A kind of preparation method of acrylic ink

Abstract

The invention discloses a method for preparing acrylic ink, comprising the following steps: S1. After acrylic acid, water-based acrylic resin, polyvinyl alcohol resin, alkyl glycoside and deionized water are placed in a homogenizer for mixing, casein is added and ultrasonically treated in an ultrasonic device to obtain an acrylic mixed emulsion; S2. The acrylic mixed emulsion, carbon black, modified sodium alginate, polycarbodiimide emulsion, polyether modified silicone and sodium carboxymethyl cellulose are placed in a dispersion kettle for dispersion to obtain a mixture; S3. The mixture is placed in a wet grinder for grinding; S4. The ground mixture is placed in a mixer, triethanolamine is added for mixing to obtain a finished ink. The ink prepared by the invention has strong adhesion, good water resistance, fast surface drying speed, good gloss of the ink, is not easy to be oxidized and decolorized, 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 ink, and in particular to a method for preparing acrylic ink. Background Art

[0002] Water-based ink is a water-based ink with water as solvent, which is mainly made of water-soluble resin, organic pigment, solvent and related additives through composite grinding. Water-based ink has the characteristics of non-toxic, odorless, environmentally friendly and safe, and does not contain volatile organic compounds (VOCs). Water-based ink is suitable for packaging and printing products with relatively strict requirements, such as packaging and printing of beverage bottles, cigarettes, food, medicines, children's toys and other products.

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

[0004] Publication No. CN118772692A discloses a high temperature resistant water-based surface printing ink for plastic substrates and a preparation method thereof, the ink comprising the following components: 30 to 50 parts of acrylic emulsion with a glass transition temperature of 98 to 109°C; 0.8 to 1.2 parts of anionic surfactant with an alkyl carbon number of 12 to 16; 14 to 17 parts of tackifying resin; 10 to 15 parts of pigment; 8 to 12 parts of solvent; 2 to 4 parts of wax; 16 to 20 parts of water. The preparation method of the ink is: take half the mass of water, half the mass of solvent, tackifying resin and pigment, blend them, grind them, add the remaining water and solvent, acrylic emulsion, surfactant, wax, blend them, sieve them, and obtain them. The high temperature resistant water-based surface printing ink for plastic substrates of the present application has heat resistance comparable to that of solvent-based inks, and has better adhesion, friction resistance, water resistance and blocking resistance. However, the solvent used in the preparation method is ethanol or isopropanol, which has a strong pungent odor during use, is flammable, and easily causes safety hazards.

[0005] Announcement No. CN101125977B discloses a water-based flexographic printing ink and a preparation method thereof, which comprises the following components and contents: 37-47.2% acrylic resin emulsion, 40-50% water-based acrylic color paste, 0.1-0.3% defoamer, 0.2-2.0% water-based wax paste, 2-8% isopropanol, 10-30% ethylene glycol, 0.5-1% ethanolamine, and the balance is water. The water-based flexographic printing ink of the present 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 smearing the plate, has clear imprints, and has low production cost. However, the preparation process of the water-soluble acrylic resin of the preparation method takes about 7 hours, and the temperature is basically maintained at 80-100°C, which is time-consuming and energy-consuming, and the ethanol or isopropanol used in the preparation process has a relatively strong irritating odor, is flammable, and is likely to cause safety hazards.

[0006] Therefore, there is an urgent need to provide a method for preparing water-based ink to solve the problems of poor adhesion, poor water resistance, slow surface drying speed, poor glossiness, and easy oxidation and discoloration of the water-based ink. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing acrylic ink to solve the problems of poor adhesion, poor water resistance, slow surface drying speed, poor glossiness and easy oxidation and discoloration of water-based ink mentioned in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for preparing acrylic ink, comprising the following steps:

[0009] S1. Weigh 20-25 parts by weight of acrylic acid, 15-20 parts by weight of water-based acrylic resin, 10-12 parts by weight of polyvinyl alcohol resin, 5-7 parts by weight of alkyl glycoside, and 55-60 parts by weight of deionized water, place them in a homogenizer and mix for 12-15 minutes, then add 15-17 parts by weight of casein and treat them in an ultrasonic device for 20-25 minutes to obtain an acrylic mixed emulsion. The frequency of the ultrasonic device is 110-115 Hz and the temperature is 52-55°C.

[0010] S2. Weigh 60-65 parts by weight of the acrylic mixed emulsion prepared in S1, 25-28 parts by weight of colorant, 20-24 parts by weight of modified sodium alginate, 10-12 parts by weight of polyether modified silicone, 8-10 parts by weight of sodium carboxymethyl cellulose, and 10-15 parts by weight of polycarbodiimide emulsion, and place them in a dispersion kettle to disperse them to obtain a mixture.

