A thermal insulation coating for buildings and a method for preparing the same

Abstract

This invention discloses a thermal insulation coating for buildings and its preparation method, belonging to the field of building coating technology. The coating is composed of acrylic emulsion, modified epoxy resin, rutile titanium dioxide, composite fillers, and additives. The composite filler is a mixture of modified nano-haloite, nano-silicon carbide, and hollow glass microspheres in a mass ratio of (2-3):(0.5-1):1. The modified nano-haloite is successively grafted with aminotrimethylene phosphate and tridecafluorooctyltrimethoxysilane, introducing phosphate anchoring groups and fluorosilicone hydrophobic segments onto its surface. The modified epoxy resin is a bio-based copolymer microsphere interpenetrating network modified epoxy resin. The preparation employs a gradient process combining high-speed grinding and dispersion with low-speed, gentle compounding, followed by thickening, viscosity adjustment, and curing before discharge. This coating exhibits high solar reflectance, high hemispherical emissivity, and low thermal conductivity, while also possessing excellent bonding strength, flexibility, temperature resistance, and weather resistance, making it suitable for building exterior wall thermal insulation projects.

Description

Technical Field

[0001] This invention belongs to the field of architectural coatings technology, specifically relating to a thermal insulation coating for buildings and its preparation method. Background Technology

[0002] Building energy consumption accounts for 46.7% of my country's total energy consumption. As the primary interface for heat exchange, the thermal insulation performance of building exterior walls directly determines the building's energy consumption level. Traditional building exterior wall insulation materials mainly include rock wool insulation boards, polystyrene foam insulation boards (EPS / XPS), and phenolic resin foam materials. While these materials offer some insulation, they suffer from several insurmountable drawbacks: rock wool insulation boards have poor water resistance and easily absorb water, leading to a decline in insulation performance; polystyrene foam boards are flammable and release toxic gases when exposed to open flames, posing serious safety hazards; and phenolic resin foam materials are highly acidic, prone to powdering, and lack sufficient weather resistance. Furthermore, these traditional insulation materials involve complex construction processes, poor adhesion to walls, and are prone to cracking and detachment, making them unsuitable for irregularly shaped walls and energy-saving renovations of existing buildings.

[0003] In recent years, building thermal insulation coatings have gradually become a research hotspot in the field of building energy conservation due to their advantages such as thin-layer construction, convenient construction, safety and environmental protection, and applicability to irregular structures. Thermal insulation coatings can be divided into four categories according to their insulation mechanism: barrier type, reflective type, radiative type and composite type. Barrier type thermal insulation coatings increase the thermal resistance of the coating by adding functional fillers with low thermal conductivity (such as hollow glass microspheres, expanded vermiculite, sepiolite, etc.) to slow down heat transfer; reflective type thermal insulation coatings reflect visible and near-infrared light in sunlight by adding high refractive index pigments (such as rutile titanium dioxide) to reduce heat absorption; radiative type thermal insulation coatings dissipate the absorbed heat into the environment in the form of infrared radiation by adding high emissivity fillers. However, the thermal insulation coatings currently on the market still have the following shortcomings: (1) Single insulation mechanism: Most products are designed based on only a single insulation mechanism, making it difficult to achieve multi-path synergistic insulation, and the overall insulation performance is limited. (2) Poor filler dispersibility: Hollow fillers such as hollow glass microspheres are prone to breakage during coating preparation due to improper stirring rate, resulting in a significant decrease in thermal insulation performance; at the same time, uneven dispersion of fillers will form a thermal bridge effect, affecting the overall thermal insulation effect. (3) Difficulty in achieving both mechanical properties and thermal insulation performance of the coating: Although increasing the content of functional fillers can improve thermal insulation performance, it often leads to a decrease in coating adhesion strength and a decrease in flexibility, affecting the durability and service life of the coating. (4) Difficulty in balancing cost and performance: High-performance thermal insulation fillers (such as silica aerogel) are expensive, which limits their large-scale engineering applications. Therefore, developing a building exterior wall thermal insulation coating that combines excellent thermal insulation performance, good workability and economy has important practical significance and application value. Summary of the Invention

[0004] The purpose of this invention is to provide a thermal insulation coating for buildings and its preparation method. This invention aims to simultaneously improve the coating's thermal insulation performance, adhesion strength, flexibility, and construction adaptability through organic-inorganic multi-component synergistic design, interfacial modification with functional fillers, and a gradient composite process.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A thermal insulation coating for buildings is made from the following raw materials in weight percentages: 25-35% acrylic emulsion, 10-20% modified epoxy resin, 12-18% rutile titanium dioxide, 12-25% composite filler, 1.0-2.0% film-forming aid, 1.0-2.0% propylene glycol, 0.4-0.8% dispersant, 0.1-0.3% wetting agent, 0.2-0.5% defoamer, 0.2-0.5% leveling agent, 0.5-1.0% thickener, 0.05-0.15% silane coupling agent, 0.1-0.3% pH adjuster, and the balance being deionized water; the composite filler is composed of modified nano halloysite, nano silicon carbide, and hollow glass microspheres in a mass ratio of (2-3):(0.5-1):1.

