G-coated MUF-PCM composite microcapsule, preparation method thereof and phase change energy storage water-based paint

Abstract

The invention relates to a G-coated MUF-PCM composite microcapsule and a preparation method thereof and a phase change energy storage water-based paint, and the preparation method of the capsule comprises the following steps: slowly adding an MUF prepolymer solution into a paraffin emulsion, uniformly stirring, slowly dropwise adding an acid solution to adjust the pH value of a system to be acidic, then carrying out curing reaction, cooling to room temperature, filtering, washing a filter cake to be neutral, and drying to obtain the G-coated MUF-PCM composite microcapsule. The MUF paraffin microcapsules are obtained; the preparation method comprises the following steps: pre-treating an MUF paraffin microcapsule, adding the pre-treated MUF paraffin microcapsule into a graphene dispersion liquid, stirring to enable graphene to be adsorbed on the surface of the MUF paraffin microcapsule, filtering, washing a filter cake, and drying to obtain the G-coated MUF-PCM composite microcapsule. The coating provided by the invention not only has heat insulation and heat storage functions of traditional coatings, but also can realize intelligent collaborative switching between heat conduction capability and heat radiation characteristics, so that heat dissipation is enhanced in summer, heat preservation is enhanced in winter, and annual self-adaptive energy saving is achieved.

Description

Technical Field

[0001] This invention relates to the field of energy-saving coatings technology, specifically to a G@MUF-PCM composite microcapsule, its preparation method, and a phase change energy storage waterborne coating. Background Technology

[0002] Energy-saving building coatings have shown great potential in reducing building heating and cooling loads due to their advantages such as convenient application and relatively low cost. Currently, mainstream energy-saving coatings are mainly based on the following technical approaches: I. High-reflectivity heat insulation coating These coatings primarily achieve high solar reflectivity (typically >0.80) in the visible and near-infrared bands (0.3-2.5 μm) by adding high-refractive-index white pigments (such as titanium dioxide) or functional fillers (such as hollow glass microspheres), thereby reducing solar radiation heat gain. The technology is relatively mature; for example, Chinese patent CN102702909A discloses a high-reflectivity thermal insulation coating formulation. However, this technology suffers from significant seasonal adaptability issues: while its high infrared emissivity (typically >0.90) is beneficial for heat dissipation through radiation in summer, in cold winter environments, it leads to substantial heat loss from the building's interior through radiation, hindering insulation and creating a contradiction of "suitable in summer, heat loss in winter." Its thermal performance is static and passive.

[0003] II. Phase Change Energy Storage and Temperature Regulation Coating To mitigate temperature fluctuations, researchers have introduced phase change materials (PCMs) into coating systems. PCMs (such as paraffin and fatty acids) can absorb or release a large amount of latent heat when undergoing a solid-liquid phase transition near their phase transition temperature, acting as a "thermal buffer" and slowing down indoor temperature changes. For example, the paper "Preparation and Thermal Properties of SiO2-Modified Graphene-Paraffin Composite Phase Change Emulsion" (Yang Zhitao et al., *New Energy Progress*, 2017) discloses a composite phase change emulsion that improves the thermal stability of the material. However, traditional PCMs generally have low thermal conductivity (paraffin approximately 0.2 W / (m·K)), resulting in slow heat storage / release rates, sluggish response, and difficulty in rapidly regulating instantaneous heat flow. More importantly, these coatings can only achieve "time shift" of energy and cannot intelligently manage the "transfer path" of heat.

[0004] III. Low-E Coatings This technology is primarily designed for winter insulation. By incorporating thin metal flakes (such as aluminum sheets) or functional fillers like antimony tin dioxide (ATO) into the coating, it reduces the emissivity of the coating in the far-infrared band (5-25μm, the main wavelength of thermal radiation from objects at room temperature), thereby suppressing radiative heat loss. However, it typically lacks significant solar reflectivity, and its low-emissivity characteristics are static, meaning it cannot actively adjust to enhance heat dissipation in summer, potentially exacerbating indoor overheating.

