Optically variable pigment as well as preparation method and application thereof

Abstract

The invention relates to an optically variable pigment as well as a preparation method and application thereof. The optically variable pigment comprises the following components in parts by mass: 60-80 parts of water, 35-50 parts of a water-based film-forming agent, 15-20 parts of photochromic microcapsules, 2-5 parts of a light stabilizer, 1-5 parts of a thickening agent, 1-5 parts of a dispersing agent, 1-5 parts of toner, 0.3-1 part of a pH regulator, 0.2-0.5 part of a defoaming agent and 0.1-0.3 part of a preservative. By adding the photochromic microcapsule, the photochromic pigment has reversible photochromic property under the action of sunlight or ultraviolet light, and a component capable of releasing formaldehyde in the preparation process is not added into the wall material of the photochromic microcapsule; the octenyl succinic acid modified starch, the waterborne polyurethane prepolymer and the compound emulsifier which are added into the wall material jointly improve the chemical stability, the mechanical stability and the long-term storage stability of the optically variable pigment microcapsule.

Description

Technical Field

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

[0002] Due to the reversible photochromic property under sunlight or ultraviolet light, organic photochromic materials have been applied to substrates such as plastics, glass, paper, leather, fabrics, etc., to prepare optical lenses, sunglasses, anti-counterfeiting inks, exterior wall coatings for buildings, interior decoration materials, films, handicrafts, textiles, shoes, luggage, toys, optical discs, etc.

[0003] The common method for preparing pigments from organic photochromic materials is to connect photochromic structural units to the main chain or side chain of a polymer by chemical copolymerization / grafting method. However, it is necessary to synthesize special photochromic compounds with active groups, which is not applicable to general photochromic compounds. Based on this, in the prior art, photochromic materials are encapsulated in microcapsules. However, most of the existing microcapsule coating materials for photochromic compounds use melamine formaldehyde resin, urea formaldehyde resin, etc., and there are formaldehyde problems. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a photochromic pigment, a preparation method thereof, and an application thereof. The coating material has no formaldehyde problem and is safe and reliable.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention provides a photochromic pigment, comprising the following components in parts by mass: 60 - 80 parts of water, 35 - 50 parts of a water-based film-forming agent, 15 - 20 parts of photochromic microcapsules, 2 - 5 parts of a light stabilizer, 1 - 5 parts of a thickener, 1 - 5 parts of a dispersant, 1 - 5 parts of a color powder, 0.3 - 1 part of a pH regulator, 0.2 - 0.5 part of an antifoaming agent, and 0.1 - 0.3 part of a preservative; wherein, the water-based film-forming agent is a water-based acrylic emulsion;

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

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

[0009] (2) Uniformly disperse octenyl succinic anhydride starch ester in an ethanol aqueous solution to obtain an octenyl succinic anhydride starch ester - ethanol solution, and the octenyl succinic anhydride starch ester - ethanol solution contains 2 - 8 wt% of octenyl succinic anhydride starch ester;

[0010] (3) Mix polypropylene glycol, 2,4-toluene diisocyanate and a catalyst, heat up to 70 - 80 °C, keep the temperature for reaction for 1 - 2 h, add 2,2-dimethylolpropionic acid under the temperature-keeping condition, continue the reaction for 1 - 2 h, and add a small amount of acetone to adjust the viscosity during this period to obtain an aqueous polyurethane prepolymer;

