Reflective heat-insulating coating and preparation method thereof

Abstract

The present invention discloses a reflective thermal insulation coating and a preparation method thereof. The reflective thermal insulation coating comprises, by weight percentage, 10-50% flaky barium sulfate, with a particle size distribution of 400 nm to 15 μm. By using flaky barium sulfate with a wide range of particle sizes as the reflective thermal insulation filler in the coating, the present invention can effectively improve the brightness, reflectivity, reflectance, and thermal insulation effect of the coating while adding a large amount.

Description

Technical Field

[0001] The present invention belongs to the technical field of reflective heat-insulating coatings, and in particular relates to a reflective heat-insulating coating and a preparation method thereof. Background Art

[0002] Thermal insulation paint is a new type of functional water-based paint that can block and reflect near-infrared heat from sunlight. When applied to the surface of a building, it can insulate and cool down the building, achieving energy conservation and consumption reduction. It also has waterproof, rust-proof and anti-corrosion functions, with a short construction period and significant results.

[0003] Thermal insulation coatings are primarily categorized as conductive and reflective. Conductive insulating coatings typically use silicates as reflective fillers, but this provides limited insulation. Reflective coatings typically use metals or metal oxides, such as zinc powder, aluminum powder, silver powder, and nano-titanium dioxide, as reflective fillers. These highly efficient reflectors significantly reduce heat buildup. Nano-titanium dioxide is a commonly used reflective filler due to its strong hiding power and stability, but its high cost limits its use in thermal insulation coatings.

[0004] Barium sulfate is often used as a reflective and thermally insulating filler in coatings to replace titanium dioxide due to its low oil absorption, high filler volume, low cost, and high whiteness. This improves the coating's gloss, but excessive amounts of barium sulfate can reduce the coating's thermal insulation. To address this issue, existing technologies use barium sulfate of a specific particle size to prepare coatings. While this effectively addresses the issue, it struggles to maintain high reflectivity and reflectance while also effectively improving the coating's thermal insulation performance. Summary of the Invention

[0005] In response to the above-mentioned deficiencies in the prior art, a reflective thermal insulation coating is provided. By using flaky barium sulfate with a wide range of particle sizes as the reflective thermal insulation filler of the coating, the brightness, reflectivity, reflectance and thermal insulation effect of the coating can be effectively improved under the premise of a large addition amount.

[0006] The present invention aims to provide a flaky barium sulfate having a particle size distribution of 400 nm to 15 μm.

[0007] In some embodiments of the present invention, the D 50 >10μm.

[0008] Another object of the present invention is to provide a method for preparing flaky barium sulfate, comprising the following steps:

[0009] Sodium sulfate and sodium chloride in a mass ratio of 1:4 to 1:10 are dissolved in water, stirred to dissolve, barium chloride is added, stirred and mixed, heated to react, and purified to obtain flaky barium sulfate.

[0010] In some embodiments of the present invention, the mass ratio of sodium sulfate to barium chloride is 1:1.2~2.

[0011] In some embodiments of the present invention, the temperature of the heating reaction is 150-200° C., and the reaction time is 24-48 hours.

[0012] In some embodiments of the present invention, the purification includes cooling to room temperature, collecting the precipitate, filtering, washing, and drying.

[0013] Another object of the present invention is to provide a reflective heat-insulating coating comprising 10 to 50% by mass of the flaky barium sulfate.

[0014] In some embodiments of the present invention, the reflective thermal insulation coating further comprises 20-60% water-based resin emulsion.

[0015] In some embodiments of the present invention, the water-based resin emulsion is selected from at least one of pure acrylic emulsion, styrene acrylic emulsion, silicone acrylic emulsion and acetate acrylic emulsion.

[0016] In some embodiments of the present invention, the aqueous resin emulsion is selected from silicone acrylic emulsion.

[0017] In some embodiments of the present invention, the reflective thermal insulation coating further includes 0.5-2.5% thickener, 0.5-2.5% plasticizer, 0.5-1% wetting agent, 0.5-1% defoaming agent, 0.1-0.5% bactericide, and the balance deionized water.

[0018] In some embodiments of the present invention, the thickener is selected from at least one of polyvinyl alcohol, polyacrylate, bentonite, cellulose, and polyurethane.

[0019] In some embodiments of the present invention, the plasticizer is selected from at least one of phthalates, fatty acid amides, silicones, chlorinated petroleum hydrocarbons, epoxy resins, polyurethanes, acrylates, glycerides, and vegetable oils.

