Vegetable oil modified rosin-based uvled ink and preparation method thereof

Abstract

The application discloses a plant oil modified rosin-based UVLED ink and a preparation method thereof, and belongs to the technical field of radiation curing inks. The ink comprises the following components in parts by weight: a plant oil modified rosin-based hyperbranched polyester resin, an active diluent, a compound photoinitiator, a pigment, a filler and an additive. The resin is prepared by the addition of rosin and fumaric acid, hyperbranched polycondensation, plant-based capping and dilution. The ink is prepared by pre-dispersion, grinding, conditioning and defoaming packaging. The application proposes a hyperbranched structure with a rigid core and a flexible shell to solve the problems of large curing shrinkage, poor adhesion and the need for additional dispersants for pigment dispersion in existing UV inks. The resin simultaneously serves as the main binder and the pigment dispersion stabilizer, and through the synergistic effect of multi-anchor adsorption and steric hindrance, the volume shrinkage of the cured body is less than or equal to 5%, no additional dispersant is needed, and the properties are stable and green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of radiation-cured ink technology, and in particular to a vegetable oil-modified rosin-based UVLED ink and its preparation method. Background Technology

[0002] UV LED inks, as an energy-curing printing material, offer advantages such as instant drying, zero volatile organic compound emissions, and low energy consumption, making them widely used in labeling, packaging, and commercial printing. Among these, resin binders prepared from rosin and vegetable oils are gradually replacing traditional petroleum-based resins due to their renewable raw materials, excellent wettability, and lower cost, becoming a research hotspot in the UV ink field.

[0003] Currently, existing technologies disclose methods for modifying rosin polyesters with drying vegetable oils such as tung oil and linseed oil. These methods introduce unsaturated functional groups into the resin structure through double bond addition reactions, giving it UV-curable activity. However, these vegetable oil-modified rosin polyesters are mostly linear or slightly branched structures, exhibiting the following technical drawbacks: First, the resin molecular chains are relatively rigid, resulting in a large volume shrinkage rate after curing (usually greater than 10%), leading to poor adhesion and easy cracking of the ink film on low surface energy substrates such as plastics and metal foils. Second, the resin molecules lack effective pigment anchoring groups on their periphery; without additional dispersants, organic pigment particles easily aggregate and settle, affecting the ink's storage stability and color performance.

[0004] To address the aforementioned issues, existing technologies attempt to add small-molecule dispersants or linear polymeric dispersants to ink formulations to improve pigment dispersion stability through electrostatic repulsion or steric hindrance effects. Simultaneously, the introduction of multifunctional monomers (such as dipentaerythritol hexaacrylate) increases crosslinking density to enhance ink film strength. However, these approaches still have shortcomings: small-molecule dispersants are prone to migration and volatilization, affecting the curing film's durability and environmental friendliness; while multifunctional monomers increase hardness, they further exacerbate curing shrinkage, making adhesion problems more prominent. Furthermore, the addition of dispersants increases formulation complexity, and the compatibility issues between dispersants and resins often lead to unstable ink viscosity and shortened shelf life. Therefore, developing a UVLED ink binder that combines low shrinkage, high pigment dispersion stability, and high bio-based content has become a pressing technical problem in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a vegetable oil-modified rosin-based UV LED ink and its preparation method.

[0006] The technical solutions provided by the embodiments of the present invention are as follows:

[0007] A vegetable oil-modified rosin-based UV LED ink and its preparation method include the following steps:

[0008] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0009] S101. React 100 parts of rosin with 12-18 parts of fumaric acid at 180-200℃ under nitrogen protection for 2-3 hours to obtain the adduct.

[0010] Rosin is a natural resin mainly composed of five isomers: abietic acid, neoabietic acid, L-pilosolic acid, D-pilosolic acid, and L-isopilosolic acid. L-pilosolic acid is a core chemical component of rosin, belonging to the terpene acid series. It contains a conjugated double bond system (C13=C14 and C8=C9) and, as a conjugated diene component, can undergo a Diels-Alder addition reaction with fumaric acid. Fumaric acid contains a carbon-carbon double bond (C=C) and, as a dienophile component, the two undergo a [4+2] cycloaddition reaction under heating conditions to form a six-membered cyclic transition state, ultimately generating a fumaric rosin adduct with three carboxyl groups. The reaction formula is as follows:

[0011]

[0012] Specifically, the electron cloud density of the conjugated double bond of L-piperic acid is relatively high, making it easy to undergo electrophilic addition to the electron-deficient region of the trans-butenedioic acid double bond. During the reaction, two new carbon-carbon σ bonds are formed simultaneously at the C1-C4 ends of the conjugated diene and the ends of the dienophile double bond, generating a six-membered ring structure.

[0013] This addition reaction transforms the monocarboxylic acid structure of rosin into a tricarboxylic acid structure, which not only increases the functionality of the molecule (from 1 carboxyl group to 3 carboxyl groups), but also introduces additional carbon-carbon double bonds into the molecular skeleton. These retained double bonds provide reaction sites for the subsequent UV curing crosslinking of hyperbranched polyester, giving the final resin photocurability. At the same time, the introduction of fumaric acid forms a six-membered ring, which increases the rigidity of the molecule and enhances the thermal stability and mechanical properties of the resin.

[0014] S102, add 8-15 parts pentaerythritol, 25-35 parts dimethylolpropionic acid and 0.1-0.3 parts nano zinc oxide, stepwise increase the temperature to 245-255℃, and keep warm under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0015] Under the catalysis of nano zinc oxide, the carboxyl groups in pentaerythritol, dimethylolpropionic acid (DMPA) and S1 product trans-butened rosin adduct undergo esterification polycondensation reaction to construct a hyperbranched polyester backbone.

