Formulations for producing infrared radiation reflective coatings

Abstract

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

Description

Technical Field

[0001] The invention relates to a formulation for producing an infrared radiation reflecting coating, a composite material having such an infrared radiation reflecting coating arranged on a substrate, and a method for producing the composite material. Background Art

[0002] In the visible wavelength range, materials with sufficiently high transmittance are called transparent. Transmittance is defined as the ratio of the light intensity after passing through an obstacle to the light intensity before passing through the obstacle. Therefore, the range of transmittance is between 0 and 1, or 0% to 100%. The visible range of the electromagnetic spectrum covers wavelengths between 400 and 850 nanometers.

[0003] An example of a material with very high transmittance is plexiglass, which has a transmittance of 92%. Other types of glass have lower transmittance, such as thermal glass, which has a transmittance of 73% to 80%. In comparison, dark sunglasses have a transmittance of about 18%.

[0004] Infrared radiation is divided into three ranges, namely: near infrared radiation from 690 nanometers to 3.0 microns, mid-infrared radiation from 3.0 microns to 50 microns, and far infrared radiation with a wavelength range from 50 microns to 1 mm. Electromagnetic radiation within the mid-infrared radiation is called thermal radiation.

[0005] Thermal radiation reflecting coatings are well known in the prior art and are used in many applications. Such coatings are often referred to as "cold coatings" or low emissivity (Low-E) coatings.

[0006] Cold coatings are able to reduce the absorption of heat energy introduced by solar radiation and thus increase the energy efficiency of buildings and other objects. For this purpose, these coatings must have a high reflectivity in the near-infrared radiation region and a high thermal emissivity in order to release the heat energy absorbed from solar radiation back to the environment.

[0007] For example, WO2020 / 069183Al, known compositions and methods of using anhydrous tricalcium phosphate as a multifunctional additive for coatings (such as coating systems) to improve solar reflection and thermal radiation performance. WO2022 / 212376Al describes a coating solution that can be sprayed onto a substrate, which reflects in the ultraviolet, visible and near-infrared ranges. The spray coating not only provides high reflectivity in all visible light wavelengths, but also provides high emissivity in the mid-infrared range for effective surface cooling.

[0008] Due to high emissivity, cold coatings are not suitable for Low-E applications. In Low-E applications, infrared radiation is reflected to reduce heat loss and minimize heat penetration into the building through low thermal emissivity. At the same time, these coatings are transparent to visible light. For this reason, Low-E coatings are typically applied to glass surfaces to reduce heat transfer and improve the energy efficiency of buildings.

[0009] In addition to special dyes, coatings made of metal or metal oxide layers (i.e. conductive materials) offer one possible way to reflect electromagnetic radiation. Therefore, Low-E applications often use metal or metal oxide layers that are vapor deposited on glass sheets.

[0010] In modern insulating glazing (e.g. double and triple glazing), the space between the glass panes is filled with a gas. In the past, air was used, but nowadays argon is most commonly used. On the side of the effectively insulating glass facing the gas, a thin, transparent, heat-reflecting layer(s) is provided. This or these layers are usually sputtered on and have very good heat-reflecting properties. Since the layer is on the side facing the gas and is protected from mechanical influences, the glass pane can be cleaned and washed without loss of properties. In practice, very thin sputtered layers can be easily damaged by machinery and cleaning.

[0011] Retrofitting such insulation in existing buildings can only be achieved by completely replacing the windows, since the subsequent sputtering of already installed windows can only be carried out on their surface facing away from the gas, which means that the sputtered layer is subsequently not protected against external influences.

[0012] Furthermore, it is known to use pigments such as graphite, silver or gold flakes to form heat reflective layers. For example, such layers are used as insulation or rescue films to reflect thermal radiation emitted by the body, thereby keeping the body warm or minimizing heat loss. However, such films are opaque.

[0013] Packaging materials are also made from such films. Plastics coated with metal films are also used to reflect the heat radiated by radiators into the room. These composite materials (plastics with a metal coating) are opaque, seal the walls and have low permeability to water vapor, which can lead to the formation of mold.

