Stabilized fine, thin aluminium effect pigments with radar transparency

Abstract

This invention deals with providing aluminium effect pigment preparation comprising: a) 10 to 30 wt.% of aluminum effect pigments obtained by grinding and having a d50 in a range of 1,5 to 7,0 µm µm and a median thickness t50 in a range of 15 to 50 nm, b) a first passivating additive based on a phosphate ester containing polymer, c) a second dispersing additive based on a propoxylated or an ethoxylated adduct of a polyamine, wherein the sum of the contents of components b) and c) is in a range of 10 to 30 wt.% and d) a balance of a solvent or solvent mixture, wherein the content ranges each refer to the total aluminum effect pigment preparation. The aluminum effect pigments exhibit radar transparency and are stable also in aqueous-based coating formulations.

Description

Stabilized fine, thin aluminium effect pigments with radar transparencyThe present invention relates to an effect pigment preparation comprising fine and thin aluminum pigments with radar transparency and two additives with passivating and dispersing properties.Aluminum effect pigments are widely used as metallic effect pigments. However, coated films containing them cause problems in radar transparency which is increasingly demanded because of the increasing use of radar systems for distance measurements and on the way to autonomous driving cars.Radar sensors are used to detect objects in the environment, such as other vehicles or pedestrians, and to measure their distance from the vehicle and their relative speeds. Radar is the acronym for “radio detection and ranging” and means radio-based detection and distance measurement. The radar sensor is therefore a sensor based on electromagnetic radiation. Radio waves are emitted by a radiation source and the radio waves reflected from surrounding objects are registered by the radar sensor. The values measured here are converted into electrical signals, which are finally evaluated in special control devices. Radar sensors primarily work in the frequency range of 76 GHz to 81 GHz, although other frequency ranges are possible in principle.However, slanted reflection surfaces can influence the measurement result. As radio beams can penetrate non-conductive materials such as plastic and for aesthetic reasons, radar sensors are usually mounted behind such panels in the vehicle, typically behind of bumpers. However, such panels, including the vehicle paintwork on them, must not be too attenuating to radio radiation.For the most accurate detection and distance measurement possible, formulations for painting a vehicle equipped with a radar sensor must therefore have sufficiently high radio wave transmission.US 2010 / 0022696 A1, WO 2020 / 208134 A1 and EP 4010438 A1 all propose mixtures of aluminum effect pigments with pearlescent pigments to obtain radar transparency.However, pearlescent pigments are expensive and for coloristic reasons they are not wanted in all automotive coating formulations.WO 2016 / 168455 A1 discloses dry effect pigment preparations, wherein the effect pigment is preferably aluminum and the preparation contains a passivating additive and a dispersive additive. Nothing in this document is said about radar transparency of the effect pigment.DE 10227657 A1 discloses dry pigment preparations with a wide range of pigments which are easy to stir-in various coating systems and provide a high Chroma.WO 2010 / 103031 discloses dry pigment preparations with a wide range of pigments which are easy to stir-in various coating systems and provide a high Chroma and are particularly usable in solvent-borne coatings or in aqueous vinyl acetate dispersions.It is an object of this invention to provide an aluminum effect pigment which is radar transparent in coatings even without additional addition of radar transparent effect pigments such as pearlescent pigments and which is gassing stable in aqueous base coats. Furthermore, the aluminum effect pigment should be compatible with a wide range of solvent borne and aqueous base coats. The aluminum effect pigments are safe to be transported. A further object is to provide an effect pigment which has a basic greyish appearance but still a metallic flop.The objects are solved by providing an aluminium effect pigment preparation comprising: a) 10 to 30 wt.% of aluminum effect pigments obtained by grinding and having a dso in a range of 1 ,5 to 10,0 pm and a median thickness tso in a range of 15 to 50 nm,b) a first passivating additive which is a polymer comprising phosphoric acid ester groups with an olefinic backbone,c) a second dispersing additive based on a propoxylated or an ethoxylated adduct of a polyamine,wherein the sum of the contents of components b) and c) is in a range of 10 to 30 wt.% andd) a balance of a solvent or solvent mixture,wherein the content ranges each refer to the total aluminum effect pigment preparation.Further preferred embodiments are displayed in claims 2 to 12.A further aspect of this invention is the use of an aluminium effect pigment preparation comprising:a) 10 to 30 wt.% of aluminum effect pigments obtained by grinding and having a dso in a range of 1 ,5 to 10,0 pm and a median thickness tso in a range of 15 to 50 nm,b) a first passivating additive which is a polymer comprising phosphoric acid ester groups with an olefinic backbone,c) a second dispersing additive based on an propoxylated or ethoxylated adduct of a polyamine,wherein the sum of the contents of components b) and c) is in a range of 10 to 30 wt.% andd) a balance of a solvent or solvent mixture, wherein the content ranges each refer to the total aluminum effect pigment preparation,in aqueous based coating formulations.Detailed description:Aluminum effect pigments:The sizes of the metal effect pigments of the invention are determined customarily by means of laser granulometry. This analysis produces a cumulative frequency distribution of the volume-averaged size distribution function. In this context, the dso value indicates that value at which 50% of the measured effect pigments have a volume-average diameter which is the same as or less than the particular value indicated. The scattered light signals are evaluated according to the Fraunhofer approximation. The size distribution is measured preferably using the particle size analyzer manufactured by Sympatec GmbH (model: Helos / BR) and following the instructions of the manufacturer.The dso of the aluminum effect pigments is in a range of 1 ,5 to 10,0 pm, preferably in a range of 1 ,7 to 9,0 pm, more preferably in a range of 1 ,7 to 8,0, even more preferably in a range of 1 ,7 to 7,0, further more preferably in a range of 2,0 to 5,0 pm and most preferably in a range of 2,2 to 4,3 pm.Below of a dso of 1 ,5 the aluminum particles become too small to yield metallic effects like flop and gloss because of the increasing effect of scattering phenomena at the edges of the platelet-shaped aluminum pigments. Above of a dso of 10,0 pm the radar transparency of coatings pigmented with these aluminum effect pigments becomes increasingly too low.The aluminum effect pigment thicknesses are determined by measurements on the basis of scanning electron microscope (SEM) images according to the method basically disclosed in paragraphs

[0124] to

[0128] of EP 1613702 B1 The metal effect pigments in the cross-section are then imaged using a scanning electron microscope at magnifications ranging from 30000x to 50000x. The pigment thickness of at least 50 different metal effect pigments is determined. For each platelet-shaped metal pigment visible in the SEM picture a value is determined which corresponds to the average thickness value of this flake to compensate different thicknesses within one flake. For example, the minimum thickness and the maximum thickness of a particular flake can be determined and averaged, thereby of course avoiding artefacts. The median pigment thickness to then represents the 50-quantil of the determined pigment thickness distribution function.The median thickness tso of the aluminum effect pigments is in a range 15 to 50 nm, preferably in a range of 18 to 40 nm and more preferably in a range of 20 to 35 nm.Below of 15 nm median thickness the aluminum effect pigments become too dark to obtain a silvery optical appearance and above of 50 nm the hiding powder is strongly decreasing. These median thicknesses are typical for so-called PVD-aluminum effect pigments which represent the highest class of aluminum effect pigments available. Deu to the small thicknesses and the rather small sizes the aluminum effect pigments obtained by grinding have rather large specific surfaces which make them difficult to be coated with commonly known technologies.It surprisingly turned out that these small and thin aluminum effect pigments can produce a reasonable optical effect of a silvery to grey metallic effect pigment and a structureless optical effect and at the same time have a high radar transparency. Coating formulations including these aluminum effect pigments do not need to be mixed with non-conducting effect pigments such as pearlescent pigments to obtain radar transparency. This opens new possibilities to the stylings of future automotive basecoats which have to consider the radar transparency.The basic aluminum effect pigments are preferably manufactured according toUS 2015344716 A1. For the grinding step lubricants like stearic acid, oleic acid or mixtures thereof may be used. More preferred is the use of special lubricants based on polycarboxides which preferably contain ethoxylated structures whose structures and manufacture are described in detail on paragraphs

