High-thixotropy UV-LED offset printing ink and preparation method thereof

Abstract

The invention provides high-thixotropy UV-LED offset printing ink and a preparation method thereof.The preparation method comprises the steps that 30%-45% of modified polyurethane acrylate prepolymer, 20%-30% of functional monomers, 5%-10% of a photoinitiator system, 8%-15% of a benzene-free thixotropic agent, 3%-8% of functional auxiliaries and 10%-20% of pigment are fully mixed and then ground; the thixotropic agent is prepared by compounding organic modified montmorillonite and a segmented copolymer of a temperature-sensitive polymer poly (N-isopropylacrylamide) and polyethylene glycol, the dynamic response characteristic of the temperature-sensitive polymer is achieved, the thixotropic index regulation range is 1.2 + / -0.05-1.8 + / -0.05, and the ink system does not contain benzene series solvents and meets the environmental protection requirement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of offset printing ink, and particularly relates to a high-thixotropy UV-LED offset printing ink and a preparation method thereof. BACKGROUND

[0002] In the printing field, UV-LED curing offset printing ink has become one of the core technologies for carbon reduction and efficiency increase in the industry by virtue of the low-temperature process of "instant drying", which significantly reduces energy consumption and VOCs emission. However, in order to obtain high thixotropy to ensure dot sharpness and ink layer uniformity, the existing formula still generally relies on traditional thixotropic agents such as benzene-based diluents or fumed silica: the benzene-based solvent not only has residual toxicity, threatens the health of operators and pollutes the working environment, but also produces competitive absorption in the main UV-LED radiation waveband of 365-405 nm, which weakens the effective excitation of the photoinitiator, resulting in insufficient curing depth, sticky surface and performance degradation in the later period; the fumed silica is prone to agglomeration due to the surface hydroxyl groups, which causes flocculation and coarsening in long-term storage, resulting in viscosity drift, pigment sedimentation and deterioration of color consistency.

[0003] At the same time, the traditional photoinitiator (such as BP / ITX system) has low matching degree with the narrow peak irradiation of UV-LED, and needs to be added in excess to meet the surface drying requirement, which aggravates the problems of migration, odor and yellowing; the traditional polyurethane acrylate prepolymer is also insufficient in hardness and resin compatibility, and it is difficult to balance high hardness, high flexibility and system stability. The current benzene-free system uses acrylate monomer or epoxy diluent to replace benzene-based solvent, but its narrow polarity window and limited solubility limit the interfacial compatibility between pigments and resins, which is prone to thixotropy index (TI) fluctuation in the shear-rest cycle, and cannot meet the stringent requirements of high-end packaging, labeling and electronic printing on the consistency of ink performance. It can be seen that the existing UV-LED curing offset printing ink cannot simultaneously achieve: (1) the environmental protection requirement of benzene-free system; (2) high efficiency curing at 365 nm wavelength; (3) stable thixotropy index range of 1.2-1.8; (4) long-term storage stability. Therefore, it is urgent to develop a new ink system that is benzene-free, low-migrating, precisely matched with UV-LED spectrum and has persistent thixotropy stability, which has become a key bottleneck that needs to be broken through in the industry. SUMMARY

[0004] The application aims to avoid the deficiencies in the prior art and provide a high-thixotropy UV-LED offset printing ink and a preparation method thereof, which has the advantages of good environmental protection, high curing efficiency, high thixotropy dynamic regulation, good hardness, good wear resistance, good compatibility, dynamic balance of viscosity and thixotropy.

[0005] To achieve the above application purposes, the following technical solutions are provided:

[0006] A high thixotropy UV-LED offset ink is provided, comprising the following components by mass percentage:

[0007] a modified polyurethane acrylate prepolymer 30%-45%,

[0008] a functional monomer 20%-30%,

[0009] a photoinitiator system 5%-10%,

[0010] a benzene-free thixotropic agent 8%-15%,

[0011] a functional auxiliary agent 3%-8%,

[0012] a pigment 10%-20%,

[0013] wherein the modified polyurethane acrylate prepolymer is prepared by reacting a polyurethane acrylate with a fluorine-containing monomer and a benzene ring modifier at a mass ratio of 5:2:1 at 60-80°C for 4-6 hours;

[0014] The introduction of the fluorine-containing group and the rigid benzene ring structure in the molecular chain significantly improves the hardness, wear resistance and compatibility with other components of the prepolymer. The introduction of the fluorine-containing group also enhances the leveling property and stain resistance of the ink, and this dual modification method is original.

[0015] Specifically, the fluorine-containing group and the rigid benzene ring structure are introduced into the traditional polyurethane acrylate molecular chain, the ink leveling property is improved by the low surface energy property of fluorine elements, and the hardness and wear resistance of the prepolymer are enhanced by the rigid backbone of the benzene ring, breaking through the limitation that the mechanical properties and compatibility of conventional prepolymers are difficult to balance.

[0016] This modification method forms strong intermolecular forces (such as hydrogen bonds and π-π stacking) between the prepolymer and components such as functional monomers and thixotropic agents, significantly improving the stability of the system.

[0017] The functional monomer is prepared by compounding a difunctional pentaerythritol tetraacrylate and a trifunctional trimethylolpropane triacrylate at a mass ratio of 2-3:1, and adding 5%-8% octadecyl acrylate;

[0018] Specifically, the difunctional pentaerythritol tetraacrylate and the trifunctional trimethylolpropane triacrylate are compounded, and 5%-8% long-chain alkyl acrylate monomer is added, which adjusts the intermolecular force through "bridge effect", achieving dynamic balance of viscosity and thixotropy.

[0019] Difunctional / trifunctional monomer compounding, long-chain alkyl acrylate: PETRA (difunctional) and TMPTA (trifunctional) are compounded at a ratio of 2:1-3:1 to form a "low viscosity-high crosslinking density" balanced system, balancing printability and film strength after curing.

[0020] Long-chain alkyl acrylate monomers participate in photocuring crosslinking through the acrylate group at one end, and the long-chain alkyl group (C18) at the other end interacts with the fluorine-containing group of the prepolymer through van der Waals force to form a "physical crosslinking point" across the molecular chain, dynamically adjusting the viscosity and thixotropy of the ink, so that the thixotropy index of the ink can be precisely controlled to 1.2-1.8 within the shear rate range of 100-1000 s -1 The traditional ink can only fluctuate within the range of 1.0-1.5.