[0014] DE 699 21 053 T2 discloses a coated glass which can be installed in windows of homes and vehicles. This type of coated glass provides effective solar protection and the radiation of the glass is low. The coating contains tin oxide with various dopants, so the coating application method described in DE 699 21 053 T2 is not suitable for retrofit solutions for existing glass.

[0015] EP 1 025 057 Bl describes a heat-insulating coating which is almost completely transparent in the visible range of the electromagnetic spectrum and has only a low absorption in the near infrared range. The coating comprises a plurality of crosslinked or polymerized cholesteric infrared-reflecting layers.

[0016] If binders are added to such transparent conductive layers in typical concentrations to improve their stability, this results in a reduced heat reflection effect, especially if at the same time the transparency of the layer in the visible wavelength range needs to be maintained.

[0017] Conductive layers containing silver nanowires are transparent in the visible wavelength range and reflect thermal radiation, especially in the range of 3 microns to 50 microns. In this case, the proportion of reflected infrared radiation depends on the silver content of the surface coating (Graubmann J. et al., "Silver Nanowires: An Advanced New Nanomaterial for Electrical, Optical and Infrared Systems," Proceedings of the SPIE Conference No. 11159, Optoelectronics and Infrared Systems: Technologies and Applications XVI, 1115903 (October 9, 2019); doi:10.1117 / 12.2532245). By increasing the silver nanowire content in the coating, increased conductivity and increased infrared reflectivity can be achieved. Therefore, a percolation network is required to achieve reflective properties in the wavelength range from 3 microns to 50 microns. A percolation network is formed when the conductive particles are packed together closely enough to transmit current over long distances.

[0018] However, these coatings are not stable to external influences such as mechanical impact or scratching and can be easily washed off by cleaning agents or water. In these systems, it has also been found that the addition of typical concentrations of binders to increase the stability of the coating leads to a loss of conductivity and infrared reflectivity, especially when transparency needs to be maintained at the same time. Therefore, the use of protective layers with commercially available binder systems on transparent surfaces leads to a reduction in the heat reflective effect on the surface.

[0019] In summary, there is still a need for formulations suitable for coating substrates, wherein the coating has high optical transparency in the visible range and ensures good thermal insulation in the infrared range by reflecting infrared radiation, in particular by reflecting radiation in the mid-infrared range. Summary of the invention

[0020] The object of the present invention is therefore to provide a formulation suitable for coating substrates, wherein the coating should have the properties of being transparent in the visible range and reflecting thermal radiation in the infrared range. At the same time, the coating should be easy to apply, it should harden at low temperatures and have mechanical stability.

[0021] The object of the invention is achieved by the formulation of independent claim 1. Further advantageous aspects, details and embodiments of the invention are derived from the dependent claims, the description and the drawings.

[0022] The invention provides a formula for producing an infrared radiation reflective coating, which comprises at least one conductive metal nano material, at least one adhesive and at least one solvent, wherein the weight ratio of the conductive metal nano material to the adhesive is greater than 0.005.

[0023] Surprisingly, it has been found that when conductive metal nanomaterials are combined with a certain proportion of a binder into a formulation for producing an infrared radiation reflective coating, the coating obtained by this method has heat reflective properties even without measuring the surface conductivity. At the same time, it also has optical transparency in the visible range of the electromagnetic spectrum. The formulation according to the invention can also be cured at low temperatures down to room temperature. In addition, there is no need to subsequently apply a conventional protective layer on the coating, thereby also avoiding the reduced infrared reflective properties associated with such a protective layer.

[0024] In the present invention, the term "conductive metal nanomaterial" should be understood as conductive metal nanoparticles, conductive metal nanowires and conductive metal nanotubes.

[0025] According to the general definition, "nanoparticles" refer to particles with a size in the range of less than 100 nanometers. Therefore, according to the official definition of ISO TC229, the prefix "nano" is used to distinguish them from particles in the submicron range (>100 nanometers).

[0026] In the context of this document, the terms "metal nanowires", and in particular "silver nanowires", include all materials that

[0027] - Mainly composed of metal particles, especially metal silver, which accounts for more than 90% by weight,

[0028] - have a "one-dimensional" geometry, such as a rod or hair with a major axis (length) and a minor axis (diameter),

[0029] - an aspect ratio (length / diameter) of at least 5, and

[0030] -Its diameter ranges from 1 nanometer to 1000 nanometers.

