Preparation method and application of nano heat-insulating metal oxide composite coating

Abstract

The invention discloses a preparation method and application of a nano heat-insulating metal oxide composite coating. The preparation method comprises the following steps: preparing a nano ATO crystal of which the surface contains silicon hydroxyl; preparing polymerizable ATO (antimony tin oxide) nano particles; and uniformly mixing the polymerizable ATO nano particles, the silane modified nano silicon dioxide, the self-emulsifying polyurethane emulsion and the auxiliary agent to obtain the required coating. Nanometer ATO crystallization and surface silicon hydroxyl modification are synchronously completed in a hydrothermal environment, and the problem of uneven coating caused by traditional two-step modification is solved; after the high-temperature reaction, cold ethanol is used for realizing shock cooling to stop crystal growth, so that the problem of thermodynamic instability of the nanocrystalline is solved; the interfacial compatibility is improved by introducing a vinyl-containing siloxane monomer; by compounding the polymerizable ATO nano particles, the silane modified nano silicon dioxide, the self-emulsifying polyurethane emulsion and the auxiliaries, a stable topological structure connected by covalent bonds is constructed, and the aging resistance, the heat insulation property and the adhesive force of the coating are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal insulation coatings, and particularly relates to a preparation method and application of a nano thermal insulation metal oxide composite coating. BACKGROUND

[0002] The current market thermal insulation products such as hollow glass, low-e glass, etc. have been widely applied and promoted. The low-e glass has low radiation characteristics, and can well block infrared rays and ultraviolet rays in sunlight, and has good heat preservation and insulation properties. The current market application of low-e glass is mainly offline low-e, but the silver layer in the low-e glass is easily affected by the environment, resulting in performance loss. In traditional applications, the low-e glass is generally compounded with white glass to prepare hollow glass, which can effectively improve the three heat transfer paths of heat radiation, heat convection and heat conduction. However, for the buildings that have been built, the use of low-e glass for replacement requires a large investment of manpower, material resources and financial resources, and the replacement glass size is a non-standard type, which cannot be used twice, resulting in a huge waste of resources.

[0003] At present, the energy-saving reconstruction of the built buildings mainly adopts the treatment method of thermal insulation materials, mainly solves the problem of heat radiation, and the market generally adopts the form of attaching thermal insulation film or brushing thermal insulation coating on the glass. The thermal insulation film is mainly divided into two types, one is a metal film, which has good infrared reflection effect, but the reflectivity of the light is also large, which is easy to produce light pollution and is not suitable for large-area application, and the other is a metal oxide conductor thermal insulation film, which mainly absorbs infrared rays in sunlight and releases the absorbed heat to the surrounding environment through heat diffusion. This kind of thermal insulation film has no obvious reflection to sunlight, which meets the requirements of building energy-saving reconstruction, but the thermal insulation film is easy to produce bubbles in the application due to the poor adhesion of the film to the glass, which has a great influence on the appearance of the glass.

[0004] In order to overcome the shortcomings of the film, at present, nano metal oxide and resin are mixed to prepare a coating, and the active functional groups of the organic silicon are introduced into the resin to react with the hydroxyl groups on the surface of the glass to produce a thermal insulation film layer with high adhesion, so as to solve the problem of blistering of the film.

[0005] At present, the metal oxides used for thermal insulation mainly have two types, one is to prepare conductive tin dioxide by doping tin dioxide with antimony or rare earth metals, and the other is to dope tungsten oxide with cesium. Both of the two materials have applications in the market, and the doped tin dioxide has higher cost performance than the doped tungsten oxide, and the current market mainstream still uses the doped tin dioxide.