[0021] In the dual-functionality (PETRA) and tri-functionality (TMPTA) monomer complex system, 5%-8% of the long-chain alkyl-containing acrylate monomer is introduced, the acrylate functional group at one end participates in photocuring crosslinking reaction, and the long-chain alkyl group at the other end forms a "flexible bridge" between molecules through hydrophobic interaction, dynamically adjusting the viscosity and thixotropy of the ink.

[0022] This design realizes decoupling regulation of crosslinking density and rheological properties, breaking through the limitation of traditional monomers that only adjust the curing speed through functionality.

[0023] The photoinitiator system is prepared by compounding 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and a new type of macromolecular photoinitiator at a mass ratio of 1:1-2;

[0024] TPO is compounded with a new type of macromolecular polybenzoyl polymer photoinitiator (1:1.5-2 mass ratio), the macromolecular initiator is synthesized by patent, has low migration and high absorption efficiency, and is especially suitable for UV-LED specific wavelength (365-405nm), and the curing efficiency is improved.

[0025] Specifically, small molecule TPO is compounded with macromolecular photoinitiator (containing polybenzoyl structure polymer), the macromolecular component enhances the light absorption efficiency of UV-LED light source (365-405nm) through the conjugation effect of polybenzoyl group, and at the same time, the migration is reduced by using the steric hindrance of polymer chain, solving the problems of high migration risk and low curing efficiency of traditional small molecule photoinitiator.

[0026] The benzene-free thixotropic agent is prepared by compounding organic modified montmorillonite and poly N-isopropyl acrylamide-polyethylene glycol block copolymer at a mass ratio of 2-5:1.

[0027] For the first time, organic modified montmorillonite is compounded with a temperature-sensitive polymer (poly N-isopropyl acrylamide grafting modifier) as a benzene-free thixotropic agent, the interlayer spacing of montmorillonite is expanded through intercalation modification, and the dynamic response characteristics (high thixotropy at room temperature and low viscosity at elevated temperature) of the temperature-sensitive polymer are combined to realize precise regulation of thixotropy, and it is completely benzene-free and environmentally friendly.

[0028] Specifically, the organic modified montmorillonite is compounded with the temperature-sensitive polymer (poly N-isopropyl acrylamide graft modification) to construct a temperature-responsive thixotropic system: at room temperature, the layered structure of montmorillonite is modified by intercalation to form a three-dimensional network skeleton, providing high thixotropy and inhibiting ink flow; when the printing friction generates heat (temperature ≥ 40℃), the temperature-sensitive polymer molecular chain stretches, destroying the network structure, and the viscosity drops sharply, significantly improving the ink transferability.

[0029] In some embodiments, the mass ratio of the polyurethane acrylate, the fluorine-containing monomer, and the benzene ring modifier is 5:2:1, the fluorine-containing monomer is hexafluorobutyl methacrylate, and the benzene ring modifier is a styrene derivative.

[0030] In some embodiments, the long-chain alkyl acrylate monomer is octadecyl acrylate.

[0031] In some embodiments, the novel macromolecular photoinitiator is a polyurethane acrylate derivative containing a polybenzoyl structure, and the polyurethane acrylate derivative containing a polybenzoyl structure includes a polybenzoyl group, a polyurethane acrylate, and an acrylate functional group.

[0032] Further, the photoactive group is a polybenzoyl group (absorbing 365-405 nm UV-LED light source);

[0033] The polymer main chain is a polyurethane acrylate (compatible with the ink system);

[0034] The linking group is an acrylate functional group (involved in curing and crosslinking).

[0035] The migration is reduced by the high molecular chain, and the light absorption efficiency is improved by the polybenzoyl structure. The curing efficiency is improved by 20% compared with traditional small molecule initiators (such as TPO), and there is no migration risk.

[0036] The high thixotropy UV-LED offset printing ink according to claim 1, wherein the poly N-isopropyl acrylamide graft modification is a block copolymer of poly N-isopropyl acrylamide and polyethylene glycol.

[0037] The poly N-isopropyl acrylamide segment provides temperature sensitivity (hydrophobic aggregation is enhanced at room temperature, and the thixotropy is reduced at high temperature);

[0038] The polyethylene glycol segment improves the compatibility with the organic montmorillonite and forms a stable intercalation structure.

[0039] Traditional thixotropic agents cannot dynamically respond to temperature changes. The design realizes precise control of thixotropy (thixotropy index 1.2-1.8) through the temperature-sensitive behavior of the poly N-isopropyl acrylamide-polyethylene glycol block copolymer.

[0040] In some embodiments, the functional adjuvant includes a dispersant, a leveling agent, and an antifoaming agent,

[0041] The mass ratio of the dispersant, the leveling agent, and the antifoaming agent is 2-3:1:1.

[0042] The dispersant includes a hyperdispersant and a wet dispersant, and the weight ratio of the hyperdispersant to the wet dispersant is 1-2:1,

[0043] The hyperdispersant is one or a mixture of two or more of a polyamide-based hyperdispersant, a polyurethane-based hyperdispersant, and a fluorine / silicon-containing modified hyperdispersant,

[0044] The wet dispersant includes one or a mixture of two or more of an anionic wet dispersant, a non-ionic wet dispersant, and a high-molecular wet dispersant;

[0045] The leveling agent is one or a mixture of two or more of a polyether-modified polysiloxane, an alkyl-modified polysiloxane, a fluorine-modified acrylate, and a reactive acrylate;

[0046] The antifoaming agent is one or a mixture of two or more of a polysiloxane-polyether copolymer, a polyurethane-silicone composite, and an ethylene oxide / propylene oxide copolymer.

[0047] Specifically, the leveling agent is a polyether-modified polysiloxane;

[0048] The antifoaming agent is a polysiloxane-polyether copolymer.

[0049] The complex system solves the pigment dispersion problem in the benzene-free system through the anchoring effect of the hyperdispersant and the rapid penetration of the wet dispersant, and the dispersion stability is improved by 50% (viscosity change <5% after 30 days of storage).

[0050] In some embodiments, the pigment is one or a mixture of two or more of titanium dioxide, carbon black, and quinacridone pigment.

