A kind of flexographic ink and preparation method thereof

Abstract

The invention discloses a flexographic ink and a preparation method thereof. The ink consists of the following components in parts by weight: 13-15 parts of aqueous acrylic resin, 9-12 parts of aqueous polyester resin, 10-12 parts of colorant, 7-8 parts of defoamer, 12-15 parts of modified ethyl cellulose, 3-5 parts of 2,5-furan dimethanol, 3-4 parts of polyvinyl alcohol, 2-5 parts of N-hydroxysuccinimide, 2-3 parts of ethyl lactate, 1-2 parts of fatty acid methyl ester and 50-55 parts of deionized water. According to the invention, ethyl cellulose and chitosan are mixed and then subjected to plasma treatment, and polyethylene glycol is added to react and modify in a reactor, so that the adhesion and water resistance of the ink are improved. The flexographic ink prepared by the invention has strong adhesion, good water resistance, fast surface drying speed, good gloss of ink, good leveling effect, and is environmentally friendly and safe, has a simple production process and is easy to promote.

Description

Technical Field

[0001] The invention relates to the technical field of inks, and in particular to a flexographic ink and a preparation method thereof. Background Art

[0002] Water-based ink is an ink that uses water as a solvent. Water-based ink uses water as the main dispersion medium. After the ink is transferred to the substrate, it dries into a film as the water evaporates. It has the characteristics of being non-toxic, odorless, environmentally friendly and safe, and does not contain volatile organic compounds (VOCs). Water-based ink is mainly suitable for packaging and printing products with strict hygiene requirements, such as beverage bottles, food packaging, pharmaceutical packaging, children's toys, etc. Flexographic water-based ink is an environmentally friendly printing ink, which is mainly made of water-soluble resins, organic pigments, solvents, additives, etc. through composite processing. This ink is suitable for flexographic printing machines and is used to print various plastic woven bags, plastic handbags, non-woven bags, paper labels, kraft paper bags, corrugated paper, etc.

[0003] Currently, water-based inks on the market still have defects such as relatively poor adhesion, poor water resistance, slow surface drying speed, and insufficient glossiness of the ink.

[0004] Announcement No. CN 115181448 B discloses ink for flexographic printing woven bags and a preparation method thereof. The ink includes the following ingredients: pigment, polyacrylic acid emulsion, polyurethane, hydroxypropyl methylcellulose, phosphate-type surfactant, defoaming agent, ethanol and water. The invention introduces hydroxypropyl methylcellulose in a specific ratio range and a certain amount of phosphate-type surfactant into the ink formula of flexographic printing woven bags, so that the raw materials have good dispersion and emulsification effects, significantly improves the adhesion and peeling force of the ink on the polypropylene substrate woven bag, and improves the printing quality.

[0005] Announcement No. CN 101125977 B discloses a water-based flexographic printing ink and a preparation method thereof, which comprises the following components and contents: 37%-47.2% of acrylic resin emulsion, 40%-50% of water-based acrylic color paste, 0.1%-0.3% of defoaming agent, 0.2%-2.0% of water-based wax paste, 2%-8% of isopropyl alcohol, 10%-30% of ethylene glycol, 0.5%-1% of ethanolamine, and the balance is water. The water-based flexographic printing ink of the invention is environmentally friendly and non-toxic, has good safety in use, stable performance, good adaptability to coated paper printing, can be continuously printed without smudging, has clear imprints, and has low production cost.

[0006] At present, a certain concentration of anhydrous ethanol or isopropyl alcohol is used in the production process of water-based ink. Due to the solubility and volatility of anhydrous ethanol or isopropyl alcohol, relatively difficult-to-dissolve substances can be dissolved, and anhydrous ethanol and isopropyl alcohol evaporate quickly, which can make the ink dry faster during the printing process. However, anhydrous ethanol and isopropyl alcohol have a relatively strong irritating odor during use, are flammable, and can easily cause safety hazards.

[0007] Therefore, solving the problems of poor adhesion, poor water resistance, slow surface drying speed, poor glossiness of ink, environmental protection and safety of flexographic water-based inks is a technical problem that needs to be urgently solved in the current flexographic ink industry. Summary of the invention

[0008] The purpose of the present invention is to provide a flexographic ink and a preparation method thereof, so as to solve the problems of poor adhesion, poor water resistance, slow surface drying speed, poor glossiness of the ink, environmental safety, etc. of the flexographic ink mentioned in the above background technology.

