Environment-friendly uv ink and preparation method thereof

Abstract

This invention provides an environmentally friendly UV ink and its preparation method, belonging to the field of UV ink preparation technology. This application constructs a rigid bio-based spirocyclic acetal framework using vanillin / pentaerythritol. After solid acid catalytic dehydration and filtration, the water is removed to reduce acid residue side reactions. An excess of isocyanate is then used for end-capping to obtain a terminal isocyanate-based prepolymer, transforming the framework into a quantitatively functionalized polyurethane platform. Through bifunctional end-capping, the carbonyl-containing photosensitive structure and the hindered tertiary amine synergy are covalently locked. Intramolecular hydrogen abstraction / electron transfer efficiently generates active free radicals, reducing the migration sources of external small molecule initiators / amines. Simultaneously, acrylic double bonds are introduced to provide the main crosslinking sites. The fully esterified latent ionization fragment remains hydrophobic and water-resistant during use, and saponifies in an alkaline hydrothermal solution during recycling to generate carboxylate, promoting ink film swelling, fragmentation, and dispersion. These three factors synergistically achieve a unified approach of low migration compliance, stability during use, and triggering deinking during recycling.

Description

Technical Field

[0001] This invention belongs to the field of UV ink preparation technology, and relates to an environmentally friendly UV ink and its preparation method. Background Technology

[0002] UV-curable inks have been widely used in the printing and packaging industry due to their advantages such as fast curing speed, no volatile organic compound emissions, and low energy consumption. However, with increasingly stringent global requirements for food safety and the recycling of packaging waste, traditional UV inks are facing three major technological bottlenecks that urgently need to be overcome.

[0003] First, there's the challenge of deinking in waste paper recycling. Traditional UV inks, after curing, form a highly cross-linked network structure, similar to thermosetting plastics. This makes them difficult to separate from paper fibers during the flotation deinking process in paper mills, resulting in "dust spots" in recycled pulp and significantly reducing pulp quality. Existing technologies typically introduce hydrophilic carboxyl groups into the resin to improve alkali solubility and aid deinking. However, this introduces a fatal flaw: the ink also exhibits hydrophilicity in everyday use environments, leading to poor water resistance, easy moisture absorption, and stickiness in printed materials, failing to meet the requirements of cold chain packaging or high-humidity environments.

[0004] Secondly, UV inks typically rely on small-molecule photoinitiators to initiate polymerization. However, these small molecules often remain in the ink layer after curing and can easily migrate into food or packaging contents, posing food safety risks. Furthermore, to overcome oxygen inhibition during polymerization, small-molecule amine additives are often added to the formulation, which further increases the risks of odor and migration.

[0005] Finally, there is the performance limitation of bio-based materials. Currently, most bio-based UV resins on the market are modified from vegetable oils such as soybean oil or linseed oil. Their long fatty chain structure results in low hardness and poor wear resistance of the cured ink film, making it difficult to replace high-performance rigid resins based on fossil raw materials such as bisphenol A. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide an environmentally friendly UV ink and its preparation method. This application constructs a rigid bio-based spirocyclic acetal framework using vanillin and pentaerythritol, and employs solid acid catalysis to dehydrate and form a high-cohesive-energy intermediate. Subsequently, excess isocyanate end-capping yields an isocyanate-terminated prepolymer, making the framework a quantitatively functionalizable polyurethane platform. Furthermore, a carbonyl photosensitive group-tertiary amine covalently coupled hydrogen donor unit is introduced, utilizing intramolecular nearest-neighbor hydrogen abstraction / electron transfer to improve initiation efficiency, thereby achieving reliable curing and reducing migration sources with lower external initiator dosage; simultaneously, hydroxyethyl acrylate provides the main crosslinking sites. The fully esterified latent ionized fragment remains hydrophobic and water-resistant with low moisture absorption during use, and saponifies in an alkaline hydrothermal solution during recycling to generate carboxylate, promoting ink film swelling, fragmentation, dispersion, and deinking. The three elements work synergistically: the rigid framework ensures that the low molecular weight system still has membrane performance; the built-in synergistic mechanism reduces migration while expanding the solidification window; and latent ionization provides recycling drive without sacrificing water resistance. This achieves overall self-consistency in low migration compliance, service life stability, and recycling triggering.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing an environmentally friendly UV ink, the method comprising:

[0009] S1: Vanillin and pentaerythritol are mixed, toluene and a solid acid catalyst are added to obtain reaction solution A. The mixture is heated to remove water until the water content reaches more than 95% of the theoretical value. The mixture is then cooled, filtered, dehydrated under reduced pressure, and dehydrated to obtain a rigid spirocyclic acetal skeleton intermediate. Isophorone diisocyanate is mixed with the rigid spirocyclic acetal skeleton intermediate and an organic bismuth catalyst is added to obtain reaction solution B. The mixture is then reacted under a nitrogen atmosphere to obtain a terminal isocyanate prepolymer.

[0010] S2: 2-hydroxy-9H-thioxanth-9-one and epichlorohydrin were added to acetonitrile, potassium carbonate and potassium iodide were added to obtain reaction solution C. The reaction was stirred under nitrogen protection, and the solution was filtered off while hot. The solvent was recovered from the filtrate under reduced pressure and excess epichlorohydrin was removed to obtain an intermediate. The intermediate was mixed with diisopropylamine to obtain reaction solution D. The reaction was carried out and distilled under reduced pressure to obtain a bifunctional end-capping agent.

[0011] S3: A mixed end-capping agent is obtained by mixing a bifunctional end-capping agent, dimethyl malate, and hydroxyethyl acrylate; 2,6-di-tert-butyl-p-cresol and p-hydroxyanisole are added to the isocyanate-terminated prepolymer to obtain a pre-reaction solution; the mixed end-capping agent is added dropwise after heating under nitrogen protection to obtain reaction solution E; the reaction is carried out at the same temperature and then de-idered under reduced pressure to obtain a latent ionized bio-based photosensitive prepolymer;

[0012] S4: Mix latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isoborneol acrylate, silicone leveling agent, polymeric dispersant and free radical stabilizer, disperse at high speed and degas under vacuum to obtain a premix; add pigment to the premix, grind with a three-roll mill to obtain a mixture, add photoinitiator, stir at low speed, and filter to obtain environmentally friendly UV ink.

[0013] As a preferred technical solution of the present invention, in step S1, the molar ratio of vanillin to pentaerythritol is (2.0-2.2):1, for example, it can be 2.00:1, 2.02:1, 2.04:1, 2.06:1, 2.08:1, 2.10:1, 2.12:1, 2.14:1, 2.16:1, 2.18:1 or 2.20:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] In some optional embodiments, the amount of toluene fed is 30-50% of the total mass of vanillin and pentaerythritol, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48% or 50%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] The solid acid catalyst is any one of Amberlyst® 15, Amberlyst® 36, Dowex® 50WX, or Lewatit® K2620.

