A thin flexographic cold foil material and its preparation process

Abstract

The present invention discloses a thin flexographic cold stamping material and a preparation process thereof, relating to the technical field of cold stamping materials. The thin flexographic cold stamping material of the present invention comprises, from bottom to top, a base film layer, a release layer, an imaging layer, an aluminum-plated layer, and a glue layer; the raw material components of the imaging layer include: a composite acrylic resin, modified polyepichlorohydrin, a pigment, ethanol, water, a coupling agent, and nano-silica; the composite acrylic resin is obtained by copolymerization of 2,4,6-tri(allyloxy)-1,3,5-triazine, acrylic acid, butyl acrylate, diallylamine hydrochloride, methyl methacrylate, and hydroxyethyl methacrylate; the modified polyepichlorohydrin is obtained by modification of POSS; the imaging layer of the thin flexographic cold stamping material prepared by the present invention has good adhesion, good flame retardancy, and good wear resistance.

Description

Technical Field

[0001] This invention relates to the field of cold stamping materials technology, specifically to a thin flexographic cold stamping material and its preparation process. Background Technology

[0002] With the development of printing technology, flexographic cold foil stamping technology has been widely used in the packaging printing field due to its high efficiency and environmental friendliness. However, in practical applications, the ink-containing imaging layer often suffers from poor adhesion and easy wear. These problems not only affect the appearance quality of the product but may also lead to inaccurate information transmission. In particular, for products requiring high safety standards, the insufficient flame retardant properties of the imaging layer are also a problem that urgently needs to be solved.

[0003] Some flexographic cold foil stamping materials currently on the market exhibit poor adhesion of the image layer when used with certain types of inks. This phenomenon mainly arises from compatibility issues between the characteristics of the flexographic hot foil stamping material itself and the inks used in the image layer. Specifically, insufficient interaction between the ink and the aluminum plating layer leads to the image layer easily peeling off or wearing away. Furthermore, when products need to meet specific environmental requirements (such as fire resistance), existing materials often cannot provide sufficient protection.

[0004] Therefore, developing a thin flexographic cold foil stamping material can improve the above-mentioned problems and enhance the adhesion, flame retardancy, and abrasion resistance of the imaging layer, which is of great significance for improving product quality and market competitiveness. This will not only help meet the growing demand for personalized packaging, but also promote the printing industry towards higher quality. Summary of the Invention

[0005] The purpose of this invention is to provide a solution to the technical problems mentioned in the background section.

[0006] The technical solution to achieve the objective of this invention is:

[0007] A thin flexographic cold foil stamping material comprises, from bottom to top, a base film layer, a release layer, an imaging layer, an aluminum plating layer, and an adhesive layer. The imaging layer comprises, by weight, 30-40 parts of composite acrylic resin, 6-12 parts of modified polyepoxychloropropane, 0.2-0.3 parts of pigment, 3-4 parts of ethanol, 47-48 parts of water, 2-3 parts of coupling agent, and 2-3 parts of nano-silica.

[0008] Furthermore, the composite acrylic resin is obtained by copolymerization of 2,4,6-tris(allyloxy)-1,3,5-triazine, acrylic acid, butyl acrylate, diallylamine hydrochloride, methyl methacrylate, and hydroxyethyl methacrylate.

[0009] Furthermore, the modified polyepoxychloropropane is obtained by reacting POSS with epichlorohydrin.

[0010] The present invention also provides a preparation process for a thin flexographic cold foil material, comprising the following steps: first, coating a release coating on a base film layer and then drying it; then, coating an imaging layer coating on the release coating and then drying it; subsequently, vacuum-plating aluminum on the imaging layer; and finally, coating an adhesive layer coating on the aluminum-plated layer and then drying it to form a thin flexographic cold foil material.

