Preparation method of high water-retention high-spectrum camouflage coating with strong adhesion

Abstract

This invention relates to a method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating, belonging to the field of hyperspectral camouflage technology. The method involves preparing a mixed solution by adding water-containing microcapsule particles and monochromatic pigment particles to a polymer resin substrate solution, followed by vacuum degassing, and then applying the film layer onto the substrate using a blade coating method. After curing, the camouflage coating is obtained. The camouflage coating can precisely mimic the visible-near-infrared spectral characteristics of vegetation backgrounds, with a Pearson similarity coefficient of no less than 96% with the target vegetation spectrum. It also possesses excellent water retention properties, stably reproducing the typical water absorption valley spectral characteristics of vegetation. Furthermore, the coating exhibits strong adhesion to the substrate, good environmental adaptability, and high application value.

Description

Technical Field

[0001] This invention belongs to the field of hyperspectral camouflage technology, specifically relating to a method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion. Background Technology

[0002] Currently, optical reconnaissance has developed hyperspectral detection technology capable of simultaneously acquiring two-dimensional spatial features and one-dimensional spectral information of targets. This technology can perform fine spectral detection of target scenes in the 250-2500nm wavelength range, accurately identifying subtle spectral differences between camouflage materials and the background. It has become an important anti-camouflage reconnaissance technology, posing a serious challenge to traditional camouflage materials. To improve the survivability of military targets under hyperspectral detection, the development of hyperspectral camouflage materials with finely matched environmental background spectra is of great significance. Vegetated environments are the most common, therefore, existing research on hyperspectral monochromatic camouflage materials has primarily focused on mimicking the reflectance spectra of plant leaves, with the core objective being to achieve "spectral" matching between the camouflage material and the vegetation background to evade hyperspectral detection identification. Plant leaves exhibit typical and stable spectral characteristics within the 250-2500 nm wavelength range. Specifically, in the ultraviolet band (250-380 nm), the reflectance is below 10% (referred to as the "low ultraviolet reflectance" characteristic). In the visible light band (400-780 nm), the reflectance of green leaves peaks near 550 nm (referred to as the "color peak" characteristic), and increases sharply in the 680-780 nm range (referred to as the "red edge" characteristic), while the reflectance of yellow leaves gradually increases from 500 nm (referred to as the "green edge" characteristic). In the near-infrared band (780-2500 nm), the reflectance in the 780-1250 nm range is typically between 40% and 60% (referred to as the "near-infrared plateau" characteristic), while distinct reflection valleys are formed at 1450 nm and 1940 nm wavelengths (referred to as the "water absorption valley" characteristic). This characteristic is mainly formed by water absorption in the leaves and is one of the key bases for hyperspectral detection and identification of vegetation and camouflage materials.

[0003] Currently, most existing hyperspectral camouflage materials have similarity coefficients with plant leaf spectra exceeding 0.9, demonstrating good simulation effects for spectral features other than water absorption characteristics. However, they still have significant shortcomings in the stable simulation of the crucial "water absorption valley" feature. Existing complex structural materials and single-layer composite membrane structures designed for water absorption characteristics exhibit significant changes in reflectance at the wavelengths corresponding to the "water absorption valley" feature after a short period of time under specific environmental temperatures, resulting in poor water retention performance and an inability to stably reproduce the water absorption spectral characteristics of vegetation over the long term. For example, Guo Li (Infrared Technology, 2012) et al. prepared a hyperspectral composite coating by directly dispersing distilled water and pigment particles in polyurethane resin and curing it. When the water content (mass concentration) was 60%, the reflectance at 1450 nm and 1940 nm wavelengths was 25% and 15%, respectively, which was close to the reflectance of green plant leaves. However, after being placed in a constant temperature and humidity environment of 50℃ and 40%RH for 5 hours, the reflectance at 1450 nm wavelength increased from 26.4% to 43.2%, a change rate as high as 63.6%, indicating extremely poor water retention stability. Lu Qixin (Journal of Bionic Engineering, 2022) et al. prepared a hyperspectral camouflage fabric by crosslinking hygroscopic calcium chloride and sodium alginate onto green fabric. After being placed outdoors for 6 days, the reflectance at 1450 nm and 1940 nm wavelengths increased by about 5%, while the overall reflectance in the visible light band decreased by about 5%, indicating a significant reduction in spectral matching. In recent patent applications, CN116376343A designed a water-containing microcapsule for hyperspectral coatings. This microcapsule can achieve high light absorption at wavelengths of 1450nm and 1940nm, which can initially mimic the "water absorption valley" spectral characteristics of vegetation. However, this patent does not mention the reflectance changes of the microcapsule under different environmental conditions, making it impossible to determine its weather resistance, water retention properties, and practical engineering application capabilities. Generally speaking, the better the water retention performance of a material, the longer its reflectance at wavelengths of 1450nm and 1940nm can remain at a low level, thus mimicking the "water absorption valley" characteristics of plant leaves more persistently, resulting in better weather resistance and better adaptability to complex and changing battlefield environments.

