Water-based thermal insulation coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to a water-based thermal insulation coating and a preparation method thereof. The coating comprises modified styrene-acrylic emulsion, a dispersing agent, a wetting agent, a thickening agent and a defoaming agent. The modified styrene-acrylic emulsion is prepared through synergistic polymerization of styrene, acrylate monomers, octaphenyl cage type polysilsesquioxane and alkenyl silicon-based aerogel, a uniform and stable multi-stage heat insulation structure can be formed, a heat conduction path is efficiently blocked, and the mechanical property and the heat stability of the coating are enhanced. In the process, performance optimization is realized through reasonable sequential addition of components and'hard core-soft shell 'gradient structure design. The coating has excellent heat insulation, weather resistance and temperature change resistance, is simple and convenient to construct, is environment-friendly and non-toxic, can remarkably reduce the surface temperature of a building, reduces energy consumption, prolongs the service life of the building, is beneficial to relieving the urban heat island effect, conforms to the development trend of green buildings, and provides an efficient and environment-friendly heat insulation technical solution.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly to an aqueous heat-insulating coating and a preparation method thereof. Background Art

[0002] With the continuous growth of global energy demand and the increasing improvement of energy conservation and emission reduction policies, the problem of building energy consumption has gradually become a hot topic of social concern. Among them, exterior wall heat-insulating coatings have received more and more research and development attention due to their significant role in improving the thermal performance of buildings and reducing cooling and heating energy consumption. As a green and environmentally friendly building material, aqueous heat-insulating coatings have been widely used in the field of building exteriors due to their low VOC emissions, easy construction, and excellent heat-insulating performance. However, the existing aqueous heat-insulating coatings still have many deficiencies in terms of performance, especially in the optimization of coating heat insulation, durability, and comprehensive mechanical properties, which urgently need to be improved.

[0003] The existing aqueous heat-insulating coatings generally achieve the heat-insulating effect by adding hollow structure materials (such as hollow glass microspheres or silicon-based aerogels) and highly reflective pigments and fillers (such as titanium dioxide). Among them, the hollow structure materials can reduce heat conduction through the construction of multi-stage heat-insulating paths, and at the same time scatter infrared radiation heat through their high surface reflectivity. However, the traditional heat-insulating method mainly has two problems: on the one hand, the dispersibility of inorganic materials such as hollow microspheres in the coating matrix is poor, and agglomeration is easy to occur, resulting in the coating being unable to form a uniform heat-insulating barrier, thus significantly reducing the heat-insulating performance; on the other hand, the combination of inorganic materials and organic polymer matrices is weak, and the interfacial stability is insufficient, and peeling or cracking is easy to occur during long-term use, seriously weakening the aging resistance and temperature resistance of the coating. In addition, in the face of extreme environments (such as ultraviolet irradiation, high temperature and high humidity conditions, rapid temperature changes, etc.), the physical and chemical stability of traditional heat-insulating coatings is low, and it is also difficult to meet the requirements of long-term use. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an aqueous heat-insulating coating and a preparation method thereof to solve the problems of uneven dispersion and poor stability of nanomaterials in the existing aqueous heat-insulating coatings, which in turn lead to insufficient heat-insulating and durable properties.

[0005] Based on the above purpose, the present invention provides an aqueous heat-insulating coating, which comprises the following components in parts by weight: 80-120 parts of modified styrene-acrylic emulsion, 0.3-1 part of dispersant, 2-4 parts of wetting agent, 0.3-0.8 part of thickener, and 0.1-0.5 part of defoamer.

[0006] Preferably, the dispersant is sodium polycarboxylate; the wetting agent is ethylene glycol monobutyl ether; the thickener is hydroxyethyl cellulose; the defoamer is an organosilicon defoamer.

