Radiation cooling coating and preparation method thereof

Abstract

The invention discloses a radiation cooling coating and a preparation method thereof, and relates to the technical field of energy-saving coatings. The invention relates to a radiation cooling coating, which comprises: a primer, the primer comprises an epoxy zinc-rich varnish and a first near-infrared reflective material, the first near-infrared reflective material / epoxy zinc-rich varnish = 3-6 wt%, and the epoxy zinc-rich varnish / first near-infrared reflective material / epoxy zinc-rich varnish = 3-6 wt%; the finishing paint comprises fluorocarbon varnish, a sunlight reflecting material and a second near-infrared reflecting material, and the average refractive index of the second near-infrared reflecting material is 0.5 or above higher than the refractive index of the fluorocarbon varnish; wherein the weight ratio of the sunlight reflecting material to the fluorocarbon varnish is 10-15wt%; the ratio of the second near-infrared reflecting material to the fluorocarbon varnish is 7-10wt%. The prepared radiation cooling coating has high infrared emissivity and sunlight reflectivity, the hardness and wear resistance of the finished paint are good, and the long-term stable radiation cooling function can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy-saving coatings, and in particular relates to a radiation cooling coating and a preparation method thereof. Background Art

[0002] In extreme weather conditions, existing thermal management technologies, including floor heating, air conditioning, and fans, consume a lot of energy, which is not conducive to the realization of the "dual carbon" goals. In this context, spectral regulation technology has attracted widespread attention. It affects the interaction between materials and light through the specific spectral design of the material, thereby changing the energy flow on the surface of the object and achieving efficient thermal management of the surface of the object. Although the current reflective thermal insulation coating can achieve thermal management functions such as heat preservation, heat insulation, and cooling without energy input, it has low efficiency and poor weather resistance, and cannot meet the existing cooling needs.

[0003] Chinese invention patent CN 201810238449.X (publication number CN108250873A) discloses an outdoor all-weather sunlight reflection and infrared radiation cooling paint, which adds micron-sized spherical microbeads, micron-sized metal-plated flakes, and / or micron-sized metal-plated spheres to the paint system, and uses layered coating to make the metal-plated flake structure achieve high sunlight reflection and high infrared radiation, thereby achieving the effect of passive cooling. However, due to the use of micron-sized metal-plated reflective materials, the reflectivity of the invention is relatively low, and the layered coating method is used, and the on-site process is relatively complicated. Summary of the invention

[0004] In order to overcome the technical problems existing in the prior art, the present application provides a radiation cooling coating and a preparation method thereof. The radiation cooling coating is prepared by selecting a specific topcoat, a primer and specific additives and a ratio. The radiation cooling coating has a high infrared emissivity and solar reflectivity. The hardness and wear resistance of the finished paint are good, and a long-term stable radiation cooling function can be achieved.

[0005] In order to achieve the above technical effects, the technical solution adopted in this application is a radiation cooling paint, comprising: A primer, wherein the primer comprises an epoxy zinc-rich varnish and a first near-infrared reflective material, wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish=3-6 wt %; A topcoat, the topcoat comprising a fluorocarbon varnish, a sunlight reflecting material, and a second near-infrared reflecting material, wherein the average refractive index of the second near-infrared reflecting material is higher than the refractive index of the fluorocarbon varnish by more than 0.5; Wherein, in terms of mass ratio, the sunlight reflective material / fluorocarbon varnish = 10-15 wt %; The second near-infrared reflective material / fluorocarbon varnish = 7-10 wt %.

[0006] As a preferred solution, the near-first near-infrared reflective material is selected from one or more of calcium carbonate, silicon carbide, metallic silicon powder, and selenium powder.

[0007] Furthermore, the first infrared reflective material is calcium carbonate.

[0008] As a preferred solution, the particle size of the first infrared reflective material is 1000-3000 nm.

[0009] Furthermore, the particle size of the first infrared reflective material is 1000-2500 nm.

[0010] As a preferred embodiment, based on the mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt%.

[0011] As a preferred embodiment, the second near-infrared reflective material is selected from one or more of barium sulfate, polytetrafluoroethylene, hollow glass microspheres, red iron oxide, copper oxide, yellow iron oxide, and zinc selenide.

