interference pigments

Abstract

It is an object of the present invention to provide a highly opaque masstone-colored interference pigment that combines a bright bluish-red absorption color with a highly chromatic bluish-red interference color, which exhibits low color flop, such that the bluish-red absorption color remains visible even at flat observation angles, so that the intensity of the interference color, which is normally reduced at flat observation angles, is compensated for by the bright absorption color at all observation angles. The present invention relates to interference pigments based on SiO2 flakes coated with α-Fe2O3 crystallites and the use of such pigments, in particular in paints, coatings, industrial and automotive paints, ceramic materials, plastics and cosmetic formulations.

Description

[Technical Field]

[0001] The present invention relates to interference pigments based on SiO flakes coated with α-FeO ​​crystallites and to the use of said pigments, in particular in paints, coatings, printing inks, plastics and cosmetic formulations. [Background technology]

[0002] WO 93 / 08237 discloses interference pigments based on transparent silicon dioxide flakes. The pigments described therein are based on SiO2 flakes coated with one or more metal oxide layers. Instead of metal oxides, the SiO2 flakes can also be coated with other materials, such as metals, sulfides, or nitrides. Deep red interference pigments based on SiO2 flakes coated with iron oxide are the subject of WO 2007 / 057111 A2 and EP 1 681 318 A2, for example. The red interference pigments known from the prior art exhibit a strong orange-red effect at steep observation angles, which is a combination of interference and absorption colors, and very high hiding power. Summary of the Invention

[0003] The object of the present invention is to provide a highly opaque masstone-colored interference pigment that combines a bright bluish-red absorption color with a highly chromatic bluish-red interference color, wherein the pigment exhibits low color flop, such that the bluish-red absorption color remains visible even at flat observation angles, and the intensity of the interference color, which is normally reduced at flat observation angles, is compensated for by the bright absorption color at all observation angles. As a result, no down-flop of orange or even dark brown is observed. In particular, the object of the present invention is to provide an interference pigment that has a bright red hue at all observation angles. Furthermore, it is desirable that the pigment have high hiding power while also having low texture, making it useful for vegan applications. Surprisingly, interference pigments based on SiO flakes and coated with α-FeO ​​crystallites of defined size do not suffer from the above drawbacks and exhibit pure, bright bluish-red hues at all viewing angles. These pigments are characterized by their relatively high hiding power, high color saturation, temperature stability, and can be widely used in a wide variety of applications.

[0004] The interference pigments according to the invention exhibit an opaque, pure, bluish-red absorption color on all substrates (white / black), and furthermore, the superimposed interference color exhibits a low angular dependence. Thus, the overall color effect (absorption color + interference color) produced by the invention is a pure bluish-red hue at all viewing angles (steep / flat). From an application point of view: - Vibrant blue-red masstone -Strong bluish-red interference color -Low angle dependency of color impression / Low color flop -High hiding power The interference pigments according to the invention having the combination of are particularly suitable for pigmenting coating formulations, paints and / or plastics. Furthermore, its excellent feel on the skin naturally leads to its use in cosmetic formulations: a particularly great advantage in this field of application is that when blended with a white pigment, the pigment mixture can replace the classic carmine red in pink formulations, potentially enabling the production of vegan cosmetics.

[0005] The present invention relates to interference pigments based on SiO2 flakes, characterized in that they are coated with crystallites of α-hematite (α-Fe2O3). Due to the above-mentioned advantageous properties, the interference pigments according to the invention are widely suitable for a large number of different applications.Accordingly, the present invention also relates to the use of these pigments in paints, coatings, industrial and automotive paints, printing inks, security printing inks, paper, plastics, films, cosmetic formulations, button pastes, pigment mixtures, dry preparations or pigment preparations, ceramic materials, ceramic colors, glazes, enrobes, enamels and glass, as absorbers for laser marking of plastics, for food coloring, for food finishing, in food and pharmaceutical coatings, for security features on documents and identification cards, for seed coloring, for radar applications and for coloring solar cells. The pigment according to the present invention is based on synthetic SiO2 flakes as a substrate, which have a generally uniform layer thickness and are preferably prepared by solidification and hydrolysis of a water-glass solution on a continuous belt according to WO 93 / 08237. Here, uniform layer thickness is understood to mean a layer thickness tolerance of 3% to 10%, preferably 3% to 5%, of the total dry layer thickness of the particles. The flaky silicon dioxide particles are generally amorphous. This type of synthetic flake has advantages over natural materials, such as mica, such as the ability to adjust the layer thickness to the desired effect and limited layer thickness tolerance. The SiO2 flakes suitable for the interference pigments according to the invention preferably have a diameter of 1 to 250 μm, in particular 1 to 65 μm. The thickness of the SiO2 flakes is preferably 250 to 500 nm, in particular 330 to 400 nm, and the average thickness of the α-Fe2O3 layers in the pigment is 85±35 nm.