[0011] (4) Mix the core material oil phase obtained in step (1) and the octenyl succinic anhydride starch ester-ethanol solution obtained in step (2), shear and emulsify to obtain an O / W type emulsion. Add the aqueous polyurethane prepolymer obtained in step (3) and an aqueous solution of a composite emulsifier to the O / W type emulsion, stir and disperse evenly, heat up to 80 - 90 °C to form a microcapsule emulsion, and spray dry to obtain the photochromic microcapsules. Among them, 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 succinic anhydride starch ester (OSA starch ester), as a modified starch derivative, has hydrophobic octenyl succinic anhydride groups in its molecular chain that are compatible with the oil-phase core material, and the hydrophilic starch main chain is anchored in the water phase to form a stable O / W interfacial layer. After being pre-dispersed in the ethanol aqueous solution in step (2), this amphiphilic structure provides a uniform initial coating layer for the subsequent emulsification of the core material. The aqueous polyurethane prepolymer diffuses to the oil-water interface in the O / W emulsion and participates in interfacial polymerization together with OSA starch ester and the composite emulsifier to form a uniform wall material layer. This interfacial reaction mechanism can avoid the brittleness problem of traditional urea-formaldehyde resin wall materials and reduce the risk of core material exposure at the same time. Specifically, during the microencapsulation process, the hydroxyl groups of octenyl succinic anhydride starch ester may crosslink 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 the toughness of the wall material through the flexibility of the starch molecular chain, reducing the rupture of microcapsules during the drying process. Polyvinyl alcohol (PVA) in the composite emulsifier forms a dense adsorption layer at the oil-water interface through strong hydrogen bond action. The branched-chain structure of polyglycerol-10 laurate can insert into the molecular gaps of PVA, playing a role in reducing the interfacial tension. Hydroxypropyl distarch phosphate enhances the Zeta potential of the emulsion through the electrostatic repulsion of phosphate groups. The triple action realizes the kinetic stability of the emulsion. During the high-temperature reaction stage at 80 - 90 °C, the thermoreversible gel property of PVA and the high-temperature resistance property of polyglycerol-10 laurate jointly maintain the stability of the emulsion and prevent high-temperature demulsification. During spray drying, the rapid film-forming properties of hydroxypropyl distarch phosphate and octenyl succinic anhydride starch ester and the viscoelasticity of polyurethane synergistically lock the core material. Therefore, octenyl succinic anhydride starch ester, aqueous polyurethane prepolymer and composite emulsifier construct a microcapsule system with mechanical strength, thermal stability and environmental adaptability through interface stabilization, crosslinking strengthening and synergistic enhancement.

[0013] In the pigment of the present invention, an aqueous acrylic emulsion is used as a film-forming agent, which can improve the adhesion, water resistance and gloss of the pigment while providing a film-forming effect.

[0014] Preferably, in the step (1), the photochromic material is at least one of spiropyran, spirooxazine, 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, in the step (2), the volume concentration of the ethanol aqueous solution is 70-80%.

[0016] Preferably, in the 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 the step (4), the mass ratio of the core material oil phase, octenyl succinic anhydride starch ester-ethanol solution, aqueous polyurethane prepolymer, and composite emulsifier aqueous solution is 1:(2-5):(1-3):(1-6).

[0018] Preferably, in the 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 polyether-modified silicone.

[0022] Preferably, the pH regulator is aminomethylpropanol.

[0023] Preferably, the defoamer is a silicone-based defoamer.

[0024] Preferably, the preservative is isothiazolinone.

[0025] In a second aspect, the present invention provides a method for preparing the photochromic pigment, comprising the following steps:

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

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

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

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

[0030] In the third aspect, the present invention provides the application of the photochromic pigment in the preparation of a photosensitive coating.

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

[0032] By adding photochromic microcapsules, the photochromic pigment of the present invention has reversible photochromic properties under sunlight or ultraviolet light. In the wall material of the photochromic microcapsules of the present invention, no component that releases formaldehyde during the preparation process is added. Through the mechanism of chemical cross-linking of the composite wall material and synergistic dispersion of multiple emulsifiers, the environmental tolerance of the photochromic core material is significantly improved. Octenyl succinic anhydride starch ester improves the emulsion stability through interfacial film formation and low viscosity characteristics. Waterborne polyurethane enhances the wall compactness through a cross-linked network. The composite emulsifier reduces the interfacial tension through multi-component synergy. The combination of octenyl succinic anhydride starch ester, waterborne polyurethane prepolymer and composite emulsifier added to the wall material jointly improves the chemical stability, mechanical stability and long-term storage stability of the photochromic pigment microcapsules. Specific Embodiments

[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 raw materials used in the following examples and comparative examples are as follows:

[0035] Waterborne acrylic emulsion: The manufacturer is Foshan Shunde Badfu Industrial Co., Ltd., and the model is RS-706T;

[0036] Spiropyran: 1-(2-Hydroxyethyl)-3,3-dimethylindolinyl-6'-nitrobenzospiropyran, the manufacturer is J&K Scientific Ltd., and the model is 217275;

[0037] Spiroxazine: 1,3,3-Trimethylindolino-6'-(1-piperidyl)spiro[2H-1-benzopyran-2,2'-indoline], the manufacturer is J&K Scientific Ltd., and the model is 1361879;

[0038] Polyvinyl alcohol: The manufacturer is Shanghai Yuanye Bio-Technology Co., Ltd., and the model is S30196;

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

[0040] Octenyl succinic anhydride modified starch: The manufacturer is Foshan Nanhai Huahao Huafeng Starch Co., Ltd.;

