Pressure-sensitive developing spray as well as preparation method and application thereof

Abstract

The invention provides a pressure-sensitive color developing spray as well as a preparation method and application thereof, and belongs to the technical field of spray color developing materials. The preparation method comprises the following steps: mixing a color former with diarylethane to obtain a capsule core material; mixing the capsule core material with novolac epoxy resin to obtain a mixed solution; mixing the mixed solution, a dispersant aqueous solution and a curing agent for curing reaction to obtain the novolac epoxy resin microcapsule, mixing the novolac epoxy resin microcapsule with a gelatin-Arabic gum mixed solution, and then gelatinizing to obtain a gelatinized microcapsule; mixing the microcapsule containing the transparent film layer with a cross-linking agent for cross-linking reaction to obtain a double-layer microcapsule; and mixing the double-layer microcapsule, a water-based resin aqueous solution and a color developing agent to obtain the pressure-sensitive color developing spray. The pressure-sensitive color developing spray can be sprayed for use, and meanwhile, the pressure-sensitive color developing spray can be broken under pressure to develop color, that is, the pressure-sensitive color developing spray can develop color under pressure under touch, and does not develop color without external pressure.

Description

Technical Field

[0001] The invention relates to the technical field of spray color developing materials, and in particular to a pressure-sensitive color developing spray and a preparation method and application thereof. Background Art

[0002] In the absence of video surveillance, people have no way of knowing whether confidential materials have been read or viewed, or whether key parts of controlled equipment have been manipulated or set by others. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a pressure-sensitive color developing spray and its preparation method and application. The pressure-sensitive color developing spray prepared by the present invention will develop color after being pressed or touched, thereby prompting the confidentiality management personnel.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a pressure-sensitive color developing spray, comprising the following steps:

[0006] Mixing a coloring agent and diarylethane to obtain a capsule core material;

[0007] Mixing the capsule core material with phenolic epoxy resin to obtain a mixed solution;

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

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

[0010] The gelled microcapsules and a crosslinking agent are mixed to perform a crosslinking reaction to obtain double-layer microcapsules;

[0011] The double-layer microcapsule, aqueous resin solution and developer are mixed to obtain the pressure-sensitive color developing spray.

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

[0013] Preferably, the colorant includes a phthalide colorant and / or a fluorane colorant, and the phthalide colorant includes crystal violet lactone.

[0014] Preferably, the mass ratio of the capsule 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, the first curing temperature is 40-50°C, the insulation time is 10-15 minutes, and the second curing temperature is 60-70°C, the insulation time is 2.5-3 hours.

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

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

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

[0019] The present invention also provides a pressure-sensitive color-developing spray prepared by the preparation method described in the above technical solution, comprising a double-layer microcapsule, an aqueous resin, a color-developing agent and water.

[0020] The present invention also provides the use of the pressure-sensitive color-developing spray described in the above technical solution as a spray color-developing material in the field of confidentiality.

[0021] The invention provides a method for preparing a pressure-sensitive color-developing spray, comprising the following steps: mixing a color-developing agent and diarylethane to obtain a capsule core material; mixing the capsule core material with a phenolic epoxy resin to obtain a mixed solution; mixing the mixed solution, a dispersant aqueous solution and a curing agent to perform a curing reaction to obtain a phenolic epoxy resin microcapsule; mixing the phenolic epoxy resin microcapsule with a gelatin-gum arabic mixed solution and then gelling to obtain a gelled microcapsule; mixing the gelled microcapsule with a crosslinking agent to perform a crosslinking reaction to obtain a double-layer microcapsule; mixing the double-layer microcapsule, an aqueous resin aqueous solution and a color developer to obtain the pressure-sensitive color-developing spray.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention mixes an aqueous resin solution and double-layer microcapsules, and can prevent the double-layer microcapsules from rupturing after spraying. At the same time, the dried aqueous resin can give the double-layer microcapsules a specific macroscopic rupture strength, thereby adjusting the sensitivity of detection; the pressure-sensitive color-developing spray prepared by the present invention has sealing and good mechanical strength, the sealing is derived from the double-layer microcapsules, and the mechanical strength is derived from the aqueous resin after drying. The pressure-sensitive color-developing spray of the present invention can be sprayed for use, and at the same time ensures color development by rupture under pressure, that is, it can develop color when touched and under pressure, and will not develop color without external pressure, and is mainly used in the field of confidentiality.