[0006] Essential to the interference pigments of the present invention are crystallites on the surface of the SiO flakes. The crystallites are distributed unevenly on the surface of the SiO flakes and consist of α-FeO. The average crystallite size is preferably ≥ 45 nm, in particular ≥ 50 nm. Nucleation and crystallite size are influenced and can be controlled, inter alia, by the reaction temperature and stirring speed, as well as the duration of the metered addition, and also by the calcination temperature and residence time in the calciner. In addition to the crystallites and their size, the total thickness of the interference pigment is crucial to the pigment's properties. The thickness of the SiO2 flake and crystallite layers is preferably selected so that the layer thickness of the interference pigment is an unweighted arithmetic mean of 494 nm (±109 nm) or less. The coating of the surface of the SiO flakes with α-FeO ​​crystallites can be carried out by wet-chemical methods and / or by CVD or PVD methods. The interference pigments according to the invention are preferably prepared by wet-chemical methods, in which known wet-chemical coating methods developed for the production of pearlescent pigments can be applied. For coating, the SiO2 flakes are suspended in water and coated by slow, controlled addition and precipitation of the corresponding inorganic iron compound, during which the pH required for precipitation and nucleation of α-Fe2O3 is set and kept constant by simultaneous addition of acid or base, followed by separation of the crystallite-coated substrate from the aqueous suspension, drying and calcination. To ensure that the crystallites are free of FeOOH and consist exclusively of α-Fe2O3, the calcination temperature is between 700 and 1000°C, preferably between 800 and 950°C. Higher calcination temperatures increase the densification of the crystallites, which in turn leads to an increase in the refractive index. The latter is responsible, among other things, for the high brightness of the interference pigments according to the invention. The duration of the calcination step is generally between 30 and 60 minutes. A longer residence time in the calciner is more favorable for the desired densification of the crystallites. CVD or PVD methods for coating SiO2 flakes with α-Fe2O3 crystallites are also suitable for preparing the interference pigments according to the invention.

[0007] To improve light, water and weather resistance, it is often recommended, depending on the field of application, to subject the interference pigments according to the present invention to inorganic or organic post-coating or post-treatment.Suitable post-coatings or post-treatments can be found, for example, in EP 0632109, U.S. Pat. No. 5,759,255, DE 4317019, DE 3929423, DE 3235017, EP 0492223, EP 0342533, EP 0268918, EP 0141174, EP 0764191, WO 98 / 13426 or EP 0465805; the disclosures of which are incorporated herein by reference. This post-coating may further enhance chemical and photochemical stability or simplify the handling of the interference pigment, especially its incorporation into various media. To improve wettability, dispersibility, and / or compatibility with user media, a functional coating comprising SiO2, SnO2, Al2O3, or ZrO2, or mixtures thereof, may be applied to the pigment surface. Furthermore, organic post-coatings using, for example, silanes are possible, as described, for example, in EP 0 090 259 A, EP 0 634 459 A, WO 99 / 57204, WO 96 / 32446, WO 99 / 57204, U.S. Pat. No. 5,759,255, U.S. Pat. No. 5,571,851, WO 01 / 92425, or in JJ Pomjee, Philips Technical Review, Vol. 44, No. 3, 81 ff. and P.H. Harding JC Berg, J. Adhesion Sci. Technol. Vol. 11 No. 4, pp. 471-493. Interference pigments comprising an organic coating, such as those comprising organosilanes, or organotitanates or organozirconates, not only exhibit the above-mentioned optical properties but also an improved stability against weathering influences, such as moisture and light, which is of particular interest, especially in the industrial coating and automotive fields. Stabilization can be improved by inorganic components of additional coatings.Overall, the respective proportions of the additional stabilizing coatings must be selected in such a way that the optical properties of the interference pigments according to the invention are not significantly affected: the substances applied here only make up a weight fraction of 0.1 to 5% by weight, preferably 0.5 to 3% by weight, of the total pigment.

[0008] The post-coating of the interference pigments according to the invention can be carried out directly on the α-FeO ​​crystallite coating of the SiO flakes in a one-pot process, but it is also possible to first isolate the interference pigments, dry and calcinate them, and then apply the post-coating. In this patent application, coating is taken to mean completely covering / enveloping the flaky substrate. The hiding power of the interference pigments according to the present invention can be further increased by combining the pigments with organic and inorganic fillers and / or with flaky, acicular, spherical, or crystalline colorants. By blending one or more colorants with the interference pigments according to the present invention, it is possible to enhance the coloring effect and achieve new coloring effects. Therefore, the present invention also relates to pigment mixtures.

[0009] Due to their significantly larger average crystallite size, the interference pigments according to the invention exhibit higher temperature and heat stability than the iron oxide pigments known from the prior art and can therefore be easily incorporated into enrobes and glazes. Depending on the desired effect, the glazes can be matte to glossy or transparent to opaque. The invention also relates to formulations comprising the interference pigments according to the invention, such as ceramic colors, coatings, ceramic tiles, cast ceramics, sanitary ware, enamels, glazes, earthenware, glassware, and pottery. The interference pigments according to the invention are further suitable for the preparation of flowable pigment preparations and dry preparations comprising a pigment according to the invention, a binder and optionally one or more additives, in particular for printing inks and paints, preferably automotive paints. The interference pigment according to the present invention is preferably suitable for the color systems of paints, coatings and printing inks.Many binders, especially water-soluble products, such as those sold by BASF, Marabu, Proll, Sericol, Hartmann, Gebr.Schmidt, Sicpa, Aarberg, Siegwerk, GSB-Wahl, Follmann, Ruco or Coates Screen INKS GmbH, are suitable for preparing printing inks for gravure printing, flexographic printing, offset printing or offset overprint varnish.Printing inks can be aqueous or solvent-based.

