Water-based flexographic printing ink and preparation method thereof

Abstract

The invention relates to the technical field of ink coatings, in particular to water-based flexographic printing ink. Comprising the following raw materials in parts by weight: 15-30 parts of a water-based acrylic resin emulsion, 8-20 parts of an organic pigment, 1-3 parts of modified corncob nanowhiskers, 1-3 parts of cerium-neodymium doped strontium tungstate nanosheets, 2-6 parts of a cyclodextrin hyperbranched emulsifier, 0.3-1 part of a pH buffer agent, 0.1-0.5 part of a flatting agent, 0.3-1 part of sodium polyacrylate and 0.1-0.2 part of a first auxiliary agent. According to the invention, hydrophobic groups are introduced to the surfaces of the modified corncob nanowhiskers through acetylation reaction, and the hydrophobic groups and carboxyl groups of the water-based acrylic resin form a dynamic hydrogen bond network, so that the problem that the storage stability and the printing leveling property of the ink are difficult to consider at the same time is solved, meanwhile, the dot expansion rate is effectively reduced, and the printing effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ink coatings, in particular to a water-based flexographic printing ink and a preparation method thereof. Background Art

[0002] Flexographic printing, also known as "flexographic printing", is a direct letterpress rotary printing method that can transfer liquid or paste ink to the substrate. It has the characteristics of a wide range of printing materials, good printing effects, and simple machine structure. The flexographic printing process is particularly suitable for water-based inks because of its low ink consumption.

[0003] In existing water-based inks, due to chemical inconsistencies between the resin system and the dispersion medium, high viscosity is required during storage to prevent sedimentation, while low viscosity is required during printing to ensure leveling. However, the molecular chain entanglement of the thickeners added to traditional water-based inks is irreversible, resulting in slow viscosity recovery after high shear, making it impossible to achieve both storage stability and print leveling. Based on this, the present invention provides a water-based flexographic printing ink and a method for preparing the same. Summary of the Invention

[0004] The purpose of the present invention is to provide a water-based flexographic printing ink and a preparation method thereof. The water-based flexographic printing ink prepared by the present invention takes into account both storage stability and printing leveling properties, and at the same time breaks through the technical bottleneck of slow drying speed of water-based ink.

[0005] To achieve the above object, the present invention provides the following technical solution: a water-based flexographic printing ink, comprising the following raw materials in parts by weight: 15-30 parts of a water-based acrylic resin emulsion, 8-20 parts of an organic pigment, 1-3 parts of modified corncob nanowhiskers, 1-3 parts of cerium-neodymium-doped strontium tungstate nanosheets, 2-6 parts of a cyclodextrin hyperbranched emulsifier, 0.3-1 part of a pH buffer, 0.1-0.5 part of a leveling agent, 0.3-1 part of polyacrylic acid sodium salt, and 0.1-0.2 part of a first auxiliary agent;

[0006] The preparation method of modified corncob nano whiskers comprises the following steps: mixing corncobs crushed to 80 meshes with a deep eutectic solvent at a solid-liquid ratio of 1:10, subjecting the obtained turbidity to constant temperature stirring at 80-85°C for 2-3 hours, filtering to obtain a solid residue, washing the solid residue with ethanol to remove oxalic acid, and vacuum drying to obtain pretreated fibers, adding the pretreated fibers to pyridine, and then dropwise adding acetic anhydride, subjecting the obtained mixture to an acetylation reaction at 100-110°C for 2-3 hours, and then circulating the mixture through a high-pressure homogenizer at a pressure of 120-150 MPa for 5-7 times to obtain modified corncob nano whiskers with a diameter of 30-50 nm and an acetylation degree of 80% or more.

[0007] Preferably, the deep eutectic solvent is formed by mixing choline chloride and oxalic acid in a molar ratio of 1:2, the mass ratio of the pretreated fiber to pyridine is 1:15, and the mass ratio of the pretreated fiber to acetic anhydride is 1:5.

