Reflective thermal insulation coating based on three-dimensional porous resin as well as preparation method and application of reflective thermal insulation coating

Abstract

The invention provides a reflective thermal insulation coating based on three-dimensional porous resin as well as a preparation method and application of the reflective thermal insulation coating. The coating is prepared from the following raw materials in parts by weight: 15 to 60 parts of polymer resin emulsion, 1 to 15 parts of good solvent, 1 to 15 parts of poor solvent, 5 to 15 parts of reflective filler, 2 to 5 parts of nano kaolin and 1 to 5 parts of silicon dioxide aerogel. The reflective filler is hollow glass microspheres jointly modified by a silane coupling agent and titanium n-butoxide. The chemical reaction between the silane coupling agent and the surfaces of the glass microspheres can enhance the binding force between the silane coupling agent and the resin matrix, and avoids the problems of aggregation and sedimentation in the coating, thereby improving the uniformity and stability of the coating. Meanwhile, titanium n-butoxide is introduced, a TiO2 coating layer is generated through a hydrolysis reaction, heat can be effectively reflected through the high reflectivity of TiO2, heat absorption of the coating is reduced, and the heat insulation effect is improved. Therefore, the double-modified hollow glass microspheres can play a better heat insulation role in the coating, and the overall heat insulation efficiency of the coating is improved.

Description

Technical Field

[0001] The invention relates to the technical field of reflective heat-insulating materials, and in particular to a reflective heat-insulating coating based on a three-dimensional porous resin, and a preparation method and application thereof. Background Art

[0002] In today's era of high energy consumption and increasing environmental awareness, seeking more effective insulation technology is essential to reducing energy consumption in buildings and industrial facilities. As a widely studied and applied technology, reflective insulation coatings can effectively reduce the absorption of sunlight and thermal radiation by the surfaces of buildings and equipment, thereby reducing internal temperatures, reducing the load on air conditioning and cooling systems, and improving energy efficiency. However, current reflective insulation coatings mostly focus on adding pigments and fillers with high reflectivity, with limited improvement methods and a lack of research on the combination of multiple materials, making it difficult to achieve efficient reflective insulation effects.

[0003] Patent 201010567589.5 discloses a heat-resistant hard coating, its composition and its manufacturing method. The composition of the heat-resistant hard coating includes at least a coating resin, a first solvent and a second solvent. The first solvent has a first volatilization rate, the second solvent has a second volatilization rate, and the second volatilization rate differs from the first volatilization rate by at least 2. During manufacturing, the composition is applied to a substrate to form a coating and dried. After drying, the coating on the substrate is cured to form a heat-resistant hard coating. The heat-resistant hard coating formed has a plurality of holes (such as nanoscale holes) evenly distributed inside, and these holes contain air. The heat-resistant hard coating of the present invention not only does not affect the optical properties, but also has hardness reinforcement and good heat-resistant effect.

[0004] Patent 201810460692.6 discloses a water-based reflective heat-insulating coating, which is composed of the following raw materials: water-based silicone-modified acrylic resin, hollow glass microspheres, rutile titanium dioxide, diatomaceous earth, sericite, red iron oxide, hollow polymer spheres, infrared reflectors, heat-insulating fillers, hydroxyethyl cellulose, dispersants, defoamers, thickeners, film-forming aids and pH regulators. The water-based reflective heat-insulating coating of the present invention has high reflection efficiency for sunlight, and at the same time has strong aging resistance, corrosion resistance, and stain resistance. The coating is environmentally friendly and non-toxic, low-cost, simple to construct, and can effectively reflect solar heat to achieve a good heat insulation effect, and its various performance indicators meet or far exceed national standards. Summary of the invention

[0005] In view of the problems existing in the existing reflective thermal insulation coating technology, such as rapid decline in reflectivity and thermal insulation effect when exposed to extreme conditions outdoors for a long time, inability to effectively protect against the transfer of external heat, and greatly reducing the energy-saving effect. The present application proposes a reflective thermal insulation coating based on a three-dimensional porous resin, and a preparation method and application thereof. From the perspectives of the matrix resin and the filler, the reflective performance of the reflective thermal insulation coating is synergistically improved to meet the current environmental protection needs of green and low-carbon building materials and energy conservation and emission reduction. Conventional coatings with polymer resin as the main matrix component have a dense structure, obvious thermal bridge effect, and good thermal conductivity. By constructing a three-dimensional porous structure in the matrix resin, the light and thermal radiation can be reflected and refracted multiple times inside the body, increasing the interaction between light and material, thereby improving the overall reflection efficiency of the coating.

