CA2389854A1

CA2389854A1 - Coating agent for coating the surface of a substrate and a method for coating the surface of substrate

Info

Publication number: CA2389854A1
Application number: CA002389854A
Authority: CA
Inventors: Anja Keller; Thomas Gruber; Karl Holdik; Wolfgang Schahl
Original assignee: Bombardier Transportation GmbH
Current assignee: Individual
Priority date: 1999-11-16
Filing date: 2000-11-14
Publication date: 2001-05-25
Also published as: CZ20021656A3; AU1700401A; NO20022268D0; NO20022268L; KR20020049053A; CN1390167A; PL355622A1; JP2003527258A; DE19954970A1; WO2001036172A1; EP1274552A1; HUP0204104A2

Abstract

The present invention relates to a coating agent for coating the surface of a substrate in the form of a foil which is provided with an upper cover layer, a middle chromophore layer and a lower carrier layer. According to the invention, the lower carrier layer is a free-flowing, hardenable adhesive an d levelling layer for gluing the foil onto the surface of the substrate and fo r covering irregularities in the surface of the substrate. A flexible, hardenable cover layer is provided. The present invention also relates to a method for coating the surface of a substrate using such a coating agent.</S DOAB>

Description

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COATING AGENT FOR COATING THE SURFACE OF A SUBSTRATE
AND A METHOD FOR COATING THE SURFACE OF SUBSTRATE
The present invention relates to a coating agent for coating the surface of a substrate, e.g., of an automotive body or a body part for a motor vehicle or a component, in particular of a car body of a railway vehicle, in the form of a film which has a top cover layer, a middle coloring layer and a bottom curable carrier layer. The present invention also relates to a method for coating the surface of a substrate with such a coating agent.
Such coating agents are known. They are used for coating product surfaces, particularly as a substitute for an enamel.
Wet enameling of substrates after first leveling the surfaces of the substrates with filler is time-consuming, labor-intensive and cost-intensive. For example, body parts of motor vehicles based on steel or aluminum or components of fiber composite materials must first be leveled after applying a corrosion-preventing layer. In doing so an equalizing filler is applied once or more times and after each application an intermediate grinding must be conducted. Then the surface smoothed in this way must be coated with a base coat and next with a top coat of enamel. The numerous production steps using different materials entail additional waiting times for airing, drying and curing. Leveling out manufacturing-related disturbances due to joints such as welds, grinding marks or rivets cannot be automated. This process is sensitive to external influences, especially dust, and it causes emissions, e.g., of solvents. Therefore, the process steps must be carried out in separate installations.