[0007] Further, the preparation steps of the modified styrene-acrylic emulsion are as follows: S1: Mix the emulsifier and deionized water to obtain an emulsifier solution; mix styrene, butyl acrylate, and isooctyl acrylate to obtain monomer mixture A; mix acrylic acid, styrene, butyl acrylate, and isooctyl acrylate to obtain monomer mixture B; mix ammonium persulfate, sodium bicarbonate, and deionized water to obtain an initiator solution. S2: Add monomer mixture A, octaphenylcage polyhedral oligomeric silsesquioxane, and vinylated silica aerogel to the emulsifier solution, stir for 20 - 40 min, then heat up to 83 - 87 °C, dropwise add the initiator solution. After the addition is complete, stir for 3.5 - 4.5 h, then dropwise add monomer mixture B and the initiator solution. After the addition is complete, stir for 3.5 - 4.5 h. Finally, cool to room temperature, add ammonia water to adjust the pH to 7.9 - 8.3 to obtain the modified styrene-acrylic emulsion.

[0008] Preferably, in step S1, the emulsifier is a mixture of Span 80 and Tween 80 in a weight ratio of 10 - 15:6 - 10.

[0009] Preferably, in the emulsifier solution of step S1, the weight ratio of the emulsifier to deionized water is 16 - 25:80 - 120.

[0010] Preferably, in monomer mixture A of step S1, the weight ratio of styrene, butyl acrylate, and isooctyl acrylate is 30 - 50:3 - 5:3 - 5.

[0011] Preferably, in monomer mixture B of step S1, the weight ratio of acrylic acid, styrene, butyl acrylate, and isooctyl acrylate is 1.5 - 2.5:15 - 25:8 - 12:15 - 25.

[0012] Preferably, in the initiator solution of step S1, the weight ratio of ammonium persulfate, sodium bicarbonate, and deionized water is 0.25 - 0.35:0.2 - 0.3:25 - 35.

[0013] Preferably, in step S2, the weight ratio of monomer mixture A, octaphenylcage polyhedral oligomeric silsesquioxane, vinylated silica aerogel, emulsifier solution, initiator solution, and monomer mixture B is 36 - 60:8 - 12:15 - 25:95 - 145:25 - 35:39.5 - 64.5.

[0014] Preferably, in step S2, the weight ratio of the first dropwise addition of the initiator solution to the second dropwise addition of the initiator solution is 8 - 12:17 - 23.

[0015] Preferably, in step S2, the alkenylated silica aerogel is obtained by modifying silica aerogel with vinyltrimethoxysilane; the weight ratio of vinyltrimethoxysilane to silica aerogel is 0.3 - 0.8:15 - 25.

[0016] Preferably, the average particle size of the silica aerogel is 10 - 20 μm, and the specific surface area is 500 - 800 m 2 / g.

[0017] Furthermore, the present invention also provides a preparation method of an aqueous heat-insulating coating, comprising the following steps: stirring a modified styrene-acrylic emulsion, a dispersant, and a wetting agent at a speed of 1000 - 1500 rpm for 10 - 20 min, then adding a thickener and an antifoaming agent, and continuing to stir at a speed of 1000 - 1500 rpm for 10 - 20 min to obtain the aqueous heat-insulating coating.

[0018] Advantages of the present invention: The aqueous heat-insulating coating provided by the present invention has multiple significant advantages. First, by using alkenylated silica aerogel as a key functional component, chemical bonding is formed between the surface vinyl functional groups and the styrene-acrylate copolymer, greatly improving the dispersibility and interfacial bonding force of the microspheres in the polymer matrix, forming a stable and uniform multi-stage heat-insulating structure, and effectively blocking the heat conduction path.

[0019] Secondly, the present invention ingeniously introduces octaphenylcage polyhedral oligomeric silsesquioxane. Its special rigid cage-like structure and phenyl functional groups form a dynamic physical crosslinking network through steric hindrance effects and π-π interactions, significantly enhancing the thermal stability and structural integrity of the coating. This nano-scale strengthening mechanism enables the coating to obtain excellent weather and temperature change resistance while maintaining its lightweight characteristics.

[0020] The innovative process design adopted by the present invention is also the key to its performance advantages. By precisely controlling the addition sequence of functional components, especially synchronously adding octaphenylcage polyhedral oligomeric silsesquioxane and the hard monomer mixture at an early stage, the formation of a synergistic action network among nano-components is promoted. At the same time, the process sequence of polymerizing the hard monomer first and then adding the soft monomer constructs a "hard core-soft shell" gradient structure, optimizing the stress distribution mechanism and achieving a perfect balance between the rigidity and elasticity of the coating.

