A barium tungstate shell phase change microcapsule, a heat-insulating and light-emitting coating and a preparation method thereof

Abstract

The application discloses a barium tungstate shell layer phase change microcapsule, a heat-insulating luminescent coating and a preparation method thereof. The phase change microcapsule comprises a lauric acid-stearic acid binary eutectic phase change core material and a barium tungstate inorganic shell layer coated on the outer surface of the core material, and the mass ratio of lauric acid to stearic acid is preferably 64:36. During preparation, the barium tungstate shell layer is generated in situ on the surface of the core material through melt blending, emulsification and dispersion, barium ion adsorption and tungstate precipitation reaction. The phase change microcapsule is compounded with acrylic resin, pigment and filler and hollow glass microbeads to prepare a composite heat-insulating luminescent coating. The coating has the advantages of phase change heat absorption, anti-leakage, heat cycle stability, ultraviolet-visible light absorption and photoluminescence response, and is suitable for building energy saving and energy equipment thermal management.

Description

Technical Field

[0001] This invention belongs to the technical fields of phase change energy storage materials, functional microcapsules, building thermal insulation coatings, and intelligent thermal management materials. Specifically, it relates to a phase change microcapsule with lauric acid-stearic acid binary eutectic as the phase change core material and barium tungstate as the inorganic functional shell, as well as a composite thermal insulation and luminescent coating containing the phase change microcapsule and its preparation method. Background Technology

[0002] With the continuous increase in building energy consumption and industrial thermal management demands, functional materials with heat storage, insulation, and intelligent response capabilities have attracted widespread attention. Phase change materials (PCMs) can absorb or release latent heat during solid-liquid phase transitions, and can be used to reduce temperature fluctuations, slow down heat transfer, and improve energy efficiency. Fatty acid-based PCMs have advantages such as high phase change enthalpy, good chemical stability, relatively low cost, and no significant supercooling or phase separation, making them promising for applications in building energy conservation and passive temperature control.

[0003] However, the phase transition temperature of single fatty acids is often difficult to match with the comfortable temperature range of buildings, and problems such as liquid leakage, volume change, and insufficient thermal cycling stability are prone to occur during solid-liquid phase transitions, limiting their direct engineering applications. While constructing binary eutectic systems can regulate the phase transition temperature, it still cannot fundamentally solve the problems of leakage and limited functionality. Microencapsulation technology can form a protective shell around the phase change core material, thereby utilizing the spatial confinement effect to suppress liquid core material leakage and improve the cycling stability of the phase change material.

[0004] Existing phase change microcapsules mostly use polymer shells, which, while providing some encapsulation, still have shortcomings in terms of heat resistance, mechanical stability, ultraviolet absorption, photoluminescence, and multifunctional integration. Barium tungstate, with its excellent chemical stability, ultraviolet-visible light absorption, and photoluminescence properties, holds promise as an inorganic functional shell for phase change microcapsules, potentially solving the problems of leakage, insufficient thermal stability, and limited coating functionality in phase change materials. Summary of the Invention

[0005] The purpose of this invention is to provide a barium tungstate shell phase change microcapsule and its composite thermal insulation and luminescent coating. The lauric acid-stearic acid binary eutectic core material achieves a suitable phase change temperature and a high latent heat of phase change, while the barium tungstate inorganic shell achieves anti-leakage, thermal stability, ultraviolet absorption and photoluminescence response. Furthermore, the microcapsules are introduced into the coating system to obtain a multifunctional coating with both static thermal insulation and dynamic latent heat regulation capabilities.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: comprising a phase change core material and an inorganic shell layer covering the outer surface of the phase change core material, wherein the phase change core material is a binary eutectic phase change material formed by lauric acid and stearic acid, the inorganic shell layer is barium tungstate, the mass ratio of lauric acid to stearic acid is (60-68):(32-40), and the phase change microcapsule has phase change heat storage, anti-leakage, ultraviolet-visible light absorption and photoluminescence response properties.

[0007] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating described in this invention, the mass ratio of lauric acid to stearic acid is 64:36, and the phase change temperature of the binary eutectic phase change material is 30-38℃.