[0011] Furthermore, the method for preparing the imaging layer coating is as follows:

[0012] Under inert gas protection, 30-40 parts by weight of composite acrylic resin, 6-12 parts by weight of modified polyepoxychloropropane, 0.2-0.3 parts by weight of pigment, 3-4 parts by weight of ethanol, 47-48 parts by weight of water, 2-3 parts by weight of coupling agent, 2-3 parts by weight of nano-silica, and 0.08-0.12 parts by weight of emulsifier are loaded into a reaction vessel and dispersed using a high-speed homogenizer at 500-700 r / min for 10-20 min until the ink is uniformly mixed. Then, the temperature is raised to 69-71℃ and the reaction is stirred for 4.5-5.5 h. After cooling to room temperature, the pH is adjusted to 8.0-9.0 by adding 25%-28% ammonia water to obtain the imaging layer coating.

[0013] Furthermore, the coupling agent includes the silane coupling agent KH-560.

[0014] Further, the preparation steps of the composite acrylic resin are as follows: 0.4-0.6 parts by weight of 2,4,6-tris(allyloxy)-1,3,5-triazine, 0.06-0.08 parts by weight of acrylic acid, 0.08-0.12 parts by weight of butyl acrylate, 2-3 parts by weight of diallylamine hydrochloride, 2-3 parts by weight of methyl methacrylate, and 2-3 parts by weight of hydroxyethyl methacrylate are mixed evenly to obtain a monomer mixture; 25-35% of the monomer mixture... The monomer mixture, 0.002-0.0024 parts by weight of initiator, and 30-50 parts by weight of isopropanol were stirred and mixed. The mixture was heated to reflux while stirring. Then, the remaining monomer mixture, 0.008-0.0096 parts by weight of initiator, and 30-50 parts by weight of isopropanol were added dropwise. The dropwise addition was stopped after 1.8-2.2 hours. The reaction was continued at the temperature for 3 hours. Ammonia water with a concentration of 25%-28% was added to adjust the pH to 8.0-9.0 to obtain the composite acrylic resin.

[0015] Further, the preparation method of the modified polyepoxychloropropane is as follows: 92-94 parts by mass of heptaphenylsilsesquioxane trisilol and 500 parts by mass of solvent dichloromethane are stirred and mixed for 1-3 hours until the heptaphenylsilsesquioxane trisilol dissolves. 70.6-71 parts by mass of catalyst boron trifluoride diethyl ether are added at room temperature and stirring is continued for 30 minutes. Then, the temperature is lowered to 17.5-18.5℃, and 93-372 parts by mass of epichlorohydrin are added dropwise over 1.8-2.2 hours. Subsequently, the temperature is raised to 39-41℃ and the reaction is continued with stirring for 4 hours. Then, the mixture is washed with saturated sodium bicarbonate solution until alkaline, and then washed with deionized water until neutral to remove unreacted catalyst. Finally, the mixture is distilled under reduced pressure at 109-111℃ for 1.8-2.2 hours to remove solvent and small molecule compounds, yielding the modified polyepoxychloropropane.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects:

[0017] (1) The present invention uses composite acrylic resin, modified polyepoxychloropropane, pigment, ethanol, water, coupling agent and nano silica as raw materials to prepare the imaging layer; wherein, the polyepoxychloropropane in the modified polyepoxychloropropane has good adhesion and flame retardant properties. Adding modified polyepoxychloropropane to the imaging layer can effectively improve the adhesion of the imaging layer on the aluminum plating layer and make the imaging layer have good flame retardancy.

[0018] (2) The composite acrylic resin of the present invention is obtained by copolymerization of 2,4,6-tris(allyloxy)-1,3,5-triazine, acrylic acid, butyl acrylate, diallylamine hydrochloride, methyl methacrylate, and hydroxyethyl methacrylate. Among them, 2,4,6-tris(allyloxy)-1,3,5-triazine, as a multifunctional monomer, has three allyl groups, which can form a dense cross-linking network during polymerization. These cross-linking points enhance the mechanical strength and thermal stability of the composite acrylic resin, enabling it to maintain good performance under high temperature or stress conditions. Acrylic acid, hydroxyethyl methacrylate, and diallylamine hydrochloride all contain hydrophilic groups, which can form hydrogen bonds or other types of chemical bonds with the aluminum plating layer, thereby improving the adhesion between the composite acrylic resin and the aluminum plating layer.