[0020] In some embodiments of the present invention, the wetting agent is selected from at least one of alkyl polyoxyethylene ether, phosphite, acrylate, ethylene glycol ether, propylene glycol ether, polypropylene glycol, Carbowet GA-100, Dynol 360, Dynol 604, Dynol 607, and Surfynol 104E.

[0021] In some embodiments of the present invention, the defoaming agent is selected from at least one of zinc stearate, aluminum stearate, potassium stearate, sodium stearate, polydimethylsiloxane, white oil, polyoxyethylene fatty alcohol ether, polyoxypropylene fatty alcohol ether, ethoxylated silicone oil, and silicone polyoxyethylene.

[0022] In some embodiments of the present invention, the fungicide is selected from at least one of copper pyrithione, LM-7012, kasone, and methylisothiazolinone.

[0023] Another object of the present invention is to provide a method for preparing the reflective thermal insulation coating, comprising the following steps:

[0024] S1. The aqueous resin emulsion, deionized water, a wetting agent, a defoamer and a fungicide are mixed to obtain a mixture;

[0025] S2. Add flaky barium sulfate to the mixture, stir, then add a thickener and a plasticizer, stir evenly, to obtain a reflective thermal insulation coating.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention adopts flaky barium sulfate as a reflective heat-insulating filler. The flaky barium sulfate has a wider particle size distribution range and can better reflect and scatter visible light and infrared rays in sunlight, effectively preventing the accumulation of solar heat on the surface of objects, and significantly improving the heat-insulating performance of the coating.

[0028] (2) The method for preparing the reflective thermal insulation coating provided by the present invention is simple and easy to operate, which is conducive to industrial production and meets market demand. In addition, the coating also has good coating properties, such as smooth and dense coating and small cracking, which further enhances its reliability and durability in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the SEM image of the flaky barium sulfate prepared in Example 1.

[0030] Figure 2 This is an SEM image of the coating surface made of the reflective thermal insulation coating prepared in Example 4.

[0031] Figure 3 This is the SEM image of the flaky barium sulfate prepared in Comparative Example 1.

[0032] Figure 4 This is the SEM image of barium sulfate prepared in Comparative Example 2.

[0033] Figure 5 This is the TEM image of barium sulfate prepared in Comparative Example 3. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a method for preparing flaky barium sulfate, and the specific preparation steps are as follows:

[0037] S1. Weigh 2.84kg of sodium sulfate and 14.20kg of sodium chloride, stir in 130kg of water until dissolved, add 4.16kg of barium chloride, and continue stirring for 15 minutes to obtain a mixture;

[0038] S2. The mixture in step S1 was transferred to a high-pressure reactor, the reactor temperature was raised to 160°C, the temperature was kept for 36 hours, the temperature was naturally cooled to room temperature, and the precipitate was collected.

[0039] S3. The precipitate in step S2 was filtered, washed with pure water 5 times, and dried at 120° C. to obtain flaky barium sulfate.

[0040] Figure 1 This is a scanning electron microscope image of the flaky barium sulfate described in Example 1. Figure 1 As shown in the figure, the flaky barium sulfate particles in Example 1 have different sizes, and the D 50 The particle size is 10.74 μm, and the particle size distribution is 400 nm ~ 15 μm, with a large particle size fluctuation range.

[0041] Example 2

[0042] This embodiment provides a method for preparing flaky barium sulfate, and the specific preparation steps are as follows:

[0043] S1. Weigh 2.84kg of sodium sulfate and 28.4kg of sodium chloride, stir in 130kg of water until dissolved, add 4.16kg of barium chloride, and continue stirring for 15min to obtain a mixture;

[0044] S2. The mixture in step S1 was transferred to a high-pressure reactor, the reactor temperature was raised to 200°C, the temperature was kept for 48 hours, the temperature was naturally cooled to room temperature, and the precipitate was collected.

[0045] S3. The precipitate in step S2 was filtered, washed 5 times with pure water, and dried at 120°C to obtain flaky barium sulfate. D 50The particle size is 11.06μm, and the particle size distribution is 400nm~15μm, with a large particle size fluctuation range.

[0046] Example 3

[0047] This embodiment provides a method for preparing flaky barium sulfate, and the specific preparation steps are as follows:

[0048] S1. Weigh 2.84kg of sodium sulfate and 11.36kg of sodium chloride, stir in 130kg of water until dissolved, add 4.16kg of barium chloride, and continue stirring for 15 minutes to obtain a mixture;

[0049] S2. Transfer the mixture in step S1 into a high-pressure reactor, heat the reactor to 150°C, keep the temperature for 24 hours, cool it to room temperature naturally, and collect the precipitate.

