Optical variable pigment, method for preparing the same, and use thereof

Abstract

The present application relates to a kind of photo-variable pigment and its preparation method and application, the photo-variable pigment includes the following mass parts of component: water 60-80 parts, water-based film forming agent 35-50 parts, photochromic microcapsule 15-20 parts, light stabilizer 2-5 parts, thickening agent 1-5 parts, dispersing agent 1-5 parts, toner 1-5 powder, pH adjusting agent 0.3-1 part, antifoam 0.2-0.5 parts and preservative 0.1-0.3 parts.The present application is by adding photochromic microcapsule, so that photo-variable pigment has reversible photochromic property under the action of sunlight or ultraviolet light, the wall material of the photochromic microcapsule of the present application does not add the component that will release formaldehyde in preparation process, and the addition of octenyl succinate starch, water-based polyurethane prepolymer and composite emulsifier in wall material collectively improves the chemical stability, mechanical stability and long-term storage stability of photo-variable pigment microcapsule.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photochromic pigments, and particularly relates to a photochromic pigment and a preparation method and application thereof. BACKGROUND

[0002] Organic photochromic materials have reversible photochromic properties under the action of sunlight or ultraviolet light, and have been applied to substrates such as plastics, glass, paper, leather, fabrics, etc. to prepare optical lenses, sunglasses, anti-counterfeiting inks, building exterior wall coatings, interior decoration materials, films, handicrafts, textiles, shoes, bags, toys, optical discs, etc.

[0003] Commonly, photochromic pigments are prepared by using a chemical copolymerization / grafting method to connect photochromic structural units to the main chain or side chain of a polymer, but special photochromic compounds with active groups need to be synthesized, which is not suitable for general photochromic compounds. Therefore, in the prior art, photochromic materials are wrapped in microcapsules, but the existing photochromic compound microcapsule coating materials mostly use melamine formaldehyde resin, urea formaldehyde resin, etc., which have a formaldehyde problem. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a photochromic pigment and a preparation method and application thereof, which do not have a formaldehyde problem and are safe and reliable.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a photochromic pigment, comprising the following components by mass fraction: water 60-80 parts, water-based film-forming agent 35-50 parts, photochromic microcapsule 15-20 parts, light stabilizer 2-5 parts, thickening agent 1-5 parts, dispersing agent 1-5 parts, color powder 1-5 parts, pH adjuster 0.3-1 part, defoaming agent 0.2-0.5 part, and preservative 0.1-0.3 part; wherein the water-based film-forming agent is a water-based acrylic emulsion.

[0007] The preparation method of the photochromic microcapsule comprises the following steps:

[0008] (1) uniformly mixing and stirring a photochromic material and an oily solvent to obtain a core material oil phase, wherein the core material oil phase contains 5-15 wt% of the photochromic material;

[0009] (2) uniformly dispersing octenyl succinate starch in an ethanol aqueous solution to obtain an octenyl succinate starch-ethanol solution, wherein the octenyl succinate starch-ethanol solution contains 2-8 wt% of the octenyl succinate starch;

[0010] (3) Mix polypropylene glycol, 2,4-toluene diisocyanate and catalyst, heat to 70-80℃, keep the reaction at the temperature for 1-2 hours, add 2,2-dimethylolpropionic acid under the keeping condition, and continue the reaction for 1-2 hours. During the reaction, add a small amount of acetone to adjust the viscosity to obtain waterborne polyurethane prepolymer.

[0011] (4) The core material oil phase obtained in step (1) and the octenyl succinate starch ester-ethanol solution obtained in step (2) are mixed and sheared to emulsify to obtain an O / W type emulsion. The aqueous polyurethane prepolymer and composite emulsifier aqueous solution obtained in step (3) are added to the O / W type emulsion, stirred and dispersed evenly, and heated to 80-90℃ to form a microcapsule emulsion. The microcapsules are spray-dried to obtain the photochromic microcapsules. The composite emulsifier is a composition of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate, and the mass concentration of the composite emulsifier in the aqueous solution of the composite emulsifier is 30-60 wt%.

