Preparation and use of lightfast fluoran color-changing dye

Abstract

The present invention relates to the technical field of fine chemicals. Disclosed are preparation and a use of a lightfast fluoran color-changing dye. According to the present invention, by optimizing the structure of a commercial fluoran dye, a preparation method for a full-color-spectrum fluoran dye having good lightfast performance is provided; and on the basis of keeping the properties of the dye, such as the color development and color changing sensitivity and the color changing fatigue resistance, the lightfast performance of the dye is improved, the lightfast duration is prolonged by 8-28 hours and is increased by 50%-80%, and the main problem of the use of such temperature-sensitive materials in the field of functional textiles is solved, thereby expanding the application field and increasing economic benefits.

Description

Preparation and application of a light-resistant fluorane color-changing dye Technical Field

[0001] The invention relates to the preparation and application of a light-resistant fluorane color-changing dye, and belongs to the technical field of fine chemical industry. Background Art

[0002] Color-changing dyes, when applied to the surface or interior of a material, can impart the property of changing color in response to external factors such as light, heat, or other physical factors. Based on their structural characteristics, there are seven main types of color-changing dyes: phenolphthalein dyes, fluorane dyes, triarylmethane dyes, phenazines, thiazines, quinones, tetrazolium salts, and spiropyrans.

[0003] Fluoran dyes are widely used in smart textiles, decorations, sensors, displays, and other fields due to their multi-responsive properties (such as temperature response, light response, humidity response, electroresponsiveness, pH response, and multi-stimulus response). However, the poor light resistance of fluoran dyes limits their development and application in long-term outdoor products. Therefore, the development of light-stable fluoran dye color-changing systems has been a research focus.

[0004] Currently, UV absorbers are incorporated into thermochromic microcapsules or smart textile surfaces due to their UV absorption capacity, protecting the dye structure from light damage. For example, Applied Surface Science 442 (2018): 71-77 reports the successful preparation of a UV-absorbing fluorosilicone acrylic polymer using 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate (BHEM), vinyltrimethoxysilane (VTMS), and hexafluorobutyl methacrylate (HFMA) as modified monomers via solution polymerization, improving its light resistance. Chinese patent CN114808472A utilizes emulsion polymerization to prepare thermochromic microcapsules with a core-shell structure. The shell polymer of the microcapsule exhibits UV resistance, resulting in a fading rate that is 60.9% lower than that of conventional color-changing microcapsules. However, simply encapsulating and coating fluoran dyes does not provide long-term improvements in their light resistance. Therefore, in addition to using external forces to improve light resistance, many scholars have also tried to obtain light resistance by designing and optimizing molecular structures. For example, in the article Dyes and Pigments 190 (2021): 109294, a fluorescent cationic coumarin dye with a rigid molecular structure was synthesized to improve light resistance; and in the article Dyes and Pigments 197 (2022): 109924, a fluoran dye containing a long alkyl chain fluorophore was reported, which has good light resistance. Therefore, the molecular structure of fluoran-type color-changing dyes needs to be optimized and designed to obtain excellent light resistance.

[0005] Summary of the Invention

[0006]

Technical Issues

[0007] Fluoran color-changing dyes have poor light resistance and lose their color-developing and color-changing abilities after being exposed to sunlight for a week, making them unsuitable for human use. Therefore, it is necessary to design and synthesize fluoran color-changing dyes with excellent light resistance.

[0008]

Technical solution

[0009] The present invention mainly designs a fluoran-type color-changing dye containing an alkylamine group, that is, based on the existing fluoran dye matrix structure, an alkylamine group is introduced, and its easy aggregation property is utilized to change the aggregation state of the dye molecular structure and improve its light resistance. 12 ), cycloalkanes with different numbers of carbon atoms, and alkyl hydrocarbon groups containing some polar groups (polar groups such as O, CO, NH, CO-NH, etc.).

[0010] The first object of the present invention is to provide a fluorane color-changing dye with good light resistance, the structure of which is shown in the following formula I:

[0011] in:

[0012] R5, R6, R8, R9, R 11 and R 12 each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen;

[0013] R7 is independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl)yl, chloro;

[0014] R 10 Independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl)yl, N-cyclohexyl;

[0015] R1, R2, R3 and R4 are optionally 1-2 alkylamino groups with different carbon atoms, wherein the alkyl group in the alkylamino group is a C2-C 12 The straight-chain alkane, cycloalkane or alkane containing a polar group (polar groups include O (ether bond), CO (carbonyl group), NH (imino group) or CO-NH2 (amide group) etc.); the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl and substituted heterocycloalkyl.

[0016] In one embodiment of the present invention, the general structural formula of the fluorane color-changing dye is shown in Formula II below:

[0017] in:

[0018] R5, R6, R7, R8, R9, R11 and R12 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino and halogen;

[0019] R1 and R4 are H.

[0020] R2 and R3 are independently selected from hydrogen, alkylamino groups with different numbers of carbon atoms, wherein the alkyl group in the alkylamino group is a straight-chain alkane, cycloalkane or alkane (C2-C12) containing a polar group with a carbon number of C2-C12; and R2 and R3 are not hydrogen at the same time.

[0021] Preferably, R2 and R3 are independently selected from hydrogen or alkylamino groups, wherein the alkyl group in the alkylamino group includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and alkyl groups (C2-C10) containing polar groups; and R2 and R3 are not hydrogen at the same time.

[0022] More preferably, R2 or R3 are independently selected from hydrogen or alkylamino, wherein the alkyl group in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and alkyl groups containing any one of hydroxyl and carboxyl groups (C2-C 10 ); and R2 and R3 are not hydrogen at the same time.

[0023] The fluorane color-changing dye with good light resistance provided by the present invention is applied in the fields of dyes, textiles, clothing, printing and painting.

