Water-based ink for packaging printing and a method for preparing the same

Abstract

This invention discloses a water-based ink for packaging printing and its preparation method, belonging to the field of ink preparation technology. The water-based ink comprises a color paste, a mica functional filler, and a dispersion medium. The color paste includes core-shell structured modified pigment particles and deionized water. The core of the modified pigment particles is a pigment particle, and the shell layers, from the inside out, are modified rosin-silica, a silica layer, and a secondary silane protective layer. The dispersion medium includes a water-based resin, a water-based acrylic emulsion, functional additives, and water. This invention also provides a preparation method for the water-based ink, including the preparation of the mica functional filler, the preparation of the color paste, and the compounding of the ink. This invention, through the synergistic compounding of a three-layer core-shell structured pigment and a silane-modified mica functional filler, significantly improves the dispersion stability, storage stability, and printability of the water-based ink, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of ink preparation technology, specifically to a water-based ink for packaging printing and its preparation method. Background Technology

[0002] Water-based inks are widely used in the packaging and printing industry due to their environmental friendliness and low volatile organic compound (VOC) emissions. Currently, packaging and printing companies typically need to stock dozens or even hundreds of spot color inks to meet the personalized color matching needs of different customers. This directly leads to high inventory costs, long production scheduling cycles, and significant waste of surplus spot color inks, greatly increasing the production and operational pressure on companies. Theoretically, if it were possible to achieve stable mixing and color matching of base color inks in any proportion, any spot color required by a customer could be formulated using a limited number of base color inks, fundamentally reducing inventory pressure and production costs, and minimizing ink waste.

[0003] As the core color-developing component of water-based inks, pigments directly determine the ink's tinting strength, batch stability, printability, and overall durability through their dispersion stability in water-based systems and their compatibility with film-forming resins. Currently, there is a significant difference in surface polarity between the organic and inorganic pigments commonly used in water-based inks for packaging printing. If they are directly mixed in water-based systems, aggregation and stratification can easily occur, leading to color shifts in the mixed inks and severely impacting printing quality and industrial applications.

[0004] Chinese Patent CN104629532B discloses a composite water-based ink modified with nano-titanium dioxide and its preparation method. It uses γ-methacryloyloxypropyltrimethoxysilane to modify nano-titanium dioxide, then copolymerizes the modified nanoparticles with acrylate monomers to prepare a modified water-based acrylic resin. The resulting water-based ink exhibits resistance to light aging, antibacterial properties, and mildew resistance. Chinese Patent CN107384005B discloses a high-color-fastness water-based ink for PVC printing. It uses a silane coupling agent to modify pigments via atomized spraying. The prepared modified pigments have the characteristics of small contact angle, good wettability, and good dispersibility. However, in the above solutions, the former only modifies the resin system and does not design a surface coating structure for the pigment particles; the latter only uses a single silane coupling agent to treat the pigment surface, which can only improve the dispersibility of a single pigment in the water-based system. Neither solution designs a multi-layer coating modification structure for different types of pigments, nor does it solve the problem of intermixing compatibility when different pigments are mixed, and thus cannot achieve stable intermixing and color matching of basic color inks. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a water-based ink for packaging printing and its preparation method. By uniformly constructing a modified rosin-silica, a silica layer, and a secondary silane protective layer on the surface of pigment particles to form a core-shell structure, the dispersion stability of the pigment in the water-based system and its compatibility with film-forming resins are improved. Combined with mica functional fillers modified with silane coupling agents, the ink's hiding power, scratch resistance, and film-forming properties are further optimized. The resulting water-based ink exhibits good storage stability, and the various colors can be uniformly mixed within a wide range of proportions, reducing the warehousing pressure and production costs for packaging printing companies.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a water-based ink for packaging printing, the ink comprising a color paste, a mica functional filler, and a dispersion medium; the mass ratio of the color paste, the mica functional filler, and the dispersion medium is (20~30):(1~2):(68~79).

[0007] Furthermore, the pigment paste comprises modified pigment particles and deionized water; the mass-to-volume ratio of the modified pigment particles and deionized water is (20~30) g: 100 mL.

[0008] Furthermore, the modified pigment particles have a core-shell structure, with the core being pigment particles and the shell consisting of modified rosin-silica, a silica layer, and a secondary silane protective layer from the inside out; the average diameter of the pigment particles is 200~300nm; and the total thickness of the shell is 20~30nm.

[0009] Furthermore, the dispersion medium comprises an aqueous resin, an aqueous acrylic emulsion, a functional additive, and deionized water, wherein the mass ratio of the aqueous resin, the aqueous acrylic emulsion, the functional additive, and the deionized water is (20~30):(20~30):5:(35~55).

