A pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating and its preparation method

Abstract

This application provides a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating and its preparation method. The preparation method includes: adding pigment to an organic solvent and stirring to obtain solution A; adding a metal salt to boiled pure water and stirring to obtain solution B; dissolving NaOH in boiled pure water and sealing and storing to obtain solution C; mixing the solutions to obtain a mixed liquid; subjecting the mixed liquid to hydrothermal reaction, centrifugation, washing, vacuum drying and grinding to obtain pigment powder; mixing the pigment powder with waterborne polyurethane to obtain a slurry; coating the slurry and drying to obtain the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating. The spectral curve of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is close to that of a locust tree leaf, thus achieving high spectral similarity to locust tree leaves. LDH restricts the outward diffusion of pigment anions between layers, delays the decomposition of chromophores in the pigment, and increases the decomposition temperature of interlayer species, thus giving the coating a wider operating temperature range.

Description

Technical Field

[0001] This invention relates to a method for preparing a green coating, specifically to a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating and its preparation method. Background Technology

[0002] Mimicking biological characteristics and achieving their specific functions is a meaningful and challenging research topic. Against the backdrop of the rapid development of hyperspectral imaging technology, the development of high-performance spectral materials that mimic green vegetation is of paramount importance.

[0003] The locust tree is one of the most widely distributed green vegetation species in the world, possessing strong cold resistance and high ornamental value, and it can absorb toxic substances from the air. The spectrum of locust tree leaves exhibits the four typical spectral characteristics of green vegetation: green reflection peak, red edge, near-infrared plateau, and moisture absorption band. Therefore, using locust tree leaves as a reference for biomimetic leaf design and the development of high-performance biomimetic green plant spectral materials is of great significance and representativeness.

[0004] In existing materials for imitating locust tree leaves, on the one hand, most coatings can only achieve the same color, making it difficult to achieve the same spectral similarity; on the other hand, organic pigments have poor heat resistance, while inorganic pigments are highly toxic and have weak coloring power. Therefore, materials for imitating locust tree leaves face the problems of low spectral similarity and poor heat resistance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the above-mentioned defects of the prior art and provide a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating and its preparation method. The coating has a spectral similarity of more than 90% with locust tree leaves. The synthesis process is simple and it is a green pigment suitable for industrial production.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, comprising the following steps:

[0007] (1) Add the pigment to an organic solvent and stir to obtain solution A. Add the metal salts Mg(NO3)2 and Al(NO3)3 to boiled pure water and stir to obtain solution B. Dissolve NaOH in boiled pure water and seal to obtain solution C. The pigment includes Acid Yellow 23 and Acid Green 25. The molar ratio of Acid Yellow 23, Acid Green 25, Mg(NO3)2 and Al(NO3)3 is 0.051~0.0533:0.0067~0.009:3:1.

[0008] (2) Pour the solution A obtained in step (1) into a three-necked flask and continuously introduce an inert atmosphere to remove the air in the flask; then pour the solution B obtained in step (1) into the three-necked flask and mix well; finally, drop the solution C obtained in step (1) into the three-necked flask. The whole process is completed by stirring under an inert saturated atmosphere to obtain a mixture.

[0009] (3) The mixture obtained in step (2) is subjected to hydrothermal reaction, centrifugation, washing, vacuum drying and grinding to obtain pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder;

[0010] (4) Using waterborne polyurethane as a binder, pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is mixed with waterborne polyurethane to obtain a slurry. The slurry is coated and dried to obtain a pigment intercalated magnesium aluminum layered bimetallic hydroxide coating. The mass ratio of pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.12 to 0.14:1.

[0011] Green vegetation, as the most widespread background in nature, makes green the most prevalent color in nature, widely used in architectural coatings, environmental purification, food additives, and cosmetics. However, due to the severe challenges of simulating complex plant tissue structures and the environmental feasibility of materials used in biomimetic green plant spectral materials, most modern green coatings can only achieve a superficial resemblance to green plants, not a true likeness; they can only achieve the same color, not the same spectrum. The leaves of the Sophora japonica tree consist of three parts: the epidermis, the mesophyll, and the veins. The epidermis is divided into upper and lower epidermis. The epidermis of angiosperm leaves is generally composed of a single cell, with a few having multiple cell structures. The epidermis is the first line of defense against external threats. In biomimetic leaf design, the epidermis typically plays a role in simulating optical green, symmetrically covering the entire material surface as a green coating, or encapsulating liquid water to ensure the material contains water to simulate the water absorption band in the spectrum. The thin-walled green tissue containing chlorophyll between the upper and lower epidermis is collectively called the mesophyll. In some angiosperms, the leaf mesophyll is clearly divided into two parts: palisade tissue and spongy tissue. Because the two sides of the leaf receive different amounts of light, the mesophyll tissue near the upper epidermis is long and columnar, arranged tightly and neatly, with its long axis often perpendicular to the leaf surface, forming a palisade-like structure; this is called palisade tissue. The mesophyll cells near the lower epidermis contain less chlorophyll, are irregularly shaped, loosely arranged, and have large and numerous intercellular spaces, resembling a sponge; these are called spongy cells. Furthermore, in mesophyll cells, mainly palisade cells, a large number of green, flattened-spherical plastids, i.e., chlorophyll, are distributed. The structural characteristics of the mesophyll tissue explain the "red edge" and "near-infrared plateau" phenomenon in the reflectance spectrum, as detailed below:

