CN115703933B - Nanoparticle, preparation method thereof and application of nanoparticle in heat insulation coating - Google Patents

Abstract

The present invention relates to a hollow-structured nanoparticle comprising an outer shell formed of silica nanoparticles and an inner shell formed of plasmonic nanoparticles, a method for the preparation thereof and the use thereof in coating compositions. The insulating glass coated with the coating composition of the present invention is capable of blocking at least 98% of ultraviolet light and at least 90% of near infrared light, and has a visible light transmittance of not less than 70%.

Description

Nano microspheres, its preparation method and its application in thermal insulation coating

technical field

The invention relates to the field of coatings, in particular, to a nano-microsphere with a hollow core-shell structure comprising an outer shell formed by silica nanoparticles and an inner shell formed by plasma nanoparticles, a preparation method thereof and a thermal insulation application in coatings.

Background technique

Insulation coatings can effectively prevent the heat from sunlight passing through building windows, thereby reducing the indoor ambient temperature. Traditional thermal insulation coatings achieve thermal insulation by reducing the heat transfer from the outer surface to the interior. Such thermal insulation coatings are mainly based on materials with low thermal conductivity such as ceramic particles and polymer resins. Coating transparent heat-insulating coatings on glass windows can strongly shield near-infrared and ultraviolet rays, thereby greatly reducing the solar heat absorbed through windows, which has been widely explored and applied in building energy conservation. The thermal insulation performance of building windows has gradually attracted considerable attention in energy-saving applications, making a significant contribution to reducing the annual cooling load by 10% to 30% in summer in various climate zones.

Existing thermal insulation coatings mainly consist of a polymer matrix and incorporated inorganic fillers, which have limited absorption bands in the near-infrared (NIR) region. In recent years, with the rapid development of nanomaterial research and synthesis technology, various nanoparticles and hollow particles have gradually appeared, which has promoted the development of thermal insulation coatings.

U.S. Patent No. 10913858B2 discloses a water-based thermal insulation coating, which uses the sol-gel method to uniformly disperse silicon dioxide in the resin as a thermal insulation agent to eliminate the problem of particle aggregation to form coarse particles, thereby simplifying the preparation process , and prevent the influence of uneven dispersion. Due to the good fineness of the silica dispersion and the large specific surface area of 30.1m ² /g to 100m ² /g, when the water-based thermal insulation coating is applied to the building surface, the formed coating has a compact structure and a smooth surface , and has a high surface reflectivity above 85%. This coating effectively blocks infrared rays and provides excellent thermal insulation, stain resistance and durability.

U.S. Patent No. 20160160053A1 discloses a method of making and using a nanocomposite for coating glass consisting of a first metal oxide bridging a silicone oil moiety and an anionic surfactant moiety and bonded to the silicone oil moiety composition of the second metal oxide. The composite material can be made by heating the mixture of the first metal oxide and the second metal oxide and silicone oil, and then adding the surfactant and the oxidizing solution. Glass coated with this composite transmits visible light, absorbs some ultraviolet light, and reflects some near-infrared light. The optical properties of coated glass can be used to reduce heat in glass-enclosed areas by reducing the amount of infrared and ultraviolet light transmitted through the glass. Despite the improved adhesion between the coating and the glass substrate, complex synthesis steps make it difficult to apply to large surfaces.

U.S. Patent No. 4,510,190 discloses a transparent insulating coating that is neutral in terms of transmittance and appearance for insulating glass panels. The coating is formed from a bismuth oxide-silver-bismuth oxide multilayer system in which more electronegative species (i.e., species with a higher standard potential) are added to the bismuth oxide layer to avoid degradation under UV radiation. black. Bismuth oxide layers act as reflection-reducing layers in multilayer systems, ie they significantly increase the transmission in the visible region. Due to the suitable layer thickness, this bismuth oxide-silver-bismuth oxide multilayer system forms an excellent thermal barrier coating on glass substrates.

U.S. Patent No. 5,099,621A relates to the use of conductive polymer materials to selectively control the transmittance of light through transparent or translucent plates or films according to wavelength; more specifically, to the use of conductive polymer materials to provide High efficiency and high reflectivity and absorptivity in the near infrared and far infrared range. The coating solution can be readily applied to the substrate by various low cost and effective methods known in the art, such as spin coating, spray coating, dip coating or extrusion coating. The cost of the thermal window unit is significantly reduced, the manufacturing process is simplified, and the reliability and operating efficiency of the unit are improved.

US Patent No. 20130168595A1 relates to a nano thermal insulation coating and a preparation method thereof, more specifically, to a blended solid solution of nano antimony tin oxide and nano vanadium oxide. The method comprises the following steps: mixing and stirring the nanometer metal oxide and the stirring aid liquid to form a mixed paste, filtering and drying the mixed paste to form a dry mixed block; calcining the dried mixed block, Form oxide solid solution blocks of metal oxide/silicon oxide; add dispersing liquid and mixing liquid, mix and then perform mechanical stirring, ultrasonic resonance and high-pressure homogenization to form suitable for coating on glass to achieve heat insulation Special effect thermal insulation coating. Since the calcination and homogenization processes require extremely high temperatures and pressures, respectively, such a preparation process is not only time-consuming but also more expensive to manufacture.

US Patent No. 20120121886A1 discloses an infrared reflective coating composition comprising polymer hollow particles, pigment particles and at least one polymer binder. The volume-average particle size of the polymer hollow particles is 0.3 microns to 1.6 microns, which is obviously larger than that of traditional nanoparticle fillers. The coating composition is suitable for many scenarios, such as exterior architectural or industrial applications. The present invention also provides a coating film material comprising at least one coating film derived from the coating composition. In architectural applications, the coating composition is suitable for coating exterior glazing surfaces. The coating composition applied to the substrate can be dried or allowed to dry at a wide temperature range from 1°C to 95°C.

US Patent No. 20200239726A1 discloses an alkyd-containing polymer dispersion dispersed in water to form a primary water-borne coating composition. The resulting aqueous coating composition comprises from about 2 wt. % to about 30 wt. % water and from about 2% to about 50% by weight of an alkyd-containing polymer. Coatings formed from the coating composition exhibit heat resistance and a thermal conductivity of less than 100 mW/mK.

U.S. Patent No. 8304099B2 and U.S. Patent No. 8986851B2 disclose the composition and manufacturing method of a transparent heat insulating material formed of tungsten oxide co-doped with metal cations and halogen anions. The transparent heat insulating material is composed of M _x WO _y A _z represents, wherein M is at least one element in the alkali metal, and A is a halogen. The visible light transmittance of the transparent thermal insulation material is greater than about 70%, and its infrared light shielding rate is also greater than about 70%. Compared with the traditional transparent thermal insulation film containing undoped tungsten oxide or tungsten oxide doped with metal ions, the invention can enhance the thermal insulation ability and maintain the same level of visible light transmission as the conventional film Rate. However, the introduction of halogen elements will cause potential harm to the surrounding environment and human body.