[0016] In some optional embodiments, the amount of the solid acid catalyst fed is 0.5-1.5% of the total mass of vanillin and pentaerythritol, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] In some optional embodiments, the reaction temperature of the reaction solution A is 108-113°C, for example, it can be 108.0°C, 108.5°C, 109.0°C, 109.5°C, 110.0°C, 110.5°C, 111.0°C, 111.5°C, 112.0°C, 112.5°C or 113.0°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] In some optional embodiments, the molar ratio of the isocyanate group of the isophorone diisocyanate to the hydroxyl group of the rigid spirocyclic acetal backbone intermediate is (2.0-2.5):1, for example, it can be 2.00:1, 2.05:1, 2.10:1, 2.15:1, 2.20:1, 2.25:1, 2.30:1, 2.35:1, 2.40:1, 2.45:1 or 2.50:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0019] In some optional embodiments, the amount of the organobismuth catalyst fed is 0.03-0.08% of the total mass of isophorone diisocyanate and rigid spirocyclic acetal skeleton, for example, it can be 0.030%, 0.035%, 0.040%, 0.045%, 0.050%, 0.055%, 0.060%, 0.065%, 0.070%, 0.075% or 0.080%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] The organic bismuth catalyst is bismuth neodecanoate or bismuth 2-ethylhexanoate.

[0021] In some optional embodiments, the reaction temperature of the reaction solution B is 65-75°C, for example, it can be 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C or 75°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the reaction time of the reaction solution B is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of the present invention, in step S2, the molar ratio of 2-hydroxy-9H-thioxanth-9-one to epichlorohydrin is 1:(8-12), for example, it can be 1:8.0, 1:8.4, 1:8.8, 1:9.2, 1:9.6, 1:10.0, 1:10.4, 1:10.8, 1:11.2, 1:11.6 or 1:12.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the 2-hydroxy-9H-thioxanth-9-one has a mass fraction of 10-20 wt.% in acetonitrile, for example, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, or 20 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some alternative embodiments, the molar ratio of potassium carbonate to 2-hydroxy-9H-thioxanthroline-9-one is (1.2-1.7):1, for example, it can be 1.20:1, 1.25:1, 1.30:1, 1.35:1, 1.40:1, 1.45:1, 1.50:1, 1.55:1, 1.60:1, 1.65:1 or 1.70:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0026] In some optional embodiments, the amount of potassium iodide added is 0.5-1% of the mass of 2-hydroxy-9H-thioxanth-9-one, for example, it can be 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95% or 1.00%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the reaction temperature of the reaction liquid C is 50-70°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the reaction time of the reaction solution C is 4-10 h, for example, it can be 4.0 h, 4.6 h, 5.2 h, 5.8 h, 6.4 h, 7.0 h, 7.6 h, 8.2 h, 8.8 h, 9.4 h or 10.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some alternative embodiments, the molar ratio of the epoxy group of the intermediate to the amino group of diisopropylamine is 1:(1-1.2), for example, it can be 1:1.00, 1:1.02, 1:1.04, 1:1.06, 1:1.08, 1:1.10, 1:1.12, 1:1.14, 1:1.16, 1:1.18 or 1:1.20, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the reaction temperature of the reaction solution D is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the reaction time of the reaction solution D is 2-6 hours, for example, it can be 2.0 hours, 2.4 hours, 2.8 hours, 3.2 hours, 3.6 hours, 4.0 hours, 4.4 hours, 4.8 hours, 5.2 hours, 5.6 hours or 6.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] As a preferred embodiment of the present invention, in step S3, the molar ratio of hydroxyl groups in the bifunctional capping agent, dimethyl malate, and hydroxyethyl acrylate in the mixed capping agent is (0.1-0.2):(0.2-0.3):(0.5-0.7), for example, it can be (0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or 0.20). ):(0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29 or 0.30):(0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68 or 0.70), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0033] In some optional embodiments, the pre-reaction liquid is heated to 65-75°C, for example to 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C or 75°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the molar ratio of hydroxyl groups in the mixed capping agent to isocyanate groups in the prepolymer is (1.02-1.05):1, for example, it can be 1.020:1, 1.023:1, 1.026:1, 1.029:1, 1.032:1, 1.035:1, 1.038:1, 1.041:1, 1.044:1, 1.047:1 or 1.050:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the amount of 2,6-di-tert-butyl-p-cresol added is 0.02-0.05% of the total mass of the mixed end-capping agent and the terminal isocyanate prepolymer, for example, it can be 0.020%, 0.023%, 0.026%, 0.029%, 0.032%, 0.035%, 0.038%, 0.041%, 0.044%, 0.047% or 0.050%, but is not limited to the values ​​listed, and other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the amount of p-hydroxyanisole added is 100-300 ppm of the total mass of the mixed end-capping agent and the terminal isocyanate prepolymer, for example, it can be 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, 200 ppm, 220 ppm, 240 ppm, 260 ppm, 280 ppm or 300 ppm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the reaction solution E is kept at a constant temperature for 3-6 hours, for example, 3.0 hours, 3.3 hours, 3.6 hours, 3.9 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5.1 hours, 5.4 hours, 5.7 hours, or 6.0 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the temperature at which the reaction solution E undergoes vacuum devolatilization after the reaction is 55-65°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, or 65°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0039] As a preferred technical solution of the present invention, in step S4, the isosorbide dimethacrylate is selected from VISIOMER® TerraISDMA;

[0040] The silicone leveling agent is any one of Evonik TEGO® Rad2100, Evonik TEGO® Rad2200N, BYK-UV3510, and BYK-UV3570;

[0041] The polymeric dispersant is DISPERBYK®-2030 or Solsperse 87000;

[0042] The free radical stabilizer is N-nitroso-N-phenylhydroxylamine aluminum salt;

[0043] The mass ratio of the latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isoborneol acrylate, silicone leveling agent, polymeric dispersant, and free radical stabilizer is (40-50):(15-20):(10-15):(0.5-1.0):(1.0-2.0):(0.02-0.03), for example, it can be (40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50):(15.0, 15.5, 16.0, 16.5, 17.0, 17.5, 18.0, 18.5, 19.0, 19.5 or 20.0):(10.0, 10.5, 11.0, 11.5, 1 2.0, 12.5, 13.0, 13.5, 14.0, 14.5 or 15.0: (0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95 or 1.00): (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0): (0.020, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.027, 0.028, 0.029 or 0.03), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0044] In some alternative embodiments, the high-speed dispersion rotation speed is 1000-1500 rpm, for example, it can be 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm or 1500 rpm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0045] In some optional embodiments, the high-speed dispersion time is 10-15 min, for example, it can be 10.0 min, 10.5 min, 11.0 min, 11.5 min, 12.0 min, 12.5 min, 13.0 min, 13.5 min, 14.0 min, 14.5 min or 15.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0046] In some optional embodiments, the pigment mass fraction in the mixture is 18-25 wt.%, for example, it can be 18 wt.%, 18.5 wt.%, 19 wt.%, 19.5 wt.%, 20 wt.%, 20.5 wt.%, 21 wt.%, 21.5 wt.%, 22 wt.%, 22.5 wt.%, 23 wt.%, 23.5 wt.%, 24 wt.%, 24.5 wt.%, or 25.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In some optional embodiments, the low-speed stirring speed is 400-600 rpm, for example, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm, 500 rpm, 520 rpm, 540 rpm, 560 rpm, 580 rpm or 600 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] In some optional embodiments, the low-speed stirring time is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0049] The photoinitiator is TPO-L or Omnirad 819.