[0016] Pentaerythritol contains four equally active primary hydroxyl groups, serving as a B4-type core monomer; DMPA molecules contain one carboxyl group (A) and two hydroxyl groups (B), belonging to the AB2-type monomer, and are key units for constructing hyperbranched structures. Under heating conditions, the carboxyl group of DMPA undergoes esterification with the hydroxyl group of another DMPA molecule or pentaerythritol, forming an ester bond and releasing one molecule of water. Due to the AB2 structure of DMPA, the reaction continuously branches and grows: after each DMPA unit is connected to the core or branch through its carboxyl group, its two hydroxyl groups continue to participate in subsequent esterification, initiating a new generation of branches;

[0017] Meanwhile, the carboxyl group in the fumarate rosin adduct also participates in esterification, introducing the rigid phenanthrene ring structure of rosin into the hyperbranched framework, increasing the glass transition temperature and mechanical strength of the resin. Nano zinc oxide, as a Lewis acid catalyst, activates the carbonyl oxygen of the carboxyl group through coordination, accelerating the nucleophilic addition-elimination reaction process.

[0018]

[0019] In the reaction formula, R represents H or the fumarate rosin adduct;

[0020] The reaction adopted a stepwise heating program (increasing by 10℃ every 30 min), slowly increasing from 180℃ to 245-255℃. Slow heating is beneficial for gradual esterification and prevents local overheating that could lead to gelation of the system. When the acid value drops below 15 mgKOH / g, it indicates that most of the free carboxyl groups in the system have participated in the reaction, the molecular weight of the hyperbranched polyester intermediate reaches the target range (number average molecular weight 1000-8000), and the degree of branching is controlled between 0.4 and 0.6.

[0021] The hyperbranched polyester intermediate formed in this stage has a three-dimensional spherical topology and retains a large number of hydroxyl groups at the ends, providing reaction sites for subsequent flexible end-capping with vegetable oil.

[0022] S103, cool to 170-190℃, add 15-25 parts of tung oil and 8-15 parts of soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product.

[0023] Hyperbranched polyesters contain a large number of unreacted hydroxyl groups at their ends, while the main components of tung oil and soybean oil are triglycerides with the following structure: R1, R2, and R3 represent the hydrocarbon groups containing double bonds in tung oil and soybean oil. Under heating conditions, the hydroxyl groups attack the ester bonds in the triglycerides, resulting in transesterification. The long-chain fatty acid structure of the vegetable oil is covalently grafted onto the periphery of the hyperbranched polyester, forming a core-shell structure with a rigid core and a flexible shell. The small amount of glycerol or monoglycerides released during the reaction are removed in the subsequent vacuum devolatilization step.

[0024]

[0025] Meanwhile, tung oil molecules contain a unique conjugated triene structure (three conjugated double bonds), which is accompanied by the addition reaction of some double bonds at this temperature. Therefore, this reaction is relatively complex, and most of them are still intact. These retained double bonds provide sufficient reaction sites for subsequent photocuring, enabling the final resin to cross-link and cure quickly. In addition, the grafted long chains of plant oils (especially the long chains of linoleic acid and oleic acid in soybean oil) endow the ink film with good flexibility and hydrophobicity. During the curing process, it can effectively absorb and disperse the internal stress generated by volume shrinkage, thereby significantly reducing the curing shrinkage rate of the ink film.

[0026] After heat preservation for 1-2 hours, the acid value of the reaction system dropped to below 10 mgKOH / g, indicating that the transesterification reaction had reached equilibrium and the end-capping rate met expectations. The final hyperbranched polyester resin product not only maintained UV curing activity, but also achieved excellent low shrinkage characteristics and substrate adhesion through the flexible segments of vegetable oil.

[0027] S104, cool to 120-140℃, add 15-25 parts of ethoxylated trimethylolpropane triacrylate for dilution, to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0028] Ethoxylated trimethylolpropane triacrylate (EO-TMPTA) is a low-viscosity trifunctional acrylate monomer. Its molecular structure contains three ethoxylated acrylate groups. Under high temperature conditions of 120-140℃, EO-TMPTA has good compatibility with hyperbranched polyester resin and can be uniformly dispersed in the resin network, significantly reducing the viscosity of the system. This transforms the resin from a high-viscosity melt state to a fluid state that facilitates subsequent pigment dispersion and ink application. After dilution, the viscosity of the resin is controlled at 50,000-80,000 mPa·s (25℃), maintaining sufficient thixotropy and body while possessing good flowability and wettability.

[0029] EO-TMPTA plays an important role in the subsequent curing process: the acrylate double bonds in its molecule can undergo chain polymerization under the initiation of free radicals generated by photoinitiators, and participate in the construction of the cross-linking network of hyperbranched resin. Since EO-TMPTA contains three polymerizable functional groups, its introduction can increase the cross-linking density, enhance the hardness and chemical resistance of the ink film. At the same time, the presence of ethoxy segments gives the monomer a certain degree of flexibility, partially offsetting the brittleness caused by multifunctionality, which is conducive to maintaining the comprehensive mechanical properties of the ink film.

[0030] S2, Pre-dispersion:

[0031] The pigment in the formulation is mixed with 30%-40% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000-1500 r / min for 20-30 min to obtain a pre-dispersed slurry.

[0032] Organic pigments exist in the form of microcrystalline particles. The original particles form agglomerates or aggregates through van der Waals forces and hydrogen bonds. When the pigment is mixed with hyperbranched polyester resin, which accounts for 30%-40% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed under high-speed shear, the resin molecules, with their low viscosity and high polarity, first wet the surface of the pigment particles, replacing the air and moisture in the interparticle spaces.

[0033] Hyperbranched polyester resin molecules have a large number of polar functional groups (carboxyl, hydroxyl and ester groups) at their ends. These groups can be firmly anchored to active sites on the surface of pigment particles (such as aromatic rings, carbonyl groups, imine groups, etc.) through hydrogen bonds, dipole-dipole interactions or van der Waals forces. Due to the three-dimensional spherical topology of hyperbranched molecules, multiple terminal functional groups can be adsorbed on the same pigment particle surface at the same time, forming a "multi-anchor" adsorption configuration, which significantly enhances the bonding strength between the resin and the pigment.

