Formulation for producing an infrared radiation reflective coating

Abstract

A formulation for producing an infrared radiation reflective coating is described. This formulation includes at least one conductive metal nanomaterial, at least one binder, and at least one solvent, and the weight ratio of the conductive metal nanomaterial to the binder is greater than 0.005.

Description

Technical Field

[0001] The present invention relates to formulations for producing infrared radiation - reflective coatings, composite materials having such infrared radiation - reflective coatings disposed on a substrate, and methods for producing such composite materials.

[0002] Background Art Materials having a sufficiently high transmittance are said to be transparent in the visible wavelength range. Transmittance is defined as the quotient of the light intensity behind an obstacle divided by the light intensity in front of the obstacle. Thus, transmittance varies from 0 to 1 or 0% to 100%. The visible range of the electromagnetic spectrum includes wavelengths from 400 nm to 850 nm.

[0003] Examples of materials having a very high light transmittance include plexiglass with a transmittance of 92%. Other types of glass, such as insulating glass, have lower transmittances, for example, in the range of 73% - 80%. In comparison, dark sunglasses have a transmittance of about 18%.

[0004] In the case of infrared radiation, three ranges are distinguished: near - infrared from 690 nm to 3.0 μm, mid - infrared from 3.0 μm to 50 μm, and far - infrared in the wavelength range from 50 μm to 1 mm. Electromagnetic radiation in the mid - infrared is called thermal radiation.

[0005] Thermal radiation - reflective coatings are known from the prior art and are used in many applications. Such coatings are often referred to as "cooling coatings" or low - emissivity ("low - E") layers.

[0006] Cooling coatings can improve the energy efficiency of buildings and other objects by reducing the absorption of thermal energy introduced by sunlight irradiation. For this purpose, these layers need to have high reflectivity in the near - infrared and a high heat - emission rate in order to release the absorbed thermal energy of sunlight radiation back to the environment.

[0007] From International Publication No. WO 2020 / 069183, compositions and methods for the use of tricalcium phosphate anhydride as a multifunctional additive for coatings, such as coating systems, for improved sunlight reflection properties and heat emission properties are known. International Publication No. WO 2022 / 212376 describes a sprayable coating solution on a substrate that reflects in the ultraviolet, visible, and near-infrared ranges. The spray coating exhibits not only a high reflection ability over all visible wavelengths but also a high emission ability in the mid-infrared range for effective surface cooling.

[0008] Cooling coatings are not suitable for so-called low-E applications because of their high emissivity. In low-E applications, infrared radiation is reflected to reduce heat loss and minimize heat ingress into buildings with a low heat emission rate. At the same time, these coatings are desired to be transparent to visible light. For this reason, typically, low-E coatings are applied on glass surfaces to reduce heat transfer and improve the energy efficiency of buildings.

[0009] In addition to special colorants, metal layers or metal oxide layers, i.e., coatings from conductive materials, show the potential to reflect electromagnetic radiation. Thus, in low-E applications, metal layers or metal oxide layers deposited on glass plates are usually used.

[0010] In modern insulating glass (e.g., double glazing and triple glazing), the volume between the glass plates is filled with gas. Previously, air was used, and currently, mainly argon is used. On the side of the glass plate of the effective insulating glass facing the gas side, a thin transparent heat-reflective layer is provided. These layers are usually sputtered on top and have very good heat reflection properties. Also, since this layer is positioned on the side facing the gas and is thus protected from mechanical influences, the plates can be washed and cleaned without losing these properties. That is, very thin sputtered layers are vulnerable to mechanical influences and cleaning.

[0011] Post - sputtering of an incorporated window can only be carried out on its surface on the side opposite to the gas, whereby protection of the sputtered layer against external influences is not provided, so that renovation of such thermal insulation materials in existing buildings is only possible by complete replacement of the window.

