阅读说明：本技术 一种热致变色防伪墨粉的制备方法 (Preparation method of thermochromic anti-counterfeiting ink powder ) 是由 王密 刘志军 曹方敏 孟鸿 黄维 羊辉 于 2019-11-25 设计创作，主要内容包括：本发明公开了热致变色防伪墨粉的制备方法,具体为：将热致变色复合物加入水相溶液中,得热致变色复合物细乳液；将壁材预聚体溶液加入热致变色复合物细乳液中得热致变色纳米胶囊分散液；将热致变色纳米胶囊分散液转换为热致变色纳米胶囊粉体；将热致变色纳米胶囊粉体、脱模剂、低玻璃化温度单体油相混合形成混合油相,将混合油相和水性分散液反应,得软性墨粉核粒子,将高玻璃化温度壳树脂单体、离子型单体加入去离子水中得细乳液,将细乳液加至软性墨粉核粒子中,并加入水溶性引发剂进行聚合反应,得热致变色防伪墨粉。该墨粉打印出的图案在不同的温度下可以呈现不同的颜色,且变色温度可调,变色速度快,变色前后颜色对比度大,防伪效果显著。(The invention discloses a preparation method of thermochromic anti-counterfeiting ink powder, which comprises the following steps: adding the thermochromic compound into the aqueous phase solution to obtain a thermochromic compound miniemulsion; adding the wall material prepolymer solution into the thermochromic compound miniemulsion to obtain a thermochromic nanocapsule dispersion liquid; converting the thermochromic nanocapsule dispersion into thermochromic nanocapsule powder; mixing thermochromic nano capsule powder, a release agent and a low glass transition temperature monomer oil phase to form a mixed oil phase, reacting the mixed oil phase with an aqueous dispersion liquid to obtain soft ink powder core particles, adding a high glass transition temperature shell resin monomer and an ionic monomer into deionized water to obtain a miniemulsion, adding the miniemulsion into the soft ink powder core particles, and adding a water-soluble initiator to carry out polymerization reaction to obtain the thermochromic anti-counterfeiting ink powder. The patterns printed by the ink powder can present different colors at different temperatures, the color change temperature is adjustable, the color change speed is high, the color contrast before and after color change is high, and the anti-counterfeiting effect is obvious.)

1. The preparation method of the thermochromic anti-counterfeiting ink powder is characterized by comprising the following steps:

step 1, preparing a thermochromic compound;

step 2, adding the thermochromic compound into an aqueous phase solution in which a surfactant is dissolved, and carrying out shearing emulsification and heating to obtain a thermochromic compound miniemulsion; adding a wall material prepolymer solution into the thermochromic compound miniemulsion to perform a polycondensation reaction to obtain a thermochromic nanocapsule dispersion liquid;

step 3, performing hydrophobic modification, washing and drying on the thermochromic nanocapsule dispersion liquid through a coupling agent to obtain thermochromic nanocapsule powder;

step 4, mixing the thermochromic nano capsule powder, the release agent and the low glass transition temperature monomer oil phase to form a mixed oil phase, and carrying out shearing dispersion and polymerization reaction on the mixed oil phase and the aqueous dispersion liquid to obtain soft ink powder core particles;

and 5, adding a high glass transition temperature shell resin monomer and an ionic monomer into deionized water to form a miniemulsion, adding the miniemulsion into the soft ink powder core particles, adding a water-soluble initiator, and carrying out polymerization reaction again to form a hydrophobic shell layer with dense charges, thereby obtaining the thermochromic anti-counterfeiting ink powder.

2. The preparation method of the thermochromic anti-counterfeiting toner according to claim 1, wherein the specific method for preparing the thermochromic compound in the step 1 is as follows:

the coloring agent, the color developing agent and the melting agent are mixed according to the ratio of 1: (1-100): (20-500), heating to 10-50 ℃ above the melting point temperature of the melting agent, stirring, and reacting to form a uniform phase to obtain a thermochromic compound;

wherein the colorant is leuco dye, including fluorane, triarylmethane, phenothiazine, spiropyran, rhodamine B lactam, phthalic acid lactone, indoline, and auramine; the color developing agent is organic acid or phenolic hydroxyl compound and derivatives thereof; the melting agent is a low boiling point alcohol.

3. The preparation method of the thermochromic anti-counterfeiting toner according to claim 2, wherein the thermochromic compound is added into the aqueous solution in which the surfactant is dissolved in the step 2, and the shearing emulsification and the temperature rise are carried out to obtain the thermochromic compound miniemulsion, which specifically comprises the following steps:

adding the thermochromic compound in a molten state into an aqueous phase solution in which a surfactant is dissolved, shearing and emulsifying at a high speed, and performing ultrasonic homogenization to uniformly disperse the thermochromic compound in the aqueous phase solution in a nano-scale liquid drop form to form a miniemulsion;

wherein the surfactant is one or more of cationic surfactant, anionic surfactant or nonionic surfactant.

4. The preparation method of the thermochromic anti-counterfeiting toner according to claim 3, wherein in the step 2, a wall material prepolymer solution is added into the thermochromic compound miniemulsion to perform a polycondensation reaction, so as to obtain a thermochromic nanocapsule dispersion liquid, which specifically comprises the following steps:

transferring the thermochromic compound miniemulsion to a three-neck flask, slowly adding a wall material prepolymer solution under the conditions of constant temperature and continuous stirring, adjusting the pH value to acidity, carrying out polycondensation reaction on the wall material prepolymer, depositing the generated polymer on the surface of a core material liquid drop, and gradually forming a compact capsule wall to obtain a thermochromic nanocapsule dispersion liquid;

the mass ratio of the thermochromic compound miniemulsion to the wall material prepolymer solution is 1: 4-4: 1.

