A pressure sensitive developing spray, its preparation method and use

Abstract

The application provides a pressure-sensitive color developing spray agent and a preparation method and application thereof, and belongs to the technical field of spray color developing materials. A color developing agent and diaryl ethane are mixed to obtain a capsule core material; the capsule core material is mixed with a phenolic aldehyde epoxy resin to obtain a mixed solution; the mixed solution, a dispersant aqueous solution and a curing agent are mixed to carry out a curing reaction to obtain a phenolic aldehyde epoxy resin microcapsule; the phenolic aldehyde epoxy resin microcapsule is mixed with a gelatin-arabic gum mixed solution to carry out gelation to obtain a gelated microcapsule; the microcapsule with a transparent film layer and a crosslinking agent are mixed to carry out a crosslinking reaction to obtain a double-layer microcapsule; and the double-layer microcapsule, an aqueous resin aqueous solution and a color developing agent are mixed to obtain the pressure-sensitive color developing spray agent. The pressure-sensitive color developing spray agent can be used by spraying, and color development under pressure is ensured, that is, color development is realized by touching and pressing, and no color development is realized without external pressure.

Description

Technical Field

[0001] This invention relates to the field of spray colorimetric materials technology, and in particular to a pressure-sensitive colorimetric spray, its preparation method, and its application. Background Technology

[0002] Without video surveillance, people cannot know whether confidential materials have been viewed or examined, or whether key parts of controlled equipment have been manipulated or modified by others. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a pressure-sensitive color-developing spray, its preparation method, and its application. The pressure-sensitive color-developing spray prepared by this invention will develop color upon pressure or contact, thereby alerting security personnel.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a pressure-sensitive colorimetric spray, comprising the following steps:

[0006] The colorant and diarylethane are mixed to obtain the core material;

[0007] The core material is mixed with phenolic epoxy resin to obtain a mixed solution;

[0008] The mixed solution, the dispersant aqueous solution and the curing agent are mixed and subjected to a curing reaction to obtain phenolic epoxy resin microcapsules;

[0009] The phenolic epoxy resin microcapsules were mixed with a gelatin-gum arabic mixture and then gelled to obtain gelled microcapsules.

[0010] The gelled microcapsules and crosslinking agent were mixed and subjected to a crosslinking reaction to obtain bilayer microcapsules;

[0011] The pressure-sensitive color-developing spray is obtained by mixing the bilayer microcapsules, the aqueous resin solution, and the color developer.

[0012] Preferably, the colorant in the core material has a mass fraction of 1-10%.

[0013] Preferably, the color-developing agent includes phthalide color-developing agents and / or fluorane color-developing agents, wherein the phthalide color-developing agent includes crystal violet lactone.

[0014] Preferably, the mass ratio of the core material to the phenolic epoxy resin is 1 to 1.5:1.

[0015] Preferably, the curing reaction includes a first curing and a second curing performed sequentially, wherein the temperature of the first curing is 40-50°C and the holding time is 10-15 min, and the temperature of the second curing is 60-70°C and the holding time is 2.5-3 h.

[0016] Preferably, the mass ratio of gelatin in the phenolic epoxy resin microcapsule to gelatin-gum arabic mixture is 1:5 to 2:1, and the mass ratio of gelatin to gum arabic in the gelatin-gum arabic mixture is 0.5 to 1:1 to 2.

[0017] Preferably, the gelation time is 1.5 to 4 hours, and the gelation is carried out under rotation at a speed of 100 to 200 rpm.

[0018] Preferably, the aqueous resin in the aqueous resin solution includes one or more of the following: aqueous polyurethane, polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymaleic anhydride, polyethylene glycol, and gum arabic.

[0019] The present invention also provides a pressure-sensitive colorimetric spray prepared by the preparation method described above, comprising bilayer microcapsules, aqueous resin, colorimetric agent and water.

[0020] This invention also provides the application of the pressure-sensitive color-developing spray described above as a spray color-developing material in the field of confidentiality.