[0006] Preferably, the modified epoxy resin is prepared by the following method: (1) Add N-phenylmaleimide and limonene to butanone solvent and stir until completely dissolved. Then add n-heptane and azobisisobutyronitrile. React at 70-80℃ for 6-8 hours under N2 environment. After the reaction is completed, centrifuge and separate. Wash the solid product with mixed solvent and diethyl ether in sequence. Vacuum dry to obtain bio-based limonene copolymer microspheres. (2) Dissolve KH-550 silane coupling agent in anhydrous ethanol / water mixed solvent to prepare a solution with a mass concentration of 2-5wt%, adjust the pH to 4-5 with acetic acid, stir and hydrolyze for 30 min, add the product obtained in step (1) to the above hydrolysate, stir and react at 50-70℃ for 2-4 h, after the reaction is completed, centrifuge and separate, wash the product repeatedly with anhydrous ethanol 3-5 times and dry to obtain silanized copolymer microspheres; (3) Add epoxy resin E-51 and reactive diluent AGE to the reactor, stir evenly, then add silane coupling agent KH560, heat to 50-80℃, react for 1-3h, then add the silanized copolymer microspheres obtained in step (2), continue stirring and reacting for 30-40min, cool to room temperature, and discharge the material.

[0007] Preferably, in step (1), the ratio of N-phenylmaleimide, limonene and butanone solvent is 1 mmol: 1 mmol: 10 mL; the volume ratio of butanone to n-heptane is 1:2; and the amount of azobisisobutyronitrile is 2-3% of the total mass of the monomers.

[0008] Preferably, the mixed solvent in step (1) is composed of butanone / n-heptane in a volume ratio of 1:2.

[0009] Preferably, in step (2), the volume ratio of anhydrous ethanol / water in the mixed solvent is 9:1; and the ratio of the product obtained in step (1) to the silane hydrolysate is 1g:10mL.

[0010] Preferably, in step (3), the amount of reactive diluent AGE is 10-20% of the mass of epoxy resin E-51; and the amount of silane coupling agent KH560 is 1-2% of the mass of epoxy resin E-51.

[0011] Preferably, the modified nano-haloite is prepared by the following method: a. Dry halloysite nanotubes at 105-110℃ for 2h to remove interlayer adsorbed water and impurities, and obtain pretreated halloysite nanotubes; b. Add 2-4 g of aminotrimethylene phosphoric acid to 200 mL of deionized water, stir well, and adjust the pH of the solution to 4-5; add 6 g of pretreated nano halloysite to the solution and stir ultrasonically until homogeneous; heat and stir in an oil bath at 90-100 ℃ for 6-10 h; after the reaction is complete, cool to room temperature, place in a vacuum container for vacuum extraction, filter and separate, take the solid product, wash with deionized water, and dry in a vacuum oven to obtain surface-grafted modified nano halloysite; c. Disperse the product obtained in step b in 200 mL of anhydrous ethanol / water mixed solvent, wherein the volume ratio of the two is 9:1, sonicate, adjust the pH to 8-9, slowly add 2-5 g of tridecafluorooctyltrimethoxysilane, stir the reaction at 50-60℃ for 4-8 h, after the reaction is completed, centrifuge, wash with anhydrous ethanol 3-5 times, vacuum dry and grind to obtain modified nano halloysite.

[0012] Preferably, the film-forming aid is decyl alcohol ester; the dispersant is sodium polyacrylate SN5040 or ammonium acrylate 5027; the wetting agent is an alkyl polyoxyethylene ether wetting agent; the defoamer is a polyether-modified silicone defoamer; the leveling agent is an acrylate leveling agent; the thickener is carboxymethyl hydroxyethyl cellulose; and the pH adjuster is ammonia.

[0013] Preferably, the nano-silicon carbide has a particle size of 30–80 nm; the hollow glass microspheres have a particle size range of 30–100 μm, a bulk density of 0.15–0.35 g / cm³, and a wall thickness of 0.8–2.0 μm.

[0014] The present invention also provides a method for preparing the above-mentioned thermal insulation coating for buildings, comprising the following steps: S1. Premixed additive phase: Add all deionized water, propylene glycol, dispersant, wetting agent and pH adjuster to the stirred tank, stir at low speed of 200-300 r / min for 5-10 min, and mix evenly to obtain the additive base liquid; S2. High-speed grinding and dispersion: Add rutile titanium dioxide, modified nano halloysite, and nano silicon carbide to the additive base liquid in batches, increase the rotation speed to 1200-1500 r / min and disperse at high speed for 25-40 min, grind until the slurry fineness is ≤30μm, add half of the defoamer in batches during the process to eliminate grinding bubbles; S3. Low-temperature composite mixing: Reduce the stirring speed to 400-600 r / min, slowly add acrylic emulsion and modified epoxy resin, stir for 10-15 min to mix into resin slurry; then slowly add hollow glass microspheres, continue to stir at low speed for 8-12 min, control the stirring shear strength throughout the process to avoid the hollow glass microspheres from breaking. S4. Compounding and blending of additives: Add the remaining defoamer, film-forming aid, silane coupling agent and leveling agent in sequence, and stir at 400-600 r / min for 10-15 min; S5. Thickening and viscosity adjustment and curing: Add thickener in batches, stir for 15-25 minutes to adjust the viscosity of the system for construction, test the pH value and fine-tune it to 8.0-9.0 with pH adjuster; cure at room temperature and low speed for 30-60 minutes, filter and discharge to obtain the building thermal insulation coating.

