A metal roof reflective heat-insulating coating formula and preparation method

Abstract

The invention discloses a formula and a preparation method of a reflective heat-insulating coating for a metal roof, comprising the following raw materials in parts by mass: 50-57 parts of styrene-acrylic emulsion, 12-15 parts of titanium dioxide, 10-15 parts of nano titanium dioxide, 16-18 parts of modified ceramic hollow microspheres, 16-20 parts of deionized water, 2-3 parts of a film-forming aid, 0.3-0.5 parts of a defoaming agent, 0.1-0.3 parts of a preservative, 0.06-0.12 parts of a multifunctional aid, 0.1-0.2 parts of a dispersant, and 0.4-0.6 parts of a thickener. The nano titanium dioxide is rutile nano titanium dioxide that has been surface treated with inorganic substances, and the modified ceramic hollow microspheres are ceramic hollow microspheres that have been modified with nano zinc oxide. The invention can significantly improve the anti-ultraviolet performance of the coating, reduce the damage of ultraviolet rays to the coating, and increase the service life by adding nano-grade titanium dioxide to the reflective thermal insulation coating for metal roofs. By adding modified ceramic hollow microspheres to the reflective thermal insulation coating for metal roofs, the heat transfer inside the building can be effectively reduced and the indoor temperature can be lowered.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a formula and a preparation method of a reflective heat-insulating coating for a metal roof. Background Art

[0002] The heat-insulating film formed by the building reflective heat-insulating coating has the characteristics of high reflection of the heat rays of sunlight and high far-infrared emission. It can effectively isolate solar radiation, achieve the effect of reducing indoor temperature, and save the power consumption of refrigeration and air conditioning. Reflective heat-insulating coating is a new material for building energy conservation and has been applied to actual building energy-saving projects. The heat-insulating principle of reflective heat-insulating coating is to use reflective materials with high reflectivity of heat rays and heat-emitting materials with high far-infrared emissivity as part of the raw materials to achieve the heat-insulating effect. The production process and formula of reflective heat-insulating coating are similar to those of conventional coatings. At present, the reflective heat-insulating coating for metal roofs has a certain reflectivity by adding titanium dioxide as a functional material to the coating, especially for the visible light and near-infrared part of sunlight. This reflective performance helps to reflect most of the heat of sunlight back into the atmosphere, thereby reducing the absorption of heat on the surface of the building. However, during long-term use, its cooling effect will gradually decrease, and the heat-blocking effect of sunlight still needs to be improved. In addition, it is easy to be eroded by ultraviolet rays in the case of long-term exposure, which affects the performance of the heat-insulating coating and reduces its service life.

[0003] In order to overcome the above shortcomings, it is necessary to seek a reflective thermal insulation coating for metal roofs so that the coating prepared has excellent thermal insulation performance and good UV protection. Summary of the invention

[0004] (1) Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a formula and preparation method of a reflective thermal insulation coating for metal roofs, which can effectively reduce heat transfer inside a building, lower indoor temperature, reduce damage to the coating caused by ultraviolet rays, and increase its service life.

[0006] (2) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a metal roof reflective thermal insulation coating, comprising the following raw materials in parts by weight: 50-57 parts of styrene-acrylic emulsion, 12-15 parts of titanium dioxide, 10-15 parts of nano titanium dioxide, 16-18 parts of modified ceramic hollow microspheres, 16-20 parts of deionized water, 2-3 parts of film-forming aid, 0.3-0.5 parts of defoaming agent, 0.1-0.3 parts of preservative, 0.06-0.12 parts of multifunctional additive, 0.1-0.2 parts of dispersant, and 0.4-0.6 parts of thickener, wherein the nano titanium dioxide is rutile nano titanium dioxide surface-treated with inorganic substances, and the modified ceramic hollow microspheres are ceramic hollow microspheres modified with nano zinc oxide.