[0050] In some optional embodiments, the photoinitiator in the environmentally friendly UV ink has a mass fraction of 0.1-0.5 wt.%, for example, it can be 0.10 wt.%, 0.14 wt.%, 0.18 wt.%, 0.22 wt.%, 0.26 wt.%, 0.30 wt.%, 0.34 wt.%, 0.38 wt.%, 0.42 wt.%, 0.46 wt.%, or 0.50 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0051] The environmentally friendly UV ink can be cured using a UV-LED light source with a wavelength of 365-405nm, preferably 385-395nm.

[0052] Secondly, the present invention provides an environmentally friendly UV ink prepared by the above-described preparation method.

[0053] This application constructs a rigid bio-based spirocyclic acetal framework, forming a skeletal intermediate with spatial rigidity and high cohesive energy through vanillin and pentaerythritol. The introduction of this framework provides the basic modulus and scratch resistance for subsequent UV-cured films, replacing the reliance on traditional petroleum-based aromatic rigid structures with bio-based rigid units. Simultaneously, the solid acid catalyst can be removed by filtration, reducing the risk of side reactions from residual free strong acid to subsequent isocyanate reactions and improving batch controllability. Subsequently, an isocyanate-terminated prepolymer is prepared using an isocyanate end-capping strategy, transforming the rigid framework into a polyurethane reaction platform that can be further functionalized. By setting the excess ratio of isocyanate groups to hydroxyl groups, the system retains quantitatively reactive terminal isocyanate groups, providing an interface and stoichiometric basis for the subsequent covalent locking of photosensitive groups, curable double bonds, and latent ionized fragments onto the same resin chain, thus forming the prerequisite for a low-migration structure.

[0054] This application constructs a bifunctional end-capping agent with an embedded photosensitive carbonyl-tertiary amine synergistic hydrogen donor, transforming the external blending of easily migrating small-molecule photosensitizers and hydrogen-donating amines in traditional systems into intramolecular covalent coupling. 2-Hydroxy-9H-thioxanth-9-one first forms a phenolate under alkaline conditions and undergoes etherification with epichlorohydrin, introducing an epoxy that can continue to react. Subsequently, the epoxy undergoes ring-opening addition with diisopropylamine to generate a β-amino alcohol structure, thus obtaining a bifunctional end-capping agent that simultaneously contains a carbonyl photosensitive structure capable of absorbing UV / LED energy, a tertiary amine structure providing synergistic hydrogen donation / electron transfer, and a hydroxyl site that can further react with the terminal isocyanate group. The objective is that, during the curing stage, the photosensitive carbonyl group absorbs photons and enters an excited state, allowing it to undergo hydrogen abstraction / electron transfer with the nearest-neighbor tertiary amine intramolecularly, directly generating initiating radicals, thereby reducing dependence on high amounts of photoinitiator; simultaneously, since both the photosensitive structure and the tertiary amine are fixed within the polymer network, their migration tendency is reduced, which is more conducive to the formation of low-migration structures. Compared with the traditional method of directly physical blending photosensitizers and amine synergists, this application reduces diffusion restrictions through intramolecular covalent coupling and provides a structural basis for further grafting the synergistic system onto the resin skeleton, thereby reducing the source of small molecule migration.

[0055] The multifunctional end-capping and latent ionization introduced in this application further form a one-way switch of "hydrophobic during use - ionization during recycling". The isocyanate-terminated prepolymer undergoes addition with the hydroxyl groups in the mixed end-capping agent to form urethane bonds, thereby introducing three key functions into the resin simultaneously: First, hydroxyethyl acrylate introduces (meth)acrylic acid double bonds, providing the main crosslinking sites for UV curing; second, the bifunctional end-capping agent introduces a built-in carbonyl photosensitive-tertiary amine synergistic system, providing a structural basis for low-migration curing; third, dimethyl malate, as a fully esterified latent ionization segment, maintains a hydrophobic and low-hygroscopic state during the neutral use period, avoiding the risk of stickiness and printability issues caused by free carboxyl groups in the half-ester, while in the alkaline hydrothermal fluid during the recycling period, the ester bonds undergo irreversible saponification to generate carboxylates, increasing the hydrophilicity and swelling dispersion tendency of the resin segments, making the ink film easier to break down and enter the dispersed phase under pulping conditions, thereby realizing the alkali-triggered deinking pathway. The addition of hindered phenol and p-hydroxyanisole as a polymerization inhibitor system in this step aims to suppress the dark reaction and thermal self-polymerization of (meth)acrylic acid double bonds during end-capping and devolatilization, thereby avoiding viscosity increase, microparticle formation, or decreased storage stability. Furthermore, by removing residual low-boiling substances and trace amounts of moisture through vacuum devolatilization at a relatively mild temperature, the risk of subsequent ureaization side reactions caused by moisture is reduced, making the resulting latent ionized bio-based photosensitive prepolymer more controllable and reproducible in terms of composition and rheology.

[0056] In this application, the prepolymer serves as the film-forming matrix, while isosorbide dimethacrylate and isobornyl acrylate act as reactive diluents and performance modifiers. The former, with its bifunctional and rigid structure, enhances crosslinking contribution and hardness, while the latter, with its cyclic hydrophobic structure, reduces odor and improves leveling and shrinkage control. Together, they achieve a usable balance between viscosity, curing speed, hardness, and water resistance. The addition of silicone leveling agents and polymeric dispersants reduces surface tension gradients, improves wetting and spreading, and inhibits defects, while also stabilizing pigment particles through adsorption anchoring / steric hindrance and improving dispersion stability after pigment refinement, thus ensuring transfer consistency and storage stability during printing. Finally, a small amount of photoinitiator is added as a "deep curing insurance," designed to compensate for curing uncertainties caused by ink shading, film thickness fluctuations, and light source mismatch. Since the system's initiation capability stems from its built-in synergistic structure, the amount of photoinitiator can be controlled at a low level, allowing for a balance between curing reliability and low migration.

