MXPA97004673A - Finishes containing interference pigments - Google Patents

Abstract

The present invention relates to: This application relates to automotive finishes of two coatings and three coatings, to articles coated through an automotive finish and to a process for their preparation, wherein the polychromism is obtained in the finish by incorporating a pigment of light interference, opaque to the upper coating or a medium coating. The invention further relates to a coating composition, which contains an opaque interference pigment at a pigment to binder ratio of less than 7/1.

Description

FINISHES CONTAINING LIGHT INTERFERENCE PIGMENTS DESCRIPTION OF THE INVENTION This application relates to a procedure to obtain unique effects of polychromism in automotive finishes, by applying an automotive finish of two coatings or three coatings to a substrate and to obtain polychromism in the finish by incorporating a light interference pigment in the upper coating or medium coating. , which is applied on a colored coating base, at a pigment to binder ratio of 0.001 / 100 to 7/100. The finishes that show a significant contrast in color and darkness depending on the angle of vision, usually referred to as "polychromism", "vertical drift", or "trajectory", are currently considered highly desirable for automotive finishes. In general, vertical drift effects in automotive finishes are currently achieved through the use of a two coat system using a base coat and a transparent top coat, wherein the base coat contains a combination of an organic pigment and / or inorganic transparent with a metal, such as aluminum, or a coated, pearled mica pigment. Recently, a new class of opaque or optically variable light interference pigments was described, for example, in the U.S. Patents. Nos. 4,879,140; 5,059,245; 4,705,300; 5,282,480; 4,434,010; 4,779,898; 4,838,648; 4,390,866; 5,135,812; 5,171,363; 5,214,530; 5,522,923; 5,527,848; 4,705,356; and US 5,607,504, which are incorporated herein by reference. Generally, these publications disclose pigments prepared by stacking a transparent dielectric layer and a semitransparent layer, (partially reflective) on one or both sides of a reflective or opaque material to form a layered material having the structure, IVh / D / Mz or -i / D / Mz / D / M, where M2 is an opaque layer, D is a dielectric material and Mi is a semitransparent layer. Generally, the color and degree of polychromism are mainly controlled by the thickness and identity of the dielectric layer, which influences the interference between the light reflected by the semitransparent layer and that reflected by the opaque layer. In general, said light interference pigments are described being produced either by plasma vapor deposition of the layers under high vacuum, or by chemical deposition. The patent of E.U.A. No. 5,437,931 discloses that some benefits are derived by protecting the semitransparent layer, M ,, with another layer of dielectric material, D ', to form a layered material having the structure, D7M1 / D / M2 O D' / Mi / D / Ma / D / Mi / D 'This complicated arrangement of layers can be extended further.