_ 2 _ European Patent 0 352 298 B1 discloses an automotive body planking and a method of producing same. This automotive body planking is made of plastic and is coated with a film, which consists of a carrier layer, a pigment layer and a clear enamel layer. The laminate is heated and pre-shaped and then inserted into an injection mold, and plastic is injected behind it, resulting in the finished automotive body planking.
U.S. Patent 5,021,278 A describes a thermoformable laminate consisting of a carrier layer, a paint layer and a protective clearcoat layer. The laminate is heated and pre-shaped and then molded onto the substrate.
European Patent 0 615 840 A1 relates to a coating film for a metal container for beverages in the form of a laminate which has, as seen from bottom to top, an adhesive layer, a coloring layer, a polyester layer and a top layer. The film is drawn with the adhesive layer onto a flat sheet of metal, which is then shaped into a can.
These known films and the methods of applying them to a metallic or fiber composite material substrate are complicated and furthermore are not suitable for such substrates in all cases, because there is usually no adhesive layer, so the films must be melted onto the substrate. In addition, the known films are not flexible enough, so they have to be pre-shaped to allow them to be applied to the substrate.
German patent application DE 197 O1 594 A1 discloses a method of producing a profile strip, in particular an edge strip for use in the furniture industry. German patent application DE 38 17 479 A1 discloses a multilayer surface film. Due to the intended application as a protective layer for smooth surfaces, there is no provision for leveling out equalizing irregularities in the substrate to be coated.
Therefore, the object of the present invention is to provide a coating agent and a method of the type described above which will allow short processing times, will be insensitive to external influences, will release the least possible emissions and will make it possible to omit any additional surface finishing.
The solution to this problem consists of a coating agent having the features of Claim 1 and a method with which this coating agent is used. According to this invention, the bottom carrier layer is a free-flowing, curable adhesive and equalizing layer for bonding the film to the surface of the substrate and for laminating irregularities in the surface of the substrate, and a flexible curable top cover layer is also provided.
Thus, with the application of a colored decorative coating, irregularities in the surface of the substrate are laminated at the same time due to the free-flowing bottom adhesive and equalizing layer, and the resulting coating after applying the coating agent has a high resistance to external influences and stresses because of the cover layer, which is then cured.
The reaction time of the bottom adhesive and equalizing layer between the surface of the substrate and the coloring layer does not play a crucial role. It may amount to seconds, minutes, hours or even days. This is of a secondary priority, because the substrate is already in its final stage and thus the surface or the substrate is adequately protected and because no additional processing steps are necessary, so that even with a longer reaction time delays in production can not occur.
Since no liquid materials need to be processed during the entire operation, there are no unwanted emissions. The process according to this invention can also be carried out on the same substrate in parallel with other processing steps, i.e., for example, in parallel with a different construction operation on a motor vehicle or a railway vehicle, because it is insensitive to emissions, in particular with respect to dust. Only one coating step is necessary. No pre-shaping of the coating agent is necessary. Apart from the net coating time, there are no waiting times, e.g., due to drying or reaction of the coating materials.
Advantageous developments are derived from the subclaims.
Equalization of irregularities in the surface of the substrate due to the bottom adhesive and equalization layer is then especially simple if this layer is at least 0.150 mm thick, preferably at least 1 mm thick because there is enough free-flowing material to fill up all depressions in the surface and to form a flat layer on the surface. To do so, the bottom adhesive and equalizing layer preferably has a viscous consistency, especially preferably a thixotropic profile of properties. Such a layer is viscous enough not to drip down from the coating agent but is free-flowing enough to allow it to equalize irregularities in the surface of the substrate.
Thixotropic layers are especially suitable because they are normally solid to viscous, but under load, i.e., when applying the coating agent to the substrate, they liquefy and are thus able to equalize irregularities especially well.