[0015] Preferably, the silane coupling agent in step S4 is KH550 or KH560.

[0016] This invention specifically modifies the main film-forming component, epoxy resin, to obtain a modified epoxy resin with both flexible segments and a rigid copolymer microsphere interpenetrating network structure. This modified resin not only imparts excellent flexibility and impact resistance to the coating, but also, through the silane groups on the microsphere surface, significantly enhances the interfacial bonding force between the organic resin matrix and inorganic functional fillers (titanium dioxide, halloysite, silicon carbide, etc.). Thus, without relying on external plasticizers, it effectively solves the problems of coating embrittlement and decreased adhesive strength caused by the addition of large amounts of inorganic fillers.

[0017] The composite filler of this invention is composed of modified nano-haloite, nano-silicon carbide, and hollow glass microspheres in a specific mass ratio of (2-3):(0.5-1):1. The modified nano-haloite is successively modified by grafting with aminotrimethylene phosphate and fluorinating with tridecafluorooctyltrimethoxysilane, simultaneously introducing hydrophilic phosphate anchoring groups and hydrophobic low surface energy fluorosilicone groups onto its surface. During coating preparation, the phosphate groups can form strong chemical bonds with the active hydroxyl groups on the surfaces of rutile titanium dioxide, nano-silicon carbide, and hollow glass microspheres, significantly improving the overall dispersion stability of the filler and effectively eliminating the thermal bridging effect caused by the agglomeration of inorganic particles. Meanwhile, the fluorosilicone segments endow the coating surface with hydrophobic self-cleaning ability; rainwater can wash away surface dust, preventing a decrease in solar reflectivity due to dust accumulation, thus maintaining excellent thermal insulation performance over a long period.

[0018] The nano-silicon carbide in this invention's composite filler possesses high infrared emissivity, enabling it to radiate away the heat absorbed by the coating, thus overcoming the limitation of single-barrier coatings relying solely on air for heat insulation. The hollow glass microspheres, with their low packing density and thin-walled hollow structure, not only provide low thermal barrier properties but also, thanks to the tubular geometric support effect of nano-haloysite, are less prone to breakage under pressure during low-to-medium speed mixing and compounding. This effectively solves the defects of traditional hollow fillers, such as easy breakage and significant attenuation of thermal insulation performance during high-speed dispersion. When these three components are blended in a specific ratio, a multi-level synergistic three-dimensional thermal insulation network of barrier, reflection, and radiation can be formed within the coating. Simultaneously, the bifunctional group design on the halloysite surface achieves self-assembly-based interfacial reinforcement between the fillers.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes a composite filler formed by the precise gradation of modified halloysite, high-infrared-emissivity silicon carbide, and low-thermal-conductivity hollow glass microspheres to create a reflective-blocking-radiative thermal insulation network system within the coating. Simultaneously, the fluorosilicone segments impart excellent hydrophobic and self-cleaning properties to the coating surface, allowing rainwater to remove accumulated dust. This effectively solves the defect of traditional thermal insulation coatings where reflectivity decreases due to long-term exposure to dust accumulation. Ultimately, this results in a multi-mechanism synergistic thermal insulation and long-lasting self-cleaning effect, leading to excellent and durable overall thermal insulation performance.

[0020] 2. This invention also significantly improves the chemical bonding and physical anchoring of the organic-inorganic interface by modifying the epoxy resin with a bio-based copolymer microsphere interpenetrating network and introducing phosphate anchoring groups and fluorosilicone hydrophobic segments onto the surface of halloysite nanotubes. This not only solves the problems of easy cracking and poor adhesion of the coating under high filler content, ensuring that the coating's bonding strength is stably maintained above 1.0 MPa, but also endows the coating with excellent flexibility (bending diameter ≤3 mm) and super weather resistance, waterproofing, and impermeability, greatly extending the service life of the exterior wall coating, significantly improving interfacial compatibility, and significantly enhancing mechanical and durability properties.

[0021] 3. The preparation process of this invention is mild and controllable, the raw materials are widely available, and the cost is controllable. The coating obtained by this invention is suitable for energy-saving protection of building exterior walls. While giving the coating excellent reflective heat insulation performance and ultra-low thermal conductivity, it further achieves high bonding strength, excellent temperature cycling resistance, impact resistance and crack resistance through organic-inorganic interface strengthening and the introduction of flexible segments. Moreover, the process window is wide and it is suitable for large-scale production and application promotion. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0023] Example 1 A thermal insulation coating for buildings is made from the following raw materials in weight percentages: 25% acrylic emulsion, 10% modified epoxy resin, 12% rutile titanium dioxide, 25% composite filler (of which the mass ratio of modified nano halloysite, nano silicon carbide, and hollow glass microspheres is 2:0.5:1), 1.0% film-forming aid (alcohol ester dodecyl), 1.0% propylene glycol, 0.4% dispersant (sodium polyacrylate SN5040), 0.1% wetting agent (alkyl polyoxyethylene ether), 0.2% defoamer (polyether modified organosilicon), 0.2% leveling agent (acrylate), 0.5% thickener (carboxymethyl hydroxyethyl cellulose), 0.05% silane coupling agent (KH550), 0.1% pH adjuster (ammonia water), and the balance being deionized water (to bring the total to 100%).

