EP2209857A1

EP2209857A1 - Aqueous coating agents, and method for the production of layers resistant to flying stones

Info

Publication number: EP2209857A1
Application number: EP08849323A
Authority: EP
Inventors: Horst HINTZE-BRÜNING; Hans-Peter Steiner; Fabrice Leroux; Anne-Lise Troutier
Original assignee: BASF Coatings GmbH; Universite Blaise Pascal Clermont Ferrand II
Current assignee: BASF Coatings GmbH; Universite Blaise Pascal Clermont Ferrand II
Priority date: 2007-11-14
Filing date: 2008-11-06
Publication date: 2010-07-28
Also published as: US20120269978A1; WO2009062623A1; CN101878274A; JP2011503305A; DE102007054249A1; KR20100110781A

Abstract

The invention relates to aqueous coating agents containing at least one water-dispersible polymer (WP) that comprises at least one functional group (a), preferably at least one cross-linking agent (V) that comprises at least two functional groups (b) which react with the functional groups (a) of the water-dispersible polymer (WP) by forming a covalent bond when the coating agent is cured, and positively charged inorganic particles in which the ratio D/d between the average particle diameter (D) and the average particle thickness (d) is >50, the charge of the organic particles being compensated at least in part by single-charged organic anions (OA). The invention further relates to a method for producing OEM composite layers that are resistant to flying stones and consist of an anti-corrosive layer which is directly applied to the substrate, a filler layer, and a final layer of coating lacquer preferably consisting of a lacquer primer and a final clear lacquer layer, at least one layer being formed from the aforementioned aqueous coating agent.

Description

Aqueous coating compositions and process for the production of stone impact resistant coatings

The provision of impact-resistant coatings on metallic substrates is of particular importance in the automotive industry. A number of requirements are placed on a filler or a rockfall protection ground. Thus, after curing, the surfacer layer is said to have a high resistance to stone chips, in particular to multilayer coating, and at the same time a good adhesion to corrosion protection coating, in particular a cathodic electrocoat, and to the basecoat, good filling properties (covering the structure of the substrate) at layer thicknesses of about 20 to 35 .mu.m and cause a good Appearance in the final clear coat. Furthermore, suitable coating materials, in particular for ecological reasons, should be low in or substantially free of organic solvents.

Aqueous coating compositions for fillers are known and described for example in EP-A-0 788 523 and EP-A-1 192 200. There, water-thinnable polyurethanes are described as binders for fillers, which are intended to ensure stone chip resistance, in particular with comparatively low layer thicknesses. When loaded in stone impact tests occur in the aqueous fillers of the prior art in OEM layer structures (corrosion protection layer (especially KTL) filler basecoat clearcoat) despite good stone chip resistance, ie a relatively small number of damage, but often damage patterns on the paint layer in which the unprotected metal substrate is exposed by uncontrolled crack propagation in the OEM layer structure and subsequent delamination at the interface between metal and KTL.

WO-A-01/04050 discloses inorganic anionic or cationic layer fillers for aqueous coating compositions having good barrier properties. known, which are modified with organic compounds for widening the spacing of the layers in the filler having at least two ionic groups which are separated by at least 4 atoms. As cationic fillers, mixed hydroxides, in particular hydrotalcite types, can be used. The coating compositions described in WO-A-01/04050 are used for coatings with very good barrier properties to gases and liquids, wherein the fillers are not intended to influence the curing process. A use of the coating agents to improve the damage after impact in OEM

Layer structures, in particular for the reduction of the exposed substrate surface, is not known. The coating compositions described in WO-A-01/04050 are only conditionally suitable for use in OEM layer structures, since the organic modifiers in the applied layer produce a high local density of charges due to the multiple charge, which increases macroscopically Hygroscopy of the cured layer leads, which in particular has negative consequences for the condensation resistance of the layer.

EP-A-0 282 619 describes solvent-based anticorrosion paints containing pulverulent mixed hydroxides, it being possible to use salicylate anions as anions. A use of the coating compositions to improve the damage patterns after impact loading in OEM layer structures, in particular for the reduction of the exposed substrate surface, is not known.

ML Nobel et al. (Progress in Organic Coatings 58 (2007), 96-104) describe coating compositions which can also be used for OEM constructions containing binders, crosslinkers and anionic fillers modified with cationic organic compounds to widen the spacing of the layers in the filler , Such cationic organic compounds are significantly more unstable in the aqueous phase than corresponding anionic compounds and, especially in the case of the ammonium compounds, tend to discolor during curing of the coating composition, which can lead to undesirable color shade shifts in the coating. Attention is drawn to an enrichment of the modified inorganic fillers at the phase boundaries between droplets of dispersed polymer and water or in the droplets, which should lead to improved rheology and increased rigidity of the layers produced with the coating composition. As a rule, an increase in the rigidity in thinner layers leads to an increased tendency to brittle fracture and thus to an increased exposure of the substrate surface, and thus a deteriorated damage pattern. A use of the methods described by ML Nobel et al. described coating composition for improving the damage after impact images in OEM layer structures, in particular for the reduction of the exposed substrate surface, is not described.