[0012] When light enters angiosperm leaves, it first passes through the transparent upper epidermis, then enters the palisade parenchyma containing abundant chloroplasts, and finally enters the spongy parenchyma containing a small number of chloroplasts. Due to the loose and porous structure of the spongy parenchyma, with its numerous cell-air interfaces, it causes strong multiple scattering of incident light, resulting in some of the incident light being reflected back into the palisade parenchyma containing abundant chloroplasts. Thus, under the influence of its differentiated mesophyll tissue structure, the angiosperm fully absorbs the incident light energy. However, because the pigments in chloroplasts absorb almost no light energy in the near-infrared band, the multiple scattering effect of the spongy parenchyma causes different angiosperm leaves with different lateral surfaces to exhibit high and similar reflectance in the near-infrared band. The influence of leaf veins on the overall leaf reflectance spectrum is negligible and can be disregarded; therefore, the main simulation targets of the plant-inspired spectral materials are the epidermis and mesophyll of the leaf.

[0013] In summary, the causes of the reflectance spectral characteristics of green vegetation are as follows:

[0014] (1) Due to the green nature of chlorophyll, chlorophyll in vegetation reflects a large amount of green light and absorbs red and purple light strongly, thus a green reflection peak at 550nm and red and purple light absorption valleys on both sides appear.

[0015] (2) The loose and porous structure of plant leaves results in a large number of air-wall interfaces inside the leaf mesophyll tissue, which leads to strong internal light reflection and the appearance of "red edges" and "near-infrared plateau" characteristics.

[0016] (3) The water content in the leaves determines the spectral characteristics of the water absorption band of green vegetation.

[0017] The invention concept is as follows: pigments intercalated between magnesium aluminum hydrotalcite layers are used to mimic chloroplasts and simulate the characteristics of the green reflection peak in the spectrum. The reflection and crystal water characteristics of the Mg / Al-LDH layer simulate the characteristics of the infrared plateau and water absorption band in the spectrum. The anionic intercalation method helps to improve the heat resistance of the pigment.

[0018] Layered double hydroxides (LDHs), also known as hydrotalcite-like compounds or anionic clays, are a class of layered functional materials with a unique structure. LDHs share a hexagonal layered crystal structure with graphite and molybdenum disulfide. LDHs are compounds formed by the interaction of positively charged layers (composed of divalent and trivalent metal ions) and interlayer anions through charge-intercalation, as well as hydrogen bonding between interlayer water molecules and the layers. LDHs possess typical layered structures, interlayer intercalation capability, tunable layer cations, exchangeable interlayer anions, and the presence of water of crystallization in the interlayers, making them widely used in catalysis, adsorption, and wastewater treatment.

[0019] This application uses two pigments, Acid Yellow 23 and Acid Green 25. Acid Yellow 23 mainly contains benzenesulfonic acid groups, pyrazole ring carboxyl groups, amide groups, and azo groups. Acid Green 25 mainly contains benzenesulfonic acid groups, anthraquinone groups, and imine groups. LDH has hydroxyl groups on its surface, and the spacing between two adjacent LDH lamellars is 0.79 nm. Since both Acid Yellow 23 and Acid Green 25 are nearly planar molecules, they can easily insert between adjacent LDH lamellars and form hydrogen bonds (such as hydrogen bonds between nitrogen atoms and protons on hydroxyl groups, hydrogen bonds between oxygen atoms on hydroxyl groups and protons on imine groups, and hydrogen bonds can also form between the two pigment molecules). The sulfonic acid groups dehydrate and condense with the hydroxyl groups on the surface of LDH to form sulfonate groups, without destroying the chromophores of the pigments.

[0020] When the molar ratio of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 is 0.051–0.0533:0.0067–0.009:3:1, and the mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.12–0.14:1, the spectral curve of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is close to that of a locust tree leaf, thus achieving high spectral similarity to locust tree leaves.

[0021] Furthermore, the LDH in this application has the following properties:

[0022] (1) It has a layered structure: LDH is formed by the alternating arrangement of magnesium aluminum metal ions and oxygen ions to form a layered structure. This structure gives the material good controllability and tunability. In the field of green plant spectral materials, the layered structure can give the incident light periodic reflection properties, so that LDH has high reflectivity to the near infrared.