5. The preparation method of the thermochromic anti-counterfeiting toner according to claim 4, wherein the wall material prepolymer is one or more of melamine resin, urea resin, phenolic resin, epoxy resin, polyurethane, polyacrylonitrile and polyimide prepolymer.

6. The method for preparing the thermochromic anti-counterfeiting toner according to claim 5, wherein the amount of the coupling agent used in the step 3 is 0.1-5% of the thermochromic nanocapsule dispersion.

7. The method for preparing the thermochromic anti-counterfeiting toner according to claim 6, wherein the low glass transition temperature monomer oil phase in the step 4 comprises a nucleating resin monomer, a crosslinking agent, a molecular weight regulator and an initiator;

wherein the nucleating resin monomer is selected from the group consisting of monovinyl monomers; the cross-linking agent mainly selects a monomer containing two or more unsaturated ethylene groups; the molecular weight regulator comprises one or more than one of the following materials: n-dodecyl mercaptan, t-dodecyl mercaptan, carbon tetrachloride or carbon tetrabromide; the initiator includes a per-azo initiator and a peroxide initiator.

8. The method for preparing a thermochromic anti-counterfeiting toner according to claim 7, wherein the aqueous dispersion in the step 4 is a suspension dispersant.

9. The method for preparing a thermochromic anti-counterfeit toner according to claim 8, wherein the high glass transition temperature shell resin monomer in step 5 is one or more selected from styrene, methacrylate, t-butyl methacrylate, N-methylolacrylamide, acrylonitrile, acrylamide and hydroxypropyl methacrylate.

10. The method for preparing a thermochromic anti-counterfeiting toner according to any one of claims 1 to 9, wherein the water-soluble initiator in step 5 is one or a mixture of more than one selected from the group consisting of potassium persulfate, ammonium persulfate, 2-bis (2-methyl-N- (2-hydroxyethyl) propionamide), and 2, 2-azobis (2-methyl-N- (1, 1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide).

Technical Field

The invention belongs to the technical field of anti-counterfeiting ink powder, and particularly relates to a preparation method of thermochromic anti-counterfeiting ink powder.

Background

Increasingly more and more about counterfeit commodities, diversity of commodity types and aesthetic property of printed products put higher requirements on printing anti-counterfeiting materials and technologies. With the development of office automation, the application of laser printing in work and life is increasingly wide, and various tickets, trademarks, outsourcing and the like also replace the traditional printing method by laser printing. The laser printing paper has high paper output speed, simple operation in the ink powder preparation and use processes and less pollution emission, and has wider prospect in anti-counterfeiting application. However, high-quality security toner for laser printers is not uncommon.

Thermochromic materials can be divided into two major classes, namely irreversible thermochromic materials and reversible thermochromic materials according to the reversibility of thermochromic; the organic reversible thermochromic material is more in quantity, and the comprehensive performance of the organic reversible thermochromic material in various thermochromic materials is optimal. The advantages are that: wide temperature sensing color change range (20-200 deg.C), obvious color change, bright color, high color change sensitivity, and low production cost. But the organic reversible thermochromic material still has some performance defects, such as poor thermal stability and working temperature below 200 ℃; the chemical stability is poor, and the discoloration is easily removed under the strong acid or strong alkali condition, which limits the application of the composite material to a certain extent.

Disclosure of Invention

In order to solve the problems, the invention provides a preparation method of a thermochromism anti-counterfeiting ink powder, wherein patterns printed by the ink powder can present different colors at different temperatures, the color-changing temperature is adjustable, the color-changing speed is high, the colors are various, the color contrast before and after color changing is large, and the anti-counterfeiting effect is obvious.

The technical scheme adopted by the invention is as follows:

a preparation method of thermochromic anti-counterfeiting ink powder is implemented according to the following steps:

step 1, preparing a thermochromic compound;

step 2, adding the thermochromic compound into an aqueous phase solution in which a surfactant is dissolved, and carrying out shearing emulsification and heating to obtain a thermochromic compound miniemulsion; adding a wall material prepolymer solution into the thermochromic compound miniemulsion to perform a polycondensation reaction to obtain a thermochromic nanocapsule dispersion liquid;

step 3, performing hydrophobic modification, washing and drying on the thermochromic nanocapsule dispersion liquid through a coupling agent to obtain thermochromic nanocapsule powder;

step 4, mixing the thermochromic nano capsule powder, the release agent and the low glass transition temperature monomer oil phase to form a mixed oil phase, and carrying out shearing dispersion and polymerization reaction on the mixed oil phase and the aqueous dispersion liquid to obtain soft ink powder core particles;

and 5, adding a high glass transition temperature shell resin monomer and an ionic monomer into deionized water to form a miniemulsion, adding the miniemulsion into the soft ink powder core particles, adding a water-soluble initiator, and carrying out polymerization reaction again to form a hydrophobic shell layer with dense charges, thereby obtaining the thermochromic anti-counterfeiting ink powder.