[0019] (3) In this invention, modified polyepoxychloropropane is prepared by reacting POSS heptaphenylsilsesquioxane trisilol with epichlorohydrin. The silanol groups in POSS heptaphenylsilsesquioxane trisilol can undergo ring-opening polymerization with the epoxy groups in epichlorohydrin, embedding POSS into the main chain of polyepoxychloropropane to form rigid sites. These rigid sites can effectively resist external forces, reduce slippage between molecular chains, improve the hardness of modified polyepoxychloropropane, and thus improve the wear resistance of the imaging layer.

[0020] (4) In this invention, composite acrylic resin, modified polyepoxychloropropane and other raw material components are composited. When the modified polyepoxychloropropane is mixed with the composite acrylic resin containing secondary amine groups, the chlorine atoms in the modified polyepoxychloropropane will undergo a nucleophilic substitution reaction with the secondary amine groups in the composite acrylic resin. Specifically, the nitrogen atoms of the secondary amine groups act as nucleophiles to attack the chlorine atoms in the modified polyepoxychloropropane to form quaternary ammonium cations. When preparing thin flexible hot stamping materials, the polar heads of the quaternary ammonium cations in the imaging layer form an interaction force with the metal surface of the aluminum plating layer, thereby further enhancing the adhesion of the imaging layer to the aluminum plating layer. Detailed Implementation

[0021] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0022] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0023] The raw materials used in the embodiments and comparative examples of this invention are as follows:

[0024] Release coating: Add ethanol and water to a mixing tank according to the formula ratio, stir evenly at a constant temperature of 28°C for 10 minutes, then add water-based oxidized polyethylene wax emulsion to the mixing tank according to the ratio, stirring while adding, and continue stirring for 45 minutes after adding to obtain the release coating.

[0025] The base film layer uses a 6U BOPET film;

[0026] The preparation steps of the adhesive coating are as follows: 40 parts by mass of xylene are placed in a reaction vessel and heated to 84°C while stirring. Then, a mixture of 2.5 parts by mass of methyl methacrylate, 2 parts by mass of hydroxyethyl methacrylate, 2 parts by mass of butyl acrylate, 2 parts by mass of glycidyl acrylate, and 0.01 parts by mass of azobisisobutyronitrile (azobisisobutyronitrile) initiator is added dropwise. The dropwise addition is completed after 3 hours, and the reaction is continued at the temperature for another 3 hours to obtain the adhesive resin base material. 20 parts by mass of xylene are added to a mixing tank and stirred uniformly at a constant temperature of 25°C for 5 minutes. Then, 60 parts by mass of the adhesive resin base material are added to the mixing tank while stirring. After the addition is completed, the stirring is continued for another 30 minutes to obtain the adhesive coating.

[0027] The coupling agent used is silane coupling agent KH-560;

[0028] The emulsifier used is OP-10;

[0029] The pigment used is phthalocyanine blue;

[0030] (Example 1)

[0031] A process for preparing a thin flexographic cold foil stamping material includes the following steps: first, coating a 0.3 μm thick release coating onto a base film layer and then drying it; then, coating a 0.3 μm thick imaging layer onto the release coating and then drying it; subsequently, depositing a 240 angstrom thick aluminum plating layer onto the imaging layer; and finally, coating a 0.3 μm thick adhesive layer onto the aluminum plating layer and then drying it to form a thin flexographic cold foil stamping material.

[0032] The preparation method of the imaging layer coating is as follows:

[0033] Under inert gas protection, 30 parts by weight of composite acrylic resin, 6 parts by weight of modified polyepoxychloropropane, 0.2 parts by weight of pigment, 3 parts by weight of ethanol, 47 parts by weight of water, 2 parts by weight of coupling agent, 2 parts by weight of nano silica, and 0.08 parts by weight of emulsifier were loaded into a reaction vessel and dispersed at 500 rpm for 10 min using a high-speed homogenizer until the ink was uniformly mixed. Then, the temperature was raised to 69°C and the reaction was stirred for 4.5 h. After cooling to room temperature, the pH was adjusted to 8.0 by adding 25% ammonia water to obtain the imaging layer coating.

