Preparation method of a radiation heat insulation functional coating

Abstract

The application discloses a preparation method of a radiation heat insulation functional coating. The method comprises the following steps: (1) dispersing chitosan powder in a dilute acid solution, adding a strong oxidizing reagent to perform an oxidation reaction, and then performing washing and drying; (2) dispersing the chitosan powder obtained in the step (1) in an acid solution, and then adding ATO nano particles to perform a reaction; (3) performing washing and drying on the ATO-chitosan obtained in the step (2) to obtain modified nano ATO functional particles; and (4) adding the modified nano ATO functional particles, organic epoxy resin, a curing agent and optional additives into a reactor according to a proportion, fully mixing and uniformly mixing to prepare the radiation heat insulation functional coating. In the application, the chitosan is applied to the coating system, the dispersity of the filler ATO is improved, and the biological compatibility and the heat insulation performance of the coating are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical raw materials and chemical product manufacturing, and particularly relates to a preparation method of a radiation heat insulation functional coating. BACKGROUND

[0002] In order to avoid the accumulation of solar energy on the surface of an object to cause temperature rise, a coating is needed to dissipate the heat. The principle of a radiation coating is to dissipate the accumulated heat on the surface of an object in the form of radiation to the outside space to reduce the residual accumulated temperature of the object. Even on cloudy days and at night, without energy input, the coating can still reduce the surface temperature of the object by radiating heat. However, the fillers used in such a functional coating have poor dispersibility in the resin, the preparation process is relatively complex, and the use cost is relatively high. At present, the preparation method of such a coating still needs further research.

[0003] ATO is often used to prepare a radiation heat insulation functional coating as a radiation functional filler. However, ATO has poor dispersibility in the slurry. In order to improve the dispersibility of ATO in the coating, silane coupling agents such as KH-550 and KH-570 are often used. Under certain conditions, ATO reacts with the coupling agent to graft organic side chains on the surface of ATO, thereby improving the compatibility of ATO with the organic resin matrix. However, this method is relatively single, and has no beneficial effect on the weather resistance and flexibility of the coating. Wood cellulose can also be used to modify ATO. However, wood cellulose is usually sulfonated before reacting with ATO, which increases the difficulty of the reaction and makes the process more complex, thereby limiting its large-scale application.

[0004] Antimony tin oxide (ATO) is a metal-doped oxide. Due to its certain radiation effect on the infrared light region of sunlight, it is often used to prepare a radiation heat insulation functional coating. However, due to its inorganic metal oxide, the compatibility of ATO with the organic polymer resin matrix is poor. In addition, the surface energy of ATO particles is high, and a certain amount of hydroxyl groups is distributed on the surface of ATO particles. The hydroxyl groups between particles are easy to form hydrogen bonds to cause aggregation. At the same time, matter tends to be relatively stable. ATO particles with high surface energy will also concentrate in large quantities to reduce their surface energy to maintain stability.

[0005] In coatings, this manifests as a large agglomeration of ATO particles, resulting in extremely uneven dispersion and consequently, inconsistent radiative thermal insulation properties. Areas with a higher concentration of functional particles exhibit stronger infrared radiation and better insulation; however, due to severe particle agglomeration, the resin cannot completely encapsulate the nanoparticles, affecting the surface smoothness of the coating and leading to defects such as pinholes and craters. This negatively impacts the coating's basic physical properties and corrosion resistance. In areas with fewer ATO particles, the coating is merely a transparent resin layer, offering no infrared radiation blocking effect. Light can directly penetrate the coating and reach the interior of the object, rendering the coating ineffective in providing thermal insulation and cooling. Therefore, improving the dispersion of ATO functional particles in the coating is crucial for enhancing its overall performance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a radiation-insulating coating to solve the technical problem of poor dispersibility of the coating system obtained by existing dispersion technology and coating preparation methods.

[0007] The present invention provides a method for preparing a radiation-insulating heat-insulating coating, comprising the following:

[0008] (1) Disperse chitosan powder in an acid solution, add a strong oxidizing agent while stirring, adjust the pH value to 1-2, and oxidize for a period of time; wash and dry the resulting chitosan powder;

[0009] (2) The chitosan powder obtained in step (1) is dispersed in an acid solution, and then the dispersed ATO nanoparticles are added under stirring and heated to carry out the reaction;

[0010] (3) The ATO-chitosan obtained in step (2) is washed and dried to obtain modified nano-ATO functional particles;

[0011] (4) The modified nano-ATO functional particles, organic epoxy resin, curing agent and optional additives obtained in step (3) are added to the reactor in proportion and mixed thoroughly to obtain a radiation heat insulation functional coating.