[0024] A second object of the present invention is to provide a method for improving the light resistance of a color-changing material, wherein the method comprises coloring the material with a fluorane color-changing dye, wherein the general structural formula of the fluorane color-changing dye is shown in Formula III below:

[0025] in:

[0026] R5, R6, R8, R9, R 11 and R 12each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen;

[0027] R7 is independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl)yl, chloro;

[0028] R 10 Independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl)yl, N-cyclohexyl;

[0029] R1, R2, R3 and R4 are optionally 1-2 alkylamino groups with different carbon atoms, wherein the alkyl group in the alkylamino group is a C2-C 12 The straight-chain alkane, cycloalkane or alkane containing a polar group (polar groups include O (ether bond), CO (carbonyl group), NH (imino group) or CO-NH2 (amide group) etc.); the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl and substituted heterocycloalkyl.

[0030] In one embodiment of the present invention, the general structural formula of the fluorane color-changing dye is shown in the following formula IV:

[0031] in:

[0032] R5, R6, R7, R8, R9, R 11 and R 12 each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen;

[0033] R1 and R4 are H.

[0034] R2 and R3 are independently selected from hydrogen, alkylamino groups with different numbers of carbon atoms, wherein the alkyl group in the alkylamino group is a carbon atom with a number of C2-C 12 Straight-chain alkanes, cycloalkanes or alkanes containing polar groups (C2-C 12 ); and R2 and R3 are not hydrogen at the same time.

[0035] Preferably, R2 and R3 are independently hydrogen or alkylamino, wherein the alkyl group in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and alkyl groups containing polar groups (C2-C 10 ); and R2 and R3 are not hydrogen at the same time.

[0036] More preferably, R2 or R3 are independently selected from hydrogen or alkylamino, wherein the alkyl group in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and alkyl groups containing any one of hydroxyl and carboxyl groups (C2-C 10 ); and R2 and R3 are not hydrogen at the same time.

[0037] In one embodiment of the present invention, the material includes textile materials, composite materials, display materials, sensor materials, and painting materials.

[0038] In one embodiment of the present invention, the textile material refers to fibers and fiber products, including fibers, yarns, fabrics, non-woven fabrics and composites thereof.

[0039] A third object of the present invention is to provide a method for synthesizing the above-mentioned fluoran color-changing dye, comprising the following steps:

[0040] The fluorane color-changing dye structural intermediate and alkylamine are mixed, and then an organic solvent and a catalyst are added, stirred, and the pH is adjusted to 8-9, and then the temperature is increased to react. After the reaction is completed, purification is performed to obtain the fluorane color-changing dye.

[0041] In one embodiment of the present invention, the synthesis method needs to be carried out under a protective gas environment.

[0042] In one embodiment of the present invention, the protective gas includes one or more of an inert gas and nitrogen.

[0043] In one embodiment of the present invention, the general structural formula of the fluorane color-changing dye structural intermediate is shown in Formula V below:

[0044] Wherein: R3 is halogen.

[0045] Furthermore, the halogen is Cl, Br, or F.

[0046] In one embodiment of the present invention, the general structural formula of the fluorane-based color-changing dye structural intermediate can also be shown as the following formula VI:

[0047] Wherein: R2 is halogen.

[0048] Furthermore, the halogen is Cl, Br, or F.

[0049] In one embodiment of the present invention, the alkyl group in the alkylamine comprises C2-C 12 Straight-chain alkanes, cycloalkanes or alkyl hydrocarbon groups containing polar groups.

[0050] In one embodiment of the present invention, the polar group includes O (ether bond), CO (carbonyl group), NH (imino group) or CO-NH2 (amide group).

[0051] In one embodiment of the present invention, the organic solvent is toluene.

[0052] In one embodiment of the present invention, the catalyst is niobium pentoxide.

[0053] In one embodiment of the present invention, the molar ratio of the fluoran-based color-changing dye structural intermediate to the alkylamine is 1:1-2.

[0054] In one embodiment of the present invention, the ratio of the molar amount of the fluorane-based color-changing dye structural intermediate to the volume of the organic solvent is 1 mol: 0.05-0.1 mL.

[0055] In one embodiment of the present invention, the molar ratio of the fluorane color-changing dye structural intermediate to the catalyst is 1:0.5-0.7.

[0056] In one embodiment of the present invention, the temperature-raising reaction is carried out at 75-85° C. for 6-9 hours.

[0057] In one embodiment of the present invention, the purification can be performed using column chromatography or gas chromatography.

[0058] The present invention fourthly provides a sun-resistant color-changing microcapsule, wherein the sun-resistant color-changing microcapsule uses the above-mentioned fluoran color-changing dye as a core material and uses a high molecular polymer, inorganic particles or inorganic particles doped with a polymer as a wall material.

[0059] In one embodiment of the present invention, the method for preparing the color-changing microcapsules comprises the following steps:

[0060] (1) Preparation of prepolymer: urea and formaldehyde solution were mixed, triethanolamine was added to adjust the pH value to 8-9, and the temperature was raised to react to obtain a viscous and transparent urea-formaldehyde prepolymer;

[0061] (2) Dispersion of capsule core: The fluoran color-changing dye, bisphenol A and solvent are mixed to prepare capsule core, and then the capsule core is mixed with water, sheared, dispersed and emulsified, and then cooled and dispersed to form an O / W emulsion;

[0062] (3) Microencapsulation and post-treatment: Mix the viscous and transparent urea-formaldehyde prepolymer with the O / W emulsion to obtain a mixed solution, then add sodium chloride and silicon dioxide, stir thoroughly, and then add acetic acid to adjust the pH to 3-4, then heat to react, cool after the reaction is completed, wash, filter, and dry to obtain color-changing microcapsules.

[0063] Furthermore, the heating reaction in step (1) is to raise the temperature to 70-80° C. and react for 1-2 hours.

[0064] Furthermore, in step (2) of the above preparation method, the solvent is a mixture of tetradecanol and hexadecanol, and the mass ratio of the mixture is 4-5:5-6.

[0065] Furthermore, in step (2) of the above preparation method, the mass ratio of the fluoran color-changing dye to bisphenol A is 1:2-8.