[0006] Chinese invention patent, publication number CN107083168A discloses the use of a hydrothermal synthesis method to prepare a nano thermal insulation coating, a co-precipitation method to prepare antimony tin oxide, and then an organic acid to form a sol. During the sol formation process, the precipitate needs to be dissolved by heating to form a sol, and then a hydrothermal method is used to prepare a crystal gel, which is mixed with a water-based resin to prepare a thermal insulation coating. In this method, the organic acid needs to be heated to promote dissolution during the preparation of the solution. In the process of large-scale application, it is subject to certain limitations due to the long reaction time, and the prepared material has poor adhesion to the glass surface. Summary of the Invention

[0007] In order to solve the problems in the prior art, the purpose of the present invention is to provide a preparation method and application of a nano thermal insulation metal oxide composite coating.

[0008] In order to achieve the above-mentioned purpose and the above-mentioned technical effect, the technical solution adopted by the present invention is:

[0009] A method for preparing a nano thermal insulation metal oxide composite coating comprises the following steps:

[0010] Step 1: preparing nano-ATO crystals containing silanol groups on the surface;

[0011] Step 2: preparing polymerizable ATO nanoparticles;

[0012] Step 3: Evenly mix the polymerizable ATO nanoparticles, silane-modified nano-silica, self-emulsifying polyurethane emulsion and additives to obtain the desired nano thermal insulation metal oxide composite coating.

[0013] Furthermore, in step 1, the step of preparing nano-ATO crystals containing silanol groups on the surface includes:

[0014] (1) dissolving a tin salt in an organic solvent A to form a solution I;

[0015] Dissolving the antimony salt in an organic solvent B containing hydrochloric acid, and adding hydrochloric acid to form a solution II;

[0016] Then, solution II and solution I are stirred and mixed to obtain a homogeneous precursor solution;

[0017] (2) Slowly add deionized water to the homogeneous precursor solution to obtain a white turbid solution, adjust the pH of the solution to neutral, and centrifuge to remove impurities;

[0018] (3) adding the precipitate to an aqueous solution containing peroxide and organic amine, and simultaneously adding a bifunctional silane coupling agent, and stirring until a red transparent solution is formed;

[0019] (4) placing the red transparent solution in a hydrothermal reactor and reacting it at 150-178°C for 10-15h, using the hydrothermal environment to simultaneously complete the crystallization of nano-ATO and the surface silanol modification;

[0020] (5) After the reaction is completed, cold ethanol is added to terminate the growth, and the nano-ATO crystals containing silanol groups on the surface are collected by centrifugation.

[0021] Furthermore, in step (2), the volume ratio of the homogeneous precursor solution to deionized water is (1-4):1.

[0022] Furthermore, in step (3), the mass ratio of the precipitate, peroxide, and organic amine is 100:(5-10):(10-15).

[0023] Furthermore, the peroxide is one or a combination of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate.

[0024] Furthermore, the organic amine is one or a combination of triethylamine, triethanolamine, and diethanolamine.

[0025] Furthermore, in step 1, the particle size of the nano-ATO crystals is 10-30 nm.

[0026] Furthermore, in step 2, the step of preparing polymerizable ATO nanoparticles includes:

[0027] Disperse nano-ATO crystals in an alkaline solution, add vinyl-containing siloxane monomers, and stir at 50-70°C for 1-4 hours for surface grafting to obtain polymerizable ATO nanoparticles.

[0028] Furthermore, in step three, the auxiliary agent includes one or a combination of film-forming agent, wetting and leveling agent, defoaming agent, photoinitiator, and near-infrared reflective functional particles.

[0029] The present invention also discloses a nano thermal insulation metal oxide composite coating prepared by the preparation method of the nano thermal insulation metal oxide composite coating.

[0030] The present invention also discloses an application method of a nano thermal insulation metal oxide composite coating, comprising the following steps:

[0031] The nano thermal insulation metal oxide composite coating is applied to the substrate surface and cured by ultraviolet light irradiation with a wavelength of 300-400nm and a light intensity of 50-100mW / cm 2 .

