Preparation method of thermochromic microcapsule and thermochromic ink

Abstract

This invention provides a method for preparing thermochromic microcapsules and a thermochromic ink, relating to the field of thermochromic microcapsule technology. The method for preparing the thermochromic microcapsules includes the following steps: S1, mixing a color-developing agent, a color-developing agent, a solvent, a polyisocyanate monomer, and an emulsifier, heating to melt, obtaining a core material, gradually adding water while stirring continuously, to obtain an emulsion; S2, adding a (HOR) structure to the emulsion... 1 )2NR 2 Diol organic amines and / or HOR 3 NHCOCONHR 3 A mixture of OH-diol oxalamide and triethanolamine was stirred for 10 min–1 h, then a water-soluble polyorganic amine was added and stirred for 1–10 h. The mixture was then demulsified, filtered, washed, and dried to obtain the thermochromic microcapsules, wherein R… 1 It is a C2-C4 alkyl group, R 2 It is a C1-C4 alkyl group, R 3 It is a C2-C4 alkyl group. The thermochromic microcapsules of this invention, through structural design, possess good mechanical strength and impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of color-changing microcapsule technology, and relates to a method for preparing thermochromic microcapsules and thermochromic ink. Background Technology

[0002] There have been numerous reports on thermochromic inks and their applications, which utilize thermochromic microcapsules to provide the thermochromic function. These thermochromic microcapsules are microcapsules with a core-shell structure, where the outer shell protects the thermochromic material within.

[0003] However, thermochromic microcapsules are generally evaluated based on their temperature range and sensitivity, with less attention paid to their stability and compatibility in applications. For example, for materials like polypropylene that require high shear forces and melt processing, the mechanical properties of the microcapsules are crucial, especially the impact strength of the outer shell under high shear forces; otherwise, rupture may occur, leading to leakage of the core material. For instance, existing technology CN116236985A prepares thermochromic microcapsules coated with silica hybrid modified epoxy resin wall material. This material consists of a silica hybrid modified epoxy resin wall material and a core material. The microcapsule wall material has high density and good mechanical properties, maintaining the integrity and elasticity of the capsule under external impact. Furthermore, in applications such as inks, poor compatibility between microcapsules and inks can lead to decreased ink storage stability and poor mechanical properties of the cured ink coating.

[0004] To address the shortcomings of existing thermochromic microcapsules in terms of impact resistance and compatibility with ink materials, this invention proposes a thermochromic microcapsule and a thermochromic ink. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing thermochromic microcapsules.

[0006] The present invention also provides a thermochromic ink.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing thermochromic microcapsules, comprising the following steps:

[0009] S1. Mix the colorant, color developer, solvent, polyisocyanate monomer and emulsifier, heat and melt to obtain the core material, gradually add water while stirring and continue stirring to obtain an emulsion;

[0010] S2. Add the structure (HOR) to the emulsion described in step S1. 1 )2NR 2 Diol organic amines and / or HOR 3 NHCOCONHR 3A mixture of OH-diol oxalamide and triethanolamine was stirred for 10 min to 2 h, then a water-soluble polyorganic amine was added and stirred for 1 to 10 h. The mixture was then demulsified, filtered, washed, and dried to obtain the thermochromic microcapsules, wherein R... 1 It is a C2-C4 alkyl group, R 2 It is a C1-C4 alkyl group, R 3 It is a C2-C4 alkyl group.

[0011] Preferably, the weight ratio of the color-developing agent, the color-developing agent, the solvent, the polyisocyanate monomer, and the emulsifier in step S1 is 1:1-2:8-50:1-10:0.1-5.

[0012] Preferably, the weight ratio of the core material to the water in step S1 is 1:1-4.

[0013] Preferably, the diol organic amine in step S2 is selected from one or a combination of N-methyldiethanolamine, N-ethyldiethanolamine and N-propyldiethanolamine.

[0014] Preferably, the ratio of the molar number of polyisocyanate monomers in the emulsion in step S2 to the sum of the molar numbers of the diol organic amine and / or diol oxalamide and triethanolamine is 1:0.1-0.7.

[0015] Preferably, the molar ratio of the diol organic amine and / or diol oxalamide to the triethanolamine in step S2 is 1:0.01-0.2.