[0012] Moreover, it is known to use pigments such as graphite flakes, silver flakes or gold flakes to produce a heat - reflective layer. Such a layer reflects, for example, the thermal radiation emitted from the human body, thereby keeping a person warm or being used as a thermal insulation sheet or rescue sheet to minimize heat loss. However, this type of sheet is not transparent.

[0013] Packaging materials are also made from such sheets. Furthermore, plastics coated with metal sheets are used to reflect heat radiated from a heating body towards a space. These composite materials (plastics with a metal coating) are not transparent, seal the wall and have a low permeability to water vapor, thereby potentially causing mold growth.

[0014] From DE69921053T2, coated glass that can be used for incorporation in windows of houses and vehicles is known. This type of coated glass has very little emission from the glass and exhibits effective sunlight protection. The coating contains tin oxide with various doping agents, and the method for applying the coating described in DE69921053T2 is not suitable for renovation solutions in existing glass.

[0015] European Patent No. 1025057 describes a thermal insulation coating that is almost completely transparent in the visible range of the electromagnetic spectrum and has only a low absorption rate in the near - infrared range. The coating includes a plurality of cross - linked or polymerized cholesteric infrared - reflecting layers.

[0016] When a binder is added to such a transparent conductive layer at a typical concentration to improve the stability of the layer, this results in a loss of the heat reflection effect, especially when it is simultaneously desired to maintain the transparency of the layer, particularly in the visible wavelength range.

[0017] A conductive layer containing silver nanowires is transparent in the visible wavelength range and reflects thermal radiation, particularly in the range of 3 μm to 50 μm. Here, the proportion of the reflected infrared radiation depends on the silver content of the surface coating (Graubmann J. et al., “Silver nanowires: a new nanomaterial with advances for electrical, optical and IR systems” Proc. SPIE 11159, Electro-Optical and Infrared Systems: Technology and Applications XVI, 1115903 (9 October 2019); doi: 10.1117 / 12.2532245). By increasing the proportion of silver nanowires in the coating, an increase in conductivity and an increase in infrared reflection can be achieved. That is, a percolation network is necessary to achieve reflection characteristics in the wavelength range of 3 μm to 50 μm. A percolation network is formed when conductive particles gather closely enough to transport current over long distances.

[0018] However, these layers are not stable against mechanical effects or external actions such as scratches, and furthermore, they may be easily washed away by detergents or water. It can also be seen that in these systems, when a binder is added at a typical concentration to improve the stability of the layer, a loss of conductivity and infrared reflection is caused, especially when it is simultaneously desired to maintain transparency. Applying a protective layer with a common commercially available binder system for a transparent surface also results in a loss of the heat reflection effect of the surface.

[0019] Accordingly, there is a need for a formulation suitable for coating a substrate, wherein the coating has high optical transparency in the visible range and good heat retention properties in the infrared range by reflection of infrared radiation, particularly radiation in the mid-infrared range.

[0020] Summary of the Invention Accordingly, an object of the present invention is to provide a formulation suitable for coating a substrate, wherein the coating desirably has transparent properties in the visible range and heat radiation reflection properties in the infrared range. At the same time, the coating is desirably easy to apply, and this coating desirably cures at a low temperature and has mechanical stability.

[0021] According to the present invention, this object is solved by the formulation according to independent claim 1. Further advantageous aspects, details and configurations of the present invention will become apparent from the dependent claims, the description and the drawings.

[0022] The present invention provides a formulation for producing an infrared radiation reflective coating. This formulation has at least one conductive metal nanomaterial, at least one binder and at least one solvent, and the weight ratio of the conductive metal nanomaterial to the binder is greater than 0.005.