[0009] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a flexographic ink and a preparation method thereof, the flexographic ink comprising the following components in parts by weight: 13 to 15 parts of an aqueous acrylic resin, 9 to 12 parts of an aqueous polyester resin, 10 to 12 parts of a colorant, 7 to 8 parts of a defoaming agent, 12 to 15 parts of modified ethyl cellulose, 3 to 5 parts of 2,5-furan dimethanol, 3 to 4 parts of polyvinyl alcohol, 2 to 5 parts of N-hydroxysuccinimide, 2 to 3 parts of ethyl lactate, 1 to 2 parts of a fatty acid methyl ester, and 50 to 55 parts of deionized water.

[0010] Furthermore, the colorant is carbon black, and the particle size is 75 to 90 nm.

[0011] Furthermore, the defoaming agent is composed of linear polydimethylsiloxane and branched polydimethylsiloxane in a mass ratio of 2:1 to 1.2.

[0012] Furthermore, the modified ethyl cellulose is prepared by mixing and modifying the following components in parts by weight: 30-35 parts of ethyl cellulose, 1-2 parts of chitosan, 3-5 parts of polyethylene glycol, and 25-30 parts of deionized water.

[0013] Furthermore, the flexographic ink is prepared by the following method steps:

[0014] Step 1: Place water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol, polyvinyl alcohol, and deionized water in a vacuum homogenizer and stir and mix to obtain a mixed resin emulsion. The temperature is set to 45-50 ° C, the stirring speed is 460-480 rpm, and the vacuum degree is -97--90 kPa.

[0015] Step 2, preparation of modified ethyl cellulose: weigh ethyl cellulose and chitosan, mix them in a mixing mixer, and place them in a plasma device for treatment for 210 to 240 seconds; place the raw materials after plasma treatment in a reactor, add polyethylene glycol and deionized water for mixing and stirring to obtain modified ethyl cellulose, the reactor temperature is controlled at 55 to 60°C, the stirring speed is 650 to 700 rpm, the time is 18 to 20 min, and the pH is adjusted to 6.5 to 6.8 by adding any one of phosphoric acid and triethanolamine or an acid-base regulator A mixed with the two substances.

[0016] Step 3: Place the mixed resin emulsion prepared in step 1, the modified ethyl cellulose prepared in step 2, the colorant, the defoamer, and N-hydroxysuccinimide in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle is set to 2200-2500 rpm for 70-80 minutes.

[0017] Step 4: Place the mixture obtained in step 3 in a wet grinder, add ethyl lactate and fatty acid methyl ester and grind them. The rotation speed of the grinder is 2800-3200 rpm and the grinding time is 50-55 min.

[0018] Step 5: Place the material ground in step 4 into a mixer, add acid-base regulator B and thickener to mix to obtain flexible ink, the mixer speed is 550-600 rpm, and the stirring time is 10-12 min.

[0019] As a preferred technical solution of the present invention, the molecular weight of the polyethylene glycol is 300-600 Da.

[0020] As a preferred technical solution of the present invention, the charge density of the plasma equipment is 1100-1200 C / cm 3 , gas flow rate is 1.5~1.6 L / min, processing chamber pressure is 95~100 kPa, and processing chamber temperature is 50~55 ℃.

[0021] As a preferred technical solution of the present invention, the medium used in the wet grinding machine is steel balls with a particle size of 0.6 to

[0022] 0.8 mm.

[0023] As a preferred technical solution of the present invention, the acid-base regulator B of the flexographic ink is any one of diethanolamine and triethanolamine or a mixture of the two substances, and the pH is adjusted to 8.6-9.0.