[0006] A reflective heat-insulating coating based on a three-dimensional porous resin, the coating comprising the following raw materials in parts by weight: 15-60 parts of a polymer resin emulsion, 1-15 parts of a good solvent, 1-15 parts of a poor solvent, 5-15 parts of a reflective filler, 2-5 parts of nano-kaolin, and 1-5 parts of a silica aerogel;

[0007] The ratio of the good solvent to the poor solvent is 1:(0.2-5);

[0008] The total amount ratio of the polymer resin emulsion to the solvent is (1-5): 1;

[0009] The reflective filler is hollow glass microspheres modified by silane coupling agent and titanium n-butoxide.

[0010] The polymer resin emulsion is any one of epoxy resin emulsion, acrylic resin emulsion, polyurethane resin emulsion and fluorocarbon resin emulsion or a mixture of two or more of them in any proportion.

[0011] The reflective filler is obtained by the following method: (a) the surface of the hollow glass microsphere is hydroxylated; (b) a silane coupling agent reacts with the hollow glass microsphere with the hydroxylation treatment to obtain a semi-modified hollow glass microsphere; (c) titanium n-butoxide reacts with the remaining hydroxyl groups on the surface of the semi-modified hollow glass microsphere to obtain a modified hollow glass microsphere.

[0012] In the above step (b), the ratio of the silane coupling agent to the hollow glass microspheres is 2:1-10:1; and in the above step (c), the ratio of the titanium n-butoxide to the hollow glass microspheres is 0.5:1-12:1.

[0013] Preferably, the usage ratio of silane coupling agent, titanium n-butoxide and hollow glass microspheres is 5:3:1.

[0014] The condensation reaction conditions in the above step (b) are: adding a certain amount of organosilane in an alkaline environment at 20-70°C and pH=10-13, and stirring for 15-60 minutes; the reaction conditions in the above step (c) are: adding a certain amount of titanium n-butoxide in a mixed solution of acidic water and alcohol solvent at 20-45°C and pH=4-7, and stirring for 15-30 minutes.

[0015] The specific preparation method of the reflective filler is as follows:

[0016] (a) The hollow glass microspheres are treated in a 0.5-5wt.% boric acid aqueous solution at 40-60°C with magnetic stirring for 30-60 minutes, then cooled to room temperature, washed with clean water, and centrifuged and dried to activate the hollow glass microspheres. The surface of the activated hollow glass microspheres is rough and a large number of active hydroxyl groups appear; (b) The silane coupling agent reacts with the hollow glass microspheres treated with surface hydroxylation to obtain semi-modified hollow glass microspheres; the reaction conditions are to add an appropriate amount of ammonia water to water to prepare an alkaline solution with a pH of 10-13. liquid; adding a silane coupling agent to the alkaline aqueous solution, stirring at 20-70°C for 15-60 minutes, and performing a dehydration condensation reaction; (c) reacting titanium n-butoxide with the remaining hydroxyl groups on the surface of the semi-modified hollow glass microspheres to obtain modified hollow glass microspheres; the reaction conditions are that water and an alcohol solvent are mixed in a ratio of 1:(4-10), and an appropriate amount of acetic acid is added to adjust the pH of the mixed solution to 4-7, stirring at 20-45°C for 15-30 minutes, and performing a hydrolysis reaction to generate a TiO2 coating layer

[0017] Then it is added to a mixed solution of silicone and ethanol. The siloxane on the silane undergoes a condensation reaction with the hydroxyl groups on the surface of the hollow glass microspheres. After the functional groups on the silane are chemically grafted to the surface of the hollow glass microspheres, the reflectivity of the glass microspheres in the infrared and ultraviolet bands can be improved. At the same time, it helps to improve the weather resistance of the coating, thereby maintaining good reflective performance in outdoor applications.

