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

Abstract

The present application relates to the field of thermal insulation coatings, and discloses a kind of building thermal insulation coatings and preparation method thereof.The coating of the present application includes water-based acrylic emulsion, hollow ceramic microbeads, nano-silica, hydrophobic silane-based adjuvant;The water-based acrylic emulsion includes isooctyl acrylate, isobornyl methacrylate, hydroxypropyl acrylate, polyethylene glycol methyl ether acrylate, glycidyl methacrylate.The heat insulation temperature difference of the coating of the present application is as high as 26.8 DEG C, and the thermal conductivity coefficient is only 0.069 W / (m·K).In the wet cold thermal cycle test, the present application does not appear blistering, peeling and cracking phenomenon after 20 cycles.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal insulation coatings, more particularly, to a building thermal insulation coating and a preparation method thereof. BACKGROUND

[0002] In the high-temperature and rainy south, the building exterior wall coating is subjected to complex and changeable climate load, especially under the alternating conditions of rain soaking, high-temperature exposure, night cooling and humidity, the traditional coating system is prone to problems such as blistering, cracking and powdering, which seriously affects the thermal insulation performance and film durability. Therefore, it is of great engineering significance to develop a water-based coating for building exterior walls that can balance thermal insulation, moisture permeability and long-term structural stability.

[0003] Existing exterior wall thermal insulation coatings generally improve weather resistance by adding infrared reflective pigments (such as titanium dioxide, hollow glass beads) or introducing fluorosilicone emulsions, but most of them do not consider the water vapor transmission capacity, resulting in the formation of moisture bubbles in the wall in humid weather, which produces significant internal stress accumulation during subsequent solar heating or night cooling, ultimately leading to blistering, peeling or cracking.

[0004] For example, patent CN109385163A discloses a transparent thermal insulation coating of PEEK modified acrylic emulsion, which uses ATRP controlled polymerization process to embed PEEK into the main chain structure, and combines various nano transparent functional materials (LaB6, WO3, ITO, etc.) to prepare a coating with full-band shielding capability. The emulsion structure of this invention is dense, and does not consider water vapor transmission design; at the same time, this kind of transparent coating material is mostly used for optical elements, glass or metal surface, which has significant differences in adaptability with rough, porous and humidity changing dramatically exterior wall substrate. This scheme does not propose durability test or structural regulation means for the real environmental working condition of "water soaking-solarization-night cooling", and its technical solution focuses more on spectral control and heat reflection efficiency, rather than service stability and structural stress regulation ability.

[0005] For another example, patent CN110396340A improves the moisture resistance of the coating and its weather resistance under high temperature and high humidity conditions by introducing fluorocarbon modified structure in the emulsion system. However, this scheme mainly focuses on constant humidity and high temperature conditions, and does not systematically consider the problem of multiple damage accumulation of the coating film under water immersion, thermal expansion and cold contraction cycles, lacking of structure recovery mechanism design under dynamic climate impact.

[0006] In summary, the existing technology has not disclosed a water-based acrylic coating suitable for building exterior walls, which can withstand the wet and hot and cold cycle impact under high temperature and rainy climate, and has good thermal insulation and non-cracking performance. SUMMARY

[0007] The present application provides a kind of building thermal insulation coating to overcome the defects of the prior art described above, which is suitable for building outer wall, can withstand the impact of hot and cold cycle in high temperature and rainy climate, and has good thermal insulation and no cracking performance.

[0008] Another object of the present application is to provide a preparation method of the building thermal insulation coating.

[0009] To solve the above technical problems, the technical solution of the present application is as follows:

[0010] A kind of building thermal insulation coating, comprising the following components by mass fraction: water-based acrylate emulsion 90-100 parts, hollow ceramic microsphere 10-30 parts, nano-silicon dioxide 1-10 parts, hydrophobic silane-based auxiliary agent 0.5-5 parts.

[0011] The water-based acrylate emulsion comprises the following monomer components by mass fraction: isooctyl acrylate 30-50 parts, isobornyl methacrylate 20-40 parts, hydroxypropyl acrylate 10-20 parts, polyethylene glycol methyl ether acrylate 5-15 parts, and glycidyl methacrylate 2-10 parts.

[0012] Preferably, the building thermal insulation coating further comprises an emulsifier and an initiator.

