A low-energy curable UV offset printing ink binder and its preparation method

Abstract

This invention relates to a low-energy curable UV offset printing ink binder and its preparation method. The binder comprises photosensitive group-modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, an active diluent composition, rosin-modified acrylate resin, reactive organic microparticles, tertiary amine-containing polyurethane acrylate resin, methacrylamide-modified nano-silica, polymerizable phosphate wetting agent, stabilizer, and process aids. This binder improves the low-energy curing efficiency of UV-LEDs through the synergistic effect of thioxanthone groups, acylphosphoxy groups, and tertiary amine groups, and reduces the influence of oxygen inhibition by utilizing mercapto groups and thioether bonds; the reactive organic microparticles improve offset rheology, ink-water balance, and anti-ink-skimming properties. This solution has the advantages of fast curing speed, good surface drying, low migration risk, and stable printability.

Description

Technical Field

[0001] This invention relates to the field of ink binder preparation technology, specifically to a low-energy curable UV offset printing ink binder and its preparation method. Background Technology

[0002] UV offset printing inks are a type of offset printing ink that achieves rapid curing using ultraviolet light irradiation. They typically consist of pigments, binders, reactive diluents, photoinitiators, and additives. Among these, the binder is the key component determining the ink's curing speed, printability, adhesion, abrasion resistance, and water-ink balance. With increasing demands for energy conservation, environmental protection, and high-speed printing, low-energy curing using UV-LED light sources has become an important development direction for UV offset printing inks. Compared to traditional mercury lamp UV curing, UV-LED light sources offer advantages such as low energy consumption, low heat radiation, long lifespan, and low ozone release. However, their narrower emission band and relatively concentrated energy per unit area place higher demands on the binder system's light absorption capacity, free radical generation efficiency, and surface curing ability. Existing low-energy curing UV offset printing ink binders often employ a blend of oligomers such as polyester acrylates, polyurethane acrylates, and epoxy acrylates with multifunctional acrylate reactive diluents, small-molecule photoinitiators, and amine co-initiators. While these systems can achieve UV curing to some extent, incomplete curing is still prone to occur under low-energy UV-LED irradiation conditions, especially with dark inks, inks with high pigment content, or thicker ink layers. Due to limited light penetration and insufficient free radical generation, incomplete deep curing, reduced ink film abrasion resistance, and insufficient adhesion are common problems. Furthermore, offset ink layers have a large contact area with air, making surface free radicals easily captured by oxygen, leading to oxygen inhibition polymerization. This causes the ink film surface to become sticky, reduces its resistance to smudging, and affects subsequent overprinting and the stability of printed material stacking.

[0003] To improve low-energy curing performance, existing technologies typically increase curing speed by increasing the amount of photoinitiator, adding amine additives, or increasing the proportion of polyfunctional acrylates. However, small-molecule photoinitiators and small-molecule amine additives may pose risks of residue and migration after curing, potentially leading to problems such as odor, yellowing, and decreased water resistance. While excessive polyfunctional acrylates can increase crosslinking density, they can also cause increased curing shrinkage, ink film brittleness, reduced adhesion, and decreased printing transfer stability. Furthermore, UV offset printing inks differ from ordinary UV coatings; their binders must also meet offset printing suitability requirements such as ink roller transfer, dot reproduction, anti-ink splatter, anti-ink piling, and water-ink balance. Existing technologies often use wax powder, fumed silica, or ordinary inert thickening resins to adjust rheological properties, but these components typically do not participate in UV crosslinking and can easily form weak interfaces in the cured film, affecting film density, abrasion resistance, and long-term stability.

[0004] Therefore, there is an urgent need to develop an offset ink binder suitable for low-energy UV-LED curing conditions, which can improve the surface and deep curing efficiency under low-energy light irradiation while maintaining good offset transferability and water-ink balance, reduce the effect of oxygen inhibition, and reduce the migration and performance degradation problems caused by small molecule photoinitiators, amine additives and inert rheology additives. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a low-energy curable UV offset printing ink binder and its preparation method. The binder comprises photosensitive group-modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, an active diluent composition, rosin-modified acrylate resin, reactive organic microparticles, tertiary amine-containing polyurethane acrylate resin, methacrylamide-modified nano-silica, polymerizable phosphate wetting agent, stabilizer, and process aids. This binder improves the low-energy curing efficiency of UV-LEDs through the synergistic effect of thioxanthone groups, acylphosphoxy groups, and tertiary amine groups, and reduces the influence of oxygen inhibition by utilizing mercapto groups and thioether bonds; the reactive organic microparticles improve offset rheology, ink-water balance, and anti-ink-skimming properties. This solution has the advantages of fast curing speed, good surface drying, low migration risk, and stable printability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A low-energy curable UV offset printing ink binder comprises the following components by weight: 36-48 parts of photosensitive group modified hyperbranched polyester acrylate resin, 9-16 parts of mercapto-containing polyurethane acrylate resin, 20-28 parts of reactive diluent composition, 6-10 parts of rosin-modified acrylate resin, 5-9 parts of reactive organic microparticles, 4-7 parts of tertiary amine-containing polyurethane acrylate resin, 0.5-1.2 parts of methacrylamide-modified nano silica, 0.8-1.6 parts of polymerizable phosphate wetting agent, 0.2-0.8 parts of stabilizer, and 0.2-0.8 parts of process aid; The photosensitive group-modified hyperbranched polyester acrylate resin contains thioxanthone groups, acylphosphoxy groups, and acrylate double bonds; the mercapto-containing polyurethane acrylate resin contains urethane bonds, thioether bonds, mercapto groups, and acrylate double bonds; the rosin-modified acrylate resin contains rosin structures, imide structures, and acrylate double bonds; the tertiary amine-containing polyurethane acrylate resin contains tertiary amine groups and acrylate double bonds; and the reactive organic microparticles contain polymerizable double bonds, tertiary amine groups, carboxyl groups, hydrophobic segments, and crosslinking structures.

[0007] Preferably, the photosensitive group modified hyperbranched polyester acrylate resin has a number average molecular weight of 2500–7000, an acrylate functionality of 8–16, an acid value not higher than 8 mg KOH / g, and a viscosity of 40–100 Pa·s at 25°C.

[0008] Preferably, based on the total mass of the photosensitive group-modified hyperbranched polyester acrylate resin, the content of thioxanthone groups is 0.2–1.5 wt%, the content of acylphosphoxy groups is 0.3–2.5 wt%, and the total content of thioxanthone groups and acylphosphoxy groups is 0.5–4.0 wt%.

[0009] Preferably, the thiol-containing polyurethane acrylate resin molecular chain contains thioether bonds introduced by sulfur-containing diols, thiols introduced by mercaptodiols, and acrylate double bonds formed by hydroxyl acrylate end capping, and the thiol content of the thiol-containing polyurethane acrylate resin is 0.08–0.35 mmol / g.

[0010] Preferably, the reactive organic microparticles have a particle size of 70-180 nm; the reactive organic microparticles are obtained by in-situ polymerization of polymeric monomers in an active diluent, wherein the polymeric monomers include rosin methacrylate, long-chain alkyl acrylates, dimethylaminoethyl methacrylate, carboxyl-containing unsaturated monomers, and hexanediol diacrylate; wherein the long-chain alkyl acrylates are one or more of lauryl acrylate and isodecyl acrylate; and the carboxyl-containing unsaturated monomers are one or more of itaconic acid and methacrylic acid.

[0011] Preferably, the reactive diluent composition comprises propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, cyclotrimethylolpropane methyl acetal acrylate, and vinyl ether carbonate monomers, with a mass ratio of 8-10:5-8:4-6:1-3, and the total amount of monofunctional acrylate reactive diluents does not exceed 6% of the total mass of the binder.

[0012] A method for preparing a low-energy curable UV offset printing ink binder, comprising the following steps: S1. Preparation of photosensitive groups modified hyperbranched polyester acrylate resin containing thioxanthone groups, acylphosphoxy groups and acrylate double bonds; S2. Preparation of thiol-containing polyurethane acrylate resins containing urethane bonds, thioether bonds, thiol groups, and acrylate double bonds; S3. Prepare reactive organic microparticles containing polymerizable double bonds, tertiary amine groups, carboxyl groups, hydrophobic segments, and cross-linked structures by in-situ polymerization in an active diluent; S4. Preparation of rosin-modified acrylate resin containing rosin structure, imide structure and acrylate double bond; S5. Preparation of tertiary amine-containing polyurethane acrylate resins containing tertiary amine groups and acrylate double bonds; S6. The photosensitive group modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, reactive diluent composition, rosin modified acrylate resin, tertiary amine-containing polyurethane acrylate resin, reactive organic microparticles, methacrylamide modified nano silica, polymerizable phosphate wetting agent, stabilizer and process aid are mixed, degassed and filtered to obtain the low-energy curable UV offset printing ink binder.

[0013] Preferably, in step S1, the photosensitive group-modified hyperbranched polyester acrylate resin is prepared by the following method: Under nitrogen protection, trimethylolpropane, dimethylolpropionic acid, sebacic acid, and itaconic anhydride were subjected to an esterification reaction at 145-165℃ for 4-8 hours. When the acid value dropped to 25-45 mg KOH / g, the temperature was lowered to 95-110℃, and glycidyl methacrylate was added in the presence of a polymerization inhibitor for a ring-opening esterification reaction for 2-4 hours. Then, a carboxyl-containing thioxanone compound and a carboxyl-containing acylphosphine oxide compound were added for a grafting reaction for 2-5 hours, and the acid value of the reaction product was controlled to be no higher than 8 mg KOH / g to obtain the photosensitive group modified hyperbranched polyester acrylate resin.

