Composite color-changing agent, preparation method and anti-counterfeiting color-changing ink

Abstract

The invention relates to the technical field of anti-counterfeiting materials, and particularly discloses a composite color-changing agent, anti-counterfeiting color-changing ink and a preparation method of the anti-counterfeiting color-changing ink. The composite color-changing agent is a composite microsphere with a core-shell-satellite structure, the core is a temperature-sensing color-changing microcapsule and is composed of a temperature-sensing color-changing core material and a polymer wall material, the shell is a transparent polymer shell and wraps the core through in-situ polymerization, the satellite is a light-sensing color-changing material and is embedded and fixed on the shell, and the shell is a transparent polymer shell and is embedded and fixed on the shell. According to the composite color-changing agent, the light-sensitive material and the temperature-sensitive material are compositely inlaid through the polymer shell, so that the problem of poor compatibility of the light-sensitive material and the temperature-sensitive material is solved, the stability and the production efficiency are improved, and the imitation difficulty is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of anti-counterfeiting materials, more particularly, it relates to a composite color-changing agent, a preparation method and an anti-counterfeiting color-changing ink. BACKGROUND

[0002] Anti-counterfeiting ink is an important means to protect product safety and crack down on counterfeiting and inferior products. Among them, temperature-sensitive color-changing and light-sensitive color-changing materials are favored due to their intuitive verification method and are widely used in high-end anti-counterfeiting packaging, bills, certificates and other fields. In order to improve the anti-counterfeiting level, the composite use of temperature-sensitive and light-sensitive color-changing technologies has become an important development direction. For example, in the prior art, temperature-sensitive color-changing microcapsules and light-sensitive color-changing microcapsules have been physically mixed and then added to the ink binder. However, this simple physical compounding method has a series of significant inherent defects: Firstly, the surface chemical properties of different types of microcapsules differ significantly, and their compatibility in the ink system is poor, which easily leads to phase separation and aggregation and sedimentation, resulting in uneven printing color and inconsistent color-changing effect, seriously affecting the reliability and appearance consistency of the anti-counterfeiting mark.

[0003] Secondly, multiple color-changing materials coexist in the same system, and their stability will interfere with each other. The solvent, resin or additive in the ink may selectively erode the wall material of a certain type of microcapsule. The thermal cycle process of the temperature-sensitive material or the photochemical reaction of the light-sensitive material may also accelerate the aging failure of the adjacent material. For example, the heat accumulation of the temperature-sensitive material may cause irreversible chemical degradation of the light-sensitive material.

[0004] Furthermore, physical mixing causes gaps between different microcapsules, increasing the contact area with oxygen, moisture and ultraviolet light in the environment, thereby accelerating the performance degradation of all active color-changing components, resulting in decreased color-changing sensitivity and shortened cycle life. In addition, the physical mixing type color-changing agent has poor adaptability during ink processing and weak shear resistance. The microcapsules are easily damaged during three-roll grinding, high-speed stirring and other processes, resulting in cross-contamination of the internal core material and loss of color-changing function.

[0005] Although some studies have attempted to design single compounds from a molecular design, the synthesis path is complex and costly, and it is difficult to balance the effectiveness and balance of temperature and light change performance. Therefore, it is still a distance from large-scale industrial application. Therefore, it is of great significance to develop a new type of composite color-changing agent technology that can fundamentally overcome the above compatibility and stability problems, and has a feasible process and controllable cost, for promoting the development of high-end anti-counterfeiting ink. SUMMARY

[0006] This application aims to overcome the shortcomings of existing physical mixing technologies, such as poor compatibility and mutual interference in stability, and provides a highly compatible temperature- and light-sensitive composite color-changing agent, its preparation method, and anti-counterfeiting color-changing ink. This composite color-changing agent integrates light-sensitive and temperature-sensitive materials through a polymer shell, solving the problem of poor compatibility between the two materials, improving stability and production efficiency, and increasing the difficulty of counterfeiting.

[0007] In a first aspect, this application provides a composite color-changing agent, employing the following technical solution: A composite color-changing agent, wherein the composite color-changing agent is a composite microsphere having a core-shell-satellite structure: The core is a thermochromic microcapsule, which is composed of a thermochromic core material and a polymer wall material; The shell is a transparent polymer shell, which is coated on the outside of the core by in-situ polymerization; The satellite is made of photosensitive color-changing material and is embedded and fixed on the shell.

