SI23451A - Multilayer color coatings with low solar absorption and high heat emission - Google Patents

Abstract

The invention refers to: i) multilayer color coatings with low solar absorption and high heat emission which can be used for leveling the highest temperature of coated surfaces exposed to direct sun light; ii) process for applying the coating; and iii) cold surfaces prepared with applying said coatings. Compositions for color coatings are made with mixing metal or metalized scales with high reflection in different binders for IR porous or IR reflecting coatings; their high heat emission is achieved with applying of porous top coating with high heat emission. Coatings can be applied with spraying or coil coating.

Description

The present invention relates to: i) color multilayer coatings with low solar absorption and high thermal emissivity, which can be used to regulate the maximum temperature of the coated surfaces exposed to direct sunlight; ii) coating process; and iii) cold surfaces prepared by applying these coatings. Dye coatings are made by mixing high reflective metal or metallized scales, for IR transparent or IR reflective dyes and various binders; their high thermal emissivity is ensured by the application of a transparent top layer with high thermal emissivity. Coatings can be applied by spray coating or coil coating.

PROBLEM SHOWING AND BACKGROUND

Overheating of buildings in southern countries is a serious problem, reflected in the high energy consumption of cooling or air-conditioning buildings exposed to the sun. It is estimated that cooling a building three to six times more than heating it. The maximum stagnation temperatures of surfaces exposed to solar radiation therefore vary in Central Europe from 40 ° C for white and up to 65 ° C for black colored areas.

Protection against thermal radiation can only be effectively applied on surfaces with low solar absorption and high thermal emissivity.

The warming of sun-exposed surfaces is due to the absorption of sunlight on the surface. The relationship between the absorbed luminous radiation and the total solar radiation is called solar absorptivity - ace and can be mathematically expressed by the following equation:

- /? (A »dl ίτ Sili cU« i

-2 where S (A) is direct solar radiation and R (A) is the reflectance of the test surface. In order to reduce the amount of absorbed radiation, solar absorptivity must be reduced; in other words, the reflectivity of the sample area, between 0.3 and 2.5 pm, must be increased. So the surface in UV-Vis-NIR must be "white".

On the other hand, all the heated objects emit energy through thermal IR radiation, that is, between 2.5-15 pm. The object that radiates the highest possible amount of energy is called a “black body.” However, the sun-exposed surfaces are not really black in terms of thermal IR radiation. They emit only a fraction of the maximum radiation. The weighted ratio between the radiated emission, 1-R (A), and the Planck distribution in the black body, r (A, T), is called thermal emissivity, er, and can be mathematically expressed as:

f ₂ 'Jri4.D (l - / iffl) d (A)

J2 5 r (4, T) (14

To achieve maximum energy loss through radiation, the surface must be “black” in the thermal IR region of the light spectrum; that is, it has a high e _T.

In the Mediterranean, facades and roofs have been painted white in the distant past to reduce solar energy absorption. If different shades of color are desired, a special coating composition must be used. In recent years, there has been a growing interest in the production of high-reflectivity coatings to prevent the building's solar surfaces from overheating. Such coatings are called "cold colors" because they reach a lower temperature when exposed to the sun than normal colors. The first method for producing such cold colors is to use inorganic IR reflective pigments as described in US 4,424,292 or US 4,624,710, or organic IR reflective pigments as described in US 6,989,056. Recently, Levinson et al. systematically screened the IR reflective properties of several pigments and used them to produce asphalt roofing shingles [Levinson, R., etal. So /. Energy Mater. Sol. Celiš, 2007; 97 (4): p. 304-314], Many "cold pigments" have already been manufactured by pigment manufacturers such as Shepherd Color Co., the Arctic - Infrared Reflective Pigments product line; and Ferro, the Cool Colors and Eclipse product line. To improve the IR reflectivity of IR non-reflective, IR transparent pigments were applied to white, highly reflective inorganic substrates such as titanium, aluminum, zinc oxide, calcium carbonate, barium sulfate and metal scales, to prepare new IR reflective pigments such as

-3described in US patent applications US2002 / 0129739 and US 2006/015922. Hollow microspheres were used to reduce the thermal conductivity of cold coatings as described in U.S. Patent Application 2005/0126441.

Most interesting is the use of cool paints to coat the metal panels used to make the facades or roofs. US2005 / 0129964 describes a solution that uses several layers, each of which is made by a specific application process. In FIG. 22808, a cold coating was prepared by adding two IR reflecting oxides, that is, titanium and zinc oxide, to the usual color composition. However, no details on the color strength are described.

