Thermal insulation coating for building walls and method for preparing same

Abstract

The application belongs to the technical field of building thermal insulation materials, and particularly relates to a thermal insulation coating for building walls and a preparation method thereof. 60 The preparation method is to prepare a high-compatibility hydrophobic aerogel filler, a zinc oxide-fullerene layered crystal filler and octa-aminophenyl cage silsesquioxane grafted kapok fiber compounded with a styrene-acrylic emulsion. The fullerene C 60 The zinc oxide-fullerene layered crystal filler is prepared from a powder and a Zn metal powder, the transmission path of photons is prolonged, heat radiation and convection heat transfer are inhibited, the hydrophobic silica aerogel is coated by kappa-carrageenan to enhance the cohesive strength of the filler-matrix interface, and finally octa-aminophenyl cage silsesquioxane is grafted on the kapok fiber to form a large number of nanoscale phonon scattering centers, which are coordinated with the hollow structure of the kapok fiber to further enhance the thermal insulation performance of the coating.

Description

Technical Field

[0001] This invention belongs to the field of building insulation materials technology, specifically relating to a building wall insulation coating and its preparation method. Background Technology

[0002] Energy conservation and emission reduction have become the core direction of the global construction industry. Building energy consumption accounts for a large proportion of the total energy consumption of human society, and heat loss from the building envelope is one of the main sources of building energy consumption. To reduce heat conduction and heat radiation losses in building envelopes, exterior wall insulation coatings, as an energy-saving material that is easy to apply, cost-effective, and not limited by the shape of the substrate, have been widely used in energy-saving construction of new buildings and energy-saving renovation of existing buildings.

[0003] However, existing thermal insulation coatings for building walls still face numerous technical bottlenecks in practical applications, severely restricting further improvements in their thermal insulation performance and long-term reliability. Firstly, regarding porous fillers, while hydrophobic silica aerogels have extremely high porosity and extremely low thermal conductivity, significant interfacial defects exist between the aerogel particles and the resin matrix after film formation. This leads to a substantial decrease in the coating's cohesive strength, making it prone to microcracks and even detachment under thermal cycling or mechanical stress, resulting in a sharp decline in thermal insulation performance. Secondly, in terms of heat radiation blocking, commonly used reflective fillers in traditional coatings, such as titanium dioxide and zinc oxide, can only effectively shield the ultraviolet band. Single-component fillers cannot form efficient photon blocking. While fiber fillers can introduce a static air layer through their hollow structure to reduce heat conduction, ordinary organic fibers (such as kapok fibers) are thin and soft. During blending with emulsions and coating film drying, the hollow fiber structure is easily collapsed and crushed due to stress and capillary contraction, leading to the loss of its thermal insulation function. Summary of the Invention

[0004] To address the aforementioned technical deficiencies, this invention presents a thermal insulation coating for building walls and its preparation method. The prepared thermal insulation coating for building walls can form a coating with low thermal conductivity, high thermal insulation performance, and high strength.

[0005] A method for preparing a thermal insulation coating for building walls includes the following steps: S1: Preparation of highly compatible hydrophobic aerogel fillers κ-carrageenan powder was dissolved in deionized water, and then methyltrimethoxysilane was added for modification to obtain a hydrophobic modified carrageenan solution. The hydrophobic silica aerogel was moistened in anhydrous ethanol, then mixed evenly in the hydrophobic modified carrageenan solution, and spray-dried to obtain a highly compatible hydrophobic aerogel filler. S2: Preparation of zinc oxide-fullerene layered crystal filler Fullerene C 60The powder and Zn metal powder were mixed and vacuum-sealed in a quartz tube, then placed in a dual-temperature zone tube furnace at 600-400℃ and held at that temperature. After cooling to room temperature, the product from the 400℃ low-temperature zone was collected to obtain Zn-C. 60 Composite crystal, combining Zn-C 60 The composite crystals were added to an SDS solution and dispersed evenly. Then, a sealed hydrothermal reaction was carried out. The filter cake was collected by filtration, washed clean, and dried to obtain zinc oxide-fullerene layered crystal packing. S3: Octaphenylamino cage-like silsesquioxane grafting of kapok fiber Acrylic acid was dissolved in deionized water, and then sodium hypophosphite catalyst was added and mixed evenly to obtain a cellulose modification solution. Octaphenylaminocage-type silsesquioxane was dissolved in tetrahydrofuran to obtain an octaphenylaminocage-type silsesquioxane grafting solution. Kapok fibers were completely immersed in the cellulose modification solution and then subjected to a high-temperature reaction to obtain modified kapok fibers. The modified kapok fibers were then immersed in the octaphenylaminocage-type silsesquioxane grafting solution, and triethylamine was added dropwise to carry out the reaction. The filter residue was collected, washed, and dried to obtain octaphenylaminocage-type silsesquioxane grafted kapok fibers. S4: Compound formulation of thermal insulation coating The highly compatible hydrophobic aerogel filler and dispersant are stirred evenly to obtain mixed slurry A. The styrene-acrylic emulsion and dispersant are mixed, and then zinc oxide-fullerene layered crystal filler and octaphenylaminocage-type silsesquioxane grafted kapok fiber are added and stirred evenly to obtain mixed slurry B. Mixed slurry A is slowly added to mixed slurry B, and film-forming agent, defoamer and antifreeze are added and stirred evenly to obtain thermal insulation coating for building walls.

