A process for efficiently preparing photochromic microspheres on a large scale

Abstract

The present application first prepares DASAs intermediate microspheres, and then generates DASAs microspheres by the reaction of the DASAs intermediate and a donor. Compared with the traditional process, the present application has a simpler preparation and synthesis method, does not need to prepare DASAs, is easy to operate, and can be produced on a large scale in industry. The DASAs microspheres prepared by the present application have a deeper color and better photochromic performance, because the DASAs molecules are not directly exposed to water and high temperature during the preparation process, and the damage rate of the DASAs molecules is low. Based on the preparation of the same kind of DASAs intermediate microspheres, different DASAs microspheres can be prepared by replacing different donors, which greatly saves the cost and simplifies the synthesis steps.

Description

Technical Field

[0001] This invention relates to the field of photochromic materials technology, and particularly to a process for the efficient and large-scale preparation of photochromic microspheres. Background Technology

[0002] Polymer microspheres not only possess the advantages of being easily separated and extracted from solid-phase carriers, but also offer advantages such as low cost, large specific surface area, good monodispersity, convenient preparation, and excellent functionality. Due to their unique properties, polymer microspheres are widely used in wastewater treatment, leather making, food, and biomedicine.

[0003] Currently, a mainstream method for preparing microspheres is solvent evaporation. Also known as in-liquid drying, solvent evaporation is widely used for packaging microspheres containing various active substances. The effectiveness of solvent evaporation in preparing microspheres lies in successfully encapsulating the active substance within the particles. The principle involves evaporating the volatile solvent dispersed in the emulsion, leaving non-volatile material to encapsulate the active substance and form microspheres.

[0004] Traditionally, the process of preparing DASAs microspheres using solvent evaporation is quite cumbersome. First, an intermediate DASA is generated by reacting an acceptor (such as isopropyl malonate) with furfural. The purified intermediate is then reacted with a donor (such as N-methylaniline) to generate DASAs. The purified DASAs and polymers (such as polycaprolactone) are then dissolved together in a volatile solvent (usually dichloromethane) as the oil phase. An aqueous phase is prepared separately, such as an aqueous solution of polyvinyl alcohol or an aqueous solution of sodium dodecyl sulfate (polyvinyl alcohol and sodium dodecyl sulfate are used as emulsifiers to form a stable emulsion from a mixture of two or more immiscible components). After the aqueous and oil phases are thoroughly mixed, the DASAs and polymers are tightly bound together to form microspheres by high-speed stirring in an emulsifier. The emulsion obtained from the emulsification is then removed by rotary evaporation to remove volatile solvents. After multiple centrifugations to remove the supernatant, most of the water and emulsifier are removed. Finally, the remaining solid-liquid mixture is dried to completely evaporate the water. After evaporation, the solids on the tin foil are ground to obtain DASAs microspheres.

[0005] While microspheres prepared using traditional solvent evaporation methods exhibit photochromic capabilities, their color is significantly lighter than that of the DASA molecules themselves. Traditional preparation processes are cumbersome and complex; the preparation of DASAs alone faces challenges in purification, complex synthesis, and high costs, limiting the possibility of large-scale production. Furthermore, water is consistently present as a solvent during the preparation process, and DASAs can undergo linear-to-cyclic isomerization in the presence of water, remaining stable in a colorless cyclic state. In addition, the high temperatures encountered during subsequent processing can damage the DASA molecular structure, preventing photoisomerization. Finally, the upper limit of the color depth of microspheres prepared using traditional processes depends on the solubility of DASAs in dichloromethane. All these factors contribute to the weak photochromic ability of DASA microspheres prepared by traditional solvent evaporation methods, resulting in a lighter color compared to the DASA molecules themselves. This significantly limits the application scenarios of DASA microspheres.

