EP1009546B1 - Substrate having a multilayer coat and method for its production - Google Patents

Abstract

The invention relates to a substrate having a multilayer coat and a method for its production, comprising the following stages: The car body which is to be coated is delivered to the pre-processing stage (2) via the intake (1). This is followed by electrophoretic enamelling (3) and burning in of the electrophoretic enamel coating. In stage (5), preparation takes place for coating with coating powder (stage 6). Stage (7) consists of drying with infrared radiation. This is followed by the cooling stage (8). In stage (9), the coating powder is applied to the substrate so as to form a coat. After intermediate drying (10), a protective layer is applied in stage (11) and then burnt in (stage 12). The car body is then conveyed from the installation via the exit (13).

Description

The invention relates to a provided with a multilayer coating Substrate, the multilayer coating a filler layer, a coloring and / or effect decorative layer and a Has protective layer, the filler layer closest to the substrate and the protective layer is arranged on the substrate most distant, whereby for the Decorative layer a decorative lacquer with a binder from the group "Acrylate resins containing carboxyl, epoxy and / or hydroxyl groups Binder "or mixtures thereof and with a crosslinker from the Group "isocyanates, aminoplast resins or TACT" or mixtures is used and a protective varnish is used for the protective layer the group "one-component clearcoats, two-component clearcoats, Powder clearcoats "is used, as well as a method for producing a such a substrate provided with a multilayer coating.

A filler layer is made from a so-called filler. On Filler is a lacquer at its core, but it has special properties and is applied with a comparatively high layer thickness. The The function of a filler layer is to compensate for annoying unevenness (in the micrometer range) on the surface of a substrate, so that the Do not pre-treat the surface of the substrate with a leveling agent the coating needs to be subjected to a coating. The above-mentioned also serves this purpose. comparatively high layer thickness of the filler. The application can be made directly to the material of the substrate take place or with the interposition of a primer and / or one Adhesion promoter. In the former case it is advisable to apply the filler on a metallic Material to use a filler with corrosion protection. at technologically obsolete fillers it was necessary after order and drying or curing the filler, the filler layer obtained undergo leveling surface treatment, for example grinding. This made use of the fact that a filler layer is usually less hard and / or better to process than the material of the substrate. modern In contrast, fillers have a self-regulating function. This means that after application of the filler to a substrate with surface defects and Drying or (pre-) crosslinking of the filler without further measures Filler layer is created, the outer surface of which is also in the micrometer range is practically flat. In other words, a filler layer is created! whose interface facing the substrate is a complement to the surface of the substrate, based on surface structures in the micrometer range, forms. A decorative layer is formed from a decorative lacquer. A decorative paint in addition to customary paint binders and crosslinkers coloring and / or effect pigments. Examples of effects Pigments are metallic pigments and mica pigments. The decorative layer is in essentially responsible for the visual impression of the with the Multilayer coated substrate on a viewer. A The protective layer is usually formed from a clear lacquer. The Clear varnish has special properties regarding its behavior mechanical stress, chemical stress and light resistance and its transmission behavior, since the protective layer of Is exposed to the environment and in particular to protect the decorative layer. Multi-layer coatings of the type described are used in particular Coating of car bodies or parts thereof from sheet steel or Aluminum sheet used, but also for coating in the automotive sector used plastic moldings.

From the literature FR 2 511 617 it is known to follow Apply layers on a primer or filler layer and then then harden the multilayer coating thus formed. This The procedure is referred to as "wet on wet" technology. Both in so far known methods is used as part of the priming or Filler layer with a usual aqueous primer or filler lacquer worked. However, it has been shown that from certain Coating thicknesses (those for leveling substrate defects become necessary if you want to work without intermediate sanding) Matting and course disorders occur.

A substrate provided with a multilayer coating or a method for its production of the type mentioned at the outset is known from references WO-A-96/38 234 and EP 0 238 037 B1. From the first-mentioned document, a method is known in which a primer and a basecoat are each applied and baked by electrophoresis, followed by a clearcoat. In EP 0 238 037 B1, an electro-dip coating is used for the primer or filler layer. This electrocoat is first baked. The decorative layer and the protective layer are then applied “wet on wet”, it being possible for the paints used for this to be aqueous paints. In particular in the case of decorative layers made of an effect lacquer, it has been shown according to this reference that a separating layer must be interposed between the primer or filler layer, so that the lacquer effect in the finished product meets the visual requirements. The requirement of a separating layer interferes because of the expense. For reasons of energy consumption, the separate baking process step required for the primer or filler layer interferes. In addition, satisfactory results can only be achieved if the separating layer is based on organic solvents. This is disturbing for environmental reasons. If an aqueous lacquer is used for the separating layer, it is also disadvantageous that rapid drying of the separating layer before the subsequent layers are applied cannot be readily achieved. As a result, the effort or the production time is increased to a disruptive degree.

In contrast, the invention is based on the technical problem with a multilayer coating provided with can be produced with little effort and unproblematic environmental behavior or to specify a process for its production.

To solve this technical problem, the invention according to claim 1 teaches that the Filler layer is formed from a pre-crosslinkable powder coating, the burned-in filler layer made of powder coating a layer thickness in the range of 30 microns to 250 µm.

Advantageous developments of the invention according to Claim 1 are the subject of the dependent claims 2 to 6.

The particular advantages of using one Powder coatings for the production of a filler layer include that it is without Solvent gets along, and that those that occur with conventional fillers Losses due to overspray can be avoided, as the non-stick powder coating can be almost completely recycled. For the application of the Powder coatings come with all current methods according to the state of the art Technology in question. Application by is particularly preferred electrostatic adhesion, preferably by applying one High voltage or by friction charging.

The coating of fabrics with powder coatings is a common practice Method. Here, the powdery dry paint is evenly applied applied the substrate to be coated, and then by Heating the substrate melted and baked the paint. in the Within the scope of the invention, however, the powder coating is different from this usual procedure, first pre-cross-linked by heating and only then baked together with the subsequent applied layers. Thus, a separate baking process step for the Filler layer dispenses with the prior art. Instead all layers of paint are baked in one step, which surprisingly meets all requirements Multi-layer coating results. This is a significant step Simplification of the coating process. By omitting one Intermediate stoving both reduce the investment also operating costs. It only needs a single baking oven Be made available and operated. This also happens saving heating energy. In addition, the entire Processing time for the coating process is shorter, so that the Plant productivity is increased.

All known paint formulations are suitable for the powder paint, e.g. those described in EP-509 392, EP-509 393, EP-322 827, EP-517 536, U.S. 5,055,524 and U.S. 4,849,283. In particular, can the powder coating consist of epoxy resins, hybrid systems with Polyester resin, including epoxidized novolaks, from cross-linking agents, preferably phenolic or amine hardeners or bicyclic Guanidines, catalysts, fillers and, if necessary, auxiliaries and additives.

The powder coatings used according to the invention preferably contain Epoxy resins, phenolic crosslinking agents, catalysts, auxiliaries as well as auxiliaries and typical powder additives, flow aids. suitable Epoxy resins are all solid epoxy resins with one Epoxy equivalent weight between 400 and 3,000, preferably 600 to 2000. These are mainly epoxy resins based on Bisphenol A and Bisphenol F. Preoxidized are preferred Novolak. These preferably have an epoxy equivalent weight from 500 to 1,000.

The epoxy resins based on bisphenol A and bisphenol F have in generally a functionality of less than 2 that epoxidized Novolac resins have a functionality greater than 2. Particularly preferred are epoxidized in the powder coatings used according to the invention Novolac resins with an average functionality in the range from 2.4 to 2.8 and with an epoxy equivalent weight in the range of 600 to 850. In the epoxidized novolac resins, the phenolic Hydroxyl groups etherified with alkyl, acrylic or similar groups. By reacting the phenolic hydroxyl groups with epichlorohydrides epoxy groups are introduced into the molecule. Starting from Novolaks form the so-called epoxy novolac. The epoxidized Novolaks are structurally related to bisphenol A resins. epoxidized Novolak resins can be made by epoxidizing novolaks, e.g. from 3 to 4 phenol cores, which are linked by methylene bridges are connected. Novolac resins can also alkyl-substituted phenols, which are reacted with formaldehyde, be used.

Suitable epoxy resins are, for example, those under the following names Commercially available products: Epikote 1004, 1055, 3003, 3004, 2017 der Shell-Chemie, DER 640, 671, 662, 663U, 664, 667 from Dow and Araldit GT 6063, 6064, 6084, 6097, 7004, 7220, 7225 from the company Ciba Geigy.

Examples of epoxy functional binders for powder coatings include Suitable polyacrylate resins containing epoxy groups, which by Copolymerization of at least one ethylenically unsaturated Monomer containing at least one epoxy group in the molecule with at least one other ethylenically unsaturated monomer that does not Contains epoxy group in the molecule can be produced, at least one the monomer is an ester of acrylic acid or methacrylic acid.

Polyacrylate resins containing epoxy groups are known (cf. e.g. EP-A-299420, DE-B-22 14 650, DE-B-27 49 576, US-A-4,091,048 and US-A-3,781,379).

As examples of the ethylenically unsaturated monomers that are at least contain an epoxy group in the molecule, glycidyl acrylate, Glycidyl methacrylate and allyl glycidyl ether called.

As examples of ethylenically unsaturated monomers that do not Epoxy group contained in the molecule, alkyl esters of acrylic and Methacrylic acid, which contain 1 to 20 carbon atoms in the alkyl radical, especially methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, butyl acrylate, butyl methyl acrylate, 2-ethylhexyl acrylate and Called 2-ethylhexyl methacrylate. More examples of ethylenic unsaturated monomers that do not contain epoxy groups in the molecule, are acids, e.g. Acrylic acid and methacrylic acid. Acid amides, like e.g. Acrylic acid and methacrylic acid amide, vinyl aromatic compounds, such as styrene, methyl styrene and vinyl toluene, nitriles such as acrylonitrile and Methacrylonitrile, vinyl and vinylidene halides such as vinyl chloride and Vinylidene fluoride, vinyl esters, such as e.g. Vinyl acetate and hydroxyl groups Monomers such as Hydroxyethyl acrylate and Hydroxyethyl methacrylate.