[0011] S3. Grind the mixture obtained in S2 in a wet grinder at a rotation speed of 3000 to 3200 rpm for 60 to 65 min.

[0012] S4. The mixed material ground in S3 is placed in a blender, and triethanolamine is added to mix to obtain ink. The blender speed is 450 to 500 rpm and the stirring time is 15 to 18 minutes.

[0013] As a preferred technical solution of the present invention, the modified sodium alginate is prepared by the following method: 40 to 42 parts by weight of sodium alginate, 7 to 10 parts by weight of sodium tripolyphosphate, 5 to 8 parts by weight of magnesium tripolyphosphate, and 50 to 55 parts by weight of deionized water are weighed, stirred and mixed for 12 to 15 minutes, and then placed in a reactor for mixing and reaction at 65 to 70° C. for 50 to 55 minutes to obtain modified sodium alginate.

[0014] As a preferred technical solution of the present invention, the speed of the homogenizer is 580-600 rpm.

[0015] As a preferred technical solution of the present invention, the casein is prepared by the following method: adding 5.8-6.0% organic acid to skimmed pure milk, stirring to adjust the pH value to 4.7-5.0, causing the casein to coagulate and precipitate, washing, filtering, dehydrating, and drying to obtain the casein, wherein the moisture content of the dried casein is 6.5-7.0%, and the organic acid is citric acid and oxalic acid in a mass ratio of 0.8-1:1.

[0016] As a preferred technical solution of the present invention, the polycarbodiimide emulsion is prepared by the following method: 35 to 40 parts by weight of polycarbodiimide, 12 to 15 parts by weight of diethylamine, 10 to 12 parts by weight of triethanolamine stearate, and 42 to 45 parts by weight of deionized water are weighed and placed in an ultrasonic device for treatment for 30 to 35 minutes to obtain the polycarbodiimide emulsion, wherein the frequency of the ultrasonic device is 95 to 100 Hz and the temperature is 50 to 55° C.

[0017] As a preferred technical solution of the present invention, the rotation speed of the dispersion kettle is 2500-2600 rpm, and the dispersion time is 50-60 min.

[0018] As a preferred technical solution of the present invention, the colorant is carbon black, and the particle size is 80 to 90 nm.

[0019] 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 mm.

[0020] As a preferred technical solution of the present invention, the pH value of the ink is 9.2-10.0, and the viscosity is 18-25 Pa·s.

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

[0022] 1. The present invention mixes sodium alginate, sodium tripolyphosphate and magnesium tripolyphosphate in a reactor for reaction. Sodium tripolyphosphate and magnesium tripolyphosphate have multiple phosphate ions, which can react with the hydroxyl and carboxyl groups in sodium alginate, introduce phosphate groups, and phosphate-modified sodium alginate can enhance the antioxidant properties of sodium alginate and improve the moisture retention properties of sodium alginate. The combination of magnesium ions in magnesium tripolyphosphate and phosphate ions forms a more stable compound, which enhances the stability of modified sodium alginate. Magnesium tripolyphosphate can cross-link with sodium alginate to form a network structure, enhance the stability, cohesion and adhesion of ink, and magnesium ions, as an element with good biocompatibility, can improve the biocompatibility between various materials. The modified sodium alginate can improve the dispersibility, weather resistance, water resistance, adhesion and leveling of ink, thereby improving the quality of printed matter.

[0023] 2. The present invention adds casein during the ink making process. Casein is a calcium-phosphorus binding protein with a hydrophilic group and a hydrophobic group in its molecular structure. This structure enables casein to form hydrogen bonds or other interactions with water molecules, thereby enhancing the binding force between casein and water molecules, increasing the viscosity of the ink, making it less likely for the ink to separate or precipitate, and increasing the adhesion and stability of the ink during the printing process. At the same time, casein can also form a protective film on the surface of the ink, improving the water resistance of the ink and preventing the oxidation of the ink surface, thereby improving the printing quality. Casein also has a good color development and brightness enhancement effect, and can significantly improve the glossiness of the ink.