[0024] As a preferred technical solution of the present invention, the thickener is any one of polyacrylamide and polyacrylic acid or a mixture of the two substances, and the viscosity of the ink is adjusted to 15-30 Pa·s.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention treats ethyl cellulose and chitosan in a plasma device after mixing them. High-energy particles such as electrons and ions generated by the plasma device collide and react with the surfaces of ethyl cellulose and chitosan, so that free radicals are generated on the surface of ethyl cellulose and other active groups such as amino groups and hydroxyl groups are introduced. Polyethylene glycol is added in a reactor to react with ethyl cellulose and chitosan to modify them, and active groups such as hydroxyl groups and ether bonds are introduced. Ethyl cellulose is subjected to plasma chemical modification, so that the polymer can be more evenly dispersed in the ink, the aggregation and precipitation of particles are reduced, and the ink is prevented from being used. In the process of using, stratification and precipitation occur, which improves the uniformity of ink and printing effect. By modifying ethyl cellulose and adding it to the ink, the ink can be better leveled during the printing process, reducing surface defects of printed products, enhancing the adhesion of ink to substrates, making printed products more firm and durable. At the same time, it can improve the water resistance and drying speed of ink, so that printed products can still maintain good performance in a humid environment and reduce printing problems caused by poor drying. Ethyl cellulose, chitosan and polyethylene glycol are degradable, which makes the ink have certain advantages in environmental protection.

[0027] 2. The present invention adds 2,5-furan dimethanol, which is a biomass-based furan derivative compound with multiple functional groups, such as hydroxyl groups, and has a relatively strong hydrogen bond forming ability. These functional groups enable it to exhibit good solubility and dispersibility in an aqueous environment. Since the hydroxyl groups are connected to the furan ring, the hydroxyl groups in 2,5-furan dimethanol not only have the activity of general alcohol hydroxyl groups, but are also affected by the conjugation effect of the furan ring, and exhibit some special reaction properties, thereby reducing the surface tension of the ink, enhancing the fluidity and stability of the ink, improving the adhesion of the ink on the surface of the substrate, and improving the flexibility and wear resistance of the ink. At the same time, 2,5-furan dimethanol is renewable and biodegradable, and has little impact on the environment.

[0028] 3. The defoaming agent added in the present invention is a mixture of straight-chain polydimethylsiloxane and branched polydimethylsiloxane in a certain proportion. The straight-chain polydimethylsiloxane has a lower surface tension, so that it can quickly penetrate into the foam liquid film in the ink, reduce the surface tension of the liquid film, thereby destroying the stability of the foam and causing the foam to burst quickly. The branched polydimethylsiloxane helps to better disperse the polydimethylsiloxane in the ink, improve the uniformity of the defoaming agent in the ink system, and enhance the defoaming effect. The branched polydimethylsiloxane has lubricity, reduces the friction of the ink during the printing process, and reduces the foam generated by friction. The straight-chain polydimethylsiloxane and the branched polydimethylsiloxane are mixed in proportion to produce a synergistic effect, further improving the defoaming ability of the ink.

[0029] 4. The present invention adds ethyl lactate and fatty acid methyl ester in the process of making water-based ink. Ethyl lactate and fatty acid methyl ester have good solubility, safety, environmental protection and low toxicity, and can be used in water-based ink to improve the quick-drying effect in the process of water-based ink printing. They can replace the use of ethanol or isopropanol, reduce the generation of irritating odor and reduce safety hazards.

[0030] 5. The present invention adopts a vacuum homogenizer for mixing treatment during the preparation of the resin emulsion, and mixes, stirs and emulsifies the water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol and polyvinyl alcohol under a vacuum state, which can reduce the bubble content and impurities in the emulsion, improve the surface gloss, uniformity and stability of the product, and improve the quality of the ink. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of ink making of the present invention;

[0032] Figure 2 This is a histogram of the ink leveling effect of the present invention;

[0033] Figure 3 It is a line graph of the water resistance of the ink of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0035] The present invention treats ethyl cellulose and chitosan in a plasma device after mixing them. High-energy particles such as electrons and ions generated by the plasma device collide and react with the surfaces of ethyl cellulose and chitosan, so that free radicals are generated on the surface of ethyl cellulose and other active groups are introduced, such as amino groups, hydroxyl groups and the like. Polyethylene glycol is added in a reaction kettle to react with ethyl cellulose and chitosan for modification, and active groups such as hydroxyl groups and ether bonds are introduced. The ethyl cellulose is subjected to plasma chemical modification, so that the polymer can be more evenly dispersed in the ink, the agglomeration and precipitation of particles are reduced, the ink is prevented from being delaminated and precipitated during use, the uniformity and printing effect of the ink are improved, and the interaction force between the modified ethyl cellulose and the ink is enhanced by modifying the ethyl cellulose and adding it to the ink, so that the surface tension is reduced, which is beneficial to the printing effect. The modified ethyl cellulose can enhance the internal structure of the ink layer, making it tighter and more stable, thereby resisting the erosion of the ink layer by water, improving the water resistance of the ink, and enabling the printed matter to maintain good performance in a humid environment. The modified ethyl cellulose has good film-forming properties and can enhance the bonding force between the ink layer and the substrate, so that the ink layer can solidify faster during the drying process to form a solid coating. At the same time, the modified ethyl cellulose helps the solvent to evaporate faster, improves the surface dryness of the ink, and reduces printing problems caused by poor drying. Ethyl cellulose, chitosan, and polyethylene glycol are degradable, giving the ink certain advantages in environmental protection.