[0066] Furthermore, in step (2) of the above preparation method, the mass ratio of the fluoran color-changing dye to the solvent is 1:50-70.

[0067] Furthermore, in step (2) of the above preparation method, the volume ratio of the capsule core to water is 1:4-7.

[0068] Furthermore, in step (2) of the above preparation method, the shearing speed is 1000-3000 r / min and the time is 1-2 h.

[0069] Furthermore, in step (2) of the above preparation method, the shear dispersion emulsification is carried out at 60-70°C; and the cooling is carried out to 30-40°C.

[0070] Furthermore, in step (2) of the above preparation method, the time for continuing to disperse is 1 to 2 hours.

[0071] Furthermore, in step (3) of the above preparation method, the volume ratio of the viscous transparent urea-formaldehyde prepolymer to the O / W emulsion is 5 to 10:1.

[0072] Furthermore, in step (3) of the above preparation method, the added sodium chloride accounts for 0.2 to 0.25 wt % of the total mass of the mixed solution.

[0073] Furthermore, in step (3) of the above preparation method, the added silicon dioxide accounts for 0.2 to 0.25 wt % of the total mass of the mixed solution.

[0074] Furthermore, in step (3) of the above preparation method, the heating reaction is carried out at 60-65° C. for 30-50 minutes.

[0075] The color-changing microcapsules provided by the present invention are used in the fields of textiles and dyeing.

[0076] The fifth aspect of the present invention provides a method for preparing a sun-resistant color-changing fabric, which comprises first preparing a thermochromic paste using microcapsules prepared with the above-mentioned fluorane color-changing dye, and then using the thermochromic paste to color the fabric, and finally obtaining a color-changing fabric with sun-resistant properties.

[0077] In one embodiment of the present invention, the fabric comprises fiber, cotton fabric, silk fabric or polyester textile.

[0078] In one embodiment of the present invention, the thermochromic paste comprises a thickener, a binder, color-changing body microcapsules and water.

[0079] In one embodiment of the present invention, the mass ratio of the thickener to the binder is 1:5-15.

[0080] In one embodiment of the present invention, the mass ratio of the thickener to the color-changing body microcapsules is 1:60-100.

[0081] In one embodiment of the present invention, the mass ratio of the thickener to water is 1:5-15.

[0082] In one embodiment of the present invention, the preparation process of the sun-fast color-changing fabric is as follows:

[0083] The fabric is fixed, and then printed using a screen printing technique. The printed fabric is then dried at 70-90° C. and cured at 90-100° C. for 2-5 minutes to obtain a sun-resistant, color-changing fabric.

[0084] The present invention provides a color-changing fabric with sun-fastness prepared according to the method.

[0085] The color-changing fabric with sun-fastness provided by the present invention is used in the fields of clothing and textiles.

[0086] Beneficial effects of the present invention:

[0087] The present invention optimizes the structure of commercial fluoran dyes to provide a preparation method for a full-color spectrum fluoran dye with good light resistance. While maintaining the color development, color change sensitivity, color change fatigue resistance and other properties of the dye, the light resistance is improved, and the light resistance time is increased by 8 to 28 hours, an increase of 50% to 80%. This solves the main problems in the application of this type of temperature-sensitive material in the field of functional textiles, expands the application field, and is beneficial to economic benefits. DETAILED DESCRIPTION

[0088] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0089] 1. Experimental Materials

[0090] The monomers used in the examples are 4-bromophthalic anhydride and m-hydroxy-N,N-diethylaniline, CAS Nos. 86-90-8 and 91-68-9, respectively, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; other chemicals are commercially available products.

[0091] 2. Test methods

[0092] (1) Light fastness test of fluoran color-changing dyes: The light fastness of the self-made dye phase change material was tested according to the American AATCC TM16 light fastness test standard. The color change was observed and the apparent depth (K / S value) was measured using an UltraScanXE computer colorimeter. The average value was then calculated. The test was conducted using a D65 light source and an observation angle of 10°.

[0093] (2) Fading rate: Use a sun exposure climate tester to simulate sun aging of the discolored fabric. Combined with the K / S value of the fabric at different sun exposure times, calculate according to the following formula:

[0094] Where: K / S0 is the initial K / S value of the fabric, K / S t is the K / S value of the fabric after t hours.

[0095] Example 1: A fluorane-based color-changing dye structure with good light resistance and its synthesis method

[0096] Under N2 protection, red 1' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of red 1' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to red 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Red 1.

[0097] Example 2: A fluorane-based color-changing dye structure with good light resistance and its synthesis method

[0098] Under N2 protection, red 1' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of red 1' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to red 1'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Red 2.

[0099] Example 3: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0100] Under N2 protection, red 2' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of red 2' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Nitrile pentoxide catalyst with a molar equivalent of 50% to red 2' and 50 mL of toluene organic solvent were added. Then, triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Red 3.

[0101] Example 4: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0102] Under N2 protection, Red 2' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of Red 2' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to Red 2'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Red 4.

[0103] Example 5: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0104] Under N2 protection, yellow 1' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of yellow 1' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to yellow 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Yellow 1.

[0105] Example 6: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0106] Under N2 protection, yellow 1' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of yellow 1' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to yellow 1'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Yellow 2.

[0107] Example 7: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0108] Under N2 protection, yellow 2' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of yellow 2' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to yellow 2', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Yellow 3.

[0109] Example 8: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0110] Under N2 protection, yellow 2' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of yellow 2' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to yellow 2'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Yellow 4.

[0111] Example 9: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0112] Under N2 protection, blue 1' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of blue 1' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to blue 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye blue 1.

[0113] Example 10: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0114] Under N2 protection, blue 1' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of blue 1' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to blue 1'. The pH was then adjusted to 8 using triethylamine. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye blue 2.

[0115] Example 11: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0116] Under N2 protection, blue 2' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of blue 2' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to blue 2', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Blue 3.

[0117] Example 12: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0118] Under N2 protection, blue 2' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of blue 2' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to blue 2'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye blue 4.

