Sun-resistant thermochromic microcapsules and methods for their preparation

Abstract

The application discloses a sun-resistant thermochromic microcapsule and a preparation method thereof, and belongs to the technical field of material science. In the application, inorganic anti-ultraviolet agent particles are covalently grafted with organic anti-ultraviolet agents by using a click chemistry method, composite anti-ultraviolet particles are prepared, and strawberry-shaped sun-resistant thermochromic microcapsules with a shell layer loaded with the composite particles are prepared. The sun-resistant thermochromic microcapsule prepared in the application can effectively absorb and reflect ultraviolet light through the composite particles on the shell layer under irradiation of sunlight or ultraviolet light, so as to protect the thermochromic dye in the core material, thereby making the microcapsule exhibit good thermochromic performance while meeting the sun-resistant requirement, and the microcapsule can be directly used in a textile color paste.

Description

Technical Field

[0001] This invention relates to a thermochromic microcapsule and its preparation method, belonging to the field of materials science and technology. Background Technology

[0002] Thermochromic materials are materials that change color in response to changes in external temperature. Among them, fluorane dyes are considered the most promising thermochromic materials due to their complete color spectrum, good color-changing stability, and bright colors. Fluorane dyes require the use of color-developing agents and solvents, and are typically encapsulated and protected using microencapsulation technology. With societal development and increasing demand for personalized and intelligent products, fluorane-based thermochromic materials have broad application prospects in textiles, anti-counterfeiting packaging, smart buildings, military industry, and smart healthcare.

[0003] Fluorescein dyes absorb certain wavelengths in the visible light spectrum to emit different colors, and also exhibit strong absorption in the ultraviolet (UV) spectrum. However, UV light, with its short wavelength and high energy carrying capacity, can damage the structure of fluorescein dyes. Experiments show that even short-term exposure can cause fluorescein dyes to lose their color, and their poor lightfastness significantly limits their outdoor use.

[0004] Currently, there are methods to improve the sun resistance of color-changing materials using organic UV absorbers. For example, Chinese patent CN112876895A describes adding color-changing microcapsules and organic UV absorbers together to a surface paint and applying it to the floor surface to obtain a floor with color-changing functionality. Patent CN215005938U describes a multi-layered pair of glasses where the color-changing material layer is placed behind an organic UV-absorbing layer to achieve a protective effect. Patent CN114808472A describes synthesizing a UV-absorbing polymer and applying it as a coating to thermochromic fabric to protect the color-changing material.

[0005] In addition, inorganic nanomaterials such as nano-titanium dioxide and nano-zinc oxide are often used to optimize the sun-resistance of functional materials due to their ultraviolet light reflection properties. For example, patent CN114059383A uses titanium dioxide nanoparticles mixed into a sun-resistant layer, which is then placed on top of a heat-sensitive layer to prepare sun-resistant heat-sensitive paper. Compared to organic UV absorbers, inorganic UV absorbers have better durability due to their UV-resistance mechanism, which relies on physical processes such as light reflection and scattering. However, while both organic UV absorbers and inorganic nanomaterials can improve the sun-resistance of materials to some extent, compatibility and migration issues exist when used alone. Summary of the Invention

[0006] [Technical Issues]

[0007] Color-changing systems using fluorane dyes as color-developing agents cannot meet people's requirements in terms of resistance to sunlight.

[0008] [Technical Solution]

[0009] Based on this, this invention patent utilizes in-situ emulsion polymerization to prepare a strawberry-type thermochromic microcapsule for textiles. By leveraging the surface composite of nano-UV stabilizers on the microcapsule, the sun-resistance of thermochromic textile materials is enhanced, solving the problem of fluorescein-based thermochromic textiles being unsuitable for prolonged outdoor use. This invention first employs click chemistry to covalently graft inorganic UV stabilizer particles with organic UV stabilizers, preparing composite UV stabilizers, and then fabricating strawberry-type sun-resistant thermochromic microcapsules with the composite particles loaded in the shell. Under sunlight or UV light irradiation, the composite particles on the shell of the sun-resistant thermochromic microcapsules prepared by this invention can effectively absorb and reflect UV light, protecting the color-changing dye in the core material. This allows the microcapsules to exhibit excellent color-changing performance while meeting sun-resistance requirements, and the microcapsules can be directly used in textile color pastes.