[0008] Preferably, the cerium-neodymium-doped strontium tungstate nanosheets are prepared by the following method: cerium nitrate hexahydrate and neodymium nitrate hexahydrate are dissolved in ethylene glycol in a molar ratio of 3:1 to form a rare earth ion solution, sodium tungstate and strontium chloride are added to form a mixed solution, the mixed solution is added to a high-pressure reactor and reacted at 180-200°C for 12-15 hours, the obtained product is centrifuged and the precipitate is collected, and calcined at 500-550°C for 2-3 hours to obtain hexagonal sheet-like nanoparticles, namely cerium-neodymium-doped strontium tungstate nanosheets.

[0009] Preferably, the ethylene glycol accounts for 35-45% of the total mass of the rare earth ion solution, and the molar ratio of rare earth ions, sodium tungstate, and strontium chloride is 1:50:50.

[0010] Preferably, the cyclodextrin hyperbranched emulsifier is prepared by the following method: β-cyclodextrin and pentaerythritol are mixed in a molar ratio of 1:5, a comonomer consisting of lactide and glycolide in a molar ratio of 7:3 is added, and melt polycondensation is carried out at 150-160° C. for 4-5 hours to generate a hyperbranched polyester, the hyperbranched polyester is dissolved in acetone, isophorone diisocyanate is added, and the reaction is carried out at a constant temperature of 60° C. for 3-4 hours, and dihydroxymethylpropionic acid in an amount of 8-10% by weight of the hyperbranched polyester is added to extend the chain, and triethylamine is added to adjust the pH to 7-8 to obtain the cyclodextrin hyperbranched emulsifier.

[0011] Preferably, the mass ratio of the hyperbranched polyester to acetone is 1:10, and the amount of isophorone diisocyanate used is 38-42% of the mass of the hyperbranched polyester.

[0012] Preferably, the first auxiliary agent is prepared by the following method: dimethyl silicone oil and 10# industrial white oil are mixed, hydrophobic fumed silica is added, and high-speed shear dispersion is carried out at 60°C and 10,000 rpm for 30 minutes, and sorbitan monooleate is added. The resulting product is processed by a colloid mill and then passed through a 250-mesh sieve to obtain a white liquid, which is the first auxiliary agent, wherein the mass ratio of dimethyl silicone oil, industrial white oil, hydrophobic fumed silica, and sorbitan monooleate is 100:150:12:5.

[0013] Preferably, the organic pigment can be selected from at least one or more combinations of permanent yellow, phthalocyanine blue and sun-fast red, and the pH buffer is an ammonia solution with a mass fraction of 0.5%.

[0014] Preferably, the leveling agent may be selected from at least one or more combinations of polyether siloxane, alkoxy acetylene glycol and dioctyl sodium sulfosuccinate.

[0015] Preferably, a method for preparing a water-based flexographic printing ink comprises the following steps:

[0016] S1: Pre-dispersion: add organic pigment, cyclodextrin hyperbranched emulsifier, polyacrylic acid sodium salt, and the first auxiliary agent into a dispersion tank and disperse at 1500-2000 rpm for 20-30 minutes to obtain a slurry;

[0017] S2: Grinding: sand-grinding the slurry with zirconium beads of 0.4 mm in diameter until the organic pigment particle size D50 is ≤ 200 nm to obtain a grind material;

[0018] S3: preparing a base material, adding modified corncob nano whiskers, pH buffer, and leveling agent to a water-based acrylic resin emulsion, and stirring at a low speed of 50 rpm for 40 to 50 minutes to obtain a base material;

[0019] S4: Mixing: adding the ground material prepared in S2 to the base material prepared in S3, and then adding cerium-neodymium-doped strontium tungstate nanosheets, stirring at 300 rpm for 30 minutes to obtain an ink blank;

[0020] S5: Post-processing: add deionized water to the ink blank to adjust the viscosity to 4 cups at 25℃ for 30-50 seconds, and filter through a 200-mesh filter to obtain a water-based flexographic printing ink.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the present invention, hydrophobic groups are introduced onto the surface of modified corncob nanowhiskers through an acetylation reaction, forming a dynamic hydrogen bond network with the carboxyl groups of the water-based acrylic resin, thereby allowing the ink to form a three-dimensional gel under low-shear storage conditions, thereby preventing pigment sedimentation. During high-shear printing, the hydrogen bonds are reversibly broken, causing a sudden drop in viscosity, ensuring smooth ink transfer, and solving the problem of balancing ink storage stability and printing leveling. At the same time, it effectively reduces the dot gain rate and improves the printing effect.

