PVD aluminum effect pigments coated by (METH)acrylate polymers with metal-oxide pretreatment and method of manufacture

Abstract

This invention is directed to coated platelet-like aluminum effect pigments, wherein the aluminium effect pigments are manufactured by PVD and wherein the coating comprises a first enveloping continuous or discontinuous layer consisting of molybdenum oxide, molybdenum hydroxide, molybdenum oxide hydrate, molybdenum peroxides and mixtures thereof or consisting of tungsten oxide, tungsten hydroxide, tungsten oxide hydrate, tungsten peroxide and mixtures thereof or of mixtures of molybdenum oxide and tungsten oxide followed by a second continuous enveloping layer comprising a polymer coating comprising or consisting of polymerized multifunctional (meth)acrylate monomers and wherein no silica layer is formed between the first layer and the (meth)acrylate coating.

Description

[0001] PVD Aluminum effect pigments coated by (meth)acrylate polymers with Metal-oxide pretreatment and method of manufacture

[0002] The present invention relates to (meth)acrylate coated aluminum effect pigments made by PVD (physical vacuum deposition) processes.

[0003] US 2001 / 0007696 A1 discloses passivation of PVD aluminum effect pigments by using various passivation agents. However many of disclosed treatments lead to agglomerated PVD aluminum pigments or to PVD aluminum effect pigments which are chemically unstable.

[0004] US 5,332,767 A1 discloses conventional aluminum pigments obtained by grinding methods which are coated with a poly(meth)acrylate. Prior to coating with poly(meth)acrylate at least one monolayer of an organofunctional silane is applied onto the surface of the pigment.

[0005] JP 2009 / 084496 discloses acrylate coating of PVD aluminum effect pigments for use in printing inks.

[0006] WO 2019 / 110490 A1 discloses PVD aluminum pigments coated with a Mo-oxide or W- oxide and a SiO2 layer. These effect pigments are not stable in alkaline media, however.

[0007] There is a strong market demand for chrome-like effects with high chemical resistance and a strong metallic character. For regulatory reasons, this is intended to replace galvanized surfaces which are, for example, banned in automotive uses. Such chrome-like effects could be achieved with poly-acrylate-coated PVD aluminum pigments, however, it is very difficult to coat PVD aluminum pigments with an acrylate or methacrylate coating of sufficient stability. The invention of such pigments also has an impact on sustainability since layers of coating could be reduced to one basecoat layer without clear coating with a corresponding positive effect on the CO2 footprint. Furthermore, coatings which are stable in alkaline media are desired. This would also allow use of one single coating with chrome- like effect in applications such as consumer electronics, household appliances, smartphones, mobile phones and the like. Applying an acrylate coating to PVD aluminum pigments is a particularly challenging task. The coating process usually leads to agglomeration of the pigments or to acrylate-coated pigment with a discontinuous acrylate polymer coating and poor to no chemical stability. Due to the PVD production process final dispersions of aluminum pigments always contain residues of so-called “release coat“ which are usually of polymeric nature. The polymeric residues hinder the coating of PVD aluminum pigments with a continuous and dense polymeric layer. Furthermore, PVD pigments are extremely thin and have therefore a very large surface area. A uniform coating of such large metal surfaces is already a challenging task but is made more difficult by the perturbation of the coating process by release-coat residues.

[0008] These needs can be met by providing coated platelet-like aluminum effect pigments, wherein the aluminium effect pigments are manufactured by PVD and wherein the coating comprises a first enveloping continuous or discontinuous layer of consisting of molybdenum oxide, molybdenum hydroxide, molybdenum oxide hydrate, molybdenum peroxides and mixtures thereof or consisting of tungsten oxide, tungsten hydroxide, tungsten oxide hydrate, tungsten peroxide and mixtures thereof or of mixtures of molybdenum oxide and tungsten oxide followed by a second continuous enveloping coating comprising a polymer coating comprising or consisting of polymerized multifunctional (meth)acrylate monomers and wherein no silica layer is formed between the first layer and the (meth)acrylate coating.

[0009] Further preferred embodiments are disclosed in claims 2 to 9.

[0010] A further need is to provide a simple cost-effect process of manufacturing such coated PVD aluminum pigments. This need can be met by providing a method of manufacturing coated platelet-like aluminum effect pigments, wherein said method comprises: dispersing a platelet-like PVD aluminum pigment in a solvent to form a first pigment mixture and contacting the first pigment mixture with a soluble metal compound dissolved in a solvent to obtain platelet-like PVD aluminum pigments coated with a metal oxide, wherein said metal of said soluble metal compound is selected from the group consisting of molybdenum, tungsten and mixtures thereof, followed by contacting the platelet-like PVD aluminum pigment coated with a metal oxide with monomers comprising multifunctional (meth)acrylate monomers and polymerizing the multifunctional (meth)acrylate monomers by thermic and / or radical polymerization to obtain platelet-like PVD pigments with a continuous enveloping polymer coating. Further preferred embodiments are disclosed in claims 11 to 13.

[0011] Detailed description:

[0012] PVD- aluminum pigments as substrates:

[0013] The PVD (physical vacuum deposition) aluminum pigment preferably has an aluminum content of at least 98 wt.-%, preferably of at least 99 wt.-%, further preferably of at least 99.9 wt.-%, further preferably of at least 99.99 wt.-%, each based on the total weight of the uncoated PVD aluminum pigment. It is used as substrate for subsequent enveloping coating layers.