[0010] Furthermore, the functional additives include dispersants, solubilizers, viscosity modifiers, defoamers, leveling agents, and preservatives. The mass ratio of the dispersant, solubilizer, viscosity modifier, defoamer, leveling agent, and preservative in the functional additives is (10~20):(5~20):(2~10):(1~5):(1~3):(1~3).

[0011] Furthermore, the dispersant is preferably aqueous dispersant 76, purchased from Shanghai Qianghan Chemical Technology Studio.

[0012] Furthermore, the co-solvent is preferably a conventional co-solvent in the field of water-based inks, including at least one of propylene glycol methyl ether and dipropylene glycol methyl ether.

[0013] Furthermore, the viscosity modifier is preferably the water-based additive VESMODY-U905, purchased from Changsha Libo Chemical Co., Ltd.

[0014] Furthermore, the defoamer is preferably a defoamer sold by Guangzhou Jiuhong New Material Technology Co., Ltd.

[0015] Furthermore, the leveling agent is preferably wetting agent PG-70, purchased from Greenqi Chemical (Shanghai) Co., Ltd.

[0016] Furthermore, the preservative is preferably CP15 bactericide, purchased from Hoffmann Materials Technology (Guangdong) Co., Ltd.

[0017] Secondly, the present invention provides a method for preparing water-based ink for packaging printing, comprising the following steps:

[0018] S1. Dry the mica powder, heat and stir it, add silane coupling agent solution dropwise, react, dry and sieve to obtain mica functional filler;

[0019] S2. Mix deionized water, dispersant, mica functional filler and water-based resin to obtain primary dispersion medium, add color paste, stir, homogenize to obtain primary ink;

[0020] S3. Add water-based acrylic emulsion and co-solvent to the primary ink, stir, adjust the pH, add viscosity modifier, and then add defoamer, leveling agent and preservative in sequence. Filter under pressure to obtain a water-based ink for packaging printing.

[0021] Further, in step S1, the drying temperature is 105~110℃, and the drying time is 2~3h; the heating and stirring temperature is 60~80℃, and the heating and stirring speed is 200~300rpm; the silane coupling agent solution includes a silane coupling agent and a solvent, and the mass ratio of the silane coupling agent to the solvent is (1~3):100; the silane coupling agent is KH561 or KH560; the solvent is anhydrous ethanol or deionized water; the rate of adding the silane coupling agent solution is 3~5mL / min; the reaction temperature is 60~80℃, and the reaction time is 30~60min; the drying temperature is 110~120℃, and the sieve mesh size is 400 mesh.

[0022] Further, in step S2, the mixing speed is 300-500 rpm, and the mixing time is 5-10 min; the mass ratio of the primary dispersion medium to the color paste is (50-60):(40-50); the stirring speed is 300-500 rpm, and the stirring time is 10-20 min; the homogenization speed is 1000-1500 rpm, and the homogenization time is 30-60 min.

[0023] Further, in step S3, the stirring speed is 150~300 rpm, the stirring time is 10~15 min; the pH adjustment endpoint is pH=8.0~9.5; and the mesh size of the pressure filter is 100~200 mesh.

[0024] Thirdly, the present invention provides a process for preparing a color paste, comprising the following steps:

[0025] A1. The pigment is ground, sieved, and activated to obtain activated pigment particles;

[0026] A2. Heat the rosin, add the silane coupling agent, raise the temperature, add the catalyst, stir, and distill under reduced pressure to obtain the modified rosin;

[0027] A3. Disperse the modified rosin and activated pigment particles in anhydrous ethanol, add tetraethyl orthosilicate solution dropwise, mix and stir, centrifuge to collect the precipitate, wash with deionized water, and dry to obtain primary coated pigment particles.

[0028] A4. Disperse the primary coated pigment particles in anhydrous ethanol, mature them, collect the precipitate by centrifugation, and wash them with an ethanol-water solution to obtain matured particles.

[0029] A5. Disperse the aging granules in deionized water, adjust the pH, add secondary silane, stir, filter, and obtain the color paste.

[0030] Furthermore, in A1, the pigment is any one of pigment red 57:1, pigment yellow 74, pigment blue 15, carbon black, and titanium dioxide.

[0031] Based on the subtractive color mixing method (CMYK), Pigment Red 57:1 was selected as the standard color for magenta, Pigment Yellow 74 as yellow, Pigment Blue 15 as cyan, and Carbon Black as black, with Titanium Dioxide added as white, forming five basic colors. In terms of classification, Carbon Black and Titanium Dioxide belong to inorganic pigments, while Pigment Red 57:1, Pigment Yellow 74, and Pigment Blue 15 are all organic pigments.