[0008] Through this structural design, the thermochromic material and the photochromic material are spatially tightly connected under the action of the polymer shell, effectively solving the problem of low compatibility between the two and avoiding mutual interference. The thermochromic core material is completely enclosed inside the core, protected by both the polymer wall material and the shell, thus significantly improving its heat resistance and solvent resistance; the photochromic material is embedded and fixed in the shell, reducing the adverse effects of external environmental factors on its structural integrity and photoresponse performance. In addition, this composite microsphere structure exhibits excellent dispersibility and stability in the ink system, solving the aggregation and sedimentation problems commonly found in traditional physical mixing methods, ensuring the uniformity and reliability of the printing effect.

[0009] More preferably, the temperature-sensitive color-changing core material is a compound system comprising a leuco dye, a color developer, and an organic solvent. The leuco dyes include, but are not limited to, phthalides, fluoresceins, triarylmethanes, phenazines, thiazides, and azines; the color developers include, but are not limited to, bisphenol A, salicylic acid, oxalic acid, benzotriazole, and haloalcohols; and the organic solvents include, but are not limited to, higher fatty alcohols, fatty acids and their esters, aromatic hydrocarbons and their ethers, and ester compounds.

[0010] More preferably, the polymer wall material is selected from one or more of urea-formaldehyde resin, melamine resin, gelatin / gum arabic composite glue, polyurethane, and melamine-formaldehyde resin. This type of polymer material has excellent film-forming properties and thermal stability. It can coat the core material through interfacial polymerization or in-situ emulsion polymerization to form a dense protective layer with a certain mechanical strength.

[0011] More preferably, the polymer shell is selected from polyacrylates, polyurethane acrylates, or silicone-acrylate hybrid resins. This type of polymer shell not only possesses excellent transparency, without affecting color change, but also exhibits good weather resistance and chemical inertness, maintaining structural stability under complex environmental conditions. Furthermore, it has moderate hardness, effectively protecting the thermochromic capsule and fixing the photochromic material, while also demonstrating good compatibility with most ink resins.

[0012] More preferably, the photochromic material is selected from one or more compounds chosen from spiropyran, spiroxazine, diarylethylene, or benzoic acid anhydrides. This type of photochromic material can rapidly undergo a reversible molecular structure transformation under light irradiation, thereby achieving a dynamic color response. Synergistically acting with the thermochromic core material, it endows the composite microspheres with dual-stimulus response characteristics. By adjusting the type and loading of the photosensitive material, its color-changing threshold and response speed can be precisely controlled. Secondly, this application provides a method for preparing a composite color-changing agent, which adopts the following technical solution: A method for preparing a composite color-changing agent includes the following steps: S1, at 300-500 rpm, the mixture of isophorone diisocyanate monomer and dibutyltin dilaurate catalyst is slowly added to the emulsion of emulsifier, and ultrasonically treated in an ice-water bath for 2-3 minutes to obtain the emulsion; S2, dilute the thermochromic microcapsules in deionized water, keeping the solid content at 10-15%, then add the photochromic material, and add the emulsion obtained in S1 dropwise at 150-300 rpm. After the addition is complete, continue stirring and reacting for 0.5-1 h, then add the ethylenediamine chain extender and continue reacting for 1-2 h to allow the emulsion to fully crosslink and solidify. S3. After the reaction is complete, the product is centrifuged and washed with deionized water 3-5 times to remove unreacted monomers and catalyst residues. Then, it is dried in a vacuum drying oven at 40-50℃ for 6-8 hours to obtain the composite color-changing agent product.

[0013] This application first prepares a pre-emulsion of isophorone diisocyanate in an independent system, and then gently mixes it with the thermochromic microcapsule system. Compared with the direct mixing of polymer raw materials and color-changing raw materials, this method is more controllable and reliable, which avoids the damage of thermochromic microcapsules to thermochromic microcapsules by high-speed shearing and can obtain a more continuous and regular polymer shell.

[0014] More preferably, in S1, the emulsifier is at least one of NP-10, Tween-80, and Span-80.

[0015] More preferably, in S1, the amount of emulsifier used is 2%-5% of the mass of isophorone diisocyanate.

[0016] More preferably, in S1, the amount of dibutyltin dilaurate is 0.1%-3% of the mass of isophorone diisocyanate.

[0017] More preferably, in S2, the mass ratio of thermochromic microcapsules to photochromic material is 1:(0.5-2).

[0018] More preferably, in S2, the mass ratio of isophorone diisocyanate to thermochromic microcapsules is 1:(3-5). This ratio effectively ensures the formation of a continuous polymer shell on the surface of the microcapsules, while avoiding increased brittleness due to excessive cross-linking.

[0019] More preferably, in S2, the amount of ethylenediamine used is 1%-3% of the mass of isophorone diisocyanate.