[0005] IV. High-radiation cooling coatings This is a promising new direction in recent years, aiming to achieve passive cooling by radiating heat to the low-temperature outer space by increasing the emissivity of the coating in specific infrared bands (especially the 8-13μm "atmospheric window"). For example, Chinese patent CN112480709A discloses a radiation cooling coating based on SiO2 / TiO2 composite particles. The main drawbacks of this technology are: first, its cooling efficiency is heavily dependent on clear, dry atmospheric conditions, and its performance deteriorates sharply in humid, cloudy, or polluted environments; second, its continuous high radiation characteristics cause significant heat loss in winter or cold nights, directly conflicting with the need for insulation, i.e., there is a seasonal contradiction of "advantages in summer and disadvantages in winter"; finally, its function is also static and cannot be adaptively switched.

[0006] In summary, existing energy-saving coatings based on a single technological approach all suffer from inherent drawbacks such as static functionality and limited seasonal adaptability. (1) High reflectivity coating: High reflectivity and high emissivity are tied together, making it impossible to achieve both winter insulation; (2) Phase change energy storage coating: It only achieves passive buffering, and its low thermal conductivity leads to slow response and cannot suppress radiative heat loss; (3) Low-emissivity coatings: have a single function, mainly serving as heat preservation, which may not be conducive to heat dissipation in summer; (4) High-emissivity coatings: their performance is limited by climate conditions, and their static high emissivity is in fundamental conflict with the winter insulation requirements.

[0007] Therefore, there is an urgent need in this field to break through the existing static and singular thermal management mechanisms of coatings and develop a new type of intelligent coating that can dynamically respond to changes in ambient temperature and autonomously and collaboratively adjust its thermal conduction and thermal radiation properties. An ideal technical solution should be able to: 1) efficiently reflect sunlight and enhance heat dissipation in summer; 2) effectively suppress heat loss in winter while utilizing solar energy gains; and 3) possess rapid thermal response and adaptive switching capabilities.

[0008] This invention is a solution to this common technical challenge of cross-seasonal adaptive thermal management. Summary of the Invention

[0009] Addressing the core shortcomings of existing building energy-saving coatings, as pointed out in the background art, namely "static function and limited seasonal adaptability," particularly the problems of high-reflectivity coatings with large heat loss in winter, phase change coatings with slow response and inability to manage heat flow, and low-emissivity / high-emissivity coatings that cannot meet the needs of both winter and summer, this paper provides a G@MUF-PCM composite microcapsule, its preparation method, and a phase change energy storage water-based coating. This coating not only possesses the heat insulation and heat storage functions of traditional coatings, but also achieves intelligent synergistic switching between heat conduction capacity and heat radiation characteristics, thereby enhancing heat dissipation in summer and heat preservation in winter, achieving year-round climate-adaptive energy saving.

[0010] The specific technical solution is as follows: The first aspect of this invention is to provide a method for preparing G@MUF-PCM composite microcapsules, comprising: The MUF prepolymer solution was slowly added to the paraffin emulsion and stirred until homogeneous. The pH of the system was adjusted to acidic by slowly adding acid solution, and then the curing reaction was carried out. The mixture was naturally cooled to room temperature, filtered, the filter cake was washed until neutral, and dried to obtain white powdered MUF paraffin microcapsules. The MUF paraffin microcapsules were pretreated by adding them to a graphene dispersion and stirring to allow the graphene to adsorb onto the surface of the MUF paraffin microcapsules. After filtration, the filter cake was washed and dried to obtain G@MUF-PCM composite microcapsules.

[0011] Furthermore, The preparation method of MUF prepolymer solution is as follows: urea and 37wt% formaldehyde solution are added to deionized water, stirred until dissolved, pH is adjusted to 8.0-8.5, melamine is added, and the mixture is reacted at 60±2℃ for 60-90 minutes to obtain a transparent MUF prepolymer solution, which is then cooled to room temperature for later use. The ratio of urea, formaldehyde solution, and melamine by weight is (8-10):(18-22):(0.8-1.2). The preparation method of paraffin emulsion is as follows: heating paraffin until completely melted, adding the melted paraffin, emulsifier and deionized water into a high-speed shear emulsifier to emulsify and form paraffin emulsion; The phase transition point of paraffin is 28-32℃; the ratio of paraffin to emulsifier by weight is (20-30):(0.5-1.0); the total amount of deionized water in the paraffin emulsion and MUF prepolymer solution is 60-80 parts.