[0012] Furthermore, in the above technical solution, the strong oxidizing agent mentioned in step (1) includes one or more of potassium permanganate, concentrated sulfuric acid, potassium dichromate, concentrated nitric acid, and carbon tetrachloride, preferably potassium permanganate or potassium dichromate. In step (1), the pH value of the system can be adjusted by controlling the amount of concentrated acid reagents such as concentrated sulfuric acid and concentrated nitric acid.

[0013] Furthermore, in the above technical solution, the washing and drying of chitosan powder in step (1) adopts conventional operations in the field. For example, washing can be done by centrifugal washing, and the drying conditions are generally: drying temperature is 25±10 ℃, and drying time is generally 12±4 h.

[0014] Furthermore, in the above technical solution, the reaction temperature in step (1) is 70±20 ℃ and the reaction time is 2-5 h.

[0015] Furthermore, in the above technical solution, the acid solution mentioned in steps (1) and (2) is selected from at least one of dilute hydrochloric acid and dilute sulfuric acid solution. The dispersion in step (2) can be carried out by mechanical stirring or ultrasonic dispersion, preferably ultrasonic dispersion. The reaction temperature in step (2) is 85±20 ℃, and the reaction time is 2-6 h.

[0016] Furthermore, in the above technical solution, the washing in steps (1) and (3) needs to be performed until the pH value of the solution is 7-8. The drying adopts conventional operation in the art.

[0017] Furthermore, the optional additives mentioned in step (4) are selected from at least one of dispersants, defoamers, leveling agents, thickeners, etc.

[0018] Furthermore, in the above technical solution, the mixing temperature in step (4) is 25±10 ℃. The stirring speed is 600±100 rpm, and the coating preparation method adopts conventional operation in the art.

[0019] Furthermore, in step (4), the coating substrate is an organic epoxy resin, the curing agent is a fatty amine, and the other additives are dispersants, defoamers, leveling agents, thickeners, etc. The auxiliary functional fillers are rust inhibitors, descaling agents, etc. The coating method is spraying, and the curing conditions are a temperature of 25±10 ℃ and a humidity of 50±15%.

[0020] Based on research findings, the applicant discovered that both ATO nanoparticles and chitosan have active groups on their surfaces capable of condensation reactions. By utilizing these active reactive groups (mainly hydroxyl groups), under suitable reaction conditions, the hydroxyl groups on the chitosan surface can be oxidized to carboxyl groups, which then undergo a condensation reaction with the hydroxyl groups on the ATO surface. This condensation reaction generates ester bonds, forming a unified whole between ATO and chitosan. Simultaneously, due to the good compatibility of chitosan with the epoxy resin matrix, the modified ATO particles bond together with the chitosan, thus improving the dispersibility of ATO in the resin matrix. When the ATO particles are more uniformly dispersed, the thermal insulation performance of the coating is more uniform throughout, and the stress concentration points caused by the aggregation of ATO particles are reduced, resulting in a significant improvement in the thermal insulation and physical properties of the coating. However, because the hydroxyl groups on the chitosan and ATO surfaces are not highly reactive, the reaction rate is slow and the conversion rate is low at room temperature. Therefore, strong acid oxidation treatment can be applied to chitosan, oxidizing the hydroxyl groups to carboxyl groups under strong acid conditions, effectively increasing the number of carboxyl groups on the particle surface. As the number of reactive groups increases, the esterification reactivity improves, and a higher reaction temperature is provided, thereby increasing the reaction rate and promoting the esterification reaction.

[0021] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0022] 1. In this invention, chitosan is applied to a coating system to improve the dispersibility of the filler ATO through a chemical grafting reaction. Simultaneously, the inherent properties of chitosan endow the coating with excellent properties such as biocompatibility and biodegradability, and improve the flexibility of the brittle polymer matrix, thereby enhancing the overall performance of the coating. The modified ATO functional coating prepared by the method of this invention has radiative heat insulation function. The addition of chitosan gives the coating certain biocompatibility and biodegradability, while also contributing to improving the toughness of the coating.

[0023] 2. Chitosan, as a natural bio-based polymer, is green, environmentally friendly, and pollution-free, making it more friendly to both humans and the environment. It can degrade naturally. Its sources are widespread and abundant in nature, which can significantly reduce operating costs.