[0012] Octenyl succinate starch ester (OSA starch ester), as a modified starch derivative, has hydrophobic octenyl succinate groups in its molecular chain that are compatible with the oil-phase core material, while the hydrophilic starch backbone is anchored in the aqueous phase, forming a stable O / W interface layer. This amphiphilic structure, after pre-dispersion in the ethanol-water solution in step (2), provides a uniform initial coating layer for subsequent core material emulsification. The aqueous polyurethane prepolymer diffuses to the oil-water interface in the O / W emulsion, participating in interfacial polymerization together with OSA starch ester and the composite emulsifier to form a uniform wall material layer. This interfacial reaction mechanism avoids the brittleness problem of traditional urea-formaldehyde resin wall materials and reduces the risk of core material exposure. Specifically, during microencapsulation, the hydroxyl groups of octenyl succinate starch ester may undergo cross-linking reactions with the isocyanate groups of the aqueous polyurethane prepolymer to form an interpenetrating network structure. This synergistic effect not only enhances the mechanical strength of the wall material but also improves its toughness through the flexibility of the starch molecular chain, reducing the rupture of microcapsules during drying. In the composite emulsifier, polyvinyl alcohol (PVA) forms a dense adsorption layer at the oil-water interface through strong hydrogen bonding. The branched structure of polyglycerol-10 laurate can insert into the intermolecular gaps of PVA, reducing interfacial tension. Hydroxypropyl distarch phosphate enhances the zeta potential of the emulsion through the electrostatic repulsion of phosphate groups. This triple effect achieves emulsion kinetic stability. During the high-temperature reaction stage of 80-90℃, the thermally reversible gel properties of PVA and the high-temperature resistance of polyglycerol-10 laurate work together to maintain emulsion stability and prevent high-temperature demulsification. During spray drying, the rapid film-forming properties of hydroxypropyl distarch phosphate and octenyl succinate starch ester, along with the viscoelasticity of polyurethane, synergistically lock in the core material. Therefore, octenyl succinate starch ester, waterborne polyurethane prepolymer, and composite emulsifier, through interfacial stabilization, cross-linking enhancement, and synergistic effects, construct a microcapsule system that combines mechanical strength, thermal stability, and environmental adaptability.

[0013] The pigment of this invention uses an aqueous acrylic emulsion as a film-forming agent, which not only provides a film-forming effect but also improves the pigment's adhesion, water resistance, and gloss.

[0014] Preferably, in step (1), the photochromic material is at least one of spiropyran, spiroxazine, benzopyran, and naphthopyran, and the oily solvent is at least one of 120# solvent oil, 150# solvent oil, 200# solvent oil, and 300# solvent oil.

[0015] Preferably, the volume concentration of the ethanol aqueous solution in step (2) is 70-80%.

[0016] Preferably, in step (3), the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, catalyst and 2,2-dimethylolpropionic acid is (1.5-2):1:(0.01-0.05):(0.08-0.1), the catalyst is dibutyltin dilaurate, and acetone is added to reduce the viscosity to below 1000 mPa·s.

[0017] Preferably, in step (4), the mass ratio of the core material oil phase, octenyl succinate starch ester-ethanol solution, aqueous polyurethane prepolymer, and composite emulsifier aqueous solution is 1:(2-5):(1-3):(1-6).

[0018] Preferably, in step (4), the mass ratio of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate is 1:(2-5):(2-5).

[0019] Preferably, the light stabilizer is UV-531 light stabilizer.

[0020] Preferably, the thickener is PEG-20000.

[0021] Preferably, the dispersant is a polyether-modified organosilicon.

[0022] Preferably, the pH adjuster is aminomethylpropanol.

[0023] Preferably, the defoamer is an organosiloxane defoamer.

[0024] Preferably, the preservative is isothiazolinone.

[0025] Secondly, the present invention provides a method for preparing the aforementioned photochromic pigment, comprising the following steps:

[0026] S1. Mix and stir water, aqueous film-forming agent, photochromic microcapsules, color powder, defoamer, thickener, dispersant and preservative to obtain the first mixture;

[0027] S2. Add light stabilizer and pH adjuster to the first mixture, stir evenly, and obtain the color-changing pigment.

[0028] Preferably, in step S1, the stirring speed is 500-1000 r / min and the stirring time is 20-30 min.

[0029] Preferably, in step S2, the stirring speed is 300-500 r / min and the stirring time is 10-20 min.