[0021] This invention provides a method for preparing a pressure-sensitive colorimetric spray, comprising the following steps: mixing a colorimetric agent and diarylethane to obtain a core material; mixing the core material with phenolic epoxy resin to obtain a mixed solution; mixing the mixed solution, an aqueous dispersant solution, and a curing agent to perform a curing reaction to obtain phenolic epoxy resin microcapsules; mixing the phenolic epoxy resin microcapsules with a gelatin-gum arabic mixture and then gelling to obtain gelled microcapsules; mixing the gelled microcapsules with a crosslinking agent to perform a crosslinking reaction to obtain bilayer microcapsules; and mixing the bilayer microcapsules, an aqueous resin solution, and a colorimetric agent to obtain the pressure-sensitive colorimetric spray.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention mixes an aqueous resin solution with bilayer microcapsules, ensuring that the bilayer microcapsules do not rupture after spraying. Simultaneously, the dried aqueous resin imparts a specific macroscopic rupture strength to the bilayer microcapsules, thereby controlling the detection sensitivity. The pressure-sensitive colorimetric spray prepared by this invention possesses sealing properties and good mechanical strength. The sealing property originates from the bilayer microcapsules, while the mechanical strength comes from the dried aqueous resin. This pressure-sensitive colorimetric spray can be sprayed and ensures that it ruptures under pressure to produce color, meaning it develops color upon contact with pressure and does not develop color without external pressure. It is primarily used in confidential applications.

[0024] The present invention also provides the application of the pressure-sensitive color-developing spray described above as a spray color-developing material in the field of confidentiality. It can form a thin layer that is not easily detected on the surface of an object. This thin layer will develop color after being pressed or touched, thereby alerting the confidentiality management personnel. Attached Figure Description

[0025] Figure 1 Metallographic micrograph of the phenolic epoxy resin microcapsules prepared in Example 1;

[0026] Figure 2 This is an optical microscope image of the bilayer microcapsules removed during the reaction in Example 1;

[0027] Figure 3 An optical microscope image of the bilayer microcapsules prepared in Example 1;

[0028] Figure 4 The image shows a comparison of the pressure-sensitive color-developing spray prepared in Example 1 before and after color development.

[0029] Figure 5 The image shows a comparison before and after color development of the pressure-sensitive color-developing spray prepared in Example 1. Detailed Implementation

[0030] This invention provides a method for preparing a pressure-sensitive colorimetric spray, comprising the following steps:

[0031] The colorant and diarylethane are mixed to obtain the core material;

[0032] The core material is mixed with phenolic epoxy resin to obtain a mixed solution;

[0033] The mixed solution, the dispersant aqueous solution and the curing agent are mixed and subjected to a curing reaction to obtain phenolic epoxy resin microcapsules;

[0034] The phenolic epoxy resin microcapsules were mixed with a gelatin-gum arabic mixture and then gelled to obtain gelled microcapsules.

[0035] The gelled microcapsules and crosslinking agent were mixed and subjected to a crosslinking reaction to obtain bilayer microcapsules;

[0036] The pressure-sensitive color-developing spray is obtained by mixing the bilayer microcapsules, the aqueous resin solution, and the color developer.

[0037] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0038] This invention mixes a colorant and diarylethane to obtain a core material.

[0039] In this invention, the mass fraction of the colorant in the core material is preferably 1-10%, more preferably 4-6%, and most preferably 5%.

[0040] In this invention, the color-developing agent preferably includes phthalide color-developing agents and / or fluorane color-developing agents, and the phthalide color-developing agent preferably includes crystal violet lactone (CVL).

[0041] In this invention, the mixing temperature is preferably 90°C. This invention does not impose any particular limitation on the specific mixing method; any method well-known to those skilled in the art can be used.

[0042] After obtaining the core material, the present invention mixes the core material with phenolic epoxy resin to obtain a mixed solution.

[0043] In this invention, the phenolic epoxy resin includes phenolic epoxy resin or urea-formaldehyde resin.

[0044] In this invention, the mass ratio of the core material to the phenolic epoxy resin is preferably 1 to 1.5:1.

[0045] In this invention, the mixing temperature is preferably 60°C. This invention does not impose any particular limitation on the specific mixing method; any method well-known to those skilled in the art can be used.

[0046] After obtaining the mixed solution, the present invention mixes the mixed solution, the dispersant aqueous solution and the curing agent to carry out a curing reaction to obtain phenolic epoxy resin microcapsules.

[0047] In this invention, the dispersant in the aqueous dispersant solution preferably includes gum arabic.

