A high-adhesion UV-curable ink and its preparation method

Abstract

This invention discloses a high-adhesion UV-curable ink and its preparation method, belonging to the field of novel ink technology. The invention involves mixing and stirring hyperbranched polyester acrylate, aliphatic polyurethane acrylate, reactive diluent monomers, and soluble colorants under light-protected, dry nitrogen conditions. Triethyl orthoformate is then added and stirred, while low-boiling byproducts are removed under vacuum. After cooling, a blocked silane coupling agent and a multi-coordinated zirconate coupling agent containing pyrophosphate oxy groups are added sequentially and stirred until homogeneous. A photoinitiator system, a NOR-type hindered amine light stabilizer, and additives are then added and stirred until homogeneous under light-protected conditions. Finally, the mixture is filtered and filled under nitrogen protection to obtain the high-adhesion UV-curable ink. This ink can be directly used in UV inkjet printers and other equipment, achieving high adhesion and long-term storage stability on substrates such as glass.

Description

Technical Field

[0001] This invention relates to the field of novel ink technology, specifically to a high-adhesion UV-curable ink and its preparation method. Background Technology

[0002] Currently, the problem of insufficient adhesion of UV-curable inkjet inks to non-absorbent substrates such as glass, metal, ceramics, and some plastics has not been fundamentally solved. Existing technologies mainly improve adhesion by adding common silane coupling agents, phosphate ester adhesion promoters, or using primer pretreatment. However, these methods can lead to decreased ink storage stability or increased process complexity, making it difficult to strike a balance between the convenience of single-component, ready-to-use inks and long-term storage stability.

[0003] To address the aforementioned issues, CN120272057A discloses a low-migration UV inkjet ink and its preparation method. This method improves crosslinking density through the synergistic effect of dynamically crosslinked polyurethane acrylate oligomers and palmitic acid-modified silica. However, it relies on the dynamic exchange of disulfide bonds and the physical filling of silica particles to restrict molecular migration, failing to solve the problem of chemical anchoring on highly polar substrates such as glass and metals. Furthermore, silica particles may face sedimentation risks during long-term storage, and their adhesion to inorganic substrates is unknown. CN121450160A discloses a water-based UV-curable inkjet ink and its preparation method. This method enhances adhesion to non-absorbent substrates by introducing rosin-based tackifying monomers and utilizes the affinity of hydrogenated phenanthrene ring structures for the substrate. However, because it is a water-based system and relies on the physical tackification of rosin monomers rather than chemical bonding, the improvement in adhesion to metals and glass is limited. Moreover, this solution does not address the surface stickiness caused by oxygen inhibition during UV curing, nor does it address the stability control of the active component during single-component storage.

[0004] In summary, existing technologies still struggle to simultaneously achieve the goals of single-component, ready-to-use, long-term non-gelling storage and strong chemical anchoring to various substrates such as glass, metal, and plastic without substrate pretreatment. Therefore, there is an urgent need to develop a high-adhesion UV-curable ink system that integrates closed-cell silane covalent anchoring, multi-coordinated zirconate surface contact anchoring, and liquid chemical dehydration. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a high-adhesion UV-curable ink and its preparation method. The invention involves mixing and stirring hyperbranched polyester acrylate, aliphatic polyurethane acrylate, reactive diluent monomers, and soluble colorants under light-protected, dry nitrogen conditions. Triethyl orthoformate is then added and stirred, while low-boiling byproducts are removed under vacuum. After cooling, a blocked silane coupling agent and a multi-coordinated zirconate coupling agent containing pyrophosphate oxy groups are added sequentially and stirred until homogeneous. A photoinitiator system, a NOR-type hindered amine light stabilizer, and additives are then added and stirred until homogeneous under light-protected conditions. Finally, the mixture is filtered and filled under nitrogen protection to obtain the high-adhesion UV-curable ink, which can be directly used in UV inkjet printers and other equipment, achieving high adhesion and long-term storage stability on substrates such as glass.

[0006] This invention proposes a high-adhesion UV-curable ink, comprising the following raw materials in parts by weight: 15-30 parts of UV reactive resin, 3-6 parts of silane coupling agent, 0.6-2.5 parts of coupling agent containing zirconate ester center, pyrophosphate oxy coordination group and unsaturated group that can participate in free radical polymerization, 4-8 parts of photoinitiator system, 0.03-0.2 parts of NOR type hindered amine light stabilizer, 0.1-5 parts of soluble colorant and 0.1-2 parts of additives, with the remainder made up to 100 parts with reactive diluent monomer.

[0007] This invention also proposes a method for preparing a high-adhesion UV-curable ink, the specific technical solution of which is as follows: Step 1: Add hyperbranched polyester acrylate, aliphatic polyurethane acrylate, and reactive diluent monomer to a reaction vessel protected from light and dry nitrogen. Then turn on the heating and stir at a constant temperature to completely dissolve the resin. Then add solvent black and increase the stirring speed to continue stirring until the solvent black is completely dissolved, resulting in a homogeneous colored liquid.

[0008] Step 2: While maintaining the system temperature, add triethyl orthoformate to the system, then continue stirring the reaction. Turn on the vacuum system to maintain a vacuum state inside the reactor and continue stirring. Then close the vacuum valve and stop heating, allowing the material inside the reactor to cool down naturally, resulting in a homogeneous mixture of resin, reactive diluent monomer, and colorant that has undergone dehydration treatment.

[0009] Step 3: Under nitrogen protection, add a closed silane coupling agent to the reactor, stir and react, then add a multi-coordinated zirconate coupling agent and continue the reaction. Photoinitiator 819, photoinitiator 184 and diphenyliodonium hexafluorophosphate are pre-dissolved in an active diluent monomer solvent and added to the reactor. Then, photoinitiator TPO-L, NOR-type hindered amine light stabilizer, wetting agent and polymerization inhibitor are added to the reactor and stirred under light-protected conditions.