[0018] The silane coupling agent is any one of KH550, KH560, KH570, diethoxydiphenylsilane, and 2-[ethoxy(dimethyl)silyl]-1,3-benzothiazole, or a mixture of two or more of them in any proportion.

[0019] The hydrolysis environment of butyl titanate is a mixture of water and alcohol solvents, and the alcohol solvent is one or more of ethanol, isopropanol, glycerol, acetone, etc.

[0020] The poor solvent is any one of isopropyl alcohol, butyl acetate, isopentane, ethylene glycol monobutyl ether, isobutyl alcohol and tetrahydrofuran, and the good solvent is water.

[0021] The coating also includes additives, which include dispersants, defoamers, leveling agents, and rheological additives; the dosage of the additives is 1-5 parts.

[0022] A method for preparing a reflective heat-insulating coating based on a three-dimensional porous resin comprises the following steps: (1) mixing a good solvent and a poor solvent evenly; (2) adding the evenly mixed solvent to a polymer resin emulsion and stirring evenly to obtain a diluted resin premix; (3) adding a functional additive to the resin premix and dispersing and mixing evenly at high speed; (4) adding nano-kaolin, a reflective filler and a silica aerogel in batches to the evenly mixed resin mixture of the above step three and dispersing at high speed until the mixture is evenly mixed.

[0023] In the above step (2), the stirring time is 5-20 min and the rotation speed is 200-700 rpm; in the above step (3), the dispersion and mixing time is 15-30 min and the rotation speed is 500-1500 rpm; in the above step (4), the high-speed dispersion time is 15-30 min and the rotation speed is 500-1500 rpm.

[0024] A reflective heat-insulating coating based on a three-dimensional porous resin is applied on a substrate to form a coating, which is then dried after curing.

[0025] The single layer thickness of the coating is 100-200 μm.

[0026] The above drying conditions are normal pressure 5-60℃, humidity 40%, time 10-60min, and the curing conditions are normal pressure 20-30℃, humidity 40%-60%, and drying for 24h;

[0027] Under low temperature conditions, the solvent evaporation rate decreases, and the constructed pore structure can move to the surface within the matrix resin and is more concentratedly distributed on the surface of the coating; under elevated temperature conditions, the solvent evaporation rate is higher, and the pore structure is more evenly dispersed in the resin matrix.

[0028] Compared with the prior art, this application has the following advantages:

[0029] (1) The present application double-modifies hollow glass microspheres by using silane coupling agent and titanium n-butoxide, which not only effectively improves its dispersibility in the resin system, but also greatly improves its heat resistance and reflectivity as a thermal insulation material. The chemical reaction between the silane coupling agent and the surface of the glass microspheres can enhance its bonding with the resin matrix, avoid aggregation and sedimentation problems in the coating, and thus improve the uniformity and stability of the coating. At the same time, the introduction of titanium n-butoxide generates a TiO coating layer through a hydrolysis reaction, which significantly improves the thermal insulation performance and reflective ability of the glass microspheres. Compared with the traditional reflective thermal insulation coating that requires TiO2 and hollow glass microspheres to be separated, the added content of the filler component is reduced, the coating density is reduced, and it is helpful to construct a reflective thermal insulation coating with a multi-level pore structure. The high reflectivity of TiO can effectively reflect heat, reduce heat absorption of the coating, and improve the thermal insulation effect. Therefore, the double-modified hollow glass microspheres can play a better thermal insulation role in the coating and improve the overall thermal insulation efficiency of the coating.

[0030] (2) The present application constructs a three-dimensional porous system with nano- and micron-scale structures inside the resin matrix, thereby enhancing the thermal insulation and mechanical properties of the resin matrix. By reasonably regulating the drying temperature and drying time, the size distribution and porosity of the pore structure inside the resin matrix can be directionally adjusted, thereby controlling the thermal conductivity and mechanical strength of the coating. During the drying process, changes in temperature and time directly affect the shrinkage behavior of the resin matrix, and then affect the formation and size distribution of pores. By precisely adjusting these parameters, a high degree of controllability of the pore structure can be achieved, so that the coating can meet the thermal insulation performance requirements while still maintaining good mechanical strength and toughness. This three-dimensional porous structure not only enhances the thermal insulation effect of the coating, but also optimizes the weight and durability of the coating, contributes to the long-term stability of the coating under different environmental conditions, and enhances its application potential in high-performance coatings. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The coating thickness of the following examples and comparative examples is 100 μm, unless otherwise specified. The additives in each example and comparative example are dispersant, defoamer, leveling agent, and rheological additive in a mass ratio of 1:1:1:1, and the dispersant, defoamer, leveling agent, and rheological additive are all conventional commercial products purchased from BYK Chemical.