[0008] Preferably, the nano titanium dioxide is prepared according to the following method:

[0009] S11, selecting rutile titanium ore as a raw material, crushing the titanium ore raw material and then performing oxidative roasting to convert titanium dioxide in the titanium ore into a rutile crystal structure;

[0010] S12, crushing the titanium ore raw material that has been oxidatively roasted in S11 to obtain fine-grained titanium dioxide powder;

[0011] S13, slurrying, dispersing and grinding the titanium dioxide powder in S12 in desalted water for wet grinding and depolymerization treatment, depositing the titanium dioxide powder after wet grinding and depolymerization treatment on its surface in the form of oxide and hydroxide through an inorganic coating agent to form an oxide coating, and aging the coated titanium dioxide powder, washing the aging coated titanium dioxide powder with desalted water to a certain conductivity and then drying;

[0012] S14, heat-treating the titanium dioxide powder that has been surface-treated in S13 to make its crystal structure more stable, thereby obtaining nano titanium dioxide.

[0013] Preferably, the inorganic coating agent is one or more of aluminum oxide, silicon oxide, and zirconium oxide.

[0014] Preferably, the modified ceramic hollow microspheres are prepared according to the following method:

[0015] S21, mixing ceramic powder and nano zinc oxide powder in proportion to form a ceramic raw material, and ball milling the mixed raw material by a ball milling device to evenly disperse the nano zinc oxide powder in the ceramic powder and refine the raw material particle size;

[0016] S22, adding an appropriate amount of foaming agent to the raw material after ball milling in S21, generating bubbles through mechanical stirring or chemical reaction to form a hollow structure, and forming hollow microspheres by extrusion molding the foamed raw material;

[0017] S23, sintering the hollow microbeads formed in S22, washing and drying the sintered hollow microbeads to remove surface impurities and residues, and obtaining modified ceramic hollow microbeads.

[0018] Preferably, the mass ratio of nano zinc oxide powder to ceramic powder in the modified ceramic hollow microspheres is (1-1.5): (2-4).

[0019] Preferably, the particle size of the modified ceramic hollow microspheres is 15-40 nm.

[0020] Preferably, the styrene acrylic emulsion is a silicone-modified styrene acrylic copolymer emulsion, and the film-forming aid is dodecyl alcohol ester.

[0021] Preferably, the thickener is one of hydroxypropyl methylcellulose, polyacrylamide, and sodium polyacrylate, and the defoaming agent is one of polyvinyl acetate, trimesic acid ester, and dimethyl silicone oil.

[0022] Preferably, the dispersant is one or more of dodecyltrimethylammonium bromide, sodium dodecyl sulfate, polyvinyl alcohol and polymethyl methacrylate.

[0023] The present invention also provides a method for preparing a reflective heat-insulating coating for a metal roof, comprising the following steps:

[0024] S1. Add styrene-acrylic emulsion, deionized water and dispersant into a reactor according to their weight fractions, and obtain a mixed solution A after stirring and dispersing;

[0025] S2, adding titanium dioxide, nano titanium dioxide, and modified ceramic hollow microspheres to the mixed solution A in the reactor in order according to their mass fractions, and stirring and dispersing to obtain a mixed solution B;

[0026] S3. Add the film-forming aid, defoaming agent, preservative, multifunctional additive and thickener to the mixed solution B in the reactor according to their weight proportions, and obtain the metal roof reflective thermal insulation coating after stirring and dispersing.

[0027] (3) Beneficial effects

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The invention can significantly improve the anti-ultraviolet performance of the coating by adding nano-scale titanium dioxide to the reflective heat-insulating coating for metal roofs, can reflect and scatter the ultraviolet part in sunlight, thereby reducing the damage of ultraviolet rays to the coating and the substrate. At the same time, the nano-scale titanium dioxide can also cooperate with other components in the coating to form a more compact coating with stronger weather resistance. Modified ceramic hollow microspheres are added to the reflective heat-insulating coating for metal roofs. The modified ceramic hollow microspheres have extremely low thermal conductivity and high thermal resistance, can form a heat-insulating barrier in the coating, and prevent heat from being conducted to the inside of an object. By reflecting and scattering the heat in sunlight, the nano-ceramic microspheres can significantly reduce the temperature of the surface of the object, improve the heat-insulating performance of the coating, so that the reflective heat-insulating coating for metal roofs can effectively reduce heat transfer inside a building, reduce indoor temperature, reduce damage to the coating caused by ultraviolet rays, and increase service life. DETAILED DESCRIPTION

[0030] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0031] The specific raw materials mentioned in the following examples can all be obtained commercially, and the techniques and equipment used are well known to those skilled in the art.