[0030] Thirdly, the present invention provides the application of the aforementioned photochromic pigment in the preparation of photosensitive coatings.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention enables photochromic pigments to exhibit reversible photochromic properties under sunlight or ultraviolet light by incorporating photochromic microcapsules. The wall material of these photochromic microcapsules does not contain any components that would release formaldehyde during the preparation process. Through a mechanism of chemical cross-linking of the composite wall material and synergistic dispersion by multiple emulsifiers, the environmental tolerance of the photochromic core material is significantly improved. Octenyl succinate starch ester enhances emulsification stability through interfacial film formation and low viscosity characteristics. Waterborne polyurethane strengthens the capsule wall density through a cross-linked network, and the composite emulsifier reduces interfacial tension through multi-component synergy. The combination of octenyl succinate starch ester, waterborne polyurethane prepolymer, and composite emulsifier in the wall material collectively improves the chemical stability, mechanical stability, and long-term storage stability of the photochromic pigment microcapsules. Detailed Implementation

[0033] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0034] The sources of the raw materials used in the following examples and comparative examples are as follows:

[0035] Water-based acrylic emulsion: Manufacturer: Foshan Shunde Badefu Industrial Co., Ltd., Model: RS-706T;

[0036] Spiropyran: 1-(2-hydroxyethyl)-3,3-dimethylindololino-6'-nitrobenzospiropyran, manufactured by Bailingwei Technology, model number 217275;

[0037] Spirooxazine: 1,3,3-Trimethylindolino-6'-(1-piperidinyl)spirophenoxazine, manufactured by Bailingwei Technology, model number 1361879;

[0038] Polyvinyl alcohol: Manufacturer: Shanghai Yuanye Biotechnology Co., Ltd., Model: S30196;

[0039] Polyglycerol-10 laurate: Manufacturer is Shandong Binzhou Jinsheng New Material Technology Co., Ltd.;

[0040] Octenyl succinate starch ester: Manufacturer: Foshan Nanhai Huahao Huafeng Starch Co., Ltd.

[0041] Hydroxypropyl distarch phosphate: Manufacturer: Foshan Nanhai Huahao Huafeng Starch Co., Ltd.

[0042] UV-531 light stabilizer: Manufacturer: Nanjing Hualiming Chemical Co., Ltd., Model: BP-12;

[0043] Polyether-modified silicone: Manufacturer: Tiger Polymer Technology Co., Ltd., Model: Tech-2754;

[0044] PEG-20000: Manufacturer is Biosharp, model number is BS906;

[0045] Aminomethylpropanol: Manufacturer: Shanghai Yuanye Biotechnology Co., Ltd., Model: S16023;

[0046] Organosiloxane defoamer: Manufacturer: Dow Chemical, Model: XIAMETER TM ACP-0544;

[0047] Isothiazolinone: Manufacturer: Changzhou Runyang Chemical Co., Ltd.; Model: GY-506;

[0048] Pigment: Manufacturer: Shanghai Teyan Chemical Pigment Co., Ltd., Model: Golden Red C Pigment Red 53:1;

[0049] Unless otherwise specified, all other materials, reagents, etc. used in the examples and comparative examples are commercially available.

[0050] Example 1

[0051] A photochromic pigment comprises the following components in parts by weight: 75 parts water, 42 parts aqueous film-forming agent, 16 parts photochromic microcapsules, 3 parts light stabilizer, 2 parts thickener, 2 parts dispersant, 3 parts colorant, 0.6 parts pH adjuster, 0.3 parts defoamer, and 0.2 parts preservative;

[0052] The aqueous film-forming agent is an aqueous acrylic emulsion, the light stabilizer is UV-531 light stabilizer, the thickener is PEG-20000, the dispersant is polyether-modified organosilicon, the pH adjuster is aminomethylpropanol, the defoamer is an organosiloxane defoamer, and the preservative is isothiazolinone.

[0053] The preparation method of the photochromic microcapsules includes the following steps:

[0054] (1) The photochromic material and the oily solvent are mixed and stirred evenly to obtain the core material oil phase; wherein the photochromic material is spiropyran, the oily solvent is 120# solvent oil, and the core material oil phase contains 12wt% of the photochromic material.

[0055] (2) Octenyl succinate starch ester is uniformly dispersed in an aqueous ethanol solution to obtain an octenyl succinate starch ester-ethanol solution; wherein the volume concentration of the aqueous ethanol solution is 75%, and the octenyl succinate starch ester-ethanol solution contains 5 wt% octenyl succinate starch ester.