[0004] Besides water retention, the adhesion of hyperspectral camouflage coatings is also a key performance indicator in their practical applications, directly affecting the coating's lifespan and camouflage effect. However, the adhesion performance of coatings reported in existing research literature is generally poor and needs further improvement. Among existing patents on hyperspectral camouflage coatings, few describe the coating's adhesion ability on the substrate. Only patent CN118222138A, which I previously participated in applying for, provides relevant performance data. This patent prepares a hyperspectral camouflage coating by directly embedding hygroscopic salt saturated aqueous solution particles and inorganic monochromatic pigments into the substrate. This coating has a surface roughness of 0.3.μ On a stainless steel substrate of m, the maximum adhesion failure strength is only 137.4 psi, indicating limited adhesion ability to the substrate, which cannot meet the needs of practical engineering applications and still needs to be further improved.

[0005] In summary, existing hyperspectral camouflage coatings generally suffer from poor water retention, inability to stably reproduce the spectral characteristics of vegetation "water absorption valleys" over long periods, and insufficient adhesion, making them unsuitable for practical engineering applications. Therefore, developing hyperspectral camouflage coatings with high water retention and high adhesion has become a key technical challenge that urgently needs to be addressed in the field of hyperspectral camouflage materials. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion. By precisely combining and synergistically integrating water-containing microcapsules with a polymer resin substrate and monochromatic pigment particles, the resulting camouflage coating can accurately simulate the color peaks, near-infrared plateaus, and water absorption valleys of vegetation spectra in the 250-2500 nm wavelength range. The coating exhibits excellent water retention performance under different temperature and humidity conditions and has high adhesion to stainless steel substrates.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion, the specific operation steps of which are as follows: Step 1: Mix 0.4-4.2 parts by weight of monochrome pigment particles and 63.8-70 parts by weight of polymer resin substrate and stir evenly to form a color solution; Step 2: Add 29.6-32 parts by weight of the aqueous microcapsule particles to the above-mentioned color solution and stir until a mixed solution is formed; Step 3: Place the above mixed solution in a vacuum degassing chamber and evacuate it for 10-30 minutes under a vacuum degree of less than 100 Pa. Then remove it and apply the mixed solution to the substrate material to form a solution layer with a thickness of 0.5-2 mm. After the solution layer has solidified into a film, a high water retention and high spectrum camouflage coating with strong adhesion is obtained.

[0008] Furthermore, in step one, the monochromatic pigment particles are monochromatic homogeneous particles and / or monochromatic microcapsule particles.

[0009] Furthermore, the monochromatic homogeneous particles are selected from one of the following pigment series: chromium oxide green, iron oxide green, malachite green, cobalt green, phthalocyanine green, titanium chromium yellow, titanium nickel yellow, titanium chromium brown, lemon yellow, lightfast yellow, iron oxide yellow, iron oxide red, cadmium red, and pigment red.

[0010] Furthermore, the monochromatic microcapsule particles comprise a pigment core material and a wall surface, wherein the core material is chlorophyll oil or xanthophyll oil, and the microcapsule particle size is 5-100 μm. μ m; The wall surface is prepared by in-situ polymerization of melamine and formaldehyde in a molar ratio of 1:2-1:4.

[0011] Furthermore, in step one, the polymer resin substrate is any one of alkyd resin, fluorocarbon resin, epoxy resin, nitrocellulose, acrylic resin, polyurethane resin, and chlorinated rubber resin.

[0012] Furthermore, in step one, the stirring rate is 200-600 rpm and the stirring time is 10-30 min; in step two, the stirring rate is 400-600 rpm and the stirring time is 10-30 min.

[0013] Furthermore, the aqueous microcapsules in step two comprise a core material and a wall surface, wherein the core material is a saturated aqueous solution of hygroscopic salt, and the particle size of the aqueous microcapsules is 5-60 nm. μ m; the wall surface is made of polyurea resin, which is formed by interfacial polymerization of 70-80 parts by weight of polyisocyanate and 20-30 parts by weight of polyethylene polyamine.

[0014] Furthermore, the substrate material in step three can be any one of tin foil substrate, stainless steel substrate, alloy substrate, glass substrate, wood substrate, and paper substrate.

[0015] Furthermore, after the camouflage coating is prepared, in the initial state, the Pearson correlation coefficient between the spectrum in the 250-2500nm solar band and the vegetation spectrum is not less than 96%, the reflectance at a wavelength of 1450nm is 15-25%, and the reflectance at a wavelength of 1940nm is 5-15%, which is consistent with the vegetation spectral characteristics in the LOPEX93 database. The camouflage coating, after being placed under natural conditions of 25°C and 30%RH for 800 hours, showed a reflectance change of less than 2.5% at wavelengths of 1450nm and 1940nm, and a Pearson correlation coefficient with vegetation greater than 96%. The camouflage coating, after being placed under dry heat conditions of 50°C and 20%RH for 150 hours, showed a reflectance change of less than 7% at wavelengths of 1450nm and 1940nm, and a Pearson correlation coefficient with vegetation greater than 94%. The camouflage coating, after being placed under 30°C and 80%RH humid heat conditions for 100 hours, showed a reflectance change of less than 2.5% at wavelengths of 1450nm and 1940nm, and a Pearson correlation coefficient with vegetation greater than 96%.

