positioned adjacent to each other, preferably characterized in that the first coating L1 and the second coating L2 are also positioned adjacent to each other or wherein a further coating L1a is positioned between the first coating L1 and the second coating L2, wherein said further coating L1a is preferably formed from a coating composition comprising at least one organic black or inorganic black pigment, which pigment is not a carbon black pigment and is transparent or substantially transparent to NIR radiation and may be the same or different pigment P-C1.

12. The multilayer coating system according to one or more of the preceding claims, characterized in that it is obtainable by a process according to which at least the basecoat composition for preparing the second coating L2 and the coating composition, preferably a clearcoat composition, for preparing the third coating L3 are co-cured to obtain the second coating L2 and the third coating L3 of the multilayer coating system.

13. A process for preparing a multilayer coating system according to one or more of the preceding claims, comprising at least steps (1), (2), (3) and (4), i.e.

14. A kit of parts comprising a spatially separated form

Primer coating composition as defined in one or more of claims 1 to 4, 8 and 11 as part (a) which can be used for preparing a first coating L1 of a multilayer coating system as defined in one or more of claims 1 to 12, and

as part (B), the basecoat composition as defined in one or more of claims 1, 5 to 8 and 11, which can be used for the preparation of a second coating L2 of a multilayer coating system as defined in one or more of claims 1 to 12, and

varnish layer composition, preferably as defined in claim 10, optionally as part (C), which can be used for the preparation of a third coating L3 of a multilayer coating system as defined in one or more of claims 1 to 12.

15. Use of a kit of parts according to claim 14 to improve, in particular to improve, preferably to improve at least 10%, in particular to improve at least 15%, the laser radar reflectivity of a multilayer coating system, preferably a multilayer coating system according to one or more of claims 1 to 12, measured at an angle of incidence of 0 °, and the flop index of a multilayer coating system, preferably a multilayer coating system according to one or more of claims 1 to 12, and to improve, in particular to improve to ≡8, preferably ≡9, more preferably ≡10, even more preferably ≡12, the flop index of a multilayer coating system, more preferably a multilayer coating system according to one or more of claims 1 to 12.