[0008] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat insulation coating described in this invention, the mass ratio of the phase change core material to the barium tungstate shell raw material is 1:(0.5-3).

[0009] This invention provides the following technical solution, which specifically includes the following steps:

[0010] S1: Lauric acid and stearic acid are melt-blended in a preset mass ratio and cooled to crystallize, thus obtaining a lauric acid-stearic acid binary eutectic phase change core material;

[0011] S2: Disperse the binary eutectic phase change core material and emulsifier in an aqueous phase to form a stable emulsion;

[0012] S3: Add barium chloride solution to the emulsion to allow barium ions to be adsorbed onto the surface of the phase change core material droplets;

[0013] S4: Continue to add sodium tungstate solution to allow barium ions to precipitate with tungstate ions, forming a barium tungstate shell in situ on the outer surface of the phase change core material.

[0014] S5: After filtration, washing and drying, barium tungstate shell phase change microcapsules are obtained.

[0015] As a preferred embodiment of the preparation method and application of barium tungstate shell phase change microcapsules and their photothermal responsive heat-insulating coating described in this invention, in step S1, the melting and blending temperature of lauric acid and stearic acid is 60-75°C, the stirring rate is 400-700 rpm, and the stirring time is 8-14 h.

[0016] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat insulation coating described in this invention, in step S2, the emulsifier is one or more of sodium dodecylbenzenesulfonate, sodium fatty alcohol ether sulfate, and alcohol ether carboxylates.

[0017] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat insulation coating described in this invention, in step S2, the emulsification stirring rate is 600-800 rpm.

[0018] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat insulation coating described in this invention, the drying time in step S5 is 24-72 h.

[0019] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating described in this invention, the composite heat-insulating and luminescent coating includes a resin matrix, pigments and fillers, hollow glass microspheres, and the barium tungstate shell phase change microcapsule as described in any one of claims 1 to 3.

[0020] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat insulation coating described in this invention, the mass fraction of the barium tungstate shell phase change microcapsule in the coating is 0-20%.

[0021] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsules and their photothermal responsive heat-insulating coating described in this invention, the composite heat-insulating and luminescent coating comprises, by weight, 30-45 parts of acrylic resin emulsion, 3-10 parts of silica, 2-8 parts of alumina, 10-20 parts of titanium dioxide, 20-35 parts of barium sulfate, 10-20 parts of hollow glass microspheres, 5-25 parts of barium tungstate shell phase change microcapsules, 1-5 parts of dispersant, 1-4 parts of defoamer, 1-4 parts of film-forming agent, 0.5-3 parts of bactericide, 0.1-1 parts of leveling agent, and an appropriate amount of water.

[0022] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive thermal insulation coating described in this invention, the coating preparation process includes the following steps:

[0023] V1: Premix the dispersant and half of the defoamer in water;

[0024] V2: Add pigments and fillers sequentially and disperse at high speed;

[0025] V3: Add hollow glass microspheres and barium tungstate shell phase change microcapsules at a low speed;

[0026] V4: Then add acrylic resin emulsion, film-forming agent, bactericide, leveling agent and half of the defoamer, and stir at low speed to obtain the coating;

[0027] V5: Apply the coating to the surface of the substrate and dry and cure it to obtain a composite heat-insulating and luminescent coating.

[0028] As a preferred embodiment of the preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive thermal insulation coating described in this invention, the barium tungstate shell phase change microcapsule or composite thermal insulation and luminescent coating is used in building energy-saving exterior walls, indoor passive temperature control, thermal management of energy equipment, solar thermal utilization, anti-counterfeiting labels or photothermal multifunctional responsive coatings.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) The present invention uses lauric acid and stearic acid to construct a binary eutectic phase change core material, which can adjust the phase change temperature to close to the indoor thermal comfort temperature range while maintaining a high phase change enthalpy, and is suitable for building energy conservation and passive temperature control scenarios.

[0031] (2) The present invention uses barium tungstate as an inorganic functional shell layer, which can effectively encapsulate fatty acid eutectic core material, suppress liquid leakage during phase change process, and improve the thermal stability and thermal cycling durability of microcapsules.