[0031] The term "nanotube" (nanotube=NT) as used herein describes structures having similar dimensions between 1 nm and 1000 nm in at least two spatial directions and a dimension in a third spatial direction that is at least five times the other two dimensions and that are at least predominantly hollow.

[0032] In the present invention, an "IR radiation-reflecting coating" means a coating that reflects an average of at least 10% of infrared radiation in 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 with a wavelength step of 5 nm, the measured reflection values ​​are added, and the sum of the reflection values ​​is divided by the number of measured values.

[0033] According to a preferred embodiment of the present invention, the weight ratio of the conductive metal nanomaterial to the binder is greater than 0.01, preferably greater than 0.02, and particularly preferably 0.05. It has been shown that the infrared reflection performance decreases with increasing binder content. According to the present invention, it is shown that when the weight ratio of the conductive metal nanomaterial to the binder is at least greater than 0.005, sufficient infrared reflectivity is already shown.

[0034] According to another 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.

[0035] The weight ratio of the conductive metal nanomaterial to the binder is particularly preferably between 0.01 and 0.5, preferably between 0.02 and 0.2, and particularly preferably between 0.05 and 0.1. It has been shown that when the weight ratio of the conductive metal nanomaterial to the binder is within the above range, there is a formulation that can produce a coating with excellent infrared reflection properties.

[0036] Preferably, the conductive metal nanomaterial is conductive metal nanoparticles, especially conductive silver nanoparticles, conductive metal nanowires, especially conductive silver nanowires, conductive metal nanotubes, especially conductive silver nanotubes.

[0037] Preferably, the adhesive is an infrared-active adhesive, wherein the infrared-active adhesive absorbs infrared radiation in the wavelength range between 3 microns and 50 microns. For the purposes of the present invention, an adhesive is referred to as an "infrared-active adhesive" when it absorbs more than 70% of the average infrared radiation in the wavelength range between 3 microns and 50 microns at concentrations known to those skilled in the art.

[0038] According to a preferred embodiment, the conductive metal nanomaterial contained in the formulation is particularly conductive silver nanoparticles, conductive silver nanowires or a mixture thereof. Using the above conductive materials, the coating produced using the formulation has particularly good performance in terms of infrared reflectivity.

[0039] If the formulation also contains conductive carbon, conductive carbon nanotubes, graphene, conductive polymers or mixtures thereof, it has particularly good performance in terms of desired infrared reflection.

[0040] WO2016 / 166074A1 describes in detail the preparation of metal nanoparticles (especially silver nanoparticles) and metal nanowires (especially silver nanowires) used as conductive metal nanomaterials in formulations for producing infrared radiation reflective coatings, which is incorporated herein by reference, and its content relating to the production of metal nanoparticles (especially silver nanoparticles) and metal nanowires (especially silver nanowires) constitutes a part of this article.

[0041] The formulation particularly preferably has one or more additives, preferably thickeners, adsorbents, wetting aids, flame retardants, polyvinyl pyrrolidone, defoamers, film formers, chemical stabilizers and color pigments, wherein the color pigments absorb a predetermined proportion of electromagnetic radiation in the wavelength range between 400 nm and 800 nm. By using additives, the mechanical properties of the coating produced using the formulation can be adjusted and improved in a targeted manner.

[0042] Unlike the formulations described in the prior art in which metal nanowires are mixed with a binder in a commercially common weight ratio, the coating produced using the formulation according to the present invention has infrared reflecting properties after drying.

[0043] Since the color pigments absorb a predetermined proportion of electromagnetic radiation in the wavelength range between 400 nm and 800 nm, only those wavelengths that can be used for applications such as interior decoration or plant growth are specifically transmitted. By adding color pigments, in addition to the infrared reflection properties of the coating, its color can be adjusted at will. Thus, the coating produced using the formulation according to the invention can be transparent, partially transparent or opaque in the visible wavelength range.

[0044] UV absorbing additives are used to protect against UV radiation and absorb a predetermined proportion of electromagnetic radiation in the wavelength range between 100 nanometers and 400 nanometers.