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention discloses a preparation method and application of a nano thermal insulation metal oxide composite coating, which utilizes a hydrothermal environment to simultaneously complete nano ATO crystallization and surface silanol modification, thereby solving the problem of uneven coating caused by the traditional two-step modification method; after a high-temperature reaction, cold ethanol is used to achieve sudden cooling to terminate crystal growth, breaking through the traditional natural cooling method, avoiding Ostwald ripening, and solving the problem of thermodynamic instability of nanocrystals; the interface compatibility is improved by introducing vinyl-containing siloxane monomers; and a stable topological structure connected by covalent bonds is constructed by compounding polymerizable ATO nanoparticles, silane-modified nano-silica, a self-emulsifying polyurethane emulsion and additives, thereby significantly improving the aging resistance, thermal insulation performance and adhesion of the coating. DETAILED DESCRIPTION

[0034] The present invention is described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0035] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0036] In one aspect, the present invention discloses a method for preparing a nano thermal insulation metal oxide composite coating, comprising the following steps:

[0037] Step 1: preparing nano-ATO crystals containing silanol groups on the surface;

[0038] Step 2: preparing polymerizable ATO nanoparticles;

[0039] Step 3: Evenly mix 5-15 parts of polymerizable ATO nanoparticles, 0.5-8 parts of silane-modified nano-silica, 50-75 parts of self-emulsifying polyurethane emulsion and 1-10 parts of additives to obtain the desired nano thermal insulation metal oxide composite coating.

[0040] In step 1, the steps of preparing nano-ATO crystals containing silanol groups on the surface include:

[0041] (1) dissolving the tin salt in an organic solvent A (mainly alcohols, such as ethanol, isopropanol, etc.) to form a transparent solution with a concentration of 0.1-0.5 mol / L, which is referred to as solution I;

[0042] Dissolve the antimony salt in an organic solvent B (such as ethylene glycol, n-butanol, etc.) containing 1-3% hydrochloric acid by mass to form a solution II with a concentration of 0.01-0.1 mol / L;

[0043] Then, solution II and solution I are stirred and mixed to obtain a homogeneous precursor solution, wherein the volume ratio of solution II to solution I is 1:1.5 to 1:3;

[0044] (2) Deionized water is slowly added dropwise to the homogeneous precursor solution at a volume ratio of (1 to 4):1 to obtain a white turbid solution, the pH of the solution is adjusted to neutral with an alkaline solution (such as sodium hydroxide), and impurities such as chloride ions in the precipitate are removed by centrifugation using deionized water;

[0045] (3) Under room temperature, the precipitate is added to an aqueous solution containing peroxide and organic amine by ordinary stirring, and then a bifunctional silane coupling agent (KH-550 or KH-560) accounting for 1-3% of the mass of the precipitate is added and stirred until a red transparent solution is formed; the mass ratio of the precipitate, peroxide, and organic amine is 100:(5-10):(10-15), the peroxide is one or a combination of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate, and the organic amine is one or a combination of triethylamine, triethanolamine, and diethanolamine;

[0046] (4) placing the red transparent solution in a hydrothermal reactor and using microwave-assisted heating (frequency 2.45 GHz, power 500-800 W) to react at 150-178 ° C for 10-15 h, using the hydrothermal environment to simultaneously complete the nano-ATO crystallization and surface silanol modification. The hydrothermal high temperature environment can hydrolyze the bifunctional silane coupling agent, and the alkoxy group is converted into silanol (-SiOH) and bonded to the ATO crystal surface;

[0047] (5) After the reaction is completed, cold ethanol, which is 0.5-1 times the mass of the precipitate and pre-cooled to 5°C, is directly injected into the hot solution to terminate the growth. Nano-ATO crystals with rich silanol groups on the surface are collected by centrifugation and have a particle size of 10-30 nm.

[0048] In step 2, the steps of preparing polymerizable ATO nanoparticles include:

[0049] The nano-ATO crystals are dispersed in an alkaline solution with a pH of 9-11. Ultrasonic dispersion is used in this process. Then, vinyl siloxane monomers (such as VTES, etc.) are added and stirred at 50-70°C for 1-4 hours for surface grafting to obtain polymerizable ATO nanoparticles.