When used in base coatings entrained by waters commonly used in the automotive field, metal-containing pigments, such as the opaque interference pigments described above, experience corrosion or oxidation upon contact with water, resulting in changes undesirable in color. The patent of E.U.A. 5,527,848 discloses a method for protecting opaque interference pigments from corrosion by external influences, such as water in a water-based paint system, through partial oxidation of the metals contained in the pigment. EP 668, 329 and EP 571,836 disclose similar opaque interference pigments, which are produced through chemical means where aluminum flakes are coated with dielectric SiO 2, precipitated by hydrolysis of tetraalkoxy silane, followed by deposition of a metal layer semitransparent such as molybdenum, chromium, iron, etc., by decomposing the corresponding hexa or pentacarbonyl compound. EP 579,091 describes another variation of this aspect, wherein the dielectric layer is treated with molybdenum, which is subsequently oxidized to its oxide and finally converted to oS2 by treatment with H2S. EP 690,105 further discloses that the semitransparent layer can be converted to its nitride through contact with ammonia. These pigments also show a strong polychromism and are very opaque and chemically stable. In this application, the interference pigments composed of a light interference layer or light interference layers and an opaque layer, such as those described above wherein a light interference layer, consisting of the transparent dielectric material and the Semitransparent layer, is applied to one or both sides of a transparent layer, are referred to as opaque interference pigments in order to distinguish them from mica pigments coated with metal oxide, and the like, which have been used in automotive finishes, in combination with a transparent pigment, for some time. The interference layer acts to generate color and polychromism causing interference between light reflected from different surfaces, for example, semitransparent and opaque layer surfaces, within the light interference layer. The opaque interference pigments provide a remarkable contrast depending on the viewing angle when used in coatings, they are still very opaque, producing saturated colors. This is an oxymoron in terms of conventional pigment technology with oxide-coated mica pigments, which are typically combined with an organic and / or inorganic pigment to obtain the desired pearlescent effects. Compared to conventional finishes containing an oxide-coated mica in combination with a transparent pigment, finishes pigmented with an opaque interference pigment provide unique optical effects, depending on the viewing angle, that are not obtained with oxide-coated micas, and a excellent exterior durability. In addition, opaque light interference pigments are incorporated into the paint of a vehicle through a simple mixing step, usually referred to as pigment agitation in the automotive industry, which does not require an intense dipping step. . While the transparent pigments used in combination with a film coated with aluminum oxide or flakes generally require intense dispersion steps, which increase the cost considerably, to be incorporated into the paint of a vehicle, due to its large area of surface, and therefore, high degree of aggregation. Opaque interference pigments are used in paints, inks, and plastics. In the inks, they are mainly used to prevent counterfeiting of money and other legal documents. The use of opaque interference pigments in automotive finishes with two coatings has been described. To impart color and metallic pearlescent effect to the coatings, particularly automotive coatings, significant amounts of the opaque interference pigments have been incorporated into the basecoat color of a basecoat / clearcoat finish. Such high ratios of pigment to binder are necessary to obtain a base coat that provides complete cover-up. However, the high cost of opaque interference pigments makes the use of finishes that have pigment / binder ratios at the appropriate scale too expensive for normal use. These publications do not disclose that the opaque interference pigment can be incorporated into a medium coating or clear coat applied over a black, white or colored base coat, at a much lower pigment to binder ratio to obtain noticeable effects of polychromism in automotive finishes of widely variable color. In this request, the terms "color base coating" and "color pigment" are intended to include base coatings or black and white pigments. It has now been discovered that the amount of the opaque interference pigment required to obtain uncommon visual effects is drastically reduced (thereby reducing cost), while expanding the available color palette, depositing on a substrate, a finish of three. coatings comprising a first coating comprising a white, black or colored opaque pigment to obtain a total cover, applying a second coating (middle coating), which contains the opaque interference pigment on the first coating, followed by a transparent coating conventional. The first coating is applied over the sizing, or it can serve as a color sizing. The second coating contains a smaller amount of the opaque interference pigment, wherein the pigment / binder ratio varies from 0.001 / 100 to 7/100 to a thickness of 8 to 40 μm. The second coating does not completely conceal the first coating. In this way, the amount of opaque interference pigment applied to the substrate is dramatically reduced, although the coated substrate exhibits unique optical effects resulting from the presence of the opaque interference pigment. In a preferred modification, the substrate is finished with a basecoat / clearcoat finish, wherein the topcoat transparent, having a thickness in the range of 25 to 75μm, is tinted with the opaque and applied interference pigment. directly on a black, white or colored base coat, which in turn is applied on the sizing, or which itself serves as a color sizing. In this modification, the middle coating is removed, which further reduces the cost, while still imparting the desired aesthetic effects. Since the interference pigments used according to the invention are opaque, they are necessarily used in small concentrations to allow the color base coating to be shown in the finishing systems of both the two coatings and the three coatings described above. Thus, the finishes of both coatings and three coatings vary in color, from yellow to orange to red to violet, blue and green, and have a high degree of polychromism. Compared with the transparent coating / base coat technology used with oxide-coated mica pigments, the finishes of the present invention provide novel, cost-effective effects, such as remarkable polychromism, without the need to use an organic pigment and / or transparent inorganic The elimination of the transparent pigment drastically reduces the theological problems in the paint, thus reducing the solvent requirements that lead to environmental contamination. In addition, the transparent pigments require expensive dispersion procedures to break up the aggregates and agglomerates formed during their manufacture. invention eliminates the need for these costly, time-consuming dispersion processes through the use of an opaque pigment in the base coat, which is typically more easily dispersed than a transparent pigment, and presents relatively fewer problems. In addition, the invention produces finishes entrained by water and entrained by solvent, which generally have improved light and weather fastness compared to finishes containing a transparent pigment. In addition, the opaque interference pigments used according to the process of the present do not require a treatment, as described in US Pat. No. 5,527,848, in order to avoid corrosion of the metal layers when they are used - with base coatings entrained by water. The present invention relates to to a procedure for coating a substratesaid coating comprises: (a) applying a first coating to a substrate, said first coating comprising an effective amount of pigmentation of an opaque pigment; (b) applying a second coating on the first coating, said second coating comprises an effective amount of polychromism production of an opaque interference pigment, but which does not completely mask the first coating. In particular, the present invention relates to a process, which is a three coat process, wherein a transparent top coat is applied to the second coat, and to a two coat procedure, wherein the second coat is a clear coat tinted (upper tinted coating), representing that the opaque interference pigment is dispersed in the upper coating. The substrate that is coated according to the method herein is not critical to the applicability of the process of the invention. However, since the process of the invention mainly tends to be used as a finishing process for transportation equipment, the most important substrates are the materials used in the bodies of automobiles, bicycles, motorcycles, vans, trucks, or other vehicles. , especially metals, such as steel, iron, and aluminum, and plastics, such as thermoplastics, such as polycarbonates, polyacrylates, and especially thermoplastic polyolefins. The first coating is applied to a substrate, which has been coated with a size coat, or is applied directly to the substrate as a size coat. Since the first coating comprises an opaque pigment, this is applied to completely cover the substrate, whether it is sizing or not. In general, the first coating contains an effective amount of opaque pigment concealment. The first coating contains an opaque pigment. In this application, the term "opaque pigment" means a pigment composed of particles that are large enough to provide good cover and a high degree of light diffusion. Generally, opacity is a function of particle size, pigments with a larger particle size having a greater opacity. The maximum opacity occurs with particles that have a size, which is approximately half the wavelength of maximum absorption. The opaque pigment used in the first coating is an opaque inorganic pigment or an opaque pigment of quinacridone, 1,4-diketo-3,6-diarylpyrrolo [3,4-c] pyrrole, azo, azomethine, methine, anthraquinone, phthalocyanine, perinone , perylene, thioindigo, iminoisoindoline, iminoisoindolinone, flavantrone, indantrone, anthrapyrimidine, and quinophthalone, or a combination thereof. Preferably, the opaque pigment used in the first coating is an inorganic pigment selected from carbon black, iron oxide, titanium dioxide, bismuth vanadate, nickel titanate and chromium tyrant, or an organic pigment which is a pigment of quinacridone, 1,4-diketo-3,6-diarylpyrrolo- [3,4-c] pyrrole, azo, phthalocyanine, iminoisoindoline, iminoisoindolinone or indantrone, or a combination thereof. The phthalocyanine pigments are generally blue and green copper phthalocyanine, which are especially applied as a mixture with titanium dioxide, for example, a 50/50 mixture, in order to cover the substrate. A black base coating provides particularly attractive finishes according to the process of the invention. As the base coat, ordinary gray sizes are also useful, which are usually composed of a mixture of titanium dioxide and carbon black. In the method of the invention, the second coating comprises an opaque interference pigment. The opaque interference pigments useful in the method of the invention generally consist of an opaque layer, which is covered by one or more layers of light interference, which act to reflect the incoming light from different points, within the layer of light. interference, to create the interference of light, resulting in color and polychromism.