Preferably, the specific method for preparing the thermochromic compound in step 1 is as follows:

the coloring agent, the color developing agent and the melting agent are mixed according to the ratio of 1: (1-100): (20-500), heating to 10-50 ℃ above the melting point temperature of the melting agent, stirring, and reacting to form a uniform phase to obtain a thermochromic compound;

wherein the colorant is leuco dye, including fluorane, triarylmethane, phenothiazine, spiropyran, rhodamine B lactam, phthalic acid lactone, indoline, and auramine; the color developing agent is organic acid or phenolic hydroxyl compound and derivatives thereof; the melting agent is a low boiling point alcohol.

Preferably, in the step 2, the thermochromic compound is added into an aqueous solution in which a surfactant is dissolved, and shearing emulsification and temperature rise are performed to obtain a thermochromic compound miniemulsion, specifically:

adding the thermochromic compound in a molten state into an aqueous phase solution in which a surfactant is dissolved, shearing and emulsifying at a high speed, and performing ultrasonic homogenization to uniformly disperse the thermochromic compound in the aqueous phase solution in a nano-scale liquid drop form to form a miniemulsion;

wherein the surfactant is one or more of cationic surfactant, anionic surfactant or nonionic surfactant.

Preferably, in the step 2, the wall material prepolymer solution is added into the thermochromic compound miniemulsion to perform a polycondensation reaction, so as to obtain a thermochromic nanocapsule dispersion liquid, which specifically comprises:

transferring the thermochromic compound miniemulsion to a three-neck flask, slowly adding a wall material prepolymer solution under the conditions of constant temperature and continuous stirring, adjusting the pH value to acidity, carrying out polycondensation reaction on the wall material prepolymer, depositing the generated polymer on the surface of a core material liquid drop, and gradually forming a compact capsule wall to obtain a thermochromic nanocapsule dispersion liquid;

the mass ratio of the thermochromic compound miniemulsion to the wall material prepolymer solution is 1: 4-4: 1.

Preferably, the wall material prepolymer is a compound system of one or more of melamine resin, urea resin, phenolic resin, epoxy resin, polyurethane, polyacrylonitrile and polyimide prepolymer.

Preferably, the amount of the coupling agent in the step 3 is 0.1-5% of the thermochromic nanocapsule dispersion liquid;

preferably, the low glass transition temperature monomer oil phase in step 4 comprises a nucleating resin monomer, a crosslinking agent, a molecular weight regulator and an initiator;

wherein the nucleating resin monomer is selected from the group consisting of monovinyl monomers; the cross-linking agent mainly selects a monomer containing two or more unsaturated ethylene groups; the molecular weight regulator comprises one or more than one of the following materials: n-dodecyl mercaptan, t-dodecyl mercaptan, carbon tetrachloride or carbon tetrabromide; the initiator includes a per-azo initiator and a peroxide initiator.

Preferably, the aqueous dispersion in step 4 is a suspension dispersant.

Preferably, the high glass transition temperature shell resin monomer in step 5 is selected from one or more of styrene, methacrylate, tert-butyl methacrylate, N-methylolacrylamide, acrylonitrile, acrylamide and hydroxypropyl methacrylate monomer.

Preferably, the water-soluble initiator in the step 5 is selected from one or more of potassium persulfate, ammonium persulfate, 2-bis (2-methyl-N- (2-hydroxyethyl) propionamide) and 2, 2-azo-bis (2-methyl-N- (1, 1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide).

Compared with the prior art, the image-text information printed by the thermochromic anti-counterfeiting toner prepared by the invention can show different colors according to different temperatures, so that the anti-counterfeiting effect is shown; and the thermochromic material has wide temperature change range, high color change definition and various colors, can effectively reduce the risk of decoding and counterfeiting, and improves the anti-counterfeiting capacity.

Drawings

FIG. 1 is a flow chart of a method for preparing a thermochromic anti-counterfeiting toner according to an embodiment of the invention;

FIG. 2 is an SEM image of a thermochromic anti-counterfeiting toner prepared in example 1 of the present invention;

FIG. 3 is a color change effect diagram of the thermochromic anti-counterfeiting toner prepared in example 1 of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a preparation method of a thermochromic anti-counterfeiting toner, which is implemented according to the following steps as shown in figure 1:

step 1, preparing a thermochromic compound; the method specifically comprises the following steps:

the coloring agent, the color developing agent and the melting agent are mixed according to the ratio of 1: (1-100): (20-500), heating to 10-50 ℃ above the melting point temperature of the melting agent, stirring, and reacting to form a uniform phase to obtain a thermochromic compound; the mass ratio of the coloring agent, the color developer, and the melting agent is preferably 1: (1-10): (20-200);

the colorant is leuco dye, including fluorane, triarylmethane, phenothiazine, spiropyran, rhodamine B lactam, phthalic acid lactone, indoline, auramine, etc., and can be selected from 2-phenylamino-3-methyl-6-diethylaminofluorane, 2-phenylamino-3-methyl-6-dibutylaminofluorane, 6- (ethyl isoamylamino) -1, 2-benzofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, o-cresol sulfonyl phthalide, dibromo-o-cresol sulfonyl, 10-diethylamino spiro [ isobenzofuran-1 (3H),7- [7H ] benzo [ c ] xanthene ] -3-one, 3-bis (4-dimethylaminophenyl) -6-dimethylamino phthalide, 7- [4- (diethylamino) -2-ethoxyphenyl ] -7- (2-methyl-1-octyl-1H-indol-3-yl) furo [3,4-b ] pyridin-5 (7H) -one, 4' - [ (9-butyl-9H-carbazole-3-) methylene ] bis [ N-methyl-N-phenyl ] aniline, 6- (diethylamino) -2- (phenylamino) -spiro [ isobenzofuran-1 (3H),9- [9H ] xanthene ] -3-one, 3-bis (4- (dimethylamino) phenyl) phthalide, spiro (isobenzofuran-1 (3H),9(9H) xanthene-2-carboxylic acid-6- (diethylamino) -3-oxo-ethyl ester or a compound system containing more than one of the xanthene-2-carboxylic acid-6- (diethylamino) -3-oxo-ethyl ester;

