A water-based digital glaze ink with an aqueous dispersant and its preparation method

Abstract

This invention discloses an aqueous dispersant for water-based digital glaze ink and its preparation method. The raw material components of the aqueous dispersant, by weight, include: 35-40 parts of acrylic monomers, 25-35 parts of amide monomers, 30-35 parts of isoborneol methacrylate, 1-3 parts of initiator, 100-300 parts of an alcohol-water mixed solvent, and 0.5-1.5 parts of triethanolamine. This aqueous dispersant is copolymerized from the above ternary monomers. Specifically: the carboxyl groups of the acrylic monomers have a strong anchoring effect on the water-based digital glaze particles, accelerating grinding efficiency through electrostatic adsorption and chelation effects; the amide groups of the amide monomers form dense hydrogen bonds with water molecules, improving the compatibility of the dispersant in the aqueous system and avoiding uneven dispersion caused by hydrophobic stratification; the rigid isoborneol side chains of the isoborneol methacrylate form steric hindrance, effectively preventing particle collision and aggregation, thereby significantly improving the storage stability of the glaze.

Description

Technical Field

[0001] This invention belongs to the field of ceramic ink technology, specifically relating to an aqueous dispersant for water-based digital glaze ink and its preparation method. Background Technology

[0002] Traditional digital engraving roller printing requires multiple rollers to layer colors, resulting in limited pattern variety and flexibility. Digital color inkjet printers ushered in the digital era for ceramics, offering greater flexibility in pattern variations, easier production transitions, and exponentially increased development frequency. In 2016, digital functional effect inks for ceramics began to be used, enabling the creation of glossy, matte, and engraved finishes based on color. From then on, a ceramic tile was no longer a flat surface; it could exhibit variations in gloss and matte finishes, and textured surfaces, elevating ceramic aesthetics to a new level. The rise of ceramic slabs saw the first application of glazes as ink using digital inkjet printers, achieving a thickness of up to 3mm. Subsequently, the industry launched water-based digital glaze products, but these are currently still in the laboratory stage.

[0003] The core component of water-based digital glaze is nano-sized ceramic powder. Its high specific surface area results in extremely high surface free energy, making it prone to forming hard agglomerates through van der Waals forces and hydrogen bonds. Common dispersants (such as sodium polyacrylate and sodium hexametaphosphate) mainly rely on electrostatic repulsion to stabilize particles, but this alone is insufficient to maintain long-term stability. Furthermore, common dispersants at high solids content can easily cause an increase in structural viscosity, exceeding the spray nozzle's applicable range (10-30 mPa). Meanwhile, the anchoring groups (such as carboxyl groups) of ordinary dispersants have insufficient chemical adsorption force on the surface of ceramic particles, making them prone to desorption during high-speed grinding and increasing grinding time. In addition, the performance limitations of ordinary dispersants systematically restrict the industrial application of water-based digital glazes. Problems such as low dispersion efficiency, poor nozzle compatibility, and large process fluctuations lead to high production costs, unstable product quality, and weak market competitiveness.

[0004] Therefore, existing water-based digital enamel inks mainly suffer from poor dispersion and storage stability, with particle sedimentation occurring after 1-3 days of standing, and a sedimentation rate of 8%-15% after 7 days, and they are prone to stratification. Simultaneously, they have low printability, with significant viscosity changes due to temperature fluctuations, and printhead clogging easily after 2-3 hours of continuous printing. Furthermore, solvent-based digital enamel inks are not environmentally friendly, with volatile organic compound (VOC) concentrations as high as 50-100 ppm. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes an aqueous dispersant for water-based digital glaze ink and its preparation method. This dispersant has high grinding efficiency for ceramic glazes, good anti-settling effect, no gel precipitation during long-term storage, and does not clog the printhead during printing, thus meeting the performance requirements of inkjet printing.

[0006] To solve the above-mentioned technical problems, a first aspect of the present invention provides an aqueous dispersant, the raw material components of which, by weight, comprise:

[0007] 35-40 parts of acrylic monomers; 25-35 parts of amide monomers; 30-35 parts of isobornyl methacrylate; 1-3 parts initiator; 100-300 parts of alcohol-water mixed solvent; 0.5-1.5 parts of triethanolamine.