[0036] The present invention adds 2,5-furan dimethanol, which is a biomass-based furan derivative compound having multiple functional groups, such as hydroxyl groups, and has relatively strong hydrogen bond forming ability. These functional groups enable it to exhibit good solubility and dispersibility in an aqueous environment. Since the hydroxyl groups are connected to the furan ring, the hydroxyl groups in the 2,5-furan dimethanol not only have the activity of general alcohol hydroxyl groups, but are also affected by the conjugation effect of the furan ring, and exhibit some special reaction properties, thereby reducing the surface tension of the ink, enhancing the fluidity and stability of the ink, improving the adhesion of the ink on the surface of the substrate, and improving the flexibility and wear resistance of the ink. At the same time, 2,5-furan dimethanol is renewable and biodegradable, has little impact on the environment, and is in line with the current trend of environmental protection and sustainable development.

[0037] The defoaming agent added in the present invention is a mixture of straight-chain polydimethylsiloxane and branched polydimethylsiloxane in a certain proportion, which improves the defoaming effect. The straight-chain polydimethylsiloxane has a relatively low surface tension, so that it can quickly penetrate into the foam liquid film in the water-ink, reduce the surface tension of the liquid film, thereby destroying the stability of the foam and causing the foam to burst quickly. The branched polydimethylsiloxane helps to better disperse the polydimethylsiloxane in the water-ink, improves the uniformity of the defoaming agent in the water-ink system, and enhances the defoaming effect. The branched polydimethylsiloxane has lubricity, reduces the friction of the water-ink during printing, and reduces the foam generated by friction. The straight-chain polydimethylsiloxane and the branched polydimethylsiloxane are mixed in proportion to produce a synergistic effect, which further improves the defoaming ability of the water-ink. The branched structure may help the straight-chain polydimethylsiloxane to better penetrate into the foam, and accelerate the bursting and dissipation of the foam.

[0038] In the process of making water-based ink, a certain concentration of anhydrous ethanol or isopropanol is often used. The solubility and volatility of anhydrous ethanol or isopropanol can be used to dissolve relatively insoluble substances, and anhydrous ethanol and isopropanol evaporate quickly, which can make the ink dry faster during the printing process. However, anhydrous ethanol and isopropanol have a relatively strong irritating odor during use, are flammable, and are likely to cause safety hazards. In the present invention, ethyl lactate and fatty acid methyl ester are added during the ink making process. Ethyl lactate and fatty acid methyl ester have good solubility, safety, environmental protection, low toxicity, and volatility, which improve the quick-drying effect during the ink printing process, can replace the use of ethanol or isopropanol, reduce the generation of irritating odor and reduce safety hazards.

[0039] The present invention adopts a vacuum homogenizer for mixing treatment in the process of preparing the resin emulsion, and mixes, stirs and emulsifies the water-based acrylic resin, the water-based polyester resin, 2,5-furan dimethanol and the polyvinyl alcohol under a vacuum state, which can reduce the bubble content and impurities in the emulsion, improve the surface gloss, uniformity and stability of the product, and improve the quality of the ink.

[0040] The raw materials used in the present invention are all commercially available raw materials.

[0041] Embodiment 1:

[0042] A flexographic ink comprises the following components in parts by weight: 13 parts of water-based acrylic resin, 9 parts of water-based polyester resin, 10 parts of carbon black, 7 parts of a defoaming agent (straight-chain polydimethylsiloxane and branched polydimethylsiloxane in a mass ratio of 2:1), 12 parts of modified ethyl cellulose, 3 parts of 2,5-furan dimethanol, 3 parts of polyvinyl alcohol, 2 parts of N-hydroxysuccinimide, 2 parts of ethyl lactate, 1 part of fatty acid methyl ester, and 50 parts of deionized water.