[0006] The efficient, large-scale preparation process for photochromic microspheres proposed in this invention easily overcomes the aforementioned shortcomings. During the preparation process, the molecular structure of DASAs is almost unaffected by high temperatures and contact with water is avoided. The resulting DASAs microspheres have a much deeper color than those prepared by traditional solvent evaporation methods. The preparation process is also simpler, and the raw materials are inexpensive, allowing for large-scale industrial production. Summary of the Invention

[0007] To address the problems in the prior art, this application proposes a process for the efficient large-scale preparation of photochromic microspheres, comprising the following steps:

[0008] S1. Prepare DASA intermediates by reacting DASA precursors with furfural;

[0009] S2, DASA intermediates and polymers are dissolved in a volatile solvent as the oil phase, and an aqueous phase is prepared. The aqueous and oil phases are thoroughly mixed and then stirred at high speed in an emulsifier to tightly bind the DASA intermediates and polymers together to form microspheres. The volatile solvent in the emulsion is then removed, followed by the removal of water and emulsifier. Finally, the remaining solid-liquid mixture is dried, and the solid is ground to obtain DASA intermediate microspheres.

[0010] S3. DASAs microspheres are generated by reacting DASAs intermediate microspheres with the donor.

[0011] Preferably, the specific process of step S1 is as follows: Isopropyl malonate and furfural are mixed, heated and stirred to react, and then successively washed with water, filtered, extracted, dried, filtered twice, purified by column chromatography and rotary evaporation to obtain yellow DASA intermediate A product.

[0012] Alternatively, 1,3-dimethylbarbituric acid is mixed with furfural, heated and stirred to react, and then successively washed with water, filtered, extracted, dried, filtered twice, purified by column chromatography and rotary evaporation to obtain yellow DASA intermediate B product.

[0013] Alternatively, 1-phenyl-3-(trifluoromethyl)-1H-pyrazole-5(4H)-one is mixed with furfural, heated and stirred to react, and then successively washed with water, filtered, extracted, dried, filtered again, purified by column chromatography and rotary evaporation to obtain the yellow DASA intermediate C product.

[0014] Preferably, the specific process of step S2 is as follows: the DASAs intermediate obtained in step S1 and polycaprolactone are dissolved together in dichloromethane to obtain a first solution; a polyvinyl alcohol aqueous solution is prepared as a second solution; the first solution is added to the second solution to prepare a mixed solution; after the mixed solution is emulsified, the dichloromethane in the resulting liquid is completely removed; the resulting suspension is centrifuged with pure water, the supernatant is removed, pure water is added again, and centrifugation is repeated several times; the solid-liquid mixture after removing the supernatant is evenly coated on a carrier and placed in a vacuum drying oven for drying; after drying, the solid on the tin foil is removed and ground to remove the clumps of solid; the resulting powder is the DASAs intermediate microspheres.

[0015] Preferably, the specific process of step S3 is as follows: a small amount of DASAs intermediate microsphere powder obtained in step S2 is placed into the first container, a small amount of N-methylaniline is added to the second container, and the first container is placed into the second container; the second container is first purged with protective gas and then evacuated, and then the second container is heated until the powder completely changes color to obtain DASAs microspheres.

[0016] Preferably, the specific process of step S1 is as follows:

[0017] Isopropyl malonate and furfural were mixed in a molar ratio of 1:1 and stirred at 35°C for 4 hours to obtain a yellow product. The yellow product was then washed with water and filtered to remove water. The intermediate product was then extracted with saturated sodium bisulfite and saturated sodium chloride aqueous solutions to remove impurities. Anhydrous magnesium sulfate or anhydrous sodium sulfate was used to further remove water from the intermediate. Anhydrous magnesium sulfate was then removed by filtration. Finally, the intermediate was purified by column chromatography using dichloromethane as the eluent. The purified intermediate was then removed by rotary evaporation to obtain a yellow DASA intermediate.

[0018] Alternatively, 1,3-dimethylbarbituric acid and furfural are mixed in a molar ratio of 1:1 and stirred at 35°C for 4 hours to obtain a yellow product. The yellow product is then washed with water and filtered to remove water. The intermediate is then extracted with saturated sodium bisulfite and saturated sodium chloride aqueous solutions to remove impurities. Anhydrous magnesium sulfate or anhydrous sodium sulfate is used to further remove water from the intermediate, followed by filtration to remove anhydrous magnesium sulfate. Finally, the intermediate is purified by column chromatography using dichloromethane as the eluent. The purified intermediate is then removed by rotary evaporation to obtain a yellow DASA intermediate.