[0012] Furthermore, the system pH value is 2.0-3.0; the curing reaction temperature is 55-65℃; and the curing reaction time is 2-3 hours.

[0013] Furthermore, The pretreatment method for MUF paraffin microcapsules is as follows: add MUF paraffin microcapsules and emulsifier to anhydrous ethanol, stir for 2-4 hours, filter, and dry.

[0014] The ratio of MUF paraffin microcapsules, emulsifier, and anhydrous ethanol by weight is 10:(0.1-0.3):(50-80). The dispersion method of graphene dispersion is as follows: dissolve the dispersant in deionized water, add graphene powder, disperse evenly, and obtain graphene dispersion. The proportions of dispersant, deionized water, and graphene powder by weight are (0.05-0.15):(20-30):(0.1-0.5); the number of graphene sheets is 1-10, and the sheet diameter is 1-5μm; the weight ratio of MUF paraffin microcapsules to graphene powder is 10:(0.1-0.5).

[0015] Furthermore, the stirring temperature is 40-50℃, and the stirring time is 1-2 hours.

[0016] A second aspect of the present invention is to provide a G@MUF-PCM composite microcapsule prepared according to the above preparation method, having a particle size of 2-15 μm.

[0017] A third aspect of the present invention is to provide a phase change energy storage waterborne coating, comprising, by weight: 45-55% silicone-acrylic emulsion, 10-20% G@MUF-PCM composite microcapsules, 2-5% hollow glass microspheres, 14-18.1% additives, and the balance being deionized water.

[0018] Furthermore, the silicone-acrylic emulsion is a single-component silicone-acrylic emulsion with a solid content of 48±2%.

[0019] Furthermore, by weight, the additives include 5-10% reflective agent, 0.3-0.8% thickener, 0.5-1% dispersant, 1-5% film-forming aid, 0.1-1% anti-flash rust inhibitor, 1-5% defoamer, 0.2-1% wetting and leveling agent, and 0.1-1% pH adjuster.

[0020] Furthermore, the reflector is rutile nano-titanium dioxide, the thickener is associative polyurethane, the dispersant is polycarboxylate, the film-forming aid is dodecyl alcohol ester, the flash rust inhibitor is an organozinc chelate solution, the defoamer is water-based organosilicon, the wetting and leveling agent is dimethylsiloxane, and the pH adjuster is aminomethylbenzene alcohol.

[0021] The beneficial effects of the above scheme are: This invention introduces phase change microcapsules with paraffin as the core material, endowing the coating with significant latent heat of phase change, achieving energy peak smoothing and temperature buffering. Simultaneously, addressing the shortcomings of traditional phase change materials such as low thermal conductivity and slow response, this invention constructs a highly thermally conductive pathway by coating the microcapsule surface with graphene, enabling the phase change material to rapidly absorb and release heat, thus resolving the contradiction between heat storage rate and response speed.

[0022] This invention constructs a specific core-shell structure microcapsule with a "paraffin core and graphene shell," organically integrating three functions—phase change latent heat buffering (heat storage), thermal conductivity switching (modulation), and infrared emissivity regulation (radiation control)—into a single filler. These functions are intelligently linked to temperature changes, ultimately achieving adaptive thermal management at the coating level: "increasing thermal resistance and suppressing radiation when cold, and promoting heat dissipation and rapid response when hot." This fundamentally overcomes the seasonal limitations of existing technologies and significantly improves the overall annual energy efficiency of building envelopes.

[0023] Addressing the limitation of existing technologies with fixed thermal conductivity, this invention creatively utilizes the significant volume change (expansion / contraction) accompanying the phase transition of paraffin as a driving force to mechanically alter the contact pressure and tightness between the outer graphene sheets. This achieves reversible and automatic switching (on / off ratio ≥ 2) of the overall thermal conductivity of the microcapsule between "high conductivity" and "low conductivity" states. This allows the coating to "open" the heat conduction pathways at high temperatures to accelerate heat dissipation and "close" the pathways at low temperatures to enhance heat preservation, thus realizing active management of the heat transfer path.