[0024] 3. Compared with the traditional method of using silane coupling agents to improve the dispersibility of ATO particles, this invention provides a new approach to modifying the surface of ATO, which improves particle dispersibility while simplifying the reaction process and reducing production costs.

[0025] In summary, the method of this invention for modifying ATO nanoparticles and preparing a radiation-insulating thermal coating has certain advantages. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the self-made temperature difference testing device used in this invention.

[0027] Among them, 1-infrared lamp, 2-thermometer, 3-foam box, 4-blank sample, 5-test plate. Detailed Implementation

[0028] The present invention will now be described in more detail with reference to specific embodiments.

[0029] Thermal insulation temperature difference test: Thermal insulation temperature difference is the most intuitive way to characterize the thermal insulation performance of a coating; however, there is currently no unified standard for testing thermal insulation temperature difference. This article refers to the thermal insulation temperature difference test method in HG / T 4341-2012 "Heat Reflective Coatings for Metal Surfaces" and uses a self-made experimental device for testing.

[0030] This apparatus uses a polystyrene foam insulation box measuring 420 mm × 330 mm × 330 mm with a wall thickness of 50 mm. The interior is divided into two sections by a 50 mm thick foam material. A 150 mm × 70 mm notch is cut at the top of each compartment. The test panel and a blank sample are placed on these notches, respectively. Two 250 W infrared lamps are placed directly above each compartment to uniformly irradiate the samples. Thermocouples are used to measure the temperature of the back of the test panel and the temperature inside the insulation box. The temperature difference between the back of the blank sample and the stable temperature of the test panel after a period of irradiation is used to represent the thermal insulation temperature difference of the sample. The sample substrate is a 150 mm × 70 mm × 2 mm sandblasted steel plate, coated with a primer + intermediate coat + topcoat system. After coating, the sample needs to be cured in a constant temperature and humidity chamber for 7 days. The test is conducted at 25 ± 10 ℃.

[0031] Example 1

[0032] 5 g of chitosan powder was dispersed in 20 mL of dilute sulfuric acid. While stirring, 0.83 g of potassium permanganate was added to adjust the pH to 1.5. The temperature was maintained at 90 °C, and the oxidation reaction was carried out for 5 h. The oxidized chitosan was then washed three times with alcohol and three times with water, and dried in an oven at 35 °C for 16 h. The dried oxidized chitosan was added to 20 mL of dilute sulfuric acid and sonicated for 30 min to disperse the oxidized chitosan powder. Then, 7.5 g of dispersed ATO particles were added while heating and stirring at 105 °C. The mixture was then maintained at 105 °C and sonicated for 6 h to ensure complete reaction. The condensation-modified ATO nanoparticles-chitosan were centrifuged and washed several times until the solution pH reached 7.5. The solution was then dried in an oven at 25 °C for 24 h to obtain modified ATO functional particles.

[0033] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0034] The resulting coating was sprayed with a spray gun after being cured for about 10 minutes, and then placed in a constant temperature and humidity chamber at 25 ℃ and 50% humidity for 7 days before its performance was tested.

[0035] Example 2

[0036] 10 g of chitosan powder was dispersed in 30 mL of dilute hydrochloric acid. While stirring, 1.8 g of potassium dichromate was added to adjust the pH to 1. The temperature was maintained at 50 °C, and the oxidation reaction was carried out for 2 h. The oxidized chitosan powder was then washed three times with alcohol and three times with water, and dried in an oven at 15 °C for 2 h. The dried oxidized chitosan powder was added to 35 mL of dilute hydrochloric acid and sonicated for 20 min to disperse the powder. Then, 20 g of dispersed ATO nanoparticles were added while heating and stirring at 65 °C. The mixture was then maintained at 65 °C and sonicated for 2 h to ensure complete reaction. The condensation-modified ATO nanoparticle-chitosan mixture was centrifuged and washed several times until the solution pH reached 7. The mixture was then dried in an oven at 25 °C for 24 h to obtain modified ATO functional particles.

[0037] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0038] The resulting coating was cured for about 10 minutes and then sprayed with a spray gun. After that, it was placed in a constant temperature and humidity chamber at 20 ℃ and 50% humidity for 7 days and then its performance was tested.