[0019] Alternatively, 1-phenyl-3-(trifluoromethyl)-1H-pyrazole-5(4H)-one and furfural are mixed in a molar ratio of 1:1 and stirred at 35°C for 4 hours to obtain a yellow product. The yellow product is then washed with water and filtered to remove water. The intermediate product is then extracted with saturated sodium bisulfite and saturated sodium chloride aqueous solutions to remove impurities. Anhydrous magnesium sulfate or anhydrous sodium sulfate is used to further remove water from the intermediate. Anhydrous magnesium sulfate is then removed by filtration. Finally, the intermediate is purified by column chromatography using dichloromethane as the eluent. The purified intermediate is then removed by rotary evaporation to obtain a yellow DASA intermediate.

[0020] Preferably, the specific process of step S2 is as follows:

[0021] First solution: Dissolve 10 mg of the DASA intermediate obtained in step S1 and 2.8 g of polycaprolactone together in 10 mL of dichloromethane; Second solution: Prepare 20 mL of a 1 wt% polyvinyl alcohol aqueous solution; After the first and second solutions are fully dissolved, add the first solution to the second solution; Emulsify the mixed solution at 8000 rpm for 10 min using an emulsifier; After emulsification, rotary evaporate the resulting liquid at 40 °C until the dichloromethane is completely removed; Add pure water to the resulting suspension and centrifuge at 8000 rpm for 3 min, then add 10 mL of pure water and centrifuge again, repeating this process three times; Coat the remaining solid-liquid mixture onto aluminum foil and dry it in a vacuum drying oven at 45 °C for one day; After drying, remove the solid from the aluminum foil and grind it with a grinding pestle, then sieve the powder through a 140-mesh sieve with a pore size of 0.106 mm to remove any clumps of solid; The resulting powder is the DASA intermediate microspheres.

[0022] Preferably, the specific process of step S3 is as follows: a small amount of DASAs intermediate microsphere powder obtained in step S2 is placed in a small glass bottle, a small amount of N-methylaniline is added to a Shrek tube, and the small glass bottle is placed in the Shrek tube, ensuring that the N-methylaniline does not exceed the glass bottle and contact the microsphere powder; nitrogen is passed through the Shrek tube and then a vacuum is drawn, which is repeated three times to ensure that the tube is in a vacuum state; then, the microsphere powder is heated at 36°C for 5 hours, after which the microsphere powder changes color and DASAs microspheres are obtained.

[0023] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.

[0024] The present invention provides a highly efficient, large-scale process for preparing photochromic microspheres, which, compared with existing technologies, has at least the following advantages:

[0025] (1) As Figure 4 As shown, this invention uses donor-acceptor Steinhaus adducts (DASAs) as the color-changing host and polycaprolactone (PCL, MW = 80,000) as the raw material to prepare DASAs / PCL photochromic microspheres. This achieves color change in solid powder with DASAs as the core. It features short photoinduced stimulation time, fast response speed, high conversion efficiency, and long service life.

[0026] (2) This invention employs a two-step synthesis method. First, DASAs intermediate microspheres are prepared. Then, the donor is heated and evaporated in a vacuum and reacted with the DASAs intermediate microspheres to obtain DASAs microspheres. The two-step synthesis method has significant advantages over the traditional one-step synthesis method using direct solvent evaporation.