[0014] According to a preferred embodiment, the PVD aluminum pigment has a median diameter dso in the range of 4 to 30 pm, preferably 5 to 25 pm, preferably 6 to 20 pm and further preferably 8 to 18 pm.

[0015] A median diameter dso means that 50% of the metal pigments have a diameter of the indicated size or below. The median diameter dso (volume averaged) of the PVD aluminum pigments can be measured by laser granulometry, for example with a Helos instrument (Malvern, Germany) using Fraunhofer approximation and according to the instructions of the manufacturer of the laser granulometry instrument.

[0016] According to another embodiment of the invention, the PVD aluminum pigment has a median thickness hso in the range of 15 to 75 nm, preferably in the range of 16 to 50 nm, further preferably in the range of 19 to 40 nm.

[0017] Below of a hso-value of 15 nm the aluminum PVD pigments become too dark and lose their enormous hiding power. Above 75 nm the PVD pigments lose their good orientation in the application medium and thus optical properties like gloss and flop decrease and furthermore the hiding power decreases with increasing thickness.

[0018] According to another embodiment of the invention the PVD aluminum pigment has a median diameter dso in the range of 6 to 18 pm and a median thickness hso in the range of 16 to 50 nm, preferably of 19 to 40 nm and most preferably 20 to 38 nm. Such kind of PVD-pigments exhibit a high hiding power and a liquid metal effect.

[0019] The median thickness of the PVD aluminum pigment can be adjusted when carrying out the physical vapor deposition. Furthermore, the median thickness hso of the PVD aluminum pigments can be measured by counting single pigment particles in a SEM according to the following method:

[0020] The PVD aluminum pigments are dispersed in a nitrocellulose-based lacquer and applied to an aluminum foil. The mixing ratio between powder and lacquer in the liquid system is about 1 :10 in terms of weight. A section of a few cm2of the thus coated aluminum foil is separated out by irradiation with high-energy Ar ions using a broad-beam ion source to create a cross-section. To ensure sufficient conductivity, the separated cross-section is sputtered with thin carbon layer having a thickness of about 5 nm. The platy aluminum pigments in the cross-section are then imaged using a scanning electron microscope at magnifications ranging from 10,000x to 30,000x. If the thickness of the flakes varies along a single flake the maximum and the minimum thickness value of the flake may be determined and the average of these values is counted as thickness value of this particular flake. At least 100 flakes are measured and the arithmetic average thickness is determined.

[0021] According to another embodiment, the PVD aluminum pigment is formed with a diffraction grating with a period preferably in a range of 5,000 to 20,000 lines / cm and more preferably in a range of 10,000 to 16,000 lines / cm. When formed with a diffraction grating, the PVD aluminum pigment has iridescent properties. The production of PVD aluminum pigments having a diffraction grating can be effected as described in U.S. Pat. No. 5,624,076 A. These PVD pigments are also described as embossed pigments. The process for producing embossed pigments or pigments with a diffraction grating is described in U.S. Pat. No. 5,624,076 A.

[0022] Embossed PVD pigments are composed only of very thin aluminum platelets with a primary layer thickness in a range of 25 to 80 nm and preferably 30 to 70 nm. The embossed PVD pigments can be produced by embossing a polymer film with a grating structure and then applying aluminum thereto by vapor deposition in a high vacuum. The aluminum film is then removed from the polymer film and the resulting film fragments are then comminuted to obtain embossed PVD pigments, as is standard practice in the production of metallic effect pigments by PVD methods. Diffractive structures comprising as many as 20,000 diffraction elements per cm can also be produced by this process. The diffraction structures are preferably grooves arranged substantially parallel to each other, i.e. formed by valleys separated from each other by ridges or peaks. The peak-to-valley heights of such structures are preferably in the range of 150 nm to 400 nm, more preferably in the range of 175 nm to 350 nm. Of course, other diffraction structures can also be used. For example, the diffraction structures may be in the form of concentric group structures arranged within another or groove structures arranged in spiral form. It is only essential that the diffraction structure elicit the desired optical effect of a multi-colored iridescence or rainbow color effect to the observer. The diffraction structures are preferably formed as reflective gratings.

[0023] Uncoated PVD aluminum pigment, which appear as mirror-like pigments, have a high metallic appearance and a high reflectivity. The PVD pigments of the present invention do have optical properties, which are nearly identical or at least very close to the optical properties of uncoated PVD aluminum pigments. According to a preferred embodiment of the invention, the PVD aluminum pigments are not colored with additional dyes or color pigments. Thus, preferably neither the first nor the second layer or any additional layer(s) comprise additional dye(s) and / or color pigment(s).

[0024] A color effect is only induced, if the PVD aluminum pigments are embossed with (a) diffraction grating(s) as described above.

[0025] First layer:

[0026] The term “continuous layer” or “discontinuous layer” for the first layer means that this layer either fully encapsulates or encapsulates only partially the respective plate-like PVD aluminum pigment. A partial encapsulation means that the respective substrate is not fully coated. The partial encapsulation or discontinuity can be realized, e.g., in the form of islands of the first layer on the respective substrate.