[0021] This structural design and process innovation enable the aqueous heat-insulating coating of the present invention to perform excellently in practical applications, significantly reducing the surface temperature of buildings, reducing energy consumption, and extending the service life of buildings. This coating is easy to construct, environmentally friendly and non-toxic, conforms to the development trend of green buildings, has a positive effect on alleviating the urban heat island effect, and provides an efficient, durable and environmentally friendly technical solution for building energy conservation. Specific embodiments

[0022] To make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0023] In the specific embodiment of the present invention, the silicon-based aerogel was purchased from Zhongning Technology, with the model number AG-DC15, an average particle size of 15 μm, and a specific surface area of 600 m 2 / g. Example

[0024] (1) Add 15 g of silicon-based aerogel, 200 g of absolute ethanol, and 0.3 g of vinyltrimethoxysilane to 300 g of deionized water, reflux and stir at 78 °C for 2 h, centrifuge, wash 3 times with absolute ethanol, and vacuum dry to obtain vinylated silicon-based aerogel; (2) Add 10 g of Span 80 and 6 g of Tween 80 to 80 g of deionized water, stir at 250 rpm for 25 min to obtain an emulsifier solution; mix 30 g of styrene, 3 g of butyl acrylate, and 3 g of isooctyl acrylate to obtain monomer mixture A; mix 1.5 g of acrylic acid, 15 g of styrene, 8 g of butyl acrylate, and 15 g of isooctyl acrylate to obtain monomer mixture B; mix 0.25 g of ammonium persulfate, 0.2 g of sodium bicarbonate, and 25 g of deionized water to obtain an initiator solution; (3) Add 36 g of monomer mixture A, 8 g of octaphenylcage polyhedral oligomeric silsesquioxane, and 15 g of vinylated silicon-based aerogel to 95 g of the emulsifier solution, stir at a speed of 250 rpm for 20 min, then raise the temperature to 83 °C, dropwise add 8 g of the initiator solution, continue to stir at a speed of 250 rpm for 3.5 h after the addition, then dropwise add 39.5 g of monomer mixture B and 17 g of the initiator solution, continue to stir at a speed of 250 rpm for 3.5 h after the addition, and finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 7.9 to obtain a modified styrene-acrylic emulsion; (4) Add 80 g of the modified styrene-acrylic emulsion, 0.6 g of a dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), 2 g of a wetting agent (ethylene glycol monobutyl ether), stir at a speed of 1000 rpm for 10 min, then add 0.3 g of a thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.1 g of an antifoaming agent (silicone antifoaming agent, model BYK-035), and continue to stir at a speed of 1000 rpm for 10 min to obtain a waterborne heat-insulating coating. Example

[0025] (1) Add 20 g of silicon-based aerogel, 250 g of absolute ethanol, and 0.5 g of vinyltrimethoxysilane to 350 g of deionized water, reflux and stir at 80 °C for 3 h, centrifuge, wash 3 times with absolute ethanol, and vacuum dry to obtain vinylated silicon-based aerogel; (2) Add 12 g of Span 80 and 8 g of Tween 80 to 100 g of deionized water, stir at 300 rpm for 30 min to obtain an emulsifier solution; mix 40 g of styrene, 4 g of butyl acrylate and 4 g of isooctyl acrylate to obtain monomer mixture A; mix 2 g of acrylic acid, 20 g of styrene, 10 g of butyl acrylate and 20 g of isooctyl acrylate to obtain monomer mixture B; mix 0.3 g of ammonium persulfate, 0.25 g of sodium bicarbonate and 30 g of deionized water to obtain an initiator solution. (3) Add 48 g of monomer mixture A, 10 g of octaphenyl silsesquioxane and 20 g of vinylated silica aerogel to 120 g of the emulsifier solution, stir at a speed of 300 rpm for 30 min, then heat up to 85 °C, add dropwise 10 g of the initiator solution, after the addition, continue to stir at a speed of 300 rpm for 4 h, then add dropwise 52 g of monomer mixture B and 20 g of the initiator solution, after the addition, continue to stir at a speed of 300 rpm for 4 h, finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 8 to obtain a modified styrene-acrylic emulsion. (4) Add 100 g of the modified styrene-acrylic emulsion, 0.8 g of a dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), 3 g of a wetting agent (ethylene glycol monobutyl ether), stir at a speed of 1200 rpm for 15 min, then add 0.5 g of a thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.3 g of an antifoaming agent (silicone antifoaming agent, model BYK-035), continue to stir at a speed of 1200 rpm for 15 min to obtain a waterborne heat-insulating coating. Example