[0016] Furthermore, the adhesion performance was tested using the pull-off method described in the national standard GB / T 5210-2006, and the average adhesion strength of the camouflage coating on the stainless steel substrate was not less than 222.9 psi.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: 1. By utilizing the strong absorption of ultraviolet bands by the components within a highly water-retaining, hyperspectral camouflage coating with strong adhesion, the "low ultraviolet reflection" spectral characteristics of vegetation can be simulated. By selectively absorbing visible light through monochromatic pigment particles, the spectral characteristics of vegetation, such as "color peaks" in the visible light band, can be simulated. By utilizing the multiple scattering effects of monochromatic pigment particles and water-containing microcapsules on light, the spectral characteristics of the "near-infrared plateau" in the near-infrared band of vegetation can be simulated. By leveraging the strong absorption of hygroscopic salt saturated aqueous solution in water-containing microcapsules at wavelengths of 1450 nm and 1950 nm, the spectral characteristics of vegetation "water absorption valleys" can be simulated.

[0018] 2. Because the water exists in the form of hygroscopic salt-bound water, the water molecules are adsorbed by the hygroscopic salt; and since the water molecules are located inside the microcapsules, their diffusion is hindered by the microcapsule polyurea resin wall material; furthermore, the diffusion coefficient of water molecules in the polymer resin substrate is extremely low, around 10. -12 ~10 -14 The camouflage coating, after being placed in different environments for a long time, can still accurately and stably reproduce the spectral characteristics of the vegetation's "water absorption valley" at wavelengths of 1450nm and 1950nm.

[0019] 3. Compared with patents CN118222138A and CN117986913A, where water evaporation leaves pores and aqueous solutions hinder contact at the substrate-substrate interface, the present invention, because water is encapsulated in microcapsules and is difficult to evaporate, greatly reduces the porosity of the camouflage coating, greatly increases the contact area between the substrate and the substrate, and the coating has good adhesion to the substrate. The average breaking strength on the stainless steel substrate is not less than 222.9 psi, and it has high practical application value.

[0020] In summary, the camouflage coating prepared by the method of the present invention can achieve the "same color and same spectrum" characteristics of plant leaves in the 250-2500nm wavelength range; in addition, it has better water retention properties and substrate adhesion performance, better weather resistance, and is more conducive to practical applications. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a high-water-retention, high-spectral-spectrum camouflage coating with strong adhesion provided by the present invention.

[0022] Figure 2 This is a schematic diagram of the preparation method of a highly water-retaining hyperspectral camouflage coating with strong adhesion provided by the present invention.

[0023] Figure 3 Visible light image of the green coating obtained in Example 1 placed in a green osmanthus leaf.

[0024] Figure 4 This is a comparison diagram of the reflectance spectra of the green coating and vegetation prepared in Example 1.

[0025] Figure 5 The reflection spectra of the green coating prepared in Example 1 on different substrates are shown.

[0026] Figure 6 The spectra of the green coating prepared in Example 1 after being placed under natural conditions of 25°C and 30%RH for 400h and 800h; under dry heat conditions of 50°C and 20%RH for 75h and 150h; and under humid heat conditions of 30°C and 80%RH for 50h and 100h are shown.

[0027] Figure 7 This is a visible light image of the yellow coating obtained in Example 2 placed in a yellow osmanthus leaf.

[0028] Figure 8 This is a comparison diagram of the reflectance spectra of the yellow coating prepared in Example 2 and the vegetation.

[0029] Figure 9 The spectra of the yellow coating prepared in Example 2 were obtained after being placed under natural conditions at 25°C and 30%RH for 400h and 800h; under dry heat conditions at 50°C and 20%RH for 75h and 150h; and under humid heat conditions at 30°C and 80%RH for 50h and 100h.

[0030] Figure 10 Visible light image of the green coating obtained in Example 3 placed on a green gardenia leaf.

[0031] Figure 11 This is a comparison diagram of the reflectance spectra of the green coating and vegetation prepared in Example 3.

[0032] Figure 12 The spectra of the green coating prepared in Example 3 were obtained after being placed under natural conditions at 25°C and 30%RH for 400h and 800h; under dry heat conditions at 50°C and 20%RH for 75h and 150h; and under humid heat conditions at 30°C and 80%RH for 50h and 100h. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to embodiments and accompanying drawings.

[0034] The sources of materials and equipment used in the following embodiments are described below: The following materials were used: polyurethane resin (DM-211) produced by Shanghai Wanjue Coatings Technology Co., Ltd.; chlorophyll oil (E10) produced by Anhui Zhanhao Bioengineering Co., Ltd.; chromium oxide green pigment (nano grade) produced by Guangzhou Metal Metallurgy Co., Ltd.; titanium chromium yellow inorganic pigment (red phase) and titanium chromium brown inorganic pigment (PBR24) produced by Hunan Kelai New Materials Co., Ltd.; a saturated aqueous solution of lithium chloride was prepared using anhydrous lithium chloride powder (analytical grade) produced by Sinopharm Chemical Reagent Co., Ltd. and deionized water (grade I) produced by Yangzhou Zhongken Food Co., Ltd.; melamine (chemically pure), formaldehyde solution (AR37%), diethylenetriamine (analytical grade AR), and isophorone diisocyanate (analytical grade AR) produced by Sinopharm Chemical Reagent Co., Ltd. were used for stirring; an electric stirrer (JJ-1) produced by Shanghai Shangyi Co., Ltd. was used for stirring; and a vacuum defoaming tank (PUJ-PCV) produced by Fujiwara Gidori Co., Ltd. was used for vacuum defoaming.