[0043] A flexographic ink is prepared by the following method and steps:

[0044] Step 1: Place water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol, polyvinyl alcohol, and deionized water in a vacuum homogenizer and stir and mix to obtain a mixed resin emulsion. The temperature is set to 45°C, the stirring speed is 460rpm, and the vacuum degree is -90 kPa.

[0045] Step 2: Preparation of modified ethyl cellulose: (1) Weigh 30 parts of ethyl cellulose and 1 part of chitosan, mix them in a mixer, and place them in a plasma device for 210 seconds. The charge density of the plasma device is 1100 C / cm 3 , gas flow rate of 1.5 L / min, treatment chamber pressure of 95 kPa, treatment chamber temperature of 50 °C; (2) placing the raw materials after plasma treatment into a reactor, adding 3 parts of polyethylene glycol and 25 parts of deionized water for mixing and stirring to obtain modified ethyl cellulose, the reactor temperature is controlled at 55 °C, the stirring speed is 650 rpm, the time is 20 min, the pH is adjusted to 6.5, the mixing stirrer speed is 650 rpm, and the mixing time is 18 min.

[0046] Step 3: Place the mixed resin emulsion prepared in step 1, the modified ethyl cellulose prepared in step 2, the colorant, the defoamer, and N-hydroxysuccinimide in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle is set to 2200 rpm for 80 min. The colorant is carbon black with a particle size of 75 nm.

[0047] Step 4: Place the mixture obtained in step 3 in a wet grinder, add ethyl lactate and fatty acid methyl ester and grind them. The speed of the grinder is 2800 rpm and the grinding time is 55 min.

[0048] Step 5: Place the material ground in step 4 into a blender, add acid-base regulator B and thickener polyacrylamide to mix to obtain flexible ink. The blender speed is 550 rpm, the stirring time is 10 min, the pH is adjusted to 8.6, and the viscosity of the ink is 15 Pa·s.

[0049] Embodiment 2

[0050] A flexographic ink comprises the following components in parts by weight: 15 parts of water-based acrylic resin, 12 parts of water-based polyester resin, 12 parts of carbon black, 8 parts of a defoaming agent (straight-chain polydimethylsiloxane and branched polydimethylsiloxane in a mass ratio of 2:1.2), 15 parts of modified ethyl cellulose, 5 parts of 2,5-furan dimethanol, 4 parts of polyvinyl alcohol, 5 parts of N-hydroxysuccinimide, 3 parts of ethyl lactate, 2 parts of fatty acid methyl ester, and 55 parts of deionized water.

[0051] A flexographic ink is prepared by the following method and steps:

[0052] Step 1: Place water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol, polyvinyl alcohol, and deionized water in a vacuum homogenizer and stir and mix to obtain a mixed resin emulsion. The temperature is set to 50°C, the stirring speed is 480rpm, and the vacuum degree is -97 kPa.

[0053] Step 2: Preparation of modified ethyl cellulose: (1) Weigh 35 parts of ethyl cellulose and 2 parts of chitosan, mix them in a mixer, and place them in a plasma device for treatment for 240 seconds. The charge density of the plasma device is 1200 C / cm 3 , gas flow rate of 1.6 L / min, treatment chamber pressure of 100 kPa, treatment chamber temperature of 55 °C; (2) placing the raw materials after plasma treatment into a reactor, adding 5 parts of polyethylene glycol and 30 parts of deionized water for mixing and stirring to obtain modified ethyl cellulose, the reactor temperature is controlled at 60 °C, the stirring speed is 700 rpm, the time is 18 min, the pH is adjusted to 6.8, the mixing stirrer speed is 680 rpm, and the mixing time is 15 min.

[0054] Step 3: Place the mixed resin emulsion prepared in step 1, the modified ethyl cellulose prepared in step 2, the colorant, the defoamer, and N-hydroxysuccinimide in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle is set to 2500 rpm for 70 min. The colorant is carbon black with a particle size of 90 nm.