[0008] Specifically, the aqueous dispersant of the present invention is copolymerized from an acrylic monomer, an amide monomer, and isobornyl methacrylate (IBOMA), a ternary monomer. Wherein, the carboxyl group (-COOH) contained in the acrylic monomer can ionize to -COO in the aqueous system. - It possesses both strong polarity and reactivity. The carboxyl groups it contains can stably adhere to the particle surface through electrostatic adsorption and chelation. The amide monomers contain amide groups (-CONH2), which have both polarity and hydrogen bonding ability, which is beneficial to improving the hydrophilicity and system compatibility of the dispersant. Isobornyl methacrylate can fundamentally prevent the anchoring dispersant particles from approaching and agglomerating through spatial physical barriers. Furthermore, the base of the isobornyl group is divided into large nonpolar bicycloalkyl groups, giving the polymer strong steric resistance protection, which can effectively improve the stability of the coating. In addition, the rigid ring structure of IBOMA provides steric resistance that can also prevent glaze particles from agglomerating. When the dispersant is adsorbed on the surface of glaze particles, a three-dimensional steric hindrance is formed around the particles, thereby preventing the particles from directly colliding and sticking together. Therefore, the aqueous dispersant of the present invention combines the advantages of each monomer group, and under the action of the initiator, it will efficiently polymerize to ensure a uniform molecular chain structure. It is suitable for the low viscosity requirements of digital printing and avoids the problem of head clogging caused by chain segment entanglement. It is especially suitable for the dispersion preparation of aqueous digital glaze, taking into account dispersion efficiency, long-term stability and printing compatibility.

[0009] In some embodiments of the present invention, the acrylic monomer is selected from at least one of acrylic acid (AA), methyl methacrylate, etc.

[0010] And / or, the amide monomer is selected from at least one of acrylamide (AM) and N-hydroxyethylacrylamide; And / or, the initiator is selected from at least one of ammonium persulfate (APS), potassium persulfate, and sodium persulfate.

[0011] In some embodiments of the present invention, the alcohol-water mixed solvent comprises isopropanol and water, wherein the mass ratio of isopropanol to water is (0.5-1.5):1.

[0012] In some embodiments of the present invention, the water is deionized water.

[0013] In some embodiments of the present invention, the weight-average molecular weight of the aqueous dispersant is not greater than 10,000, preferably 7,000-10,000.

[0014] In some embodiments of the present invention, the raw material components of the aqueous dispersant further include, by weight, 0.5-1.5 parts of hydroquinone monomethyl ether (MEHQ) and / or 2-5 parts of dodecyl mercaptan. Hydroquinone monomethyl ether primarily functions as a polymerization inhibitor, while dodecyl mercaptan facilitates precise control of the dispersant's molecular weight, meeting the low viscosity requirements of digital printing.

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned aqueous dispersant, comprising the following steps: (1) Dissolve acrylic monomers, amide monomers, isobornyl methacrylate and triethanolamine in a partially alcohol-water mixed solvent to prepare a monomer premix; (2) Add the remaining alcohol-water mixed solvent to the reaction vessel, purge with nitrogen, heat for the first time, and then add the monomer premixed liquid dropwise; heat for the second time, and then add the initiator dropwise to carry out the reaction and obtain the aqueous dispersant.

[0016] When the monomer raw materials of the aqueous dispersant of the present invention are acrylic acid, acrylamide and isobornyl methacrylate, and the initiator is ammonium persulfate, the reaction pathway is as follows: .

[0017] In some embodiments of the present invention, in step (1), the portion of the alcohol-water mixed solvent accounts for 45-55% of the total alcohol-water mixed solvent.

[0018] In some embodiments of the present invention, in step (2), the temperature of the first heating is 70-75°C, that is, the alcohol-water mixed solvent is preheated first.

[0019] In some embodiments of the present invention, in step (2), the heating rate during the first heating is 1-2℃ / min, that is, a slow heating method is adopted.