[0026] (1) Add 25 g of silica aerogel, 300 g of absolute ethanol and 0.8 g of vinyltrimethoxysilane to 400 g of deionized water, reflux and stir at 82 °C for 4 h, centrifuge, wash 3 times with absolute ethanol, and vacuum dry to obtain vinylated silica aerogel. (2) Add 115 g of Span 80 and 10 g of Tween 80 to 120 g of deionized water, stir at 350 rpm for 35 min to obtain an emulsifier solution; mix 50 g of styrene, 5 g of butyl acrylate and 5 g of isooctyl acrylate to obtain monomer mixture A; mix 2.5 g of acrylic acid, 25 g of styrene, 12 g of butyl acrylate and 25 g of isooctyl acrylate to obtain monomer mixture B; mix 0.35 g of ammonium persulfate, 0.3 g of sodium bicarbonate and 35 g of deionized water to obtain an initiator solution. (3) Add 60 g of monomer mixture A, 12 g of octaphenyl silsesquioxane, and 25 g of vinylated silica aerogel to 145 g of emulsifier solution, stir at a speed of 350 rpm for 40 min, then raise the temperature to 87 °C, add dropwise 12 g of initiator solution. After the addition is complete, continue to stir at a speed of 350 rpm for 4.5 h. Then add dropwise 64.5 g of monomer mixture B and 23 g of initiator solution. After the addition is complete, continue to stir at a speed of 350 rpm for 4.5 h. Finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 8.3 to obtain a modified styrene-acrylic emulsion; (4) Add 120 g of modified styrene-acrylic emulsion, 1 g of dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), 4 g of wetting agent (ethylene glycol monobutyl ether), stir at a speed of 1500 rpm for 20 min, then add 0.8 g of thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.5 g of defoamer (silicone defoamer, model BYK-035), continue to stir at a speed of 1500 rpm for 20 min to obtain a waterborne heat-insulating coating.

[0027] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the vinylated silica aerogel in step (3) is replaced with silica aerogel; The specific steps are as follows: (1) Add 12 g of Span 80 and 8 g of Tween 80 to 100 g of deionized water, stir at 300 rpm for 30 min to obtain an emulsifier solution; mix 40 g of styrene, 4 g of butyl acrylate, and 4 g of isooctyl acrylate to obtain monomer mixture A; mix 2 g of acrylic acid, 20 g of styrene, 10 g of butyl acrylate, and 20 g of isooctyl acrylate to obtain monomer mixture B; mix 0.3 g of ammonium persulfate, 0.25 g of sodium bicarbonate, and 30 g of deionized water to obtain an initiator solution; (2) Add 48 g of monomer mixture A, 10 g of octaphenyl silsesquioxane, and 20 g of silica aerogel to 120 g of emulsifier solution, stir at a speed of 300 rpm for 30 min, then raise the temperature to 85 °C, add dropwise 10 g of initiator solution. After the addition is complete, continue to stir at a speed of 300 rpm for 4 h. Then add dropwise 52 g of monomer mixture B and 20 g of initiator solution. After the addition is complete, continue to stir at a speed of 300 rpm for 4 h. Finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 8 to obtain a modified styrene-acrylic emulsion; (3) Stir 100 g of modified styrene-acrylic emulsion, 0.8 g of dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), and 3 g of wetting agent (ethylene glycol monobutyl ether) at a speed of 1200 rpm for 15 min. Then add 0.5 g of thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.3 g of defoamer (silicone defoamer, model BYK-035), and continue to stir at a speed of 1200 rpm for 15 min to obtain the coating.