[0051] Also provided is a preparation method of the high-thixotropy UV-LED offset printing ink described above, including the following steps:

[0052] Mixing and stirring the formula amount of the modified polyurethane acrylate prepolymer, the functional monomer, the photoinitiator system, and the benzene-free thixotropic agent at a temperature of 23-27°C and a speed of 500-800 rpm for 20-50 min to obtain a first mixture;

[0053] Adding the functional adjuvant and the pigment to the first mixture and dispersing at a speed of 2000-3000 rpm for 30-60 min to obtain a second mixture;

[0054] Grinding the second mixture to obtain the high thixotropy UV-LED offset printing ink.

[0055] In some embodiments, the temperature condition for grinding the second mixture is 23-27℃, and the grinding is performed 2-3 times at a roll speed ratio of 1:3:9, and then stirring is performed at a speed of 1000rpm-1500rpm.

[0056] Compared with the prior art, the present application has the following advantages:

[0057] The high thixotropy UV-LED offset printing ink provided by the present application is configured by a modified polyurethane acrylate prepolymer, a functional monomer, a photoinitiator, a thixotropic agent, a functional additive, and a pigment in a certain proportion. The offset printing ink has the highest compatibility with a UV-LED light source with a wavelength of 365nm. It has been verified that it can complete curing in 5s, and it performs excellently in terms of adhesion, gloss, stability, and chemical solvent resistance.

[0058] The modified polyurethane acrylate prepolymer is used. The prepolymer is modified by introducing fluorine-containing groups and rigid benzene ring structures into the molecular chain of the traditional polyurethane acrylate. This not only improves the hardness and wear resistance of the prepolymer, but also enhances its compatibility with other components. At the same time, it gives the ink good leveling. The low surface energy property of fluorine elements improves the leveling of the ink, and the rigid backbone of benzene rings enhances the hardness and wear resistance of the prepolymer, making its hardness reach 3H and its wear resistance less than 5mg / 1000 times. This breaks through the limitation that the mechanical properties and compatibility of conventional prepolymers are difficult to balance.

[0059] The functional monomer is a combination of bifunctional pentaerythritol tetraacrylate (PETRA) and trifunctional trimethylolpropane triacrylate (TMPTA), and 5%-8% of a special structure monomer, acrylate monomer with long-chain alkyl, is added. The monomer has an acrylate functional group at one end and a long-chain alkyl group at the other end, which acts as a molecular "bridge" in the ink system, adjusting the viscosity and thixotropy of the ink.

[0060] The photoinitiator system is a combination of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide (TPO) and a new type of macromolecular photoinitiator (a polymer containing a benzoyl structure synthesized by a patent) in a mass ratio of 1:1.5-2. The macromolecular photoinitiator has low mobility and good compatibility with the prepolymer and monomer, can effectively absorb the energy of specific wavelengths of the UV-LED light source, and improve the curing efficiency.

[0061] The benzene-free thixotropic agent is selected from organic modified montmorillonite and temperature-sensitive polymer (poly N-isopropyl acrylamide graft modification). The organic modified montmorillonite is modified by intercalation to expand the interlayer spacing and enhance the thickening and thixotropic effect on the ink system; the temperature-sensitive polymer provides high thixotropy at room temperature, and when the ink is heated due to friction during printing, the molecular chain is stretched, the viscosity is reduced, and the transferability of the ink is improved. That is, the thixotropic index is controlled in the range of 1.2±0.05 to 1.8±0.05, the thixotropy of the offset ink can be accurately controlled, and the materials used do not contain benzene, which meets the environmental protection requirements. DETAILED DESCRIPTION

[0062] The technical solutions of the present application are further described below in combination with preferred embodiments, and it should be understood that the following embodiments are intended to better understand the technical solutions of the present application, and are not a limitation on the present application.

[0063] Embodiment 1

[0064] The high thixotropy UV-LED offset printing ink disclosed in this embodiment comprises the following components by mass percentage:

[0065] modified polyurethane acrylate prepolymer 30%, functional monomer 20%, photoinitiator system 5%, benzene-free thixotropic agent 8%, functional additive 3%, pigment 10%,

[0066] The modified polyurethane acrylate prepolymer is prepared by mixing polyurethane acrylate, fluorine-containing monomer and benzene ring modifier, and then reacting at a temperature of 60°C for 4 hours.

[0067] The functional monomer is prepared by the following method:

[0068] Mixing difunctional pentaerythritol tetraacrylate, trifunctional trimethylolpropane triacrylate and octadecyl acrylate, adding long-chain alkyl acrylate monomer, and mixing uniformly, the mass ratio of the difunctional pentaerythritol tetraacrylate to the trifunctional trimethylolpropane triacrylate is 2:1, and the amount of the long-chain alkyl acrylate monomer added is 5%;

[0069] The photoinitiator system is prepared by mixing 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and a new type of macromolecular photoinitiator, and the mass ratio of the 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide to the new type of macromolecular photoinitiator is 1:1;

[0070] The benzene-free thixotropic agent is prepared by uniformly mixing organic modified montmorillonite and poly N-isopropyl acrylamide graft modification,

[0071] The mass ratio of the organic modified montmorillonite and the poly N-isopropyl acrylamide grafting modifier is 2:1.

[0072] In this embodiment, the mass ratio of the polyurethane acrylate, the fluorine-containing monomer and the benzene ring modifier is 5:1, the fluorine-containing monomer is hexafluorobutyl methacrylate, and the benzene ring modifier is a styrene derivative,

[0073] In this embodiment, the long-chain alkyl acrylate monomer is octadecyl acrylate.

[0074] In this embodiment, the new macromolecular photoinitiator is a polyurethane acrylate derivative containing a polybenzoyl structure, and the polyurethane acrylate derivative containing a polybenzoyl structure includes a polybenzoyl group, a polyurethane acrylate, and an acrylate functional group.

[0075] In this embodiment, the poly N-isopropyl acrylamide grafting modifier is a block copolymer of poly N-isopropyl acrylamide and polyethylene glycol.

[0076] In this embodiment, the functional adjuvant includes a dispersant, a leveling agent, and a defoaming agent,

[0077] The mass ratio of the dispersant, the leveling agent, and the defoaming agent is 3:1:1.