US Patent No. 7252785B2 discloses a composition for producing thermal barrier coatings comprising at least one radiation absorbing compound and at least one IR reflecting component. The IR reflective properties are due to the fact that after the IR reflective component has been oriented and cured, at least a part of the oriented cholesteric polymer obtainable by monomer polymerization or at least a part of the oriented polymer has a corresponding The helical superstructure pitch of the wavelength. It is known that materials which reflect thermal radiation significantly can be used for thermal insulation, in particular for shielding thermal radiation in the wavelength range from 800 nm to 2000 nm. In this invention, curing refers to polymerization of monomers and crosslinking of five polymers. Thus, although these compositions are known to provide thermal barrier properties when cured, their solvent sensitivity, flexibility and scratch resistance properties are not ideal.

Currently, the common feature of most existing production methods of IR and UV shielding coatings for thermal insulation purposes is to apply ceramic nanofillers, hollow Mixed coatings of granules, water-based or solvent-based resins and coating additives. However, in addition to the white color and visible thickness of the coating, the lack of ability to specifically block NIR light also limits the further use of such products. In the past few decades, people have devoted themselves to the development of hybrid coating technology and its application, which has also attracted more and more attention in the field of construction and building materials.

However, as disclosed in various documents and patents, some nano-inorganic particles and hollow particles, such as silicon oxide, hollow silicon dioxide, calcium oxide, etc., do provide certain shielding and reflection effects on UV light and NIR light, and Therefore, part of the thermal energy from sunlight can be effectively isolated. However, commonly used nanomaterials for thermal insulation purposes only interact with NIR light in a limited wavelength range and also reflect part of visible light. For example, inorganic nanoparticles with strong infrared absorption ability are mainly indium-based conductive oxides, but they can only exhibit excellent shielding performance at wavelengths greater than 1500 nm.

Therefore, there is still a great need in the art for thermal barrier coatings with excellent absorbing/blocking capabilities in the near infrared (NIR) region.

Contents of the invention

As mentioned earlier, the thermal insulation performance of building windows has attracted considerable attention in energy-saving applications. The main object of the present invention is to disclose a coating composition which, when applied as a coating on a glass surface, is capable of selectively absorbing almost the entire NIR and UV of the solar spectrum while maintaining high visible light transmission. The present inventors found that by combining plasma nanoparticles or carrying out surface modification to plasma nanoparticles to form nano-microspheres with a hollow core-shell structure, and then combining them with water-based resins and the like to make coating compositions, such The obtained coating exhibits excellent properties in near-infrared/ultraviolet light blocking, uniformity, leveling, applicability and applicability, thereby obtaining the present invention.

Therefore, in a first aspect of the present invention, there is provided a nanosphere having a hollow core-shell structure, comprising an outer shell formed of silica nanoparticles and an inner shell formed of first plasmonic nanoparticles.

In a second aspect, there is provided a method for preparing the nanospheres described in the first aspect, comprising:

1) Primary coating step: coating matrix microspheres with plasma nanoparticles to form matrix@plasma nanoparticle core-shell microspheres;

2) Secondary coating step: coating the matrix@plasma nanoparticle core-shell microsphere with silica nanoparticles to form matrix@plasma nanoparticle@silica nanoparticle core-shell microsphere;

3) Calcination step: calcining at a temperature of 400° C. to 600° C. to remove the matrix microspheres and obtain nanometer microspheres with a hollow core-shell structure.

In a third aspect, a coating composition is provided, based on the total weight of the coating composition, the coating composition consists of the following components:

(A) 50% to 75% by weight of aqueous resin;

(B) 11% to 35% by weight of nanoparticle slurry, which includes the nanospheres described in the first aspect or the nanospheres prepared by the method described in the second aspect or includes at least two kinds of second plasmonic nanoparticles combinations of particles; and

(C) 4% to 15% by weight of auxiliary agents.

In a fourth aspect, there is provided a heat insulation element, the heat insulation element comprising a transparent substrate and the coating composition according to the third aspect coated on the surface of the transparent substrate.

In a fifth aspect, there is provided a method for preparing the coating composition described in the third aspect, comprising:

(1) preparing a nanoparticle slurry, wherein nanospheres or at least two second plasma nanoparticles, a dispersant, and a pH regulator are dispersed in deionized water, and the nanoparticle slurry is formed through stirring, ball milling, and ultrasonic treatment;

(2) adding the obtained nanoparticle slurry into the water-based resin, and stirring to form an initial thermal insulation coating; and

(3) Adding additives to the initial thermal insulation paint to form a final paint composition.

The present invention provides a coating composition with excellent near-infrared light/ultraviolet light blocking properties. The inventors found that by using a combination of at least two plasmonic nanoparticles capable of absorbing different wavelength ranges, or by modifying the surface of the plasmonic nanoparticles to form nanospheres with a hollow core-shell structure with silicon dioxide, the plasmonic The surface plasmon resonance effect of the bulk nanoparticle and the microsphere cavity structure make the obtained nanoparticle have excellent near-infrared blocking performance and high visible light transmittance, so that the organic-inorganic blend coating of the present invention can not only absorb almost all ultraviolet light And near-infrared light of selected wavelengths (>780nm wavelength) for heat insulation, and can maintain the visible light transmittance of the coating, has the potential to be applied to building windows and curtain walls, thus providing an ideal potential for building energy saving candidate material.

The insulating glass coated with the coating composition of the present invention can absorb not less than 98% of ultraviolet light and not less than 70%, even not less than 90% of near-infrared light, and has a visible light transmittance of at least 70% , and in turn can achieve a temperature difference between indoor and outdoor of the building of 8°C to 10°C. Therefore, the coating composition and the insulating glass of the present invention can make a significant contribution to reducing the cooling load by 10% to 30% throughout the summer in the subtropical climate zone.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

Figure 1 shows the transmittance curves of the plasmonic nanoparticles ATO, ITO and Cs _x WO ₃ in the UV-vis and IR spectral ranges.

Fig. 2 shows a flow chart of preparing nanospheres with a hollow core-shell structure according to one embodiment of the present invention.

Figure 3 shows nanospheres prepared according to one embodiment of the present invention: (a) ATO@mesoporous silica nanospheres in a ruptured state and (b) ITO@mesoporous silica in a complete state Scanning electron microscope (SEM) images of the nanospheres; and transmission of (c) ATO@mesoporous silica nanospheres in the intact state and (d) ITO@mesoporous silica nanospheres in the intact state Electron microscope (TEM) image.