The opaque interference pigment is advantageously an interference pigment consisting essentially of flakes of the structure M1 / D / M2 or M? / D / M2 / D / M1, where M2 is an opaque layer which is coated on one or both sides with a transparent dielectric layer, D, which in turn is coated with a semitransparent layer, Mi. Said opaque or similar interference pigments are described in, for example, U.S. Patents. Nos. 4,879,140; 5,059,245; 4,705,300; 5,281,480; 4,434,010; 4,779,898; 4,838,648; 4,390,866; 5,135,812; 5,171,363; 5,214,530; 5,522,923; and 4,705,356. The interference pigments of the above structure, which are coated with one or more dielectric layers or additional semitransparent layers, or both, such as is described in the patent of E.U.A. 5,437,931, also have utility in the process of the invention. In general, M2 is an opaque metal layer, especially an opaque aluminum layer. Since M2 must be completely opaque, having a light transmission less than about 0.1% at 550 nm, it should generally have a thickness greater than 30 nm, especially if it is composed of aluminum. Preferably, the opaque layer is a metal layer, especially an aluminum layer having a thickness of 30 to 90 nm, preferably 30 to 70 nm, and most preferably around 50 nm. The dielectric layer, D, is any material that is transparent at visible wavelengths, having a dielectric constant preferably less than 1.70 (air = 1), most preferably less than about 1.65. The optical thickness (geometric thickness × refractive index) of the dielectric layer is adjusted based on well-known optical principles, to give rise to any desired interference color. Materials that are especially useful as the dielectric layer include MgF2, SiO2 and AI2O3, especially MgF2 and Si02. ME is a semi-transparent layer. In general, Mi is a metallic layer that has a transmission of approximately 30% to 40% at 550 nm. However, the transmission requirement changes with the wavelength, with 50% transmission being the usual target. Preferably, M1f is composed of a metal, such as chromium, molybdenum, tungsten, or iron. In order to practice the present invention, it is important that the second coating does not completely cover the first coating. In this way, at least some of the color of the first coating is shown through the second coating.