[0014] Preferably, in step S2, the mercapto-containing polyurethane acrylate resin is prepared by the following method: Diisocyanate, hydroxy acrylate, sulfur-containing diol, glycerol carbonate and 3-mercapto-1,2-propanediol are reacted until the isocyanate group content is not higher than 0.2 wt%, to obtain the mercapto-containing polyurethane acrylate resin; wherein the amount of 3-mercapto-1,2-propanediol used is such that the mercapto content in the obtained resin is 0.08–0.35 mmol / g.

[0015] Preferably, in step S3, at least one component of the reactive diluent composition is used as the reaction medium, and rosin methacrylate, long-chain alkyl acrylate, dimethylaminoethyl methacrylate, carboxyl-containing unsaturated monomer, and hexanediol diacrylate are used as polymerization monomers. Semi-continuous free radical polymerization is carried out at 70-85°C, wherein the addition time of the polymerization monomer and free radical initiator is 1.5-3 h, and the reaction is continued at the temperature for 1-2 h after the addition is completed, forming reactive organic microparticles with a particle size of 70-180 nm; in step S6, the photosensitive group modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, reactive diluent composition, and tertiary amine-containing polyurethane acrylate resin are premixed for 30-60 min, and then the reactive organic microparticles are added, and mixing is continued for 30-60 min.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses a photosensitive group-modified hyperbranched polyester acrylate resin as the main resin. This resin simultaneously contains thioxanthone groups, acylphosphoxy groups, and acrylate double bonds. The thioxanthone groups can synergistically initiate curing with the tertiary amine-containing polyurethane acrylate resin, while the acylphosphoxy groups are beneficial for improving the deep curing efficiency under low-energy UV-LED conditions. The thiol groups and thioether bonds in the thiol-containing polyurethane acrylate resin can reduce the adverse effects of oxygen inhibition on surface curing, and the polyurethane segments can improve the flexibility and adhesion of the cured film. Therefore, this invention can improve the problems of slow low-energy curing, insufficient curing, surface stickiness, and brittle film in existing UV offset printing ink binders. 2. This invention uses tertiary amine-containing polyurethane acrylate resin to replace or reduce the use of traditional small-molecule amine additives. Through the combination of rosin-modified acrylate resin, reactive organic microparticles, methacrylamide-modified nano-silica, and polymerizable phosphate wetting agents, it improves the pigment wetting properties, structural viscosity, shear recovery, ink-water balance, anti-ink-spraying properties, and abrasion resistance of the binder. Overall, this invention has the advantages of high low-energy curing efficiency, good surface drying performance, stable offset printing suitability, good overall performance of the cured film, and low risk of small-molecule additive migration. Attached Figure Description

[0017] Figure 1 This is a process flow diagram for preparing the low-energy curable UV offset printing ink binder described in this invention; Figure 2 The image shows the FTIR spectrum of the photosensitive group modified hyperbranched polyester acrylate resin in Example 1; the three spectral lines correspond to the hyperbranched polyester precursor, the acrylated hyperbranched polyester, and the photosensitive group modified hyperbranched polyester acrylate resin, respectively. Figure 3 This is a comparison FTIR image of the reactive organic particles in Example 1 and the non-reactive organic particles in Comparative Example 3; Figure 4 The image shows a SEM image of a cured film formed after coating and UV curing of UV offset ink prepared using the low-energy curable UV offset ink binder obtained in Example 1. Detailed Implementation

[0018] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1-4 The present invention provides a technical solution: Example 1 This embodiment provides a low-energy curable UV offset printing ink binder. Unless otherwise specified, all "parts" mentioned in this embodiment refer to parts by weight. Based on the preparation of 1000 g of low-energy curable UV offset printing ink binder, the raw materials used in this embodiment are as follows: 420 g of photosensitive group modified hyperbranched polyester acrylate resin, 130 g of mercapto-containing polyurethane acrylate resin, 230 g of reactive diluent composition, 75 g of rosin-modified acrylate resin, 70 g of reactive organic microparticles, 50 g of tertiary amine-containing polyurethane acrylate resin, 8 g of methacrylamide-modified nano-silica, 11 g of polymerizable phosphate wetting agent, 4 g of stabilizer, and 2 g of process aid.

[0020] The reactive diluent composition comprises propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, cyclotrimethylolpropane methyl acetal acrylate, and vinyl ether carbonate monomers in a mass ratio of 9:6:5:2. Specifically, propoxylated neopentyl glycol diacrylate is Arkema Sartomer SR9003B, ethoxylated trimethylolpropane triacrylate is Arkema Sartomer SR454, cyclotrimethylolpropane methyl acetal acrylate is Arkema Sartomer SR531, and the vinyl ether carbonate monomer is ethyleneoxyethyl allyl carbonate prepared in this embodiment. Methacrylamide-modified nano-silica is Evonik AEROSIL R 711. The polymerizable phosphate wetting agent is Sartomer CN147 type acidic acrylate wetting monomer. The stabilizer is a mixture of p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol in a mass ratio of 1:1. The process aid used is BYK-1790 defoamer.

[0021] In this embodiment, the photosensitive group-modified hyperbranched polyester acrylate resin is prepared by the following method: 120 g of trimethylolpropane, 210 g of dimethylolpropionic acid, 95 g of sebacic acid, 22 g of itaconic anhydride, 0.8 g of p-toluenesulfonic acid, and 0.3 g of hypophosphite were added to a 2 L four-necked flask equipped with a mechanical stirrer, nitrogen inlet tube, thermometer, water separator, and condenser. After purging with nitrogen for 30 min to replace the air, the mixture was stirred at 300 r / min and heated to 155 °C. The esterification reaction was carried out under nitrogen protection for 6 h. During the reaction, water was continuously removed, and the first stage of the reaction was terminated when the acid value dropped to approximately 36 mg KOH / g.

[0022] The basic reaction principle of the above esterification reaction is that the carboxyl group and the hydroxyl group undergo condensation and dehydration to form an ester bond, and the representative reaction formula is as follows: R-COOH + R'-OH → R-COO-R' + H2O; The system was then cooled to 105°C, and 0.35 g of p-hydroxyanisole, 0.35 g of 2,6-di-tert-butyl-p-cresol, and 0.45 g of triphenylphosphine were added. Next, 86 g of glycidyl methacrylate was added dropwise over 45 min. The glycidyl methacrylate was a product of Sigma-Aldrich, containing 100–200 ppm of p-hydroxyanisole stabilizer. After the addition was complete, the reaction was maintained at 105°C for 3 h to allow the residual carboxyl groups to undergo ring-opening esterification with the epoxy groups, thereby introducing methacrylate double bonds into the hyperbranched polyester structure. The representative reaction formula for this step is as follows: R-COOH+CH2(O)CH-CH2-OCOC(CH3)=CH2→R-COO-CH2-CH(OH)-CH2-OCOC(CH3)=CH2; Then, 16 g of 2-carboxythoxanone (a carboxyl-containing thioxanone compound) and 24 g of APO-COOH (a carboxyl-containing acylphosphine oxide compound) were added to the system, and the reaction was continued at 105 °C for 4 h. During the later stages of the reaction, the pressure was gradually reduced to -0.085 MPa to remove trace amounts of moisture. APO-COOH was a self-prepared intermediate in this embodiment, and its preparation method was as follows: 100 g of IGM Resins Omnirad TPO-L, 42 g of ethylene glycol, and 0.3 g of tetrabutyl titanate were added to a flask and reacted at 95 °C for 4 h for transesterification to obtain a hydroxyethyl acylphosphine oxide compound. Then, 38 g of succinic anhydride and 0.2 g of 4-dimethylaminopyridine were added, and the mixture was reacted at 85 °C for 3 h to allow the hydroxyl group to undergo ring-opening reaction with the succinic anhydride, yielding a carboxyl-terminated acylphosphine oxide compound, APO-COOH. The acid value of the obtained APO-COOH was approximately 145 mg KOH / g, and its FTIR spectrum was approximately 1180–1200 cm⁻¹. - A characteristic absorption peak for P=O appears at position ¹, around 1720 cm⁻¹. - An absorption peak for carboxyl and ester groups (C=O) appears at position ¹. The carboxyl groups in APO-COOH are further esterified and grafted with the hydroxyl groups in the hyperbranched polyester resin, fixing the acylphosphoxy groups onto the resin backbone. The representative reaction formula is as follows: R-OH + HOOC-TX → R-OCO-TX + H2O; R-OH + HOOC-APO → R-OCO-APO + H2O.

[0023] In this study, TX represents the thioxanthone group, and APO represents the acylphosphoxy group. After the reaction, the acid value of the reaction product was controlled to be 6.5 mg KOH / g, the viscosity at 25℃ to be approximately 76 Pa·s, the number-average molecular weight to be approximately 4800, and the acrylate functionality to be approximately 12, resulting in a photosensitive group-modified hyperbranched polyester acrylate resin. In this resin, based on the total mass of the resin, the thioxanthone group content was approximately 0.8 wt%, the acylphosphoxy group content was approximately 1.3 wt%, and the total content of the two was approximately 2.1 wt%. To further characterize the structural changes of the photosensitive group-modified hyperbranched polyester acrylate resin, Fourier transform infrared spectroscopy was used to test the hyperbranched polyester precursor, the acrylated hyperbranched polyester, and the photosensitive group-modified hyperbranched polyester acrylate resin. The test range was 4000–650 cm⁻¹. - ¹, ATR testing mode was used with a resolution of 4 cm. - ¹, The number of scans was 32, and the test results are as follows: Figure 2 As shown.