[0035] like Figure 1 As shown, the coating structure of the present invention consists of water-containing microcapsule particles and pigment particles embedded in a substrate. The substrate is a polymer resin material, the water-containing microcapsules are an aqueous solution of hygroscopic salt physically encapsulated in the microcapsule structure, and the pigment particles include one or more of monochromatic microcapsules and monochromatic homogeneous particles.

[0036] Example 1 See Figure 2 The preparation method of a highly water-retaining hyperspectral camouflage coating with strong adhesion is as follows: Weigh 0.4 parts by weight of chromium oxide green monochrome homogeneous particles, 3.8 parts by weight of green monochrome microcapsule particles and 63.8 parts by weight of polyurethane resin substrate into a beaker, and stir at 400 rpm for 15 min to form a color solution; Subsequently, 32.0 parts by weight of the aqueous microcapsule particles were added to the colored solution and stirred at 500 rpm for 15 min to make the aqueous microcapsule particles evenly distributed in the polyurethane resin substrate to form a mixed solution. The above mixed solution was placed in a vacuum degassing chamber and vacuumed for 10 minutes under a vacuum degree of 20 Pa. The solution was then removed and coated onto the substrate material to form a solution layer with a thickness of 1.5 mm. After the solution layer was cured for 24 hours to form a film, a high water retention and hyperspectral camouflage coating with strong adhesion was obtained.

[0037] The green monochrome microcapsule core material is chlorophyll oil, and melamine and formaldehyde with a wall molar ratio of 1:2.5 are obtained by in-situ polymerization.

[0038] The aqueous microcapsule comprises a core material and a wall surface. The core material is a saturated aqueous solution of a hygroscopic salt, such as any one or more of lithium chloride aqueous solution, calcium chloride aqueous solution, potassium chloride aqueous solution, and aluminum chloride aqueous solution. The wall surface is a polyurea resin, formed by interfacial polymerization of 70-80 parts by weight of a polyisocyanate and 20-30 parts by weight of a polyethylene polyamine. The polyisocyanate is any one or more of toluene-2,4-diisocyanate, isophorone diisocyanate, terephthalic diisocyanate, and diphenylmethane-4,4-diisocyanate. The polyethylene polyamine is any one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0039] In this embodiment, the particle size of the water-containing microcapsules is 5-60 mm. μ The core material is composed of a saturated aqueous solution of lithium chloride, and the wall material is composed of 23 parts by mass of diethylenetriamine and 77 parts by mass of isophorone diisocyanate, obtained by interfacial polymerization. The specific steps are as follows: First, 4.2 g of diethylenetriamine is added to 25 g of lithium chloride aqueous solution and stirred at 400 rpm for 10 min to form an aqueous phase; then, 1 g of dipolyhydroxystearate is added to 39 g of dichloroethane solution and stirred at 400 rpm for 10 min to form an oil phase; the oil phase and aqueous phase are mixed and sheared at 5000 rpm for 15 min to form a W / O emulsion; then, 14 g of isophorone diisocyanate is added to the system and reacted at 25°C water bath and 300 rpm for 1 h; then, triethylamine is added to the system and reacted at 70°C water bath and 300 rpm for 1 h, and the reaction is terminated to obtain a microcapsule suspension. Take the lower precipitate from the microcapsule suspension, wash it with dichloromethane, filter it, and dry it at room temperature for a period of time to obtain water-containing microcapsule powder.

[0040] The camouflage coating prepared in Example 1 was applied to a tin foil substrate and allowed to form a film. The film was then cut into leaf shapes and placed among the green leaves of an osmanthus tree. Visible light images of the resulting product are shown below. Figure 3 As shown, from Figure 3 It can be seen that the camouflage coating is the same color as the green leaves.

[0041] The reflectance spectrum of the camouflage coating was measured using a UV-Vis-NIR spectrophotometer (Shimadzu DUV-3700). Figure 4As shown, the green camouflage coating prepared in Example 1 can mimic the characteristics of "low UV reflectance," "green peak," "red edge," "near-infrared plateau," and "water absorption valley" of green plant leaves. Its reflectance is 19.3% at 1450 nm and 7.3% at 1940 nm. The Pearson correlation coefficients of this coating with the green leaves of photinia, gardenia, pothos, and osmanthus are 97%, 96%, 96%, and 98%, respectively. Table 1 shows the Pearson correlation coefficients with the green leaves of different vegetation types after initial placement and placement under different temperature and humidity conditions for a period of time.

[0042] Table 1. Green coating prepared in Example 1 at initial time and under different temperature and humidity conditions. Pearson correlation coefficient (%) with different plant leaves after a period of time In this embodiment 1, when using a tin foil substrate, the coating achieves the same color and spectrum as the green vegetation.

