Preparation method and application of a hydrophobic hyperspectral camouflage filler

Abstract

This invention discloses a method for preparing and applying a hydrophobic hyperspectral camouflage filler. The method includes the following steps: (1) mixing two metal salts and an organic pigment in deionized water to obtain solution A; mixing a biopolysaccharide, a structure-directing agent, and a precipitant in deionized water to obtain solution B; (2) mixing solution A and solution B, first shearing and stirring the mixture using a shear mixer, and then aging it at high temperature; (3) washing and drying the aged precipitate to obtain an intermediate product; (4) adding the intermediate product to a solution containing long-chain alkyl groups, reacting fully, centrifuging the solution, washing and drying the centrifuged solid to obtain the camouflage filler. This invention can prepare an intermediate product with a wrinkled surface structure, thereby increasing the grafting sites of the intermediate product and allowing it to graft more hydrophobic carbon chains. On the one hand, it improves the dispersibility of the camouflage filler in oily resin, and on the other hand, it improves the hydrophobicity of the final camouflage coating, giving it good anti-fogging performance and weather resistance.

Description

Technical Field

[0001] This invention relates to a method for preparing a hydrophobic hyperspectral camouflage filler, and also to the application of the camouflage filler obtained by the above method in the preparation of oil-based hyperspectral camouflage coatings. Background Technology

[0002] Hyperspectral camouflage materials need to simulate the same spectral characteristics as green vegetation, which requires starting from chlorophyll, water, and cellular structure in leaves. Materials simulating the role of chlorophyll mainly include green inorganic or organic pigments and chlorophyll derivatives. Materials simulating plant water molecules and cellular structure currently used mainly include hygroscopic polymers (hydrogels, polystyrene, etc.), salt materials such as molecular sieve salts, hygroscopic salts, and hydrotalcite, porous polymer materials, microcapsules, and hydrotalcite. All of these substances share a characteristic: they are difficult to dissolve in oily substances. Therefore, the film-forming agents for hyperspectral camouflage fillers are water-based adhesives and water-soluble polymers. However, water-soluble polymers can dissolve and swell in water, resulting in poor weather resistance of the hyperspectral camouflage coating, leading to poor performance in practical applications. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method for preparing a hydrophobic hyperspectral camouflage filler. The camouflage filler prepared by this method has a high spectral matching degree with green vegetation (sycamore leaves) and good hydrophobicity, thereby enabling the preparation of oil-based hyperspectral camouflage coatings. The resulting camouflage coating has good weather resistance and can maintain good camouflage performance under various climates.

[0004] Another object of the present invention is to provide the application of the camouflage filler prepared by the above method in the preparation of oil-based hyperspectral camouflage coatings.

[0005] Technical solution: The preparation method of the camouflage filler of the present invention includes the following steps:

[0006] (1) Mix two metal salts and organic pigments in deionized water to obtain solution A; mix biopolysaccharide, structure directing agent and precipitant in deionized water to obtain solution B;

[0007] (2) Mix solution A with solution B. The mixture is first sheared and stirred using a shear mixer and then placed in a reaction vessel for aging. During the shearing and stirring process, the colloidal system can better encapsulate the synthesized LDH particles, which helps to obtain LHD particles with better dispersion and more uniform size.

[0008] (3) The precipitate after shearing is washed and dried to obtain the intermediate product;

[0009] (4) Add the intermediate product to a solution containing long-chain alkyl groups. After the reaction is complete, centrifuge the solution and wash and dry the solid after centrifugation to obtain the disguised filler.

[0010] In step (1), the two metal salts are aluminum salt and magnesium salt; wherein the molar ratio of aluminum salt and magnesium salt is 1:3 to 3.5.

[0011] The aluminum salt is aluminum chloride hexahydrate; the magnesium salt is magnesium chloride hexahydrate.

[0012] In step (1), the organic pigments are alizarin green and acid yellow, and the mass ratio of alizarin green to acid yellow is 1:39-40.

[0013] In step (1), the precipitant is NaOH; the structure directing agent is hexadecyltrimethylammonium bromide (CTAB); and the natural polysaccharide is carboxymethyl cellulose.

[0014] The mass ratio of the precipitant to the metal salt is 2.02–2.03:1; the mass ratio of the structure directing agent to the metal salt is 0.024–0.025:1; and the mass ratio of the carboxymethyl cellulose to the metal salt is 0.6–0.61:1.