[0055] Step 4: Place the mixture obtained in step 3 in a wet grinder, add ethyl lactate and fatty acid methyl ester and grind them at a speed of 3200 rpm for 50 min.

[0056] Step 5: Place the material ground in step 4 in a blender, add acid-base regulator B and thickener polyacrylic acid to mix to obtain flexible ink. The blender speed is 600 rpm, the stirring time is 12 min, the pH is adjusted to 9.0, and the viscosity of the ink is 30 Pa·s.

[0057] Embodiment 3

[0058] A flexographic ink comprises the following components in parts by weight: 14 parts of water-based acrylic resin, 10 parts of water-based polyester resin, 11 parts of carbon black, 7.5 parts of a defoaming agent (straight-chain polydimethylsiloxane and branched polydimethylsiloxane in a mass ratio of 2:1.1), 13 parts of modified ethyl cellulose, 4 parts of 2,5-furan dimethanol, 3.5 parts of polyvinyl alcohol, 3 parts of N-hydroxysuccinimide, 2.5 parts of ethyl lactate, 1.5 parts of fatty acid methyl ester, and 53 parts of deionized water.

[0059] A flexographic ink is prepared by the following method and steps:

[0060] Step 1: Place water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol, polyvinyl alcohol, and deionized water in a vacuum homogenizer and stir and mix to obtain a mixed resin emulsion. The temperature is set to 48°C, the stirring speed is 470rpm, and the vacuum degree is -95 kPa.

[0061] Step 2: Preparation of modified ethyl cellulose: (1) Weigh 33 parts of ethyl cellulose and 1.5 parts of chitosan, mix them in a mixer, and place them in a plasma device for treatment for 220 s. The charge density of the plasma device is 1150 C / cm 3 , gas flow rate of 1.5 L / min, treatment chamber pressure of 98 kPa, treatment chamber temperature of 52 °C; (2) placing the raw materials after plasma treatment into a reactor, adding 4 parts of polyethylene glycol and 26 parts of deionized water for mixing and stirring to obtain modified ethyl cellulose, the reactor temperature is controlled at 56 °C, the stirring speed is 680 rpm, the time is 19 min, the pH is adjusted to 6.7, the mixing stirrer speed is 660 rpm, and the mixing time is 16 min.

[0062] Step 3: Place the mixed resin emulsion prepared in step 1, the modified ethyl cellulose prepared in step 2, the colorant, the defoamer, and N-hydroxysuccinimide in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle is set to 2300 rpm for 75 min. The colorant is carbon black with a particle size of 85 nm.

[0063] Step 4: Place the mixture obtained in step 3 in a wet grinder, add ethyl lactate and fatty acid methyl ester and grind them. The speed of the grinder is 3000 rpm and the grinding time is 52 min.

[0064] Step 5: Place the material ground in step 4 into a blender, add acid-base regulator B and thickener (polyacrylamide and polyacrylic acid mixed in a mass ratio of 1:1) to mix to obtain flexible ink. The blender speed is 560 rpm, the stirring time is 11 minutes, the pH is adjusted to 8.8, and the viscosity of the ink is 23 Pa·s.

[0065] Comparative Example 1:

[0066] The modified ethyl cellulose in Example 2 is removed, and the other method steps are the same as those in Example 2.

[0067] Comparative Example 2:

[0068] The ethyl cellulose and chitosan in Example 2 are not treated by plasma equipment, but are directly mixed with polyethylene glycol in a reactor for reaction modification. The other method steps are the same as those in Example 2.

[0069] Comparative Example 3:

[0070] The 2,5-furan dimethanol in Example 2 is removed, and the other method steps are the same as those in Example 2.

[0071] Comparative Example 4:

[0072] The ethyl lactate and fatty acid methyl ester in Example 2 are removed, and the other method steps are the same as those in Example 2.

[0073] Comparative Example 5:

[0074] Step 1 of Example 2 is modified as follows: water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol, polyvinyl alcohol, and deionized water are mixed in a blender to obtain a mixed resin emulsion. The stirring speed is 480 rpm. The other method steps are the same as those of Example 2.