[0012] Furthermore, the second near-infrared reflective material is a mixture of barium sulfate and polytetrafluoroethylene.

[0013] Furthermore, the particle size of the barium sulfate is 550-1000 nm, and the particle size of the polytetrafluoroethylene is 1-2.5 μm.

[0014] As a preferred solution, the sunlight reflecting material is selected from one or more of titanium dioxide, zinc oxide, barium titanate, metal aluminum powder, and metal silver powder.

[0015] As a preferred solution, the particle size of the sunlight reflecting material is 300-600 nm.

[0016] Furthermore, the sunlight reflecting material is titanium dioxide.

[0017] Furthermore, the particle size of the titanium dioxide is 350-550 nm.

[0018] The present application also provides a method for preparing a radiant cooling coating, comprising the following steps: 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 20 to 120 minutes at a linear speed of 10 to 30 m / s to obtain a slurry, and filter through a sieve of 80 to 100 meshes to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 20 to 120 minutes at a linear speed of 10 to 30 m / s to obtain a slurry, and filter through a sieve of 80 to 100 mesh to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0019] Technical advantages of this application: 1. The technical solution of this application adopts multi-component and multi-particle size materials to show excellent reflective performance in different bands, and through material selection, the refractive index difference between the varnish and the second near-infrared reflective material is controlled to be greater than 0.5, which can further increase the reflectivity in the infrared band and increase the cooling effect; 2. Use epoxy zinc-rich varnish as a specific primer material and fluorocarbon varnish as a specific topcoat material. Due to its local ionic bond characteristics, the fluorocarbon bond can form a Zn-FC covalent bond with the zinc element in the epoxy zinc-rich varnish, further improving the stability of the paint material; 3. Epoxy zinc-rich varnish is rich in zinc, so it has a cathodic protection effect on the steel substrate. The paint film has good toughness and is easy to construct. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 is the reflectivity curve of the radiant cooling coating provided in Example 1 of the present application; Figure 2 This is the emissivity curve of the radiative cooling coating provided in Example 1 of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0024] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0025] In the description of this application, it should be noted that the terms "upper", "lower", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0026] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] It should be noted that, in the absence of conflict, different features in the embodiments of the present application may be combined with each other.

[0028] In order to solve the problems in the prior art, the present application provides a radiation cooling coating, comprising: A primer, wherein the primer comprises an epoxy zinc-rich varnish and a first near-infrared reflective material, wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish=3-6 wt %; Epoxy zinc-rich varnish has good adhesion, weather resistance and corrosion resistance, and can provide a long-life, corrosion-resistant primer for radiant cooling coatings; First, near-infrared reflective materials can effectively reflect radiation in the near-infrared band. Near-infrared radiation is one of the main parts of solar radiation that causes temperature rise. Reflecting radiation in the infrared band can effectively achieve a cooling effect. The mass ratio of the first near-infrared reflective material to the epoxy zinc-rich varnish is 3-6 wt%. This ratio achieves a good near-infrared reflective effect without affecting the basic performance of the primer. If the ratio of the first infrared reflective material is too low, a good cooling effect cannot be achieved. If the ratio of the first infrared reflective material is too high, the coating performance of the primer will be affected. A topcoat, the topcoat comprising a fluorocarbon varnish, a sunlight reflecting material, and a second near-infrared reflecting material, wherein the average refractive index of the second near-infrared reflecting material is higher than the refractive index of the fluorocarbon varnish by more than 0.5; The fluorocarbon varnish selected in the topcoat is a high-performance coating with excellent weather resistance, corrosion resistance, chemical resistance and self-cleaning properties. As the main component of the topcoat, it can protect the effective primer. At the same time, the fluorocarbon bond contained in the topcoat can form a Zn-FC covalent bond with the zinc element in the epoxy zinc-rich due to its local ionic bond characteristics, further improving the stability and weather resistance of the paint material; Solar reflective materials are mainly used to reflect visible light and some ultraviolet radiation, reducing the heating effect of radiation on the surface of objects and further improving the cooling effect; The second near-infrared reflective material has a similar function to the first near-infrared reflective material in the primer, which can effectively reflect radiation in the near-infrared band and reduce the temperature. The second near-infrared reflective material in the topcoat needs to have a higher refractive index and reflection efficiency to further enhance the cooling effect. Therefore, the average refractive index of the second infrared reflective material needs to be higher than the refractive index of the fluorocarbon varnish by more than 0.5. This difference helps to further enhance the refraction effect of near-infrared radiation and improve the radiation cooling performance of the coating to ensure the cooling effect. Wherein, in terms of mass ratio, the sunlight reflective material / fluorocarbon varnish = 10-15 wt %; The second near-infrared reflective material / fluorocarbon varnish = 7-10 wt %; The second near-infrared reflective material in the topcoat is more than that in the primer, because the topcoat is directly exposed to the radiation in the atmosphere, and a higher content of near-infrared reflective material can effectively improve the radiation refraction efficiency and achieve a better cooling effect.