[0015] In step (2), the rotation speed of shearing and stirring is 4000-4500 r / min, and the shearing and stirring time is 3-3.5 min.

[0016] In step (3), the aging temperature is not lower than 100℃ and the aging time is 8-9h.

[0017] In step (4), the long-chain alkyl group is hexadecyltrimethoxysilane; the mass ratio of the intermediate product to hexadecyltrimethoxysilane is 5:1 to 1.5.

[0018] In step (4), the camouflage filler is obtained by drying at 80-85℃ for 6-7 hours.

[0019] The application of the camouflage filler prepared by the above method in the preparation of oil-based hyperspectral camouflage coatings, wherein the oil-based hyperspectral camouflage coatings are composed of the following components in parts by mass: 1 to 1.2 parts of camouflage filler, 0.32 to 5.2 parts of polyurethane resin, 0.16 to 2.6 parts of curing agent N-75, and 2 to 12.5 parts of organic solvent.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention can prepare intermediate products with wrinkled surface structures, thereby increasing the grafting sites of the intermediate products and allowing them to graft more hydrophobic carbon chains. This improves both the dispersibility of the camouflage filler in oily resin and the hydrophobicity of the final camouflage coating, giving it good anti-fogging performance and weather resistance. The camouflage coating formed by the camouflage coating of the present invention has a spectral similarity of up to 0.98 with green leaves (sycamore leaves) (in the 400-2500nm band) and has similar hydrophobic properties to leaves, greatly improving the practical application value of hyperspectral camouflage coatings. Attached Figure Description

[0021] Figure 1 The image shows the reflectance spectrum of the camouflage filler prepared in Example 1 in the range of 400–2500 nm and the image showing the similarity of the spectral curves.

[0022] Figure 2 Image showing the water contact angle of the camouflage filler prepared in Example 1;

[0023] Figure 3 Here is a SEM image of the camouflage filler prepared in Example 1;

[0024] Figure 4 Images showing the reflectance spectra of the oily hyperspectral camouflage coatings obtained in Examples 2-5;

[0025] Figure 5 These are contact angle images of the oily hyperspectral camouflage coatings obtained in Examples 2-5;

[0026] Figure 6 Images showing the reflectance spectra of the water-based hyperspectral camouflage coatings prepared in Comparative Examples 1-4;

[0027] Figure 7 The images show the contact angles of the water-based hyperspectral camouflage coatings prepared in Comparative Examples 1-4.

[0028] Figure 8 The figures show the water resistance test results of the HCC-4 and WCC-4 coatings prepared in Example 5 and Comparative Example 4. Detailed Implementation

[0029] Example 1

[0030] The preparation method of the hydrophobic hyperspectral camouflage filler of the present invention includes the following steps:

[0031] (1) Dissolve 0.937g of AlCl3·6H2O, 1.537g of MgCl2·6H2O, 0.05g of Alizarin Green and 1.98g of Acid Yellow in 100mL of deionized water to form solution A; dissolve 0.06g of CTAB, 1.5g of carboxymethyl cellulose and 5g of NaOH in 50mL of deionized water to obtain solution B;

[0032] (2) Mix solution A with solution B. First, use a shear stirrer to shear and stir the mixture at 4000 r / min for 3 min. Then, transfer the resulting solution to a reaction vessel and age it at 100℃ for 8 h.

[0033] (3) The precipitate obtained after aging is washed until the pH of the washing solution is neutral, and then dried at 100℃ for 4h to obtain the intermediate product C-LDH.

[0034] (4) Add 1g of intermediate product C-LDH and 0.2mL of hexadecyltrimethylsilane to 20mL of 75% ethanol solution and stir for 24h;

[0035] (5) Centrifuge the solution after the reaction, wash the solid after centrifugation, and dry it at 80℃ for 6h to obtain hydrophobic hyperspectral camouflage filler C-LDH-D.

[0036] Its microstructure is a uniform and porous cotton-like structure. This structure uses a natural polysaccharide three-dimensional network structure as a template to grow micron-sized intercalated pigment particles in a composite bilayer hydroxide. The surface of the bilayer hydroxide is grafted with long alkyl chains.