[0013] Preferably, the building thermal insulation coating further comprises a bactericide, a leveling agent, a defoaming agent, and a dispersing agent.

[0014] Further, the solid content of the water-based acrylate emulsion is 45-55%.

[0015] Further, the water-based acrylate emulsion is prepared by the following method:

[0016] S1, a part of isooctyl acrylate and hydroxypropyl acrylate are added to the emulsion pre-emulsion, an initiator is added at 70-75°C, and a primary emulsion is obtained after reaction;

[0017] S2, the remaining isooctyl acrylate and hydroxypropyl acrylate are mixed with isobornyl methacrylate to obtain a pre-emulsion A; polyethylene glycol methyl ether acrylate (PMOEAA) is pre-emulsified to obtain a pre-emulsion B, and glycidyl methacrylate (GMA) is pre-emulsified to obtain a pre-emulsion C;

[0018] S3, at 75-80°C, pre-emulsion A is continuously added to the primary emulsion, and then pre-emulsion B and pre-emulsion C are added in turn and gradually;

[0019] S4, cool to room temperature, adjust the pH to 6.5-7.5, and obtain the water-based acrylate emulsion.

[0020] Further, the total mass of the isooctyl acrylate and the hydroxypropyl acrylate in S1 accounts for 15% to 25% of the total mass of all monomer components; the mass ratio of the isooctyl acrylate to the hydroxypropyl acrylate is not less than 1:0.5 to 1.

[0021] Further, the dropping of S3 is completed within 3 hours; the pre-emulsified liquid B and the pre-emulsified liquid C are added in stages after 1.5 to 2.5 hours of the dropping of the pre-emulsified liquid A.

[0022] Preferably, in S1, a part of the isooctyl acrylate and the hydroxypropyl acrylate is added into an emulsified liquid composed of an emulsifier and deionized water, the emulsifier accounts for 2% to 5% of the total mass of the pre-emulsified system, the deionized water accounts for 20% to 35% of the mass of the pre-emulsified system, and the pre-emulsification is completed after stirring or shearing uniformly.

[0023] Preferably, in S2, the remaining isooctyl acrylate and hydroxypropyl acrylate are mixed with isobornyl methacrylate, and then added into an emulsified liquid composed of an emulsifier and deionized water, the emulsifier accounts for 2% to 5% of the total mass of the pre-emulsified liquid, and the deionized water accounts for 20% to 40% of the total mass of the pre-emulsified liquid, and the pre-emulsified liquid A is prepared after stirring or shearing uniformly.

[0024] The polyethylene glycol methyl ether acrylate is added into an emulsified liquid composed of an emulsifier and deionized water, the emulsifier accounts for 2% to 5% of the total mass of the pre-emulsified liquid, and the deionized water accounts for 25% to 35% of the mass of the pre-emulsified liquid, and the pre-emulsified liquid B is prepared after stirring or shearing uniformly; the glycidyl methacrylate is added into an emulsified liquid composed of an emulsifier and deionized water, the emulsifier accounts for 2% to 5% of the total mass of the pre-emulsified liquid, and the deionized water accounts for 25% to 35% of the mass of the pre-emulsified liquid, and the pre-emulsified liquid C is prepared after stirring or shearing uniformly.

[0025] Preferably, in D2, the pre-emulsified liquid B is dropped while the initiator is supplemented.

[0026] Further, in S1, the emulsifier and water are mixed to form an emulsified liquid; the emulsifier includes at least one of sodium dodecyl sulfate and alkylphenol polyoxyethylene ether.

[0027] Preferably, the emulsifier is mixed by sodium dodecyl sulfate and alkylphenol polyoxyethylene ether at a mass ratio of 4:1.

[0028] Preferably, the initiator includes ammonium persulfate.

[0029] Preferably, the number average molecular weight of the polyethylene glycol methyl ether acrylate is 400 to 1500.

[0030] Preferably, the hydrophobic silane-based auxiliary agent includes n-octyl triethoxysilane, methyl trimethoxysilane, and isopropyl triethoxysilane.

[0031] Further, the particle size of the hollow ceramic microbead is 5-30 microns, and the particle size of the nano-silicon dioxide is 10-80 nanometers.

[0032] Preferably, the particle size of the hollow ceramic microbead is 10-20 microns, and the particle size of the nano-silicon dioxide is 20-50 nanometers.