The bottom adhesive and equalizing layer may be designed to cover the entire surface, or just spots or lines. It is not necessary to apply the bottom layer continuously to the middle coloring layer. Application of adhesive spots or strips may be sufficient and saves material.
The bottom adhesive and equalizing layer is preferably produced on the basis of a thermally cross-linkable, moisture cross-linkable or photo-cross-linkable polymer as well as a multicomponent material based on epoxy, polyurethane or acid-curing binders. A polymer based on a polyurethane or a blend of several polyurethanes is especially suitable. The bottom adhesive and equalizing layer may also be produced, for example, on the basis of a partially cross-linked pressure-sensitive adhesive.
These are pressure-sensitive adhesives which are already cross-linked (e.g., due to electron beam curing or W
curing) but which still have an adhesiveness and a viscous consistency to guarantee the required adhesion of the coating agent to the substrate and equalization of the irregularities on the surface of the substrate. The internal cross-linking is advantageous to achieve a better cohesive strength of the adhesive, so that, for example, a high layer thickness of the adhesive can be achieved without it dripping down from the coating agent.
However, the bottom adhesive and equalizing layer may also consist of a foamed adhesive surface, foamed adhesive spots or foamed adhesive strips. Then the foam assumes the equalizing function.
The top cover layer preferably consists of a thermoplastic plastic matrix, which is completely hardened by heating or by irradiation with W light or electron beams or visible light. Hardening of the top ,' . ~ CA 02389854 2002-05-02 cover layer to form a protective layer, preferably transparent, takes place only after application of the film to the finished component. The top cover layer is thus preferably a clear, cross-linkable enamel layer, particularly a clear, thermally cross-linkable or photo-cross-linkable enamel layer which is hard enough after curing to guarantee sufficient protection of the resulting coating from external influences.
Beneath the adhesive and equalizing layer and/or above the top cover layer of the coating agent according to this invention a removable protective layer can be attached which protects the outer layers of the coating agent from damage during storage and transportation and, in the case of the top cover layer, during the application to the substrate. At this, the bottom protective layer is preferably a film of paper and/or the top protective layer is preferably a polyester film or a polyolefin film, in particular a polypropylene film.
In the method according to this invention using the coating agent according to this invention, it may be applied to the surface by rolling and/or by doctor application. Preferably a coating agent with a flexible top cover layer of a cross-linkable polymer, in particular a thermally cross-linkable or photo-cross-linkable polymer is used, and the top cover layer is thermally cross-linked or photo-cross-linked after applying the coating agent to the substrate.
When using a coating agent with a moisture-curing bottom adhesive and equalizing layer, the surface of the substrate is covered or sprayed with a liquid, preferably water, before applying the coating agent. However, when using a coating agent with a thermally curing bottom _ 7 _ adhesive and equalizing layer, the resulting composite of substrate and coating agent may be heated to harden the adhesive and equalizing layer. In this case, it is advisable to use a coating agent with a flexible top cover layer of a thermally cross-linkable polymer and to cross-link the thermally curing bottom adhesive and equalizing layer and the top cover layer at the same time after applying the coating agent to the substrate by heating the resulting composite (either by heat or by radiation, depending on the nature of the top cover layer) .
To protect the top cover layer from damage, it is preferable to use a coating agent with a top protective layer, which is removed only after applying the coating agent to the substrate.
The coating agent according to this invention may be, for example, applied to a surface having an unevenness of 0.5 mm or more and/or a surface which is provided with an anticorrosion layer, depending on the thickness of the bottom adhesive and equalizing layer.
The coating agent according to this invention is particularly suitable for coating metallic or fiber-reinforced material substrates, e.g., automotive bodies or body parts of motor vehicles or components, in particular car bodies of railway vehicles.
An embodiment of the present invention is explained in greater detail below on the basis of the accompanying drawings, which show:
Fig. 1 a schematic diagram of the structure of the coating agent according to this invention;