[0024] To address the contradiction between heat loss in high-emissivity coatings during winter and overheating in low-emissivity coatings during summer, this invention utilizes the low emissivity of graphene in the infrared band (especially the mid- and far-infrared). When the coating is in a low-temperature state requiring heat preservation, the low emissivity (ε≤0.70) of the graphene coating layer effectively suppresses radiative heat loss from the coating surface. This characteristic, combined with the aforementioned "low thermal conductivity state," works synergistically to form a thermal insulation barrier in winter. In high-temperature states requiring heat dissipation, although the low emissivity characteristic still exists, the "high thermal conductivity state" dominates. Heat is rapidly conducted to the coating surface, primarily dissipated through convection cooling paths caused by increased temperature differences, thus enhancing overall heat dissipation efficiency and overcoming the potential limitations of a fixed low emissivity on heat dissipation. Attached Figure Description

[0025] Figure 1 SEM images of the MUF paraffin microcapsules (left image) and G@MUF-PCM composite microcapsules (right image) provided in this invention; Figure 2 The DSC curves are for paraffin, MUF paraffin microcapsules, and @MUF-PCM composite microcapsules provided in this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0029] Example 1 This embodiment provides a G@MUF-PCM composite microcapsule, the preparation method of which is as follows: The MUF prepolymer solution was slowly added to the paraffin emulsion and stirred until homogeneous. The pH of the system was adjusted to 2.5 by slowly adding 0.1 mol / L hydrochloric acid solution. The system was then cured at 60℃ for 2.5 hours, allowed to cool naturally to room temperature, filtered, and the filter cake was washed three times alternately with deionized water and ethanol until neutral. After drying, white powdery MUF paraffin microcapsules (MUF-PCM) were obtained. MUF paraffin microcapsules were pretreated by adding them to a graphene dispersion and stirring at 45°C for 1.5 hours. This allowed the graphene to be adsorbed onto the surface of the MUF paraffin microcapsules via electrostatic and van der Waals forces. The mixture was then filtered, the filter cake was washed and dried to obtain graphene-coated MUF paraffin composite microcapsules (G@MUF-PCM composite microcapsules). The preparation method of MUF prepolymer solution is as follows: 9g of urea and 20g of 37wt% formaldehyde solution are added to a three-necked flask containing 50g of deionized water, heated in a water bath at 60℃, and stirred until dissolved to obtain a transparent MUF prepolymer solution, which is then cooled to 30℃ for later use; the preparation method of paraffin emulsion is as follows: 25g of n-octadecane paraffin (phase transition point ~28℃, ΔH≈245 J / g) is heated until completely melted, and the melted paraffin, 0.8g of SDBS and 20g of deionized water preheated to 60℃ are added to a high-speed shear emulsifier to emulsify and form a paraffin emulsion; The pretreatment method for MUF paraffin microcapsules is as follows: 10g of MUF paraffin microcapsules and 0.2g of SDBS are added to 60g of anhydrous ethanol, stirred, filtered, and dried. The dispersion method of graphene dispersion is as follows: Dissolve 0.08 g of dispersant cetyltrimethylammonium bromide (CTAB) in 25 g of deionized water, add 0.3 g of graphene powder (1-10 layers, 1-5 μm diameter), and disperse evenly to obtain graphene dispersion.

[0030] like Figure 1 As shown, compared to MUF paraffin microcapsules, G@MUF-PCM composite microcapsules (right figure) have graphene adsorbed on their surface.

[0031] like Figure 2 As shown, all three curves exhibit significant endothermic peaks in the 30℃ to 60℃ range, confirming that the phase transition properties of paraffin are fully preserved after microencapsulation and graphene coating. The phase transition peak position of the MUF@graphene composite material largely coincides with that of the MUF paraffin microcapsule, indicating that graphene coating did not alter its phase transition temperature. Furthermore, although its phase transition enthalpy is slightly lower than that of the pure MUF microcapsule, it remains high (greater than 130 J / g based on peak area). This demonstrates that while introducing low infrared emissivity and high thermal conductivity, the composite material effectively maintains its core function as a phase change energy storage unit, providing crucial material science evidence for the "heat storage-conduction-radiation control" triple synergy of this invention.

