Special ink for digital ink jet and preparation method thereof

Abstract

The invention provides special ink for digital ink jet and a preparation method thereof, and belongs to the technical field of ink. The special ink for digital ink jet is prepared from the following components in parts by weight: 30-40 parts of a water-based binder, 6-10 parts of a modified pigment, 0.3-0.6 part of polyethylene wax, 0.8-1.2 parts of a coalescing agent, 0.2-0.4 part of a flatting agent, 0.1-0.3 part of a defoaming agent and 10-20 parts of water, wherein the water-based binder is obtained by reacting polysorbate 60, sodium carboxymethyl cellulose, dioctadecyl dimethyl ammonium chloride, sodium bicarbonate, water, a core emulsion, a shell emulsion and a sodium persulfate aqueous solution; the modified pigment is obtained by modifying an inorganic pigment with a modification liquid. The special ink for digital ink-jet prepared by the invention can better adapt to the requirements of digital ink-jet printing by improving components and optimizing a formula, and has the advantages of strong adhesive force, good stability, fast curing, good glossiness, environmental protection and the like.

Description

Technical Field

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

[0002] Digital inkjet printing is a non-contact, pressure-free, plate-free printing technology that uses a special ink with moderate viscosity, which usually meets the following characteristics, including stability, non-toxicity, moisture retention, easy spraying, and non-corrosive to metals, to ensure long-term stable operation and high-quality output of printing equipment. In order to prevent unnecessary sputtering during spraying, the ink must also have appropriate surface tension, and the fast drying feature can prevent the ink from spreading on the paper. The components of inkjet ink usually include colorants, binders and various additives; among them, the colorant gives the ink color and plays a coloring role; the binder determines the fluidity of the ink, which can be an organic solvent, resin, oily substance, water, etc.; 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 inks are mainly divided into water-based inks, oil-based inks, solvent-based inks and thermosetting inks, each with its own unique advantages and application scenarios.

[0003] As an environmentally friendly printing material, water-based inkjet ink has been rapidly developed and widely used in recent years because of its low impact on the environment. This type of ink uses water as the main solvent. Compared with traditional solvent-based inks, it greatly reduces the emission of volatile organic compounds 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-flammability, water-based ink is safer during use. Despite its obvious advantages in environmental protection, water-based inkjet ink still has some application limitations. For example, water-based ink dries relatively slowly, especially in an environment with high humidity, which may cause smudges on the surface of the printed product and affect the image quality; water-based ink is generally not as water-resistant and light-resistant as solvent-based or UV-curable inks, and is easily affected by environmental factors, especially when used outdoors, resulting in color fading or image damage; water-based ink has poor adhesion to some non-absorbent materials (such as plastics and metals), which limits its application on these materials.

[0004] In order to solve these problems, some solutions have been proposed in the prior art. To improve the drying speed, the ink drying process can be accelerated by optimizing the ink formula, adding a fast-evaporating co-solvent, and combining improved print head technology and heating devices. In view of the poor water resistance and light resistance, special colorants and protective coatings can be introduced to enhance the stability and UV resistance of the ink. In order to improve the adhesion of the ink on non-absorbent materials, a special pretreatment liquid or primer, as well as a resin component with stronger adhesion properties, can be used. However, the above methods also face some unresolved shortcomings: while adding co-solvents to speed up the drying speed, it may also increase VOC emissions; the use of special colorants and protective coatings may increase production costs, making the price of water-based inks relatively high; for some special application scenarios, such as high humidity or strong ultraviolet radiation or wear resistance requirements, the stability of water-based inks is poor. Therefore, there is an urgent need for a special digital inkjet ink with excellent performance. Summary of the invention

[0005] The purpose of the present invention is to provide a special ink for digital inkjet, which can better meet the requirements of digital inkjet printing by adding specific water-based binders and modified colorants to improve the components, and has the advantages of strong adhesion, good stability, fast curing, good gloss, and green environmental protection.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a special ink for digital inkjet, comprising the following components: Water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer, water.

[0007] Preferably, a special ink for digital inkjet is made of the following components in parts by weight: 30-40 parts by weight of aqueous 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.