s Fig. 2 a schematic diagram of the coating agent and the substrate before coating;
Fig. 3 a schematic diagram of the finished composite of the coating agent and substrate after coating.
Fig. 1 shows schematically a sectional diagram of an embodiment of the coating agent 1 according to this invention. Coating agent 1 is composed of at least three functional layers: a top cover layer 2, a middle coloring layer 3 and a bottom adhesive and equalizing layer 4. The top cover layer 2 is flexible and can be cured to form a hard protective layer, preferably a transparent clear enamel layer. The middle coloring layer 3 is preferably formed by pigmented thermoplastics, particularly pigmented polyurethane, which do not require any additional curing. The layer thickness should be approximately 20 to 100 Vim. The choice is made according to the compatibility and adhesion to the adhesive and equalizing layer or to the top cover layer, mechanical and thermal properties and compatibility with coloring agents and pigments with which the plastic is to be pigmented. The bottom adhesive and equalizing layer consists of a suitable adhesive such as a pressure-sensitive adhesive, a hot-melt adhesive, a one-component system or a light-activatable adhesive or foamed adhesive webs, adhesive spots or adhesive tape. The function of the adhesive and equalizing layer 4 corresponds approximately to the transfer of mechanical properties of the filler in a normal automotive enamel. The choice of the material is based on compatibility and adhesion to the coloring layer or to the substrate material as well as the mechanical and thermal properties and may be based on materials available on the market. In particular, moisture cross-linking or thermally cross-linking or multicomponent polyurethane or epoxy systems are suitable. The layer thickness should be at least 150 Vim.
Layer thicknesses of 500 ~m or more, particularly 1 mm or more, are especially preferred.
Furthermore, a protective film 5, preferably made of polyester, with a layer thickness of approximately 100 ~m may be provided to protect the top cover layer 2 from mechanical damage during storage, transportation and application of the coating agent 1 to the substrate. This is preferably a rigid elastic material which acts as a surface equalizing layer in the use of application techniques such as roller or doctor application or the like, so that no rolling and grinding tracks are impressed in the film. The protective film may be removed from the top cover layer 2 after coating agent 1 has been applied to the substrate.
Finally, a temporary protective layer 6 may be provided on the bottom adhesive and equalizing layer 4 to protect the adhesive compound. This protective layer is removed before applying the coating agent 1 to the substrate.
Specifically the following materials may be used for the layers 2, 3 and 4:
As thermoplastic components of coloring layer 3 polymethyl methacrylatea (PMMA), polybutyl methacrylates (PBMA), polyurethanes (PUR), polyethylene terephthalates (PETP), polybutylene terephthalates (PBTP), polyvinylidene fluorides (PVDF), polyvinyl chlorides (PVC), polyesters (PES), polyolefins (PE, PP), polyamides (PA), polycarbonates (PC), acrylonitrile-butadiene-styrene polymers (ABS), acryl-styrene-acrylonitrile copolymers (ASA) and acrylonitrile-ethylene-propylene-diene-stryene copolymers (A-EPDM) may be used, with halogen-free polymers being preferred. As pigments and coloring agents organic or inorganic coloring agents, organic, inorganic or metallic pigments, mica effect pigments, interference pigments, pearlized pigments and liquid crystalline polymers may be used.
As materials for the top cover layer 2 in the form of a transparent, radiation-curing clear enamel layer in particular a polymerizable binder or a mixture of a thermoplastic with a polymerizable binder may be used, wherein the binder is either polymerizable in a free radical process or in a cationic process or by both methods. Depending on the reaction mechanism, suitable curing catalysts (photoinitiators) are added to the mixture.
The radically polymerizable binders are usually mono- or poly-ethylenically unsaturated compounds. Especially important are polyunsaturated binders, because they contribute to the cross-linking of the reaction system to form insoluble products. Radically polymerizable aliphatic urethane acrylates, polyether acrylates, polyester acrylates, epoxy acrylates or acrylated isocyanurates or mixtures of two or more of these classes of compounds are used.
Examples of monounsaturated compounds are acrylates, methacrylates of monohydric alcohols, acrylic acid derivatives (methyl, ethyl, butyl, isooctyl and hydroxyethyl acrylate, hydroxyethyl methacrylate, ethyl or methyl methacrylate) as well as vinyl and allyl compounds such as vinyl acetate, vinyl stearate and allyl acetate.
Examples of polyunsaturated compounds are acrylates and methacrylates of polyols such as ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, butanediol-1,4-diacrylate, butanediol-1,3-dimethacrylate, neopentyl glycol diacrylate, trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate, glycerol diacrylate and triacrylate, pentaerythritol diacrylate, triacrylate, tetraacrylate or methacrylate, dipentaerythritol tetraacrylate, pentaacrylate, hexaacrylate and -methacrylate, diacrylates and dimethacrylates of 1,4-cyclohexanediol, 1,4-dimethylol cyclohexane, polyethylene glycols or oligo esters or oligourethanes, silicone-modified acrylates and methacrylates, diacrylates, triacrylates and tetraacrylates and methacrylates of tris(2-hydroxyethyl) isocyanurates as well as (meth)acrylates of polyvinyl alcohol and copolymers of butadiene or isoprene.
The unsaturated binders may be used in the form of a mixture as well as being used as individual substances.
As photoinitiators can be used, for example, benzoin, benzil, benzophenone, benzoin alkylene ether, esters of phenyl glyoxylic acid, a-trichloroacetophenone, a-diethoxy-acetophenone, a-hydroxyacetophenone, benzil dimethyl ketal, methylbenzoyl formate, 1-benzoylcyclohexanone, a-amino-acetophenone, D,L-camphorquinone, 2,2-diethoxyacetophenone, N-dimethylethanolamine, 4-benzoyl-4'-methyldiphenyl sulfide, isopropylthioxanethones, ethyl-4-dimethylaminobenzoate, N-methyldiethanolamine, 1-hydroxyl cyclohexylphenyl ketone, bis(2,4,6-trimethylbenzoyl)-phosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-' - 12 -morpholinopropan-1, 2-hydroxy-2-methyl-1-phenyl-propan-1, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide, 1-[4-(2-hydroxyethoxy)-phenyl)-2-hydroxy-2-methyl-1-propan-1-one, [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone, 2,4,6-trimethyl-benzoylphenylphosphinic acid ethyl ester, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.