In [Orel, B et al. So /. Energy Mater. Sol. Celiš, 2007; 97 (2-3): p. 93-118] are thickness-sensitive, spectrally selective (TISS) coatings that are suitable for collecting solar energy in solar thermal collectors. They exhibit completely opposite qualities as cool colors; namely, high solar absorption, high absorption in the UV, visible and NIR parts of the light spectrum, ie between 0.3 and 2.5 pm; and low thermal emissivity, that is, high reflectivity in the thermal IR portion of the light spectrum, i.e., above 2.5 pm. They are used as hot colors; their surface warms more in the sun than the surface of normal colors with the same hue. There is no proposed option for using this approach in cold color technology.

As a first object of the present invention, it is highly desirable to develop a technology for the production of cold dyes from various color pigments without applying them to the surface of white IR reflecting materials from inorganic particles, since the process for preparing the coated pigment particles is time consuming and expensive. Another purpose is to prepare cold surfaces from these colors. A third object of the present invention is to provide a process suitable for the industrial uses of the paints thus produced.

DESCRIPTION OF THE NEW SOLUTION BY THE INVENTION

It has been found that by appropriate selection of pigments or other dyes having high IR transparency or high IR reflectance for the preparation of TISS-type paints or by applying a transparent polymer coating on top of such TISS-type paints, a layer coating exhibiting low solar absorption may be formed, it is high solar reflectance and high thermal emissivity, it is low reflectance in the thermal IR of the light spectrum.

-4Plate coat could be applied to various substrates; its performance does not depend on the basis. Applying such coatings to facades or roofs reduces overheating of these surfaces.

SHORT DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic illustration of a color multilayer based coating.

Figure 2 presents the UV-Vis-NIR-IR reflectance spectra of A) yellow TISS coating with low ace and low βγ and B) yellow multilayer coating with low solar absorption and high thermal emissivity.

Figure 3 represents the UV-Vis-NIR-IR reflectance spectra of C) light blue TISS coating with low ace and low er and D) light blue multilayer coating with low solar absorption and high thermal emissivity.

Figure 4 presents the UV-Vis-NIR-IR reflectance spectra of E) green TISS coating with low ace and low we _T , F) green TISS coating with low a _s and low er with added binder in the composition and G) green multilayer coating with low solar absorption and high thermal emissivity.

DETAILED DESCRIPTION OF THE INVENTION

TISS low ac, _n low e _T coatings are not useful for the thermal utilization of solar energy, so their conversion to cold coatings is highly desirable. This can be done by optimizing them into a colored multilayer coating showing low solar absorption and high thermal emissivity, simply by applying an additional layer of transparent topcoat. Low solar absorptivity is solar absorptivity lower than a _s = 0.85; high thermal emissivity means a heat emissivity higher than er = 0.85.

The color multilayer coating with low solar absorption and high thermal emissivity, which is an essential part of the present invention, is shown schematically in Figure 1. Number 1 indicates the base material, that is, the substrate to be provided with the coating. There are no restrictions on the substrate; the cooling effect is independent of the substrate.

The number 2 and number 3 in Figure 1 indicate two different parts of the TISS color with low ace and low er, which are indicated by number 5. Both parts of the TISS color appear in a single application step. This is not possible without the preparation of a TISS coating. The number 2 high reflective part of the TISS coating with low a _s and low e _T and a large number indicates in more detail

-5content of metallic or metallic scales. The number 3 indicates the part of the TISS coating with low »s and low e _T and high content of dye. The low value of βγ TISS paint can be increased by applying a top coat with a high value of _{T T.}

Number 4 indicates a topcoat with a high transparency in the visible part of the light spectrum and high thermal emissivity, which may also have the ability to avoid dirt.

The combination of the layers mentioned above results in a final coating that has a low ace and a high er; in other words, it is a cold coating. This configuration of the layers and their composition represent a unique solution for the production of cold surfaces. Conversion of TISS coatings with low a _s and low er into cold colors is therefore inexpensive and easily feasible; application of the top coat further increases the environmental stability of existing paint coatings.

TISS low and low _{T T} coatings are characterized by the use of dyes having NIR reflectivity or NIR transparency, which can be further functionalized to improve their compatibility and dispersion in resin binders; and using metal or metallized scales, binders, additives. Low ace values are values below 0.85; low e _T values are below 0.60.