[0078] The dispersant includes a hyperdispersant and a wet dispersant, and the weight ratio of the hyperdispersant to the wet dispersant is 1:1,

[0079] The hyperdispersant is one or a mixture of two or more of a polyamide hyperdispersant, a polyurethane hyperdispersant, and a fluorine / silicon modified hyperdispersant,

[0080] The wet dispersant includes one or a mixture of two or more of an anionic wet dispersant, a non-ionic wet dispersant, and a high molecular weight wet dispersant;

[0081] The hyperdispersant realizes long-term stable dispersion mainly through steric hindrance, and the wet dispersant promotes rapid wetting and preliminary dispersion of the pigment by reducing surface tension. The combination of the two in a ratio of 2:1 can solve the problems of difficult wetting, easy agglomeration, and poor dispersion stability of pigments in ink systems, ensuring uniform distribution of pigments in benzene-free systems and improving the tinting power, gloss, and printing suitability of inks.

[0082] The leveling agent is one or a mixture of two or more of a polyether modified polysiloxane, an alkyl modified polysiloxane, a fluorine modified acrylate, and a reactive acrylate.

[0083] The defoaming agent is a mixture of one or more than two of polysiloxane-polyether copolymer, polyurethane-silicone composite and oxirane / propylene oxide copolymer.

[0084] In this embodiment, the pigment is a mixture of one or more than two of titanium dioxide, carbon black and quinacridone pigment.

[0085] Inorganic pigment: titanium dioxide, carbon black, organic pigment: quinacridone pigment,

[0086] High light fastness, solvent resistance and migration resistance, bright color. In some publications with high color requirements and high-end packaging printing, quinacridone pigment is often used to formulate red and purple ink to obtain long-lasting bright color effect.

[0087] The preparation method of the high-thixotropy UV-LED offset printing ink described above comprises the following steps:

[0088] Mix and stir the formula amount of modified polyurethane acrylate prepolymer, functional monomer, photoinitiator system and benzene-free thixotropic agent at a temperature of 23 DEG C and a stirring speed of 500 rpm for 20 min to obtain a first mixture;

[0089] Add functional additives and pigments to the first mixture and disperse at a speed of 2000 rpm for 30 min to obtain a second mixture;

[0090] Grind the second mixture to obtain the high-thixotropy UV-LED offset printing ink.

[0091] In this embodiment, the temperature condition for grinding the second mixture is 23 DEG C, and the grinding speed ratio is 1:3:9, and then stirring at a speed of 1000 rpm.

[0092] The present application synchronously modifies polyurethane acrylate with fluorine-containing monomer (hexafluorobutyl methacrylate) and styrene derivative,

[0093] Precise control of reaction conditions: under the protection of nitrogen at 65 DEG C, the modifier is added in stages, first introduce fluorine-containing monomer for 2 hours, then add benzene ring modifier for 2 hours.

[0094] The obtained prepolymer has the following properties: surface migration of fluorine-containing segment (contact angle > 95 DEG), rigid skeleton of benzene ring (hardness >= 3H) and curing activity of acrylate.

[0095] Temperature-sensitive-light-sensitive synergistic trigger system: innovatively grafting and modifying temperature-sensitive poly-N-isopropyl acrylamide with light-responsive organically modified montmorillonite, which presents high thixotropy (thixotropic index 1.5-1.8) at 25-30℃ printing temperature and turns into low viscosity state (thixotropic index <1.1) within 10 seconds after UV-LED irradiation.

[0096] The dual regulation mechanism of "temperature stability-light control flow leveling" is realized, and the contradiction between traditional ink flow leveling and dot reproducibility is solved.

[0097] In the preparation process of the modified polyurethane acrylate prepolymer, the fluorine-containing monomer is added in two stages, 60% of the total amount is added at 60℃ for 1 hour, and the remaining 40% is added at 70℃ for 1.5 hours, and the benzene ring modifier is added at 75℃ once for 2 hours.

[0098] The organically modified montmorillonite in the benzene-free thixotropic agent is nano montmorillonite modified by [2-(methacryloyloxy)ethyl]dimethyl octadecyl ammonium bromide and perfluoro octyl triethoxy silane, and its interlayer spacing is expanded to 3.5-4.2nm;

[0099] The poly-N-isopropyl acrylamide graft modifier in the benzene-free thixotropic agent is prepared by mixing poly-N-isopropyl acrylamide with Mn≈8000 and polyethylene glycol with Mn≈2000, adding CTP chain transfer agent, azobisisobutyronitrile (AIBN) initiator and dioxane solvent to react and obtain poly-N-isopropyl acrylamide graft modifier with grafting rate of 15% and lowest critical solution temperature (LCST) ≈32℃.

[0100] The novel macromolecular photoinitiator is synthesized by mixing 4,4'-dihydroxybenzophenone, hexamethylene diisocyanate and hydroxyethyl acrylate in a molar ratio of 1:3:3, adding 0.05wt% of dibutyl tin dilaurate catalyst, and reacting at a temperature of 70℃ for 4h to obtain a product with Mw≈3500 and 6-8 benzoyl groups.

[0101] The dispersant in the functional auxiliary agent contains a specific structure of fluorine-containing polyurethane superdispersant, and its general structure is F-(CF2)4-CH2-O-CO-NH-[(CH2)6-NH-CO-O-(CH2CH2O)10-CO-NH]2-(CH2)6-NH-CO-O-CH2-(CF2)4-F

[0102] Gradient temperature control is adopted in the grinding stage: 25℃ grinding for 2 times in the first stage, 20℃ grinding for 1 time in the second stage, and 28℃ final blending in the third stage, so that the thixotropic index is stabilized at 1.5±0.03.

[0103] The double modified prepolymer obtained by the above embodiment makes the ink have the following properties simultaneously:

[0104] Pencil hardness: 3H (traditional product ≤ 2H)

[0105] Adhesion: 5B (hundred grid test)

[0106] Surface energy: 28.5 mN / m (traditional product 35-40 mN / m)

[0107] The temperature-sensitive and light-sensitive thixotropic system realizes:

[0108] Static viscosity: 12,000 mPa·s (25℃)

[0109] Shear viscosity: 800 mPa·s (shear rate 1000 s -1 )

[0110] Flow leveling time after photocuring: <15 s (traditional product >30 s)

[0111] New macromolecular photoinitiator system:

[0112] Molar extinction coefficient at 365 nm: 12,500 L·mol -1 ·cm -1

[0113] Migration rate: <0.1% (traditional TPO 2.5-3.8%)

[0114] Initiation efficiency: 92% (traditional product 70-80%).

[0115] After the ink of the embodiment is accelerated to age at 40℃ for 60 days, the thixotropic index change rate is <3%, the viscosity change rate is <5%, and the pigment sedimentation rate is <0.5%, and each performance index meets the standard requirements of GB / T 13217.1-2009.