[0032] The present invention provides a technical solution:

[0033] A reflective heat-insulating paint for metal roofs comprises the following raw materials in parts by mass: 50-57 parts of styrene-acrylic emulsion, 12-15 parts of titanium dioxide, 10-15 parts of nano titanium dioxide, 16-18 parts of modified ceramic hollow microspheres, 16-20 parts of deionized water, 2-3 parts of film-forming aid, 0.3-0.5 parts of defoaming agent, 0.1-0.3 parts of preservative, 0.06-0.12 parts of multifunctional aid, 0.1-0.2 parts of dispersant, and 0.4-0.6 parts of thickener, wherein the nano titanium dioxide is rutile nano titanium dioxide treated with inorganic substances on the surface, the modified ceramic hollow microspheres are ceramic hollow microspheres modified with nano zinc oxide, and the titanium dioxide is titanium dioxide 998.

[0034] Specifically, the nano titanium dioxide described in the present invention is prepared according to the following method:

[0035] S11, selecting rutile titanium ore as a raw material, crushing the titanium ore raw material and then performing oxidative roasting, the roasting temperature is between 800° C. and 1000° C. During the roasting process, the titanium ore is exposed to a high-temperature oxygen atmosphere so that titanium dioxide in the titanium ore is converted into a rutile crystal structure;

[0036] S12, crushing the titanium ore raw material that has been oxidatively roasted in S11 to obtain fine-grained titanium dioxide powder;

[0037] S13, the titanium dioxide powder in S12 is pulped, dispersed, and ground in desalted water for wet grinding and depolymerization treatment, and the titanium dioxide powder after wet grinding and depolymerization treatment is deposited on its surface in the form of oxides and hydroxides through an inorganic coating agent, wherein the inorganic coating agent is one or more of aluminum oxide, silicon oxide, and zirconium oxide to form an oxide coating, and the coated titanium dioxide powder is subjected to aging treatment. During this process, the coating effect is ensured by adjusting the pH value, and the coated titanium dioxide powder after aging is washed with desalted water to a certain conductivity and then dried, and the conductivity control range is between 20 and 30 us / cm, and the surface treatment is intended to improve its dispersibility, weather resistance, heat resistance and other properties;

[0038] S14, heat-treating the titanium dioxide powder that has been surface-treated in S13 to make its crystal structure more stable, further improve its optical properties and dispersibility, and obtain nano titanium dioxide.

[0039] Specifically, the modified ceramic hollow microspheres described in the present invention are prepared according to the following method:

[0040] S21, mixing ceramic powder and nano zinc oxide powder in proportion to form a ceramic raw material, wherein the mass ratio of nano zinc oxide powder to ceramic powder in the modified ceramic hollow microspheres is (1-1.5): (2-4), and in order to ensure uniform dispersion of nano zinc oxide in the ceramic powder, selecting a suitable dispersant, and subjecting the mixed raw materials to ball milling treatment by a ball milling device, so that the nano zinc oxide powder is uniformly dispersed in the ceramic powder, and the raw material particle size is refined;

[0041] S22, adding an appropriate amount of foaming agent to the raw material after ball milling in S21, generating bubbles through mechanical stirring or chemical reaction to form a hollow structure, and forming hollow microspheres by extrusion molding the foamed raw material;

[0042] S23. Sintering the hollow microbeads formed in S22, washing and drying the sintered hollow microbeads to remove surface impurities and residues to obtain modified ceramic hollow microbeads. The particle size of the modified ceramic hollow microbeads is 15-40nm. The introduction of nano zinc oxide can significantly improve the antibacterial, UV shielding, photocatalytic and other properties of the ceramic hollow microbeads.

[0043] In this embodiment, the styrene acrylic emulsion is a silicone-modified styrene acrylic copolymer emulsion of Henghe Emulsion LR-2050, and the film-forming aid is dodecyl alcohol ester.

[0044] In this embodiment, the thickener is one of hydroxypropyl methylcellulose, polyacrylamide, and sodium polyacrylate, and the defoaming agent is one of polyvinyl acetate, trimesic acid ester, and dimethyl silicone oil.

[0045] In this embodiment, the dispersant is one or more of dodecyltrimethylammonium bromide, sodium dodecyl sulfate, polyvinyl alcohol and polymethyl methacrylate.