[0020] In some embodiments of the present invention, in step (2), the monomer premixed solution is added over a period of 3-5 hours.

[0021] In some embodiments of the present invention, in step (2), the temperature of the second heating is 80-85°C. During the dropwise addition process, the temperature of the reactor is gradually increased to match the decomposition temperature of the initiator and ensure initiation efficiency. Furthermore, the initiator is added dropwise 5-15 minutes after the monomer premix is ​​added to ensure that the initiator and monomer are consumed synchronously, thus avoiding excessive monomer leading to self-polymerization.

[0022] In some embodiments of the present invention, in step (2), the initiator is added over a period of 3-5 hours.

[0023] A third aspect of the present invention provides an aqueous digital glaze ink, the raw material components of which include the above-mentioned aqueous dispersant.

[0024] In some embodiments of the present invention, the raw material components of the water-based digital glaze ink include, by weight: 35-45 parts of ceramic glaze; 10-30 parts organic solvent; 10-30 parts water; 3-10 parts of aqueous dispersant; 2-8 parts of water-based resin; Additives: 0.3-4 parts.

[0025] The aqueous dispersant of the present invention has a good dispersion effect on ceramic glazes, and is especially suitable for water-based digital glazes that are prone to agglomeration, have poor dispersion stability, high specific gravity and high solid content, but has limited dispersion effect on non-polar organic pigments.

[0026] In some embodiments of the present invention, the chemical composition of the ceramic glaze, by weight percentage, includes: SiO2 50-55%, Al2O3 20-25%, CaO 5-10%, MgO 1-5%, K2O 1-2%, Na2O 3-5%, BaO 8-10%, ZnO 1-2%, SrO 0.01-0.1%, and Fe2O3 0.01-0.1%.

[0027] In some embodiments of the present invention, the aqueous resin is selected from aqueous polyurethane resin and / or aqueous acrylic resin.

[0028] Specifically, the hydroxyl groups in the waterborne polyurethane dispersion can enhance the hydration layer, assist the "hydrophilic" mechanism of the dispersant, and improve the storage stability of the glaze after grinding, giving it good compatibility and pseudoplastic fluid characteristics. Waterborne acrylic resin and the dispersant both belong to the acrylic acid derivative class; the acrylic acid segments have good compatibility with the corresponding units of the dispersant, and the cost is relatively low. Therefore, waterborne polyurethane resin and waterborne acrylic resin can synergistically stabilize the waterborne system with the waterborne dispersant of this invention, not only without disrupting the dispersant's mechanism, but also by enhancing the hydration layer and improving the system's homogeneity, thereby increasing the dispersion effect.

[0029] In some embodiments of the present invention, the water is deionized water. Deionized water has a conductivity of less than 2 μS / cm, which does not affect the salt content in the ceramic ink. Excessive salt content can easily lead to crystal formation at the inkjet printer printhead, affecting the stability of the ink's performance and clogging the printhead, thus affecting the smoothness of ink printing.

[0030] In some embodiments of the present invention, the organic solvent is selected from isopropanol, 1,2 Any two of propylene glycol and ethylene glycol, with a mass ratio of (0.5-1.5):(0.5-1.5).

[0031] In some embodiments of the present invention, the additives include at least one of anti-settling agents, preservatives, defoamers, tension modifiers, and rheology modifiers.

[0032] In some embodiments of the present invention, the anti-settling agent BYK-240 is added in an amount of 0.1-3 parts by weight. This anti-settling agent is a water-soluble biopolymer powder. In water, the sol molecules can form a super-bound ribbon-like helical copolymer, constituting a fragile, glue-like network structure that can support the morphology of solid particles, droplets, and bubbles, and has strong emulsifying stabilizing effect and high suspension capacity.

[0033] In some embodiments of the present invention, the preservative is selected from Proxel. ® GXL, add 0.1-0.3 parts by weight.

[0034] In some embodiments of the present invention, the defoamer is selected from BYK-024 and is added in an amount of 0.01-0.1 parts by weight.

[0035] In some embodiments of the present invention, the tension regulator is selected from TEGO. ® Wet 270, add 0.02-0.15 parts by weight.