[0027] According to an embodiment of the invention, the first layer comprises or consists of metal oxide wherein said metal oxide is selected from the group consisting of molybdenum oxide, molybdenum hydroxide, molybdenum oxide hydrate, molybdenum peroxides and mixtures thereof. The molybdenum oxide usually is a mixture of different species and may involve coordination type species. It may be represented by the compositional formula:

[0028] Mo03mH2C>2 ■ nbW or Mo0(3-m)(02)m nbW (I) wherein Mo is molybdenum, O is oxygen, 0<m<1 and 1<n<2.

[0029] Also molybdenum complexes involving different ligands selected from the group of water, O2, O and mixtures thereof may be included.

[0030] The amount of elemental molybdenum by weight in relation to the amount of aluminium by weight in the coated pigment is in the range of 0.006 % to 3.000 %, preferably from 0.045 % to 1 .450 %, and further preferably from 0.060 % to 0.600 %.

[0031] The amount of elemental molybdenum may be determined by ICP-OES (inductive coupled plasma - optical emission spectroscopy).

[0032] Preferably, the molybdenum oxide coat is using a solution of polymolybdic acid peroxide which may be made by dissolving molybdenum oxide or elemental molybdenum in a hydrogen oxide solution (see for example Solid States Ionics, pp. 507-512, 1992).

[0033] According to another embodiment the first layer comprises or consists of metal oxide, wherein said metal oxide is selected from the group consisting of tungsten oxide, tungsten hydroxide, tungsten oxide hydrate, tungsten peroxide and mixtures thereof. Also tungsten complexes involving different ligands selected from the group of water, O2, O and mixtures thereof may be included.

[0034] The amount of elemental tungsten by weight in relation to the amount of aluminium by weight in the coated pigment is in the range of 0.004 % to 2.000 %, preferably from 0.040 % to 0.500 %.

[0035] The amount of elemental tungsten may be determined by ICP-OES.

[0036] Preferably, the tungsten oxide coat is prepared by using a solution of polytungstentic acid peroxide which may be prepared by dissolving tungsten oxide or elemental tungsten in a hydrogen oxide solution.

[0037] Coating the PVD aluminum substrates with metal oxides of molybdenum, tungsten or mixtures thereof is essential to modify the surface of the PVD aluminum effect pigments such that the further encapsulation by a (meth)acrylic polymer leads to a homogeneous layer of polymer. Surprisingly the observed influence by residues of release-layer polymers seems to be overcome by this treatment.

[0038] Second layer:

[0039] The second layer is a continuous enveloping layer and comprises a polymer coating comprising or consisting of polymerized multifunctional (meth)acrylate monomers. Such polymer coating is a cross-linked polymer coating. The term “continuous enveloping” means that the second layer encapsulates substantially completely, in particular completely, the respective PVD-aluminum substrate coated with the first layer.

[0040] In preferred embodiments the coating of the PVD-aluminum pigments does not comprise colored pigments or dyes. The aim of this invention is directed to silvery aluminum pigments or to diffractive aluminum pigments and therefore no coloring of color pigments or dyes which introduce an absorption color is necessary.

[0041] In preferred embodiments the average thickness of the second layer are in a range of 20 to 150 nm and more preferably in a range of 30 to 100 nm. Below of 20 nm the chemical stability is not sufficient while above 100 nm the hiding power decreases too much and optical properties such as gloss decrease.

[0042] In preferred embodiments the multifunctional (meth)acrylate monomers are trifunctional or higher functional (meth)acrylate monomers.

[0043] Examples of trifunctional or higher (meth)acrylates include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, di penta erythritol hexa(meth)acrylate (DPHA), dipentaerythritol penta(meth)acrylate, carboxylic acid modified dipentaerythritol penta(meth)acrylate, ethylene oxide modified trimethylolpropane ethylene oxide tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene oxide modified dipentaerythritol hexa(meth)acrylate, caprolactone modified dipentaerythritolhexa(meth)acrylate, hydroxy pivalic acid ditrimethylolpropane tetra(meth)acrylate, and mixtures thereof.

[0044] Particularly preferred are trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, and mixtures thereof.

[0045] In other embodiments the polymer coating may also contain polymerized bifunctional (meth)acrylate monomers or monomers with one (meth)acrylate and one vinyl function. Examples of such monomers include 1 ,3-butanediol di(meth)acrylate, 1 ,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, polypropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate, 3- methylpentanediol di(meth)acrylate, phthalic acid di(meth)acrylate, and cyclohexylene glycol di(meth)acrylate, -(2-vinyloxyethoxy) ethylacrylate, 1 ,9-nonanediol dimethacrylate, glycerol dimethacrylate, 2-hydroxy-3-acryloyloxy propyl (meth)acrylate, 1 ,9-nonanediol di(meth)acrylate, dimethylol tricyclodecane di(meth)acrylate, neopentyl glycol di(meth)acrylate, polytetraethylene glycol dia(meth)crylate and mixture thereof.

[0046] In other embodiments the polymer coating may also contain polymerized monofunctional (meth)acrylate monomers. In this variant it is more preferred that the monofunctional (meth)acrylate monomers are used as pigment surface modification as described in US 2011195244 A1.