[0050] In step three, the auxiliary agent includes one or a combination of film-forming agent, wetting and leveling agent, defoaming agent, photoinitiator, and near-infrared reflective functional particles.

[0051] The film-forming agent is one of diethylene glycol methyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether and ethylene glycol butyl ether, or a combination of several of them.

[0052] The wetting and leveling agent is one or a combination of BYK-333, BYK-346, and BYK-3455.

[0053] The defoaming agent is BYK-3455, FOAMEX 810 or a combination of the two.

[0054] The photoinitiator used is Irgacure 1173 or the like.

[0055] The near-infrared reflective functional particles use cesium tungstate with a particle size of 100-300nm. They can form an absorption-reflection synergistic insulation mechanism with nano-ATO crystals to improve the reflectivity of sunlight.

[0056] The surface of silane-modified nano-silica is treated with KH-560 to carry epoxy groups, which undergo ring-opening reactions with the carboxyl groups of polyurethane and the amino groups on the surface of ATO during UV curing to form network cross-linking points.

[0057] On the other hand, the present invention also discloses a nano thermal insulation metal oxide composite coating prepared by the preparation method of the nano thermal insulation metal oxide composite coating as described above.

[0058] The present invention also discloses an application method of a nano thermal insulation metal oxide composite coating, comprising the following steps:

[0059] When in use, the nano thermal insulation metal oxide composite coating is applied on the surface of the substrate and cured by ultraviolet light (wavelength 300-400nm, light intensity 50-100mW / cm 2 ), so that the vinyl groups and silica silanol groups on the ATO surface react with the polyurethane chains in situ to form a three-dimensional interpenetrating network structure with a core-shell-bridge structure:

[0060] Core: ATO nanocrystals, particle size 10-30nm, providing near-infrared absorption;

[0061] Shell: Vinylsiloxane layer imparts polymerizability;

[0062] Bridge: Polyurethane molecular chains connect ATO and silica through chemical bonds.

[0063] Example 1

[0064] A method for preparing a nano thermal insulation metal oxide composite coating comprises the following steps:

[0065] Step 1: preparing nano-ATO crystals containing silanol groups on the surface;

[0066] Step 2: preparing polymerizable ATO nanoparticles;

[0067] Step 3: Evenly mix 10 parts of polymerizable ATO nanoparticles, 5 parts of silane-modified nano-silica, 60 parts of self-emulsifying polyurethane emulsion and 8 parts of additives to obtain the desired nano thermal insulation metal oxide composite coating.

[0068] In step 1, the steps of preparing nano-ATO crystals containing silanol groups on the surface include:

[0069] (1) Dissolve tin salt (SnCl4·5H2O) in organic solvent A (anhydrous ethanol) to form a transparent solution with a concentration of 0.3 mol / L, which is recorded as solution I;

[0070] Dissolve antimony salt (SbCl3) in organic solvent B (n-butanol) containing 2% hydrochloric acid by mass to form solution II with a concentration of 0.1 mol / L;

[0071] Then, solution II and solution I were stirred and mixed to obtain a homogeneous precursor solution, and the volume ratio of solution II to solution I was 1:1.5;

[0072] (2) Deionized water was slowly added dropwise to the homogeneous precursor solution at a volume ratio of 2:1 to obtain a white turbid solution. The pH of the solution was adjusted to neutral with an alkaline solution (sodium hydroxide). Deionized water was used and impurities such as chloride ions in the precipitate were removed by centrifugation.