[0027] (3) The materials used in the preparation process of this invention are inexpensive and readily available, and the preparation and synthesis methods are simple and easy to operate, with great potential for low-cost industrialization. Attached Figure Description

[0028] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0029] Figure 1 Schematic diagram of the preparation of DASA molecular intermediates;

[0030] Figure 2 Schematic diagram of DASAs molecule preparation;

[0031] Figure 3 Here is a flowchart of the DASAs microsphere synthesis process;

[0032] Figure 4 This is a schematic diagram of the DASAs microsphere structure;

[0033] Figure 5DASAs-II microspheres;

[0034] Figure 6 This is a schematic diagram of the microstructure of DASAs-Ⅱ microspheres. Detailed Implementation

[0035] The invention will now be further described with reference to the accompanying drawings.

[0036] This invention provides a process for the efficient and large-scale preparation of photochromic microspheres, comprising the following steps:

[0037] S1. Prepare DASA intermediates by reacting DASA precursors with furfural;

[0038] S2, DASA intermediates and polymers are dissolved in a volatile solvent as the oil phase, and an aqueous phase is prepared. The aqueous and oil phases are thoroughly mixed and then stirred at high speed in an emulsifier to tightly bind the DASA intermediates and polymers together to form microspheres. The volatile solvent in the emulsion is then removed, followed by the removal of water and emulsifier. Finally, the remaining solid-liquid mixture is dried, and the solid is ground to obtain DASA intermediate microspheres.

[0039] S3. DASAs microspheres are generated by reacting DASAs intermediate microspheres with the donor.

[0040] Example 1

[0041] A preferred embodiment of the present invention provides a process for the efficient large-scale preparation of photochromic microspheres, the specific steps of which are as follows:

[0042] (1) Preparation of DASA intermediate I. For example... Figure 1 As shown, isopropyl malonate and furfural were mixed in a molar ratio of 1:1 and stirred at 35°C for approximately 4 hours to obtain a yellow product. The yellow product was then washed with water and filtered to remove water. The intermediate product was then extracted sequentially with saturated sodium bisulfite and saturated sodium chloride aqueous solutions to remove impurities. Anhydrous magnesium sulfate or anhydrous sodium sulfate was then used to further remove water from the intermediate, followed by filtration to remove anhydrous magnesium sulfate. Finally, the intermediate was purified using column chromatography with dichloromethane as the eluent. The purified intermediate was then purified by rotary evaporation to obtain yellow DASA intermediate I for later use.

[0043] (2) Preparation of DASA intermediate I microspheres. For example... Figure 3As shown, Solution 1: Dissolve 10 mg of DASA intermediate I obtained in step (1) and 2.8 g of polycaprolactone together in 10 mL of dichloromethane. Solution 2: Prepare 20 mL of 1 wt% polyvinyl alcohol aqueous solution. After both solutions 1 and 2 are fully dissolved, add solution 1 to solution 2. Emulsify the mixed solution at 8000 rpm for 10 min using an emulsifier. After emulsification, rotary evaporate the resulting liquid at 40 °C until the dichloromethane is completely removed. Add pure water to the resulting suspension, centrifuge at 8000 rpm for 3 min, collect the supernatant, add 10 mL of pure water, centrifuge again, and repeat three times. Coat the remaining solid-liquid mixture onto tin foil and dry it in a vacuum drying oven at 45 °C for one day. After drying, remove the solid from the tin foil, grind it with a grinding pestle, and sieve the powder through a 140-mesh sieve (0.106 mm aperture) to remove any clumps of solid. The resulting powder is the DASA intermediate I microspheres.

[0044] (3) Preparation of DASAs-I microspheres. For example... Figure 2 As shown, a small amount of the DASAs intermediate I microsphere powder obtained in step (2) was placed in a small glass bottle. A small amount of N-methylaniline was added to a Shrek tube, and the small glass bottle was placed inside the Shrek tube, ensuring that the N-methylaniline did not exceed the glass bottle and contact the microsphere powder. Nitrogen gas was passed through the Shrek tube, and then a vacuum was created. This process was repeated three times to ensure that the tube was in a vacuum state. Then, the microsphere powder was heated at 36°C for 5 hours, after which it changed color, yielding DASAs-I microspheres.