[0046] The present invention also provides a method for preparing the reflective thermal insulation coating for metal roofs as described above, comprising the following steps:

[0047] S1. Add styrene-acrylic emulsion, deionized water and dispersant into a reactor according to their weight fractions, and obtain a mixed solution A after stirring and dispersing;

[0048] S2, adding titanium dioxide, nano titanium dioxide, and modified ceramic hollow microspheres to the mixed solution A in the reactor in order according to their mass fractions, and stirring and dispersing to obtain a mixed solution B;

[0049] S3. Add the film-forming aid, defoaming agent, preservative, multifunctional additive and thickener to the mixed solution B in the reactor according to their weight proportions, and obtain the metal roof reflective thermal insulation coating after stirring and dispersing.

[0050] The invention can significantly improve the anti-ultraviolet performance of the coating by adding nano-scale titanium dioxide to the reflective heat-insulating coating for metal roofs, can reflect and scatter the ultraviolet part in sunlight, thereby reducing the damage of ultraviolet rays to the coating and the substrate. At the same time, the nano-scale titanium dioxide can also cooperate with other components in the coating to form a more compact coating with stronger weather resistance. Modified ceramic hollow microspheres are added to the reflective heat-insulating coating for metal roofs. The modified ceramic hollow microspheres have extremely low thermal conductivity and high thermal resistance, can form a heat-insulating barrier in the coating, and prevent heat from being conducted to the inside of an object. By reflecting and scattering the heat in sunlight, the nano-ceramic microspheres can significantly reduce the temperature of the surface of the object, improve the heat-insulating performance of the coating, so that the reflective heat-insulating coating for metal roofs can effectively reduce heat transfer inside a building, reduce indoor temperature, reduce damage to the coating caused by ultraviolet rays, and increase service life.

[0051] Specific implementation cases Example 1

[0052] A reflective heat-insulating coating for metal roofs, comprising the following raw materials in parts by weight: 55 parts of styrene-acrylic emulsion, 12 parts of titanium dioxide, 12 parts of nano titanium dioxide, 16 parts of modified ceramic hollow microspheres, 18 parts of deionized water, 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive, 0.15 parts of dispersant, and 0.5 parts of thickener;

[0053] During the preparation, 55 parts of styrene acrylic emulsion, 18 parts of deionized water and 0.15 parts of dispersant are added to a reactor according to their weight parts, and a mixed solution A is obtained after stirring and dispersing. Then 12 parts of titanium dioxide, 12 parts of nano titanium dioxide and 16 parts of modified ceramic hollow microspheres are added to the mixed solution A in the reactor in sequence, and a mixed solution B is obtained after stirring and dispersing. Then 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive and 0.5 parts of thickener are added to the mixed solution B in the reactor, and a metal roof reflective thermal insulation coating is obtained after stirring and dispersing. Example 2

[0054] A reflective heat-insulating coating for metal roofs, comprising the following raw materials in parts by weight: 55 parts of styrene-acrylic emulsion, 12 parts of titanium dioxide, 12 parts of nano titanium dioxide, 18 parts of deionized water, 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive, 0.15 parts of dispersant, and 0.5 parts of thickener;

[0055] During the preparation, 55 parts of styrene acrylic emulsion, 18 parts of deionized water and 0.15 parts of dispersant are added to a reactor according to their weight parts, and a mixed solution A is obtained after stirring and dispersing. Then 12 parts of titanium dioxide and 12 parts of nano titanium dioxide are added to the mixed solution A in the reactor in sequence, and a mixed solution B is obtained after stirring and dispersing. Then 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive and 0.5 parts of thickener are added to the mixed solution B in the reactor, and a metal roof reflective thermal insulation coating is obtained after stirring and dispersing. Example 3

[0056] A reflective heat-insulating coating for metal roofs, comprising the following raw materials in parts by weight: 55 parts of styrene-acrylic emulsion, 12 parts of titanium dioxide, 16 parts of modified ceramic hollow microspheres, 18 parts of deionized water, 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive, 0.15 parts of dispersant, and 0.5 parts of thickener;

[0057] During the preparation, 55 parts of styrene acrylic emulsion, 18 parts of deionized water and 0.15 parts of dispersant are added to a reactor according to their mass parts, and a mixed solution A is obtained after stirring and dispersing. Then 12 parts of titanium dioxide and 16 parts of modified ceramic hollow microspheres are added to the mixed solution A in the reactor in sequence, and a mixed solution B is obtained after stirring and dispersing. Then 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive and 0.5 parts of thickener are added to the mixed solution B in the reactor, and a metal roof reflective thermal insulation coating is obtained after stirring and dispersing. Example 4