Task and solution

In the light of the prior art, the object of the present invention is to provide coating compositions based on ecologically advantageous aqueous coating materials for impact-resistant coatings with a significantly improved damage pattern, in particular with a marked reduction in the delamination of the OEM composite at the interface between metal and corrosion protection layer and thus with a clear reduction of the exposed substrate surface after impact loading. Furthermore, the hardened coatings produced with the coating composition according to the invention should have a low tendency to absorb water and in particular a good condensation resistance. Last but not least, during curing, the coatings produced according to the invention no or only a very minor discoloration of the layer resulting.

Surprisingly, it has been found that an aqueous coating composition comprising at least one water-dispersible polymer (WP) having at least one crosslinkable functional group (a) and positively charged inorganic particles whose ratio D / d of the average particle diameter (D) to the mean particle thickness (d) > 50, whose charge is at least partially compensated by simply charged organic anions (OA), the task of the invention solves outstanding.

Furthermore, a process has been found for the production of impact-resistant OEM layer composites consisting of a corrosion protection layer applied directly to the substrate, a surfacer layer, a basecoat film and a final clearcoat film in which at least one layer is formed from the novel aqueous coating composition.

Description of the invention

As components essential to the invention, the coating composition according to the invention comprises at least one water-dispersible polymer (WP) having at least one crosslinkable functional group (a), and positively charged inorganic particles whose ratio D / d of the average particle diameter (D), in the case of non-circular particles corresponds to the particle diameter the longest surface diagonal to which the average particle thickness (d) is> 50, the positive charge of which is at least partially compensated by singly charged organic anions (OA). The water-dispersible polymers (WP) are preferably selected from the group of water-dispersible polyurethanes, polyesters, polyamides, polyepoxides, polyethers and polyacrylates, with polyurethanes and polyesters being very particularly preferred.

For the purposes of the invention, water-dispersible or water-soluble means that the polymers (WP) in the aqueous phase form aggregates with an average particle diameter of <500, preferably <200 and particularly preferably <100 nm, or are dissolved in molecular disperse form. The size of the aggregates consisting of polymer (WP) can be accomplished in a conventional manner by introducing hydrophilic groups on the polymer (WP). The water-dispersible polymers (WP) preferably have mass-average molecular weights Mw (determinable by gel permeation chromatography with polystyrene as standard) of from 1,000 to

100,000 daltons, more preferably from 1,500 to 50,000 daltons.

As a crosslinkable functional group (a) of the water-dispersible polymer (WP) are in principle all groups suitable with themselves and / or with other functional groups of the polymer (WP) and / or with other constituents of the coating composition according to the invention to form covalent bonds can react.

The crosslinking of the functional groups (a) can be induced by radiation and / or thermally induced.

Radiation-crosslinkable groups (a) are generally groups which become reactive upon irradiation with actinic radiation and, preferably, can react with other activated groups of their type to form covalent bonds which, according to a physical and / or ionic mechanism. Examples of suitable groups are CH single bonds, CC, CO, CN, CP or C-Si single or double bonds, with CC double bonds being preferred.

In the preferred embodiment of the invention, the crosslinking of the functional groups (a) is thermally induced, where the groups (a) react with themselves, that is to say with further groups (a), and / or preferably with complementary groups. On the one hand, the selection of functional groups (a) and of the complementary groups depends on the fact that they do not give rise to any undesired reactions, in particular, any premature crosslinking, in the preparation of the polymers (WP) and in the preparation, storage and application of the coating compositions , and on the other hand, in which temperature range the networking should take place.

Examples of groups which react with themselves (a) are: methylol, methylol ether, N-alkoxymethylamino and in particular alkoxysilyl groups.

Examples of preferred pairs of groups (a) and complementary groups according to the invention include: hydroxyl groups (a) with acid, acid anhydride, carbamate, optionally etherified methylol groups and / or optionally blocked isocyanate groups as functional group (b), amino groups (a ) with acid, acid anhydride, epoxy and / or isocyanate groups as functional group (b), epoxy groups a with acid and / or amino groups as functional group (b) and mercapto groups (a) with acid, acid anhydride, carbamate and / or isocyanate groups as a functional group (b). In a particularly preferred embodiment of the invention, the complemen- (b) Component of a crosslinking agent (V) ₁ which will be described below

In particular, hydroxyl, amino and / or epoxy groups are preferred as groups (a). Hydroxyl groups are particularly preferred, the OH numbers of the water-dispersible polymer (WP) according to DIN EN ISO 4629 preferably being between 10 and 200, particularly preferably between 20 and 150.

The functional groups (a) are introduced into the water-dispersible polymers (WP) via the incorporation of suitable molecular units in the manner known to one skilled in the art.