[0045] Example 2

[0046] A preferred embodiment of the present invention provides a process for the efficient large-scale preparation of photochromic microspheres, the specific steps of which are as follows:

[0047] (1) Preparation of DASA intermediate II. For example... Figure 1 As shown, 1,3-dimethylbarbituric acid and furfural were mixed in a molar ratio of 1:1 and stirred at 35°C for approximately 4 hours to obtain a yellow product. The obtained yellow product was then washed with water and filtered to remove water. The intermediate product was then extracted successively with saturated sodium bisulfite and saturated sodium chloride aqueous solutions to remove impurities. Anhydrous magnesium sulfate or anhydrous sodium sulfate was then used to further remove water from the intermediate, followed by filtration to remove anhydrous magnesium sulfate. Finally, the intermediate was purified using column chromatography with dichloromethane as the eluent. The purified intermediate was then purified by rotary evaporation to obtain the yellow DASA intermediate II for later use.

[0048] (2) Preparation of DASA intermediate II microspheres. For example... Figure 3As shown, Solution 1: Dissolve 10 mg of DASA intermediate II obtained in step (1) and 2.8 g of polycaprolactone together in 10 mL of dichloromethane. Solution 2: Prepare 20 mL of 1 wt% polyvinyl alcohol aqueous solution. After both solutions 1 and 2 are fully dissolved, add solution 1 to solution 2. Emulsify the mixed solution at 8000 rpm for 10 min using an emulsifier. After emulsification, rotary evaporate the resulting liquid at 40 °C until the dichloromethane is completely removed. Add pure water to the resulting suspension, centrifuge at 8000 rpm for 3 min, collect the supernatant, add 10 mL of pure water, centrifuge again, and repeat three times. Coat the remaining solid-liquid mixture onto tin foil and dry it in a vacuum drying oven at 45 °C for one day. After drying, remove the solid from the tin foil, grind it with a grinding pestle, and sieve the powder through a 140-mesh sieve (0.106 mm aperture) to remove any clumps of solid. The resulting powder is the DASA intermediate II microspheres.

[0049] (3) Preparation of DASAs-II microspheres. For example... Figure 2 As shown, a small amount of the DASAs intermediate II microsphere powder obtained in step (2) was placed in a small glass bottle. A small amount of N-methylaniline was added to a Shrek tube, and the small glass bottle was placed inside the Shrek tube, ensuring that the N-methylaniline did not exceed the glass bottle and contact the microsphere powder. Nitrogen gas was passed through the Shrek tube, and then a vacuum was created. This process was repeated three times to ensure the tube was under vacuum. After heating at 36°C for 5 hours, the microsphere powder changed color, yielding DASAs-II microspheres. Figure 5-6 As shown.

[0050] Example 3

[0051] A preferred embodiment of the present invention provides a process for the efficient large-scale preparation of photochromic microspheres, the specific steps of which are as follows:

[0052] (1) Preparation of DASA intermediate III. For example... Figure 1 As shown, 1-phenyl-3-(trifluoromethyl)-1H-pyrazole-5(4H)-one and furfural were mixed in a molar ratio of 1:1 and stirred at 35°C for about 4 hours to obtain a yellow product. The obtained yellow product was then washed with water and filtered to remove water. The intermediate product was then extracted successively with saturated sodium bisulfite and saturated sodium chloride aqueous solutions to remove impurities. Anhydrous magnesium sulfate or anhydrous sodium sulfate was then used to further remove water from the intermediate, followed by filtration to remove anhydrous magnesium sulfate. Finally, the intermediate was purified by column chromatography using dichloromethane as the eluent. The purified intermediate was then purified by rotary evaporation to obtain the yellow DASA intermediate III for later use.