[0023] (2) Chemical stability: LDH exhibits good chemical stability, maintaining its structure and properties under various environmental conditions, and demonstrates good long-term stability. Mg / Al-LDH, as a natural hydrotalcite, exhibits good structural stability and crystallinity;

[0024] (3) Interlayer confinement effect: The interlayer confinement effect of LDH refers to the effect caused by the interaction between layers in its layered structure. Because there are mutual attraction and repulsion between anions and cations in the interlayer, this interaction will significantly affect the physicochemical properties of LDH. Due to the existence of the interlayer confinement effect, externally introduced pigment anions need to overcome this interaction to enter the layered structure. The movement and diffusion of pigment anions that have already entered will be restricted, thereby affecting the rate and extent of ion exchange, making the ion exchange process of LDH more selective and controllable;

[0025] (4) Interlayer water of crystallization: LDH layers contain abundant hydroxyl groups, and the interlayer contains a large amount of water of crystallization. These are tightly connected to the layers through the hydroxyl groups, thus giving LDH a strong water retention capacity. Unlike ordinary free water, the stability of water of crystallization is significantly improved under light and heat conditions. The water of crystallization in LDH is completely decomposed at approximately 250℃. Furthermore, the decomposition and removal of water of crystallization precedes the decomposition and removal of pigment anions, thereby greatly improving the thermal stability of the pigment.

[0026] This invention patent describes a co-precipitation-hydrothermal reaction of pigments, metal salts, and alkaline solutions to obtain an organic / inorganic hybrid pigment with pigment intercalation Mg / Al-LDH, which is then mixed with waterborne polyurethane to prepare a coating. Unlike other green pigments, Acid Yellow 23 and Acid Green 25 not only possess the same color characteristics but also exhibit high spectral similarity to locust tree leaves, and demonstrate superior heat resistance. The strong absorption of blue-violet light by the green pigment and the strong reflection of red light by the yellow pigment contribute to the formation of the green reflection peak. Finely crystalline and uniformly dispersed Mg / Al-LDH contributes to the formation of red edges, near-infrared plateaus, and moisture absorption bands. During heat treatment, Mg / Al-LDH restricts the outward diffusion of interlayer pigment anions. This interlayer confinement effect delays the decomposition of chromophores such as carbonyl groups and benzene rings in the pigment, increasing the decomposition temperature of interlayer species, thus giving the coating a wider operating temperature range.

[0027] The method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, wherein in step (1), the molar ratio of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 is 0.0533:0.0067:3:1.

[0028] Specifically, when the molar ratio of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 is 0.0533:0.0067:3:1, the visible light peak position in the spectrum of the pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is close to the visible light peak position of locust leaf, resulting in a more realistic imitation of locust leaf effect.

[0029] The method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, wherein in step (4), the mass ratio of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to the resin is 0.12:1.

[0030] Specifically, when the mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to resin is 0.12:1, the spectral curve of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is close to that of a locust leaf, further improving the simulation effect of the imitation locust leaf.

[0031] The method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, wherein in step (1), the molar volume ratio of the pigment to the organic solvent in solution A is 6 mmol: 1.5-2.5 L; and the molar volume ratio of the metal salts Mg(NO3)2 and Al(NO3)3 in solution B to the boiled pure water is 4 mmol: 5-20 mL.

[0032] Specifically, using boiled pure water helps to remove carbon dioxide and carbonate ions from the pure water. Adding an appropriate amount of organic solvent and boiled pure water helps to dissolve pigments and metal salts, as well as subsequent hydrothermal reactions.

[0033] In the method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, in step (2), the flow rate of the inert atmosphere is 0.3–0.6 NL·min. -1 The dropping rate of solution C is 0.5–2 mL / min. -1 The pH value of the mixture is 9-10; the molar volume ratio of NaOH to boiled pure water is 9.5 mmol: 2-6 mL.

[0034] Specifically, during the mixing of the various solutions, an inert atmosphere is maintained to prevent carbon dioxide from entering the solution. Minimizing the amount of carbonate ions in LDH facilitates the insertion of pigment anions between the LDH layers.

[0035] The method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, wherein in step (2), the inert atmosphere is a mixture of nitrogen, argon, 5% H2 and 95% N2 by volume, or a mixture of 5% H2 and 95% Ar by volume; the stirring temperature is room temperature.

[0036] Specifically, inert atmospheres can mainly be nitrogen, argon, or a mixture of gases.

[0037] The method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating includes the following steps: In step (3), the hydrothermal reaction temperature is 90–180°C, and the reaction time is 12–72 h; the centrifugation speed is 3000–10000 r / min, the centrifugation time is 1–10 min, and the total number of centrifugations is 4–10; the vacuum drying temperature is room temperature–80°C, and the vacuum drying time is 2–24 h; the grinding temperature is room temperature–90°C, and the grinding time is 30–300 s.

[0038] Specifically, the hydrothermal reaction temperature is 90–180℃, and the reaction time is 12–72 h, which is conducive to the formation of LDH. Centrifugation, washing, and drying of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder helps to remove residual pigment and impurities. Grinding facilitates the dispersion of the pigment powder in waterborne polyurethane.

[0039] The method for preparing the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating includes step (4) where the drying temperature is room temperature to 50°C and the drying time is 0.5 to 6 hours.