[0050] S3. The precipitate in step S2 was filtered, washed 5 times with pure water, and dried at 120°C to obtain flaky barium sulfate. D 50 The particle size is 11.13 μm, and the particle size distribution is 400 nm ~ 15 μm, with a large particle size fluctuation range.

[0051] Example 4

[0052] This embodiment provides a method for preparing a reflective thermal insulation coating, and the specific preparation steps are as follows:

[0053] S1. By mass percentage, 40% pure acrylic emulsion, 26.25% deionized water, 0.75% Carbowet GA-100, 0.75% zinc stearate and 0.25% LM-7012 were mixed to obtain a mixture;

[0054] S2. Add 30% of the flaky barium sulfate prepared in Example 1 to the mixture in step S1, by mass percentage, stir, then add 1% of bentonite and 1% of fatty acid amide, stir evenly, to obtain a reflective thermal insulation coating.

[0055] Figure 2 This is a SEM image of the coating surface made of the reflective heat-insulating coating prepared in Example 4. Figure 2 It can be seen that the coating surface is smooth and dense, with small cracks and excellent coating quality.

[0056] Example 5

[0057] This embodiment provides a method for preparing a reflective thermal insulation coating, and the specific preparation steps are as follows:

[0058] S1. By mass percentage, 60% styrene acrylic emulsion, 26.25% deionized water, 0.75% Dynol 607, 0.75% sodium stearate and 0.25% of Kasson were mixed to obtain a mixture;

[0059] S2. Add 10% of the flaky barium sulfate prepared in Example 2 to the mixture in step S1, stir, then add 1% of polyvinyl alcohol and 1% of epoxy resin, stir evenly, and obtain a reflective thermal insulation coating.

[0060] Example 6

[0061] This embodiment provides a method for preparing a reflective thermal insulation coating, and the specific preparation steps are as follows:

[0062] S1. By mass percentage, 20% acetic acid acrylic emulsion, 24.4% deionized water, 0.6% Carbowet GA-100, 0.6% zinc stearate and 0.4% LM-7012 were mixed to obtain a mixture;

[0063] S2. Add 50% of the flaky barium sulfate prepared in Example 3 to the mixture in step S1, stir, then add 2% of bentonite and 2% of fatty acid amide, stir evenly, and obtain a reflective thermal insulation coating.

[0064] Example 7

[0065] This embodiment provides a reflective heat-insulating coating, which differs from embodiment 4 only in that the pure acrylic emulsion in step S1 of embodiment 4 is replaced with a silicone acrylic emulsion. The specific preparation steps are as follows:

[0066] S1. By mass percentage, 40% silicone acrylic emulsion, 26.25% deionized water, 0.75% Carbowet GA-100, 0.75% zinc stearate and 0.25% LM-7012 were mixed to obtain a mixture;

[0067] S2. Add 30% of the flaky barium sulfate prepared in Example 1 to the mixture in step S1, by mass percentage, stir, then add 1% of bentonite and 1% of fatty acid amide, stir evenly, to obtain a reflective thermal insulation coating.

[0068] Comparative Example 1

[0069] This comparative example provides a flaky barium sulfate, which differs from Example 1 only in the mass ratio of sodium sulfate to sodium chloride. The specific preparation steps are as follows:

[0070] S1. Weigh 2.84kg of sodium sulfate and 2.84kg of sodium chloride, stir in 130kg of water until dissolved, add 4.16kg of barium chloride with stirring, and continue stirring for 15min to obtain a mixture;

[0071] S2. The mixture in step S1 was transferred to a high-pressure reactor, the reactor temperature was raised to 160°C, the temperature was kept for 36 hours, the temperature was naturally cooled to room temperature, and the precipitate was collected.

[0072] S3. The precipitate in step S2 was filtered, washed with pure water 5 times, and dried at 120° C. to obtain flaky barium sulfate.

[0073] Figure 3 This is a scanning electron microscope image of the flaky barium sulfate prepared in Comparative Example 1. Figure 3 It can be seen that when the amount of sodium chloride added is reduced, the obtained barium sulfate is still flaky, but the particle size is significantly reduced, with the maximum particle size being about 5μm. 50 The particle size is 3.58 μm, and the particle size distribution is 500 nm ~ 5 μm, with a small particle size fluctuation range.