[0006] Furthermore, the preparation of the highly compatible hydrophobic aerogel filler in step S1 specifically includes the following steps: S1.1: Add κ-carrageenan powder to deionized water and stir in a water bath at 85-90℃ until completely dissolved to obtain a carrageenan aqueous solution with a mass fraction of 10-15%. Cool the carrageenan aqueous solution to 50-55℃, and then add 0.8-1% methyltrimethoxysilane by mass of the carrageenan aqueous solution. Keep warm and continue stirring at 200-300 rpm for 1.5-2 hours to obtain a hydrophobically modified carrageenan solution. S1.2: Wet the hydrophobic silica aerogel in anhydrous ethanol. The solid-liquid ratio of the hydrophobic silica aerogel to anhydrous ethanol is 1:(2-3) g / mL to obtain a wetted aerogel. Place the wetted aerogel in a hydrophobic modified carrageenan solution at a volume ratio of 1:(1.5-2.5) and stir at a stirring speed of 300-500 rpm for 1-1.5 h to obtain a mixed solution. S1.3: Heat the mixture at 45-50℃ for 0.5-1h, and then transfer it to a spray dryer for spray drying to obtain a highly compatible hydrophobic aerogel filler.

[0007] Furthermore, the preparation of the zinc oxide-fullerene layered crystal filler in step S2 specifically includes the following steps: S2.1: Fullerene C 60 After the powder and Zn metal powder are mixed evenly, they are vacuum-sealed in a quartz tube with a vacuum degree of 130 Pa. The quartz tube is then placed in a tube furnace with a temperature gradient of 600-400℃ and held at that temperature for 20-24 hours before being cooled to room temperature. The product from the 400℃ low-temperature zone is then collected to obtain Zn-C. 60 Composite crystal; S2.2: Dissolve sodium dodecyl sulfate in deionized water to prepare an SDS solution with a concentration of 0.08-0.1 mol / L, then add Zn-C 60 The composite crystals were added to the SDS solution at a solid-liquid ratio of 1:(15-20) g / mL, and after being ultrasonically dispersed evenly, they were transferred to a hydrothermal reactor and sealed. The reaction was carried out at 150-155℃ for 18-20 h, and the reaction product was obtained after cooling. S2.3: Filter the reaction product, collect the filter cake, rinse it with deionized water, and then dry it in a drying oven at 60℃ until constant weight to obtain zinc oxide-fullerene layered crystal packing.

[0008] Furthermore, step S3, the grafting of octaphenylamino cage-type silsesquioxane onto the kapok fibers, specifically includes the following steps: S3.1: Dissolve acrylic acid in deionized water, then add sodium hypophosphite catalyst, and sonicate for 30-40 minutes to mix evenly. The mass ratio of acrylic acid to sodium hypophosphite is 1:(0.4-0.5), to obtain a cellulose modified solution with an acrylic acid mass concentration of 10-15%. S3.2: Add octaphenylaminocage-type silsesquioxane to tetrahydrofuran at a mass ratio of 1:(10-12), and then sonicate until the octaphenylaminocage-type silsesquioxane is completely dissolved to obtain octaphenylaminocage-type silsesquioxane graft solution. S3.3: Completely immerse the kapok fiber in the cellulose modification solution obtained in step S3.1 for 3-4 hours, then transfer it to an oven at 150-155℃ for 2-2.5 hours. After cooling to room temperature, wash it with deionized water to obtain modified kapok fiber. Completely immerse the modified kapok fiber in an octaphenylaminocage-type silsesquioxane grafting solution, add 8-10% (by mass of octaphenylaminocage-type silsesquioxane) of triethylamine, and react at 50-55℃ for 10-12 hours. Then filter and collect the residue, wash it with deionized water until the deionized water is neutral, and then dry it in an oven at 105-110℃ for 1-1.5 hours to obtain octaphenylaminocage-type silsesquioxane grafted kapok fiber.

[0009] Furthermore, the compounding of the thermal insulation coating in step S4 specifically includes the following steps: S4.1: Add 12-15 parts of highly compatible hydrophobic aerogel filler and 0.3-0.5 parts of dispersant to 20-25 parts of deionized water in sequence, and stir at a stirring speed of 800-1000 rpm for 20-25 minutes to obtain mixed slurry A; S4.2: Stir 10-12 parts of styrene-acrylic emulsion and 0.2-0.3 parts of dispersant at a stirring speed of 300-500 rpm for 15-20 min, then add 4-5 parts of zinc oxide-fullerene layered crystal filler and 5-7 parts of octaphenylaminocage-type silsesquioxane grafted kapok fiber in sequence, and continue stirring for 15-20 min to obtain mixed slurry B; S4.3: At a stirring speed of 400-600 rpm, slowly add the mixed slurry A obtained in step S4.1 to the mixed slurry B obtained in step S4.2, then add 0.2-0.4 parts of film-forming agent, 0.1-0.2 parts of defoamer and 0.5-1 parts of antifreeze, and continue stirring for 20-30 minutes to obtain the thermal insulation coating for building walls.

[0010] Furthermore, the weight-average molecular weight of the κ-carrageenan powder in step S1.1 is 300-500 kDa.

[0011] Furthermore, the hydrophobic silica aerogel in step S1.2 is prepared by modifying trimethylchlorosilane and has a contact angle of 148°.

[0012] Furthermore, in step S2.1, fullerene C 60 The mass ratio of Zn metal powder to Zn metal powder is 1:(2-3).

[0013] Furthermore, in step S4, the dispersant is sodium polyacrylate dispersant, the film-forming agent is dodecyl alcohol ester, the defoamer is mineral oil defoamer, and the antifreeze agent is 1,2-propanediol.