[0119] Example 13: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0120] Under N2 protection, black 1' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of black 1' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to black 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously detected (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Black 1.

[0121] Example 14: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0122] Under N2 protection, black 1' (wherein R is -Cl) and acrylamide in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of black 1' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to black 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Black 2.

[0123] Example 15: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0124] Under N2 protection, black 2' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of black 2' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to black 2', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously detected (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Black 3.

[0125] Example 16: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0126] Under N2 protection, black 2' (wherein R is -Cl) and acrylamide in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of black 2' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to black 2', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Black 4.

[0127] Example 17: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0128] Under N2 protection, green 1' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of green 1' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to green 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluoran color-changing dye Green 1.

[0129] Example 18: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0130] Under N2 protection, green 1' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of green 1' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to green 1'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluoran color-changing dye Green 2.

[0131] Example 19: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0132] Under N2 protection, green 2' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of green 2' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to green 2', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluoran color-changing dye Green 3.

[0133] Example 20: A Fluoran-Based Color-Changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0134] Under N2 protection, green 2' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of green 2' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to green 2'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluoran color-changing dye Green 4.

[0135] Example 21: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0136] Under N2 protection, orange 1' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of orange 1' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to orange 1', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Orange 1.

[0137] Example 22: A Fluoran-Based Color-Change Dye Structure with Good Light Resistance and Its Synthesis Method

[0138] Under N2 protection, orange 1' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of orange 1' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to orange 1'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Orange 2.

[0139] Example 23: A Fluoran-type Color-changing Dye Structure with Good Light Resistance and Its Synthesis Method

[0140] Under N2 protection, orange 2' (wherein R is -Cl) and octylamine in a molar ratio of 1:1.5 were added to a 100 mL three-necked flask, and toluene was added to make the concentrations of orange 2' and octylamine 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to orange 2', and then triethylamine was used to adjust the pH to 8. The mixture was stirred mechanically, heated to 80°C, and reacted for 8 h. During the reaction, TLC was continuously monitored (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Orange 3.

[0141] Example 24: A Fluoran-Based Color-Change Dye Structure with Good Light Resistance and Its Synthesis Method

[0142] Under N2 protection, orange 2' (wherein R is -Cl) and acrylamide were added in a molar ratio of 1:1.5 to a 100 mL three-necked flask. Toluene was then added to make the concentrations of orange 2' and acrylamide 0.02 mol / L and 0.03 mol / L, respectively. Niobium pentoxide catalyst was added in an amount of 50% molar equivalent to orange 2'. Triethylamine was then used to adjust the pH to 8. The mixture was stirred mechanically and heated to 80°C for 8 h. TLC was continuously monitored during the reaction (V MeOH :V DCM =1:10 as a developing agent), when the raw material point (R f :0.35) disappeared and a new orange-yellow fluorescent spot (R f :0.45) appears, that is, the end of the reaction. Then MeOH and DCM (V MeOH :V DCM =1:10) as the elution solvent, and column chromatography was used to purify the octylamine-substituted fluorane color-changing dye Orange 4.

[0143] Example 25: A color-changing microcapsule

[0144] A method for preparing color-changing microcapsules, comprising the following steps:

[0145] (1) Preparation of prepolymer: Place urea and formaldehyde solution with a molar ratio of 1:1 into a three-necked flask, stir to dissolve the urea, then add triethanolamine dropwise to adjust the pH to 8.5, slowly heat to 80°C, and maintain the constant temperature for 1 hour to obtain a viscous and transparent urea-formaldehyde prepolymer;

[0146] (2) Dispersion of capsule core: The capsule core used is a thermosensitive dye compound, whose composition is the fluoran color-changing dye prepared in Examples 1 to 24: bisphenol A: solvent (mass ratio) = 1:4:60, wherein the solvent is a mixture of tetradecanol and hexadecanol, and the volume ratio of the two is 4:6. The capsule core and water are placed in a flask at a volume ratio of 1:5, and emulsified and dispersed at a speed of 2000 r / min in a high-speed shear disperser at 60°C water bath for 1 hour, and then transferred to a 30°C water bath and dispersed for another 1 hour to form an O / W emulsion;

[0147] (3) Microencapsulation and post-treatment: A viscous and transparent urea-formaldehyde prepolymer and an O / W emulsion were mixed in a volume ratio of 7:1 to obtain a mixed solution, and a mixture of sodium chloride and silicon dioxide accounting for 0.5 wt% of the total mass of the mixed solution was added, wherein the mass ratio of sodium chloride to silicon dioxide was 1:1. The mixture was stirred thoroughly, and then acetic acid was slowly added at 40°C to adjust the pH to 3. The mixture was reacted for 1 hour, and then heated to 65°C and continued to react for 30 minutes. The mixture was then cooled to room temperature, washed, filtered, and dried to obtain color-changing microcapsules.

[0148] Example 26: Preparation method of sun-resistant color-changing fabric

[0149] Fabric was dyed using color-changing microcapsules prepared from the fluoran color-changing dye synthesized in Examples 1-24 according to Example 25. The dyeing conditions were as follows: a thickener, a binder, 80% of the color-changing microcapsules, and deionized water were blended in a mass ratio of 1:10:80:9 and stirred for 30 minutes to prepare a thermochromic color paste. The fabric was then fixed and printed using screen printing. The printed fabric was then dried in an oven at 80°C and cured at 100°C for 5 minutes to obtain a sun-resistant color-changing fabric.

[0150] Comparative Example 1: Synthesis and purification of Rhodamine B

[0151] Under nitrogen protection, 2.96g of phthalic anhydride and 6.61g of m-hydroxy-N,N-diethylaniline were added, along with a niobium pentoxide catalyst (50% molar equivalent to phthalic anhydride). Stirring was continued, the temperature was raised to 160°C, and the reaction was allowed to proceed for 3 hours. During the reaction, TLC monitoring was performed continuously. The reaction was completed when the starting material spots disappeared and new orange-yellow fluorescent spots appeared in a UV darkroom at 365°C. The solid was then crushed and washed twice with hot saturated brine. The catalyst was dissolved in methanol and filtered to remove it, and the organic phase was concentrated by rotary evaporation. Silica column chromatography powder was added, stirred, and dried by rotary evaporation. Rhodamine B was purified by column chromatography.

