Polyurethane coating with adjustable infrared emissivity, preparation method and application

Abstract

The invention provides a polyurethane coating with adjustable infrared emissivity as well as a preparation method and application thereof. The polyurethane coating with adjustable infrared emissivity is prepared from the following components in parts by mass: 20-25 parts of polyol, 8-10 parts of isocyanate, 0.5-2 parts of a chain extension cross-linking agent, 0.02-0.05 part of a catalyst, 0.15-0.5 part of an auxiliary agent and 60-65 parts of a solvent, the obtained polyurethane coating can keep the infrared emissivity (8-14 [mu] m wave band) within the range of 0.4-0.85 under the environments of damp and hot, salt mist, ultraviolet light and the like, has good light transmission and better mechanical properties, has the advantages of low price of chemical raw materials and simple synthesis process and reaction conditions, and can meet the requirements of large-scale production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of functional organic coatings, and in particular to a polyurethane coating with adjustable infrared emissivity, a preparation method and applications thereof. Background Art

[0002] With the continuous development of infrared detection technology, various equipment and facilities in marine environments are extremely vulnerable to being captured by infrared detection equipment and causing damage. Infrared low-emissivity coatings are widely used on the surfaces of facilities due to their low cost and simple process. In recent years, with the increasing safety requirements of various types of equipment, functional coatings that balance low infrared emissivity and optical compatibility have gradually become a focus of technical research. Compared with traditional infrared low-emissivity coatings, transparent infrared low-emissivity resins can reduce the infrared radiation characteristics of the target without significantly changing the target's appearance, narrowing the infrared characteristic difference with the background, thereby improving environmental adaptability and being suitable for a wider range of application scenarios. However, most current low-emissivity coatings are opaque, making it difficult to achieve both light transmission and infrared low-emissivity functions, limiting their application in complex scenarios such as marine environments. In marine environments, equipment is susceptible to the combined effects of factors such as ultraviolet radiation, high humidity, and salt spray corrosion, requiring functional coatings to ensure its weather resistance.

[0003] High-infrared emissivity coatings are commonly used in radiative thermal insulation coatings, which achieve thermal insulation and cooling by radiating sunlight or heat absorbed by a building into the air at specific wavelengths. Unlike porous barrier or reflective insulation coatings like glass wool and foam plastics, radiative thermal insulation coatings actively release absorbed heat to the outside world as thermal radiation, thereby cooling the building interior and the external environment simultaneously, helping to mitigate the "heat island" effect.

[0004] Therefore, the tunability of infrared emissivity can enhance the active jamming capabilities of infrared camouflage coatings and achieve dynamic thermal management. By adjusting the emissivity, the thermal radiation distribution on the target surface can be actively controlled, enabling thermal signature deception. This involves simulating background thermal characteristics (such as the radiation properties of vegetation and rock) or creating false heat sources (e.g., multiple "false targets"), thereby confusing infrared monitoring equipment. This has important technological value in concealment.

[0005] Polyurethane is widely used in surface coatings for marine facilities due to its adjustable molecular structure, excellent weather resistance, and cold resistance, and has a solid application foundation. However, as a coating film-forming material, existing resin systems still suffer from issues such as difficult-to-control infrared emissivity, limited variety, and insufficient mechanical properties and weather resistance. Existing patent solutions mostly reduce emissivity through filler modification. For example, patent CN119529611A achieves infrared emissivity control by adjusting the ratio of flaky aluminum powder and black filler in the black coating. However, the coating generally lacks good light transmittance, making it difficult to meet the requirements of visible-infrared compatible camouflage applications. In CN101696260A, the optically active polyurethane urea prepared using R-1,1'-binaphthyl-2,2'-diphenol (R-BINOL) has an average infrared emissivity of 0.35-0.80 in the 8-14μm band. However, due to the rigid structure of its chain segments, its mechanical properties and weather resistance cannot meet the requirements of marine environments. Therefore, the development of a polyurethane coating with adjustable infrared emissivity, high light transmittance and high weather resistance, especially for applications under complex conditions such as marine environments, has important technical value and broad market prospects. Summary of the Invention

[0006] In view of this, the present invention aims to propose a polyurethane coating with adjustable infrared emissivity, a preparation method and an application to solve the problems in the prior art that the infrared emissivity cannot be adjusted, it is difficult to balance the light transmittance and infrared emission functions, and the mechanical properties and weather resistance cannot meet the requirements of complex environments such as the ocean.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A polyurethane coating with adjustable infrared emissivity is prepared by mixing the following components in parts by weight: 20-25 parts of polyol, 8-10 parts of isocyanate, 0.5-2 parts of chain extender and cross-linker, 0.02-0.05 parts of catalyst, 0.15-0.5 parts of auxiliary agent, and 60-65 parts of solvent.