The preferred water-dispersible polyurethanes (WP) can be prepared from building blocks, as described, for example, in DE-A-40 05 961 or EP-A-1 192 200. Into the polyurethane molecules are preferably incorporated groups capable of forming anions which, after neutralization, ensure that the polyurethane resin can be stably dispersed in water. Suitable groups capable of forming anions are preferably carboxylic acid, sulfonic acid and phosphonic acid groups, more preferably carboxyl groups. The acid number of the water-dispersible polyurethanes according to DIN EN ISO 3682 is preferably between 10 and 80 mg KOH / g, more preferably between 20 and 60 mg KOH / g. To neutralize the groups capable of forming anions, preference is given to using ammonia, amines and / or amino alcohols, for example di- and triethylamine, dimethylaminoethanolamine, diisopropanolamine, morpholines and / or N-alkylmorpholines. Hydroxyl groups are preferably used as the functional group (a), the OH numbers of the water-dispersible polyurethanes according to DIN EN ISO 4629 preferably being between 10 and 200, particularly preferably between 20 and 150. The preferred water-dispersible polyesters (WP) can be prepared from building blocks as also described, for example, in DE-A-40 05 961. In the polyester molecules, groups capable of forming anions are preferably incorporated, which after neutralization ensure that the polyester resin can be stably dispersed in water. Suitable groups capable of forming anions are preferably carboxylic acid, sulfonic acid and phosphonic acid groups, more preferably carboxylic acid groups. The acid number of the water-dispersible polyesters according to DIN EN ISO 3682 is preferably between 10 and 80 mg KOH / g, more preferably between 20 and 60 mg KOH / g. To neutralize the groups capable of forming anions, it is likewise preferred to use ammonia, amines and / or amino alcohols, for example di- and triethylamine, dimethylaminoethanolamine, diisopropanolamine, morpholines and / or N-alkylmorpholines. Hydroxyl groups are preferably used as functional group (a), the OH numbers according to DIN EN ISO 4629 of the water-dispersible polyesters preferably being between 10 and 200, particularly preferably between 20 and 150.

The water-dispersible polymers (WP) are present in the coating composition of the invention preferably in proportions of from 10 to 95% by weight, preferably from 20 to 80% by weight, based on the nonvolatile constituents of the coating composition.

The crosslinking agent (V) used in the preferred embodiment of the invention has at least two crosslinkable functional groups (b) which are used as complementary groups with the functional groups (a) of the water-dispersible polymer (WP) and / or further constituents of the binder in curing Coating react to form covalent bonds. The functional groups (b) can be reacted by radiation and / or thermally. Preference is given to thermally crosslinkable groups (b). The crosslinking agents V are preferably water-dispersible as defined above.

The crosslinking agent (V) is preferably present in the coating composition in proportions of from 5 to 50% by weight, particularly preferably from 10 to 40% by weight, based on the nonvolatile constituents of the coating composition.

Preference is given to thermally crosslinkable groups (b) in the crosslinking agent (V) ₁ which react with the preferred functional groups (a) selected from the group of the hydroxyl, amino and / or epoxy groups. Particularly preferred complementary groups (b) are selected from the group of carboxyl groups, the optionally blocked polyisocyanate groups, the carbamate groups and / or the methylol groups, which are optionally partially or fully etherified with alcohols.

Very particular preference is given to functional complementary groups (b) which react with the particularly preferred hydroxyl groups as functional groups (a), where (b) is preferably selected from the group of the optionally blocked polyisocyanate groups and / or the methylol groups, which may be partly or fully - Are always etherified with alcohols.

Examples of suitable polyisocyanates and suitable blocking agents are described, for example, in EP-A-1 192 200, wherein the blocking agents have in particular the function of an undesired reaction of the isocyanate groups with the reactive groups a of the coating composition BM and with further reactive groups and with the What - in the coating agent BM before and during application. The blocking agents are selected in such a way that the blocked isocyanate groups deblock again only in the temperature range in which the thermal crosslinking of the coating agent is to take place, in particular in the temperature range between 120 and 180 degrees C, and undergo crosslinking reactions with the functional groups (a).

Water-dispersible aminoplast resins, for example as described in EP-A-1 192 200, can be used as components containing methylol groups. It is preferred to use aminoplast resins, in particular melamine-formaldehyde resins, which react with the functional groups (a), in particular with hydroxyl groups, in the temperature range between 100 and 180.degree. C., preferably between 120 and 160.degree.

In addition to the abovementioned binders and the preferred crosslinking agents (V), the coating composition according to the invention may contain further, optionally water-dispersible binders in proportions of up to 40% by weight, preferably up to 30% by weight, based on the non-volatile constituents of Coating agent, included.

The coating composition according to the invention may also contain paint additives in effective amounts. Thus, for example, pigments and effect pigments in customary and known amounts may be part of the coating composition. The pigments can consist of organic or inorganic compounds and are listed by way of example in EP-A-1 192 200. Further usable additives are, for example, UV absorbers, free-radical scavengers, slip additives, polymerization inhibitors, defoamers, emulsifiers, wetting agents, leveling agents, film-forming auxiliaries, rheology-controlling additives and preferred additives. wise catalysts for the reaction of the functional groups a, b and / or c, and additional crosslinking agents for the functional groups a, b and / or c. Further examples of suitable coating additives are described, for example, in the textbook "Lackadditive" by Johan Bieleman, Verlag Wiley-VCH, Weinheim, New York, 1998.