The second coating is preferably a solvent-based coating. If the opaque interference pigment is treated to prevent corrosion of the opaque metal layer, and / or if the pigment is not adversely affected by contact with water, the second coating may be a water-based coating in the process of the invention. In general, the process of the invention of three coatings produces a coating that exhibits a high degree of polychromism when the second coating has a thickness in the range of 8 to 40 μm, preferably 10 to 20 μm, most preferably around 15. μm, and contains the opaque interference pigment at a pigment to binder ratio of 0.001 / 100 to 7/100, preferably at a pigment-to-binder ratio of 0.001 / 100 to 3/100, and most preferably at a ratio of binder pigment from 0.001 / 100 to 2/100. Other useful scales for the pigment-to-binder ratio of the middle coating include those that have a lower limit of 0.01 / 100 or 0.10 / 100, and an upper limit of 2/100, 3/100, 5/100 or 7/100. In general, the process of the invention of two coatings produces a coating that shows a high degree of polychromism when the second coating, which is equivalent to the top coating in an automotive finish, has a thickness in the range of 25 to 75 μm, preferably from 40 to 65 μm, most preferably around 50 μm, and contains the opaque interference pigment at a pigment to binder ratio of 0.001 / 100 to 7/100, preferably from 0.001 / 100 to 5/100, most preferably at a pigment-to-binder ratio of 0.001 / 100 to 3. / 100, most preferably at a pigment-to-binder ratio of 0.001 / 100 to 2/100. Other useful scales for the pigment-to-binder ratio of the shaded top coat include those that have a lower limit of 0.01 / 100 or 0.10 / 100, and an upper limit of 2/100, 3/100, 5/100 or 7/100 .