[0008] The present invention can effectively improve the adhesion and stability of the special ink for digital inkjet by adopting a 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 phase environment, and a monomer mixture consisting of styrene, ethyl methacrylate and p-divinylbenzene is added, styrene provides good mechanical strength and thermal stability, and ethyl methacrylate gives the emulsion good flexibility and weather resistance. P-divinylbenzene, as a cross-linking agent, promotes the cross-linking between the molecular chains inside the core layer, forming a strong and uniform core structure, and the existence of the core layer provides basic support for the subsequent shell layer, ensuring the uniform distribution and smaller particle size of the emulsion particles, thereby improving the leveling and glossiness of the ink.

[0009] Secondly, in the preparation of the shell emulsion, the same emulsifier system is used again to mix with water, and a monomer mixture consisting of epoxy resin E51, acrylic acid, n-propyl methacrylate, isooctyl acrylate, hydroxypropyl acrylate and glycidyl methacrylate is added; polar groups such as epoxy groups and carboxyl groups in epoxy resin E51 are extremely active and can chemically bond with functional groups on the surface of the substrate, greatly enhancing the adhesion strength between the ink and the substrate; glycidyl methacrylate contains not only epoxy groups but also acrylate groups, which can copolymerize with the core layer and other monomers during the polymerization process, further improving the crosslinking degree of the emulsion; in addition, acrylic acid and its derivatives give the shell layer good water resistance and chemical resistance, while the isooctyl ester group increases the flexibility of the shell layer.

[0010] Finally, in the final polymerization reaction 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 acts as an initiator to trigger a free radical polymerization reaction, so that the monomers of the core layer and the shell layer are gradually polymerized to form a stable core-shell structured acrylic emulsion. Through this step-by-step addition method, the formation order and proportion of the core layer and the shell layer can be precisely controlled to ensure that the functional monomers of each layer fully participate in the reaction to form an ideal structure and performance.

[0011] Preferably, the method for preparing the aqueous vehicle comprises the following steps: 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 are mixed, and a mixed solution 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 p-divinylbenzene is added dropwise under stirring, and stirring is continued after the addition is completed to obtain a nuclear emulsion; 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 are mixed, and a 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 and 1-3 parts by weight of glycidyl methacrylate is added dropwise under stirring, and stirring is continued after the addition is completed to obtain a shell emulsion; 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 and 100-150 parts by weight of water are mixed, heated and stirred, then 50-60 parts by weight of core emulsion and 4-6 parts by weight of sodium persulfate aqueous solution are added and stirred, then 70-80 parts by weight of shell emulsion and 4-6 parts by weight of sodium persulfate aqueous solution are added and stirred, the temperature is raised to 80-90° C. and stirring is continued, the mixture is cooled, and the pH is adjusted to neutral to obtain an aqueous binder.

[0012] Furthermore, the method for preparing the aqueous vehicle comprises the following steps: 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 are mixed, and a mixed solution 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 p-divinylbenzene is added dropwise under stirring at 100-200 rpm for 6-10 minutes. After the addition is completed, stirring is continued for 10-20 minutes to obtain a nuclear emulsion; 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 are mixed, and a 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 and 1-3 parts by weight of glycidyl methacrylate is added dropwise under stirring at 100-200 rpm for 10-15 min. After the addition is completed, stirring is continued for 10-30 min to obtain a shell emulsion; 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 and 100-150 parts by weight of water are mixed, and stirred at 75-80° C. and 100-200 rpm for 4-6 minutes; then 50-60 parts by weight of core emulsion and 4-6 parts by weight of 8-12wt% sodium persulfate aqueous solution are added, and stirred for 10-30 minutes; then 70-80 parts by weight of shell emulsion and 4-6 parts by weight of 8-12wt% sodium persulfate aqueous solution are added, and stirred for 30-50 minutes; the temperature is raised to 80-90° C. and stirring is continued for 80-100 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