[0056] (3) Polypropylene glycol, 2,4-toluene diisocyanate and catalyst are mixed, heated to 75°C, and reacted at this temperature for 1.5 h. 2,2-dimethylolpropionic acid is added under the same conditions, and the reaction is continued for another 1.5 h. During this period, acetone is added to reduce the viscosity to below 1000 mPa·s to obtain an aqueous polyurethane prepolymer. The catalyst is dibutyltin dilaurate, and the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, catalyst and 2,2-dimethylolpropionic acid is 1.7:1:0.03:0.09.

[0057] (4) Mix the core material oil phase obtained in step (1) and the octenyl succinic acid starch ester-ethanol solution obtained in step (2), and shear emulsify to obtain an O / W type emulsion. Add the aqueous polyurethane prepolymer and composite emulsifier aqueous solution obtained in step (3) to the O / W type emulsion, stir and disperse evenly, and heat to 85℃ to form a microcapsule emulsion. The inlet air temperature is 120℃, the feed rate is 300mL / h, and the inlet air rate is 150m. 3 The photochromic microcapsules were obtained by spray drying under conditions of / h; wherein the composite emulsifier is a composition of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate in a mass ratio of 1:4:3, the mass concentration of the composite emulsifier in the aqueous solution of the composite emulsifier is 50wt%, and the mass ratio of the core material oil phase, octenyl succinate starch ester-ethanol solution, aqueous polyurethane prepolymer and aqueous solution of composite emulsifier is 1:3:2:4;

[0058] The preparation method of optically variable pigments includes the following steps:

[0059] S1. Mix water, aqueous film-forming agent, photochromic microcapsules, color powder, defoamer, thickener and preservative at 800 r / min for 25 min to obtain the first mixture;

[0060] S2. Add aqueous silica sol and pH adjuster to the first mixture, and stir at 400 r / min for 15 min to obtain the color-changing pigment.

[0061] Example 2

[0062] A photochromic pigment comprises the following components in parts by weight: 60 parts water, 35 parts aqueous film-forming agent, 15 parts photochromic microcapsules, 2 parts light stabilizer, 5 parts thickener, 1 part dispersant, 1 part colorant, 0.3 parts pH adjuster, 0.2 parts defoamer, and 0.3 parts preservative.

[0063] The aqueous film-forming agent is an aqueous acrylic emulsion, the light stabilizer is UV-531 light stabilizer, the thickener is PEG-20000, the dispersant is polyether-modified organosilicon, the pH adjuster is aminomethylpropanol, the defoamer is an organosiloxane defoamer, and the preservative is isothiazolinone.

[0064] The preparation method of the photochromic microcapsules includes the following steps:

[0065] (1) The photochromic material and the oily solvent are mixed and stirred evenly to obtain the core material oil phase; wherein, the photochromic material is spiroxazine, the oily solvent is 150# solvent oil, and the core material oil phase contains 5wt% of the photochromic material.

[0066] (2) Octenyl succinate starch ester is uniformly dispersed in an ethanol aqueous solution to obtain an octenyl succinate starch ester-ethanol solution; wherein the volume concentration of the ethanol aqueous solution is 70%, and the octenyl succinate starch ester-ethanol solution contains 5 wt% octenyl succinate starch ester.

[0067] (3) Polypropylene glycol, 2,4-toluene diisocyanate and catalyst are mixed, heated to 70°C, and reacted for 2 hours. 2,2-dimethylolpropionic acid is added under the heat preservation condition, and the reaction is continued for 2 hours. During this period, acetone is added to reduce the viscosity to below 1000 mPa·s to obtain an aqueous polyurethane prepolymer. The catalyst is dibutyltin dilaurate, and the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, catalyst and 2,2-dimethylolpropionic acid is 1.5:1:0.01:0.1.