[0034] The preparation steps of the composite acrylic resin are as follows: 0.4 parts by mass of 2,4,6-tris(allyloxy)-1,3,5-triazine, 0.06 parts by mass of acrylic acid, 0.08 parts by mass of butyl acrylate, 2 parts by mass of diallylamine hydrochloride, 2 parts by mass of methyl methacrylate, and 2 parts by mass of hydroxyethyl methacrylate are mixed evenly to obtain a monomer mixture; 25% of the monomer mixture, 0.002 parts by mass of initiator, and 30 parts by mass of isopropanol are stirred and mixed, and the mixture is heated to reflux while stirring. Then, the remaining monomer mixture, 0.008 parts by mass of initiator, and 30 parts by mass of isopropanol are added dropwise. The dropwise addition is completed after 1.8 hours, and the reaction is continued at the temperature for 3 hours. Ammonia water with a concentration of 25% is added to adjust the pH to 8.0 to obtain the composite acrylic resin.

[0035] The modified polyepoxychloropropane is prepared as follows: 92 parts by mass of heptaphenylsilsesquioxane trisilol and 500 parts by mass of solvent dichloromethane are stirred and mixed for 1 hour until the heptaphenylsilsesquioxane trisilol dissolves. 70.6 parts by mass of catalyst boron trifluoride diethyl ether is added at room temperature and stirring is continued for 30 minutes. Then, the temperature is lowered to 17.5°C, and 93 parts by mass of epichlorohydrin are added dropwise over 1.8 hours. The temperature is then raised to 39°C and the reaction is continued for 4 hours. Subsequently, the mixture is washed with saturated sodium bicarbonate solution until alkaline, and then washed with deionized water until neutral to remove unreacted catalyst. Finally, the mixture is distilled under reduced pressure at 109°C for 1.8 hours to remove solvent and small molecule compounds, yielding the modified polyepoxychloropropane.

[0036] Example 2

[0037] A process for preparing a thin flexographic cold foil stamping material includes the following steps: first, coating a 0.3 μm thick release coating onto a base film layer and then drying it; then, coating a 0.3 μm thick imaging layer onto the release coating and then drying it; subsequently, depositing a 240 angstrom thick aluminum plating layer onto the imaging layer; and finally, coating a 0.3 μm thick adhesive layer onto the aluminum plating layer and then drying it to form a thin flexographic cold foil stamping material.

[0038] The preparation method of the imaging layer coating is as follows:

[0039] Under inert gas protection, 35 parts by weight of composite acrylic resin, 9 parts by weight of modified polyepoxychloropropane, 0.25 parts by weight of pigment, 3.5 parts by weight of ethanol, 47.5 parts by weight of water, 2.5 parts by weight of coupling agent, 2.5 parts by weight of nano silica, and 0.01 parts by weight of emulsifier were loaded into a reaction vessel and dispersed at 600 r / min for 15 min using a high-speed homogenizer until the ink was uniformly mixed. Then, the temperature was raised to 70℃ and the reaction was stirred for 5 h. After cooling to room temperature, the pH was adjusted to 8.5 by adding 26% ammonia water to obtain the imaging layer coating.

[0040] The preparation steps of the composite acrylic resin are as follows: 0.5 parts by weight of 2,4,6-tris(allyloxy)-1,3,5-triazine, 0.07 parts by weight of acrylic acid, 0.1 parts by weight of butyl acrylate, 2.5 parts by weight of diallylamine hydrochloride, 2.5 parts by weight of methyl methacrylate, and 2.5 parts by weight of hydroxyethyl methacrylate are mixed evenly to obtain a monomer mixture; 30% of the monomer mixture, 0.0022 parts by weight of initiator, and 40 parts by weight of isopropanol are stirred and mixed, and the mixture is heated to reflux while stirring. Then, the remaining monomer mixture, 0.0088 parts by weight of initiator, and 40 parts by weight of isopropanol are added dropwise. The dropwise addition is completed after 2 hours, and the reaction is continued at the temperature for 3 hours. Ammonia water with a concentration of 26% is added to adjust the pH to 8.5 to obtain the composite acrylic resin.