[0010] Of course, for various applications, the interference pigments according to the invention can also be used advantageously as blends with, for example, the following pigments: metallic effect pigments, for example based on iron or aluminum flakes; - pearlescent pigments based on metal oxide-coated synthetic mica flakes, natural mica flakes, glass flakes, Al2O3 flakes, Fe2O3 flakes or SiO2 flakes; -Absorbent pigments; -goniochromatic pigments; - multilayer pigments (preferably 2, 3, 4, 5 or 7 layers) based on metal oxide-coated synthetic mica flakes, natural mica flakes, glass flakes, Al2O3 flakes, Fe2O3 flakes or SiO2 flakes; -Organic dyes; -organic pigments; inorganic pigments, such as transparent and opaque white, colored and black pigments; in particular temperature-stable ceramic pigments; -Flake iron oxide; -carbon black; -Ceramic color body; Functional pigments, for example IR-reflective or conductive pigments.

[0011] In a preferred embodiment, the interference pigments according to the invention are advantageously mixed with organic and inorganic color pigments and dyes of natural or synthetic origin, such as carmine red, chromium oxide, ultramarine or spherical SiO or TiO pigments, etc. The mixing ratios vary depending on the application medium and the effect to be achieved. The interference pigments according to the invention can be mixed in any ratio with commercially available pigments and / or other commercially available fillers. For use as a carmine red substitute in vegan cosmetic formulations, blends with silver-white interference pigments, titanium dioxide or other white pigments can be specified here. Various mixing ratios allow a wide range of pink shades to cover the desired color nuances. Commercially available fillers include, for example, natural and synthetic mica, glass beads, glass powder, nylon powder, pure or filled melamine resin, talc, glass, kaolin, oxides or hydroxides of aluminum, magnesium, calcium, zinc, BiOCl, barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, carbon, boron nitride, and physical or chemical combinations of these substances. There are no limitations regarding the particle shape of the filler. Depending on the circumstances, the filler may be amorphous, flaky, spherical, or acicular, crystalline, or amorphous.

[0012] The interference pigments according to the invention are particularly suitable for decorative cosmetics and personal care applications, such as nail varnishes, lipsticks, lip glosses, rouge, compact powders, gels, lotions, soaps, toothpastes, body lotions, emulsions, soaps, shampoos, BB creams, CC creams, make-up, foundations, (volumizing) mascaras, hair, eyelash and eyebrow products, sunscreens, pre- and after-sun preparations, make-up, body lotions, bath gels, soaps, bath salts, toothpastes, hair styling gels, compact powders, loose powders, etc. In decorative cosmetics, the interference pigments according to the invention are preferably used in concentrations of 0.5 to 25% by weight, in particular 1 to 20% by weight, and particularly preferably 1 to 10% by weight, based on the formulation. In cosmetic formulations for personal care applications, the interference pigments according to the invention are preferably used in concentrations of 0.1 to 5% by weight, and particularly preferably 0.5 to 4% by weight, based on the formulation.

[0013] The interference pigments according to the invention can of course also be combined with cosmetic raw materials and auxiliaries of any kind, such as, inter alia, oils, fats, waxes, film-forming agents, surfactants, antioxidants such as, for example, vitamin C or vitamin E, stabilizers, fragrance enhancers, silicone oils, emulsifiers, solvents such as, for example, ethanol, ethyl acetate or butyl acetate, preservatives, and auxiliaries which generally determine the technical application properties, such as, for example, thickeners and rheological additives, for example, bentonite, hectorite, silicon dioxide, calcium silicate, gelatin, high molecular weight carbohydrates, and / or surfactant auxiliaries. Formulations containing interference pigments according to the invention can be of the lipophilic, hydrophilic, or hydrophobic type. In the case of heterogeneous formulations with separate aqueous and non-aqueous phases, the interference pigments according to the invention can be present in only one of the two phases or can be distributed in both phases. The pH value of the formulation may be between 1 and 14, preferably between 2 and 11, particularly preferably between 4 and 6.

[0014] There are no limitations on the concentration of the interference pigments according to the invention in the formulation. This concentration can be from 0.001% (e.g., in rinse-off products such as shower gels) to 60%, depending on the intended use. The interference pigments according to the invention can also be combined with cosmetic active compounds. Suitable active compounds are, for example, insect repellents, inorganic UV filters such as TiO, UVA / BC protection filters (e.g., OMC, B3, MBC) (including encapsulated forms), anti-aging active compounds, vitamins and their derivatives (e.g., vitamins A, C, E), tanning agents (e.g., DHA, erythrulose), and other cosmetic active compounds such as bisabolol, LPO, ectoine, emblica, allantoin, bioflavonoids, and their derivatives. Organic UV filters are generally incorporated into cosmetic formulations in amounts of 0.5 to 10% by weight, preferably 1 to 8% by weight, and inorganic filters in amounts of 0.1 to 30% by weight.

[0015] Additionally, the formulations may contain conventional skin protection or skin care active compounds such as aloe vera, avocado oil, coenzyme Q10, green tea extract, and active compound complexes. Particularly preferred active compounds are pyrimidine carboxylic acids and / or aryl oximes. Among the cosmetic applications, particular mention should be made of the use of ectoine and ectoine derivatives for caring for aging, dry or irritated skin.EP-A-0671161 describes the use of ectoine and hydroxyectoine in cosmetic preparations, such as, inter alia, powders, soaps, surfactant-containing cleansing products, lipsticks, lipsticks, makeup, skin care creams and sunscreen preparations.

[0016] The application forms of cosmetic formulations include, for example, solution, suspension, emulsion, PIT emulsion, paste, ointment, gel, cream, lotion, powder, soap, surfactant-containing cleansing preparation, oil, aerosol and spray.Other application forms include, for example, stick, shampoo and shower gel.Any desired conventional vehicle, auxiliary agent and optionally further active compound can be added to the formulation.