Usually, the gloss of the final finish is related to the particle size of the opaque interference pigment, with pigments of smaller particle size typically producing a high gloss and image clarity finishes. In general, in the methods of the invention, the first coating is applied at a rate that totally covers the substrate, preferably at a thickness in the range of 10 to 50 μm, usually around 25 μm. In the three coat process, the clear coat generally has a thickness in the range of 25 to 100 μm, usually around 50 μm. Neither the first nor the second coatings normally comprise a transparent pigment. However, it may be possible to include a small amount of a transparent pigment in the second layer. The term "transparent pigment" is a term of the art which is familiar to those in the pigment industry. In general, it refers to a pigment that fails to conceal, at normal application regimes, due to its small particle size, which minimizes the diffusion of light. Assuming effective dispersion, it is expected that pigments of smaller particle size will be more transparent than the corresponding larger particle size pigment. The present invention also relates to a substrate, which is coated through the process of the invention. In this manner, the present invention also includes a coated substrate comprising a first coating and a second coating, wherein the first coating comprises an effective amount of pigmentation of an opaque pigment; and the second coating comprises an effective amount of polychromism- (or vertical drift-) production of an interference pigment, wherein the second coating does not completely conceal the first coating. If the substrate is coated by the three coating process of the invention, the second coating is located between the first coating and a transparent top coat. All the above discussion with reference to the process also defines the finishes on the coated substrates of the invention. The coated substrate of the invention is preferably a transportation vehicle, such as a car, bicycle, motorcycle, truck, truck or boat. The present invention also relates to a coating composition that is useful as the second coating in the process of the invention. Thus, the present invention relates to a coating composition, which comprises a solvent, such as water, or preferably an organic solvent, a binder, and an opaque interference pigment, at a pigment-to-binder ratio of less than 7 / 10, preferably less than 5/100, preferably less than 3/100, most preferably less than 2/100, for example on the scale of 0.001 / 100 up, but not including, 7/100, preferably 0.001 / 100 at 5/100, most preferably on the scale of 0.001 / 100 up, but not including, 3/100, most preferably on the scale from 0.001 / 100 to 2/100. It is preferred that the pigment / binder ratio be as low as possible to obtain the desired finishing characteristics. Preferably, the binder is an organic material of high molecular weight, heat or light curable, which is conventionally used for solvent-based topcoat in automotive basecoat / clearcoat finishes. In general, said high molecular weight organic materials include polyacrylics, polymethacrylics, polyesters, polyurethanes, and copolymers thereof. Preferred coating compositions include those containing from 40 to 80% by weight of the high molecular weight organic material, and an opaque interference pigment at a pigment to binder ratio of 0.001 / 100 to 7/100., preferably from 0.001 / 100 to 5/100, most preferably at a pigment-to-binder ratio of 0.001 / 100 to 3/100, most preferably at a pigment-to-binder ratio of 0.001 / 100 to 2/100. Normally, the coating compositions also contain other ingredients, such as stabilizers, including UV absorbers and hindered amine light stabilizers, dispersants, wetting agents, anti-settling agents, and the like.

In general, the coating compositions of the present invention are useful as a automotive topcoat finish tinting. The finishing compositions of the present invention do not include ink compositions, which generally have a superior pigment-to-binder ratio.

The following examples illustrate, but do not limit, the present invention. All parts are parts by weight unless otherwise specified. The pigments used for base coatings are identified by the designation given in the Color Index, which is published jointly by the Society of Dyer and Colourists and the American Association of Textile Chemists and Colorists. All reflectance spectra were taken from painted panels using a MAG8 multiple angle spectrophotometer (available from X-RITE of Grandville MI). The reflectance spectra were obtained under normal light illumination D65 at angles away from the brightness angle (90 ° outside the illumination source). The measured values are referred to as a normal white diffusion reference point.

EXAMPLES 1-3 The following examples describe the incorporation of various types of pigment into a three coat automotive system.