[0037] Example 2

[0038] The method for preparing a camouflage coating based on the hydrophobic hyperspectral camouflage filler C-LDH-D obtained in Example 1 includes the following steps:

[0039] (1) Dissolve 5.2g of polyurethane resin in 4mL of butyl acetate solution, stir and ultrasonically defoam, then add 1g of camouflage filler C-LDH-D and 2.6g of curing agent, and finally add 10mL of butyl acetate to adjust the viscosity of the camouflage coating.

[0040] (2) The manual spraying technique is adopted. The spray gun pressure is 2.0 to 3.0 Pa, the nozzle diameter is 1.5 mm, the spraying distance is controlled at 20 to 25 cm, and the spraying is applied to the treated substrate. After spraying, it is cured at 80°C for 3 hours to obtain the camouflage coating HCC-1.

[0041] Example 3

[0042] The method for preparing a camouflage coating based on the hydrophobic hyperspectral camouflage filler C-LDH-D obtained in Example 1 includes the following steps:

[0043] (1) Dissolve 2g of polyurethane resin in 2mL of butyl acetate solution, stir and ultrasonically defoam, then add 1g of camouflage filler C-LDH-D and 1g of curing agent, and finally add 5mL of butyl acetate to adjust the viscosity of the camouflage coating.

[0044] (2) The manual spraying technique is adopted, with the spray gun pressure at 2.0 to 3.0 Pa, the nozzle diameter at 1.5 mm, and the spraying distance controlled at 20 to 25 cm. The coating is sprayed onto the treated substrate and cured at 80°C for 3 hours to obtain the camouflage coating HCC-2.

[0045] Example 4

[0046] The method for preparing a camouflage coating based on the hydrophobic hyperspectral camouflage filler C-LDH-D obtained in Example 1 includes the following steps:

[0047] (1) Dissolve 0.8g of polyurethane resin in 1mL of butyl acetate solution, stir and ultrasonically defoam, then add 1g of camouflage filler C-LDH-D and 0.4g of curing agent, and finally add 2.5mL of butyl acetate to adjust the viscosity of the camouflage coating.

[0048] (2) The manual spraying technique is adopted. The spray gun pressure is 2.0 to 3.0 Pa, the nozzle diameter is 1.5 mm, the spraying distance is controlled at 20 to 25 cm, and the spray is applied to the treated substrate. After spraying, it is cured at 80°C for 3 hours to obtain the camouflage coating HCC-3.

[0049] Example 5

[0050] The method for preparing a camouflage coating based on the hydrophobic hyperspectral camouflage filler C-LDH-D obtained in Example 1 includes the following steps:

[0051] (1) Dissolve 0.32g of polyurethane resin in 1mL of butyl acetate solution, stir and ultrasonically defoam, then add 1g of camouflage filler C-LDH-D and 0.16g of curing agent, and finally add 1.5mL of butyl acetate to adjust the viscosity of the camouflage coating.

[0052] (2) The manual spraying technique is adopted. The spray gun pressure is 2.0 to 3.0 Pa, the nozzle diameter is 1.5 mm, the spraying distance is controlled at 20 to 25 cm, and the spray is applied to the treated substrate. After spraying, it is cured at 80°C for 3 hours to obtain the camouflage coating HCC-4.

[0053] Comparative Example 1

[0054] The intermediate product C-LDH obtained in Example 1 was used to prepare a camouflage coating. Based on the camouflage coating, a camouflage coating was prepared. Specifically, 4g of waterborne polyurethane was dissolved in 5mL of water, stirred and ultrasonically defoamed, and then 1g of intermediate product C-LDH and 1.5g of curing agent were added. Finally, 2mL of water was added to the viscosity of the coating. 2) The coating was applied manually with a spray gun pressure of 2.0 to 3.0 Pa, a nozzle diameter of 1.5 mm, and a spraying distance of 20 to 25 cm. The coating was applied to the treated substrate and cured at 80°C for 3 hours to obtain the camouflage coating WCC-1.