[0024] The preparation method of the modified epoxy resin is as follows: (1) 10 mmol N-phenylmaleimide and 10 mmol limonene were added to 100 mL of butanone solvent and stirred until completely dissolved. Then, 200 mL of n-heptane and 2% azobisisobutyronitrile (AIBN) were added. The mixture was reacted at 70 °C for 8 h under N2 environment. After the reaction was completed, the solid product was separated by centrifugation. The solid product was washed with a mixture of butanone / n-heptane (volume ratio 1:2) and diethyl ether, and then dried under vacuum to obtain bio-based limonene copolymer microspheres. (2) Dissolve KH-550 silane coupling agent in a mixed solvent of anhydrous ethanol / water (volume ratio 9:1) to prepare a solution with a mass concentration of 2wt%. Adjust the pH to 4 with acetic acid and stir for 30 min to hydrolyze. Add the product obtained in step (1) to the above hydrolysate at a ratio of 1g:10mL. Stir and react at 50℃ for 4 h. After the reaction is completed, centrifuge and separate the product. Wash the product repeatedly with anhydrous ethanol 3 times and dry to obtain silanized copolymer microspheres. (3) Add epoxy resin E-51 and 10% of its mass of reactive diluent AGE into the reactor and stir evenly. Then add 1% of the mass of epoxy resin E-51 of silane coupling agent KH560, heat to 50°C, react for 3 hours, and then add the silanized copolymer microspheres obtained in step (2) (the amount added is 20% of the mass of epoxy resin E-51). Continue stirring and react for 30 minutes, cool to room temperature and discharge to obtain the product.

[0025] The method for preparing the modified nano-haloysite is as follows: (1) Dry halloysite nanotubes at 105℃ for 2h to obtain pretreated halloysite; (2) Add 2g of aminotrimethylene phosphoric acid to 200mL of deionized water, stir evenly, adjust the pH to 4, add 6g of pretreated halloysite, stir evenly by ultrasonication, heat and stir in an oil bath at 90℃ for 10h, cool, vacuum extract, filter, wash with deionized water, and vacuum dry to obtain surface-grafted modified halloysite. (3) Disperse the above product in 200 mL of anhydrous ethanol / water (volume ratio 9:1), sonicate, adjust pH to 8, slowly add 2 g of tridecafluorooctyltrimethoxysilane, stir at 50 °C for 8 h, centrifuge, wash 3 times with anhydrous ethanol, vacuum dry and grind to obtain the product.

[0026] The preparation method of the above coating is as follows: The preparation method includes the following steps: S1. Premixed additive phase: Add all deionized water, propylene glycol, dispersant, wetting agent, and pH adjuster to the stirred tank, and stir at 200 r / min for 10 min to mix evenly; S2. High-speed grinding and dispersion: Add rutile titanium dioxide, modified nano halloysite, and nano silicon carbide in batches, increase the speed to 1200r / min for high-speed dispersion for 40min, grind to fineness ≤30μm, and add half of the defoamer in batches during the process; S3. Low-temperature compounding: Reduce the rotation speed to 400 r / min, slowly add acrylic emulsion and modified epoxy resin, and stir for 15 min; then slowly add hollow glass microspheres and continue stirring at low speed for 12 min. S4. Compounding and blending of additives: Add the remaining defoamer, film-forming aid, silane coupling agent and leveling agent in sequence, and stir at 400 r / min for 15 min; S5. Thickening and viscosity adjustment and maturation: Add thickener in batches, stir for 25 minutes to adjust viscosity, test pH and fine-tune to 8.0; mature at room temperature and low speed for 60 minutes, then filter and discharge.

[0027] Example 2 A thermal insulation coating for buildings is made from the following raw materials in weight percentages: 30% acrylic emulsion, 15% modified epoxy resin, 15% rutile titanium dioxide, 18% composite filler (modified nano halloysite, nano silicon carbide, and hollow glass microspheres in a mass ratio of 2.5:0.8:1), 1.5% film-forming aid (alcohol ester dodecyl), 1.5% propylene glycol, 0.6% dispersant (ammonium acrylate 5027), 0.2% wetting agent (alkyl polyoxyethylene ether), 0.35% defoamer (polyether modified organosilicon), 0.35% leveling agent (acrylate), 0.8% thickener (carboxymethyl hydroxyethyl cellulose), 0.10% silane coupling agent (KH550), 0.2% pH adjuster (ammonia water), and the balance being deionized water.