[0047] Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl(meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy- 3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-acryloyloxy propyl (meth)acrylate, 2- (meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, isomyristyl (meth)acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl-2- hydroxyethyl phthalic acid, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxy polyethylene glycol (meth)acrylate, methoxy dipropylene glycol (meth)acrylate, ethoxy diethylene glycol (meth)acrylate, methoxy triethylene glycol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, 2-ethyl hexyl diglycol (meth)acrylate, butanediol mono(meth)acrylate, allyl (meth)acrylate, butoxyethyl (meth)acrylate, isoamyl (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, t-butylaminoethyl (meth)acrylate acrylic acid, methacrylic acid and mixtures thereof. According to this invention no silica layer is formed between the first layer and the second layer. Such pigments exhibit very good stability against alkaline media and have better hiding power and better pigment orientation leading to higher gloss, brightness and flop compared to variants with an additional silica layer. Furthermore, the step is coating with silica is not necessary which saves additional costs.

[0048] In preferred embodiments a layer of an organofunctional silane having carbon-carbon double bonds is disposed between the first and second layers. Such layer serves as adhesion promoter between the two layers and may involve only an amount in the order of about one monolayer.

[0049] Preferably the organofunctional silane having carbon-carbon double bonds are (methacryloyloxymethyl) methyl dimethoxysilane, methacryloyloxy methyl trimethoxysilane, (methacryloyloxymethyl) methyl diethoxysilane, methacryloyloxy methyltriethoxysilane, 2-acryloyloxyethyl methyl dimethoxysilane, 2-methacryloyloxy ethyl trimethoxysilane, 3-acryloyloxypropyl methyl dimethoxysilane, 2-acryloyloxyethyl trimethoxysilane, 2-methacryloyloxy ethyl triethoxysilane, 3-acryloyloxy propyl trimethoxysilane, 3-acryloyloxy propyl tripropoxysilane, 3-methacryloyloxy propyl triethoxysilane, 3-methacryloyloxy propyl trimethoxysilane, 3-methacryloyloxy propyl triacetoxysilane, 3-methacryloyloxy propyl methyl dimethoxysilane, vinyl trichlorosilane, vinylt rimethoxysilane vinyldimethoxy methylsilane, vinyltriethoxysilane, vinyltris(2- methoxyethoxy)silane, vinyltriacetoxysilane or mixtures thereof.

[0050] Particularly preferred are acrylate- and / or methacrylate-functional silanes. Organofunctional silanes which have proven very suitable in the present invention include 2-methacryloyloxyethyltrimethoxysilane, 2-methacryloyloxyethyltriethoxysilane, 3- methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, (methacryloyloxymethyl)methyldimethoxysilane, vinyltrimethoxysilane or mixtures thereof. The aforementioned compounds and also other suitable monomers that can be used in the present invention are available from, for example, Degussa AG, Frankfurt, Germany; Rohm GmbH & Co. KG, Darmstadt, Germany; Sartomer Europe, Paris, France; GE Silicons, Leverkusen, Germany; or Wacker Chemie AG, Munich, Germany. Method of coating the platelet-like PVD aluminum effect pigments:

[0051] A method of manufacturing coated platelet-like aluminum effect pigments, wherein said method comprises: dispersing a platelet-like PVD aluminum pigment in a solvent to form a first pigment mixture and contacting the first pigment mixture with a soluble metal compound dissolved in a solvent to obtain platelet-like PVD aluminum pigments coated with a metal oxide, wherein said metal of said soluble metal compound is selected from the group consisting of molybdenum, tungsten and mixtures thereof, followed by contacting the PVD aluminum pigment coated with a metal oxide with monomers comprising multifunctional (meth)acrylate monomers and polymerizing the multifunctional (meth)acrylate monomers by thermic and / or radical polymerization to obtain platelet-like PVD pigments with a continuous enveloping polymer layer.

[0052] In a preferred embodiment the soluble molybdenum compound is prepared by using a solution of polymolybdic acid peroxide which is prepared by dissolving molybdenum oxide or elemental molybdenum in a hydrogen oxide solution (see for example Solid States Ionics, pp. 507-512, 1992). Likewise, a preferred soluble tungsten compound is using a solution of polytungstenic acid peroxide which is prepared by dissolving tungsten oxide or elemental tungsten in a hydrogen oxide solution.

[0053] Organic solvents used are preferably alcohols, glycols, esters, ketones, and mixtures of these solvents. Particularly preferred is the use of alcohols, glycols or mixtures thereof, and especially preferred is the use of alcohols. As the alcohol it is advantageous to use methanol, ethanol, isopropanol, n-propanol, tert- butanol, n-butanol, isobutyl alcohol, pentanol, hexanol or mixtures thereof. Particular preference is given to using isopropanol. As glycol, it is advantageous to use butylglycol, propylglycol, ethylene glycol or mixtures thereof.

[0054] The multifunctional (meth)acrylic monomers used in the polymerisation step ensure the formation of a cross-linked (meth)acrylate polymer. In preferred embodiments the monomers comprise or consist of tri-functional (meth)acrylic monomers. Examples of such tri-functional monomers have been disclosed above.