[0056] to

[0058] and on paragraphs

[0072] to

[0126] and pre-examples 1 of US 2015344716 A1.As these lubricants are used in amounts of a few wt.% based on the amount of aluminum powder used for the grinding their final concentration in the aluminum effect pigment preparation of this invention is about in a range of 0,1 to 1,0 wt.%, preferably in a range of 0,2 to 0,7 wt.%, based on the whole aluminum effect pigment preparation.Passivating first additive b):The first passivating additive is a polymer comprising phosphoric acid ester groups with an olefinic backbone. It preferably comprises polymerized styrene components. In further preferred embodiments the passivating additive is a copolymer based on styrene monomers copolymerized with allyl alcohol, wherein the allyl alcohol is at least partially esterified with phosphoric acid. Additionally, further phenolic components may be part of the additive such as tert-butylphenol, para-1 ,1 -propyl phenol and the like as described in US 2008 / 306241 A1. The amount in mol of the styrene component to the allyl component is preferably in a range of 1 ,4 to 3,0 and more preferably in a range of 1 ,5 to 2,5.The acid number of the passivating additive is preferably in a range of 50 to 80 mg KOH / g and more preferably in a range of 55 to 70 mg KOH / g.An example of a commercially available additive is Lubrizol 2062 from Lubrizol.In preferred embodiments the ratio by weight of the amount of the first passivating additive b) to aluminum effect pigments a) is in a range of 0,20 to 0,80, more preferably in a range of 0,35 to 0,70 and most preferably in a range of 0,40 to 0,65. The exact amount may depend on the aluminum substrate used and can be determined by the skilled person. Below of a ratio of 0,20 the passivating properties may not be enough and above of a ratio of 0,80 an excess of the passivating additive b) may exist with no more beneficial effects. In some cases, such high amounts may have adverse properties of the whole coating formulation.Dispersing second additive c):The second dispersing additive is_based on a propoxylated or an ethoxylated adduct of a polyamine. It is therefore a polyamine in which polyether with terminal hydroxy groups are bonded to amine groups.In preferred embodiments this second additive the dispersing additive c) is suitable for aqueous-based and for solvent-based coating formulations.The polyamine backbone may be a polyethyleneimine, a tetrafunctional amine, a trifunctional amine or a diamine, wherein a diamine is most preferred.Diamines may be ethylene diamine, propylene diamine, butylene diamine, pentylene diamine or hexylene diamine. Most preferred is ethylene diamine. The number of ethoxy-or of propoxy-units in the polyether groups is preferably in a range of 1 to 15 and more preferably in a range of 2 to 8 per nitrogen atom.In some embodiments the polyamine is ethoxylated, wherein the degree of ethoxylation may vary. In preferred embodiments the dispersing additive c) is an ethoxylated adduct of an ethylene diamine. An example of a commercially available additive is Multranol 9181 from Covestro AG.In preferred embodiments the ratio by weight of the amount of the second dispersing additive c) to aluminum effect pigments a) is in a range of 0,30 to 0,60 and more preferred in a range of 0,35 to 0,55.Below of a ratio of 0,30 the dispersing properties may not be enough and above of a ratio of 0,60 an excess of the dispersant additive c) may exist with no more beneficial effects. In some cases, such high amounts may have adverse properties of the whole coating formulation.Aluminum effect pigment preparation:The aluminum effect pigment preparation contains aluminum effect pigments obtained by grinding in an amount in a range of 10 to 30 wt.% and preferably in a range of 15 to 25 wt.%, based on the total amount of the effect pigment preparation.Such amount ranges are close to the concentration of PVD aluminum effect pigments in dispersions which are usually in the range of 10 to 20 wt.%. These concentration ranges are much lower than for conventional aluminum effect pastes where the concentration is in a range of about 50 to 70 wt.% and even lower compared to dry aluminum effect preparations. The rather low concentration is due to the very high specific surface of the particular aluminum effect pigments.The aluminum effect pigment preparations of this invention can be regarded as pastes with a creamy consistence which can be easily managed when incorporating the pigment preparation into the final application formulation.The aluminum pigment preparation of this invention preferably does not contain binder systems. Such binder systems can be found in numerous of effect pigment preparationsand have the disadvantage that the presence of a binder always limits their availability and compatibility in various coating systems. Such binder containing preparations are of course well suited for coating formulations using similar or compatible binder, however, not to coating formulations using chemically different binders. To achieve a broad compatibility then many of such preparations must be offered with different binder systems which make their production more expensive and awkward to manage and lead to large portfolio of pigment preparations.The present aluminum effect pigment preparation is instead compatible with many of aqueous-based or solvent-based coating formulations.The two additives used in the effect pigment preparation neutralize each other to a certain extent.In preferred embodiments the ratio by weight of the first additive b) to the second additive c) is in a range of 0,5 to 1 ,4, more preferred in a range of 0,85 to 1 ,30, and most preferred in a range of 0,90 to 1 ,25.Below of a ratio of 0,5 the effect pigment preparation may contain too much of the second dispersing additive and above of a ratio of 1 ,4 the effect pigment preparation may contain too much acidic components.The balance of the composition of the effect pigment preparation is achieved with solvent or a solvent mixture.In preferred embodiments the solvent mixture contains a solvent having a boiling point of 200 °C or larger in an amount in a range of 0,00 to less than 1 ,00 wt.%, more preferably in a range of 0,20 to 0,70 wt.%, based on the whole aluminum effect pigment preparation. Therefore, the solvent or the solvent mixture a solvent mixture has a boiling point of lower than 200 °C.Generally the solvent is preferably chosen from isopropanol, 1-methoxy-2-propanol, 2-methoxy-1 -propanol, 1-ethoxy-2-propanol, 2-ethoxy-1 -propanol, n-butanol, isobutanol, n-propanol, butyl glycol, butyl glycol acetate, butyl acetate, n- propyl acetate, isopropyl acetate, 1-methoxy-2-propanol acetate, ethyl acetate, methyl acetate, ethanol, methanol, methylethyl ketone, methyl diglycol ether, methyl glycol ether, 3-methoxy-butyl acetate and mixtures thereof.Particularly for an intended use in aqueous-based coating formulations the solvents are preferably isopropanol, 1-methoxy-2-propanol, 2-methoxy-1 -propanol, 1-ethoxy-2-propanol, 2-ethoxy-1 -propanol, n-butanol, isobutanol, butyl glycol, butyl glycol acetate, n-propanol, ethanol, methanol, and mixtures thereof.Use in coating formulations and Coating formulations:The aluminum effect pigment preparations can be use in aqueous based coating or in solvent-based coating formulations. More preferably they are used in aqueous based coating formulations.Particularly preferred is their use in aqueous based automotive coating formulations which exhibit radar transparency.The aluminum effect pigment preparation is used for the coating formulation in such amounts that the final concentration of aluminum effect pigments in the coating formulation is preferably in a range of 0,2 to 1 ,2 wt.%, more preferably in a range of 0,3 to 1 ,0 wt.% and most preferably in a range of 0,4 to 0,9 wt.