the color developing agent is organic acid or phenolic hydroxyl compound and derivatives thereof, and can be one or more compound systems selected from boric acid, bisphenol A, stearic acid, laurate, 8-hydroxyquinoline, benzyl p-hydroxybenzoate, 4-hydroxycoumarin, alpha-naphthol, beta-naphthol, lauric acid, myristic acid, palmitic acid, pyrogallic acid, tannic acid, 2, 6-di-tert-butyl-p-cresol and 4-methoxyphenol;

the melting agent is low boiling point alcohol, and can be one or more than one compound system of octanol, decanol, dodecanol, tetradecanol, hexadecanol and octadecanol;

step 2, adding the thermochromic compound in a molten state into an aqueous phase solution in which a surfactant is dissolved, shearing and emulsifying at a high speed, and performing ultrasonic homogenization to uniformly disperse the thermochromic compound in the aqueous phase solution in a nano-scale liquid drop form to form a miniemulsion;

the mass ratio of the thermochromic compound to the aqueous phase solution is 1: 10-1: 2, preferably 1: 5-1: 3, the temperature of the aqueous phase solution is 60-90 ℃, preferably 70-80 ℃, the concentration of the surfactant in water is 0.1-6%, preferably 0.5-3%, the shear rate is 5000-25000rpm, preferably 10000-20000rpm, the shear time is 5-30min, the stirring speed is 300-600rpm, the polymerization temperature is 60-95 ℃, the polymerization time is 2-20 hours, preferably 5-15 hours, the capsule wall thickness of the prepared thermochromic nanocapsule is 20-200nm, preferably 50-100nm, and the color change temperature is-5-60 ℃;

wherein the surfactant is one or more of cationic surfactant, anionic surfactant or nonionic surfactant;

wherein the cationic surfactant is at least one of cetyl trimethyl ammonium bromide, dodecyl trimethyl chloride, dodecyl sniffed pyridine, dodecyl dimethyl benzyl ammonium chloride, alkyl dimethyl hydroxyethyl quaternary ammonium salt and alkyl dimethyl hydroxyethyl quaternary ammonium salt;

the anionic surfactant is at least one of fatty alcohol-polyoxyethylene ether carboxylate, sodium stearate, linear alkyl benzene sodium sulfonate, branched alkyl benzene sodium sulfonate, diisopropyl sodium zeityl sulfonate, dibutyl sodium zeityl sulfonate, alkyl sodium sulfonate, alpha-olefin sodium sulfonate, alpha-sulfo fatty acid, linear alkyl sulfate, branched alkyl sodium sulfate and fatty alcohol-polyoxyethylene ether sulfate; the nonionic surfactant is at least one of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene octadecyl ether, sorbitol monooleate polyoxyethylene ether, alkylphenol polyoxyethylene, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, alkanolamide and polyoxyethylene alkanolamide;

then transferring the thermochromic compound miniemulsion to a three-neck flask, slowly adding a wall material prepolymer solution under the conditions of constant temperature and continuous stirring, adjusting the pH value to acidity, carrying out polycondensation reaction on the wall material prepolymer, depositing the generated polymer on the surface of a core material liquid drop, and gradually forming a compact capsule wall to obtain a thermochromic nanocapsule dispersion liquid;

the mass ratio of the thermochromic compound miniemulsion to the wall material prepolymer solution is 1: 4-4: 1, preferably 1: 2-2: 1;

the wall material prepolymer is a compound system of one or more than one of melamine resin, urea resin, phenolic resin, epoxy resin, polyurethane, polyacrylonitrile and polyimide prepolymer;

step 3, performing hydrophobic modification, washing and drying on the thermochromic nanocapsule dispersion liquid through a coupling agent to obtain thermochromic nanocapsule powder;

the dosage of the coupling agent is 0.1 to 5 percent of the thermochromic nano capsule dispersion liquid, and preferably 0.5 to 2 percent;

the coupling agent is aminosilane coupling agent, epoxy silane coupling agent, alkyl silane coupling agent, acyl silane coupling agent or mixture thereof, and is selected from one or more than one compound system of KH540, KH550, KH560, KH570, KH590, A-151, A-171 and A-172;

step 4, mixing the thermochromic nano capsule powder, the release agent and the low glass transition temperature monomer oil phase to form a mixed oil phase, and carrying out shearing dispersion and polymerization reaction on the mixed oil phase and the aqueous dispersion liquid to obtain soft ink powder core particles;

the low glass transition temperature monomer oil phase comprises a nucleating resin monomer, a cross-linking agent, a molecular weight regulator and an initiator;

the usage amount of the thermochromic nano capsule powder is 3-18 wt% of the weight of the nucleating resin monomer, the release agent is wax with the melting point range of 50-100 ℃, and the usage amount of the wax is 5-20 wt% of the weight of the nucleating resin monomer;