Dyes having high NIR reflectivity or transparency are selected from, but not limited to: a group of soluble dyes comprising acidic dyes, substantive dyes, basic dyes, developed dyes, sulfur dyes, aniline dyes, and dye arrest; a group of organic pigments comprising azo pigments selected from pigments: monoase, diazo condensation, beta-naphthol, naphthol AS, varnished azo, benzimidazolone, azomethine, azomethine-azo, isoindolinone and isoindoline phthalocyanine, quinacridone, peryleneac and perinone , anthropyrimidine, flavantrone, pyrantron, antantrone, dioxazine, triarylcarbonium, quinophthalone, diketopyrrol; and a group of inorganic pigments comprising the metal oxides and hydroxides of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, cadmium, bismuth, antimony, zinc, tin, lead, aluminum, mixtures thereof, and mixed oxides of rutile and spinel type. The surface of inorganic pigments can be further modified by the use of silanes during the crushing or dispersing process. During the application process, the dyes with the dye are the enriched layer on top of the aluminum-enriched layer. This layer

-6gives the color of the coating; this means that some absorption in the visible part of the light spectrum and all other parts of the sunlight must be reflected or transferred to the lower aluminum layer. The color tones obtained with this composition are more intense and the amount of colorant used is lower than that of conventional cold colors.

Dyes are used in an amount of 0.5 to 80% w / w. dry matter, preferably 0.7 to 70% and ideally 1 to 65% w / w. dry matter per complete preparation for the production of TISS low ac and low e _T coatings.

The most important part of TISS coatings in all parts of the light spectrum are high reflective metal or metallized scales. They can be selected but not limited to: aluminum, copper, stainless steel, metallic borosilicate flakes, metallic mica flakes. It is highly desirable that the scales do not rise towards the surface, so that they can form a layer below, similar to the layer of flat metal foil, where the scales are very densely positioned, which is achieved by the choice of scales of the right diameter and flat cross section. It is highly desirable for the husks to have an average diameter greater than 10 pm, preferably greater than 15 pm. The use of such large scales also significantly improves the corrosion stability of the coated objects, due to the multilayered, less permeable structure with the scales of the rich part of the TISS. These coatings are therefore particularly suitable for the coating of façade or roof elements exposed to harsh, destructive environmental forces.

The high reflective base of the TISS coatings acts as a mirror and all the light transmitted by the upper layers reflects back, so that the reflectivity in all parts of the spectrum is increased, resulting in lower solar absorption and lower thermal emissivity. TISS coatings with such properties cannot be justified in the use of solar heat, unless they are coated with a transparent coating that increases thermal emissivity, after which they can be used as cold coatings.

Reflective scales are used at a concentration of 0.1 to 60% w / w. dry matter, preferably 0.5 to 55% and ideally 1 to 50% w / w. dry matter with respect to the whole preparation, for the production of TISS coatings with low a _s and low e _T.

-7Example binder for the preparation of TISS low-ac and low-e _T coatings is, but is not limited to: organic resins comprising acrylates, methacrylates, styrene-acrylates, styrene-methacrylates, substituted polyolefins, polystyrene and styrene copolymers, alkyd resins , saturated or unsaturated polyesters, polyimides, polyurethanes, polyethers, epoxy resins, silicones, fluorous polymers, fluorinated acrylic copolymers, vinylpyrrolidine, polypyrrolepine and mixtures thereof.

The binders are used at a concentration of 10 to 80% w / w. dry matter, preferably 15 to 78% and ideally 20 to 75% w / w. of dry matter to the whole preparation, for the preparation of a TISS coating with low ac and low e _T.

Additives such as but not limited to: dispersing auxiliaries, rheological additives, antifoaming agents and fillers are used at a concentration of 0.01 to 60% w / w. dry matter, preferably 0.1 to 55% and ideally 0.5 to 51% w / w. of dry matter per complete preparation for the production of TISS low ac and low e _T coatings.

The topcoat is applied to dry TISS paint, which gives high thermal emissivity to the multilayer coating. The topcoat is applied to a layer thick enough to change the thermal emissivity of the composite coating from low to high values, preferably above 0.9. The topcoat of colored multilayer coatings is exposed to UV light and other environmental degradation forces and must therefore be made of durable resin. The top coatings used to convert TISS coatings with low aces and low θτ to cold coatings do not contain pigments (without sanding), but mainly from polymer resin binders, crosslinkers, UV absorbers (not so essential for Lumiflon fluoropolymer ) and additives such as pyrogenic silica, rheological additives, antifoaming additives, and compounds that enhance self-cleaning properties such as multifunctional polyhedral silesquioxanes. When used as cold coatings, it is important to know how quickly their thermal emissivity increases with the thickness of the applied top coat to achieve e _T > 0.9. For economic reasons, it is advantageous to achieve high values of e _T by applying the thinnest possible top coat of varnish over the surface of TISS paint coatings with low a _s and low e _T.

