CN120504999B

CN120504999B - UV inkjet printing ink, preparation method and application

Info

Publication number: CN120504999B
Application number: CN202510999841.6A
Authority: CN
Inventors: 刘金德; 洪华星
Original assignee: Fortuna Imatek Chemical Co ltd
Current assignee: Fortuna Imatek Chemical Co ltd
Priority date: 2025-07-21
Filing date: 2025-07-21
Publication date: 2025-09-16
Anticipated expiration: 2045-07-21
Also published as: CN120504999A

Abstract

The present invention belongs to the field of UV inkjet printing ink technology, and discloses a UV inkjet printing ink, a preparation method, and an application. In response to the problem that traditional UV inks are prone to cracking on flexible substrates, a cross-linking monomer prepared from pentaerythritol tetrakis(3-mercaptopropionic acid) is designed. The cross-linking monomer extends outward through a four-arm star-shaped branch to form a uniform three-dimensional cross-linked network. Its spatial redundancy provides a flexible foundation, and its steric hindrance limits the cross-linking strength. The alkane flexible chain segments and amino alcohol structures on the side chains enhance the interfacial adhesion between the ink and the substrate while releasing stress. The two methods work together to collaboratively construct a UV inkjet printing ink with excellent flexibility and not easy to crack while maintaining adhesion.

Description

UV (ultraviolet) ink-jet printing ink, preparation method and application

Technical Field

The application relates to the technical field of ink-jet printing ink, in particular to UV ink-jet printing ink, a preparation method and application.

Background

The UV ink-jet printing ink is used as an environment-friendly functional material, and is widely applied to the fields of package printing, electronic devices, advertisement marks and the like by virtue of rapid solidification, low VOC emission, high adhesive force and excellent color stability. The technical principle of the UV ink-jet printing ink is based on a photosensitive system, and the main components of the UV ink-jet printing ink are photosensitive resin, a photoinitiator, a reactive diluent and pigment, and under the irradiation of ultraviolet rays, the photoinitiator triggers chain polymerization reaction, so that the liquid ink is solidified into a high-strength and high-durability solid film within a few seconds. When UV inks are used on flexible substrates, the products of the flexible substrates often undergo stretch-fold operations during storage and construction, and the ink layer is prone to cracking, thus presenting a number of disadvantages.

Disclosure of Invention

Aiming at the problem that the traditional UV ink is easy to crack on a flexible substrate, the application provides UV ink-jet printing ink, a preparation method and application, and designs a crosslinking monomer prepared from pentaerythritol tetra (3-mercaptopropionic acid), wherein the crosslinking monomer extends outwards through four-arm star-shaped branches to form a uniform three-dimensional crosslinking network, the space redundancy of the crosslinking network provides a flexible basis, the space steric hindrance limits the crosslinking strength, and the alkane flexible chain segment and the amino alcohol structure on the branched chain can enhance the interfacial adhesion of the ink and the substrate and release stress at the same time, and the two modes cooperate together to cooperatively construct the UV ink-jet printing ink with excellent flexibility and difficult cracking on the premise of keeping the adhesion.

In order to achieve the above purpose, the application adopts the following technical scheme:

in a first aspect, the present application provides a UV inkjet printing ink comprising:

The crosslinking monomer is prepared from pentaerythritol tetra (3-mercaptopropionic acid), and the crosslinking monomer is a four-arm star-shaped crosslinking monomer or a phosphoric acid ester four-arm star-shaped crosslinking monomer;

The four-arm star-shaped crosslinking monomer has the structural formula:

;

the structural formula of the phosphate four-arm star-shaped crosslinking monomer is as follows:

。

In a second aspect, the present invention provides a method of preparing a UV inkjet printing ink comprising the steps of:

s1, adding a second photoinitiator into pentaerythritol tetra (3-mercaptopropionic acid) and allyl glycidyl ether to obtain an intermediate product;

s2, adding 4,4' -diaminodiphenyl methane into the intermediate product to prepare a four-arm star-shaped crosslinking monomer;

And S3, mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment, grinding, and then vacuum defoaming to obtain the UV ink-jet printing ink.