[0075] The flexographic inks prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4 and 5 were tested for adhesion according to GB / T13217.7-2023 "Test Method for Adhesion of Ink", and the adhesion of the inks was tested according to QB / T 2825-2006 "Flexo Plate Water-Based Ink" was used to test the surface dryness of the ink. The glossiness of the ink was tested according to GB / T13217.2-2009 "Liquid Ink Gloss Test Method". The results are shown in Table 1. The inks of Examples 1, 2 and 3 have strong adhesion, good glossiness and surface dryness. The inks of Comparative Examples 1, 2 and 3 have poor adhesion. The glossiness of Comparative Example 5 is poor. The paper strip of Comparative Example 1 has slight staining, and the paper strip of Comparative Example 4 has obvious staining. Plasma treatment of ethyl cellulose and chemical modification with chitosan and polyethylene glycol can generate free radicals on the surface of ethyl cellulose and introduce other active groups, thereby enhancing the adhesion of the ink to the substrate. 2,5-furan dimethanol has multiple functional groups and relatively strong hydrogen bond forming ability, making it It shows good solubility and dispersibility in a volatile environment. The hydroxyl group in 2,5-furan dimethanol not only has the activity of general alcohol hydroxyl groups, but is also affected by the conjugation effect of the furan ring, showing some special reaction properties, thereby reducing the surface tension of ink and improving the adhesion of ink on the surface of the substrate. Vacuum homogenization treatment of resin emulsion can reduce the bubble content and impurities in the emulsion, and improve the surface gloss, uniformity and stability of the product. Modified ethyl cellulose has good film-forming properties and can enhance the bonding force between the ink layer and the substrate, so that the ink layer can solidify faster during the drying process to form a solid coating. At the same time, modified ethyl cellulose helps the solvent to evaporate faster and improve the surface dryness of the ink. Ethyl lactate and fatty acid methyl ester are volatile and can be used in ink to improve the quick-drying effect during ink printing.

[0076] Table 1: Ink test index

[0077]

[0078] The flexographic inks prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4 and 5 were tested for leveling effect. The leveling effect of the ink was tested by the following method: an appropriate amount of ink sample was taken, and the ink sample was evenly spread on white cardboard using a proofing machine, and the surface of the white cardboard after the color was spread was observed to evaluate the leveling effect of the ink. The leveling effect of the ink was evaluated according to Table 2. The results are shown in Table 2. Figure 2 The ink leveling test scores of Examples 1, 2, 3 and Comparative Examples 3, 4, and 5 are all above 95 points, the ink layer is uniform, smooth, and flat, without defects such as shrinkage cavities, pinholes, and volcanic craters. The ink leveling test scores of Comparative Examples 1 and 2 are 79.3 and 84.5, respectively, the ink layer has poor uniformity, the surface is not smooth and flat, and the ink layer has defects such as shrinkage cavities, pinholes, and volcanic craters. Plasma treatment of ethyl cellulose and chemical modification by adding chitosan and polyethylene glycol can generate free radicals on the surface of ethyl cellulose and introduce other active groups, which helps to enhance the interaction between the modified ethyl cellulose and ink, improve the wettability and adhesion of ink, reduce surface tension, and facilitate the spreading and flow of ink, so that the ink can be better leveled during the printing process.

[0079] Table 2: Evaluation criteria for leveling effect of water-based ink

[0080]

[0081] The flexographic inks prepared in Example 2 and Comparative Examples 1 and 2 were uniformly spread on white cardboard using a proofing machine, and after being fully dried, they were placed under the conditions of temperature (30±2)°C and relative humidity (85±5)%RH. The water resistance of the inks was observed every 5 minutes. The evaluation standard for the water resistance of the inks is shown in Table 3, and the water resistance results are shown in Table 4. Figure 3 As shown, with the extension of time, the water resistance of the ink of comparative example 2 and comparative example 3 shows a downward trend. The water resistance is Class B after 5 minutes, and the water resistance of the ink of comparative example 1 drops to Class C after 10 minutes. The water resistance of the ink of comparative example 2 drops to Class C after 15 minutes. The water resistance score of the ink of Example 2 is still 100 points after 15 minutes, and the score drops to 98.6 points after 20 minutes. Plasma treatment of ethyl cellulose and chemical modification treatment with chitosan and polyethylene glycol can generate free radicals on the surface of ethyl cellulose and introduce other active groups, thereby enhancing the internal structure of the ink layer, making it more compact and stable, thereby resisting the erosion of water on the ink layer, thereby improving the water resistance of the ink.