[0010] Step 4: Under nitrogen protection throughout the process, the uniformly mixed ink is delivered to the filtration system via a metering pump. After passing through two layers of filter membranes for pre-filtration and fine filtration, the product is then filled into a sealed, light-proof container under nitrogen protection for storage, thus obtaining a high-adhesion UV-curable ink.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Triethyl orthoformate liquid dehydrating agent completely replaces solid particles such as molecular sieves and calcium oxide. Combined with vacuum post-processing to remove by-products, and through secondary filtration to remove as much solid foreign matter as possible from the finished ink, the all-liquid characteristics ensure that the ink remains homogeneous throughout the entire storage and use cycle. There is no risk of particle abrasion of the printhead inner wall, and there is no need to worry about printing defects caused by particle agglomeration.

[0012] 2. The formula excludes anchoring monomers that are prone to oxidation and discoloration. All components are colorless or light-colored and have a high resistance to yellowing. This avoids the risk of oxidation during storage and use due to oxygen in the air, light, or trace metal ions, which can generate quinone-based colored substances, causing white ink to yellow and transparent varnish to produce color differences.

[0013] 3. By actively removing low-boiling-point byproducts generated during the preparation process through vacuum heating, the content of low-boiling-point byproducts in the finished ink is reduced to a predetermined range, ensuring the consistency of ink droplet morphology when ejected from the nozzle, and avoiding viscosity drift caused by solvent evaporation during continuous high-speed printing.

[0014] 4. Through the dual mechanisms of silane covalent anchoring and zirconate multi-tooth coordination anchoring, combined with the low-shrinkage network of hyperbranched resin and the stress-relieving effect of flexible polyurethane segments, a single ink can be applied to a variety of common industrial substrates, achieving universal adhesion of a single ink to a variety of substrates. Attached Figure Description

[0015] Figure 1 The diagram shows the printhead's printout failure state during printing of the examples and comparative samples. Figure 2 The images show ink droplet flight patterns captured by a high-speed camera during the printing of the examples and comparative samples. Detailed Implementation

[0016] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0017] This invention proposes a method for preparing a high-adhesion UV-curable ink, the specific technical solution of which is as follows: 1. Constructing a homogeneous matrix and coloring The UV resin is heated and stirred in an inert atmosphere to dissolve it, and then the colorant is added and mixed thoroughly. The hyperbranched polyester acrylate and aliphatic polyurethane acrylate in the UV resin are the main film-forming components of the ink. The hyperbranched polyester acrylate has a three-dimensional spherical branched structure with less entanglement between molecular chains, exhibiting good fluidity even at lower temperatures. The aliphatic polyurethane acrylate, on the other hand, is a linear, flexible molecule that imparts toughness and impact resistance to the cured film. Since both resins are high-viscosity liquids or semi-solids at room temperature, reactive diluents are needed to reduce their viscosity and promote mixing. These reactive diluents not only act as solvents, but the acrylate double bonds in their molecules also participate in cross-linking reactions during subsequent UV curing.

[0018] During the reaction, heating and stirring are maintained to promote the diffusion rate between the resin and the monomer. Under the action of hydrogen bonds and van der Waals forces, the resin molecules gradually untangle and are uniformly dispersed in the monomer, forming an optically transparent homogeneous solution. At the same time, the entire reaction process needs to be carried out under light-protected conditions to prevent the unsaturated double bonds in the system from undergoing accidental polymerization under natural light before the photoinitiator is added. Dry nitrogen protection isolates oxygen and moisture in the air, avoiding potential interference from oxygen to subsequent free radical curing and damage to subsequent anchoring components from moisture.

[0019] 2. Liquid-phase dehydration and removal of low-boiling-point substances Triethyl orthoformate is added to the reaction to remove water, and low-boiling byproducts are removed under vacuum. Since triethyl orthoformate is a reactive ester compound, its three ethoxy groups are highly reactive and can undergo an irreversible chemical reaction with water molecules. The oxygen atom in the water molecule attacks the central carbon atom of the triethyl orthoformate, while the ethoxy group leaves as ethanol, producing ethyl formate and two molecules of ethanol. Because the new substance generated in the reaction is still a liquid with a boiling point much lower than the acrylate component in the system, it can be removed from the reaction system by vacuum extraction. Because the dehydrating agent itself is completely soluble in the organic phase, no solid particles are introduced during the process, and the reaction product is also a volatile liquid, there is no risk of printhead clogging or uneven ink composition.

[0020] During the reaction, the system temperature needs to be maintained to increase the reaction rate, ensuring that triethyl orthoformate comes into full contact with the trace water molecules dispersed in the resin-monomer mixture and reacts rapidly. When the vacuum system is activated to maintain a vacuum state inside the reactor, low-boiling-point substances immediately begin to vaporize at temperatures far below their atmospheric boiling points. A vacuum pump is used to carry these gaseous molecules out of the reactor, thus establishing a continuous concentration gradient in the liquid phase, promoting the continuous diffusion and escape of dissolved low-boiling-point products towards the gas-liquid interface. Vacuum treatment removes byproducts from the dehydration of triethyl orthoformate, along with water, creating the necessary conditions for the subsequent addition of moisture-sensitive blocked silanes and zirconate esters.

[0021] 3. Assembly of dual anchoring and photosensitive system Add the blocked silane coupling agent, zirconate ester, and pre-dissolved photoinitiator and additives sequentially, and mix thoroughly in the dark. In the molecular structure of the blocked silane coupling agent, the active silanol groups are temporarily protected by chemically blocked groups, making them stable in anhydrous or low-water environments and preventing self-condensation. When the subsequent ink is printed onto the substrate surface and exposed to UV irradiation, heat and photoacids will cause the blocked groups to be removed, releasing highly active silanols, which then condense with the hydroxyl groups on the substrate surface to form strong covalent bonds. The multi-coordinate zirconate ester coupling agent contains an unsaturated double bond at one end, which can be grafted onto the acrylate resin network during free radical polymerization. The other end contains a pyrophosphate oxydimethylphosphate polydentate coordination structure, which can form multi-site coordination bonds with metal ions or hydroxyl groups on the surface of substrates such as metals, glass, and ceramics, producing a strong anchoring effect similar to surface contact.