The epoxy group-containing polyacrylate resin usually has Epoxy equivalent weight of 400 to 2,500, preferably 500 to 1,500, particularly preferably 600 to 1,200, a number average molecular weight (Gel permeation chromatography using a Polystyrene standards determined) from 1,000 to 15,000, preferably from 1,200 to 7,000, particularly preferably from 1,500 to 5,000 and one Glass transition temperature (TG) from 30 to 80, preferably from 40 to 70, particularly preferably from 50 to 70 ° C (measured using the differential scanning calometry (DSC)).

The epoxy group-containing polyacrylate resin is generally good known methods prepared by radical polymerization become.

Are suitable as hardeners for the epoxy group-containing polyacrylate resin for example polyanhydrides of polycarboxylic acids or of Mixtures of polycarboxylic acids, especially polyanhydrides from Dicarboxylic acids or mixtures of dicarboxylic acids.

Such polyanhydrides can be produced by the polycarboxylic acid or water is withdrawn from the mixture of polycarboxylic acids, in each case two carboxyl groups are converted to an anhydride group. Such manufacturing processes are well known and therefore need not to be explained in more detail.

To cure the epoxy resins it contains according to the invention powder coating used phenolic or amine hardener. For use bicyclic guanidines can also come.

Any phenolic resin can be used, for example, as long as it has the methylol functionality required for reactivity having. Preferred phenolic resins are under alkaline conditions reaction products of phenol, substituted phenols and Bisphenol A with formaldehyde. Under such conditions, the Methylol group either ortho or para to the aromatic Ring linked. Phenolic crosslinking agents are particularly preferred bisphenol A or bisphenol F resins containing hydroxyl groups with a hydroxy equivalent weight in the range of 180 to 600, particularly preferably used in the range from 180 to 300. such phenolic crosslinking agents are made by reacting Bisphenol-A or bisphenol-F with components containing glycidyl groups, such as. the diglycidyl ether of bisphenol-A. Such phenolic Crosslinking agents are available, for example, under the Trade name DEH 81, DEH 82 and DEH 87 from Dow DX 171 from Shell-Chemie and XB 3082 from Ciba Geigy.

The epoxy resins and the phenolic crosslinking agents are in such a ratio that the number of epoxy groups the number of phenolic OH groups is approximately 1: 1.

Such powder coatings used according to the invention contain one or several suitable catalysts for epoxy resin curing. Suitable catalysts are phosphonium salts organic or inorganic acids, imidazole and imidazole derivatives, quaternary Ammonium compounds and amines. The catalysts are in the generally in proportions of from 0.001% to about 10% by weight on the total weight of the epoxy resin and the phenolic Crosslinking agent used.

Examples of suitable phosphonium salt catalysts are Ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium chloride, Ethyltriphenylphosphonium thiocyanate, ethyltriphenylphosphonium acetate-acetic acid complex, tetrabutylphosphonium Tetrabutylphosphonium bromide and tetrabutylphosphonium acetate-acetic acid complex. This and other suitable phosphonium Catalysts are e.g. described in U.S. Patent 3,477,990 and U.S. Patent 3,341,580.

Suitable imidazole catalysts are, for example, 2-styrylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole and 2-butylimidazole. This and further imidazole catalysts are e.g. described in the Belgian Patent No. 756,693.

Some of the commercially available phenolic crosslinking agents already contain Catalysts for epoxy resin crosslinking.

Powder coatings based on polyesters containing carboxyl groups and Low molecular weight crosslinking agents containing epoxy groups are in a large number are known and are described, for example, in EP-A-389 926, EP-A-371 522, EP-A-326 230, EP-B-110 450, EP-A-110 451, EP-B-107 888, US 4,340,698, EP-B-119 164, WO 87/02043 and EP-B-10 805.

Powder coatings according to DE are also particularly suitable 43 30 404.4 A1, which are characterized in that they are as film-forming material A) 35.0-92.2% by weight of carboxyl groups containing polyesters with an acid number of 10-150 mg KOH / g, B) 0.8 20.1% by weight of low molecular weight epoxy groups Hardening agents, C) 3.7-49.3% by weight containing epoxy groups Polyacrylate resins with an epoxy equivalent weight of 350 - 2000 and D) 0.5 -13.6% by weight of low molecular weight di- and / or polycarboxylic acids and / or di- and / or polyanhydrides, the sum of Parts by weight of A), B), C) and D) each 100% by weight and that Ratio of the epoxy groups of the powder coatings to the sum of the Carboxyl and anhydride groups of the powder coatings is 0.75 - 1.25: 1.

The carboxyl groups used as component A) Polyesters have an acid number in the range of 10-150 mg KOH / g, preferably in the range of 30-100 mg KOH / g. The hydroxyl number of the Polyester resins should be <30 mg KOH / g. To be favoured Polyester with a carboxy functionality of> 2 used. The Polyesters are made according to the usual methods (compare e.g. Houben Weyl, Methods of Organic Chemistry, 4th Edition, Volume 14/2. Georg Thieme Verlag, Stuttgart 1961).

As the carboxylic acid component for the production of the polyester aliphatic, cycloaliphatic and aromatic di- and polycarboxylic acids suitable, e.g. Phthalic acid, terephthalic acid, isophthalic acid, Trimellitic acid, pyromellitic acid, adipic acid, succinic acid, glutaric acid, Pimelic acid, suberic acid, cyclohexanedicarboxylic acid, acelaic acid, Sebacic acid and the like These acids can also be in the form of their derivatives capable of esterification (e.g. anhydrides) or their transesterifiable derivatives (e.g. dimethyl ester) are used.

As an alcohol component for the production of the carboxyl groups Containing polyesters A) are the commonly used diand / or Suitable polyols, e.g. Ethylene glycol, 1,2-propanediol and 1,3-propanediol, butanediols, diethylene glycol, triethylene glycol, Tetraethylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-dimethylolcyclohexane, Glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, Ditrimethylolpropane, dipentaerythritol, diglycerin and the like

The polyesters thus obtained can be used individually or as a mixture different polyester can be used. As component A) suitable polyesters generally have a Glass transition temperature above 30 ° C.

Examples of suitable commercially available polyesters are those under following brand names commercially available products: Crylcoat 314, 340, 344, 2680, 316, 2625, 320, 342 and 2532 from UCB, Drug bos, Belgium; Grilesta 7205, 7215, 72-06, 72-08, 72-13, 72-14, 73-72, 73-93 and 7401 from Ems-Chemie; Neocrest P670, P671, P672, P678, P662 from ICI as well as Uralac P2400, Uralac P3400 and Uralac P5000 from DSM.

The acidic polyester component A) also includes unsaturated, Polyester resins containing carboxyl groups in question. These will obtained by polycondensation, for example of maleic acid, Fumaric acid or other aliphatic or cycloaliphatic Dicarboxylic acids with an ethylenically unsaturated double bond, optionally together with saturated polycarboxylic acids, as a polycarboxylic acid component. The unsaturated groups can also by the Alcohol component, e.g. by trimethylolpropane monoallyl ether, in the Polyester are introduced.

The powder coatings used according to the invention contain as Component B) 0.8-20.1% by weight of low molecular weight epoxy groups containing hardeners. An example of a particularly suitable one is a low molecular weight curing agent containing epoxy groups Triglycidyl isocyanurate (TGIC). TGIC is commercially available, for example, under the Description Araldit PT 810 (manufacturer: Ciba Geigy) available. Further suitable curing agents containing low molecular weight epoxy groups are 1,2,4-triglycidyltriazoline-3,5-dione, diglycidylphthalate and the diglycidyl ester of hexahydrophthalic acid.

Polyacrylate Resins Containing Epoxy Groups (Component C) are understood to be polymers which are obtained by copolymerization of at least an ethylenically unsaturated monomer containing at least one Contains epoxy group in the molecule, with at least one other ethylenically unsaturated monomer that does not contain an epoxy group, can be produced, at least one of the monomers being an ester of Is acrylic acid or methacrylic acid.

Polyacrylate resins containing epoxy groups are known (cf. e.g. EP-A-299 420. DE-B-22 14 650, US-A-4,091,048 and US-A-3,781,379).

As examples of ethylenically unsaturated monomers, the at least one Epoxy group in the molecule, glycidyl acrylate, Glycidyl methacrylate and allyl glycidyl ether called.

As examples of ethylenically unsaturated monomers that do not Epoxy group contained in the molecule, alkyl esters of acrylic and Methacrylic acid, which contain 1 to 20 carbon atoms in the alkyl radical, especially methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate and the corresponding methacrylates, 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate called. Other examples of ethylenically unsaturated Monomers that do not contain epoxy groups in the molecule are acids, such as. Acrylic acid and methacrylic acid, acid amides such as e.g. acrylic acid Methacrylic acid amide, vinyl aromatic compounds, such as styrene, Methyl styrene and vinyl toluene, nitriles such as acrylonitrile and methacrylonitrile, vinyl and Vinylidene halides, such as vinyl chloride and vinylidene fluoride, vinyl esters, such as. Vinyl acetate and vinyl propionate, and those containing hydroxyl groups Monomers such as Hydroxyethyl acrylate and hydroxyethyl methacrylate.

The polyacrylate resin (component C) containing epoxy groups has an epoxy equivalent weight of 350 to 2000. The polyacrylate resins containing epoxy groups usually have a number average molecular weight (determined by gel permeation chromatography using a polystyrene standard) from 1000 to 15000 and a glass transition temperature (T _G ) from 30 to 80 (measured using differential scanning calorimetry (DSC)).

The acrylic resin containing epoxy groups is generally good known methods prepared by radical polymerization become. Such epoxy groups are commercially available Polyacrylate resins, for example, are available under the name Almatex PD 7610 and Almatex PD 7690 (manufacturer: Mitsui Toatsu).