[0010] The first objective of this invention is to provide a composite UV-resistant particle comprising an inorganic UV-resistant agent and an organic UV-resistant agent, wherein the inorganic UV-resistant agent and the organic UV-resistant agent are covalently linked by CS or CC bonds.

[0011] In one embodiment of the present invention, the inorganic UV stabilizer is a nanoparticle, including one or more of nano-titanium dioxide, nano-zinc oxide, carbon black, and iron oxide red.

[0012] In one embodiment of the present invention, the organic UV stabilizer is a reagent with carbon-carbon double bonds in its structure, including 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate, 2-hydroxy-4-allyloxybenzophenone, 2-hydroxy-4-methacrylate, 2-hydroxy-4-propenylbenzophenone, or 2-hydroxy-4-(3-methacrylate-2-hydroxypropoxy)benzophenone.

[0013] A second objective of this invention is to provide a method for preparing composite UV-resistant particles, the method comprising the following steps:

[0014] (1) An inorganic UV stabilizer powder was obtained by reacting an inorganic UV stabilizer with a silane coupling agent in an alkaline alcohol-water environment.

[0015] (2) The modified inorganic UV-resistant powder, organic UV-resistant agent and initiator obtained in step (1) are reacted at high temperature, and composite UV-resistant particles are obtained after the reaction is completed.

[0016] In one embodiment of the present invention, the inorganic UV stabilizer is a nanoparticle, including one or more of nano-titanium dioxide, nano-zinc oxide, carbon black, and iron oxide red.

[0017] In one embodiment of the present invention, the silane coupling agent includes one or more of KH-580, KH-550, and KH570.

[0018] In one embodiment of the present invention, the organic UV stabilizer is a reagent with carbon-carbon double bonds in its structure, including 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate, 2-hydroxy-4-allyloxybenzophenone, 2-hydroxy-4-methacrylate, 2-hydroxy-4-propenylbenzophenone, and 2-hydroxy-4-(3-methacrylate-2-hydroxypropoxy)benzophenone.

[0019] In one embodiment of the present invention, the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptanenitrile, dodecyl peroxide, dicumyl peroxide, and di-tert-butyl peroxide.

[0020] In one embodiment of the present invention, the mass ratio of inorganic UV stabilizer to silane coupling agent in step (1) is 1:0.5-2.

[0021] In one embodiment of the present invention, the reaction conditions for step (1) are: pH 8-10, temperature 50-90℃, and reaction time 1-9h.

[0022] In one embodiment of the present invention, the mass ratio of modified inorganic UV-resistant powder to organic UV-resistant initiator in step (2) is 1:0.5-2.

[0023] In one embodiment of the present invention, the reaction conditions for step (2) are: temperature of 50-90℃, reaction time of 1-9h.

[0024] In one embodiment of the present invention, the method includes the following steps:

[0025] (1) Disperse 2 parts of inorganic UV-resistant agent in 66 parts of alcohol-water solution, slowly add 1-3 parts of silane coupling agent, then add ammonia water to adjust the pH to 8-10, heat the solution to 50-90℃, react for 1-9 hours, centrifuge, wash and dry after the reaction to obtain modified UV-resistant agent powder.

[0026] (2) Add 2 parts of the powder obtained in (1) above and 1-4 parts of organic UV-resistant agent to 100 parts of toluene, stir evenly and heat to 55-95℃, slowly add 20% of the initiator of organic UV-resistant agent, and then react for 3-7 hours. After the reaction is completed, centrifuge, wash and dry to obtain composite UV-resistant particles.

[0027] A third objective of this invention is to provide an application of the aforementioned composite UV-resistant particles in the preparation of microcapsules. In this application, the composite UV-resistant particles serve as part of the shell material and also act as an emulsifier.

[0028] In one embodiment of the present invention, the microcapsule core material is an oil-soluble component, and the composite UV-resistant particles are amphiphilic and arranged at the oil-water interface in the emulsion, which can not only enhance the stability of the emulsion, but also be loaded onto the microcapsule shell material after the reaction is completed.