[0023] 2. In the present invention, the prepared cerium-neodymium-doped strontium tungstate nanosheets catalyze the oxidative cross-linking of the resin through the variable valence characteristics of cerium ions, which can effectively improve the drying time of the ink. The characteristic absorption of neodymium ions in the near-infrared region converts light energy into heat energy, promoting solvent volatilization. At the same time, the structure of the nanosheets increases the contact area with the resin, and its surface negative charge also produces electrostatic repulsion with the pigment particles to prevent flocculation. This not only avoids the heavy metal pollution of traditional cobalt-manganese catalysis, but also breaks through the technical bottleneck of the slow drying speed of water-based inks, while meeting the needs of environmental protection and efficient production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The present invention proposes a flow chart of a water-based flexographic printing ink and a preparation method thereof. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0027] Example 1:

[0028] A water-based flexographic printing ink, comprising the following raw materials in parts by weight: 15 parts of a water-based acrylic resin emulsion, 8 parts of an organic pigment, 1 part of modified corncob nanowhiskers, 1 part of cerium-neodymium-doped strontium tungstate nanosheets, 2 parts of a cyclodextrin hyperbranched emulsifier, 0.3 parts of a pH buffer, 0.1 parts of a leveling agent, 0.3 parts of polyacrylic acid sodium salt, and 0.1 parts of a first auxiliary agent;

[0029] The preparation method of modified corncob nano whiskers includes the following steps: mixing corncobs crushed to 80 mesh with a deep eutectic solvent at a solid-liquid ratio of 1:10, stirring the resulting turbid material at a constant temperature of 80°C for 2 hours, filtering to obtain a solid residue, washing the solid residue with ethanol to remove oxalic acid, and then vacuum drying to obtain pretreated fibers, adding the pretreated fibers to pyridine, and then dropwise adding acetic anhydride, acetylating the resulting mixture at 100°C for 2 hours, and then circulating the mixture through a high-pressure homogenizer at a pressure of 120 MPa for 5 times to obtain modified corncob nano whiskers with a diameter of 30 nm and an acetylation degree of 80% or more.

[0030] The deep eutectic solvent was prepared by mixing choline chloride and oxalic acid in a molar ratio of 1:2, the mass ratio of pretreated fiber to pyridine was 1:15, and the mass ratio of pretreated fiber to acetic anhydride was 1:5.

[0031] The cerium-neodymium doped strontium tungstate nanosheets are prepared by the following method: cerium nitrate hexahydrate and neodymium nitrate hexahydrate are dissolved in ethylene glycol at a molar ratio of 3:1 to form a rare earth ion solution, sodium tungstate and strontium chloride are then added to form a mixed solution, the mixed solution is added to a high-pressure reactor and reacted at 180°C for 12 hours, the obtained product is centrifuged and the precipitate is collected, and calcined at 500°C for 2 hours to obtain hexagonal sheet-like nanoparticles, namely the cerium-neodymium doped strontium tungstate nanosheets.

[0032] Ethylene glycol accounts for 35% of the total mass of the rare earth ion solution, and the molar ratio of rare earth ions, sodium tungstate and strontium chloride is 1:50:50.

[0033] The cyclodextrin hyperbranched emulsifier is prepared by the following method: β-cyclodextrin and pentaerythritol are mixed in a molar ratio of 1:5, a comonomer consisting of lactide and glycolide in a molar ratio of 7:3 is added, and melt polycondensation is carried out at 150°C for 4 hours to generate a hyperbranched polyester, the hyperbranched polyester is dissolved in acetone, and isophorone diisocyanate is added, and the reaction is carried out at a constant temperature of 60°C for 3 hours, and dihydroxymethylpropionic acid (8% by weight of the hyperbranched polyester) is added to extend the chain, and triethylamine is added to adjust the pH to 7 to prepare the cyclodextrin hyperbranched emulsifier.

[0034] The mass ratio of the hyperbranched polyester to acetone is 1:10, and the amount of isophorone diisocyanate used is 38% of the mass of the hyperbranched polyester.