Formulations of base coatings-ground basis 1A. Formulation of ground base for pigment Red 254 and Violet pigment 19 One container was loaded with 46.2 grams of acrylourethane resin (68% solids), 25.2 grams of polymeric dispersant (55% solids) and 46.2 grams of a hydrocarbon solvent aromatic (Solvesso 100). 47.4 grams of pigment and 980 grams of steel bars with a diameter of 4 mm were added. The mixture was milled for 48 hours in a roller mill at 100 rpm. The resulting ground base contains 28% pigment with a pigment / binder ratio of 100/100 and a total non-volatile content of 56.0%. 1 B. Formulation of ground base for other pigments One vessel was charged with 38.8 grams of acrylourethane resin and 113.0 grams of an aromatic hydrocarbon solvent (Solvesso 100). 13.2 grams of pigment were added (Pigment Black 6, Pigment Yellow 110, Pigment Yellow 139, Pigment Blue 15.2, Pigment Green 7) and 980 grams of steel bars with a diameter of 4 mm or ceramic balls of 1.27 cm (PY110, PY139). The mixture was milled for 48 hours in a roller mill at 100 rpm. The milled base contains 8.0% pigment with a pigment / binder ratio of 50/100 and a total non-volatile content of 24.0%. 1 C. Ground Formulation for Pigment Yellow 184 One vessel was charged with 35.3 grams of acrylourethane resin, 63.75 grams of aromatic hydrocarbon solvent (Solvesso 100). 66 grams of pigment and 800 grams of ceramic balls of 1.27 cm were added. The mixture was milled for 24 hours in a roller mill. The ground base contains 40% pigment with a pigment / binder ratio of 277/100 and a total non-volatile content of 54.5%. 1D. Ground base formation of titanium dioxide A ground base of TiO2 was prepared by mixing the following ingredients: 604.1 grams of a TiO2 pigment (DuPont R-969) 129.8 grams of acrylourethane resin, and 161.1 grams of aromatic hydrocarbon solvent (Solvesso 100). A pint of ceramic balls of 1.27 cm was added. The milled base was dispersed for 24 hours in a roller mill. The "TiO2" dispersion contains 67.5% pigment with a total non-volatile content of 77.4%.

Formulations of base coatings-base coating 2A. Base coating formulation for PR 254 and PV 19 30.2 grams of the ground base prepared according to Example 1A, 20.3 grams of a clear solids solution (48.1% solids) containing a melamine resin catalyst, resin, were mixed. of non-aqueous dispersion and a UV absorber and 49.5 grams of an equilibrium solid color solution (58.0% solids) containing a polyester-urethane resin and solvent, and diluted with a solvent mixture containing 76 parts of xylene, 21 parts of butanol and 3 parts of methanol at a spray viscosity of 20-22 seconds as measured through a # 2 Fisher cup. 2B. Formulation of coating base for other pigments 64.3 grams of a ground base prepared according to Example 1B, 24.7 grams of a clear solids solution containing a melamine resin catalyst, a non-aqueous resin dispersion and an absorber of UV, and 11.0 grams of an equilibrium solid color solution described above, containing a polyester-urethane resin, and diluted with a solvent mixture containing 76 parts of xylene, 21 parts of butanol and 3 parts of methanol to a viscosity of spray 20-22 seconds measured through a # 2 Fisher cup. 2 C. Base coat formulation for PY 184 66.7 grams of the ground base described in Example 1C, 10.0 grams of a clear solids solution, and 23.3 grams of an equilibrium solid color solution, containing a polyester-urethane resin were mixed. , and were diluted with a solvent mixture containing 76 parts of xylene, 21 parts of butanol and 3 parts of methanol at a spray viscosity of 20-22 seconds as measured through a # 2 Fisher cup. 2D Formulation of 50/50 shade base coating for PB 15.2 and PG 7 A 50/50 shade shade was prepared by mixing the following ingredients: 57.7 grams of the ground base described in 1B, 8.6 grams of the TiO2 dispersion described in 1C, 22.7 grams of a clear solids solution and 10.0 grams of an equilibrium solid color solution described in 2A, were mixed and diluted as above. 2E. Medium coating formulations The opaque interference pigments of the structure M1 / D / M2 / D / M1 of the color described below, were formulated in medium coating formulations according to the recipes that follow. The color of the pigment was controlled by varying the thickness of the dielectric layers. Color Shade of Interference Pigment Gold-Green to Silver Gold-Yellow to Blue Silver to Red-Red to Gold These pigments were incorporated into several different media coatings by mixing the pigment and paint of the vehicle in a laboratory mixer. Each medium coating has the following formula: Pigment / Coating Binder Medium Composition 0.0015 / 100 100 gr. of transparent coating (60% solids) + 0.0009 gr. pigment 0.015 / 100 100 gr. of transparent coating (60% solids) + 0.009 gr. pigment 0.15 / 100 100 gr. of transparent coating (60% solids) + 0.09 gr. pigment 1.5 / 100 100 gr. of transparent coating (60% solids) + 0.9 gr. pigment 3/100 100 gr. of transparent coating (60% solids) + 1.80 gr. pigment 5/100 100 gr. of transparent coating (60% solids) + 3.0 gr. pigment 3A. Application of bulk shade and shade One of the base coating formulations, prepared according to examples 2A-2D, was sprayed on a panel twice at an interval of 90 seconds, as a base coat. After a flash time of 60 minutes, a medium coating formulation according to Example 2E was sprayed twice at 90 second intervals on the base coat. After an additional flash time of 60 minutes, IP rinse? nn-a cnliiri-Sn H «- re-cina transparent rovpctimißntn river and vaporized for 60 minutes. The system was baked in an oven at 128 ° C for 30 minutes. The typical dry film thicknesses of each coating, in this three-coat system, are as follows: Base coating = 10-50 microns, preferably 20-40 microns Medium coating = 8-40 microns, preferably 10-20 microns Transparent coating = 25-75 microns, preferably 40-65 microns The following table summarizes the colors obtained using various combinations of medium coating / base coat at pigment-to-binder ratios of 1.5 / 100.

