EP0952894B1 - Method for multi-layer painting - Google Patents

Abstract

Method for the production of a multi-layer paint coating in which, according to the coil-coating method, a priming layer of a coating medium is applied to both sides of a coil made of sheetmetal and then burned in. Next, sheet metal parts are punched out from the coil and deformed according to the deep-drawing method, and, when necessary, several of these sheet metal parts are assembled into a construction, to which a colouring or effect basic paint layer from a coating medium is applied, which layer is fitted with one or more clear coatings.

Description

The invention relates to a method for producing multi-layer coatings, especially for the production of multi-layer painted automobile bodies and body parts is suitable.

State of the art in the painting of motor vehicles is first Manufacture of the body. Correspondingly shaped sheet metal parts punched out and deformed, for example by deep drawing using Thermoforming aids, then generally assembled and welded then laboriously cleaned and in general, for example, by Pretreated for phosphating. Then the painting takes place, which is in today's, high quality automotive paintwork in general from one electrophoretically applied anti-corrosion primer and subsequently applied by spray painting subsequent layers consisting of a Filler layer and subsequently applied decorative purposes Painting from a color and / or effect basecoat and a die Surface sealing protective clear lacquer layer.

The total layer thickness of such automotive coatings is in the usual practice between 90 and 130 microns, which is the sum of 15 to 25 microns for the primer, 30 to 40 microns for the filler layer, 10 to 25 microns for the basecoat and 30 to 40 microns for the clear coat results. For example, EP-A1-0 448 280 describes a multi-layer coating whose total layer thickness is in the range mentioned above, but this has no clear lacquer layers. It has hitherto been necessary to exceed these layer thicknesses considerably if coatings with a particularly good visual appearance, ie with an outstanding gloss and topcoat level, are to be achieved, for example, when painting motor vehicles of the luxury and luxury classes. DE-A-42 15 070 and DE-A-38 39 905, for example, describe the application of several layers of clear lacquer to one basecoat layer. This then results in layer thicknesses of over 110 μm, for example up to 170 μm, which is undesirable on the finished vehicle for reasons of material savings and weight savings.

DE-A-195 19 665 describes a method for producing a Multi-layer painting, in which a primer layer is applied to a metal sheet applied a coating agent electrophoretically and then baked is, a color and / or effect basecoat from a coating agent is sprayed on and these are provided with one or more clear lacquer coatings a multi-layer coating with a total dry layer thickness of 70 up to 130 µm is generated and if necessary between the order of Primer layer and the application of the basecoat layer an intermediate layer applied and the clear coat or clear coat in one Total dry layer thickness of 30 to 80 microns can be applied.

The object of the invention is to provide a method for producing a Multi-layer coating, especially for the production of multi-layer coating Motor vehicle bodies and body parts, one compared to the state of the Technology show reduced overall layer thickness of the multi-layer coating comparable gloss and topcoat level or those with the usual Total layer thicknesses of the multi-layer coating an outstanding, improved Show gloss and top coat level. There should be no disadvantages in Overall property level of the multi-layer coatings result. The procedure is supposed to the handling of deep-drawing aids, such as drawing greases or oils, and the later ones Avoid cleaning them.

a) gegebenenfalls zwischen dem Auftrag der Grundierungsschicht und dem Auftrag der Basislackschicht eine Zwischenschicht aufträgt, und

c) die Klarlackschicht oder die Klarlackschichten in einer Gesamttrockenschichtdicke von 30 bis 80 µm aufbringt,

das dadurch gekennzeichnet ist, daß man als Metallblech ein Coil aus Metallblech verwendet und die Grundierungsschicht beidseitig im Coil-Coating-Verfahren aufwalzt und anschließend an das Einbrennen aus dem Coil Blechteile ausstanzt und im Tiefziehverfahren verformt und gegebenenfalls mehrere dieser Blechteile zu einer Konstruktion zusammenfügt, worauf man die Basislackschicht oder die Zwischenschicht aufbringt, und wobei man

b) die Zwischenschicht oder wenn keine Zwischenschicht aufgetragen wird die Basislackschicht aus einem elektrophoretisch abscheidbaren Überzugsmittel durch elektrophoretische Abscheidung aufträgt.

Beim erfindungsgemäßen Verfahren zur Herstellung von Mehrschichtlackierungen, insbesondere mehrschichtig lackierter Automobilkarossen oder -karossenteile, wird auf ein Coil aus Metallblech beidseitig im Coil Coating-Verfahren eine Grundierungsschicht aus einem Grundierungsüberzugsmittel aufgebracht und eingebrannt, aus dem Coil werden anschließend Blechteile ausgestanzt und im Tiefziehverfahren verformt und gegebenenfalls zu einer Automobilkarosserie zusammengefügt, worauf eine farb- und/oder effektgebende Basislackschicht und eine oder mehrere Klarlackschichten aufgebracht werden, wobei zwischen dem Auftrag der Grundierungsschicht und dem Auftrag der Basislackschicht eine Zwischenschicht aufgetragen werden kann und wobei der Auftrag der zweiten Überzugsschicht als Basislackschicht oder als Zwischenschicht durch elektrophoretische Abscheidung aus einem elektrophoretisch abscheidbaren Überzugsmittel erfolgt, wobei die Gesamttrockenschichtdicke der Mehrschichtlackierung bei 70 bis 130 µm liegt und die Gesamttrockenschichtdicke der Klarlackschicht(en) bei 30 bis 80 µm liegt. It has been shown that this object can be achieved, surprisingly, by the process for producing a multi-layer coating which is an object of the invention, in which a primer layer made of a coating agent is applied to a metal sheet and then baked, a color and / or effect-imparting base coat layer a coating agent is applied and this is provided with one or more clear lacquer coatings, a multi-layer coating with a total dry film thickness of 70 to 130 μm being produced, wherein