[0029] The fourth objective of this invention is to provide a strawberry-shaped, sun-resistant, thermochromic microcapsule, which uses the aforementioned composite UV-resistant particles as the shell material of the color-changing microcapsule and a dye as the core material.

[0030] The fifth objective of this invention is to provide a method for preparing strawberry-type, sun-resistant, thermochromic microcapsules, the method comprising the following steps:

[0031] (a) Melamine, formaldehyde and urea are mixed to obtain a urea-melamine-formaldehyde terpolymer resin prepolymer;

[0032] (b) Fluorine dye, color developer and solvent are mixed and dissolved at high temperature to obtain color-changing material;

[0033] (c) The emulsifier, color-changing dye and the urea-melamine-formaldehyde terpolymer prepolymer obtained in step (a) are mixed and reacted to obtain light-resistant thermochromic microcapsules.

[0034] In one embodiment of the present invention, the ratio of melamine, formaldehyde, and urea is 0.5-1 molar ratio of formaldehyde / (urea + melamine).

[0035] In one embodiment of the present invention, the reaction conditions for step (a) are to adjust the pH to 9-10 and react at 60-80°C for 0.5-3 hours.

[0036] In one embodiment of the present invention, the reaction conditions for step (c) are as follows: 1-3 parts of emulsifier are added to 100 parts of water, and 1-3 parts of color-changing material and 1-2 parts of prepolymer are added dropwise while emulsifying at high speed at 50-80°C. Then, the mixture is stirred and emulsified at 3000-15000 rpm for 20-60 min. After reacting for 15-45 min, the pH is adjusted to 4-5, and the reaction is continued for 1-3 h to obtain sun-resistant thermochromic microcapsules.

[0037] In one embodiment of the present invention, the selected fluorane dyes include, but are not limited to, one or more of 2-phenylamino-3-methyl-6-diethylfluorane, 2-phenylamino-3-methyl-6-dibutylfluorane, 3-dimethyl-6-diethylaminofluorane, 2-chloro-6-(diethylamino)fluorane, and 1,3-dimethyl-6-diethylaminofluorane.

[0038] In one embodiment of the present invention, the selected colorimetric agent is at least one of bisphenol A, bisphenol F, bisphenol S, and 1-hydroxy-2-naphthoic acid phenol.

[0039] In one embodiment of the present invention, the solvent used is one or a combination of two or more of octadecyl alcohol, hexadecyl alcohol, tetradecyl alcohol, dimethyl succinate, butanediol, and hexanediol.

[0040] In one embodiment of the present invention, the selected emulsifier is one or more of anionic surfactants, polymeric surfactants, and nonionic surfactants, including but not limited to the following materials: Laberg gum, styrene-maleic anhydride copolymer, sodium dodecylbenzenesulfonate, Span, and Tween.

[0041] The sixth objective of this invention is to provide a sun-resistant textile, which is prepared by printing the above-mentioned sun-resistant microcapsules onto the textile.

[0042] In one embodiment of the present invention, the textile is a fiber and fiber product, including fibers, yarns, fabrics, nonwovens and their composites.

[0043] The beneficial effects of this invention are:

[0044] The beneficial effects of this invention are that it provides a method for preparing strawberry-type thermochromic microcapsules, which have dense composite UV-resistant particles on their shells. These composite UV-resistant particles have good UV protection properties and can effectively protect the color-changing material in the microcapsule core. The color-changing fabric prepared from the strawberry-type thermochromic microcapsules exhibits good sun resistance, with a fading rate of only 28% after 10 hours of simulated sun exposure; the color-changing speed is fast, completing in just 3.3 seconds; the color-changing cycle count is greater than 500 times, demonstrating excellent fatigue resistance, with a K / S value reaching 4.49. This meets the requirements for color-changing fabrics and has broad application prospects in the field of outdoor color-changing textiles. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of a strawberry-type thermochromic microcapsule. Detailed Implementation

[0046] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0047] 1. Experimental materials:

[0048] The nano-TiO2 and ZnO mentioned in the examples, with a size of 40 nm, were purchased from Sinopharm Corporation; 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate (BHEM), CAS No. 96478-09-0; (3-mercaptopropyl)triethoxysilane (KH-580), CAS No. 14814-09-6, were all purchased from Maclean Biochemical Technology Co., Ltd.; and the orange-red fluorane color-changing dye was purchased from Haishan Technology Co., Ltd.