[0029] Preferably, the first near-infrared reflective material / epoxy zinc-rich varnish can be any value of 3 to 6 wt %, including but not limited to 3.5 wt %, 4 wt %, 5 wt %. Sunlight reflective material / fluorocarbon varnish can be any value of 10 to 15 wt %, including but not limited to 11 wt %, 12 wt %, 14 wt %. The second near-infrared reflective material / fluorocarbon varnish can be any value of 7 to 10 wt %, including but not limited to 8 wt %, 9 wt %, 9.5 wt %.

[0030] In one embodiment, the near first near-infrared reflective material is selected from one or more of calcium carbonate, silicon carbide, metal silicon powder, and selenium powder. The material has the property of reflecting light in the near-infrared band. Near-infrared light is an electromagnetic wave between visible light and mid-infrared light, and its wavelength range is approximately between 700 nanometers and 2500 nanometers. The above materials have excellent reflectivity and stability in the near-infrared band.

[0031] Exemplarily, the first infrared reflective material is calcium carbonate, which is a common inorganic compound with high whiteness and certain infrared reflective ability and relatively low cost.

[0032] As a preferred embodiment, the particle size of the first infrared reflective material is 1000-3000 nm. Exemplarily, the first infrared reflective material in the coating may be of multiple particle sizes, and may be a mixture of 1000, 1500, 2000, 2500, and 3000 nm particles. With a larger particle size, the first infrared reflective material particles may have a larger surface area and a more complex surface structure, which helps to enhance the interaction with infrared light, thereby improving the reflection efficiency; with a smaller particle size, it is easier to disperse in the primer, improving the overall uniformity of the coating. Therefore, in the coating, the technical solution of mixing large and small particle sizes is more conducive to improving the overall performance of the coating.

[0033] Preferably, the particle size of the first infrared reflective material is 1000-2500 nm. By further narrowing the particle size range, the infrared reflective performance of the material can be more accurately controlled, reducing performance fluctuations caused by excessive differences in particle sizes.

[0034] Preferably, in terms of mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt %.

[0035] As a preferred embodiment, the second near-infrared reflective material is selected from one or more of barium sulfate, polytetrafluoroethylene, hollow glass beads, red iron oxide, copper oxide, yellow iron oxide, and zinc selenide. The above materials can effectively reflect radiation in the near-infrared light band (usually referring to light with a wavelength between 700 and 2500 nm).

[0036] Furthermore, the second near-infrared reflective material is a mixture of barium sulfate and polytetrafluoroethylene.

[0037] Furthermore, the particle size of the barium sulfate is 550-1000 nm, and the particle size of the polytetrafluoroethylene is 1-2.5 μm.

[0038] Preferably, the particle size of the barium sulfate can be any value between 550-1000 nm, including but not limited to 600 nm, 800 nm, and 900 nm.

[0039] As a preferred solution, the sunlight reflecting material is selected from one or more of titanium dioxide, zinc oxide, barium titanate, metal aluminum powder, and metal silver powder.

[0040] As a preferred embodiment, the particle size of the sunlight reflecting material is 300-600 nm. The particle size of the sunlight reflecting material can be any value between 300 and 600 nm, including but not limited to 350 nm, 450 nm, and 500 nm.