-8Durable resin binders for topcoat production are selected from, but not limited to: acrylates, methacrylates, styrene-acrylates, styrene-methacrylates selected from substituted polyolefins selected from polystyrene and styrene copolymers, alkyd resins selected from saturated and unsaturated polyesters polyimides, polyurethanes, polyethers, epoxy resins, silicones, chlorosulfonated polyethylene, fluorinated polymers selected from fluorinated acrylic copolymers or fluorosilicones, vinylpyrrolidone-vinyl acetate copolymers, polyvinylpyrrolidines, polyisopropylpyrimidines, polyisopropylpyrimidines Polyurethane resins such as Desmophen and fluorinated polyurethane resins as in the Lumiflon series, combined with a suitable crosslinking agent, are particularly suitable. The topcoat can also contain many light stabilizers, such as HALS and UV absorbers, to improve UV stability. As expected, varnishes based on more polar polyurethane are better absorbed than fluoropolymer, indicating that thinner top layers of the first said varnish are needed to achieve the same thermal emissivity improvement as the TISS primer. Most of the polymer resin binders used for clear lacquers are good absorbers of thermal infrared radiation and their thermal emissivity exceeds 0.80 at sufficient thickness.

It is also highly desirable that the topcoat has self-cleaning properties originating from large contact angles for water and hexadecane. These properties can be achieved by the addition of multifunctional polyhedral silesquioxane compounds to the topcoat composition. Multifunctional polyhedral silsesquioxanes are characterized in that they contain at least one free amino group or one free hydroxyl group or one free carboxyl group, at least one perfluorinated alkyl group and at least one branched alkyl group per one molecule of silsesquioxane. Such additives can increase the static contact angle for water to 110 ° and to 40 ° for hexadecane when applied in sufficient concentration.

Multifunctional polyhedral silsesquioxanes are useful at a concentration between 0.01 and 15% w / w. dry matter, preferably 0.3 to 12% and ideally 0.5 to 10% w / w. Dry matter per complete preparation for the production of topcoat.

-9 For all the coatings mentioned above, we use organic solvents selected from, but not limited to: aliphatic hydrocarbons such as hexane, heptane, octane and the like; aromatic hydrocarbons such as benzene, toluene, xylene and the like; solvents of the type alcohol, ether, ester or ketone, such as isopropylalcohol, n-butyl alcohol, isobutyl alcohol, octyl alcohol, Cellosolve, butyl Cellosolve, diethylene glycol-monobutyl ether, methylisobutyl-ketone, propylene glycol-monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether , dipropylene glycol monobutylether, acetone, diisobutyl ketone, ethyl acetyl ketone, methylhexyl ketone, ethylbutyl ketone, ethyl acetate, isobutyl acetate, acyl acetate, 2-ethylhexyl acetate, 2-methoxypropyl acetate, etc. These organic solvents are useful singly or in a mixture of two or more.

Cold surfaces can be prepared by application of TISS low-ac and low-er coatings, which can be applied by spray coating or coil coating on any suitably formed substrate selected from, but not limited to: metal sheets, made of, but not limited to: steel, galvanized and aluminised steel, tin-coated steel, stainless steel, copper, aluminum, and their alloys; the substrate may also be polymeric material, concrete or other building materials. Before applying a cold coating, the substrate can be further protected against corrosion by a suitable primer, which can also serve to improve adhesion to the substrate.

A very high value for thermal emissivity could not be achieved by directly adding excess resin binder to the TISS coating. The corresponding TISS paint coating does not show high values for thermal emissivity. The use of a resin binder is more rational and economical when applied as a thin topcoat, since in this case less material is required to achieve er> 85. The present invention provides an optimal solution for the preparation of cool colors. This can be seen in Examples 5-7.

From the spectra shown in Figures 2-4, it can be seen that all coatings have a higher reflectance in the NIR region than in the UV-Vis region of the light spectrum, but also exhibit low reflectance in thermal IR (at λ = 2.5 pm). These are desirable properties for coatings capable of preventing overheating of the coated surfaces exposed to solar radiation.