[0045] In principle, any type of adhesive system known to those skilled in the art can be used. Adhesives are particularly preferably based on acrylates, epoxides, polyurethanes, silicones, siloxanes, polyolefins, cellulose derivatives, polythiophenes, polyanilines, perfluorinated polymers and copolymers of the above-mentioned polymers and mixtures thereof. Adhesive systems are formulations with polymers for fixing the generated metal structures. In a preferred embodiment, adhesives based on acrylates, epoxides, polyurethanes, silicones, siloxanes, polyolefins, cellulose derivatives, polythiophenes, polyanilines, perfluorinated polymers and copolymers of the above-mentioned polymers and mixtures thereof are used. The adhesive systems show particularly good performance in terms of processability and infrared reflectivity.

[0046] According to a particularly preferred embodiment, the conductive metal nanomaterial is a conductive metal nanowire, in particular a conductive silver nanowire, wherein the quotient of the length and diameter of the metal nanowire is greater than 5. The quotient of the length and diameter of the metal structure is also referred to as the aspect ratio. It has been shown that when particles with a small aspect ratio are used, these particles must have a relatively large diameter, or a higher concentration of metal nanoparticles is selected in the formulation, in order to achieve the desired effect with respect to infrared reflective properties.

[0047] The present invention also includes a composite material comprising a substrate and an infrared radiation reflecting coating disposed on the substrate, the coating being made from the above formulation. The coating produced using the formulation of the present invention improves thermal insulation performance by reflecting electromagnetic radiation having a wavelength range of between 3 microns and 50 microns and reduces thermal emission of the substrate.

[0048] Although the conductivity cannot be determined, the infrared reflection properties of the coating are also obvious. One explanation for this fact is that it is not through the percolation network, but the discrete aggregation of conductive particles, such as a large number of independent nanowires that are not directly connected, which is sufficient to produce infrared reflection properties. However, infrared reflection can only be achieved when the ratio of conductive metal nanomaterial to binder meets the ratio according to the present invention. In this case, although the conductivity cannot be detected, infrared reflection can still be observed.

[0049] Particularly preferably, the infrared radiation reflecting coating of the composite material has an average spectral transmittance of less than 30% in the wavelength range of 3 μm to 50 μm. Therefore, the coating of the composite material has a high reflectivity in the wavelength range of 3 μm to 50 μm. In the wavelength range of 3 μm to 50 μm, the infrared reflecting coating of the composite material preferably has a reflectivity greater than 20%, more preferably greater than 30%, and particularly preferably greater than 40%.

[0050] The composite material according to the invention can be used to reflect infrared radiation in the wavelength range of 3 to 50 microns in indoor environments (buildings, greenhouses, cars, public transportation), aerospace products (aircraft), mobile devices (cars) and clothing (camouflage, signature management).

[0051] While binders are used to produce coatings with good mechanical stability, the use of metal nanowires allows good surface resistance and reflection properties to be achieved without sacrificing the mechanical stability of the coating and its stability against other external influences, such as flooding.

[0052] The substrate is preferably a polymer film, a woven fabric, a knitted fabric, a textile material, glass, paper, concrete, cement, wood, gypsum, plasterboard, metal or plastic. Thus, the coating produced using the formulation according to the invention can be applied to synthetic or natural substrates that may have different flexibilities.

[0053] According to a preferred embodiment of the invention, the infrared radiation reflecting coating of the composite material has a layer thickness of at most 60 micrometers, preferably at most 30 micrometers, particularly preferably at most 15 micrometers after drying. It has been shown that the desired infrared reflecting properties are achieved to a sufficient extent with minimal material consumption by means of said layer thickness.

[0054] According to another preferred embodiment, the coating has an average spectral transmittance of at least 30% in the wavelength range of 400 nm to 800 nm. In this document, coatings having an average transmittance of at least 30% in the wavelength range of 400 nm to 800 nm are referred to as "transparent".

[0055] According to further embodiments, it is also possible to have a translucent or opaque coating. In principle, a material is called translucent if it allows light to pass through, but objects arranged behind it (such as frosted glass) cannot be seen. However, a translucent coating can of course have an average light transmittance of at least 30% in the wavelength range of 400 nm to 800 nm, which is necessary for an optically transparent coating.