[0032] Furthermore, the pigment activation process includes: placing the pigment in a plasma treatment device, evacuating it, introducing oxygen, and performing low-temperature plasma glow discharge treatment for 5 minutes under a vacuum of 30 Pa and a discharge power of 80 W.

[0033] Further, in A2, the rosin is fully hydrogenated rosin, and the molar ratio of rosin, silane coupling agent, and catalyst is 100:100:(0.5~1.4); the silane coupling agent is KH561 or KH560; the catalyst is benzyltriethylammonium chloride; the heating temperature is 75~85℃; the temperature rise is 105~115℃; the stirring speed is 200~300 rpm, and the stirring time is 3.5~4.5 h; the vacuum degree of the vacuum distillation is -0.07~-0.09 MPa, the vacuum distillation temperature is 80~90℃, and the vacuum distillation continues until no distillate flows out.

[0034] Pigment Red 57:1 is prone to yellowing, poor flowability, and gelation in water-based inks. This is because the calcium released from Pigment Red 57:1 in the water-based dispersion system reacts with resin acids to form insoluble calcium salts, resulting in precipitation and increased viscosity. To avoid this phenomenon, modified rosin is used to coat the pigment particles to prevent excessive release of calcium ions, which would cause hue shift of Pigment Red 57:1 in water-based inks.

[0035] Further, in A3, the mass-to-volume ratio of the modified rosin, activated pigment particles, tetraethyl orthosilicate solution, and anhydrous ethanol is (5~20) g: 100 g: (5~15) mL: 100 mL; the dropping rate is 1~2 mL / min, and the dropping temperature is 25~30℃; the mixing temperature is 50~55℃, and the mixing speed is 100~200 rpm; the mixing time is 4~6 h; the tetraethyl orthosilicate solution comprises tetraethyl orthosilicate and deionized water, and the mass ratio of tetraethyl orthosilicate to deionized water is 100: (8~9); the drying temperature is 60~70℃.

[0036] Further, in A4, the mass-to-volume ratio of the primary coated pigment particles to anhydrous ethanol is (5~8) g: 100 mL; the aging temperature is 40~45℃, the aging speed is 100~150 rpm, and the aging time is 12~16 h; in the ethanol aqueous solution, the volume ratio of ethanol to deionized water is (2.5~3.5): (6.5~7.5).

[0037] Further, in A5, the mass-to-volume ratio of the aging granules to deionized water is (20~30) g: 100 mL; the endpoint of pH adjustment is pH = 7.5~8.0; the mass ratio of the secondary silane to the aging granules is (2~5): 100; the secondary silane includes sodium carboxyethyl silanetriol and hydroxypropyl trimethoxysilane, and the mass ratio of sodium carboxyethyl silanetriol to hydroxypropyl trimethoxysilane is 1: (0.9~1.1); the stirring speed is 450~600 rpm, and the stirring time is 30~60 min.

[0038] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0039] This invention provides a water-based ink for packaging printing and its preparation method. The base inks, compatible with the CMYK four-color printing system, can be uniformly mixed and adjusted within a wide range of proportions, exhibiting good color rendering. The hue shift after mixing is controllable, effectively reducing the storage pressure and waste of spot color inks for packaging printing companies. This invention constructs a uniform shell layer on the surface of pigment particles. From the inside out, the shell layer consists of modified rosin-silica, a silica layer, and a secondary silane protective layer. The modified rosin-silica acts as an organic-inorganic transition layer, enhancing the bonding force between the pigment core and the inorganic silica layer, while introducing organic groups compatible with water-based resins. The silica layer provides rigid support and a chemically inert barrier, weakening the influence of the external environment on the pigment core. The secondary silane protective layer introduces hydrophilic groups on the silica layer surface, giving the pigment particles a more uniform surface charge and steric hindrance effect in the water-based medium. Through a progressively constructed shell structure, the final surfaces of organic and inorganic pigments, which originally had significantly different surface properties, are covered with a uniform hydrophilic silane layer. This reduces the differences in interfacial characteristics, resulting in modified pigment particles of different colors possessing highly similar interfacial properties. The hydrogenated rosin, amorphous silica, and secondary silane constituting the shell are all colorless and transparent or nearly colorless materials. They exhibit no characteristic absorption in the visible light band, do not introduce impurities, and do not alter the intrinsic hue of the pigment core due to chemical reactions. This fundamentally avoids hue shifts and color mismatches caused by coating. Furthermore, the total thickness of the shell is designed to be 20-30 nm, which avoids significant scattering or interference effects. Therefore, it does not affect the intrinsic hue of the pigment core and does not cause ink color darkening or hue distortion. In addition, the core-shell structure can effectively improve the dispersion uniformity and long-term storage stability of pigment particles in aqueous systems; combined with mica functional fillers modified with silane coupling agents, it can simultaneously optimize the ink's hiding power, scratch resistance and film density, making the ink suitable for the industrial mass production requirements of packaging printing. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a process for preparing water-based inks for packaging printing.