-10TISS low a _s and low e _T coatings must be applied in a suitable thickness to achieve the formation of the two-layer structure shown in FIG. 1 under number 5. For this purpose, the thickness of the coating should be between 1 and 150 pm, preferably between 2 and 120 pm and ideally between 3 and 90 pm.

A high er topcoat can be applied either by spray application or by a coil coating process to a TISS coating and must be applied in a suitable thickness to achieve high e _T values. The value of er depends on the thickness. In order to achieve a high er, the thickness of the coating should be between 1 and 200 pm, preferably between 2 and 180 pm and ideally between 3 and 150 pm.

EXAMPLES

Measurement techniques:

The optical properties of the samples were determined from the measured IR absorption and reflectance spectra of the samples, measuring at least 5 χ 5 cm ² . Visible and near-infrared (NIR) reflectance spectra were measured on a Perkin Elmer Lambda 950 UV / Vis / NIR with an integration sphere (150 mm module), while spectra were obtained in the mid-IR spectrum at Bruker IFS 66 / Using a spectrometer equipped with an integration ball (OPTOSOL), using a gold plate as a standard for diffuse reflectance. Values for solar absorptivity (as) and thermal emissivity (ey) for all samples were calculated according to the standard method: Kohl, G. Jorgensen, AW Czanderna, Performance and Durability Assessment: Optical Materials for Solar Thermal Systems, Elsevier, The Netherlands, 2004 and MG Hutchins, Spectrally selective materials for effective visible, schoolchildren and thermal radiation control, in: M. Santamouris (Ed.), Solar Thermal Technologies for Buildings, James & James, London, 2003. βτ values were calculated from black-body spectra at 80 ° C. C * values were determined from reflectance spectra (recorded on the apparatus listed above) according to CIE Technical Report: Colorimetry 3 ^rd ed. 2004, The International Commission on Illumination, Vienna, p. 17 (ISBN 3 901 906 33 9).

-11 EXAMPLE 1

Yellow TISS coating with low a _s and low βγ

Yellow pigment paste is first prepared with the following ingredients:

Desmophen® A 365 (Bayer MaterialScience AG) Bayferrox 3920 (LAXNESS)

Bentone® SD-2 (Elementis Specialties, Inc.) Disperbyk 131 (BYK) xylene

240 g

381 g

13g

168 g n-butyl acetate g

The pigment was gradually added to the Desmophen® A 365 solution in Disperbyk 161 and xylene with constant dispersion. After completion of the addition, continue to disperse for a further 15 minutes, then add Bentone® SD-2 at constant dispersion and continue to disperse for a further 15 minutes. The resulting dispersion is ground in a sand mill at about ~ 3000 rpm (RPM) to a particle size of <1 pm (ISO 1524). With constant dispersion, n-butyl acetate is added. The yellow TISS coating is made by mixing the following ingredients:

% yellow pigment paste is prepared as previously described 327 g

Alubright 3100 (Schlenk Metaliic Pigments GmbH) 274 g

410® 410 (Chem-Chemie GmbH) 10 g

4-hydroxy-4-methylpentan-2-one 12 g

Desmophen® A 365 (Bayer MaterialScience AG) 220 g

-12- n-butyl acetate 50 g xylene 50 g Additol® XL 186 (Cytec Industries inc.) 32 g Desmodur® N 75 (Bayer MaterialScience AG) 112 g

The yellow pigment paste, prepared as described above, is slowly incorporated into Alubright 3100 and Desmophen® A 365; 4-Hydroxy-4-methylpentan-2-one, n-butyl acetate, xylene, Additol® XL 186 and ΒΥΚ® 410 were added with constant dispersion. Just before application, Desmodur® N 75 is added and the appropriate diluted mixture is used immediately.

The coating composition prepared in this way can be applied by coil coating or spray application.

When properly applied by spray application, the coating thus prepared has a thickness of 10 to 100 pm on a steel base with GtO adhesion (ISO 2409) and its spectral selectivity is indicated by _s = 0.50 and e _T = 0.25 and C * = 34.64. The reflectance of the spectrum in the UV-Vis-NIR-IR region can be seen in Figure 2, code A; this coating cannot be used to collect solar thermal energy.