[0057] This application also embodies a synergistic relationship: the rigid bio-based spirocyclic framework provides a fundamental mechanical and durability platform, enabling the low-migration system to achieve usable film performance even with low small molecule content; the fully esterified latent ionization fragment avoids moisture absorption and stickiness during use, and is converted into carboxylate through alkali saponification during recycling, improving ink film dispersion and deinking tendency, achieving a one-way switch of "stable during use - triggered during recycling"; the built-in photosensitive-tertiary amine covalent coupling structure improves initiation efficiency and reduces migration risk, enabling the system to maintain a curing window with a low amount of added initiator; the combination of rigid bifunctional monomers and cyclic hydrophobic monomers at the formulation level, as well as the matching of surface / dispersing aids, further realizes a printable, grindable, and curable system. Thus, the structural latent switch, covalently locked low-migration initiation, and the rigid bio-based framework synergistically make this application more likely to simultaneously meet the comprehensive requirements of "low-migration compliance, water resistance and printability during use, and alkali-triggered dispersion and deinking during recycling".

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0059] This application utilizes a rigid bio-based spirocyclic acetal framework constructed from vanillin and pentaerythritol to provide a higher spatial rigidity and cohesive energy foundation for the cured film. This allows for the achievement of good modulus, scratch resistance, and film integrity without relying on traditional petroleum-based aromatic rigid structures, thus facilitating the maintenance of the mechanical and durability properties required for printed materials while replacing bio-based materials. Simultaneously, by setting an excess ratio of isocyanate groups to hydroxyl groups to obtain terminal isocyanate prepolymers, the rigid framework is transformed into a quantitatively end-capped polyurethane reaction platform, providing a basis for the subsequent covalent integration of photosensitive groups, curable double bonds, and latent ionized fragments into the same resin segment.

[0060] This application constructs and introduces a built-in carbonyl photosensitive-tertiary amine synergistic system: the photosensitive carbonyl structure and the tertiary amine synergistic hydrogen donor are transformed from traditional external blending to intramolecular covalent coupling and further grafted onto the prepolymer backbone. The intramolecular proximity effect is used to improve the hydrogen abstraction / electron transfer efficiency, thereby reducing the dependence on high amounts of externally added photoinitiators and free amine synergists from a mechanistic perspective. The covalently locked synergistic initiation unit can maintain a usable curing window while reducing potential migration sources.

[0061] This application introduces a fully esterified latent ionization fragment and forms a one-way switch: during the service life, it is hydrophobic and has low hygroscopicity, avoiding the risk of stickiness and printability caused by free carboxyl groups in the half-ester; under alkaline hydrothermal conditions during the recycling period, the ester bond irreversibly saponifies to generate carboxylate, which increases the hydrophilicity of the chain segment and its tendency to swell and disperse, making the cured ink film more brittle and entering the dispersed phase, thereby realizing an achievable deinking path of "stable during the service life - triggered during the recycling period".

[0062] This application exhibits synergistic effects: the rigid framework ensures that the low molecular weight system still possesses membrane performance, the built-in synergistic initiation unit reduces migration risk while ensuring curing reliability, and the fully esterified latent ionization unit provides the driving force for dispersion and deinking during recycling without sacrificing water resistance during the service life; making this application more likely to achieve a balance between "low migration compliance, water resistance and printability during the service life, and alkali-triggered dispersion and deinking during recycling". Attached Figure Description

[0063] Figure 1 The infrared spectrum of the isocyanate-terminated prepolymer prepared in Example 1 of this application;

[0064] Figure 2 The infrared spectrum of the latent ionized bio-based photosensitive prepolymer prepared in Example 1 of this application is shown. Detailed Implementation

[0065] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include any obvious substitutions and modifications made to the embodiments described herein.

[0066] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0067] Example 1

[0068] This embodiment provides an environmentally friendly UV ink and its preparation method. The preparation method of the environmentally friendly UV ink specifically includes the following steps:

[0069] S1: Vanillin and pentaerythritol were mixed at a molar ratio of 2.1:1. Toluene (40% of the total mass of vanillin and pentaerythritol) and Amberlyst® 15 (1.2% of the total mass of vanillin and pentaerythritol) solid acid catalyst were added to obtain reaction solution A. The mixture was heated to 112°C for water separation until the water content reached more than 95% of the theoretical value. The mixture was then cooled, filtered, dehydrated under reduced pressure, and dehydrated to obtain a rigid spirocyclic acetal backbone intermediate. Isophorone diisocyanate and the rigid spirocyclic acetal backbone intermediate were mixed at a molar ratio of isocyanate group to hydroxyl group of 2.3:1. Bismuth neodecanoate catalyst (0.07% of the total mass of isophorone diisocyanate and rigid spirocyclic acetal backbone) was added to obtain reaction solution B. The mixture was reacted at 72°C for 2.8 h under a nitrogen atmosphere to obtain a terminal isocyanate group prepolymer. Figure 1 The infrared spectrum of the terminal isocyanate prepolymer is shown in the range of 3400-3200 cm⁻¹. -1 The broad peak at approximately 2960-2850 cm⁻¹ can be attributed to the OH / NH stretching vibration, indicating the presence of hydrogen-bonded NH groups related to polyurethane segments and possible residual hydroxyl structures in the system; -1 The absorption in the vicinity can be attributed to the stretching vibration of the aliphatic -CH3 / -CH2-, corresponding to the hydrocarbon chain structure after the introduction of isocyanate and aliphatic skeleton; at approximately 2270 cm⁻¹ -1 The characteristic absorption observed nearby can be attributed to the -NCO stretching vibration, indicating that the terminal isocyanate groups are still retained in the prepolymer, providing reaction sites for subsequent end-capping grafting; at approximately 1730-1700 cm⁻¹ -1 The strong absorption in the vicinity can be attributed to the C=O stretching vibration, and may be accompanied by a shoulder / broadening caused by hydrogen bonding, indicating that the isocyanate and hydroxyl groups have formed a polyurethane structure; at approximately 1540-1520 cm⁻¹ -1 The absorption in the vicinity can be attributed to the amide II band, further supporting the formation of polyurethane bonds; at approximately 1260-1100 cm⁻¹ -1 The absorption in the region can be attributed to COC / CN-related stretching vibrations, which are typical characteristics of the polyurethane / acetal skeleton fingerprint region.

[0070] S2: 2-Hydroxy-9H-thioxanth-9-one and epichlorohydrin were added to acetonitrile at a molar ratio of 1:11, wherein the mass fraction of 2-hydroxy-9H-thioxanth-9-one was 18 wt.%. Potassium carbonate and potassium iodide were added to obtain reaction solution C, wherein the molar ratio of potassium carbonate to 2-hydroxy-9H-thioxanth-9-one was 1.6:1, and the amount of potassium iodide added was 0.8% of the mass of 2-hydroxy-9H-thioxanth-9-one. The reaction was stirred at 65°C for 8 h under nitrogen protection. The solution was filtered while hot to remove salt. The solvent was recovered from the filtrate under reduced pressure and excess epichlorohydrin was removed to obtain an intermediate. The intermediate was mixed with diisopropylamine to obtain reaction solution D, wherein the molar ratio of the epoxy group of the intermediate to the amino group of diisopropylamine was 1:1.15. The reaction was carried out at 75°C for 5 h, and the bifunctional end-capping agent was obtained by vacuum distillation.