[0041] Figure 2 This is a physical image of a water-based ink for packaging printing prepared according to Example 6 of the present invention. Detailed Implementation

[0042] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0043] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0044] Example 1

[0045] The preparation process of a magenta paste includes the following steps:

[0046] A1. Grind Pigment Red 57:1 and sieve it to an average particle size of 280nm. Place it in a plasma treatment device, evacuate it and introduce oxygen. Perform low-temperature plasma glow discharge treatment for 5 minutes under vacuum of 30Pa and discharge power of 80W to obtain activated pigment particles.

[0047] A2. Heat the fully hydrogenated rosin at 80℃ until it is completely melted, add KH561, raise the temperature to 110℃ and add benzyltriethylammonium chloride, and stir at 250 rpm for 4 hours. The molar ratio of fully hydrogenated rosin, KH561 and catalyst is 100:100:1.2. Distill under reduced pressure at 85℃ with a vacuum degree of -0.08 MPa until no fraction flows out to obtain modified rosin.

[0048] A3. Modified rosin and activated pigment particles were dispersed in anhydrous ethanol. Tetraethyl orthosilicate solution was added dropwise at 27°C at a rate of 1.5 mL / min. The mass ratio of tetraethyl orthosilicate to deionized water in the tetraethyl orthosilicate solution was 100:8.5. The mixture was stirred at 52°C at 150 rpm for 5 h to form modified rosin-silica on the pigment particles. The mass-volume ratio of modified rosin, activated pigment particles, tetraethyl orthosilicate solution, and anhydrous ethanol was 17 g:100 g:10 mL:100 mL. The mixture was centrifuged at 8000 rpm for 5 min, the precipitate was collected, and the precipitate was washed three times with deionized water to obtain primary coated pigment particles.

[0049] A4. The primary coated pigment particles were dispersed in anhydrous ethanol at a mass-to-volume ratio of 7 g to 100 mL. The particles were aged at 120 rpm at 42 °C for 14 h to form a silica layer on the outside of the primary coated pigment particles. The particles were centrifuged at 8000 rpm for 5 min, the precipitate was collected, and washed with an ethanol-water solution at a volume ratio of 3:7 to ethanol and deionized water to obtain the aged particles.

[0050] A5. Disperse the aging granules in deionized water at a mass-to-volume ratio of 25g:100mL; adjust the pH to pH=7.8, add secondary silane at a mass ratio of 3.5:100; the secondary silane coats the aging granules to form a secondary silane protective layer, obtaining modified pigment granules; the secondary silane is sodium carboxyethyl silanetriol and hydroxypropyltrimethoxysilane at a mass ratio of 1:1; stir at 500rpm for 45min, filter, and obtain a magenta paste containing 25g of modified pigment granules and 100mL of deionized water; the modified pigment granules have a core-shell structure with a total shell thickness of 25nm.

[0051] Example 2

[0052] The preparation process of a yellow pigment includes the following steps:

[0053] A1. Grind and sieve Pigment Yellow 74 to an average particle size of 200nm, place it in a plasma treatment device, evacuate and introduce oxygen, and perform low-temperature plasma glow discharge treatment for 5 minutes under vacuum of 30Pa and discharge power of 80W to obtain activated pigment particles.

[0054] A2. Heat the fully hydrogenated rosin at 75℃ until it is completely melted, add KH561, raise the temperature to 105℃ and add benzyltriethylammonium chloride, and stir at 200 rpm for 4.5 h. The molar ratio of fully hydrogenated rosin, KH561 and catalyst is 100:100:0.5. Distill under reduced pressure at 90℃ with a vacuum degree of -0.07 MPa until no distillate flows out to obtain modified rosin.