[0035] The first auxiliary agent is prepared by the following method: dimethyl silicone oil and 10# industrial white oil are mixed, hydrophobic fumed silica is added, and high-speed shear dispersion is carried out at 60°C and 10,000 rpm for 30 minutes. Sorbitan monooleate is then added, and the resulting product is processed by a colloid mill and passed through a 250-mesh sieve to obtain a white liquid, which is the first auxiliary agent. The mass ratio of dimethyl silicone oil, industrial white oil, hydrophobic fumed silica, and sorbitan monooleate is 100:150:12:5.

[0036] The organic pigment is permanent yellow, and the pH buffer is 0.5% by mass ammonia solution.

[0037] The leveling agent is polyether siloxane.

[0038] A method for preparing a water-based flexographic printing ink comprises the following steps:

[0039] S1: Pre-dispersion: add organic pigment, cyclodextrin hyperbranched emulsifier, polyacrylic acid sodium salt, and the first auxiliary agent into a dispersion tank and disperse at 1500 rpm for 20 minutes to obtain a slurry;

[0040] S2: Grinding: sand-grinding the slurry with zirconium beads of 0.4 mm in diameter until the organic pigment particle size D50 is ≤ 200 nm to obtain a grind material;

[0041] S3: preparing a base material, adding modified corncob nano whiskers, pH buffer, and leveling agent to a water-based acrylic resin emulsion, and stirring at a low speed of 50 rpm for 40 minutes to obtain a base material;

[0042] S4: Mixing: adding the ground material prepared in S2 to the base material prepared in S3, and then adding cerium-neodymium-doped strontium tungstate nanosheets, stirring at 300 rpm for 30 minutes to obtain an ink blank;

[0043] S5: Post-processing: add deionized water to the ink blank to adjust the viscosity to -4 cups at 25℃ for 30 seconds, and pass through a 200-mesh filter to obtain a water-based flexographic printing ink, which is suitable for high-speed printing with a printing speed greater than or equal to 200m / min.

[0044] Example 2:

[0045] A water-based flexographic printing ink, comprising the following raw materials in parts by weight: 30 parts of water-based acrylic resin emulsion, 20 parts of organic pigment, 3 parts of modified corncob nanowhiskers, 3 parts of cerium-neodymium-doped strontium tungstate nanosheets, 6 parts of cyclodextrin hyperbranched emulsifier, 1 part of pH buffer, 0.5 parts of leveling agent, 1 part of polyacrylic acid sodium salt, and 0.2 parts of a first auxiliary agent;

[0046] The preparation method of modified corncob nano whiskers includes the following steps: corncobs crushed to 80 mesh are mixed with a deep eutectic solvent at a solid-liquid ratio of 1:10, the obtained turbidity is stirred at a constant temperature of 85°C for 3 hours, and then filtered to obtain a solid residue, the solid residue is washed with ethanol to remove oxalic acid, and then vacuum dried to obtain pretreated fibers, the pretreated fibers are added to pyridine, and acetic anhydride is added dropwise, the obtained mixture is acetylated at 110°C for 3 hours, and then cyclically treated 7 times by a high-pressure homogenizer at a pressure of 150 MPa to obtain modified corncob nano whiskers with a diameter of 50 nm and an acetylation degree of 80% or more.

[0047] The deep eutectic solvent was prepared by mixing choline chloride and oxalic acid in a molar ratio of 1:2, the mass ratio of pretreated fiber to pyridine was 1:15, and the mass ratio of pretreated fiber to acetic anhydride was 1:5.

[0048] The cerium-neodymium doped strontium tungstate nanosheets are prepared by the following method: cerium nitrate hexahydrate and neodymium nitrate hexahydrate are dissolved in ethylene glycol at a molar ratio of 3:1 to form a rare earth ion solution, sodium tungstate and strontium chloride are then added to form a mixed solution, the mixed solution is added to a high-pressure reactor and reacted at 200°C for 15 hours, the obtained product is centrifuged and the precipitate is collected, and calcined at 550°C for 3 hours to obtain hexagonal sheet-like nanoparticles, namely the cerium-neodymium doped strontium tungstate nanosheets.

[0049] Ethylene glycol accounts for 45% of the total mass of the rare earth ion solution, and the molar ratio of rare earth ions, sodium tungstate and strontium chloride is 1:50:50.