[0049] 2. Testing Method:

[0050] Apparent color depth value: Take 8 random points on the surface of the dyed fabric and use a Datacolor 650 desktop spectrophotometer to measure the K / S value of the dyed fabric and take the average value.

[0051] Fading rate: The color-changing fabric was artificially subjected to simulated sun aging using a sun exposure weathering machine at a temperature of 35℃ and a humidity of 40% RH. The K / S value of the fabric was calculated using the following formula, taking into account the different sun exposure times.

[0052]

[0053] In the formula: K / S0 is the initial K / S value of the fabric, K / S t It is the K / S value of the fabric after t hours.

[0054] Color change time: Place the color-changing fabric on the heated platform and time the time required for the fabric to completely fade with a stopwatch. The temperature of the heated platform is 10°C higher than the color change temperature.

[0055] Example 1: An anti-ultraviolet composite particle

[0056] 1 g of nano-TiO2 was dispersed in 33 g of an alcohol-water solution, and 1.5 g of KH-580 was slowly added dropwise to adjust the pH to 9. The mixture was reacted at 80 °C for 5 h. After centrifugation and drying, the resulting powder was dispersed in 100 mL of toluene, and 0.4 g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate and 0.6 g of azobisisobutyronitrile (azobisisobutyronitrile) initiator were added. The mixture was reacted at 75 °C for 5 h to obtain UV-resistant composite particles. Particle size and contact angle tests showed that the UV-resistant composite particles had a particle size of 256 nm, a DPI of 0.119, and a contact angle of 84°.

[0057] Example 2: An anti-ultraviolet composite particle

[0058] 1 g of nano-ZnO was dispersed in 33 g of an alcohol-water solution, and 1.5 g of KH-580 was slowly added dropwise to adjust the pH to 9. The mixture was reacted at 80 °C for 5 h. After centrifugation and drying, the resulting powder was dispersed in 100 mL of toluene, and 0.4 g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate and 0.6 g of azobisisobutyronitrile (azobisisobutyronitrile) initiator were added. The mixture was reacted at 75 °C for 5 h to obtain UV-resistant composite particles. Particle size and contact angle tests showed that the UV-resistant composite particles had a particle size of 312 nm, a DPI of 0.122, and a contact angle of 75°.

[0059] Example 3: An anti-ultraviolet composite particle

[0060] The amount of KH-580 added was adjusted to 1g, and other conditions or parameters were the same as in Example 1.

[0061] Table 1

[0062]

[0063] Example 4: Thermochromic Microcapsules

[0064] First, melamine, formaldehyde, and urea were mixed in water and completely dissolved. The pH was then adjusted to 9, and the mixture was reacted at 60°C for 3 hours to obtain a urea-melamine-formaldehyde ternary copolymer resin prepolymer. 0.04 g of the UV-resistant composite particles obtained in Example 1 and 1.5 g of gum arabic powder were added to 100 mL of water and stirred at 6000 rpm at 65°C for 30 min. While emulsifying, 2 g of thermochromic material and 2.8 g of prepolymer were added dropwise. The temperature was then raised to 75°C, and the stirring speed was reduced to 500 rpm. After 0.5 h, the pH was adjusted to 4-5, and the mixture was reacted for 1.5 h to obtain UV-protected thermochromic microcapsules.

[0065] Example 5: Thermochromic Microcapsules

[0066] First, melamine, formaldehyde, and urea were mixed in water and completely dissolved. The pH was then adjusted to 9, and the mixture was reacted at 70°C for 2 hours to obtain a urea-melamine-formaldehyde ternary copolymer resin prepolymer. 0.08 g of the UV-resistant composite particles obtained in Example 1 and 1.5 g of gum arabic powder were added to 100 mL of water and stirred at 6000 rpm at 65°C for 30 min. While emulsifying, 2.8 g of the color-changing material and the prepolymer were added dropwise. The temperature was then raised to 75°C, and the stirring speed was reduced to 500 rpm. After 0.5 h, the pH was adjusted to 4-5, and the mixture was reacted for 1.5 h to obtain UV-protected thermochromic microcapsules.