[0055] Comparative Example 2

[0056] The intermediate product C-LDH obtained in Example 1 was used to prepare a camouflage coating. Based on the camouflage coating, a camouflage coating was prepared. Specifically, 3g of waterborne polyurethane was dissolved in 4mL of water, stirred and ultrasonically defoamed, and then 1g of intermediate product C-LDH and 1.12g of curing agent were added. Finally, 1.5mL of water-based coating viscosity was added. ; (2) Manual spraying technology was used, with a spray gun pressure of 2.0 to 3.0 Pa, a nozzle diameter of 1.5 mm, and a spraying distance of 20 to 25 cm. The coating was sprayed onto the treated substrate and cured at 80°C for 3 hours after spraying to obtain the camouflage coating WCC-2.

[0057] Comparative Example 3

[0058] The intermediate product C-LDH obtained in Example 1 was used to prepare a camouflage coating. Based on the camouflage coating, a camouflage coating was prepared. Specifically, (1) 2.25g of waterborne polyurethane was dissolved in 3mL of water, stirred and ultrasonically defoamed, and then 1g of intermediate product C-LDH and 0.84g of curing agent were added. Finally, 1.5mL of water-based coating viscosity was added. (2) Manual spraying technology was used. The spray gun pressure was 2.0-3.0Pa, the nozzle diameter was 1.5mm, and the spraying distance was controlled at 20-25cm. The coating was sprayed on the treated substrate and cured at 80℃ for 3 hours after spraying to obtain the camouflage coating WCC-3.

[0059] Comparative Example 4

[0060] The intermediate product C-LDH obtained in Example 1 was used to prepare a camouflage coating. Based on the camouflage coating, a camouflage coating was prepared. Specifically, (1) 1.68g of waterborne polyurethane was dissolved in 2mL of water, stirred and ultrasonically defoamed, and then 1g of intermediate product C-LDH and 0.63g of curing agent were added. Finally, 1mL of water was added to the viscosity of the coating. (2) The manual spraying technique was used. The spray gun pressure was 2.0-3.0Pa, the nozzle diameter was 1.5mm, and the spraying distance was controlled at 20-25cm. The coating was sprayed on the treated substrate and cured at 80℃ for 3 hours after spraying to obtain the camouflage coating WCC-4.

[0061] Figure 1 The reflectance spectrum and spectral similarity of the camouflage filler in Example 1 from 400 to 2500 nm show obvious water absorption valleys at 1450 nm and 1930 nm. This is mainly due to the presence of water of crystallization between the bilayer hydroxide layers. The weakening of the water absorption peak of C-LDH-D is mainly due to the bonding between hexadecyltrimethylsilane and the hydroxyl groups on the C-LDH surface, resulting in less adsorbed water. The spectral similarity between the intermediate product C-LDH and the camouflage filler C-LDH-D and green leaves is approximately 0.95.

[0062] Figure 2 The water contact angle of the camouflage filler in Example 1 shows that the unmodified camouflage powder C-LDH is hydrophilic with a water contact angle of 43.5°, while the camouflage filler powder C-LDH-D modified with hexadecyltrimethylsilane has good hydrophobic properties with a hydrophobic angle as high as 131.1°.

[0063] Figure 3 The image shows a SEM image of the camouflaged filler in Example 1. As can be seen from the image, the hydroxycellulose in the intermediate product C-LDH acts as a template, making the LDH sheets resemble cotton wool with high roughness. After modification with hexadecyltrimethylsilane, the cotton wool-like LDH sheets of C-LDH-D are clearly covered, and the roughness is reduced.

[0064] Figure 4 The images show the spectral curves and spectral similarity diagrams of the oil-based hyperspectral camouflage coatings in Examples 2-5. It can be seen that HCC-3 in Example 4 has the highest spectral similarity, reaching 0.98972. However, HCC-4 prepared in Example 5, while having high spectral similarity, can achieve a reflectivity of 70% in the 1000-1500nm band, thus giving it stealth capabilities in practical applications.

[0065] Figure 5 The contact angles of the oily hyperspectral camouflage coatings in Examples 2-5 show that they are all around 100°, which is similar to the water contact angle of real leaves, greatly improving the outdoor weather resistance of the hyperspectral camouflage coatings.

[0066] Figure 6The spectral curves and similarity diagrams of the waterborne hyperspectral camouflage coatings in Examples 1-4 show that the samples have low similarity to the characteristic spectra of vegetation. The "green peak" of the coating exhibits a redshift in the visible light band, which is attributed to the milky white color of the waterborne polyurethane, causing partial masking of the coating's color and resulting in the green peak shift. In the near-infrared wavelength range, the characteristic reflection peak of C-LDH is disrupted, causing the coating's simulated green leaf characteristic spectral curve to disappear. This is mainly due to the high polarity of the waterborne epoxy resin; these polar groups can chemically react with the hydroxyl groups on the C-LDH surface, forming covalent and hydrogen bonds, thus altering the final optical properties of the coating.