[0024] Depend on Figure 2 It can be seen that the hyperbranched polyester precursor is at approximately 1720 cm⁻¹ - A distinct C=O absorption peak appears near ¹, and at approximately 3440 cm⁻¹ - The presence of an OH absorption peak near ¹ indicates that it possesses a polyester backbone and residual hydroxyl structure. After acrylate modification, the peak appears at approximately 1635 cm⁻¹ in the spectrum. - ¹ and approximately 810 cm - The presence or enhancement of absorption peaks related to the double bonds of acrylate near ¹ indicates that glycidyl methacrylate has participated in the ring-opening esterification reaction and introduced polymerizable double bonds into the resin. - The P=O related absorption peak is more pronounced near ¹ and is located at approximately 1600 cm⁻¹. - The presence or enhancement of aromatic ring-related absorption near the resin, while retaining characteristic absorption peaks such as C=O, C=C, and =CH, indicates that the thioxanone group, acylphosphoxy group, and acrylate double bond have been jointly introduced into the resin structure.

[0025] In this embodiment, the mercapto-containing polyurethane acrylate resin was prepared by the following method: 180 g of isophorone diisocyanate, 0.25 g of dibutyltin dilaurate, and 0.20 g of p-hydroxyanisole were added to a 1 L dry four-necked flask, and the mixture was heated to 50°C under dry nitrogen protection. The isophorone diisocyanate used was Covestro Desmodur I, and the hydroxy acrylate used was Sigma-Aldrich 2-hydroxyethyl acrylate. 72 g of 2-hydroxyethyl acrylate was added dropwise to the reaction system over 1 h, with the temperature controlled not to exceed 60°C during the addition. After the addition was completed, the reaction was maintained at this temperature for 1.5 h to allow some of the isocyanate groups to react with the hydroxy acrylate, generating an acrylate-terminated isocyanate prepolymer.

[0026] Subsequently, 52 g of thiodiethylene glycol, 36 g of glycerol carbonate, and 12 g of 3-mercapto-1,2-propanediol were added, and the reaction was continued at 65°C for 4 h until the isocyanate group content, as determined by di-n-butylamine back titration, was no higher than 0.2 wt%. Thiodiethylene glycol was a product of Sigma-Aldrich, glycerol carbonate was JEFFSOL Glycerine Carbonate from Huntsman, and 3-mercapto-1,2-propanediol was a product of TCI. The basic reaction principle of this resin is the reaction of isocyanate groups with hydroxyl groups to form urethane bonds, and the representative reaction formula is as follows: R-NCO + R'-OH → R-NHCOO-R'; In this resin structure, 2-hydroxyethyl acrylate introduces acrylate double bonds, thiodiglycol introduces thioether bonds, 3-mercapto-1,2-propanediol introduces polymerized thiol groups, and glycerol carbonate introduces carbonate structures. Iodometric analysis revealed that the thiol content of the obtained thiol-containing polyurethane acrylate resin was 0.18 mmol / g, and its viscosity at 25°C was approximately 32 Pa·s.

[0027] In this embodiment, the vinyl ether carbonate monomer is ethyleneoxyethyl allyl carbonate, which is prepared by the following method: 88 g of 2-hydroxyethyl vinyl ether, 105 g of triethylamine, and 200 g of anhydrous dichloromethane were added to a 500 mL three-necked flask. The mixture was cooled to 0–5°C in an ice-water bath. 106 g of allyl chloroformate was added dropwise under nitrogen protection over 1.5 h, with the reaction temperature controlled not to exceed 10°C during the addition. After the addition was complete, the temperature was raised to 25°C and reacted for 3 h. The triethylamine hydrochloride was removed by filtration. After removing dichloromethane from the filtrate under reduced pressure, low-boiling substances were removed at 60°C and -0.09 MPa to obtain ethyleneoxyethyl allyl carbonate. Its representative reaction formula is as follows: CH2=CH-O-CH2CH2-OH+ClCOOCH2CH=CH2+Et3N→CH2=CH-O-CH2CH2-OCOOCH2CH=CH2+Et3N·HCl; This monomer contains both vinyl ether and carbonate structures, which can be used to adjust the polarity, flexibility, and shrinkage of the binder system.

[0028] In this embodiment, the rosin-modified acrylate resin was prepared by the following method: 260 g of maleic rosin was added to a 1 L four-necked flask and heated to 125 °C to melt it. Then, 0.25 g of p-hydroxyanisole, 0.6 g of p-toluenesulfonic acid, and 0.5 g of triphenylphosphine were added, followed by the dropwise addition of 68 g of 2-hydroxyethyl acrylate over 1 h. The mixture was then reacted at 120 °C for 3 h to allow the carboxyl groups or anhydride structures in the maleic rosin to undergo esterification with the hydroxyacrylate. Next, 32 g of N-(2-hydroxyethyl)phthalimide was added, and the reaction was continued for 2 h to obtain a rosin-modified acrylate resin containing rosin, imide, and acrylate double bonds. The resulting resin had an acid value of 42 mg KOH / g and exhibited a high-viscosity, transparent amber-colored resin at 25 °C. The rosin structure in this resin improves the adhesion of the binder and the wettability of the pigment, the imide structure improves the cohesive strength of the cured film, and the acrylate double bonds participate in subsequent UV curing crosslinking.

[0029] In this embodiment, the tertiary amine-containing polyurethane acrylate resin was prepared by the following method: 220 g of polytetrahydrofuran diol, 96 g of isophorone diisocyanate, 0.18 g of dibutyltin dilaurate, and 0.16 g of p-hydroxyanisole were added to a 1 L dry four-necked flask. The mixture was heated to 70 °C and reacted for 2 h under nitrogen protection to obtain an isocyanate-terminated prepolymer. Subsequently, 32 g of N-methyldiethanolamine was added, and the mixture was reacted at 65 °C for 1.5 h to graft tertiary amine groups into the polyurethane chain. Finally, 48 g of 2-hydroxyethyl acrylate was added, and the reaction continued for 2 h until the isocyanate group content was no higher than 0.2 wt%, yielding a tertiary amine-containing polyurethane acrylate resin containing tertiary amine groups and acrylate double bonds. The tertiary amine value of the obtained tertiary amine-containing polyurethane acrylate resin was 0.65 mmol / g, and the viscosity at 25 °C was approximately 45 Pa·s. In this resin, the tertiary amine group can undergo photoinduced electron transfer and hydrogen donation reactions with the thioxanthone group to generate free radicals that can initiate the polymerization of acrylates. At the same time, the acrylate double bond allows the resin to enter the curing network.

[0030] In this embodiment, the reactive organic microparticles were prepared by in-situ semi-continuous free radical polymerization in an reactive diluent. 90 g of SR9003B and 70 g of SR531 from the reactive diluent composition were added to a 2 L reactor as the reaction medium, along with 3 g of a polymerizable phosphate wetting agent as a dispersion stabilizing component. After purging with nitrogen for 30 min, the temperature was raised to 78°C, and the stirring speed was controlled at 600 r / min. The polymerizable phosphate wetting agent was used to improve the dispersion stability of the reactive organic microparticles in the reactive diluent. Separately, 90 g of rosin methacrylate, 65 g of lauryl acrylate, 35 g of isodecyl acrylate, 42 g of dimethylaminoethyl methacrylate, 18 g of itaconic acid, 20 g of hexanediol diacrylate, and 4.0 g of azobisisobutyronitrile were mixed evenly and used as the monomer dropping solution. Rosin methacrylate was prepared by pre-esterification of maleic rosin and glycidyl methacrylate. Specifically, 100 g of maleic rosin, 38 g of glycidyl methacrylate, 0.2 g of triphenylphosphine, and 0.1 g of p-hydroxyanisole were added to a reactor and reacted at 105 °C for 3 h to allow the carboxyl groups in maleic rosin to undergo a ring-opening esterification reaction with the epoxy groups in glycidyl methacrylate. The resulting rosin methacrylate had an acid value of 8 mg KOH / g. Lauryl acrylate, isodecanyl acrylate, and dimethylaminoethyl methacrylate were reagent-grade products from Sigma-Aldrich. Hexanediol diacrylate was SR238 from Arkema Sartomer.

[0031] The above monomer dropwise solution was uniformly added to the reactor over 2.5 h, and the reaction was continued at 78 °C for 1.5 h after the addition was completed. During the reaction, rosin methacrylate and long-chain alkyl acrylates provided hydrophobic segments, dimethylaminoethyl methacrylate provided tertiary amine groups, itaconic acid provided carboxyl groups, and hexanediol diacrylate formed a small amount of cross-linked structure. By controlling the amount of hexanediol diacrylate and the polymerization conversion rate, some unreacted double bonds that could participate in subsequent UV curing were retained in the obtained microparticles. After the reaction, a reactive organic microparticle dispersion with a mass content of approximately 60 wt% was obtained. The D50 particle size of the obtained reactive organic microparticles was determined to be 118 nm by dynamic light scattering. FTIR detection showed that the microparticle dispersion had a density of 10 nm at 810 cm⁻¹. - The presence of characteristic absorption peaks of acrylate double bonds in the vicinity indicates that it contains polymerizable double bonds that can participate in subsequent UV curing.