[0067] Example 6: Thermochromic Microcapsules

[0068] First, melamine, formaldehyde, and urea were mixed in water and completely dissolved. The pH was then adjusted to 10, and the mixture was reacted at 80°C for 1 hour to obtain a urea-melamine-formaldehyde ternary copolymer resin prepolymer. 0.08 g of the UV-resistant composite particles obtained in Example 2 and 1.5 g of gum arabic powder were added to 100 mL of water and stirred at 6000 rpm at 65°C for 30 min. While emulsifying, 2 g of the color-changing material and 2.8 g of the prepolymer were added dropwise. The temperature was then raised to 75°C, and the stirring speed was reduced to 500 rpm. After 0.5 h, the pH was adjusted to 4-5, and the mixture was reacted for 1.5 h to obtain UV-protected thermochromic microcapsules.

[0069] Example 7: Thermochromic Microcapsules

[0070] First, melamine, formaldehyde, and urea were mixed in water and completely dissolved. The pH was then adjusted to 9.5, and the mixture was reacted at 80°C for 0.5 hours to obtain a urea-melamine-formaldehyde ternary copolymer resin prepolymer. 0.08 g of the UV-resistant composite particles obtained in Example 3 and 1.5 g of gum arabic powder were added to 100 mL of water and stirred at 6000 rpm at 65°C for 30 minutes. While emulsifying, 2 g of the color-changing material and 2.8 g of the prepolymer were added dropwise. The temperature was then raised to 75°C, and the stirring speed was reduced to 500 rpm. After 0.5 hours, the pH was adjusted to 4-5, and the mixture was reacted for 1.5 hours to obtain UV-protected thermochromic microcapsules.

[0071] Example 8: A thermochromic fabric

[0072] The microcapsules from Examples 4-7 were added to printing pigments to prepare UV-protected thermochromic fabrics. The prepared thermochromic fabrics were subjected to artificial sun aging tests (see Table 1) and color-changing performance tests (see Table 2).

[0073] Comparative Example 1: Compared with Example 5, no composite particles were added.

[0074] No UV-resistant composite particles were added during the preparation of the microcapsules. 1.5g of gum arabic powder was added to 100mL of water, and the mixture was stirred at 6000rpm for 30min at 65℃. While emulsifying, 2g of color-changing material and 2.8g of prepolymer were added dropwise. The temperature was then raised to 75℃, and the stirring speed was reduced to 500rpm. After 0.5h, the pH was adjusted to 4-5, and the reaction was allowed to proceed for 1.5h to obtain thermochromic microcapsules. These microcapsules were then added to printing paste to prepare UV-protected thermochromic fabrics. Artificial sun exposure aging tests (see Table 1) and color-changing performance tests (see Table 2) were conducted on the prepared color-changing fabrics.

[0075] Comparative Example 2: Compared with Example 5, TiO2 was not modified.

[0076] 0.08 g of nano-TiO2 and 1.5 g of gum arabic powder were added to 100 mL of water and stirred at 6000 rpm for 30 min at 65 °C. While emulsifying, 2 g of color-changing material and 2.8 g of prepolymer were added dropwise. The temperature was then raised to 75 °C, and the stirring speed was reduced to 500 rpm. After 0.5 h, the pH was adjusted to 4-5, and the reaction was allowed to proceed for 1.5 h to obtain UV-protected thermochromic microcapsules. The above microcapsules were added to printing paste to prepare UV-protected thermochromic fabrics. The prepared thermochromic fabrics were subjected to artificial sunlight aging tests (see Table 1) and color-changing performance tests (see Table 2).