EXAMPLE 2

Yellow multilayer coating with low solar absorption and high thermal emissivity

The transparent topcoat is first prepared by mixing:

Lumiflon-LF 200 (Asahi Glass Co., Ltd.) (grams) 107.8 g

Desmodur® N 75 (Bayer MaterialScience AG) 25.5 g

Just before application, Desmodur® N 75 was added to Lumiflon and a suitable diluted mixture was used immediately.

-13With proper application of the spray coating method to the coating, made as indicated in Example 1, in a suitable thickness between 1 and 80 pm on a steel base, a yellow multilayer coating with low solar absorption and high thermal emissivity is obtained and its spectral selectivity is indicated as a _s = 0.51 in βγ = 0.88 and C * = 32.95. With the application of the topcoat, the thermal emissivity approached 1, allowing the surface to emit more energy with increased radiation in thermal IR than those without the topcoat. The stagnation temperature is therefore lower. The reflectance spectra in the UV-Vis-NIR-IR region can be seen in Figure 2, code B; this multilayer coating can be used as a cold paint to prevent the exposed surfaces of the sun from overheating.

EXAMPLE 3

TISS light-meter with low «s and low θτ coating

The coating composition and colored samples were prepared according to Example 1, except with the change to use the same amount of Heliogen® Blau L 6700 F as the coating preparation instead of Bayferrox 3920.

When properly applied by spray application, the prepared coating thus has a thickness of 10 to 100 pm on a steel base with GtO adhesion (ISO 2409) and its spectral selectivity is denoted as = 0.65 and e _T = 0.25 and C * = 38.78. The reflectance of the spectrum in the UV-Vis-NIR-IR region can be seen in Figure 3, code C; this coating cannot be used to collect solar thermal energy in unglazed reservoirs because it has a lower efficiency than normal black paint.

EXAMPLE 4

Light-blue multi-layer coating with low solar absorption and high thermal emissivity

The topcoat was prepared as described in Example 2. When applied properly with a spray method onto the coating, made as indicated in Example 3, in

-14example thickness between 1 and 80 pm on a steel base, a light-blue multilayer coating with low solar absorption and high thermal emissivity was obtained and its spectral selectivity is stated as as = 0.51 and e _T = 0.87 and C * = 34.65. By applying the topcoat of the session, the thermal emissivity approximated 1, which allowed the surface to emit more energy with increased radiation in thermal IR than those without the topcoat. The stagnation temperature is therefore lower. The reflectance spectra in the UVVis-NIR-IR region are shown in Figure 3, code D; this multilayer coating can be used as a cold paint to prevent the exposed surfaces of the sun from overheating.

EXAMPLE 5

Green TISS coating with low a _s and low θτ

We first prepared green pigment paste from the following ingredients:

Xylene 265.80 g

Dysperbyk 161 43.94 g

PK4047 (Ferro) 395.27 g

Lumiflon 200 (Asahi Glass Co) 161.77 g n-butyl acetate 133.23 g

The pigment was gradually added to the solution of Lumiflon 200 and Disperbyk 161 in xylene with continuous dispersion. After the addition is complete, continue dispersing for a further 15 minutes, then add Bentone® SD-2 with constant dispersion and continue dispersing for a further 15 minutes. The resulting dispersion is ground in a sand mill at about ~ 3000 rpm (RPM) to a particle size of <1 pm (ISO 1524). With constant dispersion, n-butyl acetate was added.

-15The green TISS coating is made by mixing the following ingredients:

% green pigment paste made as described previously 19.5 g

Alubright 3100 (Schlenk Metallic Pigments GmbH) 4, g

410® 410 (ΒΥΚ-Chemie GmbH) 0.12 g

4-hydroxy-4-methylpentan-2-one 0.6 g

3,875 th most common

Lumiflon 200 (Asahi Glass Co) g / 7-butyl acetate 2.75 g xylene 2.5 g

Desmodur® N 75 (Bayer MaterialScience AG) 1.3 g

The green pigment paste made as described above is slowly embedded in Alubright 3100 and Lumiflon LF 200, and n-butyl acetate, xylene and ΒΥΚ® 410 are added with constant dispersion. Just before application, Desmodur® N 75 is added, the mixture is diluted and used immediately. .

The composition thus prepared can be suitably diluted by coil coating or spray application.

For a suitable application with a 30 pm manual coating, the coating thus selected has a spectral selectivity of as = 0.67 and θτ = 0.40 with a coating of 10 to 100 pm thick on a steel base. The reflectance spectrum in the UV-Vis-NIR-IR region is shown in Figure 4, code E; this coating cannot be used to collect solar thermal energy.