[0032] Example 2 This embodiment provides a G@MUF-PCM composite microcapsule, the preparation method of which is as follows: The MUF prepolymer solution was slowly added to the paraffin emulsion and stirred until homogeneous. The pH of the system was adjusted to 3.0 by slowly adding 0.1 mol / L hydrochloric acid solution. The system was then cured at 65°C for 2 hours and allowed to cool naturally to room temperature. The mixture was filtered, and the filter cake was washed three times alternately with deionized water and ethanol until neutral. After drying, white powdery MUF paraffin microcapsules (MUF-PCM) were obtained. The MUF paraffin microcapsules were pretreated by adding them to a graphene dispersion and stirring at 50°C for 1 hour. This allowed the graphene to be adsorbed onto the surface of the MUF paraffin microcapsules by electrostatic and van der Waals forces. The mixture was then filtered, the filter cake was washed and dried to obtain graphene-coated MUF paraffin composite microcapsules (G@MUF-PCM composite microcapsules). The preparation method of MUF prepolymer solution is as follows: 8g of urea and 22g of 37wt% formaldehyde solution are added to a three-necked flask containing 40g of deionized water, heated in a water bath at 60℃, and stirred until dissolved to obtain a transparent MUF prepolymer solution, which is then cooled to 30℃ for later use; the preparation method of paraffin emulsion is as follows: 30g of n-octadecane paraffin (phase transition point ~28℃, ΔH≈245 J / g) is heated until completely melted, and the melted paraffin, 1.0g of SDBS and 20g of deionized water preheated to 60℃ are added to a high-speed shear emulsifier to emulsify and form a paraffin emulsion; The pretreatment method for MUF paraffin microcapsules is as follows: 10g of MUF paraffin microcapsules and 0.3g of SDBS are added to 80g of anhydrous ethanol, stirred, filtered, and dried. The dispersion method of graphene dispersion is as follows: Dissolve 0.15 g of dispersant cetyltrimethylammonium bromide (CTAB) in 30 g of deionized water, add 0.5 g of graphene powder (1-10 layers, 1-5 μm diameter), and disperse evenly to obtain graphene dispersion.

[0033] Example 3 This embodiment provides a G@MUF-PCM composite microcapsule, the preparation method of which is as follows: The MUF prepolymer solution was slowly added to the paraffin emulsion and stirred until homogeneous. The pH of the system was adjusted to 2.0 by slowly adding 0.1 mol / L hydrochloric acid solution. The system was then cured at 55°C for 3 hours and allowed to cool naturally to room temperature. The mixture was filtered, and the filter cake was washed three times alternately with deionized water and ethanol until neutral. After drying, white powdery MUF paraffin microcapsules (MUF-PCM) were obtained. MUF paraffin microcapsules were pretreated by adding them to a graphene dispersion and stirring at 40°C for 2 hours. This allowed the graphene to be adsorbed onto the surface of the MUF paraffin microcapsules via electrostatic and van der Waals forces. The mixture was then filtered, the filter cake was washed and dried to obtain graphene-coated MUF paraffin composite microcapsules (G@MUF-PCM composite microcapsules). The preparation method of MUF prepolymer solution is as follows: 10g of urea and 18g of 37wt% formaldehyde solution are added to a three-necked flask containing 60g of deionized water, heated in a water bath at 60℃, and stirred until dissolved to obtain a transparent MUF prepolymer solution, which is then cooled to 30℃ for later use; the preparation method of paraffin emulsion is as follows: 20g of n-octadecane paraffin (phase transition point ~28℃, ΔH≈245 J / g) is heated until completely melted, and the melted paraffin, 0.5g of SDBS and 20g of deionized water preheated to 60℃ are added to a high-speed shear emulsifier to emulsify and form a paraffin emulsion; The pretreatment method for MUF paraffin microcapsules is as follows: 10g of MUF paraffin microcapsules and 0.1g of SDBS are added to 50g of anhydrous ethanol, stirred, filtered, and dried. The dispersion method of graphene dispersion is as follows: dissolve 0.05 g of dispersant cetyltrimethylammonium bromide (CTAB) in 20 g of deionized water, add 0.1 g of graphene powder (1-10 layers, 1-5 μm diameter), and disperse evenly to obtain graphene dispersion.