The photoinitiators may be added to the binders as individual components or as mixtures.
As adhesives pressure-sensitive adhesives may be used, where thermally aftercuring systems may also be used. As non-curable, highly viscous liquids, the polymers applied to the middle coloring layer 3 have a certain tackiness (so-called "tack") and they are bonded to the surface of the substrate by contact pressure. The thermally aftercuring systems are cross-linked together subsequently. The processing temperature is usually between 10 °C and 40 °C.
Furthermore, reactive hot-melt adhesives may be used, which set up due to cooling and partial crystallization of the backbone polymers. By adding other reactive components, this system can be adjusted to be moisture cross-linking or thermally cross-linking. Of the moisture-curing one-component systems, polyurethane systems are preferred. The curing reaction is only started with addition of sufficient moisture. The moisture is supplied by moistening the surface of the substrate before applying coating agent 1. A relative atmospheric humidity of 40 % should be present during processing.
To achieve sufficient, through curing with a thick layer, the moisture, preferably water, may be microencapsulated.
The capsules are destroyed by application of the coating agent to the surface, thus releasing the moisture content. The capsule material remains as a filler in the adhesive and equalizing layer 4. Microencapsulated adhesives exist, for example, as epoxy resins, acrylates, polyesters and polyurethanes.
In the case of thermally curing one-component systems, the curing agent is activated by temperature. The curing agent is previously blocked or is present as a solid in the resin.
Finally, one-component systems are conceivable in which the reactive component is present in the resin in micro-encapsulated form. During application of the coating agent 1, the capsules are destroyed and the reactive component is released, so that the curing reaction may begin.
As another possibility, two-component systems or three-component systems based on polyurethane or epoxy systems may be used. In this case, the second and/or third component (curing agent and activator components) may be encapsulated or may be present in the applied layer by means of a separatable protective group, and then they are activated by thermal treatment, at room temperature or by light (W or visible light) or by moisture. In doing so, the reactive component is released from the encapsulation or the protective group is split off. Both the encapsulation and the protective group that may be split off may remain in the layer. Another possibility is to provide the curing agent or activator component in a non-reactive molecular state in the uncross-linked system, which is converted by inter- or intramolecular ' CA 02389854 2002-05-02 rearrangement to the reactive state after exposure to temperature, moisture, UV light or visible light and thus leads to curing of the adhesive and equalizing layer 4.
The activator or curing agent components may also be pre-coated as contact reaction partners on one of the surfaces to be bonded, and may diffuse into the equalizing and adhesive layer of the film composite, where they lead to curing of the composite there or at the interface. There is the possibility of either spraying all components onto the adhesive and equalizing layer before application of the film and then applying the film immediately or providing individual components (activator or curing agent) on the substrate surface to be bonded. There is the possibility here of applying the curing agent or activator by means of a thin film, in which case the film is either in the form of a curing agent film or an activator film or it may be applied wet.
Especially preferred are photo-cross-linkable adhesives because they have a mean to high adhesive strength and elasticity and they pre-cure rapidly. The final strength (reaction in the dark) may be achieved only after several hours or days. The photoinitiator disintegrates on exposure to radiation, preferably light, into a compound which initiates polymerization. This proceeds further after termination of the light exposure and in areas not exposed to light (reaction in the dark).
The adhesive and equalizing layer 4 may also be in the form of a foamed adhesive web, adhesive tape or adhesive spots. In this case, the adhesive surfaces and the core of the adhesive tape form a unit of the same adhesive polymer. The polymer is present both as a pure viscoelastic adhesive and as an adhesive tape core in a foamed and closed-cell structure. Because of its viscoelastic properties, the polymer is capable of flowing into the surface roughness and thus increasing the active surface area and thus the peeling resistance.
In addition, other substances such as those generally used in films may also be added to the coating agent l in each layer and in individual layers; these additives might include, for example, stabilizers (antioxidants, light protectants (W absorbers, HALS), metal deactivators, thio synergists), processing aids, flow control aids, thixotropy agents and foam suppressants.
Furthermore, fillers, fibers, lubricants, antistatic agents, plasticizers and flame retardants may also be added.
The material for the curable top cover layer 2 of thermoplastics and binders may be obtained in the known way by extrusion. The thermoplastics are melted in the extruder. The binders, curing agents and optional additives, are blended and added to the molten thermoplastic in the extruder. This yields a reactive mixture, which is obtained in the form of granules, powders or film.
The ratio between binders, curing agents and additives on the one hand and thermoplastics on the other hand is 1:1 to 1:5, but preferably especially 1:3.
The top cover layer 2 is coextruded with the middle coloring layer 3 and the bottom adhesive and equalizing layer 4 in one operation to form a multilayer film. The reactive radiation-curable mixture of thermoplastic, binders, curing agents and optional additives may be prepared as a transparent film in a layer thickness of 15-100 ~m and cured with W light, for example.