[0009] Furthermore, the isocyanate is at least one of fluorinated isocyanate, isophorone diisocyanate, isophorone diisocyanate trimer, and diphenylmethane diisocyanate.

[0010] Furthermore, the fluorinated isocyanate is obtained by reacting one or more of 3-perfluorooctylpropanol, 3-perfluorobutylpropanol, 3-perfluorohexylpropanol, 2,2,3,3,3-pentafluoro-1-propanol, and 1H,1H,2H,2H-perfluorooctanol with isophorone diisocyanate trimer.

[0011] Furthermore, the polyol is at least one of perfluoropolyether diol, hexafluoro-1,10-decanediol, and hydroxy-terminated polybutadiene polyol.

[0012] Furthermore, the chain extending cross-linking agent is at least one of triethanolamine and 1,4-butanediol.

[0013] Furthermore, the auxiliary agent comprises 0.1 to 0.2 parts of a leveling agent and 0.05 to 0.2 parts of a wetting agent.

[0014] Furthermore, the catalyst is dibutyltin dilaurate.

[0015] Furthermore, the solvent is at least one of xylene, cyclohexanone, butyl acetate, and butyl acetate.

[0016] The present application also proposes a method for preparing a polyurethane coating with adjustable infrared emissivity, which is used to prepare the aforementioned polyurethane coating with adjustable infrared emissivity, comprising the following steps:

[0017] S1: Dehydrate the polyol under vacuum conditions at a temperature of 100°C to 140°C for 1 to 3 hours, and dry the solvent with 4A molecular sieves before entering S2;

[0018] S2: The measured polyol, isocyanate, catalyst and solvent are placed in a three-necked flask and stirred to mix. Nitrogen is introduced into the three-necked flask to exhaust the air. The reaction time is 1 to 3 hours and the reaction temperature is 50°C to 80°C. After the reaction is completed, the process proceeds to S3;

[0019] S3: Add the crosslinking agent, leveling agent and wetting agent into a three-necked flask, the reaction temperature is 20°C to 80°C, the reaction time is 1 to 2 hours, and after the reaction is completed, proceed to S4;

[0020] S4: The obtained resin coating is coated and then cured at a curing temperature of 50° C. to 80° C. for 6 to 24 hours. After the curing is completed, a polyurethane coating with adjustable infrared emissivity is obtained.

[0021] Vacuum dehydration reduces the boiling point of water in polyols by lowering the air pressure, effectively removing free water other than hydroxyl groups (-OH), preventing water from reacting with isocyanate to generate CO2 bubbles, and preventing the formation of pores after the coating is cured; 4A molecular sieve removes trace water in the solvent by physical adsorption, ensuring that the reaction system is in an anhydrous environment, avoiding the failure of isocyanate hydrolysis, and preventing water from participating in the cross-linking reaction to form unstable urea bonds (-NHCONH-), affecting the regular arrangement of polar groups in the molecular chain; nitrogen atmosphere can isolate moisture and oxygen in the air, preventing isocyanate from reacting with water to generate amine by-products, and preventing polyols from oxidative deterioration, ensuring the prepolymer The concentration of -NCO groups is controllable, laying the foundation for subsequent cross-linking density adjustment; the chain extender cross-linking agent is added after the prepolymer is formed to prevent the cross-linker from competing with isocyanate for the -OH group of the polyol, ensuring that the cross-linking reaction proceeds in an orderly manner between the prepolymer molecular chains and accurately controlling the cross-linking density; the leveling agent and wetting agent can synergistically reduce the surface tension of the coating, promote uniform spreading of the wet film, and reduce surface wrinkles or shrinkage holes caused by uneven solvent evaporation during curing; the curing temperature is 50-80°C, which is lower than the thermal decomposition temperature of polyurethane (usually >200°C), which can prevent thermal oxidative aging of the molecular chain and provide sufficient energy to completely react the residual -NCO groups to form a dense cross-linked network.