[0014] A thermal insulation coating for building walls is prepared by the above-mentioned method for preparing a thermal insulation coating for building walls.

[0015] The beneficial effects are: 1. This invention utilizes fullerene C 60 After uniform mixing of powder and Zn metal powder, the mixture was vacuum-sealed and placed in a dual-temperature zone tube furnace. Zinc oxide-fullerene layered crystal filler was prepared via thermal diffusion doping-layered induced self-assembly, constructing a structure based on fullerene C... 60 A layered, ordered structure of alternating molecular layers and zinc oxide crystal layers was subjected to a hydrolysis-crystallization reaction in a hydrothermal environment under the guidance of a micellar soft template constructed with SDS surfactant, inducing newly formed ZnO nanocrystals to crystallize along C2. 60The molecular layers are oriented and eventually self-assemble to form alternating stacked zinc oxide-fullerene layered crystals. When incorporated into thermal insulation coatings, the ZnO layer, as a direct wide-bandgap semiconductor, exhibits extremely strong ultraviolet absorption and scattering capabilities, while C… 60 The layers, due to their conjugated π-electron system, can effectively absorb visible light and long-wave ultraviolet light. When light waves are incident, the alternating layered arrangement causes drastic changes in the refractive index between adjacent layers, resulting in high-density interface reflection and multiple scattering. This causes the photon transmission path within the pores to be extremely extended and absorbed and attenuated layer by layer, greatly suppressing thermal radiation and thus improving the thermal insulation performance of the coating.

[0016] 2. This invention modifies κ-carrageenan extracted from red algae (seaweed) by hydrophobic modification, and then coats the surface of hydrophobic silica aerogel. The siloxane segments exhibit excellent affinity with the hydrophobic silica aerogel surface, allowing for firm adsorption and effective coating. Carrageenan itself possesses good film-forming properties and thermal stability, participating in the formation of a continuous phase during coating drying. The hydroxyl and sulfate groups on its polysaccharide backbone form a dense hydrogen bond network with the carboxyl and hydroxyl groups on the acrylic segments of the styrene-acrylic emulsion. Simultaneously, the grafted hydrophobic siloxane segments interpenetrate and fuse with the hydrophobic regions of the emulsion polymer chains, creating a physically interpenetrating and chemically bonded interface layer between the filler surface and the resin matrix. This structure significantly enhances the cohesive strength of the filler-matrix interface, thereby improving the overall strength of the coating.

[0017] 3. In this invention, kapok fibers are first modified with acrylic acid and sodium hypophosphite to leave double bond functional groups on the cellulose surface. Then, under the catalysis of triethylamine, POSS molecules undergo a Michael addition reaction with the aromatic amine groups on an octaphenylamino cage-like silsesquioxane, thereby firmly chemically bonding POSS molecules to the kapok fibers. The rigid cubic cage-like skeleton of POSS molecules can resist the compression and damage to the hollow structure of kapok fibers by external forces. Furthermore, the sub-nanometer-scale gaps between POSS cages can further bind air molecules in a very small space, maintaining the thermal conductivity of kapok fibers close to that of still air. Moreover, the rigid cubic cage-like skeleton of POSS molecules can be grafted onto the fiber surface and can also form a large number of nanoscale phonon scattering centers, shortening the mean free path of hot-carrying phonons and significantly suppressing the thermal conductivity of the solid. In synergy with the hollow structure of kapok fibers, the thermal insulation performance of the coating is further enhanced. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0019] Unless otherwise specified, all parts mentioned in the following examples refer to parts by weight.

[0020] Example 1 A method for preparing a thermal insulation coating for building walls specifically includes the following steps: S1: Preparation of highly compatible hydrophobic aerogel fillers S1.1: Add κ-carrageenan powder with a weight-average molecular weight of 300 kDa to deionized water and stir in an 85°C water bath until completely dissolved to obtain a 10% carrageenan aqueous solution. Cool the carrageenan aqueous solution to 50°C, then add 0.8% (by weight) of methyltrimethoxysilane to the carrageenan aqueous solution. Keep the solution warm and continue stirring at 200 rpm for 1.5 h to obtain a hydrophobically modified carrageenan solution. S1.2: The hydrophobic silica aerogel was wetted in anhydrous ethanol. The hydrophobic silica aerogel was prepared by modifying trimethylchlorosilane and had a contact angle of 148°. The solid-liquid ratio of the hydrophobic silica aerogel to anhydrous ethanol was 1:2 g / mL to obtain the wetted aerogel. The wetted aerogel was placed in a hydrophobic modified carrageenan solution at a volume ratio of 1:1.5 and stirred at 300 rpm for 1 h to obtain the mixed solution. S1.3: The mixture is heated at 45°C for 0.5 h, and then transferred to a spray dryer for spray drying to obtain a highly compatible hydrophobic aerogel filler.

[0021] S2: Preparation of zinc oxide-fullerene layered crystal filler S2.1: Fullerene C 60 After the powder and Zn metal powder are mixed evenly, they are vacuum-sealed in a quartz tube at a vacuum level of 130 Pa. Fullerene C 60 The mass ratio of Zn metal powder to Zn was 1:2. The quartz tube was then placed in a dual-temperature zone tube furnace with a temperature gradient of 600-400℃, held at that temperature for 20 hours, and then cooled to room temperature. The product from the 400℃ low-temperature zone was then collected to obtain Zn-C. 60 Composite crystal; S2.2: Dissolve sodium dodecyl sulfate in deionized water to prepare an SDS solution with a concentration of 0.08 mol / L, then add Zn-C 60 The composite crystals were added to the SDS solution at a solid-liquid ratio of 1:15 g / mL, and after being ultrasonically dispersed, they were transferred to a hydrothermal reactor and sealed. The reaction was carried out at 150°C for 18 h, and the reaction product was obtained after cooling. S2.3: Filter the reaction product, collect the filter cake, rinse it with deionized water, and then dry it in a drying oven at 60℃ until constant weight to obtain zinc oxide-fullerene layered crystal packing.