[0036] In some embodiments of the present invention, the rheology modifier is selected from Rheovis. ® HS 1250, the amount added is 0.05-0.2 parts by weight.

[0037] A fourth aspect of the present invention provides an inkjet-printed ceramic tile, comprising an inkjet-printed layer, the inkjet-printed layer being formed by inkjet printing with the aforementioned water-based digital glaze ink.

[0038] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The aqueous dispersant of the present invention is copolymerized from acrylic monomers, amide monomers and isobornyl methacrylate ternary monomers, wherein: the carboxyl groups of the acrylic monomers have a strong anchoring effect on the aqueous digital glaze particles, and accelerate the grinding efficiency through electrostatic adsorption and chelation effects; the amide groups of the amide monomers form dense hydrogen bonds with water molecules, improving the compatibility of the dispersant in the aqueous system and avoiding uneven dispersion caused by hydrophobic stratification; the rigid isobornyl side chains of isobornyl methacrylate form steric hindrance, effectively preventing particle collision and agglomeration, thereby significantly improving the storage stability of the glaze. Therefore, the present invention solves the technical problems of insufficient dispersion ability and easy precipitation of existing aqueous dispersants through the synergistic effect of the strong anchoring of carboxyl groups, the hydrophilicity of amide groups and the steric hindrance of the rigid side chains of isobornyl methacrylate.

[0039] (2) The aqueous dispersant ternary monomer of the present invention polymerizes efficiently under the action of an initiator, ensuring a uniform molecular chain structure. Combined with triethanolamine, it achieves both the low viscosity requirements of digital printing and avoids the nozzle clogging problem caused by chain segment entanglement. It is especially suitable for the dispersion preparation of aqueous digital glazes, taking into account dispersion efficiency, long-term stability and printability. It achieves a sedimentation rate of 2.7-4.9% after 7 days and 6.3-7.9% after 15 days at 70±2℃, and has good storage stability. It will not clog the nozzle during continuous printing. Detailed Implementation

[0040] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0041] The raw materials used in the following examples and comparative examples are as follows: Waterborne polyurethane resin: Impranil DL 1620; Water-based acrylic resin: Joncryl ® 8367; Aqueous acid-alcohol resin: Additol ® VXW 6208; Rheology modifier: Rheovis ® HS 1250; Defoamer: BYK-024; Preservative: Proxel ® GXL; Anti-settling agent: BYK-240; Tension regulator: TEGO ® Wet 270.

[0042] Example 1 An aqueous dispersant, characterized in that its raw material components, by weight, include: 40 parts acrylic acid, 30 parts acrylamide, 30 parts isobornyl methacrylate, 2 parts ammonium persulfate, 100 parts isopropanol, 100 parts deionized water, 1 part hydroquinone monomethyl ether, 3.5 parts dodecyl mercaptan, and 1 part triethanolamine.

[0043] A method for preparing an aqueous dispersant includes the following steps: (1) Add acrylic acid, acrylamide and isobornyl methacrylate to a beaker, and add half of the isopropanol, deionized water, dodecyl mercaptan, hydroquinone monomethyl ether and triethanolamine in sequence. Stir at 300 rpm for 30 min until the monomer is completely dissolved to obtain monomer premix. (2) Transfer the monomer premix to a constant-pressure dropping funnel, then add the remaining isopropanol and deionized water to the reactor, start mechanical stirring, purge the air in the reactor with nitrogen for 30 min, and simultaneously start a constant-temperature water bath to preheat the solvent. Dissolve ammonium persulfate in deionized water to prepare an 8% initiator solution. When the temperature in the reactor stabilizes at 70℃, start adding the monomer premix at a rate of 40 g / h over 3 hours; after adding for 5 min, add the initiator solution simultaneously at a rate of 10 g / h over 3 hours to ensure that the free radicals and monomers are in excess. During the adding stage, raise the temperature to 80-82℃, increase the stirring speed to 450 rpm, and maintain the nitrogen flow rate at 0.2 L / min. After the addition is complete, raise the temperature to 85℃ and continue the reaction for 1 hour to quickly consume the residual monomer through high temperature. After the reaction is complete, lower the temperature to 45℃, slowly add 25% ammonia to adjust the pH to 7.5, and stir for 30 min. The solution was desolventized at 65°C until the solid content was 40±2%; it was then filtered through a 300-mesh filter cloth to obtain a light brown transparent liquid, which is the aqueous dispersant of this embodiment. The weight average molecular weight of the aqueous dispersant is 7000.