[0022] The photoinitiator is pre-dissolved using an active monomer diluent, allowing it to enter the system in a molecular state. Under subsequent UV irradiation, it can efficiently absorb UV light energy, thereby breaking down and generating free radicals, initiating the chain polymerization of acrylate double bonds. The NOR-type hindered amine light stabilizer in the additives inhibits surface oxygen polymerization by capturing peroxide free radicals generated during curing, without interfering with the photoinitiator's absorption of photons. The wetting agent reduces the surface tension of the ink, ensuring good spreading on the substrate surface, while the polymerization inhibitor p-hydroxyanisole prevents thermal polymerization of the system during storage and handling by capturing trace amounts of free radicals.

[0023] 4. Precision filtration and oxygen-free sealing After being filtered through two stages of filter membranes under nitrogen protection, the ink is filled and sealed in a light-proof environment to obtain the desired UV-curable ink. The mixed ink may still contain small amounts of insoluble matter, including undissolved additive particles, mechanical impurities introduced by equipment or the environment, and potentially formed micro-gel particles. Although these particulate impurities are extremely small, if they remain in the ink, they will clog the tiny nozzles of the piezoelectric printhead during subsequent inkjet printing, causing ink droplet deflection, broken lines, or even no ink output. Therefore, a two-stage filtration system is needed to remove these tiny particles. The first-stage filter membrane acts as a pre-filter, trapping larger particles to prevent them from quickly clogging the second-stage filter membrane. The second-stage, more precise filter membrane acts as a fine filter, thoroughly removing even smaller particles to ensure that printhead life is not affected.

[0024] Nitrogen protection is required throughout the filtration process because residual air may remain in the filter membrane and tubing. Air contains oxygen and moisture, and prolonged contact with the ink can cause oxidation or hydrolysis of sensitive components. Subsequently, the prepared ink is filled into light-proof, sealed containers under a nitrogen atmosphere to prevent the photoinitiator from slowly decomposing during storage and to prevent the entry of outside air. This results in a clean, high-adhesion UV-curable ink that can be directly used in UV inkjet printers.

[0025] The following specific embodiments and comparative examples further illustrate the high adhesion UV curing ink provided by the present invention. Table 1 shows the information of the various raw materials used in the embodiments.

[0026] Table 1 Raw Material Information Table

[0027] Example 1

[0028] S1: In a jacketed reactor equipped with a stirrer, heating and temperature control system, vacuum interface and nitrogen inlet, dry nitrogen is introduced into the reactor at a flow rate of 5 L / min for 15 min to replace the air inside the reactor. Then the exhaust valve is closed. Under light-proof conditions, 12 parts by mass of hyperbranched polyester acrylate, 7 parts by mass of aliphatic polyurethane acrylate, 14 parts by mass of isobornyl acrylate, 10 parts by mass of cyclotrimethylolpropane methyl acetal acrylate, 14 parts by mass of 2-phenoxyethyl acrylate, 8 parts by mass of tetrahydrofuran acrylate, 11 parts by mass of dipropylene glycol diacrylate and 9.6 parts by mass of 4-acryloylmorpholine are added to the reactor in sequence. Then the stirring is turned on at a speed of 400 rpm, and the heating is turned on at a heating rate of 2℃ / min to raise the temperature inside the reactor to 40℃. After reaching 40℃, the temperature is kept constant and stirred for 30 min. Then 2 parts by mass of solvent black 27 are added to the reactor, the stirring speed is increased to 1000 rpm and stirring is continued for 60 min to obtain a homogeneous black transparent liquid system.

[0029] S2: Maintain the temperature of the system inside the reactor at 40℃, add 0.8 parts by mass of triethyl orthoformate into the reactor while stirring, adjust the speed to 500 rpm, continue stirring for 30 min, then turn on the vacuum system to reduce the pressure inside the reactor to -0.095 MPa at a pressure reduction rate of -0.01 MPa / min, maintain the vacuum degree and continue stirring for 60 min, then close the vacuum valve and stop heating, adjust the speed to 200 rpm and allow the material to cool naturally to 30℃ to obtain a homogeneous mixture that has completed the dehydration treatment.

[0030] S3: Under nitrogen protection and light-proof conditions in the reactor, add 3.5 parts by weight of vinyltributanone oxime silane and 0.8 parts by weight of 3-(1,3-dimethylbutenyl)aminopropyltriethoxysilane sequentially to the reactor. After each silane is added, stir at 400 rpm for 10 min. Then add 1.0 part by weight of polycoordinated zirconate NZ38 containing pyrophosphate acyloxy group and continue stirring for 15 min. Add an additional 1.0 part by weight of 2-phenoxyethyl acrylate to the mixing cup, followed by 0.8 parts by weight of photoinitiator. 819, 1.0 parts by mass of photoinitiator 184, and 0.1 parts by mass of diphenyliodonium hexafluorophosphate were stirred at 300 rpm for 15 min at 40 °C to form a pre-dissolved solution. The pre-dissolved solution was added to a reaction vessel, followed by the sequential addition of 3.8 parts by mass of photoinitiator TPO-L, 0.08 parts by mass of NOR-type hindered amine light stabilizer HALS, 0.3 parts by mass of tetramethyldecynyl diol wetting agent, and 0.02 parts by mass of p-hydroxyanisole polymerization inhibitor. The mixture was stirred at 500 rpm in the dark for 40 min to obtain a black transparent coarse ink.

[0031] S4: Under nitrogen protection, connect the reactor outlet to a metering pump. Connect a 0.45μm PTFE membrane filter and a 0.22μm PTFE membrane filter in series at the pump outlet. Then turn on the metering pump and pump the coarse ink through the two-stage filters at a flow rate of 5L / h. Maintain nitrogen protection during the filtration process. Collect the filtered ink into an intermediate storage tank under nitrogen protection. After filtration, fill the ink into a high-barrier aluminum foil bag under a nitrogen atmosphere, leaving 5% of the volume at the top of the bag. Fill the bag with dry nitrogen for 10s and then seal it immediately to obtain the desired high-adhesion UV-curable ink.

