A digital inkjet special ink and a preparation method thereof

Abstract

The application provides a kind of digital ink-jet special ink and its preparation method, belong to ink technical field, the digital ink-jet special ink includes the following component is made: 30-40 parts by weight water-based binder, 6-10 parts by weight modified color material, 0.3-0.6 parts by weight polyethylene wax, 0.8-1.2 parts by weight film-forming aid, 0.2-0.4 parts by weight leveling agent, 0.1-0.3 parts by weight defoaming agent, 10-20 parts by weight water;Wherein, the water-based binder is obtained by reaction of polysorbate 60, sodium carboxymethyl cellulose, dioctadecyldimethylammonium chloride, sodium bicarbonate, water, core emulsion, shell emulsion and sodium persulfate aqueous solution;The modified color material is obtained by modifying inorganic color material with modified liquid.The digital ink-jet special ink prepared by the application can better adapt to the requirements of digital ink-jet printing by improving components and optimizing formula, has the advantages of strong adhesion, good stability, fast curing, good gloss, green environmental protection and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ink, and particularly relates to a special ink for digital inkjet and a preparation method thereof. BACKGROUND

[0002] Digital inkjet printing is a printing technology that is contactless, pressureless and plateless. It uses a special ink with moderate viscosity, which usually meets the following characteristics, including stability, non-toxicity, moisturizing, easy jetting, non-corrosion to metal, etc., to ensure long-term stable operation and high-quality output of the printing equipment. In order to prevent unnecessary splashing phenomenon during jetting, the ink also needs to have appropriate surface tension, and the characteristic of fast drying can avoid the ink from bleeding on the paper. The composition of inkjet ink usually includes colorants, binders and various additives; among them, the colorants give the ink color and play the role of coloring; the binders determine the fluidity of the ink, which can be organic solvents, resins, oily substances, water, etc.; the additives are used to optimize various properties of the ink, such as adjusting viscosity, enhancing adhesion, improving thermal stability and light resistance, and adjusting surface tension. Inkjet ink is mainly divided into water-based ink, oil-based ink, solvent-based ink and heat-set ink, each of which has its unique advantages and application scenarios.

[0003] Water-based inkjet ink, as an environmentally friendly printing material, has obtained rapid development and wide application in recent years due to its relatively small impact on the environment. This ink uses water as the main solvent, which greatly reduces the emission of volatile organic compounds compared to traditional solvent-based inks, and reduces the negative impact on air quality and human health. Water-based inkjet ink has good color vividness and a wide color gamut, which can meet various needs from home photo printing to professional graphic design. Due to its low toxicity and non-flammable characteristics, water-based ink is safer to use. Although it has obvious advantages in environmental protection, water-based inkjet ink still has some application limitations. For example, the drying speed of water-based ink is relatively slow, especially in a humid environment, which may cause bleeding on the surface of the printed product, affecting the image quality; the water resistance and light resistance of water-based ink are usually not as good as those of solvent-based or UV-curable inks, especially when used outdoors, which is easily affected by environmental factors, resulting in color fading or image damage; the adhesion of water-based ink to some non-absorbent materials (such as plastic, metal) is poor, limiting its application on these materials.

[0004] To solve these problems, some solutions have also been proposed in the prior art. To improve the drying speed, the ink formula can be optimized, a fast-evaporating co-solvent can be added, and improved printhead technology and heating devices can be combined to speed up the ink drying process. To address the poor water resistance and light resistance, special pigments and protective coatings can be introduced to enhance the stability and UV resistance of the ink. To improve the adhesion of the ink on non-absorbent materials, special pretreatment liquids or primers can be used, as well as resin components with stronger adhesion properties. However, these methods also face some unresolved shortcomings: the addition of co-solvents may increase VOC emissions while speeding up the drying process; the use of special pigments and protective coatings may increase production costs, making water-based inks relatively expensive; and for some special application scenarios, such as high humidity or strong UV radiation or wear resistance requirements, water-based inks have poor stability. Therefore, there is an urgent need for a digital inkjet ink with excellent performance. SUMMARY

[0005] The purpose of the present application is to provide a digital inkjet ink that can better adapt to the requirements of digital inkjet printing by adding specific water-based binders and modified pigments to improve the components, with the advantages of strong adhesion, good stability, fast curing, good gloss, and green environmental protection.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] The present application provides a digital inkjet ink, comprising the following components:

[0008] Water-based binder, modified pigment, polyethylene wax, film-forming aid, leveling agent, defoamer, water.

[0009] Preferably, a digital inkjet ink is made of the following components by weight:

[0010] 30-40 parts by weight of water-based binder, 6-10 parts by weight of modified pigment, 0.3-0.6 parts by weight of polyethylene wax, 0.8-1.2 parts by weight of film-forming aid, 0.2-0.4 parts by weight of leveling agent, 0.1-0.3 parts by weight of defoamer, and 10-20 parts by weight of water.