%, each referred to the total coating formulation.Such rather low concentrations are possible because of the very high hiding power of these thin, fine aluminum effect pigments.The coating formulation will contain in quite similar amounts the two additives b) and c) which corresponds to usual amounts of such additives used therein.Very preferred coating formulations are so-called low solid coating formulations (having non-volatile amounts of smaller than 30 wt.% and preferably smaller than 10 wt.%) This is again a certain analogy to PVD aluminum effect pigments as these aluminum pigments can best evolve their optical properties at low pigment to binder ratios.Presently various uni grey or grey color tones with certain glitter effects are very in fashion in automotive coatings. However, these coatings lack a distinct metallic flop.Particularly the fine, thin aluminum effect pigments of this invention can fill this gap.Coating systems pigmented with these aluminum effect pigments result in an optical appearance with a greyish and structure less base tone (typically characterized by the 45° observation angle in the CIELAB color system) and additionally a metallic flop. Such coatings can have the attractive grey basic tone and additionally metallic flop which can be hardly reached when combining an uni grey tone which always contains white and black color pigments with conventional aluminum flakes.Such coating formulation, as used according to the present invention for coating a vehicle equipped with a radar sensor, has sufficiently high radio wave transmission. To characterize the radar behavior the radar attenuation can be used. However, this parameter may strongly depend on the whole measurement set-up. A better choice is the relative dielectric constant, which is also referred to as permittivity e, which is particularly used to characterize the radio wave transmission, as is also described in F. Pfeiffer, “Analyse und Optimierung von Radomen fur automobile Radarsensoren”, dissertation, Technical University of Munich, 2009. The smaller the permittivity e, the less the radio waves are attenuated. Typically, the vehicle paintwork resulting from the coating formulation has a permittivity e of at most 20, and more preferably at most 10 in the frequency range of 76 GHz to 81 GHz. With such permittivity, the paint formulation is particularly suitable for use in painting a vehicle equipped with a radar sensor. This parameter is a measure of the coating film containing the effect pigments and is independent of the details of the measurement set-up.The permittivity e in the frequency range of 76 GHz to 81 GHz is determined by using a commercially available Radom scanner. After calibration, the ABS measuring plates used, which have a thickness of 1 ,5 mm, are measured before and after application of the coating formulation. In both cases, the radio beams are irradiated perpendicular to the surface of the measuring plates. The permittivity e can finally be determined from the measured values, whereby it is constant over the frequency range selected in the present case. The commercially available Radom scanner used here is the device “Radom Measurement System” from the company perisens GmbH, Feldkirchen near Munich, Germany.Further aspects of this invention are also dedicated to the use of the fine, thin aluminum effect pigments without the addition of passivating additive b) and dispersing additive c) in solvent-borne automotive coating formulations.Herein a first aspect is the use of aluminum effect pigments obtained by grinding and having a dso in a range of 1 ,5 to 10,0 pm and a median thickness tso in a range of 15 to 50 nm in solvent-born automotive coating formulations.In a second aspect according to aspect 1 the solvent-borne automotive coating formulation is used to form radar transparent coating film on a plastic substrate.In a third aspect according to aspects 1 or 2 the aluminum effect pigments have a concentration in a range of 0,2 to 1 ,2 wt.%, preferably in a range of 0,3 to 1 ,0 wt.% and more preferably in a range of 0,4 to 0,9 wt.%, each referred to the total coating formulation.In a fourth aspect according to aspects 1 to 3, the dso values of the aluminum effect pigments are in a range of 1 ,7 to 7,0 pm, preferably in a range of 2,0 to 5,0 pm and more preferably in a range of 2,2 to 4,3 pm.In a fifth aspect according to aspects 1 to 4, the tso values of the aluminum effect pigments are in a range of 18 to 40 nm and preferably in a range of 20 to 35 nm.A sixth aspect refers to a solvent-borne coating formulation containing aluminum effect pigments obtained by grinding and having a dso in a range of 1 ,5 to 7,0 pm and a median thickness tso in a range of 15 to 50 nm.In a seventh aspect according to aspect 6, the solvent-borne automotive coating formulation is used to form radar transparent coating film on a plastic substrate.In an eighth aspect according to aspects 6 and 7 the aluminum effect pigments have a concentration in a range of 0,2 to 1 ,2 wt.%, preferably in a range of 0,3 to 1 ,0 wt.% and more preferably in a range of 0,4 to 0,9 wt.%, each referred to the total coating formulation.In a ninth aspect according to aspects 6 to 8, the dso values of the aluminum effect pigments are in a range of 1 ,7 to 6,0 pm, preferably in a range of 2,0 to 5,0 pm and more preferably in a range of 2,2 to 4,3 pm.In a tenth aspect according to aspects 6 to 9, the tso values of the aluminum effect pigments are in a range of 18 to 40 nm and preferably in a range of 20 to 35 nm.EXAMPLESPre-Example 1a (according to pre-example of US 2015344716 A1):Atomization of aluminum powder:First aluminum muzzles were introduced into an induction furnace and melted. Then the molten aluminum was transferred into an induction furnace with a forehearth. The molten aluminum present in liquid form in the forehearth at a temperature of approximately 720° C was atomized or sprayed vertically upwards through an atomizing nozzle attached to the forehearth. A closed nozzle was used to atomize the molten aluminum. The aluminum particles formed during the atomization solidify and cool in flight. The atomization, which is also called spraying, took place with hot gas at approximately 600° C being fed in. The hot gas used for the atomization was compressed, then heated in gas heaters and then incorporated into the molten aluminum to be atomized. The aluminum particles were separated out by means of centrifugal force. The powdered aluminum grit separated out there had a dso of <20 pm. The gas-solid separation took place in a filter. The further separation of this aluminum grit took place by further screening steps. This resulted in a very fine powdered aluminum grit produced with a dso.grit of 1 ,5 pm.Pre-Example 1b:Production of Grinding Additive (on the basis of EP 1 304210 A1)50 g Pripol 1009 (hydrogenated C36 dimer acid from Unichema) and 89 g MPEG 750 (methoxy polyethylene glycol) were weighed out into a glass reaction vessel and heated to 80° C. under N2 protective gas and accompanied by stirring. Then 0,8 g p-toluenesulfonic acid (catalyst) was added and heated to 180°C. Any water of reaction forming was separated out via a water separator. The progress of the reaction was controlled using the acid number. The acid number was determined according to DIN 53402. The reaction was stopped after the acid number reached approximately 24 mg KOH / g additive. This corresponds to a level of esterii cation of approx. 67%. The average molecular weight of the ester formed was approx. 1750 g / mol.Pre-Example 1c: GrindingFor the wet grinding of the very fine aluminum grit produced according to step a), 1200 g of this metal grit was introduced into a stirred ball mill with 2,5 kg ceramic balls (diameter: 0,6 mm) and 2000 g isopropanol as well as 80 g grinding additive according to Ex. 1 b and ground at 1200 rpm for 20 h. The grinding product was separated from the ceramic balls by rinsing with solvent and filtered off via a laboratory nutsche filter. The filter cake wasthen set to a solids content of 60 wt.