[0032] Example 2

[0033] The difference from the preparation method in Example 1 is as follows: S1: The heating rate is 1℃ / min, the constant temperature stirring temperature is 35℃, and the stirring time is 20min; S2: Vacuum stirring time 45 min, then cool to 25℃; S3: After adding zirconate ester, stir for 10 min, the pre-dissolution temperature is 35℃, and the stirring time is 30 min in the dark. S4: The metering pump flow rate is 3L / h, and the other steps are the same.

[0034] Example 3

[0035] The difference from the preparation method in Example 1 is as follows: S1: The heating rate is 3℃ / min, the constant temperature stirring temperature is 45℃, and the stirring time is 40min; S2: Vacuum stirring time 90 min, then cool to 35℃; S3: After adding zirconate ester, stir for 20 minutes. The pre-dissolution temperature is 45℃, and the stirring time is 50 minutes in the dark. S4: The metering pump flow rate is 8L / h, and the other steps are the same.

[0036] Example 4

[0037] The difference from the preparation method in Example 1 is as follows: S1: 18.95 parts by weight of hyperbranched polyester acrylate, 11.05 parts by weight of aliphatic polyurethane acrylate, 9.4 parts by weight of isobornyl acrylate, 6.7 parts by weight of cyclotrimethylolpropane methyl acetal acrylate, 8.4 parts by weight of 2-phenoxyethyl acrylate, 6 parts by weight of tetrahydrofuran acrylate, 8 parts by weight of dipropylene glycol diacrylate, 7 parts by weight of 4-acryloylmorpholine, and 5 parts by weight of solvent black 27. S2: Add 1.5 parts by weight of triethyl orthoformate; S3: Add 4.9 parts by weight of vinyltributylone oxime silane, 1.1 parts by weight of 3-(1,3-dimethylbutenyl)aminopropyltriethoxysilane, 2.5 parts by weight of polycoordinate zirconate NZ38 with pyrophosphate acyloxy, 1.1 parts by weight of photoinitiator 819, 1.4 parts by weight of photoinitiator 184, 5.35 parts by weight of photoinitiator TPO-L, 0.15 parts by weight of diphenyliodonium hexafluorophosphate, 0.2 parts by weight of NOR-type hindered amine light stabilizer, 1.9 parts by weight of tetramethyldecynyl diol wetting agent, and 0.1 parts by weight of p-hydroxyanisole polymerization inhibitor. The remaining steps are the same.

[0038] Example 5

[0039] The difference from the preparation method in Example 1 is as follows: S1: Add 9.5 parts by weight of hyperbranched polyester acrylate, 5.5 parts by weight of aliphatic polyurethane acrylate, 16 parts by weight of isoborneol acrylate, 11.5 parts by weight of cyclotrimethylolpropane methyl acetal acrylate, 14.8 parts by weight of 2-phenoxyethyl acrylate, 10 parts by weight of tetrahydrofuran acrylate, 13 parts by weight of dipropylene glycol diacrylate, 11 parts by weight of 4-acryloylmorpholine, and 0.1 parts by weight of solvent black 27; S2: Add 0.3 parts by weight of triethyl orthoformate; S3: Add 2.5 parts by weight of vinyltributylone oxime silane, 0.5 parts by weight of 3-(1,3-dimethylbutenyl)aminopropyltriethoxysilane, 0.6 parts by weight of polycoordinate zirconate NZ38 with pyrophosphate acyloxy, 0.55 parts by weight of photoinitiator 819, 0.7 parts by weight of photoinitiator 184, 2.65 parts by weight of photoinitiator TPO-L, 0.1 parts by weight of diphenyliodonium hexafluorophosphate, 0.03 parts by weight of NOR-type hindered amine light stabilizer, 0.095 parts by weight of tetramethyldecynyl diol wetting agent, and 0.005 parts by weight of p-hydroxyanisole polymerization inhibitor. The remaining steps are the same.

[0040] Example 6

[0041] The difference from the preparation method in Example 1 is as follows: S1: Replace dipropylene glycol diacrylate with tripropylene glycol diacrylate, and the remaining steps are the same.

[0042] Example 7

[0043] The difference from the preparation method in Example 1 is as follows: S1: Replace dipropylene glycol diacrylate with hexanediol diacrylate, and the rest of the steps are the same.

[0044] Example 8

[0045] The difference from the preparation method in Example 1 is as follows: S3: Replace vinyltributanone oxime silane with phenyltributanone oxime silane, and the remaining steps are the same.

[0046] Example 9

[0047] The difference from the preparation method in Example 1 is as follows: S3: Replace vinyltributanone oxime silane with methyltributanone oxime silane, and the remaining steps are the same.

[0048] Comparative Example 1 The difference from the preparation method in Example 1 is as follows: S2: Replace triethyl orthoformate with 3A molecular sieve, and the rest of the steps are the same.

[0049] This comparative example prepares a UV-curable ink using a solid dehydrating agent instead of a liquid dehydrating agent.

[0050] Comparative Example 2 The difference from the preparation method in Example 1 is as follows: S1: Replace 2-phenoxyethyl acrylate with an equal part by weight of methacrylated dopamine, and the remaining steps are the same.

[0051] This comparative example prepares a UV-curable ink from monomers that are easily oxidized.

[0052] Comparative Example 3 The difference from the preparation method in Example 1 is as follows: S2: Without turning on the vacuum system, continue stirring at atmospheric pressure and then let it cool naturally. The remaining steps are the same.

[0053] This comparative preparation yields a UV-curable ink without vacuum removal of low-boiling-point byproducts.

[0054] Comparative Example 4 The difference from the preparation method in Example 1 is as follows: S3: Do not add a blocked silane coupling agent, but make up the difference with an equal part by mass of 2-phenoxyethyl acrylate, and the remaining steps are the same.

[0055] This comparative example prepares a UV-curable ink lacking silane covalent anchoring.