[0116] Example 2

[0117] The high thixotropy UV-LED offset printing ink disclosed in the embodiment comprises the following components in mass percentage:

[0118] Modified polyurethane acrylate prepolymer 45%, functional monomer 30%, photoinitiator system 10%, benzene-free thixotropic agent 15%, functional additive 8%, pigment 20%,

[0119] The modified polyurethane acrylate prepolymer is prepared by mixing polyurethane acrylate, fluorine-containing monomer and benzene ring modifier, and then reacting at a temperature of 80℃ for 6 hours to obtain the modified polyurethane acrylate prepolymer;

[0120] The functional monomer is prepared by the following method:

[0121] Mix difunctional pentaerythritol tetraacrylate, trifunctional trimethylolpropane triacrylate and octadecyl acrylate, add a long-chain alkyl acrylate monomer, and mix evenly, wherein the mass ratio of the difunctional pentaerythritol tetraacrylate to the trifunctional trimethylolpropane triacrylate is 3:1, and the amount of the long-chain alkyl acrylate monomer added is 8%;

[0122] The photoinitiator system is prepared by: mixing 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and a novel macromolecular photoinitiator, wherein the mass ratio of the 2,4,6-trimethylbenzoyl-diphenylphosphine oxide to the novel macromolecular photoinitiator is 1:2;

[0123] The benzene-free thixotropic agent is prepared by uniformly mixing organic modified montmorillonite and poly (N-isopropylacrylamide) grafted modified material;

[0124] The mass ratio of the organically modified montmorillonite to the poly (N-isopropylacrylamide) grafted modified product is 5:1.

[0125] In this embodiment, the mass ratio of the polyurethane acrylate, the fluorine-containing monomer and the benzene ring modifier is 5:2:1, the fluorine-containing monomer is hexafluorobutyl methacrylate, and the benzene ring modifier is a styrene derivative.

[0126] In this embodiment, the long-chain alkyl acrylate monomer is octadecyl acrylate.

[0127] In this embodiment, the novel macromolecular photoinitiator is a polyurethane acrylate derivative containing a polybenzoyl structure, and the polyurethane acrylate derivative containing a polybenzoyl structure comprises polybenzoyl groups, polyurethane acrylate, and acrylate functional groups.

[0128] The highly thixotropic UV-LED offset ink according to claim 1, wherein the poly (N-isopropylacrylamide) grafted modified product is a block copolymer of poly (N-isopropylacrylamide) and polyethylene glycol.

[0129] In this embodiment, the functional additives include dispersants, leveling agents and defoaming agents.

[0130] The mass ratio of the dispersant, the leveling agent and the defoaming agent is 2:1:1.

[0131] The dispersant includes a hyperdispersant and a wetting dispersant, and the weight ratio of the hyperdispersant to the wetting dispersant is 2:1.

[0132] The superdispersant is one or a mixture of two or more of a polyamide superdispersant, a polyurethane superdispersant, and a fluorine / silicon-containing modified superdispersant,

[0133] The wetting dispersant includes one or a mixture of two or more of an anionic wetting dispersant, a nonionic wetting dispersant, and a high-molecular wetting dispersant.

[0134] The leveling agent is one or a mixture of two or more of a polyether-modified polysiloxane, an alkyl-modified polysiloxane, a fluorine-modified acrylate, and a reactive acrylate.

[0135] The defoaming agent is one or a mixture of two or more of a polysiloxane-polyether copolymer, a polyurethane-silicone composite, and an ethylene oxide / propylene oxide copolymer.

[0136] In this embodiment, the pigment is one or a mixture of two or more of titanium dioxide, carbon black, and quinacridone pigments.

[0137] The preparation method of the high-thixotropy UV-LED offset printing ink described above comprises the following steps:

[0138] The modified polyurethane acrylate prepolymer, the functional monomer, the photoinitiator system, and the benzene-free thixotropic agent in the formula amount are mixed and stirred at a temperature condition of 27°C at a rotation speed of 800 rpm for 50 min to obtain a first mixture.

[0139] The functional auxiliary agent and the pigment are added to the first mixture, and are dispersed at a rotation speed of 3000 rpm for 30 min to 60 min to obtain a second mixture.

[0140] The second mixture is ground to obtain the high-thixotropy UV-LED offset printing ink.

[0141] In this embodiment, the second mixture is ground at a temperature condition of 27°C at a roll speed ratio of 1:3:9 for 2 to 3 times, and is then stirred at a rotation speed of 1500 rpm.

[0142] Embodiment 3

[0143] The high-thixotropy UV-LED offset printing ink disclosed in this embodiment comprises the following components in mass percentage:

[0144] The modified polyurethane acrylate prepolymer is 34%, the functional monomer is 25%, the photoinitiator system is 8%, the benzene-free thixotropic agent is 10%, the functional auxiliary agent is 5%, and the pigment is 18%.

[0145] The modified polyurethane acrylate prepolymer is prepared by the following method: the polyurethane acrylate is mixed with a fluorine-containing monomer and a benzene ring modifier, and then is reacted at a temperature condition of 70°C for 5 hours to obtain the modified polyurethane acrylate prepolymer.

[0146] The functional monomer is prepared by the following method:

[0147] The bifunctional pentaerythritol tetraacrylate, trifunctional trimethylolpropane triacrylate and octadecyl acrylate are mixed, and long-chain alkyl acrylate monomer is added, and mixed uniformly, the mass ratio of the bifunctional pentaerythritol tetraacrylate and the trifunctional trimethylolpropane triacrylate is 2.5:1, and the long-chain alkyl acrylate monomer is added in an amount of 5% to 8%;

[0148] The photoinitiator system is prepared by the following method: 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and a new type of macromolecular photoinitiator are mixed, and the mass ratio of the 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and the new type of macromolecular photoinitiator is 1:1.5;

[0149] The benzene-free thixotropic agent is prepared by the following method: organic modified montmorillonite and poly N-isopropyl acrylamide graft modification are mixed uniformly,

[0150] The mass ratio of the organic modified montmorillonite and the poly N-isopropyl acrylamide graft modification is 3:1.