[0023] Surprisingly, in a formulation used to produce an infrared radiation reflective coating, when the conductive metal nanomaterial is used in combination with a defined proportion of binder, the coating thus obtained has been found to have heat reflection properties even when the surface conductivity cannot be measured. At the same time, optical transparency also exists in the visible range of the electromagnetic spectrum. Furthermore, the formulation according to the present invention can cure at low temperatures up to room temperature. Furthermore, there is no need to subsequently apply a conventional protective layer onto the coating, thereby also avoiding the reduction of infrared reflection properties associated with such a protective layer.

[0024] Within the scope of the present invention, the expression "conductive metal nanomaterial" is understood to mean conductive metal nanoparticles, conductive metal nanowires, and conductive metal nanotubes.

[0025] According to the general definition, "nanoparticles" is the name for particles having a size in the range of less than 100 nm. Therefore, the use of the prefix "nano" represents a distinction from particles in the sub-micrometer range (greater than 100 nm) according to the official definition by ISO TC 229.

[0026] Within the scope of this document, the terms "metal nanowire", especially "silver nanowire", refer to - Materials mainly composed of particles having a metal content of more than 90% by weight, especially metallic silver. - Materials having a "one-dimensional" shape such as a rod or hair, having a major axis (length) and a minor axis (diameter). - Materials having an aspect ratio (length / diameter) of at least 5, and - Materials having a diameter in the range of 1 nm to 1000 nm All of these materials are grouped together.

[0027] As used herein, the term "nanotube" (nanotube = NT) represents a structure having similar dimensions in the range of 1 nm to 1000 nm in at least two spatial directions, and having a dimension in the third spatial direction that is at least 5 times the other two dimensions, and being at least mostly hollow.

[0028] Within the scope of the present invention, the term "infrared radiation-reflective coating" is understood to mean that the coating reflects at least 10% of the infrared radiation averaged over the wavelength range of 3 μm to 50 μm. To determine the reflected infrared radiation, the infrared reflection of the coating is determined in the wavelength range of 3 μm to 50 μm, for example, in wavelength steps of 5 nm, the measured reflection values are added, and the sum of the reflection values is divided by the number of measurement values.

[0029] According to a preferred embodiment of the present invention, the weight ratio of the conductive metal nanomaterial to the binder is more than 0.01, preferably more than 0.02, and particularly preferably 0.05. It has been found that as the binder ratio increases, the infrared reflection characteristics decrease. It has been found that infrared reflection is sufficient up to the weight ratio of the conductive metal nanomaterial to the binder according to the present invention of at least more than 0.005.

[0030] According to a further preferred embodiment of the present invention, the weight ratio of the conductive metal nanomaterial to the binder is less than 2, preferably less than 1, and particularly preferably less than 0.5.

[0031] Particularly preferably, the weight ratio of the conductive metal nanomaterial to the binder is 0.01 to 0.5, preferably 0.02 to 0.2, and particularly preferably 0.05 to 0.1. It has been found that there is a formulation that can produce a coating having excellent infrared reflection characteristics when the weight ratio of the conductive metal nanomaterial to the binder is within the above range.

[0032] Preferably, the conductive metal nanomaterial is a conductive metal nanoparticle, particularly a conductive silver nanoparticle, a conductive metal nanowire, particularly a conductive silver nanowire, a conductive metal nanotube, particularly a conductive silver nanotube.

[0033] Preferably, the binder is an infrared-active binder, and the infrared-active binder absorbs infrared radiation in the wavelength range of 3 μm to 50 μm. The "infrared-active binder" in the sense of the present invention exists when the binder absorbs more than 70% of the infrared radiation averaged over the wavelength range of 3 μm to 50 μm at a concentration customary to those skilled in the art.

[0034] According to a preferred embodiment, the conductive metal nanomaterial contained in the formulation is particularly a conductive silver nanoparticle, a conductive silver nanowire or a mixture thereof. By the above-mentioned conductive materials, particularly good characteristics of the coating produced using this formulation are achieved from the viewpoint of its infrared reflectivity.

[0035] When the complex further contains conductive carbon, carbon nanotubes, graphene, conductive polymers or mixtures thereof, particularly good properties can be obtained from the perspective of desired infrared reflection.