[0028] The preparation method of the modified epoxy resin is as follows: (1) 10 mmol N-phenylmaleimide and 10 mmol limonene were added to 100 mL of butanone solvent and stirred until completely dissolved. Then, 200 mL of n-heptane and 2% azobisisobutyronitrile (AIBN) were added. The mixture was reacted at 75 °C for 7 h under N2 environment. After the reaction was completed, the solid product was separated by centrifugation. The solid product was washed with butanone / n-heptane (volume ratio 1:2) mixed solvent and diethyl ether in sequence. The product was then dried under vacuum to obtain bio-based limonene copolymer microspheres. (2) Dissolve KH-550 silane coupling agent in a mixed solvent of anhydrous ethanol / water (volume ratio 9:1) to prepare a solution with a mass concentration of 3.5wt%. Adjust the pH to 4.5 with acetic acid and stir for 30 min to hydrolyze. Add the product obtained in step (1) to the above hydrolysate at a ratio of 1g:10mL. Stir and react at 60℃ for 3 h. After the reaction is completed, centrifuge and separate the product. Wash the product repeatedly with anhydrous ethanol 3 times and dry to obtain silanized copolymer microspheres. (3) Add epoxy resin E-51 and AGE (15% of its mass) to the reactor and stir evenly. Then add silane coupling agent KH560 (1.5% of the mass of epoxy resin E-51), heat to 65°C, react for 2 hours, and then add the silanized copolymer microspheres obtained in step (2) (30% of the mass of epoxy resin E-51). Continue stirring and react for 30 minutes, cool to room temperature and discharge to obtain the product.

[0029] The method for preparing the modified nano-haloysite is as follows: (1) Dry halloysite nanotubes at 105℃ for 2h to obtain pretreated halloysite; (2) Add 3g of aminotrimethylene phosphoric acid to 200mL of deionized water, stir evenly, adjust the pH to 4.5, add 6g of pretreated halloysite, stir evenly by ultrasonication, heat and stir in an oil bath at 95℃ for 8h, cool, vacuum extract, filter, wash with deionized water, and vacuum dry to obtain surface-grafted modified halloysite. (3) Disperse the above product in 200 mL of anhydrous ethanol / water (volume ratio 9:1), sonicate, adjust pH to 8, slowly add 3.5 g of tridecafluorooctyltrimethoxysilane, stir at 55 °C for 6 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry and grind to obtain the product.

[0030] The preparation method of the above coating is as follows: The preparation method includes the following steps: S1. Premixed additive phase: Add all deionized water, propylene glycol, dispersant, wetting agent, and pH adjuster to the stirred tank, and stir at 250 r / min for 8 min to mix evenly; S2. High-speed grinding and dispersion: Add rutile titanium dioxide, modified nano halloysite, and nano silicon carbide in batches, increase the rotation speed to 1350r / min and disperse at high speed for 35min, grind until the fineness is ≤30μm, and add half of the defoamer in batches during the process; S3. Low-temperature compounding: Reduce the rotation speed to 500 r / min, slowly add acrylic emulsion and modified epoxy resin, and stir for 12 min; then slowly add hollow glass microspheres and continue stirring at low speed for 10 min. S4. Compounding and blending of additives: Add the remaining defoamer, film-forming aid, silane coupling agent and leveling agent in sequence, and stir at 500 r / min for 12 min; S5. Thickening and viscosity adjustment and maturation: Add thickener in batches, stir for 20 minutes to adjust viscosity, test pH and fine-tune to 8.5; mature at room temperature and low speed for 45 minutes, then filter and discharge.

[0031] Example 3 A thermal insulation coating for buildings is made from the following raw materials in weight percentages: 35% acrylic emulsion, 20% modified epoxy resin, 18% rutile titanium dioxide, 12% composite filler (modified nano halloysite, nano silicon carbide, and hollow glass microspheres in a mass ratio of 3:1:1), 2.0% film-forming aid (alcohol ester dodecyl), 2.0% propylene glycol, 0.8% dispersant (sodium polyacrylate SN5040), 0.3% wetting agent (alkyl polyoxyethylene ether), 0.5% defoamer (polyether modified organosilicon), 0.5% leveling agent (acrylate), 1.0% thickener (carboxymethyl hydroxyethyl cellulose), 0.15% silane coupling agent (KH550), 0.3% pH adjuster (ammonia), and the balance being deionized water.

[0032] The preparation method of the modified epoxy resin is as follows: (1) 10 mmol N-phenylmaleimide and 10 mmol limonene were added to 100 mL of butanone solvent and stirred until completely dissolved. Then, 200 mL of n-heptane and 3% azobisisobutyronitrile (AIBN) were added. The mixture was reacted at 80 °C for 6 h under N2 environment. After the reaction was completed, the solid product was separated by centrifugation. The solid product was washed with a mixture of butanone / n-heptane (volume ratio 1:2) and diethyl ether in sequence. The product was then dried under vacuum to obtain bio-based limonene copolymer microspheres. (2) Dissolve KH-550 silane coupling agent in a mixed solvent of anhydrous ethanol / water (volume ratio 9:1) to prepare a solution with a mass concentration of 5wt%. Adjust the pH to 5 with acetic acid and stir for 30 min to hydrolyze. Add the product obtained in step (1) to the above hydrolysate at a ratio of 1g:10mL. Stir and react at 60℃ for 3 h. After the reaction is completed, centrifuge and separate the product. Wash the product repeatedly with anhydrous ethanol 3 times and dry to obtain silanized copolymer microspheres. (3) Add epoxy resin E-51 and AGE (15% of its mass) to the reactor and stir evenly. Then add silane coupling agent KH560 (2% of the mass of epoxy resin E-51), heat to 65°C, react for 2 hours, and then add the silanized copolymer microspheres obtained in step (2) (20% of the mass of epoxy resin E-51). Continue stirring and react for 30 minutes, cool to room temperature and discharge to obtain the product.