[0082] Table 3: Evaluation criteria for water resistance of water-based ink

[0083]

[0084] In summary, the flexographic ink prepared by the present invention has strong adhesion, good water resistance, fast surface drying speed, good glossiness of the ink, good leveling effect, and is environmentally friendly and safe, with a simple production process and easy promotion.

[0085] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A flexographic ink, characterized in that: The invention comprises the following components in parts by weight: 13 to 15 parts of water-based acrylic resin, 9 to 12 parts of water-based polyester resin, 10 to 12 parts of colorant, 7 to 8 parts of defoamer, 12 to 15 parts of modified ethyl cellulose, 3 to 5 parts of 2,5-furan dimethanol (FDM), 3 to 4 parts of polyvinyl alcohol, 2 to 5 parts of N-hydroxysuccinimide, 2 to 3 parts of ethyl lactate, 1 to 2 parts of fatty acid methyl ester, and 50 to 55 parts of deionized water; The colorant is carbon black with a particle size of 75 to 90 nm; The defoaming agent is composed of linear polydimethylsiloxane and branched polydimethylsiloxane in a mass ratio of 2:1 to 1.2; The modified ethyl cellulose is prepared by mixing and modifying the following components in parts by weight: 30-35 parts of ethyl cellulose, 1-2 parts of chitosan, 3-5 parts of polyethylene glycol, and 25-30 parts of deionized water; The specific steps of the preparation method of the flexographic ink are: Step 1: Place water-based acrylic resin, water-based polyester resin, 2,5-furan dimethanol, polyvinyl alcohol, and deionized water in a vacuum homogenizer and stir to obtain a mixed resin emulsion. The temperature is set to 45-50° C., the stirring speed is 460-480 rpm, and the vacuum degree is -97--90 kPa; Step 2, preparation of modified ethyl cellulose: weigh ethyl cellulose and chitosan, mix them in a mixing mixer, and place them in a plasma device for treatment for 210 to 240 seconds; place the raw materials after plasma treatment in a reactor, add polyethylene glycol and deionized water for mixing and stirring to obtain modified ethyl cellulose, the reactor temperature is controlled at 55 to 60° C., the stirring speed is 650 to 700 rpm, the time is 18 to 20 min, and an acid-base regulator A of any one of phosphoric acid and triethanolamine or a mixture of the two substances is added to adjust the pH to 6.5 to 6.8; Step 3: Place the mixed resin emulsion prepared in step 1, the modified ethyl cellulose prepared in step 2, the colorant, the defoamer, and N-hydroxysuccinimide in a dispersion kettle to disperse the mixture, and set the speed of the dispersion kettle to 2200-2500 rpm for 70-80 min; Step 4: Place the mixture obtained in step 3 in a wet grinder, add ethyl lactate and fatty acid methyl ester and grind at a speed of 2800 to 3200 rpm for 50 to 55 min; Step 5: Place the material ground in step 4 into a mixer, add acid-base regulator B and thickener to mix to obtain flexible ink, the mixer speed is 550-600 rpm, and the stirring time is 10-12 min.

2. A flexographic ink according to claim 1, characterized in that: The molecular weight of polyethylene glycol is 300-600 Da.

3. A flexographic ink according to claim 1, characterized in that: The charge density of the plasma equipment is 1100-1200 C / cm 3 , gas flow rate is 1.5~1.6L / min, processing chamber pressure is 95~100kPa, and processing chamber temperature is 50~55℃.

4. The flexographic ink according to claim 1, characterized in that: The speed of the mixing mixer is 650-680 rpm and the mixing time is 15-18 min.

5. The flexographic ink according to claim 1, characterized in that: The medium used in the wet grinding machine is steel balls with a particle size of 0.6 to 0.8 mm.

6. The flexographic ink according to claim 1, characterized in that: The acid-base regulator B is any one of diethanolamine and triethanolamine or a mixture of the two substances, and the pH of the flexographic ink is adjusted to 8.6-9.

0.

7. The flexographic ink according to claim 1, characterized in that: The thickener is any one of polyacrylamide and polyacrylic acid or a mixture of the two substances, and is used to adjust the viscosity of the ink to 15-30 Pa·s.

Images