[0056] Comparative Example 5 The difference from the preparation method in Example 1 is as follows: S3: Do not add NZ38, a multicoordinate zirconate containing pyrophosphate oxy groups, but make up the difference with an equal mass of 2-phenoxyethyl acrylate. All other steps are the same.

[0057] This comparative example prepares a UV-curable ink lacking zirconate ester multidentate coordination anchoring.

[0058] Comparative Example 6 The difference from the preparation method in Example 1 is as follows: S1: Replace the hyperbranched polyester acrylate with the same amount of ordinary linear difunctional polyester acrylate, and the remaining steps are the same.

[0059] This comparative example shows a UV-curable ink prepared by replacing hyperbranched resin with ordinary linear resin.

[0060] Experimental Example 1 The UV-curable inks prepared in Examples 1-9 and Comparative Examples 1-6 were coated onto the surface of a glass slide using a wire rod coater, with a film thickness of 15 μm. The coating was then applied under a 365 nm LED-UV lamp at a speed of 800 mJ / cm². 2 Energy curing is used to form a cured ink film. Then, according to GB / T9286-2021 "Cross-cut Test for Paints and Varnishes", a cross-cut grid is drawn on the cured ink film using a 1mm spacing cross-cut knife, with the cut depth penetrating to the glass substrate. After removing debris with a soft brush, adhesive tape with an adhesion strength of 10±1N / 25mm is applied to the grid area. The area is repeatedly compacted with a rubber roller for 100s. Then, the tape is peeled off at a uniform speed within 0.5~1.0s in a direction perpendicular to the ink film surface. The area of ​​coating peeling off within the grid area is graded according to the standard: Grade 0: The cut edges are completely smooth with no peeling off; Grade 1: A small amount of coating peeling off at the intersection of the cuts, but the peeling area does not exceed 5%; Grade 2: The peeling area is greater than 5% but not more than 15%; Grade 3: The peeling area is greater than 15% but not more than 35%; Grade 4: The peeling area is greater than 35% but not more than 65%; Grade 5: The peeling area exceeds 65%.

[0061] According to GB / T 24148.9-2014 "Plastic Unsaturated Polyester Resins (UP-R) Part 9: Determination of Total Volume Shrinkage", 50 mL of each of the UV-curable inks prepared in Examples 1-9 and Comparative Examples 1-6 were taken, and their density ρ1 at 25°C was accurately measured using a hydrometer. The inks were then coated onto the surface of glass slides using a wire rod coater, with a film thickness of 15 μm. The films were then cured under a 365 nm LED-UV lamp at a pressure of 800 mJ / cm². 2 Energy curing is used to form a cured ink film. After complete curing, 1-2g of ink block is removed from the ink film, and the density ρ2 of the cured ink film is measured by the immersion method. The ink curing volume shrinkage rate is calculated according to the formula = [(ρ2-ρ1) / ρ2] ×100%.

[0062] Table 2 Curing properties of ink samples in the experimental group Example 1 Level 0 4.2 Example 2 Level 0 4.6 Example 3 Level 0 4.8 Example 4 Level 0 5.1 Example 5 Level 0 5.2 Example 6 Level 0 4.7 Example 7 Level 0 4.9 Example 8 Level 0 4.3 Example 9 Level 0 4.4 Comparative Example 1 Level 1 6.8 Comparative Example 2 Level 2 6.3 Comparative Example 3 Level 1 6.7 Comparative Example 4 Level 4 6.6 Comparative Example 5 Level 3 6.9 Comparative Example 6 Level 2 8.2 As can be seen from Table 2, the adhesion of the sample from the examples is better than that of the comparative examples, and the curing volume shrinkage rate is lower than that of the comparative examples. This indicates that the present invention can effectively improve the adhesion strength of multiple substrates and suppress curing internal stress through the synergistic effect of closed silane and zirconate dual chemical anchoring, liquid dehydration and low shrinkage resin network.

[0063] In Comparative Example 1, a solid dehydrating agent was used to replace triethyl orthoformate. The solid particles settled and agglomerated, clogging the nozzle and causing spraying defects. At the same time, the residual moisture caused the closed silane to hydrolyze and condense prematurely, the anchoring sites failed, the particles themselves destroyed the continuous phase of the ink film, the interfacial bonding force decreased, and the stress concentration was aggravated during shrinkage.

[0064] In Comparative Example 2, conventional acrylate monomers were replaced with methacrylated dopamine. During storage and curing, the catechol structure of the catechol was oxidized to generate quinone colored substances, which interfered with free radical polymerization. The crosslinking density of the ink film was insufficient, the cohesive force was weakened, and the oxidized by-products plasticized the network structure, making it difficult to effectively control curing shrinkage.

[0065] In Comparative Example 3, the low-boiling byproducts were not removed by vacuum. The ethanol and ethyl formate generated from the reaction of triethyl orthoformate remained in the system. During curing, they were violently vaporized, forming microbubble defects that damaged the density of the ink film. At the same time, the bubbles reduced the effective cross-linking volume of the cured film, resulting in an artificially high shrinkage rate.

[0066] Comparative Example 4 did not add a blocked silane coupling agent and relied solely on zirconate ester multidentate coordination anchoring. It lacked covalent condensation with hydroxyl-containing substrates, and the coordination bonds were easily hydrolyzed under humid and hot conditions. Furthermore, it lacked rigid support for silane crosslinking points, and the low shrinkage advantage of hyperbranched resins could not be fully utilized.

[0067] Comparative Example 5, without the addition of multi-coordinated zirconate containing pyrophosphate oxy groups, relies solely on closed-type silane covalent anchoring. This results in insufficient anchoring force for substrates such as metals and ceramics, where coordination is the primary function. The network formed by silane condensation is brittle, lacks the multi-toothed bridging of zirconate, and the curing internal stress is difficult to dissipate effectively.

[0068] Comparative Example 6 replaced hyperbranched polyester acrylate with ordinary linear bifunctional polyester acrylate. During the curing of linear resin, the molecular chains were tightly packed, resulting in a significant increase in volume shrinkage. The internal stress generated by the high shrinkage caused the ink film to peel off from the substrate surface, which confirmed the key role of the three-dimensional spherical structure of hyperbranched resin in reducing shrinkage and ensuring adhesion.