[0041] Furthermore, the sunlight reflecting material is titanium dioxide.

[0042] Furthermore, the particle size of the titanium dioxide is 350-550 nm.

[0043] The present application also provides a method for preparing a radiant cooling coating, comprising the following steps: 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 20 to 120 minutes at a linear speed of 10 to 30 m / s to obtain a slurry, and filter through a sieve of 80 to 100 meshes to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 20 to 120 minutes at a linear speed of 10 to 30 m / s to obtain a slurry, and filter through a sieve of 80 to 100 mesh to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0044] The present application scheme is further explained below in conjunction with specific embodiments. Specific embodiments

[0045] Example 1 A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 1000 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish=3wt%; The topcoat comprises a fluorocarbon varnish, a sunlight reflecting material (titanium dioxide with a particle size of 300 nm), and a second near-infrared reflecting material (barium sulfate with a particle size of 550 nm), wherein the average refractive index of the second near-infrared reflecting material is higher than the refractive index of the fluorocarbon varnish by 1, and in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 10 wt %, and the second near-infrared reflecting material / fluorocarbon varnish = 7 wt %.

[0046] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 20 minutes at a linear speed of 10 m / s to obtain a slurry, and filter through an 80-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 20 minutes at a linear speed of 10 m / s to obtain a slurry, and filter through an 80-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0047] The radiant cooling coating obtained in Example 1 was tested. The test results are shown in Figure 1 , Figure 2 The prepared radiation cooling coating has high emissivity and reflectivity.

[0048] Example 2 A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 1500 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish=5wt%; The topcoat comprises a fluorocarbon varnish, a sunlight reflecting material (zinc oxide with a particle size of 400 nm), and a second near-infrared reflecting material (barium sulfate), wherein the average refractive index of the second near-infrared reflecting material is 0.8 higher than the refractive index of the fluorocarbon varnish, and in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 13 wt %, and the second near-infrared reflecting material / fluorocarbon varnish = 8 wt %.

[0049] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0050] Example 3 A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 3000 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 3-6 wt %; The topcoat comprises a fluorocarbon varnish, a sunlight reflecting material (titanium dioxide with a particle size of 600 nm), and a second near-infrared reflecting material (barium sulfate), wherein the average refractive index of the second near-infrared reflecting material is 0.7 higher than the refractive index of the fluorocarbon varnish, and in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 15 wt %, and the second near-infrared reflecting material / fluorocarbon varnish = 10 wt %.

[0051] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 120 minutes at a linear speed of 30 m / s to obtain a slurry, and filter through a 100-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 120 min at a linear speed of 30 m / s to obtain a slurry, and filter through a 100-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0052] Example 4 This embodiment is substantially the same as Embodiment 2, except that the second near-infrared reflective material is a mixture of barium sulfate and polytetrafluoroethylene, and the mass ratio of barium sulfate to polytetrafluoroethylene is 1:1.

[0053] A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 1500 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt %; A topcoat comprising a fluorocarbon varnish, a sunlight reflecting material (zinc oxide with a particle size of 400 nm), and a second near-infrared reflecting material (barium sulfate and polytetrafluoroethylene in a mass ratio of 1:1), wherein the average refractive index of the second near-infrared reflecting material is 0.8 higher than the refractive index of the fluorocarbon varnish, and in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 13 wt %, and the second near-infrared reflecting material / fluorocarbon varnish = 8 wt %.

[0054] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0055] Example 5 A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (selenium powder with a particle size of 2000 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish=5wt%; The topcoat comprises fluorocarbon varnish, sunlight reflecting material (metal silver powder with a particle size of 500 nm), and a second near-infrared reflecting material (red iron oxide), wherein the average refractive index of the second near-infrared reflecting material is 0.6 higher than the refractive index of the fluorocarbon varnish, and by mass ratio, the sunlight reflecting material / fluorocarbon varnish = 13wt%, and the second near-infrared reflecting material / fluorocarbon varnish = 9wt%.