[0071] S3: A mixed end-capping agent was obtained by mixing a bifunctional end-capping agent, dimethyl malate, and hydroxyethyl acrylate in a hydroxyl molar ratio of 0.18:0.28:0.6. 2,6-Di-tert-butyl-p-cresol and p-hydroxyanisole were added to the isocyanate-terminated prepolymer to obtain a pre-reaction solution. The mixture was heated to 72°C under nitrogen protection and then the mixed end-capping agent was added dropwise to obtain reaction solution E. The molar ratio of hydroxyl groups in the mixed end-capping agent to isocyanate groups in the isocyanate-terminated prepolymer was 1.04:1. The amount of 2,6-di-tert-butyl-p-cresol added was 0.04% of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer. The amount of p-hydroxyanisole added was 250 ppm of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer. The reaction was kept at the temperature for 5 h and then de-idered under reduced pressure at 62°C to obtain a latent ionized bio-based photosensitive prepolymer. Figure 2 The infrared spectrum of the latent ionized bio-based photosensitive prepolymer is shown, with the 3400-3200 cm⁻¹ region. -1 The broad peak at approximately 2960-2850 cm⁻¹ can also be attributed to the OH / NH stretching vibration, indicating that the system retains the NH and a small amount of hydroxyl-related structures of the polyurethane segments after end-capping; -1 The absorption can be attributed to aliphatic -CH3 / -CH2- stretching vibrations, corresponding to the main resin chain and side hydrocarbon chain structures; and Figure 1 In comparison, approximately 2270cm -1 The weakening or even disappearance of the characteristic -NCO absorption near the end indicates that the terminal isocyanate groups have been consumed by the mixed end-capping agent, and the end-capping reaction is nearing completion; at approximately 1740-1700 cm⁻¹ -1 The strong absorption can be attributed to the C=O stretching vibration, and the peak shape in this region is relatively wider, reflecting the introduction of various carbonyl environments (such as acrylate fragments, diester latent ionization fragments, and photosensitive carbonyl structures) after end-capping, which superimpose with the original carbonyl group; at approximately 1640-1630 cm⁻¹ -1 The weaker absorption observed nearby can be attributed to the C=C stretching vibration of acrylate, indicating the introduction of UV-curable double bonds; at approximately 1260-1100 cm⁻¹ -1 The absorption can be attributed to ester-based COC and urethane-related CO / CN vibrations, further supporting the introduction of ester fragments and network-based curable structures at the end caps; at approximately 990-810 cm⁻¹ -1 The characteristic absorption in the vicinity can be attributed to alkenyl-related out-of-plane vibrations / fingerprint region absorption, which is consistent with the spectroscopic performance after the introduction of the acrylate structure.

[0072] S4: A latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isobornyl acrylate, silicone leveling agent Evonik TEGO® Rad 2100, polymeric dispersant DISPERBYK®-2030, and free radical stabilizer N-nitroso-N-phenylhydroxylamine aluminum salt are mixed at a mass ratio of 48:18:14:0.8:1.8:0.025 and dispersed at high speed at 1400 rpm for 14 min. Vacuum degassing is then performed to obtain a premix. Pigment is added to the premix, and the mixture is milled using a three-roll mill to obtain a final mixture. The pigment mass fraction in the final mixture is 18 wt.%. Photoinitiator TPO-L is added, and the mixture is stirred at low speed at 550 rpm for 28 min. Filtration yields an environmentally friendly UV ink. The photoinitiator mass fraction in the environmentally friendly UV ink is 0.4 wt.%.

[0073] Example 2

[0074] This embodiment provides an environmentally friendly UV ink and its preparation method. The preparation method of the environmentally friendly UV ink specifically includes the following steps:

[0075] S1: Vanillin and pentaerythritol are mixed at a molar ratio of 2.0:1. Toluene (30% of the total mass of vanillin and pentaerythritol) and Amberlyst® 36 (0.5% of the total mass of vanillin and pentaerythritol) solid acid catalyst are added to obtain reaction solution A. The mixture is heated to 108°C for water separation until the water content reaches more than 95% of the theoretical value. The mixture is then cooled, filtered, dehydrated under reduced pressure, and dehydrated to obtain a rigid spirocyclic acetal backbone intermediate. Isophorone diisocyanate and the rigid spirocyclic acetal backbone intermediate are mixed at a molar ratio of isocyanate group to hydroxyl group of 2.0:1. Bismuth neodecanoate catalyst (0.03% of the total mass of isophorone diisocyanate and rigid spirocyclic acetal backbone) is added to obtain reaction solution B. The mixture is reacted at 65°C for 2 hours under a nitrogen atmosphere to obtain a terminal isocyanate group prepolymer.

[0076] S2: 2-hydroxy-9H-thioxanth-9-one and epichlorohydrin were added to acetonitrile in a molar ratio of 1:8, wherein the mass fraction of 2-hydroxy-9H-thioxanth-9-one was 10 wt.%. Potassium carbonate and potassium iodide were added to obtain reaction solution C, wherein the molar ratio of potassium carbonate to 2-hydroxy-9H-thioxanth-9-one was 1.2:1, and the amount of potassium iodide added was 0.5% of the mass of 2-hydroxy-9H-thioxanth-9-one. The reaction was stirred at 50°C for 4 h under nitrogen protection. The solution was filtered while hot to remove salt. The solvent was recovered from the filtrate under reduced pressure and excess epichlorohydrin was removed to obtain an intermediate. The intermediate was mixed with diisopropylamine to obtain reaction solution D, wherein the molar ratio of the epoxy group of the intermediate to the amino group of diisopropylamine was 1:1. The reaction was carried out at 60°C for 2 h, and the bifunctional end-capping agent was obtained by vacuum distillation.

[0077] S3: A mixed end-capping agent was obtained by mixing a bifunctional end-capping agent, dimethyl malate, and hydroxyethyl acrylate in a hydroxyl molar ratio of 0.1:0.2:0.5. 2,6-Di-tert-butyl-p-cresol and p-hydroxyanisole were added to the isocyanate-terminated prepolymer to obtain a pre-reaction solution. The mixture was heated to 65°C under nitrogen protection and then the mixed end-capping agent was added dropwise to obtain reaction solution E. The molar ratio of hydroxyl groups in the mixed end-capping agent to isocyanate groups in the isocyanate-terminated prepolymer was 1.02:1. The amount of 2,6-di-tert-butyl-p-cresol added was 0.02% of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer, and the amount of p-hydroxyanisole added was 100 ppm of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer. The reaction was kept at a constant temperature for 3 hours and then de-idered at 55°C under reduced pressure to obtain a latent ionized bio-based photosensitive prepolymer.