EXAMPLE 6

Attempt to prepare a green TISS coating with low »s and high _T

-16Green TISS resin-rich coating is made by mixing the following ingredients:

% green pigment paste made as described previously 19.5 g

Alubright 3100 (Schlenk Metallic Pigments GmbH) 4,5 g

410® 410 (ΒΥΚ-Chemie GmbH) 0.12 g

4-hydroxy-4-methylpentan-2-one 0.6 g

Lumiflon 200 (Asahi Glass Co) 12 g n-butyl acetate 2.75 g xylene 2.5 g

Desmodur® N 75 (Bayer MaterialScience AG) 4.6 g

The green pigment paste made as described in Example 5 was slowly embedded in Alubright 3100 and Lumiflon LF 200, and nbutyl acetate, xylene and 410® 410 were added with constant dispersion. Just before application, Desmodur® N 75 was added, the mixture was diluted and used immediately. .

The composition thus prepared can be suitably diluted by coil coating or spray application.

In a suitable application with a manual coating, in the case of a 10 to 100 pm thick coating on a steel substrate, its spectral selectivity is indicated as as = 0.687 and e _T = 0.46. The reflectance spectrum in the UV-Vis-NIR-IR region is shown in Figure 4, code F; this coating cannot be used to collect solar thermal energy, nor can it be treated as a cool color. Very high values of thermal emissivity cannot be achieved by simply adding excess binder to the TISS coating.

-17 EXAMPLE 7

Green multilayer coating with low solar absorption and high thermal emissivity

The topcoat was prepared as described in Example 2. Appropriate spray-coating process as in Example 5, in a suitable thickness of 1 to 80 pm on a steel substrate, gave a light blue multilayer coating with low solar absorption and high thermal emissivity and its spectral selectivity are indicated by _s = 0.64 and βτ = 0.89. With the application of the topcoat, the thermal emissivity approached 1, which allowed the surface to emit more energy with increased radiation in thermal IR than without the topcoat. The stagnation temperature is therefore lower. The reflectance spectrum in the UV-Vis-NIR-IR region is shown in Figure 5, code G; this multilayer coating can be used as a cold paint to prevent sun-exposed surfaces from overheating.

A color multilayer coating with a low value for solar absorption and a high value for thermal emissivity according to the invention, wherein the low solar absorbance is lower than ac = 0.85 and the high thermal emissivity is higher than er = 0.85, characterized in that it is prepared with two successive application rates of TISS coatings with low solar absorption and low thermal emissivity as the first layer in contact with the substrate, and a transparent top coat with high thermal emissivity as the second layers. The first layer is prepared using dyes with NIR reflectance or NIR transparency, in an amount of 0.5 to 80% w / w. dry matter per complete preparation; and using metal or metallized scales, in a concentration of 0.1 to 60% w / w. dry matter per complete preparation; and using a binder at a concentration of 10 to 80% w / w. dry matter per complete preparation; and using additives at a concentration of 0.01 to 60% w / w. dry matter per complete preparation; and using solvents to prepare them. The dyes used are selected from: a group of soluble dyes comprising acidic dyes, substantive dyes, basic dyes, developed dyes, sulfur dyes, aniline dyes, and dye arrest; groups of organic pigments comprising azo pigments selected from pigments: monoase, diazo condensation, beta-naphthol, naphthol AS,

-18lacinated azo, benzimidazolone, azomethine, azomethine-azo, isoindolinone and isoindoline phthalocyanine, quinacridone, perylene and perinone, thioindigo, anthraquinone, anthropyrimidine, flavantrone, pyranthrone, anthronron, dioxazine, triaryllopropylcarbonyl; and groups of inorganic pigments comprising metal oxides and hydroxides of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, cadmium, bismuth, antimony, zinc, tin, lead, aluminum, mixtures thereof, and mixed oxides of rutile and spinel type. The metal or metallized scales used have an average diameter greater than 10 pm and are selected from the groups consisting of: aluminum, copper, stainless steel, borosilicate scales, metallic mica scales. The binder used is selected from organic resins comprising acrylates, methacrylates, styrene acrylates, styrene methacrylates, substituted polyolefins, polystyrene and styrene copolymers, alkyd resins, saturated or unsaturated polyesters or polyamides, polyimides, polyurethanes, polyurethanes, polyurethanes, polyurethanes , chlorosulfonated polyethylene, fluorinated polymers, fluorinated acrylic copolymers or fluorosilicones, vinylpyrrolidone-vinyl acetate copolymers, polyvinylpyrrolidone, polyisopropyl acrylate, polyurethanes, wax dispersions based on polyethylene, polypropylene. The transparent topcoat has a high thermal emissivity and is applied as a second layer in the preparation of the multilayer colored product using extremely durable resin binders, crosslinkers and additives for their application, applied in a sufficient thickness to allow the thermal emissivity of the colored multilayer to exceed 0.85.