[0028] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the octaphenylcage polyhedral oligomeric silsesquioxane in step (3) is replaced with cage polyhedral oligomeric silsesquioxane; The specific steps are as follows: (1) Add 20 g of silicon-based aerogel, 250 g of absolute ethanol, and 0.5 g of vinyltrimethoxysilane to 350 g of deionized water, reflux and stir at 80 °C for 3 h, centrifuge, wash 3 times with absolute ethanol, and dry in vacuum to obtain alkenylated silicon-based aerogel; (2) Add 12 g of Span 80 and 8 g of Tween 80 to 100 g of deionized water, stir at 300 rpm for 30 min to obtain an emulsifier solution; Mix 40 g of styrene, 4 g of butyl acrylate, and 4 g of isooctyl acrylate to obtain monomer mixture A; Mix 2 g of acrylic acid, 20 g of styrene, 10 g of butyl acrylate, and 20 g of isooctyl acrylate to obtain monomer mixture B; Mix 0.3 g of ammonium persulfate, 0.25 g of sodium bicarbonate, and 30 g of deionized water to obtain an initiator solution; (3) Add 48 g of monomer mixture A, 10 g of cage polyhedral oligomeric silsesquioxane, and 20 g of alkenylated silicon-based aerogel to 120 g of emulsifier solution, stir at a speed of 300 rpm for 30 min, then heat up to 85 °C, dropwise add 10 g of initiator solution, continue to stir at a speed of 300 rpm for 4 h after dropping, then dropwise add 52 g of monomer mixture B and 20 g of initiator solution, continue to stir at a speed of 300 rpm for 4 h after dropping. Finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 8 to obtain the modified styrene-acrylic emulsion; (4) Stir 100 g of modified styrene-acrylic emulsion, 0.8 g of dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), and 3 g of wetting agent (ethylene glycol monobutyl ether) at a speed of 1200 rpm for 15 min. Then add 0.5 g of thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.3 g of defoamer (silicone defoamer, model BYK-035), and continue to stir at a speed of 1200 rpm for 15 min to obtain the coating.

[0029] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that: the octaphenyl silsesquioxane in step (3) is added with monomer mixture B; The specific steps are as follows: (1) Add 20 g of silica aerogel, 250 g of absolute ethanol, and 0.5 g of vinyltrimethoxysilane to 350 g of deionized water, reflux and stir at 80 °C for 3 h, centrifuge, wash 3 times with absolute ethanol, and vacuum dry to obtain vinyl-functionalized silica aerogel; (2) Add 12 g of Span 80 and 8 g of Tween 80 to 100 g of deionized water, stir at 300 rpm for 30 min to obtain an emulsifier solution; mix 40 g of styrene, 4 g of butyl acrylate, and 4 g of isooctyl acrylate to obtain monomer mixture A; mix 2 g of acrylic acid, 20 g of styrene, 10 g of butyl acrylate, and 20 g of isooctyl acrylate to obtain monomer mixture B; mix 0.3 g of ammonium persulfate, 0.25 g of sodium bicarbonate, and 30 g of deionized water to obtain an initiator solution; (3) Add 48 g of monomer mixture A and 20 g of vinyl-functionalized silica aerogel to 120 g of the emulsifier solution, stir at 300 rpm for 30 min, then raise the temperature to 85 °C, dropwise add 10 g of the initiator solution, continue to stir at 300 rpm for 4 h after the addition, then dropwise add 52 g of monomer mixture B, 10 g of octaphenyl silsesquioxane, and 20 g of the initiator solution, continue to stir at 300 rpm for 4 h after the addition, and finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 8 to obtain a modified styrene-acrylic emulsion; (4) Add 100 g of the modified styrene-acrylic emulsion, 0.8 g of a dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), 3 g of a wetting agent (ethylene glycol monobutyl ether), stir at 1200 rpm for 15 min, then add 0.5 g of a thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.3 g of an antifoaming agent (silicone antifoaming agent, model BYK-035), continue to stir at 1200 rpm for 15 min to obtain a coating.