[0024] The present invention also provides the use of the pressure-sensitive color-developing spray described in the above technical solution as a spray color-developing material in the field of confidentiality, which can form an imperceptible thin layer on the surface of an object. The thin layer will show color after being pressed or touched, thereby alerting the confidentiality management personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a metallographic microscope image of the phenolic epoxy resin microcapsules prepared in Example 1;

[0026] Figure 2 This is an optical microscope image of the double-layer microcapsules taken out during the reaction in Example 1;

[0027] Figure 3 This is an optical microscope image of the double-layer microcapsule prepared in Example 1;

[0028] Figure 4 This is a comparison diagram of the pressure-sensitive color developing spray prepared in Example 1 before and after color development;

[0029] Figure 5 The following is a comparison chart of the pressure-sensitive color developing spray prepared by repeating Example 1 before and after color development. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing a pressure-sensitive color developing spray, comprising the following steps:

[0031] Mixing a coloring agent and diarylethane to obtain a capsule core material;

[0032] Mixing the capsule core material with phenolic epoxy resin to obtain a mixed solution;

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

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

[0035] The gelled microcapsules and a crosslinking agent are mixed to perform a crosslinking reaction to obtain double-layer microcapsules;

[0036] The double-layer microcapsule, aqueous resin solution and developer are mixed to obtain the pressure-sensitive color developing spray.

[0037] In the present invention, unless otherwise specified, the raw materials used are all commercially available products in the art.

[0038] The invention mixes a coloring agent and diarylethane to obtain a capsule core material.

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

[0040] In the present invention, the coloring agent preferably includes a phthalide coloring agent and / or a fluorane coloring agent, and the phthalide coloring agent preferably includes crystal violet lactone (CVL).

[0041] In the present invention, the mixing temperature is preferably 90° C. The present invention has no particular limitation on the specific manner of mixing, and any manner well known to those skilled in the art may be used.

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

[0043] In the present invention, the novolac epoxy resin includes novolac epoxy resin or urea-formaldehyde resin.

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

[0045] In the present invention, the mixing temperature is preferably 60° C. The present invention has no particular limitation on the specific manner of mixing, and any manner well known to those skilled in the art may be used.

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

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

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

[0049] In the present 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 capsule core material (oil phase) in the water.

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

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

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

[0053] In the present invention, the mixed solution and the dispersant aqueous solution are preferably heated to 60°C, and after being dispersed for 5 to 10 minutes, the system temperature drops to 50°C, the reactants are placed in a reaction bottle, and the curing agent is added.

[0054] In the present invention, the curing reaction preferably includes a first curing and a second curing performed in sequence. The temperature of the first curing is preferably 40-50°C, and the insulation time is preferably 10-15 minutes. During the first curing process, the phenolic epoxy resin has begun to react, while the temperature of the small oil droplets themselves has not changed much, so the particle size is well maintained and will not aggregate into large oil droplets due to temperature increase; the temperature of the second curing is preferably 60-70°C, and the insulation time is preferably 2.5-3 hours.

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

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

[0057] In the present invention, preferably, a gelatin aqueous solution and a gum arabic aqueous solution are mixed to obtain the gelatin-gum arabic mixed solution.

[0058] In the present invention, if the mixed solution obtained by mixing the aqueous gelatin solution and the aqueous gum arabic solution is light yellow, if there are impurities observed with the naked eye, it is preferred to perform suction filtration to remove the impurities.

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

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

[0061] In the present invention, gelatin and water are preferably mixed, heated to 40° C., and then stirred to accelerate dissolution to obtain the gelatin aqueous solution.

[0062] In the present invention, gum arabic is preferably mixed with water to obtain the gum arabic aqueous solution.

[0063] After obtaining the gelatin-gum arabic mixture, the present invention preferably performs a 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, 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 the present 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 and has good affinity for gelatin and gum arabic.

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

[0067] In the present invention, the progress of the reaction is preferably detected during the gelation process, and the detection 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, and the pH value of the system is adjusted at the minimum rotation 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), and the rotation speed is stabilized at 100-200 rpm. Samples are taken for observation. A very thin transparent film layer is formed around the phenolic epoxy resin microcapsules, which is easy to break. At this time, the reaction is not complete. The gelation is continued. After a period of reaction, the temperature is naturally cooled to room temperature, and an ice bath is started. When the system temperature drops below 10°C, it is observed that the system becomes viscous. Samples are taken for observation. The capsules are well preserved, indicating that the gelation is complete.