-%. The aluminum flakes obtained had a dso -value of 4,0 pm and a median thickness tso of 30 nm.Pre-Example 2c: The same procedure as in Pre-Example 1a to 1c, but the grinding time was extended to about 30 h yielding an aluminum flake with a dso of 2,5 pm and a median thickness tso of 20 nm.Pre-Example 3c: The same procedure as in Pre-Example 1a to 1c, but the aluminum powder had a dso.grit of 1 ,8 pm and the grinding was conducted in a ball mill with a grinding time of about 25 h yielding an aluminum flake with a dso of 8,5 pm and a median thickness tso of 25 nm. The filter cake was then set to a solids content of 50 wt.-%.Example 1:A mixer was charged with 2,17 kg of 1-methoxy-2-propanol and 1 kg of Multranol 9181 (Covestro) was dissolved therein under stirring. Then 2.0 kg Lubrizol 2062H were added to the solution and stirred until a clear solution was obtained. Another vessel was charged with 3,33 kg of the aluminum filter cake obtained from Pre-Example 1c having a dso of 4,0 pm and a non-volatile content of 60% in further 1 ,5 kg of 1-methoxy-2-propanol. To this dispersion the first solution containing the additive mixture was dosed within 10 min under stirring at room temperature. The resulting paste had a content of aluminum effect pigments of 20 wt.%.Example 2:A mixer was charged with 2,17 kg of 1-methoxy-2-propanol and 1 kg of Multranol 9181 was dissolved therein under stirring. Then 2,0 kg Lubrizol 2062H were added to the solution and stirred until a clear solution was obtained. Another vessel was charged with 3,33 kg of Pre-Example 2c having a dso of 2,5 pm and a non-volatile content of 60% in 1 ,5 kg of 1-methoxy-2-propanol. To this dispersion the first solution containing the additive mixture was dosed within 10 min under stirring at room temperature. The resulting paste had a content of aluminum effect pigments of 20 wt.%.Comparative Example 1a: SiO2 coating of 4 pm aluminum pigmentIn a 1 I double jacketed reactor equipped with thermostat, reflux condenser and anchor stirrer 50,0 g of the aluminum effect pigment paste of pre-example 1c (corresponding to 30 g Al) were dispersed in 158 g isopropanol. 20,6 g of tetra ethoxy silane were added and the dispersion was heated up to 80 °C. 36 g of water was added and 10 g of ethylenediamine dissolved in 40 g of isopropanol were dosed into the reaction mixture within 1 hour and the reaction was further stirred for 3 hours. 1 g of Dynasylan Octeo dissolved in 6 g isopropanol and 2,4 g of Dynasylan AMMO were added to the reaction mixture. After 2 hours of stirring, it was cooled down to 40 °C and the coated aluminum pigments were separated by filtration through a Buchner funnel.Comparative Example 1b: hybrid Mo-oxide / SiO2 coating according to WO 2022 / 263375 A1 of 4 pm aluminum pigment5.0 g Molybdic acid (MoOs * H2O) were dispersed in 15 g H2O2 and stirred until a clear solution is obtained (approx. 1 h). In a 1 I double jacketed reactor equipped with thermostat, reflux condenser and anchor stirrer 139 g of the aluminum effect pigment paste of pre-example 1c (corresponding to 83,5 g Al) were dispersed in 320 g isopropanol. The dispersion was heated up to 40 °C. 0,20 g of the peroxo molybdic acid solution were added together with 15,1 g of water and the dispersion stirred for 60 minutes. 1215,1 g tetraethoxy silane were added and the dispersion was heated to 80 °C. 12,0 g ethylene diamine dissolved in 40 g isopropanol were continuously dosed during 60 min to the mixture and it was stirred for further 3 h. 3,50 g diphenyl dimethoxy silane dissolved in 100 ml isopropanol were added and then 14,4 g tetraethoxy silane were dosed into the mixtures over one hour. The dispersion was further stirred for 120 min and then 5g of Dynasylan Octeo dissolved in 6 g isopropanol and 2,4 g of Dynasylan AMMO were added to the reaction mixture. After 2 hours of stirring, it was cooled down to 40 °C and the coated aluminum pigments were separated by filtration through a Buchner funnel.Comparative Example 2a: SiO2 coating of 2,5 pm aluminum pigmentLike Comparative Example 1 a, but the Pre-Example 2c was used as aluminum effect pigment instead and the amounts of tetraethoxy silane, water, and the organofunctional silanes were increased by 25%.Comparative Example 2b: hybrid SiO2 coating of 2,5 pm aluminum pigmentLike Comparative Example 1 b, but the Pre-Example 2c was used as aluminum effect pigment instead and the amounts of tetraethoxy silane, water, diphenyl dimethoxy silane and the further organofunctional silanes were increased by 25%.In further experiments the amounts of tetraethoxy silane, ethylene diamine, and water were varied, but no better results were obtained.Comparative Example 3:Procedure like in Example 1 , but without the addition of Multranol 9181.Comparative Example 4 - 9: Procedures like in Example 1 or Example 2, but with different passivating additives listed in table 1. The concentrations refer to the delivery form of the additive named. No second additive was added here. The concentration of aluminum flakes was always 20 wt.%. The amount of 1-methoxy-2-propanol was adapted in each sample and is listed in table 1. In recipes displaying butanol or polypropylenglycol additionally these solvents were added to the aluminum effect pigment dispersion substituting an appropriate amount of 1-methoxy-2-propanol as described in Examples 1 and 2.Example 3:A mixer was charged with 6,0 kg of 1-methoxy-2-propanol and 1 ,0 kg of Multranol 9181 was dissolved therein under stirring. Then 2,0 kg Lubrizol 2062H were added to the solution and stirred until a clear solution was obtained. Another vessel was charged with 4,0 kg of Pre-Example 3c having a dso of 8,5 pm and a non-volatile content of 50%. To this dispersion the first solution containing the additive mixture was dosed within 10 min under stirring at room temperature. The resulting paste had a content of aluminum effect pigments of 15 wt.%.Table 1: Comparative Examples only with passivation additiveSample Metal Passivation Additive pigment Amount Solvent (dso) Name additive Comp. 20% Isopropanol 2,5 pm Lubrizol 12% Example 34% 1-methoxy-2-propanol, 20623a 12% Butanol2% DMEA 100%Comp. 20% Isopropanol 4 pm Lubrizol 12% Example 34% 1-methoxy-2-propanol 20623b 12% Butanol2% DMEA 100%Comp. 20% Isopropanol 2,5 pm Lubrizol 10% Example 4 49% 1-methoxy-2-propanol, 20631 % DMEA 100%Comp. 20% Isopropanol 2,5 pm Xi ran 8% Example 5 50% 1-methoxy-2-propanol, 1000MA2% DMEA 100%Comp. Ex. 20% Isopropanol 2,5 pm Resydrol 8% 6 50% 1-methoxy-2-propanol, VAX 55382% DMEA 100%Comp. Ex. 20% Isopropanol 2,5 pm BYK 4510 10% 7a 49% 1-methoxy-2-propanol,1% DMEAComp. Ex. 20% Isopropanol, 4 pm BYK 4510 10% 7b 49% 1-methoxy-2-propanol,1% DMEA 100%Comp. Ex. 20% Isopropanol, 2,5 pm Nacorr XR- 10% 8 55% 1-methoxy-2-propanol 419Comp. E. 20% Isopropanol 2,5 pm Nacorr 4426 10% 9 55% 1-methoxy-2-propanol* Dimethyl ethanol amineComparative Examples 10 to 19:Like in Example 1 or 2, but different additives and amounts of additives and sometimes different solvents were used which are displayed in table 2. The concentrations refer to the delivery form of the additive named. The concentration of aluminum effect pigments was always 20 wt.%.Table 2: Comparative Examples with different combinations of first and second additivesdso of Passivation Dispersing additive Solvent Al pig- AdditiveSample ment name amount name amount Comp. 20% Isopropanol 2,5 pm Lubrizol 8% Disperbyk 4% Ex. 10 55% 1-ethoxy-2- 2062 2012propanol DMEA 1%Comp. 20% Isopropanol 2,5 pm Lubrizol 12% Disperbyk 4% Ex. 10a 44% 1 -methoxyl2062 2012propanolComp. 20% Isopropanol 4 pm Lubrizol 10% Disperbyk 2% Ex. 11 40% 1 -methoxyl2062 2060propanol +PPG * 8% Comp. 20% Isopropanol 2,5 pm Lubrizol 12% Disperbyk 9,5% Ex. 11a 38% 1 -methoxyl2062 2060propanolComp. 