[0069] Experimental Example 2 According to GB / T 6753.3-1986 "Test Method for Storage Stability of Coatings", the UV-curable inks prepared in Examples 1-9 and Comparative Examples 1-6 and sealed in high-barrier aluminum foil bags were used. Their viscosity η1 was measured at 45°C. Each experimental group of inks was stored in a constant temperature drying oven at 60°C for 14 days. Samples were taken and their viscosity η2 was measured at 45°C using a rotational viscometer. The viscosity change rate was calculated according to the formula = [(η2-η1) / η1] ×100%.

[0070] The UV-curable inks prepared in Examples 1-9 and Comparative Examples 1-6 were injected into ink cartridges and equipped with Konica printheads. The inks were continuously printed for 8 hours at a printhead temperature of 45°C and an ejection voltage of 12V. The printed pattern was set as a full-width dense barcode or a full-page grid pattern. After printing was completed, the number of missing nozzles was counted, and the missing rate was calculated according to the formula: (number of missing nozzles / total number of nozzles) × 100%.

[0071] Table 3 Storage stability of the experimental group inks Example 1 8.22 8.41 2.13 0.02 Example 2 8.81 9.03 2.47 0.04 Example 3 8.73 8.96 2.68 0.07 Example 4 9.84 10.14 3.01 0.11 Example 5 9.48 9.79 3.22 0.13 Example 6 10.07 10.33 2.56 0.06 Example 7 8.79 9.04 2.79 0.09 Example 8 8.96 9.16 2.18 0.06 Example 9 9.64 9.86 2.31 0.05 Comparative Example 1 11.88 12.88 8.42 12.45 Comparative Example 2 10.23 10.92 6.71 6.78 Comparative Example 3 13.15 14.09 7.13 4.56 Comparative Example 4 11.02 11.52 4.52 1.87 Comparative Example 5 11.31 11.92 5.18 3.14 Comparative Example 6 14.24 15.37 7.94 8.93 From Table 3 and Figure 1 As can be seen from the results, the initial viscosity of the sample in the example is lower, the viscosity increase after storage is smaller, the viscosity change rate is lower, and the ink loss rate is lower, indicating that the design of the present invention can effectively reduce the initial viscosity of the ink, suppress the viscosity increase during storage, and ensure the smoothness of printing.

[0072] In Comparative Example 1, solid molecular sieves were used to replace triethyl orthoformate. The solid particles became ineffective after absorbing water and becoming saturated during storage. The residual moisture caused the closed silane to slowly hydrolyze and condense, resulting in a significant increase in the viscosity of the system. The molecular sieve particles settled and agglomerated, clogging the nozzles and causing a significant increase in the spray failure rate. At the same time, the initial viscosity of the particles themselves increased.

[0073] Comparative Example 2 replaced conventional acrylate monomers with methacrylated dopamine. Its catechol structure is easily oxidized and self-polymerized during storage to generate high molecular weight products, which gradually increases the viscosity. Oxidation byproducts and unreacted monomers further polymerize in the nozzle heating zone to form a gel, clogging the nozzle. At the same time, the highly polar dopamine monomer increases the initial viscosity of the sample.

[0074] In Comparative Example 3, no vacuum removal of low-boiling byproducts was performed. The ethanol and ethyl formate produced by the reaction of triethyl orthoformate remained in the ink. These low-boiling substances volatilized violently at the printhead operating temperature, generating bubbles that interfered with the ink droplet ejection pattern and caused droplet loss. Furthermore, the continuous escape of low-boiling substances caused the component ratio to shift, and the viscosity change was uncontrollable. The initial viscosity was higher due to the presence of low-boiling substances.

[0075] Comparative Example 4 did not add a blocked silane coupling agent, and the system contained only zirconate. Zirconate is sensitive to moisture. In the absence of silane synergy, some hydrolysis products participated in cross-linking, causing a slight increase in viscosity. Moreover, these hydrolysis products will accumulate during use, causing blockage of the nozzle filter and resulting in a high rate of spray failure.

[0076] Comparative Example 5 did not add zirconate ester and relied solely on blocked silane. The tendency of silane self-condensation still occurred slowly during long-term storage, leading to an increase in viscosity. The silane hydrolysis products were small molecule alcohols that did not form solid particles. The loss of spray rate was higher than that of the example. The initial viscosity was higher due to the lack of viscosity-reducing assistance from zirconate ester.

[0077] Comparative Example 6 replaced the hyperbranched resin with ordinary linear resin. The linear resin molecular chains are more prone to physical entanglement and aggregation during storage, which greatly increases the initial viscosity and viscosity change rate. The linear resin has poor dispersion stability for pigments and additives and is prone to forming soft agglomerates. During printing, the agglomerates get stuck at the nozzle, resulting in a significant increase in the spray failure rate.

[0078] Experimental Example 3 According to GB / T 22237-2008 "Determination of Surface Tension of Surfactants", the UV-curable inks prepared in Examples 1-9 and Comparative Examples 1-6 were sealed and kept in a constant temperature water bath at 45°C for 30 minutes. Then, using a surface tension meter, the cleaned and ignited platinum plate was hung on the balance arm, the sample stage was raised so that the platinum plate was immersed in the liquid surface about 1 mm, and then the sample stage was lowered to remove the liquid surface. The maximum tensile force value was recorded and converted into surface tension.

[0079] According to GB / T 44378-2024 "Methods for Counting and Classifying the Size of Insulating Liquid Particles", the membrane filtration-microscopy counting method was adopted. A 0.22 μm PTFE filter membrane was taken in the clean bench, pre-wetted, and assembled into a vacuum filtration device. 100 mL of each of the UV-curable inks prepared in Examples 1-9 and Comparative Examples 1-6 were filtered at a flow rate of about 10 mL / min. The filter membrane was rinsed with anhydrous ethanol and dried at 45°C for 30 min. The filter membrane was placed on a glass slide, and then 10 sites were observed under a microscope of 200-400x magnification. The number of particles not less than 5 μm was counted, and the particle concentration per unit volume was calculated.