[0152] Comparative Example 2: Synthesis and purification of aminofluoran dyes

[0153] Under nitrogen protection, 3.26g of 4-aminophthalic anhydride and 6.61g of m-hydroxy-N,N-diethylaniline were added, along with a niobium pentoxide catalyst (50% molar equivalent of 4-aminophthalic anhydride). Stirring was continued, the temperature was raised to 160°C, and the reaction was allowed to proceed for 3 hours. During the reaction, TLC monitoring was performed continuously. The reaction was completed when the starting material spot disappeared and a new orange-yellow fluorescent spot appeared under a UV darkroom at 365°C. The solid was then crushed and washed twice with hot saturated brine. The catalyst was removed by filtration using methanol, and the organic phase was concentrated by rotary evaporation. Silica column chromatography powder was added, mixed thoroughly, and dried by rotary evaporation. Purification by column chromatography yielded 5-aminofluoran dye.

[0154] Comparative Example 3: Synthesis and purification of 5-bromorubin fluoran dye

[0155] Under nitrogen protection, 4.54g of 4-bromophthalic anhydride and 6.61g of m-hydroxy-N,N-diethylaniline were added, along with a niobium pentoxide catalyst (50% molar equivalent of 4-bromophthalic anhydride). Stirring was continued, the temperature was raised to 160°C, and the reaction was allowed to proceed for 3 hours. During the reaction, TLC monitoring was performed continuously. The reaction was completed when the starting material spot disappeared and a new fluorescent spot appeared in a UV darkroom at 365°C. The solid was then crushed and washed twice with hot saturated brine. The catalyst was removed by filtration using methanol, and the organic phase was concentrated by rotary evaporation. Silica column chromatography powder was added, mixed thoroughly, and dried by rotary evaporation. Purification by column chromatography yielded 5-bromo red fluoran dye.

[0156] Comparative Example 4: Synthesis and purification of 5-bromofluoran dyes

[0157] Under N2 protection, 4.54 g of 4-bromophthalic anhydride and 2.48 g of m-methoxyphenol were added, along with a niobium pentoxide catalyst (50% mol equivalent to 4-bromophthalic anhydride). The mixture was then stirred continuously and heated to 160°C for 3 hours. During the reaction, TLC monitoring was performed continuously. The reaction was completed when the starting material spot disappeared and a new fluorescent spot appeared in a 365-wavelength UV darkroom. The solid was then crushed and washed twice with hot saturated brine. The catalyst was then removed by filtration using methanol, and the organic phase was concentrated by rotary evaporation. Silica column chromatography powder was added, stirred, and dried by rotary evaporation. The mixture was purified by column chromatography to obtain a 5-bromofluoran dye.

[0158] Comparative Example 5: Synthesis and purification of 5-bromo blue fluoran dyes

[0159] Under nitrogen protection, 4.54g of 4-bromophthalic anhydride and 11.61g of m-hydroxy-N,N-di-p-tolylaniline were added, along with a niobium pentoxide catalyst (50% mol equivalent of 4-bromophthalic anhydride). Stirring was continued, the temperature was raised to 160°C, and the reaction was allowed to proceed for 3 hours. During the reaction, TLC monitoring was performed continuously. The reaction was completed when the starting material spot disappeared and a new fluorescent spot appeared in a UV darkroom at 365°C. The solid was then crushed and washed twice with hot saturated brine. The catalyst was removed by filtration using methanol, and the organic phase was concentrated by rotary evaporation. Silica column chromatography powder was added, stirred, and dried by rotary evaporation. Purification by column chromatography yielded 5-bromofluoran dye.

[0160] Comparative Example 6: Synthesis and purification of 5-bromo-black fluoran dye

[0161] Step (1): In a nitrogen atmosphere, 0.662 g of m-hydroxy-N,N-diethylaniline and 0.908 g of 4-bromophthalic anhydride (molar ratio of 1:1) were added to 50 mL of toluene solvent and 0.5 g of niobium pentoxide catalyst, and the mixture was heated to reflux and reacted for 4 hours. After the reaction, the mixture was cooled to 50°C, and 5 mL of 35% NaOH aqueous solution was added to the mixture. The mixture was then heated to 90°C and kept warm for 6 hours. Finally, the mixture was poured into ice, acidified with concentrated hydrochloric acid, and then allowed to stand at room temperature for 2 hours. The suspension was filtered, and the solid was recrystallized from ethanol. The solid was dried to obtain Intermediate 1.

[0162] Step (2): 0.392 g of intermediate 1 and 0.263 g of ODB-1 were weighed in a molar ratio of 1:1.5, stirred evenly in 50 mL of toluene solvent, 0.5 g of niobium pentoxide catalyst was added, and then the mixture was heated to reflux and reacted for 5 h. During the reaction, the generated water was separated. After the reaction, the organic phase obtained was concentrated with 20 mL of 25% NaOH aqueous solution to recover the solvent, and the residue was recrystallized from ethanol to obtain 5-bromo-fluoran dye.

[0163] Comparative Example 7: Synthesis and purification of 5-bromo-green fluoran dyes

[0164] Step (1): In a nitrogen atmosphere, 0.662 g of m-hydroxy-N,N-diethylaniline and 0.908 g of 4-bromophthalic anhydride (molar ratio of 1:1) were added, followed by the addition of 50 mL of toluene solvent and 0.5 g of niobium pentoxide catalyst, the mixture was heated to reflux and reacted for 4 hours. After the reaction, the mixture was cooled to 50°C, and 5 mL of 35% NaOH aqueous solution was added to the mixture. The mixture was then heated to 90°C and kept warm for 6 hours. Finally, the mixture was poured into ice, acidified with concentrated hydrochloric acid, and allowed to stand at room temperature for 2 hours. The suspension was filtered, the solid was recrystallized from ethanol, and the solid was dried to obtain Intermediate 2.