[0033] A preparation method of the building thermal insulation coating comprises the following steps: sequentially adding hollow ceramic microbeads and nano-silicon dioxide in a water-based acrylic emulsion; after dispersion and stabilization, slowly adding a hydrophobic silane additive dropwise and uniformly mixing; after adjusting the pH to 6.5-7.5, the building thermal insulation coating is obtained.

[0034] Further, the hollow ceramic microbeads are added, and the dispersion is carried out under the shearing condition of a rotation speed of 2000-3000 rpm for 10-20 minutes; the nano-silicon dioxide is added, and the dispersion is continuously carried out for 5-10 minutes.

[0035] Further, in the preparation process, the system temperature is not higher than 40 DEG C.

[0036] The present application optimizes the polymerization path of the nucleation-growth stage, adopts step-by-step emulsification and multi-stage dropping strategy, so that the water-based acrylic emulsion has the particle size grading control ability in the particle formation process, provides basic support for building ordered and dense microskeleton of the coating film. At the same time, the directional distribution of the functional monomers (PMOEAA and GMA) realizes the hydrophilic adjustment and self-crosslinking enhancement of the coating film interface, and cooperatively improves the film forming uniformity and durability; the micron-sized hollow ceramic microbeads and nano-SiO2 are accurately matched in particle size, further build a multi-level thermal resistance and interface composite structure in the coating, and significantly reduce the thermal conductivity.

[0037] Compared with the prior art, the beneficial effects of the technical scheme of the present application are:

[0038] The building thermal insulation coating provided by the present application exhibits superior comprehensive performance in terms of thermal insulation performance, structural stability and weather resistance. The thermal insulation temperature difference of the present application is as high as 26.8 DEG C, and the thermal conductivity is only 0.069 W / (m·K). In the wet and cold heat cycle test, the present application does not appear to have blistering, peeling and cracking after 20 cycles, which reflects that the bimodal particle size structure and the functional monomer synergistic control strategy of the present application have significant advantages in thermal resistance performance and stress relief capacity. The above results fully prove that the present application realizes the efficient thermal insulation and long-term stable effect of the coating in the complex climate environment by reasonably designing the polymerization process and the formula system. DETAILED DESCRIPTION

[0039] The application will be further described in connection with the following specific examples which do not limit the application in any way. Unless otherwise stated, the reagents, methods and apparatus used in the examples are those conventional in the art.

[0040] Unless otherwise stated, the reagents and materials used in the following examples are commercially available.

[0041] The emulsifier used in the following embodiments is a mixture of sodium dodecyl sulfate and alkyl phenol polyoxyethylene ether in a mass ratio of 4:1. The number average molecular weight of the polyethylene glycol methyl ether acrylate used is 400-1500.

[0042] Example 1

[0043] Add 8 parts of isooctyl acrylate and 4 parts of hydroxypropyl acrylate to an emulsion. The emulsion is composed of emulsifier and deionized water, the amount of emulsifier is 2% of the total mass of the pre-emulsion system, and the amount of deionized water is 20% of the total mass of the pre-emulsion system. After stirring uniformly, add 0.3 parts of ammonium persulfate initiator at 70°C and react for 40 minutes.

[0044] Add 22 parts of isooctyl acrylate, 6 parts of hydroxypropyl acrylate, and 20 parts of isobornyl methacrylate to an emulsion composed of emulsifier and deionized water, respectively, the amount of emulsifier is 3% of the total mass of the pre-emulsion system, and the amount of deionized water is 20%, mix and pre-emulsify as Group A; add 5 parts of polyethylene glycol methyl ether acrylate to an emulsion composed of emulsifier and deionized water, the amount of emulsifier is 3% of the total mass of the pre-emulsion, and the amount of deionized water is 25% of the mass of the pre-emulsion, stir or shear uniformly to prepare pre-emulsion B; add 2 parts of glycidyl methacrylate to an emulsion composed of emulsifier and deionized water, the amount of emulsifier is 2% of the total mass of the pre-emulsion, and the amount of deionized water is 25% of the mass of the pre-emulsion, stir or shear uniformly to prepare pre-emulsion C. The three groups of emulsions are completed by dropping at 75°C for 3 hours, Group A is dropped first, Group B starts dropping at 1.5 hours and simultaneously adds 0.2 parts of initiator, Group C starts dropping at 2 hours, after dropping is completed, keep warm for 20 minutes, cool to room temperature, and adjust pH to 6.5. The obtained water-based acrylate emulsion has a solid content of about 45%.