[0032] (3) The barium tungstate shell not only serves as a structural protective layer, but also endows the microcapsules with ultraviolet-visible light absorption and photoluminescence properties, transforming the phase change microcapsules from a single heat storage material into a light-thermal dual-response functional material.

[0033] (4) After the microcapsules are added to the thermal insulation coating, the coating can absorb external heat and delay the internal temperature rise while maintaining low thermal conductivity, thus achieving a combination of static insulation and dynamic thermal buffering.

[0034] (5) The process of this invention is simple, the raw materials are readily available, and the preparation conditions are mild, making it suitable for further scale-up preparation and application to building exterior walls, energy equipment shells, and multifunctional passive temperature control coatings. Attached Figure Description

[0035] Figure 1 This is a scanning electron microscope image of the phase change microcapsules prepared in Example 4 of this invention;

[0036] Figure 2 This is a transmission electron microscope image of the phase change microcapsules prepared in Example 4 of this invention;

[0037] Figure 3 These are side views of the filter paper leakage experiments used in Examples 2-6 of this invention to prepare phase change microcapsules.

[0038] Figure 4 The UV-Vis absorption test results are shown for the phase change microcapsules prepared in Examples 2-6 and the coatings prepared in Examples 7-10 of this invention.

[0039] Figure 5These are photoluminescence test images of the phase change microcapsules prepared in Examples 2-6 and the coatings prepared in Examples 7-10 of this invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments are for illustrative purposes only and should not be construed as limiting the scope of protection of the present invention. Without departing from the essence of the present invention, those skilled in the art can make equivalent substitutions or adjustments to the types of raw materials, proportions, stirring conditions, coating thickness, and application methods.

[0041] Example 1

[0042] Lauric acid and stearic acid were weighed and placed in a beaker at a mass ratio of 64:36. The beaker was placed in a 70°C constant-temperature magnetically stirred water bath and stirred continuously at 500 rpm for 12 h to allow the two fatty acids to fully mix and diffuse in the molten liquid phase. After stirring, the liquid mixture was allowed to cool naturally at room temperature and crystallize to obtain a lauric acid-stearic acid binary eutectic phase change core material.

[0043] Example 2

[0044] Take 3 g of the lauric acid-stearic acid binary eutectic phase change core material obtained in Example 1 and 0.25 g of the surfactant sodium dodecylbenzenesulfonate, and place them in a beaker equipped with deionized water. Emulsify the core material at a constant stirring rate of 700 rpm to obtain stably dispersed phase change core material droplets. Separately, completely dissolve 0.955 g of barium chloride and 1.145 g of sodium tungstate in deionized water to prepare barium salt solution and tungstate solution, respectively, with a core / shell ratio of 1:0.5.

[0045] Under continuous stirring, the barium salt solution was slowly added to the emulsion while stirring continued for 30 minutes, allowing the Ba salt solution to be dissolved. 2+ Adsorbed onto the surface of the emulsion droplets. Then, a tungstate solution was slowly added dropwise, causing WO4 to... 2- with Ba 2+ A precipitation reaction occurs, forming an inorganic barium tungstate shell in situ on the surface of the phase change core material droplets. After the reaction is complete, the mixture is filtered, washed three times with anhydrous ethanol and deionized water, and dried at room temperature for 48 h to obtain a white lauric acid-stearic acid / barium tungstate phase change microcapsule powder.

[0046] Example 3

[0047] The difference between this embodiment and Example 1 is that when the core-shell ratio is adjusted to 1:1, the amount of barium chloride added is 1.190g and the amount of sodium tungstate added is 2.289g. The rest of the preparation process is the same as in Example 1, and white lauric acid-stearic acid / barium tungstate microcapsule powder is obtained.

[0048] Example 4

[0049] The difference between this embodiment and Example 1 is that when the core-shell ratio is adjusted to 1:1.5, the amount of barium chloride added is 2.865g and the amount of sodium tungstate added is 3.434g. The rest of the preparation process is the same as in Example 1, and white lauric acid-stearic acid / barium tungstate microcapsule powder is obtained.