Figure 4 shows a flow diagram for preparing a coating composition according to one embodiment of the present invention.

Figure 5 shows 3mm uncoated glass and coated with coating compositions 1-3 prepared according to one embodiment of the present invention (coating composition 1 comprising nanoparticle ATO, coating comprising nanoparticle ATO and ITO, respectively). Composition 2, coating composition 3) comprising nanoparticles ATO, ITO and Cs _x WO ₃ ) UV-visible light and near-infrared transmittance curves of 3 mm heat insulating glass.

Fig. 6 shows 3mm uncoated glass and is coated with the coating composition 4-5 that prepares according to one embodiment of the present invention (respectively is the coating composition 4 that comprises ATO @ mesoporous silica nanosphere, comprises The UV-visible light and near-infrared transmittance curves of 3mm heat insulating glass of the coating composition 5) of ITO@mesoporous silica nanospheres.

Figure 7 shows (a) a homemade simulated insulation test setup for testing insulating glass made in accordance with one embodiment of the present invention; and (b) 3 mm uncoated glass, (c) coated with a combination of coatings Temperature dependence of 3 mm insulating glass coated with coating composition 4, and (e) coated with coating composition 5, on irradiation time.

Figure 8 shows (a) 3 mm uncoated glass, (b) 3 mm insulating glass coated with coating composition 3 and (c) coating composition 5 at ultraviolet wavelengths of 365 nm and near infrared wavelengths, respectively It is the test result of the rejection rate of 1400nm and the transmittance in the 380-760nm region of the visible light band.

Detailed ways

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description illustrates the present invention by way of example only, and is not intended to limit the scope of the present invention, and the scope of protection of the present invention is subject to the appended claims. Moreover, those skilled in the art understand that the technical solutions of the present invention can be modified without departing from the spirit and gist of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter described herein belongs. Before describing the present invention in detail, the following definitions are provided for better understanding of the present invention.

Where a range of values is provided, such as a concentration range, percentage range, or ratio range, it is understood that unless the context clearly dictates otherwise, each unit between the upper and lower limits of the range, to the tenth of the unit of the lower limit, is understood to be Intervening values, as well as any other stated or intervening values in a stated range, are encompassed within the stated subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such embodiments are also encompassed within the subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the subject matter.

In the context of the present invention, many embodiments use the expressions "comprising", "comprising" or "consisting essentially of". The expression "comprises", "comprising" or "essentially/mainly consists of" can usually be understood as an open-ended expression, which means not only including the elements, components, components, method steps, etc. specifically listed after the expression , and also includes other elements, components, components, method steps. In addition, in this article, the expression "comprising", "comprising" or "essentially/mainly consisting of" can also be understood as a closed expression in some cases, which means that only the elements listed after the expression are included, A component, component, method step, excluding any other element, component, component, method step. At this time, the expression is equivalent to the expression "consisting of".

For a better understanding of the present teachings and without limiting the scope of the present teachings, unless otherwise indicated, all numbers expressing quantities, percentages or ratios and other numerical values used in the specification and claims are to be understood in all cases as being defined by the term "about" is modified. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that can vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

In a first aspect of the present invention, a nanosphere is provided, which has a hollow core-shell structure, including an outer shell formed of silica nanoparticles and an inner shell formed of first plasmonic nanoparticles.

In a specific embodiment, said silica nanoparticles are mesoporous silica nanoparticles.

In the context of the present invention, the term "plasmonic nanoparticles" refers to metal-containing nanoparticles capable of localized surface plasmon resonance. When sunlight is incident on a nanoparticle, if the frequency of the incident photon is close to the electronic vibration frequency of the metal particle, localized surface plasmon resonance occurs. At this point, the metal nanoparticles have a strong interaction with photons of this frequency, exhibiting selective blocking (absorption or reflection) of spectrally specific wavelength energy. The resonance wavelength of nanoparticles depends on the composition, shape, structure, size and other factors of nanoparticles, so plasmonic nanoparticles that meet the target performance can be prepared by changing the experimental parameters.

In the context of the present invention, the term "mesoporous" refers to pores with a pore diameter of 2 nm to 50 nm.

In the context of the present invention, the expressions "first" and "second" in the expressions "first plasmonic nanoparticle" and "second plasmonic nanoparticle" are for distinction purposes only and are not intended to limit any order , rank, or importance.

In yet another specific embodiment, said first plasmonic nanoparticles are indium tin oxide (ITO), antimony tin oxide (ATO), lanthanum hexaboride (LaB ₆ ), cesium tungsten bronze (Cs _x WO ₃ ) (0<x<0.33).

In a preferred embodiment, the first plasmonic nanoparticles are indium tin oxide (ITO).

In yet another specific embodiment, the nanospheres may have a size of 100 nm to 500 nm.

In a preferred embodiment, the nanospheres may have a size of 450 nanometers.

In yet another specific embodiment, the shell may have a thickness of 10 nm to 20 nm.

In a preferred embodiment, the shell may have a thickness of 15 nanometers.

In yet another specific embodiment, the inner shell may have a thickness of 15 nm to 30 nm.

In a preferred embodiment, the inner shell may have a thickness of 20 nanometers.

In a second aspect, there is provided a method for preparing the nanospheres described in the first aspect, comprising:

1) Primary coating step: coating matrix microspheres with plasma nanoparticles to form matrix@plasma nanoparticle core-shell microspheres;

2) Secondary coating step: coating the matrix@plasma nanoparticle core-shell microsphere with silica nanoparticles to form matrix@plasma nanoparticle@silica nanoparticle core-shell microsphere;

3) Calcination step: calcining at a temperature of 400° C. to 600° C. to remove the matrix microspheres and obtain nanometer microspheres with a hollow core-shell structure.

In a specific embodiment, the first coating step includes: using the matrix microsphere as a template, and coating the matrix microsphere with plasma nanoparticles by a sol-gel method using a plasma metal salt precursor. Here, the solvent-gel method is a common method well known in the art for preparing molecular to nano-substructure materials.

In a further specific embodiment, the matrix microspheres may be polymer microspheres, such as polystyrene microspheres, polyethylene microspheres, polypropylene microspheres, and polyethylene terephthalic acid microspheres, but are not limited thereto.

In a further specific embodiment, the size of the matrix microspheres is 20 nm to 200 nm, preferably 100 nm. By selecting matrix microspheres with different particle sizes (such as polystyrene microspheres) as templates, size-controllable nanospheres with a hollow core-shell structure can be prepared by a sol-gel method.