[0022] S3: Octaphenylamino cage-like silsesquioxane grafting of kapok fiber S3.1: Dissolve acrylic acid in deionized water, then add sodium hypophosphite catalyst, and sonicate for 30 min to mix evenly. The mass ratio of acrylic acid to sodium hypophosphite is 1:0.4, to obtain a cellulose modified solution with an acrylic acid mass concentration of 10%. S3.2: Add octaphenylaminocage-type silsesquioxane to tetrahydrofuran at a mass ratio of 1:10, and then sonicate until the octaphenylaminocage-type silsesquioxane is completely dissolved to obtain octaphenylaminocage-type silsesquioxane graft solution. S3.3: The kapok fiber was completely immersed in the cellulose modification solution prepared in step S3.1 for 3 hours, then transferred to an oven at 150°C for 2 hours. After cooling to room temperature, it was washed with deionized water to obtain modified kapok fiber. The modified kapok fiber was completely immersed in an octaphenylaminocage-type silsesquioxane grafting solution, and 8% of triethylamine by mass of the octaphenylaminocage-type silsesquioxane was added dropwise. The reaction was carried out at 50°C for 10 hours, then filtered and the residue was collected. The residue was washed with deionized water until the deionized water was neutral, and then dried in an oven at 105°C for 1 hour to obtain octaphenylaminocage-type silsesquioxane grafted kapok fiber.

[0023] S4: Compound formulation of thermal insulation coating S4.1: Add 12 parts of highly compatible hydrophobic aerogel filler and 0.3 parts of sodium polyacrylate dispersant to 20 parts of deionized water in sequence, and stir at 800 rpm for 20 min to obtain mixed slurry A; S4.2: Stir 10 parts of styrene-acrylic emulsion and 0.2 parts of sodium polyacrylate dispersant at 300 rpm for 15 min, then add 4 parts of zinc oxide-fullerene layered crystal filler and 5 parts of octaphenylaminocage-type silsesquioxane grafted kapok fiber in sequence, and continue stirring for 15 min to obtain mixed slurry B. S4.3: At a stirring speed of 400 rpm, slowly add the mixed slurry A obtained in step S4.1 to the mixed slurry B obtained in step S4.2, then add 0.2 parts of dodecyl alcohol ester, 0.1 parts of mineral oil defoamer and 0.5 parts of 1,2-propanediol, and continue stirring for 20 minutes to obtain a thermal insulation coating for building walls.

[0024] Example 2 A method for preparing a thermal insulation coating for building walls specifically includes the following steps: S1: Preparation of highly compatible hydrophobic aerogel fillers S1.1: Add κ-carrageenan powder with a weight average molecular weight of 400 kDa to deionized water and stir in a 90°C water bath until completely dissolved to obtain a 12% carrageenan aqueous solution. Cool the carrageenan aqueous solution to 55°C, and then add 0.9% methyltrimethoxysilane by mass of the carrageenan aqueous solution. Keep warm and continue stirring at 250 rpm for 2 hours to obtain a hydrophobically modified carrageenan solution. S1.2: The hydrophobic silica aerogel was wetted in anhydrous ethanol. The hydrophobic silica aerogel was prepared by modifying trimethylchlorosilane and had a contact angle of 148°. The solid-liquid ratio of the hydrophobic silica aerogel to anhydrous ethanol was 1:2.5 g / mL to obtain the wetted aerogel. The wetted aerogel was placed in a hydrophobic modified carrageenan solution at a volume ratio of 1:2 and stirred at 400 rpm for 1 h to obtain the mixed solution. S1.3: The mixture is heated at 50°C for 0.5 hours and then transferred to a spray dryer for spray drying to obtain a highly compatible hydrophobic aerogel filler.

[0025] S2: Preparation of zinc oxide-fullerene layered crystal filler S2.1: Fullerene C 60 After the powder and Zn metal powder are mixed evenly, they are vacuum-sealed in a quartz tube at a vacuum level of 130 Pa. Fullerene C 60 The mass ratio of Zn metal powder to Zn was 1:2.5. The quartz tube was then placed in a dual-temperature zone tube furnace with a temperature gradient of 600-400℃, held at that temperature for 22 hours, and then cooled to room temperature. The product from the 400℃ low-temperature zone was then collected to obtain Zn-C. 60 Composite crystal; S2.2: Dissolve sodium dodecyl sulfate in deionized water to prepare an SDS solution with a concentration of 0.09 mol / L, then add Zn-C 60 The composite crystals were added to the SDS solution at a solid-liquid ratio of 1:18 g / mL, and after being ultrasonically dispersed, they were transferred to a hydrothermal reactor and sealed. The reaction was carried out at 150°C for 20 h, and the reaction product was obtained after cooling. S2.3: Filter the reaction product, collect the filter cake, rinse it with deionized water, and then dry it in a drying oven at 60℃ until constant weight to obtain zinc oxide-fullerene layered crystal packing.