[0011] The present application can effectively improve the adhesion and stability of the special ink for digital inkjet by using the specific water-based binder. First, in the preparation process of the core emulsion, polysorbate 60, sodium carboxymethyl cellulose and dioctadecyl dimethyl ammonium chloride are mixed with water as emulsifiers and stabilizers to form a stable aqueous environment, and then a monomer mixture composed of styrene, ethyl methacrylate and p-divinylbenzene is added. Styrene provides good mechanical strength and thermal stability, while ethyl methacrylate provides good flexibility and weather resistance. P-divinylbenzene acts as a crosslinking agent to promote the crosslinking between the molecular chains in the core layer, forming a strong and uniform core structure. The existence of the core layer provides a foundation support for the subsequent shell layer, ensuring the uniform distribution of emulsion particles and smaller particle size, thereby improving the leveling property and gloss of the ink.

[0012] Secondly, in the preparation of the shell emulsion, the same emulsifier system is mixed with water again, and a monomer mixture composed of epoxy resin E51, acrylic acid, n-propyl methacrylate, isooctyl acrylate, hydroxypropyl acrylate and glycidyl methacrylate is added. The epoxy groups and polar groups such as carboxyl groups in epoxy resin E51 have high activity and can chemically bond with the functional groups on the surface of the substrate, greatly enhancing the adhesion strength between the ink and the substrate. Glycidyl methacrylate not only contains epoxy groups, but also has acrylate groups, which can copolymerize with the core layer and other monomers during polymerization, further improving the crosslinking degree of the emulsion. In addition, the shell layer has good water resistance and chemical resistance due to the presence of acrylic acid and its derivatives, and the shell layer has increased flexibility due to the presence of isooctyl ester groups.

[0013] Finally, in the final polymerization stage, polysorbate 60, sodium carboxymethyl cellulose, dioctadecyl dimethyl ammonium chloride and sodium bicarbonate are mixed with water, and the core emulsion and sodium persulfate are added in sequence, and then the shell emulsion and sodium persulfate are added. Sodium persulfate as an initiator triggers the free radical polymerization reaction, making the monomers of the core layer and the shell layer gradually polymerize to form a stable core-shell structure type acrylate emulsion. Through this step-by-step addition method, the formation sequence and proportion of the core layer and the shell layer can be accurately controlled, ensuring that the functional monomers of each layer fully participate in the reaction to form the ideal structure and performance.

[0014] Preferably, the preparation method of the water-based binder comprises the following steps:

[0015] Mix 0.3-0.6 parts by weight of polysorbate 60, 0.1-0.3 parts by weight of sodium carboxymethyl cellulose and 0.1-0.3 parts by weight of dioctadecyl dimethyl ammonium chloride with 30-50 parts by weight of water, and then add a mixture composed of 10-15 parts by weight of styrene, 6-10 parts by weight of ethyl methacrylate and 0.3-0.6 parts by weight of p-divinylbenzene under stirring conditions. After the dropwise addition is completed, continue stirring to obtain the core emulsion.

[0016] Mix 0.6-0.8 parts by weight of polysorbate 60, 0.4-0.6 parts by weight of sodium carboxymethyl cellulose, 0.2-0.4 parts by weight of distearyl dimethyl ammonium chloride with 50-70 parts by weight of water, under stirring conditions, drop in the mixed solution consisting of 5-8 parts by weight of epoxy resin E51, 4-6 parts by weight of acrylic acid, 6-8 parts by weight of n-propyl methacrylate, 2-5 parts by weight of isooctyl acrylate, 2-5 parts by weight of hydroxypropyl acrylate, 1-3 parts by weight of glycidyl methacrylate, after drop completion, continue stirring, to obtain a shell emulsion;

[0017] Mix 1-2 parts by weight of polysorbate 60, 1-2 parts by weight of sodium carboxymethyl cellulose, 0.4-0.6 parts by weight of distearyl dimethyl ammonium chloride, 0.4-0.6 parts by weight of sodium bicarbonate with 100-150 parts by weight of water, heat and stir, then add 50-60 parts by weight of core emulsion and 4-6 parts by weight of aqueous sodium persulfate solution and stir, then add 70-80 parts by weight of shell emulsion and 4-6 parts by weight of aqueous sodium persulfate solution and stir, continue to stir at 80-90℃, cool, adjust the pH to neutral, to obtain a water-based binder.