[0055] In preferred embodiments the PVD aluminum pigments coated with a metal oxide are further coated with an organofunctional silane having carbon-carbon double bonds before contacting with monomers comprising multifunctional (meth)acrylate monomers. The organofunctional silane can bind very well via its Si-OH groups obtained after hydrolysis of the alkoxy groups with the metal oxide formed on the aluminium pigment surface or directly with the aluminum pigment surface (in case of an incomplete metal oxide coating) and the organic part with carbon - carbon double bonds can polymerize with (meth)acrylic monomers. Examples of such organofunctional silanes have been disclosed above.

[0056] The first and second layers can be formed in two different solvents (two-pot) or in one solvent (one-pot). In the two-pot method the PVD aluminium effect pigments coated with metal oxide are separated from the solvent used to form the first layer and then redispersed in a second solvent before conducting the polymerization to form the second layer. In a preferred variant formation of the first and second layers are conducted using the same dispersion of the PVD aluminum pigment in a solvent. Such one-pot synthesis is less cost intensive, less time consuming and needs lesser amounts of solvent.

[0057] The temperatures of the reactions are in a range of 50 °C to the boiling point of the solvent used. If the polymerization is done thermically a solvent with a boiling point of at least 80 °C is preferred. In preferred embodiments the temperature is in a range of 60 °C to 90 °C.

[0058] When the polymerization is conducted by radical polymerization a suitable polymerization initiator is added. Specific examples of the polymerization initiator include peroxides such as benzoyl peroxide, lauryl peroxide, isobutyl peroxide and methyl ethyl ketone peroxide, and azo compounds such as AIBN (azobisisobutyronitrile). The invention is not limited to the use of a particular initiator.

[0059] The polymerization can also be conducted by a mixture of radical polymerization and thermal polymerization.

[0060] In a further embodiment the coated platelet-like aluminum effect pigments of this invention can be used in formulations for single-layer coatings of automotive interior coatings, consumer electronics, household appliances, smartphones, mobile phones, coffee machines and toys. In a particularly preferred embodiment the coated platelet-like aluminum effect pigments of this invention can be used in formulations for single-layer coatings of consumer electronics, household appliances, smartphones, mobile phones, coffee machines and toys. A further embodiment is directed to formulations containing the coated platelet-like aluminum effect pigments of this invention for single-layer coatings of automotive interior coatings, consumer electronics, household appliances, smartphones, mobile phones, coffee machines and toys and particularly for single-layer coatings of consumer electronics, household appliances, smartphones, mobile phones, coffee machines and toys.

[0061] A_Examples

[0062] Example 1 :

[0063] 250 g of Metalure L-56161 PVD pigment manufactured by ECKART; dso: about 11 pm; nonvolatile content: 10%) was dispersed in 188.6 g isopropanol for 30 min. After heating to 40 °C 0.025 g molybdic acid in 0.075 g hydrogen peroxide (30% in water) was added and stirred for 1 h. Then 0.25 g 3-methacryloxypropyltrimethoxysilane (Dynasylan MEMO) was added and the temperature was raised to 85 °C. Over a period of 5 hours a solution of 0.83 g initiator (AIBN (azobisisobutyronitrile)) and 9.00 g trimethylolpropantrimethacrylate (TMPTMA) in 150 g of isopropanol was dosed in the reactor. After stirring for 5 hours to complete the encapsulation the obtained slurry was filtered, and a polymer encapsulated PVD pigment paste was obtained. To this polymer encapsulated PVD pigment paste isopropanol was further added to obtain a dispersion with a non-volatile amount of 10% by weight.

[0064] SEM images show a homogeneous acrylic coated surface of the starting material. A drawdown of the pigment shows good appearance of the coated pigment with only a slight loss of coverage compared to the starting material (1 .61 versus 1 .97).

[0065] Example 2:

[0066] 100 g of Metalure LR 10450PM (PVD aluminum pigment manufactured by ECKART; dso: about 10 pm; nonvolatile content: 15%) was dispersed in 163 g isopropanol for 30 min. After heating to 40 °C 0.150 g molybdic acid in 0.450 g hydrogen peroxide (30% in water) was added and stirred for 1 h. Then 0.15 g 3-methacryloxypropyltrimethoxysilane (Dynasylan MEMO) was added and the temperature was raised to 85 °C. Over a period of 5 hours a solution of 0.50 g AIBN and 8.00 g trimethylolpropantrimethacrylate (TMPTMA) in 150 g of isopropanol was dosed in the reactor. After stirring for 5 hours to complete the encapsulation the obtained slurry was filtered, and a polymer encapsulated PVD paste was obtained. Isopropanol was added to this polymer encapsulated PVD pigment paste to obtain a dispersion with a non-volatile amount of 10% by weight.

[0067] Example 3:

[0068] 250 g of Metalure L-56161 was dispersed in 188.6 g isopropanol for 30 min. After heating to 40 °C a solution obtained by dissolving 0.10 g of elemental tungsten in 0.90 g hydrogen peroxide (30% in water) was added and stirred for 1 h. Then 0.50 g 3- methacryloxypropyltrimethoxysilane (Dynasylan MEMO) was added and the temperature was raised to 85 °C. Over a period of 5 hours a solution of 0.83 g AIBN and 13.33 g trimethylolpropantrimethacrylate (TMPTMA) in 150 g of isopropanol was dosed in the reactor. After stirring for 5 hours to complete the encapsulation the obtained slurry was filtered, and a polymer encapsulated PVD pigment paste was obtained. Isopropanol was added to this this polymer encapsulated PVD pigment paste to obtain a dispersion with a non-volatile amount of 10% by weight.