[0034] Testing revealed that the G@MUF-PCM composite microcapsules prepared in this invention exhibit a thermal conductivity of 0.15-0.19 W / (m·K) at 20℃ (solid paraffin) and 0.44-0.46 W / (m·K) at 35℃ (liquid paraffin), with a thermal conductivity on / off ratio (35℃ thermal conductivity / 20℃ thermal conductivity) ≥2.3. Simultaneously, its infrared emissivity (8-13.5 μm) is 0.63-0.71, significantly lower than that of uncoated MUF paraffin microcapsules (infrared emissivity >0.90). Furthermore, after 200 thermal cycles, its phase transition enthalpy retention rate is >89%, demonstrating excellent cycling stability.

[0035] In this invention, the G@MUF-PCM composite microcapsules prepared by the above method are combined with a formula amount of silicone-acrylic emulsion, hollow glass microspheres, additives and deionized water to prepare a phase change energy storage waterborne coating. The preparation method is as follows: (1) Add some water, dispersant, wetting agent, half of the defoamer and pH adjuster to the dispersion tank and mix evenly at low speed (400 rpm); (2) Slowly add nano titanium dioxide and hollow glass microspheres, increase the speed to 1200 rpm, and disperse for 20 minutes until the fineness is ≤50 μm; (3) Reduce the speed to 500 rpm, slowly add G@MUF-PCM composite microcapsules, and stir for 15 minutes to make them uniformly wetted and dispersed; (4) Add waterborne silicone-acrylic emulsion and film-forming aid, and stir at 500 rpm for 10 minutes to mix evenly; (5) Add anti-flash rust inhibitor. The thickener is pre-diluted and slowly added to adjust the viscosity to 95-105 KU. Add the remaining defoamer and stir at 300 rpm for 5 minutes; (6) filter with 200 mesh filter cloth, package, and mature at room temperature for 48 hours.

[0036] In this invention, the G@MUF-PCM composite microcapsules provided in Examples 1-3 were used to prepare the phase change energy storage waterborne coatings of Examples 4-6 using the above method. The components of the phase change energy storage waterborne coatings of Examples 4-6 are shown in the table below:

[0037] The coatings obtained from Examples 4-6 and the comparative examples were used to prepare standard boards (dry film thickness 200±10 μm), and the test results are as follows:

[0038] The test standards / methods for the above test items are as follows: ASTM E903, ASTM E408, DSC, heat flow method, heat flow method, calculated value, and DSC.

[0039] Thermal conductivity on / off ratio = High-temperature thermal conductivity / Low-temperature thermal conductivity. Wherein, high-temperature thermal conductivity refers to the coating's thermal conductivity measured above the paraffin phase transition point (e.g., 35°C), and low-temperature thermal conductivity refers to the coating's thermal conductivity measured below the paraffin phase transition point (e.g., 20°C). This ratio reflects the coating's intelligent control over its thermal conductivity as it changes with temperature.

[0040] Comparative Example Except for replacing 15.0% G@MUF-PCM with an equal amount of uncoated MUF-PCM microcapsules, the rest of the formulation, raw materials and process steps are exactly the same as in Example 4.

[0041] As shown in the table above, both the embodiments and comparative examples of this invention exhibit high reflectivity, proving that the microcapsules and graphene coating have minimal impact on the surface optical properties. However, the infrared emissivity of the coating of this invention is significantly reduced, which is directly attributed to the graphene coating layer. This characteristic is key to suppressing radiative heat loss in winter. Meanwhile, both the coating of this invention and the comparative examples retain effective phase transition enthalpy, proving that the graphene coating process does not damage the core material's heat storage capacity. Furthermore, the coating of this invention exhibits high thermal conductivity, showing a clear "switching" effect, while the comparative examples show no change. This proves the effectiveness of the "paraffin phase transition volume change driving graphene network reconstruction" mechanism, ensuring rapid heat conduction in summer.

[0042] Both the embodiments and comparative examples of this invention exhibit good cycle stability, proving that the MUF wall material encapsulation is effective.