[0041] Hydroxypropyl distarch phosphate: The manufacturer is Foshan Nanhai Huahao Huafeng Starch Co., Ltd.;

[0042] UV-531 light stabilizer: The manufacturer is Nanjing Hualiming Chemical Co., Ltd., and the model is BP-12;

[0043] Polyether modified silicone: The manufacturer is Tiger Polymer Technology Co., Ltd., and the model is Tech-2754;

[0044] PEG-20000: The manufacturer is Biosharp, and the model is BS906;

[0045] 2-Amino-2-methyl-1-propanol: The manufacturer is Shanghai Yuanye Bio-Technology Co., Ltd., and the model is S16023;

[0046] Organosiloxane defoamer: The manufacturer is Dow Chemical, and the model is XIAMETER TM ACP-0544;

[0047] Isothiazolinone: The manufacturer is Changzhou Runyang Chemical Co., Ltd., and the model is GY-506;

[0048] Color powder: The manufacturer is Shanghai Teyan Chemical Pigment Co., Ltd., and the model is Golden Red C Pigment Red 53:1;

[0049] Other materials, reagents, etc. used in the examples and comparative examples can be obtained from commercial channels without special instructions.

[0050] Example 1

[0051] A photochromic pigment, comprising the following components in parts by mass: 75 parts of water, 42 parts of waterborne film-forming agent, 16 parts of photochromic microcapsules, 3 parts of light stabilizer, 2 parts of thickener, 2 parts of dispersant, 3 parts of color powder, 0.6 part of pH regulator, 0.3 part of defoamer and 0.2 part of preservative;

[0052] The waterborne film-forming agent is a waterborne acrylic emulsion, the light stabilizer is UV-531 light stabilizer, the thickener is PEG-20000, the dispersant is polyether modified silicone, the pH regulator is 2-amino-2-methyl-1-propanol, the defoamer is an organosiloxane defoamer, and the preservative is isothiazolinone;

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

[0054] (1) Mix the photochromic material and the oily solvent evenly by stirring to obtain the core material oil phase; wherein, the photochromic material is spiropyran, the oily solvent is solvent oil No. 120, and the core material oil phase contains 12 wt% of the photochromic material;

[0055] (2) Disperse octenyl succinic anhydride starch ester evenly in the ethanol aqueous solution to obtain the octenyl succinic anhydride starch ester - ethanol solution; wherein, the volume concentration of the ethanol aqueous solution is 75%, and the octenyl succinic anhydride starch ester - ethanol solution contains 5 wt% of octenyl succinic anhydride starch ester;

[0056] (3) Mix polypropylene glycol, 2,4 - tolylene diisocyanate and a catalyst, heat up to 75 °C, keep the temperature for reaction for 1.5 h, add 2,2 - dimethylolpropionic acid under the insulation condition, and continue the reaction for 1.5 h. During this period, add acetone to reduce the viscosity to below 1000 mPa·s to obtain the aqueous polyurethane prepolymer; wherein, the catalyst is dibutyltin dilaurate, and the mass ratio of polypropylene glycol, 2,4 - tolylene diisocyanate, the 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 anhydride starch ester - ethanol solution obtained in step (2), shear and emulsify to obtain an O / W type emulsion. Add the aqueous polyurethane prepolymer obtained in step (3) and the composite emulsifier aqueous solution to the O / W type emulsion, stir and disperse evenly, heat up to 85 °C to form a microcapsule emulsion, and perform spray drying under the conditions of an inlet air temperature of 120 °C, a feeding rate of 300 mL / h, and an inlet air rate of 150 m 3 / h to obtain the photochromic microcapsules; wherein, the composite emulsifier is a composition of polyvinyl alcohol, polyglycerol - 10 laurate and hydroxypropyl distarch phosphate with a mass ratio of 1:4:3, the mass concentration of the composite emulsifier in the composite emulsifier aqueous solution is 50 wt%, and the mass ratio of the core material oil phase, the octenyl succinic anhydride starch ester - ethanol solution, the aqueous polyurethane prepolymer, and the composite emulsifier aqueous solution is 1:3:2:4;

[0058] A preparation method of a photochromic pigment, comprising the following steps:

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

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

[0061] Example 2

[0062] A photochromic pigment, comprising the following components in parts by mass: 60 parts of water, 35 parts of a waterborne film-forming agent, 15 parts of photochromic microcapsules, 2 parts of a light stabilizer, 5 parts of a thickener, 1 part of a dispersant, 1 part of color powder, 0.3 part of a pH regulator, 0.2 part of an antifoaming agent, and 0.3 part of a preservative;