[0041] The modified polyepoxychloropropane is prepared as follows: 93 parts by mass of heptaphenylsilsesquioxane trisilol and 500 parts by mass of solvent dichloromethane are stirred and mixed for 2 hours until the heptaphenylsilsesquioxane trisilol dissolves. 70.8 parts by mass of catalyst boron trifluoride diethyl ether is added at room temperature and stirring is continued for 30 minutes. Then, the temperature is lowered to 18°C, and 233 parts by mass of epichlorohydrin are added dropwise over 2 hours. The temperature is then raised to 40°C and the reaction is continued for 4 hours. Subsequently, the mixture is washed with saturated sodium bicarbonate solution until alkaline, and then washed with deionized water until neutral to remove unreacted catalyst. Finally, the mixture is distilled under reduced pressure at 110°C for 2 hours to remove solvent and small molecule compounds, yielding the modified polyepoxychloropropane.

[0042] Example 3

[0043] A process for preparing a thin flexographic cold foil stamping material includes the following steps: first, coating a 0.3 μm thick release coating onto a base film layer and then drying it; then, coating a 0.3 μm thick imaging layer onto the release coating and then drying it; subsequently, depositing a 240 angstrom thick aluminum plating layer onto the imaging layer; and finally, coating a 0.3 μm thick adhesive layer onto the aluminum plating layer and then drying it to form a thin flexographic cold foil stamping material.

[0044] The preparation method of the imaging layer coating is as follows:

[0045] Under inert gas protection, 40 parts by weight of composite acrylic resin, 12 parts by weight of modified polyepoxychloropropane, 0.3 parts by weight of pigment, 4 parts by weight of ethanol, 48 parts by weight of water, 3 parts by weight of coupling agent, 3 parts by weight of nano silica, and 0.12 parts by weight of emulsifier were loaded into a reaction vessel and dispersed at 700 r / min for 20 min using a high-speed homogenizer until the ink was uniformly mixed. Then the temperature was raised to 71℃ and the reaction was stirred for 5.5 h. After cooling to room temperature, the pH was adjusted to 9.0 by adding 28% ammonia water to obtain the imaging layer coating.

[0046] The preparation steps of the composite acrylic resin are as follows: 0.6 parts by weight of 2,4,6-tris(allyloxy)-1,3,5-triazine, 0.08 parts by weight of acrylic acid, 0.12 parts by weight of butyl acrylate, 3 parts by weight of diallylamine hydrochloride, 3 parts by weight of methyl methacrylate, and 3 parts by weight of hydroxyethyl methacrylate are mixed evenly to obtain a monomer mixture; 35% of the monomer mixture, 0.0024 parts by weight of initiator, and 50 parts by weight of isopropanol are stirred and mixed, and the temperature is raised to reflux while stirring. Then, the remaining monomer mixture, 0.0096 parts by weight of initiator, and 50 parts by weight of isopropanol are added dropwise. The dropwise addition is completed after 2.2 hours, and the reaction is continued at the temperature for 3 hours. Ammonia water with a concentration of 28% is added to adjust the pH to 9.0 to obtain the composite acrylic resin.

[0047] The modified polyepoxychloropropane is prepared as follows: 94 parts by mass of heptaphenylsilsesquioxane trisilol and 500 parts by mass of solvent dichloromethane are stirred and mixed for 3 hours until the heptaphenylsilsesquioxane trisilol dissolves. 71 parts by mass of catalyst boron trifluoride diethyl ether is added at room temperature and stirring is continued for 30 minutes. Then, the temperature is lowered to 18.5°C, and 372 parts by mass of epichlorohydrin are added dropwise over 2.2 hours. The temperature is then raised to 41°C and the reaction is continued for 4 hours. Subsequently, the mixture is washed with saturated sodium bicarbonate solution until alkaline, and then washed with deionized water until neutral to remove unreacted catalyst. Finally, the mixture is distilled under reduced pressure at 111°C for 2.2 hours to remove solvent and small molecule compounds, yielding the modified polyepoxychloropropane.