Insofar used according to the invention as binders Powder coatings as component D) 0.5-13.6% by weight of low molecular weight diand / or Polycarboxylic acids and / or di- and / or polyanhydrides. Saturated, aliphatic and / or are preferred as component D) cycloaliphatic dicarboxylic acids used, e.g. glutaric, Adipic acid, pimelic acid, suberic acid, acelaic acid, cyclohexanedicarboxylic acid, Sebacic acid, malonic acid, dodecanedioic acid and Succinic acid. In addition, as component D) too aromatic di- and polycarboxylic acids, such as phthalic acid, Terephthalic acid, isophthalic acid, trimellitic acid and pyromellitic acid, of course also in the form of their anhydrides, insofar as they exist. Dodecanedioic acid (= 1.10-gdecanedicarboxylic acid) is particularly preferred as component D) used.

The amounts of the powder coating components A) to D) are such chosen that the ratio of the epoxy groups from B) and C) to the Sum of the carboxyl and anhydride groups from A) and D) 0.75-1.25: 1 is. This ratio is preferably 0.9-1.1: 1.

The powder coating material can contain 50 to 90%, preferably 60 to 80% by weight of binder and 10 to 50% by weight, preferably 20 to 40% by weight, of fillers. Glycidyl group-functionalized crystalline silica modifications are suitable as fillers. They are usually used in the range from 10 to 50% by weight, based on the total weight of the powder coating. In some cases, however, filler contents of more than 50% by weight are also possible. The crystalline silica modifications include quartz, cristobalite, tridymite, keatite, stishovite, melanophlogite, coesite and fibrous silica. The crystalline silica modifications are glycidyl group functionalized, the glycidyl group functionalization being achieved by a surface treatment. These are, for example, silica modifications based on quartz, cristobalite and fused silica, which are produced by treating the crystalline silica modifications with epoxysilanes. The glycidyl group-functionalized silica modifications are available on the market for example under the names Silbond ^R 600 EST and Silbond ^R 6000 EST (manufacturer: Quarzwerke GmbH) and are produced by reacting crystalline silica modifications with epoxysilanes. The powder coatings advantageously contain 10 to 40% by weight, based on the total weight of the powder coating, of glycidyl group-functionalized crystalline silica modifications.

The powder coating can also contain other inorganic fillers, for example Titanium oxide, barium sulfate and silicate-based fillers such as Talc, Contain kaolin, magnesium, aluminum silicate, mica and the like. In addition, the powder coatings can, if necessary, also auxiliaries and additives contain. Examples of these are leveling agents, pouring aids and Degassing agents such as benzoin.

The powder coatings are produced by known methods (cf. e.g. Product information from BASF Lacke + Farben AG, "Powder coatings", 1990) by homogenization and dispersion, for example by means of an extruder, screw kneader, etc. After The powder coating is produced by grinding and, if necessary, by Sifting and sieving set to the desired grain size distribution. To support non-destructive outgassing, the Powder coating can also be added to degassing agents, preferably Benzoylphenylmethanol (Benzoin®) in concentrations up to 2% by weight, preferably 0.4% by weight.

For the decorative layer, all common aqueous decorative lacquers are made from mentioned group usable. For this purpose, for example, on the References EP 89497 or EP 38127 referenced. As a crosslinker come isocyanates, aminoplast resins and / or TACT (Tris [alkoxycarbonylamino] triazines, in particular as in the literature reference US-5084541) into consideration.

A decorative lacquer is preferred which contains an aqueous polymer dispersion containing (i) an acrylate polymer based on 30 to 60% by weight of C ₁ -C ₈ -alkyl (meth) acrylate monomers, 30 to 60% by weight. % vinyl aromatic monomers and 0.5 to 10% by weight (meth) acrylic acid and (ii) a non-associative thickener which is an acrylate copolymer based on (C ₁ -C ₆ ) -alkyl (meth) acrylate and Contains (meth) acrylic acid.

The acrylate polymer of component (i) used can contain the linear and branched chain derivatives as C ₁ -C ₈ alkyl (meth) acrylate monomer units, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl and Isopropyl (meth) acrylate, n-butyl and isobutyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferred. (Meth) acrylamide monomers and their derivatives can also be present as further monomers.

As vinyl aromatic monomers, as monomer units in the acrylate polymer component (i) may e.g. Styrene, alkylstyrene and Be called vinyl toluene.

The acrylate polymer can be known from the prior art Processes, for example emulsion polymerization. The acrylate polymer is preferably in the form of a dispersion used. During the manufacturing process, the quantitative ratio between the monomers and the water preferably set so that the resulting dispersion has a solids content of 30 to 60 wt .-%, preferably 35 to 60 wt .-%, and directly to Production of the base coating composition can be used can. A particularly suitable acrylate polymer is commercially available as an aqueous one Dispersion under the name Acronal 290 D (BASF AG; Ludwigshafen) available.

To produce a dispersion of the acrylate polymer, an anionic emulsifier is preferably used alone or as a mixture with others as the emulsifier.
to use a filler with a corrosion protection effect on a metallic material. In the case of fillers which have now become technologically obsolete, it was necessary to subject the filler layer obtained to an equalizing surface treatment, for example grinding, after the filler had been applied and dried or cured. This made use of the fact that a filler layer is usually less hard and / or better to process than the material of the substrate. In contrast, modern fountain pens have a self-regulating function. This means that after the filler has been applied to a substrate with surface defects and (pre-) drying or (pre-) crosslinking of the filler, a filler layer is formed without further measures, the outer surface of which is practically flat even in the micrometer range. In other words, a filler layer is formed, the interface of which faces the substrate forms a complement to the surface of the substrate, based on surface structures in the micrometer range. A decorative layer is formed from a decorative lacquer. In addition to customary paint binders and crosslinking agents, a decorative paint has in particular color and / or effect pigments. Examples of effect pigments are metallic pigments and micapigments. The decorative layer is essentially responsible for the visual impression of the substrate provided with the multilayer coating on an observer. A protective layer is usually formed from a clear lacquer. The clearcoat must have special properties with regard to its behavior in relation to mechanical stress, chemical stress and light resistance as well as its transmission behavior, since the protective layer is exposed to the environment and in particular is intended to protect the decorative layer. Multi-layer coatings of the type described are used in particular for the coating of motor vehicle bodies or parts thereof made of sheet steel or aluminum plate, but also for the coating of plastic molded parts used in the motor vehicle sector.

Examples of anionic emulsifiers are the alkali salts of Sulfuric acid half-esters of alkylphenols or alcohols, furthermore the Sulfuric acid half esters of oxyethylated alkylphenols or oxyethylated alcohols, preferably the alkali salts of Sulfuric acid half ester reacted with 4 to 5 moles of ethylene oxide per mole Nonylphenol, alkyl or aryl sulfonate, sodium lauryl sulfate, Sodium lauryl ethoxylate sulfate and secondary sodium alkane sulfonates, their Carbon chain contains 8 - 20 carbon atoms. The amount of anionic emulsifier is 0.1 to 5.0 wt .-%, based on the Monomers, preferably 0.5 to 3.0% by weight. It can also increase the stability of the aqueous dispersions is additionally a nonionic Emulsifier of the ethoxylated alkylphenol or fatty alcohol type, e.g. an addition product of 1 mole of nonylphenol and 4 to 30 moles Ethylene oxide mixed with the anionic emulsifier become.

The glass transition temperature of the acrylate polymer is preferably between 15 ° C and 35 ° C, particularly preferably between 20 ° C and 25 ° C.

The acrylate polymer used preferably has a number average Molar mass (determination: gel permeation chromatography with polystyrene as standard) from 200,000 to 2,000,000, preferably from 300,000 to 1,500,000.

According to the invention, acrylate copolymers with non-associative groups which contain (C ₁ -C ₆ ) -alkyl (meth) acrylate and (meth) acrylic acid as monomer units are used as thickener component (ii) in the decorative lacquer. A preferred copolymer contains (meth) acrylic acid as monomer units and at least two different (C ₁ -C ₆ ) alkyl (meth) acrylate monomers. The (meth) acrylic acid is present in the copolymer preferably in amounts from 40% by weight to 60% by weight, particularly preferably from 46% by weight to 55% by weight, based on the amount of the entire copolymer. The (C ₁ -C ₆ ) alkyl (meth) acrylate monomer I is preferably in amounts of 30% by weight to 50% by weight, in particular 36% by weight to 46% by weight, and the (meth) acrylate polymer II preferably in amounts of 1% by weight to 10% by weight, in particular 2% by weight to 8% by weight, in each case based on the amount of the entire copolymer. The rheology aid should give the decorative lacquer the desired viscosity, in particular at the pH, which is generally alkaline. A particularly preferred thickener, when it is in the form of a dispersion, is thin and thickens at a neutral or basic pH. The acrylate copolyer is suitably used as a finished dispersion. Dispersions of this type preferably contain fatty alcohol alkoxylates, in particular C ₈ -C ₂₂ fatty alcohol ethoxylates. A particularly suitable acrylate copolymer dispersion is commercially available under the name Viscalex HV 30 (Allied Corporation, Great Britain).

The thickener is preferably in one in the decorative lacquer used Amount of 0.5 to 5.0% by weight, in particular approximately 0.3 to 1.5% by weight, based on the solids content. Usually the Thickener as a dispersion with a concentration of 5 to 45% by weight, preferably used from 7 to 35 wt .-%.

The decorative lacquer can also contain other thickeners or rheology aids, such as ionic layered silicates, xanthan gum, diurea compounds, Polyurethane thickeners, bentonite, waxes and wax copolymers contain.

As an auxiliary binder, the decorative lacquer can also be epoxy-functional and / or contain carboxyl-functional components, as usual Glycidyl compounds, e.g. Glycidyl acrylate or glycidyl methacrylate. Suitable carboxyl-functional crosslinkers are, for example Carboxylic acids, especially saturated, straight-chain, aliphatic Dicarboxylic acids with 3 to 20 carbon atoms in the molecule, dodecane-1,12-diacid is preferably used.

Polyvinyl alcohol can also be used as a further auxiliary binder become. It was found that the addition of polyvinyl alcohol in an amount up to 10 wt .-%, preferably from 1 to 5 wt .-%, the Compatibility with the protective lacquers applied to the decorative lacquer can be improved. Polyvinyl alcohol is solvent-repellent, so that solvent or possibly contained in the protective lacquer other components due to the repulsive effect of the Polyvinyl alcohol does not penetrate the decorative paint and the color can change.