[0069] Example 4:

[0070] 250 g of Metalure L-56161 was dispersed in 188.6 g isopropanol for 30 min. After heating to 40 °C a solution obtained by dissolving 0.10 g of elemental tungsten in 0.90 g hydrogen peroxide (30% in water) was added and stirred for 1 h. Then 0.25 g 3-methacryloxy- propyltrimethoxysilane (Dynasylan MEMO) was added and the temperature was raised to 85 °C. Over a period of 5 hours a solution of 0.83 g AIBN and 13.33 g trimethy lol- propantrimethacrylate (TMPTMA) in 150 g of isopropanol was dosed in the reactor. After stirring for 5 hours to complete the encapsulation the obtained slurry was filtered, and a polymer encapsulated PVD pigment paste was obtained. Isopropanol was added to this polymer encapsulated PVD pigment paste to obtain a dispersion with a non-volatile amount of 10% by weight.

[0071] Comparative Example 1 : (according to example 12 of US 2001 / 0007696 A1)

[0072] 250 g of Metalure L-56161 was dispersed in 230 g of Dowanol PM for 30 min at 20 °C. Afterwards 2.50 g (NH4)6Mo?024 x 4H2O in 50 g water was added dropwise over a period of 60 minutes. After a reaction time of 1 hour the reaction product was filtered off and washed twice with 200 ml of water.

[0073] This procedure leads to a destruction of the PVD pigments by oxidation.

[0074] Comparative Example 2: (according to example 7 of US 2001 / 0007696 A1)

[0075] 125 g of Metalure L-56161 was solvent exchanged to mineral spirit (nonvolatile content: 20%) and afterwards dispersed in further 260 g mineral spirit. The temperature was raised to 120 °C and 1 .52 g 3-methacryloxypropyltrimethoxysilane in 3.00 g mineral spirit was added. Then 0.06 g vinyl phosphonic acid in 4.00 g of mineral spirit and 0.06 g of water was added and stirred for 1 hour at 120 °C. Afterwards 2.40 g of trimethylol- propantrimethacrylate in 4.00 g of white spirit and within 30 min 0.11 g of AIBN in 2.00 g of white spirit were added to the reactor. The stirring was continued over a period of 5 hours at 120 °C. After cooling to about 40 °C the pigment was filtered off and a polymer encapsulated pigment paste was received. This procedure leads to a total agglomeration of the PVD pigments with nearly no more coverage at all (0.13 versus 1 .97).

[0076] Comparative Example 3a:

[0077] 300 g of Metalure L-56161 was dispersed in 188.6 g isopropanol for 30 min. After heating to 40 °C 0.30 g 3-methacryloxy propyltrimethoxysilane (Dynasylan MEMO) was added and the temperature was raised to 85 °C. Over a period of 3 hours a solution of 0.86 g AIBN and 10.0 g trimethylolpropantrimethacrylate (TMPTMA) in 15 g of isopropanol was dosed in the reactor. After stirring for 3 hours to complete the encapsulation the obtained slurry was filtered, and a polymer encapsulated PVD pigment paste was obtained. Isopropanol was added to this polymer encapsulated PVD pigment paste to obtain a dispersion with a non-volatile amount of 10% by weight.

[0078] Comparative Example 3b:

[0079] Like Comparative Example 3a, but 16 g TMPTMA were used as monomers instead.

[0080] Comparative Example 3c:

[0081] Like Comparative Example 3a, but as monomers a mixture of 3,69 g TMPTMA, 2.62 g 2- (2-vinyloxyethoxy) ethylacrylate (VEEA-AI) and 3.69 g (SR238 from Sartomer) were used instead.

[0082] Comparative Example 4: )According to Example 1 B1 from WO 2019 / 110490 A1 (Mo- 0xide / SiO2 coated PVD pigment)):

[0083] 300 g of a commercially available PVD aluminum pigment dispersion (Metalure A 41010 BG; containing 30 g aluminum and residues of polyacrylate used as release coat) were dispersed under stirring in 300 g isopropanol.

[0084] A defined amount 0.075 g of peroxomolybdenum acid solution in 0.225 g hydrogen peroxide (30% in water) was added and stirred for 30 min. The dispersion was heated to 70 °C and stirred for further 45 min. 21 .4 g tetraethoxy silane and 21 .4 g water were added and stirred for further 1 h.

[0085] Then 4.5 g of a 25-wt-% solution of ammonia in water were dosed within 1 h to the reaction mixture. After 5 h of reaction period 5 g Hydrosil 2776 were added. The reaction mixture was stirred for further 2h and then was cooled down to room temperature and filtered using a Buchner funnel isolating the coated PVD pigment. The pigment was finally combined with isopropanol to yield a pigment dispersion with a pigment content of 10 wt.-%.

[0086] Comparative Example 5: Uncoated Metalure L-56161.

[0087] Comparative Example 76 Uncoated Metalure LR 10450PM.