[0053] (2) Preparation of DASA intermediate III microspheres. For example... Figure 3As shown, Solution 1: Dissolve 10 mg of DASA intermediate III obtained in step (1) and 2.8 g of polycaprolactone together in 10 mL of dichloromethane. Solution 2: Prepare 20 mL of 1 wt% polyvinyl alcohol aqueous solution. After both solutions 1 and 2 are fully dissolved, add solution 1 to solution 2. Emulsify the mixed solution at 8000 rpm for 10 min using an emulsifier. After emulsification, rotary evaporate the resulting liquid at 40 °C until the dichloromethane is completely removed. Add pure water to the resulting suspension, centrifuge at 8000 rpm for 3 min, collect the supernatant, add 10 mL of pure water, centrifuge again, and repeat three times. Coat the remaining solid-liquid mixture onto tin foil and dry it in a vacuum drying oven at 45 °C for one day. After drying, remove the solid from the tin foil, grind it with a grinding pestle, and sieve the powder through a 140-mesh sieve (0.106 mm aperture) to remove any clumps of solid. The resulting powder is the DASA intermediate III microspheres.

[0054] (3) Preparation of DASAs-Ⅲ microspheres. For example... Figure 2 As shown, a small amount of the DASAs intermediate III microsphere powder obtained in step (2) was placed in a small glass bottle. A small amount of dihydroindole was added to a Shrek tube, and the small glass bottle was placed inside the Shrek tube, ensuring that the dihydroindole did not exceed the glass bottle and contact the microsphere powder. Nitrogen gas was passed through the Shrek tube, and then a vacuum was created. This process was repeated three times to ensure that the tube was in a vacuum state. Then, the microsphere powder was heated at 36°C for 5 hours, after which it changed color, yielding DASAs-III microspheres.

[0055] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A process for the efficient large scale preparation of photochromic microspheres, characterized in that, It comprises the following steps: S1, preparing DASAs intermediate by reacting DASAs precursor with furfural; S2, dissolving DASAs intermediate and polymer in volatile solvent as oil phase, configuring water phase, mixing oil phase and water phase thoroughly, then stirring by high speed of emulsifying machine to make DASAs intermediate and polymer combine closely to form microspheres, removing volatile solvent in emulsion, then removing water and emulsifier, finally drying solid-liquid mixture, grinding solid after drying to obtain DASAs intermediate microspheres; S3, generating DASAs microspheres by reacting DASAs intermediate microspheres with donor.

2. The process for the efficient large scale preparation of photochromic microspheres according to claim 1, wherein, The specific process of step S1 is: mixing malonic acid isopropyl ester with furfural, heating and stirring to react, then sequentially performing water washing, suction filtration, extraction, drying, secondary suction filtration, column chromatography purification and rotary evaporation to obtain yellow DASAs intermediate A product; Or, mixing 1,3-dimethyl barbituric acid with furfural, heating and stirring to react, then sequentially performing water washing, suction filtration, extraction, drying, secondary suction filtration, column chromatography purification and rotary evaporation to obtain yellow DASAs intermediate B product; Or, mixing 1-phenyl-3-(trifluoromethyl)-1H-pyrazole-5(4H)-ketone with furfural, heating and stirring to react, then sequentially performing water washing, suction filtration, extraction, drying, secondary suction filtration, column chromatography purification and rotary evaporation to obtain yellow DASAs intermediate C product.

3. The process for efficient mass production of photochromic microspheres according to claim 1, wherein, The specific process of step S2 is: dissolving DASAs intermediate obtained in step S1 and polycaprolactone in dichloromethane to obtain first solution; configuring polyvinyl alcohol aqueous solution as second solution; adding first solution to second solution to prepare mixed solution; after emulsification of mixed solution, removing dichloromethane in obtained liquid completely; centrifuging obtained suspension with pure water, then adding pure water again, centrifuging again, repeating multiple times; uniformly coating solid-liquid mixture after removing upper clear liquid on carrier, drying in vacuum drying box; grinding solid on tin paper after drying, removing agglomerated solid; obtained powder is DASAs intermediate microspheres.

4. The process for efficient mass production of photochromic microspheres according to claim 1, wherein, The specific process of step S3 is: taking a small amount of DASAs intermediate microspheres powder obtained in step S2 into first container, taking a small amount of N-methyl aniline into second container, putting first container into second container; first passing protective gas to second container, then vacuumizing, then heating second container to make powder completely change color to obtain DASAs microspheres.