[0050] The cyclodextrin hyperbranched emulsifier is prepared by the following method: β-cyclodextrin and pentaerythritol are mixed in a molar ratio of 1:5, a comonomer consisting of lactide and glycolide in a molar ratio of 7:3 is added, and melt polycondensation is carried out at 160°C for 5 hours to generate a hyperbranched polyester, the hyperbranched polyester is dissolved in acetone, isophorone diisocyanate is added, and the reaction is carried out at a constant temperature of 60°C for 4 hours, and dihydroxymethylpropionic acid (10% by weight of the hyperbranched polyester) is added to extend the chain, and triethylamine is added to adjust the pH to 8 to prepare the cyclodextrin hyperbranched emulsifier.

[0051] The mass ratio of the hyperbranched polyester to acetone is 1:10, and the amount of isophorone diisocyanate used is 42% of the mass of the hyperbranched polyester.

[0052] The first auxiliary agent is prepared by the following method: dimethyl silicone oil and 10# industrial white oil are mixed, hydrophobic fumed silica is added, and high-speed shear dispersion is carried out at 60°C and 10,000 rpm for 30 minutes. Sorbitan monooleate is then added, and the resulting product is processed by a colloid mill and passed through a 250-mesh sieve to obtain a white liquid, which is the first auxiliary agent. The mass ratio of dimethyl silicone oil, industrial white oil, hydrophobic fumed silica, and sorbitan monooleate is 100:150:12:5.

[0053] The organic pigment is sun-fast scarlet, and the pH buffer is 0.5% by mass ammonia solution.

[0054] The leveling agent is dioctyl sodium sulfosuccinate.

[0055] A method for preparing a water-based flexographic printing ink comprises the following steps:

[0056] S1: Pre-dispersion: add organic pigment, cyclodextrin hyperbranched emulsifier, polyacrylic acid sodium salt, and the first auxiliary agent into a dispersion tank and disperse at 2000 rpm for 30 minutes to obtain a slurry;

[0057] S2: Grinding: sand-grinding the slurry with zirconium beads of 0.4 mm in diameter until the organic pigment particle size D50 is ≤ 200 nm to obtain a grind material;

[0058] S3: preparing a base material, adding modified corncob nano whiskers, pH buffer, and leveling agent to a water-based acrylic resin emulsion, and stirring at a low speed of 50 rpm for 50 minutes to obtain a base material;

[0059] S4: Mixing: adding the ground material prepared in S2 to the base material prepared in S3, and then adding cerium-neodymium-doped strontium tungstate nanosheets, stirring at 300 rpm for 30 minutes to obtain an ink blank;

[0060] S5: Post-processing: add deionized water to the ink blank to adjust the viscosity to -4 cups at 25℃ for 50 seconds, and pass through a 200-mesh filter to obtain a water-based flexographic printing ink, which is suitable for high-precision printing with a printing speed of ≤100m / min.

[0061] Example 3:

[0062] A water-based flexographic printing ink, comprising the following raw materials in parts by weight: 23 parts of a water-based acrylic resin emulsion, 14 parts of an organic pigment, 2 parts of modified corncob nanowhiskers, 2 parts of cerium-neodymium-doped strontium tungstate nanosheets, 4 parts of a cyclodextrin hyperbranched emulsifier, 0.7 parts of a pH buffer, 0.3 parts of a leveling agent, 0.7 parts of polyacrylic acid sodium salt, and 0.15 parts of a first auxiliary agent;

[0063] The preparation method of modified corncob nano whiskers includes the following steps: corncobs crushed to 80 mesh are mixed with a deep eutectic solvent at a solid-liquid ratio of 1:10, the obtained turbidity is stirred at a constant temperature of 83°C for 2.5 hours, and then filtered to obtain a solid residue, the solid residue is washed with ethanol to remove oxalic acid, and then vacuum dried to obtain pretreated fibers, the pretreated fibers are added to pyridine, and acetic anhydride is added dropwise, the obtained mixture is acetylated at 105°C for 2.5 hours, and then cyclically treated six times by a high-pressure homogenizer at a pressure of 135 MPa to obtain modified corncob nano whiskers with a diameter of 40 nm and an acetylation degree of 80% or more.