[0017] The ointments, pastes, creams and gels may contain conventional vehicles such as animal and vegetable fats, waxes, paraffins, starches, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonite, silica, talc and zinc oxide, or mixtures of these substances. Powders and sprays can contain customary vehicles such as lactose, talc, silicic acid, aluminum hydroxide, calcium silicates and polyamide powder, or mixtures of these substances. Sprays can additionally contain customary propellants, such as chlorofluorocarbons, propane / butane, or dimethyl ether. The solutions and emulsions may contain conventional vehicles such as solvents, solubilizers and emulsifiers, for example, water, ethanol, isopropanol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butyl glycol, oils, especially cottonseed oil, peanut oil, corn germ oil, olive oil, castor oil and sesame oil, glycerol fatty acid esters, polyethylene glycol and fatty acid esters of sorbitan, or mixtures of these substances. Suspensions may contain conventional vehicles such as liquid diluents, for example, water, ethanol or propylene glycol, suspending agents, for example, ethoxylated isostearyl alcohol, polyoxyethylene sorbitol esters and polyoxyethylene sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar and tragacanth, or mixtures of these substances. Soaps may contain conventional vehicles such as alkali metal salts of fatty acids, salts of fatty acid semiesters, fatty acid protein hydrolysates, isothionates, lanolin, fatty alcohols, vegetable oils, vegetable extracts, glycerin, sugars, or mixtures of these substances. Surfactant-containing cleansing products may include conventional vehicles such as fatty alcohol sulfates, fatty alcohol ether sulfates, sulfosuccinic acid semiesters, fatty acid protein hydrolysates, isothionates, imidazolinium derivatives, methyl taurate, sarcosinates, fatty acid amide ether sulfates, alkylamidobetaines, fatty alcohols, fatty acid glycerides, fatty acid diethanolamides, vegetable and synthetic oils, lanolin derivatives, ethoxylated glycerol fatty acid esters, or mixtures of these materials. Face and body oils may contain conventional vehicles such as synthetic oils, e.g., fatty acid esters, fatty alcohols, silicone oils, natural oils, e.g., vegetable oils and oily plant extracts, paraffin oil, lanolin oil, or mixtures of these substances.

[0018] Cosmetic preparations can exist in various forms. Thus, they can be, for example, solutions, anhydrous preparations, emulsions or microemulsions of the water-in-oil (W / O) or oil-in-water (O / W) type, multiple emulsions, such as those of the water-in-oil-in-water (W / O / W) type, gels, solid sticks, ointments, or aerosols. It is also advantageous to apply ectoines encapsulated in collagen matrices and other common encapsulating materials, for example, as cellulose encapsulations, in gelatin, wax matrices, or liposomes. Wax matrices, as described in DE-A-4308282, have proven particularly advantageous. Emulsions are preferred. O / W emulsions are particularly preferred. Emulsions, W / O emulsions, and O / W emulsions can be obtained by conventional methods.

[0019] Further embodiments are oily lotions based on natural or synthetic oils and waxes, lanolin, fatty acid esters, especially triglycerides of fatty acids, or oily-alcoholic lotions based on lower alcohols, such as ethanol, or glycerol, for example propylene glycol, and / or polyols, such as glycerin, together with oils, waxes and fatty acid esters, for example triglycerides of fatty acids. Solid sticks consist of natural or synthetic waxes and oils, fatty alcohols, fatty acids, fatty acid esters, lanolin, and other fatty bodies. If a preparation is formulated as an aerosol, the customary propellants, such as alkanes, fluoroalkanes and chlorofluoroalkanes, are generally used.

[0020] Cosmetic preparations can also be used to protect hair from photochemical damage, preventing changes in color, bleaching, or mechanical damage. In this case, rinse-off shampoos, lotions, gels, or emulsions are suitable, and the respective preparations are applied before or after shampooing, coloring or bleaching, or perming. The preparations can also be selected as lotions or gels for styling and treatment, as lotions or gels for brushing or setting water waves, or as hairsprays, perms, hair colorants, or hair bleaching products. Preparations with photoprotective properties can contain adjuvants such as surfactants, thickeners, polymers, emollients, preservatives, foam stabilizers, electrolytes, organic solvents, silicone derivatives, oils, waxes, anti-greasing agents, dyes and / or pigments for coloring the composition itself or the hair, or other ingredients commonly used in hair care.

[0021] The present invention also relates to formulations, in particular those comprising, in addition to the interference pigments according to the invention, at least one component selected from the group consisting of absorbers, astringents, antimicrobial substances, antioxidants, antiperspirants, antifoaming agents, antidandruff active compounds, antistatic agents, binders, biological additives, bleaching agents, chelating agents, deodorizing agents, emollients, emulsifiers, emulsion stabilizers, dyes, humectants, film-forming agents, fillers, fragrances, flavorings, insect repellents, preservatives, anticorrosive agents, cosmetic oils, solvents, oxidizing agents, botanical ingredients, buffer substances, reducing agents, surfactants, propellant gases, opacifiers, UV filters and UV absorbers, denaturants, aloe vera, avocado oil, coenzyme Q10, green tea extract, viscosity modifiers, fragrances, inorganic pigments such as, for example, transparent or opaque white, colored and black pigments, metallic pigments, temperature-stable ceramic pigments, ceramic color bodies, functional pigments such as, for example, IR-reflecting pigments or conductive pigments, and vitamins.