a) optionally applying an intermediate layer between the application of the primer layer and the application of the basecoat layer, and

c) the clear lacquer layer or the clear lacquer layers are applied in a total dry layer thickness of 30 to 80 μm,

which is characterized in that a coil of sheet metal is used as the metal sheet and the primer layer is rolled on both sides in the coil coating process and then stamped out of the coil from the coil sheet metal parts and deformed in the deep-drawing process and, if necessary, several of these sheet metal parts are combined to form a construction, whereupon one applies the basecoat layer or the intermediate layer, and wherein one

b) the intermediate layer or, if no intermediate layer is applied, the basecoat layer is applied from an electrophoretically depositable coating agent by electrophoretic deposition.

In the method according to the invention for the production of multi-layer coatings, in particular multi-layer painted automobile bodies or body parts, a primer layer made of a primer coating agent is applied and baked onto a coil made of sheet metal on both sides in the coil coating process, sheet metal parts are subsequently punched out of the coil and deformed in the deep-drawing process and optionally, if necessary assembled into an automobile body, onto which a color and / or effect basecoat and one or more clearcoat layers are applied, an intermediate layer being able to be applied between the application of the primer layer and the application of the basecoat layer, and the application of the second coating layer as a basecoat layer or as an intermediate layer by electrophoretic deposition from an electrophoretically depositable coating agent, the total dry film thickness of the multilayer coating being 70 to 130 µm and the total dry layer thickness of the clear lacquer layer (s) is 30 to 80 µm.

The primer layer is made of a primer coating agent and in a Layer thickness created that in the baked state is an electrically conductive Coating layer results. After punching out and deforming the primed and possibly to a construction, in particular a body Assembled sheet metal parts can then pass through the immediately following second layer electrophoretic deposition from an electrophoretically depositable aqueous Coating agents are applied, preferably to an electrically insulating leads second coating layer. A second coating layer can be used Intermediate layer are formed and baked, whereupon as a third coating layer a basecoat layer of a color and / or effect coating agent, preferably by spraying, which is applied with one or more Clear lacquer coating layers is provided.

According to a preferred embodiment of the invention, the second Coating layer a color and / or effect basecoat from one Aqueous coating compositions which can be deposited electrophoretically by electrophoretic Deposition formed, which is overcoated with one or more layers of clear lacquer becomes.

When working with an intermediate layer as the second coating layer is preferred worked in such a way that the total dry layer thickness of the lacquer structure is 80 to 130 µm, is particularly preferably less than 110 μm.

If the second, electrophonetically deposited coating layer is a color and / or effect basecoat layer, the total dry layer thickness of the Paint build-up preferred at 70 to less than 110 µm.

In summary, there are two preferred for the invention Embodiments:

A first is in a process for producing a multi-layer coating, in particular multi-layer painted automobile bodies or body parts, in which on a coil made of sheet metal on both sides in the coil coating process Primer layer applied from a primer coating and is burned in, sheet metal parts are then punched out of the coil and in Thermoforming process deformed and possibly to a construction, in particular be assembled into an automobile body, whereupon further Coating layers are applied, which is characterized in that as Primer coating used one that applied to the Layer thickness and in the baked state to an electrically conductive Primer coating layer leads to what after baking the first Coating layer an electrically insulating second coating layer as Intermediate layer of an electrophoretically depositable aqueous coating agent is electrophoretically deposited and baked, followed by the third Coating layer a basecoat layer of a color and / or effect, Coating agent, preferably by spraying, applied and optionally directly is burned in with a fourth, transparent coating layer from one Clear lacquer coating agent is overcoated. Basecoat and the Coating layer of a clear lacquer coating agent baked together, whereupon optionally one or more additional transparent coating layers are applied become. The total dry layer thickness of the lacquer structure is 70 to 130 µm, preferably at 80 to 130 microns, particularly preferably below 110 microns and the Dry layer thickness of the transparent coating layer or the total layer thickness the transparent cover layers is 30 to 80 μm, preferably 40 to 60 μm microns. The clear lacquer layer can consist of one or more layers, the first clear coat preferably before applying the further clear coat is branded. If several layers of clear lacquer are applied, they can can be created from the same or different clear lacquer coating agents.