The crosslinkers known in the paint field are further crosslinkers like melamine resins that react with free OH groups can.

The decorative lacquer can be used in addition to the polymers described above contain other compatible water-dilutable resins, such as e.g. Aminoplast resins, polyesters, polyurethanes and acrylated polyurethanes and urethanized acrylates used as additives to achieve certain paint properties such as improved adhesion or generally serve as grinding resins for pigments.

The auxiliary binder and / or the crosslinking agent can be used in an amount of up to 10 wt .-%, in particular from 0.5 to 10 wt .-% are used.

The decorative paint used generally has a solids content from about 15 to 60% by weight. The solids content varies with that Effect type of the decorative lacquer. For metallic paints, for example preferably at 12 to 25% by weight. For plain-colored paints, it is higher, for example at 14 to 45% by weight

Ammonia can be used to neutralize components (i) and (ii) and / or amines (especially alkylamines), amino alcohols and cyclic Amines, such as di- and triethylamine, aminomethylpropanol, Dimethylaminoethanolamine, diisopropanolamine, morpholine, N-alkylmorpholine, be used. For neutralization be easy volatile amines preferred. The aqueous coating agent is usually adjusted to a pH between 6 and 9, preferably 7 to 8.5.

The decorative lacquer can contain organic solvents in an amount of up to 15% by weight. contain. Examples of organic solvents are naphthalenes, Suitable for gasolines and alcohols. Can be used as further liquid components the basecoats of the invention alkylene glycols, such as ethylene glycol, Propylene glycol, butylene glycol, 1,4-butanediol, 1,6-hexanediol, Neopentyl glycol and other diols, such as dimethylolcyclohexane.

As a pigment, the decorative paint can be used for painting Automotive bodies contain pigments, such as Effect pigments as well as organic and inorganic coloring Pigments. Examples of suitable effect pigments are commercially available Aluminum bronzes, aluminum bronzes chromated according to DE-OS 36 36 183, commercially available stainless steel bronzes as well as other usual Metal flakes and flake pigments and non-metallic Effect pigments, e.g. Pearlescent or interference pigments. examples for Suitable coloring pigments are based on inorganic Titanium dioxide, iron oxides, carbon black and the like. Examples of color pigments organic bases are indanthrene blue, cromophthal red, irgazine orange, Sicotrans yellow, heliogen green and the like. Furthermore, can Corrosion protection pigments, e.g. Zinc phosphate. In addition, the decorative paint can also be used in the field of paint chemistry Contain usual fillers. These include silica, magnesium silicate, Talc, titanium dioxide and barium sulfate. The percentage of pigments and Fillers in the decorative lacquer can total 3 to 25 wt .-%, based on the Solids content. The pigment can be in any way added, e.g. as an aqueous slurry or as a paste. The pigments can, for example, with a grinding resin, such as an auxiliary binder, Dispersing agents or water are rubbed. With plain colors It is preferred to paint the pigments in dispersing agents and water suspend. If aluminum or flakes are used, then this if necessary in solvent and possibly a mixture of water and Slurrying agent or in the main binder or in one other auxiliary binders. The amount of component (i) can vary depending on the pigment used. Are the pigments organic and / or inorganic color pigments Component A preferably in an amount of 25 to 50% by weight, based on the solids content. Are the pigments Effect pigments, component A is preferably in an amount of 15 to 30 wt .-%, based on the solids content.

The decorative lacquer can contain film-forming aids as a further component. Dicarboxylic acid dialkyl esters, 1,2-propylene glycol, high-boiling gasolines and naphthalenes into consideration have a boiling point above 100 ° C., preferably above 140 ° C. The Decorative varnish may also contain other auxiliaries and additives contain. Examples include catalysts, auxiliaries, Defoaming agents, dispersion aids, wetting agents, preferably carboxy-functional dispersants,. Antioxidants, UV absorbers, Radical scavengers, leveling agents, biocides and / or water retention agents.

The decorative lacquer can optionally be applied to the filler layer still with water to adjust the solids content, solvent or rheology aids to adjust the application technology Properties and, if necessary, a base for pH regulation are added. If the viscosity is not yet in the desired range, do so can again rheology aids (ii) or other thickeners, if necessary in a Amount from 0.001 to 0.006% by weight, based on the solids content, be added.

There are also known powder coatings as decorative coatings or colored paint layer.

All common clearcoats can be used as aqueous protective lacquers. The use of the following protective lacquers is particularly preferred.

A first preferred protective lacquer is an aqueous powder lacquer dispersion and characterized in that the aqueous powder coating dispersion can be produced by an aqueous dispersion of a powder coating with a Glass temperature of 20 to 90 ° C, preferably 40 to 70 ° C, one Viscosity of 10 to 1000 mPas, preferably 50 to 300 mPas, at a shear rate of 500 s-1 and a solids content of 10 to 50%, preferably 20 to 40%, of a grinding process Maintaining a temperature of 0 to 60 ° C, preferably 5 to 35 ° C, is subjected. The specific energy input during the The grinding process is preferably 20 to 500 Wh / kg, in particular 50 up to 250 Wh / kg.

In terms of chemical composition, it is aqueous Powder coating dispersion, for example, constructed so that it from a solid, powdery component A and an aqueous component B consists, wherein component A is a powder coating containing a) at least one epoxy binder containing 30 to 45%, preferably 30 to 35% of glycidyl-containing monomers, optionally with containing vinyl aromatic compounds, preferably styrene, b) at least one crosslinking agent, preferably straight-chain, aliphatic dicarboxylic acids and / or carboxy-functional polyesters and c) optionally catalysts, auxiliaries, additives typical of powder coating, such as Degassing agents, leveling agents, UV absorbers, radical scavengers, Antioxidants and component B. An aqueous dispersion is included a) at least one non-ionic thickener and b) optionally Catalysts, auxiliaries, defoamers, dispersion aids, Wetting agents, preferably carboxy-functional dispersants, Antioxidants, UV absorbers, radical scavengers, small amounts of solvents, Plasticizers, biocides and / or water retention agents.

As an epoxy functional binder for component A. For example, suitable epoxy group-containing polyacrylate resins Copolymerization of at least one ethylenically unsaturated Monomer containing at least one epoxy group in the molecule with at least one other ethylenically unsaturated monomer that does not Contains epoxy group in the molecule can be produced, at least one the monomer is an ester of acrylic acid or methacrylic acid. such Polyacrylate resins containing epoxy groups are e.g. known from EP-A-299 420, DE-B-22 14 650, DE-B-27 49 576, US-A-4,091,048 and US-A-3,781,379).

As examples of ethylenically unsaturated monomers that do not Epoxy group contained in the molecule, alkyl esters of acrylic and Methacrylic acid, which contain 1 to 210 carbon atoms in the alkyl radical, especially methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate and Called 2-ethylhexyl methacrylate. More examples of ethylenic unsaturated monomers that do not contain epoxy groups in the molecule are acid amides, e.g. Acrylic acid and methacrylic acid amide, vinyl aromatic compounds, such as styrene, methyl styrene and vinyl toluene, Nitriles, such as acrylonitrile and methacrylonitrile, vinyl and vinylidene halides, such as vinyl chloride and vinylidene fluoride, vinyl esters, e.g. Vinyl acetate and monomers containing hydroxyl groups, e.g. Hydroxyethyl acrylate and Hydroxyethyl methacrylate.

The epoxy group-containing polyacrylate resin usually has Epoxy equivalent weight of 400 to 2500, preferably 420 to 700 number average molecular weight (gel permeation chromatography determined using a polystyrene standard) from 2,000 to 20,000, preferably from 3,000 to 10,000, and one Glass transition temperature (TG) from 30 to 80, preferably from 40 to 70, particularly preferably from 40 to 60 ° C (measured using the Differential Scanning Calorimetry (DSC)). Very particularly preferred become approx. 50 ° C. Mixtures of two or two can also be used more acrylic resins are coming.

The epoxy group-containing polyacrylate resin is generally good known methods can be prepared by polymerization.

Crosslinkers are carboxylic acids, especially saturated, straight-chain, Aliphatic dicarboxylic acids with 3 to 20 carbon atoms in the molecule are suitable. Decane-1,12-dicarboxylic acid is very particularly preferably used. To modify the properties of the finished powder clearcoats optionally other crosslinkers containing carboxyl groups are used become. Examples include saturated branched or unsaturated ones straight-chain di- and polycarboxylic acids as well as polymers with Called carboxyl groups.

Components A which have an epoxy functional are also suitable Crosslinker and an acid functional binder included.

Examples of acidic binders are acidic ones Suitable polyacrylate resins by copolymerization of at least an ethylenically unsaturated monomer containing at least one Contains acid group in the molecule, with at least one other ethylenically unsaturated monomer that has no acid group in the molecule contains, can be produced.

The epoxy group-containing binder or the epoxy group-containing binder Crosslinkers and the carboxyl or binder are usually used used in an amount such that 0.5 per epoxide group equivalent to 1.5, preferably 0.75 to 1.25 equivalents of carboxyl groups available. The amount of carboxyl groups present can be determined by Titration can be determined with an alcoholic KOH solution.

The binder contains vinyl aromatic compounds, in particular Styrene. To limit the risk of cracking, the salary lies but not more than 35% by weight. 10 to 25% by weight are preferred.

Components A may contain one or more suitable ones Catalysts for epoxy curing. Suitable catalysts are phosphonium salts of organic or inorganic acids, quaternary ammonium compounds, amines, imidazole and Imidazole derivatives, The catalysts are generally in proportions from 0.001% to about 2% by weight based on the total weight the epoxy resin and the crosslinking agent.

Examples of suitable phosphonium catalysts are Ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium chloride, Ethyltriphenylphosphonium thiocyanate, ethyltriphenylphosphonium acetate-acetic acid complex, tetrabutylphosphonium Tetrabutylphosphonium bromide and tetrabutylphosphonium acetate-acetic acid complex. This and other suitable phosphonium Catalysts are e.g. described in U.S. Patent 3,477,990 and U.S. Patent 3,341,580.