[0036] The production of metal nanoparticles, particularly silver nanoparticles, and metal nanowires, particularly silver nanowires, used as conductive metal nanomaterials in formulations for producing infrared radiation-reflective coatings is described in detail in WO 2016 / 166074, which is hereby incorporated by reference in its entirety for the production of metal nanoparticles, particularly silver nanoparticles, and metal nanowires, particularly silver nanowires, and forms part of the components of this document.

[0037] Particularly preferably, the formulation has one or more additives, which are preferably thickeners, adsorbents, wetting aids, flame retardants, polyvinylpyrrolidone, defoamers, film formers, chemical stabilizers and coloring pigments, and the coloring pigments absorb a predetermined proportion of electromagnetic radiation in the wavelength range of 400 nm to 800 nm. By using the additives, the mechanical properties of the coatings produced using the formulation can be selectively adjusted and improved.

[0038] Unlike the prior art which describes formulations having metal nanowires mixed with commercially available weight ratios of binders, the coatings produced using the formulations according to the present invention have infrared reflection properties after drying.

[0039] Since the coloring pigments absorb a predetermined proportion of electromagnetic radiation in the wavelength range of 400 nm to 800 nm, only the wavelengths that can be used, for example, in applications in the fields of interior decoration or plant growth are selectively transmitted. That is, by adding the coloring pigments, in addition to the infrared reflection properties of the coating, its coloring can be adapted in any manner. That is, the coatings produced using the formulations according to the present invention may be formed to be transparent, partially transparent or opaque in the visible wavelength range.

[0040] The ultraviolet absorption additive serves the role of protecting from ultraviolet radiation and absorbs a predetermined proportion of electromagnetic radiation in the wavelength range of 100 nm to 400 nm.

[0041] Basically, any type of binder system known to those skilled in the art can be used. Particularly preferably, the binder is a binder based on acrylate, epoxide, polyurethane, silicone, siloxane, polyolefin, cellulose derivative, polythiophene, polyaniline, perfluorinated polymer and copolymers of the aforementioned polymers, and mixtures thereof. The binder system is a formulation having a polymer, which is used to fix the fabricated metal structure. That is, in a preferred embodiment, a binder system based on acrylate, epoxide, polyurethane, silicone, siloxane, polyolefin, cellulose derivative, polythiophene, polyaniline, perfluorinated polymer and copolymers of the aforementioned polymers, and mixtures thereof is used. The aforementioned binder system exhibits particularly good properties from the viewpoints of processability and infrared reflection characteristics.

[0042] According to a particularly preferred embodiment, the conductive metal nanomaterial is a conductive metal nanowire, particularly a conductive silver nanowire, and the quotient from the length and diameter of the metal nanowire is greater than 5. The quotient from the length and diameter of the metal structure is also referred to as the aspect ratio. When using particles with a smaller aspect ratio, it has been found that in order to achieve a desirable effect from the viewpoint of infrared reflection characteristics, these particles need to have a relatively large diameter or a higher concentration of metal nanoparticles in the formulation needs to be selected.

[0043] The present invention also includes a composite material having a substrate and an infrared radiation-reflective coating disposed on the substrate, wherein the coating is manufactured from the formulation described above. The coating manufactured by using the formulation according to the present invention improves the thermal insulation property by reflecting electromagnetic radiation in the wavelength range of 3 μm to 50 μm and reduces the heat release of the substrate.

[0044] The infrared reflection characteristics of the coating were shown, but the conductivity could not be determined. One explanation for this fact is that, in order to bring about infrared reflection characteristics, a discrete aggregate of conductive particles, i.e., for example, a number of individual nanowires that are not directly connected, is sufficient instead of a percolation network. However, infrared reflection is achieved only when the ratio of the conductive metal nanomaterial to the binder is at the ratio according to the present invention. In these cases, the conductivity cannot be determined, but IR reflection is observed.