[0088] B Testing methods:

[0089] B1 Determination of OD:

[0090] The samples were incorporated into the following paint system: Table 1 : Ingredients of test lacquer in parts per weight.

[0091] The viscosity was adjusted to 17 sec for a DIN-cup 4 mm by adding appropriate amounts of a butyl acetate I xylenel :1 mixture . A draw-down was prepared using a 50 pm squeegee on a Hostaphanfoil. The optical density was measured using a densitometer of Heilland TRD 2. Results are displayed in table 2. The draw-downs were visually evaluated with respect to possible formations of agglomerates and / or spots of the metal pigments.

[0092] B2 Optical Properties (Flop, brightness, gloss) :

[0093] A binder system, composed of Hagedorn 0H07 EN Nitrocellulose H 7 in ethanol (obtainable from Hagedorn AG, Osnabruck, Germany) in a 1 :1 solvent blend of ethyl acetate and propylene glycol monomethyl ether was prepared. 15 wt-% of the PVD pigment sample (dispersion with 10 wt.% PVD Pigment) was added and homogenized. Formulations were based on weight ratios of metals content to binder, with a binder-to-pigment weight ratio of 31 :69. The samples were drawn down with a 36 pm on a flat BYK drawdown card.

[0094] Gloss data were collected using a BYK Micro Tri-gloss meter. Additional optical data were collected using a BYK Mac meter. The results of these measurements are summarized in table 2.

[0095] The flop is calculated according to the well-known formula.

[0096] B3 Coating of a plastic substrate:

[0097] 10 g of the dispersions (10 wt.% of pigment) of the samples of coated or uncoated PVD pigments were dispersed in 2.5 g butylglycol with the aid of 0.5 g of a dispersing additive. 70 g of an aqueous acrylate binder system having a composition displayed in table 2 were added and the pH was adjusted to a range of 7.6 to 8.0. The basecoat should have a viscosity of in a range of 80 to 120 mPas measured at a shear rate of 1000 1 / s with a Brookfield viscosimeter. The viscosity was adjusted by further addition of water. A plastic substrate (ABS / PC Blend) was coated with this basecoat using a Langguth (Erichsen GmbH, model 480) under the following spraying conditions: pistol conditions: 1 .1 .0 / 6 runs drying time: 10 min room temperature and 15 min at 80°C.

[0098] The thickness of this base coat was about 2 to 4 pm. The parameters were set in such a way that an opaque coating was achieved for a non-agglomerated sample. Table 2: Composition of 1K Lacquer:

[0099] Chemical resistance test:

[0100] The coated ABC panels were subjected to several droplets of 10%HCL and 1 M NaOH solutions. The assessment of chemical stability tests was made visually according to degree of graying / degradation. Each of the drop areas was evaluated with points from 0 to 3: 0 = no change 1 = slight grayish 2 = grayish (pigments still obvious) 3 = total degradation (no pigments left)

[0101] Assessment of the drops were made after 0.5h, 1 h, 2h and 3h each. A sum of all points were made for the acidic and the alkalic solutions and the total sum. Altogether a scale of 0 (best) to 24 (worst; 8 areas x 3 points) was possible.

[0102] Toyotatest:

[0103] The coated panels were subjected to a treatment with 0.1 M NaOH at 55 °C for 4 hours. A 0.1 M NaOH solution was poured into a Teflon dish with a diameter of 4 cm which was mounted in a slip-proof manner onto the coated panel. The panel was put into an oven at 55 °C for 4 hours. Afterwards each of the drop areas was evaluated with a point system of 0 to 3 points: 0 = no change

[0104] 1 = slight grayish

[0105] 2 = grayish (pigments still obvious)

[0106] 3 = total degradation (no pigments left) The samples of Comparative Examples 1 and 2 were not further processed. In Comparative Example the aluminum pigments had apparently reacted with the water used for washing and were essentially oxidized too much. In Comparative Example 2 the coated effect pigments were too strongly agglomerated.

[0107] Table 3: Results of testing of optical properties:

[0108] The samples of Comparative Examples 3a and 3b visually had a white and milky impression. Generally the inventive Examples had a lower hiding power compared to the uncoated substrates (Comp. Examples 5 and 6), which is normal as the aluminum content decreased after the coatings. Also optical properties like brightness (L15°), flop and gloss decreased compared to the uncoated substrates but were still acceptable. Table 4: Results of testing of chemical stability

[0109] All inventive Examples 1 to 4 show a very good stability in the Toyota test and a moderate stability in the chemical testing. The stability against alkaline media is generally very good while they are more unstable against acidic media. Without any pretreatment with a metal oxide (Comp. Examples 3a to 3c) essentially no gain in stability seems to be reached in comparison to an uncoated PVD pigment (Comp. Example 5). The acrylate coating here seems not to be enveloping the aluminium substrate sufficiently. Furthermore, the sample of Comp. Example 3c was partially agglomerated in this coating. A Mo-oxide I SiO2 coated sample (Comp. Example 4) has superior stability against acidic media, but very poor to no stability against strong alkaline media. Only the samples with pre-coating of a Mo-oxide or a W-oxide seem to enable a dense encapsulating continuous polymer layer. Therefore, the PVD aluminum pigments coated according to this invention are a useful supplement with complementary properties with respect to the Mo-oxide / SiO2 coated pigments.