[0013] In addition, the present invention further improves the adhesion, stability and glossiness of the special ink for digital inkjet by modifying inorganic pigments such as titanium dioxide. First, in the process of preparing the modified pigment, the inorganic pigment such as titanium dioxide is mixed with sodium polyacrylate in water and subjected to hydrothermal and ultrasonic treatment to fully wet and activate it, wherein the sodium polyacrylate effectively prevents the agglomeration of the inorganic pigment particles and ensures their uniform dispersion, and then the wet inorganic pigment is mixed with the allyl trimethoxysilane modification liquid and heated to form a coating on the surface of the inorganic pigment, which chemically bonds with the hydroxyl groups on the surface of the inorganic pigment through the siloxane functional group, and at the same time, the allyl part can undergo a cross-linking reaction with the polymer in the subsequently added aqueous binder, thereby establishing a strong chemical bridge between the inorganic pigment and the binder, and this bridging effect greatly enhances the compatibility between the inorganic pigment and the binder, allowing the pigment to be more tightly bound to the surface of the printing medium, thereby improving the adhesion and stability of the ink; Moreover, the surface properties of the modified inorganic pigments have changed, which helps to reduce the contact angle of the ink printed on the substrate and improve the wettability, so that the ink can be spread more evenly on the printing medium to form a smoother and flatter coating, thereby improving the gloss of the ink; because the dispersibility and stability of the modified pigments have been significantly improved, the ink is not prone to particle sedimentation or aggregation during storage and use, ensuring the consistency and long-term stability of the ink.

[0014] Preferably, the method for preparing the modified colorant comprises the following steps: 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 are mixed, heated and stirred, then ultrasonically treated, centrifuged, and the supernatant is discarded to obtain a wet inorganic pigment; 3-5 parts by weight of allyltrimethoxysilane is mixed with 40-60 parts by weight of ethanol aqueous solution, stirred to obtain a modified liquid; the wet inorganic pigment and the modified liquid are mixed, heated and stirred, filtered, and dried to obtain a modified pigment.

[0015] Furthermore, the preparation method of the modified colorant comprises the following steps: 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°C and 200-400rpm for 20-50min, then ultrasonically treated at a power of 100-300W and a frequency of 20-40kHz for 10-30min, centrifuged, and the supernatant is discarded to obtain a wet inorganic colorant; 3-5 parts by weight of allyltrimethoxysilane are mixed with 40-60 parts by weight of 70-85wt% ethanol aqueous solution, stirred at 35-45°C 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°C and 200-400rpm for 30-50min, filtered, and dried to obtain a modified colorant.

[0016] Preferably, the inorganic colorant is any one of titanium dioxide, zinc white, red iron oxide, chromium oxide green, and carbon black.

[0017] Furthermore, the inorganic colorant is titanium dioxide.

[0018] Preferably, the film-forming aid is any one of butyl carbitol, dipropylene glycol ethyl ether, propylene glycol methyl ether and tripropylene glycol butyl ether.

[0019] Furthermore, the film-forming aid is butyl carbitol.

[0020] Preferably, the leveling agent is a water-based acrylic leveling agent with a viscosity (20° C.) of 20,000-40,000 mPa•s.

[0021] Preferably, the defoaming agent is an organosilicon defoaming agent with a viscosity (20° C.) of 600-800 mPa•s.

[0022] The present invention also provides a method for preparing a special ink for digital inkjet, comprising the following steps: Accurately weigh each component according to the formula, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer and water into a high-speed mixer, and stir at 400-600 rpm for 15-30 minutes to obtain the special digital inkjet ink.

[0023] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The present invention provides a special ink for digital inkjet and a preparation method thereof. By adding an aqueous binder obtained by reacting polysorbate 60, sodium carboxymethyl cellulose, dioctadecyl dimethyl ammonium chloride, sodium bicarbonate, water, a core emulsion, a shell emulsion and an aqueous sodium persulfate solution, and a modified colorant, the adhesion fastness, stability and glossiness of the ink are further improved, the ink can better meet the requirements of digital inkjet printing, and has the advantages of being green and environmentally friendly.

[0024] 2. The present invention can effectively improve the adhesion and stability of digital inkjet ink by adopting a specific water-based binder. 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 phase environment. The addition of styrene provides good mechanical strength and thermal stability, while ethyl methacrylate gives the emulsion good flexibility and weather resistance. Divinylbenzene is used as a cross-linking agent to promote the cross-linking between the molecular chains inside the core layer. The existence of the core layer provides basic support for the subsequent shell layer, ensuring the uniform distribution and smaller particle size of the emulsion particles, thereby improving the leveling and glossiness of the ink.