[0056] Particularly preferably, the infrared radiation reflective coating has no measurable electrical conductivity. In this case, the electrical conductivity cannot be measured using the measurement methods known to those skilled in the art (e.g., a four-point measuring device). By combining the adhesive with the conductive metal structure, a coating whose electrical conductivity cannot be measured but still produces an infrared reflective effect is formed.

[0057] Contrary to the prevailing belief in the prior art, it has been demonstrated that when metal nanowires are used in a formulation for producing an infrared radiation reflecting coating, no conductive network is required to produce the infrared reflecting properties.

[0058] The invention also comprises a method for producing one of the above-mentioned composite materials, the method comprising the following steps:

[0059] a) providing a substrate,

[0060] b) providing one of the above formulations,

[0061] c) applying the formulation provided in step b) to the substrate provided in step a),

[0062] d) drying the article obtained in step c) to form a composite material consisting of a substrate and an infrared radiation reflecting coating arranged on the substrate.

[0063] After drying, a layer having infrared reflecting properties is formed on the substrate.

[0064] In step d), drying is carried out at a temperature of T < 200° C., preferably T < 100° C., particularly preferably T < 50° C., most preferably T < 30° C. The coating can be dried at room temperature or at a temperature of up to 200° C. For energy saving reasons, a person skilled in the art will select the lowest possible temperature at which the adhesive develops its adhesive properties and the layer dries within an acceptable period of time.

[0065] According to another preferred embodiment, after step a) and before step c), the substrate surface is pretreated by plasma pretreatment, corona pretreatment, cleaning, chemical pretreatment or application of a primer. In step c), the formulation provided in step b) is applied to the substrate pretreated in this way.

[0066] In some embodiments, substrate pretreatment is necessary, for example by plasma pretreatment or corona pretreatment, by cleaning to remove foreign matter, by chemical pretreatment or by applying a primer. Pretreatment can improve wetting and adhesion of the formulation to the substrate. In each individual case, the person skilled in the art can select the most advantageous type of pretreatment based on his or her expertise.

[0067] In step c), the formulation provided in step b) is preferably applied by means of a spiral scraper, screen printing, transfer printing, flow coating, spraying or brushing. In each individual case, the preferred method of application depends on the type of substrate. For example, when applying to walls, screen printing is not possible, and when applying to fabrics, brushing the substrate is rarely used. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The following will combine Figure 1 The invention is described in more detail with reference to exemplary embodiments. Figure 1 Shown is a comparison of heat reflectance of uncoated and coated concrete test specimens. DETAILED DESCRIPTION

[0069] Example 1: PET film coating

[0070] Silver nanowires were produced by a polyol process according to the method described in DE102010017706B4. The silver nanowire concentrate obtained by this method (4.0% by weight of silver) was made into an aqueous and alcoholic formulation with a weight of 0.3% silver nanowires. For this purpose, 7.5 grams of silver nanowire concentrate were mixed with 74.5 grams of water or alcohol in a plastic container with a screw cap and evenly dispersed by shaking. 13 grams of SURFLINK and 5 grams of acrylate adhesive were then added to the dispersion. The weight ratio of silver nanowires to acrylate adhesive was 0.06.

[0071] SURFLINK is an additive commercially available from HeiQ RAS that is used to activate the silver nanowire network. It is a mixture of 1 to 10% by weight ethanolamine and up to 2.0% by weight hydroxypropyl methylcellulose in water.

[0072] The formulations prepared in this way were applied to PET films of approximately 10×10 cm in wet film thickness using a stainless steel scraper at 12 μm, 24 μm and 40 μm. The coated substrates were dried in an oven at 150° C. for 3 minutes or at room temperature for 24 hours. The conductivity of the coating was measured using a four-point measuring device (RCHEK 4Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1-19990 ohms / square). The measurements were performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that infrared radiation had a significant reflection in the wavelength range of 3 μm to 50 μm.

[0073] Example 2 (Comparative Example): PET Film Coating

[0074] Silver nanowires were produced by a polyol process according to the method described in DE102010017706B4. The silver nanowire concentrate obtained by this method (4.0% by weight of silver) was made into an aqueous and alcoholic formulation with a weight of 0.3% silver nanowires. For this purpose, 7.5 grams of silver nanowire concentrate were mixed with 14.5 grams of water or alcohol in a plastic container with a screw cap and evenly dispersed by shaking. 13 grams of SURFLINK and 60 grams of acrylate adhesive were then added to the dispersion. The weight ratio of silver nanowires to acrylate adhesive was 0.005.