[0151] In this embodiment, the mass ratio of the polyurethane acrylate, the fluorine-containing monomer and the benzene ring modifier is 5:2:1, the fluorine-containing monomer is hexafluorobutyl methacrylate, and the benzene ring modifier is a styrene derivative,

[0152] In this embodiment, the long-chain alkyl acrylate monomer is octadecyl acrylate.

[0153] In this embodiment, the new type of macromolecular photoinitiator is a polyurethane acrylate derivative containing a multi-benzoyl structure, and the polyurethane acrylate derivative containing a multi-benzoyl structure includes a multi-benzoyl group, a polyurethane acrylate, and an acrylate functional group.

[0154] The high-thixotropy UV-LED offset printing ink according to claim 1, wherein the poly N-isopropyl acrylamide graft modification is a block copolymer of poly N-isopropyl acrylamide and polyethylene glycol.

[0155] In this embodiment, the functional adjuvant includes a dispersant, a leveling agent and a defoaming agent,

[0156] The mass ratio of the dispersant, the leveling agent and the defoaming agent is 2.5:1:1.

[0157] The dispersant includes a super dispersant and a wet dispersant, and the weight ratio of the super dispersant to the wet dispersant is 1.5:1,

[0158] The superdispersant is one or a mixture of two or more of a polyamide superdispersant, a polyurethane superdispersant, and a fluorine / silicon-containing modified superdispersant,

[0159] The wetting dispersant includes one or a mixture of two or more of an anionic wetting dispersant, a nonionic wetting dispersant, and a high-molecular wetting dispersant;

[0160] The leveling agent is one or a mixture of two or more of a polyether-modified polysiloxane, an alkyl-modified polysiloxane, a fluorine-modified acrylate, and a reactive acrylate.

[0161] The defoaming agent is one or a mixture of two or more of a polysiloxane-polyether copolymer, a polyurethane-silicone composite, and an ethylene oxide / propylene oxide copolymer.

[0162] In this embodiment, the pigment is one or a mixture of two or more of titanium dioxide, carbon black, and quinacridone pigments.

[0163] The preparation method of the high-thixotropy UV-LED offset printing ink described above comprises the following steps:

[0164] The modified polyurethane acrylate prepolymer, the functional monomer, the photoinitiator system, and the benzene-free thixotropic agent in the formula amount are mixed and stirred at a temperature condition of 25°C at a rotation speed of 700 rpm for 30 min to obtain a first mixture.

[0165] The functional auxiliary agent and the pigment are added to the first mixture, and are dispersed at a rotation speed of 2500 rpm for 40 min to obtain a second mixture.

[0166] The second mixture is ground to obtain the high-thixotropy UV-LED offset printing ink.

[0167] In this embodiment, the temperature condition for grinding the second mixture is 25°C, and the grinding is performed 2-3 times at a roller speed ratio of 1:3:9, and then stirring is performed at a rotation speed of 1200 rpm.

[0168] Effect verification:

[0169] To further illustrate the effect of the present application, the following experiments are performed, wherein the modified polyurethane acrylate prepolymer, the functional monomer, the benzene-free thixotropic agent, the functional auxiliary agent, and the pigment in the following experimental examples are the same as in Embodiment 1.

[0170] Experimental Example 1

[0171] 40% of the modified polyurethane acrylate prepolymer, 25% of the functional monomer, 8% of the photoinitiator system, 12% of the benzene-free thixotropic agent, 5% of the functional auxiliary agent, and 10% of the pigment are weighed.

[0172] The prepolymer, monomer, photoinitiator and thixotropic agent were mixed and stirred for 30 minutes.

[0173] Add additives and pigments and disperse at high speed for 1 hour until the fineness reaches 4.5μm.

[0174] The ink obtained after three-roll grinding had a thixotropic index of 1.6 and a curing time of ≤1 second.

[0175] Experimental Example 2

[0176] The difference between Experimental Example 2 and Experimental Example 1 is that the proportion of the benzene-free thixotropic agent is adjusted to 10%, and the rest is the same as Example 1. The thixotropic index is 1.4, which is suitable for high-speed printing.

[0177] Prepolymer preparation:

[0178] The polyurethane acrylate is reacted with a fluorine-containing monomer and a benzene ring modifier at 60-80° C. for 4-6 hours to obtain a modified prepolymer.

[0179] Ink preparation:

[0180] The modified prepolymer, functional monomer, photoinitiator, benzene-free thixotropic agent, functional additive and pigment are mixed, dispersed at high speed (2000-3000 rpm) for 30 minutes, and then ground with three rollers to a fineness of ≤5 μm.

[0181] Performance testing:

[0182] Thixotropic index (25°C): 1.5-1.8 (shear rate 100-1000s -1 );

[0183] Curing speed (365nm LED): ≤1 second;

[0184] Abrasion resistance (Taber test): ≤5mg / 1000 times.

[0185] Thixotropic index test:

[0186] The thixotropic index of the highly thixotropic UV-LED offset inks prepared in Experimental Example 1 and Experimental Example 2 was tested. The results are shown in Table 1. The offset ink prepared in Example 1 has better thixotropic performance.

[0187] Table 1 Thixotropic index test of high thixotropic UV-LED offset ink

[0188] Example Test Conditions Thixotropic Index Example 1 25°C, shear rate 100 s -1 -1000 s -1 ]]> 1.6 Example 2 25°C, shear rate 100 s -1 -1000 s -1 , adjusting the proportion of thixotropic agent to 10% 1.4

[0189] Experimental Example 3

[0190] The highly thixotropic UV-LED offset ink provided in Example 1 of the present application was tested for performance changes under different shear rates and temperatures.

[0191] As shown in Table 2, the thixotropic index of the high thixotropy UV-LED offset ink provided by Example 1 of the present application increases with the increase of temperature and shear rate, and the apparent viscosity decreases accordingly,

[0192] The principle is that the thixotropic agent used is compounded by organic modified montmorillonite and poly N-isopropyl acrylamide grafting modification, which has temperature responsive thixotropy characteristics. At room temperature 25℃, the layered structure of montmorillonite forms a three-dimensional network skeleton through intercalation modification to improve the thixotropy of the ink and inhibit the flow of the ink. When the temperature gradually increases to 40℃ and above, based on the temperature sensitivity of poly N-isopropyl acrylamide grafting modification, the molecular chain is stretched, the grid structure is destroyed, the viscosity is reduced, and the transferability of the ink is significantly improved. With the increase of shear rate, the grid structure of the ink system is destroyed to a higher degree under the action of mechanical force, thereby improving the thixotropic index of the ink system and reducing the apparent viscosity. In terms of printing adaptability, when the temperature reaches 35℃ to 40℃, based on the increase of the thixotropic index and the decrease of the viscosity of the ink system, the ink flying rate is reduced to the minimum.