[0063] The waterborne film-forming agent is a waterborne acrylic emulsion, the light stabilizer is a UV-531 light stabilizer, the thickener is PEG-20000, the dispersant is a polyether-modified silicone, the pH regulator is aminomethylpropanol, the antifoaming agent is a silicone oxygen-containing antifoaming agent, and the preservative is isothiazolinone;

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

[0065] (1) Mix and stir a photochromic material and an oily solvent evenly to obtain a core material oil phase; wherein, the photochromic material is spirooxazine, the oily solvent is 150# solvent oil, and the core material oil phase contains 5 wt% of the photochromic material;

[0066] (2) Uniformly disperse octenyl succinic anhydride starch ester in an ethanol aqueous solution to obtain an octenyl succinic anhydride starch ester-ethanol solution; wherein, the volume concentration of the ethanol aqueous solution is 70%, and the octenyl succinic anhydride starch ester-ethanol solution contains 5 wt% of octenyl succinic anhydride starch ester;

[0067] (3) Mix polypropylene glycol, 2,4-toluene diisocyanate and a catalyst, heat up to 70 °C, keep the temperature for reaction for 2 h, add 2,2-dimethylolpropionic acid under the heat preservation condition, continue the reaction for 2 h, and add acetone during the period to reduce the viscosity to below 1000 mPa·s to obtain an aqueous polyurethane prepolymer; wherein, the catalyst is dibutyltin dilaurate, and the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, the 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 anhydride starch ester-ethanol solution obtained in step (2), carry out shear emulsification to obtain an O / W type emulsion, add the aqueous polyurethane prepolymer obtained in step (3) and an aqueous solution of a compound emulsifier to the O / W type emulsion, stir and disperse evenly, heat up to 90 °C to form a microcapsule emulsion, at an inlet air temperature of 120 °C, a feeding rate of 300 mL / h, and an inlet air rate of 150 m 3Spray drying is carried out under the condition of / h to obtain the photochromic microcapsules; wherein, the composite emulsifier is a composition of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate with a mass ratio of 1:2:5, the mass concentration of the composite emulsifier in the aqueous solution of the composite emulsifier is 30 wt%, and the mass ratio of the core material oil phase, octenyl succinic anhydride starch ester-ethanol solution, aqueous polyurethane prepolymer and aqueous solution of the composite emulsifier is 1:2:1:1;

[0069] A preparation method of a photochromic pigment comprises the following steps:

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

[0071] S2. Add aqueous silica sol and a pH regulator to the first mixture and stir at a rotation speed of 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 mass: 80 parts of water, 50 parts of an aqueous film-forming agent, 20 parts of photochromic microcapsules, 5 parts of a light stabilizer, 1 part of a thickener, 5 parts of a dispersant, 5 parts of color powder, 1 part of a pH regulator, 0.5 part of a defoamer and 0.1 part of a 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 silicone, the pH regulator is aminomethyl propanol, the defoamer is a silicone oxygen alkane defoamer, and the preservative is isothiazolinone;

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

[0076] (1) Mix and stir a photochromic material and an oily solvent evenly to obtain a core material oil phase; wherein, the photochromic material is spiropyran, the oily solvent is 120# solvent oil, and the core material oil phase contains 15 wt% of the photochromic material;

[0077] (2) Uniformly disperse octenyl succinic anhydride starch ester in an ethanol aqueous solution to obtain an octenyl succinic anhydride starch ester-ethanol solution; wherein, the volume concentration of the ethanol aqueous solution is 80%, and the octenyl succinic anhydride starch ester-ethanol solution contains 15 wt% of octenyl succinic anhydride starch ester;

[0078] (3) Mix polypropylene glycol, 2,4-toluene diisocyanate and a catalyst, heat up to 80 °C, keep the temperature for reaction for 1 h, add 2,2-dimethylolpropionic acid under the insulation condition, and continue the reaction for 1 h. During this period, add acetone to reduce the viscosity to below 1000 mPa·s to obtain an aqueous polyurethane prepolymer; wherein, the catalyst is dibutyltin dilaurate, and the mass ratio of polypropylene glycol, 2,4-toluene diisocyanate, the 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 anhydride starch ester-ethanol solution obtained in step (2), shear and emulsify to obtain an O / W type emulsion. Add the aqueous polyurethane prepolymer obtained in step (3) and an aqueous solution of a composite emulsifier to the O / W type emulsion, stir and disperse evenly, heat up to 80 °C to form a microcapsule emulsion, and perform spray drying under the conditions of an inlet air temperature of 120 °C, a feeding rate of 300 mL / h, and an inlet air rate of 150 m 3 / h to obtain the photochromic microcapsules; wherein, the composite emulsifier is a composition of polyvinyl alcohol, polyglycerol-10 laurate and hydroxypropyl distarch phosphate with a mass ratio of 1:5:2, the mass concentration of the composite emulsifier in the aqueous solution of the composite emulsifier is 60 wt%, and the mass ratio of the core material oil phase, the octenyl succinic anhydride starch ester-ethanol solution, the aqueous polyurethane prepolymer and the aqueous solution of the composite emulsifier is 1:5:3:6;