[0018] Further, the preparation method of the water-based binder comprises the following steps:

[0019] Mix 0.3-0.6 parts by weight of polysorbate 60, 0.1-0.3 parts by weight of sodium carboxymethyl cellulose, 0.1-0.3 parts by weight of distearyl dimethyl ammonium chloride with 30-50 parts by weight of water, under stirring conditions at 100-200 rpm, drop in the mixed solution consisting of 10-15 parts by weight of styrene, 6-10 parts by weight of ethyl methacrylate, 0.3-0.6 parts by weight of p-divinylbenzene, the drop time is 6-10 min, after drop completion, continue stirring for 10-20 min, to obtain a core emulsion;

[0020] Mix 0.6-0.8 parts by weight of polysorbate 60, 0.4-0.6 parts by weight of sodium carboxymethyl cellulose, 0.2-0.4 parts by weight of distearyl dimethyl ammonium chloride with 50-70 parts by weight of water, under stirring conditions at 100-200 rpm, drop in the mixed solution consisting of 5-8 parts by weight of epoxy resin E51, 4-6 parts by weight of acrylic acid, 6-8 parts by weight of n-propyl methacrylate, 2-5 parts by weight of isooctyl acrylate, 2-5 parts by weight of hydroxypropyl acrylate, 1-3 parts by weight of glycidyl methacrylate, the drop time is 10-15 min, after drop completion, continue stirring for 10-30 min, to obtain a shell emulsion;

[0021] Mix 1-2 parts by weight of polysorbate 60, 1-2 parts by weight of sodium carboxymethyl cellulose, 0.4-0.6 parts by weight of distearyl dimethyl ammonium chloride, 0.4-0.6 parts by weight of sodium bicarbonate with 100-150 parts by weight of water, stir at 75-80℃, 100-200rpm for 4-6min; then add 50-60 parts by weight of core emulsion and 4-6 parts by weight of 8-12wt% sodium persulfate aqueous solution and stir for 10-30min; then add 70-80 parts by weight of shell emulsion and 4-6 parts by weight of 8-12wt% sodium persulfate aqueous solution and stir for 30-50min; continue to stir at 80-90℃ for 80-100h, cool to room temperature, adjust the pH to neutral, to obtain the aqueous binder.

[0022] In addition, the present application further improves the adhesion, stability and gloss of the digital inkjet special ink by modifying the inorganic colorant such as titanium dioxide. First, in the process of preparing the modified colorant, the inorganic colorant such as titanium dioxide is mixed with sodium polyacrylate in water and subjected to hydrothermal and ultrasonic treatment, fully wetting and activating it, wherein the sodium polyacrylate effectively prevents the agglomeration of inorganic colorant particles, ensuring uniform dispersion, then the wet inorganic colorant is mixed with allyltrimethoxysilane modification liquid and heated, a coating layer can be formed on the surface of the inorganic colorant, which is chemically bonded to the hydroxyl groups on the surface of the inorganic colorant through the siloxane functional group, and the allyl part can crosslink with the polymer in the subsequent addition of the aqueous binder, thereby establishing a firm chemical bridge between the inorganic colorant and the binder, which greatly enhances the compatibility between the inorganic colorant and the binder, allowing the colorant to be more closely bound to the surface of the printing medium, thereby improving the adhesion and stability of the ink;

[0023] Moreover, the surface properties of the modified inorganic colorant have changed, which helps to reduce the contact angle of the ink printed on the substrate, improve the wettability, and make the ink spread more evenly on the printing medium, forming a smoother and more uniform coating, thereby improving the gloss of the ink; due to the significant improvement in the dispersibility and stability of the modified colorant, the ink is less likely to have particle sedimentation or aggregation during storage and use, ensuring the consistency and long-term stability of the ink.

[0024] Preferably, the preparation method of the modified colorant comprises the following steps:

[0025] Take 5-15 parts by weight of inorganic colorant, 0.1-0.4 parts by weight of sodium polyacrylate and 30-50 parts by weight of water, heat and stir, then ultrasonic treatment, centrifugation, discard the supernatant, to obtain wet inorganic colorant; take 3-5 parts by weight of allyltrimethoxysilane and 40-60 parts by weight of ethanol aqueous solution, stir to obtain modification liquid; mix the above wet inorganic colorant with the modification liquid, heat and stir, filter, dry to obtain the modified colorant.

[0026] Further, the preparation method of the modified colorant comprises the following steps:

[0027] 5-15 parts by weight of inorganic colorant, 0.1-0.4 parts by weight of sodium polyacrylate and 30-50 parts by weight of water are mixed, stirred at 50-60℃ and 200-400rpm for 20-50min, then treated by ultrasonic with power of 100-300W and frequency of 20-40kHz for 10-30min, centrifuged, and the supernatant is discarded to obtain wet inorganic colorant; 3-5 parts by weight of allyltrimethoxysilane and 40-60 parts by weight of 70-85wt% ethanol aqueous solution are mixed, stirred at 35-45℃ and 200-400rpm for 10-30min to obtain a modified liquid; the wet inorganic colorant and the modified liquid are mixed, stirred at 50-60℃ and 200-400rpm for 30-50min, filtered, and dried to obtain the modified colorant.

[0028] Preferably, the inorganic colorant is any one of titanium white, zinc white, red iron oxide, chromium oxide green and carbon black.

[0029] Further, the inorganic colorant is titanium white.

[0030] Preferably, the film-forming aid is any one of butyl carbitol, dipropylene glycol ethyl ether, propylene glycol methyl ether and tripropylene glycol butyl ether.