[0034] Under high-speed shearing at 1000-1500 r / min, the mechanical force generated by the fluid overcomes the binding force inside the pigment aggregates, causing the aggregates to be gradually broken up and separated into individual primary particles or small aggregates. At the same time, hyperbranched resin molecules adsorbed on the particle surface form a dense adsorption layer around the particles. This adsorption layer maintains the stability of the dispersion system through two mechanisms: first, ionized groups (such as carboxylates) in the adsorption layer cause the particle surface to carry the same charge, generating electrostatic repulsion; second, the flexible fatty acid long chains around the resin molecules extend into the medium, forming a steric hindrance layer (entropy effect), preventing collisional aggregation between particles.

[0035] After 20-30 minutes of pre-dispersion, the pigment particles are initially dissociated and fully encapsulated by the resin, forming a pre-dispersed slurry with a certain degree of fluidity, providing uniform feed for the subsequent grinding and dispersing process.

[0036] S3, Grinding and Dispersing:

[0037] The pre-dispersed slurry obtained in T1 is ground 3-5 times using a three-roll mill until the fineness is ≤6μm to obtain the ground slurry;

[0038] The pre-dispersed slurry passes through the narrow gap (roller gap typically 5-30 μm) between the feed roller, intermediate roller, and discharge roller of a three-roll mill. The three rollers rotate relative to each other at different speeds (the discharge roller rotates the fastest, the feed roller the slowest), generating intense shearing, extrusion, and stretching forces. As the slurry passes through the roller gap, the pigment aggregates are subjected to forces as high as 10...5 -10 6 s -1 The shear rate is reduced, the van der Waals forces and mechanical interlocking forces inside the aggregates are overcome, and they gradually dissociate into individual primary pigment particles (the original particle size is usually 0.05-0.5 μm).

[0039] During the shearing process, the surface of the newly exposed pigment particles is immediately wetted and adsorbed by the surrounding hyperbranched polyester resin molecules. The polar functional groups (carboxyl, hydroxyl, ester groups) at the ends of the resin molecules form multi-point anchoring with the pigment surface, ensuring that the particles are wrapped by the resin as soon as they are dispersed, preventing them from re-aggregating. The purpose of grinding 3-5 times is to ensure that all pigment particles undergo multiple shearing and adsorption processes, ensuring uniformity and sufficiency of dispersion.

[0040] As the number of grinding passes increases, the average particle size of the pigment particles gradually decreases and the particle size distribution tends to be concentrated. When the fineness reaches ≤6μm (measured by a scraper fineness gauge), it indicates that there are no visible agglomerates in the system. The pigment particles are basically in the form of primary particles or small-sized aggregates. At this time, the hyperbranched resin molecules form a complete adsorption layer on the pigment surface. Through the synergistic effect of electrostatic repulsion and steric hindrance, the particles maintain a stable separation state. This dispersion state provides a stable pigment base slurry for subsequent conditioning and color adjustment.

[0041] S4, Color Adjustment:

[0042] The grinding slurry obtained from T2 is mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, compound photoinitiator, filler and additives, and stirred at 500-800 r / min for 30-60 min until uniform to obtain ink;

[0043] The grinding slurry contains pigment particles that have been fully coated with hyperbranched resin, but at this point the total amount of resin in the system has not yet reached the final ratio, and it lacks functional components such as photoinitiators and fillers. Adding the remaining vegetable oil-modified rosin-based hyperbranched polyester resin to the grinding slurry can, on the one hand, adjust the viscosity and rheology of the system so that the ink reaches the viscosity range and flowability required for printing; on the other hand, the addition of extra resin further enhances the steric hindrance layer around the pigment particles and improves dispersion stability.

[0044] The composite photoinitiator is composed of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 2-isopropylthioxanthone (ITX) in a weight ratio of 2:1:1. During stirring, it is dissolved in the reactive diluent and resin medium. The three photoinitiators have complementary absorption characteristics at wavelengths of 365nm and 395nm, and synergistically absorb the energy of the light source. The photoinitiator molecules remain in a molecularly dispersed state in the solution, which prepares for the rapid generation of free radicals during subsequent UV curing.

[0045] The addition of fillers plays a role in regulating ink properties and reducing costs. Kaolin particles with silane reagent-modified surfaces are uniformly dispersed in the system under stirring. Their oleophilic surfaces are well compatible with the resin medium and fill the gaps between pigment particles, improving the thixotropic properties and anti-ink-splatter performance of the ink. Additives (such as leveling agents and stabilizers) are evenly distributed during stirring. Leveling agents reduce the surface tension of the ink and improve the uniformity of ink layer spreading during printing. Stabilizers (hindered amines) capture trace free radicals in the system and prevent storage gelation caused by dark reactions.

[0046] Low-speed stirring at 500-800 r / min avoids high-speed shearing from destroying the established pigment dispersion structure, while ensuring thorough mixing of each component. After stirring for 30-60 min, the system reaches a thermodynamic and kinetic homogeneous state. The components maintain stability through van der Waals forces, hydrogen bonds, and steric hindrance, forming a finished ink with suitable viscoelasticity, thixotropy, and storage stability.

[0047] S5. De-bubbling packaging:

[0048] The ink obtained from T3 is degassed under vacuum for 15-30 minutes, filtered, and packaged to obtain the finished ink.

[0049] During the T3 conditioning and color matching process, high-speed stirring inevitably introduces air into the ink system, forming microbubbles. These bubbles are dispersed in the viscous ink medium in the form of tiny air cavities. If the bubbles remain in the finished ink, they will cause defects such as pinholes, white spots, and broken lines in the ink layer during printing, which will seriously affect the quality of the printed products.