[0080] Table 4 Surface tension and filtration performance of experimental group samples Example 1 29.2 16 Example 2 29.8 21 Example 3 30.1 24 Example 4 30.6 32 Example 5 29.6 34 Example 6 30.2 23 Example 7 30.3 27 Example 8 29.9 18 Example 9 29.5 22 Comparative Example 1 32.6 186 Comparative Example 2 27.8 94 Comparative Example 3 28.9 78 Comparative Example 4 31.2 46 Comparative Example 5 30.8 52 Comparative Example 6 27.2 116 As can be seen from Table 4, the surface tension of the sample in the example is within a suitable range for inkjet printing, and the particle concentration per unit volume is significantly lower than that in the comparative example. This indicates that the present invention, through liquid dehydration of triethyl orthoformate, all-liquid formulation design and two-stage precision filtration, can effectively avoid the introduction of solid impurities and maintain stable surface wetting performance of the ink.

[0081] In Comparative Example 1, solid molecular sieves were used to replace triethyl orthoformate. The molecular sieve particles were difficult to completely remove during the grinding and dispersion process, and some micron-sized fragments remained in the ink, resulting in a significant increase in particle concentration after filtration. At the same time, the surface polarity of the molecular sieves changed after absorbing moisture, causing the surface tension of the ink to rise beyond the suitable range of the printhead, which affected the stability of ink droplet ejection.

[0082] Comparative Example 2 replaced the conventional acrylate monomer with methacrylated dopamine. Its catechol structure is easily oxidized to generate colored quinones. Some of these oxidation products exist in the form of colloidal particles, which cannot be completely retained by the ultrafiltration membrane, resulting in an increase in particle concentration. At the same time, the oxidation byproducts have surface activity, which significantly reduces the surface tension of the ink, making the wetting too strong and causing ink droplet diffusion.

[0083] In Comparative Example 3, no vacuum removal of low-boiling byproducts was performed. The ethanol and ethyl formate generated from the reaction of triethyl orthoformate remained in the ink. These low-boiling substances slowly evaporated during filtration and storage, causing a shift in the ink component ratio and a decrease in surface tension. At the same time, the evaporation of low-boiling substances may carry trace impurities to form aerosol particles, resulting in an increase in particle concentration after filtration.

[0084] Comparative Example 4 did not add a blocked silane coupling agent, and the system contained only zirconate. Zirconate is sensitive to moisture and partially hydrolyzes during storage to form insoluble zirconium hydrate particles. These small particles penetrate the filter membrane, causing the particle concentration to increase. At the same time, the hydrolysis products of zirconate change the interfacial properties and increase the surface tension.

[0085] Comparative Example 5 did not add multi-coordinated zirconate containing pyrophosphate oxy groups. Relying solely on blocked silanes, the silane self-condensation tendency formed nano-sized polysiloxane gel particles during long-term storage. Some of these particles penetrated the filter membrane, leading to an increase in particle concentration. At the same time, the silane condensation consumed the polar groups in the system, causing a slight increase in surface tension.

[0086] Comparative Example 6 replaced the hyperbranched resin with ordinary linear resin. Linear resin has poor dispersion stability for pigments and additives and is prone to forming soft agglomerates. These agglomerates partially deform and penetrate the filter membrane during filtration, resulting in a significant increase in particle concentration. At the same time, the uneven polarity distribution of linear resin leads to a decrease in ink surface tension and affects the wetting behavior of the printhead.

[0087] Experiment Example 4 Take 30-50 mL of ink samples prepared in the examples and comparative examples and place them in an aluminum foil bag. Equilibrate in a 45°C incubator for 30 min. Then, load them into individual ink cartridges. After loading, perform a 5 min low-frequency pre-spray to remove air from the ink supply tube. Then, select a representative nozzle that can be sprayed for droplet flight photography. The printhead is at 45°C, the spray voltage is 12V, and continuous printing lasts for 8 h. Immediately after 8 h, switch to a high-speed camera for photography. The shooting frame rate is 100,000-200,000 fps, and the shooting area is the flight area 1.5-2.0 mm below the nozzle exit. The shooting results are as follows. Figure 2 As shown.

[0088] from Figure 2 As can be seen, the ink prepared in Example 1 forms a continuous and symmetrical liquid column when ejected from the printhead. A single main droplet can be clearly seen, with a short tail filament appearing at around 50 μs. The tail filament breaks rapidly after 100-150 μs. During 200-400 μs, the main droplet is approximately spherical, with a basically vertical flight trajectory and no obvious satellite droplets. This indicates that the dehydration of triethyl orthoformate liquid, vacuum removal of low-boiling byproducts, and two-stage filtration together reduce the interference of bubbles, particles, and viscosity drift on the ejection process.

[0089] In Comparative Example 1, when 3A molecular sieve was used instead of triethyl orthoformate, the ink produced had a longer tail filament, a slight deviation in the spray direction, and localized small satellite droplets or intermittent incomplete spraying. When molecular sieve fragments or particles approached the nozzle, the main droplet became smaller, the spraying speed decreased, or occasional spray interruption occurred.

[0090] Comparative Example 2 introduces methacrylated dopamine. It can be seen that because this component is easily oxidized to form colored quinones or colloidal particles, microgels or local viscosity unevenness are formed near the nozzle. This causes irregular small droplets to appear when the main droplet breaks. Therefore, the droplet size of the sample is uneven, there are more satellite droplets, and the number of scattered points at the spray edge increases.

[0091] Comparative Example 3 did not undergo vacuum removal of low-boiling-point byproducts. Because the residues of low-boiling-point substances such as ethanol and methyl formate will volatilize and generate bubbles at the printhead operating temperature, they will interfere with the normal ejection pattern of ink droplets. This will cause fluctuations in the volume of the main droplet when the sample is ejected, and small bubbles or tiny scattered spots will appear around the droplet. Satellite droplets will be randomly distributed, and the flight trajectory will show obvious fluctuations.