[0031] Further, the film-forming aid is butyl carbitol.

[0032] Preferably, the leveling agent is an aqueous acrylate leveling agent with viscosity (20℃) of 20000-40000mPa•s.

[0033] Preferably, the defoaming agent is a silicone defoaming agent with viscosity (20℃) of 600-800mPa•s.

[0034] The application further provides a preparation method of the digital ink special for inkjet, comprising the following steps:

[0035] According to the formula, each component is accurately weighed, the aqueous binder, the modified colorant, the polyethylene wax, the film-forming aid, the leveling agent, the defoaming agent and water are added into a high-speed mixer, stirred at 400-600rpm for 15-30min to obtain the digital ink special for inkjet.

[0036] Compared with the prior art, the application has the following advantages and beneficial effects:

[0037] 1. The present application provides a kind of digital inkjet special ink and its preparation method, by adding the water-based binder obtained by the reaction of polysorbate 60, sodium carboxymethyl cellulose, distearyl dimethyl ammonium chloride, sodium bicarbonate, water, core emulsion, shell emulsion and aqueous solution of sodium persulfate, and modified colorant, further improve the adhesion, stability and gloss of ink, better adapt to the requirements of digital inkjet printing, and have the advantages of green environmental protection.

[0038] 2, The present application can effectively improve the adhesion and stability of digital inkjet special ink by using specific water-based binder. In the preparation process of core emulsion, polysorbate 60, sodium carboxymethyl cellulose and distearyl dimethyl ammonium chloride are mixed with water as emulsifier and stabilizer to form a stable aqueous environment. Styrene provides good mechanical strength and thermal stability, and ethyl methacrylate gives the emulsion good flexibility and weather resistance. Divinylbenzene is used as crosslinking agent to promote the crosslinking between the molecular chains in the core layer. The existence of core layer provides foundation support for the subsequent shell layer, ensures the uniform distribution of emulsion particles and smaller particle size, thereby improving the leveling property and gloss of ink.

[0039] 3, The present application also modifies inorganic colorant to further improve the adhesion, stability and gloss of digital inkjet special ink. Mixing wet inorganic colorant with allyltrimethoxysilane modified liquid and heating treatment can form a coating layer on the surface of inorganic colorant. The coating layer is chemically bonded to the hydroxyl groups on the surface of inorganic colorant through siloxane functional groups, and the allyl part can crosslink with the polymer in the subsequent water-based binder, thereby establishing a firm chemical bridge between inorganic colorant and binder. This bridging effect greatly enhances the compatibility between inorganic colorant and binder, making the colorant more closely combined on the surface of printing medium, thereby improving the adhesion and stability of ink. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0041] Embodiment 1

[0042] The present embodiment provides a kind of digital inkjet special ink, which is made of the following components by weight:

[0043] 35 parts by weight of water-based binder, 8 parts by weight of modified colorant, 0.5 parts by weight of polyethylene wax, 1 part by weight of film-forming aid, 0.3 parts by weight of leveling agent, 0.2 parts by weight of defoaming agent, 15 parts by weight of water. The film-forming aid is butyl carbitol. The leveling agent is an aqueous acrylate leveling agent, brand MODAREZ PW336, viscosity (20℃) 30000 mPa•s, manufacturer France Xianchuang. The defoaming agent is a silicone defoaming agent, brand BYK-037, viscosity (20℃) 700 mPa•s, manufacturer Germany BIK.

[0044] The preparation method of the water-based binder comprises the following steps:

[0045] 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of distearyl dimethyl ammonium chloride are mixed with 40 parts by weight of water, and a mixed solution composed of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate, 0.5 parts by weight of p-divinylbenzene is added dropwise under the condition of stirring at 150 rpm, the dropwise adding time is 8 min, after the dropwise adding is completed, continue to stir for 15 min, to obtain a core emulsion;

[0046] 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of distearyl dimethyl ammonium chloride are mixed with 60 parts by weight of water, and a mixed solution composed of 6.5 parts by weight of epoxy resin E51, 5 parts by weight of acrylic acid, 7 parts by weight of n-propyl methacrylate, 3.5 parts by weight of isooctyl acrylate, 3.5 parts by weight of hydroxypropyl acrylate, 2 parts by weight of glycidyl methacrylate is added dropwise under the condition of stirring at 150 rpm, the dropwise adding time is 12 min, after the dropwise adding is completed, continue to stir for 20 min, to obtain a shell emulsion; wherein the epoxy equivalent weight of epoxy resin E51 is 180-190 g / eq, the viscosity (25℃) is 7000-10000 mPa•s;

[0047] 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of distearyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate are mixed with 120 parts by weight of water, stirred at 78℃, 150 rpm for 5 min; then 55 parts by weight of core emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution are added and stirred for 20 min; then 75 parts by weight of shell emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution are added and stirred for 40 min; continue to stir for 90h at 85℃, cool to room temperature, adjust the pH to neutral, to obtain a water-based binder.