[0050] When ink is placed under vacuum conditions (typically -0.08 to -0.1 MPa), the air pressure above the liquid surface decreases. According to Henry's Law, the solubility of gas in ink decreases as the air pressure decreases. The air dissolved in the ink (mainly oxygen and nitrogen) becomes supersaturated and precipitates out, forming new bubbles. At the same time, the internal pressure of the existing microbubbles is greater than the external environmental pressure, causing the bubble volume to expand rapidly, increasing buoyancy. After the bubbles rise to the liquid surface, they burst and release gas. Continuing to evacuate the vacuum for 15-30 minutes can remove more than 90% of the entrained gas in the ink.

[0051] During the degassing process, the vacuum level should not be too high and the time should not be too long to avoid excessive extraction of low-boiling-point components (such as trace amounts of residual monomers or additives) which would affect the ink performance. At the same time, the system temperature is usually kept at room temperature or slightly above room temperature (25-40℃) to reduce the ink viscosity and promote bubble migration and escape.

[0052] After degassing, the ink is filtered through a filter screen (usually a 200-400 mesh stainless steel mesh or nylon filter bag) to remove large particulate impurities that may be introduced during grinding and mixing (such as undispersed pigment agglomerates, filler hard particles, external contaminants, etc.). Filtration ensures that the ink fineness meets the quality standard of ≤6μm and prevents clogging of the anilox roller or rubber blanket during printing.

[0053] The filtered ink is packaged in a light-proof, airtight container to prevent oxygen and moisture from entering and causing the photoinitiator to decompose or the resin to undergo a dark reaction. The packaging containers are usually opaque aluminum foil bags or dark plastic drums. Nitrogen purging can further extend the shelf life. The final product ink is a vegetable oil-modified rosin-based hyperbranched UVLED ink with excellent dispersion stability and low shrinkage characteristics.

[0054] Preferably, the composite photoinitiator is composed of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 2-isopropylthioxanthone (ITX) in a weight ratio of 2:1:1.

[0055] Preferably, the pigment is an organic pigment or carbon black, selected from one or more of yellow pigments, red pigments, blue pigments, and black pigments.

[0056] Preferably, the filler is kaolin with a surface modified by silane reagent, which has an oil absorption value of 40-60g / 100g and an average particle size of 1-3μm.

[0057] Preferably, the vegetable oil-modified rosin-based hyperbranched polyester resin has a number average molecular weight of 1000-8000, a branching degree of 0.4-0.6, and contains mixed functional groups of hydroxyl, carboxyl and fatty acid long chains at the end.

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

[0059] 1. This invention employs a hyperbranched molecular structure design with a rigid core and a flexible shell, combined with the flexible end-capping and internal plasticizing mechanism of long-chain vegetable oils. This solves the technical problems of high curing shrinkage and poor adhesion on low surface energy substrates in traditional UV inks, achieving excellent performance with a curing volume shrinkage rate of ≤5% and a Grade 1 adhesion to PE substrates. This invention constructs a "hard core-soft shell" microscopic phase separation structure by covalently grafting long chains of tung oil and soybean oil onto the periphery of a hyperbranched polyester backbone. The flexible long chains can freely rotate and rearrange their conformation during photocuring, effectively absorbing and dispersing the volume shrinkage stress generated by the crosslinking reaction, thus preventing ink film cracking and warping. Simultaneously, the long-chain alkyl groups improve the resin's wettability on non-polar substrates, enabling the ink to maintain good adhesion strength on low surface energy materials such as plastics and metal foils.

[0060] 2. This invention uses hyperbranched polyester resin as the sole pigment dispersion stabilizer, combined with the synergistic mechanism of multi-anchor adsorption and steric hindrance, which solves the problems of migration, volatilization and formulation complexity caused by the need to add small molecule dispersants in the prior art, and achieves the effect of long-term stable dispersion without dispersants.

[0061] Hyperbranched resins contain numerous carboxyl groups, hydroxyl groups, and long fatty acid chains at their ends, which can be anchored to the surface of pigment particles at multiple points through hydrogen bonds and van der Waals forces. At the same time, the flexible long chains extend into the medium to form an entropy barrier. This integrated design of "resin as dispersant" avoids the migration risk of small molecule additives, allowing the ink to remain free of precipitation and with a viscosity change of ≤10% after 12 months of storage at 40°C.

[0062] 3. This invention uses renewable resources such as rosin, tung oil, and soybean oil as raw materials, combined with bulk polymerization technology, to solve the problems of traditional inks' dependence on petroleum-based raw materials and VOC emissions, achieving green and environmentally friendly indicators. In this invention, the total proportion of rosin and vegetable oil in the main resin exceeds 40%, reducing the consumption of petrochemical resources at the source. The entire synthesis process is solvent-free, with no volatile organic compound emissions, and the finished ink has 100% solid content, fully meeting the environmental access standards of high-end fields such as cigarette packaging and food packaging. Attached Figure Description

[0063] Figure 1 This is a flowchart illustrating the preparation process of the ink of the present invention;

[0064] Figure 2 The viscosity change curves are shown in the embodiments and comparative examples of the present invention. Detailed Implementation

[0065] The technical solutions of this invention are described below. It should also be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments; those skilled in the art can also use other alternative methods to implement some well-known technologies.

[0066] In the following examples and comparative examples, the composite photoinitiators were composed of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 2-isopropylthioxanthone (ITX) in a weight ratio of 2:1:1.

[0067] Example 1: Preparation of vegetable oil-modified rosin-based hyperbranched UV LED ink:

[0068] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0069] S101. 100 parts of rosin and 15 parts of fumaric acid were reacted at 190°C under nitrogen protection for 2.5 h to obtain the adduct;

[0070] S102, add 10 parts pentaerythritol, 30 parts dimethylolpropionic acid and 0.2 parts nano zinc oxide, stepwise increase the temperature to 250℃, and keep it at the temperature under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0071] S103, cool down to 180℃, add 15 parts tung oil and 15 parts soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product.