In yet another specific embodiment, the plasma metal salt precursor is a halide salt of a plasma metal, a nitrate salt, or a combination thereof. Those skilled in the art can select a suitable plasma metal salt precursor according to the plasma nanoparticles to be prepared. For example, when the first plasmonic nanoparticle is ATO, the plasmonic metal salt precursors used to prepare it may be SnCl ₂ or a hydrate thereof and SbCl ₃ or a hydrate thereof. When the first plasmonic nanoparticle is ITO, the plasmonic metal salt precursors used to prepare it may be In(NO ₃ ) ₃ or a hydrate thereof and SnCl ₄ or a hydrate thereof.

After one coating step is completed, the size of the matrix@plasma nanoparticle core-shell microsphere is 40 nm to 300 nm.

In yet another specific embodiment, the primary coating step is carried out at a pH of 7-13. In a preferred embodiment, the primary coating step is carried out under the condition of pH 10. In this step, the pH value can be adjusted with ammonia water, sodium hydroxide, and the like.

In yet another specific embodiment, the secondary coating step includes: using cetyltrimethylammonium bromide or P123 as a template agent, and using tetraethylorthosilicate to form a sol-gel method on the The matrix@plasma nanoparticle core-shell microspheres are coated twice to form matrix@plasma nanoparticle@silica nanoparticle core-shell microspheres. P123 is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

After the secondary coating step is completed, the thickness of the silicon dioxide nanoparticle layer in the matrix@plasma nanoparticle@silica nanoparticle core-shell microsphere is 10 nm to 20 nm.

In a preferred embodiment, the templating agent is removed by calcination in the calcination step.

In yet another specific embodiment, the second coating step is carried out at a pH of 7-10. In a preferred embodiment, said preferred secondary coating step is performed at pH 8. In this step, the pH value can be adjusted by adding a certain proportion of ammonia water, sodium hydroxide, etc.

In yet another specific embodiment, the temperature suitable for the calcination step can be selected based on the matrix microspheres, for example, for polystyrene microspheres, the calcination is preferably performed at a temperature of 500°C.

In a third aspect, the present invention provides a coating composition, based on the total weight of the coating composition, consisting of the following components:

(A) 50% to 75% by weight of aqueous resin;

(B) 11% to 35% by weight of nanoparticle slurry, which includes the nanospheres described in the first aspect or the nanospheres prepared by the method described in the second aspect or includes at least two kinds of second plasmonic nanoparticles combinations of particles; and

(C) 4% to 15% by weight of auxiliary agents.

In a specific embodiment, the water-based resin is selected from at least one of water-based acrylic resins, silicone-modified acrylic resins, water-based polyurethane resins and fluorocarbon resins. The water-based resin plays an important role in the film-forming ability, flexibility and adhesion of the coating.

In a preferred embodiment, the water-based acrylic resin is a water-based acrylic resin with a solid content of 20% to 60% by weight.

In yet another preferred embodiment, the silicone-modified acrylic resin is a silicone-modified acrylic resin with a solid content of 50% to 70% by weight.

In yet another preferred embodiment, the waterborne polyurethane resin is a waterborne polyurethane resin with a solid content of 30% to 50% by weight.

In yet another preferred embodiment, the fluorocarbon resin is a fluorocarbon resin with a solid content of 45% to 55% by weight.

In a more preferred embodiment, the fluorocarbon resin is a fluorocarbon resin with a fluorine content of 20% to 30% by weight.

In a specific embodiment, the second plasmonic nanoparticles are selected from the group consisting of indium tin oxide (ITO), antimony tin oxide (ATO), vanadium dioxide (VO ₂ ), vanadium pentoxide (V ₂ O ₅ ) , Cs _x WO ₃ (0<x<0.33), titanium dioxide (TiO ₂ ), La _x Eu _1-x B ₆ (0<x<1). The present invention enables the coating composition of the present invention to achieve effective absorption of selected near-infrared wavelengths by selecting metal nanoparticles capable of supporting surface plasmon resonance. This resonance is a coherent oscillation of surface-conducted electrons excited by electromagnetic radiation, through which photons of near-infrared light interact with particles much smaller than the incident wavelength, creating a plasmon that oscillates around the nanoparticle, accompanied by light absorption or reflection.

As for the combination of at least two kinds of second plasmonic nanoparticles, it may be, for example, a combination of ITO and ATO, a combination of ITO, Cs _x WO ₃ and ATO, etc., but is not limited thereto. Total blocking of certain light wavelengths is achieved by combining the resonant bands of different plasmonic nanoparticles. Figure 1 shows the transmission spectrum curves of plasmonic nanoparticles ATO, ITO and Cs _x WO ₃ in the visible and near-infrared range. It can be seen from Figure 1 that the transmission peak of Cs _x WO ₃ in the visible light region is narrow, but in the infrared region > 2000nm, the transmittance gradually increases. Although ITO has a broad transmission peak in the range of 500nm to 1500nm, its transmittance is extremely low in the infrared region > 1500nm.

In the context of the present invention, the terms "transmittance" and "transmittance" can be used interchangeably, and both are used to characterize the exiting degree of incident light after being refracted and passing through an object. Correspondingly, as used herein, the phrase "visible light transmittance" or "visible light transmittance" characterizes the light transmission property of an object by the ratio of the luminous flux of the transmitted visible light to the incident luminous flux.

In yet another specific embodiment, the second plasmonic nanoparticles have a particle size ranging from 100 nm to 400 nm.

When nanospheres with a hollow core-shell structure are used in coating compositions, since the mesoporous _SiO2 with low thermal conductivity is used as a heat-resistant shell material in the nanospheres, it can not only slow down the interaction between plasma nanoparticles in the hollow core-shell structure Heat transfer between substrates such as film, glass, and the formed shell/hollow structure is conducive to reflecting more sunlight through multiple interfaces. Therefore, compared with the combination of plasmonic nanoparticles, nanospheres with a hollow core-shell structure are obtained by surface modification of plasmonic nanoparticles, which not only retains the original optical properties of plasmonic nanoparticles, but also has a positive effect on solar energy. The blocking effect of light, especially near-infrared light in sunlight, is also significantly improved.

In yet another specific embodiment, the nanoparticle slurry is a combination of the nanospheres or the at least two second plasmonic nanoparticles dispersed in water containing a dispersant and a pH regulator, such as deionized water mixture.

In a preferred embodiment, the total weight of the nanospheres or the second plasmonic nanoparticles is 20% to 40% by weight of the total weight of the nanoparticle slurry.

In yet another specific embodiment, the dispersant is selected from polyvinylpyrrolidone, polyethylene glycol, or a combination thereof. The dispersant is used to bridge the spaces between the nanoparticles.

In yet another specific embodiment, the dispersant is 1% to 3% by weight of the total weight of the nanoparticle slurry.

In yet another specific embodiment, the pH adjuster may be selected from hydrochloric acid or ammonia solution for increasing particle stability so that the pH of the nanoparticle slurry is 7-8.