[0048] The preparation method of the modified colorant comprises the following steps:

[0049] Take 10 parts by weight of titanium dioxide, 0.3 parts by weight of sodium polyacrylate (average molecular weight of 4500) and 40 parts by weight of water are mixed, stirred at 55℃, 300rpm for 30min, then placed in the power of 200W, frequency of 25kHz ultrasonic treatment for 20min, centrifugation, discard the supernatant, get wet titanium dioxide; take 3.5 parts by weight of allyl trimethoxysilane and 50 parts by weight of 80wt% ethanol aqueous solution are mixed, stirred at 40℃, 300rpm for 20min, get modified liquid; the above wet titanium dioxide and modified liquid are mixed, stirred at 55℃, 300rpm for 40min, filtration, drying, get modified colorant. Among them, the titanium dioxide is anatase titanium dioxide, D50 particle size is 0.5-1μm.

[0050] The embodiment provides a preparation method of a digital inkjet special ink, including the following steps:

[0051] According to the formula, accurately weigh each component, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoaming agent and water into a high-speed mixer, and stir at 500rpm for 20min to obtain the digital inkjet special ink.

[0052] Example 2

[0053] The embodiment provides a digital inkjet special ink, which is prepared from the following components by weight:

[0054] 30 parts by weight of water-based binder, 6 parts by weight of modified colorant, 0.3 parts by weight of polyethylene wax, 0.8 parts by weight of film-forming aid, 0.2 parts by weight of leveling agent, 0.1 parts by weight of defoaming agent and 10 parts by weight of water. The film-forming aid is butyl carbitol. The leveling agent is a water-based acrylate leveling agent with a brand of MODAREZ PW336, a viscosity (20℃) of 30000mPa·s and a manufacturer of France Xianchuang. The defoaming agent is a silicone defoaming agent with a brand of BYK-037, a viscosity (20℃) of 700mPa·s and a manufacturer of Germany BIK.

[0055] The preparation method of the water-based binder is the same as that in Example 1.

[0056] The preparation method of the modified colorant is the same as that in Example 1.

[0057] The embodiment provides a preparation method of a digital inkjet special ink, including the following steps:

[0058] According to the formula, accurately weigh each component, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoaming agent and water into a high-speed mixer, and stir at 400rpm for 15min to obtain the digital inkjet special ink.

[0059] Example 3

[0060] The embodiment provides a digital inkjet special ink, which is prepared from the following components by weight:

[0061] 40 parts by weight of the water-based binder, 10 parts by weight of the modified colorant, 0.6 parts by weight of polyethylene wax, 1.2 parts by weight of a film-forming aid, 0.4 parts by weight of a leveling agent, 0.3 parts by weight of a defoaming agent and 20 parts by weight of water. The film-forming aid is butyl carbitol. The leveling agent is a water-based acrylate leveling agent, with a trade name of MODAREZ PW336, a viscosity (20 DEG C) of 30000 mPa s and a manufacturer of Sinochem France. The defoaming agent is a silicone defoaming agent, with a trade name of BYK-037, a viscosity (20 DEG C) of 700 mPa s and a manufacturer of BYK Germany.

[0062] The water-based binder is prepared by the same method as in Embodiment 1.

[0063] The modified colorant is prepared by the same method as in Embodiment 1.

[0064] The embodiment provides a preparation method of a digital inkjet special ink, which comprises the following steps:

[0065] The components are accurately weighed according to the formula, the water-based binder, the modified colorant, the polyethylene wax, the film-forming aid, the leveling agent, the defoaming agent and water are added into a high-speed stirrer, and stirring is performed at 600 rpm for 30 min to obtain the digital inkjet special ink.

[0066] Comparative Example 1

[0067] The difference between the comparative example and Embodiment 1 is that the preparation method of the water-based binder is different, and the preparation method of the water-based binder comprises the following steps:

[0068] 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose and 40 parts by weight of water are mixed, a mixed solution composed of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate and 0.5 parts by weight of p-divinylbenzene is added dropwise under stirring at 150 rpm, the dropwise adding time is 8 min, and after the dropwise adding is completed, stirring is continuously performed for 15 min to obtain a core emulsion;

[0069] Mix 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose with 60 parts by weight of water, under the condition of stirring at 150 rpm, add dropwise a mixed solution composed of 6.5 parts by weight of epoxy resin E51, 5 parts by weight of acrylic acid, 7 parts by weight of n-propyl methacrylate, 3.5 parts by weight of isooctyl acrylate, 3.5 parts by weight of hydroxypropyl acrylate, and 2 parts by weight of glycidyl methacrylate, the dropwise adding time is 12 min, after the dropwise adding is completed, continue stirring for 20 min, to obtain a shell emulsion; wherein the epoxy equivalent weight of the epoxy resin E51 is 180-190 g / eq, and the viscosity (25℃) is 7000-10000 mPa•s;