[0055] A3. Modified rosin and activated pigment particles were dispersed in anhydrous ethanol. Tetraethyl orthosilicate solution was added dropwise at 25°C at a rate of 1 mL / min. The mass ratio of tetraethyl orthosilicate to deionized water in the tetraethyl orthosilicate solution was 100:9. The mixture was stirred at 55°C at 100 rpm for 4 h to form modified rosin-silica on the pigment particles. The mass-volume ratio of modified rosin, activated pigment particles, tetraethyl orthosilicate solution, and anhydrous ethanol was 5 g:100 g:5 mL:100 mL. The mixture was centrifuged at 8000 rpm for 5 min, the precipitate was collected, and the precipitate was washed three times with deionized water to obtain primary coated pigment particles.

[0056] A4. The primary coated pigment particles were dispersed in anhydrous ethanol at a mass-to-volume ratio of 8 g:100 mL. The particles were aged at 100 rpm at 40 °C for 16 h to form a silica layer on the outside of the primary coated pigment particles. The particles were centrifuged at 8000 rpm for 5 min, the precipitate was collected, and washed with an ethanol-water solution at a volume ratio of 2.5:7.5 to ethanol and deionized water to obtain the aged particles.

[0057] A5. Disperse the aging granules in deionized water at a mass-to-volume ratio of 20g:100mL; adjust the pH to pH=7.5, add secondary silane at a mass ratio of 5:100; the secondary silane coats the aging granules to form a secondary silane protective layer, obtaining modified pigment granules; the secondary silane is sodium carboxyethyl silanetriol and hydroxypropyltrimethoxysilane at a mass ratio of 1:0.9; stir at 450rpm for 60min, filter, and obtain a yellow pigment paste containing 20g of modified pigment granules and 100mL of deionized water; the modified pigment granules have a core-shell structure with a total shell thickness of 20nm.

[0058] Example 3

[0059] The preparation process of a black paste includes the following steps:

[0060] A1. Grind and sieve the carbon black to an average particle size of 300nm, place it in a plasma treatment device, evacuate it and introduce oxygen, and perform low-temperature plasma glow discharge treatment for 5 minutes under a vacuum of 30Pa and a discharge power of 80W to obtain activated pigment particles.

[0061] A2. Heat the fully hydrogenated rosin at 85℃ until it is completely melted, add KH560, raise the temperature to 115℃ and add benzyltriethylammonium chloride, and stir at 300 rpm for 3.5 h. The molar ratio of fully hydrogenated rosin, KH560 and catalyst is 100:100:1.4. Distill under reduced pressure at 80℃ with a vacuum degree of -0.09 MPa until no distillate flows out to obtain modified rosin.

[0062] A3. Modified rosin and activated pigment particles were dispersed in anhydrous ethanol. Tetraethyl orthosilicate solution was added dropwise at 30°C at a rate of 2 mL / min. The mass ratio of tetraethyl orthosilicate to deionized water in the tetraethyl orthosilicate solution was 100:8. The mixture was stirred at 50°C for 6 hours at 150 rpm to form modified rosin-silica on the pigment particles. The mass-volume ratio of modified rosin, activated pigment particles, tetraethyl orthosilicate solution, and anhydrous ethanol was 20 g: 100 g: 15 mL: 100 mL. The mixture was centrifuged at 8000 rpm for 5 minutes, the precipitate was collected, and the precipitate was washed three times with deionized water to obtain primary coated pigment particles.

[0063] A4. Disperse the primary coated pigment particles in anhydrous ethanol, with a mass-to-volume ratio of 5 g:100 mL; mature at 45 °C for 12 h at 150 rpm to form a silica layer on the outside of the primary coated pigment particles; centrifuge at 8000 rpm for 5 min, collect the precipitate, and wash with an ethanol-water solution, with a volume ratio of ethanol to deionized water of 3.5:6.5; to obtain matured particles.

[0064] A5. Disperse the aging particles in deionized water at a mass-to-volume ratio of 30g:100mL; adjust the pH to pH=8.0, add secondary silane at a mass ratio of 2:100; the secondary silane coats the aging particles to form a secondary silane protective layer, resulting in modified pigment particles; the secondary silane is sodium carboxyethyl silanetriol and hydroxypropyltrimethoxysilane at a mass ratio of 1:1.1; stir at 600rpm for 30min, filter, and obtain a black pigment paste containing 30g of modified pigment particles and 100mL of deionized water; the modified pigment particles have a core-shell structure with a total shell thickness of 30nm.

[0065] Example 4

[0066] like Figure 1 As shown, a water-based ink for packaging printing is prepared by means of:

[0067] S1. Dry mica powder at 107℃ for 2.5h, heat to 70℃ and stir at 250rpm. Add silane coupling agent solution dropwise at 4mL / min. The silane coupling agent solution is KH561 and anhydrous ethanol with a mass ratio of 2:100. React at 70℃ for 45min. After the reaction is completed, dry at 115℃ and pass through a 400-mesh sieve to obtain mica functional filler.