[0072] S104, cooled to 130℃, and diluted with 20 parts of ethoxylated trimethylolpropane triacrylate to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0073] S2, Pre-dispersion:

[0074] 20 parts of organic red pigment were mixed with 30% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000 r / min for 30 min to obtain a pre-dispersed slurry.

[0075] S3, Grinding and Dispersing:

[0076] The pre-dispersed slurry obtained in T1 was ground four times using a three-roll mill until the fineness was ≤6μm to obtain the ground slurry;

[0077] S4, Color Adjustment:

[0078] The grinding slurry obtained from T2 was mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, 10 parts of compound photoinitiator, 10 parts of filler and 3 parts of additives, and stirred at 600 r / min for 30 min until uniform to obtain ink.

[0079] S5. De-bubbling packaging:

[0080] The ink obtained from T3 is degassed under vacuum for 30 minutes, filtered, and packaged to obtain the finished ink.

[0081] Example 2: Preparation of vegetable oil-modified rosin-based hyperbranched UV LED ink:

[0082] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0083] S101. 100 parts of rosin and 15 parts of fumaric acid were reacted at 190°C under nitrogen protection for 2.5 h to obtain the adduct;

[0084] S102, add 10 parts pentaerythritol, 30 parts dimethylolpropionic acid and 0.2 parts nano zinc oxide, stepwise increase the temperature to 250℃, and keep it at the temperature under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0085] S103, cool down to 180℃, add 20 parts tung oil and 10 parts soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product;

[0086] S104, cooled to 130℃, and diluted with 20 parts of ethoxylated trimethylolpropane triacrylate to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0087] S2, Pre-dispersion:

[0088] 20 parts of carbon black were mixed with 30% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin and dispersed at 1000 r / min for 30 min to obtain a pre-dispersed slurry.

[0089] S3, Grinding and Dispersing:

[0090] The pre-dispersed slurry obtained in T1 was ground four times using a three-roll mill until the fineness was ≤6μm to obtain the ground slurry;

[0091] S4, Color Adjustment:

[0092] The grinding slurry obtained from T2 was mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, 10 parts of compound photoinitiator, 10 parts of filler and 3 parts of additives, and stirred at 600 r / min for 30 min until uniform to obtain ink.

[0093] S5. De-bubbling packaging:

[0094] The ink obtained from T3 is degassed under vacuum for 30 minutes, filtered, and packaged to obtain the finished ink.

[0095] Example 3: Preparation of vegetable oil-modified rosin-based hyperbranched UVLED ink:

[0096] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0097] S101. 100 parts of rosin and 15 parts of fumaric acid were reacted at 190°C under nitrogen protection for 2.5 h to obtain the adduct;

[0098] S102, add 10 parts pentaerythritol, 25 parts dimethylolpropionic acid and 0.2 parts nano zinc oxide, stepwise heat up to 250℃, and keep warm under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0099] S103, cool down to 180℃, add 20 parts tung oil and 10 parts soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product;

[0100] S104, cooled to 130℃, and diluted with 20 parts of ethoxylated trimethylolpropane triacrylate to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0101] S2, Pre-dispersion:

[0102] 20 parts of organic red pigment were mixed with 30% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000 r / min for 30 min to obtain a pre-dispersed slurry.

[0103] S3, Grinding and Dispersing:

[0104] The pre-dispersed slurry obtained in T1 was ground four times using a three-roll mill until the fineness was ≤6μm to obtain the ground slurry;

[0105] S4, Color Adjustment:

[0106] The grinding slurry obtained from T2 was mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, 10 parts of compound photoinitiator, 10 parts of filler and 3 parts of additives, and stirred at 600 r / min for 30 min until uniform to obtain ink.

[0107] S5. De-bubbling packaging:

[0108] The ink obtained from T3 is degassed under vacuum for 30 minutes, filtered, and packaged to obtain the finished ink.

[0109] Example 4: Preparation of vegetable oil-modified rosin-based hyperbranched UV LED ink:

[0110] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0111] S101. 100 parts of rosin and 15 parts of fumaric acid were reacted at 190°C under nitrogen protection for 2.5 h to obtain the adduct;

[0112] S102, add 10 parts pentaerythritol, 30 parts dimethylolpropionic acid and 0.2 parts nano zinc oxide, stepwise increase the temperature to 250℃, and keep it at the temperature under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0113] S103, cool down to 180℃, add 20 parts tung oil and 10 parts soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product;

[0114] S104, cooled to 130℃, and diluted with 20 parts of ethoxylated trimethylolpropane triacrylate to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0115] S2, Pre-dispersion:

[0116] 30 parts of organic red pigment were mixed with 30% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000 r / min for 30 min to obtain a pre-dispersed slurry.

[0117] S3, Grinding and Dispersing:

[0118] The pre-dispersed slurry obtained in T1 was ground four times using a three-roll mill until the fineness was ≤6μm to obtain the ground slurry;

[0119] S4, Color Adjustment:

[0120] The grinding slurry obtained from T2 was mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, 10 parts of compound photoinitiator, 10 parts of filler and 3 parts of additives, and stirred at 600 r / min for 30 min until uniform to obtain ink.

[0121] S5. De-bubbling packaging:

[0122] The ink obtained from T3 is degassed under vacuum for 30 minutes, filtered, and packaged to obtain the finished ink.

[0123] Example 5: Preparation of vegetable oil-modified rosin-based hyperbranched UVLED ink:

[0124] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0125] S101. 100 parts of rosin and 15 parts of fumaric acid were reacted at 190°C under nitrogen protection for 2.5 h to obtain the adduct;

[0126] S102, add 10 parts pentaerythritol, 30 parts dimethylolpropionic acid and 0.2 parts nano zinc oxide, stepwise increase the temperature to 250℃, and keep it at the temperature under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0127] S103, cool down to 180℃, add 20 parts tung oil and 10 parts soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product;

[0128] S104, cooled to 130℃, and diluted with 20 parts of ethoxylated trimethylolpropane triacrylate to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0129] S2, Pre-dispersion:

[0130] The pigment in the formulation was mixed with 30% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000 r / min for 30 min to obtain a pre-dispersed slurry.