[0040] Specifically, the coating is dried at a temperature of room temperature to 50°C, which is similar to the air temperature range.

[0041] A pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is obtained by the preparation method of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating as described in any one of the above methods.

[0042] Application of a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating as described above on a coating imitating locust tree leaves.

[0043] This application describes a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating that can be applied to mimic locust tree leaf coatings, achieving spectral similarity to locust tree leaves. When the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is applied to a target object, it is difficult to identify by spectroscopic instruments, thus achieving a superior biomimetic effect.

[0044] Beneficial effects: The spectral curve of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is close to that of a locust leaf, thus mimicking the appearance of a locust leaf through spectral similarity. LDH restricts the outward diffusion of pigment anions between layers, delays the decomposition of chromophores in the pigment, and increases the decomposition temperature of interlayer species, thereby giving the coating a wider operating temperature range. Attached Figure Description

[0045] Figure 1 This is a ground reflectance spectrum of locust tree leaves.

[0046] Figure 2 This is a schematic diagram of the model structure of the pigment intercalation magnesium-aluminum layered bimetallic hydroxide pigment powder in an embodiment of the present invention.

[0047] Figure 3 This is a chromaticity coordinate diagram of pigment intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder in an embodiment of the present invention.

[0048] Figure 4 This is a ground reflectance spectrum of pigment intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder in the 400nm-2500nm range in an embodiment of the present invention.

[0049] Figure 5This is a ground reflectance spectrum of pigment intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder in the 400nm-700nm range in an embodiment of the present invention.

[0050] Figure 6 This is a ground reflectance spectrum of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating in the 400nm to 2500nm range in an embodiment of the present invention.

[0051] Figure 7 This is a ground reflectance spectrum of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating in the 400nm-1000nm range in an embodiment of the present invention.

[0052] Figure 8 This is a ground reflectance spectrum of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating in the 400nm-600nm range in an embodiment of the present invention.

[0053] Figure 9 This is an optical photograph of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating in an embodiment of the present invention.

[0054] Figure 10 The images shown are XRD patterns of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder and magnesium-aluminum layered bimetallic hydroxide in embodiments of the present invention.

[0055] Figure 11 The images shown are FTIR spectra of pigment powder, pigment, and magnesium-aluminum layered bimetallic hydroxide in the embodiments of the present invention.

[0056] Figure 12 These are XPS spectra of pigment powder and magnesium-aluminum layered bimetallic hydroxide pigment powder in the embodiments of the present invention.

[0057] Figure 13 The images shown are TG spectra of pigment powder, pigment, and magnesium-aluminum layered bimetallic hydroxide in the embodiments of the present invention.

[0058] Figure 14 These are FTIR spectra of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powders at different temperatures in embodiments of the present invention.

[0059] Figure 15 These are GC-MS spectra of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powders at different temperatures in embodiments of the present invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0061] This invention provides a method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, mainly comprising the steps of preparing pigment-intercalated magnesium-aluminum layered bimetallic hydroxide powder and preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating. First, pigment-intercalated magnesium-aluminum layered bimetallic hydroxide powder is prepared, and then a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is prepared based on the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide powder.

[0062] Examples 1 to 5 mainly involve the preparation of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder.

[0063] Example 1

[0064] A method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating includes the following steps:

[0065] (1) Add the pigment to 20 mL of ethylene glycol and stir to obtain solution A. Add the metal salts Mg(NO3)2 and Al(NO3)3 to 10 mL of boiled pure water and stir to obtain solution B. Dissolve 9.5 mmol NaOH in 5 mL of boiled pure water and seal to obtain solution C. The pigments include Acid Yellow 23 (AY23) and Acid Green 25 (AG25). The molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.048 mmol, 0.012 mmol, 3 mmol, and 1 mmol, respectively.

[0066] (2) Pour solution A obtained in step (1) into a three-necked flask and continuously purge with N2 for half an hour to remove air from the flask; then pour solution B obtained in step (1) into the three-necked flask and mix well; finally, drop solution C obtained in step (1) into the three-necked flask. The entire process is completed by stirring under N2 to obtain a mixture; the flow rate of N2 is 0.4 NL·min. -1 The dropping rate of solution C is 1 mL / min. -1 The pH value of the mixture is 10;

[0067] (3) The mixture obtained in step (2) was subjected to hydrothermal reaction, centrifugation, washing, vacuum drying and grinding to obtain pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder; the hydrothermal reaction temperature was 150℃ and the reaction time was 12h; the centrifugation speed was 8000r / min, the centrifugation time was 3min, the total number of centrifugations was 4, the vacuum drying temperature was 70℃ and the vacuum drying time was 24h, the grinding temperature was room temperature and the grinding time was 60s.