[0045] Control the temperature not higher than 40°C, add 10 parts of hollow ceramic microbeads (particle size about 5 μm) to 90 parts of the emulsion, shear and disperse at 2000 rpm for 10 minutes, then add 1 part of pre-dispersed nano-silicon dioxide with particle size about 10 nm, continue to disperse for 5 minutes. Finally, add 0.5 parts of n-octyl triethoxysilane, stir uniformly, adjust pH to 6.5-7.5, and obtain a building thermal insulation coating.

[0046] Example 2

[0047] Ten parts of isooctyl acrylate and ten parts of hydroxypropyl acrylate were added to the emulsion. The emulsion consisted of an emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion system and the deionized water accounting for 25% of the total mass of the pre-emulsion system. After stirring evenly, 0.5 parts of ammonium persulfate initiator were added at 70°C and reacted for 40 minutes.

[0048] 30 parts of isooctyl acrylate, 5 parts of hydroxypropyl acrylate, and 30 parts of isobornyl methacrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion system and deionized water accounting for 35%. After mixing, this pre-emulsion was prepared as group A. 10 parts of polyethylene glycol methyl ether acrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion and deionized water accounting for 25%. After stirring or shearing until homogeneous, pre-emulsion B was prepared. 5 parts of glycidyl methacrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 2% of the total mass of the pre-emulsion and deionized water accounting for 25%. After stirring or shearing until homogeneous, pre-emulsion C was prepared. The three emulsions were added dropwise over 3 hours at 75°C. Group A was added first, Group B was added dropwise starting from the second hour with an additional 0.25 parts of initiator, and Group C was added dropwise starting from the 2.5-hour mark. After addition, the mixture was kept at this temperature for 30 minutes, cooled to room temperature, and the pH was adjusted to 7.0. The resulting aqueous acrylic emulsion had a solid content of approximately 55%.

[0049] Controlling the temperature to not exceed 40℃, add 20 parts of hollow ceramic microspheres (particle size approximately 10μm) to 95 parts of the emulsion, and shear and disperse at 2500rpm for 15 minutes. Then add 1 part of nano-silica with a particle size of approximately 20nm and disperse for 8 minutes. Finally, add 2 parts of methyltrimethoxysilane, stir evenly, and adjust the pH to 6.5–7.5 to obtain the building thermal insulation coating.

[0050] Example 3

[0051] 15 parts of isooctyl acrylate and 15 parts of hydroxypropyl acrylate were added to the emulsion. The emulsion consisted of an emulsifier and deionized water, with the emulsifier accounting for 4% of the total mass of the pre-emulsion system and the deionized water accounting for 35% of the total mass of the pre-emulsion system. After stirring evenly, 0.5 parts of ammonium persulfate initiator were added at 75°C and reacted for 40 minutes.

[0052] 35 parts of isooctyl acrylate, 5 parts of hydroxypropyl acrylate, and 40 parts of isobornyl methacrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 5% of the total mass of the pre-emulsion system and the deionized water accounting for 40%. After mixing, the mixture was pre-emulsified to form group A. 15 parts of polyethylene glycol methyl ether acrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion and the deionized water accounting for 35%. After stirring or shearing evenly, pre-emulsion B was obtained. 10 parts of glycidyl methacrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion and the deionized water accounting for 35%. After stirring or shearing evenly, pre-emulsion C was obtained. The three emulsions were added dropwise over 3 hours at 80°C. Group A was added first, Group B was added dropwise starting from the second hour with an additional 0.5 parts of initiator, and Group C was added dropwise starting from the 2.5-hour mark. After addition, the mixture was kept at this temperature for 40 minutes, cooled to room temperature, and the pH was adjusted to 7.5. The resulting aqueous acrylic emulsion had a solid content of approximately 55%.

[0053] Controlling the temperature to not exceed 40℃, add 30 parts of hollow ceramic microspheres (particle size approximately 30μm) to 100 parts of the emulsion, and shear and disperse at 3000rpm for 20 minutes. Then add 10 parts of nano-silica with a particle size of approximately 80nm and disperse for 10 minutes. Finally, add 5 parts of isopropyltriethoxysilane, stir evenly, and adjust the pH to 6.5–7.5 to obtain the building thermal insulation coating.