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

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

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

[0072] In the present invention, deionized water is preferably added to the gelled product, stirred, and stirring is stopped until the double-layer microcapsules sink to the bottom, the upper turbid aqueous solution is poured out, and water is added for a second water wash, and then the water washing steps are 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 double-layer microcapsules.

[0074] In the present invention, the cross-linking agent is preferably formaldehyde.

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

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

[0077] In the present invention, the temperature of the cross-linking reaction is preferably 10° C., and during the cross-linking reaction, sampling is preferably performed until the capsule is placed on glass or paper without breaking, that is, the double-layer microcapsule is stably formed.

[0078] In the present invention, after the cross-linking reaction is completed, it is preferably washed with water and concentrated in sequence to obtain a double-layer microcapsule concentrated solution, and the double-layer microcapsule concentrated solution is used for subsequent reactions.

[0079] In the present invention, the mass fraction of the double-layer microcapsules in the double-layer microcapsule concentrate is preferably 70% to 90%.

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

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

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

[0083] In the present invention, the developer preferably includes sodium dodecyl sulfate or bisphenol A.

[0084] In the present invention, the mass ratio of the double-layer microcapsules to the aqueous resin in the aqueous resin solution is preferably 0.5-1:1-2.

[0085] In the present invention, the mass ratio of the double-layer microcapsule to the developer is preferably 10:1-10.

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

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

[0088] The present invention also provides a pressure-sensitive color-developing spray prepared by the preparation method described in the above technical solution, comprising a double-layer microcapsule, an aqueous resin, a color-developing agent and water.

[0089] In the present invention, the diameter of the double-layer microcapsule is preferably 1-50 μm, more preferably 20-30 μm; the core material of the double-layer 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 complex coacervation.

[0090] In the present invention, the volume fraction of the double-layer microcapsules in the pressure-sensitive color-developing spray is preferably 0.5% to 25%, more preferably 1% to 20%, and most preferably 5% to 15%.

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

[0092] The present invention also provides the use of the pressure-sensitive color-developing spray described in the above technical solution as a spray color-developing material in the field of confidentiality.

[0093] In the present invention, the application preferably comprises the following steps:

[0094] The pressure-sensitive color developing spray is filled into a sprayer for use, shaken evenly, and then sprayed for use.

[0095] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0096] Raw materials and equipment:

[0097] The solvent in the capsule core is diarylethane, and the coloring agent is CVL (crystal violet lactone);

[0098] Capsule wall material: phenolic epoxy resin, Wuxi Resin Plant of Bluestar Chemical New Materials Co., Ltd., 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 Silu Instrument Co., Ltd.), XHF-D high-speed disperser (homogenizer, Ningbo Xinzhi Biotechnology Co., Ltd.), XJP-H200 metallographic microscope (JVC Company), S3500 laser particle size analyzer (Microtrac, USA).

[0101] Example 1

[0102] 1. Preparation of double-layer microcapsules

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

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

[0105] Figure 1 This is a metallographic microscope image of the prepared phenolic epoxy resin microcapsules, which shows that the average particle size is 30 μm.

[0106] (3) Preparation of the second layer of capsule wall: 2.5g gelatin / 50mL aqueous solution and 2.5g gum arabic / 50mL aqueous solution were prepared respectively. The gelatin was heated to 40℃ and stirred to accelerate dissolution. The gelatin aqueous solution (containing 2.5g gelatin) and the gum arabic aqueous solution (containing 2.5g gum arabic) were mixed (gelatin and gum arabic are light yellow after mixing. If there are impurities observed by naked eyes, they can be filtered out). The mixture was added to a three-necked flask, and the speed was controlled at 100rpm and the temperature was 45℃. At this time, a small amount of the mixed solution was taken and a 15% HAC solution was added to adjust the pH value to 3-5. The solution should undergo complex coagulation and turn milky white. This can be used to judge that there is no problem with the raw materials. 10mL of the washed and concentrated phenolic epoxy resin microcapsules were added to the gelatin-gum arabic solution (where the mass ratio of phenolic epoxy resin to gelatin is 1:5) and dispersed at a stable stirring speed. The pH value of the system was adjusted at the minimum speed that can maintain the stability of the system. After the system is dispersed and stabilized, add 15% HAC solution by mass to adjust the pH value to 3-5, stabilize the speed at 100rpm, continue the reaction for 1.5h, take samples and observe, a very thin transparent film layer is formed around the epoxy resin microcapsules, which is easy to break. Stop heating, cool naturally to room temperature, start ice bath, and when the system temperature drops below 10°C, it can be observed that the system becomes viscous, take samples and observe, and the capsules are well preserved. Slowly add deionized water, stir slightly, stop stirring, and wait for the double-layer microcapsules to sink to the bottom, pour out the upper turbid aqueous solution, and add water to wash again, wash 3 times. After the system is clarified, add 2mL formaldehyde as a cross-linking agent, and adjust the pH value to 9-10 with a mass fraction of 10% NaOH solution, slowly stir and solidify the capsule shell below 10°C, take samples until the capsules are stably formed (not broken when placed on glass or paper), and obtain a solution containing double-layer microcapsules, and then concentrate to obtain a solution containing double-layer microcapsules.