. . ' CA 02389854 2002-05-02 Polymerization is preferably initiated in the transparent layer by means of UV radiators such as low-pressure, medium-pressure or high-pressure mercury lamps, xenon lamps, argon lamps, metal halide lamps, flash discharge lamps, laser beams or electron beams (electron beam curing). The wavelength for curing with W/VIS light is preferably 200-600 nm.
The bottom side of the resulting film may also be coated separately with the adhesive, in which case adhesive spots or adhesive strips may also be applied. The foamed adhesive webs, adhesive strips or adhesive spots are also applied separately.
The following examples show how this method can be carried out in detail. In these examples, parts refer to parts by weight and percentages are percent by weight, unless otherwise indicated.
Example 1 A photoactive mixture is prepared by mixing:
Material Ebecryl 40 23 alkoxylated PETIA (UCB) Ebecryl IRR 264 41- triacrylate of a tris(2-hydroxyethyl) 45.2 isocyanurate (UCB) Ebecryl 1290 11 aliphatic UR-Ac (UCB) Ebecryl 5129 11 aliphatic UR-Ac (UCB) Ebecryl 350 5 silicone diacrylate (UCB) Tinuvin 952 1 HALS additive (Ciba SC) Tinuvin 400 1 UV absorber (Ciba SC) Irgacure 184 6 photoinitiator (Ciba SC) Lucirin TPO 1 photoinitiator (BASF) . . CA 02389854 2002-05-02 This mixture is metered into a melt of polyrnethyl methacrylate Lucryl G55 or Lucryl G87e (BASF) in a continuous process:
Material Parts Lucryl G55 3 Mixture Example 1 1 Curing conditions under UV light 2*2 - 3 m/min; 120 W/cm In this embodiment, Lucryl 55 PMMA was selected as the thermoplastic for the coloring layer because it is identical to the thermoplastic component of the clear top layer and therefore has the best adhesion and compatibility. In addition, pigments and coloring agents may easily be incorporated into the melt at approximately 220 °C.
Furthermore, metallic pigments were used in this embodiment (aluminum flakes PCR 501 from Eckart Company, a powdered non-leaving pigment which is coated with Si02 and has a particle size distribution of 10 to 60 ~,m) or a red metallic gloss pigment (Iriodin ~ 504 mica flakes from Merck, a powdered mica coated with d-Fe203 having a particle size distribution of 10 to 60 Vim).
Example 2 Material Ebecryl 2000 43 aliphatic UR-Ac (UCB) Ebecryl IRR 264 25.5 aliphatic triacrylate of a UR-Ac in HDDA (UCB) Lucirin TPO-L 0.5 photoinitiator (BASF) CGI 184 3 photoinitiator (Ciba SC) Tinuvin 292 2 HALS additive (Ciba SC) Tinuvin 400 2 UV absorber (Ciba SC) SR 9003 7 propoxylated neopentyl glycol diacrylate (Cray Valley) Ebecryl 350 2 silicone diacrylate (UCB) CN 965 10 aliphatic UR-Ac (Cray Valley) SR 344 5 polyethylene glycol diacrylate (Cray Valley) This mixture was metered into a melt of thermoplastic polyurethane KU-1-8602 or KU-2-8602 (Bayer) in a continuous process:
Material Parts Mixture Example 2 1 Curing conditions under UV light: 2*2 - 4 m/min; 120 W/cm Figs. 2 and 3 illustrate the function of the adhesive and equalizing layer 4 in application of the coating agent 1 to a substrate 10. Coating agent 1 may be applied to roughly prepared surfaces having an unevenness of up to 0.5 mm or more and to surfaces 11 having a temporary corrosion protection, coated, for example, with a two-component EP metal ground coat from Lankwitzer Lackfabrik [Lankwitz Enamel Factory]. After cutting the coating agent 1 and removing the protective film 6 from the bottom adhesive and equalizing layer 4, coating agent 1 is pressed tightly against the surface 11 of the metallic substrate 10 by means of rollers and/or optionally large-area doctor blades. The free-flowing adhesive compound of the bottom adhesive and equalizing layer 4 is distributed over the irregularities 12 in the surface 11 of the substrate 10. The rigid protective film 5 supports a uniform and planar distribution of the adhesive compound ~ - 19 -over the surface. When the desired levelness has been achieved, protective film 5 may be removed from the top cover layer 2. Then the top cover layer 2 is cured by radiation or by heating, thus yielding an abrasion-resistant end state. Thus, the surface 11 of the substrate 10 is finish-coated. The reaction time of the adhesive compound may readily amount to several hours or even days, but this does not play a role because the surface 11 is already in its final state and is thus adequately protected from external effects, so that substrate 10 can be processed further without any waiting time.
In the case of a moisture-curing adhesive and equalizing layer 4, the surface 11 of the substrate 10 is preferably covered with a thin film of water, e.g., by spraying with water before applying the coating agent 1.
If thermally cross-linking systems such as polyurethane systems are used as the adhesive and equalizing layer 4, and their reaction temperature should preferably be approximately 50 °C to 70 °C, then the required thermal threshold value is reached by heating the entire layer composite after application of coating agent 1, and that either by heating in the case of thermally curing top cover layers 2 or by radiation in the case of photo-cross-linkable top cover layers 2. Studies have shown that sufficient thermal heating to a depth of approximately 2 mm is achieved through the process management, e.g., 2*2-3 m/min, 120 W/cm.