[0075] The formulations prepared in this manner were applied to PET films of approximately 10×10 cm in wet film thickness using a stainless steel scraper at 12 μm, 24 μm and 40 μm. The coated substrates were dried in an oven at 150°C for 3 minutes or at room temperature for 24 hours. The conductivity of the coating was measured using a four-point measuring device (RCHEK 4Point Meter, manufacturer EDTM, model #RC2175). No conductivity could be detected within the measuring range of the device (1-19990 ohms / square). Measurements were performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed no increase in the reflection of infrared radiation in the wavelength range of 3 μm to 50 μm.

[0076] Example 3 (Comparative Example): Coating on Fabrics, Woven Fabrics, Knitted Fabrics

[0077] The formulation according to Example 2 was produced using an acrylate adhesive and qualitatively tested for homogeneity. The formulation was applied directly to fabrics, plastic woven fabrics and knitted fabrics. The coated substrates were dried in an oven at 150° C. for 3 minutes or at room temperature for 24 hours.

[0078] The conductivity of the coating was measured using a four-point measuring device (RCHEK 4Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1-19990 ohms / square). The measurement was performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed no increase in the reflection of infrared radiation in the wavelength range of 3 microns to 50 microns.

[0079] Example 4: Coating on fabrics, woven fabrics, knitted fabrics

[0080] The formulation according to Example 1 was produced using an acrylate adhesive and qualitatively tested for homogeneity. The formulation was applied directly to fabrics, plastic woven fabrics and knitted fabrics. The coated substrates were dried in an oven at 150° C. for 3 minutes or at room temperature for 24 hours.

[0081] The conductivity of the coating was measured using a four-point measuring device (RCHEK 4Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measuring range of the device (1-19990 ohms / square). The measurement was performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that the infrared radiation had a significant reflection in the wavelength range of 3 microns to 50 microns.

[0082] Example 5: Coating of white painted or painted wall test specimens

[0083] The formulation according to Example 1 was produced using an acrylate adhesive and the homogeneity of the formulation was qualitatively tested. The formulation was applied to white painted and painted wall test specimens using a brush or paint roller. Drying was carried out at room temperature for approximately 24 hours.

[0084] Even after drying, the color of the painted wall test sample remained unchanged. Measurements were made using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed significant reflection of infrared radiation in the wavelength range of 3 microns to 50 microns.

[0085] Example 6: Coating of Concrete Test Specimens

[0086] The formulation according to Example 1 was produced using an acrylate adhesive and the homogeneity of the formulation was qualitatively tested. The formulation was applied to the concrete test specimens using a brush or a paint roller. Drying was allowed to proceed for approximately 24 hours at room temperature.

[0087] The measurements were performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that infrared radiation had obvious reflection in the wavelength range of 3 μm to 50 μm. Figure 1 Corresponding measurement results showing a comparison of heat reflection between uncoated and coated concrete test specimens. A clear increase in the reflection of infrared radiation is clearly visible in the coated test specimen. When a heat source with a temperature of 33°C is used, the measurement of the uncoated concrete specimen body results in a temperature of 25.2°C, while the coated concrete specimen body shows a temperature of 29.8°C.

[0088] Example 7: Coating of Gypsum Test Specimens

[0089] The formulation according to Example 1 was produced using an acrylate adhesive and tested qualitatively for homogeneity. The formulation was applied to a plaster test specimen using a brush or a paint roller. Drying was allowed to proceed for approximately 24 hours at room temperature.

[0090] The measurement was performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that the infrared radiation had a significant reflection in the wavelength range of 3 microns to 50 microns. The conductivity of the coating was measured using a four-point measurement device (RCHEK4Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measurement range of the device (1-19990 ohms / square).

[0091] Example 8: Coating of Wood Test Specimens

[0092] The formulation according to Example 1 was produced using an acrylate adhesive and the homogeneity of the formulation was qualitatively tested. The formulation was applied to the wooden test specimens using a brush or a paint roller. Drying was carried out at room temperature for approximately 24 hours.

[0093] The measurements were performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that infrared radiation had obvious reflection in the wavelength range of 3 μm to 50 μm.