[0044] A water-based digital glaze ink, the raw material components of which, by weight, include: 35 parts ceramic glaze, 5 parts isopropanol, 5 parts 1,2-propanediol, 10 parts deionized water, 3 parts water-based dispersant (in this embodiment), 2 parts water-based polyurethane resin, 0.05 parts rheology modifier, 0.01 parts defoamer, 0.13 parts preservative, and 0.1 parts anti-settling agent.

[0045] The chemical composition of the ceramic glaze, by weight percentage, includes: 50% SiO2, 21% Al2O3, 8% CaO, 3% MgO, 2% K2O, 3% Na2O, 9% BaO, 2% ZnO, 0.01-0.1% SrO and 0.01-0.1% Fe2O3.

[0046] A method for preparing a water-based digital glaze includes the following steps: (1) Mix a portion of waterborne polyurethane (50%), isopropanol, 1,2-propanediol and deionized water, as well as rheology modifiers, defoamers, preservatives, antisettling agents and waterborne dispersants, and perform the first grinding at a speed of 1500 rpm. (2) After adding the ceramic glaze, the mixture is ground a second time at a speed of 2500 rpm until the particle size distribution of the slurry is D50=0.5-0.9μm and D97=1-2μm. Finally, the viscosity of the ground slurry is adjusted to 20-30 mPa·s (25℃) with the remaining waterborne polyurethane, isopropanol, 1,2-propanediol and deionized water. After filtration, the waterborne digital glaze of this embodiment is obtained.

[0047] Example 2 An aqueous dispersant, characterized in that its raw material components, by weight, include: 40 parts acrylic acid, 25 parts acrylamide, 35 parts isobornyl methacrylate, 2 parts ammonium persulfate, 100 parts isopropanol, 100 parts deionized water, 1 part hydroquinone monomethyl ether, 3.5 parts dodecyl mercaptan, and 1 part triethanolamine.

[0048] A method for preparing an aqueous dispersant includes the following steps: (1) Add acrylic acid, acrylamide and isobornyl methacrylate to a beaker, and add half of the isopropanol, deionized water, dodecyl mercaptan, hydroquinone monomethyl ether and triethanolamine in sequence. Stir at 300 rpm for 30 min until the monomer is completely dissolved to obtain monomer premix. (2) Transfer the monomer premix to a constant-pressure dropping funnel, then add the remaining isopropanol and deionized water to the reactor, start mechanical stirring, purge the air in the reactor with nitrogen for 30 min, and simultaneously start a constant-temperature water bath to preheat the solvent. Dissolve ammonium persulfate in deionized water to prepare an 8% initiator solution. When the temperature in the reactor stabilizes at 70℃, start adding the monomer premix at a rate of 40 g / h over 3 hours; after adding for 5 min, add the initiator solution simultaneously at a rate of 10 g / h over 3 hours to ensure that the free radicals and monomers are in excess. During the adding stage, raise the temperature to 80-82℃, increase the stirring speed to 450 rpm, and maintain the nitrogen flow rate at 0.2 L / min. After the addition is complete, raise the temperature to 85℃ and continue the reaction for 1 hour to quickly consume the residual monomer through high temperature. After the reaction is complete, lower the temperature to 45℃, slowly add 25% ammonia to adjust the pH to 7.5, and stir for 30 min. The solution was desolventized at 65°C until the solid content was 40±2%; it was then filtered through a 300-mesh filter cloth to obtain a light brown transparent liquid, which is the aqueous dispersant of this embodiment. The weight average molecular weight of the aqueous dispersant is 7000.