[0050] Example 5

[0051] The difference between this embodiment and Example 1 is that when the core-shell ratio is adjusted to 1:2, the amount of barium chloride added is 3.821g and the amount of sodium tungstate added is 4.578g. The rest of the preparation process is the same as in Example 1, and white lauric acid-stearic acid / barium tungstate microcapsule powder is obtained.

[0052] Example 6

[0053] The difference between this embodiment and Example 1 is that when the core-shell ratio is adjusted to 1:3, the amount of barium chloride added is 5.730g and the amount of sodium tungstate added is 6.867g. The rest of the preparation process is the same as in Example 1, and white lauric acid-stearic acid / barium tungstate microcapsule powder is obtained.

[0054] Example 7

[0055] By weight, 3 parts of dispersant and 1.3 parts of defoamer were added to pre-prepared deionized water, premixed at low speed and dispersed evenly. Then, 6 parts of silica, 5.2 parts of alumina, 16 parts of titanium dioxide and 28 parts of barium sulfate were slowly added in order of increasing density, and dispersed at high speed for 25 minutes.

[0056] After the pigments and fillers were evenly dispersed, the mixture was stirred at low speed, and 14.4 parts of hollow glass microspheres and 6.19 parts of barium tungstate shell phase change microcapsules obtained in Example 2 were added to prevent the hollow glass microspheres and microcapsules from breaking under high-speed shear. Then, 1.3 parts of the remaining defoamer were added, followed by 37.4 parts of acrylic resin emulsion, 2 parts of film-forming agent, 2 parts of bactericide, and 0.6 parts of leveling agent. The mixture was stirred at low speed for 20 minutes to obtain a composite thermal insulation and luminescent coating. The coating was poured into a mold, smoothed with a scraper, and dried at room temperature for 72 hours to obtain a composite thermal insulation and luminescent coating. When the phase change microcapsule components in the coating were 0, 6.19, 13.07, 16.60, and 23.52 parts, the corresponding coating numbers were named Coating A, Coating B, Coating C, Coating E, and Coating E, respectively.

[0057] Example 8

[0058] The difference between this embodiment and embodiment 7 is that the amount of barium tungstate shell phase change microcapsules obtained in embodiment 2 is adjusted to 13.07 parts, while the rest of the preparation process is the same as in embodiment 7, resulting in a composite heat-insulating and luminescent coating.

[0059] Example 9

[0060] The difference between this embodiment and embodiment 7 is that the amount of barium tungstate shell phase change microcapsules obtained in embodiment 2 is adjusted to 16.60 parts, while the rest of the preparation process is the same as in embodiment 7, resulting in a composite heat-insulating and luminescent coating.

[0061] Example 10

[0062] The difference between this embodiment and embodiment 7 is that the amount of barium tungstate shell phase change microcapsules obtained in embodiment 2 is adjusted to 23.52 parts, while the rest of the preparation process is the same as in embodiment 7, resulting in a composite heat-insulating and luminescent coating.

[0063] Comparative Example 1

[0064] By weight, 3 parts of dispersant and 1.3 parts of defoamer were added to pre-prepared deionized water, premixed at low speed and dispersed evenly. Then, 6 parts of silica, 5.2 parts of alumina, 16 parts of titanium dioxide and 28 parts of barium sulfate were slowly added in order of increasing density, and dispersed at high speed for 25 minutes.

[0065] After the pigments and fillers are evenly dispersed, the stirring speed is switched to low, and 14.4 parts of hollow glass microspheres are added to prevent them from breaking under high-speed shearing. Then, 1.3 parts of the remaining defoamer are added, followed by 37.4 parts of acrylic resin emulsion, along with 2 parts of film-forming agent, 2 parts of bactericide, and 0.6 parts of leveling agent. The mixture is stirred at low speed for 20 minutes to obtain a composite thermal insulation and luminescent coating. The coating is poured into a mold, smoothed with a scraper, and dried at room temperature for 72 hours to obtain a composite thermal insulation and luminescent coating layer.