Claims

Claims:1 . Coated platelet-like aluminum effect pigments, wherein the aluminium effect pigments are manufactured by PVD and wherein the coating comprises a first enveloping continuous or discontinuous layer consisting of molybdenum oxide, molybdenum hydroxide, molybdenum oxide hydrate, molybdenum peroxides and mixtures thereof or consisting of tungsten oxide, tungsten hydroxide, tungsten oxide hydrate, tungsten peroxide and mixtures thereof or of mixtures of molybdenum oxide and tungsten oxide followed by a second continuous enveloping layer comprising a polymer coating comprising or consisting of polymerized multifunctional (meth)acrylate monomers and wherein no silica layer is formed between the first layer and the (meth)acrylate coating.

2. Coated platelet-like aluminum effect pigments according to claim 1 , wherein the coating does not comprise colored pigments.

3. Coated platelet-like aluminum effect pigments according to any of claims 1 or 2, wherein a layer of an organofunctional silane having carbon-carbon double bonds is disposed between the first and the second layer.

4. Coated platelet-like aluminum effect pigments according to any of preceding claims, wherein the second coating contains or consists of at least one trifunctional (meth)acrylate monomer selected from the group consisting of trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, propionic acid modified dipentaerythritol penta(meth)acrylate, di penta erythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate (DPHA), dipentaerythritol penta(meth)acrylate, carboxylic acid modified dipentaerythritol penta(meth)acrylate, ethylene oxide modified trimethylolpropane ethylene oxide tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene oxide modified dipentaerythritol hexa(meth)acrylate, caprolactone modified dipentaerythritolhexa(meth)acrylate, hydroxy pivalic acid ditrimethylolpropane tetra(meth)acrylate, and mixtures thereof.

5. Coated platelet-like aluminum effect pigments according to any of preceding claims, wherein a layer of an organofunctional silane having carbon-carbon double bonds is disposed between the first and the second layer.

6. Coated platelet-like aluminum effect pigments according to claim 5, wherein the organofunctional silane having carbon-carbon double bonds is selected from the group consisting of (methacryloyloxymethyl) methyl dimethoxysilane, methacryloyloxy methyl trimethoxysilane, (methacryloyloxymethyl) methyl diethoxysilane, methacryloyloxy methyltriethoxysilane, 2-acryloyloxyethyl methyl dimethoxysilane, 2-methacryloyloxy ethyl trimethoxysilane, 3-acryloyloxypropyl methyl dimethoxysilane, 2-acryloyloxyethyl trimethoxysilane, 2-methacryloyloxy ethyl triethoxysilane, 3-acryloyloxy propyl trimethoxysilane, 3-acryloyloxy propyl tripropoxysilane, 3-methacryloyloxy propyl triethoxysilane, 3-methacryloyloxy propyl trimethoxysilane, 3-methacryloyloxy propyl triacetoxysilane, 3-methacryloyloxy propyl methyl dimethoxysilane, vinyl trichlorosilane, vinylt rimethoxysilane vinyl imethoxymethylsilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltriacetoxysilane or mixtures thereof.

7. Coated platelet-like aluminum effect pigments according to any of preceding claims, wherein the amount of elemental molybdenum in relation to the aluminium of the pigment is in the range of 0.006 % to 3.000 % and the amount of elemental tungsten to aluminum is in a range of 0.004 % to 2.000 %.

8. Coated platelet-like aluminum effect pigments according to any of preceding claims, wherein the PVD aluminum pigment has a median diameter dso in the range of 4 to 30 pm.

9. Coated platelet-like aluminum effect pigments according to any of preceding claims, wherein the PVD aluminum pigment has a median thickness hso in the range of 15 to 75 nm.

10. Method of manufacture of coated platelet-like aluminum effect pigments according to claims 1 to 9, wherein said method comprises: dispersing a platelet-like PVD aluminum pigment in a solvent and contacting a soluble metal compound dissolved in a solvent and plate-like PVD aluminum pigments to obtain platelet-like PVD aluminum pigments with a metal oxide, wherein said metal of said soluble metal compound is selected from the group consisting of molybdenum, tungsten and mixtures thereof, followed by contacting the pre-coated PVD aluminum pigment from step a) with monomers comprising multifunctional (meth)acrylate monomers by thermic and / or radicalpolymerization to obtain platelet-like PVD pigments with a continuous enveloping polymer layer.11 . Method of manufacture of coated platelet-like aluminum effect pigments according to claim 10, wherein the monomers comprise or consist of three-functional (meth)acrylic monomers.

12. Method of manufacture of coated platelet-like aluminum effect pigments according to claims 10 to 11 , wherein the metal oxide precoated PVD aluminum pigments are further coated with an organofunctional silane having carbon-carbon double bonds before coating with the second polymer layer.

13. Method of manufacture of coated platelet-like aluminum effect pigments according to claims 10 to 12, wherein all coating steps are conducted in the same dispersion of the PVD aluminum pigment in a solvent.

14. Use of the coated platelet-like aluminum effect pigment of claims 1 to 9 in formulations for single-layer coatings of consumer electronics, household appliances, smartphones, mobile phones, coffee machines, and toys.

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