[0080] A method for preparing a photochromic pigment, comprising the following steps:

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

[0082] S2. Add aqueous silica sol and a pH regulator to the first mixture, and stir at a rotation speed of 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 addition amount of the composite emulsifier remains unchanged, 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 addition amount of the composite emulsifier remains unchanged, 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 lies in that: in step (4), no aqueous polyurethane prepolymer is added, and an equal amount of octenyl succinic anhydride starch ester is used to make up for the missing amount.

[0089] Comparative Example 2

[0090] The difference between Comparative Example 2 and Example 1 lies in that: in step (4), no octenyl succinic anhydride starch ester is added, and an equal amount of aqueous polyurethane prepolymer is used to make up for the missing amount.

[0091] Comparative Example 3

[0092] The difference between Comparative Example 3 and Example 1 lies in that: the addition amount of the compound emulsifier remains unchanged, no polyvinyl alcohol is added, and a mixture of polyglyceryl-10 laurate and hydroxypropyl distarch phosphate with a mass ratio of 4:3 is used to make up for the missing amount.

[0093] Comparative Example 4

[0094] The difference between Comparative Example 4 and Example 1 lies in that: the addition amount of the compound emulsifier remains unchanged, no polyglyceryl-10 laurate is added, and a mixture of polyvinyl alcohol and hydroxypropyl distarch phosphate with a mass ratio of 1:3 is used to make up for the missing amount.

[0095] Comparative Example 5

[0096] The difference between Comparative Example 5 and Example 1 lies in that: the addition amount of the compound emulsifier remains unchanged, no hydroxypropyl distarch phosphate is added, and a mixture of polyvinyl alcohol and polyglyceryl-10 laurate with a mass ratio of 1:4 is used to make up for the missing amount.

[0097] Performance test

[0098] 1. Embedding rate test of photochromic microcapsules

[0099] Specific test method: Weigh 1 g of microcapsules into a beaker, add 50 mL of n-hexane and shake for 1 min, filter, collect the filtrate and rotary evaporate it to a constant mass to obtain the mass W1 of the oil on the surface of the microcapsules; take the same mass of microcapsules into a beaker, add 50 mL of absolute ethanol, break the microcapsules by an ultrasonic cell disruptor, centrifuge to obtain the supernatant, repeat the above operation twice for the precipitate, combine the supernatants and rotary evaporate them to a constant mass to obtain the total oil mass W2 of the microcapsules. The calculation formula for the embedding rate is as follows: Specific data are shown in Table 1.

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

[0101] Specific test method: According to the ISO105-B02 method, 5 g of the color-changing pigments of Examples 1-5 and Comparative Examples 1-5 in equal amounts 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 were measured using a colorimetric instrument under the excitation of ultraviolet light (wavelengths 254 nm and 365 nm), and the color difference ΔE was calculated, as shown in Table 1. The color difference ΔE represents the magnitude of 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 Encapsulation rate and chemical fatigue resistance test results of each group of samples

[0103]

[0104]

[0105] Combining 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 relatively optimal level.

[0106] Combining the results of Example 1 and Comparative Examples 1-2 in Table 1, it can be seen that when waterborne polyurethane and octenyl succinic anhydride starch ester are lacking, the degree of crosslinking 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 light irradiation, indicating that the wall material structure formed by the waterborne polyurethane prepolymer and octenyl succinic anhydride starch ester can synergistically improve the protection ability of the microcapsules for the photochromic material and reduce the influence of the external environment (light, heat, oxygen).

[0107] Combining the results of Example 1 and Comparative Examples 3-5 in Table 1, it can be seen that the lack of any one of the composite emulsifiers will disrupt the emulsification balance, resulting in uneven particle size, core material leakage or a decrease in mechanical strength, indicating that the composite emulsifier synergistically improves the environmental tolerance and stability of the photochromic core material.