[0025] 3. The present invention also modifies the inorganic pigment, further improving the adhesion, stability and glossiness of the digital inkjet ink. The wet inorganic pigment is mixed with the allyl trimethoxysilane modification liquid and heated to form a coating on the surface of the inorganic pigment, which chemically bonds with the hydroxyl groups on the surface of the inorganic pigment through the siloxane functional group. At the same time, the allyl part can undergo a cross-linking reaction with the polymer in the subsequently added aqueous binder, thereby establishing a strong chemical bridge between the inorganic pigment and the binder. This bridging effect greatly enhances the compatibility between the inorganic pigment and the binder, allowing the pigment to be more tightly bonded to the surface of the printing medium, thereby improving the adhesion and stability of the ink. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0027] Example 1 This embodiment provides a special ink for digital inkjet, comprising the following components in parts by weight: 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 defoamer, and 15 parts by weight of water. The film-forming aid is butyl carbitol. The leveling agent is a water-based acrylic leveling agent with the brand name MODAREZ PW336 and a viscosity (20°C) of 30,000 mPa•s, manufactured by Pioneer of France. The defoamer is a silicone defoamer with the brand name BYK-037 and a viscosity (20°C) of 700 mPa•s, manufactured by BYK of Germany.

[0028] The preparation method of the aqueous vehicle comprises the following steps: 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of dioctadecyl dimethyl ammonium chloride and 40 parts by weight of water were mixed, and a mixed solution consisting of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate and 0.5 parts by weight of p-divinylbenzene was added dropwise under stirring at 150 rpm for 8 minutes. After the addition was completed, stirring was continued for 15 minutes to obtain a core emulsion; 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of dioctadecyl dimethyl ammonium chloride and 60 parts by weight of water were mixed, and a mixed solution consisting 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 was added dropwise under stirring at 150 rpm for 12 minutes. After the addition was completed, stirring was continued for 20 minutes to obtain a shell emulsion; wherein the epoxy equivalent of the epoxy resin E51 was 180-190 g / eq and the viscosity (25° C.) was 7000-10000 mPa•s; 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of dioctadecyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate and 120 parts by weight of water are mixed, and stirred at 78° C. and 150 rpm for 5 minutes; 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 minutes; 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 minutes; the temperature is raised to 85° C. and stirring is continued for 90 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

[0029] The preparation method of the modified colorant comprises the following steps: 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, stir at 55°C and 300rpm for 30 minutes, then place it in an ultrasonic treatment at a power of 200W and a frequency of 25kHz for 20 minutes, centrifuge, discard the supernatant, and obtain wet titanium dioxide; take 3.5 parts by weight of allyltrimethoxysilane and 50 parts by weight of 80wt% ethanol aqueous solution, mix them, stir at 40°C and 300rpm for 20 minutes, and obtain a modified liquid; mix the above wet titanium dioxide with the modified liquid, stir at 55°C and 300rpm for 40 minutes, filter, and dry to obtain a modified colorant. Among them, the titanium dioxide is anatase titanium dioxide with a D50 particle size of 0.5-1μm.

[0030] This embodiment provides a method for preparing a special ink for digital inkjet, comprising the following steps: Accurately weigh each component according to the formula, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer and water into a high-speed mixer, and stir at 500 rpm for 20 minutes to obtain the digital inkjet ink.

[0031] Example 2 This embodiment provides a special ink for digital inkjet, comprising the following components in parts by weight: 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 defoamer, and 10 parts by weight of water. The film-forming aid is butyl carbitol. The leveling agent is a water-based acrylic leveling agent with the brand name MODAREZ PW336, the viscosity (20°C) is 30000mPa•s, and the manufacturer is Pioneer, France. The defoamer is a silicone defoamer with the brand name BYK-037, the viscosity (20°C) is 700mPa•s, and the manufacturer is BYK, Germany.

[0032] The preparation method of the aqueous vehicle is the same as that of Example 1.

[0033] The preparation method of the modified colorant is the same as that of Example 1.

[0034] This embodiment provides a method for preparing a special ink for digital inkjet, comprising the following steps: Accurately weigh each component according to the formula, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer and water into a high-speed mixer, and stir at 400 rpm for 15 minutes to obtain the digital inkjet ink.