[0030] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that: the addition order of monomer mixture A and monomer mixture B in step (3) is replaced; The specific steps are as follows: (1) Add 20 g of silica aerogel, 250 g of absolute ethanol, and 0.5 g of vinyltrimethoxysilane to 350 g of deionized water, reflux and stir at 80 °C for 3 h, centrifuge, wash 3 times with absolute ethanol, and vacuum dry to obtain vinyl-functionalized silica aerogel; (2) Add 12 g of Span 80 and 8 g of Tween 80 to 100 g of deionized water, stir at 300 rpm for 30 min to obtain an emulsifier solution; mix 40 g of styrene, 4 g of butyl acrylate and 4 g of isooctyl acrylate to obtain monomer mixture A; mix 2 g of acrylic acid, 20 g of styrene, 10 g of butyl acrylate and 20 g of isooctyl acrylate to obtain monomer mixture B; mix 0.3 g of ammonium persulfate, 0.25 g of sodium bicarbonate and 30 g of deionized water to obtain an initiator solution; (3) Add 52 g of monomer mixture B, 10 g of octaphenylcage polyhedral oligomeric silsesquioxane and 20 g of vinylated silica aerogel to 120 g of the emulsifier solution, stir at a speed of 300 rpm for 30 min, then heat up to 85 °C, dropwise add 10 g of the initiator solution, after the dropping is completed, continue to stir at a speed of 300 rpm for 4 h, then dropwise add 48 g of monomer mixture A and 20 g of the initiator solution, after the dropping is completed, continue to stir at a speed of 300 rpm for 4 h, finally, cool to room temperature, add ammonia water (concentration 28 wt%) to adjust the pH to 8 to obtain a modified styrene-acrylic emulsion; (4) Add 100 g of the modified styrene-acrylic emulsion, 0.8 g of a dispersant (sodium polycarboxylate, model NOPCO SN-Dispersant5040), 3 g of a wetting agent (ethylene glycol monobutyl ether), stir at a speed of 1200 rpm for 15 min, then add 0.5 g of a thickener (hydroxyethyl cellulose, model Natrosol 250MBR) and 0.3 g of an antifoaming agent (silicone antifoaming agent, model BYK-035), continue to stir at a speed of 1200 rpm for 15 min to obtain a coating.

[0031] Performance test: Preparation of coating specimens: Uniformly coat the waterborne heat-insulating coatings prepared in Examples 1-3 and Comparative Examples 1-4 on a standard cement asbestos board substrate (size 150 mm × 70 mm × 4 mm), use a wire bar coater to control the wet film thickness to be 200 ± 10 μm, and cure for 7 days under standard environmental conditions (temperature 23 ± 2 °C, relative humidity 50 ± 5%) to obtain coating specimens.

[0032] Heat insulation: According to GB / T 25261-2018, use a JTRG-IV type building heat insulation tester, set the radiation intensity to 1000 W / m 2 , fix a T-type thermocouple 30 cm away from the heat source on the surface of the coating specimen, record the maximum temperature difference value between the front and back surfaces of the coating specimen within 60 min, and take the arithmetic mean of the measured values at 5 points for each sample. The results are shown in Table 1.

[0033] Adhesion: According to GB / T 5210-2006, use an electronic universal testing machine to measure the bonding strength between the coating and the substrate. The results are shown in Table 1.

[0034] Weather resistance: According to GB / T 1865-2009, using a xenon lamp aging chamber (irradiation intensity 0.55 W / m², blackboard temperature 65 ± 3 °C), after continuous irradiation for 500 hours, evaluate the chalking of the coating according to GB / T 1766-2008, and test the adhesion of the coating on the sample after aging, and calculate the adhesion retention rate after aging; Temperature resistance and changeability: According to JG / T25-2017, conduct 20 freeze-thaw cycles of -20 °C / 50 °C, evaluate the cracking of the coating according to GB / T1766-2008, and test the adhesion of the coating on the sample after freeze-thaw cycles, and calculate the adhesion retention rate.