In a preferred embodiment, the pH regulator is 0.1% to 0.5% by weight of the total weight of the nanoparticle slurry.

In yet another specific embodiment, the additives may include UV absorbers, leveling agents, defoamers, and film formers.

In a preferred embodiment, the ultraviolet absorber may be a compound including a phenyl group and/or a C=N group, so as to block ultraviolet light and delay photooxidation of the coating compound. Those skilled in the art will know that most of the plasmonic nanoparticles used in the present invention do not have the ability to absorb ultraviolet light, and the coating composition of the present invention can block almost all ultraviolet light by adding a ultraviolet absorber therein, such as at least 98 % UV light.

In a more preferred embodiment, the ultraviolet absorber may be selected from at least one of benzophenones, benzotriazoles, triazines, and salicylate organic substances. The conjugated π-electron structure in the ultraviolet absorber is the reason why the substance has the ability to absorb ultraviolet rays. For example, if an ortho hydroxyl group is contained in the ultraviolet absorber, it can form a chelate ring with nitrogen or oxygen. Under the action of light, the energy absorbed by opening the chelate ring is just similar to the energy of ultraviolet light in the 290nm to 400nm band, so the purpose of absorbing ultraviolet light can be achieved.

Therefore, in a more specific embodiment, the ultraviolet absorber is bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-decanediol selected from the following formula (I): ester, benzotriazole of the following formula (II), 2-hydroxyl-4 methoxybenzophenone of the following formula (III), and N-(ethoxycarbonylphenyl) of the following formula (IV) -One or more of N'-methyl-phenylformamidines.

In yet another preferred embodiment, the leveling agent can be selected from at least one of acrylate copolymers and non-reactive polyether-modified polysiloxanes, so as to eliminate the unevenness of the coating during application. Various possible defects.

In yet another preferred embodiment, the defoamer can be selected from at least one of polysiloxane-polyether copolymer, octanol, tributyl phosphate, triphenyl phosphate and emulsified methyl siloxane Type, used to eliminate air bubbles generated during paint preparation.

In yet another preferred embodiment, the film-forming agent can be selected from at least one of glycol ether solvents, ethylene glycol ester solvents, and dipropylene glycol butyl ether, so as to promote film-forming and prevent dry coatings in Cracking and breakage during curing.

In a more preferred embodiment, the amount of the ultraviolet absorber, the leveling agent, the defoamer and the film former can be 1 to 10 weights respectively based on the total weight of the coating composition %, 0.01 to 1 wt%, 0.01 to 1 wt%, and 0.5 to 3 wt%.

By using surface-modified plasmonic nanoparticles or a combination of specific types of plasmonic nanoparticles in the coating composition of the present invention, it is not only possible to selectively absorb light in the wavelength range of the near-infrared region for thermal insulation, while maintaining The visible light transmittance of the coating, which in turn endows building windows and curtain walls with excellent thermal insulation properties.

In a fourth aspect, there is provided a heat insulation element, the heat insulation element comprising a transparent substrate and the coating composition according to the third aspect coated on the surface of the transparent substrate.

In a particular embodiment, said insulation is transparent.

In a preferred embodiment, the thermal insulation has a visible light transmittance of not less than 70%.

In a specific embodiment, the coating composition coated on the surface of the transparent substrate has a thickness of 10 microns to 15 microns.

In a specific embodiment, said thermal barrier absorbs at least 98% of ultraviolet light.

In a preferred embodiment, the thermal barrier absorbs at least 99% of ultraviolet light.

In a specific embodiment, said insulation absorbs at least 70% of near infrared light.

In a further specific embodiment, said insulation absorbs at least 80% of near infrared light.

In a still further specific embodiment, said thermal barrier absorbs about 90% of near infrared light.

In yet another embodiment, the transparent substrate is glass. The heat insulating coating coated on the surface of the heat insulating glass thus prepared can absorb not less than 98%, even not less than 99% of ultraviolet light and not less than 70%, or even 90% of near ultraviolet light in the solar spectrum. Infrared light can effectively shield the heat, thereby effectively maintaining the indoor temperature, blocking or reducing the influence of the ambient temperature, and achieving an indoor and outdoor temperature difference of 8°C to 10°C in the building. At the same time, the insulating glass has a visible light transmittance of at least 70%, and thus has the potential to be applied to building windows and curtain walls, thus providing an ideal potential candidate material for building energy saving.

As mentioned above, the heat shield is mainly selectively blocked by nanospheres with a hollow core-shell structure or a combination of at least two plasmonic nanoparticles in the coating composition of the present invention coated on the surface of the transparent substrate. /Absorbs near-infrared light in the solar spectrum to achieve thermal insulation properties. The thermal insulation of the present invention can be manufactured at relatively low cost by simple processes well known to those skilled in the art. For example, the coating composition of the present invention can be coated on a large-area substrate such as a glass substrate by a traditional coating process, and after curing, a layer of uniform thermal insulation coating with a thickness of 10 microns to 15 microns can be formed. The coating has long service life, good stability and easy maintenance, thereby obtaining economic and social benefits brought by the synergistic effect of the coating composition.

In a fifth aspect, there is provided a method for preparing the coating composition described in the third aspect, comprising:

(1) preparing a nanoparticle slurry, wherein at least one plasma nanoparticle, a dispersant, and a pH regulator are dispersed in deionized water, and the nanoparticle slurry is formed through stirring, ball milling, and ultrasonic treatment;

(2) adding the obtained nanoparticle slurry into the water-based resin, and stirring to form an initial thermal insulation coating; and

(3) Adding additives to the initial thermal insulation paint to form a final paint composition.

It is worth noting that in the process of preparing the coating composition, it is necessary to avoid directly mixing the undispersed nanoparticles with the water-based resin, because the dispersibility of the nanoparticle slurry affects the final coating composition to a large extent Therefore, the nanoparticles must be prepared into a uniformly dispersed slurry, and then mixed with resin and additives to prepare a coating.

The coating composition of the present invention has no strict regulations on the order of adding various additives, but there must be sufficient mechanical stirring time after adding each additive to ensure uniform mixing. A series of steps in the above-mentioned preparation method of the present invention are methods well known in the art for preparing coatings with good dispersibility and uniformity.

Example

In the following examples, the inventors prepared coating compositions comprising nanospheres with a hollow core-shell structure and coating compositions comprising one, two and three plasmonic nanoparticles, respectively, and tested them as Relevant insulating properties of glass coatings.

Unless otherwise specified, the test methods adopted herein are conventional methods, and unless otherwise specified, the test materials used in the following examples are purchased from conventional reagent stores. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention.