[0035] Example 3 This embodiment provides a special ink for digital inkjet, comprising the following components in parts by weight: 40 parts by weight of water-based binder, 10 parts by weight of modified colorant, 0.6 parts by weight of polyethylene wax, 1.2 parts by weight of film-forming aid, 0.4 parts by weight of leveling agent, 0.3 parts by weight of defoamer, and 20 parts by weight of water. The film-forming aid is butyl carbitol. The leveling agent is a water-based acrylic leveling agent with the brand name MODAREZ PW336, the viscosity (20°C) is 30000mPa•s, and the manufacturer is Pioneer, France. The defoamer is a silicone defoamer with the brand name BYK-037, the viscosity (20°C) is 700mPa•s, and the manufacturer is BYK, Germany.

[0036] The preparation method of the aqueous vehicle is the same as that of Example 1.

[0037] The preparation method of the modified colorant is the same as that of Example 1.

[0038] This embodiment provides a method for preparing a special ink for digital inkjet, comprising the following steps: Accurately weigh each component according to the formula, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer and water into a high-speed mixer, and stir at 600 rpm for 30 minutes to obtain the digital inkjet ink.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the preparation method of the aqueous vehicle is different, which is as follows: The preparation method of the aqueous vehicle comprises the following steps: 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose and 40 parts by weight of water were mixed, and a mixed solution consisting of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate and 0.5 parts by weight of p-divinylbenzene was added dropwise under stirring at 150 rpm for 8 minutes. After the addition was completed, stirring was continued for 15 minutes to obtain a core emulsion; 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose and 60 parts by weight of water were mixed, and a mixed solution consisting 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 was added dropwise under stirring at 150 rpm for 12 minutes. After the addition was completed, stirring was continued for 20 minutes to obtain a shell emulsion; wherein the epoxy equivalent of the epoxy resin E51 was 180-190 g / eq and the viscosity (25° C.) was 7000-10000 mPa•s; 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 and 120 parts by weight of water are mixed, and stirred at 78° C. and 150 rpm for 5 minutes; 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 minutes; 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 minutes; the temperature is raised to 85° C. and stirring is continued for 90 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that the preparation method of the aqueous vehicle is different, which is as follows: The preparation method of the aqueous vehicle comprises the following steps: 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of dioctadecyl dimethyl ammonium chloride and 40 parts by weight of water were mixed, and a mixed solution consisting of 12 parts by weight of styrene and 8 parts by weight of ethyl methacrylate was added dropwise under stirring at 150 rpm for 8 minutes. After the addition was completed, stirring was continued for 15 minutes to obtain a core emulsion; 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of dioctadecyl dimethyl ammonium chloride and 60 parts by weight of water were mixed, and a mixed solution consisting 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 was added dropwise under stirring at 150 rpm for 12 minutes. After the addition was completed, stirring was continued for 20 minutes to obtain a shell emulsion; wherein the epoxy equivalent of the epoxy resin E51 was 180-190 g / eq and the viscosity (25° C.) was 7000-10000 mPa•s; 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of dioctadecyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate and 120 parts by weight of water are mixed, and stirred at 78° C. and 150 rpm for 5 minutes; 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 minutes; 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 minutes; the temperature is raised to 85° C. and stirring is continued for 90 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that the preparation method of the aqueous vehicle is different, which is as follows: The preparation method of the aqueous vehicle comprises the following steps: 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of dioctadecyl dimethyl ammonium chloride and 40 parts by weight of water were mixed, and a mixed solution consisting of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate and 0.5 parts by weight of p-divinylbenzene was added dropwise under stirring at 150 rpm for 8 minutes. After the addition was completed, stirring was continued for 15 minutes to obtain a core emulsion; 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of dioctadecyl dimethyl ammonium chloride and 60 parts by weight of water were mixed, and a mixed solution consisting 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 and 3.5 parts by weight of hydroxypropyl acrylate was added dropwise under stirring at 150 rpm for 12 minutes. After the addition was completed, stirring was continued for 20 minutes to obtain a shell emulsion; wherein the epoxy equivalent of the epoxy resin E51 was 180-190 g / eq and the viscosity (25° C.) was 7000-10000 mPa•s; 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of dioctadecyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate and 120 parts by weight of water are mixed, and stirred at 78° C. and 150 rpm for 5 minutes; 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 minutes; 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 minutes; the temperature is raised to 85° C. and stirring is continued for 90 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that the preparation method of the aqueous vehicle is different, which is as follows: The preparation method of the aqueous vehicle comprises the following steps: 0.4 parts by weight of polysorbate 60, 0.2 parts by weight of sodium carboxymethyl cellulose, 0.2 parts by weight of dioctadecyl dimethyl ammonium chloride and 40 parts by weight of water were mixed, and a mixed solution consisting of 12 parts by weight of styrene, 8 parts by weight of ethyl methacrylate and 0.5 parts by weight of p-divinylbenzene was added dropwise under stirring at 150 rpm for 8 minutes. After the addition was completed, stirring was continued for 15 minutes to obtain a core emulsion; 0.7 parts by weight of polysorbate 60, 0.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of dioctadecyl dimethyl ammonium chloride and 60 parts by weight of water were mixed, and a mixed solution consisting 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 stirring at 150 rpm for 12 min. After the addition was completed, stirring was continued for 20 min to obtain a shell emulsion; 1.5 parts by weight of polysorbate 60, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.5 parts by weight of dioctadecyl dimethyl ammonium chloride, 0.5 parts by weight of sodium bicarbonate and 120 parts by weight of water are mixed, and stirred at 78° C. and 150 rpm for 5 minutes; 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 minutes; 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 minutes; the temperature is raised to 85° C. and stirring is continued for 90 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