[0043] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing G@MUF-PCM composite microcapsules, characterized in that, include: The MUF prepolymer solution was slowly added to the paraffin emulsion and stirred until homogeneous. The pH of the system was adjusted to acidic by slowly adding acid solution, and then the curing reaction was carried out. The mixture was naturally cooled to room temperature, filtered, the filter cake was washed until neutral, and dried to obtain white powdered MUF paraffin microcapsules. The MUF paraffin microcapsules were pretreated by adding them to a graphene dispersion and stirring to allow the graphene to adsorb onto the surface of the MUF paraffin microcapsules. After filtration, the filter cake was washed and dried to obtain G@MUF-PCM composite microcapsules.

2. The preparation method according to claim 1, characterized in that, The preparation method of MUF prepolymer solution is as follows: urea and 37wt% formaldehyde solution are added to deionized water, stirred until dissolved, pH is adjusted to 8.0-8.5, melamine is added, and the mixture is reacted at 60±2℃ for 60-90 minutes to obtain a transparent MUF prepolymer solution, which is then cooled to room temperature for later use. The ratio of urea, formaldehyde solution, and melamine by weight is (8-10):(18-22):(0.8-1.2). The preparation method of paraffin emulsion is as follows: heating paraffin until completely melted, adding the melted paraffin, emulsifier and deionized water into a high-speed shear emulsifier to emulsify and form paraffin emulsion; The phase transition point of paraffin is 28-32℃; the ratio of paraffin to emulsifier by weight is (20-30):(0.5-1.0); the total amount of deionized water in the paraffin emulsion and MUF prepolymer solution is 60-80 parts.

3. The preparation method according to claim 1, characterized in that, The system pH value is 2.0-3.0; the curing reaction temperature is 55-65℃, and the curing reaction time is 2-3 hours.

4. The preparation method according to claim 1, characterized in that, The pretreatment method for MUF paraffin microcapsules is as follows: add MUF paraffin microcapsules and emulsifier to anhydrous ethanol, stir, filter, and dry. The ratio of MUF paraffin microcapsules, emulsifier, and anhydrous ethanol by weight is 10:(0.1-0.3):(50-80). The dispersion method of graphene dispersion is as follows: dissolve the dispersant in deionized water, add graphene powder, disperse evenly, and obtain graphene dispersion. The proportions of dispersant, deionized water, and graphene powder by weight are (0.05-0.15):(20-30):(0.1-0.5); the number of graphene sheets is 1-10, and the sheet diameter is 1-5μm; the weight ratio of MUF paraffin microcapsules to graphene powder is 10:(0.1-0.5).

5. The preparation method according to claim 1, characterized in that, The stirring temperature is 40-50℃, and the stirring time is 1-2 hours.

6. A G@MUF-PCM composite microcapsule, characterized in that, Prepared by the method according to any one of claims 1-5.

7. A phase change energy storage water-based coating, characterized in that, The product comprises, by weight: 45-55% silicone-acrylic emulsion, 10-20% G@MUF-PCM composite microcapsules, 2-5% hollow glass microspheres, 14-18.1% additives, and the balance being deionized water, wherein the G@MUF-PCM composite microcapsules are provided by claim 6.

8. The phase change energy storage waterborne coating according to claim 7, characterized in that, The silicone-acrylic emulsion is a single-component silicone-acrylic emulsion with a solid content of 48±2%.

9. The phase change energy storage waterborne coating according to claim 7, characterized in that, The additives, by weight ratio, include 5-10% reflective agent, 0.3-0.8% thickener, 0.5-1% dispersant, 1-5% film-forming aid, 0.1-1% anti-flash rust inhibitor, 1-5% defoamer, 0.2-1% wetting and leveling agent, and 0.1-1% pH adjuster.

10. The phase change energy storage waterborne coating according to claim 9, characterized in that, The reflective agent is rutile nano-titanium dioxide, the thickener is associative polyurethane, the dispersant is polycarboxylate, the film-forming aid is dodecyl alcohol ester, the anti-flash rust inhibitor is an organozinc chelate solution, the defoamer is water-based organosilicon, the wetting and leveling agent is dimethylsiloxane, and the pH adjuster is aminomethylbenzyl alcohol.

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