[0045] Particularly preferably, the infrared radiation-reflective coating of the composite material has an average spectral transmittance of less than 30% in the wavelength range of 3 μm to 50 μm. That is, the coating of the composite material has high reflectivity in the wavelength range of 3 μm to 50 μm. Preferably, the infrared radiation-reflective coating of the composite material has a reflectance of more than 20%, preferably more than 30%, particularly preferably more than 40% in the wavelength range of 3 μm to 50 μm.

[0046] The composite material according to the present invention can be used to reflect infrared radiation in the wavelength range of 3 μm to 50 μm indoors (buildings, greenhouses, automobiles, public transportation), in aerospace and space products (aircraft), in mobility (automobiles), and in clothing (camouflage, signature management).

[0047] Despite using a binder to produce a coating with good mechanical stability, by using metal nanowires, good surface durability and reflection characteristics can be achieved without impairing the mechanical stability of the coating and its stability against other external influences (e.g., immersion in water).

[0048] Preferably, the substrate is a polymer sheet, fabric, knitted fabric, textile material, glass, paper, concrete, cement, wood, gypsum, gypsum board, metal or plastic. That is, the coating produced using the formulation according to the invention can be applied onto synthetic or natural substrates which may have different flexibilities.

[0049] According to a preferred embodiment of the invention, the infrared-radiation-reflective coating of the composite material has a layer thickness of at most 60 μm, preferably at most 30 μm, particularly preferably at most 15 μm after drying. It has been found that with the aforementioned layer thicknesses, the desired infrared reflection properties are achieved to a sufficient extent while minimizing material consumption.

[0050] According to a further preferred embodiment, the coating has an average spectral transmittance of at least 30% in the wavelength range from 400 nm to 800 nm. In the context of this document, a coating having an average transmittance of at least 30% in the wavelength range from 400 nm to 800 nm is referred to as "transparent".

[0051] According to a further embodiment, this may be a translucent or opaque coating. Basically, a material which allows light to pass through but does not allow an object arranged behind the material, such as milk glass, to be recognized is referred to as translucent or durchscheinend. However, a translucent coating can reliably have at least 30% average transmittance, which is required for an optically transparent coating, in the wavelength range from 400 nm to 800 nm.

[0052] Particularly preferably, the infrared-radiation-reflective coating has no measurable conductivity. In such a case, the conductivity is not measurable by measurement methods known to those skilled in the art (for example, a four-point measuring device). By combining the binder with a conductive metal structure, a coating is formed which has no measurable conductivity but still has an IR reflection effect.

[0053] Contrary to the main opinion in the prior art, it has been found that when using metal nanowires in a formulation for manufacturing an infrared radiation reflective coating, a conductive network is not necessary to generate infrared reflection characteristics.

[0054] The present invention also relates to a method for manufacturing one of the above composite materials, the method comprising the following steps: a) providing a substrate, b) providing one of the above formulations, c) applying the formulation provided in step b) onto the substrate provided in step a), d) drying the object obtained in step c) to form a composite material comprising the substrate and an infrared radiation reflective coating disposed on the substrate including.

[0055] After drying, a layer having infrared reflection characteristics is formed on the substrate.

[0056] Preferably, the drying in step d) is carried out at a temperature T of less than 200 ° C, preferably T of less than 100 ° C, particularly preferably T of less than 50 ° C, particularly preferably T of less than 30 ° C. The coating can be dried at room temperature or at a temperature up to 200 ° C. For reasons of energy efficiency, those skilled in the art will select the lowest possible temperature at which the binder exhibits its binding properties and the layer dries within an acceptable period.

[0057] According to a further preferred embodiment, after step a) and before step c), pretreating the surface of the substrate by plasma pretreatment, corona pretreatment, washing, chemical pretreatment or application of a primer is carried out. In step c), the formulation provided in step b) is applied onto the substrate pretreated in such a manner.