[0165] Step (2): 0.392 g of intermediate 2 and 0.254 g of ODB-2 were weighed in a molar ratio of 1:1.5, stirred evenly in 50 mL of toluene solvent, 0.5 g of niobium pentoxide catalyst was added, and then the mixture was heated to reflux and reacted for 5 h. During the reaction, the generated water was separated. After the reaction, the organic phase obtained was concentrated with 20 mL of 25% NaOH aqueous solution to recover the solvent, and the residue was recrystallized from ethanol to obtain 5-bromo green fluoran dye.

[0166] Comparative Example 8: Synthesis and purification of 5-bromo orange fluoran dye

[0167] Step (1): In a nitrogen atmosphere, 0.384 g of PSD-1 and 0.454 g of 4-bromophthalic anhydride (molar ratio 1:1) were added, 50 mL of toluene solvent and 0.5 g of niobium pentoxide catalyst were added, the temperature was raised to reflux and the reaction was continued for 4 hours. After the reaction was completed, the mixture was cooled to 50° C., and an appropriate amount of 35% NaOH aqueous solution was added to the mixture. The mixture was then heated to 90° C. and kept warm for 6 hours. Finally, the mixture was poured into ice, acidified with concentrated hydrochloric acid, and allowed to stand at room temperature for 2 hours. The suspension was filtered, the solid was recrystallized from ethanol, and the solid was dried to obtain Intermediate 3.

[0168] Step (2): 0.419 g of intermediate 3 and 0.167 g of ODB-3 were weighed in a molar ratio of 1:1.5, stirred evenly in 50 mL of toluene solvent, 0.5 g of niobium pentoxide catalyst was added, and then the mixture was heated to reflux and reacted for 5 h. During the reaction, the generated water was separated. After the reaction, the organic phase obtained was mixed with an appropriate amount of 25% concentrated recovery solvent, and the residue was recrystallized from ethanol to obtain 5-bromo orange fluoran dye.

[0169] Comparative Example 9: 6-Amide-substituted orange fluoran dye color-changing fluoran dye

[0170] Step (1): 50 mmol of 3-(diethylamino)phenol and 25 mmol of 3-nitrophthalic anhydride were added to 50 mL of chlorobenzene. After complete dissolution, 25 mmol of trifluoromethanesulfonic acid was added. The mixture was then preheated in an oil bath at 135°C and refluxed under a nitrogen atmosphere for 2 days. After completion of the reaction, the mixture was cooled to room temperature and the solvent was removed by rotary evaporation. Column chromatography was performed using a dichloromethane / methanol eluent to obtain a purple-red powder, i.e., the product, ph-NO2.

[0171] Step (2): Place 1 mmol of ph-NO2, 20 mg of Pd / C, and 4 mL of ethyl acetate in a three-necked flask. Dissolve 1.5 mmol of H3PO2 and 4.5 mmol of NaH2PO2·H2O in 4 mL of H2O and pour the mixture into the three-necked flask. The flask is then placed in an 85°C oil bath for 5 hours. After cooling to room temperature, the mixture is extracted with dichloromethane. The extracted product is dried over anhydrous sodium sulfate and then eluted by column chromatography using petroleum ether / ethyl acetate / triethylamine to obtain a pink powder, the product ph-NH2.

[0172] Step (3): 2 mmol ph-NH2 and 3 mmol triethylamine were dissolved in 10 mL DCM; 12 mmol propionyl chloride was slowly added dropwise in an ice-water bath, and the mixture was reacted at room temperature for 2 h. The solvent was removed by rotary evaporation, and column chromatography was performed using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a light pink powder, which was the final product, the red target fluoran dye.

[0173] Comparative Example 10: 6-Amide-substituted chromophore dye

[0174] Step (1): 50 mmol of 3-(diethylamino)phenol and 25 mmol of 3-nitrophthalic anhydride were added to a three-necked flask containing 50 mL of chlorobenzene. After complete dissolution, 25 mmol of trifluoromethanesulfonic acid was added. The three-necked flask was then preheated in an oil bath at 135°C and refluxed under a nitrogen atmosphere for 2 days. After completion of the reaction, the mixture was cooled to room temperature and the solvent was removed by rotary evaporation. Column chromatography was performed using dichloromethane / methanol as the eluent to obtain a purple-red powder, i.e., the product, ph-NO2.

[0175] Step (2): 1 mmol ph-NO2, 20 mg Pd / C, and 4 mL ethyl acetate (EtOAc) were placed in a three-necked flask. 1.5 mmol H3PO2 and 4.5 mmol NaH2PO2·H2O were evenly dissolved in 4 mL H2O and poured into the same three-necked flask. The flask was then placed in an 85°C oil bath for 5 h. After cooling to room temperature, the mixture was extracted with dichloromethane. The extracted product was dried over anhydrous sodium sulfate and then subjected to column chromatography using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a pink powder, the product ph-NH2.

[0176] Step (3): 2mmol ph-NH2 and 3mmol triethylamine were dissolved in 10mL DCM; 12mmol phenylacetyl chloride was slowly added dropwise in an ice-water bath, and the mixture was reacted at room temperature for 2h. The solvent was removed by rotary evaporation, and column chromatography was performed using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a light pink powder, which was the final product, the red target fluoran dye.

[0177] Comparative Example 11: 6-Benzamide-substituted chromophore fluoran dye

[0178] Step (1): 50 mmol of 3-(diethylamino)phenol and 25 mmol of 3-nitrophthalic anhydride were added to 50 mL of chlorobenzene. After complete dissolution, 25 mmol of trifluoromethanesulfonic acid was added. The mixture was then preheated in an oil bath at 135°C and refluxed under a nitrogen atmosphere for 2 days. After completion of the reaction, the mixture was cooled to room temperature and the solvent was removed by rotary evaporation. Column chromatography was performed using dichloromethane / methanol as the eluent to obtain a purple-red powder, i.e., the product, ph-NO2.