[0022] This preparation method eliminates moisture interference through vacuum dehydration and solvent drying, conducts segmented reactions under nitrogen protection, precisely controls the cross-linking density and molecular chain structure, combines a leveling agent to optimize the surface morphology, and cures at 50-80°C for 6-24 hours to form a stable microphase separation structure. Ultimately, the infrared emissivity is adjustable in a wide range of 0.4-0.85, and the coating has few defects, strong weather resistance, high process repeatability, and is suitable for industrial production.

[0023] The present application also proposes the application of a polyurethane coating with adjustable infrared emissivity as described above in the fields of ships, marine infrastructure, marine detectors, and building energy conservation.

[0024] Compared with the prior art, the polyurethane coating with adjustable infrared emissivity, its preparation method and application described in the present invention have the following advantages:

[0025] 1) The obtained polyurethane coating can maintain the infrared emissivity (8-14μm band) in the range of 0.4 to 0.85 in environments such as humidity, heat, salt fog, and ultraviolet light, while also having good light transmittance and good mechanical properties.

[0026] 2) Its chemical raw materials are inexpensive, and the synthesis process and reaction conditions are simple, which can meet the needs of large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1This is the FTIR spectrum of the fluorinated isocyanate described in the embodiment of the present invention;

[0028] Figure 2 This is a water contact angle test diagram of the sample described in Example 1 of the present invention;

[0029] Figure 3 This is a water contact angle test diagram of the sample described in Example 2 of the present invention;

[0030] Figure 4 This is a water contact angle test diagram of the sample described in Example 3 of the present invention;

[0031] Figure 5 This is a water contact angle test diagram of the sample described in Comparative Example 1 of the present invention;

[0032] Figure 6 This is a water contact angle test diagram of the sample described in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. It should be noted that, unless there is a conflict, the features in the embodiments and embodiments of the present invention may be combined with each other.

[0034] Example 1

[0035] This example provides a polyurethane coating with adjustable infrared emissivity. The preparation method is as follows: 10 parts of IPDIT (isophorone diisocyanate trimer) and 10 parts of EAC (butyl acetate) are added to a three-necked flask equipped with a magnetic stirrer, a dropping funnel, and an N2 line and mixed. 4.17 parts of 3-perfluorobutyl propanol and 4.17 parts of EAC are mixed to obtain a mixture, which is then added dropwise to the three-necked flask over 30 minutes. The ratio of n(IPDIT):n(perfluorobutyl propanol) is 1:1. 0.02 parts of DBTDL (dibutyltin dilaurate) is used as a catalyst. The reaction is carried out at 40°C and stirred under an N2 atmosphere until the residual -NCO group reaches the theoretical value. The di-n-butylamine method is used for determination. The solvent is removed by distillation under reduced pressure, and the system is cooled to 25°C to obtain FIPDIT-1 (a fluorinated isocyanate) as a light yellow oily product.

[0036] The hydroxy-terminated polybutadiene was added to the reactor and dehydrated under vacuum at 120°C for 2 hours. 20.38 parts of the hydroxy-terminated polybutadiene after dehydration was placed in another reactor, and 22.5 parts of xylene, 42.5 parts of cyclohexanone, 5 parts of FIPDIT-1, 2.5 parts of isophorone diisocyanate, 0.02 parts of dibutyltin dilaurate, 0.5 parts of triethanolamine, 0.5 parts of 1,4-butanediol, 0.2 parts of a short-chain fluorocarbon-modified polymer leveling agent, and 0.2 parts of a polyether-modified siloxane wetting agent were added. The mixture was stirred at controlled temperature at 25°C for 2 hours, allowed to stand for 1 hour to eliminate bubbles, and a low-radiation intensity transparent polyurethane coating was obtained. The coating was applied to the surface of an ITO-PMMA substrate, a tinplate plate or a steel plate. After surface drying at room temperature, the coating was cured at 60°C for 8 hours to obtain a low-radiation transparent polyurethane coating with a hard segment content of 29.43%.