[0024] 3. The present invention adds polycarbodiimide emulsion to the ink, mixes polycarbodiimide, diethylamine and triethanolamine stearate in an ultrasonic device for ultrasonic treatment, and the amino group (-NH-) in diethylamine and the hydroxyl group (-OH) in triethanolamine stearate react with polycarbodiimide under ultrasonic treatment, and hydrophilic groups such as amino group and hydroxyl group are introduced into polycarbodiimide, thereby improving the solubility of polycarbodiimide in water. The active functional group -N=C=N- in polycarbodiimide can react chemically with other compounds to form chemical bonds or ionic bonds, thereby improving the adhesion and durability of the ink, and polycarbodiimide has high temperature resistance and can be applied to printed products that need to withstand high temperature environments. As an emulsifier and wetting agent, triethanolamine stearate reduces the surface tension between ink and printing plate, promotes the uniform spreading and leveling of ink on the plate, enhances the adhesion of ink to substrates, improves the firmness and durability of printed products, and thus improves printing quality and stability. Diethylamine can accelerate the drying speed of ink, reduce the surface tension of water-based ink, and thus reduce the drying time during printing, improve the spreadability and fluidity of ink, and at the same time, the amino group (-NH-) in diethylamine can react with certain functional groups on the surface of the substrate to form chemical bonds, thereby enhancing the adhesion between ink and substrates.

[0025] 4. The present invention adds alkyl glycoside, which has dispersibility, can prevent ink from agglomeration or precipitation, reduce the surface tension of ink, make the ink dry and solidify faster, shorten the printing cycle, improve printing efficiency, and improve the uniformity and stability of ink. Alkyl glycoside can improve the wettability and adhesion between ink and printed matter, so that the ink can be better combined with the printed matter during the printing process, and improve the firmness and durability of the printed matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure is a flow chart of the preparation of the ink of the present invention;

[0027] Figure 2 It is a line graph of the water resistance of the ink of the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] Sodium tripolyphosphate and magnesium tripolyphosphate have multiple phosphate ions, which can react with the hydroxyl and carboxyl groups in sodium alginate to introduce phosphate groups. Phosphate-modified sodium alginate can enhance the antioxidant properties of sodium alginate and improve the moisture retention properties of sodium alginate. The combination of magnesium ions and phosphate ions in magnesium tripolyphosphate forms a more stable compound, which enhances the stability of the modified sodium alginate. Magnesium tripolyphosphate can also undergo a cross-linking reaction with sodium alginate to form a network structure, thereby enhancing the stability, cohesion and adhesion of ink. At the same time, magnesium ions, as an element with good biocompatibility, can improve the biocompatibility between various materials. Modified sodium alginate can reduce the surface tension of ink, so that the ink is more evenly distributed when applied to the surface of the substrate. At the same time, modified sodium alginate can promote the uniform dispersion of various components in the ink, enhance the adhesion between inks, and improve the continuity, strength and water resistance of inks. Modified sodium alginate can improve the dispersibility, weather resistance, water resistance, adhesion, and leveling of water-based ink, and improve the quality of printed products. Sodium tripolyphosphate, magnesium tripolyphosphate, and sodium alginate are all environmentally friendly materials, and their modified products also have good environmental performance. In water-based ink, this modified product can reduce the use of organic solvents and reduce the emission of volatile organic compounds (VOCs) in water-based ink, thereby reducing pollution to the environment.

[0030] Casein is a calcium-phosphorus binding protein with hydrophilic and hydrophobic groups in its molecular structure. This structure enables casein to form hydrogen bonds or other interactions with water molecules, thereby enhancing the binding force between casein and water molecules, increasing the viscosity of ink, making it less likely for the ink to separate or precipitate, and improving the adhesion and stability of the ink during the printing process. At the same time, casein can also form a protective film on the surface of the ink, improving the water resistance of the ink and preventing the oxidation of the ink surface, thereby improving the printing quality. Casein also has good color development and brightness enhancement effects, and can significantly improve the gloss of the ink.

[0031] In the process of preparing the acrylic mixed emulsion, the present invention first adds acrylic acid, water-based acrylic resin, polyvinyl alcohol resin, alkyl glycoside and deionized water into a homogenizer for stirring and mixing, and then adds casein for treatment in an ultrasonic device. The mixing and stirring by the homogenizer helps to break the agglomeration between the resins so that the resins are better dispersed in water. The addition of casein for treatment in the ultrasonic device can promote the corresponding chemical reaction between the water-soluble resin and the casein, thereby improving the quality and performance of the ink and making the ink have better water resistance, adhesion and durability.