[0056] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 70 minutes at a linear speed of 15 m / s to obtain a slurry, and filter through an 80-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 80 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 80-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0057] Comparative Example 1 This comparative example is basically the same as Example 4, except that the average refractive index of the second near-infrared reflective material is 0.3 higher than the refractive index of the fluorocarbon varnish.

[0058] A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 1500 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt %; A topcoat comprising a fluorocarbon varnish, a sunlight reflecting material (zinc oxide with a particle size of 400 nm), and a second near-infrared reflecting material (barium sulfate and polytetrafluoroethylene in a mass ratio of 1:1), wherein the average refractive index of the second near-infrared reflecting material is 0.3 higher than the refractive index of the fluorocarbon varnish, and in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 13 wt %, and the second near-infrared reflecting material / fluorocarbon varnish = 8 wt %.

[0059] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0060] Comparative Example 2 This comparative example is basically the same as Example 2, except that the fluorocarbon varnish is replaced by ester glue varnish.

[0061] A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising epoxy zinc-rich varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 1500 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt %; A topcoat comprising an ester glue varnish, a sunlight reflecting material (zinc oxide with a particle size of 400 nm), and a second near-infrared reflecting material (barium hydroxide and polytetrafluoroethylene in a mass ratio of 1:1), wherein the average refractive index of the second near-infrared reflecting material is 0.8 higher than the refractive index of the ester glue varnish, and in terms of mass ratio, the sunlight reflecting material / ester glue varnish = 13 wt %, and the second near-infrared reflecting material / ester glue varnish = 8 wt %.

[0062] 1. Preparation of primer: Add water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, ester glue varnish, sunlight reflective material and second near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating.

[0063] Comparative Example 3 This comparative example is basically the same as Example 2, except that the epoxy zinc-rich varnish is replaced by ordinary epoxy varnish.

[0064] A method for preparing a radiant cooling coating comprises the following steps: Raw materials: primer, the primer comprising ordinary epoxy varnish and a first near-infrared reflective material (metal silicon powder with a particle size of 1500 nm), wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt %; A topcoat comprising a fluorocarbon varnish, a sunlight reflecting material (zinc oxide with a particle size of 400 nm), and a second near-infrared reflecting material (barium sulfate and polytetrafluoroethylene in a mass ratio of 1:1), wherein the average refractive index of the second near-infrared reflecting material is 0.8 higher than the refractive index of the fluorocarbon varnish, and in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 13 wt %, and the second near-infrared reflecting material / fluorocarbon varnish = 8 wt %.

[0065] 1. Preparation of primer: Add water, ordinary epoxy varnish and the first near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a primer layer; 2. Preparation of topcoat: Add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 60 minutes at a linear speed of 20 m / s to obtain a slurry, and filter through a 90-mesh sieve to obtain a topcoat layer; 3. Combine primer and topcoat to get multi-layer radiation cooling coating. Example

[0066] The radiation cooling coatings prepared in Example 2, Examples 4-5 and Comparative Examples 1-3 were tested, with a coating thickness of 1 mm, and the reflectivity, adhesion, cooling effect and average radiation cooling power were tested. The test method is as follows: Overall infrared emissivity: The samples coated with the radiative cooling coating were passed through a Fourier transform infrared spectrometer (FTIR) equipped with an integrating sphere to measure the overall infrared emissivity.

[0067] Adhesion: Apply radiation cooling paint on a sandblasted steel plate of 150mm×70mm×4mm and maintain for 168h; perform the tape tear test according to the provisions of GB / T9286-1998, use a single-edged tool to cut 3 parallel lines in the parallel and vertical directions along the long side of the sample, with a spacing of 3mm each and a grid number of 4. The highest is level 0 and the lowest is level 5.

[0068] Cooling effect: The time taken for metal plates of the same size (150mm×70mm×4mm) coated with radiation coating to cool to 30 degrees after being heated to 75 degrees at the same room temperature.

[0069] The test results are shown in Table 1.