[0022] The interference pigments according to the invention can be used for the internal coloring of foods, for the finishing of foods, in food coatings, for example in mass coloring or as color coatings, in pharmaceutical coatings, for example in dragées and tablets. Coloring of pharmaceutical and food products is carried out by adding the interference pigments in the desired mixing ratio to the product to be colored in an amount of 0.005 to 15% by weight, preferably 0.01 to 100% by weight. The mixture of natural or nature-identical dyes, organic or inorganic color pigments or color extracts of natural fruits and plants approved in the food sector allows the coloring effect of the interference pigments according to the invention in the products to be affected and at the same time allows the achievement of novel iridescent coloring effects.

[0023] Suitable natural or nature-identical dyes are, in particular, E101, E104, E110, E124, E131, E132, E140, E141, E151 and E160a. Furthermore, it is also possible to mix other colored pigments, such as E171, E172, E153, etc., with the interference pigments according to the invention. The proportion of dyes other than the interference pigments according to the present invention in the food or pharmaceutical product is preferably in the range of 0.5 to 25% by weight. Fruit and plant extracts, such as carrot juice, beetroot juice, elderberry juice, hibiscus juice, paprika extract, and aronia extract, can also be used as dyes. The total concentration of all pigments in the product to be pigmented should not exceed 50% by weight of the product, which will generally depend on the specific application.

[0024] Various active compound mixtures, such as vitamins, enzymes, trace elements, proteins, carbohydrates, essential fats and / or minerals, can also be added to food and pharmaceutical products, preferably in an amount not exceeding 25% by weight of the total active compounds in the food and pharmaceutical product. The amount of active compound or active compound mixture is preferably between 0.01 and 20% by weight of the product. The coloring of the product is carried out by adding the interference pigments, alone or in combination with further pigments or colorants, directly or in the presence of water and / or organic solvents in the desired mixing ratio, simultaneously or successively, to the product to be colored during or after its preparation, before or after shaping (for example in the case of extrusion, pelleting, foaming, granulation, etc.). It is also possible to mix the interference pigments according to the invention with dust or loose powder.

[0025] The interference pigment according to the present invention can also be applied to the surface after molding, either alone or in a pigment mixture, to color food and pharmaceutical products.In this case, the interference pigment is usually mixed with a coating medium, and then applied to the product using a suitable coating and spraying device.Then, the coating or coating composition ensures that the interference pigment adheres appropriately to the product surface.The latter is then colored appropriately. When incorporated into the product matrix itself, the interference pigments according to the invention are preferably used in amounts of 0.5 to 40% by weight, in particular 1 to 30% by weight. When coloring the surfaces of food and pharmaceutical products, the amount used in the coloring or coating solutions used is in the range of 0.1 to 25% by weight, in particular 1 to 15% by weight. When the interference pigments according to the invention are used in finely divided products, the amount used is in the range of 0.05 to 50% by weight, in particular 2 to 10% by weight.

[0026] The coating solution preferably contains water or an organic solvent such as ethanol or isopropanol. The film-forming agent used in the coating solution is preferably a cellulose derivative such as hydroxypropylmethylcellulose. Particularly preferred is a coating solution containing a cellulose derivative, which contains 5 to 80% by mass of a suitable organic solvent instead of water. Compared to aqueous coating solutions, alcoholic or alcoholic / aqueous cellulose-containing coating solutions offer significant application advantages, namely: -Colder dry air is used during spray application Heat-sensitive products, such as vitamin-containing foods, can be very easily colored with red interference pigments.

[0027] Suitable products for coloring include, in particular, coatings for all kinds of foods, in particular colored sugar and shellac coatings (alcoholic and aqueous), oil and wax coatings, gum arabic coatings, and cellulose-based (e.g., HPMC = hydroxypropylmethylcellulose) coatings, starch and protein derivatives, carrageenan, and other coatings known to those skilled in the art. In this case, the interference pigments according to the invention are generally mixed with a coating medium and then applied to the food or pharmaceutical product using suitable coating and spraying equipment or by hand. The coating or coating composition then ensures appropriate adhesion of the pigment to the surface of the food or pharmaceutical product. This surface is then appropriately colored. The coating or coating solution preferably contains 0.1 to 20% by weight, in particular 2 to 15% by weight, of the interference pigment. A preferred dry powder mixture for coating comprises a cellulose derivative (e.g., hydroxypropylmethylcellulose, sodium carboxymethylcellulose, etc.), a release agent (e.g., lecithin or stearic acid, etc.), a gloss enhancer (e.g., maltodextrin and / or dextrose, etc.), and an interference pigment according to the present invention. This type of dry powder mixture preferably contains the interference pigment according to the present invention in an amount of 0.01 to 50% by weight, particularly 0.5 to 40% by weight, based on the powder mixture. Dyes, flavorings, vitamins, sweeteners, etc. can also be added to these dry powder mixtures, if necessary.