[0026] S3: Octaphenylamino cage-like silsesquioxane grafting of kapok fiber S3.1: Dissolve acrylic acid in deionized water, then add sodium hypophosphite catalyst, and sonicate for 35 min to mix evenly. The mass ratio of acrylic acid to sodium hypophosphite is 1:0.4, resulting in a cellulose-modified solution with an acrylic acid mass concentration of 12%. S3.2: Add octaphenylaminocage-type silsesquioxane to tetrahydrofuran at a mass ratio of 1:11, and then sonicate until the octaphenylaminocage-type silsesquioxane is completely dissolved to obtain octaphenylaminocage-type silsesquioxane graft solution. S3.3: The kapok fiber was completely immersed in the cellulose modification solution prepared in step S3.1 for 4 hours, then transferred to an oven at 155°C for 2 hours. After cooling to room temperature, it was washed with deionized water to obtain modified kapok fiber. The modified kapok fiber was completely immersed in an octaphenylaminocage-type silsesquioxane grafting solution, and 9% of triethylamine by mass of the octaphenylaminocage-type silsesquioxane was added dropwise. The reaction was carried out at 55°C for 10 hours. The filter residue was then collected and washed with deionized water until the deionized water was neutral. The residue was then dried in an oven at 105°C for 1.5 hours to obtain octaphenylaminocage-type silsesquioxane grafted kapok fiber.

[0027] S4: Compound formulation of thermal insulation coating S4.1: Add 14 parts of highly compatible hydrophobic aerogel filler and 0.4 parts of sodium polyacrylate dispersant to 22 parts of deionized water in sequence, and stir at 900 rpm for 25 min to obtain mixed slurry A; S4.2: Stir 11 parts of styrene-acrylic emulsion and 0.3 parts of sodium polyacrylate dispersant at 500 rpm for 15 min, then add 5 parts of zinc oxide-fullerene layered crystal filler and 5 parts of octaphenylaminocage-type silsesquioxane grafted kapok fiber in sequence, and continue stirring for 20 min to obtain mixed slurry B. S4.3: At a stirring speed of 500 rpm, slowly add the mixed slurry A obtained in step S4.1 to the mixed slurry B obtained in step S4.2, then add 0.3 parts of dodecyl alcohol ester, 0.1 parts of mineral oil defoamer and 1 part of 1,2-propanediol, and continue stirring for 25 minutes to obtain the thermal insulation coating for building walls.

[0028] Example 3 A method for preparing a thermal insulation coating for building walls specifically includes the following steps: S1: Preparation of highly compatible hydrophobic aerogel fillers S1.1: Add κ-carrageenan powder with a weight-average molecular weight of 500 kDa to deionized water and stir in a 90°C water bath until completely dissolved to obtain a 15% carrageenan aqueous solution. Cool the carrageenan aqueous solution to 55°C, then add 1% methyltrimethoxysilane by mass of the carrageenan aqueous solution, and continue stirring at 300 rpm for 2 hours to obtain a hydrophobically modified carrageenan solution. S1.2: The hydrophobic silica aerogel was wetted in anhydrous ethanol. The hydrophobic silica aerogel was prepared by modifying trimethylchlorosilane and had a contact angle of 148°. The solid-liquid ratio of the hydrophobic silica aerogel to anhydrous ethanol was 1:3 g / mL to obtain the wetted aerogel. The wetted aerogel was placed in a hydrophobic modified carrageenan solution at a volume ratio of 1:2.5 and stirred at 500 rpm for 1.5 h to obtain the mixed solution. S1.3: The mixture is heated at 50°C for 1 hour, and then transferred to a spray dryer for spray drying to obtain a highly compatible hydrophobic aerogel filler.

[0029] S2: Preparation of zinc oxide-fullerene layered crystal filler S2.1: Fullerene C 60 After the powder and Zn metal powder are mixed evenly, they are vacuum-sealed in a quartz tube at a vacuum level of 130 Pa. Fullerene C 60 The mass ratio of Zn metal powder to Zn was 1:3. The quartz tube was then placed in a dual-temperature zone tube furnace with a temperature gradient of 600-400℃, held at that temperature for 24 hours, and then cooled to room temperature. The product from the 400℃ low-temperature zone was then collected to obtain Zn-C. 60 Composite crystal; S2.2: Dissolve sodium dodecyl sulfate in deionized water to prepare a 0.1 mol / L SDS solution, then add Zn-C... 60 The composite crystals were added to the SDS solution at a solid-liquid ratio of 1:20 g / mL, and after being ultrasonically dispersed, they were transferred to a hydrothermal reactor and sealed. The reaction was carried out at 155℃ for 20 h, and the reaction product was obtained after cooling. S2.3: Filter the reaction product, collect the filter cake, rinse it with deionized water, and then dry it in a drying oven at 60℃ until constant weight to obtain zinc oxide-fullerene layered crystal packing.