[0070] Table 1 Sample Overall infrared radiation rate / % Adhesion Cooling effect / s Example 2 93.5% Level 1 268 Example 4 94.1% Level 0 255 Example 5 92.6% Level 0 283 Comparative Example 1 90.5% Level 1 329 Comparative Example 2 93.8% Level 2 273 Comparative Example 3 93.0% Level 2 310 Observing Table 1, it can be seen that Example 4 has the best comprehensive performance. Comparing Example 2 with Example 4, it can be seen that the use of a mixture of barium sulfate and polytetrafluoroethylene as the second near-infrared reflective material can significantly increase the infrared emissivity, thereby improving the cooling effect; comparing Example 4 with Comparative Example 1, it can be seen that when the average refractive index of the second near-infrared reflective material is higher than the refractive index of the fluorocarbon varnish by 0.3, the infrared reflectivity and the cooling effect are both reduced; comparing Example 4 with Comparative Example 2, after the fluorocarbon varnish is replaced with the ester glue varnish, the adhesion of the coating decreases, which may be due to the fact that the fluorocarbon varnish can form a Zn-FC covalent bond with the zinc element in the epoxy zinc-rich varnish, further improving the stability of the paint material, while the ester glue varnish cannot play this role; comparing Example 4 with Comparative Example 3, after the epoxy zinc-rich varnish is replaced with the ordinary epoxy varnish, the adhesion also decreases, and the cooling effect becomes worse.

[0071] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A radiation cooling paint, characterized in that: include A primer, wherein the primer comprises an epoxy zinc-rich varnish and a first near-infrared reflective material, wherein, by mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish=3-6 wt %; A topcoat, the topcoat comprising a fluorocarbon varnish, a sunlight reflecting material, and a second near-infrared reflecting material, wherein the average refractive index of the second near-infrared reflecting material is higher than the refractive index of the fluorocarbon varnish by more than 0.5; Wherein, in terms of mass ratio, the sunlight reflecting material / fluorocarbon varnish = 10-15 wt %; The second near-infrared reflective material / fluorocarbon varnish=7-10 wt %.

2. The radiant cooling paint according to claim 1, characterized in that: The first near-infrared reflective material is selected from one or more of calcium carbonate, silicon carbide, metallic silicon powder, and selenium powder.

3. The radiant cooling paint according to claim 1, characterized in that: The particle size of the first infrared reflective material is 1000-3000 nm.

4. The radiant cooling paint according to claim 1, characterized in that: In terms of mass ratio, the first near-infrared reflective material / epoxy zinc-rich varnish = 5 wt %.

5. The radiant cooling paint according to claim 1, characterized in that: The second near-infrared reflective material is selected from one or more of barium sulfate, polytetrafluoroethylene, hollow glass microspheres, red iron oxide, copper oxide, yellow iron oxide, and zinc selenide.

6. The radiant cooling paint according to claim 1, characterized in that: The sunlight reflecting material is selected from one or more of titanium dioxide, zinc oxide, barium titanate, metal aluminum powder and metal silver powder.

7. The radiant cooling paint according to claim 1, characterized in that: The particle size of the sunlight reflecting material is 300-600 nm.

8. A method for preparing a radiant cooling coating according to any one of claims 1 to 7, characterized in that: The following steps are involved: Preparation of primer: adding water, epoxy zinc-rich varnish and the first near-infrared reflective material into a high-speed disperser, dispersing to obtain a slurry, filtering to obtain a primer layer; Preparation of topcoat: adding water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, dispersing to obtain slurry, filtering to obtain a topcoat layer; By combining the primer and the topcoat, a multi-layer radiation cooling coating can be obtained.

9. The method for preparing a radiant cooling coating according to claim 8, characterized in that: The primer preparation is specifically to add water, epoxy zinc-rich varnish, and the first near-infrared reflective material into a high-speed disperser, disperse for 20min to 120min at a linear speed of 10 to 30m / s to obtain a slurry, and filter through a sieve of 80 to 100 meshes to obtain a primer layer.

10. The method for preparing a radiation cooling coating according to claim 8, characterized in that: The topcoat preparation is specifically to add water, fluorocarbon varnish, sunlight reflective material, and second near-infrared reflective material into a high-speed disperser, disperse for 20min to 120min at a linear speed of 10 to 30m / s to obtain a slurry, and filter through a sieve of 80 to 100 meshes to obtain a topcoat layer.

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