[0033] Example 1

[0034] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres after surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 8g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min, then the mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 4.8g of titanium n-butoxide is added, and stirred at 500rpm for 30min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0035] Then, the reflective heat-insulating coating based on three-dimensional porous resin was prepared: 10g good solvent (isopropanol) and 2g water were mixed evenly and 36g epoxy resin, 18g polyurethane resin and 6g fluorocarbon resin were added and mixed at 300rpm for 5min. 5g functional additives, 5g nano-kaolin, 4g silica aerogel and 14g modified hollow glass microspheres were added respectively and dispersed at 500rpm for 20min. The above coating composition was coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0036] Example 2

[0037] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres after surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 16g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min, then the mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 0.8g of titanium n-butoxide is added, and stirred at 500rpm for 30min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0038] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 10g good solvent (butyl acetate), 2g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed at 300rpm for 5min. 5g functional additive, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 60℃ drying conditions for 10min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0039] Example 3

[0040] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 15g good solvent (tetrahydrofuran), 15g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed at 300rpm for 5min. 5g functional additive, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0041] Example 4

[0042] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 2g good solvent (isopropanol), 10g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed and stirred at 300rpm for 5min to mix evenly. 5g functional additive, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0043] Example 5

[0044] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 15g good solvent (isopropanol), 15g water are mixed evenly and 18g epoxy resin, 9g polyurethane resin, 3g fluorocarbon resin are added and mixed at 300rpm for 5min. 5g functional additive, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0045] Example 6

[0046] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres after surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 3.2g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min, then the mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 19.2g of titanium n-butoxide is added, and stirred at 500rpm for 30min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0047] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 10g good solvent (isopropanol), 2g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed at 300rpm for 5min. 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0048] Example 7

[0049] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 4g good solvent (isopropanol) and 4g water are mixed evenly and 15g epoxy resin is added and stirred at 300rpm for 5min to mix evenly. 1g functional additive, 2g nano kaolin, 1g silica aerogel and 5g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0050] Example 8

[0051] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 5g good solvent (isopropanol) and 10g water were mixed evenly and 40g epoxy resin was added and stirred at 300rpm for 5min to mix evenly. 3g functional additive, 4g nano kaolin, 5g silica aerogel and 8g modified hollow glass microspheres (same as Example 1) were added respectively and dispersed at 500rpm for 20min. The above coating composition was coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0052] Comparative Example 1

[0053] Compared with Example 1, the difference is that the reflective filler is ordinary hollow glass microspheres. Others are the same as Example 1.

[0054] Comparative Example 2

[0055] Compared with Example 1, the difference is that the reflective filler is hollow glass microspheres half-modified with silane coupling agent. Others are the same as Example 1.

[0056] 3 wt.% of boric acid was added to deionized water, and the pH was adjusted to 4. The hollow glass microspheres were acid-treated to hydroxylate their surfaces and collected for later use. 0.5 g of 25% ammonia water was dispersed in 10 g of pure water to form a uniform mixed solution, 1.6 g of glass microspheres with surface hydroxylation were added to the mixed solution, the temperature was raised to 60°, and 8 g of diethoxydiphenylsilane was added dropwise, and stirred at 300 rpm for 45 min. After the treatment was completed, the solution was centrifuged, repeatedly washed with pure water and dried to obtain hollow microspheres with improved dispersibility and surface modification, which were collected for later use.

[0057] Comparative Example 3

[0058] Compared with Example 1, the difference is that the reflective filler is a modified hollow glass microsphere, but the amount of silane coupling agent or titanium n-butoxide used is changed. Others are the same as Example 1.