[0073] (3) At room temperature, the precipitate was added to an aqueous solution containing peroxide and organic amine by ordinary stirring, and then a bifunctional silane coupling agent (KH-560) accounting for 3% of the precipitate mass was added and stirred until a red transparent solution was formed; the mass ratio of the precipitate, peroxide, and organic amine was 100:10:15, the peroxide was hydrogen peroxide, and the organic amine was triethylamine;

[0074] (4) The red transparent solution was placed in a hydrothermal reactor and subjected to microwave-assisted heating (frequency 2.45 GHz, power 500 W) at 160 ° C for 12 h. The nano-ATO crystallization and surface silanol modification were completed simultaneously in a hydrothermal environment. The hydrothermal high temperature environment can hydrolyze the bifunctional silane coupling agent, converting the alkoxy group into silanol (-SiOH) and bonding to the ATO crystal surface.

[0075] (5) After the reaction is completed, cold ethanol (1 times the mass of the precipitate) pre-cooled to 5°C is directly injected into the hot solution to terminate the growth, and nano-ATO crystals with rich silanol groups on the surface are collected by centrifugation, with a particle size of 20 nm.

[0076] In step 2, the steps of preparing polymerizable ATO nanoparticles include:

[0077] The nano-ATO crystals were dispersed in an alkaline solution (sodium hydroxide) with a pH of 11. Ultrasonic dispersion was used in this process. Then, a vinyl siloxane monomer (VTES) was added and stirred at 60°C for 3 hours for surface grafting to obtain polymerizable ATO nanoparticles.

[0078] In step three, the additives include 2 parts of film-forming agent, 2 parts of wetting and leveling agent, 2 parts of defoaming agent, 1 part of photoinitiator, and 1 part of near-infrared reflective functional particles.

[0079] The film-forming agent is diethylene glycol methyl ether.

[0080] The wetting and leveling agent is BYK-333.

[0081] The defoamer is BYK-3455.

[0082] Irgacure 1173 was used as the photoinitiator.

[0083] The near-infrared reflective functional particles are made of cesium tungstate with a particle size of 100nm. They can form an absorption-reflection synergistic insulation mechanism with nano-ATO crystals to improve the reflectivity of sunlight.

[0084] The surface of silane-modified nano-silica is treated with KH-560 to carry epoxy groups, which undergo ring-opening reactions with the carboxyl groups of polyurethane and the amino groups on the surface of ATO during UV curing to form network cross-linking points.

[0085] A nano thermal insulation metal oxide composite coating is prepared by the method for preparing the nano thermal insulation metal oxide composite coating as described above.

[0086] A method for applying a nano thermal insulation metal oxide composite coating comprises the following steps:

[0087] When in use, the nano thermal insulation metal oxide composite coating is applied on the surface of the substrate and cured by ultraviolet light (wavelength 300nm, light intensity 50mW / cm 2 ), so that the vinyl groups and silica silanol groups on the ATO surface react with the polyurethane chains in situ to form a three-dimensional interpenetrating network structure with a core-shell-bridge structure:

[0088] Core: ATO nanocrystals, particle size 20nm, providing near-infrared absorption;

[0089] Shell: Vinylsiloxane layer imparts polymerizability;

[0090] Bridge: Polyurethane molecular chain connects ATO and silica through chemical bonds;

[0091] This structure makes the infrared blocking rate of the coating attenuate by less than 5% after aging at 85°C for 500 hours.

[0092] Example 2

[0093] A method for preparing a nano thermal insulation metal oxide composite coating comprises the following steps:

[0094] Step 1: preparing nano-ATO crystals containing silanol groups on the surface;

[0095] Step 2: preparing polymerizable ATO nanoparticles;

[0096] Step 3: Evenly mix 15 parts of polymerizable ATO nanoparticles, 1 part of silane-modified nano-silica, 50 parts of self-emulsifying polyurethane emulsion and 1 part of additive to obtain the desired nano thermal insulation metal oxide composite coating.