[0068] (4) Mix the core material oil phase obtained in step (1) and the octenyl succinic acid starch ester-ethanol solution obtained in step (2), and shear emulsify to obtain an O / W type emulsion. Add the aqueous polyurethane prepolymer and composite emulsifier aqueous solution obtained in step (3) to the O / W type emulsion, stir and disperse evenly, and heat to 90℃ to form a microcapsule emulsion. The inlet air temperature is 120℃, the feed rate is 300mL / h, and the inlet air rate is 150m. 3The photochromic microcapsules were obtained by spray drying under conditions of / h; wherein the composite emulsifier is a composition of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate in a mass ratio of 1:2:5, the mass concentration of the composite emulsifier in the aqueous solution of the composite emulsifier is 30wt%, and the mass ratio of the core material oil phase, octenyl succinate starch ester-ethanol solution, aqueous polyurethane prepolymer and aqueous solution of composite emulsifier is 1:2:1:1;

[0069] The preparation method of optically variable pigments includes the following steps:

[0070] S1. Mix water, aqueous film-forming agent, photochromic microcapsules, color powder, defoamer, thickener and preservative at a speed of 500 r / min for 30 min to obtain the first mixture;

[0071] S2. Add aqueous silica sol and pH adjuster to the first mixture, and stir at 300 r / min for 20 min to obtain the color-changing pigment.

[0072] Example 3

[0073] A photochromic pigment comprises the following components in parts by weight: 80 parts water, 50 parts aqueous film-forming agent, 20 parts photochromic microcapsules, 5 parts light stabilizer, 1 part thickener, 5 parts dispersant, 5 parts colorant, 1 part pH adjuster, 0.5 parts defoamer, and 0.1 parts preservative.

[0074] The aqueous film-forming agent is an aqueous acrylic emulsion, the light stabilizer is UV-531 light stabilizer, the thickener is PEG-20000, the dispersant is polyether-modified organosilicon, the pH adjuster is aminomethylpropanol, the defoamer is an organosiloxane defoamer, and the preservative is isothiazolinone.

[0075] The preparation method of the photochromic microcapsules includes the following steps:

[0076] (1) The photochromic material and the oily solvent are mixed and stirred evenly to obtain the core material oil phase; wherein, the photochromic material is spiropyran, the oily solvent is 120# solvent oil, and the core material oil phase contains 15wt% of the photochromic material.

[0077] (2) Octenyl succinate starch ester is uniformly dispersed in an aqueous ethanol solution to obtain an octenyl succinate starch ester-ethanol solution; wherein the volume concentration of the aqueous ethanol solution is 80%, and the octenyl succinate starch ester-ethanol solution contains 15 wt% octenyl succinate starch ester.

[0078] (3) Polypropylene glycol, 2,4-toluene diisocyanate and catalyst are mixed, heated to 80°C, and reacted for 1 hour. Under the condition of heat preservation, 2,2-dimethylolpropionic acid is added and the reaction is continued for 1 hour. During the reaction, acetone is added to reduce the viscosity to below 1000 mPa·s to obtain an aqueous polyurethane prepolymer. The catalyst is dibutyltin dilaurate, and the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, catalyst and 2,2-dimethylolpropionic acid is 2:1:0.05:0.08.

[0079] (4) Mix the core material oil phase obtained in step (1) and the octenyl succinic acid starch ester-ethanol solution obtained in step (2), and shear emulsify to obtain an O / W type emulsion. Add the aqueous polyurethane prepolymer and composite emulsifier aqueous solution obtained in step (3) to the O / W type emulsion, stir and disperse evenly, and heat to 80℃ to form a microcapsule emulsion. The inlet air temperature is 120℃, the feed rate is 300mL / h, and the inlet air rate is 150m. 3 The photochromic microcapsules were obtained by spray drying under conditions of / h; wherein the composite emulsifier was a composition of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate in a mass ratio of 1:5:2, the mass concentration of the composite emulsifier in the aqueous solution of the composite emulsifier was 60wt%, and the mass ratio of the core material oil phase, octenyl succinate starch ester-ethanol solution, aqueous polyurethane prepolymer and aqueous solution of composite emulsifier was 1:5:3:6;

[0080] The preparation method of optically variable pigments includes the following steps:

[0081] S1. Mix water, aqueous film-forming agent, photochromic microcapsules, color powder, defoamer, thickener and preservative at a speed of 1000 r / min for 20 min to obtain the first mixture;

[0082] S2. Add aqueous silica sol and pH adjuster to the first mixture, and stir at 500 r / min for 10 min to obtain the color-changing pigment.

[0083] Example 4

[0084] The difference between Example 4 and Example 1 is that the amount of composite emulsifier added remains the same, and the mass ratio of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate is 4:1:3.

[0085] Example 5

[0086] The difference between Example 5 and Example 1 is that the amount of composite emulsifier added remains the same, and the mass ratio of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate is 3:4:1.