[0131] S3, Grinding and Dispersing:

[0132] The pre-dispersed slurry obtained in T1 was ground four times using a three-roll mill until the fineness was ≤6μm to obtain the ground slurry;

[0133] S4, Color Adjustment:

[0134] The grinding slurry obtained from T2 was mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, 10 parts of compound photoinitiator, 10 parts of filler and 3 parts of additives, and stirred at 600 r / min for 30 min until uniform to obtain ink.

[0135] S5. De-bubbling packaging:

[0136] The ink obtained from T3 is degassed under vacuum for 30 minutes, filtered, and packaged to obtain the finished ink.

[0137] Example 6: Preparation of vegetable oil-modified rosin-based hyperbranched UV LED ink:

[0138] S1. Preparation of vegetable oil-modified rosin-based hyperbranched polyester resin:

[0139] S101. 100 parts of rosin and 15 parts of fumaric acid were reacted at 190°C under nitrogen protection for 2.5 h to obtain the adduct;

[0140] S102, add 10 parts pentaerythritol, 30 parts dimethylolpropionic acid and 0.2 parts nano zinc oxide, stepwise increase the temperature to 250℃, and keep it at the temperature under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate;

[0141] S103, cool down to 180℃, add 20 parts tung oil and 10 parts soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product;

[0142] S104, cooled to 130℃, and diluted with 20 parts of ethoxylated trimethylolpropane triacrylate to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

[0143] S2, Pre-dispersion:

[0144] The pigment in the formulation was mixed with 30% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000 r / min for 30 min to obtain a pre-dispersed slurry.

[0145] S3, Grinding and Dispersing:

[0146] The pre-dispersed slurry obtained in T1 was ground four times using a three-roll mill until the fineness was ≤6μm to obtain the ground slurry;

[0147] S4, Color Adjustment:

[0148] The grinding slurry obtained from T2 was mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, 5 parts of compound photoinitiator, 10 parts of filler and 3 parts of additives, and stirred at 600 r / min for 30 min until uniform to obtain ink.

[0149] S5. De-bubbling packaging:

[0150] The ink obtained from T3 is degassed under vacuum for 30 minutes, filtered, and packaged to obtain the finished ink.

[0151] Comparative Example 1:

[0152] Compared with Example 5, in Comparative Example 1, after rosin reacts with fumaric acid to obtain an adduct, the S102 hyperbranching step was not performed. Instead, it was directly reacted with tung oil and soybean oil at 220°C with a catalyst to obtain vegetable oil modified rosin-based polyester resin, with other conditions remaining unchanged.

[0153] Comparative Example 2:

[0154] Compared with Example 5, Comparative Example 2 did not perform the flexible end-capping step with tung oil and soybean oil, and all other conditions remained the same.

[0155] Comparative Example 3:

[0156] Compared with Example 5, in Comparative Example 3, the rosin was not added with fumaric acid, and the other conditions remained unchanged.

[0157] Comparative Example 4:

[0158] Compared with Example 5, in Comparative Example 4, a conventional mercury lamp photoinitiator (such as the 1173+184 combination, with the same total amount as in Example 5) was used instead of the compound photoinitiator of the present invention, while the other conditions remained unchanged.

[0159] Comparative Example 5:

[0160] Compared with Example 5, Comparative Example 5 did not perform a pre-dispersion step. Instead, the vegetable oil-modified rosin-based hyperbranched polyester resin was directly ground and dispersed with other components, while the other conditions remained unchanged.

[0161] Performance testing:

[0162] 1. National Standard Test:

[0163] This invention measures ink fineness according to GB / T 13217.3-2022 "Ink Fineness Test Method", ink viscosity according to GB / T13217.4-2020 "Ink Viscosity Test Method", ink adhesion on PE substrate according to GB / T 13217.7-2023 "Ink Adhesion Test Method", ink tinting strength according to GB / T 14624.2-1993 "Ink Tinting Strength Test Method", and ink flowability according to GB / T 14624.3-1993 "Ink Flowability Test Method".

[0164] 2. Curing volume shrinkage rate test

[0165] Test principle: Based on the principle that the mass remains unchanged before and after curing (in practice, deviations may occur due to sampling errors, initiator decomposition, etc.) while the volume changes, the volume shrinkage rate is calculated by measuring the density of the ink before and after curing.

[0166] Test steps:

[0167] According to ISO 3521 standard, the volume shrinkage rate is determined using the density method, and the steps are as follows:

[0168] (1) Using pure water at 25℃ as a control, calculate the precise volume V1 of the specific gravity bottle.

[0169] (2) Weigh the clean and dry empty specific gravity bottle m0, fill it with liquid ink and weigh m1. The ink mass m = m1 - m0. Calculate the liquid ink density ρ1 = m / V1 based on the nominal volume V1 of the specific gravity bottle.

[0170] (3) Apply an appropriate amount of ink to the polytetrafluoroethylene mold, control the film thickness to about 0.5 mm, and cure completely at a linear speed of 60 m / min under a 395 nm LED light source.

[0171] (4) Peel the cured ink film off the mold and weigh the ink film mass m2 using an analytical balance.

[0172] (5) After cutting the ink film into pieces, put it into a specific gravity bottle, add a wetting solution of known density (such as anhydrous ethanol), and determine the volume V2 of the ink film by the displacement method, and calculate ρ2=m2 / V2.

[0173] Calculation formula: Volume shrinkage rate = (ρ2-ρ1) / ρ2×100%.

[0174] 3. Pigment dispersion stability test

[0175] Test principle: The high-temperature accelerated aging method is used to simulate the storage stability of ink under normal temperature conditions. The dispersion stability of pigments is evaluated by measuring the change trend of ink viscosity and fineness and the precipitation.

[0176] Test steps:

[0177] (1) Take a freshly prepared ink sample and determine the initial viscosity η0 according to GB / T 13217.4-2020 and the initial fineness F0 according to GB / T13217.3-2022.