the aqueous dispersion adopts a suspension dispersant, which is one or more materials selected from calcium phosphate, magnesium hydroxide, calcium carbonate, polyvinyl alcohol and hydroxypropyl methyl cellulose, and is preferably a dispersion stabilizer containing inorganic magnesium hydroxide colloid which is difficult to dissolve in water, wherein the particle diameter D50 of the magnesium hydroxide is 0.3-0.5 mu m, the concentration of the suspension dispersant is preferably 0.5-5 wt% of the mass part of water or the using amount of the dispersant in the dispersion accounts for 1-20 wt% of the low Tg monomer oil phase;

preferably, the mass ratio of the low Tg monomer oil phase to the aqueous dispersion is from 1:2 to 1: 10; the suspension granulation temperature is preferably 20-60 ℃, the rotating speed is 6000-25000rpm, and the average grain diameter of oil drops is 4-15 μm, preferably 5-10 μm; the stirring speed is 100-1000rpm, preferably 200-600rpm, the reaction temperature is preferably 60-95 ℃, and the polymerization time is 2-20h, preferably 5-15 h; the Tg of the soft ink powder core particles is 40-60 ℃;

wherein, the nucleating resin monomer is mainly selected from a single vinyl monomer and comprises one or more than one of the following materials: aromatic vinyl monomers such as styrene, methylstyrene or α -methylstyrene; acrylic monomers such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl methacrylate, glycidyl (meth) acrylate, and lauryl (meth) acrylate;

the cross-linking agent is mainly selected from monomers containing two or more unsaturated ethylene groups, and comprises one or more of the following materials: divinylbenzene, divinylsulfone, ethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, 1, 4-butanediol dimethacrylate, 1, 6-hexanediol dimethacrylate, allyl methacrylate, pentaerythritol triacrylate, or the like. The amount of the cross-linking agent accounts for 0.1 to 1 weight percent of the weight of the core resin monomer;

the molecular weight regulator comprises one or more than one of the following materials: n-dodecyl mercaptan, t-dodecyl mercaptan, carbon tetrachloride or carbon tetrabromide, etc., in an amount of generally 0.1 to 5% by weight, preferably 0.5 to 3% by weight, based on the weight of the core resin monomer;

the initiator mainly comprises a per-azo initiator and a peroxide initiator, and the azo initiator mainly comprises azobisisoheptonitrile, azobisisobutyronitrile, azobisisovaleronitrile or dimethyl azobisisobutyrate and the like; the peroxide initiator mainly comprises Benzoyl Peroxide (BPO), dilauroyl peroxide (LPO), tert-butyl peroxy-2-ethyl hexanoate, tert-butyl peroxydiethylacetate or tert-butyl peroxyisobutyrate, etc. The oil-soluble initiator is one or more than one of the above materials, and the dosage is generally 1-20 wt% of the weight of the core resin monomer, and preferably 3-10 wt%;

step 5, adding a high glass transition temperature shell resin monomer and an ionic monomer into deionized water to form a miniemulsion, adding the miniemulsion into the soft ink powder core particles, adding a water-soluble initiator, and carrying out polymerization reaction again to form a hydrophobic shell layer with dense charges, so as to obtain the thermochromic anti-counterfeiting ink powder;

in the polymerization, the shell-forming reaction temperature is preferably 60-95 ℃ and the polymerization time is 2-10h, preferably 3-8 h. The average particle size of the prepared core-shell structure toner particles is 4-15 μm, preferably 5-10 μm;

the high glass transition temperature shell resin monomer is mainly selected from one or more than one of monomers capable of forming polymers with the glass transition temperature of over 60 ℃ such as styrene, methacrylate, tert-butyl methacrylate, N-hydroxymethyl acrylamide, acrylonitrile, acrylamide, hydroxypropyl methacrylate and the like. The high glass transition temperature shell resin monomer is generally used in an amount of 2 to 10 wt%, preferably 3 to 6 wt%, based on the weight of the soft core resin monomer. The glass transition temperature of the shell resin is 60-90 ℃;

the ionic monomer includes a cationic monomer and an anionic monomer. The cationic monomer mainly comprises tertiary amine and quaternary ammonium salt monomers containing unsaturated double bonds, such as one or more of diethylaminoethyl methacrylate, dimethyl diallyl ammonium chloride, methacryloyloxyethyl ammonium trichloride, diethylaminoethyl acrylate and 4-dimethyl aminostyrene;

the anionic monomer mainly comprises sulfonic acid, sulfuric acid, phosphoric acid, carboxylic acid and acrylic acid monomers containing unsaturated double bonds, such as one or more of (methyl) acrylic acid, vinylsulfonic acid (sodium and potassium), sodium styrenesulfonate, 2-acrylamido-2-methyl-1-propanesulfonic Acid (AMPS), allylsulfonic acid (sodium and potassium), methacrylic sulfonic acid (sodium and potassium) and 3-sulfopropyl acrylic acid (sodium and potassium). The amount of ionic monomer used is generally from 1 to 20% by weight, preferably from 3 to 15% by weight, based on the weight of the high glass transition temperature shell resin monomer;

the water-soluble initiator is selected from one or more of potassium persulfate, ammonium persulfate, 2-bis (2-methyl-N- (2-hydroxyethyl) propionamide) and 2, 2-azo bis (2-methyl-N- (1, 1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide). The amount of the aqueous initiator is 1 to 40 wt%, preferably 3 to 30 wt% based on the rigid shell monomer.