A second independent and particularly preferred embodiment of the invention consists in a method for producing a multi-layer coating, in particular multilayered painted automobile bodies or body parts, in which on a coil a sheet of primer made from sheet metal on both sides in the coil coating process a primer coating is applied and baked, from the coil then stamped sheet metal parts and deformed in the deep-drawing process and if necessary to be assembled into an automobile body, whereupon without Applying intermediate layers of a color and / or effect basecoat is applied from an aqueous coating agent and baked and then with is provided with one or more clear lacquer coatings, characterized in that is that one is used as a primer coating agent, which in the applied layer thickness and in the baked state to an electrically conductive Primer coating layer, the basecoat layer consists of an electrophoretic separable aqueous coating agent by electrophoretic deposition is formed, the total dry film thickness of the clear coat or Clear lacquer layers at 30 to 80 microns, preferably 40 to 60 microns and the Total dry layer thickness of the multi-layer coating at 70 to 130 microns, preferred is 70 to 110 µm. The clear lacquer layer can consist of one or more layers exist, the first clear coat preferably before application of the other Clear lacquer layers are baked. If several layers of clear lacquer are applied, so they can be created from the same or different clear lacquer coating agents become.

It has been shown that excellent properties due to the invention Procedure can be achieved, although this is more common the elimination Spray filler layers enabled. Even with thick layers when applying clear lacquer are the total layer thicknesses according to the method of the invention Multi-layer coatings produced comparatively low.

In the process according to the invention for the generation of the first Coating layer usable primer coating agents in particular around liquid coating agents that can be applied in the coil coating process. It can be coating agents on an aqueous basis or on an organic basis Act solvent. They can be physically drying. As a rule, they are crosslinkable to form covalent bonds. It can be self- or third-party networking systems.

The process according to the invention for the production of the first coating layer Primer coatings that can be used contain one or more film-forming agents Binder. They can, especially if the binders are not self-crosslinking or are physically drying (thermoplastic), optionally also crosslinking agents contain. Both the binder component and the crosslinker component are not subject to any restrictions; it can be standard paint, the specialist common resins can be used. For example, as a film-forming Binders polyester, polyurethane, epoxy and / or polymer resins used become.

The selection of the crosslinkers that may be included is based on the Functionality of the binders, i.e. the crosslinkers are made from the usual Crosslinkers known to those skilled in the art are selected such that they have a function of the Binders have complementary, reactive functionality. Examples of such Complementary functionalities between binder and crosslinker are: Hydroxyl / methylol ether, hydroxyl / blocked isocyanate. If with each other compatible, several such complementary functionalities can also be used coexist. If necessary, in the primer coatings Crosslinkers used can be present individually or in a mixture.

It is preferred in the process according to the invention if the primer coating compositions applied in the coil coating process contain constituents which impart electrical conductivity and which give the first coating layer in the baked state a resistivity which is sufficiently low for the electrophoretic deposition of a further coating layer from an electrophoretically depositable coating composition, generally below 10 ⁸ Ohm.cm, for example between 10 ³ and 10 ⁸ Ohm.cm. This also ensures spot weldability of the primer coating layer. Examples of such electrical conductivity-imparting components are particulate inorganic or organic electrical conductors or semiconductors, as are customary for this purpose and are known to the person skilled in the art, for example iron oxide black, graphite, carbon black, metal powder, for example made of aluminum, zinc, copper or stainless steel, molybdenum disulfide. The electrical conductivity imparting components are contained in the primer coating agent in such an amount that the desired resistivity of the primer coating layer is achieved in the baked state. Based on the solids content of the primer coating composition, the proportion of the constituent (s) conferring electrical conductivity is, for example, between 1 and 30% by weight. The proportion can easily be determined by a specialist; it depends, for example, on the specific weight, the specific electrical conductivity and the particle size of the components imparting electrical conductivity. One or more of these components can be present in combination.

Preferably contain those that can be used in the process according to the invention Primer coating pigments and / or fillers. As pigments or Fillers come, for example, with common, inorganic or organic pigments and / or fillers in question. Examples are carbon black, titanium dioxide, iron oxide pigments, Kaolin, talc, silicon dioxide and in particular corrosion protection pigments, such as Zinc chromate, strontium chromate, lead silicate, zinc phosphate, aluminum phosphate, Strontiumaluminiumpolyphosphathydrat.

The primer coating compositions which can be used in the process according to the invention can also contain conventional additives. Examples of this are common Paint additives, such as wetting agents, dispersing agents, emulsifiers, leveling agents, Corrosion inhibitors, anti-foaming agents and in particular lubricants, for example Waxes such as polyethylene wax, molybdenum disulfide, graphite.

In the case of the method according to the invention for producing primer layers suitable coating agents which can be applied in the coil coating process and which do not special or insufficient quantities of electrical conductivity Contain ingredients, are coating agents, from which compliance a low dry layer thickness of, for example, 1 to 3 µm coating layers can be generated, the one for deposition in the baked state subsequent coating layer from an electrophoretically depositable Coating agent sufficient electrical conductivity and spot welding ability exhibit.

In the preferred in the method according to the invention for the production of Primer layers suitable, which can be applied in the coil coating process Coating agents which mediate on account of their content of electrical conductivity Constituents in a higher dry layer thickness of, for example, 2 to 15 μm, can be applied preferably from 3 to 10 microns, it is Coating agents from which coating layers can be produced, which in the baked state one for the deposition of a subsequent coating layer sufficiently low from an electrophoretically depositable coating agent have specific electrical resistance and are spot weldable.