[0048] In this invention, the concentration of the dispersant aqueous solution is preferably 1 to 10 g / mL, more preferably 3 g / mL.

[0049] In this invention, the dispersant is preferably dissolved in water to obtain the dispersant aqueous solution, which acts as a stabilizer to stably disperse the oil droplets of the core material (oil phase) in the water.

[0050] In this invention, the mass ratio of the core material to the dispersant is preferably 1 to 10:1.

[0051] In this invention, the preferred mass ratio of the phenolic epoxy resin to the curing agent is 1:0.5 to 2.

[0052] In this invention, the curing agent preferably includes T31, 590, C20 curing agent, ethylenediamine, m-phenylenediamine, phenylenediamine, polyamide, or diethylenetriamine.

[0053] In this invention, the mixed solution and the dispersant aqueous solution are first heated to 60°C. After dispersion for 5-10 minutes, the system temperature drops to 50°C. The reactants are then placed in a reaction flask, and the curing agent is added.

[0054] In this invention, the curing reaction preferably includes a first curing and a second curing performed sequentially. The temperature of the first curing is preferably 40-50°C, and the holding time is preferably 10-15 min. During the first curing process, the phenolic epoxy resin has already started to react, while the temperature of the small oil droplets themselves does not change significantly. Therefore, the particle size is well maintained and will not aggregate into large oil droplets due to temperature rise. The temperature of the second curing is preferably 60-70°C, and the holding time is preferably 2.5-3 h.

[0055] After obtaining phenolic epoxy resin microcapsules, the present invention mixes the phenolic epoxy resin microcapsules with a gelatin-gum arabic mixture and then gels them to obtain gelled microcapsules.

[0056] In this invention, the preferred mass ratio of gelatin in the phenolic epoxy resin microcapsule and gelatin-gum arabic mixture is 1:5 to 2:1, and the preferred mass ratio of gelatin to gum arabic in the gelatin-gum arabic mixture is 0.5 to 1:1 to 2.

[0057] The present invention preferably involves mixing an aqueous solution of gelatin and an aqueous solution of gum arabic to obtain the gelatin-gum arabic mixture.

[0058] In this invention, if the mixed solution obtained by mixing the gelatin aqueous solution and the gum arabic aqueous solution is pale yellow, and if impurities are visible to the naked eye, it is preferable to remove the impurities by filtration.

[0059] In this invention, the mixing speed is preferably 100 rpm and the temperature is preferably 45°C.

[0060] In this invention, the concentrations of both the gelatin aqueous solution and the gum arabic aqueous solution are preferably 0.05 g / mL.

[0061] In this invention, gelatin is preferably mixed with water, heated to 40°C, and then stirred to accelerate dissolution, thereby obtaining the gelatin aqueous solution.

[0062] The present invention preferably involves mixing gum arabic with water to obtain the gum arabic aqueous solution.

[0063] After obtaining the gelatin-gum arabic mixture, the present invention preferably performs quality inspection on the gelatin-gum arabic mixture to determine whether the raw materials are qualified. The quality inspection preferably includes the following steps:

[0064] Take the gelatin-gum arabic mixture and add HAC (acetic acid) solution to adjust the pH value to 3-5 (more preferably 4). If it re-coagulates and turns milky white, it proves that the raw material is qualified.

[0065] In this invention, the mass fraction of the HAC solution is preferably 5-15%, more preferably 10%. The acetic acid in the HAC solution is an organic acid, which has a good affinity for gelatin and gum arabic.

[0066] In this invention, the gelation temperature is preferably room temperature, the time is preferably 1.5 to 4 hours, the gelation is carried out under rotation, and the rotation speed is preferably 100 to 200 rpm.

[0067] In this invention, it is preferable to monitor the reaction process during the gelation process, and the monitoring preferably includes the following steps:

[0068] After the phenolic epoxy resin microcapsules are mixed with the gelatin-gum arabic mixture, they are dispersed at a stable stirring speed. The pH value of the system is adjusted starting with the minimum stirring speed that can maintain the stability of the system. After the system is dispersed and stabilized, HAC solution (preferably 5-15% by mass, more preferably 10%) is added dropwise to adjust the pH value to 3-5 (preferably 4). The stirring speed is kept stable at 100-200 rpm. When a sample is taken for observation, a very thin transparent film layer forms around the phenolic epoxy resin microcapsules, which is easily broken. At this time, the reaction is not complete. The gelation continues. After the reaction has been carried out for a period of time, the system is allowed to cool naturally to room temperature and then an ice bath is started. When the system temperature drops below 10°C, the system is observed to become viscous. When a sample is taken for observation, the capsules are intact. This indicates that the gelation has been completed.