In the embodiment, soft toner core particles are obtained through suspension granulation and polymerization of a low-Tg monomer, a toner and a colorant in an aqueous dispersion, and then a hydrophobic rigid shell layer with dense charges is formed outside the soft toner core particles through in-situ polymerization of a high-Tg shell monomer and an ionic monomer emulsion, so that core-shell structure toner particles are obtained. The toner is a thermochromic nanocapsule, the core material is a thermochromic compound, the capsule wall is formed by the polycondensation reaction of the prepolymer of the wall material, and the thermochromic performance of the toner can be adjusted by changing the composition of the thermochromic compound and the proportion of the thermochromic compound in the toner.

Example 1

The embodiment 1 of the invention provides a preparation method of thermochromic anti-counterfeiting ink powder, which comprises the following steps:

firstly, 1 part of 2-phenylamino-3-methyl-6-dibutylaminofluorane, 2 parts of bisphenol A and 60 parts of n-tetradecanol are placed in a three-necked bottle provided with a stirring device, the temperature is increased to 90 ℃, and the temperature is kept unchanged under the condition of stirring speed of 600rpm for reaction for 1 hour to obtain a thermochromic compound in a molten state;

uniformly mixing 20 parts of melamine, 60 parts of 37% formaldehyde solution and 80 parts of water, adjusting the pH value to 8-9 by using triethanolamine, stirring and heating to 70 ℃, and reacting until the melamine is completely dissolved to obtain melamine resin prepolymer aqueous solution;

60 parts of the thermochromic compound is dropped into 280 parts of aqueous phase solution with 2 parts of sodium dodecyl sulfate and 2 parts of polyvinyl alcohol (PVA1788) dissolved at 70 ℃, and dispersed in a high-speed dispersion machine at the stirring speed of 20000rpm for 10min to obtain uniformly mixed miniemulsion, wherein the particle size of oil drop particles is about 250 nm. Adding melamine resin prepolymer aqueous solution into the thermochromic compound miniemulsion, adjusting the pH value to 4-5 with acetic acid, and reacting for 3h at the constant temperature of 70 ℃ and the stirring speed of 600 rpm; then, 20g of 10% silane coupling agent (KH550) ethanol solution is dripped, the mixture is continuously stirred for 1h, then washed for 3 times by water and isopropanol respectively, centrifugally separated, and then dried in vacuum for 24h at the temperature of 45 ℃ to obtain thermochromic nanocapsule powder, the particle size of the thermochromic nanocapsule is about 300nm, and the thermochromic nanocapsule is heated to the temperature of more than 40 ℃ to generate a black-to-colorless fading phenomenon;

slowly adding 100 parts of deionized water dissolved with 20 parts of magnesium chloride into 200 parts of deionized water dissolved with 9 parts of sodium hydroxide, shearing at a high speed for dispersing for 1h, and then performing ultrasonic ageing for 4h at room temperature to obtain magnesium hydroxide suspension dispersion liquid (D50:350 nm);

76 parts of styrene, 24 parts of n-butyl acrylate, 8 parts of thermochromic nanocapsules, 0.6 part of divinylbenzene, 2.0 parts of n-dodecyl mercaptan, 10 parts of ester wax (WE-4, manufactured by Nippon oil & fat Co., Ltd.), 6 parts of azobisisobutyronitrile, ultrasonically dispersing for 10min, and stirring at 1000rpm for 30min to obtain a mixed oil phase;

the mixed oil phase was added to a magnesium hydroxide suspension dispersion, and sheared at 4500rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5min to form primary oil droplet particles having an average particle diameter of 20 μm, followed by shearing at 9000rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5 min. Then transferring the mixture into a three-mouth bottle, and heating the mixture to 90 ℃ for polymerization reaction for 5 hours under the condition of stirring speed of 300 rpm;

adding 2 parts of styrene, 3 parts of methyl methacrylate, 0.5 part of butyl acrylate and 0.5 part of oleyl dimethyl benzyl ammonium chloride into 50 parts of deionized water, emulsifying at high speed of 10000rpm for 5min by a high-speed dispersion machine (Ultratalax T50 manufactured by IKA), and adding into the suspension dispersion system for dispersing for 30 min;

dissolving 1 part of potassium persulfate in 10 parts of deionized water, adding the solution into the suspension dispersion system, carrying out polymerization reaction at 80 ℃ for 5 hours, filtering and drying the product, and adding 2% of silicon dioxide (R504 manufactured by Degussa corporation) for treatment to obtain the thermochromic core-shell-structure toner particles with the average particle size of 8 microns, wherein the thermochromic core-shell-structure toner particles are shown in figure 2.

An image printed with this toner particle undergoes a black to white color change upon heating above 50 c, as shown in fig. 3.

Example 2

The embodiment 2 of the invention provides a preparation method of thermochromic anti-counterfeiting ink powder, which comprises the following steps:

firstly, 0.6 part of dibromo-o-cresol sulfolene, 9 parts of stearic acid and 60 parts of n-dodecanol are put into a three-necked bottle provided with a stirring device, the temperature is raised to 90 ℃, and the temperature is kept unchanged under the condition of stirring speed of 600rpm for reaction for 1 hour to obtain a thermochromic compound in a molten state;

uniformly mixing 20 parts of melamine, 60 parts of 37% formaldehyde solution and 80 parts of water, adjusting the pH value to 8-9 by using triethanolamine, stirring and heating to 70 ℃, and reacting until the melamine is completely dissolved to obtain melamine resin prepolymer aqueous solution;