20% Isopropanol 4 pm Lubrizol 15% Disparlon 5% Ex. 12 55% 1 -methoxyl2062 320propanol +PPG* 5% Comp. 20% Isopropanol 2,5 pm Lubrizol 8% Solsperse 4% Ex. 13 50% Methoxy2062 40000propanolComp. 20% Isopropanol 2,5 pm Lubrizol 12% Solsperse 8,5% Ex. 13a 39% 1 -methoxyl2062 40000propanolComp. 20% Isopropanol, 4 pm Lubrizol 15 % Multranol 5% Ex. 14 35% Methoxy2062 9181 +propanol PPG* 5%Comp. 20% Isopropanol, 2,5 pm Lubrizol 8% Additol 4% Ex. 15 34% 1 -methoxyl2062 XL250propanol, DMEA 2%12% ButanolComp. 20% Isopropanol, 2,5 pm Lubrizol 12% Additol XL 5% Ex. 15a 44% 1 -methoxyl2062 250propanolComp. 20% Isopropanol, 4 pm BYK 4509 9% Multranol 6% Ex. 16 45% 1 -methoxyl9181propanolComp. 20% Isopropanol, 2,5 pm Lubrizol 6% Solsperse 5% Ex. 17a 49% 1 -methoxyl2062 W150propanolComp. 20% Isopropanol, 4 pm Lubrizol 6% Solsperse 5% Ex. 17b 49% 1 -methoxyl2062 W150propanolComp. 20% Isopropanol, 2,5 pm Lubrizol 12% Solsperse 10% Ex. 17c 44% 1 -methoxyl2062 W150propanolComp. 20% Isopropanol, 2,5 pm BYK 4510 8% DB 2055 2% Ex. 18a 50% 1-ethoxy-2- propanolComp. 20% Isopropanol, 4pm BYK 4510 8% DB 2055 2% Ex. 18b 50% 1 -methoxylpropanolComp. 2,5 pm Lubrizol 12% DB 2055 10% Ex. 19 2062* Pluriol P900 PolypropylenglykolComparative Example 20: Uni grey light coating formulationA uniform light grey coating formulation without metallic effect pigments was made by using 15,0 g of Heliobeit UN 101 (Heliobeit), 0,3 g Hostatint Black A-NY 100 ST (Clariant), 0,2 g Hostatint Black A-NB 100 ST, 90 g of testing system B4 described below and 15 g of Butyl acetate / Xylol 1:1 mixture in conventional manner.Comparative Example 21: Uni grey dark coating formulationA uniform dark grey coating formulation without metallic effect pigments was made by using 15,0 g of Heliobeit UN 101 (Heliobeit), 1 ,6 g Hostatint Black A-NY 100 ST (Clariant), 90 g of testing system B4 described below and 15 g of Butyl acetate / Xylol 1:1 mixture in conventional manner.B Testing:B1: Gassing testsTesting system 1 : A commercially available test system fur aqueous based automotive base coats. The binder system was based on an acrylate-based copolymer with polyether and polyurethane components. The concentration of aluminum pigments was 1.9 wt.% and 265 g of the final testing formulation were filled in an appropriate glass flunsh. The test was passed according to the following criteria:The test was considered to be passed when after 7d: a maximum of 5 ml and after 14d a maximum of 15 ml gas evolved (after correction to a blind probe).The test was considered to be passed very well when further less or up to 24 ml gas were developed after 28 days. When more than 24 mL of gas evolved before 14 days (outgassing) simply the number of days is displayed. Results are displayed in table 3.This first gassing test system was used as a first measure for evaluating the desired properties. When this test was not passed by a sample no further testing was done usually.When this first test was passed other properties like the processability of the resulting aluminum effect pigment dispersion, hiding power and optical properties were evaluated. When all these properties were well passed the radar transparency was measured and further gassing tests in systems 2 to 8 were conducted.Herein the pigmentation of aluminum effect pigments was always 0,7 wt.% when not mentioned otherwise. A concentration of only 0,7 wt.% of the fine aluminum effect pigments is enough to yield full coverage hiding power in all coating systems. Results are displayed in table 4.Testing system 2: A commercially available low-solid system designed especially for PVD aluminum effect pigments. Such system is especially valuable as the aluminumpigments employed in this invention have average thicknesses in a range comparable to PVD pigments and thus very high specific areas.Testing system 3: A similar testing system to system 2, but additionally with Fe20s & FesO4 particles which usually means enhanced conditions.Testing system 4: A commercially available refinish testing system. Here the concentration of aluminum effect pigments was 1 ,0 wt.%.Testing system 5: A similar testing system to system 4, but additionally with Fe2Os particles which usually means enhanced conditions. Here the concentration of aluminum effect pigments was 0,25 wt.%.Testing system 6: Commercially available water-based testing system.Testing system 7: Commercially available water-based testing system.Testing system 8: Commercially available water-based testing system.The testing systems used herein represent standard testing systems provided by big coating companies.Only samples which passed gassing testing system 1 and all other tests regarding optical properties and hiding power and constitution of the paste were further evaluated in gassing tests 2 to 7. The results thereof are represented in table 6.B2 Paste consistency:The consistency of the paste resulting from the addition of additives to the fine thin aluminum effect pigments was noted by a qualitative system:Note 1 : Creamy paste means a metal effect paste which has a homogenous composition and is easily manageable.Note 2: fairly acceptableNote 3: A stab-proof paste in contrast has a solid consistency and cannot be managed further. A complete homogenization here is impossible because of a thick, dry consistency of the sample.Samples denoted to note 1 or 2 passed the test. Samples denoted to note 3 were not acceptable.B3 Optical properties:Drawdowns on black / white contrast paper were prepared from the formulations of gassing testing system 1. The optical properties and hiding power were evaluated in a qualitative manner. Results are displayed in table 4a. No evaluation was made if the first gassing test was clearly failed.B4 Radar transparency:A binder formulation consisting of cellulose ester, amino resins, organic solvents and saturated polyester resin was used. The effect pigment dispersion was added under careful stirring and the ratio of the weight of the effect pigments to the binder was 1 :41 (0,7 wt.% aluminum pigments of Examples 1 and 3 and 0,8 wt.% of Example 3). Viscosity was adjusted using a 1 :1 solvent mixture of butyl acetate and xylol.Spray coatings of the medium solid formulations were applied to ABS panels having a black / white visual opacity sticker and a thickness of 1 ,5 mm using a spray-coating apparatus APL 1.2 from Company Oerter, Germany. Each formulation was sprayed as often until full-tone coverage of each sprayed sample was achieved. The dry film thickness was about 15 pm.The radar transparency measurements were conducted with microwave radiation at a frequency of 76.5 GHz using as a measurement system an RMS -D-77 / 79G apparatus from Perisens GmbH, Germany. The data displayed in column 3 of table 4 were background corrected to account for loss produced by the uncoated substrate. The radar attenuation is expressed in decibel (dB) and must be lower than 3.0 and for very good results lower than 1.0. Further the relative permittivity e was determined and should be lower than 10 for very good radar transparency.Results are displayed in table 5.B5 Test according to “Recommendations on the TRANSPORT OF DANGEREOUS GOODS - Manual of Tests and Criteria sub-class 4.3 (UN digital library): 10,0 g of a sample was weighted into an Erlenmeyer flask with ground joint and 30 ml of water were added. The Erlenmeyer flask was tempered to 20 °C and a filled burette was connected. The gas evolution was observed after the first minute and thereafter every hour for the first 7 hours. In case of no evolution the test was stopped. If the gasdevelopment was uneven or still increasing after 7 hours, the measuring time is extended up to a maximum of 5 days.B6 Flop and Gloss:The pigment preparations of Examples 1 and 2 were prepared in several solvent-based and aqueous-based coating systems. The lightness values L* were measured at different observing angles using a Byk-mac apparatus with appropriate calibration in the Cl Lab system and the gloss at 60° was measured using a micro-tri gloss apparatus from Byk-Gardner.The flop was calculated according to the well-known formula (I):Flop = 2,69 x (L*15° - L*HO")1 11 / L*45"086(I)The systems used were as follows:a) The same coating system was used as in case of gassing testing system 2 with an aluminum effect pigment concentration of 0,7 wt.