[0074] Comparative Example 2

[0075] This comparative example provides a barium sulfate, which differs from Example 1 in that no sodium chloride is added, the heating reaction temperature is changed from 160° C. to 80° C., and the heating reaction time is changed from 36 h to 24 h. The specific preparation steps are as follows:

[0076] S1. Weigh 2.84kg of sodium sulfate and stir in 130kg of water until dissolved. Add 4.16kg of barium chloride with stirring and continue stirring for 15min to obtain a mixture;

[0077] S2. The mixture in step S1 was transferred to a high-pressure reactor, the reactor temperature was raised to 80°C, the temperature was kept for 24 hours, the temperature was naturally cooled to room temperature, and the precipitate was collected.

[0078] S3. The precipitate in step S2 was filtered, washed with pure water 5 times, and dried at 120° C. to obtain barium sulfate.

[0079] Figure 4 The scanning electron microscope image of the barium sulfate prepared in Comparative Example 2 is Figure 4 It can be seen that the D of barium sulfate 50 The particle size is 1.62 μm, and the particle size distribution is mainly between 1 and 2 μm.

[0080] Comparative Example 3

[0081] This comparative example provides a barium sulfate, which differs from Example 1 in that the barium chloride in step S1 is replaced with concentrated sulfuric acid, and the sodium sulfate and sodium chloride are replaced with barium hydroxide octahydrate. The specific preparation steps are as follows:

[0082] S1. Weigh 3.15 kg of barium hydroxide octahydrate and stir it in 56 kg of water until dissolved to obtain a barium hydroxide solution. Weigh 9.5 kg of pure water and 1.00 kg of 98% concentrated sulfuric acid and mix them thoroughly to obtain a sulfuric acid solution.

[0083] S2. The barium hydroxide solution and sulfuric acid solution in step S1 were transferred to a high-pressure reactor, and 10 kg of water was added. The mixture and the sulfuric acid solution were added for about 30 minutes. After the addition was completed, the mixture was stirred for 30 minutes and the precipitate was collected.

[0084] S3. The precipitate in step S2 is filtered, washed with pure water 5 times, and dried at 100° C. to obtain barium sulfate.

[0085] Figure 5 This is a perspective electron microscope image of the barium sulfate prepared in Comparative Example 3. Figure 5 It can be seen that the D of barium sulfate 50 The particle size is 410nm and is in the range of 100~500nm.

[0086] Comparative Example 4

[0087] This comparative example provides a reflective heat-insulating coating, which differs from Example 4 only in that the flaky barium sulfate prepared in Example 1 in step S2 of Example 4 is replaced with the flaky barium sulfate prepared in Comparative Example 1. The specific preparation steps are as follows:

[0088] S1. By mass percentage, 40% pure acrylic emulsion, 26.25% deionized water, 0.75% Carbowet GA-100, 0.75% zinc stearate and 0.25% LM-7012 were mixed to obtain a mixture;

[0089] S2. By mass percentage, 30% of the flaky barium sulfate prepared in Comparative Example 1 was added to the mixture in step S1, stirred, and then 1% of bentonite and 1% of fatty acid amide were added and stirred evenly to obtain a reflective thermal insulation coating.

[0090] Comparative Example 5

[0091] This comparative example provides a reflective heat-insulating coating, which differs from Example 4 only in that the flaky barium sulfate prepared in Example 1 in step S2 of Example 4 is replaced with the barium sulfate prepared in Comparative Example 2. The specific preparation steps are as follows:

[0092] S1. By mass percentage, 40% pure acrylic emulsion, 26.25% deionized water, 0.75% Carbowet GA-100, 0.75% zinc stearate and 0.25% LM-7012 were mixed to obtain a mixture;

[0093] S2. In terms of mass percentage, 30% of the barium sulfate prepared in Comparative Example 2 was added to the mixture in step S1, stirred, and then 1% of bentonite and 1% of fatty acid amide were added and stirred evenly to obtain a reflective thermal insulation coating.

[0094] Comparative Example 6

[0095] This comparative example provides a reflective heat-insulating coating, which differs from Example 4 only in that the flaky barium sulfate prepared in Example 1 in step S2 of Example 4 is replaced with the barium sulfate prepared in Comparative Example 3. The specific preparation steps are as follows:

[0096] S1. By mass percentage, 40% pure acrylic emulsion, 26.25% deionized water, 0.75% Carbowet GA-100, 0.75% zinc stearate and 0.25% LM-7012 were mixed to obtain a mixture;

[0097] S2. In percentage by mass, 30% of the barium sulfate prepared in Comparative Example 3 was added to the mixture in step S1, stirred, and then 1% of bentonite and 1% of fatty acid amide were added and stirred to obtain a reflective thermal insulation coating.