[0048] Comparative Example 1

[0049] The difference between Comparative Example 1 and Example 2 is that the composite acrylic resin is obtained only by copolymerizing acrylic acid, butyl acrylate, diallylamine hydrochloride, methyl methacrylate, and hydroxyethyl methacrylate, while the remaining steps and components are the same as in Example 2.

[0050] Comparative Example 2

[0051] The difference between Comparative Example 2 and Example 2 is that the composite acrylic resin is obtained only by copolymerization of 2,4,6-tris(allyloxy)-1,3,5-triazine, acrylic acid, butyl acrylate, methyl methacrylate, and hydroxyethyl methacrylate, while the remaining steps and components are the same as in Example 2.

[0052] Comparative Example 3

[0053] The difference between Comparative Example 3 and Example 2 is that the composite acrylic resin is obtained only by copolymerizing acrylic acid, butyl acrylate, methyl methacrylate and hydroxyethyl methacrylate, while the remaining steps and components are the same as in Example 2.

[0054] Comparative Example 4

[0055] The difference between Comparative Example 4 and Example 2 is that the raw material components of the imaging layer are only composite acrylic resin, polyepoxychloropropane, pigment, ethanol, water, coupling agent, and nano silica; the remaining steps and components are the same as in Example 2.

[0056] Comparative Example 5

[0057] The difference between Comparative Example 5 and Example 2 is that the raw material components of the imaging layer are only composite acrylic resin, pigment, ethanol, water, coupling agent and nano silica; the remaining steps and components are the same as in Example 2.

[0058] Comparative Example 6

[0059] The difference between Comparative Example 6 and Example 2 is that the raw material components of the imaging layer only use composite acrylic resin, heptaphenylsilsesquioxane trisilol, pigment, ethanol, water, coupling agent, and nano silica; the remaining steps and components are the same as in Example 2.

[0060] Example of effect

[0061] Adhesion: According to GB / T1720-88 standard for testing the adhesion of paint film, the adhesion of the imaging layer of the thin flexographic cold foil materials prepared in Examples 1-3 and Comparative Examples 1-6 to the aluminum plating layer was determined using a QFD electric paint film adhesion tester. The degree of adhesion of the imaging layer to the aluminum plating layer was evaluated according to 7 levels. The higher the level, the lower the adhesion.

[0062] Hardness: The hardness of the imaging layer was determined according to GB / T 6739—2006 Standard for Determination of Hardness of Paint and Varnish by Pencil Method. The pencil tip inserted into the cart of the hand-push pencil hardness tester should be at a 45° angle to the surface of the imaging layer. The imaging layers were tested under a 500g weight load.

[0063] The table below shows the performance data of the thin flexographic cold stamping materials obtained in Examples 1-3 and Comparative Examples 1-6:

[0064] Adhesion rating hardness Example 1 1 5H Example 2 1 5H Example 3 1 5H Comparative Example 1 2 4H Comparative Example 2 4 5H Comparative Example 3 4 4H Comparative Example 4 2 2H Comparative Example 5 3 2H Comparative Example 6 4 5H

[0065] Comparing the data from the examples and comparative examples in the table above, it can be seen that the thin flexographic cold foil printing material prepared in the examples has better adhesion and wear resistance of the imaging layer. The difference between Comparative Example 1 and Example 2 is that the composite acrylic resin in Example 2 also contains 2,4,6-tris(allyloxy)-1,3,5-triazine. The introduction of 2,4,6-tris(allyloxy)-1,3,5-triazine increases the crosslinking density of the composite acrylic resin. In addition, the introduction of the rigid triazine ring not only improves the adhesion of the imaging layer but also improves the wear resistance of the imaging layer.