[0016] Preferably, the weight ratio of the emulsion to the water-soluble polyorganic amine in step S2 is 1:0.01-0.2.

[0017] Preferably, the water-soluble polyorganic amine in step S2 has the structure NH2R. 4 NH2, where R 4 It is a C2-C6 alkylene group or -(CH2CH2O). n - where n = 4-50.

[0018] More preferably, the water-soluble polyorganic amine in step S2 is selected from a combination of a first water-soluble polyorganic amine with a molecular weight not exceeding 100 and a second water-soluble polyorganic amine with a molecular weight of 300-5000 in a weight ratio of 9:1 to 1:9.

[0019] A thermochromic ink comprising 1-20% by weight of the thermochromic microcapsules prepared by the method described in any of the above technical solutions.

[0020] The beneficial effects of this invention are:

[0021] 1. The thermochromic microcapsules of the present invention have a core-shell structure, with a core layer and a shell consisting of two layers, namely a first shell layer and a second shell layer from the inside out. The first shell layer covering the core layer has a high crosslinking density, high compactness, many hydrogen bonds, and good rigidity, providing protection for the core layer. The second shell layer covering the first shell layer has a lower crosslinking density, a looser structure, and high impact resistance. The present invention uses a combination of a first shell layer and a second shell layer, which results in excellent impact resistance of the microcapsules. Furthermore, the relatively loose second shell layer can increase compatibility with polymers in inks, allowing polymers in inks to permeate through the loose second shell layer, thus ensuring good compatibility of the microcapsules in inks.

[0022] 2. The present invention provides a simple and effective method for preparing thermochromic microcapsules by selecting raw materials and controlling the amount of feed. Furthermore, the raw materials used to prepare the first outer shell layer contain highly polar tertiary amine or amide structures, which can form more hydrogen bonds in the shell wall, thus improving the mechanical strength of the first outer shell layer. The second outer shell layer is a polyurea polymer, which has high impact resistance, further enhancing the impact resistance of the thermochromic microcapsules of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0024] On the one hand, this invention proposes a method for preparing thermochromic microcapsules, the steps of which include:

[0025] S1. Mix the colorant, color developer, solvent, polyisocyanate monomer and emulsifier, heat and melt to obtain the core material, gradually add water while stirring and continue stirring to obtain an emulsion;

[0026] S2. Add the structure (HOR) to the emulsion from step S1. 1 )2NR 2 Diol organic amines and / or HOR 3 NHCOCONHR 3 A mixture of OH-diol oxalamide and triethanolamine was stirred for 10 min to 2 h, then a water-soluble polyorganic amine was added and stirred for 1 to 10 h. The mixture was then demulsified, filtered, washed, and dried to obtain the thermochromic microcapsules, wherein R... 1 It is a C2-C4 alkyl group, R 2 It is a C1-C4 alkyl group, R 3 It is a C2-C4 alkyl group.

[0027] This invention employs an emulsion interfacial polymerization method, encapsulating the color-developing agent, color-developing agent, solvent, and polyisocyanate monomer of a thermochromic material within a core. A raw material capable of reacting with the polyisocyanate monomer is added to the outside of the emulsion, causing a polymerization reaction at the interface. This forms a cross-linked first outer shell layer at the emulsion interface. Due to the presence of both chemical and physical cross-linking structures (hydrogen bonds), the first outer shell layer exhibits high cross-linking density and high mechanical strength. A second outer shell layer covers the first outer shell layer. The second outer shell layer has a relatively lower cross-linking density and a looser structure, and is made of polyurea, thus providing good impact resistance and cushioning. This invention uses a combination of a rigid first outer shell layer and an impact-resistant second outer shell layer as the outer shell layer, providing good protection for the core. Furthermore, the looser polar structure of the second outer shell layer offers better compatibility with inks.

[0028] In a preferred embodiment of the present invention, the weight ratio of the color-developing agent, color-developing agent, solvent, polyisocyanate monomer, and emulsifier in step S1 is 1:1-2:8-50:1-10:0.1-5. For example, the weight ratio of the color-developing agent, color-developing agent, solvent, polyisocyanate monomer, and emulsifier can be any value among 1:1:8:1:0.1, 1:2:20:5:2, 1:2:30:7:4, 1:1.5:25:5:3, 1:2:50:10:5, etc.