[0059] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres after surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 10g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min, then the mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 2.5g of butyl titanate is added, and stirred at 500rpm for 30min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0060] Comparative Example 4

[0061] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 10g good solvent (butyl acetate), 2g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed and stirred at 300rpm for 5min to mix evenly. 5g functional additives, 5g nano kaolin, 4g silica aerogel, 10g titanium dioxide and 14g silane coupling agent semi-modified hollow glass microspheres (same as comparative example 2) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 60℃ drying conditions for 10min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0062] Comparative Example 5

[0063] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 2g good solvent (isopropanol), 14g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed and stirred at 300rpm for 5min to mix evenly. 5g functional additives, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0064] Comparative Example 6

[0065] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 8g good solvent (isopropanol), 2g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed and stirred at 300rpm for 5min to mix evenly. 5g functional additive, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0066] Comparative Example 7

[0067] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 15g good solvent (isopropanol), 3g water are mixed evenly and 18g epoxy resin, 9g polyurethane resin, 3g fluorocarbon resin are added and mixed and stirred at 300rpm for 5min to mix evenly. 5g functional additives, 3g nano kaolin, 2g silica aerogel and 6g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0068] Comparative Example 8

[0069] Preparation of reflective heat-insulating coating based on three-dimensional porous resin: 10g good solvent (isopropanol), 2g water are mixed evenly and 36g epoxy resin, 18g polyurethane resin, 6g fluorocarbon resin are added and mixed and stirred at 300rpm for 5min to mix evenly. 5g functional additives, 5g nano kaolin, 4g silica aerogel and 14g modified hollow glass microspheres (same as Example 1) are added respectively and dispersed at 500rpm for 20min. The above coating composition is coated and placed under 80℃ drying conditions for 10min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0070] Comparative Example 9

[0071] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. The mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 4.8g of titanium n-butoxide is added, and stirred at 500rpm for 30min; then 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres with surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 8g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0072] Then, the reflective heat-insulating coating based on three-dimensional porous resin was prepared: 10g good solvent (isopropanol) and 2g water were mixed evenly and 36g epoxy resin, 18g polyurethane resin and 6g fluorocarbon resin were added and mixed at 300rpm for 5min. 5g functional additives, 5g nano-kaolin, 4g silica aerogel and 14g modified hollow glass microspheres were added respectively and dispersed at 300rpm for 20min. The above coating composition was coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0073] Comparative Example 10

[0074] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres after surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 19.2g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min, then the mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 8g of titanium n-butoxide is added, and stirred at 500rpm for 30min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0075] Then, the reflective heat-insulating coating based on three-dimensional porous resin was prepared: 10g good solvent (isopropanol) and 2g water were mixed evenly and 36g epoxy resin, 18g polyurethane resin and 6g fluorocarbon resin were added and mixed at 300rpm for 5min. 5g functional additives, 5g nano-kaolin, 4g silica aerogel and 14g modified hollow glass microspheres were added respectively and dispersed at 500rpm for 20min. The above coating composition was coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0076] Comparative Example 11

[0077] 3wt.% boric acid is added to deionized water, and the pH is adjusted to 4. The hollow glass microspheres are acid-treated to make their surfaces hydroxylated and collected for later use. 0.5g of 25% ammonia water is dispersed in 10g of pure water to form a uniform mixed solution, 1.6g of glass microspheres after surface hydroxylation are added to the mixed solution, the temperature is raised to 60°, and 0.8g of diethoxydiphenylsilane is added dropwise, and stirred at 300rpm for 45min, then the mixed solution is adjusted to a weak acid environment of pH 6, cooled to 25°C, 8g of titanium n-butoxide is added, and stirred at 500rpm for 30min; finally, centrifuged, repeatedly washed with pure water and dried, and the surface-modified hollow microspheres with improved dispersibility, reflectivity and heat resistance are obtained and collected for later use.

[0078] Then, the reflective heat-insulating coating based on three-dimensional porous resin was prepared: 10g good solvent (isopropanol) and 2g water were mixed evenly and 36g epoxy resin, 18g polyurethane resin and 6g fluorocarbon resin were added and mixed at 300rpm for 5min. 5g functional additives, 5g nano-kaolin, 4g silica aerogel and 14g modified hollow glass microspheres were added respectively and dispersed at 500rpm for 20min. The above coating composition was coated and placed under 10℃ drying conditions for 60min, and then cured in a curing box at 25℃ and 40% humidity for 24h.