60 parts of the thermochromic compound is dropped into 280 parts of aqueous phase solution with 2 parts of sodium dodecyl sulfate and 2 parts of polyvinyl alcohol (PVA1788) dissolved at 70 ℃, dispersed in a high-speed dispersion machine at the stirring speed of 20000rpm for 10min to obtain uniformly mixed miniemulsion, the particle size of oil drop particles is about 250nm, melamine resin prepolymer aqueous solution is added into the thermochromic compound miniemulsion, the pH value is adjusted to 4-5 by acetic acid, and the reaction is carried out for 3h at the constant temperature of 70 ℃ and the stirring speed of 600 rpm; then 20g of 10% silane coupling agent (KH550) ethanol solution is dripped, the mixture is continuously stirred for 1h, and then is respectively washed with water and isopropanol for 3 times, centrifugally separated and then dried in vacuum for 24h at the temperature of 45 ℃ to obtain the thermotropic nano capsule powder. The thermochromic nanocapsules have a particle size of about 300nm and are heated to above 40 ℃ to generate a black-to-colorless fading phenomenon;

slowly adding 100 parts of deionized water dissolved with 20 parts of magnesium chloride into 200 parts of deionized water dissolved with 9 parts of sodium hydroxide, shearing at a high speed for dispersing for 1h, and then performing ultrasonic ageing for 4h at room temperature to obtain magnesium hydroxide suspension dispersion liquid (D50:350 nm);

76 parts of styrene, 24 parts of n-butyl acrylate, 8 parts of thermochromic nanocapsules, 0.6 part of divinylbenzene, 2.0 parts of n-dodecyl mercaptan, 10 parts of ester wax (WE-4, manufactured by Nippon oil & fat Co., Ltd.), 6 parts of azobisisobutyronitrile, ultrasonically dispersing for 10min, and stirring at 1000rpm for 30min to obtain a mixed oil phase;

the mixed oil phase was added to a magnesium hydroxide suspension dispersion, and sheared at 4500rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5min to form primary oil droplet particles having an average particle diameter of 20 μm, followed by shearing at 9000rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5 min. Then transferring the mixture into a three-mouth bottle, and heating the mixture to 90 ℃ for polymerization reaction for 5 hours under the condition of stirring speed of 300 rpm;

adding 2 parts of styrene, 3 parts of methyl methacrylate, 0.5 part of butyl acrylate and 0.5 part of oleyl dimethyl benzyl ammonium chloride into 50 parts of deionized water, emulsifying at high speed of 10000rpm for 5min by a high-speed dispersion machine (Ultratalax T50 manufactured by IKA), and adding into the suspension dispersion system for dispersing for 30 min;

dissolving 1 part of potassium persulfate in 10 parts of deionized water, adding the solution into the suspension dispersion system, carrying out polymerization reaction at 80 ℃ for 5 hours, filtering and drying the product, and adding 2% of silicon dioxide (R504 manufactured by Degussa corporation) for treatment to obtain the thermochromic core-shell structure toner particles with the average particle size of 8 microns.

An image printed with this toner particle undergoes a color change from orange-red to pale yellow upon heating above 25 ℃.

Example 3

The embodiment 3 of the invention provides a preparation method of thermochromic anti-counterfeiting ink powder, which comprises the following steps:

firstly, placing 1.2 parts of 3, 3-bis (4- (dimethylamino) phenyl) phthalide, 2.4 parts of 4-hydroxycoumarin and 60 parts of n-hexadecanol in a three-necked bottle with a stirring device, heating to 90 ℃, and keeping the temperature unchanged under the condition of stirring speed of 600rpm for reaction for 1h to obtain a thermochromic compound in a molten state;

uniformly mixing 20 parts of melamine, 60 parts of 37% formaldehyde solution and 80 parts of water, adjusting the pH value to 8-9 by using triethanolamine, stirring and heating to 70 ℃, and reacting until the melamine is completely dissolved to obtain melamine resin prepolymer aqueous solution;

60 parts of the thermochromic compound is dropped into 280 parts of aqueous phase solution with 2 parts of sodium dodecyl sulfate and 2 parts of polyvinyl alcohol (PVA1788) dissolved at 70 ℃, and dispersed in a high-speed dispersion machine at the stirring speed of 20000rpm for 10min to obtain uniformly mixed miniemulsion, wherein the particle size of oil drop particles is about 250 nm. Adding melamine resin prepolymer aqueous solution into the thermochromic compound miniemulsion, adjusting the pH value to 4-5 with acetic acid, and reacting for 3h at the constant temperature of 70 ℃ and the stirring speed of 600 rpm; then 20g of 10% silane coupling agent (KH550) ethanol solution is dripped, the mixture is continuously stirred for 1h, and then is respectively washed with water and isopropanol for 3 times, centrifugally separated and then dried in vacuum for 24h at the temperature of 45 ℃ to obtain the thermotropic nano capsule powder. The thermochromic nanocapsules have a particle size of about 300nm and are heated to above 40 ℃ to generate a black-to-colorless fading phenomenon;

slowly adding 100 parts of deionized water dissolved with 20 parts of magnesium chloride into 200 parts of deionized water dissolved with 9 parts of sodium hydroxide, shearing at a high speed for dispersing for 1h, and then performing ultrasonic ageing for 4h at room temperature to obtain magnesium hydroxide suspension dispersion liquid (D50:350 nm);