[0032] The present invention adds polycarbodiimide emulsion to ink, mixes polycarbodiimide, diethylamine and triethanolamine stearate in an ultrasonic device for ultrasonic treatment, and hydrophilic groups such as amino (-NH-) in diethylamine and hydroxyl (-OH) in triethanolamine stearate can react with polycarbodiimide under ultrasonic treatment, and hydrophilic groups are introduced into polycarbodiimide to improve the solubility of polycarbodiimide in water. The active functional group -N=C=N- in polycarbodiimide makes polycarbodiimide have high-efficiency reaction activity, can react chemically with other compounds, form chemical bonds or ionic bonds, improve the adhesion and durability of ink, and polycarbodiimide has high temperature resistance. Under high temperature conditions, water-based ink with polycarbodiimide added can still maintain good performance and stability.

[0033] Triethanolamine stearate has good emulsifying properties, which can make the pigments and resins in water-based inks disperse better in water, avoid precipitation or stratification, and thus improve the printing quality and stability of inks. Triethanolamine stearate can be used as a wetting agent to reduce the surface tension between inks and printing plates, and promote the uniform spreading and leveling of inks on plates. At the same time, the addition of triethanolamine stearate can also enhance the adhesion of inks to substrates. By improving the interaction between inks and substrate surfaces, inks can be better adhered to substrates, improving the firmness and durability of printed products.

[0034] Diethylamine can accelerate the drying speed of water-based ink, help reduce the drying time during printing, and improve production efficiency. At the same time, diethylamine can reduce the surface tension of water-based ink, making it easier for the ink to wet the surface of the substrate, and improve the spreadability and fluidity of the ink. The amino group (-NH-) in diethylamine can react with certain functional groups on the surface of the substrate to form a chemical bond, thereby enhancing the adhesion between the ink and the substrate.

[0035] As a surfactant, alkyl glycoside has the function of wetting and stabilizing dispersion. In water-based ink, alkyl glycoside can effectively disperse pigments and fillers to prevent agglomeration or precipitation, thereby maintaining the uniformity and stability of the ink. Alkyl glycoside can significantly reduce the surface tension of the ink, making it easier for the ink to wet paper or other printing media, thereby helping to improve the fluidity and spreadability of the ink, so that the ink can be evenly and smoothly covered on the printing medium during the printing process, thereby improving the printing quality. The presence of alkyl glycoside can also improve the adaptability of the ink to paper. It can improve the wettability and adhesion between the ink and the paper, so that the ink can better combine with the paper during the printing process, thereby improving the firmness and durability of the printed product. Due to the excellent dispersibility and ability of alkyl glycoside to reduce surface tension, the ink can be dried and cured faster, which helps to shorten the printing cycle and improve printing efficiency.

[0036] The siloxane part of polyether modified silicone has the property of reducing surface tension, making it easier for ink to wet and spread on various substrates, improving the ink's adhesion, water resistance and printing effect. At the same time, as a kind of silicone defoamer, polyether modified silicone has better anti-foaming ability and thermal stability, which can effectively eliminate foam in ink and inhibit the generation of foam, thereby ensuring the stability of ink and printing quality.

[0037] like Figure 1 The present invention provides a method for preparing acrylic ink, comprising the following steps:

[0038] S1. Preparation of acrylic mixed emulsion: (1) Preparation of casein: Add organic acid to skimmed pure milk, stir to adjust the pH value, make the casein coagulate and precipitate, wash, filter, dehydrate and dry to obtain the casein; (2) Weigh acrylic acid, water-based acrylic resin, polyvinyl alcohol resin, alkyl glycoside and deionized water, place them in a homogenizer to mix, add casein and treat in an ultrasonic device to obtain an acrylic mixed emulsion. S2. Preparation of mixed materials: (1) Preparation of modified sodium alginate: weigh sodium alginate, sodium tripolyphosphate, magnesium tripolyphosphate, and deionized water, stir and mix, and place in a reactor for mixing and reaction to obtain modified sodium alginate; (2) Preparation of polycarbodiimide emulsion: weigh polycarbodiimide, diethylamine, stearic acid triethanolamine, and deionized water, and place in an ultrasonic device for treatment to obtain polycarbodiimide emulsion; (3) Weigh the acrylic mixed emulsion prepared in S1, carbon black, modified sodium alginate, polyether-modified silicone, sodium carboxymethyl cellulose, and polycarbodiimide emulsion, and place in a dispersion kettle for dispersion to obtain a mixed material. S3. Place the mixed material prepared in S2 in a wet grinder for grinding. S4. Place the mixed material ground in S3 in a mixer, add triethanolamine, and mix to obtain ink.

[0039] The raw materials used in the present invention are all commercially available raw materials.