[0087] Comparative Example 1

[0088] The difference between Comparative Example 1 and Example 1 is that: in step (4), waterborne polyurethane prepolymer is not added, and an equal amount of octenyl succinic starch ester is used to make up the missing amount.

[0089] Comparative Example 2

[0090] The difference between Comparative Example 2 and Example 1 is that octenyl succinic starch ester is not added in step (4), and an equal amount of waterborne polyurethane prepolymer is used to make up the missing amount.

[0091] Comparative Example 3

[0092] The difference between Comparative Example 3 and Example 1 is that the amount of composite emulsifier added remains the same, polyvinyl alcohol is not added, and polyglycerol-10 laurate and hydroxypropyl distarch phosphate in a mass ratio of 4:3 are used to make up the missing amount.

[0093] Comparative Example 4

[0094] The difference between Comparative Example 4 and Example 1 is that the amount of composite emulsifier added remains the same, polyglycerol-10 laurate is not added, and the missing amount is made up by polyvinyl alcohol and hydroxypropyl distarch phosphate in a mass ratio of 1:3.

[0095] Comparative Example 5

[0096] The difference between Comparative Example 5 and Example 1 is that the amount of composite emulsifier added remains the same, hydroxypropyl distarch phosphate is not added, and the missing amount is made up by polyvinyl alcohol and polyglycerol-10 laurate in a mass ratio of 1:4.

[0097] Performance testing

[0098] 1. Encapsulation efficiency test of photochromic microcapsules

[0099] Specific testing method: Weigh 1g of microcapsules into a beaker, add 50mL of n-hexane, shake for 1min, filter, collect the filtrate, and rotary evaporate until constant mass is obtained to obtain the oil mass W1 on the surface of the microcapsules; take the same mass of microcapsules into a beaker, add 50mL of anhydrous ethanol, and break the cell walls of the microcapsules using an ultrasonic cell disruptor, centrifuge to obtain the supernatant, repeat the above operation twice, combine the supernatants, and rotary evaporate until constant mass is obtained to obtain the total oil mass W2 of the microcapsules. The formula for calculating the encapsulation rate is: See Table 1 for specific data.

[0100] 2. Chemical fatigue resistance test of color-changing pigments in each group

[0101] Specific testing method: Following ISO 105-B02, equal amounts (5g) of the color-changing pigments from Examples 1-5 and Comparative Examples 1-5 were continuously irradiated under a xenon lamp for 48 hours. The L, A, B (before irradiation) and L', A', B' (after irradiation) values ​​of each product under ultraviolet light (wavelengths 254nm, 365nm) excitation were measured using a colorimeter, and the color difference value ΔE was calculated, as shown in Table 1. The color difference value ΔE represents the magnitude of the color difference, and the calculation formula is ΔE = [(L - L')] 2 +(A-A') 2 +(B-B') 2 ] 1 / 2 The data is shown in Table 1.

[0102] Table 1. Embedding efficiency and chemical fatigue resistance test results for each group of samples.

[0103]

[0104]

[0105] Based on the results of Examples 1-3 and Examples 4-5 in Table 1, it can be seen that when the mass ratio of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate is 1:(2-5):(2-5), the stability of the microcapsules reaches a better level.

[0106] Based on the results of Example 1 and Comparative Examples 1-2 in Table 1, it can be seen that when waterborne polyurethane and octenyl succinate starch ester are lacking, the degree of cross-linking of the wall material decreases, the encapsulation rate of the photochromic microcapsules decreases significantly, and the color difference of the pigment increases significantly after 48 hours of ultraviolet irradiation. This indicates that the wall material structure formed by the waterborne polyurethane prepolymer and octenyl succinate starch ester can synergistically improve the protective ability of the microcapsules for the photochromic material and reduce the influence of the external environment (light, heat, oxygen).

[0107] Based on the results of Example 1 and Comparative Examples 3-5 in Table 1, it can be seen that the absence of any one of the composite emulsifiers will disrupt the emulsion balance, leading to uneven particle size, core material leakage, or decreased mechanical strength. This indicates that the composite emulsifiers synergistically improve the environmental tolerance and stability of the photochromic core material.