[0033] The method for preparing the modified nano-haloysite is as follows: (1) Dry halloysite nanotubes at 105℃ for 2h to obtain pretreated halloysite; (2) Add 4g of aminotrimethylene phosphoric acid to 200mL of deionized water, stir evenly, adjust the pH to 5, add 6g of pretreated halloysite, stir evenly by ultrasonication, heat and stir in an oil bath at 100℃ for 6h, cool, vacuum extract, filter, wash with deionized water, and vacuum dry to obtain surface-grafted modified halloysite. (3) Disperse the above product in 200 mL of anhydrous ethanol / water (volume ratio 9:1), sonicate, adjust pH to 8, slowly add 3.5 g of tridecafluorooctyltrimethoxysilane, stir at 55 °C for 6 h, centrifuge, wash 3 times with anhydrous ethanol, and vacuum dry and grind to obtain the product.

[0034] The preparation method of the above coating is as follows: The preparation method includes the following steps: S1. Premixed additive phase: Add all deionized water, propylene glycol, dispersant, wetting agent, and pH adjuster to the stirred tank, and stir at 300 r / min for 5 min to mix evenly; S2. High-speed grinding and dispersion: Add rutile titanium dioxide, modified nano halloysite, and nano silicon carbide in batches, increase the speed to 1500r / min and disperse at high speed for 25min, grind to fineness ≤30μm, and add half of the defoamer in batches during the process; S3. Low-temperature compounding: Reduce the rotation speed to 600 r / min, slowly add acrylic emulsion and modified epoxy resin, and stir for 10 min; then slowly add hollow glass microspheres and continue stirring at low speed for 8 min. S4. Compounding and blending of additives: Add the remaining defoamer, film-forming aid, silane coupling agent and leveling agent in sequence, and stir at 600 r / min for 10 min; S5. Thickening and viscosity adjustment and maturation: Add thickener in batches, stir for 15 minutes to adjust viscosity, test pH and fine-tune to 9.0; mature at room temperature and low speed for 30 minutes, then filter and discharge.

[0035] Comparative Example 1 The only difference from Example 1 is that unmodified nano-haloite is used instead of modified nano-haloite in the composite filler, while the other components and preparation methods are the same.

[0036] Comparative Example 2 The only difference from Example 1 is that ordinary epoxy resin E-51 is used instead of modified epoxy resin, while the other components and preparation methods are the same.

[0037] Comparative Example 3 The only difference from Example 1 is that unmodified nano-haloite was used instead of modified nano-haloite in the composite filler, and ordinary epoxy resin E-51 was used instead of modified epoxy resin. All other components and preparation methods are the same.

[0038] Comparative Example 4 The only difference from Example 1 is that the composite filler does not contain modified nano halloysite, but is composed only of nano silicon carbide and hollow glass microspheres in a mass ratio of 0.5:1. The other components and preparation methods are the same.

[0039] Comparative Example 5 The only difference from Example 1 is that the composite filler does not contain nano-silicon carbide, but is composed of modified nano-haloite and hollow glass microspheres in a 2:1 mass ratio. The other components and preparation methods are the same.

[0040] Comparative Example 6 The only difference from Example 1 is that the composite filler does not contain hollow glass microspheres, but is composed only of modified nano halloysite and nano silicon carbide in a mass ratio of 2:0.5. The other components and preparation methods are the same.

[0041] Comparative Example 7 The only difference from Example 1 is that the mass ratio of modified nano halloysite, nano silicon carbide, and hollow glass microspheres in the composite filler is 1:1:1, while the other components and preparation methods are the same.

[0042] The coatings prepared in Examples 1-3 and Comparative Examples 1-7 were tested for performance according to GB / T 25261-2018 "Reflective Thermal Insulation Coatings for Buildings" and JG / T 235-2014 "Reflective Thermal Insulation Coatings for Buildings" standards. The results are shown in Table 1.

[0043] The test methods are as follows: solar reflectance is tested according to the method specified in GB / T 25261-2018; hemispherical emissivity is tested using the radiometer method according to JG / T 235-2014; thermal conductivity is tested using the heat flow meter method according to GB / T 10295-2008; bond strength is tested according to GB / T 5210-2006; flexibility is tested according to GB / T 1731-2020 (bending diameter around the axis); temperature change resistance is tested according to JG / T 25-2017; water resistance is tested according to GB / T 1733-1993; artificial weathering resistance is tested according to GB / T 23987-2009; and workability is tested according to the method specified in GB / T 25261-2018.

[0044] Table 1 Performance Test Results Table 1 Performance Test Results As can be seen from the results in Table 1 above, Examples 1 to 3 outperform the comparative examples in all performance indicators, especially in terms of solar reflectance, hemispherical emissivity, and thermal conductivity, demonstrating the significant advantages of the technical solution of this invention. Specifically, the solar reflectance of Examples 1 to 3 all reach above 0.91, while that of the comparative examples is generally below 0.82; the hemispherical emissivity is not lower than 0.90; and the thermal conductivity is lower than 0.045 W / (m·K). Furthermore, the overall performance, including bonding strength, flexibility, resistance to temperature changes, water resistance, and resistance to artificial weathering, is also significantly better than that of the comparative examples, indicating that the coating of this invention maintains excellent thermal insulation while also possessing good mechanical properties and durability. In addition, Examples 1-3 showed no abnormalities in the temperature change resistance and water resistance tests, while the comparative examples exhibited varying degrees of cracking, blistering, or loss of gloss, further verifying the reliability and long-term stability of the coating of this invention in practical applications. In summary, Examples 1 to 3 demonstrate significant advantages in all key performance aspects, fully proving the effectiveness of the technical solution of this invention in improving the overall performance of the coating. This comparative result clearly demonstrates that the present invention achieves a synergistic improvement in thermal insulation performance and physical and mechanical properties by optimizing the components and proportions, providing an important technical reference for the development of similar products.