[0070] Mix 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of sodium bicarbonate with 120 parts by weight of water, stir at 78℃, 150 rpm for 5 min; then add 55 parts by weight of core emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution and stir for 20 min; then add 75 parts by weight of shell emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution and stir for 40 min; continue to stir at 85℃ for 90h, cool to room temperature, adjust the pH to neutral, to obtain the water-based link material.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that the preparation method of the water-based link material is different, which is as follows: the preparation method of the water-based link material comprises the following steps:

[0073] Mix 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of distearyl dimethyl ammonium chloride with 40 parts by weight of water, under the condition of stirring at 150 rpm, add dropwise a mixed solution composed of 12 parts by weight of styrene and 8 parts by weight of ethyl methacrylate, the dropwise adding time is 8 min, after the dropwise adding is completed, continue stirring for 15 min, to obtain the core emulsion;

[0074] Mix 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of distearyl dimethyl ammonium chloride with 60 parts by weight of water, under the condition of stirring at 150 rpm, add dropwise a mixed solution composed of 6.5 parts by weight of epoxy resin E51, 5 parts by weight of acrylic acid, 7 parts by weight of n-propyl methacrylate, 3.5 parts by weight of isooctyl acrylate, 3.5 parts by weight of hydroxypropyl acrylate, and 2 parts by weight of glycidyl methacrylate, the dropwise adding time is 12 min, after the dropwise adding is completed, continue stirring for 20 min, to obtain the shell emulsion; wherein the epoxy equivalent weight of the epoxy resin E51 is 180-190 g / eq, and the viscosity (25℃) is 7000-10000 mPa•s;

[0075] Mix 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of distearyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate with 120 parts by weight of water, stir at 78℃, 150rpm for 5min; then add 55 parts by weight of core emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution and stir for 20min; then add 75 parts by weight of shell emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution and stir for 40min; continue to stir at 85℃ for 90h, cool to room temperature, adjust the pH to neutral, to obtain the aqueous binder.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that the preparation method of the aqueous binder is different, which is as follows: the preparation method of the aqueous binder comprises the following steps:

[0078] Mix 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of distearyl dimethyl ammonium chloride with 40 parts by weight of water, under the condition of stirring at 150rpm, add dropwise a mixed liquid composed of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate, 0.5 parts by weight of p-divinylbenzene, the dropwise adding time is 8min, continue to stir for 15min after the dropwise adding is completed, to obtain the core emulsion;

[0079] Mix 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of distearyl dimethyl ammonium chloride with 60 parts by weight of water, under the condition of stirring at 150rpm, add dropwise a mixed liquid composed of 6.5 parts by weight of epoxy resin E51, 5 parts by weight of acrylic acid, 7 parts by weight of n-propyl methacrylate, 3.5 parts by weight of hydroxypropyl acrylate, the dropwise adding time is 12min, continue to stir for 20min after the dropwise adding is completed, to obtain the shell emulsion; wherein the epoxy equivalent weight of the epoxy resin E51 is 180-190g / eq, and the viscosity (25℃) is 7000-10000mPa•s;

[0080] Mix 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of distearyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate with 120 parts by weight of water, stir at 78℃, 150rpm for 5min; then add 55 parts by weight of core emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution and stir for 20min; then add 75 parts by weight of shell emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution and stir for 40min; continue to stir at 85℃ for 90h, cool to room temperature, adjust the pH to neutral, to obtain the aqueous binder.

[0081] Comparative Example 4

[0082] The difference between the present comparative example and example 1 is that the preparation method of the water-based binder is different, specifically as follows: the preparation method of the water-based binder comprises the following steps:

[0083] 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of distearyl dimethyl ammonium chloride and 40 parts by weight of water were mixed, and a mixed solution composed of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate, 0.5 parts by weight of p-divinylbenzene was added dropwise under the condition of stirring at 150 rpm, the dropwise adding time was 8 min, and after the dropwise adding was completed, stirring was continued for 15 min to obtain a core emulsion;

[0084] 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of distearyl dimethyl ammonium chloride and 60 parts by weight of water were mixed, and a mixed solution composed of 5 parts by weight of acrylic acid, 7 parts by weight of n-propyl methacrylate, 3.5 parts by weight of isooctyl acrylate, 3.5 parts by weight of hydroxypropyl acrylate and 2 parts by weight of glycidyl methacrylate was added dropwise under the condition of stirring at 150 rpm, the dropwise adding time was 12 min, and after the dropwise adding was completed, stirring was continued for 20 min to obtain a shell emulsion;

[0085] 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of distearyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate and 120 parts by weight of water were mixed, and stirring was carried out at 78°C and 150 rpm for 5 min; then 55 parts by weight of the core emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution were added and stirred for 20 min; then 75 parts by weight of the shell emulsion and 5 parts by weight of 10wt% sodium persulfate aqueous solution were added and stirred for 40 min; the temperature was increased to 85°C and stirring was continued for 90h, and then the pH was adjusted to neutral after cooling to room temperature to obtain the water-based binder.