[0067] Figure 7 The contact angles of the water-based hyperspectral camouflage coatings in Comparative Examples 1 to 4 show that their contact angles are all below 10°, indicating extremely high hydrophilicity, which makes the coatings unusable in humid environments.

[0068] Figure 8 The figures show the water resistance test results of the HCC-4 and WCC-4 coatings prepared in Example 5 and Comparative Example 4. Figure 8 The leftmost image shows actual photos of acidic, alkaline, and neutral water droplets on the coating and leaves. On the water-based coating (WCC-4), the droplets spread out and were absorbed, while the oil-based coating (HCC-4) and the leaves had similar hydrophobic angles. After immersing both HCC-4 and WCC-4 coatings in pure water for 5 hours, the water soaked in HCC-4 did not change color, while the water soaked in WCC-4 turned green. Simultaneously, after immersing both HCC-4 and WCC-4 coatings in boiling water for 2 hours, the water soaked in HCC-4 did not change color, while the water soaked in WCC-4 turned green. The water turning green is because the stability of the organic pigment depends on the integrity of the composite material structure. When the coating begins to expand and break down, organic pigment molecules are released from the camouflage filler into the surrounding water, causing the water to turn green and the coating to fade. The HCC-4 coating remained intact and showed no fading after immersion in pure water, demonstrating extremely high performance for outdoor applications.

Claims

1. A method for preparing a hydrophobic hyperspectral camouflage filler, characterized in that, Includes the following steps: (1) Two metal salts and an organic pigment are mixed in deionized water to obtain solution A; biopolysaccharide, a structure directing agent and a precipitant are mixed in deionized water to obtain solution B; the precipitant is NaOH; the structure directing agent is hexadecyltrimethylammonium bromide; the biopolysaccharide is carboxymethyl cellulose; (2) Mix solution A with solution B. First, use a shear mixer to shear and stir the mixture, and then age it at high temperature. (3) The aged precipitate is washed and dried to obtain the intermediate product; (4) Add the intermediate product to a solution containing long-chain alkyl groups. After the reaction is complete, centrifuge the solution and wash and dry the solid after centrifugation to obtain the disguised filler. Based on the above-mentioned camouflage filler, an oil-based hyperspectral camouflage coating is formulated. The oil-based hyperspectral camouflage coating is composed of the following components in parts by mass: 1~1.2 parts camouflage filler, 0.32~5.2 parts polyurethane resin, 0.16~2.6 parts curing agent, and 2~12.5 parts organic solvent. The camouflage coating formed by the above-mentioned camouflage paint has a spectral similarity of up to 0.98 with that of the sycamore leaf in the 400~2500nm wavelength range.

2. The preparation method according to claim 1, characterized in that: In step (1), the two metal salts are aluminum salt and magnesium salt; wherein the molar ratio of aluminum salt and magnesium salt is 1:3~3.

5.

3. The preparation method according to claim 1, characterized in that: In step (1), the organic pigments are alizarin green and acid yellow, and the mass ratio of alizarin green to acid yellow is 1:39~40.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the precipitant to the metal salt is 2.02~2.03:1; the mass ratio of the structure directing agent to the metal salt is 0.024~0.025:1; and the mass ratio of the carboxymethyl cellulose to the metal salt is 0.6~0.61:

1.

5. The preparation method according to claim 1, characterized in that: In step (2), the rotation speed of shearing and stirring is 4000~4500 r / min, and the shearing and stirring time is 3~3.5 min.

6. The preparation method according to claim 1, characterized in that: In step (3), the aging temperature is not lower than 100℃ and the aging time is 8~9h.

7. The preparation method according to claim 1, characterized in that: In step (4), the long-chain alkyl group is hexadecyltrimethoxysilane; the mass ratio of the intermediate product to hexadecyltrimethoxysilane is 5:1~1.

5.

8. The preparation method according to claim 1, characterized in that: In step (4), the camouflage filler is obtained by drying at 80~85℃ for 6~7h.

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