[0049] A water-based digital glaze ink, the raw material components of which, by weight, include: 40 parts ceramic glaze, 10 parts isopropanol, 10 parts 1,2-propanediol, 20 parts deionized water, 6 parts water-based dispersant (in this embodiment), 5 parts water-based polyurethane resin, 0.1 parts rheology modifier, 0.05 parts defoamer, 0.2 parts preservative, and 1.5 parts anti-settling agent.

[0050] The chemical composition of the ceramic glaze, by weight percentage, includes: 50% SiO2, 21% Al2O3, 8% CaO, 3% MgO, 2% K2O, 3% Na2O, 9% BaO, 2% ZnO, 0.01-0.1% SrO and 0.01-0.1% Fe2O3.

[0051] A method for preparing a water-based digital glaze includes the following steps: (1) Mix a portion of waterborne polyurethane (50%), isopropanol, 1,2-propanediol and deionized water, as well as rheology modifiers, defoamers, preservatives, antisettling agents and waterborne dispersants, and perform the first grinding at a speed of 1500 rpm. (2) After adding the ceramic glaze, the mixture is ground a second time at a speed of 2500 rpm until the particle size distribution of the slurry is D50=0.5-0.9μm and D97=1-2μm. Finally, the viscosity of the ground slurry is adjusted to 20-30 mPa·s (25℃) with the remaining waterborne polyurethane, isopropanol, 1,2-propanediol and deionized water. After filtration, the waterborne digital glaze of this embodiment is obtained.

[0052] Example 3 An aqueous dispersant, characterized in that its raw material components, by weight, include: 35 parts acrylic acid, 35 parts acrylamide, 35 parts isobornyl methacrylate, 2 parts ammonium persulfate, 100 parts isopropanol, 100 parts deionized water, 1 part hydroquinone monomethyl ether, 3.5 parts dodecyl mercaptan, and 1 part triethanolamine.

[0053] A method for preparing an aqueous dispersant includes the following steps: (1) Add acrylic acid, acrylamide and isobornyl methacrylate to a beaker, and add half of the isopropanol, deionized water, dodecyl mercaptan, hydroquinone monomethyl ether and triethanolamine in sequence. Stir at 300 rpm for 30 min until the monomer is completely dissolved to obtain monomer premix. (2) Transfer the monomer premix to a constant-pressure dropping funnel, then add the remaining isopropanol and deionized water to the reactor, start mechanical stirring, purge the air in the reactor with nitrogen for 30 min, and simultaneously start a constant-temperature water bath to preheat the solvent. Dissolve ammonium persulfate in deionized water to prepare an 8% initiator solution. When the temperature in the reactor stabilizes at 70℃, start adding the monomer premix at a rate of 40 g / h over 3 hours; after adding for 5 min, add the initiator solution simultaneously at a rate of 10 g / h over 3 hours to ensure that the free radicals and monomers are in excess. During the adding stage, raise the temperature to 80-82℃, increase the stirring speed to 450 rpm, and maintain the nitrogen flow rate at 0.2 L / min. After the addition is complete, raise the temperature to 85℃ and continue the reaction for 1 hour to quickly consume the residual monomer through high temperature. After the reaction is complete, lower the temperature to 45℃, slowly add 25% ammonia to adjust the pH to 7.5, and stir for 30 min. The solution was desolventized at 65°C until the solid content was 40±2%; it was then filtered through a 300-mesh filter cloth to obtain a light brown transparent liquid, which is the aqueous dispersant of this embodiment. The weight average molecular weight of the aqueous dispersant is 7000.

[0054] A water-based digital glaze ink, the raw material components of which, by weight, include: 45 parts ceramic glaze, 15 parts isopropanol, 15 parts 1,2-propanediol, 30 parts deionized water, 10 parts water-based dispersant (in this embodiment), 8 parts water-based acrylic resin, 0.2 parts rheology modifier, 0.1 parts defoamer, 0.3 parts preservative, and 3 parts anti-settling agent.

[0055] The chemical composition of the ceramic glaze, by weight percentage, includes: 50% SiO2, 21% Al2O3, 8% CaO, 3% MgO, 2% K2O, 3% Na2O, 9% BaO, 2% ZnO, 0.01-0.1% SrO, and 0.01-0.1% Fe2O3.