[0058] In some particular embodiments, for example, pretreatment of the substrate is required by plasma pretreatment or corona pretreatment, by cleaning to remove foreign matter, by chemical pretreatment, or by application of a primer. By the pretreatment, improved wetting is achieved, and better adhesion of the formulation on the substrate is also achieved. A person skilled in the art can select the most convenient type of pretreatment for each individual case based on their expertise.

[0059] Preferably, in step c), the application of the formulation provided in step b) is carried out by a spiral doctor blade, screen printing, transfer printing, flood coating, spraying or brushing. The type of application preferably used in each individual case depends on the type of substrate. For example, in the case of application on a wall, screen printing is not possible, and in the case of application on a fabric substrate, it is not common to brush the substrate using a brush.

Brief Description of the Drawings

[0060] The present invention will be described in more detail below based on examples in connection with FIG. 1.

Figure 1

[0061] Route for Implementing the Invention Example 1: Coating of a PET Sheet According to the method described in German Patent Specification No. 102010017706 (DE102010017706B4), silver nanowires were produced by the polyol method. From the concentrate of silver nanowires having 4.0% by weight of silver thus obtained, aqueous and alcoholic formulations having a silver nanowire content of 0.3% by weight were produced. For this purpose, 7.5 g of the silver nanowire concentrate was mixed with 74.5 g of water or alcohol in a plastic screw-cap container and homogenously dispersed by shaking. Then, 13 g of SURFLINK and 5 g of an acrylate binder were added to the dispersion. The weight ratio of silver nanowires to the acrylate binder is 0.06.

[0062] SURFLINK is an additive commercially available from HeiQ RAS for the activation of silver nanowire networks. This is a mixture of 1% to 10% by weight of ethanolamine in water and up to 2.0% by weight of hydroxypropyl methylcellulose.

[0063] From the formulation thus produced, using a stainless steel doctor blade, wet film thicknesses of 12 μm, 24 μm and 40 μm were applied onto a PET sheet of approximately 10×10 cm size. The coated substrate was dried in an oven at 150 °C for 3 minutes or at room temperature for 24 hours. The conductivity of the coating was measured by a four-point measuring device (RCHEK 4 Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1 to 19990 ohms / square). From measurements with a commercially available infrared camera (model: Flir One Pro from Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm.

[0064] Example 2 (Comparative Example): Coating of PET Sheet Silver nanowires were produced by the polyol method according to the method described in German Patent Invention No. 102010017706. From the concentrate of silver nanowires having 4.0% by weight of silver obtained in this way, aqueous and alcoholic formulations having a silver nanowire content of 0.3% by weight were produced. For this purpose, 7.5 g of the silver nanowire concentrate was mixed with 14.5 g of water or alcohol in a plastic screw-cap container and homogenously dispersed by shaking. Then, 13 g of SURFLINK and 60 g of an acrylate binder were added to the dispersion. The weight ratio of silver nanowires to the acrylate binder is 0.005.

[0065] From the formulation thus produced, using a stainless steel doctor blade, wet film thicknesses of 12 μm, 24 μm and 40 μm were applied onto a PET sheet of approximately 10×10 cm size. The coated substrate was dried in an oven at 150 °C for 3 minutes or at room temperature for 24 hours. The conductivity of the coating was measured by a four-point measuring device (RCHEK 4 Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1 - 19990 ohms / square). From measurements with a commercially available infrared camera (model: Flir One Pro by Flir), it was found that infrared radiation was enhanced and not reflected in the wavelength range of 3 μm to 50 μm.

[0066] Example 3 (comparative example): Coating on fabric, woven fabric, knitted fabric The formulation according to Example 2 was produced using an acrylate binder and qualitatively investigated for the homogeneity of the formulation. This formulation was applied directly to fabric, plastic woven fabric and knitted fabric. The coated substrate was dried in an oven at 150 °C for 3 minutes or at room temperature for 24 hours.