[0066] The difference between Comparative Example 2 and Example 2 is that the composite acrylic resin in Example 2 also incorporates diallylamine hydrochloride. Diallylamine hydrochloride contains hydrophilic groups, which can form hydrogen bonds or other types of chemical bonds with the aluminum plating layer, thereby improving the adhesion between the composite acrylic resin and the aluminum plating layer. Furthermore, the secondary amine in the composite acrylic resin can react with the chlorine atoms in the modified polyepoxychloropropane to form a quaternary ammonium salt. The positively charged nature of the quaternary ammonium salt generates an electrostatic attraction between it and the slightly negatively charged metal surface of the aluminum plating layer. At the same time, the nitrogen atoms in the quaternary ammonium cation can form coordinate bonds with the unpaired electrons on the surface of the aluminum plating layer, achieving chemical adsorption. The synergistic effect of these interactions, such as electrostatic attraction and chemical adsorption, significantly enhances the adhesion between the imaging layer and the aluminum plating layer, making it less likely for the imaging layer to peel off from the aluminum plating layer when subjected to external mechanical stress.

[0067] The difference between Comparative Example 3 and Example 2 is that the composite acrylic resin in Example 2 also incorporates 2,4,6-tris(allyloxy)-1,3,5-triazine and diallylamine hydrochloride, resulting in a thinner flexographic cold foil material with better adhesion of the imaging layer.

[0068] The difference between Comparative Examples 4 and 5 and Example 2 is that the raw material components of the imaging layer in Example 2 also include polyepoxychloropropane modified with heptaphenylsilsesquioxane trisilol. The introduction of heptaphenylsilsesquioxane trisilol-modified polyepoxychloropropane has two advantages: firstly, the heptaphenylsilsesquioxane trisilol introduces rigid sites to increase the wear resistance of the imaging layer; secondly, polyepoxychloropropane has good adhesion, and the chlorine atoms in the modified polyepoxychloropropane react with the secondary amine in the composite acrylic resin to form a quaternary ammonium salt. The positively charged nature of the quaternary ammonium salt generates an electrostatic attraction between it and the slightly negatively charged metal surface of the aluminum plating layer. At the same time, the nitrogen atoms in the quaternary ammonium cation can also form coordinate bonds with the unpaired electrons on the surface of the aluminum plating layer to achieve chemical adsorption. The synergistic effect of these interactions, such as electrostatic attraction and chemical adsorption, significantly enhances the adhesion between the imaging layer and the aluminum plating layer, making it less likely for the imaging layer to peel off from the aluminum plating layer when subjected to external mechanical stress.

[0069] The difference between Comparative Example 6 and Example 2 is that the raw material components of the imaging layer in Example 2 also include polyepoxychloropropane. Polyepoxychloropropane has good adhesion, and the chlorine atoms in the modified polyepoxychloropropane react with the secondary amine in the composite acrylic resin to form a quaternary ammonium salt. The positively charged nature of the quaternary ammonium salt generates an electrostatic attraction between it and the slightly negatively charged metal surface of the aluminum plating layer. At the same time, the nitrogen atoms in the quaternary ammonium cation can form coordinate bonds with the unpaired electrons on the surface of the aluminum plating layer to achieve chemical adsorption. The synergistic effect of these interactions, such as electrostatic attraction and chemical adsorption, significantly enhances the adhesion between the imaging layer and the aluminum plating layer, making it less likely for the imaging layer to peel off from the aluminum plating layer when subjected to external mechanical stress.

[0070] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thin flexographic cold foil stamping material, comprising, from bottom to top, a base film layer, a release layer, an imaging layer, an aluminum plating layer, and an adhesive layer, characterized in that, The imaging layer comprises, by weight, 30-40 parts of composite acrylic resin, 6-12 parts of modified polyepoxychloropropane, 0.2-0.3 parts of pigment, 3-4 parts of ethanol, 47-48 parts of water, 2-3 parts of coupling agent, 2-3 parts of nano-silica, and 0.08-0.12 parts of emulsifier; the composite acrylic resin is obtained by copolymerization of 2,4,6-tris(allyloxy)-1,3,5-triazine, acrylic acid, butyl acrylate, diallylamine hydrochloride, methyl methacrylate, and hydroxyethyl methacrylate; the modified polyepoxychloropropane is obtained by reacting POSS with epichlorohydrin.