[0029] In this invention, the color-developing agent is not particularly limited and can be crystal violet lactone or 2-phenylamino-6-diethylaminofluorane, or a combination of two thereof; the color-developing agent is not particularly limited and can be bisphenol A, bisphenol F, 3-diethylamino-7,8-phenylfluorane, or 1,5-dihydroxynaphthalene, or a combination of two or more thereof; the solvent does not contain active hydrogen atoms, i.e., it does not react with isocyanate groups at 100°C, and can be n-hexadecane, n-octadecane, n-eicosane, n-docosahexadecane, or diphenyl carbonate, or a combination of two or more thereof; the polyisocyanate monomer is not particularly limited and can be isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate, etc. The emulsifier may be a nonionic surfactant, an anionic surfactant, or a combination of two or more of the following: a nonionic surfactant alone, a nonionic surfactant alone, or a combination of a nonionic surfactant and anionic surfactant, such as a combination of AEO-3 and sodium dodecylbenzenesulfonate in a weight ratio of 2:1, a combination of Span 80 and sodium dodecylbenzenesulfonate in a weight ratio of 3:1, a combination of Span 20 and Span 80 in a weight ratio of 2:1, or a combination of AEO-3 and AEO-9 in a weight ratio of 1:1.

[0030] In a preferred embodiment of the present invention, the weight ratio of the core material to water in step S1 is 1:1-4. The concentration of the obtained emulsion can be adjusted by changing the weight ratio of the core material to water. For example, the weight ratio of the core material to water can be any value among 1:1, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, etc.

[0031] In a preferred embodiment of the present invention, the diol organic amine in step S2 is selected from one or a combination of N-methyldiethanolamine, N-ethyldiethanolamine, and N-propyldiethanolamine. In the present invention, the diol oxalamide can be selected from N,N'-bis(hydroxyethyl)oxalamide or N,N'-bis(3-hydroxypropyl)oxalamide.

[0032] In a preferred embodiment of the present invention, the ratio of the molar number of polyisocyanate monomers in the emulsion to the sum of the molar numbers of diol organic amines and / or diol oxalamide and triethanolamine in step S2 is 1:0.1-0.7.

[0033] In this invention, diol organic amines and / or diol oxalamides refer to a single diol organic amine, a single diol oxalamide, or a combination of diol organic amines and diol oxalamides; diol organic amines and / or diol oxalamides with triethanolamines refer to a combination of two diol organic amines and triethanolamines, a combination of two diol oxalamides and triethanolamines, or a combination of three diol organic amines, diol oxalamides, and triethanolamines. Diol organic amines, diol oxalamides, and triethanolamines all contain active hydrogen that can react with isocyanate groups at 100°C. By controlling the molar ratio in the above technical solutions, both chemical and physical cross-linking structures can be formed during interfacial polymerization, and the polyisocyanate monomers in the core cannot be completely consumed by the first outer shell layer, allowing the remaining polyisocyanate monomers to continue forming the second outer shell layer. If the polyisocyanate monomers in the core are completely consumed by the first outer shell layer, the second outer shell layer cannot be formed. For example, the ratio of the molar number of polyisocyanate monomers to the sum of the molar numbers of diol organic amines and / or diol oxalamides and triethanolamines can be any value among 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, etc.

[0034] In a preferred embodiment of the present invention, the molar ratio of diol organic amine and / or diol oxalamide to triethanolamine in step S2 is 1:0.01-0.2. By controlling the molar ratio in the above technical solution, the crosslinking density of the first outer shell layer can be controlled, avoiding the first outer shell layer being too hard and brittle due to excessively high crosslinking density, and also avoiding the first outer shell layer being too rigid due to excessively low crosslinking density, both of which will affect the protective ability of the first outer shell layer. Furthermore, the molar ratio of diol organic amine and / or diol oxalamide to triethanolamine can be 1:0.03-0.15. For example, it can be the molar ratio of diol organic amine to triethanolamine, the molar ratio of diol oxalamide to triethanolamine, or the molar ratio of diol organic amine and diol oxalamide to triethanolamine. The molar ratio can be any value among 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, etc.