[0097] In step 1, the steps of preparing nano-ATO crystals containing silanol groups on the surface include:

[0098] (1) Dissolve the tin salt in organic solvent A (anhydrous ethanol) to form a transparent solution with a concentration of 0.5 mol / L, which is recorded as solution I;

[0099] Dissolving the antimony salt in an organic solvent B (ethylene glycol) containing 1-3% hydrochloric acid by mass to form a solution II with a concentration of 0.05 mol / L;

[0100] Then, solution II and solution I were stirred and mixed to obtain a homogeneous precursor solution, and the volume ratio of solution II to solution I was 1:2;

[0101] (2) Deionized water was slowly added dropwise to the homogeneous precursor solution at a volume ratio of 3:1 to obtain a white turbid solution. The pH of the solution was adjusted to neutral with an alkaline solution (sodium hydroxide). Deionized water was used and impurities such as chloride ions in the precipitate were removed by centrifugation.

[0102] (3) Under room temperature, the precipitate was added to an aqueous solution containing peroxide and organic amine by ordinary stirring, and then a bifunctional silane coupling agent (KH-560) accounting for 1% of the precipitate mass was added and stirred until a red transparent solution was formed; the mass ratio of precipitate, peroxide, and organic amine was 100:5:12, the peroxide was hydrogen peroxide, and the organic amine was diethanolamine;

[0103] (4) The red transparent solution was placed in a hydrothermal reactor and subjected to microwave-assisted heating (frequency 2.45 GHz, power 800 W) at 170 ° C for 10 h. The nano-ATO crystallization and surface silanol modification were completed simultaneously in a hydrothermal environment. The hydrothermal high temperature environment can hydrolyze the bifunctional silane coupling agent, converting the alkoxy group into silanol (-SiOH) and bonding to the ATO crystal surface.

[0104] (5) After the reaction is completed, the growth is terminated by directly injecting cold ethanol, which is 0.5 times the mass of the precipitate and pre-cooled to 5°C, into the hot solution, and the nano ATO crystals with a surface rich in silicon hydroxyl groups are collected by centrifugation, with a particle size of 30 nm.

[0105] In step two, the preparation of the polymerizable ATO nanoparticles includes:

[0106] The nano ATO crystals are dispersed in an alkaline solution with a pH of 9, and the process uses ultrasonic dispersion, and then vinyl siloxane monomers (VTES) are added, and surface grafting is performed at 65°C for 2 h to obtain polymerizable ATO nanoparticles.

[0107] In step three, the additives include 0.2 parts of a film-forming agent, 0.2 parts of a wetting and leveling agent, 0.2 parts of an antifoaming agent, 0.2 parts of a photoinitiator, and 0.2 parts of near-infrared reflective functional particles.

[0108] The film-forming agent is diethylene glycol methyl ether.

[0109] The wetting and leveling agent is BYK-346.

[0110] The antifoaming agent is FOAMEX 810.

[0111] The photoinitiator is Irgacure 1173.

[0112] The near-infrared reflective functional particles are cesium tungstate with a particle size of 300 nm, which can form an absorption-reflection synergistic heat insulation mechanism with the nano ATO crystals to improve solar reflectance.

[0113] The surface of the silane-modified nano silicon dioxide is treated with KH-560 to have epoxy groups, which undergo ring-opening reaction with the carboxyl groups of the polyurethane and the amino groups on the surface of the ATO in ultraviolet curing, forming network crosslinking points.

[0114] A nano heat-insulating metal oxide composite coating prepared by the preparation method of the nano heat-insulating metal oxide composite coating described above.

[0115] An application method of a nano heat-insulating metal oxide composite coating, including the following steps:

[0116] In use, the nano heat-insulating metal oxide composite coating is applied to the surface of a substrate, and cured by ultraviolet light irradiation (wavelength 400 nm, light intensity 100 mW / cm 2 ), so that the vinyl groups on the surface of the ATO, the silicon hydroxyl groups of the silicon dioxide, and the polyurethane chain undergo in-situ crosslinking reaction to form a three-dimensional interpenetrating network structure with a core-shell-bridge structure:

[0117] Core: ATO nanocrystals with a particle size of 30 nm, providing near-infrared absorption;

[0118] Shell: Vinylsiloxane layer imparts polymerizability;

[0119] Bridge: Polyurethane molecular chains connect ATO and silica through chemical bonds.