[0035] Table 1 Performance test results Maximum temperature difference value / °C Bonding strength / MPa Weather resistance (chalking grade) Retention rate of adhesion after aging / % Temperature change resistance (number of cracks) Retention rate of adhesion after freeze-thaw cycles / % Example 1 14.1 3.3 Grade 0 86.9 No cracks 84.6 Example 2 14.3 3.2 Grade 0 88.2 No cracks 85.8 Example 3 14.4 3.0 Grade 0 87.5 No cracks 85.2 Comparative example 1 12.1 2.9 Grade 0 85.3 No cracks 83.6 Comparative example 2 11.5 3.1 Grade 1 82.1 1 fine crack 80.7 Comparative example 3 12.9 2.8 Grade 0 84.4 1 fine crack 82.4 Comparative example 4 13.2 2.1 Grade 2 68.9 3 fine cracks 67.5 Data analysis: From the data of Examples 1-3 in Table 1, it can be seen that the waterborne heat-insulating coating prepared by the present invention has excellent comprehensive performance, which can be attributed to its unique multi-layer structure design and material combination. The excellent heat-insulating performance of this coating stems from the multi-stage heat-insulating structure formed by the silicon-based aerogel and the polymer matrix. This structure effectively blocks the heat conduction path and reduces heat transfer. At the same time, the coating shows high bonding strength, excellent weather resistance and temperature resistance and changeability. This coating can significantly reduce the surface temperature of buildings, reduce energy consumption, extend the service life of buildings, and can effectively alleviate the urban heat island effect in practical applications, providing an ideal exterior wall protection solution for green buildings.

[0036] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that Example 2 shows better comprehensive performance than Comparative Example 1, especially in terms of heat insulation. This may be due to the introduction of vinyl functional groups on the surface of the vinylated silicon-based aerogel, which enables it to undergo chemical bonding with the styrene-acrylate copolymer during the emulsion polymerization process. This covalent bond connection can effectively improve the dispersion of the silicon-based aerogel, thus forming a more uniform heat conduction path blocking and improving the heat insulation.

[0037] From the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that Example 2 shows more excellent heat insulation, weather resistance and temperature resistance and changeability than Comparative Example 2. This difference may be related to the special structure of octaphenylcage polyhedral oligomeric silsesquioxane (POSS). The rigid structure of the benzene ring can enhance the steric hindrance effect of the POSS core and delay the thermal motion of the polymer chain segments; secondly, the π-π interaction between the phenyl group and the styrene-acrylate chain segments may form dynamic physical crosslinking points, which dissipate energy through a reversible dissociation-recombination process during heating. This multiple action mechanism jointly maintains the structural integrity of the coating during long-term aging.

[0038] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that the difference in the addition timing of octaphenyl silsesquioxane leads to obvious changes in the coating properties. In Example 2, this component was added early together with monomer mixture A, while in Comparative Example 3, it was added late together with monomer mixture B. This adjustment of the process timing may have a profound impact on the microstructure of the material. In Example 2, octaphenyl silsesquioxane may form a synergistic network with vinylated silica aerogel at the initial stage of polymerization. This early synergy may enable the two nanostructured components to establish interactions during the emulsion particle formation stage. The rigid skeleton of the octaphenyl cage structure may act as a molecular-level connection bridge, linking the surface of vinylated microspheres with the polymer backbone. This spatial close arrangement between the nano-components may form a multi-level thermal insulation barrier, enhancing the scattering and blocking effects of thermal radiation. In addition, the octaphenyl cage structure added late in Comparative Example 3 is difficult to penetrate into the interior of the already formed polymer network and may be mainly distributed in the outer region of the emulsion particles, unable to establish effective interactions with the internal hollow microspheres. This separated distribution state weakens the synergistic effect of the two functional components, resulting in a decrease in thermal insulation performance.

[0039] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that the addition order of monomer mixtures A and B has a significant impact on the coating properties, which may be closely related to the microstructure of the formed polymer. In Example 2, the mixture A rich in styrene hard monomers was added first, and then the mixture B containing a higher proportion of acrylate soft monomers was added, while in Comparative Example 4, this order was reversed. The order adopted in Example 2 may promote the formation of a "hard core-soft shell" structure, that is, first constructing a stable rigid core mainly with styrene and then forming an elastic shell mainly with acrylate. This gradient structure may optimize the stress distribution and transfer mechanism, enabling the coating to have an appropriate elastic response ability while maintaining overall rigidity. In addition, the initially formed hard core may provide a more compatible chemical environment for octaphenyl silsesquioxane, promoting the formation of a more stable interaction between its phenyl ring and the benzene ring of the styrene unit through π-π stacking. This strong interaction may construct a network structure with a nano-enhancement effect, improving the ultraviolet aging resistance of the material. In contrast, the early polymerization of soft monomers in Comparative Example 4 may form an overly soft initial structure, making it difficult for the later added hard monomers to form an effective reinforcing phase, and the overall rigid-flexible balance of the structure is destroyed. This unbalanced microstructure may cause incoordinated expansion and contraction of the coating during temperature changes, forming stress concentration regions and microcracks. The polymerization order in Example 2 may also optimize the formation process of the crosslinked network, making the distribution of crosslinking points more uniform, thereby improving the structural stability and durability of the coating under environmental stress.