The abovementioned additives are present in the coating material according to the invention preferably in proportions of up to 40% by weight, preferably up to 30% by weight and particularly preferably up to 20% by weight, based on the non-volatile constituents of the coating composition ,

The positively charged inorganic particles (AT) according to the invention are anisotropic in shape and have a ratio D / d of the average particle diameter (D), in the case of non-circular platelets the particle diameter corresponds to the longest surface diagonal of the particles, to the mean particle thickness (d)> 50, preferably D / d> 100, more preferably D / d> 150, on. The average particle diameters can be determined by the evaluation of TEM (transmission electron microscopy) images, while the particle thicknesses are accessible experimentally via X-ray structure analysis, AFM (Atomic Force Microscopy) profile measurements on single platelets and computational knowledge of the molecular structure , The particle diameter (D) of the inorganic particles (AT) is preferably between 50 and 1000 nm, more preferably between 100 and 500 nm, the average particle thickness (d) is preferably between 0.1 and 1.0 nm, more preferably between 0.2 and 0.75 nm. Usually, the determined by the X-ray diffraction layer distances between the electrically charged inorganic particles are given. The layer spacing comprises the sum of the layer thickness (d) of a particle and the distance between two such particles. The latter depends on the nature of the counterions in it, which neutralize the electrical charge carriers of the particles. as well as the presence of swelling electrically neutral molecules such as water or organic solvents. For example, it is known that the layer spacing in montmorillonite varies between 0.97 and 1.5 nm as a function of the water content of most naturally occurring environmental conditions (J. Phys. Chem. B, 108 (2004) 1255).

Preferably, the cationically charged inorganic particles (AT) modified with the singly charged organic anions (OA) are in amounts of from 0.1 to 30% by weight, preferably between 0.5 and 25% by weight, more preferably between 1 and 20 wt .-%, based on the nonvolatile constituents of the coating composition, in the coating composition according to the invention. They can be incorporated into the coating composition according to the invention in solid (powdered form) or in a preferred embodiment of the invention in aqueous suspension.

The preparation of the positively charged inorganic particles (AT) can be achieved by replacing the naturally occurring or the synthesis-related anions of the layered minerals with those of the singly charged organic anions (OA) according to known methods or by synthesis in the presence of the singly charged ones organic anions (OA) take place. For this purpose, for example, the positively charged inorganic particles (AT) in a suitable liquid medium, which is able to swell the spaces between the individual layers and in which the singly charged organic anions (OA) are dissolved, suspended and then again isolated (Langmuir 21 (2005), 8675).

In the ion exchange, preferably more than 15 mol%, particularly preferably more than 30 mol%, of the synthesis-related anions replaced by the singly charged organic anions (OA). Depending on the size and the spatial orientation of the organic counterions, the layer structures are generally widened, wherein the distance between the electrically charged layers is preferably widened by at least 0.2 nm, preferably by at least 0.5 nm.

The preferably singly charged singly charged organic anions (OA) used for at least partial compensation of the charge and for widening the inorganic particles (AT) are constructed as follows. The charge carriers for the singly charged organic anions are preferably anions of the carboxylic acid, the sulfonic acid and / or the phosphonic acid. The low molecular weight organic anions (OA) preferably have molecular weights of <1,000 daltons, more preferably <500 daltons.

Within the meaning of the invention, particularly preferred as positively charged inorganic particles (AT) are the mixed hydroxides of the formula:

(M ₍ _1.x) ²⁺ M _x ³⁺ (OH) ₂ ) (A _{x / y} ^y -) n H ₂ O

where M ^{2+ represent} divalent cations, M ³⁺ trivalent cations and A anions with a valency y, where x has a value of 0.05 to 0.5. Particularly preferred divalent cations M ²⁺ calcium, zinc and / or magnesium ions and trivalent cations M ³⁺ aluminum ions and as anions A chloride ions, phosphate ions, sulfate ions and / or carbonate ions, because these ions largely ensure that no change in the Coloring occurs during curing of the layer according to the invention. The synthesis of the mixed hydroxides is known (for example, Eilji Kanezaki, Preparation of Layered Double Hydroxides in Interface Science and Technology, VoM, Chapter 12, pa- Ge 345ff - Elsevier, 2004, ISBN 0-12-088439-9). It usually takes place from the mixtures of the salts of the cations in the aqueous phase at defined, constant basic pH values. The mixed hydroxides containing the anions of the metal salts are obtained as inorganic counterions embedded in the interstices. The synthesis in the presence of carbon dioxide is usually obtained the mixed hydroxide with embedded carbonate ions. If the synthesis is carried out in the absence of carbon dioxide or carbonates in the presence of organic anions (OA) or their acid precursors, the mixed hydroxide with intervening organic anions (coprecipitation method or template method) is generally obtained. An alternative synthetic route for preparing the mixed hydroxides is the hydrolysis of the metal alcoholates in the presence of the desired anions to be incorporated (US Pat. No. 5,514,473). Furthermore, it is possible to introduce the organic anions to be stored by ion exchange on mixed hydroxides with incorporated carbonate ions. This can be done, for example, in particular in the preparation of hydrotalcites and hydrocalumites by rehydration of the amorphous calcined mixed oxide in the presence of the desired anions to be deposited. The CaI- cination of the mixed hydroxide containing embedded carbonate ions, at temperatures <800 ⁰ C provides the amorphous mixed oxide to obtain the layer structures (rehydration method). Alternatively, the ion exchange can be carried out in an aqueous or alcoholic aqueous medium in the presence of the acid precursors of the organic anions to be stored. Depending on the acidity of the precursor of the organic anion to be stored, treatment with dilute mineral acids is necessary in order to remove the carbonate ions.