[0064] The deep eutectic solvent was prepared by mixing choline chloride and oxalic acid in a molar ratio of 1:2, the mass ratio of pretreated fiber to pyridine was 1:15, and the mass ratio of pretreated fiber to acetic anhydride was 1:5.

[0065] The cerium-neodymium doped strontium tungstate nanosheets are prepared by the following method: cerium nitrate hexahydrate and neodymium nitrate hexahydrate are dissolved in ethylene glycol at a molar ratio of 3:1 to form a rare earth ion solution, sodium tungstate and strontium chloride are then added to form a mixed solution, the mixed solution is added to a high-pressure reactor and reacted at 190°C for 13 hours, the obtained product is centrifuged and the precipitate is collected, and calcined at 530°C for 2.5 hours to obtain hexagonal sheet-like nanoparticles, namely the cerium-neodymium doped strontium tungstate nanosheets.

[0066] Ethylene glycol accounts for 40% of the total mass of the rare earth ion solution, and the molar ratio of rare earth ions, sodium tungstate and strontium chloride is 1:50:50.

[0067] A cyclodextrin hyperbranched emulsifier is prepared by the following method: β-cyclodextrin and pentaerythritol are mixed in a molar ratio of 1:5, a comonomer consisting of lactide and glycolide in a molar ratio of 7:3 is added, and melt polycondensation is carried out at 155°C for 4.5 hours to generate a hyperbranched polyester, the hyperbranched polyester is dissolved in acetone, isophorone diisocyanate is added, and the reaction is carried out at a constant temperature of 60°C for 3.5 hours, and dihydroxymethylpropionic acid (9% by weight of the hyperbranched polyester) is added to extend the chain, and triethylamine is added to adjust the pH to 7.5 to prepare a cyclodextrin hyperbranched emulsifier.

[0068] The mass ratio of the hyperbranched polyester to acetone is 1:10, and the amount of isophorone diisocyanate used is 40% of the mass of the hyperbranched polyester.

[0069] The first auxiliary agent is prepared by the following method: dimethyl silicone oil and 10# industrial white oil are mixed, hydrophobic fumed silica is added, and high-speed shear dispersion is carried out at 60°C and 10,000 rpm for 30 minutes. Sorbitan monooleate is then added, and the resulting product is processed by a colloid mill and passed through a 250-mesh sieve to obtain a white liquid, which is the first auxiliary agent. The mass ratio of dimethyl silicone oil, industrial white oil, hydrophobic fumed silica, and sorbitan monooleate is 100:150:12:5.

[0070] Phthalocyanine blue is selected as the organic pigment, and the pH buffer is an ammonia solution with a mass fraction of 0.5%.

[0071] Alkoxy acetylene glycol is selected as the leveling agent.

[0072] A method for preparing a water-based flexographic printing ink comprises the following steps:

[0073] S1: Pre-dispersion: add organic pigment, cyclodextrin hyperbranched emulsifier, polyacrylic acid sodium salt, and the first auxiliary agent into a dispersion tank and disperse at 1800 rpm for 25 minutes to obtain a slurry;

[0074] S2: Grinding: sand-grinding the slurry with zirconium beads of 0.4 mm in diameter until the organic pigment particle size D50 is ≤ 200 nm to obtain a grind material;

[0075] S3: preparing a base material, adding modified corncob nano whiskers, pH buffer, and leveling agent to a water-based acrylic resin emulsion, and stirring at a low speed of 50 rpm for 45 minutes to obtain a base material;

[0076] S4: Mixing: adding the ground material prepared in S2 to the base material prepared in S3, and then adding cerium-neodymium-doped strontium tungstate nanosheets, stirring at 300 rpm for 30 minutes to obtain an ink blank;

[0077] S5: Post-processing: add deionized water to the ink blank to adjust the viscosity to -4 cups at 25℃ for 40 seconds, and pass through a 200-mesh filter to obtain a water-based flexographic printing ink, which is suitable for ordinary printing at a printing speed of 100-200m / min.

[0078] Comparative Example 1: The difference between this comparative example and Experiment 1 is that this comparative example does not contain modified corncob nanowhiskers, and the other components are exactly the same as those in Example 3.