Suitable imidazole catalysts are, for example, 2-styrylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole and 2-butylimidazole. This and further imidazole catalysts are e.g. described in the Belgian Patent No. 756,693.

In addition, components A may also contain auxiliaries and additives contain. Examples of these are leveling agents, antioxidants, UV absorbers, Free radical scavengers, trickle aids and degassing agents, such as for example benzoin. Leveling agents based on Polyacrylates, polysiloxanes or fluorine compounds. usable Antioxidants are reducing agents such as hydrazides and phosphorus compounds and radical scavengers e.g. 2,6 di-tert-butylphenol derivatives.

UV absorbers that can be used are preferably triazines and benzotriphenol. As Radical scavengers are preferably 2,2,6,6 tetramethylpiperidine derivatives used.

As a further component, the aqueous component B contains Powder coating dispersion at least one non-ionic thickener a). Non-ionic associative thickeners a) are preferably used. Structural features of such associative thickeners a) are: aa) a hydrophilic Scaffolding that ensures sufficient water solubility and hydrophobic groups leading to an associative interaction in the aqueous Are medium capable.

Long-chain alkyl radicals, for example, such as. Dodecyl, hexadecyl or octadecyl residues, or alkaryl residues, such as. Octylphenyl or nonylphenyl radicals used. As a hydrophilic Frameworks are preferably polyacrylates, cellulose ethers or particularly preferably used polyurethanes that are hydrophobic Contain groups as polymer building blocks.

Particularly preferred as hydrophilic frameworks are polyurethanes which Contain polyether chains as building blocks, preferably from Polyethylene oxide. Serve in the synthesis of such polyether polyurethanes the di- and / or polyisocyanates, preferably aliphatic diisocyanates, particularly preferably optionally alkyl-substituted 1,6-hexamethylene diisocyanate, to link the hydroxyl-terminated Polyether building blocks with each other and to link the Polyether building blocks with the hydrophobic end group building blocks, the for example monofunctional alcohols and / or amines with the already long-chain alkyl radicals or aralkyl radicals mentioned.

Component B can also contain catalysts, leveling agents, Contain antioxidants, UV absorbers, radical scavengers and wetting agents. in the the most important here are those already listed for component A. Substances into consideration. Component B can also contain auxiliaries, Defoamers, dispersion aids, biocides, solvents and Neutralizing agent may be added. Come as a defoamer preferably modified polysiloxanes. Dispersion aids are e.g. preferably ammonium or metal salts of polycarboxylates. Neutralizers that can be used are amines, ammonia and Metal hydroxides.

Component A is produced by known methods (cf. e.g. Product information from BASF Lacke + Farben AG, "Powder coatings", 1990) by homogenization and dispersion, for example by means of an extruder, screw kneader, etc. To The powder coatings are produced by grinding and, if necessary, by Sifting and sieving prepared for dispersion. From the powder can then by wet grinding or by stirring in dry ground powder coating the aqueous powder clear coating dispersion getting produced. Wet grinding is particularly preferred. The average grain size obtained is between 1 and 25 microns. preferably less than 20 µm, most preferably 3 to 10 µm. It's important, that during the milling process the dispersion only had small amounts Contains solvents. It may therefore be required the grinder before Free solvent residues at the beginning of the grinding process.

The dispersion can before or after wet grinding or Entering component A in the water 0 to 5 wt .-% of a Defoamer mixture, an ammonium and / or alkali salt, one carboxyl-functional or nonionic dispersing aid, Wetting agent and / or thickener mixture and the other additives be added. Defoamers, dispersing agents, Wetting and / or thickening agents first dispersed in water. Then small portions of component A are stirred in. Subsequently defoamers, dispersing agents, thickeners and Wetting agent dispersed. Finally, again in small Portions of component A stirred in. The adjustment of the pH is preferably carried out with ammonia or amines. The pH can increase initially that a strongly basic dispersion is formed. However, the pH drops again within several hours or days to the values given above. The powder coating dispersions can be with the methods known from liquid coating technology to the Apply the decorative layer. In particular, they can be sprayed be applied. There are also electrostatically assisted ones Rotation or pneumatic application into consideration. The on the Decorative layer applied powder clearcoat dispersion is usually before Branding vented. This is conveniently done first Room temperature and then at a slightly elevated temperature. In the As a rule, the elevated temperature is 40 to 70 ° C., preferably 50 to 65 ° C. Flash off for 2 to 10 minutes, preferably 4 to Carried out for 8 minutes at room temperature. At an elevated temperature is flashed off again during the same period. With a Protective lacquer of the type described above can have layer thicknesses of 30 to 50 µm can be achieved.

A second preferred protective lacquer is a two-component clear lacquer containing (1) a hydroxy functional binder or a mixture from hydroxy-functional binders, (2) Tris (alkoxycarbonylamino) triazine or a mixture of Tris (alkoxycarbonylamino) triazines and (3) free polyisocyanates or one Mixture of free polyisocyanates.

Hydroxy-functional binders are preferably those on the Basis of hydroxy-functional polyacrylates, hydroxy-functional Polyesters and / or hydroxy-functional polyurethanes.

Polyacrylate resins, the hydroxyl numbers, are preferably used from 40 to 240, preferably 60 to 210, very particularly preferably 100 to 200, acid numbers from 0 to 35, preferably 0 to 23, very particularly preferably 3.9 to 15.5, glass transition temperatures from -35 to + 70 ° C, preferably -20 to + 40 ° C, very particularly preferably -10 to + 15 ° C and number average molecular weights of 1,500 to 30,000, preferably 2,000 have up to 15,000, very particularly preferably 2,500 to 5,000.

TG =

Glasübergangstemperatur des Polyacrylatharzes

n =

Anzahl der im Polyacrylatharz einpolymerisierten verschiedenen Monomeren.

W_n =

Gewichtsanteil des n-ten Monomers

TG_n=

Glasübergangstemperatur des Homopolymers aus dem n-ten Monomer

The glass transition temperature of the polyacrylate resins is determined by the type and amount of the monomers used. The selection of the monomers can be carried out by a person skilled in the art with the aid of the following formula, with which the glass transition temperatures of polyacrylate resins can be approximately calculated:

TG =

Glass transition temperature of the polyacrylate resin

n =

Number of different monomers polymerized in the polyacrylate resin.

W _n =

Weight fraction of the nth monomer

TG _n =

Glass transition temperature of the homopolymer from the nth monomer

Measures to control the molecular weight (e.g. selection appropriate polymerization initiators, use of Chain transfer agents, etc.) are part of the expertise of the Average specialist and need not be explained here.

As a hydroxy functional binder component are also special preferably polyester resins or alkyd resins are used which can be prepared, by (a) a cycloaliphatic or aliphatic polycarboxylic acid or a mixture of such polycarboxylic acids, (b) an aliphatic or cycloaliphatic polyol with more than two hydroxyl groups in the molecule or a mixture of such polyols, (c) an aliphatic or cycloaliphatic diol or a mixture of such diols and (d) an aliphatic linear or branched saturated monocarboxylic acid or a mixture of such monocarboxylic acids in a molar Ratio of (a): (b): (c): (d) = 1.0: 0.2 - 1.3: 0.0 - 1.1: 0.0 - 1.4, preferably 1.0: 0.5-1.2: 0.0-0.6: 0.2-0.9 to a polyester resin or alkyd resin are implemented.

Examples of component (a) are: Hexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, Endomethylene tetrahydrophthalic acid, oxalic acid, malonic acid, Succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, Azelaic acid and sebacic acid.

Examples of component (b) are: pentaerythritol, Trimethylolpropane, trimethylolethane and glycerin.

Examples of component (c) are: ethylene glycol, Diethylene glycol, propylene glycol, neopentyl glycol, 2-methyl-2-propylpropanediol-1,3,2-ethyl-2-butylpropanediol-1,3, 2,2,4-trimethyl-1,5, 2,2,5-trimethylhexanediol-1,6, hydroxypivalic acid neopentyl glycol ester and dimethylolcyclohexane.

Examples of component (d) are: 2-ethylhexanoic acid, Lauric acid, isooctanoic acid, isononanoic acid and Monocarboxylic acid mixtures made from coconut fat or palm kernel fat be won.

The production of hydroxyl-bearing polyester and / or Alkyd resins are e.g. in Ullmann's encyclopedia of technical chemistry, third edition, 14th volume, Urban & Schwarzenberg, Munich, Berlin 1863, Pages 80 to 89 and pages 99 to 105, in the books: Résines Alkydes-Polyesters by J. Bourry, Paris Verlag Dunod 1952, Alkyd Resins by C.R. Martens, Reinhold Publishing Corporation, New York 1961 and Alkyd Resin Technology by T.C. Patton, Interscience Publishers 1962 described.

Protective lacquers based on polyurethane are also suitable.

All known compounds are suitable as crosslinking agents Consideration, e.g. Polyisocyanate, melamine resins, etc. is preferred for this preferred protective lacquer, however, that it the crosslinking agents (2) and (3) contains.

eingesetzt, wobei R=Methyl, Butyl-.....Gruppen bedeuten. Ebenso können Derivate der genannten Verbindungen zum Einsatz kommen. Bevorzugt werden für die Komponente (2) Tris(Alkoxycarbonylamino)Triazine eingesetzt, wie sie in der US-PS 5,084,541 beschrieben sind.As component (2) are tris (alkoxycarbonylamino) triazines of the formula

used, where R = methyl, butyl -... groups. Derivatives of the compounds mentioned can also be used. Tris (alkoxycarbonylamino) triazines such as are described in US Pat. No. 5,084,541 are preferably used for component (2).

The carbamate groups react preferentially with OH carriers sterically as little hindered hydroxyl groups. amino groups cannot cross-link the tris (alkoxycarbonylamino) triazine. It is coming rather, the carbalkoxy group is split off.

Component (3) contains at least one as a crosslinking agent optionally in one or more organic, if appropriate water-dilutable solvents, dissolved or dispersed, preferably non-blocked di- and / or polyisocyanate.