[0043] like Figure 5 As shown, changing the substrate material has almost no effect on the coating's reflection spectrum. This is related to the transmission of light within the coating: when near-collimated sunlight is incident on the upper surface of the coating (air-substrate interface) through air, part of the incident light is reflected by the interface, and part enters the substrate, undergoing multiple absorptions and scatterings. The absorbed light energy is related to the substrate, water-containing microcapsules, and pigment particles, while the scattered light energy is related to the water-containing microcapsules and pigment particles. Subsequently, a small amount of remaining light energy reaches the lower surface of the coating (substrate-substrate interface), where interface reflection occurs again. The reflected light energy continues to undergo multiple absorptions and scatterings, and some of the scattered light reaches the upper surface of the coating and is transmitted out, forming the coating's reflected light energy together with the interface-reflected light energy. From the above analysis, it can be seen that the coating's reflection spectrum is mainly related to the multiple absorptions and scatterings of light by the internal substrate and particulate fillers. Therefore, the interface reflection at the lower surface of the coating has a relatively small impact on the coating's reflected light. Therefore, those skilled in the art can reasonably expect that applying alloy substrates and wood substrates to the technical solution of this invention can also achieve the beneficial effects of this invention.

[0044] Subsequently, the water retention performance of the green camouflage coating was tested under various working conditions, and its spectrum was as follows: Figure 6As shown, the camouflage coating can still mimic the various spectral characteristics of green leaves in the 250-2500nm range. Under natural and dry heat conditions, the coating loses water, resulting in an increase in reflectivity at wavelengths of 1450nm and 1940nm. However, under humid heat conditions, it decreases slightly. This is because the lithium chloride solution in the water-containing microcapsules of the coating adsorbs moisture from the environment under high humidity conditions, thereby increasing the moisture content in the material and leading to enhanced light absorption. Specifically, after being placed under natural conditions of 25℃ and 30%RH, the coating showed little spectral change. After 400 hours, its Pearson similarity to the vegetation was greater than 96%. At wavelengths of 1450nm and 1940nm, the reflectance increased from 19.41% and 7.30% to 20.97% and 7.97%, respectively, with the increase in reflectance being less than 2%. After 800 hours, the Pearson similarity to the vegetation was greater than 96%, with the increase in reflectance at 1450nm and 1940nm being 2.13% and 1%, respectively. Under dry heat conditions of 50℃ and 20%RH, after 75 hours, the coating showed a Pearson similarity to the vegetation greater than 95%, with the reflectance at 1450nm and 1940nm increasing significantly. The reflectance increases at 40 nm wavelength by 3.36% and 1.68%, respectively, and after 150 h, the Pearson similarity coefficient with the vegetation is greater than 94%. At 1450 nm and 1940 nm wavelengths, the reflectance increases by 6.98% and 1.68%, respectively. After 50 h of exposure to 30℃ and 80%RH humid heat conditions, the Pearson similarity coefficient with the vegetation is greater than 96%, and the reflectance decreases at 1450 nm and 0.01%, respectively. After 100 h, the Pearson similarity coefficient with the vegetation is greater than 96%, and the reflectance decreases at 1450 nm and 0.01%, respectively. These data indicate that the reflectance changes of the coating material prepared in Example 1 at 1450 nm and 1940 nm wavelengths are low under natural, dry heat, and humid heat conditions, suggesting that the material has high water retention capacity and can stably reproduce the spectral characteristics of the vegetation's "water absorption valley."

[0045] Example 2 A method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion is as follows: Weigh 0.5 parts by weight of titanium chromium brown monochrome homogeneous particles and 67.5 parts by weight of fluorocarbon resin substrate into a beaker, stir at 400 rpm for 15 min to form a color solution, then weigh 32.0 parts by weight of water-containing microcapsule particles and add them to the color solution, stir at 500 rpm for 15 min to make the water-containing microcapsule particles evenly distributed in the substrate to form a mixed solution. The above mixed solution was placed in a vacuum degassing chamber and vacuumed for 10 minutes under a vacuum degree of 20 Pa. The solution was then removed and coated onto the substrate material to form a solution layer with a thickness of 1 mm. After the solution layer was cured for 24 hours to form a film, a high water retention and high spectrum camouflage coating with strong adhesion was obtained.

[0046] The aqueous microcapsule core material is composed of a saturated aqueous solution of lithium chloride, and the wall material is composed of 25 parts by mass of diethylenetriamine and 75 parts by mass of isophorone diisocyanate, obtained by interfacial polymerization. The specific steps are as follows: First, 4g of diethylenetriamine is added to 25g of lithium chloride aqueous solution and stirred at 400rpm for 10min to form an aqueous phase; then, 1g of dipolyhydroxystearate is added to 39g of dichloroethane solution and stirred at 400rpm for 10min to form an oil phase; the oil phase and aqueous phase are mixed and sheared at 5000rpm for 15min to form a W / O emulsion; then, 12g of isophorone diisocyanate is added to the system and reacted at 25°C water bath and 300rpm for 1h; then, triethylamine is added to the system and reacted at 70°C water bath and 300rpm for 1h, and the reaction is terminated to obtain a microcapsule suspension. Take the lower precipitate from the microcapsule suspension, wash it with dichloromethane, filter it, and dry it at room temperature for a period of time to obtain water-containing microcapsule powder.