[0078] S4: A latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isoborneol acrylate, silicone leveling agent Evonik TEGO® Rad 2200N, polymeric dispersant Solsperse 87000, and free radical stabilizer N-nitroso-N-phenylhydroxylamine aluminum salt are mixed at a mass ratio of 40:15:10:0.5:1.0:0.02 and dispersed at 1000 rpm for 10 min. Vacuum degassing is then performed to obtain a premix. Pigment is added to the premix, and the mixture is milled using a three-roll mill to obtain a final mixture. The pigment mass fraction in the final mixture is 20 wt.%. Photoinitiator TPO-L is added, and the mixture is stirred at 400 rpm for 20 min. Filtering yields an environmentally friendly UV ink. The photoinitiator mass fraction in the environmentally friendly UV ink is 0.1 wt.%.

[0079] Example 3

[0080] This embodiment provides an environmentally friendly UV ink and its preparation method. The preparation method of the environmentally friendly UV ink specifically includes the following steps:

[0081] S1: Vanillin and pentaerythritol were mixed at a molar ratio of 2.15:1. Toluene (35% of the total mass of vanillin and pentaerythritol) and a solid acid catalyst, Dowex® 50WX (0.8% of the total mass of vanillin and pentaerythritol), were added to obtain reaction solution A. The mixture was heated to 109°C for water separation until the water content reached more than 95% of the theoretical value. The mixture was then cooled, filtered, and subjected to desolventizing and dehydration under reduced pressure to obtain a rigid spirocyclic acetal backbone intermediate. Isophorone diisocyanate and the rigid spirocyclic acetal backbone intermediate were mixed at a molar ratio of isocyanate group to hydroxyl group of 2.1:1. Bismuth 2-ethylhexanoate (0.05% of the total mass of isophorone diisocyanate and rigid spirocyclic acetal backbone) were added to obtain reaction solution B. The mixture was reacted at 68°C for 2.2 h under a nitrogen atmosphere to obtain a terminal isocyanate group prepolymer.

[0082] S2: 2-hydroxy-9H-thioxanth-9-one and epichlorohydrin were added to acetonitrile in a molar ratio of 1:9, wherein the mass fraction of 2-hydroxy-9H-thioxanth-9-one was 12 wt.%. Potassium carbonate and potassium iodide were added to obtain reaction solution C, wherein the molar ratio of potassium carbonate to 2-hydroxy-9H-thioxanth-9-one was 1.4:1, and the amount of potassium iodide added was 0.6% of the mass of 2-hydroxy-9H-thioxanth-9-one. The reaction was stirred at 55°C for 6 h under nitrogen protection. The solution was filtered while hot to remove salt, and the solvent was recovered from the filtrate under reduced pressure and excess epichlorohydrin was removed to obtain an intermediate. The intermediate was mixed with diisopropylamine to obtain reaction solution D, wherein the molar ratio of the epoxy group of the intermediate to the amino group of diisopropylamine was 1:1.05. The reaction was carried out at 65°C for 3 h, and the bifunctional end-capping agent was obtained by vacuum distillation.

[0083] S3: A mixed end-capping agent was obtained by mixing a bifunctional end-capping agent, dimethyl malate, and hydroxyethyl acrylate in a hydroxyl molar ratio of 0.12:0.22:0.55. 2,6-Di-tert-butyl-p-cresol and p-hydroxyanisole were added to the isocyanate-terminated prepolymer to obtain a pre-reaction solution. The mixture was heated to 68°C under nitrogen protection and then the mixed end-capping agent was added dropwise to obtain reaction solution E. The molar ratio of hydroxyl groups in the mixed end-capping agent to isocyanate groups in the isocyanate-terminated prepolymer was 1.03:1. The amount of 2,6-di-tert-butyl-p-cresol added was 0.03% of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer, and the amount of p-hydroxyanisole added was 150 ppm of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer. The reaction was kept at the temperature for 4 hours and then de-idered at 58°C under reduced pressure to obtain a latent ionized bio-based photosensitive prepolymer.

[0084] S4: A latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isobornyl acrylate, silicone leveling agent N, BYK-UV3510, polymeric dispersant DISPERBYK®-2030, and free radical stabilizer N-nitroso-N-phenylhydroxylamine aluminum salt are mixed at a mass ratio of 42:16:11:0.6:1.2:0.022 and dispersed at 1100 rpm for 11 min. Vacuum degassing is then performed to obtain a premix. Pigment is added to the premix, and the mixture is milled using a three-roll mill to obtain a final mixture. The pigment mass fraction in the final mixture is 22 wt.%. Photoinitiator Omnirad 819 is added, and the mixture is stirred at 450 rpm for 22 min. Filtering yields an environmentally friendly UV ink. The photoinitiator mass fraction in the environmentally friendly UV ink is 0.2 wt.%.

[0085] Example 4

[0086] This embodiment provides an environmentally friendly UV ink and its preparation method. The preparation method of the environmentally friendly UV ink specifically includes the following steps:

[0087] S1: Vanillin and pentaerythritol are mixed at a molar ratio of 2.2:1. Toluene (50% of the total mass of vanillin and pentaerythritol) and Lewatit® K2620 solid acid catalyst (1.5% of the total mass of vanillin and pentaerythritol) are added to obtain reaction solution A. The mixture is heated to 113°C for water separation until the water content reaches more than 95% of the theoretical value. The mixture is then cooled, filtered, dehydrated under reduced pressure, and dehydrated to obtain a rigid spirocyclic acetal backbone intermediate. Isophorone diisocyanate and the rigid spirocyclic acetal backbone intermediate are mixed at a molar ratio of isocyanate group to hydroxyl group of 2.5:1. Bismuth 2-ethylhexanoate organic bismuth catalyst (0.08% of the total mass of isophorone diisocyanate and rigid spirocyclic acetal backbone) are added to obtain reaction solution B. The mixture is reacted at 75°C for 3 hours under a nitrogen atmosphere to obtain a terminal isocyanate group prepolymer.

[0088] S2: 2-Hydroxy-9H-thioxanth-9-one and epichlorohydrin were added to acetonitrile at a molar ratio of 1:12, wherein the mass fraction of 2-hydroxy-9H-thioxanth-9-one was 20 wt.%. Potassium carbonate and potassium iodide were added to obtain reaction solution C, wherein the molar ratio of potassium carbonate to 2-hydroxy-9H-thioxanth-9-one was 1.7:1, and the amount of potassium iodide added was 1% of the mass of 2-hydroxy-9H-thioxanth-9-one. The reaction was stirred at 70°C for 10 h under nitrogen protection. The solution was filtered while hot to remove salt, and the solvent was recovered from the filtrate under reduced pressure and excess epichlorohydrin was removed to obtain an intermediate. The intermediate was mixed with diisopropylamine to obtain reaction solution D, wherein the molar ratio of the epoxy group of the intermediate to the amino group of diisopropylamine was 1:1.2. The reaction was carried out at 80°C for 6 h, and the bifunctional end-capping agent was obtained by vacuum distillation.