[0035] In a preferred embodiment of the present invention, the weight ratio of the emulsion to the water-soluble polyorganic amine in step S2 is 1:0.01-0.2. For example, the weight ratio of the emulsion to the water-soluble polyorganic amine can be 1:0.01-0.15, and for example, the weight ratio can be any value among 1:0.01, 1:0.02, 1:0.05, 1:0.06, 1:0.08, 1:0.1, 1:0.12, 1:0.13, 1:0.14, 1:0.15, etc.

[0036] In a preferred embodiment of the present invention, the water-soluble polyorganic amine in step S2 has the structure NH2R. 4 NH2, where R 4 It is a C2-C6 alkylene group or -(CH2CH2O). n - where n = 4-50. For example, water-soluble polyamines can be small molecule diamines, such as ethylenediamine, 1,4-butanediamine, and 1,6-hexanediamine, or polymeric diamines, such as polyethylene glycolamines. Polyethylene glycolamines can be polyethylene glycolamine-2000 (2000 represents the number average molecular weight), polyethylene glycolamine-1000, etc.

[0037] In a more preferred embodiment of the present invention, the water-soluble polyorganic amine in step S2 is selected from a combination of a first water-soluble polyorganic amine with a molecular weight not exceeding 100 and a second water-soluble polyorganic amine with a molecular weight of 300-5000 in a weight ratio of 9:1 to 1:9. Using a combination of two polyorganic amines with different molecular weights can form a second outer shell layer with different crosslinking densities, which can further improve the impact resistance of the second outer shell layer. For example, the weight ratio of the first water-soluble polyorganic amine and the second water-soluble polyorganic amine can be any value from 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, etc.

[0038] On the other hand, this invention proposes a thermochromic ink comprising thermochromic microcapsules prepared by the method described in any of the above-mentioned technical solutions, at a weight percentage of 1-20%. For example, the weight percentage of the thermochromic microcapsules in the ink can be any value selected from 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%. In this invention, the film-forming polymer material of the ink is not particularly limited and can be epoxy resin and its modified forms, polyurethane and its modified forms, acrylic resin and its modified forms, unsaturated polyester resin, etc.

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Examples 1-8

[0041] Example 1

[0042] Mix 100g crystal violet lactone, 100g 1,5-dihydroxynaphthalene, 800g n-eicosane, 100g IPDI and 10g emulsifier (AEO-3 and sodium dodecylbenzenesulfonate in a weight ratio of 2:1), heat to 80℃ to melt, and obtain the core material. Gradually add 3330g water while stirring continuously to obtain an emulsion.

[0043] A mixture of 0.27 mol N-methyldiethanolamine and 0.03 mol triethanolamine was added to the above emulsion and stirred for 60 min. Then 50 g of 1,4-butanediamine was added and stirred for 3 h. Sodium chloride was added to break the emulsion. The mixture was filtered, and the filtered solid was washed twice with pure water and once with anhydrous ethanol. The solid was dried overnight in a vacuum oven at 30 °C to obtain thermochromic microcapsules.

[0044] Example 2

[0045] The difference between Example 2 and Example 1 is that in Example 1, the amount of N-methyldiethanolamine was adjusted from 0.27 mol to 0.28 mol, and the amount of triethanolamine was adjusted from 0.03 mol to 0.02 mol. The remaining steps remained unchanged.

[0046] Example 3

[0047] The difference between Example 3 and Example 1 is that in Example 1, N-methyldiethanolamine was replaced with an equimolar amount of N,N'-bis(hydroxyethyl)oxalamide. The remaining steps remained unchanged.

[0048] Example 4

[0049] The difference between Example 4 and Example 1 is that in Example 1, 1,4-butanediamine is replaced with an equal weight of a combination of 1,4-butanediol and polyethylene glycolamine-1000 in a weight ratio of 3:1. The remaining steps remain unchanged.

[0050] Example 5

[0051] 100g of 2-anilino-6-diethylaminofluorane, 200g of bisphenol A, 2960g of n-docosahexanes, 700g of HMDI and 40g of emulsifier (a combination of Span 80 and sodium dodecylbenzenesulfonate in a weight ratio of 3:1) were mixed and heated to 80°C to melt, thus obtaining the core material. 10000g of water was gradually added while stirring continuously to obtain an emulsion.