[0047] The camouflage coating prepared in Example 2 was applied to a tin foil substrate and, after film formation, cut into leaf shapes and placed among yellow osmanthus leaves. Visible light images are shown below. Figure 7 As shown in the figure, the coating and vegetation are the same color. The reflectance spectrum of the coating was measured using a UV-Vis-NIR spectrophotometer (Shimadzu DUV-3700). Figure 8 It can be seen that the yellow coating prepared in Example 2 can mimic the characteristics of yellow plant leaves, including "low UV reflectance," "green edges," "near-infrared plateau," and "water absorption valley." The reflectance is 19.9% ​​at 1450nm and 7.8% at 1940nm. The Pearson correlation coefficients of this coating with yellow leaves of gardenia, ivy, pothos, and osmanthus are 96%, 97%, 96%, and 98%, respectively. Table 2 shows the Pearson correlation coefficients with yellow leaves of different vegetation after initial placement and placement under different temperature and humidity conditions for a period of time. Therefore, it achieves "same color and spectrum" with yellow vegetation.

[0048] Table 2. Example 2: Yellow coating preparation at initial time and under different temperature and humidity conditions. Pearson correlation coefficient (%) between yellowing leaves of different vegetation after a period of time When the substrate material is changed, the reflection spectrum of the coating is almost unaffected.

[0049] Subsequently, the water retention performance of the yellow camouflage coating was tested under various working conditions, and its spectrum was as follows: Figure 9 As shown, the coating can still mimic the various spectral characteristics of yellow leaves in the 250-2500nm range. Under natural and dry heat conditions, the coating loses water, resulting in an increase in reflectance at wavelengths of 1450nm and 1940nm, while it still slightly decreases under humid heat conditions. Specifically, after being placed under natural conditions of 25℃ and 30%RH, the coating shows little spectral change. After 400 hours, the Pearson similarity coefficient with the vegetation is greater than 96%, with reflectance increases of 1.11% and 0.14% at wavelengths of 1450nm and 1940nm, respectively. After 800 hours, the Pearson similarity coefficient with the vegetation is greater than 96%, with reflectance increases of 1.75% and 0.95% at wavelengths of 1450nm and 1940nm, respectively. Under dry heat conditions of 50℃ and 20%RH, after 75 hours, the coating shows a Pearson similarity coefficient with the vegetation greater than 96%, with reflectance increases of 1.75% and 0.95% at wavelengths of 1450nm and 1940nm, respectively. The reflectance increases were 2.79% and 1.60%, respectively. After 150 hours of exposure, the Pearson similarity coefficient with the vegetation was greater than 95%, and the reflectance increases at wavelengths of 1450 nm and 1940 nm were 4.81% and 1.70%, respectively. After 50 hours of exposure at 30°C and 80% RH, the Pearson similarity coefficient with the vegetation was greater than 96%, and the reflectance decreases at wavelengths of 1450 nm and 0.42%, respectively. After 100 hours, the Pearson similarity coefficient with the vegetation was greater than 96%, and the reflectance decreases at wavelengths of 1450 nm and 0.67%, respectively. These data indicate that the reflectance changes of the coating material prepared in Example 2 were low under natural, dry, and humid conditions, demonstrating high water retention capacity and the ability to stably reproduce the spectral characteristics of the vegetation's "water absorption valley."

[0050] Example 3 A method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion is as follows: Weigh 0.4 parts by weight of homogeneous chromium oxide green particles and 70 parts by weight of polyurethane resin substrate into a beaker, and stir at 400 rpm for 15 min to form a color solution; then weigh 29.6 parts by weight of water-containing microcapsule particles and add them to the color solution, and stir at 500 rpm for 15 min to make the water-containing microcapsule particles evenly distributed in the polyurethane resin substrate to form a mixed solution. The above mixed solution was placed in a vacuum degassing chamber and vacuumed for 20 minutes under a vacuum degree of 20 Pa. The solution was then removed and coated onto the substrate material to form a solution layer with a thickness of 1.8 mm. After the solution layer was cured for 24 hours to form a film, a high water retention and high spectrum camouflage coating with strong adhesion was obtained.

[0051] The aqueous microcapsule core material is composed of a saturated aqueous solution of lithium chloride, and the wall surface is composed of 28 parts by mass of diethylenetriamine and 72 parts by mass of isophorone diisocyanate, obtained by interfacial polymerization. The specific steps are as follows: First, 4g of diethylenetriamine is added to 25g of lithium chloride aqueous solution and stirred at 400rpm for 10min to form an aqueous phase; then, 1g of dipolyhydroxystearate is added to 39g of dichloroethane solution and stirred at 400rpm for 10min to form an oil phase; the oil phase and aqueous phase are mixed and sheared at 5000rpm for 15min to form a W / O emulsion; then, 12g of isophorone diisocyanate is added to the system and reacted at 25°C water bath and 300rpm for 1h; then, triethylamine is added to the system and reacted at 70°C water bath and 300rpm for 1h, and the reaction is terminated to obtain a microcapsule suspension. Take the lower precipitate from the microcapsule suspension, wash it with dichloromethane, filter it, and dry it at room temperature for a period of time to obtain water-containing microcapsule powder.