[0079] Test example:

[0080] The coatings obtained in the embodiments and comparative examples were tested for resistance to artificial weathering and reflective thermal insulation performance. The test methods and standards were based on HG / T 4758-2014 "Water-based acrylic resin coatings" and GB / T25261-2018 "Reflective thermal insulation coatings for buildings". The test results are shown in Tables 1 and 2 below.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085] The reflective heat-insulating coatings obtained in Examples 1-5 have good construction performance, and the cured coating is flat and dense, without bubbles, pinholes, delamination and other phenomena. The light and heat reflection performance meets the standard requirements of GB / T 25261-2018 "Reflective Heat-Insulating Coatings for Buildings". Compared with Example 1, Example 2 has a higher drying temperature, a shorter drying time, and a shorter curing drying time for the coating. The multi-level pore structure is more dispersed in the coating, which effectively reduces the overall thermal conductivity of the coating. However, the multi-level pore structure on the surface of the coating is more sparsely dispersed than Example 1, which is dried at low temperature for a long time, so the reflective performance is slightly reduced. The content of poor solvents in Examples 3 and 4 has increased, and the number of phase-separated structures of solvents and resins in the coating composition has increased. Although the reflective performance of the coating is enhanced, the overall density of the coating has decreased, and the aging resistance has also decreased. The resin content in Example 5 has decreased, and the overall density of the coating has not increased, resulting in a slightly insufficient aging resistance of the coating.

[0086] By comparing the coating performance of the glass microspheres added in the coating of Example 1 of the present application and Comparative Examples 1, 2, and 3, it is found that the hollow microspheres modified by the composite of silane / titanium n-butoxide in the present application example provide a better photothermal reflection effect for the coating. In the present application example, an appropriate amount of poor solvent is added, and the coating reflective performance of the reentrant pore structure of stable arrangement is constructed in the resin matrix. It is well improved; then compared with the performance of Comparative Example 4, it is found that compared with the excessive use of poor solvents, the durability caused by the large-scale phase separation inside the coating composition is insufficient, and the problem of reduced reflective performance is found that the good solvent / poor solvent mixed in the proper proportion of the present application example is more excellent in heat insulation performance, and the coating has better aging resistance. In the present application, by screening and regulating the good solvent and the poor solvent of the resin, a double-scale (micrometer-millimeter-level) reentrant pore structure is constructed inside the polymer resin, on the one hand, the reflective performance of the coating to photothermal radiation is improved, and on the other hand, the conventional coating is improved due to the thermal bridge effect, the high thermal conductivity and the poor insulation performance of the dense structure of the polymer resin. By comparing the performance of the embodiment with comparative examples 4, 5 and 6, it is found that excessively high content of the resin component, too low solid content and poor drying conditions will affect the overall performance of the coating.

[0087] In Comparative Example 8, the coating drying temperature is too high, which leads to accelerated resin curing. The microporous structure constructed by the phase separation of the poor solvent and the resin has not yet been cured like the surface transfer coating, so the coating reflection effect is greatly reduced. In Comparative Example 9, the modification of the hollow glass microspheres is carried out by first using titanium n-butoxide and then silane. Due to the steric hindrance effect, there are not enough sites on the surface of the microspheres for the growth of the silane coupling agent added later. Therefore, the test results are similar to those of Comparative Example 11. Due to the lack of sufficient silane coupling agent to modify the glass microspheres, the microspheres have poor dispersion in the coating mixture, the uneven texture of the coating leads to reduced long-term durability, and powdering occurs after 800 hours of artificial accelerated aging. The amount of silane coupling agent used in Comparative Example 10 exceeds the specified range, resulting in insufficient sites on the surface of the hollow glass microspheres for titanium n-butoxide modification and coating with titanium dioxide, resulting in poor reflection effects of the hollow glass microspheres and the coatings prepared therefrom.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A reflective heat-insulating coating based on a three-dimensional porous resin, characterized in that: The coating comprises the following raw materials in parts by weight: 15-60 parts of polymer resin emulsion, 1-15 parts of good solvent, 1-15 parts of poor solvent, 5-15 parts of reflective filler, 2-5 parts of nano kaolin, and 1-5 parts of silicon dioxide aerogel; The mass ratio of the good solvent to the poor solvent is 1:(0.2-5); The mass ratio of the polymer resin emulsion to the total amount of the solvent is (1-5): 1; The reflective filler is hollow glass microspheres modified by a silane coupling agent and titanium n-butoxide.