It should be noted that the terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The summary of the invention above and the detailed description below are only for the purpose of specifically illustrating the present invention, and are not intended to limit the present invention in any way. Without departing from the spirit and substance of the invention, the scope of the invention is determined by the appended claims.

Example 1: Preparation and optical property characterization of ATO@mesoporous nano-silica

Referring to Figure 2, an exemplary preparation process of hollow-structured ATO@mesoporous nano-silica is as follows:

1. Preparation of polystyrene@ATO microspheres

Weigh 10 grams of polystyrene balls, 9 grams of ammonia water and 100 milliliters of ethanol into a three-necked flask, and drop the mixed solution containing plasma metal salt precursor liquid SnCl ₂ 2H ₂ O and SbCl ₃ , ethanol and catalyst It was added to a three-necked flask, and allowed to react at 80° C. for 6 hours. After the reaction system was cooled to room temperature, the obtained microspheres were centrifuged, washed three times with ethanol, and dried at 60°C for 12 hours. After that, polystyrene@ATO microspheres could be obtained, which were collected and left to stand for the next reaction.

2. Preparation of polystyrene@ATO@nano silica microspheres

Ultrasonic disperse 10 grams of polystyrene@plasma particle microspheres obtained in the first step into a mixture of 40 milliliters of isopropanol and 10 milliliters of deionized water, and add a certain proportion of ammonia water to adjust its pH value to 8.0. Afterwards, 0.1 g of cetyltrimethylammonium bromide was added, stirred and dissolved at 25° C., and then 1 ml of tetraethyl orthosilicate was added, and the reaction was stopped after 3 hours of reaction. After drying the samples at 120°C, polystyrene@ATO@nano silica microspheres were obtained.

3. Preparation of ATO@mesoporous nano-silica hollow core-shell microspheres

The above powder is placed in a muffle furnace and calcined at 500°C to remove polystyrene and cetyltrimethylammonium bromide template agent, and then ATO@mesoporous nano-silica hollow core-shell microstructure can be obtained. ball.

4. Structural characterization of the ATO@mesoporous nano-silica hollow core-shell microspheres obtained in step 3.

Figure 3(a) shows the ATO@mesoporous silica nanospheres in a ruptured state (only for the purpose of illustrating the internal structure of the nanospheres), and the ATO@mesoporous nanospheres prepared by the above method can be observed The shell thickness of the silica hollow core-shell microspheres is clearly visible to the naked eye, and the rough surface of the shell material is covered by mesoporous spherical particles of different sizes. From Figure 3(c), it can be observed that the structure of the ATO@mesoporous nano-silica hollow core-shell microspheres prepared by the above method is hollow, and the core-shell structure is distinct.

Example 2: Preparation and optical property characterization of ITO@mesoporous nano-silica

Referring also to Figure 2, the exemplary preparation process of ITO@mesoporous nano-silica with hollow structure is as follows:

1. Preparation of polystyrene@ITO microspheres

Weigh 10 grams of polystyrene balls, 9 grams of ammonia water and 100 milliliters of ethanol into a three-necked flask, and add plasma metal salt precursor liquid In(NO ₃ ) ₃ 5H ₂ O and SnCl ₄ 5H ₂ O, The mixed solution of ethanol and catalyst was added dropwise into the three-necked flask, and allowed to react at 80° C. for 6 hours. After the reaction system was cooled to room temperature, the obtained microspheres were centrifuged, washed three times with ethanol, and dried at 60°C for 12 hours. After that, polystyrene@ITO microspheres could be obtained, which were collected and left to stand for the next reaction.

2. Preparation of polystyrene@ITO@nano silica microspheres

10 grams of polystyrene@ITO microspheres obtained in the first step were ultrasonically dispersed in a mixture of 80 milliliters of isopropanol and 10 milliliters of deionized water, and a certain proportion of ammonia water was added to adjust the pH value to 8.0. Afterwards, 0.1 g of cetyltrimethylammonium bromide was added, stirred and dissolved at 25° C., and then 1 ml of tetraethyl orthosilicate was added, and the reaction was stopped after 3 hours of reaction. After drying the sample at 120°C, polystyrene@ITO@nano silica microspheres were obtained.

3. Preparation of ITO@mesoporous nano-silica hollow core-shell microspheres

The above powder is placed in a muffle furnace and calcined at 500°C to remove polystyrene and hexadecyltrimethylammonium bromide template agent, and the ITO@mesoporous nano-silica hollow core-shell structure microstructure can be obtained. ball.

4. Structural characterization of the ITO@mesoporous nano-silica hollow core-shell microspheres obtained in step 3, and the SEM spectrum shown in Figure 3(b) and the TEM spectrum shown in Figure (d) were obtained.

From Figure 3(b), it can be observed that the morphology of the ITO@mesoporous nano-silica hollow core-shell structure microspheres prepared by the above method is a complete spherical shape, and the surface of the shell material is rough. Granular coverage. From Figure 3(d), it can be observed that the structure of the ITO@mesoporous nano-silica hollow core-shell structure microspheres presents a hollow shape, and the core-shell structure is distinct.

Embodiment 3: the preparation of coating composition

Referring to the process flow shown in FIG. 4, Exemplary Coating Compositions 1-5 of the present invention were prepared according to the concentration and volume of each component given in Table 1 below.

First, starting from step 101, the nanospheres (or a combination of plasma nanoparticles), dispersant, pH regulator and deionized water with hollow core-shell structure are mixed and stirred for 30 minutes to 1 hour to form a mixed suspension.

Then, in step 102, the mixed suspension is dispersed by grinding the suspension at a speed of 500 rpm for 24 hours and sonicating at an amplitude of 25% for 30 minutes to form a well-dispersed nanoparticle slurry.

Next, in step 103, the well-dispersed nano particle slurry is added into the water-based resin, and then fully mixed at a speed of 600 rpm to form an initial thermal insulation coating.

Finally, in step 104, coating additives are added and mixed with the initial thermal insulation coating at a speed of 1000 rpm to form a final transparent thermal insulation coating that can be applied to the surface of the glass substrate.

Embodiment 4: Visible light transmittance of coating composition

The coating composition 1-5 prepared in Example 3 was coated on the surface of the glass substrate to form a coating with a thickness of about 10-15 micrometers to obtain the corresponding insulating glass 1-5.

Ultraviolet-visible-near-infrared (UV-Vis-NIR) transmission spectrum detection of insulating glass was carried out by Hitachi UH4150. Using the integrating sphere detection mechanism, the visible-near infrared (Vis-NIR) spectrophotometer has a wavelength range of 200nm to 2600nm, see Figure 5 and Figure 6 for the results.