[0056] A method for preparing a water-based digital glaze includes the following steps: (1) Mix a portion of waterborne polyurethane (50%), isopropanol, 1,2-propanediol and deionized water, as well as rheology modifiers, defoamers, preservatives, antisettling agents and waterborne dispersants, and perform the first grinding at a speed of 1500 rpm. (2) After adding the ceramic glaze, the mixture is ground a second time at a speed of 2500 rpm until the particle size distribution of the slurry is D50=0.5-0.9μm and D97=1-2μm. Finally, the viscosity of the ground slurry is adjusted to 20-30 mPa·s (25℃) with the remaining waterborne polyurethane, isopropanol, 1,2-propanediol and deionized water. After filtration, the waterborne digital glaze of this embodiment is obtained.

[0057] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in the different raw material components of the water-based digital glaze ink. Comparative Example 1 uses an equal amount of sodium polyacrylate to replace the water-based dispersant in Example 1.

[0058] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the raw material components of the aqueous dispersant are different. Comparative Example 2 uses an equal amount of glycerol monomethacrylate to replace isobornyl methacrylate in Example 1.

[0059] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the raw material components of the aqueous dispersant are different. Comparative Example 3 uses an equal amount of butyl acrylate (BA) to replace isobornyl methacrylate in Example 1.

[0060] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the raw material components of the aqueous dispersant are different. The aqueous dispersant of Comparative Example 4 does not contain acrylic acid.

[0061] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the raw material components of the aqueous dispersant are different. The aqueous dispersant of Comparative Example 5 does not contain acrylamide.

[0062] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the raw material components of the water-based digital glaze ink are different. Comparative Example 6 uses an equal amount of water-based acid alcohol resin to replace the water-based polyurethane of Example 1.

[0063] Performance testing The performance of the water-based digital glaze ink samples prepared in Examples 1-3 and Comparative Examples 1-6 was tested. Viscosity was measured according to standard GB / T 2794-2013 using a BROONFEI-ASTCC instrument at room temperature, with a shear rate of 400 s⁻¹. -1Specific gravity was tested according to standard GB / T 1033.1-2008 using the falling ball method; surface tension was tested according to standard GB / T 22237-2008 at room temperature; sedimentation rate was tested according to the international standard ISO 20379:2018, under the following conditions: after standing in a constant temperature oven at 70±2℃ for 7 days, the volume of the supernatant V1 was read, and the sedimentation rate was calculated as (40-V1) / 40×100%.

[0064] Meanwhile, water-based digital glaze ink samples were continuously printed for 3 hours, and the printhead clogging was recorded.

[0065] The test results are shown in Table 1.

[0066] Table 1:

[0067] As shown in Table 1, the water-based digital glaze inks prepared in Examples 1-3 all have good anti-settling properties, achieving a sedimentation rate of 2.7-4.9% after 7 days and 6.3-7.9% after 15 days at 70±2℃. They also have good storage stability and do not clog the printhead during continuous printing.

[0068] Compared to Example 1, Comparative Example 1, using sodium polyacrylate as the aqueous dispersant for the ink, while maintaining a reasonably good dispersion state in the short term, showed a significantly faster sedimentation rate. The core reason is that the anti-settling mechanism of sodium polyacrylate relies solely on charge adsorption and electrostatic repulsion of the double layer. This mechanism lacks long-term effectiveness in maintaining the stability of the dispersion system and cannot meet the stability requirements for long-term storage and use of water-based digital glazes.

[0069] Compared with Example 1, Comparative Example 2 uses glycerol monomethacrylate instead of IBOMA to prepare an aqueous dispersant. Since glycerol monomethacrylate does not have the steric hindrance of the IBOMA molecular structure, it cannot form a steric barrier on the surface of the glaze particles, and therefore the dispersing performance is significantly reduced.

[0070] Comparative Example 3, compared to Example 1, used BA instead of IBOMA to prepare the aqueous dispersant. As shown in Table 1, the system almost completely precipitated after 15 days of standing. This phenomenon clearly demonstrates that the introduction of BA not only failed to positively improve the anti-settling effect of the aqueous digital glaze, but also, due to its weak steric hindrance effect from its one-dimensional molecular chain structure, could not effectively inhibit the agglomeration and sedimentation of glaze particles, leading to a sharp decrease in system stability.