[0032] In the above-mentioned in-situ polymerization process of reactive organic microparticles, a representative free radical polymerization reaction can be represented as: nCH2=C(R)-COOR' → [-CH2-C(R)(COOR')-] n ; Wherein, R is H or CH3, and R' is rosinyl, long-chain alkyl, dimethylaminoethyl, or other structural groups. Hexanediol diacrylate participates in copolymerization to form micro-crosslinking points, enabling the particles to maintain a stable particle size and a certain internal crosslinking structure.

[0033] The preparation method of the low-energy curable UV offset printing ink binder is as follows: Based on 1000 g of binder, weigh 420 g of photosensitive group-modified hyperbranched polyester acrylate resin, 130 g of mercapto-containing polyurethane acrylate resin, 75 g of rosin-modified acrylate resin, and 50 g of tertiary amine-containing polyurethane acrylate resin and add them to a planetary stirred tank. Stir at 50°C under light-protected conditions for 30 min. Take 116.7 g of the reactive organic microparticle dispersion, and based on a solid content of 60 wt%, calculate that it contains 70 g of reactive organic microparticles. The non-microparticle components in this dispersion are included in the total amount of the reactive diluent composition and polymerizable phosphate wetting agent according to their composition. Separately take the reactive diluent composition, and combine it with the reactive diluent accompanying the reactive organic microparticle dispersion to make a total of 230 g, reserving 20 g for pre-wetting treatment of methacrylamide-modified nano-silica. Add the remaining reactive diluent composition to the planetary stirred tank and continue stirring for 30 min to form a uniform, transparent, or slightly turbid resin liquid.

[0034] The reactive organic microparticle dispersion was then slowly added to the system over a period of 20 minutes, followed by stirring for another 45 minutes. 8 g of methacrylamide-modified nano-silica was pre-wetted with the reserved 20 g reactive diluent composition and dispersed at high speed for 10 minutes (2500 r / min), then added to a planetary stirred tank. Based on the actual amount of polymerizable phosphate wetting agent carried over from the reactive organic microparticle dispersion, polymerizable phosphate wetting agent was added to bring the total amount of polymerizable phosphate wetting agent in the final binder to 11 g. Finally, 4 g of stabilizer and 2 g of BYK-1790 defoamer were added.

[0035] After all materials are added, the mixture is degassed for 40 minutes at 50°C and a vacuum of -0.085 MPa, and then filtered through a 5 μm stainless steel filter to obtain a low-energy curing UV offset printing ink binder.

[0036] Example 2 This embodiment provides a low-energy curable UV offset printing ink binder. Unless otherwise specified, all "parts" mentioned in this embodiment refer to parts by weight. Based on the preparation of 1000 g of low-energy curable UV offset printing ink binder, the raw materials used in this embodiment are as follows: 390 g of photosensitive group-modified hyperbranched polyester acrylate resin, 145 g of mercapto-containing polyurethane acrylate resin, 255 g of reactive diluent composition, 65 g of rosin-modified acrylate resin, 75 g of reactive organic microparticles, 45 g of tertiary amine-containing polyurethane acrylate resin, 9 g of methacrylamide-modified nano-silica, 12 g of polymerizable phosphate wetting agent, 3 g of stabilizer, and 1 g of process aid.

[0037] The reactive diluent composition comprises propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, cyclotrimethylolpropane methyl acetal acrylate, and vinyl ether carbonate monomers in a mass ratio of 8:7:5:2. The propoxylated neopentyl glycol diacrylate used is Arkema Sartomer SR9003B, the ethoxylated trimethylolpropane triacrylate is Arkema Sartomer SR454, the cyclotrimethylolpropane methyl acetal acrylate is Arkema Sartomer SR531, and the vinyl ether carbonate monomer is ethyleneoxyethyl allyl carbonate. The methacrylamide-modified nano silica used was AEROSIL R 711 from Evonik. The polymerizable phosphate wetting agent was Sartomer CN147 type acidic acrylate wetting monomer. The stabilizer was a mixture of p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol in a mass ratio of 1:1. The process aid was BYK-1790 type defoamer.

[0038] In this embodiment, the photosensitive group-modified hyperbranched polyester acrylate resin was prepared according to the basic method of Example 1. Specifically, 115 g of trimethylolpropane, 220 g of dimethylolpropionic acid, 90 g of sebacic acid, 20 g of itaconic anhydride, 0.8 g of p-toluenesulfonic acid, and 0.3 g of hypophosphite were added to a 2 L four-necked flask. Under nitrogen protection, the temperature was raised to 150 °C for esterification reaction for 5.5 h. When the acid value dropped to about 38 mg KOH / g, the temperature was lowered to 105 °C, and 0.35 g of p-hydroxyanisole, 0.35 g of 2,6-di-tert-butyl-p-cresol, and 0.45 g of triphenylphosphine were added. Then, 80 g of glycidyl methacrylate was added dropwise over a period of 45 min. After the addition was completed, the reaction was maintained at the temperature for 3 h. Subsequently, 10 g of 2-carboxythioxanthone and 32 g of APO-COOH were added, and the reaction was continued at 105 °C for 4 h. Trace amounts of water were removed under reduced pressure in the later stages of the reaction to obtain a photosensitive group-modified hyperbranched polyester acrylate resin. The resulting resin had an acid value of 7.1 mg KOH / g, a viscosity of approximately 88 Pa·s at 25 °C, a number-average molecular weight of approximately 5600, and an acrylate functionality of approximately 10. Based on the total mass of the resin, the thioxanthone group content was approximately 0.5 wt%, the acylphosphoxy group content was approximately 1.7 wt%, and the total content of both was approximately 2.2 wt%.

[0039] In this embodiment, the mercapto-containing polyurethane acrylate resin was prepared according to the basic method of Example 1. Specifically, 180 g of isophorone diisocyanate, 0.25 g of dibutyltin dilaurate, and 0.20 g of p-hydroxyanisole were added to a 1 L dry four-necked flask. Under nitrogen protection, the temperature was raised to 50°C, and 68 g of 2-hydroxyethyl acrylate was added dropwise over 1 h. After the addition was completed, the reaction was maintained at this temperature for 1.5 h. Subsequently, 58 g of thiodiethylene glycol, 32 g of glycerol carbonate, and 18 g of 3-mercapto-1,2-propanediol were added, and the reaction was continued at 65°C for 4 h until the isocyanate group content was no higher than 0.2 wt%, thus obtaining the mercapto-containing polyurethane acrylate resin. The obtained resin had a mercapto content of 0.28 mmol / g and a viscosity of approximately 38 Pa·s at 25°C.

[0040] In this embodiment, the preparation methods of ethyleneoxyethyl allyl carbonate, APO-COOH, rosin-modified acrylate resin, and tertiary amine-containing polyurethane acrylate resin are the same as in Example 1. The resulting rosin-modified acrylate resin has an acid value of 40 mg KOH / g; the resulting tertiary amine-containing polyurethane acrylate resin has a tertiary amine value of 0.60 mmol / g and a viscosity of approximately 48 Pa·s at 25°C.

[0041] In this embodiment, the reactive organic microparticles were prepared by in-situ semi-continuous free radical polymerization in an active diluent. 80 g of SR9003B, 80 g of SR531, and 3 g of polymerizable phosphate wetting agent were added to a 2 L reactor. After purging with nitrogen for 30 min, the temperature was raised to 80 °C, and the stirring speed was controlled at 650 r / min. Separately, 85 g of rosin methacrylate, 55 g of lauryl acrylate, 45 g of isodecyl acrylate, 46 g of dimethylaminoethyl methacrylate, 20 g of itaconic acid, 24 g of hexanediol diacrylate, and 4.2 g of azobisisobutyronitrile were mixed thoroughly to form a monomer dropping solution. This monomer dropping solution was added dropwise to the reactor over 2.5 h. After the addition was completed, the reactor was kept at 80 °C for another 1.5 h to obtain a reactive organic microparticle dispersion with a mass content of approximately 60 wt%. The D50 particle size of the reactive organic microparticles was determined to be 145 nm using dynamic light scattering; FTIR analysis showed that its particle size at 810 cm⁻¹ was within the range of 145 nm. - ¹The area still exhibits characteristic absorption peaks of acrylate double bonds.

[0042] The preparation method of the low-energy curable UV offset printing ink binder is as follows: Based on 1000 g of binder, weigh 390 g of photosensitive group-modified hyperbranched polyester acrylate resin, 145 g of mercapto-containing polyurethane acrylate resin, 65 g of rosin-modified acrylate resin, and 45 g of tertiary amine-containing polyurethane acrylate resin, and add them to a planetary stirred tank. Stir at 50°C under light-protected conditions for 30 min. Take 125 g of the reactive organic microparticle dispersion, and based on a reactive organic microparticle content of 60 wt%, calculate that it contains 75 g of reactive organic microparticles. The non-microparticle components in this dispersion are included in the total amount of the reactive diluent composition and polymerizable phosphate wetting agent according to their composition. Separately take the reactive diluent composition, and make it total 255 g with the reactive diluent accompanying the reactive organic microparticle dispersion, reserving 22 g for pre-wetting treatment of methacrylamide-modified nano-silica. Add the remaining reactive diluent composition to the planetary stirred tank and continue stirring for 30 min.