[0037] Preferably, the molar fraction of the fluorinated alcohol is 45 to 50 parts, the molar fraction of isophorone diisocyanate trimer is 50 to 55 parts, the catalyst is 0.02 to 0.05 parts, the reaction time of the fluorinated alcohol and isophorone diisocyanate trimer is 1 to 2 hours, and the reaction temperature is 30 to 50°C.

[0038] Preferably, the leveling agent is at least one of a short-chain fluorocarbon-modified polymer leveling agent, a short-chain fluorocarbon-modified polyacrylate leveling agent or a modified silane leveling agent.

[0039] Example 2

[0040] This example provides a polyurethane coating with adjustable infrared emissivity, which is prepared as follows: 10 parts of IPDIT and 10 parts of EAC are added to a three-necked flask equipped with a magnetic stirrer, a dropping funnel, and an N2 conduit and mixed; 5.67 parts of 3-perfluorohexylpropanol are mixed with 5.67 parts of EAC to obtain a mixture, which is added dropwise to the three-necked flask over 30 minutes, wherein n(IPDIT):n(perfluorohexylpropanol)=1:1; 0.02 parts of DBTDL is used as a catalyst; the reaction is carried out at 40°C and stirred under an N2 atmosphere until the residual -NCO group reaches the theoretical value. The di-n-butylamine method is used for determination. The solvent is removed by distillation under reduced pressure, and the system is cooled to 25°C to obtain a light yellow oily product FIPDIT-2.

[0041] The hydroxy-terminated polybutadiene was added to the reactor and dehydrated under vacuum at 120°C for 2 hours. 20.38 parts of the hydroxy-terminated polybutadiene after dehydration was placed in another reactor, and 22.5 parts of xylene, 42.5 parts of cyclohexanone, 5 parts of FIPDIT-2, 2.5 parts of isophorone diisocyanate, 0.02 parts of dibutyltin dilaurate, 0.5 parts of triethanolamine, 0.5 parts of 1,4-butanediol, 0.2 parts of a short-chain fluorocarbon-modified polymer leveling agent, and 0.2 parts of a polyether-modified siloxane wetting agent were added. The mixture was stirred at 25°C for 2 hours and allowed to stand for 1 hour to eliminate bubbles to obtain a low-radiation intensity transparent polyurethane coating. The coating was applied to the surface of an ITO-PMMA substrate, a tinplate plate or a steel sample. After surface drying at room temperature, the coating was cured at 60°C for 8 hours to obtain a low-radiation transparent polyurethane coating with a hard segment content of 29.43%.

[0042] Example 3

[0043] This embodiment provides a polyurethane coating with adjustable infrared emissivity. The preparation method is as follows: polyethylene glycol (molecular weight 2000) is added to a three-necked flask, and the mixture is dehydrated at 120°C in a vacuum for 2 hours. 25 parts of the dehydrated polyethylene glycol are placed in a reactor, and 3 parts of hexafluoro-1,10-decanediol, 22.5 parts of xylene, 42.5 parts of cyclohexanone, 10 parts of FIPDIT-2, 5.5 parts of diphenylmethane diisocyanate, and dibutyl dilaurate dissolved in cyclohexanone and xylene are added. 0.02 parts of tin, 0.5 parts of triethanolamine, 0.5 parts of 1,4-butanediol, 0.2 parts of short-chain fluorocarbon modified polymer leveling agent, and 0.2 parts of polyether modified siloxane wetting agent are stirred at 25°C for 2 hours, allowed to stand for 1 hour to eliminate bubbles, and a high-radiation-intensity transparent polyurethane coating is obtained. The coating is applied to an ITO-PMMA substrate, a tinplate plate or a steel sample surface, and after surface drying at room temperature, it is cured at 60°C for 8 hours to obtain a high-radiation transparent polyurethane coating with a hard segment content of 37.08%.