[0043] Comparative Example 5 The difference between this comparative example and Example 1 is that the modified colorant is replaced by titanium dioxide, wherein the titanium dioxide is anatase titanium dioxide with a D50 particle size of 0.5-1 μm.

[0044] Comparative Example 6 The difference between this comparative example and Example 1 is that the preparation method of the modified colorant is different, which is as follows: The preparation method of the modified colorant comprises the following steps: 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, stir at 55°C and 300rpm for 30min, then place it in ultrasonic treatment at a power of 200W and a frequency of 25kHz for 20min, centrifuge, discard the supernatant, and obtain wet titanium dioxide; take 3.5 parts by weight of 3-aminopropyltriethoxysilane and 50 parts by weight of 80wt% ethanol aqueous solution, stir at 40°C and 300rpm for 20min to obtain a modified solution; mix the above wet titanium dioxide with the modified solution, stir at 55°C and 300rpm for 40min, filter, and dry to obtain a modified colorant. Among them, the titanium dioxide is anatase titanium dioxide with a D50 particle size of 0.5-1μm.

[0045] Performance Testing The digital inkjet ink obtained in the above examples 1-3 and comparative examples 1-6 was subjected to a printing test on a flexographic printing press (polyethylene terephthalate film). The adhesion fastness test was based on the method in GB / T 13217.7-2009; the glossiness test was based on the method in GB / T13217.2-2009; the adhesion test was based on the method in GB / T 9286-2021, 0-5 levels, 5 being the worst; the stability test method was as follows: the digital inkjet ink was first placed at -5°C for 2 days, then placed at room temperature for 1 day, then placed at 80°C for 2 days, then cooled to room temperature after being taken out, and the test was completed; the fluidity was determined based on the method in GB / T 14624.3-1993, and the fluidity change rate = (initial fluidity - fluidity after the test) / initial fluidity × 100%. The results are shown in Table 1.

[0046] Table 1: Test results of various properties of ink

[0047] It can be seen from the above performance test results that the special digital inkjet inks prepared in Examples 1-3 have excellent adhesion fastness, glossiness and stability, especially the special digital inkjet ink of Example 1 has the most outstanding comprehensive performance. This is because the present invention significantly improves the adhesion fastness, glossiness and stability of the special digital inkjet ink by adopting specific aqueous binders and modified colorants.

[0048] In comparison, since Comparative Examples 1-6 did not adopt the necessary technical solutions, their corresponding performance tests were significantly worse than those of Examples 1-3. No specific water-based binder was used in Comparative Examples 1-4, and no modified colorant was used in Comparative Examples 5-6. It can be seen from the results that this resulted in decreased adhesion, glossiness and stability of the digital inkjet ink. The above experimental results further demonstrate the importance of the technical solutions defined in the present invention for its technical effects.

[0049] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A special ink for digital inkjet, characterized in that: It comprises the following components in parts by weight: 30-40 parts by weight of an aqueous vehicle, 6-10 parts by weight of a modified colorant, 0.3-0.6 parts by weight of a polyethylene wax, 0.8-1.2 parts by weight of a film-forming aid, 0.2-0.4 parts by weight of a leveling agent, 0.1-0.3 parts by weight of a defoaming agent, and 10-20 parts by weight of water; the aqueous vehicle is obtained by reacting polysorbate 60, sodium carboxymethyl cellulose, dioctadecyl dimethyl ammonium chloride, sodium bicarbonate, water, a core emulsion, a shell emulsion, and an aqueous sodium persulfate solution.