[0066] Test Example 1

[0067] The thermal properties of the phase change microcapsules prepared in Examples 1-6 were characterized in this test. The highest phase change enthalpy of this binary eutectic core material system was 210.3 J·g. -1 The core material was encapsulated within a barium tungstate shell. The relationship between the energy storage performance of the resulting phase change microcapsules and the core / shell mass ratio is shown in Table 1. Table 1. Thermal performance test results under different core / shell mass ratios.

[0068] Table 1. Thermal performance test data under different core-shell mass ratios

[0069] serial number Phase transition temperature (°C) <![CDATA[Phase change enthalpy value (J·g -1 )]]> Packaging efficiency (%) Example 1 34.7 210.3 / Example 2 35.1 35.8 17 Example 3 36.3 58.9 28 Example 4 35.6 126.2 60 Example 5 34.3 88.3 42 Example 6 35.2 65.2 31

[0070] Experimental results show that the energy storage performance and encapsulation efficiency of phase change microcapsules exhibit a trend of first increasing and then decreasing with the change of the core / shell mass ratio. When the core / shell mass ratio is 1:1.5, the phase change microcapsules prepared in Example 4 achieve optimal thermal performance, with a phase change enthalpy of 126.2 J / g and an encapsulation efficiency of 42%. The mechanism is analyzed as follows: On the one hand, when the core material ratio is low, the energy storage capacity is limited. On the other hand, as the core material ratio increases, although the theoretical energy storage density increases, the thickness of the barium tungstate shell decreases accordingly, leading to a reduction in the mechanical strength of the microcapsule shell. Under the mechanical stirring action during the preparation process, the shell structure is prone to cracking, resulting in core material leakage and ultimately a decrease in encapsulation quality and thermal performance. Therefore, by optimizing the core / shell ratio to 1:1.5, it is possible to ensure that the barium tungstate shell forms a complete and dense coating structure, effectively improving the overall thermal performance and reliability of the microcapsules.

[0071] Test Example 2

[0072] Further microscopic morphology characterization revealed the structural advantages of the material. Figure 1 and Figure 2 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Example 4, respectively, confirm that the phase change microcapsule sample exhibits a highly regular and uniformly distributed perfect spherical geometry. The microcapsule surface displays excellent smoothness and density, and the shell-encapsulation structure is complete and continuous, without any obvious cracks, holes, or structural defects. This morphological feature not only strongly confirms the high efficiency and success rate of the microencapsulation process in this study, but also indicates that this dense core-shell architecture can significantly improve the mechanical strength and chemical stability of the microcapsules, thereby ensuring their performance reliability and durability in practical applications and long-term service.

[0073] Test Example 3

[0074] The phase change microcapsules obtained in Example 4 were tested for thermal stability and thermal cycling durability. Table 2 shows that the barium tungstate shell effectively blocks heat transfer, significantly delaying the thermal decomposition process of the microcapsules and improving the thermal stability of the material. After 500 melt-solidification thermal cycles, the microcapsules exhibited high phase change enthalpy retention, demonstrating excellent cycling durability.

[0075] In addition, the filter paper leakage test conducted in Examples 1 to 6 was performed by... Figure 3 Comparison of test data revealed that, under heating conditions, the uncoated eutectic phase change material exhibited significant wetting and diffusion on filter paper, while the phase change microcapsules encapsulated with a barium tungstate shell showed no significant core material leakage after heating. Experimental results confirm that the dense barium tungstate inorganic shell structure constructed through in-situ interfacial reaction effectively encapsulates the core material, significantly improving the microcapsule's anti-leakage performance and ensuring the structural integrity and safety of the material during long-term service.

[0076] Table 2. Thermal cycling data of phase change microcapsule samples in Example 4 after 300 cycles.

[0077] serial number Phase transition temperature (°C) <![CDATA[Phase change enthalpy value (J·g -1 )]]> Enthalpy decrease rate / % Phase change microcapsules 35.6 126.20 / Phase change microcapsules-300 35.4 108.91 13.7

[0078] Test Example 4

[0079] This test aims to evaluate the effect of the phase change microcapsules prepared in this invention on the thermal conductivity of the insulating coating. The coating samples prepared in Examples 7-10 and Comparative Example 1 were tested using a thermal conductivity meter, and the measurement results are shown in Table 3.