%b) The same coating system as used for the radar applications but with additional clear coat.c) Low solid conventional coating for plastic substrates,The following ingredients were mixed (Table 3a):Position Substance Amount Supplierin wt.%1 Dow Corning 57, 10% in Xylol 0,4 www.dow.com2 Syntalat A 333, 40% Xylol / n- 3,3 www.synthopol.com Butanol3 Degalan M 748, 40% in 14,1 www.evonik.com Xylol / Butyl acetate / methoxypropyl acetate 1 :2:24 Byk 392 0,4 www.byk.com5 1 -methoxy-2-proanol 36,26 Butyl acetate 21,77 Xylol 16,68 Solvent Naphta 10,9The viscosity was adjusted to 11 s in a DIN 4 mm cup. To this coating formulation the effect pigment preparations of Examples 1 and 2 were added such that the concentration of aluminum effect pigment was 0,7 wt.%, referred to the total coating composition.ABS panels were coated with this formulation and dried for 30 min at 80 °C.d) Solvent-based coatings formulation suitable for PVD aluminum pigments for plastic panelsThe following dispersions were prepared:Table 3b:Position Substance Amount Supplierin wt.%1 NO E 1160 isopropanol 30, 43,5 www.dow.com9% in butyl acetate2 butyl acetate 26,53 xylol 26,54 butyldiglycol 0,65 butylglycol 1,66 Byk 358 N 0,3 www.byk.com7 Byk 3740 1,0 www.byk.comTo this coating formulation the effect pigment preparations of Examples 1 and 2 were added such that the concentration of aluminum effect pigment was 0,7 wt.%, referred to the total coating composition. The viscosity was adjusted with a butyl acetate / xylol 1 :1 mixture to 17 sec in a DIN 4 cup.ABS panels were coated with this formulation and dried for 30 min at 80 °C.e) Low-solid Chrome-Effect-Paint for Automotive OEM:The following dispersions were prepared:Table 3c:Position Substance Amount in wt.% Supplier Laponite Solution:1 Water, demin. 94,02 Laponite RD 3,03 Pluriol P900 3,0100,0Varnish1 Water, demin. 29,12 Setaqua 6801 (24% in water 9,8demin.)3 Daotan TW 6452 (30% in 8,9water demin.)4 DMEA (10% in water demin.) 2,05 Cymel 325 (80% in iso1,5butanol)6 n-butanol 2,57 Lubrizol 2062 1,5 Lubrizol8 n-butanol 1,59 Agitan 282 0,2 Munzing10 Butylglycol 3,011 Laponite Solution 40Laponite-Solution:Pos. 1 was weighed in a suitable container and mixed with a gear ring stirrer.Pos. 2: was added quickly but evenly and without lumps while stirring at low speed and further mixed for 5 minutes.Pos. 3: was added under stirring and further mixed for 2 minutes.Varnish:Pos. 1 was weighed in a suitable container and mixed with a gear ring stirrerPos. 2, 3 and 4 were each added slowly under stirring and further stirred for about 2 minutes.Pos. 5 and Pos. 6 were weighed together in a suitable container, mixed with a spatula and added under stirring and stirred further for 5 minutes with obvious vortex.Pos. 7 and Pos. 8 were weighed together in a suitable container mixed with a spatula and were added under stirring and stirred further for 5 minutes with obvious vortex.Pos. 9 was added slowly under stirring and stirred for 2 minutes with obvious vortex. Pos. 10 was added slowly under stirring and stirred for 5 minutes with obvious vortex. Pos. 11 was added slowly under stirring and stirred for 10 minutes with obvious vortex.To 40% of the aluminum effect pigment preparations of Example 1 and Example 2 were added each 60% of butylglycol and stirred for 10 min with a gear ring stirrer. From this paste an amount was added under stirring to the varnish such that the final concentration of aluminum effect pigments was 0,7 wt.% of the total varnish.The viscosity was adjusted to 70 - 80 mPas at a shear rate of 1000 s1using a rheometer of Anton Paar (Rheo-Lab QC with a (Z3) CC 25 mm spindle in a concentric cylinder geometry.The varnished was sprayed on ABS panels in two spray coats and dried for 20 min under 80 °C. The final thickness of the coating film was 7 pm.B7 Coatings systems for qualitative determination of compatibility:For distinct Examples and Comparative Examples further tests were conducted in solvent based and in aqueous-based coating systems to evaluate the compatibility of the aluminum effect pigment preparation samples with these coating systems. Results are displayed in table 4b. Evaluated were the paste consistency as described in section B2 and the optical properties as described in section B3.The systems were as follows:i) The following ingredients were mixed in consecutive order and relative amounts:CAB 381-2, 20% in butyl acetate 85 22,50 www.eastman.com CAB 551-0.2, 20% in butyl acetate 85 9,00Viacryl SC 303, 65% in butyl acetate / xylene 12,87 www.allnex.com Maprenal MF 590, 55% in isobutanol / xylene 3,96 www.ineos.com Resamin HF 480 0,45 www.allnex.com Byk P 104 0,20 www.byk.com Borchi Gol MA, 0,4% in xylene 1,98 www.borchers.com Butanol 2,88Cerafak 106 19,80 www.byk.com Methoxy propanol 4,86Methoxy propyl acetate 1 ,98Butyl acetate 3,60Solvesso 150 2,97Butyl glycol acetate 2,95Sum: 100,002 g of the aluminium effect pigment preparation samples were mixed with 18 g of thesolvent-based lacquer described above.ii) the coating system used for the radar attenuation measurements.iii) Coating system e) as described in section B6.From all samples drow-dawns were made on a 36 pm hiding chart. Hiding power, optical impression and the formation of spots were evaluated qualitatively, whereas the samplefor Example 2 which gave excellent results in every aspect was set as standard for the evaluation of the hiding power. This sample was rated with a “0” whereas other sampleswere rated with notes compared to this sample (negative notes mean less hiding).C Results and Discussion:Table 4a: Results for the first gassing test and qualitative tests on paste consistency, optical properties and hiding power in testing system 1 Sample Al- Additives 1 / Gassing Paste optical Hiding Spots pigme 2: test process impression power nt dso (Testing -abilitysystem 1) (note)Example 4,0 pm Lubrizol 2062 / 7d: 4 mlbrilliant1 Multranol 9181 14d: 9 ml 1 0 no optics28d: 14 mlExample 2,5 pm Lubrizol 2062 / 7d: 1 ml very2 Multranol 9181 14d: 3 ml good brilliant21d: 8 ml 1 hiding no optics28d: 12 ml strength0Comp. 2,5pm Lubrizol 2062 / 7d: 11 ml3 weak optics -3Ex. 3a 14d: failedComp. 4 pm 11d: failed weak optics, strong Ex. 1a -4 agglomeratesComp. 4 pm — 7d: 4 ml weak optics, Agglo-4Ex. 1b 14d: 9 ml merates Comp. 2,5 pm 14d: failed weak optics strong Ex. 2a -4 agglomerates Comp. 2,5 pm — 7d: 2 ml weak optics Agglo-4Ex. 2b 14d: 7 ml merates Comp. 4 pm Lubrizol 2062 / 7d: 19 mL3 weak optics, -3Ex. 3b 14d: failedComp. 2,5pm Lubrizol 2063 / 1d: failed— — — — Ex. 4Comp. 2,5pm Xiran 1000MA 1d: failed— — — — Ex. 5 / —Comp. 2,5pm Resyd ro I VAX 1d: failed— — — — Ex. 6 5538 / —Comp. 2,5pm BYK 4510 Z 7d: failed— — — — Ex. 7aComp. 4 pm BYK 4510 / 3d: failed— — — — Ex. 7bComp. Nacorr XR-419 7d: failed— — — — Ex. 8 / —Comp. Nacorr 4426 / 2d: failed— — — — E. 9Comp. 2,5 pm Lubrizol 2062 / 7d: 7mlEx. 10 Disperbyk 14d: 19 ml — — — —2012Comp. 2,5 pm Lubrizol 2062 / 7d: 1 mlEx. 10a Disperbyk 14d: 3 ml 1 Grey, dull -1 no 2012 28d: 7 mlComp. 4 pm Lubrizol 7d: 4ml Optic weakEx. 11 2062H / 14d: 16 ml 2 WhiteDisperbyk -2 no 20602% +PPG 8%Comp. 2,5 pm Lubrizol 7d: 1 mlEx. 11a 2062H / 14d: 5 ml3 dull -1 no Disperbyk 28d: 13 ml2060Comp. 4 pm Lubrizol 7d: 2 ml Optic weakEx. 12 2062H / 14d: 4 ml 2 White, lowlow no Disparlon 320 hiding5% + PPG 5%Comp. 2,5pm Lubrizol 2062 / 7d: failedEx. 13 Solsperse — — — —4000Comp. 2,5 pm Lubrizol 2062 / 7d: 5 mlMore whitish,Ex. 13a Solsperse 14d: 8 ml 1 0 no a bit dull40000 28d: 14 mlComp. 