[0039] Example 3

[0040] 12 g of chitosan powder was dispersed in 40 mL of dilute sulfuric acid. While stirring, 4.3 g of concentrated nitric acid was added to adjust the pH to 1.5, and the temperature was maintained at 65 °C for 3.5 h for oxidation. The oxidized chitosan powder was then washed three times with alcohol and three times with water, and dried in an oven at 25 °C for 10 h. The dried chitosan was then added to 20 mL of dilute sulfuric acid and sonicated for 30 min to disperse it. Then, while heating and stirring at 85 °C, 30 g of dispersed ATO nanoparticles were added, and the mixture was sonicated for 4 h to ensure complete reaction. The condensation-modified ATO nanoparticle-chitosan mixture was centrifuged and washed several times until the solution pH reached 8, and then dried in an oven at 25 °C for 24 h to obtain modified ATO functional particles.

[0041] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0042] The resulting coating was cured for about 10 minutes and then sprayed with a spray gun. After that, it was placed in a constant temperature and humidity chamber at 20 ℃ and 60% humidity for 7 days and then its performance was tested.

[0043] Example 4

[0044] 8 g of chitosan powder was dispersed in 20 mL of dilute sulfuric acid. While stirring, 3.6 g of potassium permanganate was added to adjust the pH to 2.5, and the temperature was maintained at 60 °C for 3.5 h for oxidation. The oxidized chitosan powder was then washed three times with alcohol and three times with water, and dried in an oven at 25 °C for 24 h. The dried chitosan was added to 40 mL of dilute sulfuric acid and sonicated for 30 min to disperse the oxidized chitosan. Then, 24 g of dispersed ATO nanoparticles were added while heating and stirring at 90 °C. The mixture was then maintained at 90 °C and sonicated for 6 h to ensure complete reaction. The condensation-modified ATO nano-chitosan was centrifuged and washed several times until the solution pH reached 7. The solution was then dried in an oven at 25 °C for 24 h to obtain modified ATO functional particles.

[0045] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0046] The resulting coating was cured for about 10 minutes and then sprayed with a spray gun. After that, it was placed in a constant temperature and humidity chamber at 25 ℃ and 65% humidity for 7 days and then its performance was tested.

[0047] Example 5

[0048] 5 g of chitosan powder was dispersed in 20 mL of dilute sulfuric acid. While stirring, 1.3 g of carbon tetrachloride was added to adjust the pH to 1.5. The temperature was maintained at 80 °C for 4.5 h for oxidation. The oxidized chitosan powder was then washed three times with alcohol and three times with water, and dried in an oven at 25 °C for 24 h. The dried chitosan was added to 20 mL of dilute sulfuric acid and sonicated for 30 min to disperse the oxidized chitosan. Then, 12.5 g of dispersed ATO nanoparticles were added while heating and stirring at 100 °C. The mixture was then maintained at 100 °C and sonicated for 4 h to ensure complete reaction. The condensation-modified nano-ATO-chitosan was centrifuged and washed several times until the solution pH reached 7. The solution was then dried in an oven at 25 °C for 24 h to obtain modified ATO functional particles.

[0049] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0050] The resulting coating was cured for about 10 minutes and then sprayed with a spray gun. After that, it was placed in a constant temperature and humidity chamber at 25 ℃ and 50% humidity for 7 days to test its performance.

[0051] Example 6

[0052] 15 g of chitosan powder was dispersed in 40 mL of dilute hydrochloric acid. While stirring, 4.2 g of potassium permanganate was added to adjust the pH to 1.5. The temperature was maintained at 85 °C for 3.5 h of oxidation reaction. The oxidized chitosan powder was then washed three times with alcohol and three times with water, and dried in an oven at 25 °C for 24 h. The dried chitosan was then added to 20 mL of dilute sulfuric acid and sonicated for 30 min to disperse the oxidized chitosan. Then, while heating and stirring at 95 °C, 37.5 g of dispersed ATO nanoparticles were added. The mixture was then maintained at 95 °C and sonicated for 3 h to ensure complete reaction. The condensation-modified ATO nanoparticles-chitosan were centrifuged and washed several times until the solution pH reached 7. The solution was then dried in an oven at 25 °C for 48 h to obtain modified ATO functional particles.

[0053] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0054] The resulting coating was cured for about 10 minutes and then sprayed with a spray gun. After that, it was placed in a constant temperature and humidity chamber at 20 ℃ and 50% humidity for 7 days to test its performance.