The primary color of the finish is controlled through the identity of the pigment used in the base coat and the middle coat. The degree of polychromism is controlled through the pigment / binder ratio of the opaque interference pigment in the middle coating and the thickness of the middle coating. In each case, the finished panel shows a uniform polychromism at a pigment / binder ratio of 0.001 5/100.

EXAMPLE 4 FINISHING TWO COATINGS 4A. Clear Matte Coating Formulation The gold opaque interference pigment described in Example 2 E was incorporated into four clear coat formulations to produce clear, tinted coating formulations, having pigment to binder ratios of 0.0015 / 100, 0.01 5/100, 1 .5 / 100 and 5/100, mixing the pigment and the clear coating in a laboratory mixer in the amounts shown below. The transparent coating is a conventional automotive formulation composed of a mixture of acrylic resins (60% solids) in a mixture of ester and hydrocarbon solvents, which contains 3.9% stabilizer (UV absorber / hindered amine light stabilizer) .

Relationship Pigment / Coating of Clear Coating Matizado Composition (1) 0.001 5/1 00 100 gr. of transparent coating (60% solids) + 0.0009 gr. pigment (2) 0. 1 5/1 00 100 gr. of transparent coating (60% solids) + 0.09 gr. pigment (3) 1 .5 / 1 00 100 gr. of transparent coating (60% solids) + 0.9 g r. pigment (4) 5/1 00 100 gr. of transparent coating (60% solids) + 3.0 gr. pigment 4B. Matte transparent application and base coat One of the base coat formulations, described in Examples 2A (Violet Pigment 19) and 2B (Black Pigment 6) was sprayed on a panel twice at a 90 second interval as a coating of base. After a time of vaporization of 60 minutes, one of the nuanced clear coating formulations, described in Example 4A, was sprayed four times at 90 second intervals on the base coat. The sprayed panel was then "vaporized" for 60 minutes. Then, the two coat panel was baked in an oven at 129 ° C for 30 minutes. Typically, the dry base coating has a thickness of about 25 μm. The dry matted transparent coating film typically has a thickness of about 50 μm. Each of the finishes shows polychromism. Panels with PV 19 as the base coat and the red to gold interference pigment in the top coat have a different polychromism and a primary gold color with a blue-red background when viewed at 90 °. The panels with PB 6 as the base coat and the interference pigment from red to gold in the upper coating, have a black color with a golden interference color when viewed at 90 °, and a different polychromism. Finishes were obtained with each of the following combinations of basecoat / clearcoat pigment, preparing the basecoat formulation according to Example 2, the clearcoat formulation matted according to Example 4A, and applying the finished according to Example 4B.