Claims

1. A coating agent (1) in the form of a film, which has a top cover layer (2), a middle coloring layer (3) and a bottom curable adhesive layer (4), for coating the surface (11) of a substrate (10), wherein the bottom curable adhesive layer (4) is a free-flowing adhesive layer for bonding the film to the surface (11) of the substrate (10), and wherein a flexible curable top layer (2) is provided, characterized in that the bottom adhesive layer (4) is also an equalizing layer for laminating irregularities (12) in the surface (11) of the substrate (10), whereby the adhesive and equalizing layer (4) has a layer thickness of at least 0.150 mm and has a viscous consistency with a thixotropic profile of properties.

2. The coating agent according to Claim 1, characterized in that the bottom adhesive and equalizing layer (4) is designed in spots, lines or as a full area.

3. The coating agent according to Claim 1 or 2, characterized in that the bottom adhesive and equalizing layer (4) is produced on the basis of a thermally cross-linkable, moisture-cross-linkable or photo-cross-linkable polymer or a multicomponent material based on epoxy curing, polyurethane-curing or acid-curing binders.

4. The coating agent according to Claim 3, characterized in that the adhesive and equalizing layer (4) contains moisture, preferably microcapsules which contain water.

5. The coating agent (1) in the form of a film which has a top cover layer (2), a middle pigmenting layer (3) and a bottom curable adhesive layer (4), for coating the surface (11) of a substrate (10), wherein the bottom curable adhesive layer (4) is a free-flowing adhesive layer for bonding the film to the surface (11) of the substrate (10), and wherein a flexible, curable cover layer (2) is provided, characterized in that the bottom adhesive layer (4) is also an equalizing layer for laminating irregularities (12) in the surface (11) of the substrate (10), whereby the adhesive and equalizing layer (4) has a layer thickness of at least 0.150 mm and is produced on the basis of a thermally cross-linkable, moisture-cross-linkable or photo-cross-linkable polymer or a multicomponent material based on epoxy-curing, polyurethane-curing or acid-curing binders and it has microcapsules which contain moisture.