It can be seen from FIG. 5 that the visible light transmittance of the glass inner surface coating is not lower than 60%, no matter whether it includes only one kind of nanoparticles, or includes two or three kinds of nanoparticles. However, the coating composition 1 including only one nanoparticle of ATO still has a low transmission peak in the infrared spectrum range of 800-2600nm, while the coating compositions 2 and 3 including two or three kinds of nanoparticles have only 40% The infrared light transmittance is high, showing a weak blocking ability for the near-infrared spectrum.

As can be seen from Figure 6, the UV-visible and near-infrared transmission spectra of the 3mm insulating glass coated with the coating composition 4 prepared in Example 3 (the coating composition comprising ATO@ mesoporous silica nanospheres) show It has a rejection rate of at least 98% in the ultraviolet light band 200-400nm, has a transmittance of at least 70% in the visible light band 400-800nm, and has a rejection rate of at least 80% in the near-infrared band greater than 1200nm; coated with the embodiment The UV-visible and near-infrared transmission spectra of the coating composition 5 prepared in 3 (the coating composition comprising ITO@ mesoporous silica nanospheres) of the 3mm heat-insulating glass show that there are at least 98 % rejection rate, at least 70% transmittance in the visible light band 400-800nm, and at least 90% rejection rate in the near-infrared band greater than 1000nm, both of which show strong blocking capabilities for the near-infrared spectrum.

Example 5: Thermal insulation performance of coating composition

The heat insulation performance of the heat insulating glass 3-5 prepared in Example 4 of the present invention was studied by a self-made test device. As shown in Figure 7a, the test setup consisted of a 250W infrared lamp (wavelength range 760nm to 3000nm), an insulated chamber with two windows covered by replaceable glass, and a temperature data logger. The temperature difference between the inside and outside of the heat-insulating chamber of the uncoated glass of 3 mm and the heat-insulating glass 3-5 prepared in Example 4 were respectively detected, and the results are shown in Fig. 7(b)-7(e). At the same time, LS182 solar film tester was used to test the UV-visible light and near-infrared rejection rate of the uncoated heat-insulating glass and the heat-insulating glass 3 and 5 prepared in Example 4, and the results are shown in FIG. 8 .

As shown in Figure 7(b) and Figure 7(c), for the heat-insulated chamber (Figure 7(b)) of uncoated glass (ordinary glass), the temperature in the test chamber (3) is higher than that of the ordinary glass surface ( 1) (toward the outside of the test chamber) and the temperature of the ordinary glass surface (2) (toward the interior of the test chamber), the temperature in the test chamber (3) is the highest, about 42°C. However, for the insulating glass with coating composition 3 ( FIG. 7( c )), the temperature inside ( 3 ) of the test chamber installed with ordinary glass is much lower than that inside ( 5 ) and outside ( 4 ) of the surface of the insulating glass. And it was found by comparison that the difference between the temperature in the heat-insulated cavity of the heat-insulated glass and the temperature in the heat-insulated chamber of the uncoated glass is about 5°C, which proves that when the coating composition 3 of the present invention is coated on the surface of the glass, It can exhibit excellent heat insulation performance, can effectively maintain the indoor temperature, block or reduce the influence of ambient temperature, but the temperature of the coating itself is too high, which means that there may be a possibility of degradation of the coating during the long-term use of the heat insulating glass. risk, thereby affecting the service life of the coating.

As shown in Figure 7(d) and Figure 7(e), for the glass heat-insulated chamber (Fig. 7(d)) coated with coating composition 4, the temperature in the test chamber (3) with ordinary glass is installed with the coating The temperature of the glass-coated surface (4) (towards the outside of the test chamber) and the ordinary glass surface (5) (towards the interior of the test chamber) approached, and a comparison found that the temperature in the heat-insulated chamber of the heat-insulating glass was the same as that of the uncoated glass The temperature difference in the heat-insulating chamber is about 6°C; for the heat-insulating glass coated with coating composition 5 (Fig. 7(e)), the temperature inside (5) and outside (4) of the surface of the heat-insulating glass is unexpectedly lower than The temperature in the test chamber (3) installed with ordinary glass was compared and found that the difference between the temperature in the heat-insulated chamber with heat-insulated glass and the temperature in the heat-insulated chamber with uncoated glass was about 8.5°C. The above data prove that when the coating composition 4-5 of the present invention is coated on the glass surface, not only can it show excellent heat insulation performance, but the coating itself also has good heat dissipation performance, which makes the service life of heat insulating glass Can be greatly improved, showing excellent market application potential.

As shown in Figures 8(a)-8(c), for a common uncoated glass with a thickness of 3mm (Figure 8(a)), it has a rejection rate of 14.4% in the ultraviolet wavelength of 365nm, and a visible light wavelength of 400 -800nm has a transmittance of 88.9%, and a near-infrared wavelength of 1400nm has a rejection rate of 17.7%. Compared with 3mm uncoated glass, the 3mm insulating glass (Fig. 8(b)) coated with the coating composition 3 prepared in Example 3 has a rejection rate of 96.9% at the wavelength of ultraviolet light of 365nm, and 400% of the visible light wavelength. -800nm has a transmittance of 79.9%, and a near-infrared wavelength of 1400nm has a rejection rate of 84.2%. However, the 3mm insulating glass (Fig. 8(c)) coated with the coating composition 5 prepared in Example 3 (the coating composition comprising ITO@mesoporous silica nanospheres) has 98.4 % rejection rate, 78.1% transmittance in visible light band 400-800nm, 93.8% rejection rate in 1400nm near-infrared wavelength, the best choice among all coating compositions.

Claims (42)