[0028] Suitable products for coloring or coating are, for example, confectionery, cake decorations, tablets, dragees, chewing gum, gummy products, fondant products, marzipan products, filling compositions, cocoa and fat glazes, chocolate and chocolate-containing products, ice cream, cereals, snack products, coatings, cake coating compositions, sprinkle sugar, nonpareils, jellies and gelatin products, hard candy, liquorice, powdered sugar, candy floss, fat, sugar and cream compositions, puddings, desserts, glazes for cakes, chilled dishes, lemonades and carbonated drinks, drinks containing stabilisers (such as, for example, carboxymethylcellulose), acidic and non-acidic dairy products, such as, for example, quark, yogurt, cheese, cheese rinds, sausage rinds, etc. In the case of sugar-coated or coated food and pharmaceutical products, the interference pigments according to the invention can be combined with flavors (powdered or liquid flavors), acids and / or sweeteners, such as aspartame, to enhance the visual effect of the flavor as well. The present invention therefore relates to all formulations in the food and pharmaceutical sector which contain the interference pigments according to the invention as colorants, alone or in combination with further pigments / pigment mixtures or dyes (natural or nature-identical).

[0029] An even greater field of application is in the pharmaceutical and OTC sector, for coloring or as coatings for tablets, gelatin capsules, dragees, ointments, cough syrups, etc. In combination with conventional coatings such as those of the polymethacrylate and cellulose type, for example HPMC, the interference pigments according to the invention can be used in a variety of ways to color and finish products.

[0030] The present invention further relates to the use of the interference pigments according to the invention in paints, coatings, printing inks, security printing inks, plastics, ceramic materials, glass, glazes, as tracers, as absorbents for laser marking of plastics and paper, in cosmetic formulations, for the internal coloring of food, for the finishing of food, for example as a liquid color or color coating, and in pharmaceutical coatings, such as dragees and tablets. The pigments according to the invention are also suitable for the preparation of pigment preparations and for the preparation of dry preparations, such as granules, chips, pellets, briquettes, etc. Dry preparations are particularly suitable for paints and printing inks. The pigments according to the invention are radar-transparent and are therefore also suitable for radar applications, particularly in the automotive sector. Furthermore, the interference pigments according to the invention can be used for tinting solar cells, for example by applying a paint containing the pigment according to the invention to a solar panel.

[0031] The following examples are intended to illustrate but not limit the invention. Unless otherwise specified, percentages are by weight. [Example]

[0032] Example 1 100 g of SiO2 flakes (average flake thickness 365 nm) are suspended in 2 l of demineralized water and heated to 85°C with stirring. Sufficient FeCl3 solution (7% Fe content) is then metered in until the desired cut-off point is reached. During this metered addition, the pH value of the suspension is kept constant at 3.1 by adding 30% KOH. Once the addition of FeCl3 is complete, the pH of the suspension is adjusted to 6.5 using 30% KOH. The pigment precursor is then filtered off, washed, and dried at 110°C. Finally, the pigment is calcined at 900°C and sieved. The resulting bluish red interference pigment exhibits the following L, a, b values: Black paint card (measured with a Byk-mac I spectrophotometer, measuring angle 75°): L * =14.07 a * =20.82 b * =16.62 Black paint card (measured with a Byk-mac I spectrophotometer, measuring angle 15°): L * =72.03 a * =74.63 b * =21.35 White paint card (measured with a Byk-mac I spectrophotometer, measuring angle 45°): L * =27.58 a * =34.52 b * =29.50 The pigments according to the invention have the following PSD (particle size distribution) values ​​(measured using a Malvern Mastersizer 3000): D 10 =9.4μm D 50 =19.5μm D 90 =35.0μm

[0033] Comparative Example 1: Example 1 from EP 1 681 318 A2 100 g of silica flakes (average flake thickness: 365 nm) are heated to 75 °C in 2 l of demineralized water. 1120 ml of FeCl3 solution (corresponding to 130% of Fe2O3) are added with stirring. The pH of the reaction mixture is kept constant at 3 by adding sodium hydroxide solution (30%). After the addition of the FeCl3 solution, the pH is increased to pH 5 using sodium hydroxide solution (30%). The product is filtered off and rinsed with deionized water. After drying at 110 °C, calcination is carried out at 800 °C. Black paint card (measured with a Byk-mac I spectrophotometer, measuring angle 75°): L * =14.62 a * =21.85 b * =18.67 Black paint card (measured with a Byk-mac I spectrophotometer, measuring angle 15°): L * =74.97 a * =74.57 b * =41.77 White paint card (measured with a Byk-mac I spectrophotometer, measuring angle 45°): L * =28.69 a * =35.67 b * =34.18 The pigment according to Comparative Example 1 has the following PSD (particle size distribution) values ​​(measured using a Malvern Mastersizer 3000): D 10 =8.9μm D 50 =18.9μm D 90 =34.9μm

[0034] The pigment from Example 1 is particularly suitable for cosmetic and food applications due to its color purity and brightness. b * value (measured using a Byk-mac I spectrophotometer) - as an indicator of blue content (b* In a direct comparison of the blue content (lower values ​​indicate higher blue content) at three observation angles typical of pearlescent pigments, it is clear that the pigment according to Example 1 is significantly bluer than the pigment from Comparative Example 1 at all three observation angles: [Table 1]