[0178] (2) Seal the ink sample in a light-proof container and store it in a constant temperature oven at 40±1℃.

[0179] (3) Samples were taken out at 1, 3, 6 and 12 months respectively, and after being restored to 25±0.5℃, the viscosity and fineness were measured again, and at the same time, it was observed whether there was precipitation or stratification.

[0180] (4) Record the viscosity η at each time point. t and fineness F t .

[0181] Judgment criteria: After being placed at a constant temperature of 40℃ for 12 months, if the ink shows no visible sedimentation or stratification, the viscosity change rate is ≤20%, and the fineness remains ≤6μm, then the pigment dispersion stability is deemed qualified.

[0182] 4. Curing speed test

[0183] At room temperature, UV ink was uniformly coated onto the glass substrate surface using a wire-bar coater, controlling the wet film thickness to 30 μm. Curing was then performed using a UV curing machine under the following conditions: power 80 W / cm². 2 The light source was 10 cm away. After curing, the ink film was completely dry (no stickiness, no ink residue) was determined by touch. The shortest time required for the ink to fully cure was recorded.

[0184] The performance test data of the above embodiments and comparative examples are shown in Tables 1, 2, and 3 below.

[0185] Table 1. Basic performance data of inks in the examples and comparative examples

[0186] Data Analysis:

[0187] The preparation process of the ink of this invention is as follows: Figure 1As shown, the process includes four steps: pre-dispersion, grinding and dispersion, conditioning and color adjustment, and degassing and packaging. First, the pigment and a portion of vegetable oil-modified rosin-based hyperbranched polyester resin are pre-dispersed in a high-speed disperser to ensure the resin fully wets the pigment particle surface. Then, the mixture is ground 3-5 times using a three-roll mill until the fineness is ≤6μm, utilizing the multi-anchor adsorption effect of the vegetable oil-modified rosin-based hyperbranched polyester resin to stabilize the pigment dispersion. Next, the remaining resin, photoinitiator, filler, and additives are added, and the mixture is stirred at low speed until homogeneous. Finally, the ink is degassed, filtered, and packaged under vacuum to obtain the finished ink. This process ensures high pigment dispersion and long-term storage stability of the ink.

[0188] A comparative analysis of the data in Table 1 leads to the following conclusions:

[0189] (1) Hyperbranched structure is the core factor in achieving low shrinkage, high adhesion and excellent storage stability. Comparing Example 5 and Comparative Example 1 (without hyperbranched structure), the viscosities of the two are similar (83000 vs 82000 mPa·s), but the volume shrinkage of Example 5 is only 4.4%, which is much lower than the 10.5% of Comparative Example 1; the adhesion is grade 1, which is better than the grade 3 of Comparative Example 1. It should be noted that Comparative Example 1 is a linear rosin polyester with a molecular weight of only 1000-5000 Da. Although the molecular weight is low, the linear molecular chains are prone to severe chain entanglement, resulting in a relatively high viscosity. Example 5 has a hyperbranched structure. The repeated esterification of pentaerythritol and DMPA exponentially increases the molecular weight to 3000-8000 Da, but its three-dimensional spherical structure can significantly reduce chain entanglement. Therefore, the viscosity can still be controlled at a level comparable to that of Comparative Example 1. This precisely proves that, under the premise of comparable viscosity, hyperbranched topology significantly improves ink film curing shrinkage and substrate adhesion by virtue of its internal free volume, stress dispersion mechanism and high-density end-group anchoring effect.

[0190] (2) The flexible end-capping of vegetable oil and the rigid skeleton of rosin synergistically regulate shrinkage and adhesion. Comparative Example 2 (without flexible end-capping) showed worse shrinkage (7.2%) and adhesion (grade 3) than Example 5 (4.4%, grade 1), but the curing speed was the same (1.0 s), indicating that the flexible long chains do not participate in the photocuring reaction, but rather reduce shrinkage and improve adhesion by absorbing internal stress. Comparative Example 3 also showed a decrease in shrinkage (6.8%) and adhesion (grade 2), demonstrating that the rigid skeleton introduced by fumaric acid addition helps maintain dimensional stability and interfacial bonding. Both are indispensable.

[0191] (3) The photoinitiator system must be compatible with the UV LED light source. Comparative Example 4 used a conventional mercury lamp initiator (1173+184), and the curing speed was reduced to 8s, while Example 5 (TPO+819+ITX compound) only required 1.0s. Other performances were similar, indicating that under 385-395nm LED light source, the proprietary compound initiator is the key to achieving rapid curing.

[0192] (4) A reasonable pre-dispersion process is the basis for ensuring fineness, adhesion and coloring power. Comparative Example 5 omitted the pre-dispersion step and directly ground it, which led to the deterioration of fineness (12μm), the decrease of coloring power (85%), the decrease of adhesion to level 3, and extremely poor subsequent storage stability (viscosity change rate +42.2%). In contrast, all examples were pre-dispersioned, with fineness ≤6μm, coloring power ≥97% and adhesion level 1.

[0193] (5) The ratio of tung oil to soybean oil can adjust the curing speed and viscosity. Example 1 (tung oil: soybean oil = 15:15) had a curing speed of 1.5s and a viscosity of 78000mPa·s; Example 5 (20:10) had a curing speed of 1.0s and a viscosity of 83000mPa·s. The higher the proportion of tung oil, the greater the double bond density and the faster the curing, but the viscosity of the system increases slightly, and the overall performance is still excellent.

[0194] In summary, this invention successfully prepared a bio-based UVLED ink with low shrinkage (≤5.1%), high adhesion (Grade 1), rapid curing (≤1.5s), and excellent storage stability by combining a hyperbranched skeleton, flexible end capping with vegetable oil, rigid introduction of rosin, and a special photoinitiator. Comparative Examples 1-5 verified the necessity and synergistic effect of each technical feature from different perspectives.