[0030] S3: Octaphenylamino cage-like silsesquioxane grafting of kapok fiber S3.1: Dissolve acrylic acid in deionized water, then add sodium hypophosphite catalyst, and sonicate for 40 min to mix evenly. The mass ratio of acrylic acid to sodium hypophosphite is 1:0.5, resulting in a cellulose modified solution with an acrylic acid mass concentration of 15%. S3.2: Add octaphenylaminocage-type silsesquioxane to tetrahydrofuran at a mass ratio of 1:12, and then sonicate until the octaphenylaminocage-type silsesquioxane is completely dissolved to obtain octaphenylaminocage-type silsesquioxane grafting solution. S3.3: The kapok fiber was completely immersed in the cellulose modification solution prepared in step S3.1 for 4 hours, then transferred to an oven at 155°C for 2.5 hours. After cooling to room temperature, it was washed with deionized water to obtain modified kapok fiber. The modified kapok fiber was completely immersed in an octaphenylaminocage-type silsesquioxane grafting solution, and 10% of the mass of the octaphenylaminocage-type silsesquioxane was added dropwise. The mixture was reacted at 55°C for 12 hours, then filtered and the residue was collected. The residue was washed with deionized water until the deionized water was neutral, and then dried in an oven at 110°C for 1.5 hours to obtain octaphenylaminocage-type silsesquioxane grafted kapok fiber.

[0031] S4: Compound formulation of thermal insulation coating S4.1: Add 15 parts of highly compatible hydrophobic aerogel filler and 0.5 parts of sodium polyacrylate dispersant to 25 parts of deionized water in sequence, and stir at 1000 rpm for 25 min to obtain mixed slurry A; S4.2: Stir 12 parts of styrene-acrylic emulsion and 0.3 parts of sodium polyacrylate dispersant at 500 rpm for 20 min, then add 5 parts of zinc oxide-fullerene layered crystal filler and 7 parts of octaphenylaminocage-type silsesquioxane grafted kapok fiber in sequence, and continue stirring for 20 min to obtain mixed slurry B; S4.3: At a stirring speed of 600 rpm, slowly add the mixed slurry A obtained in step S4.1 to the mixed slurry B obtained in step S4.2, then add 0.4 parts of dodecyl alcohol ester, 0.2 parts of mineral oil defoamer and 1 part of 1,2-propanediol, and continue stirring for 30 minutes to obtain the thermal insulation coating for building walls.

[0032] Comparative Example 1: The difference from Example 1 is that step S1 is removed in this comparative example, and the highly compatible hydrophobic aerogel filler in step S4.1 is replaced with an equal mass of hydrophobic silica aerogel filler. The remaining steps are the same as in Example 1.

[0033] Comparative Example 2: The difference from Example 1 is that step S2.1 is removed in this comparative example, and the Zn-C in step S2.2 is removed. 60 The composite crystals were replaced with an equal mass of mixed powder, which consisted of fullerene C40 in a mass ratio of 1:2. 60 The powder is composed of Zn metal powder, and the remaining steps are the same as in Example 1.

[0034] Comparative Example 3: The difference from Example 1 is that step S3 is removed in this comparative example, and the octaphenylaminocage-type silsesquioxane-grafted kapok fibers in step S4.2 are replaced with an equal mass of methyltrimethoxysilane-modified kapok fibers. The concentration of the methyltrimethoxysilane modification solution is 1%, and the remaining steps are the same as in Example 1.

[0035] Sample preparation: Prepare 18 silicate cement mortar substrates with dimensions of 10cm×10cm×5mm, and coat them with the coatings prepared in Examples 1-3 and Comparative Examples 1-3 respectively. Divide them into 6 groups of three. Control the dry film thickness of the coating on the cement mortar substrate to be 1±0.1mm. Cure for 7 days to obtain test samples. Set up a group of cement mortar substrates without coating as blank samples for thermal insulation performance, flexibility and thermal insulation stability tests.

[0036] Thermal insulation performance test: The thermal insulation performance of the test samples from Examples 1-3 and Comparative Examples 2-3, as well as the blank group, was tested according to the standard GB / T25261-2018 "Reflective Thermal Insulation Coatings for Buildings". Simulated sunlight was used, with the coatings of each test sample facing a 500W / m² direction. 2 The substrate was continuously irradiated with a full-spectrum xenon lamp light source for 90 minutes, and the temperature at the center point on the back of the substrate was monitored and recorded using thermocouples, as shown in Table 1.

[0037] Table 1: Substrate back temperature after irradiation of the samples

[0038] As shown in Table 1, after the test samples of Examples 1-3 were continuously irradiated by a xenon lamp source for 90 minutes, the temperature at the center point on the back of the substrate was significantly lower than that of the blank group, indicating that the coating of the present invention has excellent heat insulation performance. Comparative Example 2 removed the thermal diffusion doping process in step S2.1 and replaced the Zn-C60 composite crystal with a simple mixture of fullerene C60 powder and Zn metal powder. Its substrate back temperature was much higher than that of Example 1, which proves that the alternating stacked zinc oxide-fullerene layered crystals prepared by the present invention can greatly suppress thermal radiation, thereby improving the thermal insulation performance of the coating. Comparative Example 3 removed the POSS grafting process in step S3 and replaced the octaphenylamino cage-type silsesquioxane-grafted kapok fiber with kapok fiber modified with a common silane coupling agent. Its substrate back temperature was significantly higher than that of Example 1. This is because although the silane coupling agent can form a hydrophobic protective layer on the fiber surface, it cannot introduce rigid POSS nanocages as phonon scattering centers on the fiber wall surface, nor can it construct sub-nanometer-scale voids on the fiber periphery to bind air molecules. At the same time, lacking the mechanical support of the POSS cubic cage-shaped skeleton, the hollow structure of the kapok fiber is prone to collapse during coating drying and film formation, resulting in a decrease in thermal insulation function. This proves that the octaphenylamino cage-type silsesquioxane-modified kapok fiber can further enhance thermal insulation performance through phonon scattering centers, resistance to external forces, and binding of air molecules.