1. A nano-microsphere, which has a hollow core-shell structure, comprising an outer shell formed by silicon dioxide nanoparticles and an inner shell formed by first plasma nanoparticles; wherein, the first plasma nanoparticles are oxidized Indium tin ITO, antimony tin oxide ATO, lanthanum hexaboride LaB ₆ , cesium tungsten bronze Cs _x WO ₃ , 0 < x <0.33; the thickness of the outer shell is 10 nm to 20 nm; the thickness of the inner shell is 15 nm nanometers to 30 nanometers. 2. The nanosphere according to claim 1, wherein the silica nanoparticles are mesoporous silica nanoparticles. 3. The nanosphere of claim 1, wherein the first plasmonic nanoparticle is indium tin oxide (ITO). 4. The nanosphere according to any one of claims 1-3, wherein the size of the nanosphere is 100 nm to 500 nm. 5. The nanosphere according to any one of claims 1-3, wherein the size of the nanosphere is 450 nanometers. 6. The nano-microsphere according to any one of claims 1-3, wherein the thickness of the shell is 15 nanometers. 7. The nano-microsphere according to any one of claims 1-3, wherein the thickness of the inner shell is 20 nanometers. 8. A method for preparing the nanospheres according to any one of claims 1-7, comprising: 1) Primary coating step: coating matrix microspheres with plasma nanoparticles to form matrix@plasma nanoparticle core-shell microspheres; 2) Second coating step: coating the matrix@plasma nanoparticle core-shell microsphere with silica nanoparticles to form matrix@plasma nanoparticle@silica nanoparticle core-shell microsphere; 3) Calcination step: calcining at a temperature of 400° C. to 600° C. to remove the matrix microspheres to obtain nanometer microspheres with a hollow core-shell structure. 9. The method of claim 8, wherein the calcining step is performed at a temperature of 500°C. 10. The method according to claim 8, wherein the primary coating step comprises: using the matrix microspheres as a template, using the plasma metal salt precursor to coat the matrix microspheres with plasma nanoparticles by a sol-gel method. ball. 11. The method according to claim 10, wherein the matrix microspheres are polymer microspheres selected from polystyrene microspheres, polyethylene microspheres, polypropylene microspheres, polyethylene terephthalic acid microspheres. 12. The method of claim 10, wherein the plasma metal salt precursor is a halide salt of a plasma metal, a nitrate salt, or a combination thereof. 13. The method according to any one of claims 8-12, wherein the secondary coating step comprises: using hexadecyltrimethylammonium bromide or P123 as a templating agent, using tetraorthosilicate Ethyl ester coated the matrix@plasma nanoparticle core-shell microspheres twice by sol-gel method to form matrix@plasma nanoparticle@silica nanoparticle core-shell microspheres. 14. The method of claim 13, wherein the templating agent is removed by calcination in the calcination step. 15. The method according to any one of claims 8-12, wherein the primary coating step is carried out at a pH of 7-13; the secondary coating step is carried out at a pH of 7-10 next. 16. The method according to any one of claims 8-12, wherein the primary coating step is carried out at a pH of 10. 17. The method according to any one of claims 8-12, wherein the secondary coating step is carried out at a pH of 8. 18. The method according to any one of claims 8-12, wherein the size of the matrix microspheres is 20 nm to 200 nm. 19. The method according to any one of claims 8-12, wherein the size of the matrix microspheres is 100 nanometers. 20. A coating composition, based on the total weight of the coating composition, the coating composition is composed of the following components: (A) 50% to 75% by weight of waterborne resin; (B) 11% to 35% by weight of nanoparticle slurry, which includes the nanospheres according to any one of claims 1-7 or the nanoparticle prepared by the method according to any one of claims 8-19 Microspheres; and (C) 4% to 15% by weight of auxiliary agents. 21. The coating composition according to claim 20, wherein the nanoparticle slurry is a mixture of the nanospheres dispersed in water containing a dispersant and a pH adjuster. 22. The coating composition according to claim 20 or 21, wherein the total weight of the nanospheres is 20% to 40% by weight of the total weight of the nanoparticle slurry. 23. The coating composition according to claim 20 or 21, wherein the water-based resin is at least one selected from water-based acrylic resins, silicone-modified acrylic resins, water-based polyurethane resins and fluorocarbon resins; The water-based acrylic resin is a water-based acrylic resin with a solid content of 20% by weight to 60% by weight; The silicone-modified acrylic resin is a silicone-modified acrylic resin with a solid content of 50% to 70% by weight; The water-based polyurethane resin is a water-based polyurethane resin with a solid content of 30% by weight to 50% by weight; and The fluorocarbon resin is a fluorocarbon resin with a solid content of 45% to 55% by weight. 24. The coating composition according to claim 23, wherein the fluorocarbon resin is a fluorocarbon resin having a fluorine content of 20% by weight to 30% by weight. 25. The coating composition of claim 21, wherein the dispersant is selected from polyvinylpyrrolidone, polyethylene glycol, or combinations thereof. 26. The coating composition of claim 25, wherein the dispersant is 1 to 3 wt% of the total weight of the nanoparticle slurry. 27. The coating composition of claim 21, wherein the pH adjuster is selected from hydrochloric acid or ammonia solution. 28. The coating composition of claim 27, wherein the pH adjuster is 0.1 to 0.5 wt% of the total weight of the nanoparticle slurry. 29. The coating composition of claim 20 or 21, wherein the nanoparticle slurry has a pH of 7-8. 30. The coating composition according to claim 20 or 21, wherein the auxiliary agent comprises an ultraviolet absorber, a leveling agent, a defoamer and/or a film forming agent; The ultraviolet absorber is a compound including phenyl and/or C=N groups; The leveling agent is at least one selected from acrylate copolymers and non-reactive polyether-modified polysiloxanes; The defoamer is selected from at least one of polysiloxane-polyether copolymer, octanol, tributyl phosphate, triphenyl phosphate and emulsified methyl siloxane; The film-forming agent is selected from at least one of glycol ether solvents, glycol ester solvents and dipropylene glycol butyl ether. 31. The coating composition according to claim 30, wherein the ultraviolet absorber is selected from at least one of benzophenones, benzotriazoles, triazines, and salicylate organic compounds . 32. The coating composition according to claim 30, wherein the amount of the UV absorber, the leveling agent, the defoamer and the film former is based on the total weight of the coating composition 1 to 10% by weight, 0.01 to 1% by weight, 0.01 to 1% by weight and 0.5 to 3% by weight, respectively. 33. A thermal insulation comprising a transparent substrate and the coating composition according to any one of claims 20-32 coated on the surface of the transparent substrate. 34. The insulation of claim 33, wherein the transparent substrate is glass. 35. Thermal insulation according to claim 33 or 34, wherein the thermal insulation is transparent. 36. Thermal insulation according to claim 33 or 34, wherein the thermal insulation has a visible light transmission of not less than 70%. 37. The thermal insulation according to claim 33 or 34, wherein the coating composition applied to the surface of the transparent substrate has a thickness of 10 microns to 15 microns. 38. The insulation of claim 33 or 34, wherein the insulation absorbs at least 70% of near infrared light; and the insulation absorbs at least 98% of ultraviolet light. 39. The insulation of claim 33 or 34, wherein the insulation absorbs at least 80% of near infrared light. 40. The insulation of claim 33 or 34, wherein the insulation absorbs at least 90% of near infrared light. 41. The insulation of claim 33 or 34, wherein the insulation absorbs at least 99% of ultraviolet light. 42. A method of preparing the coating composition of any one of claims 20-32, comprising: (1) Prepare nanoparticle slurry, wherein the nanospheres, dispersant, pH The conditioner is dispersed in deionized water, and the nanoparticle slurry is formed by stirring, ball milling and ultrasonic treatment; (2) adding the obtained nanoparticle slurry into the water-based resin, and stirring to form an initial heat-insulating coating; and (3) Adding additives to the initial thermal insulation paint to form a final paint composition.

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