[0040] Embodiment 1

[0041] A method for preparing acrylic ink, comprising the following preparation steps:

[0042] S1. Preparation of acrylic mixed emulsion: (1) Preparation of casein: Add 5.8% organic acid (the organic acid is composed of citric acid and oxalic acid in a mass ratio of 0.8:1) to skimmed pure milk, stir and adjust the pH value to 4.7 to make the casein coagulate and precipitate, wash, filter, dehydrate and dry to obtain casein. The moisture content of the dried casein is 6.5%; (2) Weigh 20 parts by weight of acrylic acid, 15 parts by weight of aqueous acrylic resin, 10 parts by weight of polyvinyl alcohol resin, 5 parts by weight of alkyl glycoside and 55 parts by weight of deionized water, place in a homogenizer and mix for 12 minutes, then add 15 parts by weight of casein and treat in an ultrasonic device for 20 minutes to obtain an acrylic mixed emulsion. The speed of the homogenizer is 600 rpm, the frequency of the ultrasonic device is 115 Hz and the temperature is 55°C.

[0043] S2. Preparation of mixed materials: (1) Preparation of modified sodium alginate: Weigh 40 parts by weight of sodium alginate, 7 parts by weight of sodium tripolyphosphate, 5 parts by weight of magnesium tripolyphosphate, and 50 parts by weight of deionized water, stir and mix for 12 minutes, and then place in a reactor and react at 65°C for 55 minutes to obtain modified sodium alginate; (2) Preparation of polycarbodiimide emulsion: Weigh 35 parts by weight of polycarbodiimide, 12 parts by weight of diethylamine, 10 parts by weight of triethanolamine stearate, and 42 parts by weight of deionized water and place in an ultrasonic device. The polycarbodiimide emulsion was prepared by treating the mixture for 30 minutes, the frequency of the ultrasonic equipment was 100 Hz, and the temperature was 55°C; (3) 60 parts by weight of the acrylic mixed emulsion prepared in S1, 25 parts by weight of carbon black (particle size of 80-90 nm), 20 parts by weight of modified sodium alginate, 10 parts by weight of polyether modified silicone, 8 parts by weight of sodium carboxymethyl cellulose, and 10 parts by weight of polycarbodiimide emulsion were weighed and placed in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle was 2500 rpm, and the dispersion time was 60 minutes.

[0044] S3. The mixture obtained in S2 is placed in a wet grinder for grinding. The rotation speed of the grinder is 3000 rpm, the grinding time is 65 min, and the medium used in the wet grinder is steel balls with a particle size of 0.6 mm.

[0045] S4. The mixture ground in S3 is placed in a blender, and triethanolamine is added to mix to obtain ink. The blender speed is 450 rpm, and the stirring time is 18 min. The pH value of the ink is 9.2, and the viscosity is 18 Pa·s.

[0046] Embodiment 2

[0047] A method for preparing acrylic ink, comprising the following preparation steps:

[0048] S1. Preparation of acrylic mixed emulsion: (1) Preparation of casein: Add 6.0% organic acid (the organic acid is composed of citric acid and oxalic acid in a mass ratio of 1:1) to skimmed pure milk, stir and adjust the pH value to 5.0 to make the casein coagulate and precipitate, wash, filter, dehydrate and dry to obtain casein. The moisture content of the dried casein is 7.0%; (2) Weigh 25 parts by weight of acrylic acid, 20 parts by weight of aqueous acrylic resin, 12 parts by weight of polyvinyl alcohol resin, 7 parts by weight of alkyl glycoside and 60 parts by weight of deionized water, place in a homogenizer and mix for 15 minutes, then add 17 parts by weight of casein and treat in an ultrasonic device for 25 minutes to obtain an acrylic mixed emulsion. The speed of the homogenizer is 580 rpm, the frequency of the ultrasonic device is 110 Hz and the temperature is 52°C.

[0049] S2. Preparation of mixed materials: (1) Preparation of modified sodium alginate: Weigh 42 parts by weight of sodium alginate, 10 parts by weight of sodium tripolyphosphate, 8 parts by weight of magnesium tripolyphosphate, and 55 parts by weight of deionized water, stir and mix for 15 minutes, and then place in a reactor to mix and react at 70°C for 50 minutes to obtain modified sodium alginate; (2) Preparation of polycarbodiimide emulsion: Weigh 40 parts by weight of polycarbodiimide, 15 parts by weight of diethylamine, 12 parts by weight of triethanolamine stearate, and 45 parts by weight of deionized water, and place in an ultrasonic device for treatment for 35 minutes to obtain a polycarbodiimide emulsion. The frequency of the ultrasonic device is 95 Hz and the temperature is 50°C. (3) 65 parts by weight of the acrylic mixed emulsion prepared in S1, 28 parts by weight of carbon black (particle size of 80-90 nm), 24 parts by weight of modified sodium alginate, 12 parts by weight of polyether-modified silicone, 10 parts by weight of sodium carboxymethyl cellulose, and 15 parts by weight of polycarbodiimide emulsion were weighed and placed in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle was 2600 rpm and the dispersion time was 50 min.