[0092] Comparative Example 4 did not contain a blocked silane coupling agent, resulting in a slight decrease in spray stability. However, the main droplet could still be formed, the tail filament was slightly longer, and there were a few satellite droplets. The trajectory deviation was not particularly severe.

[0093] Comparative Example 5 does not contain multi-coordinated zirconate containing pyrophosphate oxy groups. The system is stable only by the blocked silane. Due to the tendency of silane self-condensation, the viscosity increases and nano-sized polysiloxane gel particles are formed, resulting in a decrease in the repeatability of the main droplet diameter and velocity. Small satellite droplets and slight jet deviation appear in the high-speed graph.

[0094] Comparative Example 6 replaced hyperbranched resin with ordinary linear bifunctional polyester acrylate. The linear resin molecular chain entanglement and soft agglomeration formed, which significantly increased the initial viscosity and viscosity after standing. This resulted in a slow jet breakage process, the liquid column could not quickly shrink into a single spherical main droplet, the tail filament was significantly elongated and the breakage was delayed, there were more satellite droplets, and even droplet tailing and trajectory oscillation occurred.

Claims

1. A high-adhesion UV-curable ink, characterized in that: The UV-curable ink is formulated from the following raw materials in parts by weight, totaling 100 parts by weight: 15-30 parts UV reactive resin, 3-6 parts silane coupling agent, 0.6-2.5 parts polycoordinate zirconate coupling agent containing pyrophosphate oxy group, 4-8 parts photoinitiator system, 0.03-0.2 parts NOR-type hindered amine light stabilizer, 0.1-5 parts soluble colorant, and 0.1-2 parts additives, with the remainder made up to 100 parts by reactive diluent monomer; the polycoordinate zirconate coupling agent containing pyrophosphate oxy group is a coupling agent that simultaneously contains a zirconate ester center, a pyrophosphate oxy group, and an unsaturated group that can participate in free radical polymerization.

2. The high-adhesion UV-curable ink according to claim 1, characterized in that: The UV-reactive resin is a hyperbranched polyester acrylate and an aliphatic polyurethane acrylate; the photoinitiation system is composed of a photoinitiator and functional additives, the photoinitiator includes photoinitiator 819, photoinitiator 184, and photoinitiator TPO-L, the functional additive is diphenyliodonium hexafluorophosphate; the additives include tetramethyldecynyl diol wetting agent and p-hydroxyanisole polymerization inhibitor.

3. A method for preparing a high-adhesion UV-curable ink according to any one of claims 1 to 2, characterized in that, It is prepared by the following steps: S1: Add hyperbranched polyester acrylate, aliphatic polyurethane acrylate and reactive diluent monomer to a reaction vessel protected from light and dry nitrogen. Then turn on the heating and stir at a constant temperature to completely dissolve the resin. Then add solvent black and increase the stirring speed to continue stirring until the solvent black is completely dissolved to obtain a uniform colored liquid. S2: While maintaining the system temperature, add triethyl orthoformate to the system, then continue stirring the reaction. Turn on the vacuum system to maintain a vacuum state in the reactor and continue stirring. Then close the vacuum valve and stop heating, allowing the material in the reactor to cool down naturally, to obtain a homogeneous mixture of resin, reactive diluent monomer and colorant that has completed dehydration treatment. S3: Under nitrogen protection, add silane coupling agent to the reactor, stir and react, then add multi-coordinate zirconate coupling agent and continue the reaction. Photoinitiator 819, photoinitiator 184 and diphenyliodonium hexafluorophosphate are pre-dissolved in an active diluent monomer solvent and added to the reactor. Then, photoinitiator TPO-L, NOR-type hindered amine light stabilizer, wetting agent and polymerization inhibitor are added to the reactor and stirred under light-protected conditions. S4: Under nitrogen protection throughout the process, the uniformly mixed ink is delivered to the filtration system through a metering pump. After passing through two layers of filter membranes for pre-filtration and fine filtration, the product is then filled into a sealed, light-proof container under nitrogen protection for storage, thus obtaining a high-adhesion UV-curable ink.

4. The method for preparing a high-adhesion UV-curable ink according to claim 3, characterized in that: The reactive diluent monomer S1 is composed of monofunctional acrylates and difunctional acrylates; the monofunctional acrylate is a combination of isobornyl acrylate, cyclotrimethylolpropane methyl acetal acrylate, 2-phenoxyethyl acrylate, tetrahydrofuran acrylate, and 4-acryloylmorpholine; the difunctional acrylate is one or more of dipropylene glycol diacrylate, tripropylene glycol diacrylate, and hexanediol diacrylate.

5. The method for preparing a high-adhesion UV-curable ink according to claim 3, characterized in that: The heating rate of S1 is 1~3℃ / min; the constant temperature stirring temperature is 35~45℃, and the stirring time is 20~40min.

6. The method for preparing a high-adhesion UV-curable ink according to claim 3, characterized in that: The amount of triethyl orthoformate added in S2 is 0.3~1.5 parts by weight.

7. The method for preparing a high-adhesion UV-curable ink according to claim 3, characterized in that: The continuous stirring time in S2 is 45~90 min; the natural cooling time is 25~35℃.

8. The method for preparing a high-adhesion UV-curable ink according to claim 4, characterized in that: The silane coupling agent S3 is a combination of blocked oxime silane and blocked amino silane. The blocked oxime silane is one or more of vinyltributanone oxime silane, methyltributanone oxime silane, and phenyltributanone oxime silane. The blocked amino silane is 3-(1,3-dimethylbutenyl)aminopropyltriethoxysilane. The mass ratio of the blocked oxime silane to the blocked amino silane is 4.4:

1.

9. The method for preparing a high-adhesion UV-curable ink according to claim 4, characterized in that: The reaction time in S3 is 10-20 min; the pre-dissolution temperature is 35-45℃; and the stirring reaction time is 30-50 min.

10. The method for preparing a high-adhesion UV-curable ink according to claim 4, characterized in that: The flow rate of the metering pump described in S4 is 3~8 L / h.

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