4 pm Lubrizol 2062 7d: 5 ml weak opticsEx. 14 / Metolat 388 14d: 9 ml 2 low no + PPG 5%Comp. 2,5pm Lubrizol 2062 / 7d: 19 ml weak optics3 -4 no Ex. 15 Additol XL250 9d: FailedComp. 2,5 pm Lubrizol 2062 / 7d: 4 ml Grey, dullEx. 15a Additol XL 250 14d: 8 ml 3 -3 no 28d: 16 mlComp. 4 pm BYK 4509 / 3d: failed— —Ex. 16 Multranol 9181Comp. 2,5 pm Lubrizol 2062 / 7d: 18 mlEx. 17a Solsperse 8d: failed — —W150Comp. 4 pm Lubrizol 2062 / 7d: 8 mlEx. 17b Solsperse 14d: 19 ml — —W150Comp. 2,5 pm Lubrizol 2062 / 7d: 1 ml-3Ex. 17c Solsperse 14d: 4 ml 3 Grey, dull no W150 28d: 8 mlComp. 2,5 pm BYK 4510 / 3d: failed— —Ex. 18a DB 2055Comp. 4 pm BYK4510 Z 1d: failed— —Ex. 18b DB 2055Comp. 2,5 pm BYK4510 / 7d: 2mlMore whitish,Ex. 19 DB 2055 14d: 9 ml 1 0 no a bit dull28d: 11 mlInventive Examples 1 and 2 pass all tests and are satisfying in every respect. Thealuminum effect pigments coated with silica do not pass the gassing test and had a bad hiding power and optics due to agglomeration. Coating with a hybrid silica layer and a pretreatment with Mo-oxide according to Comp. Examples 2a, b improved the results, but still the hiding power and optical properties were not acceptable. It seems that the very fine and thin aluminum effect pigments employed here have such high specific surface that they cannot be stabilized with silica coatings or variants thereof in a satisfactory manner.Most of the comparative examples did not pass the first gassing test. The main problem here was to homogenize the fine thin aluminum effect pigments from their filter cake form to such extent that the passivating agent could be evenly adsorbed on the pigmentssurface and that the paste had such consistency that it could be further managed. For some samples the gassing test was passed when using higher amounts of additives (e.g.Comp. Examples 10a, 11a, 13a, 15a), but still the optical properties and / or the hidingpower was worse compared to Examples 1 or 2 including the test results displayed in table 4b.Surprisingly, this problem could be solved by choosing the particulate dispersing additives of this invention.Many other combinations of passivating additives and dispersing did not lead to satisfying results.This dispersion and the gassing test results could be improved by adding a high-boiling solvent like Pluriol P900. The paste consistency was improved but lead to bad optical properties (“whitening”). Apparently, the addition of significant amounts of a low- volatile solvent causes problems when the paste is applied to an aqueous-borne coatingformulation (Comparative Examples 11, 12, 14).Only specific combinations of a passivating additive and a dispersing additive led to the outstanding results of the inventive Examples.Table 4b: Dispersion behaviour in various testing systems:Sample Testing System i) of Testing system ii) of Testing system iii) of section B7 (solventsection B7 (solventsection B7 based) based)Hiding Spots Hiding Spots Hiding Spots power power power Example 0 no 0 no 0 no 2Comp. -2 yes -0,5 no -1 no Ex. 10aComp. -0,5 yes -0,5 no -2 no Ex. 11aComp. -1 yes -0,4 no -1 no Ex. 13aComp. -3 many -3 no -4 no Ex. 15aComp. -2 yes -1 no -4 no Ex. 17cComp. -5 yes -5 no -2 no Ex. 19Table 5: Results of Radar damping measurements:Sample Attenuation / BC* Attenuation / Relative Permittivity + substrate BC e / BCExample 1 0,79 0,08 5,42 Example 2 0,82 0,11 4,02 Example 3 1,12 0,41 12,30BC*: base coat (pigmented with aluminum effect pigments)The radar attenuation of the inventive examples 1 and 2 is extremely small although no pearlescent pigments were added in these experiments. The relative permittivity values of these coatings are far below of 10 which is a very good result. These fine, thin aluminum effect pigments can be used without problems in radar transparent coatings. The radar attenuation of inventive example 3 is slightly higher and the calculated relative permittivity is 12,3. This aluminum effect pigment has a larger size, however, the results are still satisfying.Table 6: Further Results in different Gassing test systemsSample Gassing test Result CommentExample 1 7d: 4 ml passed4pm 14d: 9 ml28d: 14 mlExample 2 Testing System 1 7d: 1 ml passed2,5pm 14d: 3 ml21d: 8 ml28d: 12 mlExample 1 7d: 1 ml passed4pm 14d: 4ml21d: 8 ml28d: 11 mlTesting System 2Example 2 7d: 0 ml passed2,5pm 14d: 0 ml21d: 0 ml28d: 0 mlExample 1 7d: 1 ml passed 4pm 14d: 4 ml21d: 8 mlTesting System 3 28d: 11 mlExample 2 Iron Oxide 7d: 1 ml passed 2,5pm 14d: 3 ml21d: 3 ml28d: 4 mlExample 1 7d: 0 ml passed 4pm 14d: 1 ml21d: 5 mlTesting System 4 28d: 7 mlExample 2 Refinish 7d: 0 ml passed 2,5pm 14d: 0 ml21d: 1 ml28d: 4 mlExample 1 7d: 0 ml passed 4pm 14d: 0 ml21d: 0 mlTesting System 5 28d: 0 mlExample 2 Refinish Iron Oxide 7d: 0 ml passed 2,5pm 14d: 0 ml21d: 0 ml28d: 0 mlExample 1 7d: 1 ml passed 4pm 14d: 4 ml21d: 6 ml28d: 9 mlTesting System 6Example 2 7d: 4 ml passed 2,5pm 14d: 4 ml21d: 8 ml28d: 13 mlExample 1 7d: 4 ml passed 4pm Testing System 7 14d: 8 ml21d: 11 ml28d: 13 mlExample 2 7d: 6 ml passed2,5pm 14d: 8 ml21d: 14 ml28d: 17 mlExample 1 7d: 0 ml passed4pm 14d: 1 ml21d: 3 ml28d: 4 mlTesting System 8Example 2 7d: 0 ml passed2,5pm 14d: 0 ml21d: 1 ml28d: 1 mlAll additional gassing tests were all passed by Example 1 and 2. Additionally both Examples 1 and 2 each passed the 4.3 test excellently with 0 mL of gas development after seven hours.Table 7a: Optical Properties in Coating system 6B a) with additional clear coat Sample L*15° L*25° L*45° L*75° L*HO° FlopExample 1 109,5 92,6 62,1 39,9 30,3 9,88Example 2 80,6 70,5 51 ,6 36,3 27,1 7,51Coating formulation used for radar measurements with clear coating (conventional, medium solid composition according to 6B b)):Flop Gloss Sample L*15° L*25° L*45° L*75° L*iio° 60° Pre-example1c 81 ,8 75,3 60,9 47,4 37,4 5,30 96,4 Example 1 81 ,1 75,4 62,1 48,6 38,0 5,03 94,9 Pre-example2c 64,1 60,0 50,8 41 ,7 32,9 4,18 96,2 Example 2 58,4 55,1 48,0 40,9 33,0 3,49 94,1ComparativeExample 20 61,8 61,6 61,2 61,1 61,9 — —(uni grey light)ComparativeExample 21 47,8 47,1 46,6 46,4 47,5 — —(uni grey dark)The flop here was rather low. It seems that the fine, thin aluminum effect pigments are not well suited in such systems because of their extremely high specific surface.However, when compared to the conventional uni grey color tones of Comparative Examples 20 and 21 a match of the lightness L* can be found at the medium angle 45° for Example 2 and Pre-example 2 with Comp. Example 21 and for Example 1 and PreExample 1 with Comparative Example 20, respectively. But while the uni grey color tones exhibit no flop, a certain metallic flop is clearly visible for the coatings according to the invention.Table 7c) Optical Properties of Coating system 6B c)Flop Gloss Sample L*15° L*25° L*45° L*75° L*iio° 60°Pre-example 1c 124,1 97,2 59,5 37,3 28,6 12,63 62,7 Example 1 122,1 96,9 60,0 38,1 29,5 12,13 66,0Pre-example 2c 99,7 82,4 56,3 37,9 28,1 9,63 62,2 Example 2 94,8 78,2 52,9 35,9 26,8 9,60 67,8Table 7d: Optical Properties of Coating system 6B d) (without additional clear coat)Flop Gloss Sample L*15° L*25° L*45° L*75° L*iio° 60° Pre-example 1c 141,9 96,3 50,5 30,8 24,8 18,23 96,7Example 1 141,8 99,1 52,1 30,8 24,1 17,86 80,5Pre-example 2c 120,0 89,3 52,5 32,9 25,1 13,96 83,4Example 2 111,1 84,6 51,6 32,8 24,5 12,82 71,9Optical results of coating formulation 6B e)Sample L*15” L*25” L*45” L*75” L*HO’ Flop Example 1 116,3 95,5 60,9 38,4 29,3 11,16 Example 2 88,6 74,9 51,6 34,8 25,7 8,985The best optical results were achieved in coating systems c) to e) which all are low-solid systems which are usually used for PVD aluminum effect pigments. The fine, thin aluminum effect pigments used herein do have specific surfaces comparable to those of PVD pigments and therefore they develop their optical properties best in such systems. In these coatings structure-less metallic coatings were achievable.