[0050] S3. The mixture obtained in S2 is placed in a wet grinder for grinding. The rotation speed of the grinder is 3200 rpm, the grinding time is 60 min, and the medium used in the wet grinder is steel balls with a particle size of 0.6 mm.

[0051] S4. The mixture ground in S3 is placed in a blender, and triethanolamine is added to obtain ink. The blender speed is 500 rpm, and the stirring time is 15 min. The pH value of the ink is 10.0, and the viscosity is 25 Pa·s.

[0052] Embodiment 3

[0053] A method for preparing acrylic ink, comprising the following preparation steps:

[0054] S1. Preparation of acrylic mixed emulsion: (1) Preparation of casein: Add 6.0% organic acid (the organic acid is composed of citric acid and oxalic acid in a mass ratio of 0.9:1) to skimmed pure milk, stir and adjust the pH value to 4.8 to make the casein coagulate and precipitate, wash, filter, dehydrate and dry to obtain casein. The moisture content of the dried casein is 6.8%; (2) Weigh 22 parts by weight of acrylic acid, 18 parts by weight of aqueous acrylic resin, 11 parts by weight of polyvinyl alcohol resin, 6 parts by weight of alkyl glycoside and 58 parts by weight of deionized water, place in a homogenizer and mix for 13 minutes, then add 16 parts by weight of casein and treat in an ultrasonic device for 22 minutes to obtain an acrylic mixed emulsion. The speed of the homogenizer is 590 rpm, the frequency of the ultrasonic device is 112 Hz and the temperature is 54°C.

[0055] S2. Preparation of mixed materials: (1) Preparation of modified sodium alginate: Weigh 41 parts by weight of sodium alginate, 8 parts by weight of sodium tripolyphosphate, 6 parts by weight of magnesium tripolyphosphate, and 52 parts by weight of deionized water, stir and mix for 13 minutes, and then place in a reactor and mix and react at 68°C for 53 minutes to obtain modified sodium alginate; (2) Preparation of polycarbodiimide emulsion: Weigh 38 parts by weight of polycarbodiimide, 13 parts by weight of diethylamine, 11 parts by weight of triethanolamine stearate, and 43 parts by weight of deionized water and place in an ultrasonic The mixture was treated in an ultrasonic device for 32 min to obtain a polycarbodiimide emulsion. The frequency of the ultrasonic device was 98 Hz and the temperature was 52 °C. (3) 62 parts by weight of the acrylic mixed emulsion prepared in S1, 26 parts by weight of carbon black (80-90 nm), 22 parts by weight of modified sodium alginate, 11 parts by weight of polyether modified silicone, 9 parts by weight of sodium carboxymethyl cellulose and 12 parts by weight of polycarbodiimide emulsion were weighed and placed in a dispersion kettle to disperse the mixture. The speed of the dispersion kettle was 2500 rpm and the dispersion time was 55 min.

[0056] S3. The mixture obtained in S2 was placed in a wet grinder for grinding. The rotation speed of the grinder was 3100 rpm, the grinding time was 62 min, and the medium used in the wet grinder was steel balls with a particle size of 0.6 mm.

[0057] S4. The mixture ground in S3 is placed in a blender, and triethanolamine is added to obtain ink. The blender speed is 480 rpm, and the stirring time is 16 min. The pH value of the ink is 9.5, and the viscosity is 20 Pa·s.

[0058] Comparative Example 1:

[0059] The difference from Example 1 is that the modified sodium alginate in Example 1 is removed.

[0060] Comparative Example 2:

[0061] The difference from Example 1 is that the casein in Example 1 is removed.

[0062] Comparative Example 3:

[0063] The difference from Example 1 is that the polycarbodiimide emulsion in Example 1 is removed.

[0064] Comparative Example 4:

[0065] The difference from Example 1 is that the alkyl glycoside in Example 1 is removed.

[0066] The inks prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3 and 4 were tested for adhesion according to GB / T 13217.7-2023 “Test Method for Adhesion of Ink”, the gloss of the inks was tested according to GB / T13217.2-2009 “Test Method for Gloss of Liquid Ink”, and the surface drying property of the inks was tested according to QB / T 2825-2006 “Flexo Plate Water-Based Ink”. The results are shown in Table 1.