[0020] Thirdly, this application provides an anti-counterfeiting color-changing ink, which adopts the following technical solution: An anti-counterfeiting color-changing ink includes components A and B, which are stored separately and mixed in a weight ratio of 5:1 when used. Component A includes the following components in parts by weight: 100 parts epoxy resin, 8-10 parts reactive diluent, 30-50 parts solvent, 0.5-1 part leveling agent, 0.6-1 part defoamer, 0.3-0.5 parts thixotropic agent, and 8-15 parts composite color-changing agent. Component B is a polyetheramine, a fatty amine, or an anhydride curing agent.

[0021] In summary, this application has the following beneficial effects: (1) This application provides a dual anti-counterfeiting color-changing material and ink with temperature-sensitive and light-sensitive properties, and solves the problems of poor physical compatibility and easy separation of temperature-sensitive and light-sensitive materials, thereby improving the stability of the ink and the consistency of printing effect; (2) The color-changing material adopts a dual composite structure, and the resulting composite microspheres have high mechanical strength, can withstand grinding and shearing during ink preparation, and have a very low breakage rate, thus ensuring production efficiency and product yield. (3) Because the temperature-sensitive and light-sensitive materials are physically composited and inlaid, they can produce color-changing behavior that cannot be achieved by physical mixing. The synergistic effect that is difficult to imitate increases the technical and cost threshold for imitation. Detailed Implementation

[0022] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0023] Furthermore, it should be understood that the one or more method steps mentioned in this application do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of the method steps or limit the scope of implementation of this application. Changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered as within the scope of implementation of this application.

[0024] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0025] The thermochromic microcapsules use Ranbar Green SW4360, which appears emerald green at low temperatures and is colorless at high temperatures, with a temperature range of 0-70℃. The photochromic material uses Ranbar Red DP1610, which changes from colorless to a bright red under ultraviolet light.

[0026] Example Example 1: Preparation of composite color-changing agent: S1, at 300 rpm, a mixture of 100 g isophorone diisocyanate monomer and 0.1 g dibutyltin dilaurate catalyst was slowly added to 30 g NP-10 aqueous emulsion (water-to-emulsion ratio of 9:1), and the mixture was ultrasonically treated in an ice-water bath for 3 min to obtain the emulsion. S2, 300g of thermochromic microcapsules were diluted in deionized water to maintain a solid content of 12%, and then 500g of photochromic material was added. The emulsion obtained in S1 was added dropwise at 150rpm and a dropping rate of 1 drop / s. After the addition was completed, the reaction was stirred for 0.5h. Then 1g of ethylenediamine chain extender was added and the reaction was continued for 1h to allow the emulsion to fully crosslink and solidify. S3. After the reaction is complete, the product is centrifuged and washed three times with deionized water to remove unreacted monomers and catalyst residues. Then, it is dried in a vacuum drying oven at 45°C for 8 hours to obtain the composite color-changing agent product.

[0027] Example 2 Preparation of composite color-changing agent: S1, at 300 rpm, a mixture of 100 g isophorone diisocyanate monomer and 0.1 g dibutyltin dilaurate catalyst was slowly added to 40 g NP-10 aqueous emulsion (water-to-emulsion ratio of 9:1), and the mixture was ultrasonically treated in an ice-water bath for 3 min to obtain the emulsion. S2, 400g of thermochromic microcapsules were diluted in deionized water to maintain a solid content of 12%, and then 400g of photochromic material was added. The emulsion obtained in S1 was added dropwise at 150rpm and a dropping rate of 1 drop / s. After the addition was completed, the reaction was stirred for 0.5h. Then 2g of ethylenediamine chain extender was added and the reaction was continued for 1h to allow the emulsion to fully crosslink and solidify. S3. After the reaction is complete, the product is centrifuged and washed three times with deionized water to remove unreacted monomers and catalyst residues. Then, it is dried in a vacuum drying oven at 45°C for 8 hours to obtain the composite color-changing agent product.

[0028] Example 3 Preparation of composite color-changing agent: S1, at 300 rpm, a mixture of 100 g isophorone diisocyanate monomer and 0.1 g dibutyltin dilaurate catalyst was slowly added to 50 g NP-10 aqueous emulsion (water-to-emulsion ratio of 9:1), and the mixture was ultrasonically treated in an ice-water bath for 3 min to obtain the emulsion. S2, 500g of thermochromic microcapsules were diluted in deionized water to maintain a solid content of 12%, and then 300g of photochromic material was added. The emulsion obtained in S1 was added dropwise at 150rpm and a dropping rate of 1 drop / s. After the addition was completed, the reaction was stirred for 0.5h. Then 3g of ethylenediamine chain extender was added and the reaction was continued for 1h to allow the emulsion to fully crosslink and solidify. S3. After the reaction is complete, the product is centrifuged and washed three times with deionized water to remove unreacted monomers and catalyst residues. Then, it is dried in a vacuum drying oven at 45°C for 8 hours to obtain the composite color-changing agent product.