[0193] Table 2 Influence of shear rate and temperature change on the thixotropy of offset ink

[0194]

[0195] Experimental Example 4

[0196] Matching test of high thixotropy UV-LED offset ink and UV-LED light source:

[0197] Take the high thixotropy UV-LED offset ink prepared in Example 1 to test its matching degree under 365nm-405nm UV-LED light source, which specifically includes curing efficiency, curing degree, surface hardness, wear resistance, adhesion, gloss, ink system stability, light initiator absorption efficiency, ink color change, chemical solvent resistance and flexibility;

[0198] The curing efficiency test is based on the standard ink layer thickness, with light intensity 1000mW / cm 2 Irradiation, record the time of complete curing of the ink;

[0199] The curing depth test uses UV-LED light source to vertically irradiate the cured ink, tests the penetration depth of the ink layer, and observes the curing effect;

[0200] The surface hardness test uses pencil hardness test method to test the cured ink;

[0201] The wear resistance test uses Taber wear tester to detect the mass loss after 1000 cycles;

[0202] Adhesion test is tested by grid method to evaluate adhesion level;

[0203] Gloss test is tested by gloss meter to evaluate the value of 60° angle;

[0204] Ink system stability test is to observe whether there is precipitation and stratification after 24h;

[0205] Photoinitiator absorption efficiency test is to detect the change of absorption peak intensity of photoinitiator by spectrometer;

[0206] Ink color change test is to compare the color difference (ΔE) before and after curing, and the test standard is “ASTM D2244 color difference detection standard”;

[0207] Chemical solvent resistance test is to observe the change after the cured ink is soaked in ethanol and ethyl acetate for 1h;

[0208] Flexibility test is to observe whether the cured ink cracks after bending.

[0209] The results are shown in Table 3, and the high thixotropy UV-LED offset ink has the highest matching degree with the 365nm UV-LED light source, and the complete deep curing is achieved in 5s, and the performance indicators after curing are also significantly higher than those of the other groups.

[0210] The principle is that the high thixotropy UV-LED offset ink provided in embodiment 1 includes a photoinitiator system prepared by compounding 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide and a new type of macromolecular photoinitiator, wherein the new type of macromolecular photoinitiator is a polymer with a multi-benzoyl structure, which can enhance the light absorption efficiency of the 365nm-405nm UV-LED light source through the conjugation effect of the multi-benzoyl group, and at the same time, the migration is reduced by using the steric hindrance of the polymer chain, thereby realizing high curing efficiency.

[0211] Table 3 Performance index test of high thixotropy UV-LED offset ink under different light sources

[0212]

[0213]

[0214] Experimental example 5

[0215] Performance comparison test of high thixotropy UV-LED offset ink and traditional ink

[0216] The high thixotropy UV-LED offset ink prepared in embodiment 1 and any traditional ink on the market are taken to test the shear rate 100s -1 ~1000s -1The change of the thixotropic index in the range was evaluated, and the high-speed printing stability and storage stability of the two inks were evaluated.

[0217] The results are shown in Table 4. In the shear rate range of 100 s -1 ~1000s -1 The thixotropic index of the conventional ink fluctuates by ±0.1~±0.15, and the thixotropic index of the high-thixotropy UV-LED offset printing ink provided in Embodiment 1 fluctuates by ±0.05. Compared with the conventional ink, the change of the thixotropic index of the high-thixotropy UV-LED offset printing ink provided in Embodiment 1 is more stable, which also indicates that the high-thixotropy UV-LED offset printing ink provided in Embodiment 1 can achieve more precise dynamic adjustment of the thixotropic index by adjusting the shear rate.

[0218] The principle is that the modified polyurethane acrylate prepolymer contained in the high-thixotropy UV-LED offset printing ink provided in Embodiment 1 has benzene ring structure and long-chain alkyl, which can provide stable steric hindrance under the synergistic action of the two, thereby improving the stability of the thixotropic index. The presence of the benzene ring structure improves the compatibility of the ink system, makes the thixotropic agent uniformly dispersed in the system, and makes it have the excellent performance of keeping the thixotropic index stable for a long time. The high-thixotropy UV-LED offset printing ink provided in Embodiment 1 also includes a functional monomer prepared by compounding bifunctional pentaerythritol tetraacrylate, trifunctional trimethylolpropane triacrylate, and octadecyl acrylate. The monomer can further improve the dynamic balance performance of the ink viscosity and thixotropy by adjusting the intermolecular force through the "bridge effect".

[0219] Table 4 Performance comparison of high-thixotropy UV-LED offset printing ink and conventional ink

[0220]

[0221] Experimental Example 6

[0222] An offset printing ink was prepared using unmodified polyurethane acrylate:

[0223] 40% of the polyurethane acrylate, 25% of the functional monomer, 8% of the photoinitiator system, and 10% of the thixotropic agent were weighed, and mixed and stirred at a temperature of 25°C and a speed of 600 rpm for 30 min to obtain a first mixture;

[0224] 5% of the functional additive and 10% of the pigment were added to the first mixture, and dispersed at a speed of 2000 rpm~3000 rpm for 60 min to obtain a second mixture;

[0225] The second mixture was circulated and ground twice by a three-roll grinder at a temperature of 25°C and a roll speed ratio of 1:3:9, and then stirred at a speed of 1200 rpm to make the fineness ≤5 um, to obtain a high-thixotropy UV-LED offset printing ink.

[0226] The rest of the components and their mass ratio are unchanged in the comparative example except for the unmodified polyurethane acrylate.

[0227] Experimental Example 7

[0228] Performance test of high thixotropy UV-LED offset ink:

[0229] The offset ink prepared in Example 1 and Comparative Example 6 was tested for performance indicators, including hardness, wear resistance, compatibility, and comprehensive performance.

[0230] The hardness test included pencil hardness test according to ASTM D3363 standard at an angle of 45° and a load of 1 kg. The hardness test also included Shore hardness test using a Shore hardness tester.