[0094] Example 9: Coating of wallpaper

[0095] The formulation according to Example 1 was produced using an acrylate adhesive and qualitatively tested for homogeneity. The formulation was applied to solid and patterned wallpapers using a brush and paint roller or using a transfer printing method or using a . Drying was carried out at room temperature for approximately 24 hours or in an oven at 150° C. for 10 minutes.

[0096] The measurement was performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that the infrared radiation had a significant reflection in the wavelength range of 3 microns to 50 microns. The conductivity of the coating was measured using a four-point measurement device (RCHEK4Point Meter, manufacturer EDTM, model #RC2175). The conductivity could not be detected within the measurement range of the device (1-19990 ohms / square).

[0097] Example 10: Coating of paper

[0098] The formulation according to Example 1 was produced using an acrylate adhesive and the homogeneity of the formulation was qualitatively tested. The formulation was applied to white paper using a brush. Drying was carried out at room temperature for approximately 24 hours or in an oven at 120° C. for 5 minutes.

[0099] The measurements were performed using a commercial infrared thermal imager (model: Flir One Pro, manufacturer: Flir), and the results showed that infrared radiation had obvious reflection in the wavelength range of 3 μm to 50 μm.

Claims

1. A formulation for producing an infrared radiation reflective coating, wherein the formulation contains at least one conductive metal nanomaterial, at least one binder and at least one solvent, wherein the weight ratio of the conductive metal nanomaterial to the binder is 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. A 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 conductive metal nanoparticles, in particular conductive silver nanoparticles, conductive metal nanowires, in particular conductive silver nanowires, and conductive metal nanotubes, in particular conductive silver nanotubes.

5. The formulation according to any one of claims 1 to 4, characterized in that The formulation further comprises conductive carbon, conductive carbon nanotubes, graphene, conductive polymers, or mixtures thereof.

6. The formulation according to any one of claims 1 to 5, characterized in that The formulation has one or more additives, wherein the additives are preferably thickeners, adsorbents, wetting aids, flame retardants, polyvinyl pyrrolidone, defoamers, film formers, chemical stabilizers and color pigments, wherein the color pigments absorb a predetermined proportion of electromagnetic radiation in the wavelength range between 400 nanometers and 800 nanometers.

7. The formulation according to any one of claims 1 to 6, characterized in that The adhesives mentioned are adhesives based on acrylates, epoxies, polyurethanes, silicones, siloxanes, polyolefins, cellulose derivatives, polythiophenes, perfluorinated polymers and copolymers of the polymers mentioned, 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, in particular a conductive silver nanowire, wherein the quotient of the length and the diameter of the metal nanowire is preferably greater than 5.

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

10. The composite material according to claim 9, characterized in that The substrate is a polymer film, a woven fabric, a knitted fabric, a textile material, glass, paper, concrete, cement, wood, gypsum, plasterboard, metal or plastic.

11. The composite material according to claim 9 or 10, characterized in that 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, characterized in that The coating has an average spectral transmittance of at least 30% in the wavelength range of 400 nanometers to 800 nanometers.

13. The composite material according to any one of claims 9 to 12, characterized in that The coating has a reflectivity 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, characterized in that The coating has no measurable electrical conductivity.

15. A method for producing a composite material according to any one of claims 9 to 14, comprising the following steps a) providing a substrate, b) providing a formulation according to any one of claims 1 to 8, c) applying the formulation provided in step b) to the substrate provided in step a), d) drying the object obtained in step c) to form a composite material consisting of a substrate and an infrared radiation reflecting coating arranged on said substrate.

16. The method according to claim 15, characterized in that The drying in step d) is carried out at a temperature of T<200°C, preferably T<100°C, particularly preferably T<50°C, and more preferably T<30°C.

17. The method according to claim 15 or 16, characterized in that After step a) and before step c), the substrate surface is pretreated by plasma pretreatment, corona pretreatment, cleaning, chemical pretreatment or application of a primer, and in step c), the formulation provided in step b) is applied to the pretreated substrate.

18. The method according to any one of claims 15 to 17, characterized in that In step c), the formulation provided in step b) is applied by spiral blade, screen printing, transfer printing, flow coating, spraying or brushing.

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