5. The process for efficient mass production of photochromic microspheres according to claim 2, wherein, The specific process of step S1 is: The malonic acid isopropyl ester and furfural are mixed in a molar ratio of 1:1, stirred at 35°C for 4h to obtain a yellow product; then the yellow product is washed with water, filtered, and the water is removed; then the intermediate product is extracted with saturated sodium bisulfite and saturated sodium chloride solution to remove impurities, and then anhydrous magnesium sulfate or anhydrous sodium sulfate is used to further remove water from the intermediate, and then the anhydrous magnesium sulfate is removed by filtration; finally, the intermediate is purified by column chromatography, and dichloromethane is used as the eluent; finally, the purified intermediate is obtained, and the solvent is removed by rotary evaporation to obtain a yellow DASAs intermediate; Alternatively, 1,3-dimethylbarbituric acid and furfural are mixed in a molar ratio of 1:1, stirred at 35°C for 4h to obtain a yellow product; then the yellow product is washed with water, filtered, and the water is removed; then the intermediate product is extracted with saturated sodium bisulfite and saturated sodium chloride solution to remove impurities, and then anhydrous magnesium sulfate or anhydrous sodium sulfate is used to further remove water from the intermediate, and then the anhydrous magnesium sulfate is removed by filtration; finally, the intermediate is purified by column chromatography, and dichloromethane is used as the eluent; finally, the purified intermediate is obtained, and the solvent is removed by rotary evaporation to obtain a yellow DASAs intermediate; Alternatively, 1-phenyl-3-(trifluoromethyl)-1H-pyrazol-5(4H)-one and furfural are mixed in a molar ratio of 1:1, stirred at 35°C for 4h to obtain a yellow product; then the yellow product is washed with water, filtered, and the water is removed; then the intermediate product is extracted with saturated sodium bisulfite and saturated sodium chloride solution to remove impurities, and then anhydrous magnesium sulfate or anhydrous sodium sulfate is used to further remove water from the intermediate, and then the anhydrous magnesium sulfate is removed by filtration; finally, the intermediate is purified by column chromatography, and dichloromethane is used as the eluent; finally, the purified intermediate is obtained, and the solvent is removed by rotary evaporation to obtain a yellow DASAs intermediate.

6. The process for efficient mass production of photochromic microspheres according to claim 3, wherein, The specific process of step S2 is as follows: First solution: 10mg of the DASAs intermediate obtained in step S1 and 2.8g of polycaprolactone are dissolved in 10mL of dichloromethane; second solution: 20ml of a 1wt% polyvinyl alcohol aqueous solution is prepared; after the first and second solutions are fully dissolved, the first solution is added to the second solution; the mixed solution is emulsified with an emulsifier at 8000rpm for 10min; after emulsification, the obtained liquid is rotary evaporated at 40°C until the dichloromethane is completely removed; the obtained suspension is centrifuged at 8000rpm for 3min, and the supernatant is collected and then 10mL of pure water is added, and the mixture is centrifuged again, and the process is repeated three times; the remaining solid-liquid mixture is spread on tin paper and placed in a vacuum drying oven at 45°C for drying; after drying, the solid on the tin paper is taken out and ground with a pestle, and the powder is sieved through a 140-mesh sieve with a pore size of 0.106mm to remove clumped solids; the obtained powder is the DASAs intermediate microspheres.

7. The process for efficient mass production of photochromic microspheres according to claim 4, wherein, The specific process of the step S3 is as follows: a small amount of the DASAs intermediate microsphere powder obtained in the step S2 is put into a small glass bottle, a Schlenk tube is taken and a small amount of N-methylaniline is taken, the small glass bottle is put into the Schlenk tube, and the N-methylaniline cannot exceed the glass bottle to contact the microsphere powder; the Schlenk tube is connected with nitrogen and vacuumized, and the process is repeated for three times, so that the Schlenk tube is in a vacuum state; then the microsphere powder is discolored after heating at 36 DEG C for 5 h to obtain the DASAs microsphere.

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