[0035] Example 2 - Post-coating of the pigment of Example 1 A 2% by weight aqueous solution containing 2.55 g of sodium hypophosphite (NaH2PO2·H2O) was added slowly to a 5% by weight aqueous solution containing 3.90 g of zirconium oxychloride (ZrOCl2·8H2O) at room temperature while stirring, slowly enough to prevent the formation of a white precipitate. 4.1 g of 35% by weight hydrochloric acid was added to the resulting clear solution to produce a mixed solution of zirconium oxychloride and sodium hypophosphite. The pigment from Example 1 was suspended in 1000 ml of deionized water. 2.95 g of cerium(III) chloride (CeCl3·7H2O) was added to the suspension, and the temperature was maintained at approximately 70°C. The pH was adjusted to 2.5 with 10% HCl. The zirconium oxychloride and sodium hypophosphite solution was added over 60 minutes, while the pH was kept constant at 2.5 with 10% NaOH. The pH was then increased to 7.0 over 60 minutes by adding 10% NaOH. 1.5 g of 3-aminopropyltrimethoxysilane (CAS No. 13822-56-5), 1.5 g of 3-glycidyloxypropyltrimethoxysilane (CAS No. 2530-83-8), and 0.5 g of n-hexyltrimethoxysilane (CAS No. 3069-19-0) are added successively to the suspension over 15 minutes, each time while maintaining the pH at 7.0 with 10% HCl or 10% NaOH. The surface-treated pigment is filtered off, washed with water, dried at 140°C, and sieved (325 mesh). Effect pigments exhibit very good humidity and weather resistance.

[0036] Usage example Example A1: lipstick [Table 2] preparation The ingredients of Phase B are heated to 80°C and melted. The raw materials of Phase A are added and everything is mixed thoroughly. The lipstick composition is then stirred in a casting machine maintained at a temperature of 75°C until there are no air bubbles inside. The homogeneous melt is poured into a casting mold preheated to 55°C. The mold is then cooled (approximately 1 hour) and the casting is removed cold and placed in a lipstick case. The lipstick is then briefly flame treated. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2)Sensient Cosmetic Technologies (3) Elkem (4) Kobo Products (5) Elementis Specialties (6) Alpha Quimica (7) Seppic (8)PIC Quimica (9) BASF AG

[0037] Example A2: Facial toner (micellar water) [Table 3] preparation Add Phase B to Phase A with vigorous stirring. After homogenization, add Phase C, then adjust the pH to 5.0-5.5. Slowly add Phase D to the premixed Phase E and mix everything with Phases A / B / C while stirring. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2) Seppic (3) Lubrizol (4) BASF AG (5) Vantage Personal Care

[0038] Example A3: eye shadow [Table 4] preparation Mix the ingredients of Phase B and add Phase A. While stirring, add the mixture of Phase C. Press the powder at 40-50 bar. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2) China Chemical Reagent (3) Dow Corning (4) BASF AG (5) Shin-Etsu Silicone

[0039] Example A4: Lip gloss [Table 5] preparation The ingredients of Phase B are mixed with stirring. The ingredients of Phase A are added with stirring, followed by Phase C. Finally, the mixture is transferred to a suitable container. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2)Sensient Cosmetic Technologies (3) Innospec (4) BASF AG (5) Croda (6) Sasol Germany GmbH (7)IOI Oleo GmbH (8)Evonik Nutrition & Care GmbH

[0040] Example A5: Manicure [Table 6] preparation The interference pigment is mixed well with the nail polish base for 10 minutes (1000 rpm). manufacturer (1) International Lacquers SA

[0041] Example A6: Lip gloss [Table 7] preparation Heat Phase B to 70°C and homogenize with stirring. Allow to cool slowly to 50°C with stirring and add the interference pigment (Phase A). Allow to cool further to 35°C and add Phase C, then transfer to a suitable container. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2) DKSH GmbH (3) Kahl GmbH & Co.KG (4) IES Lab

[0042] Example A7: Rouge [Table 8] preparation Mix the ingredients of Phase A and Phase C separately. Add Phase C to Phase B and mix. Add Phase A to the mixture of Phases B and C and homogenize everything with an Ultra-Turrax at 8000 rpm. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2) IES Lab (3) Croda (4) BASF AG (5) Nordmann, Rassmann GmbH

[0043] Example A8: lipstick [Table 9] preparation The ingredients of Phase B are heated to 80-85°C and melted. The raw materials of Phase A are added and everything is mixed thoroughly. The lipstick composition is then stirred in a casting machine maintained at 80°C until there are no air bubbles inside. This homogeneous melt is poured into a casting mold preheated to 55°C. The mold is then cooled (approximately 1 hour), and the casting is removed at low temperature and placed in a lipstick case. Finally, the lipstick is briefly flame-treated. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2) BASF AG (3) Koster Keunen Holland BV (4) Henry Lamotte Oils GmbH (5)IES Lab

[0044] Example A9: Lip gloss [Table 10] preparation Heat Phase B to 90-95°C with stirring until a clear emulsion is formed. Cool to a temperature of 55-60°C and add Phase A with stirring. Cool further to 45-50°C and then transfer to a suitable container. manufacturer (1)Merck KGaA / EMD Performance Materials Corp. (2) Essential Ingredients (3) INOLEX Chemical Company (4) Strahl & Pitsch (5) BASF AG (6) Penreco (7) Ineos Oligomers

[0045] Example A10: Hard caramel production [Table 11] Sugar and water are heated to 100°C, then glucose syrup is added. The solution is then heated to 145°C. After adding the interference pigments, coloring solution, and flavoring, the caramel solution is poured into a greased mold using a funnel. Finally, it is allowed to cool for 2 hours. The interference pigments can be mixed with the sugar or added as a mixture with the glucose syrup. This variation does not contain acid, as acid can cause excessive caramelization.