[0231] The wear resistance test included Taber wear resistance test according to ASTM D4060 standard using CS-10 grinding wheel with a load of 1 kg and 1000 rotations to detect the mass loss. The wear resistance test also included friction coefficient test using a friction coefficient tester to test the dynamic and static friction coefficients.

[0232] The compatibility test included viscosity stability test by storing the high thixotropy UV-LED offset ink at 25℃ for 7 days to detect the viscosity change rate. The compatibility test also included SEM microstructure observation to observe the phase separation.

[0233] The comprehensive performance test included adhesion test according to ASTM D3359 standard by grid method to test the adhesion of the ink. The comprehensive performance test also included chemical resistance test by immersing the cured ink in ethanol and ethyl acetate for 1 h to observe the changes.

[0234] The results are shown in Table 5, and the performance indicators of the high thixotropy UV-LED offset ink of Example 1 are significantly higher than those of the offset ink of Comparative Example 1,

[0235] The principle is that the modified polyurethane acrylate polymer used in Example 1 includes polyurethane acrylate, fluorine-containing monomer, and benzene ring modifier. During preparation, the fluorine-containing monomer reacts with the polyurethane acrylate, allowing the fluorine-containing group of the fluorine-containing monomer to be introduced into the polyurethane acrylate molecular chain. The addition of benzene ring modifier introduces benzene ring structure into the polyurethane acrylate molecular chain. Based on the high stability characteristics of the benzene ring structure, the rigidity and hardness of the modified polyurethane acrylate polymer are increased, thereby improving the wear resistance of the offset ink after curing, making it not easy to be damaged under external forces such as friction. At the same time, the benzene ring structure can improve the compatibility of the modified polyurethane acrylate polymer with other components, and can enhance the stability of the entire offset ink system.

[0236] Table 5 Offset ink performance index test

[0237]

[0238]

[0239] Comparative Example 1

[0240] The benzene-free thixotropic agent was replaced with an equivalent amount of fumed silica, and the remaining components were the same as in Example 1. The test results showed that the viscosity increased by 18% after 30 days of storage, the thixotropic index fluctuation range widened to ±0.12, and the printing dot blurring rate reached 12%.

[0241] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A highly thixotropic UV-LED offset printing ink, characterized in that: The following components are included in mass percentage: Modified polyurethane acrylate prepolymer 30% to 45%, Functional monomer 20% to 30%, Photoinitiator system 5% to 10%, Benzene-free thixotropic agent 8% to 15%, Functional additives 3% to 8%, Pigment 10% to 20%, The modified polyurethane acrylate prepolymer is prepared by reacting polyurethane acrylate with a fluorine-containing monomer and a benzene ring modifier in a mass ratio of 5:2:1 at 60-80°C for 4-6 hours; The functional monomer is prepared by compounding difunctional pentaerythritol tetraacrylate and trifunctional trimethylolpropane triacrylate in a mass ratio of 2 to 3:1, and adding 5% to 8% octadecyl acrylate; The photoinitiator system is prepared by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and a novel macromolecular photoinitiator in a mass ratio of 1:1 to 2; The benzene-free thixotropic agent is prepared by compounding organic modified montmorillonite and poly (N-isopropylacrylamide)-polyethylene glycol block copolymer in a mass ratio of 2 to 5:

1.

2. The highly thixotropic UV-LED offset ink according to claim 1, characterized in that: The mass ratio of the polyurethane acrylate, the fluorine-containing monomer and the benzene ring modifier is 5:2:1, the fluorine-containing monomer is hexafluorobutyl methacrylate, and the benzene ring modifier is a styrene derivative.

3. The highly thixotropic UV-LED offset ink according to claim 1, characterized in that: The long-chain alkyl acrylate monomer is octadecyl acrylate.

4. The highly thixotropic UV-LED offset ink according to claim 1, characterized in that: The novel macromolecular photoinitiator is a polyurethane acrylate derivative containing a polybenzoyl structure, wherein the polyurethane acrylate derivative containing a polybenzoyl structure comprises polybenzoyl groups, polyurethane acrylate and acrylate functional groups.

5. The highly thixotropic UV-LED offset ink according to claim 1, characterized in that: The poly N-isopropylacrylamide grafted modified product is a block copolymer of poly N-isopropylacrylamide and polyethylene glycol.

6. The highly thixotropic UV-LED offset ink according to claim 1, characterized in that: The functional additives include dispersants, leveling agents and defoamers. The mass ratio of the dispersant, the leveling agent and the defoaming agent is 2 to 3:1:

1.

7. The highly thixotropic UV-LED offset ink according to claim 6, characterized in that: The dispersant includes a hyperdispersant and a wetting dispersant, and the weight ratio of the hyperdispersant to the wetting dispersant is 1 to 2:

1. The hyperdispersant is one or a mixture of two or more of a polyamide hyperdispersant, a polyurethane hyperdispersant, and a fluorine / silicon modified hyperdispersant. The wetting and dispersing agent includes one or a mixture of two or more of anionic wetting and dispersing agents, nonionic wetting and dispersing agents and polymeric wetting and dispersing agents; The leveling agent is one or a mixture of two or more of polyether-modified polysiloxane, alkyl-modified polysiloxane, fluorine-modified acrylate and reactive acrylic acid; The defoaming agent is one or a mixture of two or more of polysiloxane-polyether copolymer, polyurethane-organic silicon composite and ethylene oxide / propylene oxide copolymer.

8. The highly thixotropic UV-LED offset ink according to claim 1, characterized in that: The pigment is titanium dioxide, carbon black and quinacridone pigment or a mixture of two or more thereof.

9. The method for preparing the highly thixotropic UV-LED offset ink according to any one of claims 1 to 7, characterized in that: The following steps are involved: Mixing the modified polyurethane acrylate prepolymer, functional monomer, photoinitiator system and benzene-free thixotropic agent in the formulated amount at a temperature of 23° C. to 27° C. and a speed of 500 rpm to 800 rpm for 20 min to 50 min to obtain a first mixture; Adding functional additives and pigments to the first mixture, dispersing at a speed of 2000 rpm to 3000 rpm for 30 min to 60 min to obtain a second mixture; The second mixture is ground to obtain the highly thixotropic UV-LED offset printing ink.

10. The method for preparing a highly thixotropic UV-LED offset printing ink according to claim 9, wherein: The second mixture is ground at a temperature of 23-27° C. with a roller speed ratio of 1:3:9 for 2-3 times, and then stirred at a speed of 1000 rpm-1500 rpm.

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