[0098] Performance Testing

[0099] The reflective thermal insulation coatings prepared in Examples 4 to 7 and Comparative Examples 4 to 6 were subjected to performance testing. Specifically, the coatings were applied to the same aluminum plate using an applicator to form a 500 μm thick dry film coating. The lightness (L*), solar reflectance, near-infrared reflectance, hemispherical emissivity, and thermal insulation performance of the coatings were tested.

[0100] Brightness was tested using a colorimeter.

[0101] The solar reflectance and near-infrared reflectance of the coating are tested according to the provisions of 6.4 of JG / T235-2014.

[0102] The hemispherical emissivity of the coating is tested according to the provisions of 6.5 of JG / T235-2014.

[0103] The thermal insulation temperature difference of the coating is tested according to the provisions of Appendix B of GBT25261-2018.

[0104] The test results are shown in Table 1 below:

[0105] Table 1. Performance test results of reflective thermal insulation coatings.

[0106] sample Lightness L* Solar reflectance (%) Near infrared reflectance (%) Hemispherical reflectivity (%) Insulation temperature difference (℃) Example 4 99.63 94.2 93.8 95.3 24.5 Example 5 99.62 94.3 93.6 95.6 24.3 Example 6 99.59 94.1 93.7 95.4 24.6 Example 7 99.57 98.6 97.3 91.7 27.8 Comparative Example 4 99.37 82.4 82.0 82.9 15.8 Comparative Example 5 99.11 81.1 79.6 79.5 13.2 Comparative Example 6 98.24 78.3 71.7 73.3 8.9

[0107] As shown in Table 1, the reflective thermal insulation coatings prepared in Examples 4-7 all had lightness L* values ​​close to 99.6, demonstrating high brightness. Their solar reflectances were all above 94%, demonstrating excellent solar radiation reflectivity. Their near-infrared reflectances were all close to 93.7%, demonstrating high near-infrared radiation reflectivity. Their hemispherical emissivities were all above 95%, demonstrating high thermal radiation reflectivity. Their thermal insulation temperature differences were all above 24°C, demonstrating excellent thermal insulation performance. Furthermore, the reflective thermal insulation coatings prepared in Examples 4-7 of the present invention all exhibited superior lightness, solar reflectance, far-infrared reflectance, hemispherical emissivity, and thermal insulation temperature difference compared to the reflective thermal insulation coatings prepared in Comparative Examples 4-6 of the present invention, demonstrating excellent thermal insulation performance.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, technicians can still modify or replace the specific implementation methods of the present invention with equivalents, but these modifications or changes do not depart from the scope of protection of the pending claims of the present application.

Claims

1. A reflective heat-insulating coating, characterized in that: The invention comprises 10-50% of flaky barium sulfate and 20-60% of aqueous resin emulsion in terms of mass percentage. The particle size of the flaky barium sulfate is distributed in a wide range of 400nm-15μm.

2. The reflective heat-insulating coating according to claim 1, characterized in that: The D of the flake barium sulfate 50 >10μm.

3. The reflective heat-insulating coating according to claim 1, characterized in that: The water-based resin emulsion is selected from at least one of pure acrylic emulsion, styrene acrylic emulsion, silicone acrylic emulsion and acetate acrylic emulsion.

4. The reflective heat-insulating coating according to claim 3, characterized in that: The aqueous resin emulsion is selected from silicone acrylic emulsion.

5. The reflective heat-insulating coating according to claim 1, characterized in that: Calculated by mass percentage, the reflective heat-insulating coating further includes 0.5-2.5% thickener, 0.5-2.5% plasticizer, 0.5-1% wetting agent, 0.5-1% defoaming agent, 0.1-0.5% bactericide, and the balance deionized water.

6. The reflective heat-insulating coating according to any one of claims 1 to 2, characterized in that: The preparation method of the flaky barium sulfate comprises the following steps: Sodium sulfate and sodium chloride in a mass ratio of 1:4 to 1:10 are dissolved in water, stirred to dissolve, barium chloride is added, stirred and mixed, heated to react, and purified to obtain flaky barium sulfate.

7. The reflective heat-insulating coating according to claim 6, characterized in that: The mass ratio of the sodium sulfate to the barium chloride is 1:1.2-2.

8. The reflective heat-insulating coating according to claim 6, wherein: The heating reaction temperature is 150-200° C. and the time is 24-48 hours.

9. A method for preparing the reflective thermal insulation coating according to any one of claims 1 to 5, characterized in that: The steps include: S1. The aqueous resin emulsion, deionized water, a wetting agent, a defoamer and a fungicide are mixed to obtain a mixture; S2. Add flaky barium sulfate to the mixture, stir, then add a thickener and a plasticizer, stir evenly, to obtain a reflective thermal insulation coating.

Images