[0046] Example A11: Gelatin product manufacturing [Table 12] First, gelatin is softened with twice the amount of water at 60°C. Sugar and water are heated to 100°C, after which glucose syrup is added. The mixture is further heated to 120°C and then cooled to approximately 85°C. The interference pigment, citric acid, flavoring, and gelatin solution are stirred, and the degassed gelatin mixture is poured into a greased mold using a funnel. The product is allowed to cool for approximately 16 hours.

[0047] Further embodiments: The bluish red interference pigment may again be mixed directly with the sugar or may be introduced together with the glucose syrup. Instead of pouring into a mould, the traditional method of using a negative mould made from moulding powder for the manufacture of gelatin products can also be used.

[0048] Example A12: tablet coating a) White tablet with an initial mass of 1 kg, d = 8 mm, W = 200 mg [Table 13] Total amount applied: 200g This is the surface area of ​​the tablet. 2 This corresponds to 1.2 mg of polymer per 1000 ml.

[0049] Preparation of film coating solution -The interference pigment is stirred in water. Optionally, additional dyes are then added. Finally, the film-forming agent (HPMC) is dispersed into the suspension. As the viscosity increases, the stirring speed must be increased accordingly. After approximately 40-60 minutes, the HPMC is completely dissolved and the solution can be sprayed onto the tablets. - Spray application is carried out by standard coating methods.

[0050] Example A13: ceramics 1) Preparation of printing paste To create fine color screen and relief-like prints on ceramic substrates using ceramic colors, a screen printing oil is used to prevent the color paste from flowing after printing and produce prints with sharp edges. For this purpose, additives are used to known binders, consisting of finely divided natural or synthetic waxes and / or finely divided inorganic silicates or oxides that can be incorporated into the silicate structure of the flux during firing. The interference pigment according to Example 1 is weighed out and homogenized with corresponding amounts of frit and printing medium (in this example, Screen Printing Oil 221-ME and Screenprint Bulk 803035MR—both commercially available products from Ferro—for a series of experiments (see Table 1).

[0051] In the following Examples 1 to 19, frits having the following compositions were weighed out and homogenized. [Table 14] The corresponding raw materials for the preparation of the printing paste, i.e. the initial masses of interference pigment, frit and printing oil for the paste preparation, are given in the table below: [Table 15]

[0052] The following steps 2 to 4 are unrelated to the composition of the printing paste. 2) Tile printing The resulting printing paste can be applied to the tile by standard printing methods, slip printing, spray application, or transfer printing. In all cases, the printed tile is dried in a drying cabinet or fume hood at temperatures between 60 and 110°C to evaporate the solvents present in the printing oil. In an embodiment according to the invention, the printing paste is applied to the tile using a squeegee and a printing screen. 3) Firing the printed tiles The printed and dried tiles are then fired in a firing oven using the temperature profile shown in FIG. 180 minutes: heated to 1100℃, 3 minutes: Hold at 1100℃ 120 minutes: Rapid cooling to 600°C, 300 minutes: Slowly cool to room temperature. The glazed tiles of Examples 1 to 19 are characterized by the fact that the desired optical effect is stable and reproducible when used at high temperatures >1100°C.

Claims

1. α-Fe 2 O 3 SiO 2 Flake-based interference pigments.

2. The SiO 2 2. The interference pigment according to claim 1, wherein the flakes have a diameter of 1 to 250 μm.

3. The SiO 2 3. The interference pigment according to claim 1, wherein the flakes have a thickness of 250 to 500 nm.

4. The α-Fe 2 O 3 4. The interference pigment according to claim 1, wherein the average crystallite size is ≧45 nm.

5. 5. The interference pigment according to claim 1, wherein the average total thickness of the interference pigment is 494 nm±109 nm.

6. 6. The interference pigment according to claim 1, wherein an organic or inorganic post-coating is additionally applied to the interference pigment.

7. The α-Fe 2 O 3 The SiO 2 7. A process for preparing interference pigments according to claim 1, characterized in that the coating of the flakes is carried out by wet chemical methods in a fluidized bed and / or by CVD or PVD methods.

8. 7. Use of the interference pigments according to any one of claims 1 to 6 in paints, coatings, industrial and automotive paints, printing inks, security printing inks, paper, plastics, films, cosmetic formulations, button pastes, pigment mixtures, dry preparations or pigment preparations, ceramic materials, ceramic colours, glazes, enrobes, enamels and glass, as absorbers for the laser marking of plastics, for food colouring, for food finishes, in food and pharmaceutical coatings, for security features on documents and identification cards, for seed colouring, for radar applications and for the colouring of solar cells.

9. A formulation comprising an interference pigment according to any one of claims 1 to 6.

10. 10. The formulation according to claim 9, characterized in that in addition to the interference pigment, it comprises at least one component selected from the group consisting of absorbents, astringents, antimicrobial substances, antioxidants, antiperspirants, antifoaming agents, antidandruff active compounds, antistatic agents, flavorings, binders, biological additives, bleaching agents, chelating agents, deodorizing agents, printing oils, emollients, emulsifiers, emulsion stabilizers, dyes, humectants, film-forming agents, frits, fillers, fragrances, flavors, insect repellents, preservatives, anticorrosive agents, cosmetic oils, solvents, oxidizing agents, fragrances, botanical ingredients, proteins, buffer substances, reducing agents, abrasives, sweeteners, surfactants, propellant gases, opacifiers, UV filters, UV absorbers, denaturants, aloe vera, avocado oil, coenzyme Q10, green tea extract, organic pigments, inorganic pigments, viscosity modifiers, vitamins, enzymes, trace elements, carbohydrates.

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