[0044] Comparative Example 1

[0045] The preparation method of this comparative example is as follows:

[0046] Hydroxyl-terminated polybutadiene was added to a reactor and dehydrated under vacuum at 120°C for 2 hours. 20.38 parts of the dehydrated hydroxyl-terminated polybutadiene was then transferred to another reactor, where 5 parts of IPDIT, 22.5 parts of xylene, 42.5 parts of cyclohexanone, 2.2 parts of isophorone diisocyanate, and 0.02 parts of dibutyltin dilaurate were added. After a 2-hour reaction, 0.5 parts of triethanolamine, 0.5 parts of 1,4-butanediol, 0.2 parts of a short-chain fluorocarbon-modified polymer leveling agent, and 0.2 parts of a polyether-modified siloxane wetting agent were added. The mixture was stirred at 25°C for 2 hours and allowed to stand for 1 hour to eliminate bubbles, resulting in a low-emissivity, transparent polyurethane coating. This coating was then applied to an ITO-PMMA substrate, tinplate, or steel sample. After surface drying at room temperature, it was cured at 60°C for 8 hours to produce a low-emissivity, transparent polyurethane coating with a hard segment content of 28.69%.

[0047] Comparative Example 2

[0048] The preparation method of this comparative example is as follows:

[0049] Polytetrahydrofuran diol (molecular weight 2000) was added to a reactor, and the mixture was vacuum-dehydrated at 120°C for 2 hours. 20 parts of the dehydrated polytetrahydrofuran diol were placed in another reactor, and 5 parts of IPDIT, 22.5 parts of xylene, 42.5 parts of cyclohexanone, 2.5 parts of isophorone diisocyanate, 0.02 parts of dibutyltin dilaurate, 0.5 parts of triethanolamine, 0.5 parts of 1,4-butanediol, 0.2 parts of a short-chain fluorocarbon-modified polymer leveling agent, and 0.2 parts of a polyether-modified siloxane wetting agent were added. The mixture was stirred at controlled temperature at 25°C for 2 hours, and allowed to stand for 1 hour to eliminate bubbles to obtain a polyurethane coating of Comparative Example 2. The coating was applied to an ITO-PMMA substrate, a tinplate plate or a steel sample surface. After surface drying at room temperature, the coating was cured at 60°C for 8 hours to obtain a polyurethane coating with a hard segment content of 29.82%.

[0050] The performance test results of the coatings of Examples 1, 2, and 3 and Comparative Examples 1 and 2 are as follows:

[0051] Infrared emissivity test results: The infrared emissivity of the coating in the 8-14 μm band was measured using an IR-2 dual-band emissivity meter. The results are shown in Table 1.

[0052] Table 1 Sample infrared emissivity test results

[0053]

[0054] Mechanical properties, transmittance, haze, and adhesion test results: The tensile strength of the resin coating was tested according to the standard GB / T1040.1-2006, and the transmittance and haze were tested using the WGT-S transmittance / haze meter from Shanghai Shenguang Instrument Co., Ltd. The results are shown in Table 2:

[0055] Table 2 Test results of sample mechanical properties, transmittance, haze and adhesion

[0056]

[0057] Chemical resistance test: Chemical resistance was measured in accordance with GB / T1763-79. The cured polyurethane was placed in different solvents for the specified time, taken out, and blotted dry with filter paper. The coating surface was observed for gloss loss, discoloration, blistering, spotting, or shedding. The results are shown in Table 3.

[0058] Table 3 Chemical resistance test results of samples

[0059]

[0060] 5 = coating is not affected; 4 = discoloration, loss of gloss; 3 = film blistering;

[0061] 2 = softened; 1 = film partially peeled off from tinplate; 0 = completely peeled off from tinplate

[0062] Water contact angle: The water contact angle was measured by an OCA20 contact angle meter from DATAPHYSICS, Germany. The results are shown in Table 4:

[0063] Table 4 Water contact angle test results of samples

[0064]

[0065] UV aging resistance test: The UV aging resistance test was carried out using a UV accelerated aging test chamber, and the infrared emissivity (8-14 μm) test was carried out before and after UV aging treatment. The results are shown in Table 5.

[0066] Table 5 Infrared emissivity test results of samples after UV aging treatment

[0067]

[0068] Salt spray resistance test: The salt spray test was carried out in accordance with the standard GB / T2423.65, and the infrared emissivity (8-14μm) was tested before and after salt spray treatment. The results are shown in Table 6.