2. A preparation process for a thin flexographic cold foil stamping material as described in claim 1, characterized in that, The process includes the following steps: first, a release layer coating is applied to the base film layer and then dried; then, an imaging layer coating is applied to the release layer and then dried; subsequently, aluminum is vacuum-plated onto the imaging layer; and finally, an adhesive layer coating is applied to the aluminum-plated layer and then dried, forming a thin flexographic cold foil material.

3. The preparation process of the thin flexographic cold foil stamping material according to claim 2, characterized in that, The preparation method of the imaging layer coating is as follows: Under inert gas protection, 30-40 parts by weight of composite acrylic resin, 6-12 parts by weight of modified polyepoxychloropropane, 0.2-0.3 parts by weight of pigment, 3-4 parts by weight of ethanol, 47-48 parts by weight of water, 2-3 parts by weight of coupling agent, 2-3 parts by weight of nano-silica, and 0.08-0.12 parts by weight of emulsifier are loaded into a reaction vessel and dispersed using a high-speed homogenizer at 500-700 r / min for 10-20 min until uniformly mixed. Then, the temperature is raised to 69-71℃ and the reaction is stirred for 4.5-5.5 h. After cooling to room temperature, the pH is adjusted to 8.0-9.0 by adding 25%-28% ammonia water to obtain the imaging layer coating.

4. The preparation process of the thin flexographic cold foil stamping material according to claim 3, characterized in that, The coupling agent includes the silane coupling agent KH-560.

5. The preparation process of the thin flexographic cold foil stamping material according to claim 3, characterized in that, The preparation steps of the composite acrylic resin are as follows: 0.4-0.6 parts by weight of 2,4,6-tris(allyloxy)-1,3,5-triazine, 0.06-0.08 parts by weight of acrylic acid, 0.08-0.12 parts by weight of butyl acrylate, 2-3 parts by weight of diallylamine hydrochloride, 2-3 parts by weight of methyl methacrylate, and 2-3 parts by weight of hydroxyethyl methacrylate are mixed evenly to obtain a monomer mixture; 25-35% of the monomer mixture, 0.002-0.0024 parts by weight of initiator and 30-50 parts by weight of isopropanol were stirred and mixed, and the mixture was heated to reflux while stirring. Then, the remaining monomer mixture, 0.008-0.0096 parts by weight of initiator and 30-50 parts by weight of isopropanol were added dropwise. The dropwise addition was stopped after 1.8-2.2 hours. The reaction was continued at the temperature for 3 hours. Ammonia water with a concentration of 25%-28% was added to adjust the pH to 8.0-9.0 to obtain the composite acrylic resin.

6. The preparation process of the thin flexographic cold foil stamping material according to claim 3, characterized in that, The modified polyepoxychloropropane is prepared as follows: 92-94 parts by mass of heptaphenylsilsesquioxane trisilol and 500 parts by mass of dichloromethane solvent are stirred and mixed for 1-3 hours until the heptaphenylsilsesquioxane trisilol dissolves. 70.6-71 parts by mass of boron trifluoride ether catalyst are added at room temperature and stirring is continued for 30 minutes. Then, the temperature is lowered to 17.5-18.5℃, and 93-372 parts by mass of epichlorohydrin are added dropwise over 1.8-2.2 hours. The temperature is then raised to 39-41℃ and the reaction is continued for 4 hours. Subsequently, the mixture is washed with saturated sodium bicarbonate solution until alkaline, and then washed with deionized water until neutral to remove unreacted catalyst. Finally, the mixture is distilled under reduced pressure at 109-111℃ for 1.8-2.2 hours to remove solvent and small molecule compounds, yielding the modified polyepoxychloropropane.