[0067] The conductivity of the coating was measured by a four-point measuring device (RCHEK 4 Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1 to 19,990 ohms per square). From the measurement by a commercially available infrared camera (model: Flir One Pro of Flir), it was found that infrared radiation was enhanced and not reflected in the wavelength range of 3 μm to 50 μm.

[0068] Example 4: Coating on Fabric, Woven Fabric, Knitted Fabric The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. This formulation was directly applied to fabric, plastic woven fabric, and knitted fabric. The coated substrate was dried in an oven at 150 °C for 3 minutes or at room temperature for 24 hours.

[0069] The conductivity of the coating was measured by a four-point measuring device (RCHEK 4 Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1 to 19,990 ohms per square). From the measurement by a commercially available infrared camera (model: Flir One Pro of Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm.

[0070] Example 5: Coating of White or Colored Brush-Painted Wall Test Pieces The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. The formulation was applied to both white wall test pieces and colored brush-painted wall test pieces with a brush or a paint roller. Drying was carried out at room temperature for about 24 hours.

[0071] It was recognizable that the color of the colored wall test pieces did not change after drying. From the measurement by a commercially available infrared camera (model: Flir One Pro of Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm.

[0072] Example 6: Coating of Concrete Test Specimens The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. The formulation was applied to the concrete test specimens with a brush or a paint roller. Drying was carried out at room temperature for about 24 hours.

[0073] From measurements with a commercially available infrared camera (model: Flir One Pro by Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm. Figure 1 shows the corresponding measurements of thermal reflection compared between an uncoated concrete test specimen and a coated concrete test specimen. In the case of the coated test specimen, it can be clearly recognized that the reflection of infrared radiation has increased significantly. When using a heat source with a temperature of 33 °C, the measurement for the uncoated concrete piece resulted in a temperature of 25.2 °C, while for the coated concrete piece, a temperature of 29.8 °C was shown.

[0074] Example 7: Coating of Gypsum Test Specimens The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. The formulation was applied to the gypsum test specimens with a brush or a paint roller. Drying was carried out at room temperature for about 24 hours.

[0075] From measurements with a commercially available infrared camera (model: Flir One Pro by Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm. The conductivity of the coating was measured with a four-point measuring device (RCHEK 4 Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1 to 19990 ohms / square).

[0076] Example 8: Coating of Wood Test Specimens The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. The formulation was applied to wood test pieces with a brush or a paint roller. Drying was carried out at room temperature for about 24 hours.

[0077] From measurements using a commercially available infrared camera (model: Flir One Pro by Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm.

[0078] Example 9: Coating of wallpaper The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. The formulation was applied to both single - colored wallpaper pieces and patterned wallpaper pieces either by brushing and using a paint roller or by coating using a transfer printing method. Drying was carried out at room temperature for about 24 hours or at 150 °C in an oven for 10 minutes.

[0079] From measurements using a commercially available infrared camera (model: Flir One Pro by Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm. The conductivity of the coating was measured using a four - point measuring device (RCHEK 4 Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1 to 19990 ohms / square).

[0080] Example 10: Coating of paper The formulation according to Example 1 was produced using an acrylate binder, and the homogeneity of the formulation was qualitatively investigated. The formulation was applied to white paper with a brush. Drying was carried out at room temperature for about 24 hours or at 120 °C in an oven for 5 minutes.

[0081] From measurements using a commercially available infrared camera (model: Flir One Pro by Flir), it was found that infrared radiation was significantly reflected in the wavelength range of 3 μm to 50 μm.

Claims

1. A formulation for producing an infrared radiation-reflective coating, said formulation having at least one conductive metal nanomaterial, at least one binder, and at least one solvent, and the weight ratio of the conductive metal nanomaterial to the binder being greater than 0.

005.