[0120] The rest is the same as in Example 1.

[0121] Example 3

[0122] A method for preparing a nano thermal insulation metal oxide composite coating comprises the following steps:

[0123] Step 1: preparing nano-ATO crystals containing silanol groups on the surface;

[0124] Step 2: preparing polymerizable ATO nanoparticles;

[0125] Step 3: Evenly mix 5 parts of polymerizable ATO nanoparticles, 8 parts of silane-modified nano-silica, 75 parts of self-emulsifying polyurethane emulsion and 10 parts of additives to obtain the desired nano thermal insulation metal oxide composite coating.

[0126] In step 1, the steps of preparing nano-ATO crystals containing silanol groups on the surface include:

[0127] (1) Dissolve the tin salt in organic solvent A (anhydrous ethanol) to form a transparent solution with a concentration of 0.3 mol / L, which is recorded as solution I;

[0128] The antimony salt is dissolved in an organic solvent B (n-butanol) containing 2% hydrochloric acid by mass to form a solution II with a concentration of 0.1 mol / L;

[0129] Then, solution II and solution I were stirred and mixed to obtain a homogeneous precursor solution, and the volume ratio of solution II to solution I was 1:3;

[0130] (2) Deionized water was slowly added dropwise to the homogeneous precursor solution at a volume ratio of 4:1 to obtain a white turbid solution. The pH of the solution was adjusted to neutral with an alkaline solution (sodium hydroxide). Deionized water was used and impurities such as chloride ions in the precipitate were removed by centrifugation.

[0131] (3) At room temperature, the precipitate was added to an aqueous solution containing peroxide and organic amine by ordinary stirring, and then a bifunctional silane coupling agent (KH-560) accounting for 1% of the precipitate mass was added and stirred until a red transparent solution was formed; the mass ratio of the precipitate, peroxide, and organic amine was 100:8:14, the peroxide was hydrogen peroxide, and the organic amine was triethanolamine;

[0132] (4) The red transparent solution was placed in a hydrothermal reactor and subjected to microwave-assisted heating (frequency 2.45 GHz, power 600 W) at 178 ° C for 10 h. The nano-ATO crystallization and surface silanol modification were completed simultaneously in a hydrothermal environment. The hydrothermal high temperature environment can hydrolyze the bifunctional silane coupling agent, converting the alkoxy group into silanol (-SiOH) and bonding to the ATO crystal surface.

[0133] (5) After the reaction is completed, cold ethanol (0.6 times the mass of the precipitate) pre-cooled to 5°C is directly injected into the hot solution to terminate the growth, and nano-ATO crystals with rich silanol groups on the surface are collected by centrifugation, with a particle size of 30 nm.

[0134] In step 2, the steps of preparing polymerizable ATO nanoparticles include:

[0135] Nano-ATO crystals were dispersed in an alkaline solution with a pH of 10 using ultrasonic dispersion. Vinylsiloxane monomer (VTES) was then added and stirred at 70°C for 1 hour for surface grafting to obtain polymerizable ATO nanoparticles.

[0136] In step three, the additives include 3 parts of film-forming agent, 2 parts of wetting and leveling agent, 2 parts of defoaming agent, and 3 parts of photoinitiator.

[0137] The film-forming agent is ethylene glycol methyl ether.

[0138] The wetting and leveling agent is BYK-3455.

[0139] The defoamer is BYK-3455.

[0140] Irgacure 1173 was used as the photoinitiator.

[0141] The surface of silane-modified nano-silica is treated with KH-560 to carry epoxy groups, which undergo ring-opening reactions with the carboxyl groups of polyurethane and the amino groups on the surface of ATO during UV curing to form network cross-linking points.

[0142] A nano thermal insulation metal oxide composite coating is prepared by the method for preparing the nano thermal insulation metal oxide composite coating as described above.