[0071] Compared to Example 1, Comparative Example 4 lacks acrylic acid components in its aqueous dispersant preparation materials. This absence directly causes the dispersant to lose its core functions of charge adsorption and double-layer electrostatic repulsion. These functions are crucial for the dispersant to anchor glaze particles. The lack of acrylic acid directly results in the dispersant failing to effectively bind with the glaze particles, ultimately leading to unstable dispersion of the glaze particles and severe agglomeration and sedimentation in the system.

[0072] Compared to Example 1, Comparative Example 5 did not contain acrylamide in its raw materials, resulting in insufficient hydrophilic groups in the dispersant molecules and a severe lack of hydrophilicity. Since the water-based digital glaze system is an aqueous environment, the dispersant with insufficient hydrophilicity cannot fully dissolve and spread in the aqueous phase, failing to achieve effective compatibility with the glaze particles and the aqueous system, ultimately preventing stable dispersion of the water-based digital glaze.

[0073] Comparative Example 6, compared to Example 1, used a waterborne alkyd resin to replace the waterborne polyurethane in the ink. The results showed that this replacement solution could not meet the requirements for waterborne digital glaze inks. The reason for this is that alkyd resins typically have a high molecular weight, which leads to an abnormally high system viscosity and imparts excessive thixotropy to the system, thus compromising the key printing compatibility properties required for waterborne digital glaze inks, such as low viscosity and good flowability.

[0074] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. An aqueous dispersant, characterized in that, Its raw material components, by weight, include: 35-40 parts of acrylic monomers; 25-35 parts of amide monomers; 30-35 parts of isobornyl methacrylate; 1-3 parts initiator; 100-300 parts of alcohol-water mixed solvent; 0.5-1.5 parts of triethanolamine.

2. The aqueous dispersant according to claim 1, characterized in that, The acrylic monomer is selected from at least one of acrylic acid and methyl methacrylate; And / or, the amide monomer is selected from at least one of acrylamide and N-hydroxyethylacrylamide; And / or, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

3. The aqueous dispersant according to claim 1 or 2, characterized in that, The alcohol-water mixed solvent includes isopropanol and water, and the mass ratio of isopropanol to water is (0.5-1.5):

1.

4. The aqueous dispersant according to claim 1, characterized in that, Its raw material components, by weight, also include 0.5-1.5 parts hydroquinone monomethyl ether and / or 2-5 parts dodecyl mercaptan.

5. A method for preparing an aqueous dispersant as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Dissolve acrylic monomers, amide monomers, isobornyl methacrylate and triethanolamine in a partially alcohol-water mixed solvent to prepare a monomer premix; (2) Add the remaining alcohol-water mixed solvent to the reaction vessel, purge with nitrogen, heat for the first time, and then add the monomer premixed liquid dropwise; heat for the second time, and then add the initiator dropwise to carry out the reaction and obtain the aqueous dispersant.

6. The method for preparing the aqueous dispersant according to claim 5, characterized in that, In step (2), the temperature of the first heating is 70-75℃; and / or the temperature of the second heating is 80-85℃.

7. A water-based digital enamel ink, characterized in that, Its raw material components include the aqueous dispersant as described in any one of claims 1-4.

8. The water-based digital enamel ink according to claim 7, characterized in that, Its raw material components, by weight, include: 35-45 parts of ceramic glaze; 10-30 parts organic solvent; 10-30 parts water; 3-10 parts of aqueous dispersant; 2-8 parts of water-based resin; Additives: 0.3-4 parts.

9. The water-based digital enamel ink according to claim 8, characterized in that, The waterborne resin is selected from waterborne polyurethane resin and / or waterborne acrylic resin.

10. An inkjet-printed ceramic tile, characterized in that, It includes an inkjet-printed layer, which is formed by inkjet printing with the water-based digital glaze ink as described in any one of claims 7-9.

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