[0055] Example 7

[0056] Add 5 g of chitosan to 20 mL of dilute sulfuric acid and sonicate for 30 min to disperse the chitosan powder. Then, heat and stir at 105 °C while adding 7.5 g of dispersed ATO particles. Maintain the temperature at 105 °C and sonicate for 6 h to ensure complete reaction. Centrifuge and wash the condensation-modified ATO nanoparticles-chitosan several times until the solution pH is 7.5. Dry in an oven at 25 °C for 24 h to obtain modified ATO functional particles.

[0057] Take 8 g of modified particles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0058] The resulting coating was sprayed with a spray gun after being cured for about 10 minutes, and then placed in a constant temperature and humidity chamber at 25 ℃ and 50% humidity for 7 days before its performance was tested.

[0059] Comparative Example 1

[0060] Take 8 g of ATO nanoparticles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, and 3.6 g of leveling agent in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0061] The resulting coating was sprayed with a spray gun after being cured for about 10 minutes, and then placed in a constant temperature and humidity chamber at 25 ℃ and 50% humidity for 7 days before its performance was tested.

[0062] Comparative Example 2

[0063] Take 8 g of ATO nanoparticles and add them to deionized water. After stirring and dispersing, add 0.8 g of dispersant, 0.2 g of defoamer, 3.6 g of leveling agent, and 6.4 g of chitosan in sequence. After dispersing evenly, add 30 g of organic epoxy resin, stir evenly, add auxiliary functional filler, and finally add 2.8 g of fatty amine curing agent. Mix thoroughly to obtain radiation heat insulation functional coating.

[0064] The resulting coating was sprayed with a spray gun after being cured for about 10 minutes, and then placed in a constant temperature and humidity chamber at 25 ℃ and 50% humidity for 7 days before its performance was tested.

[0065] The experimental results obtained from the examples and comparative examples are listed in Table 1.

[0066] Table 1

[0067] Hemispherical emissivity Thermal insulation temperature difference, °C Example 1 0.89 14.8 Example 2 0.89 13.6 Example 3 0.92 16.9 Example 4 0.89 15.2 Example 5 0.90 16.2 Example 6 0.87 15.1 Example 7 0.87 14.2 Comparative Example 1 0.81 9.8 Comparative Example 2 0.83 10.5

Claims

1. A method for preparing a radiation-insulating functional coating, comprising the following: (1) Disperse chitosan powder in an acid solution, add a strong oxidizing agent while stirring, adjust the pH value to 1-2, and oxidize for a period of time; wash and dry the resulting chitosan powder; (2) The chitosan powder obtained in step (1) is dispersed in an acid solution, and then the dispersed ATO nanoparticles are added under stirring and heated to carry out the reaction; (3) The ATO-chitosan obtained in step (2) is washed and dried to obtain modified nano-ATO functional particles; (4) The modified nano-ATO functional particles, organic epoxy resin, curing agent and optional additives obtained in step (3) are added to the reactor in proportion and mixed thoroughly to obtain a radiation heat insulation functional coating.

2. The preparation method according to claim 1, characterized in that, The strong oxidizing agent mentioned in step (1) includes one or more of potassium permanganate, concentrated sulfuric acid, potassium dichromate, and concentrated nitric acid.

3. The preparation method according to claim 2, characterized in that, The strong oxidizing agent mentioned in step (1) is selected from potassium permanganate or potassium dichromate.

4. The preparation method according to claim 1, characterized in that, The drying conditions in step (1) are: drying temperature of 25±10 ℃ and drying time of 12±4 h.

5. The preparation method according to claim 1, characterized in that, The acid solution mentioned in steps (1) and (2) is selected from at least one of dilute hydrochloric acid and dilute sulfuric acid solution.

6. The preparation method according to claim 1, characterized in that, The dispersion described in step (2) is performed using ultrasonic dispersion.

7. The preparation method according to claim 1, characterized in that, The reaction temperature in step (1) is 70±20℃ and the reaction time is 2-5 h. The reaction temperature in step (2) is 85±20℃ and the reaction time is 2-6 h.

8. The preparation method according to claim 1, characterized in that, The washing steps (1) and (3) are to be performed until the pH of the solution is 7-8.

9. The preparation method according to claim 1, characterized in that, The additives mentioned in step (4) are selected from at least one of dispersants, defoamers, leveling agents, and thickeners.

10. The preparation method according to claim 1, characterized in that, The mixing temperature in step (4) is 25±10℃.

11. The preparation method according to claim 1, characterized in that, The curing agent in step (4) is a fatty amine, and the optional additives include one or more of the following: dispersant, defoamer, leveling agent, and thickener.

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