[0068] S2. Deionized water, dispersant, mica functional filler and waterborne resin are mixed at 400 rpm for 7 min to obtain a primary dispersion medium. The magenta paste prepared in Example 1 is added. The mass ratio of the primary dispersion medium to the color paste is 50:50. After stirring at 400 rpm for 15 min, the mixture is homogenized at 1300 rpm for 45 min to obtain a primary ink.

[0069] S3. Add water-based acrylic emulsion and co-solvent to the primary ink, stir at 220 rpm for 13 minutes, adjust the pH to pH=8.5, add viscosity modifier, and then add defoamer, leveling agent and preservative in sequence. Stir at 220 rpm for 5 minutes after each addition, filter under pressure with a 150-mesh sieve to obtain a water-based ink for packaging printing.

[0070] In the aforementioned inks, the mass ratio of color paste, mica functional filler, and dispersion medium is 25:1.5:73.5. In the dispersion medium, the mass ratio of water-based resin, water-based acrylic emulsion, functional additives, and deionized water is 25:25:5:45. In the functional additives, the mass ratio of dispersant, cosolvent, viscosity modifier, defoamer, leveling agent, and preservative is 15:12:6:3:2:2.

[0071] Example 5

[0072] like Figure 1 As shown, a water-based ink for packaging printing is prepared by means of:

[0073] S1. Dry mica powder at 110℃ for 2 hours, heat to 80℃ and stir at 200 rpm. Add silane coupling agent solution dropwise at 3 mL / min. The silane coupling agent solution is KH561 and anhydrous ethanol with a mass ratio of 3:100. React at 80℃ for 30 min. After the reaction is completed, dry at 120℃ and pass through a 400-mesh sieve to obtain mica functional filler.

[0074] S2. Deionized water, dispersant, mica functional filler and waterborne resin are mixed at 500 rpm for 5 min to obtain a primary dispersion medium. The mass ratio of the primary dispersion medium to the color paste is 55:45. The yellow color paste prepared in Example 2 is added, and the mixture is stirred at 500 rpm for 10 min and then homogenized at 1500 rpm for 30 min to obtain a primary ink.

[0075] S3. Add water-based acrylic emulsion and co-solvent to the primary ink, stir at 150 rpm for 15 minutes, adjust the pH to pH=8.0, add viscosity modifier, and then add defoamer, leveling agent and preservative in sequence. Stir at 150 rpm for 5 minutes after each addition, filter under pressure with a 200-mesh sieve to obtain a water-based ink for packaging printing.

[0076] In the aforementioned inks, the mass ratio of color paste, mica functional filler, and dispersion medium is 20:1:79. In the dispersion medium, the mass ratio of water-based resin, water-based acrylic emulsion, functional additives, and deionized water is 20:20:5:55. In the functional additives, the mass ratio of dispersant, cosolvent, viscosity modifier, defoamer, leveling agent, and preservative is 10:5:5:1:1:1.

[0077] Example 6

[0078] like Figure 1 As shown, a water-based ink for packaging printing is prepared by means of:

[0079] S1. Dry mica powder at 105℃ for 3 hours, heat to 60℃ and stir at 300 rpm. Add silane coupling agent solution dropwise at 5 mL / min. The silane coupling agent solution is KH560 and anhydrous ethanol with a mass ratio of 1:100. React at 60℃ for 60 min. After the reaction is completed, dry at 110℃ and pass through a 400-mesh sieve to obtain mica functional filler.

[0080] S2. Deionized water, dispersant, mica functional filler and waterborne resin are mixed at 300 rpm for 10 min to obtain a primary dispersion medium. The mass ratio of the primary dispersion medium to the color paste is 60:40. Add the black color paste prepared in Example 3, stir at 300 rpm for 20 min and then homogenize at 1000 rpm for 60 min to obtain a primary ink.

[0081] S3. Add water-based acrylic emulsion and co-solvent to the primary ink, stir at 300 rpm for 10 minutes, adjust the pH to pH=9.5, add viscosity modifier, then add defoamer, leveling agent and preservative in sequence, stirring at 300 rpm for 5 minutes after each addition, filter under pressure using a 100-mesh sieve, to obtain the following... Figure 2The image shows a water-based ink for packaging printing.

[0082] In the aforementioned inks, the mass ratio of color paste, mica functional filler, and dispersion medium is 30:2:68. In the dispersion medium, the mass ratio of water-based resin, water-based acrylic emulsion, functional additives, and deionized water is 30:30:5:45. In the functional additives, the mass ratio of dispersant, cosolvent, viscosity modifier, defoamer, leveling agent, and preservative is 20:20:10:2:3:3.