[0040] Those of ordinary skill in the art should understand that any discussion of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, and they are not provided in detail for the sake of brevity.

Claims

1. A water-based heat-insulating paint, characterized in that, By weight parts, it includes the following components: 80 - 120 parts of modified styrene-acrylic emulsion, 0.3 - 1 part of dispersant, 2 - 4 parts of wetting agent, 0.3 - 0.8 part of thickener, and 0.1 - 0.5 part of defoamer; The preparation steps of the said modified styrene-acrylic emulsion are as follows: S1: Mix the emulsifier and deionized water to obtain an emulsifier solution; mix styrene, butyl acrylate, and isooctyl acrylate to obtain monomer mixture A; mix acrylic acid, styrene, butyl acrylate, and isooctyl acrylate to obtain monomer mixture B; mix ammonium persulfate, sodium bicarbonate, and deionized water to obtain an initiator solution; S2: Add monomer mixture A, octaphenylcage polyhedral oligomeric silsesquioxane, and vinylated silica aerogel into the emulsifier solution, stir for 20 - 40 min, then heat up to 83 - 87 °C, dropwise add the initiator solution. After the dropping is completed, stir for 3.5 - 4.5 h, then dropwise add monomer mixture B and the initiator solution. After the dropping is completed, stir for 3.5 - 4.5 h. Finally, cool to room temperature, add ammonia water to adjust the pH to 7.9 - 8.3 to obtain the modified styrene-acrylic emulsion; In the emulsifier solution in step S1, the weight ratio of the emulsifier to deionized water is 16 - 25:80 - 120; in monomer mixture A, the weight ratio of styrene, butyl acrylate, and isooctyl acrylate is 30 - 50:3 - 5:3 - 5; in monomer mixture B, the weight ratio of acrylic acid, styrene, butyl acrylate, and isooctyl acrylate is 1.5 - 2.5:15 - 25:8 - 12:15 - 25; in the initiator solution, the weight ratio of ammonium persulfate, sodium bicarbonate, and deionized water is 0.25 - 0.35:0.2 - 0.3:25 - 35; In step S2, the weight ratio of monomer mixture A, octaphenylcage polyhedral oligomeric silsesquioxane, vinylated silica aerogel, emulsifier solution, initiator solution, and monomer mixture B is 36 - 60:8 - 12:15 - 25:95 - 145:25 - 35:39.5 - 64.

5.

2. The water-based heat-insulating coating according to claim 1, characterized in that, In step S1, the emulsifier is a mixture of span 80 and tween 80 with a weight ratio of 10 - 15:6 - 10.

3. The waterborne heat-insulating coating according to claim 1, wherein In step S2, the weight ratio of the first dropwise addition of the initiator solution to the second dropwise addition of the initiator solution is 8 - 12:17 - 23.

4. The water-based heat-insulating paint according to claim 1, characterized in that, In step S2, the vinylated silica aerogel is obtained by modifying silica aerogel with vinyltrimethoxysilane; the weight ratio of vinyltrimethoxysilane to silica aerogel is 0.3 - 0.8:15 - 25.

5. The water-based heat-insulating paint according to claim 1, wherein The dispersant is polycarboxylate salt; the wetting agent is ethylene glycol monobutyl ether; the thickener is hydroxyethyl cellulose; the defoamer is silicone defoamer.

6. A preparation method of the waterborne heat-insulating coating according to any one of claims 1-5, characterized in that, It includes the following steps: Stir the modified styrene-acrylic emulsion, dispersant, and wetting agent at a speed of 1000 - 1500 rpm for 10 - 20 min, then add the thickener and defoamer, and continue to stir at a speed of 1000 - 1500 rpm for 10 - 20 min to obtain the waterborne heat-insulating coating.