[0069] In this invention, the acetic acid in the HAC solution is an organic acid, which has a good affinity for gelatin and gum arabic.

[0070] After the gelation is completed, the present invention preferably washes the obtained gelation product with water to obtain the gelated microcapsules.

[0071] In this invention, the water washing is preferably performed 3 to 5 times.

[0072] In this invention, deionized water is added to the gelled product, stirred, and after stirring is stopped and the bilayer microcapsules settle to the bottom, the turbid aqueous solution on top is poured out, and water is added for a second water wash. The water washing steps are then repeated.

[0073] After obtaining the gelled microcapsules, the present invention mixes the gelled microcapsules with a crosslinking agent to carry out a crosslinking reaction to obtain bilayer microcapsules.

[0074] In this invention, the crosslinking agent is preferably formaldehyde.

[0075] In this invention, the volume ratio of the gelled microcapsules to the crosslinking agent is preferably 10:2 to 4, more preferably 10:3.

[0076] In this invention, the crosslinking reaction is preferably carried out at a pH of 9 to 10, and the alkaline condition is preferably provided by a NaOH solution, wherein the mass fraction of the NaOH solution is preferably 5 to 15%, more preferably 10%.

[0077] In this invention, the temperature of the crosslinking reaction is preferably 10°C, and during the crosslinking reaction, it is preferable to take samples until the capsule is placed on glass or paper without breaking, that is, the double-layer microcapsule is stably formed.

[0078] In this invention, after the crosslinking reaction is completed, it is preferable to wash with water and concentrate in sequence to obtain a double-layer microcapsule concentrate, which is used for subsequent reactions.

[0079] In this invention, the mass fraction of the bilayer microcapsules in the bilayer microcapsule concentrate is preferably 70% to 90%.

[0080] After obtaining the bilayer microcapsules, the present invention mixes the bilayer microcapsules, an aqueous resin solution, and a color developer to obtain the pressure-sensitive color-developing spray.

[0081] In this invention, the aqueous resin in the aqueous resin solution preferably includes one or more of the following: aqueous polyurethane, polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymaleic anhydride, polyethylene glycol, and gum arabic.

[0082] In this invention, the mass fraction of the aqueous resin solution is preferably 2%.

[0083] In this invention, the colorimetric agent preferably includes sodium dodecyl sulfate or bisphenol A.

[0084] In this invention, the preferred mass ratio of the bilayer microcapsules to the aqueous resin in the aqueous resin solution is 0.5-1:1-2.

[0085] In this invention, the mass ratio of the bilayer microcapsule to the colorimetric agent is preferably 10:1 to 10.

[0086] In this invention, the double-layer microcapsules and aqueous resin solution are first mixed to obtain a mixture, and then the mixture is stirred with a color developer for 10-30 minutes and then allowed to stand for 24 hours to obtain the pressure-sensitive color developer spray.

[0087] In this invention, the mass fraction of the color developer in the pressure-sensitive color-developing spray is preferably 0.5-10%, more preferably 1-5%.

[0088] The present invention also provides a pressure-sensitive colorimetric spray prepared by the preparation method described above, comprising bilayer microcapsules, aqueous resin, colorimetric agent and water.

[0089] In this invention, the diameter of the bilayer microcapsule is preferably 1-50 μm, more preferably 20-30 μm; the core material of the bilayer microcapsule includes diarylethane and a colorant, the first layer of the capsule wall is phenolic epoxy resin, and the second layer of the capsule wall is prepared by gelatin-gum arabic coagulation.

[0090] In this invention, the volume fraction of the bilayer microcapsules in the pressure-sensitive colorimetric spray is preferably 0.5% to 25%, more preferably 1% to 20%, and most preferably 5% to 15%.

[0091] In this invention, the mass fraction of the aqueous resin in the pressure-sensitive colorimetric spray is preferably 0.05% to 10%, more preferably 1% to 5%.

[0092] This invention also provides the application of the pressure-sensitive color-developing spray described above as a spray color-developing material in the field of confidentiality.