[0079] Comparative Example 2: This comparative example differs from Experiment 1 in that the commercially available defoaming agent BYK-22 is used in place of the first auxiliary agent, and the remaining components are identical to those in Example 3.

[0080] Comparative Example 3: The difference between this comparative example and Experiment 1 is that this comparative example does not contain cerium-neodymium-doped strontium tungstate nanosheets, and the other components are exactly the same as those in Example 3.

[0081] Performance test: The water-based flexographic printing inks prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test data obtained are recorded in the following table:

[0082]

[0083] By comparing and analyzing the data in the table, it can be seen that the dot gain rate, drying time, color saturation, storage stability and ink flying during use of the water-based flexographic printing inks prepared in Examples 1-3 are all better than those of the water-based flexographic printing inks prepared in Comparative Examples 1-3;

[0084] This indicates that the modified corncob nanowhiskers introduce hydrophobic groups onto their surfaces through an acetylation reaction, forming a dynamic hydrogen bond network with the carboxyl groups of the water-based acrylic resin. This allows the ink to form a three-dimensional gel under low-shear storage conditions, preventing pigment sedimentation. During high-shear printing, the hydrogen bonds reversibly break, causing a sharp drop in viscosity and ensuring smooth ink transfer. This solves the problem of high-solids inks struggling to balance storage stability and print leveling, while effectively reducing dot gain and improving printing quality.

[0085] The prepared cerium-neodymium-doped strontium tungstate nanosheets catalyze the oxidative cross-linking of the resin through the valence-varying characteristics of cerium ions, which can effectively improve the drying time of the ink. The characteristic absorption of neodymium ions in the near-infrared region converts light energy into heat energy, promoting solvent volatilization. At the same time, the structure of the nanosheets increases the contact area with the resin, and its surface negative charge also produces electrostatic repulsion with the pigment particles to prevent flocculation. This not only avoids the heavy metal pollution of traditional cobalt-manganese catalysis, but also breaks through the technical bottleneck of the slow drying speed of water-based inks, while meeting the needs of environmental protection and efficient production.

[0086] By comparing and analyzing the relevant data in the table, it can be seen that the water-based flexographic printing ink prepared by the present invention takes into account both storage stability and printing leveling, and at the same time breaks through the technical bottleneck of slow drying speed of water-based ink. This shows that the water-based flexographic printing ink provided by the present invention has a broader market prospect and is more suitable for promotion.

[0087] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0088] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A water-based flexographic printing ink, characterized in that: The invention comprises the following raw materials in parts by weight: 15-30 parts of water-based acrylic resin emulsion, 8-20 parts of organic pigment, 1-3 parts of modified corncob nano whiskers, 1-3 parts of cerium-neodymium-doped strontium tungstate nanosheets, 2-6 parts of cyclodextrin hyperbranched emulsifier, 0.3-1 part of pH buffer, 0.1-0.5 part of leveling agent, 0.3-1 part of polyacrylic acid sodium salt, and 0.1-0.2 part of a first auxiliary agent; The preparation method of modified corncob nano whiskers comprises the following steps: mixing corncobs crushed to 80 meshes with a deep eutectic solvent at a solid-liquid ratio of 1:10, subjecting the obtained turbidity to constant temperature stirring at 80-85°C for 2-3 hours, filtering to obtain a solid residue, washing the solid residue with ethanol to remove oxalic acid, and vacuum drying to obtain pretreated fibers, adding the pretreated fibers to pyridine, and then dropwise adding acetic anhydride, subjecting the obtained mixture to an acetylation reaction at 100-110°C for 2-3 hours, and then circulating the mixture through a high-pressure homogenizer at a pressure of 120-150 MPa for 5-7 times to obtain modified corncob nano whiskers with a diameter of 30-50 nm and an acetylation degree of 80% or more.

2. The water-based flexographic printing ink according to claim 1, characterized in that The deep eutectic solvent is formed by mixing choline chloride and oxalic acid in a molar ratio of 1:2, the mass ratio of the pretreated fiber to pyridine is 1:15, and the mass ratio of the pretreated fiber to acetic anhydride is 1:

5.