2. The formulation according to claim 1, characterized in that the weight ratio of the conductive metal nanomaterial to the binder is greater than 0.01, preferably greater than 0.02, and particularly preferably greater than 0.

05.

3. The formulation according to claim 1 or 2, characterized in that the weight ratio of the conductive metal nanomaterial to the binder is less than 2, preferably less than 1, and particularly preferably less than 0.

5.

4. The formulation according to any one of claims 1 to 3, characterized in that the conductive metal nanomaterial is a conductive metal nanoparticle, particularly a conductive silver nanoparticle, a conductive metal nanowire, particularly a conductive silver nanowire, a conductive metal nanotube, particularly a conductive silver nanotube.

5. The formulation according to any one of claims 1 to 4, characterized in that the formulation further contains conductive carbon, conductive carbon nanotubes, graphene, a conductive polymer, or a mixture thereof.

6. The formulation according to any one of claims 1 to 5, characterized in that the formulation has one or more additives, and the additives are preferably a thickener, an adsorbent, a wetting aid, a flame retardant, polyvinylpyrrolidone, an antifoaming agent, a film-forming agent, a chemical stabilizer, and a coloring pigment, and the coloring pigment absorbs a predetermined proportion of electromagnetic radiation in the wavelength range of 400 nm to 800 nm.

7. The formulation according to any one of claims 1 to 6, characterized in that the binder is a binder based on acrylate, epoxide, polyurethane, silicone, siloxane, polyolefin, cellulose derivative, polythiophene, perfluorinated polymer, and copolymers of the aforementioned polymers, and mixtures thereof.

8. The formulation according to any one of claims 1 to 7, characterized in that the conductive metal nanomaterial is a conductive metal nanowire, particularly a conductive silver nanowire, and preferably the quotient of the length and diameter of the metal nanowire is greater than 5.

9. A composite material having a substrate and an infrared radiation - reflective coating disposed on the substrate, wherein the coating is manufactured from the formulation according to any one of claims 1 to 8.

10. The composite material according to claim 9, wherein the substrate is a polymer sheet, a fabric, a knitted fabric, a textile material, glass, paper, concrete, cement, wood, gypsum, a gypsum board, a metal or a plastic.

11. The composite material according to claim 9 or 10, wherein the coating has a dry layer thickness of at most 60 μm, preferably at most 30 μm, particularly preferably at most 15 μm.

12. The composite material according to any one of claims 9 to 11, wherein the coating has an average spectral transmittance of at least 30% in the wavelength range of 400 nm to 800 nm.

13. The composite material according to any one of claims 9 to 12, wherein the coating has a reflectance of more than 20%, preferably more than 30%, particularly preferably more than 40% in the wavelength range of 3 μm to 50 μm.

14. The composite material according to any one of claims 9 to 13, wherein the coating has no measurable conductivity.

15. A method for manufacturing the composite material according to any one of claims 9 to 14, comprising: a) providing a substrate; b) providing the formulation according to any one of claims 1 to 8; c) applying the formulation provided in step b) onto the substrate provided in step a); d) drying the object obtained in step c) to form a composite material comprising a substrate and an infrared radiation - reflective coating disposed on the substrate The method comprising the steps.

16. The method according to claim 15, wherein the drying in step d) is carried out at a temperature T of less than 200 °C, preferably less than 100 °C, particularly preferably less than 50 °C, and most preferably less than 30 °C.

17. Before step a) and before step c), a step of pre - treating the surface of the substrate by plasma pre - treatment, corona pre - treatment, washing, chemical pre - treatment or application of a primer is carried out, and in step c), the formulation provided in step b) is applied onto the pre - treated substrate. The method according to claim 15 or 16 is characterized by this.

18. The method according to any one of claims 15 to 17, characterized in that in step c), the application of the formulation provided in step b) is carried out by means of a spiral doctor blade, screen printing, transfer printing, flood coating, spraying or brushing.

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