[0054] Example 4

[0055] Ten parts of isooctyl acrylate and five parts of hydroxypropyl acrylate were added to the emulsion. The emulsion consisted of an emulsifier and deionized water, with the emulsifier accounting for 2% of the total mass of the pre-emulsion system and the deionized water accounting for 30% of the total mass of the pre-emulsion system. After stirring evenly, 0.5 parts of ammonium persulfate initiator were added at 75°C and reacted for 40 minutes.

[0056] 25 parts of isooctyl acrylate, 10 parts of hydroxypropyl acrylate, and 20 parts of isobornyl methacrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 4% of the total mass of the pre-emulsion system and the deionized water accounting for 30%. After mixing, the pre-emulsion was prepared as group A. 12 parts of polyethylene glycol methyl ether acrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion and the deionized water accounting for 30%. After stirring or shearing evenly, pre-emulsion B was prepared. 8 parts of glycidyl methacrylate were added to an emulsion composed of emulsifier and deionized water, with the emulsifier accounting for 3% of the total mass of the pre-emulsion and the deionized water accounting for 30%. After stirring or shearing evenly, pre-emulsion C was prepared. The three emulsions were added dropwise over 3 hours at 80°C. Group A was added first, Group B was added dropwise starting from the second hour with an additional 0.25 parts of initiator, and Group C was added dropwise starting from the 2.5-hour mark. After addition, the mixture was kept at this temperature for 30 minutes, cooled to room temperature, and the pH was adjusted to 6.5. The resulting aqueous acrylic emulsion had a solid content of approximately 48%.

[0057] Controlling the temperature to no higher than 40℃, add 15 parts of hollow ceramic microspheres (particle size approximately 20μm) to 95 parts of the emulsion, and shear and disperse at 2800rpm for 18 minutes. Then add 8 parts of nano-silica with a particle size of approximately 50nm and disperse for 9 minutes. Finally, add 5 parts of methyltrimethoxysilane, stir evenly, and adjust the pH to 6.5–7.5 to obtain the building thermal insulation coating.

[0058] Comparative Example 1

[0059] The technical solution is similar to that of Example 2, and the amount of each component in the obtained coating is the same as that of Example 2. The difference is that the water-based acrylic emulsion is prepared by the following method: isooctyl acrylate, hydroxypropyl acrylate, isobornyl methacrylate, polyethylene glycol methyl ether acrylate, glycidyl methacrylate, and emulsifier are mixed together with deionized water and pre-emulsified at room temperature for 20 minutes to obtain a monomer pre-emulsified emulsion.

[0060] The emulsion was added dropwise over 3 hours at 75°C to a reaction system containing deionized water and ammonium persulfate initiator. After the addition was complete, the reaction was continued at this temperature for another 30 minutes, then cooled to room temperature, and the pH was adjusted to 7.0 to obtain an aqueous acrylate emulsion.

[0061] Comparative Example 2

[0062] The technical solution is similar to that of Example 2, except that the pre-emulsified emulsions of Group A, Group B and Group C are added dropwise within 1 hour.

[0063] Comparative Example 3

[0064] The technical solution is similar to that of Example 2, except that the pre-emulsified groups A, B, and C are mixed into one emulsion and added dropwise together.

[0065] Comparative Example 4

[0066] The technical solution is similar to that of Example 2, except that group C is added first, followed by group B.

[0067] Comparative Example 5

[0068] The technical solution is similar to that of Example 2, except that polyethylene glycol methyl ether acrylate is not added, and methyl methacrylate is used instead of isobornyl methacrylate.

[0069] Comparative Example 6

[0070] The technical solution is similar to that of Example 2, except that 3 parts of isooctyl acrylate and 6 parts of hydroxypropyl acrylate are added to the emulsion (composed of 2.5 parts of emulsifier and 85 parts of deionized water), stirred evenly, and then 0.5 parts of ammonium persulfate initiator are added at 70°C and reacted for 40 minutes to form primary latex particles with a particle size of about 30 nm.

[0071] Comparative Example 7

[0072] The technical solution is similar to that of Example 2, except that isooctyl acrylate and hydroxypropyl acrylate are added to the emulsion, stirred evenly, and then ammonium persulfate initiator is added at 85°C for 40 minutes.