The charge carriers for the singly charged anions (OA) are preferably anionic groups (AG), which function as simple negative charges. stabilize tion in the aqueous phase, such as particularly preferred singly charged anions of the carboxylic acid, the sulfonic acid and / or the phosphonic acid.

In a further preferred embodiment of the invention, the singly charged organic anions (OA) additionally carry functional crosslinkable groups (c) which react with the functional groups (a) of the binder, in particular of the water-dispersible polymer (WP), and / or the functional groups (O). b) react the crosslinking agent during curing of the coating agent to form covalent bonds. The groups (c) can be radiation and / or thermally curable. Preference is given to thermally curable groups (c), as listed above in the description of groups (a) and (b). The functional groups (c) are particularly preferably selected from the group of hydroxyl, epoxy and / or amino groups.

The functional groups (c) are preferably separated from the anionic groups of the singly charged organic anions (OA) by a spacer (SP), where (SP) is selected from the group optionally containing heteroatoms, such as nitrogen, oxygen and / or sulfur , modified and optionally substituted aliphatic and / or cycloaliphatic having a total of 3 to 30 carbon atoms, preferably between 4 and 20 carbon atoms, more preferably between 5 and 15 carbon atoms, optionally with hetero atoms, such as nitrogen, oxygen and / or sulfur, modified and optionally substituted aromatics having a total of 3 to 20 carbon atoms, preferably between 4 and 18 carbon atoms, more preferably between 6 and 15 carbon atoms, and / or the partial structures of the above-mentioned cycloaliphatic and aromatic, wherein in the substructures at least 3 carbon atoms and / or Heteroatoms between the functional group (c) and the anionic group (AG) are located.

The spacers (SP) of the singly charged organic anions (OA) are particularly preferably substituted or unsubstituted phenyl or cyclohexyl radicals which have the functional group c in the m- or p-position to the anionic group (AG). In particular, carboxyl and / or amino groups are used here as functional group c, and carboxylate and / or sulfonate groups as anionic group (AG).

Very particularly preferred are as simply charged organic anions (OA) m- or p-aminobenzenesulfonate, m- or p-hydroxybenzenesulfonate, m- or p-aminobenzoate and / or m- or p-hydroxybenzoate.

In the case of the abovementioned preferred hydrotalcites, which preferably contain carbonate as anion (A) for the synthesis, more than 15 mol%, particularly preferably more than 30 mol%, of the anions (A) are preferably exchanged by the singly charged organic ions during the ion exchange Anions (OA) replaced.

The modification of the cationically charged inorganic particles (AT) is preferably carried out in a separate process prior to incorporation into the coating composition according to the invention, this process being particularly preferably carried out in an aqueous medium. The electrically charged inorganic particles (AT) modified with the organic counterions are preferably prepared in a synthesis step. The particles thus produced have only a very low intrinsic color, they are preferably colorless. The preferred cationically charged particles modified with organic anions (OA) can be prepared in a synthesis step, in particular from the metal salts of the cations and the organic anions. An aqueous alkaline solution of the organic low molecular organic anion (OA) is preferably used in an aqueous mixture of salts of divalent cations M ²⁺ and the trivalent cations M ³⁺ entered until the desired stoichiometry is set. The addition is preferably carried out in CO ₂ -free atmosphere, preferably in an inert gas atmosphere, for example under nitrogen, with stirring at temperatures between 10 and 100 degrees C, preferably at room temperature, the pH of the aqueous reaction mixture, preferably by adding alkaline hydroxides, preferred NaOH, in the range of 8 to 12, preferably between 9 and 11 is maintained. After addition of the aqueous mixture of the metal salts, the resulting suspension is aged at the abovementioned temperatures over a period of 0.1 to 10 days, preferably 3 to 24 hours, the resulting precipitate, preferably by centrifugation, isolated and deionized several times Washed water. Thereafter, a suspension of the cationically charged particles (AT) modified with the organic anions (OA) with a solids content of 5 to 50% by weight, preferably of 10 to 40% by weight, is prepared from the purified precipitate with water ,

The thus prepared suspensions of the inorganic particles (AT) modified with the singly charged organic anions (OA) can, in principle, be incorporated during each phase in the process according to the invention for preparing the coating composition, that is before, during and / or after the addition of the remainder Components of the coating agent. The crystallinity of the layered double mixed hydroxides obtained depends on the chosen synthesis parameters, the type of cations used, the ratio of the M ²⁺ / M ³⁺ cations and the type and amount of anions used, and should be as high as possible.