[0077] Comparative Example 3: Compared with Example 5, TiO2 was only grafted with KH-580

[0078] 1g of nano-TiO2 was dispersed in 33g of alcohol-water solution, and 1.5g of KH-580 was slowly added dropwise. The pH was adjusted to 9, and the reaction was carried out at 80℃ for 3h. After centrifugation and drying, the resulting TiO2 powder grafted only with KH-580 was obtained. 0.08g of the obtained TiO2 powder grafted only with KH-580 and 1.5g of gum arabic powder were added to 100mL of water, and the mixture was stirred at 6000rpm for 30min at 65℃. While emulsifying, 2g of color-changing material and 2.8g of prepolymer were added dropwise. The temperature was then raised to 75℃, and the stirring speed was reduced to 500rpm. After 0.5h, the pH was adjusted to 4-5, and the reaction was carried out for 1.5h to obtain UV-protected thermochromic microcapsules. The above microcapsules were added to printing paste to prepare UV-protected thermochromic fabrics. The prepared thermochromic fabrics were subjected to artificial sun exposure aging tests (see Table 1) and color-changing performance tests (see Table 2).

[0079] Comparative Example 4: ZnO unmodified compared to Example 6

[0080] 1g of nano-ZnO was dispersed in 33g of alcohol-water solution, and 1.5g of KH-580 was slowly added dropwise. The pH was adjusted to 9, and the reaction was carried out at 80℃ for 3h. After centrifugation and drying, the resulting TiO2 powder grafted only with KH-580 was obtained. 0.08g of the obtained TiO2 powder grafted only with KH-580 and 1.5g of gum arabic powder were added to 100mL of water, and the mixture was stirred at 6000rpm at 65℃ for 30min. While emulsifying, 2g of color-changing material and 2.8g of prepolymer were added dropwise. The temperature was then raised to 75℃, and the stirring speed was reduced to 500rpm. After 0.5h, the pH was adjusted to 4-5, and the reaction was carried out for 1.5h to obtain UV-protected thermochromic microcapsules. The above microcapsules were added to printing paste to prepare UV-protected thermochromic fabrics. The prepared thermochromic fabrics were subjected to artificial sun exposure aging tests (see Table 1) and color-changing performance tests (see Table 2).

[0081] Comparative Example 5: Compared with Example 5, only an organic ultraviolet absorber was added.

[0082] 0.08 g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate and 1.5 g of gum arabic powder were added to 100 mL of water. The mixture was stirred at 6000 rpm for 30 min at 65 °C. While emulsifying, 2 g of color-changing material and 2.8 g of prepolymer were added dropwise. The temperature was then raised to 75 °C, and the stirring speed was reduced to 500 rpm. After 0.5 h, the pH was adjusted to 4-5, and the reaction was allowed to proceed for 1.5 h. Due to the poor compatibility between the UV absorber and the microcapsules, the UV absorber precipitated and separated during the reaction, causing the emulsion to break down and preventing the acquisition of the microcapsule product.

[0083] Comparative Example 6: Compared with Example 5, TiO2 is in the micrometer range.

[0084] 1g of ordinary TiO2 was dispersed in 33g of alcohol-water solution, and 1.5g of KH-580 was slowly added dropwise. The pH was adjusted to 9, and the reaction was carried out at 80℃ for 3h. After centrifugation and drying, the resulting TiO2 powder grafted only with KH-580 was obtained. 0.08g of the obtained particles and 1.5g of gum arabic powder were added to 100mL of water, and the mixture was stirred at 6000rpm for 30min at 65℃. While emulsifying, 2g of color-changing material and 2.8g of prepolymer were added dropwise. The temperature was then raised to 75℃, and the stirring speed was reduced to 500rpm. After 0.5h, the pH was adjusted to 4-5, and the reaction was carried out for 1.5h to obtain UV-protected thermochromic microcapsules. The above microcapsules were added to printing paste to prepare UV-protected thermochromic fabrics. The prepared thermochromic fabrics were subjected to artificial sun aging tests (see Table 1) and color-changing performance tests (see Table 2). Comparative Example 7: Compared with Example 5, no initiator was added.