6. The coating agent according to Claim 5, characterized in that the microcapsules contain water.

7. The coating agent according to Claim 5 or 6, characterized in that the bottom adhesive and equalizing layer (4) has a viscous consistency.

8. The coating agent according to Claim 7, characterized in that the bottom adhesive and equalizing layer (4) has a thixotropic profile of properties.

9. The coating agent according to one of Claims 1 to 8, characterized in that the bottom adhesive and equalizing layer (4) has a layer thickness of at least 1 mm.

10. The coating agent according to one of Claims 1 to 9, characterized in that the bottom adhesive and equalizing layer (4) is produced on the basis of a polyurethane or a mixture of several polyurethanes.

11. The coating agent according to one of Claims 1 to 10, characterized in that the bottom adhesive and equalizing layer (4) is produced on the basis of a partially cross-linked pressure-sensitive adhesive.

12. The coating agent according to one of Claims 1 to 11, characterized in that the bottom adhesive and equalizing layer (4) consists of a foamed adhesive web, foamed adhesive spots or foamed adhesive strips.

13. The coating agent according to one of Claims 1 to 12, characterized in that the top cover layer (2) is a cross-linkable clear lacquer layer, in particular a thermally cross-linkable or photo-cross-linkable clear lacquer layer.

14. The coating agent according to one of Claims 1 to 13, characterized in that a removable protective layer (6; 5) is applied beneath the bottom adhesive and equalizing layer (4) and/or above the top cover layer (2).

15. The coating agent according to Claim 14, characterized in that the bottom protective layer (6) is a paper film and/or the top protective layer (5) is a polyester film or a polyolefin film, in particular a polypropylene film.

16. A method for coating the surface (11) of a substrate (10) with a film which has a top cover layer (2), a middle coloring layer (3) and a bottom carrier layer (4), characterized in that a coating agent (1) according to one of Claims 1 through 15 is used.

17. The method according to Claim 16, characterized in that the coating agent (1) is applied to the surface (11) of the substrate (10) by rolling and/or by doctor application.

18. The method according to Claim 16 to 17, characterized in that a coating agent (1) with a flexible top cover layer (2) of a cross-linkable, in particular thermally cross-linkable or photo-cross-linkable polymer is used, and the top cover layer (2) is thermally cross-linked or photo-cross-linked after applying the coating agent (1) to the substrate.

19. The method according to one of Claims 16 to 18, characterized in that when using a coating agent (1) with a moisture-curing bottom adhesive and equalizing layer (4), the surface (11) of the substrate (10) is covered with a liquid, preferably water, before applying the coating agent (1).

20. The method according to Claim 19, characterized in that the moisture, preferably water, is introduced in the form of microcapsules provided in the adhesive and equalizing layer (4).

21. The method according to one of Claims 16 to 20, characterized in that when using a coating agent (1) with a thermally curing bottom adhesive and equalizing layer (4), the resulting composite of the substrate (10) and the coating agent (1) is heated.

22. The method according to Claim 21, characterized in that a coating agent (1) with a flexible top cover layer (2) of a thermally cross-linkable polymer is used, and the thermally curing bottom adhesive and equalizing layer (4) and the top cover layer (2) are cross-linked simultaneously after applying the coating agent (1) to the substrate (10) by heating the resulting composite.

23. The method according to one of Claims 16 to 22, characterized in that a coating agent (1) with a top protective layer (5), which is removed after applying the coating agent (1) to the substrate (10), is used.

24. The method according to one of Claims 16 to 23, characterized in that the coating agent (1) is applied to a surface (11) which has an unevenness (12) of up to 0.5 mm and/or is provided with a corrosion-preventing layer.

25. The method according to one of Claims 16 to 24, characterized in that the coating agent (1) is applied to a metallic substrate (10) or a fiber-reinforced material substrate.

26. A use of a coating agent (1) according to one of Claims 1 to 15 or a method according to one of Claims 16 to 25 for coating an automotive body or a body part for motor vehicles or for coating a component, in particular a car body of a railway vehicle.