The polyisocyanate component is any organic polyisocyanates with aliphatic, cycloaliphatic, araliphatic and / or aromatically bound, free isocyanate groups. Prefers are polyisocyanates with 2 to 5 isocyanate groups per molecule and with Viscosities from 100 to 2,000 mPas (at 23 ° C) are used. If necessary, small amounts can still be added to the polyisocyanates organic solvent, preferably 1 to 25 wt .-%, based on pure Polyisocyanate, are added so as to incorporate the To improve isocyanates and, if necessary, the viscosity of the Polyisocyanate to a value within the above ranges lower. Solvents suitable as additives for the polyisocyanates are, for example, ethoxyethyl propionate, butyl acetate and the like.

Examples of suitable isocyanates are, for example, in "Methods of organic chemistry ", Houben-Weyl, volume 14/2, 4th edition, Georg Thieme Verlag Stuttgart 1963, pages 61 to 70, and by W. Siefken, Liebigs Ann. Chem. (1949) 562, 75 to 136. For example are suitable in the description of the polyurethane resins (A2) mentioned isocyanates and / or polyurethane prepolymers containing isocyanate groups, by the reaction of polyols with an excess of Polyisocyanates can be prepared and preferred are low viscous.

Isocyanurate groups and / or biuret groups and / or can also be used Allophanate groups and / or urethane groups and / or urea groups and / or polyisocyanates containing uretdione groups become. Polyisoeyanate containing urethane groups for example by reacting some of the isocyanate groups with Polyols such as Trimethylolpropane and glycerin.

Aliphatic or cycloaliphatic polyisocyanates, especially hexamethylene diisoeyanate, dimerized and trimerized Hexamethylene diisocyanate, isophorone diisocyanate, 2-isocyanatopropylcyclohexyl isocyanate, Dicyclohexylmethane-2,4'-diisocyanate or dicyclohexylmethane-4,4'-diisocyanate or mixtures used from these polyisocyanates. Very particularly preferred are mixtures of uretdione and / or isocyanurate groups and / or Allophanate group-containing polyisocyanates based on Hexamethylene diisocyanate, as obtained by catalytic oligomerization of Hexamethylene diisocyanate using appropriate Catalysts are created, used. The polyisocyanate component can otherwise also from any mixtures of the examples mentioned Polyisocyanates exist.

The polyisocyanate component is used in the invention Coating agents advantageously in such an amount used that the ratio of the hydroxyl groups of the binder (A) to the isocyanate groups of the crosslinkers (2) and (3) between 1: 2 and 2: 1, particularly preferably between 1: 1.5 and 1.5: 1.

The crosslinker mixture preferably contains 1 to 99% by weight, especially preferably 5 to 90% by weight of tris (alkoxycarbonylamino) triazine and preferably 99 to 1% by weight, particularly preferably 95 to 10% by weight free isocyanate or a mixture of free polyisocyanates.

In addition to the components mentioned, the protective lacquer can also Contain light stabilizers, for example triazine compounds. Further rheological agents can also be added.

In a preferred variant, the protective lacquer is in the form of at least two separate components (I) and (II), which are only immediately before Application mixed together, kept. It is preferred that the tris (alkoxycarbonylamino) triazine in admixture with the hydroxy-functional binder component I and the free Polyisocyanate component II of the protective lacquer or Forms two-component clear lacquer. In the case of a two-component system the protective lacquer is designed such that a) one component (1) a hydroxy-functional binder or a mixture of hydroxy functional binders and tris (alkoxycarbonylamino) triazine and b) the second component (II) free isocyanate or a mixture contains free polyisocyanates. The making of the two Components (I) and (II) are carried out according to the usual methods from the individual components with stirring. The production of the protective lacquer from components (I) and (II) also takes place by means of stirring or Disperse using the commonly used ones Devices, for example using a dissolver or the like. or by means of likewise Usually used 2-component dosing and mixing systems or by means of the in DE-A-195 10 651, page 2, line 62, to page 4, Line 5, described process for the preparation of aqueous 2-component polyurethane blankets.

A preferred embodiment of the invention is thereby characterized in that the decorative layer has a layer thickness in the range of 10 µm to 100 µm and that the protective layer has a layer thickness has in the range of 20 microns to 150 microns. In particular, it is advantageous if the filler layer has a layer thickness in the range from 50 μm to 80 μm, preferably from 60 microns to 70 microns, if the decorative layer Layer thickness in the range from 15 microns to 17 microns, preferably from 15 microns up to 16 µm, and if the protective layer has a layer thickness in Range from 35 µm to 50 µm, preferably from 40 µm to 45 µm, having. In this way, on the one hand, an optimal Surface quality and on the other hand an optimal decorative effect reached.

The filler layer can rest directly on the substrate material. It but can at least between the substrate and the filler layer another layer, for example a corrosion protection layer, be arranged.

A preferred use of the invention is that the Substrate is a metal sheet, preferably a motor vehicle body sheet. A further use is that the substrate is a plastic molding, preferably an automotive plastic molding based on PVC.

a) auf das Substrat wird ein vernetzbarer Pulverlack aufgetragen,

b) der Pulverlack wird mittels Bestrahlung oder Erwärmung für 1 min. bis 10 min. bei einer Temperatur im Bereich von 130 Grad C bis 240 Grad C getrocknet und vorvernetzt,

c) auf den getrockneten und vorvernetzten Pulverlack wird ein wäßriger Dekoriack aufgetragen und angetrocknet,

d) auf den Dekorlack wird ein wäßriger Schutzlack aufgetragen,

e) der Verbund aus Pulverlack, Dekorfack und Schutzlack wird bei einer Temperatur im Bereich von 120 Grad C bis 180 Grad C eingebrannt und vernetzt.

According to the invention, the object is further achieved by a method for producing a substrate provided with a multi-layer coating, in particular a motor vehicle body panel or a motor vehicle molded part, according to one of claims 1 to 6, with the following subsequent method steps (according to the independent claim 7):

a) a crosslinkable powder coating is applied to the substrate,

b) the powder coating is irradiated or heated for 1 min. up to 10 min. dried and pre-crosslinked at a temperature in the range from 130 degrees C to 240 degrees C,

c) an aqueous decorative coating is applied to the dried and pre-crosslinked powder coating and dried,

d) an aqueous protective lacquer is applied to the decorative lacquer,

e) the composite of powder coating, decorative pack and protective coating is baked and crosslinked at a temperature in the range from 120 degrees C to 180 degrees C.

Expedient developments of the invention according to claim 7 are the subject of dependent claims 8 to 10.

Before step a), an electro-dip coating with subsequent Burn in the lacquer layer.

In particular, it is preferred if the powder coating for 2 min. up to 6 min, preferably for 3 min. up to 4 min., at a temperature of 180 degrees C. is dried to 220 degrees C and pre-crosslinked, preferably by means of Passing the substrate provided with the powder coating through an IR irradiation zone.

A coating that meets all requirements is obtained if the combination of powder coating, decorative coating and protective coating in one Temperature in the range of 130 degrees C to 150 degrees C, preferably at 150 degrees C, baked and cross-linked.

One particularly with regard to energy consumption and environmental protection is advantageous embodiment of the method according to the invention characterized in that one of organic solvents practically free aqueous decorative varnish and one of organic Solvents practically free aqueous protective lacquer or an aqueous Powder clearcoat dispersion are used and that the Puiverlack, the Decorative paint and the protective paint in a circulating air operated Paint device applied and baked. Hereinafter the invention is illustrated by examples.

Example 1: Powder coating for the filler layer example 1 Production of a powder coating premix

The following items are weighed: 120.30 kg 20.1% epoxy resin 228.30 kg 38.1% polyester 121.80 kg 20.3% TIO ₂ 118.80 kg 19.8% filler 2.40 kg 0.4% benzoin 2.40 kg 0.4% wax 6.00 kg 1.0% flow additive 600,00kg 100.0%

Then 5 min. mixed in an overhead mixer.

extrusion

The premix is fed to the extruder, here:
1 screw extruder, type Buss PCS 100.
That is, extrudate is rolled on a cooling belt as a skin, cooled, broken and obtained as chips.

Grinding and sifting

The chips are fed to an ACM 40 classifier mill and sighted inline with a cyclone sifter.

The resulting coarse material G1 is discharged with a cellular wheel sluice and represents the useful goods. The fine material is separated from the air flow on an absolute filter (surface filter made of PE needle felt) and also discharged via a cellular wheel sluice. Particle size distribution:
x ₁₀ > 10 µm; x ₉₀ <40 µm.

Example 2: Decorative paints for the decorative layer Example 2.1

A. 22 parts by weight of water, 2 parts by weight of Solvesso 200 (C ₁₀ -C ₁₃ aromatics mixture) and 1 part by weight of butylglycol were placed in a reaction vessel. 30 parts by weight of Acronal 290 D (aqueous dispersion, solids content 50.0%) were added with stirring.

B. A mixture of 7.6 parts by weight of water and 2 parts by weight of Viscalex HV 30 (solids content 30.6%) was slowly added to the mixture obtained in A.
The pH of the mixture obtained was adjusted to 8.0 with dimethylethanolamine (DMEA).

C. A mixture of 5 parts by weight of aluminum flakes and 5 parts by weight of butylglycol was stirred smoothly in a separate mixer.
With vigorous stirring, the aluminum slurry obtained in C. was added in portions to the mixture obtained in B.
The viscosity of the paint obtained was adjusted to 110 mPas using 25 parts by weight of water. The solids content was 18.85%.

Example 2.2

A. 22 parts by weight of water, 2 parts by weight of Solvesso 200 (C ₁₀ -C ₁₃ aromatics mixture) and 1 part by weight of butylglycol were placed in a reaction vessel. 25 parts by weight of Acronal 290 D (aqueous dispersion, solids content 50.0%) were added with stirring.

B. A mixture of 7.6 parts by weight of water and 2 parts by weight of Viscalex HV 30 (solids content 30.6%) was slowly added to the mixture obtained in A.
The pH of the mixture obtained was adjusted to 8.0 with 0.4 part by weight of dimethylethanolamine (DMEA).