[0052] A mixture of 0.7 mol N-ethyldiethanolamine, 0.63 mol N,N'-bis(hydroxyethyl)oxalamide and 0.07 mol triethanolamine was added to the above emulsion and stirred for 90 min. Then, 1400 g of polyethylene glycolamine-1000 was added and stirred for 2 h. Sodium chloride was added to break the emulsion. The mixture was filtered, and the filtered solid was washed twice with pure water and once with anhydrous ethanol. The solid was dried overnight in a vacuum oven at 30 °C to obtain thermochromic microcapsules.

[0053] Example 6

[0054] The difference between Example 6 and Example 5 is that in Example 5, N-ethyldiethanolamine was adjusted from 0.7 mol to 0.3 mol, and N,N'-bis(hydroxyethyl)oxalamide was adjusted from 0.63 mol to 1.03 mol. The remaining steps remained unchanged.

[0055] Example 7

[0056] The difference between Example 7 and Example 5 is that in Example 5, N-ethyldiethanolamine was adjusted from 0.7 mol to 1 mol, and N,N'-bis(hydroxyethyl)oxalamide was adjusted from 0.63 mol to 0.33 mol. The remaining steps remained unchanged.

[0057] Example 8

[0058] The difference between Example 8 and Example 5 is that in Example 5, the polyethylene glycolamine-1000 was adjusted to an equal weight of polyethylene glycolamine-1000 and 1,6-hexanediamine in a weight ratio of 4:1. The remaining steps remained unchanged.

[0059] Comparative Example 1

[0060] A mixture of 0.54 mol N-methyldiethanolamine and 0.06 mol triethanolamine was added to 4440 g of the emulsion from Example 1, and the mixture was stirred for 60 min. Then, 50 g of 1,4-butanediamine was added, and the mixture was stirred for 3 h. Sodium chloride was added to break the emulsion, and the mixture was filtered. The filtered solid was washed twice with pure water and once with anhydrous ethanol. The solid was dried overnight in a vacuum oven at 30 °C to obtain thermochromic microcapsules.

[0061] Comparative Example 2

[0062] A mixture of 0.54 mol N-methyldiethanolamine and 0.06 mol triethanolamine was added to 4440 g of the emulsion from Example 1. The mixture was stirred for 60 min, and sodium chloride was added to break the emulsion. The mixture was filtered, and the filtered solid was washed twice with pure water and once with anhydrous ethanol. The solid was dried overnight in a vacuum oven at 30°C to obtain thermochromic microcapsules.

[0063] Comparative Example 3

[0064] The difference between Comparative Example 3 and Example 1 is that in Example 1, triethanolamine was replaced with an equimolar amount of N-methyldiethanolamine. The remaining steps remained unchanged.

[0065] Impact resistance test

[0066] Ten g of the thermochromic microcapsules from Examples 1-8 and Comparative Examples 1-3 were taken respectively, and pressed at 5 MPa for 10 seconds using a tablet press. The pressure was then removed, and the breakage of the microcapsules was observed. The lower the breakage rate, the better the impact resistance of the microcapsules. The results are shown in Table 1 below.

[0067] Table 1

[0068] Example 1 6.5 Example 5 5.3 Comparative Example 1 11.8 Example 2 7.2 Example 6 4.7 Comparative Example 2 12.2 Example 3 4.1 Example 7 6.1 Comparative Example 3 10.5 Example 4 6.1 Example 8 5.0

[0069] As can be seen from the data in Table 1 above, the thermochromic microcapsules of the present invention have good impact resistance and a low breakage rate under external force because the outer shell is composed of a first outer shell layer with high cross-linking density and good rigidity and a second outer shell layer with low cross-linking density and relatively loose structure.

[0070] Application testing

[0071] The thermochromic ink consists of 162g of component A and 30g of component B. Component A comprises 100g of epoxy resin E-44, 10g of 1,6-hexanediol diglycidyl ether, 40g of butyl acetate, 0.6g of polyether-modified silicone oil leveling agent, 1g of dimethyl silicone oil defoamer, 10g of thermochromic microcapsules, and 0.4g of fumed silica. Component B is polyetheramine D230.