The crystallinity of the mixed hydroxide phase can be expressed as the calculated size of the coherent scattering domains from the analysis of the corresponding X-ray diffraction lines, eg the reflections [003] and [110] in the case of the Mg-Al hydrotalcite. For example, Eliseev et al. (Doklady Chemistry 387 (2002), 777) explain the influence of thermal aging on the increase of the domain size of the investigated Mg-Al hydrotalcite and explain this with the progressive incorporation still existing tetredrically coordinated aluminum in the mixed hydroxide layer as octahedrally coordinated aluminum, demonstrated by the relative intensities of the corresponding signals in the ²⁷ AI NMR spectrum.

Preferably, the preferred aqueous coating compositions of this invention are prepared by first mixing all of the components of the laminating agent other than the modified inorganic particles (AT) and the crosslinking agent (V). In the resulting mixture, the modified inorganic particles (AT) or preferably prepared preferably the above-mentioned process suspension of the modified with the organic counterions electrically charged particles (AT) with stirring until the suspension is completely dissolved, which by optical methods , in particular by visual inspection, is pursued. The resulting mixture is preferably heated at temperatures between 10 and 50 degrees C for a period of 2 to 30 minutes, preferably 5 to 20 minutes, preferably at room temperature, while stirring with ultrasound to obtain a finely divided, homogeneous treated dispersion of the preparation of the inorganic particles AT, wherein in a particularly preferred embodiment, the tip of an ultrasonic source is immersed in the mixture. During the ultrasonic treatment, the temperature of the mixture may rise by 10 to 60K. The dispersion thus obtained is preferably aged for at least 12 hours with stirring at room temperature. Thereafter, the crosslinking agent (V) is added with stirring and the dispersion is preferably adjusted with water to a solids content of 15 to 50 wt .-%, preferably 20 to 40 wt .-% adjusted

The coating materials of the invention are preferably applied in such a wet film thickness that after curing in the finished layers a dry film thickness between 1 and 100 .mu.m, preferably between 5 and 75 .mu.m, more preferably between 10 and 60 .mu.m, in particular between 15 and 50 microns results.

The application of the coating composition according to the invention can be carried out by customary application methods, such as, for example, spraying, roasting, brushing, pouring, dipping or rolling. Preferably, spray application methods are used, such as compressed air spraying, airless spraying, high rotation spraying and electrostatic spraying (ESTA). The application is usually carried out at temperatures of a maximum of 70 to 80 degrees C, so that suitable application viscosities can be achieved without causing a change or damage to the coating agent and its possibly reprocessed overspray in the momentarily acting thermal load.

Radiation curing of the applied layer with the coating composition according to the invention with radiation-crosslinkable groups is achieved. follows with actinic radiation, in particular with UV radiation, preferably in an inert atmosphere, as described for example in WO-A-03/016413.

The preferred thermal curing of the applied layer of the coating composition of the invention with thermally crosslinkable groups is carried out by the known methods, such as by heating in a convection oven or by irradiation with infrared lamps. Advantageously, the thermal curing is carried out at temperatures between 100 and 180 degrees C, preferably between 120 and 160 degrees C, for a time between 1 minute and 2 hours, preferably between 2 minutes and 1 hour, more preferably between 10 and 45 minutes. If substrates, such as metals, are used, which are highly resistant to high temperatures, the curing can also be carried out at temperatures above 180 ° C. In general, however, it is advisable not to exceed temperatures of 160 to 180 degrees C. If, on the other hand, substrates are used, such as plastics, which can only be thermally loaded to a maximum limit, the temperature and the time required for the hardening process must be matched to this maximum limit.

Within the scope of the present invention, it has further been found that the exposed substrate surface after impact loading of substrates coated with OEM layer assemblies can be significantly reduced when using the coating agents described above.

Very particular preference is given to the use of the abovementioned coating compositions for the production of surfacer layers which have a markedly reduced exposure of the substrate surface after impact loading. In particular, in classic bodies for OEM series painting, in which on the metallic substrate and / or A multilayered structure consisting of an electrodeposited layer, preferably a cathodically deposited layer, a surfacer layer, and a final topcoat layer, preferably consisting of a basecoat film and a final clearcoat film, is formed from a plastic substrate Coating agents produced filler layers particularly advantageous.

The invention furthermore relates to a process for producing high-impact coatings in which the coating composition according to the invention comprising at least one water-dispersible polymer (WP) having at least one crosslinkable functional group (a) and at least one aqueous suspension of positively charged inorganic particles whose ratio D / d of the average particle diameter (D) to the average particle thickness (d)> 50, the positive charge of which is at least partially compensated with singly charged organic anions (OA), applied to a substrate and / or a precoated substrate and then cured becomes. In a preferred method, the coating composition according to the invention is applied to a substrate precoated with an electrodeposition coating layer. Particularly preferred is the coating of metal and / or plastic substrates, which are precoated with a cathodic dip. The electrocoat material, in particular the cathodic dip paint, is preferably cured before application of the coating composition according to the invention.