[0080] Table 3. Test data of thermal conductivity of coating.

[0081] serial number First measurement of W / (m·K) Second measurement W / (m·K) Third measurement W / (m·K) Average value W / (m·K) Example 7 0.091 0.091 0.090 0.091 Example 8 0.100 0.103 0.100 0.101 Example 9 0.114 0.111 0.111 0.112 Example 10 0.124 0.124 0.126 0.125 Comparative Example 1 0.084 0.086 0.085 0.085

[0082] As shown in Table 3, after the phase change microcapsules prepared in this invention are introduced into the thermal insulation coating, the overall coating still maintains a low thermal conductivity, demonstrating excellent thermal insulation potential. Analysis of Comparative Example 1 reveals that with the increase in the amount of phase change microcapsules added in Examples 7 to 10, the average thermal conductivity of the coating shows a regular, slight increase, but all remain within the excellent insulation range. This trend indicates that by precisely controlling the amount of microcapsules added, the thermal response capability and heat storage regulation function of the coating can be significantly enhanced while ensuring low thermal conductivity, thereby achieving synergistic optimization of thermal insulation and intelligent temperature control.

[0083] Test Example 5

[0084] This test aims to analyze the optical response characteristics of the phase change microcapsules and their composite coatings prepared in Examples 2 to 6 of this invention. The relevant test results are as follows: Figure 4 and Figure 5 As shown. Regarding light absorption characteristics, pure barium tungstate exhibits strong absorption primarily in the ultraviolet region, consistent with its wide bandgap semiconductor properties. The phase change microcapsule samples prepared in Examples 2-6 show optical absorption profiles essentially consistent with pure barium tungstate, with only slight fluctuations in absorption intensity. In contrast, the coating systems prepared in Examples 7-10 demonstrate significantly enhanced light-harvesting capabilities, with a substantial increase in absorption intensity across the entire ultraviolet region and a noticeable redshift at the absorption band edge. This broadened and enhanced light absorption characteristic confirms that the composite coating system constructed in this invention possesses superior solar energy harvesting capabilities, breaking through the wavelength response limitations of traditional materials.

[0085] In terms of luminescent properties, pure barium tungstate exhibits a strong broadband emission band, a characteristic primarily derived from [WO4]. 2- The tetrahedral complex has an internal self-O 2p Orbit towards W 5dThe intrinsic charge transfer transitions of the orbitals and radiative recombination induced by lattice defects (such as oxygen vacancies) are key factors. The emission spectra of the samples in Examples 4 and 7 exhibit a dramatic blue shift and narrowing. Analysis suggests this is due to other additives in the coating altering the local dielectric environment and optical field distribution of the phase change microcapsules, resulting in selective reabsorption or photon scattering effects on specific wavelengths of emitted light. The introduction of phase change microcapsules successfully breaks the single thermal functional boundary of traditional thermal insulation coatings, endowing the material with excellent photoluminescence properties.

[0086] The raw materials used in this invention are widely available, and the preparation process does not require complex equipment, making it suitable for large-scale production. The resulting barium tungstate-shell phase change microcapsules and their composite coatings possess multiple functions, including phase change heat storage, leakage resistance, thermal cycling stability, thermal insulation, ultraviolet absorption, and photoluminescence. They can be applied to energy-saving building exterior walls, indoor thermal comfort control, energy equipment casings, solar thermal management, and multifunctional intelligent coatings, showing promising industrial application prospects.

Claims

1. A method for preparing and applying a barium tungstate-shell phase change microcapsule and its photothermal responsive insulating coating, characterized in that, It includes a phase change core material and an inorganic shell layer covering the outer surface of the phase change core material, wherein the phase change core material is a binary eutectic phase change material formed by lauric acid and stearic acid, the inorganic shell layer is barium tungstate, and the mass ratio of lauric acid to stearic acid is (60-68):(32-40).