[0068] The molar ratio of pigment to metal salt is approximately (0.048 + 0.012) / (3 + 1) ≈ 1.5%, and the molar ratio of Acid Yellow 23 to Acid Green 25 is approximately 0.048 / 0.012 ≈ 4. Therefore, the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder is denoted as 1.5% YG-4. The molecular formula of Acid Yellow 23 is C2. 16 H9N4Na3O9S2, the molecular formula of Acid Green 25 is C 28 H 20 The structural formulas of N2Na2O8S2, Acid Yellow 23, and Acid Green 25 are as follows:

[0069]

[0070] Example 2

[0071] The difference from Example 1 is that in step (2), the molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.051 mmol, 0.009 mmol, 3 mmol, and 1 mmol, respectively.

[0072] The molar ratio of pigment to metal salt is approximately (0.051+0.009) / (3+1)≈1.5%, and the molar ratio of Acid Yellow 23 to Acid Green 25 is approximately 0.051 / 0.009≈6. Therefore, the pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is denoted as 1.5% YG-6.

[0073] Example 3

[0074] The difference from Example 1 is that in step (2), the molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.0533 mmol, 0.0067 mmol, 3 mmol, and 1 mmol, respectively.

[0075] The molar ratio of pigment to metal salt is approximately (0.0533+0.0067) / (3+1)≈1.5%, and the molar ratio of Acid Yellow 23 to Acid Green 25 is approximately 0.0533 / 0.0067≈8. Therefore, the pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is denoted as 1.5% YG-8.

[0076] Example 4

[0077] The difference from Example 1 is that in step (2), the molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.0545 mmol, 0.0055 mmol, 3 mmol, and 1 mmol, respectively.

[0078] The molar ratio of pigment to metal salt is approximately (0.0545+0.0055) / (3+1)≈1.5%, and the molar ratio of Acid Yellow 23 to Acid Green 25 is approximately 0.0545 / 0.0055≈10. Therefore, the pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is denoted as 1.5% YG-10.

[0079] Example 5

[0080] The difference from Example 1 is that in step (2), the molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.0554 mmol, 0.0046 mmol, 3 mmol, and 1 mmol, respectively.

[0081] The molar ratio of pigment to metal salt is approximately (0.0554+0.0046) / (3+1)≈1.5%, and the molar ratio of Acid Yellow 23 to Acid Green 25 is approximately 0.0554 / 0.0046≈12. Therefore, the pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is denoted as 1.5% YG-12.

[0082] The molar amounts of pigments in Examples 1 to 5 are shown in Table 1. n(AY23) represents the molar amount of Acid Yellow 23, and n(AG25) represents the molar amount of Acid Green 25, both in units of 10. -3 mmol.

[0083] Table 1. Molar amounts of Acid Yellow 23 and Acid Green 25 in each sample

[0084]

[0085] like Figure 2 As shown, in the pigment intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder obtained in this application, Acid Yellow 23 and Acid Green 25 are inserted between the layers of the LDH. When light shines on the LDH layers, transmission and reflection occur. The pigment can absorb some wavelengths of light, thus allowing the coating to display colors in other wavelengths. When light is reflected between the layers of the LDH, it is beneficial for the pigment to fully absorb the light.

[0086] like Figure 3 As shown, the chromaticity coordinates of each sample are close to those of the locust tree leaves.

[0087] like Figure 1 and Figure 4 As shown, the reflection characteristics of each sample, such as green peak, red edge, near-infrared plateau, and water peak, are similar to the corresponding reflection characteristics of locust leaves.

[0088] like Figure 1 and Figure 7 As shown, the peak value of the reflection peak of locust leaves in the yellow-green band (492nm~597nm) of the visible light spectrum is located at 552nm, 13.0%. Figure 4 and Figure 5 As shown in Table 2, the peak reflectance of sample 1.5%YG-4 is at 524 nm (3.4%), the peak reflectance of sample 1.5%YG-6 is at 538 nm (4.1%), the peak reflectance of sample 1.5%YG-8 is at 549 nm (4.0%), the peak reflectance of sample 1.5%YG-10 is at 558 nm (2.4%), and the peak reflectance of sample 1.5%YG-12 is at 562 nm (2.9%). Combined with Table 2, in the yellow-green band (492 nm–597 nm) of the visible light spectrum, the peak reflectance values ​​of samples 1.5%YG-6 and 1.5%YG-8 are closer to the peak reflectance value of locust tree leaves (552 nm, 13.0%), and both the correlation coefficient γ and the spectral angle cosθ are relatively high.

[0089] Table 2. Correlation coefficient γ and spectral angle cosθ for each sample

[0090]

[0091] In addition, other parameters of samples 1.5% YG-8, 1.5% YG-10, AY23, AG25, and Mg / Al-LDH (a pigment-free intercalated magnesium-aluminum layered bimetallic hydroxide) were characterized, such as... Figure 10 As shown, d(003) represents the interlaminar spacing of LDH. The interlaminar spacing of all three samples is 0.79 nm, indicating fine crystallization. Different pigment intercalation contents do not affect the interlaminar spacing of LDH. This may be due to the limited arrangement direction and orientation of pigment anions in the interlayer, as well as the constraints of layer folding and aggregation, resulting in small changes in interlaminar spacing. The slight decrease in diffraction peak intensity of samples 1.5% YG-8 and 1.5% YG-10 is because pigment intercalation hinders the normal fine crystallization of LDH.