[0089] S3: A mixed end-capping agent was obtained by mixing a bifunctional end-capping agent, dimethyl malate, and hydroxyethyl acrylate in a hydroxyl molar ratio of 0.2:0.3:0.7. 2,6-Di-tert-butyl-p-cresol and p-hydroxyanisole were added to the isocyanate-terminated prepolymer to obtain a pre-reaction solution. The mixture was heated to 75°C under nitrogen protection and then the mixed end-capping agent was added dropwise to obtain reaction solution E. The molar ratio of hydroxyl groups in the mixed end-capping agent to isocyanate groups in the isocyanate-terminated prepolymer was 1.05:1. The amount of 2,6-di-tert-butyl-p-cresol added was 0.05% of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer. The amount of p-hydroxyanisole added was 300 ppm of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer. The reaction was kept at a constant temperature for 6 hours and then de-idered at 65°C under reduced pressure to obtain a latent ionized bio-based photosensitive prepolymer.

[0090] S4: A latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isoborneol acrylate, silicone leveling agent BYK-UV3570, polymeric dispersant Solsperse87000, and free radical stabilizer N-nitroso-N-phenylhydroxylamine aluminum salt are mixed at a mass ratio of 50:20:15:1.0:2.0:0.03 and dispersed at 1500 rpm for 15 min. Vacuum degassing is then performed to obtain a premix. Pigment is added to the premix, and the mixture is ground using a three-roll mill to obtain a final mixture. The pigment mass fraction in the final mixture is 25 wt.%. Photoinitiator Omnirad819 is added, and the mixture is stirred at 600 rpm for 30 min. Filtering yields an environmentally friendly UV ink. The photoinitiator mass fraction in the environmentally friendly UV ink is 0.5 wt.%.

[0091] Comparative Example 1

[0092] This comparative example provides an environmentally friendly UV ink and its preparation method. The difference from Example 1 is that step S2 is omitted, and in S3, the bifunctional capping agent is replaced by a hydroxyl equivalent such as benzyl alcohol. Other operating steps and process parameters are exactly the same as in Example 1.

[0093] Comparative Example 2

[0094] This comparative example provides an environmentally friendly UV ink and its preparation method. The difference from Example 1 is that dimethyl malate is replaced with 1-methyl malate in S3. Other operating steps and process parameters are exactly the same as in Example 1.

[0095] Comparative Example 3

[0096] This comparative example provides an environmentally friendly UV ink and its preparation method. The difference from Example 1 is that neopentyl glycol is used in S1 to replace the rigid spirocyclic acetal skeleton intermediate. Other operating steps and process parameters are exactly the same as in Example 1.

[0097] Comparative Example 4

[0098] This comparative example provides an environmentally friendly UV ink and its preparation method. The difference from Example 1 is that isoborol is used instead of dimethyl malate in S3, while the other operation steps and process parameters are exactly the same as in Example 1.

[0099] The performance of the environmentally friendly UV inks of Examples 1-4 and Comparative Examples 1-4 was tested, and the specific process is as follows:

[0100] The overall migration of the test sample was determined according to GB31604.8-2021;

[0101] The water resistance of the sample was tested according to GB / T1733-1993 (immersion in water at 25℃ for 48 hours).

[0102] The deinking performance (ERIC reduction rate) of the samples was tested according to GB / T46182-2025.

[0103] The solvent resistance of the sample was tested according to GB / T23989 (300 ethanol wipes).

[0104] The test results are shown in Table 1.

[0105] Table 1. Performance test results of environmentally friendly UV inks in Examples 1-4 and Comparative Examples 1-4

[0106]

[0107] As shown in Table 1, the test results of Example 1 and Comparative Example 1 reveal that omitting steps S2 and S3 and replacing the bifunctional end-capping agent with hydroxyl equivalents such as benzyl alcohol results in the system lacking the covalent coupling synergy of "photosensitive carbonyl-tertiary amine" on the same molecular chain. During the curing stage, the initiation and hydrogen donation synergy degenerates from an intramolecular process to a system dependent on external initiation and diffusion collisions, leading to a decrease in the crosslinking integrity and density of the cured network. Unreacted or low-molecular-weight components are more likely to remain, thus increasing the overall migration. Due to insufficient network density and interfacial cohesion, aqueous media are more likely to penetrate along micro-defects and cause swelling or local instability, resulting in relatively poor water resistance. On the other hand, although latent ionized fragments still exist, the ink film as a whole is tougher and less brittle, and is less likely to break into peelable and dispersible fine particles under pulping dispersion and flotation shearing conditions. The ink tends to remain on the fiber surface in the form of flakes or agglomerates, thus reducing the deinking efficiency. Due to insufficient cross-linking density and solvent-resistant skeleton, the ink film is more likely to swell, soften, and undergo pigment / resin migration during solvent wiping, resulting in decreased solvent resistance and a greater risk of more obvious color fading or even premature exposure of the substrate.

[0108] As shown in Table 1, the test results of Example 1 and Comparative Example 2 indicate that replacing dimethyl malate with 1-methyl malate in S3 introduces a half-ester structure containing free carboxyl groups, changing the latent ionization from fully latent to a partially pre-ionized / highly polar state. During use, the free acid and its tendency to salt increase the system's affinity for water and hygroscopicity, and may form ion pairs or hydrogen bonds with amine cooperating groups, leading to the film layer being more prone to water absorption, whitening, swelling, and even local blistering, resulting in relatively poor water resistance. Due to the increased proportion of polar functional groups and the presence of more easily migrating small-molecule acidic fragments, the dissolution tendency in the food simulation liquid is enhanced, and the overall migration amount increases. For deinking, half-esters do indeed more easily form ionized groups in alkaline pulping, but due to the stronger water sensitivity and network defects they bring during use, the ink film may exhibit uneven softening and agglomeration during pulping, making it difficult to stably form an ideal particle size distribution that can be floated, thus reducing deinking efficiency. Because water sensitivity and ion association weaken the cross-linked network's resistance to solvents, softening and pigment carry-out are more likely to occur during solvent wiping, resulting in decreased solvent resistance.

[0109] As shown in Table 1, the test results of Example 1 and Comparative Example 3 reveal that in S1, neopentyl glycol replaced the rigid spirocyclic acetal backbone intermediate, eliminating the rigid spirocyclic acetal bio-based backbone and using a more flexible aliphatic diol to construct the prepolymer. This reduced the rigidity plateau and cohesive energy of the cured film, resulting in a more flexible and malleable network after crosslinking. The densification level and scratch / swelling resistance were weakened, making it more prone to dissolution or diffusion in the simulated solution, leading to an overall increase in migration. Due to insufficient backbone rigidity, aqueous media more easily cause chain segment relaxation and swelling, resulting in a relative decrease in water resistance. Regarding deinking, a rigid backbone facilitates controlled fragmentation / peeling under alkaline pulping shear conditions, while a flexible network tends to extend into sheets or form a tough residual film, resulting in lower fragmentation efficiency and difficulty in sufficient dispersion and flotation, thus reducing deinking efficiency. In terms of solvent wiping resistance, a flexible backbone typically leads to higher solvent penetration and swelling, making it more prone to accelerated color fading and early exposure during wiping, thus reducing solvent wiping resistance.