[0029] Example 4: Preparation of anti-counterfeiting color-changing ink: Preparation of Component A: 100g of epoxy resin E-44 was added to 40g of ethyl acetate and stirred at 750rpm for 15min. Then, 10g of the composite color-changing agent prepared in Example 1 was added and stirred until homogeneous. Next, 10g of neopentyl glycol diglycidyl ether, 0.6g of polyester-modified siloxane and 1g of dimethyl silicone oil were added in sequence. The stirring speed was maintained at 750rpm and stirred for 30min to ensure that the components were fully mixed. Finally, 0.4g of nano silica was added and stirred at the same speed for 10min to obtain Component A. Component B is polyetheramine T403.

[0030] Example 5: Preparation of anti-counterfeiting color-changing ink: The preparation method is the same as in Example 4, except that the composite color-changing agent is replaced with the composite color-changing agent prepared in Example 2.

[0031] Example 6: Preparation of anti-counterfeiting color-changing ink: The preparation method is the same as in Example 4, except that the composite color-changing agent is replaced with the composite color-changing agent prepared in Example 3.

[0032] Comparative Example Comparative Example 1: Preparation of Composite Color Changing Agent The thermochromic microcapsules were diluted in deionized water to maintain a solid content of 10%. Then, the photochromic material was added, and the temperature was raised to 35-45℃. After stirring at 100-200 rpm for 2-4 hours, isophorone diisocyanate monomer, dibutyltin dilaurate catalyst, and ethylenediamine chain extender were added. The reaction was carried out at a water bath temperature of 25-30℃ and a stirring speed of 150-250 rpm for 4-6 hours. After washing and centrifugation, the product was obtained after freeze-drying.

[0033] Comparative Example 2: Preparation of Anti-counterfeiting Color-Changing Ink The preparation method is the same as in Example 4, except that the composite color-changing agent is replaced with the composite color-changing agent prepared in Comparative Example 1.

[0034] Comparative Example 3: Preparation of Anti-counterfeiting Color-Changing Ink The preparation method is the same as in Example 4, except that the composite color-changing agent is replaced with thermochromic microcapsules and photochromic materials that are not encapsulated by a polymer shell.

[0035] Performance testing Strength test The composite color change agents prepared in Examples 1-3 and Comparative Example 1 were subjected to strength tests using a tablet press. Specifically, the composite color change agents were tableted under a pressure of 5 kg using a tablet press, and the breakage was observed to obtain the breakage rate. The results are recorded in Table 1 below.

[0036] As shown in Table 1, the composite color-changing agents prepared in Examples 1-3 exhibited higher mechanical strength under external force, with breakage rates all below 3%, while the composite color-changing agent in Comparative Example 1 had a breakage rate of 16.7%, significantly lower than that of Examples 1-3. This indicates that the composite color-changing agent prepared by pre-emulsifying the monomer before mixing and reacting with the color-changing material has superior compressive strength. This is because high-speed shearing can destroy the microcapsule structure. In Comparative Example 1, when preparing the color-changing material, low-speed stirring was used. Due to the excessively rapid reaction of the monomer, the material could not be mixed evenly, resulting in irregular, brittle gels or solid blocks, and failing to obtain a complete and continuous polymer shell. This application uses a pre-emulsification method to ensure that the monomer and emulsifier are fully and evenly mixed to form a stable emulsion system, thereby effectively controlling the reaction rate and the quality of microcapsule formation.

[0037] Table 1. Test results of composite color-changing agent strength Ink stability test The anti-counterfeiting color-changing inks prepared in Examples 4-6 and Comparative Examples 2-3 were mixed evenly at a mass ratio of 5:1 for component A and component B, and then coated onto the surface of a PVC substrate. The mixture was dried at 80°C for 3 hours and cured at room temperature for 24 hours to form an ink layer with a thickness of 50 μm.

[0038] First, conduct a UV aging test: use a UV aging chamber to age the ink layer, set the aging conditions to 60℃ and 50% humidity, and continuously irradiate the UV-A lamp for 168 hours.

[0039] Next, a temperature change cycle test was conducted: the UV-aged ink layer was placed in a 45℃ water bath for 1 minute, then placed in an ice water bath for 1 minute, and the cycle was repeated 300 times.