[0043] The reactive organic microparticle dispersion was then slowly added to the system over a period of 20 minutes, followed by stirring for another 45 minutes. Nine g of methacrylamide-modified nano-silica was pre-wetted with the reserved 22 g reactive diluent composition and dispersed at high speed for 10 minutes (2500 r / min), then added to a planetary stirred tank. Based on the actual amount of polymerizable phosphate wetting agent carried over from the reactive organic microparticle dispersion, polymerizable phosphate wetting agent was added to bring the total amount of polymerizable phosphate wetting agent in the final binder to 12 g. Finally, 3 g of stabilizer and 1 g of BYK-1790 defoamer were added.

[0044] After all materials are added, the mixture is degassed for 35 minutes at 50°C and a vacuum of -0.085 MPa, and then filtered through a 5 μm stainless steel filter to obtain a low-energy curing UV offset printing ink binder.

[0045] Example 3 This embodiment provides a low-energy curable UV offset printing ink binder. Unless otherwise specified, all "parts" mentioned in this embodiment refer to parts by weight. Based on the preparation of 1000 g of low-energy curable UV offset printing ink binder, the raw materials used in this embodiment are as follows: 450 g of photosensitive group modified hyperbranched polyester acrylate resin, 100 g of mercapto-containing polyurethane acrylate resin, 220 g of reactive diluent composition, 85 g of rosin-modified acrylate resin, 55 g of reactive organic microparticles, 60 g of tertiary amine-containing polyurethane acrylate resin, 10 g of methacrylamide-modified nano-silica, 12 g of polymerizable phosphate wetting agent, 5 g of stabilizer, and 3 g of process aid.

[0046] The reactive diluent composition comprises propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, cyclotrimethylolpropane methyl acetal acrylate, and vinyl ether carbonate monomers in a mass ratio of 10:5:4:2. The propoxylated neopentyl glycol diacrylate used is Arkema Sartomer SR9003B, the ethoxylated trimethylolpropane triacrylate is Arkema Sartomer SR454, the cyclotrimethylolpropane methyl acetal acrylate is Arkema Sartomer SR531, and the vinyl ether carbonate monomer is ethyleneoxyethyl allyl carbonate. The methacrylamide-modified nano silica used was AEROSIL R 711 from Evonik. The polymerizable phosphate wetting agent was Sartomer CN147 type acidic acrylate wetting monomer. The stabilizer was a mixture of p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol in a mass ratio of 1:1. The process aid was BYK-1790 type defoamer.

[0047] In this embodiment, the photosensitive group-modified hyperbranched polyester acrylate resin was prepared according to the basic method of Example 1. Specifically, 125 g of trimethylolpropane, 200 g of dimethylolpropionic acid, 100 g of sebacic acid, 24 g of itaconic anhydride, 0.8 g of p-toluenesulfonic acid, and 0.3 g of hypophosphite were added to a 2 L four-necked flask. Under nitrogen protection, the temperature was raised to 160 °C for esterification reaction for 6.5 h. When the acid value dropped to about 34 mg KOH / g, the temperature was lowered to 105 °C, and 0.35 g of p-hydroxyanisole, 0.35 g of 2,6-di-tert-butyl-p-cresol, and 0.45 g of triphenylphosphine were added. Then, 92 g of glycidyl methacrylate was added dropwise over 50 min. After the addition was completed, the reaction was maintained at the temperature for 3 h. Subsequently, 22 g of 2-carboxythioxanthone and 18 g of APO-COOH were added, and the reaction was continued at 105 °C for 4 h. Trace amounts of moisture were removed under reduced pressure in the later stages of the reaction to obtain a photosensitive group-modified hyperbranched polyester acrylate resin. The resulting resin had an acid value of 6.2 mg KOH / g, a viscosity of approximately 68 Pa·s at 25 °C, a number-average molecular weight of approximately 4300, and an acrylate functionality of approximately 14. Based on the total mass of the resin, the thioxanthone group content was approximately 1.2 wt%, the acylphosphoxy group content was approximately 0.9 wt%, and the total content of both was approximately 2.1 wt%.

[0048] In this embodiment, the mercapto-containing polyurethane acrylate resin was prepared according to the basic method of Example 1. Specifically, 180 g of isophorone diisocyanate, 0.25 g of dibutyltin dilaurate, and 0.20 g of p-hydroxyanisole were added to a 1 L dry four-necked flask. Under nitrogen protection, the temperature was raised to 50°C, and 78 g of 2-hydroxyethyl acrylate was added dropwise over 1 h. After the addition was completed, the reaction was maintained at this temperature for 1.5 h. Subsequently, 48 g of thiodiethylene glycol, 40 g of glycerol carbonate, and 8 g of 3-mercapto-1,2-propanediol were added, and the reaction was continued at 65°C for 4 h until the isocyanate group content was no higher than 0.2 wt%, thus obtaining the mercapto-containing polyurethane acrylate resin. The obtained resin had a mercapto content of 0.11 mmol / g and a viscosity of approximately 30 Pa·s at 25°C.

[0049] In this embodiment, the preparation methods of ethyleneoxyethyl allyl carbonate, APO-COOH, and rosin-modified acrylate resin are the same as in Example 1. The resulting rosin-modified acrylate resin has an acid value of 43 mg KOH / g and exhibits a high-viscosity, transparent amber-colored resinous state at 25°C.

[0050] In this embodiment, the tertiary amine-containing polyurethane acrylate resin was prepared according to the basic method of Example 1. Specifically, 220 g of polytetrahydrofuran diol, 96 g of isophorone diisocyanate, 0.18 g of dibutyltin dilaurate, and 0.16 g of p-hydroxyanisole were added to a 1 L dry four-necked flask and reacted at 70 °C for 2 h under nitrogen protection to obtain an isocyanate-terminated prepolymer; then 38 g of N-methyldiethanolamine was added and reacted at 65 °C for 1.5 h; finally, 44 g of 2-hydroxyethyl acrylate was added and the reaction continued for 2 h until the isocyanate group content was not higher than 0.2 wt%, thus obtaining the tertiary amine-containing polyurethane acrylate resin. The obtained resin had a tertiary amine value of 0.76 mmol / g and a viscosity of approximately 52 Pa·s at 25 °C.

[0051] In this embodiment, the reactive organic microparticles were prepared by in-situ semi-continuous free radical polymerization in an active diluent. 100 g of SR9003B, 60 g of SR531, and 3 g of polymerizable phosphate wetting agent were added to a 2 L reactor. After purging with nitrogen for 30 min, the temperature was raised to 75°C, and the stirring speed was controlled at 600 r / min. Separately, 95 g of rosin methacrylate, 70 g of lauryl acrylate, 25 g of isodecyl acrylate, 36 g of dimethylaminoethyl methacrylate, 16 g of methacrylic acid, 18 g of hexanediol diacrylate, and 3.8 g of azobisisobutyronitrile were mixed thoroughly to form a monomer dropwise solution. This monomer dropwise solution was added dropwise to the reactor over 2 h. After the addition was completed, the reactor was kept at 75°C for another 2 h to obtain a reactive organic microparticle dispersion with a mass content of approximately 60 wt%. The D50 particle size of the reactive organic microparticles was determined to be 92 nm using dynamic light scattering; FTIR analysis showed that its particle size at 810 cm⁻¹ was [missing value]. - ¹The area still exhibits characteristic absorption peaks of acrylate double bonds.

[0052] The preparation method of the low-energy curable UV offset printing ink binder is as follows: Based on 1000 g of binder, weigh 450 g of photosensitive group-modified hyperbranched polyester acrylate resin, 100 g of mercapto-containing polyurethane acrylate resin, 85 g of rosin-modified acrylate resin, and 60 g of tertiary amine-containing polyurethane acrylate resin, and add them to a planetary stirred tank. Stir at 50°C under light-protected conditions for 30 min. Take 91.7 g of the reactive organic microparticle dispersion, and based on a reactive organic microparticle content of 60 wt%, calculate that it contains 55 g of reactive organic microparticles. The non-microparticle components in this dispersion are included in the total amount of the reactive diluent composition and polymerizable phosphate wetting agent according to their composition. Separately take the reactive diluent composition, and make it total 220 g with the reactive diluent accompanying the reactive organic microparticle dispersion, reserving 25 g for pre-wetting treatment of methacrylamide-modified nano-silica. Add the remaining reactive diluent composition to the planetary stirred tank and continue stirring for 30 min.

[0053] The reactive organic microparticle dispersion was then slowly added to the system over a period of 20 minutes, followed by stirring for another 45 minutes. 10 g of methacrylamide-modified nano-silica was pre-wetted with the reserved 25 g reactive diluent composition and dispersed at high speed for 10 minutes (2500 r / min), then added to a planetary stirred tank. Based on the actual amount of polymerizable phosphate wetting agent carried over from the reactive organic microparticle dispersion, polymerizable phosphate wetting agent was added to bring the total amount of polymerizable phosphate wetting agent in the final binder to 12 g. Finally, 5 g of stabilizer and 3 g of BYK-1790 defoamer were added.

[0054] After all materials are added, the mixture is degassed for 40 minutes at 50°C and a vacuum of -0.085 MPa, and then filtered through a 5 μm stainless steel filter to obtain a low-energy curing UV offset printing ink binder.

[0055] Comparative Example 1 This comparative example provides a UV offset printing ink binder, which differs from Example 1 in that the photosensitive group modified hyperbranched polyester acrylate resin in Example 1 is replaced with hyperbranched polyester acrylate resin without grafted thioxanthone groups and acylphosphoxy groups, and a small molecule photoinitiator is added.