[0110] As shown in Table 1, the test results of Example 1 and Comparative Example 4 indicate that in S3, the use of isobornol to replace dimethyl malate changed the introduced end-capping segment from a "dicarboxylic acid diester structure that can undergo saponification and ionization during recycling" to an "inert alcohol structure that only provides hydrophobic volume effect." Therefore, the effective introduction of latent ionization segments into the resin was removed. Due to the lack of triggering groups that can be converted to carboxylate under alkaline pulping conditions, the cured ink film is difficult to enter the dispersed phase of the slurry through the ionization-driven swelling-fragmentation-dispersion path during recycling. The ink layer tends to remain as a hydrophobic continuous phase or remain in the form of larger fragments, leading to a decrease in deinking efficiency. Meanwhile, the bridged-ring hydrophobic structure of isobornol improves the hydrophobicity of the end-capping segments and reduces the penetration of aqueous media. The swelling of the ink film in water is suppressed, resulting in generally little or no change in water resistance and less likelihood of surface defects. Regarding overall migration, Example 1, by covalently introducing a latent trigger fragment into the solidified network and allowing for ionization dispersion during the recovery period, can reduce the risk of release of some low-molecular-weight molecules during use. Comparative Example 4, lacking such a trigger fragment, suffers from insufficient polarity regulation and dispersion driving force. After solidification, extractable low-molecular-weight molecules are more likely to remain in the hydrophobic network and migrate in the food simulant / solvent medium, thus increasing the overall migration amount. Regarding solvent wiping resistance, the steric hindrance of isoborneol may reduce the effective density of local crosslinking and increase the free volume of chain segments. This makes the surface more prone to softening and pigment migration during repeated solvent wiping, thus deteriorating the solvent wiping resistance.

[0111] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an environmentally friendly UV ink, characterized by, The preparation method includes: S1: Vanillin and pentaerythritol are mixed in a molar ratio of (2.0-2.2):1, toluene and a solid acid catalyst are added to carry out a water separation reaction. After the reaction, the catalyst is separated and toluene and the generated water are removed to obtain a rigid spirocyclic acetal skeleton intermediate. Isophorone diisocyanate is mixed with the rigid spirocyclic acetal skeleton intermediate, wherein the molar ratio of the isocyanate group of the isophorone diisocyanate to the hydroxyl group of the rigid spirocyclic acetal skeleton intermediate is (2.0-2.5):

1. An organobismuth catalyst is added to react and obtain a terminal isocyanate group prepolymer. S2: 2-hydroxy-9H-thioxanth-9-one and epichlorohydrin are added to acetonitrile, wherein the molar ratio of 2-hydroxy-9H-thioxanth-9-one to epichlorohydrin is 1:(8-12). Potassium carbonate and potassium iodide are added, the mixture is stirred and reacted, the salts are separated and the solvent and excess epichlorohydrin are removed to obtain an intermediate. The intermediate is reacted with diisopropylamine, wherein the molar ratio of the epoxy group of the intermediate to the amino group of diisopropylamine is 1:(1-1.2). The mixture is then distilled under reduced pressure to obtain a bifunctional end-capping agent. S3: A mixed end-capping agent is obtained by mixing a bifunctional end-capping agent, dimethyl malate, and hydroxyethyl acrylate in a hydroxyl molar ratio of (0.1-0.2):(0.2-0.3):(0.5-0.7); 2,6-di-tert-butyl-p-cresol and p-hydroxyanisole are added to the isocyanate-terminated prepolymer to obtain a pre-reaction solution. The mixture is then added dropwise after heating under nitrogen protection. The molar ratio of hydroxyl groups in the mixed end-capping agent to isocyanate groups in the isocyanate-terminated prepolymer is (1.02-1.05):

1. The reaction is carried out, and the mixture is then devoured under reduced pressure to obtain a latently ionized bio-based photosensitive prepolymer. S4: A premixed liquid is obtained by mixing, dispersing and degassing a latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isoborneol acrylate, silicone leveling agent, polymeric dispersant and free radical stabilizer; pigment is added to the premixed liquid and ground and dispersed to obtain a mixture; a photoinitiator is added, stirred and filtered to obtain an environmentally friendly UV ink.

2. The preparation method of the environment-friendly UV ink according to claim 1, characterized in that, In S1: The amount of toluene added is 30-50% of the total mass of vanillin and pentaerythritol.

3. The preparation method of the environment-friendly UV ink according to claim 1, characterized in that, In S1: The solid acid catalyst is any one of Amberlyst® 15, Amberlyst® 36, Dowex® 50WX or Lewatit® K2620; The amount of the solid acid catalyst fed is 0.5-1.5% of the total mass of vanillin and pentaerythritol.

4. The preparation method of the environment-friendly UV ink according to claim 1, characterized in that, In S1: The amount of the organic bismuth catalyst fed is 0.03-0.08% of the total mass of isophorone diisocyanate and rigid spirocyclic acetal skeleton.

5. The method for preparing an environmentally friendly UV ink according to claim 1, characterized in that, In S2: The 2-hydroxy-9H-thioxanth-9-one has a mass fraction of 10-20 wt.% in acetonitrile. The molar ratio of potassium carbonate to 2-hydroxy-9H-thioxanth-9-one is (1.2-1.7):1; The amount of potassium iodide added is 0.5-1% of the mass of 2-hydroxy-9H-thioxanth-9-one.

6. The method according to claim 1, wherein the UV ink is an environmentally friendly UV ink. In S3: The amount of 2,6-di-tert-butyl-p-cresol added is 0.02-0.05% of the total mass of the mixed end-capping agent and the isocyanate-terminated prepolymer; The amount of p-hydroxyanisole added is 100-300 ppm of the total mass of the mixed capping agent and the terminal isocyanate prepolymer.

7. The method according to claim 1, wherein the UV ink is an environmentally friendly UV ink. In S4: The isosorbide dimethacrylate is selected from VISIOMER® TerraISDMA; The silicone leveling agent is any one of Evonik TEGO® Rad2100, Evonik TEGO® Rad2200N, BYK-UV3510, and BYK-UV3570; The polymeric dispersant is DISPERBYK®-2030 or Solsperse 87000; The free radical stabilizer is N-nitroso-N-phenylhydroxylamine aluminum salt.

8. The method according to claim 1, wherein the UV ink is an environmentally friendly UV ink. In S4: The mass ratio of the latent ionized bio-based photosensitive prepolymer, isosorbide dimethacrylate, isoborneol acrylate, silicone leveling agent, polymeric dispersant, and free radical stabilizer is (40-50):(15-20):(10-15):(0.5-1.0):(1.0-2.0):(0.02-0.03); The pigment in the mixture has a mass fraction of 18-25 wt.%; The photoinitiator is TPO-L or Omnirad 819; The photoinitiator in the environmentally friendly UV ink has a mass fraction of 0.1-0.5 wt.%.

9. An environmentally friendly UV ink prepared by the preparation method according to any one of claims 1-8.

Images