Coatings having a pigment / binder ratio of 0.0015 / 100, 0.015 / 100, 1.5 / 100, and 5/100 and a thickness of about 50 μm were applied for each of the coating pigment combinations base / transparent coating, described above. In each case, a finish showing polychromism was obtained. The reflectance measurements are similar to those obtained with the three coating systems described in Example 3, as shown by comparing the reflectance measured at 25 ° from the brightness angle of a panel with PB 6 in the basecoat and opaque interference pigment from Red to Gold at a pigment to binder ratio of 1.5 / 100 in the middle coating (L = 43.4, A = 33.3, B = 43.2), or the top coating (L = 44.4, A = 33.3, B = 42.9), or with PV 19 in the base coat and the opaque interference pigment from Red to Gold at a pigment to binder ratio of 3/10 in the middle coating (L = 52.3 , A = 38.9, B = 50.2) or the upper coating (L = 53.4, A = 39.6, B = 50.4), or with red iron oxide in the base coat and the opaque interference pigment from Red to Gold at a ratio of pigment to binder of 0.15 / 100 in the middle coating (L = 30.4, A = 31.8, B = 32.6) or the top coating (L = 30.4, A = 32.2, B = 33.1). Comparing the reflectance spectra of panels painted at various angles in relation to the brightness angle (90 ° outside the illumination source), it was observed that the relative reflection of the finishes of the invention is greater than that which could be expected with proportional base of the reflectance of a covered panel to completely conceal with the opaque interference pigment as the base coat in a conventional automotive basecoat / clearcoat finish. In this way, a pigmented base coat with carbon black on top covered with the red to gold interference pigment at a P / A ratio of 1.5 / 100 shows a maximum reflection% at 650 nm and angles of 15 And 25 °, that is to say, respectively 384% and 368% in relation to the panel covered with a conventional automotive basecoat / clearcoat finish, having a pigmented basecoat with the same interference pigment at a ratio of P / A of 15/100, while one would expect the reflectance to be only around 10% on a strictly proportional basis. This beneficial disparity can be observed with a black base coat, since the black base coat does not show any color reflection. It is more difficult to measure the effect when using a colored base coat, since the base coat is also added to the total reflectance, but the advantage is still evident. Since quinacridone (PV 19) (Ciba's RT-385-D) does not reflect light at approximately 410 nm and the opaque interference pigment from red to blue if it does, a comparison can be made with this system. In this way, an overcoated PV 19 basecoat as the second coating with an opaque blue to red interference pigment at a P / A ratio of 1.5 / 100 demonstrates a higher reflectance than would be expected with respect to to the reflectance of a covered panel to conceal a P / A ratio of 15/100 with the same interference pigment and then covered with a top coating; the observed reflectance being 136% at 15 ° and 161% at 25 ° against the expected 10%. Based on these observations, it is expected that a finish prepared according to the method of the invention has a reflection greater than that proportional to the maximum reflection in relation to a finish containing an amount of concealment of the same interference pigment as the coating base in a conventional basecoat / clearcoat finish. However, this advantage may be more or less difficult to measure depending on the coloristic properties of the base coat and the opaque interference pigment in the middle coat or top coat.

Claims (2)

1 - . 1 - A method for coating a substrate, said method comprising: (a) applying a first coating to a substrate, said first coating comprising an effective amount of pigmentation of an opaque pigment; (b) applying a second coating on the first coating, said second coating comprises an effective amount of polychromism production of an opaque interference pigment, but which does not completely mask the first coating.

2 - A method according to claim 1, which is a three coat process, wherein a transparent top coat is applied on the second coat. 3. A process according to claim 1, which is a two-coat process, wherein the second coating is a shaded top coat. 4. A method according to claim 1 to 3, wherein the opaque interference pigment essentially consists of scales of the structure M! / D / M2 or M? / D / M2 / D / M1, where M2 is an opaque layer that is coated on one or both sides with a transparent dielectric layer, D, which in turn is coated with a semitransparent layer, M ,. 5. - A method according to claim 1 to 4, wherein the first coating is a coating entrained by the waters. 6. A coated substrate comprising a first coating and a second coating, wherein the first coating comprises an effective amount of pigmentation of an opaque pigment; and the second coating comprises an effective amount of polychrome production of an interference pigment, but does not completely conceal the first coating. 7. A coating composition, which comprises a solvent, a binder and an opaque interference pigment at a pigment to binder ratio of less than 7/100. 8. A coating composition according to claim 7, wherein the coating composition is a nuanced automotive clear coat formulation. 9. The use of a coated composition according to claim 7, as an automotive finish of clear matting.