[0179] Step (2): 1 mmol ph-NO2, 20 mg Pd / C, and 4 mL ethyl acetate were placed in a three-necked flask. 1.5 mmol H3PO2 and 4.5 mmol NaH2PO2·H2O were uniformly dissolved in 4 mL H2O and poured into the same three-necked flask. The flask was then placed in an 85°C oil bath for 5 hours. After cooling to room temperature, the mixture was extracted with dichloromethane. The extracted product was dried over anhydrous sodium sulfate and then subjected to column chromatography using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a pink powder, the product ph-NH2.

[0180] Step (3): 2 mmol ph-NH2 and 3 mmol triethylamine were dissolved in 10 mL DCM; 12 mmol benzoyl chloride was slowly added dropwise in an ice-water bath, and the mixture was reacted at room temperature for 2 h. The solvent was removed by rotary evaporation, and column chromatography was performed using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a light pink powder, which was the final product, the red target fluoran dye.

[0181] Comparative Example 12: A Bistable Electrochromic Fluoran Dye

[0182] For specific synthesis and purification, please refer to the patent "A method for preparing a bistable electrochromic fluoran dye and its device".

[0183] Step (1): 50 mmol of 3-(diethylamino)phenol and 25 mmol of 3-nitrophthalic anhydride were added to 50 mL of chlorobenzene. After complete dissolution, 25 mmol of trifluoromethanesulfonic acid was added. The mixture was then preheated in an oil bath at 135°C and refluxed under a nitrogen atmosphere for 2 days. After completion of the reaction, the mixture was cooled to room temperature and the solvent was removed by rotary evaporation. Column chromatography was performed using dichloromethane / methanol as the eluent to obtain a purple-red powder, i.e., the product, ph-NO2.

[0184] Step (2): 1 mmol ph-NO2, 20 mg Pd / C, and 4 mL ethyl acetate were placed in a three-necked flask. 1.5 mmol H3PO2 and 4.5 mmol NaH2PO2·H2O were uniformly dissolved in 4 mL H2O and poured into the same three-necked flask. The flask was then placed in an 85°C oil bath for 5 hours. After cooling to room temperature, the mixture was extracted with dichloromethane. The extracted product was dried over anhydrous sodium sulfate and then subjected to column chromatography using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a pink powder, the product ph-NH2.

[0185] Step (3): 2 mmol ph-NH2 and 3 mmol triethylamine were dissolved in 10 mL DCM; 12 mmol p-nitrobenzoyl chloride was slowly added dropwise in an ice-water bath, and the mixture was reacted at room temperature for 2 h. The solvent was removed by rotary evaporation, and column chromatography was performed using petroleum ether / ethyl acetate / triethylamine as the eluent to obtain a light pink powder, which was the final product, the red target fluoran dye.

[0186] Table 1 Fluoran dye sunlight resistance test

[0187] The results show that in the structure of fluorane color-changing dyes, R2 and R3 are independently selected from hydrogen, ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and alkyl groups containing polar groups such as OH (hydroxyl), COOH (carboxyl), NH (amino), CO-NH2 (acylamino); and R2 and R3 are not hydrogen at the same time, the light resistance of the dye will be correspondingly improved.

[0188] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A fluorane-based color-changing dye with good light resistance, characterized in that, The structure is as shown in Formula I below: Wherein: R5, R6, R8, R9, R 11 and R 12 each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen; R7 is independently selected from N,N - diethyl, methoxy, N,N - bis(p - tolyl), chloro; R 10 independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl), N-cyclohexyl; Any one or two of R1, R2, R3 and R4 are alkylamino groups with different numbers of carbon atoms, wherein the alkyl group in the alkylamino group is a straight-chain alkane, cycloalkane or alkane containing a polar group with C2-C 12 number of carbon atoms; the remaining groups are selected from one or more of hydrogen, alkyl group, substituted alkyl group, alkenyl group, substituted alkenyl group, heterocyclic alkyl group and substituted heterocyclic alkyl group.

2. The fluorane type color-changing dye according to claim 1, characterized in that, The general structural formula of the fluorane-based color-changing dye is shown as the following formula II: Wherein: R5, R6, R7, R8, R9, R 11 and R 12 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen; R1 and R4 are H; R2 and R3 are each independently selected from hydrogen and alkylamino groups with different numbers of carbon atoms, wherein the alkyl group in the alkylamino group is a straight-chain alkane, cycloalkane or alkane containing a polar group with C2-C 12 carbon atoms; and R2 and R3 are not both hydrogen at the same time.

3. The fluorane-based color-changing dye according to claim 2, characterized in that, R2 and R3 are independently selected from hydrogen or alkylamino, wherein the alkyl in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, or an alkane containing a polar group; and R2 and R3 are not both hydrogen at the same time.

4. The fluorane-based color-changing dye according to claim 3, wherein R2 or R3 is independently selected from hydrogen or alkylamino, wherein the alkyl in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, or an alkyl containing any one of hydroxyl and carboxyl; and R2 and R3 are not both hydrogen at the same time.

5. Application of the fluorane - type color - changing dye with good light - fastness according to any one of claims 1 to 4 in the fields of dyes, textiles, clothing, printing, and painting.

6. A method for improving the lightfastness of a color-changing material, characterized in that, The method is to color the material with a fluorane-based color-changing dye, and the general structural formula of the fluorane-based color-changing dye is shown as the following formula III: Wherein: R5, R6, R8, R9, R 11 and R 12 are each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, substituted aminocyclohexane, and halogen; R7 is independently selected from N,N - diethyl, methoxy, N,N - bis(p - tolyl), chloro; R 10 independently selected from N,N-diethyl, methoxy, N,N-di(p-tolyl), N-cyclohexyl; Any one or two of R1, R2, R3 and R4 are alkylamino groups with different numbers of carbon atoms, wherein the alkyl group in the alkylamino group is a straight-chain alkane, cycloalkane or alkane containing a polar group with C2-C 12 carbon atoms; the remaining groups are selected from one or more of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl and substituted heterocycloalkyl.