[0083] Comparative Example 1

[0084] A water-based ink for packaging printing differs from Example 4 in that, in S2, the magenta paste prepared in Example 1 is not used; instead, the ground pigment red 57:1 is directly added to the primary dispersion medium, with the amount added being consistent with the mass of pigment red 57:1 in the color paste. Other operating steps and process parameters are exactly the same as in Example 4.

[0085] Performance testing:

[0086] Color mixing test: The water-based ink (magenta ink) for packaging printing prepared in Example 4 and Comparative Example 1 was mixed with the water-based ink (yellow ink) for packaging printing prepared in Example 5 at a mass ratio of (80~20):(20~80) of magenta ink to yellow ink. The mixture was analyzed using a colorimeter, and the test results were expressed as color difference ΔE.

[0087] Table 1. Color mixing test results of the inks prepared in Example 4, Comparative Example 1, and Example 5.

[0088]

[0089] As shown in Table 1, the magenta ink prepared in Example 4 and the yellow ink prepared in Example 5 can be uniformly mixed within the ratio range of (20~80):(80~20), with ΔE below 1.5 NBS. This is within an acceptable range where there is a slight deviation but it is difficult to detect with the naked eye. This indicates that the three-layer core-shell structure makes the surface characteristics of pigment particles of different hues tend to be consistent, and the hue stability is good after mixing.

[0090] The magenta ink prepared in Comparative Example 1 and the yellow ink prepared in Example 5, when mixed in the range of (20~80):(80~20), both exhibited a ΔE higher than 3.2 NBS, which is a deviation clearly perceptible to the naked eye. When the ratio was adjusted to 50:50, the ΔE reached its maximum of 4.5 NBS. At the same time, a small amount of precipitation was found in the mixed ink. It is speculated that this is because the probability of collision between the two pigment particles is highest when mixed in equal proportions. The significant differences in surface polarity, surface charge, and steric hindrance between the uncoated pigment red (57:1) and the core-shell structured yellow pigment lead to the most severe aggregation of pigment particles, resulting in precipitation and causing the measured hue to deviate significantly from the theoretical mixed color.

[0091] The embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. An aqueous ink for package printing, characterized by, The ink comprises a color paste, a mica functional filler, and a dispersion medium; the mass ratio of the color paste, mica functional filler, and dispersion medium is (20~30):(1~2):(68~79); the color paste comprises modified pigment particles and deionized water; the mass-to-volume ratio of the modified pigment particles and deionized water is (20~30) g:100 mL; the modified pigment particles have a core-shell structure, with the core being pigment particles and the shell layers consisting of modified rosin-silica, a silica layer, and a secondary silane protective layer from the inside out; the average diameter of the pigment particles is 200~300 nm; the total thickness of the shell layers is 20~30 nm. 0nm; The dispersion medium includes an aqueous resin, an aqueous acrylic emulsion, functional additives, and deionized water, wherein the mass ratio of the aqueous resin, aqueous acrylic emulsion, functional additives, and deionized water is (20~30):(20~30):5:(35~55); The functional additives include a dispersant, a cosolvent, a viscosity modifier, a defoamer, a leveling agent, and a preservative, wherein the mass ratio of the dispersant, cosolvent, viscosity modifier, defoamer, leveling agent, and preservative is (10~20):(5~20):(2~10):(1~5):(1~3):(1~3).

2. The method of preparing a water-based ink for packaging printing according to claim 1, characterized by, Includes the following steps: S1. Dry the mica powder, heat and stir it, add silane coupling agent solution dropwise, react, dry and sieve to obtain mica functional filler; S2. Mix deionized water, dispersant, mica functional filler and water-based resin to obtain primary dispersion medium, add color paste, stir, homogenize to obtain primary ink; S3. Add water-based acrylic emulsion and co-solvent to the primary ink, stir, adjust the pH, add viscosity modifier, and then add defoamer, leveling agent and preservative in sequence. Filter under pressure to obtain a water-based ink for packaging printing.

3. The method of preparing a water-based ink for packaging printing according to claim 2, characterized by, In step S1, the drying temperature is 105-110℃, and the drying time is 2-3 hours; the heating and stirring temperature is 60-80℃, and the heating and stirring speed is 200-300 rpm; the silane coupling agent solution includes a silane coupling agent and a solvent, and the mass ratio of the silane coupling agent to the solvent is (1-3):100; the silane coupling agent is KH561 or KH560; the solvent is anhydrous ethanol or deionized water; the rate of adding the silane coupling agent solution is 3-5 mL / min; the reaction temperature is 60-80℃, and the reaction time is 30-60 minutes; the drying temperature is 110-120℃, and the sieve used for sieving has a mesh size of 400.