2. The preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating according to claim 1, characterized in that, The mass ratio of lauric acid to stearic acid is 64:36, and the phase transition temperature of the binary eutectic phase change material is 30-38℃.

3. The preparation method and application of a barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating according to claim 1 or 2, characterized in that, The mass ratio of the phase change core material to the barium tungstate shell material is 1:(0.5-3).

4. The preparation method and application of a barium tungstate shell phase change microcapsule and its photothermal responsive insulating coating according to any one of claims 1 to 3, characterized in that, The specific preparation process of phase change microcapsules includes the following steps: S1: Lauric acid and stearic acid are melt-blended in a preset mass ratio and cooled to crystallize, thus obtaining a lauric acid-stearic acid binary eutectic phase change core material; S2: Disperse the binary eutectic phase change core material and emulsifier in an aqueous phase to form a stable emulsion; S3: Add barium chloride solution to the emulsion to allow barium ions to be adsorbed onto the surface of the phase change core material droplets; S4: Continue to add sodium tungstate solution to allow barium ions to precipitate with tungstate ions, forming a barium tungstate shell in situ on the outer surface of the phase change core material. S5: After filtration, washing and drying, barium tungstate shell phase change microcapsules are obtained.

5. The preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating according to claim 4, characterized in that, In step S1, the melt blending temperature of lauric acid and stearic acid is 60-75°C, the stirring rate is 400-700 rpm, and the stirring time is 8-14 h.

6. The preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating according to claim 4, characterized in that, In step S2, the emulsifier is one or more of sodium dodecylbenzenesulfonate, sodium fatty alcohol ether sulfate, and alcohol ether carboxylates.

7. The preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating according to claim 4, characterized in that, In step S2, the emulsification stirring rate is 600-800 rpm.

8. The preparation method and application of the barium tungstate shell phase change microcapsule and its photothermal responsive thermal insulation coating according to claim 4, characterized in that, In step S5, the drying time is 24–72 h.

9. The preparation method and application of a barium tungstate shell phase change microcapsule and its photothermal responsive heat-insulating coating according to claims 1-8, characterized in that, The composite thermal insulation and luminescent coating comprises a resin matrix, pigments and fillers, hollow glass microspheres, and barium tungstate shell phase change microcapsules as described in any one of claims 1 to 3.

10. The composite thermal insulation and luminescent coating according to claim 9, characterized in that, The barium tungstate shell phase change microcapsules have a mass fraction of 0–20% in the coating.

11. The composite thermal insulation and luminescent coating according to claims 9-10, characterized in that, By weight, the coating comprises: 30-45 parts acrylic resin emulsion, 3-10 parts silica, 2-8 parts alumina, 10-20 parts titanium dioxide, 20-35 parts barium sulfate, 10-20 parts hollow glass microspheres, 5-25 parts barium tungstate shell phase change microcapsules, 1-5 parts dispersant, 1-4 parts defoamer, 1-4 parts film-forming agent, 0.5-3 parts bactericide, 0.1-1 parts leveling agent, and an appropriate amount of water.

12. A method for preparing the composite thermal insulation and luminescent coating as described in claim 10 or 11, characterized in that, The preparation process of the composite thermal insulation and luminescent coating includes the following steps: V1: Premix the dispersant and half of the defoamer in water; V2: Add pigments and fillers sequentially and disperse at high speed; V3: Add hollow glass microspheres and barium tungstate shell phase change microcapsules at a low speed; V4: Then add acrylic resin emulsion, film-forming agent, bactericide, leveling agent and half of the defoamer, and stir at low speed to obtain the coating; V5: Apply the coating to the surface of the substrate and dry and cure it to obtain a composite heat-insulating and luminescent coating.

13. The application of the barium tungstate shell phase change microcapsules according to any one of claims 1 to 8 or the composite thermal insulation and luminescent coating according to any one of claims 9 to 12 in building energy-saving exterior walls, indoor passive temperature control, thermal management of energy equipment, solar thermal utilization, anti-counterfeiting labels or light-heat multifunctional responsive coatings.

Images