The primer coating agent is coated on both sides in the coil coating process Rolled sheet metal. Is it a primer coating agent, which contains no special electrical conductivity-imparting components, so it is applied in a sufficiently low dry layer thickness, which is a electrophoretic deposition of a further coating layer from a Adequate electrical conductivity for electrophoretically depositable coating agents guaranteed, i.e. in a dry layer thickness that is not yet electrically insulating for example 1 to 3 µm. However, if it is one of the im preferred primer coating composition according to the invention, which is the first coating layer in the baked state one for electrophoretic Deposition of a further coating layer from an electrophoretic depositable coating agent sufficiently low specific resistance contains imparting electrical conductivity imparting components, so that Primer coating agent in a dry layer thickness of, for example, 2 to 15 µm, preferably applied from 3 to 10 µm. Branding the Primer coating layer takes place briefly at high temperatures, for example within 30 to 60 seconds, for example in a 300 to 370 ° C are called convection ovens, whereby maximum object temperatures (PMT, peak metal temperature) between 200 and 260 ° C.

From the metal coil provided with the burned-in primer layer on both sides sheet metal parts with the desired shape are punched out and in the usual way then deformed in the deep-drawing process. The deformed parts can become one Construction, especially a body to be assembled. examples for Suitable joining techniques are gluing and / or clinching and / or screwing and / or Welding, for example spot welding. Welding processes are preferred.

A second coating layer is applied to the primer layer Electro dip coating applied. This can be an intermediate layer act if subsequently a basecoat layer that with one or more Clear coating is provided as a third coating layer, preferably by Spray, is applied. The second is preferred Coating layer around a basecoat on the one or more clearcoat be applied.

To produce the second coating layer in the invention Process for the intermediate layer or the basecoat layer, the second Coating layer is applied, electrophoretically depositable coating agent used. For this purpose, the known anodic or cathodic are in particular separable electrodeposition paints (ETL).

The ETL coating agents are, in particular, aqueous Coating agents with a solid up to 50% by weight, for example up to 20% by weight, the lower limit being, for example, 10% by weight. The solid will formed from binders customary for electrocoating, at least some of the binders are ionic and / or convertible into ionic groups Carries substituents and, if appropriate, groups capable of chemical crosslinking, and any crosslinking agents, fillers, pigments or conventional paint additives.

The ionic groups or groups of the binders which can be converted into ionic groups can be anionic or groups which can be converted into anionic groups, acidic groups such as -COOH, -SO ₃ H and / or -PO ₃ H ₂ and the corresponding anionic groups neutralized with bases. They can also be cationic or convertible into cationic groups, for example basic groups, preferably nitrogen-containing basic groups; these groups can be present in quaternized form or they are converted into ionic groups using a conventional neutralizing agent, for example an organic monocarboxylic acid, such as, for example, formic acid or acetic acid. Examples are amino, ammonium, for example quaternary ammonium, phosphonium and / or sulfonium groups.

In the process according to the invention, the second Coating layer, for example the usual cathodic electrocoat materials (KTL) based on cationic or basic binders. Such basic resins are, for example, primary, secondary and / or tertiary Resins containing amino groups, the amine numbers of e.g. at 20 to 250 mg KOH / g lie. The weight average molecular weight (Mw) of the base resins is preferably 300 to 10,000. Examples of such base resins are amino (meth) acrylate resins, Amino epoxy resins, amino epoxy resins with terminal double bonds, Amino epoxy resins with primary OH groups, aminopolyurethane resins, amino group-containing polybutadiene resins or modified epoxy resin-carbon dioxide-amine reaction products. These base resins can be self-crosslinking or they are used in a mixture with known crosslinkers. Examples of such Crosslinkers are aminoplast resins, blocked polyisocyanates, crosslinkers with terminal double bonds, polyepoxide compounds or crosslinkers, the Contain transesterifiable groups.

The usual anionic group-containing anodically depositable electrocoat binders and paints (ATL) can also be used in the process according to the invention to produce the second coating layer. These are, for example, binders based on polyesters, epoxy resin esters, (meth) acrylic copolymer resins, maleate oils or polybutadiene oils with a weight average molecular weight (Mw) of, for example, 300 to 10,000 and an acid number of 35 to 300 mg KOH / g. The binders carry -COOH, -SO ₃ H and / or -PO ₃ H ₂ groups. After neutralization of at least some of the acidic groups, the resins can be converted into the water phase. The binders can be self-crosslinking or externally crosslinking. The lacquers can therefore also contain customary crosslinking agents, for example triazine resins, crosslinking agents which contain groups capable of transesterification or blocked polyisocyanates.

It is preferred in the process according to the invention to use an ATL coating agent as the ETL coating agent to use, especially when realizing the particular preferred and independent embodiment of the present invention, in which the color and / or effect basecoat as a second coating layer is deposited electrophoretically.

In addition to the base resins and any crosslinking agents present, the ETL coating agents contain pigments, fillers and / or additives common in paint. The usual inorganic and / or organic colored pigments and / or effect pigments and / or fillers in question. As Pigments come, for example, the usual inorganic and / or organic Colored pigments and / or effect pigments, such as Titanium dioxide, iron oxide pigments, Carbon black, phthalocyanine pigments, quinacridone pigments, metal pigments, e.g. made of titanium, Aluminum or copper, interference pigments, e.g. coated with titanium dioxide Aluminum, coated mica, graphite effect pigments, flaky Iron oxide or platelet-shaped copper phthalocyanine pigments in question. examples for Fillers are kaolin, talc or silicon dioxide.