[0093] In this invention, the application preferably includes the following steps:

[0094] Fill the pressure-sensitive colorimetric spray into a sprayer, shake well, and then spray.

[0095] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0096] Raw materials and equipment:

[0097] The solvent in the capsule core is diarylethane, and the colorant is CVL (crystal violet lactone).

[0098] Capsule wall material: phenolic epoxy resin, Wuxi Resin Factory of Bluestar Chemical New Materials Co., Ltd., and water-soluble curing agent Tianjin Ningping Chemical Products Co., Ltd.;

[0099] Dispersant: Gum arabic powder, chemically pure, from Xilong Chemical Plant, Shantou City, Guangdong Province;

[0100] Experimental equipment: D2004W electric mixer (Shanghai Sile Instrument Co., Ltd.), XHF-D high-speed disperser (homogenizer, Ningbo Xinzhi Biotechnology Co., Ltd.), XJP-H200 metallographic microscope (JVC Corporation), S3500 laser particle size analyzer (Microtrac, USA).

[0101] Example 1

[0102] 1. Preparation of bilayer microcapsules

[0103] (1) Preparation of core material: CVL was heated to 90°C and dissolved in diarylethane to prepare a 10% (w / w) CVL solution (core material, 1g). Then, 1g of phenolic epoxy resin was dissolved in the core material at 60°C to obtain a mixture. 5g of gum arabic was dissolved in 150mL of water as a dispersant for the core material.

[0104] (2) Preparation of phenolic epoxy resin microcapsules: Before homogenization, the mixture and dispersant in (1) were heated to 60°C. After dispersion for 9.9 min, the system temperature dropped to 50°C. The resulting reactants were placed in a reaction flask, 1 g of curing agent was added, and the reaction environment temperature was adjusted to 40°C. After curing for 10 min, the temperature was increased to 70°C, and then reacted at 70°C for 2.5 h to obtain phenolic epoxy resin microcapsules (average particle size 30 μm).

[0105] Figure 1 The metallographic micrograph of the prepared phenolic epoxy resin microcapsules shows that the average particle size is 30 μm.

[0106] (3) Preparation of the second capsule wall: Prepare 2.5g gelatin / 50mL aqueous solution and 2.5g gum arabic / 50mL aqueous solution respectively. Heat the gelatin to 40℃ and stir to accelerate dissolution. Mix the gelatin aqueous solution (containing 2.5g gelatin) and gum arabic aqueous solution (containing 2.5g gum arabic) (the mixture of gelatin and gum arabic is pale yellow; if impurities are visible to the naked eye, they can be removed by filtration). Add the mixture to a three-necked flask, control the rotation speed at 100rpm, and the temperature at 45℃. At this time, take a small amount of the mixed solution and add 15% HAC solution to adjust the pH value to 3-5. The solution should undergo re-coagulation and turn milky white, which can be used to determine that the raw materials are fine. Add 10mL of concentrated phenolic epoxy resin microcapsules (washed with water) to the gelatin-gum arabic solution (the mass ratio of phenolic epoxy resin to gelatin is 1:5), and disperse at a stable stirring speed. Start adjusting the pH value of the system at the minimum rotation speed that can maintain the stability of the system. After the system has dispersed and stabilized, a 15% HAC solution was added dropwise to adjust the pH to 3-5. The reaction was continued for 1.5 hours at a stable rotation speed of 100 rpm. A sample was taken for observation; a very thin, transparent film formed around the epoxy resin microcapsules, which was easily ruptured. Heating was stopped, and the system was allowed to cool naturally to room temperature. An ice bath was then initiated. When the system temperature dropped below 10°C, the system became viscous. A sample was taken for observation; the capsules remained intact. Deionized water was slowly added with slight stirring. After stirring was stopped and the bilayer microcapsules settled to the bottom, the turbid upper aqueous solution was poured off, and water was added for a second wash, three times. After the system became clear, 2 mL of formaldehyde was added as a crosslinking agent, and the pH was adjusted to 9-10 with a 10% NaOH solution. The capsule shells were solidified by slow stirring below 10°C. Samples were taken until the capsules were stably formed (they did not break when placed on glass or paper), resulting in a solution containing bilayer microcapsules. This solution was then concentrated to obtain a final solution containing bilayer microcapsules.