[0073] Comparative Example 8

[0074] 50 parts of isooctyl acrylate, 5 parts of hydroxypropyl acrylate, and 30 parts of isobornyl methacrylate were mixed and pre-emulsified to form group A; 10 parts of polyethylene glycol methyl ether acrylate and 1 part of glycidyl methacrylate were emulsified to form groups B and C, respectively.

[0075] Comparative Example 9

[0076] The hollow ceramic microspheres have a particle size of approximately 2 μm, and the nano-silica particles have a particle size of approximately 120 nm.

[0077] Detection methods

[0078] 1. Thermal insulation performance test

[0079] Thermal insulation performance was tested using the temperature difference chamber method. Thermal insulation coating was applied to a metal test plate (approximately 1 mm thick) to serve as a partition between the hot and cold sides, with the middle sealed to form a heat flow channel. One side was heated to 80°C, and a temperature probe was placed on the other side to record the maximum temperature difference over 24 hours.

[0080] 2. Durability test under wet and cold thermal cycling

[0081] Immerse the test piece in water at 23 ± 2°C for 18 h, then place the test piece in a low-temperature box at -20 ± 2°C. Freeze it for 3 h starting from when the temperature in the box reaches -18°C. Then take the test piece out of the low-temperature box and immediately put it into a constant-temperature box at 50 ± 2°C for 3 h. Take out the test piece and repeat the above operations. After the 10th, 15th, and 20th cycles are completed, compare and check with the control sample. It is required that at least 2 out of 3 test pieces meet the requirements to be judged as qualified. After the thermal shock resistance test is carried out for 15 or more cycles, there should be no cracking, peeling, or blistering phenomena on the protective layer of the test piece.

[0082] Analysis and Explanation

[0083] I. Emulsion Particle Size Structure

[0084] In Examples 1 - 4 of the present invention, through the "nucleation - growth" two-stage polymerization path and combined with the multi-component staggered feeding strategy, hierarchical regulation and design of the latex particle structure are achieved. Specifically, in the nucleation stage, by controlling the initial monomer ratio, initiation conditions, and shear pre-emulsification operation, it is beneficial to form nucleation particles with smaller size and concentrated distribution, providing a good foundation for subsequent structure construction; in the growth stage, various functional monomers are fed in groups, especially the hydrophilic monomer PMOEAA and the crosslinking monomer GMA are added staggeredly, which can respectively dominate the hydrophilic regulation and structure fixation of the shell layer, helping to achieve the separate control of the growth rate and spatial distribution of the inner and outer layer particles, reflecting the ability to construct the "structural hierarchy" of latex particles.

[0085] In contrast, Comparative Example 1 lacked a nucleation step, with all monomers added simultaneously. The particle growth path was singular, lacking particle size distribution guidance and making it difficult to form a hierarchical structure. Comparative Example 2 had a significantly shortened addition time, resulting in an excessively rapid reaction rate, drastic fluctuations in monomer concentration, poor controllability of the polymerization process, and a high degree of overlap between nucleation and growth stages, easily leading to structural disorder. In Comparative Example 3, the functional monomers were not added in stages; PMOEAA and GMA participated in the reaction simultaneously in the early stages of polymerization, easily interfering with the gradual construction of the particle structure and reducing the distinctness of particle hierarchy. In Comparative Example 4, the addition order was abnormal; crosslinking monomer group C was added before hydrophilic monomer group B, easily causing premature crosslinking and formation of the shell structure, hindering the effective arrangement of hydrophilic monomers on the outer layer of the particles. In Comparative Example 5, the flexible regulating monomer PMOEAA was removed, and the more rigid methyl methacrylate replaced the main chain monomer, weakening the steric hindrance and interchain regulation capabilities between particles, leading to a more rigid structure and an unbalanced particle distribution. In Comparative Example 6, the proportion of nucleating monomers was too low, and the hydrophobic induction force was insufficient, resulting in a weak foundation for the primary particle structure and making it difficult to support the orderly construction of subsequent multi-level structures. In Comparative Example 7, the nucleation temperature was significantly increased, the initiation rate was too fast, and the particles in the system were densely generated but randomly distributed, losing the initial conditions for synergistic growth. In Comparative Example 8, the proportions of the components were uncoordinated, the hydrophobic nucleus-particle driving force was too strong, and the shell regulation was insufficient, leading to uncontrolled structural expansion during the polymerization process and making it difficult to construct a well-ordered particle population.