[0039] Flexibility and thermal conductivity variation test: Referring to standard GB / T1731-2020 "Determination of Flexibility of Paint Film and Putty Film", test samples were prepared using the coatings of Examples 1-3, Comparative Examples 1 and 3 for bending tests. Three samples were prepared for each group for testing. The dry film formed by the coating on the test sample was measured to see if it cracked. Then, referring to standard GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method", the thermal conductivity of the dry film of the test sample after the flexibility test was tested. The average value of each group was taken. The results are shown in Table 2.

[0040] Table 2: Coating flexibility and thermal conductivity

[0041] As shown in Table 2, the coating flexibility tests of Examples 1-3 all showed no cracks or peeling, low thermal conductivity, and the changes in thermal conductivity were all at extremely low levels.

[0042] In Comparative Example 1, the preparation of highly compatible hydrophobic aerogel filler in step S1 was omitted. Instead, unmodified silica aerogel without κ-carrageenan hydrophobic modification was used directly. This resulted in slight cracking and a significant increase in thermal conductivity in the coating. This is because the unmodified hydrophobic aerogel has poor interfacial compatibility with the water-based styrene-acrylic emulsion. The filler is unevenly dispersed in the coating and undergoes localized agglomeration. After film formation, obvious interfacial defects and stress concentration points are formed between the filler and the resin matrix. Under drying shrinkage and mechanical stress, microcracks are generated. Simultaneously, the voids in the interfacial debonding areas become thermal bridge channels, significantly increasing the thermal conductivity. This demonstrates that the effective coating of aerogel with modified carrageenan achieves a tight interfacial bond and structural stability between the filler and the matrix, resulting in a coating with both high stability and high strength.

[0043] Comparative Example 3, where ordinary silane coupling agent-modified kapok fiber replaced POSS-grafted kapok fiber, also showed slight cracking in its coating, but the thermal conductivity increased significantly. This is because the silane-modified kapok fiber only provides surface hydrophobic protection and cannot resist the compression and collapse of the hollow fiber structure through the rigid POSS cage-like skeleton. During film formation, the fiber wall is compressed and compacted, resulting in the loss of hollow air vesicles and some fibers becoming solid, leading to an increase in thermal conductivity. This demonstrates that the mechanical support of the POSS-grafted kapok fiber can prevent external forces from damaging the kapok fiber and improve its thermal insulation stability.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a thermal insulation coating for building walls, characterized in that, Includes the following steps: S1: Preparation of highly compatible hydrophobic aerogel fillers κ-carrageenan powder was dissolved in deionized water, and then methyltrimethoxysilane was added for modification to obtain a hydrophobic modified carrageenan solution. The hydrophobic silica aerogel was moistened in anhydrous ethanol, then mixed evenly in the hydrophobic modified carrageenan solution, and spray-dried to obtain a highly compatible hydrophobic aerogel filler. S2: Preparation of zinc oxide-fullerene layered crystal filler Fullerene C 60 The powder and Zn metal powder were mixed and vacuum-sealed in a quartz tube, then placed in a dual-temperature zone tube furnace at 600-400℃ and held at that temperature. After cooling to room temperature, the product from the 400℃ low-temperature zone was collected to obtain Zn-C. 60 Composite crystal, combining Zn-C 60 The composite crystals were added to an SDS solution and dispersed evenly. Then, a sealed hydrothermal reaction was carried out. The filter cake was collected by filtration, washed clean, and dried to obtain zinc oxide-fullerene layered crystal packing. S3: Octaphenylamino cage-like silsesquioxane grafting of kapok fiber Acrylic acid was dissolved in deionized water, and then sodium hypophosphite catalyst was added and mixed evenly to obtain a cellulose modification solution. Octaphenylaminocage-type silsesquioxane was dissolved in tetrahydrofuran to obtain an octaphenylaminocage-type silsesquioxane grafting solution. Kapok fibers were completely immersed in the cellulose modification solution and then subjected to a high-temperature reaction to obtain modified kapok fibers. The modified kapok fibers were then immersed in the octaphenylaminocage-type silsesquioxane grafting solution, and triethylamine was added dropwise to carry out the reaction. The filter residue was collected, washed, and dried to obtain octaphenylaminocage-type silsesquioxane grafted kapok fibers. S4: Compound formulation of thermal insulation coating The highly compatible hydrophobic aerogel filler and dispersant are stirred evenly to obtain mixed slurry A. The styrene-acrylic emulsion and dispersant are mixed, and then zinc oxide-fullerene layered crystal filler and octaphenylaminocage-type silsesquioxane grafted kapok fiber are added and stirred evenly to obtain mixed slurry B. Mixed slurry A is slowly added to mixed slurry B, and film-forming agent, defoamer and antifreeze are added and stirred evenly to obtain thermal insulation coating for building walls.

2. The method for preparing a thermal insulation coating for building walls according to claim 1, characterized in that, Step S1, the preparation of the highly compatible hydrophobic aerogel filler, specifically includes the following steps: S1.1: Add κ-carrageenan powder to deionized water and stir in a water bath at 85-90℃ until completely dissolved to obtain a carrageenan aqueous solution with a mass fraction of 10-15%. Cool the carrageenan aqueous solution to 50-55℃, and then add 0.8-1% methyltrimethoxysilane by mass of the carrageenan aqueous solution. Keep warm and continue stirring at 200-300 rpm for 1.5-2 hours to obtain a hydrophobically modified carrageenan solution. S1.2: Wet the hydrophobic silica aerogel in anhydrous ethanol. The solid-liquid ratio of the hydrophobic silica aerogel to anhydrous ethanol is 1:(2-3) g / mL to obtain a wetted aerogel. Place the wetted aerogel in a hydrophobic modified carrageenan solution at a volume ratio of 1:(1.5-2.5) and stir at a stirring speed of 300-500 rpm for 1-1.5 h to obtain a mixed solution. S1.3: Heat the mixture at 45-50℃ for 0.5-1h, and then transfer it to a spray dryer for spray drying to obtain a highly compatible hydrophobic aerogel filler.