[0067] Table 1: Ink test index

[0068]

[0069] As can be seen from Table 1, the ink adhesion of Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4 is 99.5%, 99.1%, 99.3%, 81.2%, 83.5%, 87.9% and 86.2% respectively. The ink adhesion of Example 1 is 18.4%, 16.1%, 11.7% and 13.4% higher than that of Comparative Examples 1, 2, 3 and 4. The gloss values ​​of the ink of Example 1 are 19.3%, 18.9%, 19.4%, 18.7%, 17.8%, 19.0% and 18.9% respectively. The gloss value of the ink of Example 1 is 7.8% higher than that of Comparative Example 2. There is no significant difference in gloss values ​​between the Example and Comparative Examples 1, 3 and 4. The surface dryness of the ink is tested. Comparative Examples 3 and 4 show obvious staining on the paper strips.

[0070] The ink adhesion of Comparative Examples 1, 2, 3, and 4 is relatively poor, the glossiness of the ink of Comparative Example 2 is poor, and the staining on the inspection paper strips of Comparative Examples 3 and 4 is relatively obvious, and the surface drying speed is poor. Magnesium tripolyphosphate can undergo a cross-linking reaction with sodium alginate to form a network structure, enhance the stability and adhesion of the ink, and the modified sodium alginate can improve the dispersibility, weather resistance, and adhesion of the ink, thereby improving the quality of the printed matter. Casein forms hydrogen bonds or other interactions with water molecules, enhances the binding force of casein with water molecules, increases the viscosity of the ink, makes the ink less likely to separate or precipitate, and improves the adhesion and stability of the ink during the printing process. At the same time, casein also has good color development and brightness enhancement effects, and can significantly improve the glossiness of the ink. The active functional group -N=C=N- in polycarbodiimide can react chemically with other compounds to form chemical bonds or ionic bonds, thereby improving the adhesion and durability of ink. Diethylamine can accelerate the drying speed of ink and reduce the surface tension of water-based ink, thereby reducing the drying time during printing. Alkyl polyglycoside has dispersibility, which can prevent ink from agglomerating or precipitating, reduce the surface tension of ink, make the ink dry and solidify faster, and improve the firmness and durability of printed products. Therefore, adding modified sodium alginate, casein, polycarbodiimide emulsion and alkyl polyglycoside to ink can effectively improve the adhesion of ink, casein can enhance the gloss of ink, and adding polycarbodiimide emulsion and alkyl polyglycoside to ink can improve the surface dryness of ink.

[0071] The inks prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3 and 4 were evenly spread on white cardboard using a proofing machine, and after being fully dried, they were placed under conditions of temperature (30±2)°C and relative humidity (85±5)%RH, and 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 2.

[0072] Table 2: Evaluation criteria for water resistance of water-based ink

[0073]

[0074] Depend on Figure 2 It can be seen that the ink of Examples 1, 2 and 3 has good water resistance, and the water resistance score is still 100 points within 15 minutes, and the water resistance scores after 30 minutes are 90.8 points, 91.2 points and 89.5 points respectively. The water resistance of Comparative Examples 1, 2, 3 and 4 is relatively poor, and the water resistance scores after 15 minutes are reduced to 79.8 points, 81.3 points, 94.7 points and 93.2 points respectively, and the water resistance scores after 30 minutes are reduced to 61.5 points, 63.8 points, 81.8 points and 80.7 points respectively. The water resistance scores of Comparative Examples 1, 2, 3 and 4 after 30 minutes are 32.3%, 29.7%, 9.9% and 11.1% lower than those of Example 1 respectively. The water resistance of Comparative Examples 1 and 2 is significantly different from that of the examples.

[0075] Modified sodium alginate can reduce the surface tension of ink, making the ink more evenly distributed when applied to the surface of the substrate. At the same time, modified sodium alginate can promote the uniform dispersion of various components in the ink, enhance the adhesion between the ink, and improve the continuity, strength and water resistance of the ink. Casein can form a protective film on the surface of the ink to improve the water resistance of the ink.

[0076] The inks prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3 and 4 were evenly spread on white cardboard using a proofing machine, and after being fully dried, they were placed outdoors under natural light to observe the degree of oxidative discoloration of the inks. The results are shown in Table 3.

[0077] Table 3: Ink oxidation color change table

[0078]

[0079] The oxidative discoloration of ink is divided into four levels: extremely light oxidative discoloration, mild oxidative discoloration, severe oxidative discoloration, and extremely heavy oxidative discoloration. As shown in Table 3, the ink in the embodiment has no oxidative discoloration within 90 days, and has mild oxidative discoloration on the 120th day. Comparative Examples 1 and 2 have mild oxidative discoloration on the 60th day, severe oxidative discoloration on the 90th day, and extremely heavy oxidative discoloration on the 120th day. Comparative Examples 3 and 4 have extremely light oxidative discoloration on the 90th day, and have mild oxidative discoloration on the 120th day.