The pigments can be dispersed into pigment pastes, e.g. under use of known paste resins. It is particularly so in the case of ATL coating agents possible to use pigment pastes, such as those known to those skilled in the art Manufacture of two-coat basecoat / clearcoat type suitable water-based paints that can be applied by spraying can be used. such Pigment pastes can be obtained by rubbing the pigments in one special water-thinnable paste resin.

The usual additives are possible as additives, such as for ETL coating agents in particular are known. Examples include wetting agents, neutralizing agents, Leveling agents, catalysts, corrosion inhibitors, anti-foaming agents, solvents, in particular, however, light stabilizers, if appropriate in combination with Antioxidants.

In the method according to the invention, if a Intermediate layer was applied for the generation of the third coating layer known, e.g. color and / or effect that can be applied by spraying Basecoat coating agents are used as they are used for the production of Basecoat / clearcoat two-coat paints are used and in large numbers are known for example from the patent literature.

Those for the production of the third coating layer in the process according to the invention Usable basecoats can be physically drying or with training covalent bonds can be crosslinked. For those under training covalent Binding-crosslinking basecoats can be self- or externally crosslinking Act systems.

Those in the method according to the invention for producing the third coating layer usable color and / or effect basecoats are preferably liquid Coating agent. It can be a one- or multi-component coating agent act, one-component are preferred. It can be systems based act organic solvents or are preferably water-based paints, their binder systems in a suitable manner, e.g. anionic, cationic or non-ionic are stabilized.

In the process according to the invention for the production of the third The basecoat coating agents that can be used are conventional Coating systems that use one or more common base resins as film-forming binders contain. You can, if the base resins are not self-crosslinking or self-drying are, if appropriate, also contain crosslinkers. Both the base resin component and the crosslinker component is also not subject to any restrictions. As a film maker Binders can for example be polyester, polyurethane and / or (Meth) acrylic copolymer resins can be used. In the case of the preferred Waterborne basecoats are preferably polyurethane resins, particularly preferred at least in a proportion of 15 wt .-%, based on the solid resin content of the Water-based paint. The selection of the crosslinkers that may be included not critical, it depends on the functionality of the base resins, i.e. the crosslinker are selected so that they are complementary to the functionality of the base resins, have reactive functionality. Examples of such complementary. Functionalities between base resin and crosslinker are: hydroxyl / methylol ether, Hydroxyl / Free Isocyanate, Hydroxyl / Blocked Isocyanate, Carboxyl / Epoxy. Provided compatible with each other, several such complementary Functionalities are present in a basecoat next to each other. The possibly in The crosslinkers used in the basecoats can be present individually or in a mixture.

The method according to the invention for generating the third The basecoats used in the coating layer contain the usual physical ones drying and / or chemically crosslinking binders inorganic and / or organic colored pigments and / or effect pigments, such as e.g. titanium dioxide, Iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, Quinacridone pigments, metal pigments, e.g. made of titanium, aluminum or copper, Interference pigments, e.g. Titanium dioxide coated aluminum, coated Mica, graphite effect pigments, platelet-shaped iron oxide or platelet-shaped Copper phthalocyanine pigments.

Furthermore, those used for the production of the third coating layer Basecoats contain paint additives, e.g. Fillers, catalysts, Leveling agents, anti-cratering agents or, in particular, light stabilizers, if appropriate Combination with antioxidants.

The color and / or the preferably applied by spraying as the third coating layer effect basecoat can exist as a two-layer basecoat system from a first, modified basecoat and a second, the actual Color of the basecoat layer determining the multilayer coating can be applied. The first basecoat is modified, for example by adding additional contains modifying binder components or filler components. He can for example, from the actual color applied afterwards determining basecoat are made by mixing with the additional Components.

n ≤ 90 im mit ΔE* = 0,3 gekennzeichneten Bereich des CIE-x,y-Diagramms,

n ≤ 50 im mit ΔE* = 0,5 gekennzeichneten Bereich des CIE-x,y-Diagramms,

n ≤ 40 im mit ΔE* = 0,7 gekennzeichneten Bereich des CIE-x,y-Diagramms,

n ≤ 30 im mit ΔE* = 0,9 gekennzeichneten Bereich des CIE-x,y-Diagramms.

It is preferred if the electrocoat used to produce the second coating layer, which is the intermediate layer, has a color tone which is close to or identical to that of the basecoat used to produce the third coating layer. In the context of the present invention, it is preferred to understand each other as closely as possible color tones that the difference in color, consisting of brightness difference, color tone difference and color difference, between the respective color tones of the second and third coating layers determined with opaque coating and a measurement geometry of (45/0) is an n -fold ΔE * (CIELAB) value does not exceed, the ΔE * (CIELAB) reference value being that which is found in the CIE-x, y diagram (chromaticity diagram) familiar to the person skilled in the art, based on DIN 6175, for the hue of third coating layer and the following relationship applies:

n ≤ 90 in the area of the CIE x, y diagram marked with ΔE * = 0.3,

n ≤ 50 in the area of the CIE x, y diagram marked with ΔE * = 0.5,

n ≤ 40 in the area of the CIE x, y diagram marked with ΔE * = 0.7,

n ≤ 30 in the area of the CIE x, y diagram marked ΔE * = 0.9.