[0107] Figure 2 This is an optical microscope image of the double-layer microcapsules taken out during the reaction. The surrounding transparent spheres are the uncoated gelatin-arabic gum. Figure 3 The optical microscope image of the prepared double-layer microcapsule shows that a second capsule wall has been formed.

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

[0109] Take 10mL of the concentrated double-layer microcapsule concentrate (the mass fraction of the double-layer microcapsule is 70%), and then mix it with a 2% mass fraction of aqueous polyurethane aqueous solution to obtain a mixed solution, and dissolve sodium dodecyl sulfate in the mixed solution, stir for 10 minutes, and then stand for 24 hours. Finally, fill it into the sprayer for use, shake it evenly before use, and then spray it for pressure sensitivity test.

[0110] The mass fraction of the color developer in the obtained pressure-sensitive color developing spray is 10%, the volume fraction of the double-layer microcapsule is 25%, and the mass fraction of the water-based resin is 10%.

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

[0112] The rupture strength of double-layer microcapsules was tested using a 1 / 10,000 electronic balance

[0113] Place the double-layer microcapsule particles on the tray of an electronic balance (Jince QL-E series electronic analytical balance, accuracy d = 0.0001g), and use a probe to slowly apply vertical pressure to the double-layer microcapsule until the double-layer microcapsule ruptures. The value displayed on the balance will change from small to large, and then from large to small. The maximum value recorded in this process is the rupture pressure of the double-layer microcapsule. Several double-layer microcapsules were randomly selected for testing, and the results are shown in Table 1. The average of the values ​​in Table 1 was obtained to obtain an average strength of 0.0033g, or 3.3 mg force.

[0114] Table 1. Test results of bursting strength of double-layer microcapsules

[0115]

[0116] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a pressure-sensitive color developing spray, characterized in that: The following steps are involved: Mixing a coloring agent and diarylethane to obtain a capsule core material; Mixing the capsule core material with phenolic epoxy resin to obtain a mixed solution; The mixed solution, the dispersant aqueous solution and the curing agent are mixed to perform a curing reaction to obtain phenolic epoxy resin microcapsules; The phenolic epoxy resin microcapsules are mixed with a gelatin-gum arabic mixture and then gelled to obtain gelled microcapsules; The gelled microcapsules and a crosslinking agent are mixed to perform a crosslinking reaction to obtain double-layer microcapsules; The double-layer microcapsule, aqueous resin solution and developer are mixed to obtain the pressure-sensitive color developing spray.

2. The preparation method according to claim 1, characterized in that: The mass fraction of the coloring agent in the capsule core material is 1-10%.

3. The preparation method according to claim 1 or 2, characterized in that: The color former includes a phthalide color former and / or a fluorane color former, and the phthalide color former includes crystal violet lactone.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the capsule core material to the phenolic epoxy resin is 1 to 1.5:

1.

5. The preparation method according to claim 1, characterized in that: The curing reaction includes a first curing and a second curing performed sequentially, wherein the first curing is performed at a temperature of 40 to 50° C. and a heat preservation time of 10 to 15 minutes, and the second curing is performed at a temperature of 60 to 70° C. and a heat preservation time of 2.5 to 3 hours.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the phenolic epoxy resin microcapsules to the gelatin in the gelatin-gum arabic mixture is 1:5-2:1, and the mass ratio of the gelatin to the gum arabic in the gelatin-gum arabic mixture is 0.5-1:1-2.

7. 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, and the rotation speed is 100 to 200 rpm.

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

9. The pressure-sensitive color developing spray prepared by the preparation method according to any one of claims 1 to 8, characterized in that: It includes double-layer microcapsules, water-based resin, developer and water.

10. Use of the pressure-sensitive color-developing spray according to claim 9 as a spray color-developing material in the field of confidentiality.

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