76 parts of styrene, 24 parts of n-butyl acrylate, 8 parts of thermochromic nanocapsules, 0.6 part of divinylbenzene, 2.0 parts of n-dodecyl mercaptan, 10 parts of ester wax (WE-4, manufactured by Nippon oil & fat Co., Ltd.), 6 parts of azobisisobutyronitrile, ultrasonically dispersing for 10min, and stirring at 1000rpm for 30min to obtain a mixed oil phase;

the mixed oil phase was added to a magnesium hydroxide suspension dispersion, and sheared at 4500rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5min to form primary oil droplet particles having an average particle diameter of 20 μm, followed by shearing at 9000rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5 min. Then transferring the mixture into a three-mouth bottle, and heating the mixture to 90 ℃ for polymerization reaction for 5 hours under the condition of stirring speed of 300 rpm;

adding 2 parts of styrene, 3 parts of methyl methacrylate, 0.5 part of butyl acrylate and 0.5 part of oleyl dimethyl benzyl ammonium chloride into 50 parts of deionized water, emulsifying at high speed of 10000rpm for 5min by a high-speed dispersion machine (Ultratalax T50 manufactured by IKA), and adding into the suspension dispersion system for dispersing for 30 min;

dissolving 1 part of potassium persulfate in 10 parts of deionized water, adding the solution into the suspension dispersion system, carrying out polymerization reaction at 80 ℃ for 5 hours, filtering and drying the product, and adding 2% of silicon dioxide (R504 manufactured by Degussa corporation) for treatment to obtain the thermochromic core-shell structure toner particles with the average particle size of 8 microns.

An image printed with the toner particles is heated to above 52 ℃ to undergo a color change from cyan to pale green.

Example 4

The embodiment 4 of the invention provides a preparation method of thermochromic anti-counterfeiting ink powder, which comprises the following steps:

firstly, 1 part of 3, 3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide, 4 parts of bisphenol A, 43 parts of n-tetradecanol and 22 parts of n-hexadecanol are placed in a three-neck flask provided with a stirring device, the temperature is increased to 90 ℃, and the temperature is kept unchanged under the condition of stirring speed of 600rpm for reaction for 1 hour to obtain a thermochromic compound in a molten state;

uniformly mixing 20 parts of melamine, 60 parts of 37% formaldehyde solution and 80 parts of water, adjusting the pH value to 8-9 by using triethanolamine, stirring and heating to 70 ℃, and reacting until the melamine is completely dissolved to obtain melamine resin prepolymer aqueous solution;

60 parts of the thermochromic compound is dropped into 280 parts of aqueous phase solution with 2 parts of sodium dodecyl sulfate and 2 parts of polyvinyl alcohol (PVA1788) dissolved at 70 ℃, and dispersed in a high-speed dispersion machine at the stirring speed of 20000rpm for 10min to obtain uniformly mixed miniemulsion, wherein the particle size of oil drop particles is about 250 nm. Adding melamine resin prepolymer aqueous solution into the thermochromic compound miniemulsion, adjusting the pH value to 4-5 with acetic acid, and reacting for 3h at the constant temperature of 70 ℃ and the stirring speed of 600 rpm; then 20g of 10% ethanol solution of silane coupling agent (KH550) is dripped, the mixture is continuously stirred for 1h, and then is respectively washed with water and isopropanol for 3 times, centrifugally separated and then dried in vacuum for 24h at the temperature of 45 ℃ to obtain the thermotropic nano capsule powder. The thermochromic nanocapsules have a particle size of about 300nm and are heated to above 40 ℃ to generate a black-to-colorless fading phenomenon;

slowly adding 100 parts of deionized water dissolved with 20 parts of magnesium chloride into 200 parts of deionized water dissolved with 9 parts of sodium hydroxide, shearing at a high speed for dispersing for 1h, and then performing ultrasonic ageing for 4h at room temperature to obtain magnesium hydroxide suspension dispersion liquid (D50:350 nm);

76 parts of styrene, 24 parts of n-butyl acrylate, 8 parts of thermochromic nanocapsules, 0.6 part of divinylbenzene, 2.0 parts of n-dodecyl mercaptan, 10 parts of ester wax (WE-4, manufactured by Nippon oil & fat Co., Ltd.), 6 parts of azobisisobutyronitrile, ultrasonically dispersing for 10min, and stirring at 1000rpm for 30min to obtain a mixed oil phase;

the mixed oil phase was added to a magnesium hydroxide suspension dispersion, and sheared at 4500rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5min to form primary oil droplet particles having an average particle diameter of 20 μm, followed by shearing at 9000rpm by a high speed disperser (Ultratalax T50, manufactured by IKA) for 5 min. Then transferring the mixture into a three-mouth bottle, and heating the mixture to 90 ℃ for polymerization reaction for 5 hours under the condition of stirring speed of 300 rpm;

adding 2 parts of styrene, 3 parts of methyl methacrylate, 0.5 part of butyl acrylate and 0.5 part of oleyl dimethyl benzyl ammonium chloride into 50 parts of deionized water, emulsifying at high speed of 10000rpm for 5min by a high-speed dispersion machine (Ultratalax T50 manufactured by IKA), and adding into the suspension dispersion system for dispersing for 30 min;

dissolving 1 part of potassium persulfate in 10 parts of deionized water, adding the solution into the suspension dispersion system, carrying out polymerization reaction at 80 ℃ for 5 hours, filtering and drying the product, and adding 2% of silicon dioxide (R504 manufactured by Degussa corporation) for treatment to obtain the thermochromic core-shell structure toner particles with the average particle size of 8 microns.

An image printed with this toner particle undergoes a color change from violet to bluish when heated above 33 ℃.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.