[0080] Sodium alginate is modified to introduce phosphate groups. Phosphate-modified sodium alginate can enhance the antioxidant properties of sodium alginate. Casein can form a protective film on the surface of ink to prevent oxidation of the ink surface. Therefore, adding modified sodium alginate and casein to ink can delay the oxidation and discoloration of ink and improve the quality of ink.

[0081] In summary, the ink prepared by the present invention has strong adhesion, good water resistance, fast surface drying speed, good glossiness of the ink, is not easy to be oxidized and decolorized, is environmentally friendly and safe, has a simple production process, and is easy to promote.

[0082] 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 method for preparing acrylic ink, characterized in that: The following steps are involved: S1. Weigh 20 to 25 parts by weight of acrylic acid, 15 to 20 parts by weight of aqueous acrylic resin, 10 to 12 parts by weight of polyvinyl alcohol resin, 5 to 7 parts by weight of alkyl glycoside, and 55 to 60 parts by weight of deionized water, mix in a homogenizer for 12 to 15 minutes, add 15 to 17 parts by weight of casein and treat in an ultrasonic device for 20 to 25 minutes to obtain an acrylic mixed emulsion; S2. Weigh 60 to 65 parts by weight of the acrylic mixed emulsion prepared in S1, 25 to 28 parts by weight of the colorant, 20 to 24 parts by weight of modified sodium alginate, 10 to 12 parts by weight of polyether-modified silicone, 8 to 10 parts by weight of sodium carboxymethyl cellulose, and 10 to 15 parts by weight of polycarbodiimide emulsion, and place them in a dispersion kettle to disperse the mixture; S3. The mixture obtained in S2 was placed in a wet grinder and ground at a speed of 3000 to 3200 rpm for 60 to 65 min; S4. The mixture after grinding in S3 is placed in a mixer, triethanolamine is added and mixed to obtain ink, the mixer speed is 450 to 500 rpm, and the stirring time is 15 to 18 min; The modified sodium alginate is prepared by the following method: 40 to 42 parts by weight of sodium alginate, 7 to 10 parts by weight of sodium tripolyphosphate, 5 to 8 parts by weight of magnesium tripolyphosphate, and 50 to 55 parts by weight of deionized water are weighed, stirred and mixed for 12 to 15 minutes, and then placed in a reactor for mixing and reacting at 65 to 70° C. for 50 to 55 minutes to obtain the modified sodium alginate.

2. The method for preparing an acrylic ink according to claim 1, characterized in that: The speed of the homogenizer is 580-600 rpm.

3. The method for preparing an acrylic ink according to claim 1, characterized in that: The frequency of the ultrasonic equipment is 110-115 Hz and the temperature is 52-55°C.

4. The method for preparing an acrylic ink according to claim 1, characterized in that: Casein is prepared by the following method: adding 5.8-6.0% organic acid to skimmed pure milk, stirring and adjusting the pH value to 4.7-5.0 to coagulate and precipitate the casein, washing, filtering, dehydrating and drying to obtain the casein, wherein the moisture content of the dried casein is 6.5-7.0%.

5. The method for preparing an acrylic ink according to claim 4, characterized in that: The organic acid is composed of citric acid and oxalic acid in a mass ratio of 0.8 to 1:

1.

6. The method for preparing an acrylic ink according to claim 1, characterized in that: The polycarbodiimide emulsion is prepared by the following method: 35-40 parts by weight of polycarbodiimide, 12-15 parts by weight of diethylamine, 10-12 parts by weight of stearic acid triethanolamine and 42-45 parts by weight of deionized water are weighed and placed in an ultrasonic device for treatment for 30-35 minutes to obtain the polycarbodiimide emulsion, wherein the frequency of the ultrasonic device is 95-100 Hz and the temperature is 50-55° C.

7. The method for preparing an acrylic ink according to claim 1, characterized in that: The rotation speed of the dispersion kettle is 2500-2600rpm, and the dispersion time is 50-60min.

8. The method for preparing an acrylic ink according to claim 1, characterized in that: The colorant is carbon black with a particle size of 80 to 90 nm.

9. The method for preparing an acrylic 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 mm.

10. The method for preparing an acrylic ink according to claim 1, characterized in that: The pH of ink is 9.2-10.0, and the viscosity is 18-25 Pa·s.

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