[0056] This comparative example is based on the preparation of 1000 g of UV offset printing ink binder. The raw materials used are as follows: 402 g of hyperbranched polyester acrylate resin without photosensitive groups, 130 g of thiol-containing polyurethane acrylate resin, 230 g of reactive diluent composition, 75 g of rosin-modified acrylate resin, 70 g of reactive organic microparticles, 50 g of tertiary amine-containing polyurethane acrylate resin, 8 g of methacrylamide-modified nano silica, 11 g of polymerizable phosphate wetting agent, 4 g of stabilizer, 2 g of process aid, and 18 g of small molecule photoinitiator.

[0057] The hyperbranched polyester acrylate resin without grafted photosensitive groups was prepared according to the front-end method of photosensitive group modified hyperbranched polyester acrylate resin in Example 1, but after the ring-opening esterification reaction of glycidyl methacrylate, 2-carboxythioxanthone and APO-COOH were not added for grafting reaction. The resulting resin had an acid value of 7.0 mg KOH / g, a viscosity of approximately 70 Pa·s at 25°C, a number-average molecular weight of approximately 4300, and an acrylate functionality of approximately 12.

[0058] The small molecule photoinitiator is composed of Omnirad TPO-L and 2-isopropylthioxanthone in a mass ratio of 2:1. The mercapto-containing polyurethane acrylate resin, rosin-modified acrylate resin, reactive organic microparticles, tertiary amine-containing polyurethane acrylate resin, reactive diluent composition, methacrylamide-modified nano-silica, polymerizable phosphate wetting agent, stabilizer, and process aids are all prepared using the same raw materials or methods as in Example 1.

[0059] The preparation method of this comparative example is as follows: According to the above formula, the hyperbranched polyester acrylate resin without photosensitive groups, the thiol-containing polyurethane acrylate resin, the rosin-modified acrylate resin, the tertiary amine-containing polyurethane acrylate resin and the small molecule photoinitiator were added to a planetary stirred tank and stirred at 50°C under light-proof conditions for 30 min; then the reactive diluent composition and the reactive organic microparticle dispersion were added and stirred for another 45 min; subsequently, the methacrylamide-modified nano silica, polymerizable phosphate wetting agent, stabilizer and process aids pre-wetted with reactive diluent were added, and the mixture was degassed at 50°C under vacuum of -0.085 MPa for 40 min, and then filtered through a 5 μm stainless steel filter to obtain the UV offset printing ink binder of Comparative Example 1.

[0060] Comparative Example 2 This comparative example provides a UV offset printing ink binder, which differs from Example 1 in that the mercapto-containing polyurethane acrylate resin in Example 1 is replaced with a common polyurethane acrylate resin that does not contain mercapto groups and thioether bonds.

[0061] The comparative example is based on the preparation of 1000 g of UV offset printing ink binder. The raw materials used are as follows: 420 g of photosensitive group modified hyperbranched polyester acrylate resin, 130 g of ordinary polyurethane acrylate resin, 230 g of reactive diluent composition, 75 g of rosin modified acrylate resin, 70 g of reactive organic microparticles, 50 g of tertiary amine-containing polyurethane acrylate resin, 8 g of methacrylamide modified nano silica, 11 g of polymerizable phosphate wetting agent, 4 g of stabilizer, and 2 g of process aid.

[0062] The ordinary polyurethane acrylate resin was prepared by the following method: 180 g of isophorone diisocyanate, 120 g of polytetrahydrofuran glycol, 0.25 g of dibutyltin dilaurate, and 0.20 g of p-hydroxyanisole were added to a 1 L dry four-necked flask. The mixture was heated to 70 °C and reacted for 2 h under nitrogen protection to obtain an isocyanate-terminated prepolymer. Subsequently, 86 g of 2-hydroxyethyl acrylate was added, and the reaction was continued at 65 °C for 3 h until the isocyanate group content was not higher than 0.2 wt%, thus obtaining the ordinary polyurethane acrylate resin. The obtained ordinary polyurethane acrylate resin had a viscosity of approximately 35 Pa·s at 25 °C, and no mercapto-characteristic content was detected.

[0063] The photosensitive group modified hyperbranched polyester acrylate resin, rosin modified acrylate resin, reactive organic microparticles, tertiary amine-containing polyurethane acrylate resin, reactive diluent composition, methacrylamide modified nano silica, polymerizable phosphate wetting agent, stabilizer and process aid were all prepared using the same raw materials or methods as in Example 1.

[0064] The preparation method of this comparative example is as follows: According to the above formula, photosensitive group modified hyperbranched polyester acrylate resin, ordinary polyurethane acrylate resin, rosin modified acrylate resin and tertiary amine-containing polyurethane acrylate resin are added to a planetary stirred tank and stirred at 50°C under light-proof conditions for 30 min; then, an active diluent composition and a reactive organic microparticle dispersion are added and stirred for another 45 min; subsequently, methacrylamide-modified nano silica pre-wetted with active diluent, polymerizable phosphate wetting agent, stabilizer and process aid are added, and the mixture is degassed at 50°C under vacuum of -0.085 MPa for 40 min, and then filtered through a 5 μm stainless steel filter to obtain the UV offset printing ink binder of Comparative Example 2.

[0065] Comparative Example 3 This comparative example provides a UV offset printing ink binder, which differs from Example 1 in that the reactive organic microparticles in Example 1 are replaced with non-reactive organic microparticles.

[0066] The comparative example is based on the preparation of 1000 g of UV offset printing ink binder. The raw materials used are as follows: 420 g of photosensitive group modified hyperbranched polyester acrylate resin, 130 g of mercapto-containing polyurethane acrylate resin, 230 g of reactive diluent composition, 75 g of rosin modified acrylate resin, 70 g of non-reactive organic microparticles, 50 g of tertiary amine-containing polyurethane acrylate resin, 8 g of methacrylamide modified nano silica, 11 g of polymerizable phosphate wetting agent, 4 g of stabilizer, and 2 g of process aid.

[0067] The non-reactive organic microparticles were prepared by in-situ free radical polymerization in an active diluent. 90 g of SR9003B and 70 g of SR531 were added to a 2 L reactor as the reaction medium. After purging with nitrogen for 30 min, the temperature was raised to 78 °C, and the stirring speed was controlled at 600 r / min. Separately, 150 g of methyl methacrylate, 80 g of butyl acrylate, 40 g of lauryl acrylate, and 4.0 g of azobisisobutyronitrile were mixed evenly to prepare the monomer drop solution. This monomer drop solution was uniformly added to the reactor over 2.5 h. After the addition was completed, the reactor was kept at 78 °C for 3 h to obtain a dispersion of non-reactive organic microparticles. Dynamic light scattering analysis showed that the D50 particle size of the obtained non-reactive organic microparticles was 125 nm; no significant 810 cm⁻¹ particle size was observed in FTIR detection. - ¹Characteristic absorption peak of acrylate double bond.

[0068] The photosensitive group modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, rosin modified acrylate resin, tertiary amine-containing polyurethane acrylate resin, reactive diluent composition, methacrylamide modified nano silica, polymerizable phosphate wetting agent, stabilizer and process aid were all prepared using the same raw materials or methods as in Example 1.

[0069] The preparation method of this comparative example is as follows: According to the above formula, photosensitive group modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, rosin modified acrylate resin and tertiary amine-containing polyurethane acrylate resin were added to a planetary stirred tank and stirred at 50°C under light-proof conditions for 30 min; a non-reactive organic microparticle dispersion was taken, so that the amount of non-reactive organic microparticles in the dispersion was 70 g, and the non-microparticle components in the dispersion were included in the total amount of the reactive diluent composition according to their composition; the reactive diluent composition was then added, so that the total amount of the reactive diluent composition in the final binder was 230 g, and stirring was continued for 30 min; then the non-reactive organic microparticle dispersion was added, and stirring was continued for 45 min; then methacrylamide modified nano silica, polymerizable phosphate wetting agent, stabilizer and process aids pre-wetted with reactive diluent were added, and the mixture was degassed at 50°C under vacuum of -0.085 MPa for 40 min, and filtered through a 5 μm stainless steel filter to obtain the UV offset printing ink binder of Comparative Example 3.

[0070] To compare the structural differences between reactive and non-reactive organic microparticles, the reactive organic microparticle dispersion prepared in Example 1 and the non-reactive organic microparticle dispersion prepared in Comparative Example 3 were coated into thin films and placed under light-protected conditions to form stable test films. Fourier transform infrared spectroscopy was then used for testing. The test range was 4000–650 cm⁻¹. - ¹, ATR testing mode was used with a resolution of 4 cm. - ¹, The number of scans was 32, and the test results are as follows: Figure 3 As shown. By Figure 3 As can be seen, the reactive organic microparticles prepared in Example 1 have a reaction time of approximately 1720 cm⁻¹. - ¹ It has a C=O absorption peak near 1160 cm⁻¹ - ¹ It has a C–O–C absorption peak near 1635 cm⁻¹, and at approximately 1635 cm⁻¹ - ¹ and approximately 810 cm - The presence of characteristic absorption peaks related to acrylate double bonds near ¹ indicates that its structure still contains polymerizable double bonds that can participate in subsequent UV curing. In contrast, although the non-reactive organic microparticles prepared in Comparative Example 3 also exhibit absorption peaks such as C=O, C–H, and C–O–C, their absorption peaks are lower at approximately 1635 cm⁻¹. - ¹ and approximately 810 cm - The significant weakening or absence of the double bond characteristic absorption peak near ¹ indicates that there are fewer double bond structures in this non-reactive organic microparticle that can participate in the UV curing reaction, making it difficult to effectively integrate into the crosslinking network during the subsequent UV curing process.