[0052] The camouflage coating prepared in Example 3 was applied to a tin foil substrate and allowed to form a film. The film was then cut into leaf shapes and placed among green gardenia leaves. Visible light images of the resulting coating are shown below. Figure 10 As shown, from Figure 10 It can be seen that the camouflage coating is the same color as the green leaves.

[0053] The reflectance spectrum of the camouflage coating was measured using a UV-Vis-NIR spectrophotometer (Shimadzu DUV-3700). Figure 11 As shown, the green camouflage coating prepared in Example 3 can mimic the characteristics of "low UV reflectance," "green peak," "red edge," "near-infrared plateau," and "water absorption valley" of green plant leaves. Its reflectance is 21.1% at 1450 nm and 9.2% at 1940 nm. The Pearson correlation coefficients of this coating with the green leaves of photinia, gardenia, pothos, and osmanthus are 96%, 96%, 96%, and 97%, respectively. Table 3 shows the Pearson correlation coefficients with the green leaves of different vegetation types after initial placement and placement under different temperature and humidity conditions for a period of time.

[0054] Table 3. Green coating prepared in Example 3 at initial time and under different temperature and humidity conditions. Pearson correlation coefficient (%) with different plant leaves after a period of time When the substrate material is changed, the reflection spectrum of the coating is almost unaffected.

[0055] Subsequently, the water retention performance of the green camouflage coating was tested under various working conditions, and its spectrum was as follows: Figure 12As shown, the coating can still mimic the various spectral characteristics of green leaves in the 250-2500nm range. Under natural and dry heat conditions, the coating loses water, resulting in an increase in reflectance at wavelengths of 1450nm and 1940nm, while it still slightly decreases under humid heat conditions. Specifically, after being placed under natural conditions of 25℃ and 30%RH, the coating shows little spectral change. After 400 hours, the Pearson similarity coefficient with the vegetation is greater than 96%, with reflectance increases of 1.35% and 1.06% at wavelengths of 1450nm and 1940nm, respectively. After 800 hours, the Pearson similarity coefficient with the vegetation is still greater than 96%, with reflectance increases of 1.82% and 1.52% at wavelengths of 1450nm and 1940nm, respectively. Under dry heat conditions of 50℃ and 20%RH, after 75 hours, the coating shows a Pearson similarity coefficient with the vegetation greater than 96%, with reflectance increases of 1.82% and 1.52% at wavelengths of 1450nm and 1940nm, respectively. The reflectance increases were 2.99% and 1.76%, respectively. After 150 hours of exposure, the Pearson similarity coefficient with the vegetation was greater than 95%, and the reflectance increases at wavelengths of 1450 nm and 1940 nm were 4.28% and 1.76%, respectively. After 50 hours of exposure at 30°C and 80% RH, the Pearson similarity coefficient with the vegetation was greater than 96%, and the reflectance decreases at wavelengths of 1450 nm and 0.23%, respectively. After 100 hours, the Pearson similarity coefficient with the vegetation was greater than 96%, and the reflectance decreases at wavelengths of 1450 nm and 0.23%, respectively. These data indicate that the reflectance changes of the coating material prepared in Example 3 were low under natural, dry heat, and humid heat conditions, demonstrating high water retention capacity and the ability to stably reproduce the spectral characteristics of the vegetation's "water absorption valley."

[0056] The adhesion performance of the camouflage coatings obtained by the preparation methods of Examples 1, 2, and 3 on stainless steel substrates was tested. Twenty roughness tests were performed at different locations on each stainless steel substrate using a Contour GT-K (Bruker, Germany) optical profilometer. The roughness was described using the arithmetic mean height Sa in surface roughness testing. The adhesion performance test was conducted using the pull-off method described in the national standard GB / T 5210-2006. Before the test, an AB glue was used to fix the spindle to the coating surface. After the glue was completely cured, a pulling force was applied to the spindle using an automatic hydraulic pump system to separate the coating from the substrate. The area of ​​failure and the type of failure were recorded during the test. When the adhesion failure occurred between the coating and the substrate material, and the area of ​​coating adhesion failure was 100%, it was recorded as 100% A / B type. The test results are shown in Table 4.

[0057] Table 4. Adhesion performance of coatings on stainless steel substrates in the three examples. As shown in Table 4, the roughness of the camouflage coating substrates obtained by the methods in Examples 1, 2, and 3 is within 0.3. μ Near m, after being pulled apart, the coating failure type was 100% A / B, and the average breaking strength was greater than 222.9 psi, indicating good coating adhesion and high practical application value. My previously filed patent CN 118222138A describes a hyperspectral camouflage coating with a surface roughness of 0.3. μ The maximum adhesion breaking strength on a stainless steel substrate is 137.4 psi; the maximum adhesion strength of the coating in the embodiment of patent application CN117986913A on a stainless steel sheet is 133.4 psi; the maximum adhesion breaking strength of the coating in the embodiment of this invention is 247.2 psi, an increase of more than 80%. This is because in the previous patent, the evaporation of the hygroscopic salt solution inside the coating left pores inside the material, reducing the density of the coating and thus reducing the adhesion strength between the material and the substrate. On the other hand, the hygroscopic salt solution may also remain at the material-substrate interface, hindering direct contact between the resin substrate and the substrate. The present invention effectively solves the above two problems by microencapsulating the hygroscopic salt solution and using it as a water-containing filler in the coating, thereby improving the overall adhesion performance of the coating.