2. The reflective heat-insulating coating based on three-dimensional porous resin according to claim 1, characterized in that: The polymer resin emulsion is any one of epoxy resin emulsion, acrylic resin emulsion, polyurethane resin emulsion, and fluorocarbon resin emulsion, or a mixture of two or more of them in any proportion; the silane coupling agent is any one of KH550, KH560, KH570, diethoxydiphenylsilane, and 2-[ethoxy(dimethyl)silyl]-1,3-benzothiazole, or a mixture of two or more of them in any proportion; the poor solvent is any one of isopropanol, butyl acetate, isopentane, ethylene glycol monobutyl ether, isobutyl alcohol, and tetrahydrofuran, and the good solvent is water.

3. The reflective heat-insulating coating based on three-dimensional porous resin according to claim 1, characterized in that: The reflective filler is obtained by the following method: (a) the surface of the hollow glass microsphere is hydroxylated; (b) a silane coupling agent reacts with the hollow glass microsphere with the surface hydroxylation to obtain a semi-modified hollow glass microsphere; (c) titanium n-butoxide reacts with the remaining hydroxyl groups on the surface of the semi-modified hollow glass microsphere to obtain a modified hollow glass microsphere coated with a surface layer of TiO2.

4. The reflective heat-insulating coating based on three-dimensional porous resin according to claim 3, characterized in that: In the step (b), the mass ratio of the silane coupling agent to the hollow glass microspheres is (2-10):1; and in the step (c), the mass ratio of the titanium n-butoxide to the hollow glass microspheres is (0.5-12):

1.

5. The reflective heat-insulating coating based on three-dimensional porous resin according to claim 3, characterized in that: The condensation reaction conditions in the step (b) are as follows: adding a certain amount of ammonia water to water to prepare an alkaline solution with a pH of 10-13; adding organosilane to the alkaline aqueous solution, stirring for 15-60 minutes at 20-70° C., and performing a dehydration condensation reaction; the reaction conditions in the step (c) are as follows: mixing water and an alcohol solvent in a ratio of 1:(4-10), adding a certain amount of acetic acid to the mixed solution to make the mixed solution pH = 4-7, the temperature range is 20-45° C., stirring for 15-30 minutes, and performing a hydrolysis reaction to generate a TiO2 coating layer.

6. The reflective heat-insulating coating based on three-dimensional porous resin according to claim 1, characterized in that: The coating also includes additives, which include dispersants, defoamers, leveling agents, and rheological additives; the dosage of the additives is 1-5 parts.

7. A method for preparing a reflective heat-insulating coating based on a three-dimensional porous resin according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (1) mixing a good solvent and a poor solvent evenly; (2) adding the evenly mixed solvent into a polymer resin emulsion and stirring evenly to obtain a diluted resin premix; (3) adding a functional additive into the resin premix, and dispersing and mixing evenly at high speed; and (4) adding nano-kaolin, a reflective filler and a silica aerogel in batches into the evenly mixed resin mixture of the above step three, and dispersing at high speed until the mixture is evenly mixed.

8. The preparation method according to claim 7, characterized in that: The stirring time in step (2) is 5-20 minutes, and the rotation speed is 200-700 rpm; the dispersing and mixing time in step (3) is 15-30 minutes, and the rotation speed is 500-1500 rpm.

9. An application of a reflective heat-insulating coating based on a three-dimensional porous resin, characterized in that: The coating according to any one of claims 1 to 6 or the coating obtained by the preparation method according to any one of claims 7 to 8 is applied on a substrate to form a coating, and then dried after curing.

10. The use according to claim 9, characterized in that: The thickness of the single layer of the coating is 100-200μ; the curing conditions are room temperature 20-30°C, the curing humidity is maintained between 40%-60%, and the curing is carried out for 24 hours; the drying conditions are normal pressure 5-60°C, humidity 40%, and the drying time is 10-60 minutes.

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