[0107] Figure 2 This is an optical microscope image of the bilayered microcapsules removed during the reaction; the surrounding transparent spherical objects are uncoated gelatin-gum arabic. Figure 3 An optical microscope image of the prepared bilayer microcapsules shows the formation of a second capsule wall.

[0108] 2. Preparation of pressure-sensitive colorimetric spray

[0109] Take 10 mL of the concentrated bilayer microcapsule concentrate (70% by mass) and mix it with a 2% aqueous polyurethane solution to obtain a mixture. Simultaneously, dissolve sodium dodecyl sulfate in the mixture and stir for 10 min, then let it stand for 24 h. Finally, fill the mixture into a sprayer. Shake well before use and spray. Perform a pressure-sensitive test.

[0110] The obtained pressure-sensitive colorimetric spray contains 10% colorimetric agent by mass, 25% bilayer microcapsules by volume, and 10% water-based resin by mass.

[0111] Figure 4 This is a comparison image of the pressure-sensitive color-developing spray prepared in Example 1 before and after color development. Figure 5 The comparison diagram before and after color development of the pressure-sensitive color-developing spray prepared in Example 1 shows that the spray of the present invention will develop color after being pressed or touched.

[0112] The fracture strength of the double-layer microcapsules was tested using an electronic balance with a strength of 0.0001%.

[0113] The bilayer microcapsule particles were placed on the tray of an electronic balance (JinCe QL-E series electronic analytical balance, accuracy d = 0.0001g). Vertical pressure was slowly applied to the bilayer microcapsule using a probe until it ruptured. The value displayed on the balance increased and then decreased. The maximum value during this process was recorded as the rupture pressure of the bilayer microcapsule. Several bilayer microcapsules were randomly selected for testing, and the results are shown in Table 1. The average value in Table 1 was calculated to obtain an average strength of 0.0033g, or 3.3 milligram force.

[0114] Table 1. Test results of the burst strength of the double-layered microcapsules

[0115]

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a pressure-sensitive colorimetric spray, characterized in that, Includes the following steps: The colorant and diarylethane are mixed to obtain the core material; The core material is mixed with phenolic epoxy resin to obtain a mixed solution; The mixed solution, the dispersant aqueous solution and the curing agent are mixed and subjected to a curing reaction to obtain phenolic epoxy resin microcapsules; The phenolic epoxy resin microcapsules were mixed with a gelatin-gum arabic mixture and then gelled to obtain gelled microcapsules. The gelled microcapsules and crosslinking agent were mixed and subjected to a crosslinking reaction to obtain bilayer microcapsules; The pressure-sensitive colorimetric spray is obtained by mixing the bilayer microcapsules, the aqueous resin solution, and the colorimetric agent. The mass ratio of the core material to the phenolic epoxy resin is 1:

1. The mass ratio of gelatin in the phenolic epoxy resin microcapsule and gelatin-gum arabic mixture is 1:5, and the mass ratio of gelatin to gum arabic in the gelatin-gum arabic mixture is 1:

1.

2. The preparation method according to claim 1, characterized in that, The colorant in the core material has a mass fraction of 1-10%.

3. The preparation method according to claim 1 or 2, characterized in that, The color-developing agent includes phthalide color-developing agents and / or fluorane color-developing agents, wherein the phthalide color-developing agent includes crystal violet lactone.

4. The preparation method according to claim 1, characterized in that, The curing reaction includes a first curing and a second curing performed sequentially. The temperature of the first curing is 40~50℃ and the holding time is 10~15min. The temperature of the second curing is 60~70℃ and the holding time is 2.5~3h.

5. The preparation method according to claim 1, characterized in that, The gelation time is 1.5 to 4 hours, and the gelation is carried out under rotation at a speed of 100 to 200 rpm.

6. The preparation method according to claim 1, characterized in that, The aqueous resin in the aqueous solution includes one or more of the following: aqueous polyurethane, polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymaleic anhydride, polyethylene glycol, and gum arabic.

7. The pressure-sensitive colorimetric spray prepared by the method according to any one of claims 1 to 6, characterized in that, It includes bilayer microcapsules, aqueous resin, color developer, and water.

8. The application of the pressure-sensitive colorimetric spray according to claim 7 as a spray colorimetric material in the field of confidentiality.

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