In a further preferred method, a final topcoat is applied to the layer formed from the coating composition according to the invention, preferably a basecoat and finally a clearcoat material in two further stages. It will be in In a particularly preferred process, first the layer of the coating composition according to the invention is cured and thereafter an aqueous basecoat is preferably applied in a first step and after an intermediate aeration for a time between 1 to 30 minutes, preferably between 2 and 20 minutes, at temperatures between 40 and 90 Grade C, preferably between 50 and 85 degrees C, and in a second step with a clearcoat, preferably a two-component clearcoat, overcoated, wherein basecoat and clearcoat are cured together. In a further preferred embodiment of the invention, the filler layer produced with the coating composition according to the invention before application of the basecoat film for a time between 1 to 30 minutes, preferably between 2 and 20 minutes, at temperatures between 40 and 90 degrees C, preferably between 50 and 85 degrees C ventilated. After that, filler layer, basecoat layer and clearcoat layer are cured together.

The coatings produced with the coating composition according to the invention, in particular the OEM structures, consisting of a substrate from an electrodeposited corrosion protection layer, from the surfacer layer produced with the coating composition according to the invention and a final topcoat layer, preferably from a colorant basecoat and a final clear coat, show excellent resistance to impact, especially against stone chipping. Compared to commercially available fillers, a reduction in the proportion of the damaged surface and a very significant reduction in the proportion of the completely removed surface, that is to say the area fraction of the unprotected metal substrate, are observed in particular. In addition to these outstanding properties, the coatings produced with the coating compositions of the invention have an excellent Resistance to condensation, excellent adhesion to the anticorrosive layer and to the basecoat as well as excellent stability of the inherent color after curing. Furthermore, filler layers having a comparatively low stoving temperature and a good topcoat level can be achieved with the coating composition according to the invention.

The following examples are intended to illustrate the invention.

Examples

Preparation Example 1: Synthesis and Modification of Hydrotalcite

To a 0.21 molar aqueous solution of 4-aminobenzenesulfonic acid (4-absa) is added an aqueous mixture of MgCl 2 .6H 2 O (0.52 molar) and AlCl 3 .6H 2 O (0.26 molar) at room temperature under nitrogen atmosphere with constant stirring 3 hours, wherein the metered amount of cations is chosen so that a molar ratio of the 4-para counterion to the trivalent Al cation of 4: 1 results. The pH is kept constant at pH = 10 by addition of a 3 molar NaOH solution.

After addition of the aqueous mixture of the metal salts, the resulting suspension is aged at room temperature for 3 hours. The resulting precipitate is isolated by centrifugation and washed 4 times with deionized water. The resulting suspension of the white reaction product

Mg2Al (OH) 6 (4-absa) -2H2O (hydrotalcite suspension) has a solids content of 26.3% by weight and a pH of 10.

Preparation Example 2 Formulation of the Coating Composition According to the Invention

16.1 g of the hydrotalcite suspension prepared according to Example 1 are mixed with stirring in 88.9 g of an aqueous polyurethane dispersion a solids content of 40 wt .-% (DAOTAN VTW 1225 Fa. CYTEC Corp. with an OH number according to DIN EN ISO 4629 of 45 and an acid number according to DIN EN ISO 3682 of 40 mg KOH / g) until the hydrotalcite Suspension is completely dissolved (visual inspection). The resulting dispersion is treated with ultrasound for 15 minutes at room temperature with stirring, the tip of an ultrasonic source (Sonotrode UP 100H from Hielscher GmbH) being immersed in the dispersion and the amplitude and pulse rate be set to 100% at a working frequency of 30 kHz. During the ultrasonic treatment, the temperature of the dispersion rises to 65 degrees C.

The resulting dispersion is aged for 12 hours and then admixed with stirring at room temperature with 9.6 g of melamine-formaldehyde resin (Maprenal MF 900 from Ineos Melamines GmbH). After addition of another 50 g of deionized water results in an aqueous dispersion having a solids content of 28.0 wt .-% and a pH of 7.4.

Example 3 Application of the Coating Composition According to the Invention and Testing of Stone Stripping Strength

The coating composition prepared according to Example 2 according to the invention is applied to pretreated and precoated with a cathodic dip paint steel panels (steel panels from. Fa. Chemetall: thickness of the baked cathodic dew lacquer: 21 +/- 2 microns, thickness of the substrate: 750 microns) by spraying ( Automatic coater from Köhne). The resulting layer of the coating composition of the invention is cured for 20 minutes at 140 degrees C, resulting in a dry film thickness of 30 +/- 3 microns. The evaluation of TEM images of cross sections of the baked coating agent shows that the ratio (D / d) of the average particle size diameter (D) of the dispersed hydrotalcite particles whose average particle thickness (d) is about 200.