7. The method according to claim 6, characterized in that, The general structural formula of the fluorane type color-changing dye is shown as the following formula Ⅳ: Wherein: R5, R6, R7, R8, R9, R 11 and R 12 each independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, substituted alkoxy, substituted carbonyl, acylamino, and halogen; R1 and R4 are H; R2 and R3 are independently selected from hydrogen and alkylamino groups with different numbers of carbon atoms, wherein the alkyl group in the alkylamino group is a straight-chain alkane, cycloalkane or alkane containing a polar group with C2-C 12 carbon atoms; and R2 and R3 are not both hydrogen at the same time.

8. The method according to claim 7, wherein R2 and R3 are independently selected from hydrogen or alkylamino, wherein the alkyl in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and an alkyl containing a polar group; and R2 and R3 are not both hydrogen at the same time.

9. The method according to claim 8, characterized in that, R2 or R3 is selected from hydrogen or alkylamino, wherein the alkyl in the alkylamino includes ethyl, propyl and isopropyl, butyl and its isomers, pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers, decyl and its isomers, and an alkyl containing any one of hydroxyl and carboxyl; and R2 and R3 are not both hydrogen at the same time.

10. The method according to any one of claims 6 to 9, characterized in that, The materials include textile materials, composite materials, display materials, sensing materials, and painting materials, etc.

11. According to the method described in claim 10, characterized in that, The textile materials refer to fibers and fiber products, including fibers, yarns, fabrics, non - woven fabrics, and their composites.

12. A method for synthesizing a fluorane-based color-changing dye according to any one of claims 1 to 4, characterized in that, Comprising the following steps: Mix the fluorane - type color - changing dye structure intermediate and alkylamine, then add an organic solvent and a catalyst, stir, adjust the pH to 8 - 9, then raise the temperature for reaction. After the reaction is completed, purify to obtain the fluorane - type color - changing dye.

13. The method according to claim 12, wherein The synthesis method needs to be carried out under a protective gas environment.

14. The method according to claim 12, wherein The general structural formula of the structural intermediate of the fluorane-based color-changing dye is shown as the following formula Ⅴ: Wherein: R3 is a halogen.

15. The method according to claim 12, characterized in that, The general structural formula of the structural intermediate of the fluorane color-changing dye can also be shown as the following formula VI: Wherein: R2 is a halogen.

16. The method according to claim 12, characterized in that, The alkyl group in the alkylamine includes C2-C 12 linear alkanes, cycloalkanes or alkyl hydrocarbon groups containing polar groups.

17. The method according to claim 12, wherein The organic solvent is toluene; the catalyst is niobium pentoxide.

18. The method according to claim 12, characterized in that The molar ratio of the fluorane - type color - changing dye structure intermediate to alkylamine is 1:1 - 2; the molar amount of the fluorane - type color - changing dye structure intermediate to the volume of the organic solvent is 1mol:0.05 - 0.1 mL; the molar ratio of the fluorane - type color - changing dye structure intermediate to the catalyst is 1:0.5 - 0.

7.

19. The method according to claim 12, wherein The temperature - raising reaction is carried out at 75 - 85 °C for 6 - 9 h.

20. A lightfast discoloration microcapsule, characterized in that The light-fast color-changing microcapsules use the fluorane color-changing dye described in any one of claims 1 to 4 as the core material and a polymer, inorganic particles, or an inorganic particle-doped polymer as the wall material.

21. The lightfast color-changing microcapsule according to claim 20, wherein The method for preparing the color-changing microcapsules comprises the following steps: (1) Preparation of prepolymer: Mix urea and formaldehyde solution, then add triethanolamine to adjust the pH value to 8-9, raise the temperature for reaction to obtain a viscous transparent urea-formaldehyde prepolymer; (2) Dispersion of core: Mix the above-mentioned fluorane color-changing dye, bisphenol A, and a solvent to prepare the core, then mix the core and water, shear and disperse for emulsification, continue to disperse after cooling to form an O / W type emulsion; (3) Microencapsulation and post-treatment: Mix the viscous transparent urea-formaldehyde prepolymer with the O / W type emulsion to obtain a mixed solution, then add sodium chloride and silicon dioxide, stir well, then add acetic acid to adjust the pH to 3-4, then heat for reaction, after the reaction is completed, cool, wash, filter, and dry to obtain the color-changing microcapsules.

22. The lightfast color-changing microcapsule according to claim 21, wherein In step (2), the solvent is a mixed solution of myristyl alcohol and cetyl alcohol, and the mixing mass ratio is 4-5:5-6; the mass ratio of the fluorane color-changing dye to bisphenol A is 1:2-8; the mass ratio of the fluorane color-changing dye to the solvent is 1:50-70; the volume ratio of the core to water is 1:4-7.

23. The lightfast discolorable microcapsule according to claim 21, wherein In step (3), the volume ratio of the viscous transparent urea-formaldehyde prepolymer to the O / W type emulsion is 5-10:1; sodium chloride accounts for 0.2-0.25 wt% of the total mass of the mixed solution; silicon dioxide accounts for 0.2-0.25 wt% of the total mass of the mixed solution.

24. The application of the color-changing microcapsules described in any one of claims 20 to 23 in the fields of textiles and dyeing.

25. A method for preparing a lightfast color-changing fabric, characterized in that, The method is to first prepare a thermochromic color paste using the color-changing microcapsules described in any one of claims 20 to 23, then use the thermochromic color paste to color the fabric, and finally obtain a color-changing fabric with light-fast performance; The composition of the thermochromic color paste includes a thickener, a binder, color-changing microcapsules, and water; the mass ratio of the thickener to the binder is 1:5-15; the mass ratio of the thickener to the color-changing microcapsules is 1:60-100; the mass ratio of the thickener to water is 1:5-15.

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