C. A mixture of 5 Parts by weight of aluminum flakes and 5 parts by weight of butyl glycol smooth touched.

D. In another separate mixer, 5 parts by weight of glycidyl methacrylate dodecanedioic acid were dispersed in 25 parts by weight of water and ground to a particle size of less than 5 μm.
The mixture obtained in B was stirred into the dispersion obtained in D with vigorous stirring.
The aluminum slurry obtained in C was then added portionwise to the resulting mixture.
The viscosity of the paint obtained was adjusted to 110 mPas using 25 parts by weight of water. The solids content was 18.35%.

Example 2.3

It was according to the procedure described in Example 2.2 Paint preparation prepared, except that in step D 10 Parts by weight of glycidyl methacrylate / dodecanedioic acid in 20 parts by weight Water were dispersed.

The solids content was 20.35%.

Example 2.4

A. 22 parts by weight of water, 2 parts by weight of Solvesso 200 (C ₁₀ -C ₁₃ aromatics mixture) and 1 part by weight of butylglycol were placed in a reaction vessel. 30 parts by weight of Acronal 290 D (aqueous dispersion, solids content 50.0%) were added with stirring.

B. A mixture of 7.6 parts by weight of water and 2 parts by weight of Viscalex HV 30 (solids content 30.6%) was slowly added to the mixture obtained in A.
The pH of the mixture obtained was adjusted to 8.0 with 0.4 part by weight of dimethylethanolamine (DMEA).

C. A mixture of 5 parts by weight of aluminum flakes and 5 parts by weight of butylglycol was stirred smoothly in a separate mixer.
In another separate mixer, 10 parts by weight of a polyester obtained from 9.8% by weight of neopentyl glycol, 6.2% by weight of hexahydrophthalic acid, 22.9% by weight of Pripol (commercial product from Unichema), 11 , 1 wt .-% hexanediol and 2.0 wt .-% xylene as a solvent, and 2.2 parts by weight of melamine Cymel 303 (cyanamide) dispersed in 12.8 parts by weight of water.
The mixture obtained in B was stirred into the dispersion obtained in D with vigorous stirring.
The aluminum slurry obtained in C was then added portionwise to the resulting mixture.

The solids content of the paint was 26.83%.

Example 2.5

A. 22 parts by weight of water, 2 Parts by weight of Lusolvan FBH (commercial product of BASF AG, Ludwigshafen) and 1 part by weight of butyl glycol. With stirring 30 parts by weight of Acronat 290 D (aqueous dispersion, Solids content 50.0%) added.

B. A mixture of 7.6 parts by weight of water and 2 parts by weight of Viscalex HV 30 (solids content 30.6%) was slowly added to the mixture obtained in A.
The pH of the mixture obtained was adjusted to 8.0 with dimethylethanolamine (DMEA).

C. 30 parts by weight of an Irgazinrot DPP BO paste (pigment content 43.2% by weight) were added to the mixture obtained in step B and the mixture was stirred until smooth.
The viscosity of the paint obtained was adjusted to 110 mPas with 5 parts by weight of water.

Example 2.6

A. 22 parts by weight of water, 2 Parts by weight of Lusolvan FBH (commercial product of BASF AG, Ludwigshafen) and 1 part by weight of butyl glycol. With stirring 25 parts by weight parts by weight of Aeronal 290 D (aqueous Dispersion, solids content 50.0%) added.

B. A mixture of 7.6 parts by weight of water and 2 parts by weight of Viscalex HV 30 (solids content 30.6%) was slowly added to the mixture obtained in A.
The pH of the mixture obtained was adjusted to 8.0 with dimethylethanolamine (DMEA).

C. In a separate mixer, 28.79 parts by weight of one Irgazinrot DPP BO paste (pigment content 43.2% by weight), 1.17 Parts by weight of Disperbyk 190 (dispersing aid) and 0.03 Parts by weight of the copolymer used in step B dispersed and ground to a particle size below 5 microns.

D. In another separate mixer, 5 parts by weight of glycidyl methacrylate / dodecanedioic acid were dispersed in 25 parts by weight of water and ground to a particle size of less than 5 μm.
The mixture obtained in B was stirred into the dispersion obtained in D with vigorous stirring.
The pigment paste obtained in C was then added in portions to the mixture obtained.
The solids content was 28.06%.

Example 2.7

The procedure described in Example 2.6 was repeated, except that in step A 20 parts by weight of the acrylate dispersion and in step D 10 Parts by weight of glycidymethacrylate / dodecanedioic acid were used.

Example 2.8

A. 22 parts by weight of water, 2 Parts by weight of Lusolvan FBH (commercial product of BASF AG, Ludwigshafen) and 1 part by weight of butyl glycol. With stirring 15 parts by weight of Acronal 290 D (aqueous dispersion, Solids content 50.0%) acrylic dispersion added.

B. A mixture of 7.6 parts by weight of water and 2 parts by weight of Viscalex HV 30 (solids content 30.6%) was slowly added to the mixture obtained in A.
The pH of the mixture obtained was adjusted to 8.0 with dimethylethanolamine (DMEA).

C. In a separate mixer, 28.79 parts by weight of one Irgazinrot DPP BO paste (pigment content 43.2% by weight), 1.17 Parts by weight of Disperbyk 190 and 0.03 parts by weight of that in step B copolymer used and dispersed to a particle size ground below 5 µm.

D. In another separate mixer, 10 parts by weight of one Polyester obtained from 9.8% by weight of neopentyl glycol, 6.2 % By weight hexahydrophthalic acid, 22.9% by weight Pripol (commercial product from Unichema), 11.1% by weight of hexanediol and 2.0% by weight of xylene as Solvent, and 2.2 parts by weight of melamine Cymel 303 (cyanamide) dispersed in 12.8 parts by weight of water.

With vigorous stirring, the dispersion obtained in D was added to B obtained mixture stirred. Then the in step B prepared pigment preparation stirred.

The solids content was 29.04%.

Example 3: Protective lacquers for the protective layer Example 3.1

A. Preparation of an acrylate resin: 21.1 parts of xylene are introduced and heated to 130 ° C. The template is at 130 ° C within 4 h via two separate feed tanks initiator: 4.5 parts TBPEH (tert-butyl perethylhexanoate) mixed with 4.86 parts xylene and Monomers: 10.78 parts methyl methacrylate, 25.5 parts n-butyl methacrylate, 17.39 parts of styrene and 23.95 parts of glycidyl methacrylate added. The mixture is then heated to 180 ° C and in Vacuum <100 mbar the solvent removed.

B. Preparation of a powder clearcoat: 77.5 parts of acrylic resin, 18.8 parts Dodecanedicarboxylic acid (see hardener), 2 parts Tinuvin 1130 (UV absorber), 0.9 parts Tinuvin 144 (HALS), 0.4 parts Additol XL 490 (Leveling agent) and 0.4 parts of benzoin (degassing agent) intimately mixed on a Henschel fluid mixer, on a BUSS PLK 46 extruder extruded on a Hosohawa ACM 2 mill ground and sieved through a 125 µm sieve.

C. Preparation of a dispersion: Desalinated water in 400 parts 0.6 parts Troykyd D777 (defoamer), 0.6 parts Orotan 731 K. (Dispersing agent), 0.06 part of Surfinol TMN 6 (wetting agent) and 16.5 Divide RM8 (Rohm & Haas, nonionic associative thickener Polyurethane base) dispersed. Then 94 in small portions Parts of the powder clear lacquer stirred in. Then still once 0.6 parts Troykyd D777, 0.6 parts Orotan 731 K, 0.06 parts Dispersed Surfinol TMN 6 and 16.5 parts of RM8. Finally 94 parts of the powder clear lacquer are stirred in in small portions. The material is ground in a sand mill for 3.5 hours. The finally measured average particle size 4 µm. The material is filtered through a 50 µm filter and finally 0.05% Byk 345 (leveling agent) is added.

D. Application of the dispersion: The slurry is coated with water-based paint coated steel panels applied using a cup gun. The The sheet is flashed off at room temperature for 5 minutes and at 60 ° C. for 5 minutes.

The sheet is then 30 min at a temperature of 140 ° C. baked. With a layer thickness of 40 µm, a high-gloss clear lacquer film manufactured with MEK resistance (> 100 double strokes). The clear coat film has good resistance to condensation.

Example 3.2 3.2.1. Manufacture of binder solutions A. Acrylic resin A

In a laboratory reactor with a usable volume of 4 1 equipped with a stirrer, two dropping funnels for the monomer mixture resp. Initiator solution, nitrogen inlet tube, thermometer and Reflux coolers become 899 g of a fraction more aromatic Weighed in hydrocarbons with a boiling range of 158 ° C - 172 ° C. The solvent is heated to 140 ° C. After reaching 140 ° C are a monomer mixture of 727 g of n-butyl methyl acrylate, 148 g Cyclohexyl methacrylate, 148 g styrene, 445 g 4-hydroxibutyl acrylate and 15 g Acrylic acid within 4 hours, and an initiator solution of 29 g of t-butyl perethyl hexanoate in 89 g of the aromatic described Solvent evenly metered into the reactor within 4.5 hours. With the dosage of the monomer mixture and the initiator solution started at the same time. After the end of the initiator metering, the Reaction mixture held at 140 ° C for two more hours and then cooled. The resulting polymer solution has a solids content of 62% determined in a convection oven for 1 h at 130 ° C), an acid number of 9 and a viscosity of 21 dPas (measured on a 60% solution the polymer solution in the aromatic solvent described below Use an ICI-plate-cone viscometer at 23 ° C).

B. Acrylate resin B

In a laboratory reactor with a useful volume of 4 I equipped with a stirrer, two dropping funnels for the monomer mixture resp. Initiator solution, nitrogen inlet tube, thermometer and Reflux coolers become 897 g of a fraction more aromatic Weighed in hydrocarbons with a boiling range of 158 ° C - 172 ° C. The solvent is heated to 140 ° C, after reaching 140 ° C are a monomer mixture of 487g t-butyl acrylate, 215g n-butyl methacrylate, 143 g styrene, 572 g hydroxypropyl methacrylate and 14 g Acrylic acid within 4 hours, and an initiator solution of 86 g of t-butyiperethylhexanoate in 86g of the described aromatic Solvent evenly metered into the reactor within 4.5 hours. With the dosage of the monomer mixture and the initiator solution started at the same time. After the end of the initiator metering, the Reaction mixture held at 140 ° C for two more hours and then cooled. The resulting polymer solution has a solids content of 62% determined in a forced air oven for 1 h at 130 ° C), an acid number of 10 and a viscosity of 23 dPas (measured on a 60% solution the polymer solution in the aromatic solvent described below Use an ICI Piatte cone viscometer at 23 ° C).