[0092] like Figure 11 As shown, both 1.5% YG-8 and 1.5% YG-10 samples exhibited characteristic absorption peaks (1500 cm⁻¹) of the benzene ring skeleton. -1 (Left and right), characteristic absorption peak of sulfonic acid group (1170cm) -1 and 1032cm -1 The characteristic absorption peaks of Mg / Al-LDH (OH, 3482 cm⁻¹) and Mg / Al-LDH are also present. -1and 1635cm -1 Al-O or Mg-O, 596 cm -1 ).

[0093] like Figure 12 As shown, samples 1.5% YG-8 and 1.5% YG-10 have consistent Mg and Al orbitals with Mg / Al-LDH, and have consistent surface composition and structure, indicating that the pigments are mainly present between the lamellae rather than on the surface of LDH.

[0094] like Figure 13 As shown, the TG curve of sample 1.5% YG-8 shows two distinct weight loss processes. The first stage of weight loss occurs between 30 and 200 °C, corresponding to the loss of surface free water and interlayer crystal water. The second stage occurs between 200 and 500 °C, corresponding to the decomposition of layer hydroxyl groups and some interlayer pigment anions. The initial decomposition temperature T of 1.5% YG-8 is [not specified in the original text]. onset The initial decomposition temperatures were 321℃. From the TG analysis, the initial decomposition temperatures of 1.5% YG-8, AG25, AY23, and Mg / Al-LDH were 321℃, 228℃, 293℃, and 304℃, respectively, with the 1.5% YG-8 sample showing a significantly improved heat resistance. This improved heat resistance confirms that the pigment was successfully intercalated into the layers of Mg / Al-LDH.

[0095] like Figure 14 As shown, the FTIR spectra of sample 1.5% YG-8 at initial, 350℃, and 500℃ all exhibited characteristic absorption peaks of the benzene ring skeleton (1500 cm⁻¹). -1 The characteristic absorption peaks of the carbonyl group (around 1845 cm⁻¹) and the carbonyl group (around -1 (Left and right). For example Figure 15 As shown, at 350℃, the variety of pyrolysis products increases significantly, and decomposition fragments of the pigment appear. At this point, the pigment undergoes vigorous thermal decomposition. At 500℃, the absorption peaks of the pyrolysis products are significantly weaker than at 350℃, and the pigment pyrolysis reaction gradually ceases. Pigments located between the Mg / Al-LDH layers are protected by the LDH layer. By hindering the diffusion of pigments between layers, the pigments are protected from external photothermal damage, delaying the decomposition of chromophores such as benzene rings and carbonyl groups in the pigment, thereby improving heat resistance. Therefore, at 350℃, the absorption peaks of carbonyl groups and benzene rings belonging to the pigment are significantly enhanced, at which point the LDH layer gradually decomposes and loses its protective function. Figure 15 The molecular formula of the pigment pyrolysis products appearing in the process is C7H5NS, C 11 H 11 N3O3, the structural formulas are as follows:

[0096]

[0097] Example 6

[0098] The pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder (denoted as P, 0.2 g) obtained in Example 3 was mixed with waterborne polyurethane F0411 (denoted as F0411, 2 g) at room temperature for 10 s to obtain a slurry. The slurry was coated and dried at room temperature for 0.5 h to obtain a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating.

[0099] If the mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.1:1, then the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is denoted as m(P):m(F0411)=0.1.

[0100] Example 7

[0101] The pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder (denoted as P, 0.24 g) obtained in Example 3 was mixed with waterborne polyurethane F0411 (denoted as F0411, 2 g) at room temperature for 10 s to obtain a slurry. The slurry was coated and dried at room temperature for 0.5 h to obtain a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating.

[0102] The mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.12:1. Therefore, the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is denoted as m(P):m(F0411)=0.12.

[0103] Example 8

[0104] The pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder (denoted as P, 0.28 g) obtained in Example 3 was mixed with waterborne polyurethane F0411 (denoted as F0411, 2 g) at room temperature for 10 s to obtain a slurry. The slurry was coated and dried at room temperature for 0.5 h to obtain a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating.

[0105] The mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.14:1. Therefore, the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is denoted as m(P):m(F0411)=0.14.

[0106] Example 9

[0107] The pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder (denoted as P, 0.32 g) obtained in Example 3 was mixed with waterborne polyurethane F0411 (denoted as F0411, 2 g) at room temperature for 10 s to obtain a slurry. The slurry was coated and dried at room temperature for 0.5 h to obtain a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating.

[0108] The mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.16:1. Therefore, the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is denoted as m(P):m(F0411)=0.16.

[0109] Example 10

[0110] The pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder (denoted as P, 0.36 g) obtained in Example 3 was mixed with waterborne polyurethane F0411 (denoted as F0411, 2 g) at room temperature for 10 s to obtain a slurry. The slurry was coated and dried at room temperature for 0.5 h to obtain a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating.