As a clear lacquer coating agent for the production of the fourth and possibly further Coating layers or in the case of the particularly preferred and independent Embodiment of the present invention for the generation of the third and if necessary, further coating layers are basically all the usual clearcoats or transparent colored or colorless pigmented coating agent. there it can be a one- or multi-component clear lacquer coating agent. she can be solvent-free (liquid or as a powder clear coat), or it can be Act systems based on solvents or are water-borne clear varnishes, the binder systems of which are suitable, e.g. are anionically, cationically or non-ionically stabilized. With the water-dilutable Clear lacquer systems can be water-soluble or water-dispersed Systems, for example emulsion systems or powder slurry systems. The Clear lacquer coating agents harden more covalently when stoved to form Bonds due to chemical crosslinking.

The clear lacquers which can be used in the process according to the invention are to conventional clear lacquer coating compositions which are one or more conventional base resins contain film-forming binders. You can if the base resins don't are self-crosslinking, optionally also contain crosslinkers. Both the The base resin component and the crosslinker component are not subject to anything Restriction. As film-forming binders (base resins), for example Polyester, polyurethane and / or (meth) acrylic copolymer resins can be used.

The selection of the crosslinking agents which may be present is not critical, it is directed according to the functionality of the base resins, i.e. the crosslinkers are selected so that they are a reactive functionality that is complementary to the functionality of the base resins exhibit. Examples of such complementary functionalities between base resin and crosslinkers are: carboxyl / epoxy, hydroxyl / methylol ether, hydroxyl / free Isocyanate, hydroxyl / blocked isocyanate, (meth) acrylolyl / CH-acidic group. Provided compatible with each other, several such complementary Functionalities are present side by side in a clear coat. The possibly in the crosslinkers used in the clearcoats can be present individually or in a mixture.

In addition to the chemically crosslinking binders and optionally crosslinkers the clear lacquers which can be used in the process according to the invention can be customary lacquers Additives such as Catalysts, leveling agents, dyes, but especially Rheology controllers, such as microgels, NAD (= non-aqueous dispersions), disubstituted Urea ("sagging control agents") and light stabilizers if necessary in Combined with antioxidants.

The transparent coating can be in a single layer or in the form of several Layers of the same or several different transparent Coating agents are applied. The transparent one is useful However, coating layer as fourth layer or in the case of the particularly preferred and independent embodiment of the present invention as a third layer applied only a clear coat. Those are preferred Clear coating agents used that have the lowest possible tendency to run off, for example, high-solids clearcoats with a correspondingly adjusted rheological behavior. Powder clearcoats are particularly preferred.

Metal sheets rolled up into coils are used as substrates for the process according to the invention, for example with a sheet thickness of 0.7 to 1.3 mm typical for body construction, for example made of iron, zinc, aluminum or corresponding alloys. Galvanized sheet metal, for example galvanized steel sheet, is preferred. The metal surfaces can be pretreated, for example provided with phosphating and optionally passivation. The metal surfaces can have the roughness with average roughness values (R _a values, cf. DIN / EN 10130) that are customary in the state of the art for shaping using deep-drawing aids, for example from 0.6 to 1.8 μm. In the process according to the invention, however, it is preferred to use metal sheets with lower surface roughnesses with R _a values below 0.6 μm, for example from 0.15 to 0.6 μm, which have hitherto been unusual in automobile construction. An artificial roughening of the metal sheet surface is not necessary.

The first coating layer, namely the primer, is placed on these substrates. on both sides from the primer coating agent in the coil coating process rolled on. Does the primer coating contain no electrical conductivity mediating components, it is applied in a dry layer thickness, the one for electrophoretic deposition one another coating layer made of an electrophoretically depositable coating agent ensures sufficient electrical conductivity, for example in a Dry layer thickness from 1 to 3 µm. However, if it is one of the im preferred primer coating composition according to the invention, which is the first coating layer in the baked state one for electrophoretic Deposition of a further coating layer from an electrophoretic depositable coating agent sufficiently low specific resistance contains imparting electrical conductivity imparting components, so that Primer coating agent in a dry layer thickness of, for example, 2 to 15 µm, preferably applied from 3 to 10 µm. Branding the Primer coating layer takes place briefly at high temperatures, for example within 30 to 60 seconds, for example in a 300 to 370 ° C are called convection ovens, whereby maximum object temperatures (PMT, peak metal temperature) between 200 and 260 ° C.

From the metal coil provided with the burned-in primer layer on both sides sheet metal parts with the desired shape are now punched out and in the usual manner then deformed in the deep-drawing process. The deformed parts can then if necessary together with components made of other materials Construction, in particular a body to be put together, for example by gluing and / or clinching and / or screwing and / or preferably welding. Components made of other materials can be, for example otherwise act on pre-coated or uncoated metals or plastics, preferred are components with electrically conductive and electrophoretic coatable surface.

The second coating layer made of an electrophoretically depositable coating agent is applied to the substrate thus obtained, which preferably has a resistivity of generally less than 10 ⁸ ohm.cm, in particular 10 ³ to 10 ⁸ ohm.cm, and in particular at elevated temperatures, for example baked between 130 and 180 ° C. If the second coating layer from the electrophoretically depositable coating agent is applied as an intermediate layer, this is preferably done in dry layer thicknesses of, for example, 5 to 40 μm, particularly preferably from 10 to 30 μm, while the application as a color and / or effect-imparting base lacquer layer, preferably in a color tone dependent dry layer thickness of, for example, 10 to 50 microns, particularly preferably from 15 to 40 microns. The second coating layer generally has practically no electrical conductivity, ie it has a specific resistance of more than 10 ⁹ ohm.cm in the baked state. In the case of the particularly preferred and independent embodiment of the present invention, it is a color and / or effect basecoat layer.