[0086] Comparative Example 5

[0087] The difference between the present comparative example and example 1 is that the modified colorant is replaced by titanium dioxide. The titanium dioxide is sharp titanium dioxide, and the D50 particle size is 0.5-1 μm.

[0088] Comparative Example 6

[0089] The difference between the present comparative example and example 1 is that the preparation method of the modified colorant is different, specifically as follows: the preparation method of the modified colorant comprises the following steps:

[0090] Take 10 parts by weight of titanium dioxide, 0.3 parts by weight of sodium polyacrylate (average molecular weight 4500) and 40 parts by weight of water, stir at 55℃, 300rpm for 30min, then ultrasonic treatment at power of 200W, frequency of 25kHz for 20min, centrifugal, discard the supernatant, get wet titanium dioxide; take 3.5 parts by weight of 3-aminopropyl triethoxysilane and 50 parts by weight of 80wt% ethanol aqueous solution, stir at 40℃, 300rpm for 20min, get modified liquid; mix the above wet titanium dioxide and modified liquid, stir at 55℃, 300rpm for 40min, filter, dry, get modified colorant. Among them, the titanium dioxide is anatase titanium dioxide, the D50 particle size is 0.5-1μm.

[0091] Performance test

[0092] The digital ink special ink obtained in the above examples 1-3 and comparative examples 1-6 is subjected to printing test (polyethylene terephthalate film) on a flexographic printing machine. The adhesion test refers to the method in GB / T 13217.7-2009; the gloss test refers to the method in GB / T 13217.2-2009; the adhesion test refers to the method in GB / T 9286-2021, 0-5 level, 5 level is the worst; the stability test method is as follows: the digital ink special ink is first placed at-5℃ for 2 days, then taken out and placed at room temperature for 1 day, then placed at 80℃ for 2 days, then taken out and cooled to room temperature, the test is completed; the flow degree is determined according to the method in GB / T 14624.3-1993, the flow degree change rate=(initial flow degree-test flow degree) / initial flow degree×100%. The results are shown in Table 1.

[0093] Table 1: Performance test results of ink

[0094]

[0095] From the above performance test results, it can be seen that the digital ink special ink prepared in examples 1-3 has excellent adhesion, gloss and stability, especially the digital ink special ink of example 1 has the most outstanding comprehensive performance, because the specific water-based binder and modified colorant are used in the present application, which significantly improves the adhesion, gloss and stability of the digital ink special ink.

[0096] In comparison, comparative examples 1-6 do not use the necessary technical solutions, resulting in a significant difference in the corresponding performance test compared with examples 1-3. In comparative example 1-4, a specific water-based binder is not used, and in comparative examples 5-6, a modified colorant is not used, which can be seen from the results that it leads to the decrease of the adhesion, gloss and stability of the digital ink special ink. The above experimental results further prove the importance of the technical solutions defined in the present application to its technical effects.

[0097] The above describes the preferred embodiments of the present application. It should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the scope of the present application.

Claims

1. A special ink for digital inkjet printing, characterized in that, Includes the following components by weight: 30-40 parts by weight of water-based binder, 6-10 parts by weight of modified colorant, 0.3-0.6 parts by weight of polyethylene wax, 0.8-1.2 parts by weight of film-forming aid, 0.2-0.4 parts by weight of leveling agent, 0.1-0.3 parts by weight of defoamer, and 10-20 parts by weight of water; Methods for preparing water-based binders include: Mix 0.3-0.6 parts by weight of polysorbate 60, 0.1-0.3 parts by weight of sodium carboxymethyl cellulose, 0.1-0.3 parts by weight of dioctadecyl dimethyl ammonium chloride, and 30-50 parts by weight of water. Under stirring, add dropwise a mixture consisting of 10-15 parts by weight of styrene, 6-10 parts by weight of ethyl methacrylate, and 0.3-0.6 parts by weight of divinylbenzene. After the addition is complete, continue stirring to obtain a core emulsion. Mix 0.6-0.8 parts by weight of polysorbate 60, 0.4-0.6 parts by weight of sodium carboxymethyl cellulose, 0.2-0.4 parts by weight of dioctadecyl dimethyl ammonium chloride, and 50-70 parts by weight of water. Under stirring, add dropwise a mixture consisting of 5-8 parts by weight of epoxy resin E51, 4-6 parts by weight of acrylic acid, 6-8 parts by weight of n-propyl methacrylate, 2-5 parts by weight of isooctyl acrylate, 2-5 parts by weight of hydroxypropyl acrylate, and 1-3 parts by weight of glycidyl methacrylate. After the addition is complete, continue stirring to obtain a shell emulsion. Mix 1-2 parts by weight of polysorbate 60, 1-2 parts by weight of sodium carboxymethyl cellulose, 0.4-0.6 parts by weight of dioctadecyl dimethyl ammonium chloride, 0.4-0.6 parts by weight of sodium bicarbonate with 100-150 parts by weight of water, heat and stir, then add 50-60 parts by weight of core emulsion and 4-6 parts by weight of sodium persulfate aqueous solution and stir, then add 70-80 parts by weight of shell emulsion and 4-6 parts by weight of sodium persulfate aqueous solution and stir, raise the temperature to 80-90℃ and continue stirring, cool, and adjust the pH to neutral to obtain an aqueous binder; Methods for preparing modified pigments include: Take 5-15 parts by weight of inorganic pigment, 0.1-0.4 parts by weight of sodium polyacrylate, and 30-50 parts by weight of water, mix, heat and stir, then sonicate, centrifuge, discard the supernatant, and obtain a moist inorganic pigment; take 3-5 parts by weight of allyltrimethoxysilane and 40-60 parts by weight of ethanol aqueous solution, stir, and obtain a modified solution; mix the above moist inorganic pigment with the modified solution, heat and stir, filter, and dry to obtain a modified pigment; The inorganic pigment is any one of titanium dioxide, zinc dioxide, iron oxide red, chromium oxide green, and carbon black.