[0108] In summary, the microcapsules of the present invention employ specific wall materials and emulsifiers, enabling the wall material to form a denser interfacial film during the microencapsulation process. This prevents the wall material from cracking, ensures the functional stability of the photochromic material, and improves the microencapsulation efficiency.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A photochromic pigment, characterized in that, The product comprises the following components in parts by weight: 60-80 parts water, 35-50 parts aqueous film-forming agent, 15-20 parts photochromic microcapsules, 2-5 parts light stabilizer, 1-5 parts thickener, 1-5 parts dispersant, 1-5 parts colorant, 0.3-1 part pH adjuster, 0.2-0.5 parts defoamer, and 0.1-0.3 parts preservative; wherein the aqueous film-forming agent is an aqueous acrylic emulsion. The preparation method of the photochromic microcapsules includes the following steps: (1) The photochromic material and the oily solvent are mixed and stirred evenly to obtain the core material oil phase, wherein the core material oil phase contains 5-15 wt% of the photochromic material; (2) Octenyl succinate starch ester is uniformly dispersed in an aqueous ethanol solution to obtain an octenyl succinate starch ester-ethanol solution, wherein the octenyl succinate starch ester-ethanol solution contains 2-8 wt% octenyl succinate starch ester. (3) Mix polypropylene glycol, 2,4-toluene diisocyanate and catalyst, heat to 70~80℃, keep the temperature for 1~2h, add 2,2-dimethylolpropionic acid under the keeping temperature condition, and continue the reaction for 1~2h. During the reaction, add a small amount of acetone to adjust the viscosity to obtain waterborne polyurethane prepolymer. (4) The core material oil phase obtained in step (1) and the octenyl succinate starch ester-ethanol solution obtained in step (2) are mixed and sheared to emulsify, resulting in an O / W type emulsion. The aqueous polyurethane prepolymer and composite emulsifier aqueous solution obtained in step (3) are added to the O / W type emulsion, stirred and dispersed evenly, and heated to 80-90℃ to form a microcapsule emulsion. The microcapsules are then spray-dried to obtain the photochromic microcapsules. The mass ratio of the core material oil phase, octenyl succinate starch ester-ethanol solution, aqueous polyurethane prepolymer, and composite emulsifier aqueous solution is 1:(2-5):(1-3):(1-6). The composite emulsifier is a composition of polyvinyl alcohol, polyglycerol-10 laurate, and hydroxypropyl distarch phosphate. The mass ratio of polyvinyl alcohol, polyglycerol-10 laurate, and hydroxypropyl distarch phosphate is 1:(2-5):(2-5). The mass concentration of the composite emulsifier in the composite emulsifier aqueous solution is 30-60 wt%.

2. The photochromic pigment as described in claim 1, characterized in that, In step (1), the photochromic material is at least one of spiropyran, spiroxazine, benzopyran and naphthopyran, and the oily solvent is at least one of 120# solvent oil, 150# solvent oil, 200# solvent oil and 300# solvent oil.

3. The photochromic pigment as described in claim 1, characterized in that, The volume concentration of the ethanol aqueous solution in step (2) is 70-80%.

4. The photochromic pigment as described in claim 1, characterized in that, In step (3), the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, catalyst and 2,2-dimethylolpropionic acid is (1.5-2):1:(0.01-0.05):(0.08-0.1). The catalyst is dibutyltin dilaurate. Acetone is added to reduce the viscosity to below 1000 mPa·s.

5. The photochromic pigment as described in claim 1, characterized in that, Each component of the pigment is selected from at least one of the following (I) to (VI): (I) The light stabilizer is UV-531 light stabilizer; (II) The thickener is PEG-20000; (III) The dispersant is a polyether-modified organosilicon; (IV) The pH adjuster is aminomethylpropanol; (V) The defoamer is an organosiloxane defoamer; (VI) The preservative is isothiazolinone.

6. The method for preparing the photochromic pigment according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix and stir water, aqueous film-forming agent, photochromic microcapsules, color powder, defoamer, thickener, dispersant and preservative to obtain the first mixture; S2. Add light stabilizer and pH adjuster to the first mixture, stir evenly, and obtain the color-changing pigment.

7. The method for preparing the photochromic pigment as described in claim 6, characterized in that, In step S1, the stirring speed is 500-1000 r / min and the stirring time is 20-30 min; and / or, in step S2, the stirring speed is 300-500 r / min and the stirring time is 10-20 min.

8. The use of the photochromic pigment according to any one of claims 1-5 in the preparation of photosensitive coatings.

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