[0058] A reflective heat-insulating coating for metal roofs, comprising the following raw materials in parts by mass: 55 parts of styrene-acrylic emulsion, 12 parts of titanium dioxide, 12 parts of nano titanium dioxide that has not been surface-treated with inorganic substances, 16 parts of modified ceramic hollow microspheres, 18 parts of deionized water, 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional aid, 0.15 parts of dispersant, and 0.5 parts of thickener;

[0059] During the preparation, 55 parts of styrene acrylic emulsion, 18 parts of deionized water and 0.15 parts of dispersant are added to a reactor according to their weight parts, and a mixed solution A is obtained after stirring and dispersion. Then 12 parts of titanium dioxide, 12 parts of nano titanium dioxide that has not been surface treated with inorganic substances and 16 parts of modified ceramic hollow microspheres are added to the mixed solution A in the reactor in sequence, and a mixed solution B is obtained after stirring and dispersion. Then 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive and 0.5 parts of thickener are added to the mixed solution B in the reactor, and a metal roof reflective thermal insulation coating is obtained after stirring and dispersion. Example 5

[0060] A reflective heat-insulating coating for metal roofs, comprising the following raw materials in parts by weight: 55 parts of styrene-acrylic emulsion, 12 parts of titanium dioxide, 12 parts of nano titanium dioxide, 16 parts of unmodified ceramic hollow microspheres, 18 parts of deionized water, 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive, 0.15 parts of dispersant, and 0.5 parts of thickener;

[0061] During the preparation, 55 parts of styrene acrylic emulsion, 18 parts of deionized water and 0.15 parts of dispersant are added to a reactor according to their weight parts, and a mixed solution A is obtained after stirring and dispersing. Then 12 parts of titanium dioxide, 12 parts of nano titanium dioxide and 16 parts of unmodified ceramic hollow microspheres are added to the mixed solution A in the reactor in sequence, and a mixed solution B is obtained after stirring and dispersing. Then 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive and 0.5 parts of thickener are added to the mixed solution B in the reactor, and a metal roof reflective thermal insulation coating is obtained after stirring and dispersing. Comparative Example 1

[0062] A metal roof reflective heat-insulating coating, comprising the following raw materials in parts by weight: 55 parts of styrene-acrylic emulsion, 12 parts of titanium dioxide, 18 parts of deionized water, 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive, 0.15 parts of dispersant, and 0.5 parts of thickener;

[0063] During the preparation, 55 parts of styrene acrylic emulsion, 18 parts of deionized water and 0.15 parts of dispersant are added to a reactor according to their mass parts, and a mixed solution A is obtained after stirring and dispersing. Then 12 parts of titanium dioxide are added to the mixed solution A in the reactor, and a mixed solution B is obtained after stirring and dispersing. Then 2 parts of film-forming aid, 0.35 parts of defoaming agent, 0.2 parts of preservative, 0.08 parts of multifunctional additive and 0.5 parts of thickener are added to the mixed solution B in the reactor, and a metal roof reflective thermal insulation coating is obtained after stirring and dispersing.

[0064] Performance Testing

[0065] The metal roof reflective heat-insulating coatings of Examples 1-5 and Comparative Example 1 were respectively applied to the flat surface of metal roof materials, with a coating thickness of 30-50 μm. The coatings were tested for performance, and the test items were as follows: thermal insulation temperature difference attenuation, hemispherical reflectivity: JG / T235-2008 "Architectural Reflective Heat-Insulating Coatings"; solar reflectivity: ASTMC1549, and the test results are shown in Table 1.

[0066] Table 1 Performance test table

[0067]

[0068] Experiments have proved that: from the performance test results in Table 1, it can be seen that Example 1, by adding nano-scale titanium dioxide and modified ceramic hollow microspheres to the existing metal roof reflective insulation coating, reflects sunlight more fully, has the highest solar emission ratio and hemispherical emissivity, has the best thermal insulation performance, and has excellent ultraviolet reflectivity, which can significantly improve the service life of the coating.

[0069] All technical features in this embodiment can be freely combined according to actual needs.

[0070] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present technical solution is within the protection scope of the present invention.