3. The method for preparing a thermal insulation coating for building walls according to claim 1, characterized in that, Step S2, the preparation of zinc oxide-fullerene layered crystal filler, specifically includes the following steps: S2.1: Fullerene C 60 After the powder and Zn metal powder are mixed evenly, they are vacuum-sealed in a quartz tube with a vacuum degree of 130 Pa. The quartz tube is then placed in a tube furnace with a temperature gradient of 600-400℃ and held at that temperature for 20-24 hours before being cooled to room temperature. The product from the 400℃ low-temperature zone is then collected to obtain Zn-C. 60 Composite crystal; S2.2: Dissolve sodium dodecyl sulfate in deionized water to prepare an SDS solution with a concentration of 0.08-0.1 mol / L, then add Zn-C 60 The composite crystals were added to the SDS solution at a solid-liquid ratio of 1:(15-20) g / mL, and after being ultrasonically dispersed evenly, they were transferred to a hydrothermal reactor and sealed. The reaction was carried out at 150-155℃ for 18-20 h, and the reaction product was obtained after cooling. S2.3: Filter the reaction product, collect the filter cake, rinse it with deionized water, and then dry it in a drying oven at 60℃ until constant weight to obtain zinc oxide-fullerene layered crystal packing.

4. The method for preparing a thermal insulation coating for building walls according to claim 1, characterized in that, Step S3, grafting octaphenylamino cage-type silsesquioxane onto kapok fibers, specifically includes the following steps: S3.1: Dissolve acrylic acid in deionized water, then add sodium hypophosphite catalyst, and sonicate for 30-40 minutes to mix evenly. The mass ratio of acrylic acid to sodium hypophosphite is 1:(0.4-0.5), to obtain a cellulose modified solution with an acrylic acid mass concentration of 10-15%. S3.2: Add octaphenylaminocage-type silsesquioxane to tetrahydrofuran at a mass ratio of 1:(10-12), and then sonicate until the octaphenylaminocage-type silsesquioxane is completely dissolved to obtain octaphenylaminocage-type silsesquioxane graft solution. S3.3: Completely immerse the kapok fiber in the cellulose modification solution obtained in step S3.1 for 3-4 hours, then transfer it to an oven at 150-155℃ for 2-2.5 hours. After cooling to room temperature, wash it with deionized water to obtain modified kapok fiber. Completely immerse the modified kapok fiber in an octaphenylaminocage-type silsesquioxane grafting solution, add 8-10% of triethylamine by mass of the octaphenylaminocage-type silsesquioxane, and react at 50-55℃ for 10-12 hours. Then filter and collect the residue, wash it with deionized water until the deionized water is neutral, and then dry it in an oven at 105-110℃ for 1-1.5 hours to obtain octaphenylaminocage-type silsesquioxane grafted kapok fiber.

5. The method for preparing a thermal insulation coating for building walls according to claim 1, characterized in that, Step S4, the compounding of the thermal insulation coating, specifically includes the following steps: S4.1: Add 12-15 parts of highly compatible hydrophobic aerogel filler and 0.3-0.5 parts of dispersant to 20-25 parts of deionized water in sequence, and stir at a stirring speed of 800-1000 rpm for 20-25 minutes to obtain mixed slurry A; S4.2: Stir 10-12 parts of styrene-acrylic emulsion and 0.2-0.3 parts of dispersant at a stirring speed of 300-500 rpm for 15-20 min, then add 4-5 parts of zinc oxide-fullerene layered crystal filler and 5-7 parts of octaphenylaminocage-type silsesquioxane grafted kapok fiber in sequence, and continue stirring for 15-20 min to obtain mixed slurry B; S4.3: At a stirring speed of 400-600 rpm, slowly add the mixed slurry A obtained in step S4.1 to the mixed slurry B obtained in step S4.2, then add 0.2-0.4 parts of film-forming agent, 0.1-0.2 parts of defoamer and 0.5-1 parts of antifreeze, and continue stirring for 20-30 minutes to obtain the thermal insulation coating for building walls.

6. The method for preparing a thermal insulation coating for building walls according to claim 2, characterized in that, The κ-carrageenan powder in step S1.1 has a weight-average molecular weight of 300-500 kDa.

7. The method for preparing a thermal insulation coating for building walls according to claim 2, characterized in that, The hydrophobic silica aerogel in step S1.2 was prepared by modifying trimethylchlorosilane and had a contact angle of 148°.

8. The method for preparing a thermal insulation coating for building walls according to claim 3, characterized in that, In step S2.1, fullerene C 60 The mass ratio of Zn metal powder to Zn metal powder is 1:(2-3).

9. The method for preparing a thermal insulation coating for building walls according to claim 5, characterized in that, In step S4, the dispersant is sodium polyacrylate, the film-forming agent is dodecyl alcohol ester, the defoamer is mineral oil defoamer, and the antifreeze is 1,2-propanediol.

10. A thermal insulation coating for building walls, characterized in that, It is prepared by the method of any one of claims 1-9 for preparing thermal insulation coating for building walls.

Images