Claims

Claims:

1. Aluminium effect pigment preparation comprising:a) 10 to 30 wt.% of aluminum effect pigments obtained by grinding and having a dso in a range of 1 ,5 to 10,0 pm and a median thickness to in a range of 15 to 50 nm, b) a first passivating additive which is a polymer comprising phosphoric acid ester groups with an olefinic backbone,c) a second dispersing additive based on a propoxylated or an ethoxylated adduct of a polyamine,wherein the sum of the contents of components b) and c) is in a range of 10 to 30 wt.% andd) a balance of a solvent or solvent mixture,wherein the content ranges each refer to the total aluminum effect pigment preparation.

2. Aluminium effect pigment preparation according to claim 1 , wherein the dso of the aluminum effect pigments is in a range of 1 ,7 to 9,0 pm.

3. Aluminium effect pigment preparation according to claim 1 or 2, wherein the median thickness tso of the aluminum effect pigments is in a range of 18 to 40 nm.

4. Aluminium effect pigment preparation according to any of the preceding claims, wherein the passivating additive b) is a polymer having an olefinic backbone and comprises polymerized styrene components.

5. Aluminium effect pigment preparation according to claim 4, wherein the passivating additive b) is a copolymer based on styrene monomers copolymerized with allyl alcohol, wherein the allyl alcohol is at least partially esterified with phosphoric acid.

6. Aluminium effect pigment preparation according to any of the preceding claims, wherein the polyamine of dispersing additive c) is a diamine.

7. Aluminium effect pigment preparation according to claim 6, wherein the additive c) is an ethoxylated adduct of a diamine, preferably of ethylene diamine.

8. Aluminium effect pigment preparation according to any of the preceding claims, wherein the ratio by weight of the amount of the first passivating additive b) to aluminum effect pigments a) is in a range of 0,20 to 0,80.

9. Aluminium effect pigment preparation according to any of the preceding claims, wherein the ratio by weight of the amount of the second dispersing additive c) to aluminum effect pigments a) is in a range of 0,30 to 0,60.

10. Aluminium effect pigment preparation according to any of the preceding claims, wherein the ratio of first additive b) to second additive c) is in a range of 0,5 to 1 ,4.

11. Aluminium effect pigment preparation according to any of the preceding claims, wherein the solvent mixture contains a solvent having a boiling point of 200 °C or larger in an amount in a range of 0,00 to less than 1 ,00 wt.%, more preferably in a range of 0,20 to 0,70 wt.%, based on the whole aluminum effect pigment preparation.

12. Aluminium effect pigment preparation according to any of the preceding claims, wherein the solvent is chosen from the group consisting of isopropanol, 1 -methoxylpropanol, 2-methoxy-1 -propanol, 1-ethoxy-2-propanol, 2-ethoxy-1 -propanol, n-butanol, isobutanol, n-propanol, butyl glycol, butyl glycol acetate, butyl acetate, n-propyl acetate, isopropyl acetate, 1-methoxy-2-propanol acetate, ethyl acetate, methyl acetate, ethanol, methanol, methylethyl ketone, methyl diglycolether, methyl glycolether, 3-methoxy-butyl acetate and mixtures thereof.

13. Use of the aluminum effect pigment preparation of claims 1 to 12 in aqueous based coating formulations.

14. Use of the aluminum effect pigment preparation of claims 1 to 12 in aqueous based automotive coating formulations.

15. Aqueous based coating formulation containing the aluminum effect pigment preparation of claims 1 to 12.

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