4. The method for preparing a water-based ink for packaging printing according to claim 2, characterized in that, In step S2, the mixing speed is 300-500 rpm and the mixing time is 5-10 min; the mass ratio of the primary dispersion medium to the color paste is (50-60):(40-50); the stirring speed is 300-500 rpm and the stirring time is 10-20 min; the homogenization speed is 1000-1500 rpm and the homogenization time is 30-60 min.

5. The method for preparing water-based ink for packaging printing according to claim 2, characterized in that, In step S3, the stirring speed is 150~300 rpm and the stirring time is 10~15 min; the pH adjustment endpoint is pH=8.0~9.5; and the mesh size of the pressure filter is 100~200 mesh.

6. The method for preparing a water-based ink for packaging printing according to claim 2, characterized in that, The preparation process of the color paste includes the following steps: A1. The pigment is ground, sieved, and activated to obtain activated pigment particles; A2. Heat the rosin, add the silane coupling agent, raise the temperature, add the catalyst, stir, and distill under reduced pressure to obtain the modified rosin; A3. Disperse the modified rosin and activated pigment particles in anhydrous ethanol, add tetraethyl orthosilicate solution dropwise, mix and stir, centrifuge to collect the precipitate, wash with deionized water, and dry to obtain primary coated pigment particles. A4. Disperse the primary coated pigment particles in anhydrous ethanol, mature them, collect the precipitate by centrifugation, and wash them with an ethanol-water solution to obtain matured particles. A5. Disperse the aging granules in deionized water, adjust the pH, add secondary silane, stir, filter, and obtain the color paste.

7. The method for preparing a water-based ink for packaging printing according to claim 6, characterized in that, In A1, the pigment is any one of pigment red 57:1, pigment yellow 74, pigment blue 15, carbon black, and titanium dioxide.

8. The method for preparing water-based ink for packaging printing according to claim 6, characterized in that, In A2, the rosin is fully hydrogenated rosin, and the molar ratio of rosin, silane coupling agent, and catalyst is 100:100:(0.5~1.4); the silane coupling agent is KH561 or KH560; the catalyst is benzyltriethylammonium chloride; the heating temperature is 75~85℃; the temperature rise is 105~115℃; the stirring speed is 200~300 rpm, and the stirring time is 3.5~4.5 h; the vacuum degree of the vacuum distillation is -0.07~-0.09 MPa, the vacuum distillation temperature is 80~90℃, and the vacuum distillation continues until no distillate flows out.

9. The method for preparing a water-based ink for packaging printing according to claim 6, characterized in that, In A3, the mass-to-volume ratio of the modified rosin, activated pigment particles, tetraethyl orthosilicate solution, and anhydrous ethanol is (5~20) g: 100 g: (5~15) mL: 100 mL; the dropping rate is 1~2 mL / min, and the dropping temperature is 25~30℃; the mixing and stirring temperature is 50~55℃, and the mixing and stirring speed is 100~200 rpm; the mixing and stirring time is 4~6 h; the tetraethyl orthosilicate solution includes tetraethyl orthosilicate and deionized water, and the mass ratio of tetraethyl orthosilicate to deionized water is 100: (8~9); the drying temperature is 60~70℃.

10. The method for preparing a water-based ink for packaging printing according to claim 6, characterized in that, In A4, the mass-to-volume ratio of the primary coated pigment particles to anhydrous ethanol is (5~8) g: 100 mL; the aging temperature is 40~45℃, the aging speed is 100~150 rpm, and the aging time is 12~16 h; in the ethanol aqueous solution, the volume ratio of ethanol to deionized water is (2.5~3.5): (6.5~7.5).

11. The method for preparing a water-based ink for packaging printing according to claim 6, characterized in that, In A5, the mass-to-volume ratio of the aging granules to deionized water is (20~30) g: 100 mL; the endpoint of pH adjustment is pH = 7.5~8.0; the mass ratio of the secondary silane to the aging granules is (2~5): 100; the secondary silane includes sodium carboxyethyl silanetriol and hydroxypropyl trimethoxysilane, and the mass ratio of sodium carboxyethyl silanetriol to hydroxypropyl trimethoxysilane is 1: (0.9~1.1); the stirring speed is 450~600 rpm, and the stirring time is 30~60 min.

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