The one obtained by electrodeposition and electric in the burned-in state insulating coating can, but does not have to cover the entire surface of the extend three-dimensional substrate. So it is for example in the invention Preferred method (especially for the particularly preferred and independent Embodiment of the present invention, in which the color and / or Effect basecoat layer from an electrophoretically separable Coating agent is applied) an entire first coating by application a primer from the primer coating agent and a second coating from the ETL coating material essentially only on outer areas, especially on visible surfaces of a three-dimensional substrate, i.e. for example, not in narrow cavities in a body.

Then the order, preferably a spray order, is applied to the third Coating layer, for example from a color and / or effect basecoat or in the case of the particularly preferred and independent embodiment of the present invention from a clear lacquer coating composition.

A spray application of the third coating layer from the color and / or effect Basecoat is applied, for example, in a dry film thickness depending on the color from 10 to 25 µm, for example by compressed air spraying, airless spraying or ESTA high-speed rotation spraying.

Following the application of a third, color and / or effect Basecoat top coat is applied, for example, after a short flash-off phase, e.g. at 20 to 80 ° C, the application of the clearcoat, preferably in the wet-on-wet process. The fourth coating layer is made from a conventional liquid paint or powder clear coat (in this case it is a dry-on-wet application) applied and together with the third coating layer at elevated temperatures, for example baked from 80 to 160 ° C. If necessary, further layers of clear lacquer can be used the same or different clear coat coating agents are applied. According to the invention, work is carried out so that the layer thickness of the transparent Coating layer or the total layer thickness of the transparent coating layers 30 to 80 microns, preferably 40 to 60 microns.

It is also possible, if not preferred, to give the color and / or effect Basecoat layer in the wet-on-wet process on the non-baked second Apply coating layer and the two coating layers together before Burn in the application of the transparent coating layer or coating layers.

In the case of the particularly preferred and independent embodiment of the The inventive method, the clearcoat is applied to the second, the preferably burned-in color and / or effect-giving ETL coating layer. As The clear lacquer coating layer becomes a conventional liquid clear lacquer or a powder clear lacquer applied and baked, for example, at temperatures of 80 to 160 ° C. If necessary, further layers of clear lacquer from the same or from it various clear lacquer coating agents can be applied. According to the invention worked that the layer thickness of the transparent coating layer or Total layer thickness of several transparent coating layers at 30 to 80 µm, is particularly preferably 40 to 60 μm.

That applied as a third coating layer, preferably by spray application Basecoat and preferably by spray application as the fourth or in the case of particularly preferred and independent embodiment of the invention as a third Coating layer applied clear coat may, but need not extend all over the three-dimensional substrate. So it is in The inventive method preferably the third and / or fourth coating layer in the essential only on outer areas, especially on visible surfaces of a three-dimensional substrate, i.e. for example not in narrow Cavities in a body.

(1) Blech mit R_a-Wert zwischen 0,6 und 1,8 µm/1 bis 3 µm dicke Grundierungsschicht ohne elektrische Leitfähigkeit vermittelnde Bestandteile/Elektrotauchlackschicht/spritzapplizierte Basislackschicht/Klarlackschicht

(2) Blech mit R_a-Wert zwischen 0,6 und 1,8 µm/2 bis 15 µm dicke Grundierungsschicht mit elektrische Leitfähigkeit vermittelnden Bestandteilen/Elektrotauchlackschicht/spritzapplizierte Basislackschicht/Klarlackschicht

(3) Blech mit R_a-Wert kleiner 0,6 µm/1 bis 3 µm dicke Grundierungsschicht ohne elektrische Leitfähigkeit vermittelnde Bestandteile/Elektrotauchlackschicht/spritzapplizierte Basislackschicht/Klarlackschicht

(4) Blech mit R_a-Wert kleiner 0,6 µm/2 bis 15 µm dicke Grundierungsschicht mit elektrische Leitfähigkeit vermittelnden Bestandteilen/Elektrotauchlackschicht/spritzapplizierte Basislackschicht/Klarlackschicht

(5) Blech mit R_a-Wert zwischen 0,6 und 1,8 µm/l bis 3 µm dicke Grundierungsschicht ohne elektrische Leitfähigkeit vermittelnde Bestandteile/elektrophoretisch applizierte Basislackschicht/Klarlackschicht

(6) Blech mit R_a-Wert zwischen 0,6 und 1,8 µm/2 bis 15 µm dicke Grundierungsschicht mit elektrische Leitfähigkeit vermittelnden Bestandteilen/elektrophoretisch applizierte Basislackschicht/Klarlackschicht

(7) Blech mit R_a-Wert kleiner 0,6 µm/1 bis 3 µm dicke Grundierungsschicht ohne elektrische Leitfähigkeit vermittelnde Bestandteile/elektrophoretisch applizierte Basislackschicht/Klarlackschicht

(8) Blech mit R_a-Wert kleiner 0,6 µm/2 bis 15 µm dicke Grundierungsschicht mit elektrische Leitfähigkeit vermittelnden Bestandteilen/elektrophoretisch applizierte Basislackschicht/Klarlackschicht

In the following, examples of automobile bodies painted in multiple layers or parts thereof, which can be produced by the method according to the invention, are given in ascending order with regard to their preferred construction. Variant (8) represents the cheapest variant of variants (1) - (8). The statements made above apply with regard to the electrocoat, basecoat and clearcoat layers.