[0085] 1g of nano-TiO2 was dispersed in 33g of alcohol-water solution, and 1.5g of KH-580 was slowly added dropwise to adjust the pH to 9. The reaction was carried out at 80℃ for 3h. After centrifugation and drying, the resulting powder was dispersed in 100mL of toluene, and 0.4g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate was added. The reaction was carried out at 75℃ for 5h to obtain UV-resistant composite particles. 0.08g of the UV-resistant composite particles and 1.5g of gum arabic powder were added to 100mL of water. The mixture was stirred at 6000rpm at 65℃ for 30min. While emulsifying, 2.8g of 2g of color-changing material and prepolymer were added dropwise. The temperature was then raised to 75℃, and the stirring speed was reduced to 500rpm. After 0.5h, the pH was adjusted to 4-5, and the reaction was carried out for 1.5h to obtain UV-protected thermochromic microcapsules. The microcapsules were added to printing pigments to prepare thermochromic fabrics with UV protection. Artificial sun exposure aging tests (see Table 1) and color-changing performance tests (see Table 2) were conducted on the prepared color-changing fabrics. The results showed that the directly composited UV-resistant composite particles had the disadvantages of rapid fading and poor sun resistance during sun exposure.

[0086] Table 2. Artificial Sun Exposure Aging Test of Fabrics

[0087] Sunlight performance Fading rate (%) after 10 hours of continuous sun exposure Example 4 56％ Example 5 28％ Example 6 32％ Example 7 45％ Comparative Example 1 92％ Comparative Example 2 72％ Comparative Example 3 75％ Comparative Example 4 82％ Comparative Example 6 90％ Comparative Example 7 88％

[0088] Table 3. Fabric color change performance test

[0089]

[0090]

[0091] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A sun-resistant microcapsule, characterized in that, A method for preparing sun-resistant thermochromic microcapsules, using composite UV-resistant particles as the shell material and thermochromic dye as the core material, includes the following steps: (a) First, melamine, formaldehyde and urea are mixed in water and completely dissolved. Then, the pH is adjusted to 9 and the mixture is reacted at 70°C for 2 hours to obtain a urea-melamine-formaldehyde terpolymer resin prepolymer. (b) The fluorane dye, color developer and solvent were mixed and dissolved at high temperature to obtain the color-changing material; the fluorane dye was an orange-red fluorane color-changing dye, purchased from Haishan Technology Co., Ltd. (c) Take 0.08g of UV-resistant composite particles and 1.5g of gum arabic powder and add them to 100mL of water. Stir at 6000rpm for 30min at 65℃. While emulsifying, add 2.8g of color-changing material and prepolymer dropwise. Then raise the temperature to 75℃ and reduce the stirring speed to 500rpm. After 0.5h, adjust the pH to 4-5 and react for 1.5h to obtain UV-protected thermochromic microcapsules. A method for preparing composite UV-resistant particles includes the following steps: 1g of nano-TiO2 is dispersed in 33g of an alcohol-water solution, 1.5g of KH-580 is slowly added dropwise, the pH value is adjusted to 9, and the reaction is carried out at 80℃ for 5h. After centrifugation and drying, the resulting powder is dispersed in 100mL of toluene, 0.4g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate and 0.6g of initiator azobisisobutyronitrile are added, and the reaction is carried out at 75℃ for 5h to obtain UV-resistant composite particles; the size of nano-TiO2 is 40nm; the particle size of composite UV-resistant particles is 256nm, the DPI is 0.119, and the contact angle is 84°.

2. The sun-resistant microcapsule according to claim 1, characterized in that, The selected colorimetric reagent is at least one of bisphenol A, bisphenol F, bisphenol S, and 1-hydroxy-2-naphthoic acid phenol.

3. The sun-resistant microcapsule according to claim 1, characterized in that, The selected solvent is one or more of octadecyl alcohol, hexadecyl alcohol, tetradecyl alcohol, dimethyl succinate, butanediol, and hexanediol.

4. A sun-resistant textile, characterized in that, Sun-resistant textiles are prepared by printing on textiles using the sun-resistant microcapsules described in any one of claims 1-3.

5. The sun-resistant textile according to claim 4, characterized in that, The textiles are fibers and fiber products, including fibers, yarns, fabrics, nonwovens and their composites.

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