[0069] Table 6 Infrared emissivity test results of samples after salt spray aging treatment

[0070]

[0071] In the aforementioned embodiments, the fluorinated polyurethanes all exhibited good salt spray aging resistance, the infrared radiation performance did not change, and the coating surface did not change significantly. However, after 350 hours of salt spray aging treatment, defects appeared on the surfaces of Comparative Examples 1 and 2.

[0072] exist Figure 1 Medium 1192cm -1 The nearby peak is the characteristic absorption of -CF2-, and the original isocyanate trimer does not appear. Figure 1 The characteristic peaks in , indicate that 3-perfluorobutylpropanol and 3-perfluorohexylpropanol have been successfully grafted onto the isocyanate trimer.

[0073] like Figure 5-6 As shown, the contact angles of Comparative Examples 1 and 2 without adding fluorine-containing carbon chains are both low, and there is no hydrophobic effect. Figure 2-4 As shown, in the embodiments in which fluorine-containing carbon chains are added, the water contact angle is greater than 105°, which has a good hydrophobic effect. Moreover, as the length of the fluorine-containing carbon chain increases, the hydrophobic effect becomes more excellent.

[0074] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A polyurethane coating with adjustable infrared emissivity, characterized in that: The polyurethane coating with adjustable infrared emissivity is prepared according to the following components in parts by mass: 20-25 parts of polyol, 8-10 parts of isocyanate, 0.5-2 parts of chain extender and crosslinker, 0.02-0.05 parts of catalyst, 0.15-0.5 parts of auxiliary agent, and 60-65 parts of solvent.

2. The polyurethane coating with adjustable infrared emissivity according to claim 1, characterized in that: The isocyanate is at least one of fluorine-containing isocyanate, isophorone diisocyanate, isophorone diisocyanate trimer, and diphenylmethane diisocyanate.

3. The polyurethane coating with adjustable infrared emissivity according to claim 2, characterized in that: The fluorinated isocyanate is obtained by reacting one or more of 3-perfluorooctyl propanol, 3-perfluorobutyl propanol, 3-perfluorohexyl propanol, 2,2,3,3,3-pentafluoro-1-propanol, and 1H,1H,2H,2H-perfluorooctanol with isophorone diisocyanate trimer.

4. The polyurethane coating with adjustable infrared emissivity according to claim 1, characterized in that: The polyol is at least one of perfluoropolyether diol, hexafluoro-1,10-decanediol, and hydroxy-terminated polybutadiene polyol.

5. The polyurethane coating with adjustable infrared emissivity according to claim 1, characterized in that: The chain extending cross-linking agent is at least one of triethanolamine and 1,4-butanediol.

6. The polyurethane coating with adjustable infrared emissivity according to claim 1, characterized in that: The auxiliary agent comprises 0.1 to 0.2 parts of a leveling agent and 0.05 to 0.2 parts of a wetting agent.

7. The polyurethane coating with adjustable infrared emissivity according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate.

8. The polyurethane coating with adjustable infrared emissivity according to claim 1, characterized in that: The solvent is at least one of xylene, cyclohexanone, butyl acetate and butyl acetate.

9. A method for preparing a polyurethane coating with adjustable infrared emissivity, characterized in that: The method for preparing the polyurethane coating with adjustable infrared emissivity according to any one of claims 1 to 8 comprises the following steps: S1: Dehydrate the polyol under vacuum conditions at a temperature of 100°C to 140°C for 1 to 3 hours, and dry the solvent with 4A molecular sieves before entering S2; S2: The measured polyol, isocyanate, catalyst and solvent are placed in a three-necked flask and stirred to mix. Nitrogen is introduced into the three-necked flask to exhaust the air. The reaction time is 1 to 3 hours and the reaction temperature is 50°C to 80°C. After the reaction is completed, the process proceeds to S3; S3: Add the crosslinking agent, leveling agent and wetting agent into a three-necked flask, the reaction temperature is 20°C to 80°C, the reaction time is 1 to 2 hours, and after the reaction is completed, proceed to S4; S4: The obtained resin coating is coated and then cured at a curing temperature of 50° C. to 80° C. for 6 to 24 hours. After the curing is completed, a polyurethane coating with adjustable infrared emissivity is obtained.

10. Use of the polyurethane coating with adjustable infrared emissivity according to any one of claims 1 to 8 in the fields of ships, marine infrastructure, marine detectors, and building energy conservation.

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