[0071] The results indicate that there is a significant difference between the reactive organic microparticles in Example 1 and the non-reactive organic microparticles in Comparative Example 3 in terms of retention of polymerizable double bonds.

[0072] Experimental testing and results analysis To verify the technical effect of the low-energy curing UV offset printing ink binder of the present invention, the binders obtained in Examples 1-3 and Comparative Examples 1-3 were mixed with the same carbon black pigment, filler, and conventional additives to prepare UV offset printing ink samples. The binder was used in quantities of 70 parts by weight, carbon black pigment in quantities of 15 parts by weight, calcium carbonate filler in quantities of 10 parts by weight, polyethylene wax powder in quantities of 2 parts by weight, dispersant in quantities of 1 part by weight, and other conventional additives in quantities of 2 parts by weight. Each group of samples was milled three times using a three-roll mill to control the ink fineness to be no higher than 10 μm, and then allowed to stand at 25°C for 24 h before performance testing. Unless otherwise specified, each group of tests was performed in triplicate, and the results in the table are average values.

[0073] To observe the surface morphology of the cured film, a UV offset ink sample prepared using the low-energy curable UV offset ink binder obtained in Example 1 was applied to the surface of a corona-treated PET film using a wire rod coater. The wet film thickness was controlled to be 5 μm, and the film was cured under a 395 nm UV-LED light source with an irradiation energy of 90 mJ / cm². The resulting cured film was cut to an appropriate size, fixed on a sample stage, and after gold sputtering, its surface morphology was observed using a scanning electron microscope. The test results are as follows: Figure 4 As shown. By Figure 4 As can be seen, the surface of the cured film obtained in Example 1 is relatively continuous and dense, with no obvious large-scale cracks, pores, particle detachment, or severe phase separation observed. This indicates that the photosensitive group-modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, reactive organic microparticles, and methacrylamide-modified nano-silica in the binder system have good compatibility and curing network integrity. The micro-rough structure on the surface of the cured film is beneficial to improving the mechanical interlocking and wear resistance of the film layer, while no obvious weak interfaces are formed, which is consistent with the subsequent adhesion, wear resistance, and anti-adhesion test results.

[0074] Viscosity testing was conducted according to the relevant methods in GB / T 13217.4-2020 "Ink Viscosity Test Methods", and a rotational rheometer was used for testing, taking into account the characteristics of high-viscosity offset ink systems. The test temperature was 25℃, and the shear rate was set to 10 s⁻¹. - ¹, record the apparent viscosity; simultaneously perform a shear recovery test at 40℃, first at 1 s - ¹The initial low-shear viscosity was determined by shearing for 60 s, followed by shearing for 1000 s. - ¹Shearing for 60 seconds simulates high-speed shearing of the ink roller, then switching back to 1 second. -¹The viscosity is then recovered for 180 s, and the ratio of the recovered viscosity to the initial low-shear viscosity is calculated as the viscosity recovery rate. A higher viscosity recovery rate indicates that the binder is more likely to recover its structure after high shear, which helps reduce the risks of ink splatter, ink buildup, and dot gain.

[0075] UV curing performance testing was conducted using a 395 nm UV-LED light source with an irradiance of 600 mW / cm². Each ink sample was coated onto the corona-treated PET film and coated paper surfaces using a wire-bar coater, with a wet film thickness controlled at 5 μm to obtain the cured film. Different irradiation energies were obtained by adjusting the conveyor speed, and the minimum curing energy required for the ink surface to achieve no obvious finger-tack was recorded. After curing, samples were taken for FTIR testing at 810 cm⁻¹. - ¹The double bond conversion rate was calculated based on the changes in the characteristic peaks of the acrylate double bonds in the vicinity. The surface drying performance was evaluated in accordance with the relevant approach of GB / T 13217.5-2023 "Ink Drying Test Methods". Combined with the characteristics of UV-cured inks, the surface drying was judged by lightly touching the coating surface with a clean fingertip; the absence of obvious adhesion and drag marks was used as the criterion for determining surface drying.

[0076] Adhesion testing was conducted according to the tape peel test method in GB / T 13217.7-2023 "Test Method for Adhesion of Inks". After the cured ink film was placed at 25℃ and 50% relative humidity for 24 hours, standard tape was applied to the ink film surface, pressed, and then rapidly peeled off at approximately 180°. The extent of ink film detachment was observed, and the adhesion retention rate was calculated. The adhesion retention rate was calculated as the percentage of the area of ​​ink film that did not detach after tape peeling out relative to the total test area. Cross-cut adhesion performance was conducted according to GB / T9286-2021. The cured film was divided into a 1 mm grid, and tape was peeled off, with evaluations ranging from 0 to 5, where lower grades indicate better adhesion. Hardness testing was conducted according to GB / T 6739-2022, using the pencil hardness method to evaluate the surface hardness of the cured film. Abrasion resistance testing was conducted using a rotary friction method. The sample was rubbed 100 times under a 500 g load by a CS-10 grinding wheel, and the mass loss was recorded; lower mass loss indicates better abrasion resistance. The anti-adhesion test was conducted following the same methodology as the ink anti-adhesion test. Two cured samples were stacked face-to-face and pressed at 50℃ and 0.5 MPa for 4 hours. After cooling, the ease of peeling and surface transfer were observed. The anti-adhesion grade was evaluated from 1 to 5, where 1 indicates that the sample could be easily separated with no surface transfer, 2 indicates slight adhesion but no obvious ink layer transfer, 3 indicates slight ink layer transfer upon separation, 4 indicates obvious adhesion with local ink layer damage, and 5 indicates severe adhesion with large-area ink layer transfer. The migration content was tested using solvent extraction. The cured ink film was cut into samples with an area of ​​1 dm², placed in 50 mL of acetonitrile, and extracted at 40℃ in the dark for 24 hours. The extract was filtered through a 0.22 μm filter membrane, and the content of migratable organic components in the extract was determined by high-performance liquid chromatography (HPLC) and converted to mg / dm² based on the sample area. Each group of samples was tested in triplicate, and the average value was taken.

[0077] The performance test results of each embodiment and comparative example are shown in the table below.

[0078] As can be seen from the data in the table, Examples 1–3 achieved good surface drying at relatively low UV-LED irradiation energies, with a minimum energy requirement of 78–88 mJ / cm², significantly lower than Comparative Examples 1 and 2. Although Comparative Example 1 incorporated a small-molecule photoinitiator, under the same pigment masking conditions, the photoinitiator was not fixed within the resin backbone, leading to uneven local distribution, residual migration after curing, and insufficient matching between free radical generation sites and resin crosslinking sites. Therefore, Comparative Example 1 exhibited a double bond conversion rate of only 73.5% at irradiation energy of 90 mJ / cm², increasing the minimum energy required for surface drying to 118 mJ / cm², and showing slight finger-tap adhesion. In contrast, the introduction of thioxanthone groups and acylphosphono groups into the hyperbranched polyester acrylate resin backbone in Examples 1–3 improved the dispersion stability and reaction site matching of the photosensitive structure in the binder, resulting in more complete surface and deep curing.

[0079] In Comparative Example 2, after replacing the mercapto-containing polyurethane acrylate resin with a common polyurethane acrylate resin that does not contain mercapto groups and thioether bonds, the minimum energy required for surface drying increased from 82 mJ / cm² in Example 1 to 105 mJ / cm², and the double bond conversion rate also decreased to 77.8% at 90 mJ / cm². This result indicates that oxygen inhibition has a significant impact on surface curing during the UV offset ink thin-layer curing process. The mercapto-containing polyurethane acrylate resins in Examples 1–3 contain mercapto groups, thioether bonds, urethane bonds, and acrylate double bonds. The mercapto groups can reduce the adverse effects of surface oxygen inhibition on free radical polymerization through chain transfer, while the polyurethane segments are beneficial for improving film flexibility and adhesion stability. Therefore, Examples 1–3 can maintain a high double bond conversion rate and good touch-drying condition even under low-energy curing conditions, while Comparative Example 2 shows surface stickiness and a decrease in cured film hardness.

[0080] The main difference between Comparative Example 3 and Example 1 is that the reactive organic microparticles were replaced with non-reactive organic microparticles. Test results showed that the minimum energy required for surface drying in Comparative Example 3 was 86 mJ / cm², close to that of Example 1, indicating that the non-reactive organic microparticles had little direct impact on the UV curing speed. However, its viscosity recovery rate was only 61%, significantly lower than 86% in Example 1, 89% in Example 2, and 82% in Example 3. Simultaneously, the cross-cut adhesion grade of Comparative Example 3 decreased to level 2, the adhesion retention rate after tape peeling decreased to 91.8%, the abrasion resistance loss increased to 15.7 mg, and the anti-blocking grade also decreased to level 3. These results indicate that although non-reactive organic microparticles can increase the viscosity of the system to some extent, they cannot participate in UV cross-linking and easily form inert dispersed phases and weak interfaces in the cured film, leading to a decrease in the integrity, abrasion resistance, and adhesion stability of the cured film. The reactive organic microparticles in Examples 1–3 contain polymerizable double bonds, tertiary amine groups, carboxyl groups, hydrophobic segments, and crosslinking structures. They can provide a recoverable weak structure during ink transfer and participate in crosslinking during UV curing, thus achieving both rheological regulation and curing film enhancement.