[0086] In summary, this invention establishes a dynamic control mechanism for the particle formation process by rationally setting the polymerization path, monomer ratio, and dropwise order. From a process design perspective, it has the potential to achieve graded optimization of particle size structure, providing a stable particle structure basis for subsequent improvement of emulsion coating performance.

[0087] II. Thermal Insulation Performance

[0088] As shown in Table 1, the building insulation coatings prepared in Examples 1-4 all exhibited excellent thermal insulation performance. Tested using the temperature difference chamber method, their insulation temperature difference reached 26.8℃, and their thermal conductivity was stably controlled between 0.069 and 0.076 W / (m·K). This invention employs bimodal particle size latex particles, combined with the synergistic design of hollow ceramic microspheres and nano-silica particles, to construct a multi-scale thermal resistance structure that alternates between dense and porous micro-nano composites. This effectively suppresses the direct conduction and rapid diffusion of heat within the coating, thereby significantly improving thermal insulation performance.

[0089] In Comparative Examples 1, 5, and 8, the unimodal particle size increased significantly, resulting in the loss of an effective core-shell structure and thermal resistance layers. The heat flow channels in the coating became continuous, leading to a significant decrease in thermal insulation performance, with the insulation temperature difference dropping to less than 19°C, and a significant increase in thermal conductivity. Furthermore, the other comparative examples also failed to form the expected bimodal particle size structure, resulting in particle aggregation, disordered distribution, or imbalanced synergistic structure. Their insulation temperature differences were generally less than 22°C, and their thermal conductivity increased significantly, making it difficult to achieve effective heat shielding.

[0090] Table 1 Thermal insulation performance

[0091] Temperature difference (℃) Thermal conductivity W / (m·K) Example 1 24.6 0.076 Example 2 26.8 0.069 Example 3 25.2 0.072 Example 4 25.9 0.070 Comparative Example 1 18.1 0.121 Comparative Example 2 20.3 0.102 Comparative Example 3 21.2 0.097 Comparative Example 4 20.8 0.099 Comparative Example 5 17.5 0.132 Comparative Example 6 21.0 0.100 Comparative Example 7 20.7 0.101 Comparative Example 8 18.7 0.126 Comparative Example 9 19.4 0.115

[0092] III. Durability under wet and cold thermal cycling

[0093] As shown in Table 2, Examples 1-4 all exhibited excellent structural stability in the wet-cold-heat cycling test, showing no blistering, cracking, or peeling during 20 cycles. The bimodal particle size structure of the latex particles constructed in this invention forms a dense, continuous phase with smaller particles embedded within it, creating a microscopic support framework that effectively disperses stress and inhibits crack propagation. PMOEAA provides flexibility and water stability, while GMA provides a cross-linked structure to enhance mechanical strength, ensuring excellent continuity and integrity even during repeated hot-cold cycles. The synergistic effect of the multi-level structure of the latex particles constructed in this invention with the inorganic components (hollow ceramic microspheres, nano-silica) endows the coating with good toughness and structural stability.

[0094] In contrast, Comparative Example 1 showed a loose single-particle structure and a film layer prone to blistering. Although Comparative Examples 2 and 3 retained primary particles, particle size control failed in the subsequent drop-addition stage, disrupting the shell construction rhythm. The latex particle interface layer was unclear or the functional monomers were distributed in a disordered manner. Ultimately, the adhesion between particles was weak during the cycling process, which easily led to coating defects such as cracks and blistering. In Comparative Example 4, the crosslinking monomers entered the system prematurely, causing the particle shell to solidify too early, affecting the shell's ductility and the arrangement of hydrophilic monomers, which increased the shell's brittleness and reduced its stress resistance.

[0095] In Comparative Examples 5 and 8, the key functional monomers were adjusted, but an effective flexible / cross-linked synergistic shell structure could not be constructed, resulting in a lack of toughness. Under temperature cycling shock, cracks easily propagate and the adhesion layer peels off severely. The structural hierarchy of Comparative Example 6 is unclear, with a soft core and a brittle outer layer, making it prone to breakage under cyclic stress. In Comparative Example 9, the hollow ceramic microspheres are too small and the SiO2 is too large, which destroys the particle intercalation structure, leading to instability of the cohesive structure and inability to properly release thermal expansion stress, causing blistering and interface instability. Although the overall structure of Comparative Example 7 is acceptable, the primary particle preparation temperature is too high, and there are micro-defects in the particle structure. After 20 cycles, it shows slight cracks, and its durability is slightly inferior to that of the embodiments of the present invention.