The coatings are characterized by their application to a substrate selected but not limited to sheet metal / foil made of steel, galvanized steel, galvanized and aluminised steel, galvanized steel, stainless steel, copper, aluminum and their alloys; the base may also be polymeric material, concrete and other building materials.

The coatings are applied by spray application or by applying to (metal) strips, in the thickness of 1 to 150 pm and by applying a top coat with high thermal emissivity in the thickness of 1 to 200 pm.

Claims (8)

PATENT APPLICATIONS 1. A color multilayer coating with a low value for solar absorption and a high value for thermal emissivity, wherein the solar absorbance is lower than a _s = 0.85 and the high thermal emissivity is higher than e _T = 0.85, characterized in that it is prepared by successive, two-stage application of TISS coatings with low solar absorption and low thermal emissivity as the first layer in contact with the substrate and a transparent top coat with high thermal emissivity as the other layers. The coating of claim 1, wherein the first layer is made using dyes with NIR reflectance or NIR transparency, in an amount of 0.5 to 80% w / w. dry matter per complete preparation; and using metal or metallized scales in a concentration of 0.1 to 60% w / w. dry matter per complete preparation; and using a binder at a concentration of 10 to 80% w / w. dry matter per complete preparation; and using additives at a concentration of 0.01 to 60% w / w. dry matter per complete preparation; and the use of solvents for their preparation. The coating according to claim 2, wherein the dyes used are selected from: a group of soluble dyes comprising acidic dyes, substantive dyes, basic dyes, developed dyes, sulfur dyes, aniline dyes and a dye arrest; groups of organic pigments comprising azo pigments selected from pigments: monoase, diazo condensation, beta-naphthol, naphthol AS, varnished azo, benzimidazolone, azomethine, azomethine-azo, isoindolinone and isoindoline phthalocyanine, quinacridone, peryleneoin and perinone , anthropyrimidine, flavantrone, pyrantron, antantrone, dioxazine, triarylcarbonium, quinophthalone, diketopyrrol; and groups of inorganic pigments comprising metal oxides and hydroxides of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, cadmium, bismuth, antimony, zinc, tin, lead, aluminum, mixtures thereof, and mixed oxides of rutile and spinel type. -204. The coating according to claims 2 to 3, wherein the metal or metallized flakes used have an average diameter greater than 10 pm and are selected from the groups consisting of aluminum, copper, stainless steel, borosilicate metallized mica. The coating according to claims 2 to 4, wherein the binder used is selected from organic resins comprising: acrylates, methacrylates, styrene-acrylates, styrene methacrylates selected from substituted polyolefins selected from polystyrene and styrene copolymers, alkyd resins selected from saturated or unsaturated polyesters of polyamides, polyurethanes, polyethers, epoxy resins, silicones, chlorosulfonated polyethylenes, fluorinated polymers selected from fluorinated acrylic copolymers, vinylpyrrolidines, polyvinylpyrrolidines, polyvinylpyrrolidines 6. The coating according to claims 1 to 5, wherein the transparent topcoat has a high thermal emissivity and is applied as a second layer in the preparation of multi-layer colored coating, using very durable resin binders, crosslinkers and additives for their preparation, applied in sufficient thickness, thus that the thermal emissivity of the multilayer paint exceeds 0.85. Coatings according to Claims 1 to 6, characterized by application to a substrate selected but not limited to sheet metal / foil made of steel, galvanized steel, galvanized and aluminised steel, galvanized steel, stainless steel, copper, aluminum and their alloys ; the substrate may be polymeric material, concrete and other building materials. 8. The coating according to claims 1 to 7, characterized by application by a spray application process. -219. Coating according to claims 1 to 7, characterized by the coil coating process. The coating according to claims 1 to 9, characterized by the application of TISS with low solar absorption and low thermal emissivity in the thickness of 1 to 150 pm and the application of a top coat with high thermal emissivity in the thickness of 1 to 200 pm.