C. alkyd resin C

In a laboratory reactor with a usable volume of 4 1 equipped with a stirrer, water separator, reflux condenser, nitrogen inlet pipe and thermometer are 1330 g Hexahydrophthalic anhydride, 752 g 1, 1, 1 trimethylol propane, 249 g 1,4-dimethylolcyclohexane, 204 g 1,6-hexanediol, 136 g isononanoic acid (as Isomer mixture of 3,3,5-trimethylhexanoic acid and 3,5,5-trimethylhexanoic acid) and 75 g of xylene as an entrainer. The Water separator is precipitated with xylene. The contents of the reactor will heated within 8 hours to 210 ° C so that an even Reflux of the entrainer occurs. The reactor contents are at 210 ° C held until an acid number of 17.1 and a viscosity of 15 dPas, measured on a 60% solution of the reaction mixture in the in the aromatic solvents described for acrylic resins A and B, is reached. Then it is cooled to 140 ° C and the contents of the reactor with so much of the aromatic solvent mentioned that a non-volatile content of 61% (determined in a convection oven for 60 min 130 ° C) results. The alkyd resin solution prepared in this way has an acid number of 17.1 and a viscosity of 15 dPas (measured on an ICI plate cone viscometer at 23 ° C).

3.2.2 Production of two-component clear coats A. Component 1

Component 1 of the two-component clear lacquers is prepared by weighing the binder solution, then adding the amounts of triazine crosslinking agent, solvent, UV absorber, radical scavenger and leveling agent indicated in Table 1 with stirring and stirring well. The amounts in this and the following tables are to be understood as weights. Comp.1a Comp. 1b Comp. 1c Comp.1d Comp. 1e Comp. 1f Acrylate resin A 79.6 55.0 Acrylate resin B 62.8 50.0 Alkyd resin C 72.0 62.0 Triazine Crosslinker US 5,084,541 13 12.8 10.0 Tiniuvin 400 1.3 1.3 1.0 1.0 Tiniuvin 123 1.0 1.0 1.5 1.5 Tiniuvin 384 1.2 1.2 Tiniuvin 292 1.0 1.0 Silicon-1-1-sung 2.5 2.5 2.5 2.5 3.0 3.0 Diglycol acetate 4.0 4.0 10.0 10.0 9.0 9.0 Buytlglycol acetate 4.0 4.0 8.0 8.0 5.5 5.5 Methoxipropyl acetate 3.0 3.6 8.0 8.4 Solventnaphta® 5.1 5.1 butyl 4.6 15.6 5.8 5.8 3.2 3.2

B. Component 2

Component 2 consists of a solution of commercially available isocyanurate trimers in a suitable solvent. It is prepared by stirring in the solvent in the isocyanurate form according to Table 2. Component 2a Component 2b Desmodur Z 4470 63.5 26.5 Tolonate HDT 90 24.8 Basonat Hl 190 B / S 61.8 Solventnaphra 5.85 5.85 butyl 5.85 5.85

C. Production of clear coats

The clear coats are produced by mixing components 1 and 2 in accordance with the proportions given in table 3 and applying them immediately after the mixing. Alternatively, special two-component systems can be used for the application, which are known to the average person skilled in the art and therefore need not be described in more detail here. Table 3 also contains properties of the clearcoats, which the invention illustrates. Klarlack1 Klarlack2 Klarlack3 Klarlack4 Klarlack5 Klarlack6 Comp.1a 73.9 Comp. 1b 93.5 Comp. 1c 77.0 Comp.1d 91.0 Comp. 1e 76.7 Comp. 1f 86.7 Comp.2a 26.1 6.5 Comp.2b 23.0 9.0 23.3 13.3 scratch resistance bad Good bad Good bad Good JV (grade) 4.0 4.0 4.5 4.5 3.0 3.0 rockfall bad Good bad Good bad Good

Example 4: Preparation of one provided with a multilayer coating Substrate.

Using 180-grit sandpaper, artificial scratch marks are created (cf. Fig. 1) on a sheet of material customary in vehicle body construction. On this sheet with surface defects was initially a Powder coating as a filler according to Example 1 by means of application electrostatic adhesion applied. That with the powder coating filler provided sheet (Fig. 2) was then for 4 min. irradiated with IR, whereby set a temperature of approx. 200 ° C. Here, the powder paint filler melted and cross-linked. By DSC investigation was in present example no residual reactivity from the crosslinking reaction detectable from polyester and epoxy resin. There was a practical one smooth filling surface. Following the IR radiation was a Decorative paint according to Example 2.1 with the usual spraying process applied to what is a drying process for film formation joined. A powder clear lacquer dispersion was applied to the dried decorative lacquer sprayed according to Example 3.1. In the end it was coated sheet of a baking process stage at 150 ° C for 20 min. subjected.

The following resulted for the finished multilayer coating Layer thicknesses. Filler layer: 60 µm, decorative layer: 16 µm, protective layer: 40 µm. The surface of the multilayer coating made one flawless visual impression. In particular there were none Signs of the surface defects of the sheet can be seen. The Stone chip resistance according to VDA621-427 with 2 x 500 g steel gravel and 2 bar air pressure gave a KW1.

A second sheet was compared to a water filler coated (Fig. 3). A comparison of FIGS. 2 and 3 shows that the coating according to the invention with powder coating according to FIG much smoother surface than the coating with water filler 3 results.

The perthormetric measurement of the powder coating filler shows one complete equalization of the sanding marks (Fig. 2) while a Water filler painted in a conventional manner with 35 µm considerable Leaves markings (Fig. 3).

4 shows an example of the process of body painting.

Via the inlet 1, the body to be coated enters the Pretreatment stage 2. This is followed by the electrocoating 3 and the stoving 4 of the electrocoat layer. In stage 5 preparation for coating with powder coating (level 6). At level 7 is dried with IR radiation. This is followed by cooling stage 8. The powder coating is applied in step 9 to the powder coating layer. To Passing through the intermediate drying 10 becomes a protective layer in stage 11 applied and then baked in level 12. Over the spout 13 the body is transported out of the system.

Claims (10)

1. Substrate provided with a multilayer coating which exhibits a surfacer layer, a colour and/or effect decorative layer and a protective layer, the surfacer layer being closest to the substrate and the protective layer furthest from the substrate, the aqueous decorative coating material used for the decorative layer comprising a binder from the group "acrylate resins, carboxyl-, epoxy-, and/or hydroxyl-containing binders" or mixtures thereof and comprising a crosslinker from the group "isocyanates, amino resins or TACT" or mixtures thereof and the aqueous protective coating material used for the protective layer being from the group "one-component clearcoats, two-component clearcoats, transparent powder coating materials",
   characterized in that the surfacer layer is formed from a precrosslinkable powder coating material,
   the baked surfacer layer of powder coating material having a layer thickness in the range from 30 µm to 250 µm.
2. Substrate provided with a multilayer coating according to Claim 1, characterized in that the baked decorative layer has a layer thickness in the range of 10 µm to 100 µm and in that the baked protective layer has a layer thickness in the range from 20 µm to 150 µm.
3. Substrate provided with a multilayer coating according to Claim 1 or 2, characterized in that the baked surfacer layer has a layer thickness in the range of 50 µm to 80 µm, preferably from 60 µm to 70 µm, in that the baked decorative layer has a layer thickness in the range of 15 µm to 17 µm, preferably from 15 µm to 16 µm, and in that the baked protective layer has a layer thickness in the range from 35 µm to 50 µm, preferably from 40 µm to 45 µm.
4. Substrate provided with a multilayer coating according to one of Claims 1 to 3, characterized in that the surfacer layer lies directly on the substrate material.
5. Substrate provided with a multilayer coating according to one of Claims 1 to 4, characterized in that the substrate is a metal panel, preferably a motor vehicle bodywork panel.
6. Substrate provided with a multilayer coating according to one of Claims 1 to 4, characterized in that the substrate is a plastics moulding, preferably a motor vehicle plastics moulding based on SMC.
7. Process for preparing a substrate provided with a multilayer coating, especially a motor vehicle bodywork panel or a motor vehicle plastics moulding, according to one of Claims 1 to 6, comprising the following process steps:

   a) a crosslinkable powder coating material (6) is applied to the substrate,

   b) the powder coating material is dried (7) and precrosslinked by means of irradiation or heating for from 1 minute to 10 minutes at a temperature in the range from 130 degrees C to 240 degrees C,

   c) an aqueous decorative coating material (9) is applied to the dried and precrosslinked powder coating material and is dried,

   d) an aqueous protective coating material (11) is applied to the decorative coating material,

   e) the assembly of powder coating material, decorative coating material and protective coating material is baked (12) and crosslinked at a temperature in the range from 120 degrees C to 180 degrees C.
8. Process according to Claim 7, in which the powder coating material is dried and precrosslinked for from 2 minutes to 6 minutes, preferably for from 3 minutes to 4 minutes, at a temperature of from 180 degrees C to 220 degrees C, preferably by the passage of the substrate that has been provided with a powder coating material through an IR irradiation zone.
9. Process according to one of Claims 7 and 8, in which the assembly of powder coating material, decorative coating material and protective coating material is baked and crosslinked at a temperature in the range from 130 degrees C to 150 degrees C, preferably at 150 degrees C.
10. Process according to one of Claims 7 to 9, in which an aqueous decorative coating material which is virtually free from organic solvents and an aqueous protective coating material which is virtually free from organic solvents, or an aqueous transparent powder coating dispersion, are used and in which the powder coating material, the decorative coating material and the protective coating material are applied and baked in a coating unit which is operated with circulating air.

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