[0072] E-44 was added to 1,6-hexanediol diglycidyl ether and mixed at 500 rpm for 10 min. The stirring speed was then adjusted to 1500 rpm, and thermochromic microcapsules were added. The mixture was mixed for 15 min, and the stirring speed was adjusted to 600 rpm. Leveling agent, defoamer, and fumed silica were added sequentially, and the mixture was stirred for 20 min to obtain component A. After component A and component B were mixed evenly, the mixture was applied to a substrate and heated at 60℃ for 2 h, 90℃ for 1 h, and 120℃ for 1 h to obtain an epoxy resin coating with a thickness of 30±2 μm.

[0073] The thermochromic microcapsules are those used in Examples 1-4 and Comparative Examples 1-3, respectively. The tensile strength and impact strength of the ink coating are shown in Table 2 below.

[0074] Tensile strength was tested according to GB / T528-2009. Impact strength was tested according to GB / T 2571-1995. The blank sample was the ink without thermochromic microcapsules.

[0075] Table 2

[0076]

[0077] As shown in Table 2 above, the addition of the thermochromic microcapsules of this invention to epoxy resin ink has virtually no impact on the tensile strength of the ink coating; the tensile strength of the ink coating changes little, but the impact strength is improved, indicating good compatibility with epoxy resin. In contrast, the thermochromic microcapsules used in the comparative example show a decrease in both tensile strength and impact strength, indicating poor compatibility with epoxy resin.

[0078] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing thermochromic microcapsules, characterized in that the steps include... include: S1. Mix the colorant, color developer, solvent, polyisocyanate monomer and emulsifier, heat and melt to obtain the core material, gradually add water while stirring and continue stirring to obtain an emulsion; S2. Add the structure (HOR) to the emulsion described in step S1. 1 )2NR 2 Diol organic amines and HOR 3 NHCOCONHR 3 A mixture of at least one of OH-diol oxalamide and triethanolamine is stirred for 10 min to 2 h, then a water-soluble polyorganic amine is added, and the mixture is stirred for 1 to 10 h. The mixture is then demulsified, filtered, washed, and dried to obtain the thermochromic microcapsules, wherein R... 1 It is a C2-C4 alkylene group, R 2 It is a C1-C4 alkyl group, R 3 It is a C2-C4 alkylene group; The ratio of the number of moles of polyisocyanate monomers in the emulsion to the number of moles of the mixture is 1:0.1-0.

7.

2. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The weight ratio of the color-developing agent, the color-developing agent, the solvent, the polyisocyanate monomer, and the emulsifier in step S1 is 1:1-2:8-50:1-10:0.1-5.

3. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The weight ratio of the core material to the water in step S1 is 1:1-4.

4. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The diol organic amine mentioned in step S2 is selected from one or a combination of N-methyldiethanolamine, N-ethyldiethanolamine and N-propyldiethanolamine.

5. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, In step S2, a substance with the structure (HOR) is added to the emulsion described in step S1. 1 )2NR 2 Diol organic amines and HOR 3 NHCOCONHR 3 A mixture of one of the substances in OH-diol oxalamide and triethanolamine, wherein the molar ratio of the diol organic amine to triethanolamine is 1:0.01-0.2, or the molar ratio of the diol oxalamide to triethanolamine is 1:0.01-0.2; or, In step S2, a substance with the structure (HOR) is added to the emulsion described in step S1. 1 )2NR 2 Diol organic amines and HOR 3 NHCOCONHR 3 The mixture is formed by OH diol oxalamide and triethanolamine, wherein the ratio of the sum of the molar numbers of the diol organic amine and the diol oxalamide to the molar number of triethanolamine is 1:0.01-0.

2.

6. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, In step S2, the weight ratio of the emulsion to the water-soluble polyorganic amine is 1:0.01-0.

2.

7. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The water-soluble polyorganic amine described in step S2 has the structure NH2R. 4 NH2, where R 4 It is a C2-C6 alkylene group or -(CH2CH2O). n - where n = 4-50.

8. The method for preparing thermochromic microcapsules according to claim 7, characterized in that, The water-soluble polyorganic amine mentioned in step S2 is selected from a combination of a first water-soluble polyorganic amine with a molecular weight not exceeding 100 and a second water-soluble polyorganic amine with a molecular weight of 300-5000 in a weight ratio of 9:1 to 1:

9.

9. A thermochromic ink, characterized in that, The thermochromic microcapsules are prepared by the method of any one of claims 1-8, which contains 1-20% by weight of the ink.

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