(1) Sheet with an R _a value between 0.6 and 1.8 µm / 1 to 3 µm thick primer layer without constituents imparting electrical conductivity / electrocoat layer / spray-applied basecoat layer / clearcoat layer

(2) Sheet with R _a value between 0.6 and 1.8 µm / 2 to 15 µm thick primer layer with components that impart electrical conductivity / electrocoat layer / spray-applied basecoat layer / clearcoat layer

(3) Sheet with an R _a value of less than 0.6 µm / 1 to 3 µm thick primer layer without constituents imparting electrical conductivity / electrocoat layer / spray-applied basecoat layer / clearcoat layer

(4) Sheet with an R _a value of less than 0.6 µm / 2 to 15 µm thick primer layer with components that impart electrical conductivity / electrocoat layer / spray-applied basecoat layer / clearcoat layer

(5) Sheet with R _a value between 0.6 and 1.8 µm / l to 3 µm thick primer layer without constituents imparting electrical conductivity / electrophoretically applied basecoat / clearcoat

(6) Sheet with R _a value between 0.6 and 1.8 µm / 2 to 15 µm thick primer layer with components that impart electrical conductivity / electrophoretically applied basecoat / clearcoat

(7) Sheet with an R _a value of less than 0.6 µm / 1 to 3 µm thick primer layer without constituents imparting electrical conductivity / electrophoretically applied basecoat / clearcoat

(8) Sheet with an R _a value of less than 0.6 µm / 2 to 15 µm thick primer layer with components that impart electrical conductivity / electrophoretically applied basecoat / clearcoat

In the case of the process according to the invention with a multi-layer coating provided substrates are preferably automobile bodies or parts from that. However, it can also be other industrial goods such as Household appliance housings, facade parts, automotive parts.

By measuring the gloss and determining the long- and short-wave portions of the Surface structure of the outer clear lacquer surfaces from after Automobile parts and bodies produced according to the method was found that the inventive method compared to the production of to the prior art in a reduced overall layer thickness multi-layer lacquered Automobile parts or bodies allowed, the multi-coat paint one good gloss that meets the requirements of automotive OEM painting and have a topcoat. Analogously, it was found that the Process according to the invention preferably for the production of automotive parts or bodies can be used, the multi-layer paintwork one outstanding, improved gloss and topcoat level, even if the State-of-the-art conventional total layer thicknesses adhered to and not be crossed, be exceeded, be passed. Those produced by the process according to the invention Motor vehicle parts or bodies have multi-layer paintwork with Comparable to the state of the art comparable overall property level. The method according to the invention can be used separately Thermoforming aids and cleaning them when shaping the Sheet metal parts can be avoided.

Claims (8)

1. Method of producing a multi-layer lacquer coating, in which a primer layer is applied from a coating composition to a metal sheet and is then stoved, a colour- and/or effect-giving base lacquer layer is applied from a coating composition and is provided with one or more clear lacquer coatings, there being produced a multi-layer lacquer coating having an overall dry layer thickness of from 70 to 130 µm, wherein

   a) an intermediate layer is optionally applied between application of the primer layer and application of the base lacquer layer, and

   c) the clear lacquer layer or the clear lacquer layers is/are applied in an overall dry layer thickness of from 30 to 80 µm,
   which method is characterised in that a coil of sheet metal is used as the metal sheet and the primer layer is applied by rolling to both sides by the coil coating method and, following stoving, sheet metal parts are punched out of the coil and are formed by the deep-drawing method, and a plurality of such sheet metal parts are optionally combined to form an assembly, to which the base lacquer layer or the intermediate layer is applied, and wherein

   b) the intermediate layer or, if no intermediate layer is applied, the base lacquer layer is applied from an electrophoretically depositable coating composition by electrophoretic deposition.
2. Method according to claim 1, characterised in that the colour- and/or effect-giving base lacquer layer is applied directly as the second coating layer, without the previous application of an intermediate layer, by electrophoretic deposition from an electrophoretically depositable coating composition.
3. Method according to claim 1 or 2, characterised in that the clear lacquer layer or the clear lacquer layers is/are applied in an overall dry layer thickness of from 40 to 60 µm.
4. Method according to claim 1, 2 or 3, characterised in that the multi-layer lacquer coating is applied in an overall dry layer thickness of less than 110 µm.
5. Method according to any one of the preceding claims, characterised in that it is carried out for the lacquering of motor vehicle bodies or motor vehicle body parts.
6. Method according to any one of the preceding claims, characterised in that a coating composition having constituents imparting electrical conductivity is used as the coating composition for producing the primer layer.
7. Method according to any one of the preceding claims, characterised in that an anodically depositable electro-dipcoating lacquer is used as the coating composition for producing the second coating layer.
8. Method according to any one of the preceding claims, characterised in that sheet metal coils having a surface roughness with R_a values of less than 0.6 µm are used.