[0108] In summary, the microcapsules of the present invention adopt specific wall materials and emulsifiers, enabling the wall material to form a denser interfacial film during the microencapsulation process, which can prevent the rupture of the wall material, ensure the functional stability of the photochromic material, and improve 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 rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A photochromic pigment, characterized in that, It comprises the following components in parts by mass: 60 - 80 parts of water, 35 - 50 parts of waterborne film-forming agent, 15 - 20 parts of photochromic microcapsules, 2 - 5 parts of light stabilizer, 1 - 5 parts of thickener, 1 - 5 parts of dispersant, 1 - 5 parts of color powder, 0.3 - 1 part of pH regulator, 0.2 - 0.5 part of defoamer, and 0.1 - 0.3 part of preservative; wherein, the waterborne film-forming agent is a waterborne acrylic emulsion; The preparation method of the photochromic microcapsules comprises the following steps: (1) Mix and stir evenly the photochromic material and the oily solvent to obtain the core material oil phase, and the core material oil phase contains 5 - 15wt% of the photochromic material; (2) Uniformly disperse octenyl succinic anhydride starch ester in the ethanol aqueous solution to obtain the octenyl succinic anhydride starch ester - ethanol solution, and the octenyl succinic anhydride starch ester - ethanol solution contains 2 - 8wt% of octenyl succinic anhydride starch ester; (3) Mix polypropylene glycol, 2,4 - tolylene diisocyanate and the catalyst, heat up to 70 - 80 °C, keep the temperature for reaction for 1 - 2 h, add 2,2 - dimethylolpropionic acid under the temperature - keeping condition, continue the reaction for 1 - 2 h, and add a small amount of acetone to adjust the viscosity during this period to obtain the waterborne polyurethane prepolymer; (4) Mix the core material oil phase obtained in step (1) and the octenyl succinic anhydride starch ester - ethanol solution obtained in step (2), perform shear emulsification to obtain an O / W type emulsion, add the waterborne polyurethane prepolymer obtained in step (3) and the composite emulsifier aqueous solution to the O / W type emulsion, stir and disperse evenly, heat up to 80 - 90 °C to form the microcapsule emulsion, and perform spray drying to obtain the photochromic microcapsules, wherein, 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 composite emulsifier aqueous solution is 30 - 60wt%.

2. The photochromic pigment according to claim 1, wherein In step (1), the photochromic material is at least one of spiropyran, spirooxazine, 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 according to claim 1, characterized in that, In step (2), the volume concentration of the ethanol aqueous solution is 70 - 80%.

4. The photochromic pigment according to claim 1, characterized in that, In step (3), the mass ratio of polypropylene glycol, 2,4 - tolylene diisocyanate, the 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 add acetone to reduce the viscosity to below 1000 mPa·s.

5. The photochromic pigment according to claim 1, characterized in that, In step (4), the mass ratio of the core material oil phase, the octenyl succinic anhydride starch ester - ethanol solution, the waterborne polyurethane prepolymer and the composite emulsifier aqueous solution is 1:(2 - 5):(1 - 3):(1 - 6).

6. The photochromic pigment according to claim 1, characterized in that, In step (4), the mass ratio of polyvinyl alcohol, polyglycerol - 10 laurate and hydroxypropyl distarch phosphate is 1:(2 - 5):(2 - 5).

7. The photochromic pigment according to claim 1, wherein Each component in the pigment is selected from at least one of the following (I) - (VI): (I) The light stabilizer is UV - 531 light stabilizer; (II) The thickener is PEG - 20000; (III) The dispersant is a polyether-modified silicone; (IV) The pH regulator is aminomethyl propanol; (V) The defoamer is a silicone oxygen alkane defoamer; (VI) The preservative is isothiazolinone.

8. The preparation method of the optically variable pigment according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Mix and stir water, a waterborne film-forming agent, photochromic microcapsules, color powder, defoamer, thickener, dispersant and preservative to obtain a first mixture; S2. Add a light stabilizer and a pH regulator to the first mixture, and stir evenly to obtain the color-changing pigment.

9. The preparation method of the photochromic pigment according to claim 8, characterized in that, In the step S1, the stirring speed is 500-1000 r / min and the time is 20-30 min; and / or in the step S2, the stirring speed is 300-500 r / min and the time is 10-20 min.

10. Use of the photochromic pigment according to any one of claims 1-7 in the preparation of a photosensitive coating.

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