3. The water-based flexographic printing ink according to claim 2, characterized in that The cerium-neodymium-doped strontium tungstate nanosheets are prepared by the following method: dissolving cerium nitrate hexahydrate and neodymium nitrate hexahydrate in ethylene glycol at a molar ratio of 3:1 to form a rare earth ion solution, then adding sodium tungstate and strontium chloride to form a mixed solution, adding the mixed solution to a high-pressure reactor and reacting at 180-200° C. for 12-15 hours, centrifuging the obtained product and collecting the precipitate, and calcining the precipitate at 500-550° C. for 2-3 hours to obtain hexagonal sheet-shaped nanoparticles, namely the cerium-neodymium-doped strontium tungstate nanosheets.

4. The water-based flexographic printing ink according to claim 3, characterized in that The ethylene glycol accounts for 35-45% of the total mass of the rare earth ion solution, and the molar ratio of rare earth ions, sodium tungstate and strontium chloride is 1:50:

50.

5. The water-based flexographic printing ink according to claim 1, characterized in that The cyclodextrin hyperbranched emulsifier is prepared by the following method: β-cyclodextrin and pentaerythritol are mixed in a molar ratio of 1:5, a comonomer consisting of lactide and glycolide in a molar ratio of 7:3 is added, and melt polycondensation is carried out at 150-160°C for 4-5 hours to generate a hyperbranched polyester, the hyperbranched polyester is dissolved in acetone, isophorone diisocyanate is added, and the reaction is carried out at a constant temperature of 60°C for 3-4 hours, dihydroxymethylpropionic acid in an amount of 8-10% by weight of the hyperbranched polyester is added to extend the chain, and triethylamine is added to adjust the pH to 7-8 to prepare the cyclodextrin hyperbranched emulsifier.

6. The water-based flexographic printing ink according to claim 5, characterized in that The mass ratio of the hyperbranched polyester to acetone is 1:10, and the amount of isophorone diisocyanate used is 38-42% of the mass of the hyperbranched polyester.

7. The water-based flexographic printing ink according to claim 5, characterized in that The first auxiliary agent is prepared by the following method: dimethyl silicone oil and 10# industrial white oil are mixed, hydrophobic fumed silica is added, and high-speed shear dispersion is carried out at 60°C and 10,000 rpm for 30 minutes. Sorbitan monooleate is then added, and the resulting product is processed by a colloid mill and passed through a 250-mesh sieve to obtain a white liquid, which is the first auxiliary agent. The mass ratio of dimethyl silicone oil, industrial white oil, hydrophobic fumed silica, and sorbitan monooleate is 100:150:12:

5.

8. The water-based flexographic printing ink according to claim 1, characterized in that The organic pigment can be selected from at least one or more combinations of permanent yellow, phthalocyanine blue and sun-fast red, and the pH buffer is an ammonia solution with a mass fraction of 0.5%.

9. The water-based flexographic printing ink according to claim 8, characterized in that The leveling agent may be selected from at least one or more combinations of polyether siloxane, alkoxy acetylene glycol and dioctyl sodium sulfosuccinate.

10. A method for preparing a water-based flexographic printing ink, characterized in that: Using the water-based flexographic printing ink according to any one of claims 1 to 9, comprising the following steps: S1: Pre-dispersion: add organic pigment, cyclodextrin hyperbranched emulsifier, polyacrylic acid sodium salt, and the first auxiliary agent into a dispersion tank and disperse at 1500-2000 rpm for 20-30 minutes to obtain a slurry; S2: Grinding: sand-grinding the slurry with zirconium beads of 0.4 mm in diameter until the organic pigment particle size D50 is ≤ 200 nm to obtain a grind material; S3: preparing a base material, adding modified corncob nano whiskers, pH buffer, and leveling agent to a water-based acrylic resin emulsion, and stirring at a low speed of 50 rpm for 40 to 50 minutes to obtain a base material; S4: Mixing: adding the ground material prepared in S2 to the base material prepared in S3, and then adding cerium-neodymium-doped strontium tungstate nanosheets, stirring at 300 rpm for 30 minutes to obtain an ink blank; S5: Post-processing: add deionized water to the ink blank to adjust the viscosity to 4 cups at 25℃ for 30-50 seconds, and filter through a 200-mesh filter to obtain a water-based flexographic printing ink.

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