In a third aspect, the present application provides the use of a UV inkjet printing ink in UV inkjet printing.

The beneficial technical effects are as follows:

in the UV ink-jet printing ink, a cross-linking network is formed through the four-arm star-shaped structure of the cross-linking monomer, on one hand, branches of the cross-linking network can provide enough cross-linking sites, on the other hand, the spatial extensibility of the branch structure has certain spatial redundancy in folding so as to release stress, an amino alcohol structure is formed by epoxy groups and amino groups on the branches, the interface adhesion force can be enhanced through hydrogen bonds formed on the surface of an amino alcohol structure substrate, further, the adhesion force is stronger on the substrate, and the soft chain segment of the branches enables the ink to release stress through local sliding of molecular chains in folding or stretching after being dried. The four-arm star-shaped structure of the crosslinking monomer extends outwards through four branches to form a uniform three-dimensional crosslinking network, the space redundancy of the four-arm star-shaped structure provides a flexible foundation, the alkane flexible chain segment on the branched chain and the amino alcohol structure release stress, and the two modes cooperate together to enhance the flexibility on the premise of keeping the adhesiveness, so that the effect of avoiding ink cracking is achieved.

Drawings

FIG. 1 is a schematic diagram of a method for preparing the UV ink-jet printing ink according to the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more apparent, the present application will be described in further detail with reference to the following examples. It should not be understood that the scope of the application is limited to the following examples. All other embodiments obtained by a person skilled in the art without making any inventive effort are within the scope of the protection of the present application without departing from the idea of the method of the application described above.

In the present application, the terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

As used in this disclosure, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Furthermore, the terms "first," "second," and the like, if any, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The four-arm star-shaped crosslinking monomer has the structural formula:

;

。

In a possible embodiment, the mass ratio of the four-arm star-shaped crosslinking monomer, reactive diluent, first photoinitiator, wetting dispersant and pigment is (58-63): 22-25): 2.3-2.6): 0.5-0.7): 9.5.

The reactive diluent provides fluidity and participates in crosslinking, the proportion is too low, curing is insufficient, the flexibility is reduced when too high, the photoinitiator ensures enough photoinitiation efficiency, the curing is incomplete when too low, excessive crosslinking can be initiated when too high, and the brittleness is increased. The viscosity, the curing rate and the mechanical properties are balanced by the accurate proportioning.

In one possible implementation, the reactive diluent is one of 1, 6-hexanediol diacrylate and tripropylene glycol diacrylate, the first photoinitiator is TPO-L, the wetting dispersant is one of BYK-331 and Tego Wet 270, and the pigment is one of phthalocyanine blue BGS, C.I. pigment Red 122 and C.I. pigment yellow 74.

1, 6-Hexanediol diacrylate is a short chain reactive diluent, provides high reactivity, tripropylene glycol diacrylate is a long chain reactive diluent, can enhance flexibility, and has a TPO-L absorption peak of 365nm, matched with an ultraviolet light source, and high curing efficiency. BYK-331 and Tego Wet 270 can optimize pigment dispersion to prevent agglomeration.

In a possible implementation, the starting material of the four-arm star-shaped crosslinking monomer further includes a second photoinitiator, where the second photoinitiator is one of Irgacure 184, irgacure 907, and Darocur 1173.

In a second aspect, the present invention also provides a method for preparing UV inkjet printing ink, comprising the steps of:

In one possible implementation, the preparation of the intermediate product in S1 comprises the steps of mixing pentaerythritol tetra (3-mercaptopropionic acid) and allyl glycidyl ether in a molar ratio of 1 (4.2-4.4) to obtain a mixture, adding a second photoinitiator accounting for 0.45% -0.55% of the total mass of the mixture, and reacting for 2-3 hours in a water bath at 38-42 ℃ under the protection of nitrogen to obtain the intermediate product.