[0058] In practical applications, the preparation method of this invention allows for the flexible selection of different types of monochromatic homogeneous particles, such as chromium oxide green, iron oxide green, malachite green, cobalt green, phthalocyanine green, titanium chromium yellow, titanium nickel yellow, titanium chromium brown, lemon yellow, lightfast yellow, iron oxide yellow, iron oxide red, cadmium red, and pigment red series pigments, depending on the specific application environment. This enables the prepared anti-counterfeiting coating to blend seamlessly with the surrounding environment, achieving excellent camouflage and compatibility effects.

[0059] Those skilled in the art should understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion, characterized in that, The specific steps are as follows: Step 1: Mix 0.4-4.2 parts by weight of monochrome pigment particles and 63.8-70 parts by weight of polymer resin substrate and stir evenly to form a color solution; Step 2: Add 29.6-32 parts by weight of the aqueous microcapsule particles to the above-mentioned color solution and stir until a mixed solution is formed; Step 3: Place the above mixed solution in a vacuum degassing chamber and evacuate it for 10-30 minutes under a vacuum degree of less than 100 Pa. Then remove it and apply the mixed solution to the substrate material to form a solution layer with a thickness of 0.5-2 mm. After the solution layer has solidified into a film, a high water retention and high spectrum camouflage coating with strong adhesion is obtained.

2. The method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating according to claim 1, characterized in that, In step one, the monochrome pigment particles are monochrome homogeneous particles and / or monochrome microcapsule particles.

3. The method for preparing a highly water-retaining hyperspectral camouflage coating with strong adhesion according to claim 2, characterized in that, The monochromatic homogeneous particles are selected from one of the following pigment series: chromium oxide green, iron oxide green, malachite green, cobalt green, phthalocyanine green, titanium chromium yellow, titanium nickel yellow, titanium chromium brown, lemon yellow, lightfast yellow, iron oxide yellow, iron oxide red, cadmium red, and pigment red.

4. The method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating according to claim 2, characterized in that, The monochromatic microcapsule particles comprise a pigment core material and a wall surface, wherein the core material is chlorophyll oil or xanthophyll oil, and the microcapsule particle size is 5-100 μm. μ m; The wall surface is prepared by in-situ polymerization of melamine and formaldehyde in a molar ratio of 1:2-1:

4.

5. The method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating according to claim 1, characterized in that, In step one, the polymer resin substrate is any one of alkyd resin, fluorocarbon resin, epoxy resin, nitrocellulose, acrylic resin, polyurethane resin, and chlorinated rubber resin.

6. The method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating according to claim 1, characterized in that, In step one, the stirring rate is 200-600 rpm and the stirring time is 10-30 min; in step two, the stirring rate is 400-600 rpm and the stirring time is 10-30 min.

7. The method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating according to claim 1, characterized in that, The aqueous microcapsules in step two consist of a core material and a wall surface. The core material is a saturated aqueous solution of hygroscopic salt, and the particle size of the aqueous microcapsules is 5-60 nm. μ m; the wall surface is made of polyurea resin, which is formed by interfacial polymerization of 70-80 parts by weight of polyisocyanate and 20-30 parts by weight of polyethylene polyamine.

8. The method for preparing a highly adhesive, water-retaining, hyperspectral camouflage coating according to claim 1, characterized in that, The substrate material in step three can be any one of tin foil substrate, stainless steel substrate, alloy substrate, glass substrate, wood substrate, and paper substrate.

9. The camouflage coating prepared by the method according to any one of claims 1-8, characterized in that, After the camouflage coating is prepared, in the initial state, the Pearson correlation coefficient between the spectrum in the 250-2500nm solar band and the vegetation spectrum is not less than 96%, the reflectance at 1450nm wavelength is 15-25%, and the reflectance at 1940nm wavelength is 5-15%, which is consistent with the vegetation spectral characteristics in the LOPEX93 database. The camouflage coating, after being placed under natural conditions of 25°C and 30%RH for 800 hours, showed a reflectance change of less than 2.5% at wavelengths of 1450nm and 1940nm, and a Pearson correlation coefficient with vegetation greater than 96%. The camouflage coating, after being placed under dry heat conditions of 50°C and 20%RH for 150 hours, showed a reflectance change of less than 7% at wavelengths of 1450nm and 1940nm, and a Pearson correlation coefficient with vegetation greater than 94%. The camouflage coating, after being placed under 30°C and 80%RH humid heat conditions for 100 hours, showed a reflectance change of less than 2.5% at wavelengths of 1450nm and 1940nm, and a Pearson correlation coefficient with vegetation greater than 96%.

10. The camouflage coating according to claim 9, characterized in that, The adhesion performance was tested using the pull-off method described in the national standard GB / T 5210-2006, and the average adhesion strength of the camouflage coating on the stainless steel substrate was not less than 222.9 psi.

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