[0040] The color change time and color recovery time of the ink layer before and after UV aging and temperature cycling tests were tested respectively, and the results were recorded in Table 2.

[0041] As shown in Table 2, the anti-counterfeiting color-changing inks prepared in Examples 4-6 exhibited minimal changes in color-changing and recoloring times after UV aging and temperature cycling tests, demonstrating good environmental stability. In contrast, the inks in Comparative Examples 2-3 showed significant color-changing sluggishness. In particular, Comparative Example 3, where thermochromic capsules and photochromic materials were directly added to the ink system, resulted in an ink layer with good initial color-changing ability, but its color-changing performance significantly decreased after aging tests. The color-changing time was extended to 4-6 times the initial value, and the recoloring time was extended to 2-3 times the initial value. This indicates that untreated color-changing materials are prone to performance degradation under complex environmental conditions. This application, by optimizing the microcapsule structure and emulsification process, significantly improves the weather resistance and thermal stability of the color-changing material, enabling it to maintain excellent color-changing response capabilities even under long-term use and extreme environments.

[0042] Table 2 Test Results of Color-Changing Performance of Anti-counterfeiting Color-Changing Ink The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A composite color-changing agent, characterized in that, The composite color-changing agent is a composite microsphere with a core-shell-satellite structure. The core is a thermochromic microcapsule composed of a thermochromic core material and a polymer wall material. The shell is a transparent polymer shell that is coated on the core through in-situ polymerization. The satellite is a photochromic material that is embedded and fixed on the shell.

2. The composite color-changing agent according to claim 1, characterized in that, The temperature-sensitive color-changing core material is a compound system containing leuco dyes, color developers, and organic solvents.

3. The composite color-changing agent according to claim 1, characterized in that, The polymer wall material is selected from one or more of urea-formaldehyde resin, melamine resin, gelatin / gum arabic composite glue, polyurethane, and melamine-formaldehyde resin.

4. The composite color-changing agent according to claim 1, characterized in that, The polymer shell is selected from polyacrylates, polyurethane acrylates, or silicone-acrylate hybrid resins.

5. The composite color-changing agent according to claim 1, characterized in that, The photosensitive color-changing material is selected from one or more of spiropyran, spiroxazine, diarylethylene, or fumonisin compounds.

6. A method for preparing the composite color-changing agent according to any one of claims 1-5, characterized in that, Includes the following steps: S1, at 300-500 rpm, the mixture of isophorone diisocyanate monomer and dibutyltin dilaurate catalyst is slowly added to the emulsion of emulsifier, and ultrasonically treated in an ice-water bath for 2-3 minutes to obtain the emulsion; S2, dilute the thermochromic microcapsules in deionized water, keeping the solid content at 10-15%, then add the photochromic material, and add the emulsion obtained in S1 dropwise at 150-300 rpm. After the addition is complete, continue stirring and reacting for 0.5-1 h, then add the ethylenediamine chain extender and continue reacting for 1-2 h to allow the emulsion to fully crosslink and solidify. S3. After the reaction is complete, the product is centrifuged and washed with deionized water 3-5 times to remove unreacted monomers and catalyst residues. Then, it is dried in a vacuum drying oven at 40-50℃ for 6-8 hours to obtain the composite color-changing agent product.

7. The method for preparing the composite color-changing agent according to claim 6, characterized in that, In S1, the emulsifier is at least one of NP-10, Tween-80 and Span-80, and the amount of the emulsifier is 2%-5% of the mass of isophorone diisocyanate.

8. The method for preparing the composite color-changing agent according to claim 6, characterized in that, In S1, the amount of dibutyltin dilaurate is 0.1%-3% of the mass of isophorone diisocyanate; in S2, the amount of ethylenediamine is 1%-3% of the mass of isophorone diisocyanate.

9. The method for preparing the composite color-changing agent according to claim 6, characterized in that, In S2, the mass ratio of thermochromic microcapsules to photochromic material is 1:(0.5-2), and the mass ratio of isophorone diisocyanate to thermochromic microcapsules is 1:(3-5).

10. A type of anti-counterfeiting color-changing ink, characterized in that, The product comprises components A and B, which are stored separately and mixed in a weight ratio of 5:1 when used. Component A comprises the following components in parts by weight: 100 parts epoxy resin, 8-10 parts reactive diluent, 30-50 parts solvent, 0.5-1 part leveling agent, 0.6-1 part defoamer, 0.3-0.5 parts thixotropic agent, and 8-15 parts composite color-changing agent as described in any one of claims 1-5. Component B is a polyether amine, a fatty amine, or an anhydride curing agent.

Images