[0111] The mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.18:1. Therefore, the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating is denoted as m(P):m(F0411)=0.18.

[0112] The masses of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder and waterborne polyurethane F0411 in Examples 6 to 10 are shown in Table 3. m(P) represents the mass of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder, and m(F0411) represents the mass of waterborne polyurethane F0411. The units are all in g.

[0113] Table 3. Mass of pigment powder and waterborne polyurethane F0411 in each sample

[0114]

[0115] like Figure 6 As shown, the spectral oscillation at 1735 nm is significant because the polyurethane begins to cross-link, resulting in a weakening of the moisture absorption band and the appearance of urethane spectral fluctuations at 1735 nm. In summary, F0411 affects the powder's spectrum, primarily in the near-infrared region, causing spectral oscillations at 1735 nm and a weakening of the moisture absorption band.

[0116] like Figure 6 , Figure 7 as well as Figure 8 As shown, with the increase of the mass ratio m(P):m(F0411) of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane, the position of the wave crest of waterborne polyurethane does not change. The reflectivity in the visible light band depends on the mass ratio of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane; the higher the mass ratio, the lower the reflectivity; the lower the mass ratio, the higher the reflectivity. Figure 8As shown, the peak value of the reflection peak of sample m(P):m(F0411)=0.1 is located at 555nm, 10.05%; the peak value of the reflection peak of sample m(P):m(F0411)=0.12 is located at 545nm, 13.78%; the peak value of the reflection peak of sample m(P):m(F0411)=0.14 is located at 546nm, 12.6%; the peak value of the reflection peak of sample m(P):m(F0411)=0.16 is located at 546nm, 12.6%; and the peak value of the reflection peak of sample m(P):m(F0411)=0.18 is located at 552nm, 6.9%.

[0117] As shown in Table 4, the reflectance curves of samples m(P):m(F0411) = 0.12 and m(P):m(F0411) = 0.14 are much closer to those of locust tree leaves. Especially in the visible and near-infrared bands (400nm~1000nm), the similarity between the reflectance of samples m(P):m(F0411) = 0.12 and m(P):m(F0411) = 0.14 and the reflectance of locust tree leaves is as high as 0.99 or more.

[0118] Table 4. Correlation coefficient γ and spectral angle cosθ for each sample

[0119]

[0120] like Figure 9 As shown, with the increase of the mass ratio m(P):m(F0411) of pigment-intercalated magnesium-aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane, the higher the mass of powder, the thicker the coating, the worse the dispersion effect, and the easier it is for the surface of the dried coating to crack. On the other hand, the less powder, the thinner the coating, and the easier it is for bubbles to form on the surface. Relatively speaking, the samples with m(P):m(F0411) = 0.12 and m(P):m(F0411) = 0.14 have better surface conditions, with neither bubbles nor cracks appearing.

[0121] Example 11

[0122] (1) Add the pigment to 15 mL of boiled pure water and stir to obtain solution A. Add the metal salts Mg(NO3)2 and Al(NO3)3 to 5 mL of boiled pure water and stir to obtain solution B. Dissolve 9.5 mmol NaOH in 2 mL of boiled pure water and seal to obtain solution C. The pigments include Acid Yellow 23 and Acid Green 25. The molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.051 mmol, 0.009 mmol, 3 mmol, and 1 mmol, respectively.

[0123] (2) Pour the solution A obtained in step (1) into a three-necked flask and continuously purge it with Ar for half an hour to remove air from the flask; then pour the solution B obtained in step (1) into the three-necked flask and mix well; finally, drop the solution C obtained in step (1) into the three-necked flask. The entire process is completed by stirring under Ar to obtain a mixture; the flow rate of Ar is 0.3 NL·min. -1 The dropping rate of solution C is 0.2 mL / min. -1 ;

[0124] (3) The mixture obtained in step (2) is subjected to hydrothermal reaction, centrifugation, washing, vacuum drying and grinding to obtain pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder; the hydrothermal reaction temperature is 90℃ and the reaction time is 24h; the centrifugation speed is 3000r / min, the centrifugation time is 1min, the total number of centrifugations is 4, the vacuum drying temperature is 80℃ and the vacuum drying time is 2h, the grinding temperature is 50℃ and the grinding time is 30s;

[0125] (4) The obtained pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is mixed with water-based polyurethane F0411 at room temperature for 10s to obtain a slurry. The slurry is coated and dried at 50℃ for 0.5h to obtain a pigment intercalated magnesium aluminum layered bimetallic hydroxide coating.

[0126] Example 12

[0127] (1) Add the pigment to 25 mL of alcohol and stir to obtain solution A. Add the metal salts Mg(NO3)2 and Al(NO3)3 to 20 mL of boiled pure water and stir to obtain solution B. Dissolve 9.5 mmol NaOH in 6 mL of boiled pure water and seal to obtain solution C. The pigments include Acid Yellow 23 and Acid Green 25. The molar amounts of Acid Yellow 23, Acid Green 25, Mg(NO3)2, and Al(NO3)3 are 0.0533 mmol, 0.0067 mmol, 3 mmol, and 1 mmol, respectively.