[0143] A method for applying a nano thermal insulation metal oxide composite coating comprises the following steps:

[0144] When in use, the nano thermal insulation metal oxide composite coating is applied on the surface of the substrate and cured by ultraviolet light (wavelength 400nm, light intensity 100mW / cm 2 ), so that the vinyl groups and silica silanol groups on the ATO surface react with the polyurethane chains in situ to form a three-dimensional interpenetrating network structure with a core-shell-bridge structure:

[0145] Core: ATO nanocrystals, particle size 30nm, providing near-infrared absorption;

[0146] Shell: Vinylsiloxane layer imparts polymerizability;

[0147] Bridge: Polyurethane molecular chains connect ATO and silica through chemical bonds.

[0148] The rest is the same as in Example 1.

[0149] Parts or structures not specifically described in the present invention may adopt existing technologies or existing products and will not be described in detail here.

[0150] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a nano thermal insulation metal oxide composite coating, characterized in that: The following steps are involved: Step 1: preparing nano-ATO crystals containing silanol groups on the surface; Step 2: preparing polymerizable ATO nanoparticles; Step 3: Evenly mix the polymerizable ATO nanoparticles, silane-modified nano-silica, self-emulsifying polyurethane emulsion and additives to obtain the desired nano thermal insulation metal oxide composite coating.

2. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 1, characterized in that: In step 1, the steps of preparing nano-ATO crystals containing silanol groups on the surface include: (1) dissolving a tin salt in an organic solvent A to form a solution I; Dissolving the antimony salt in an organic solvent B containing hydrochloric acid, and adding hydrochloric acid to form a solution II; Then, solution II and solution I are stirred and mixed to obtain a homogeneous precursor solution; (2) Slowly add deionized water to the homogeneous precursor solution to obtain a white turbid solution, adjust the pH of the solution to neutral, and centrifuge to remove impurities; (3) adding the precipitate to an aqueous solution containing peroxide and organic amine, and simultaneously adding a bifunctional silane coupling agent, and stirring until a red transparent solution is formed; (4) placing the red transparent solution in a hydrothermal reactor and reacting it at 150-178°C for 10-15h, using the hydrothermal environment to simultaneously complete the crystallization of nano-ATO and the surface silanol modification; (5) After the reaction is completed, cold ethanol is added to terminate the growth, and the nano-ATO crystals containing silanol groups on the surface are collected by centrifugation.

3. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 2, characterized in that: In step (2), the volume ratio of the homogeneous precursor solution to deionized water is (1-4):

1.

4. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 2, characterized in that: In step (3), the mass ratio of the precipitate, peroxide and organic amine is 100:(5-10):(10-15).

5. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 2, characterized in that: The peroxide is one or a combination of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; The organic amine is one or a combination of triethylamine, triethanolamine and diethanolamine.

6. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 1, characterized in that: In step 1, the particle size of the nano-ATO crystal is 10-30 nm.

7. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 1, characterized in that: In step 2, the steps of preparing polymerizable ATO nanoparticles include: Disperse nano-ATO crystals in an alkaline solution, add vinyl-containing siloxane monomers, and stir at 50-70°C for 1-4 hours for surface grafting to obtain polymerizable ATO nanoparticles.

8. The method for preparing a nano thermal insulation metal oxide composite coating according to claim 1, characterized in that: In step three, the auxiliary agent includes one or a combination of film-forming agent, wetting and leveling agent, defoaming agent, photoinitiator, and near-infrared reflective functional particles.

9. A nano thermal insulation metal oxide composite coating prepared by the method for preparing the nano thermal insulation metal oxide composite coating according to any one of claims 1 to 8.

10. The application method of the nano thermal insulation metal oxide composite coating according to claim 9, characterized in that: The following steps are involved: The nano thermal insulation metal oxide composite coating is applied to the substrate surface and cured by ultraviolet light irradiation with a wavelength of 300-400nm and a light intensity of 50-100mW / cm 2 .