Claims

1. A reflective thermal insulation coating for metal roofs, characterized in that: The invention comprises the following raw materials in parts by weight: 50-57 parts of styrene-acrylic emulsion, 12-15 parts of titanium dioxide, 10-15 parts of nano titanium dioxide, 16-18 parts of modified ceramic hollow microspheres, 16-20 parts of deionized water, 2-3 parts of film-forming aid, 0.3-0.5 parts of defoaming agent, 0.1-0.3 parts of preservative, 0.06-0.12 parts of multifunctional aid, 0.1-0.2 parts of dispersant, and 0.4-0.6 parts of thickener, wherein the nano titanium dioxide is rutile nano titanium dioxide treated with inorganic substances on the surface, and the modified ceramic hollow microspheres are ceramic hollow microspheres modified with nano zinc oxide; The nano titanium dioxide is prepared according to the following method: S11, selecting rutile titanium ore as a raw material, crushing the titanium ore raw material and then performing oxidative roasting to convert titanium dioxide in the titanium ore into a rutile crystal structure; S12, crushing the titanium ore raw material that has been oxidatively roasted in S11 to obtain fine-grained titanium dioxide powder; S13, slurrying, dispersing and grinding the titanium dioxide powder in S12 in desalted water for wet grinding and depolymerization treatment, depositing the titanium dioxide powder after wet grinding and depolymerization treatment on its surface in the form of oxide and hydroxide through an inorganic coating agent to form an oxide coating, and aging the coated titanium dioxide powder, washing the aging coated titanium dioxide powder with desalted water to a certain conductivity and then drying; S14, heat-treating the titanium dioxide powder that has been surface-treated in S13 to make its crystal structure more stable, thereby obtaining nano titanium dioxide; The inorganic coating agent is one or more of aluminum oxide, silicon oxide, and zirconium oxide; The modified ceramic hollow microspheres are prepared according to the following method: S21, mixing ceramic powder and nano zinc oxide powder in proportion to form a ceramic raw material, and ball milling the mixed raw material by a ball milling device to evenly disperse the nano zinc oxide powder in the ceramic powder and refine the raw material particle size; S22, adding an appropriate amount of foaming agent to the raw material after ball milling in S21, generating bubbles through mechanical stirring or chemical reaction to form a hollow structure, and forming hollow microspheres by extrusion molding the foamed raw material; S23, sintering the hollow microbeads formed in S22, washing and drying the sintered hollow microbeads to remove surface impurities and residues, and obtaining modified ceramic hollow microbeads.

2. A metal roof reflective thermal insulation coating according to claim 1, characterized in that: The mass ratio of nano zinc oxide powder to ceramic powder in the modified ceramic hollow microspheres is (1-1.5): (2-4).

3. A metal roof reflective thermal insulation coating according to claim 1, characterized in that: The particle size of the modified ceramic hollow microspheres is 15-40 nm.

4. A metal roof reflective thermal insulation coating according to claim 1, characterized in that: The styrene-acrylic emulsion is a silicone-modified styrene-acrylic copolymer emulsion, and the film-forming aid is dodecyl alcohol ester.

5. The metal roof reflective thermal insulation coating according to claim 1, characterized in that: The thickener is one of hydroxypropyl methylcellulose, polyacrylamide, and sodium polyacrylate, and the defoamer is one of polyvinyl acetate, trimesic acid ester, and dimethyl silicone oil.

6. The metal roof reflective thermal insulation coating according to claim 1, characterized in that: The dispersant is one or more of dodecyltrimethylammonium bromide, sodium dodecyl sulfate, polyvinyl alcohol and polymethyl methacrylate.

7. A method for preparing the reflective thermal insulation coating for metal roofs according to any one of claims 1 to 6, characterized in that: The steps include: S1. Add styrene-acrylic emulsion, deionized water and dispersant into a reactor according to their weight fractions, and obtain a mixed solution A after stirring and dispersing; S2, adding titanium dioxide, nano titanium dioxide, and modified ceramic hollow microspheres to the mixed solution A in the reactor in order according to their mass fractions, and obtaining a mixed solution B after stirring and dispersion; S3. Add the film-forming aid, defoaming agent, preservative, multifunctional additive and thickener to the mixed solution B in the reactor according to their weight proportions, and obtain the metal roof reflective thermal insulation coating after stirring and dispersing.

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