2. The digital inkjet ink according to claim 1, characterized in that, The preparation method of the water-based binder includes the following steps: Mix 0.3-0.6 parts by weight of polysorbate 60, 0.1-0.3 parts by weight of sodium carboxymethyl cellulose, 0.1-0.3 parts by weight of dioctadecyl dimethyl ammonium chloride, and 30-50 parts by weight of water. Add dropwise a mixture consisting of 10-15 parts by weight of styrene, 6-10 parts by weight of ethyl methacrylate, and 0.3-0.6 parts by weight of divinylbenzene under stirring at 100-200 rpm for 6-10 minutes. After the addition is complete, continue stirring for 10-20 minutes to obtain a core emulsion. Mix 0.6-0.8 parts by weight of polysorbate 60, 0.4-0.6 parts by weight of sodium carboxymethyl cellulose, 0.2-0.4 parts by weight of dioctadecyl dimethyl ammonium chloride, and 50-70 parts by weight of water. Under stirring at 100-200 rpm, add dropwise a mixture consisting of 5-8 parts by weight of epoxy resin E51, 4-6 parts by weight of acrylic acid, 6-8 parts by weight of n-propyl methacrylate, 2-5 parts by weight of isooctyl acrylate, 2-5 parts by weight of hydroxypropyl acrylate, and 1-3 parts by weight of glycidyl methacrylate. The dropwise addition time is 10-15 min. After the dropwise addition is complete, continue stirring for 10-30 min to obtain a shell emulsion. Mix 1-2 parts by weight of polysorbate 60, 1-2 parts by weight of sodium carboxymethyl cellulose, 0.4-0.6 parts by weight of dioctadecyl dimethyl ammonium chloride, 0.4-0.6 parts by weight of sodium bicarbonate with 100-150 parts by weight of water, and stir at 75-80℃ and 100-200 rpm for 4-6 min; then add 50-60 parts by weight of core emulsion and 4-6 parts by weight of 8-12 wt% sodium persulfate aqueous solution and stir for 10-30 min; then add 70-80 parts by weight of shell emulsion and 4-6 parts by weight of 8-12 wt% sodium persulfate aqueous solution and stir for 30-50 min; heat to 80-90℃ and continue stirring for 80-100 h, cool to room temperature, and adjust the pH to neutral to obtain an aqueous binder.

3. The digital inkjet ink according to claim 2, characterized in that, The method for preparing the modified pigment includes the following steps: Take 5-15 parts by weight of inorganic pigment, 0.1-0.4 parts by weight of sodium polyacrylate, and 30-50 parts by weight of water, mix them, stir at 50-60℃ and 200-400 rpm for 20-50 min, then sonicate at 100-300W and 20-40kHz for 10-30 min, centrifuge, discard the supernatant, and obtain a moist inorganic pigment; take 3-5 parts by weight of allyltrimethoxysilane and 40-60 parts by weight of 70-85wt% ethanol aqueous solution, mix them, stir at 35-45℃ and 200-400 rpm for 10-30 min, and obtain a modified solution; mix the above moist inorganic pigment with the modified solution, stir at 50-60℃ and 200-400 rpm for 30-50 min, filter, and dry to obtain the modified pigment.

4. The digital inkjet ink according to claim 1, characterized in that, The film-forming aid is any one of butyl carbitol, dipropylene glycol ethyl ether, propylene glycol methyl ether, and tripropylene glycol butyl ether.

5. The digital inkjet ink according to claim 1, characterized in that, The leveling agent is a water-based acrylic leveling agent.

6. The digital inkjet ink according to claim 1, characterized in that, The defoamer is an organosilicone defoamer.

7. The method for preparing digital inkjet ink according to any one of claims 1-6, characterized in that, Includes the following steps: Accurately weigh each component according to the formula, add water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer, and water to a high-speed mixer, and stir at 400-600 rpm for 15-30 minutes to obtain the digital inkjet ink.

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