[0045] Comparative Example 1, using unmodified halloysite instead of modified halloysite, showed a decrease in solar reflectance from 0.91 to 0.75, hemispherical emissivity from 0.90 to 0.78, thermal conductivity from 0.042 to 0.081, bond strength from 1.26 MPa to 0.94 MPa, and flexibility from 2 mm to 4 mm. It also exhibited fine network cracks during temperature deformation, slight blistering during water resistance, and after 1000 hours of aging, achieved grade 1 powdering and grade 2 discoloration. This indicates that the unmodified halloysite lacks phosphate anchoring groups on its surface, preventing effective chemical bonding with fillers such as titanium dioxide and silicon carbide. This results in poor filler dispersibility, increased interfacial defects, and thermal bridging effects, leading to severe deterioration of both thermal insulation and mechanical properties. Comparative Example 2 also showed a decline in overall performance, indicating that the unmodified ordinary epoxy resin lacks flexible segments and copolymer microsphere reinforcement structures, resulting in significantly insufficient coating flexibility and cohesion, and weak interfacial bonding. Comparative Example 3, which uses both unmodified halloysite and ordinary epoxy resin, shows a sharp deterioration in performance, becoming the worst in the entire group. This data indicates that there is a significant chemical crosslinking synergistic effect between the phosphate / fluorosilicone groups on the surface of the modified halloysite and the active side groups of the modified epoxy resin. Both are indispensable and together constitute the core technical basis for the excellent comprehensive performance of the coating of this invention.

[0046] The results of Comparative Examples 4-6 demonstrate that the absence of halloysite not only results in the loss of the tubular geometric support effect (making the microspheres more fragile), but also severs the chemical bonding network between fillers, leading to a significant enhancement of the thermal bridging effect and a substantial deterioration in both thermal insulation and durability. The absence of silicon carbide, on the other hand, degrades the three-dimensional thermal insulation network of barrier-reflection-radiation into a two-dimensional structure, interrupting the radiative heat dissipation channel and significantly weakening the synergistic effect of reflective and barrier insulation. The absence of hollow glass microspheres results in the loss of lightweight barrier function, increased coating density, and decreased thermal resistance. Simultaneously, the hollow structure of the microspheres eliminates the scattering effect on light, leading to a simultaneous deterioration in reflective performance. These three indispensable experimental results fully demonstrate that modified halloysite, nano-silicon carbide, and hollow glass microspheres form an inseparable functional whole through the physical-thermal coupling mechanism of tubular support, infrared radiation, and hollow barrier. No binary combination can achieve the comprehensive performance advantages of this synergistic combination. Furthermore, the results in Comparative Example 7 also demonstrate that even with the same three substances, an imbalance in the proportions (too little halloysite cannot effectively support the microspheres, and too much silicon carbide leads to increased coating brittleness) will result in a comprehensive decline in performance. In summary, this invention achieves a comprehensive breakthrough in the coating's reflective heat insulation performance, barrier heat insulation performance, mechanical properties, and durability through the synergistic interfacial chemistry of modified halloysite and modified epoxy, the functional synergy of the ternary composite filler, and precise formulation design. The overall performance of Examples 1-3 is far superior to all comparative examples, fully demonstrating the advanced nature, non-obviousness, and significant industrial practical value of the technical solution of this invention.

[0047] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A thermal insulation coating for buildings, characterized in that, It is made from the following raw materials by weight percentage: 25-35% acrylic emulsion, 10-20% modified epoxy resin, 12-18% rutile titanium dioxide, 12-25% composite filler, 1.0-2.0% film-forming aid, 1.0-2.0% propylene glycol, 0.4-0.8% dispersant, 0.1-0.3% wetting agent, 0.2-0.5% defoamer, 0.2-0.5% leveling agent, 0.5-1.0% thickener, 0.05-0.15% silane coupling agent, 0.1-0.3% pH adjuster, and the balance being deionized water; the composite filler is composed of modified nano halloysite, nano silicon carbide, and hollow glass microspheres in a mass ratio of (2-3):(0.5-1):

1.