[0128] (2) Pour solution A obtained in step (1) into a three-necked flask and continuously purge with N2 for half an hour to remove air from the flask; then pour solution B obtained in step (1) into the three-necked flask and mix well; finally, drop solution C obtained in step (1) into the three-necked flask. The entire process is completed by stirring under N2 to obtain a mixture; the flow rate of N2 is 0.6 NL·min. -1 The dropping rate of solution C is 2 mL / min. -1 ;

[0129] (3) The mixture obtained in step (2) was subjected to hydrothermal reaction, centrifugation, washing, vacuum drying and grinding to obtain pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder; the hydrothermal reaction temperature was 180℃ and the reaction time was 72h; the centrifugation speed was 10000r / min and the centrifugation time was 10min, the total number of centrifugations was 5; the vacuum drying temperature was 80℃ and the vacuum drying time was 2h; the grinding temperature was room temperature and the grinding time was 300s.

[0130] (4) The obtained pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is mixed with water-based polyurethane F0411 at room temperature for 10s to obtain a slurry. The slurry is coated and dried at room temperature for 6h to obtain a pigment intercalated magnesium aluminum layered bimetallic hydroxide coating.

[0131] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, characterized in that, Includes the following steps: (1) Add the pigment to an organic solvent and stir to obtain solution A. Add the metal salts Mg(NO3)2 and Al(NO3)3 to boiled pure water and stir to obtain solution B. Dissolve NaOH in boiled pure water and seal to obtain solution C. The pigments include Acid Yellow 23 and Acid Green 25. The molar ratio of Acid Yellow 23, Acid Green 25, Mg(NO3)2 and Al(NO3)3 is 0.0533:0.0067:3:

1. (2) Pour the solution A obtained in step (1) into a three-necked flask and continuously introduce an inert atmosphere to remove the air in the flask; then pour the solution B obtained in step (1) into the three-necked flask and mix well; finally, drop the solution C obtained in step (1) into the three-necked flask. The whole process is completed by stirring under an inert atmosphere to obtain a mixture. (3) The mixture obtained in step (2) is subjected to hydrothermal reaction, centrifugation, washing, vacuum drying and grinding to obtain pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder; (4) Using waterborne polyurethane as a binder, pigment-intercalated magnesium aluminum layered bimetallic hydroxide pigment powder is mixed with waterborne polyurethane to obtain a slurry. The slurry is coated and dried to obtain a pigment-intercalated magnesium aluminum layered bimetallic hydroxide coating. The mass ratio of pigment-intercalated magnesium aluminum layered bimetallic hydroxide pigment powder to waterborne polyurethane is 0.12~0.14:

1. The coating is a coating that imitates locust tree leaves. The pigment intercalated between the magnesium aluminum layered double hydroxide layers is used to imitate chloroplasts.

2. The method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating according to claim 1, characterized in that: In step (4), the mass ratio of pigment intercalated magnesium aluminum layered bimetallic hydroxide pigment powder to resin is 0.12:

1.

3. The method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating according to claim 1, characterized in that: In step (1), the molar volume ratio of pigment to organic solvent in solution A is 6 mmol: 1.5~2.5 L; the molar volume ratio of metal salts Mg(NO3)2 and Al(NO3)3 in solution B to boiled pure water is 4 mmol: 5~20 mL.

4. The method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating according to claim 3, characterized in that: In step (2), the flow rate of the inert atmosphere is 0.3~0.6 NL·min. -1 The dropping rate of solution C is 0.5~2 mL·min. -1 The pH value of the mixture is 9-10; the molar volume ratio of NaOH to boiled pure water is 9.5 mmol: 2-6 mL.

5. The method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating according to claim 1, characterized in that: In step (2), the inert atmosphere is a mixture of nitrogen, argon, 5% H2 and 95% N2 by volume, or a mixture of 5% H2 and 95% Ar by volume; the stirring temperature is room temperature.

6. The method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating according to claim 1, characterized in that: In step (3), the hydrothermal reaction temperature is 90–180 °C and the reaction time is 12–72 h; the centrifugation speed is 3000–10000 r / min and the centrifugation time is 1–10 min, with a total of 4–10 centrifugations; the vacuum drying temperature is room temperature–80 °C and the vacuum drying time is 2–24 h; the grinding temperature is room temperature–90 °C and the grinding time is 30–300 s.

7. The method for preparing a pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating according to claim 1, characterized in that: In step (4), the drying temperature is room temperature to 50 ℃, and the drying time is 0.5 to 6 h.

8. A pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating, characterized in that, The pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating was prepared using the method described in any one of claims 1-7.

9. The application of the pigment-intercalated magnesium-aluminum layered bimetallic hydroxide coating as described in claim 8 on a coating imitating locust tree leaves.

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