[0195] Table 2. Pigment Dispersion Stability Data - Viscosity for Examples and Comparative Examples

[0196] Table 3 Pigment Dispersion Stability Data - Fineness for Examples and Comparative Examples

[0197] Data Analysis:

[0198] The pigment dispersion stability of the ink was evaluated by the changes in viscosity and fineness over 12 months. Relevant data are shown in Table 2. Figure 2 Table 3. Hyperbranched topology is a decisive factor in ensuring the long-term storage stability of inks. From... Figure 2As can be clearly seen, all examples (Examples 1-6) exhibited a gradual increase in viscosity during the 12-month accelerated aging process, with the rate of change controlled within 10%. Combined with the fineness curves in Table 3, the fineness remained consistently ≤6 μm, without any precipitation or stratification. However, Comparative Example 1 (without hyperbranching), despite having an initial viscosity similar to Example 5, experienced a sharp increase in viscosity over 12 months, with a rate of change exceeding 30%. The fineness gradually deteriorated from ≤5 μm initially to 8 μm, with a small amount of precipitation appearing. This directly demonstrates that the linear structure, lacking high-density end-group anchoring, cannot effectively stabilize pigment particles. Comparative Example 3 (without rosin rigidity) also showed a significant increase in viscosity and trace precipitation, further illustrating that the absence of a rigid framework weakens the bonding strength between the resin and the pigment. Comparative Example 2 (without flexible end caps), although showing no precipitation, still had a higher viscosity change rate (16%) than all other examples, indicating that the steric hindrance effect of the flexible long chains has an auxiliary effect on dispersion stability. Comparative Example 5 (without pre-dispersion) performed the worst, with viscosity surging by over 40%, fineness deteriorating to 15 μm, and significant precipitation, confirming that pre-dispersion is a prerequisite for establishing an initial stable dispersion. Notably, Comparative Example 4 used a mercury lamp photoinitiator, and its storage stability was comparable to the examples, indicating that the type of initiator does not affect pigment dispersion stability. In summary, the hyperbranched structure, through the synergistic effect of multi-point anchoring adsorption and steric hindrance, achieved dispersion stability far superior to linear resins under similar viscosity conditions.

[0199] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A vegetable oil-modified rosin-based UV LED ink and its preparation method, characterized in that, The ink comprises the following components in parts by weight: 100 parts of vegetable oil-modified rosin-based hyperbranched polyester resin; 5-15 parts of compound photoinitiator; 10-30 parts pigment; 5-15 parts of filler; 1-5 parts of auxiliary agent; The preparation steps of the vegetable oil-modified rosin-based hyperbranched polyester resin are as follows: S1, Double Bond Bonus: 100 parts of rosin and 12-18 parts of fumaric acid were reacted at 180-200℃ under nitrogen for 2-3 hours to obtain the adduct; S2, hyperbranched polycondensation: Add 8-15 parts pentaerythritol, 25-35 parts dimethylolpropionic acid and 0.1-0.3 parts nano zinc oxide, stepwise increase the temperature to 245-255℃, and keep warm under nitrogen protection until the acid value is ≤15 mgKOH / g to obtain hyperbranched polyester intermediate; S3, Vegetable oil flexible end capping: Cool down to 170-190℃, add 15-25 parts of tung oil and 8-15 parts of soybean oil in a nitrogen atmosphere, keep warm for 1-2 hours, and obtain hyperbranched polyester resin product. S4, Active Dilution: Cool to 120-140℃ and dilute with 15-25 parts of reactive diluent to obtain vegetable oil modified rosin-based hyperbranched polyester resin.

2. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The vegetable oil-modified rosin-based hyperbranched polyester resin serves as both the main binder for inks and a dispersing stabilizer for pigments.

3. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The stepwise heating program described in S2 is to increase the temperature by 10°C every 30 minutes until the target temperature range is reached. The active diluent mentioned in S4 is ethoxylated trimethylolpropane triacrylate.

4. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The composite photoinitiator is composed of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-isopropylthioxanthrone in a weight ratio of 2:1:

1.

5. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The pigment is an organic pigment or carbon black, selected from one or more of yellow pigments, red pigments, blue pigments, and black pigments.

6. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The filler is kaolin with a surface modified by silane reagent, with an oil absorption value of 40-60g / 100g and an average particle size of 1-3μm.

7. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The vegetable oil-modified rosin-based hyperbranched polyester resin has a number average molecular weight of 1000-8000 Da, a branching degree of 0.4-0.6, and contains a mixture of functional groups at the ends, including hydroxyl, carboxyl, and fatty acid long chains.

8. A method for preparing vegetable oil-modified rosin-based UV LED ink according to claim 1, characterized in that, Includes the following steps: T1, Pre-dispersion: The pigment in the formulation is mixed with 30%-40% of the total amount of vegetable oil modified rosin-based hyperbranched polyester resin, and dispersed at 1000-1500 r / min for 20-30 min to obtain a pre-dispersed slurry. T2. Grinding and dispersing: The pre-dispersed slurry obtained in T1 is ground 3-5 times using a three-roll mill until the fineness is ≤6μm to obtain the ground slurry; T3, Color Adjustment: The grinding slurry obtained from T2 is mixed with the remaining vegetable oil-modified rosin-based hyperbranched polyester resin, compound photoinitiator, filler and additives, and stirred at 500-800 r / min for 30-60 min until uniform to obtain ink; T4, De-bubbling packaging: The ink obtained from T3 is degassed under vacuum for 15-30 minutes, filtered, and packaged to obtain the finished ink.

9. The vegetable oil-modified rosin-based UV LED ink and its preparation method according to claim 1, characterized in that, The ink meets the following performance indicators: Fineness: ≤6μm; Viscosity: 70,000-90,000 mPa·s (25℃); Curing volume shrinkage rate: ≤5%; PE substrate adhesion: Grade 1; Storage stability: No precipitation was observed after 12 months of constant temperature storage at 40℃.

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