2. The building thermal insulation coating according to claim 1, characterized in that, The modified epoxy resin is prepared by the following method: (1) Add N-phenylmaleimide and limonene to butanone solvent and stir until completely dissolved. Then add n-heptane and azobisisobutyronitrile. React at 70-80℃ for 6-8 hours under N2 environment. After the reaction is completed, centrifuge and separate. Wash the solid product with mixed solvent and diethyl ether in sequence. Vacuum dry to obtain bio-based limonene copolymer microspheres. (2) Dissolve KH-550 silane coupling agent in a mixed solvent of anhydrous ethanol / water to prepare a solution with a mass concentration of 2-5 wt%. Adjust the pH to 4-5 with acetic acid and stir for 30 min to hydrolyze. Add the product obtained in step (1) to the above hydrolysate and stir at 50-70℃ for 2-4 h. After the reaction is completed, centrifuge and separate the product. Wash the product repeatedly with anhydrous ethanol 3-5 times and dry to obtain silanized copolymer microspheres. (3) Add epoxy resin E-51 and reactive diluent AGE to the reactor, stir evenly, then add silane coupling agent KH560, heat to 50-80℃, react for 1-3h, then add the silanized copolymer microspheres obtained in step (2), continue stirring and reacting for 30-40min, cool to room temperature, and discharge the material.

3. The building thermal insulation coating according to claim 2, characterized in that, In step (1), the ratio of N-phenylmaleimide, limonene and butanone solvent is 1 mmol: 1 mmol: 10 mL; the volume ratio of butanone to n-heptane is 1:2; and the amount of azobisisobutyronitrile is 2-3% of the total mass of the monomers.

4. The building thermal insulation coating according to claim 2, characterized in that, In step (1), the mixed solvent is composed of butanone / n-heptane in a volume ratio of 1:

2.

5. The thermal insulation coating for buildings according to claim 2, characterized in that, In step (2), the volume ratio of anhydrous ethanol / water in the mixed solvent is 9:1; the ratio of the product obtained in step (1) to the silane hydrolysate is 1g:10mL.

6. The building thermal insulation coating according to claim 2, characterized in that, In step (3), the amount of reactive diluent AGE is 10-20% of the mass of epoxy resin E-51; the amount of silane coupling agent KH560 is 1-2% of the mass of epoxy resin E-51.

7. The building thermal insulation coating according to claim 1, characterized in that, The modified nano-haloysite is prepared using the following method: a. Dry halloysite nanotubes at 105-110℃ for 2h to remove interlayer adsorbed water and impurities, and obtain pretreated halloysite nanotubes; b. Add 2-4 g of aminotrimethylene phosphoric acid to 200 mL of deionized water, stir well, and adjust the pH of the solution to 4-5; add 6 g of pretreated nano halloysite to the solution and stir ultrasonically until homogeneous; heat and stir in an oil bath at 90-100 ℃ for 6-10 h; after the reaction is complete, cool to room temperature, place in a vacuum container for vacuum extraction, filter and separate, take the solid product, wash with deionized water, and dry in a vacuum oven to obtain surface-grafted modified nano halloysite; c. Disperse the product obtained in step b in 200 mL of anhydrous ethanol / water mixed solvent, wherein the volume ratio of the two is 9:1, sonicate, adjust the pH to 8-9, slowly add 2-5 g of tridecafluorooctyltrimethoxysilane, stir the reaction at 50-60℃ for 4-8 h, after the reaction is completed, centrifuge, wash with anhydrous ethanol 3-5 times, vacuum dry and grind to obtain modified nano halloysite.

8. The thermal insulation coating for buildings according to claim 1, characterized in that, The film-forming aid is 12-ol ester; the dispersant is sodium polyacrylate SN5040 or ammonium acrylate 5027; the wetting agent is an alkyl polyoxyethylene ether wetting agent; the defoamer is a polyether-modified silicone defoamer; the leveling agent is an acrylate leveling agent; the thickener is carboxymethyl hydroxyethyl cellulose; and the pH adjuster is ammonia.

9. The thermal insulation coating for buildings according to claim 1, characterized in that, The silicon carbide nanoparticles have a particle size of 30–80 nm; the hollow glass microspheres have a particle size range of 30–100 μm and a bulk density of 0.15–0.35 g / cm³. 3 The wall thickness is 0.8–2.0 μm.

10. A method for preparing a building thermal insulation coating according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Premixed additive phase: Add all deionized water, propylene glycol, dispersant, wetting agent and pH adjuster to the stirred tank, stir at low speed of 200-300 r / min for 5-10 min, and mix evenly to obtain the additive base liquid; S2. High-speed grinding and dispersion: Add rutile titanium dioxide, modified nano halloysite, and nano silicon carbide to the additive base liquid in batches, increase the rotation speed to 1200-1500 r / min and disperse at high speed for 25-40 min, grind until the slurry fineness is ≤30μm, add half of the defoamer in batches during the process to eliminate grinding bubbles; S3. Low-temperature composite mixing: Reduce the stirring speed to 400-600 r / min, slowly add acrylic emulsion and modified epoxy resin, stir for 10-15 min to mix into resin slurry; then slowly add hollow glass microspheres, continue to stir at low speed for 8-12 min, control the stirring shear strength throughout the process to avoid the hollow glass microspheres from breaking. S4. Compounding and blending of additives: Add the remaining defoamer, film-forming aid, silane coupling agent and leveling agent in sequence, and stir at 400-600 r / min for 10-15 min; S5. Thickening and viscosity adjustment and curing: Add thickener in batches, stir for 15-25 minutes to adjust the viscosity of the system for construction, test the pH value and fine-tune it to 8.0-9.0 with pH adjuster; cure at room temperature and low speed for 30-60 minutes, filter and discharge to obtain the building thermal insulation coating.

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