[0081] Based on the results of adhesion, hardness, and abrasion resistance, Examples 1–3 all exhibited adhesion retention rates exceeding 97%, cross-cut adhesion ratings of 0, pencil hardness reaching 2H–3H, and abrasion resistance mass loss controlled within 6.9–8.2 mg. This is because the rosin-modified acrylate resin in this invention improves pigment wetting and substrate transfer compatibility; the imide structure enhances the cohesive strength of the film; the methacrylamide-modified nano-silica can combine with the resin network through surface reactive groups, improving the film's abrasion resistance and anti-blocking properties; and the polymerizable phosphate wetting agent improves pigment dispersion and interfacial adhesion, reducing the risk of water resistance or migration caused by non-reactive wetting agent residue. The synergistic effect of these components makes the examples superior to the comparative examples in terms of low-energy curing, surface drying, adhesion, abrasion resistance, and anti-blocking properties.

[0082] The migration content test results showed that the migration content of Examples 1–3 was 1.5–1.8 mg / dm², significantly lower than that of Comparative Example 1 (5.9 mg / dm²). This difference mainly stemmed from the different forms of the photosensitive structure. Comparative Example 1 used a small molecule photoinitiator to compensate for curing activity, and the small molecule photoinitiator and its pyrolysis residues were more likely to form migratable components in the cured film. In contrast, Examples 1–3 grafted thioxanthone groups and acylphosphonic groups onto hyperbranched polyester acrylate resin, and used tertiary amine-containing polyurethane acrylate resin instead of traditional small molecule amine additives. Multiple functional components could enter the crosslinking network through acrylate double bonds, thus reducing the migration risk of unreacted small molecule components and free additives.

[0083] In summary, Examples 1–3 exhibited good overall performance in terms of low-energy UV-LED curing efficiency, surface dryness, double bond conversion rate, adhesion, abrasion resistance, anti-blocking properties, rheological recovery, and low migration risk. Comparative Example 1 shows that it is difficult to achieve the same low-energy curing and low migration effects by using only ordinary hyperbranched acrylate resin and adding a small molecule photoinitiator; Comparative Example 2 shows that the lack of mercapto-containing polyurethane acrylate resin makes the surface oxygen inhibition problem more obvious; Comparative Example 3 shows that although the viscosity can be adjusted by using non-reactive organic microparticles, it is difficult to simultaneously achieve shear recovery, film integrity, and abrasion resistance.

[0084] Therefore, this invention, through the combination of photosensitive group-modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, tertiary amine-containing polyurethane acrylate resin, and reactive organic microparticles, can effectively improve the problems of insufficient low-energy curing, surface stickiness, migration of small molecule additives, and weakening of film performance by inert rheology additives in existing UV offset printing ink binders.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-energy curable UV offset printing ink binder, characterized in that, The composition by weight includes the following components: 36-48 parts of photosensitive group modified hyperbranched polyester acrylate resin, 9-16 parts of mercapto-containing polyurethane acrylate resin, 20-28 parts of reactive diluent composition, 6-10 parts of rosin modified acrylate resin, 5-9 parts of reactive organic microparticles, 4-7 parts of tertiary amine-containing polyurethane acrylate resin, 0.5-1.2 parts of methacrylamide modified nano silica, 0.8-1.6 parts of polymerizable phosphate wetting agent, 0.2-0.8 parts of stabilizer, and 0.2-0.8 parts of process aid; The photosensitive group-modified hyperbranched polyester acrylate resin contains thioxanthone groups, acylphosphoxy groups, and acrylate double bonds; the mercapto-containing polyurethane acrylate resin contains urethane bonds, thioether bonds, mercapto groups, and acrylate double bonds; the rosin-modified acrylate resin contains rosin structures, imide structures, and acrylate double bonds; the tertiary amine-containing polyurethane acrylate resin contains tertiary amine groups and acrylate double bonds; and the reactive organic microparticles contain polymerizable double bonds, tertiary amine groups, carboxyl groups, hydrophobic segments, and crosslinking structures.

2. The low-energy curable UV offset printing ink binder according to claim 1, characterized in that, The photosensitive group modified hyperbranched polyester acrylate resin has a number average molecular weight of 2500–7000, an acrylate functionality of 8–16, an acid value not higher than 8 mg KOH / g, and a viscosity of 40–100 Pa·s at 25℃.

3. The low-energy curable UV offset printing ink binder according to claim 1, characterized in that, Based on the total mass of the photosensitive group-modified hyperbranched polyester acrylate resin, the content of thioxanthone groups is 0.2–1.5 wt%, the content of acylphosphoxy groups is 0.3–2.5 wt%, and the total content of thioxanthone groups and acylphosphoxy groups is 0.5–4.0 wt%.

4. The low-energy curable UV offset printing ink binder according to claim 1, characterized in that, The thiol-containing polyurethane acrylate resin molecular chain contains thioether bonds introduced by sulfur-containing diols, thiols introduced by mercaptodiols, and acrylate double bonds formed by hydroxyl acrylate end capping, and the thiol content of the thiol-containing polyurethane acrylate resin is 0.08–0.35 mmol / g.

5. The low-energy curable UV offset printing ink binder according to claim 1, characterized in that, The reactive organic microparticles have a particle size of 70-180 nm; the reactive organic microparticles are obtained by in-situ polymerization of polymeric monomers in an active diluent, wherein the polymeric monomers include rosin methacrylate, long-chain alkyl acrylates, dimethylaminoethyl methacrylate, carboxyl-containing unsaturated monomers, and hexanediol diacrylate; wherein the long-chain alkyl acrylates are one or more of lauryl acrylate and isodecyl acrylate; and the carboxyl-containing unsaturated monomers are one or more of itaconic acid and methacrylic acid.

6. The low-energy curable UV offset printing ink binder according to claim 1, characterized in that, The reactive diluent composition comprises propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, cyclotrimethylolpropane methyl acetal acrylate, and vinyl ether carbonate monomers, in a mass ratio of 8-10:5-8:4-6:1-3, and the total amount of monofunctional acrylate reactive diluents does not exceed 6% of the total mass of the binder.

7. A method for preparing a low-energy curable UV offset printing ink binder, used to prepare the low-energy curable UV offset printing ink binder according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Preparation of photosensitive groups modified hyperbranched polyester acrylate resin containing thioxanthone groups, acylphosphoxy groups and acrylate double bonds; S2. Preparation of thiol-containing polyurethane acrylate resins containing urethane bonds, thioether bonds, thiol groups, and acrylate double bonds; S3. Prepare reactive organic microparticles containing polymerizable double bonds, tertiary amine groups, carboxyl groups, hydrophobic segments, and cross-linked structures by in-situ polymerization in an active diluent; S4. Preparation of rosin-modified acrylate resin containing rosin structure, imide structure and acrylate double bond; S5. Preparation of tertiary amine-containing polyurethane acrylate resins containing tertiary amine groups and acrylate double bonds; S6. The photosensitive group modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, reactive diluent composition, rosin modified acrylate resin, tertiary amine-containing polyurethane acrylate resin, reactive organic microparticles, methacrylamide modified nano silica, polymerizable phosphate wetting agent, stabilizer and process aid are mixed, degassed and filtered to obtain the low-energy curable UV offset printing ink binder.

8. The method for preparing a low-energy curable UV offset printing ink binder according to claim 7, characterized in that, In step S1, the photosensitive group-modified hyperbranched polyester acrylate resin is prepared by the following method: Under nitrogen protection, trimethylolpropane, dimethylolpropionic acid, sebacic acid, and itaconic anhydride were subjected to an esterification reaction at 145-165℃ for 4-8 hours. When the acid value dropped to 25-45 mg KOH / g, the temperature was lowered to 95-110℃, and glycidyl methacrylate was added in the presence of a polymerization inhibitor for a ring-opening esterification reaction for 2-4 hours. Then, a carboxyl-containing thioxanone compound and a carboxyl-containing acylphosphine oxide compound were added for a grafting reaction for 2-5 hours, and the acid value of the reaction product was controlled to be no higher than 8 mg KOH / g to obtain the photosensitive group modified hyperbranched polyester acrylate resin.

9. The method for preparing a low-energy curable UV offset printing ink binder according to claim 7, characterized in that, In step S2, the mercapto-containing polyurethane acrylate resin is prepared by the following method: Diisocyanate, hydroxy acrylate, sulfur-containing diol, glycerol carbonate and 3-mercapto-1,2-propanediol are reacted until the isocyanate group content is not higher than 0.2 wt%, to obtain the mercapto-containing polyurethane acrylate resin; wherein the amount of 3-mercapto-1,2-propanediol used is such that the mercapto content in the obtained resin is 0.08–0.35 mmol / g.

10. The method for preparing a low-energy curable UV offset printing ink binder according to claim 7, characterized in that, In step S3, using at least one component of the reactive diluent composition as the reaction medium, rosin methacrylate, long-chain alkyl acrylate, dimethylaminoethyl methacrylate, carboxyl-containing unsaturated monomers, and hexanediol diacrylate are used as polymerization monomers. Semi-continuous free radical polymerization is carried out at 70-85°C, wherein the addition time of the polymerization monomers and free radical initiators is 1.5-3 h. After the addition is completed, the reaction is continued at the temperature for 1-2 h to form reactive organic microparticles with a particle size of 70-180 nm. In step S6, the photosensitive group modified hyperbranched polyester acrylate resin, mercapto-containing polyurethane acrylate resin, reactive diluent composition, and tertiary amine-containing polyurethane acrylate resin are premixed for 30-60 min, and then the reactive organic microparticles are added and mixing is continued for 30-60 min.

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