For comparison purposes, a commercial filler (FU43-9000 Fa. BASF Coatings AG: reference filler) is applied to the pretreated and precoated with a cathodic dip paint steel panels in accordance with the manufacturer for 20 minutes at 150 degrees C, that also has a dry film thickness of 30 + / - 3 microns results. For the production of an OEM layer structure, a commercially available aqueous basecoat material (FV95-9108 from BASF Coatings AG) is first applied to the boards precoated in this way, flashed off at 80 ° C. for 10 minutes, and finally a solvent-containing 2-component Clearcoat (FF95-0118 Fa. BASF Coatings AG) applied. The aqueous basecoat and the clearcoat are cured together at 140 ° C. for 20 minutes, after which the basecoat film has a dry film thickness of about 15 .mu.m and the clearcoat film has a dry film thickness of 45 .mu.m. The thus coated panels are stored for 3 days at 23 degrees C and 50% relative humidity.

Checking the rocking strength:

The coated steel panels prepared as described above are subjected to a rockfall test according to DIN 55996-1, wherein in each case 500 g of cooled iron granules (4 to 5 mm particle diameter, Fa. Würth, Bad Friedrichshall) are used and an air pressure of 2 bar at the bombardment (Model 508 VDA Fa. Erichsen) is set.

After cleaning the test panels thus damaged, they are immersed in a solution of an acidic copper salt, whereby elemental copper is deposited at the locations of the steel substrate at which the coating has been completely removed by the bombardment. The damage pattern on each 10 cm ^{2 of} the damaged and post-treated test panels are recorded by means of image processing software (SIS analysis, BASF Coatings AG, Münster). The proportions of the surfaces damaged by bombardment and the proportions of the completely removed surfaces, in each case based on the total surface, are evaluated. Table 1 shows the results.

Table 1: Damage patterns of the layer structure produced by the coating material according to the invention and the reference filler

Compared with the layer structures produced with the reference filler, the layer structures produced with the coating material according to the invention as a filler material have a reduction of the proportion of the damaged surface by 50% and a very significant reduction of the proportion of the completely ablated surface, that is the surface area of the unprotected metal substrate to over 80% up.

The adhesion to the cathodic dip coat and base coat layer is excellent, resulting in significantly reduced delamination at the layer boundaries.

In addition, the coating produced with the coating composition according to the invention has an excellent condensation water content. Resistance and a virtually unchanged own color after baking on.

Claims

claims:

1. An aqueous coating composition comprising at least one water-dispersible polymer (WP) having at least one crosslinkable functional group (a) and positively charged inorganic particles (AT) whose ratio D / d of the average particle diameter (D) to the average particle thickness (d) > 50, characterized in that the charge is at least partially compensated with singly charged organic anions (OA).

2. Aqueous coating composition according to claim 1, characterized in that it comprises at least one crosslinking agent (V) having at least two functional groups (b), which with the functional groups (a) of the water-dispersible polymer (WP) during curing of the coating composition to form covalent bonds react, contains.

3. An aqueous coating composition according to claim 1 or 2, characterized in that the singly charged organic anions (OA) have an anionic group (AG) and / or at least one functional group (c), which with the functional groups (a) and / or (b) reacts upon curing of the coating agent to form a covalent bond.

4. An aqueous coating composition according to claim 3, characterized the functional group (c) is a hydroxyl group, an epoxy group and / or an amino group.

5. Aqueous coating composition according to one of claims 3 or 4, characterized in that the singly charged organic anions (OA) have a spacer (SP) between anionic group (AG) and functional group (c), wherein (SP) is selected from the group of optionally heteroatoms, such as nitrogen, oxygen and / or sulfur, modified and optionally substituted aliphatic and / or cycloaliphatic having a total of 3 to 30 carbon atoms, optionally with heteroatoms, such as nitrogen, oxygen and / or sulfur, modified and optionally substituted Aromatics with a total of 3 to 20 carbon atoms and / or the substructures of the above

Cycloaliphaten and aromatics, wherein in the substructures at least 3 carbon atoms and / or heteroatoms between the functional group (c) and the anionic group (AG) are.

6. An aqueous coating composition according to any one of claims 3 to 5, characterized in that the anionic group (AG) is selected from the group of monovalent anions of carboxylic acid groups, sulfonic acid groups and / or phosphonic acid groups.

7. An aqueous coating composition according to any one of claims 1 to 6, characterized in that the inorganic particles (AT) at least one mixed hydroxide of the general formula (M ₍ _1.x) ²⁺ M _x ³⁺ (OH) ₂ ) (A _{x / y} ^y -) n H ₂ O

wherein M ²⁺ divalent cations, M ³⁺ trivalent cations and (A) represent anions with a valency y and wherein at least a part of the anions (A) is replaced by the singly charged organic anions (OA).

8. An aqueous coating composition according to claim 7, characterized in that M ²⁺ calcium, zinc and / or magnesium ions are selected as divalent cations and / or are selected as trivalent cations M 3 ⁺ aluminum ions and / or as anions (A) Chloride ions, phosphate ions, sulfate ions and / or carbonate ions can be used.

9. A process for the production of impact resistant OEM composite layers, consisting of a directly applied to the substrate corrosion protection layer, a filler layer, a

Basecoat film and a final clearcoat film, characterized in that at least one layer of the aqueous coating composition according to one of claims 1 to 8 is formed.

10. The method according to claim 9, characterized in that the filler layer is formed from the aqueous coating composition according to one of claims 1 to 8.