2. The digital inkjet ink according to claim 1, characterized in that: The preparation method of the aqueous vehicle comprises the following steps: 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 are mixed, and a mixed solution 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 p-divinylbenzene is added dropwise under stirring, and stirring is continued after the addition is completed to obtain a nuclear emulsion; 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 are mixed, and a 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 and 1-3 parts by weight of glycidyl methacrylate is added dropwise under stirring, and stirring is continued after the addition is completed to obtain a shell emulsion; 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 and 100-150 parts by weight of water are mixed, heated and stirred, then 50-60 parts by weight of core emulsion and 4-6 parts by weight of sodium persulfate aqueous solution are added and stirred, then 70-80 parts by weight of shell emulsion and 4-6 parts by weight of sodium persulfate aqueous solution are added and stirred, the temperature is raised to 80-90° C. and stirring is continued, the mixture is cooled, and the pH is adjusted to neutral to obtain an aqueous binder.

3. The digital inkjet ink according to claim 2, characterized in that: The preparation method of the aqueous vehicle comprises the following steps: 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 are mixed, and a mixed solution 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 p-divinylbenzene is added dropwise under stirring at 100-200 rpm for 6-10 minutes. After the addition is completed, stirring is continued for 10-20 minutes to obtain a nuclear emulsion; 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 are mixed, and a 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 and 1-3 parts by weight of glycidyl methacrylate is added dropwise under stirring at 100-200 rpm for 10-15 min. After the addition is completed, stirring is continued for 10-30 min to obtain a shell emulsion; 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 and 100-150 parts by weight of water are mixed, and stirred at 75-80° C. and 100-200 rpm for 4-6 minutes; then 50-60 parts by weight of core emulsion and 4-6 parts by weight of 8-12wt% sodium persulfate aqueous solution are added, and stirred for 10-30 minutes; then 70-80 parts by weight of shell emulsion and 4-6 parts by weight of 8-12wt% sodium persulfate aqueous solution are added, and stirred for 30-50 minutes; the temperature is raised to 80-90° C. and stirring is continued for 80-100 hours, cooled to room temperature, and the pH is adjusted to neutral to obtain an aqueous binder.

4. The digital inkjet ink according to claim 1, characterized in that: The preparation method of the modified colorant comprises the following steps: 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 are mixed, heated and stirred, then ultrasonically treated, centrifuged, and the supernatant is discarded to obtain a wet inorganic pigment; 3-5 parts by weight of allyltrimethoxysilane is mixed with 40-60 parts by weight of ethanol aqueous solution, stirred to obtain a modified liquid; the wet inorganic pigment and the modified liquid are mixed, heated and stirred, filtered, and dried to obtain a modified pigment.

5. The digital inkjet ink according to claim 4, characterized in that: The preparation method of the modified colorant comprises the following steps: 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°C and 200-400rpm for 20-50min, then ultrasonically treated at a power of 100-300W and a frequency of 20-40kHz for 10-30min, centrifuged, and the supernatant is discarded to obtain a wet inorganic colorant; 3-5 parts by weight of allyltrimethoxysilane are mixed with 40-60 parts by weight of 70-85wt% ethanol aqueous solution, stirred at 35-45°C 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°C and 200-400rpm for 30-50min, filtered, and dried to obtain a modified colorant.

6. The digital inkjet ink according to claim 4 or 5, characterized in that: The inorganic colorant is any one of titanium dioxide, zinc white, iron oxide red, chromium oxide green and carbon black.

7. 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.

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

9. The digital inkjet ink according to claim 1, characterized in that: The defoamer is an organosilicon defoamer.

10. The method for preparing the special ink for digital inkjet according to any one of claims 1 to 9, characterized in that: The following steps are involved: Accurately weigh each component according to the formula, add the water-based binder, modified colorant, polyethylene wax, film-forming aid, leveling agent, defoamer and water into a high-speed mixer, and stir at 400-600 rpm for 15-30 minutes to obtain the special digital inkjet ink.

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