[0096] Table 2: Whether blistering / peeling / cracking occurred after humid and cold-heat cycling.

[0097] 10 cycles 15 cycles 20 cycles Example 1 No No No Example 2 No No No Example 3 No No No Example 4 No No No Comparative Example 1 Partial test piece bubbling Large area bubbling Bubbling, peeling Comparative Example 2 No A small amount of cracking Obvious crack propagation Comparative Example 3 No A small amount of bubbling Multiple test piece bubbling, cracking Comparative Example 4 No Shell peeling Peeling, pulverization Comparative Example 5 A small amount of bubbling Large area bubbling, cracking Severe damage Comparative Example 6 No Peeling Peeling Comparative Example 7 No No A small amount of cracking Comparative Example 8 No Weak area peeling Multiple point damage Comparative Example 9 No Interface microcracking Cracking, bubbling

[0098] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A building thermal insulation coating, characterized in that, It includes the following components by weight: 90-100 parts of water-based acrylic emulsion, 10-30 parts of hollow ceramic microspheres, 1-10 parts of nano-silica, and 0.5-5 parts of hydrophobic silane additives; The aqueous acrylic emulsion comprises the following monomer components by weight: 30-50 parts of isooctyl acrylate, 20-40 parts of isobornyl methacrylate, 10-20 parts of hydroxypropyl acrylate, 5-15 parts of polyethylene glycol methyl ether acrylate, and 2-10 parts of glycidyl methacrylate. The aqueous acrylic emulsion was prepared by the following method: S1. After pre-emulsifying a portion of isooctyl acrylate and hydroxypropyl acrylate in an emulsion, an initiator is added at 70-75°C, and a primary emulsion is obtained after the reaction. S2. The remaining isooctyl acrylate and hydroxypropyl acrylate are mixed with isobornyl methacrylate and pre-emulsified to obtain pre-emulsion A; polyethylene glycol methyl ether acrylate is pre-emulsified to obtain pre-emulsion B; and glycidyl methacrylate is pre-emulsified to obtain pre-emulsion C. S3. At 75~80℃, preemulsion A is continuously added dropwise to the primary emulsion, followed by preemulsion B and preemulsion C. After the addition is complete, continue to keep warm for 20~40 minutes. S4. Cool to room temperature and adjust the pH to 6.5~7.5 to obtain an aqueous acrylic emulsion; In S1, the total mass of isooctyl acrylate and hydroxypropyl acrylate accounts for 15% to 25% of the total mass of all monomer components; S3 is added dropwise within 3 hours. Pre-emulsion B and pre-emulsion C are added in stages 1.5 to 2.5 hours after pre-emulsion A is added dropwise. The hollow ceramic microspheres have a particle size of 5~30 μm, and the nano-silica has a particle size of 10~80 nm.

2. The building thermal insulation coating according to claim 1, characterized in that, The water-based acrylic emulsion has a solid content of 45-55%.

3. The building thermal insulation coating according to claim 1, characterized in that, The mass ratio of isooctyl acrylate to hydroxypropyl acrylate is not less than 1:0.5~1.

4. The building thermal insulation coating according to claim 1, characterized in that, S1 mixes an emulsifier and water to form an emulsion; the emulsifier includes at least one of sodium dodecyl sulfate and alkylphenol polyoxyethylene ether.

5. A method for preparing the building thermal insulation coating according to any one of claims 1 to 4, characterized in that, Includes the following steps: Hollow ceramic microspheres and nano-silica are added sequentially to an aqueous acrylic emulsion; after dispersion and stabilization, hydrophobic silane additives are slowly added dropwise and mixed evenly; after adjusting the pH to 6.5~7.5, the building thermal insulation coating is obtained.

6. The method for preparing the building thermal insulation coating according to claim 5, characterized in that, Add hollow ceramic microspheres and disperse them for 10-20 minutes under shear conditions at a speed of 2000-3000 rpm; add nano-silica and continue to disperse for 5-10 minutes.

7. The method for preparing the building thermal insulation coating according to claim 5, characterized in that, During the preparation process, the system temperature should not exceed 40℃.