The thiol (-SH) of pentaerythritol tetra (3-mercaptopropionic acid) and alkenyl (C=C) of allyl glycidyl ether are subjected to addition reaction of thiol-ene clicking through a free radical chain reaction under the action of a second photoinitiator to form a star-shaped structure with four active epoxy groups, so that sites are provided for subsequent functional modification, the star-shaped structure can form a three-dimensional cross-linked network, the chain entanglement problem of a linear structure is avoided, the mechanical property after curing is enhanced, the moderate degree of freedom of movement is given to a molecular chain segment by the spatial ductility of a branched structure, brittleness caused by too strong rigidity is avoided, the mole ratio is controlled to ensure that the thiol and the alkenyl are fully reacted to avoid residual unreacted monomers, the second photoinitiator accelerates the clicking reaction to avoid side reactions, and the reaction formula is as follows:

。

Under a feasible implementation condition, the preparation method of the four-arm star-shaped crosslinking monomer S2 comprises the steps of adding 4,4' -diaminodiphenyl methane into the intermediate product, wherein the mass ratio of the intermediate product to the 4,4' -diaminodiphenyl methane is 25 (10-12), the adding rate of the 4,4' -diaminodiphenyl methane is 3-5g/min, and triethylamine is dropwise added in the reaction process, and the reaction is carried out for 3.5-6 hours under the condition that the pH=8+/-0.2,70-80 ℃ is maintained, so that the four-arm star-shaped crosslinking monomer is obtained.

The epoxy group from allyl glycidyl ether and the amino group of 4,4' -diaminodiphenyl methane undergo nucleophilic ring-opening reaction to generate an amino alcohol structure, the pH is regulated and controlled by triethylamine, the protonation of the amino group is prevented, and the reaction efficiency is ensured. The hydroxyl in the amino alcohol and the amino or ether bond oxygen atoms of the adjacent chain segments form intermolecular hydrogen bonds, and meanwhile, the hydroxyl is easy to form hydrogen bonds with a base material, so that the adhesive force with the base material is improved, the allyl glycidyl ether is used as a flexible chain segment, so that after ink is dried, stress can be released through local sliding of a molecular chain during folding or stretching, cracking is prevented, the flexibility is improved, the benzene ring structure of the 4,4 '-diaminodiphenyl methane provides rigidity, the mechanical property is kept, each 4,4' -diaminodiphenyl methane molecule reacts with epoxy groups of two different four-arm star-shaped molecules respectively through two amino groups, and the crosslinking network and the crosslinking density are enlarged, wherein the reaction formula is as follows:

。

Under a feasible implementation condition, the preparation method of the UV ink-jet printing ink in S3 comprises the steps of mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment at 35-40 ℃, grinding in a sand mill until the fineness is less than or equal to 200nm, and performing vacuum defoaming at 40-45 ℃ for 30-60min to obtain the UV ink-jet printing ink.

Under a feasible implementation condition, the preparation method of the UV ink-jet printing ink further comprises the steps of mixing the four-arm star-shaped crosslinking monomer with di [2- (methacryloyloxy) ethyl ] phosphate in a mass ratio of 14 (11-11.5), carrying out vacuum reaction for 2.5-3.5 hours at 65-68 ℃ to obtain the phosphate modified four-arm star-shaped crosslinking monomer, mixing the phosphate modified four-arm star-shaped crosslinking monomer, a first photoinitiator, a reactive diluent and pigment, grinding, and carrying out vacuum deaeration to obtain the UV ink-jet printing ink.

The four-arm star-shaped crosslinking monomer is combined with a phosphate group of di [2- (methacryloyloxy) ethyl ] phosphate through nucleophilic substitution to form a phosphate functionalized structure, the interfacial binding force of molecular polarity and a substrate is enhanced, meanwhile, the steric hindrance of the phosphate group can balance the rigidity and flexibility of a crosslinked network, the acrylate double bond of the di [2- (methacryloyloxy) ethyl ] phosphate can be used for UV curing crosslinking, and carbonyl C=O in the molecule can form a hydrogen bond with the substrate to enhance the adhesive force, and the reaction formula is as follows:

。

The following describes in detail, with reference to various embodiments, a UV inkjet printing ink, a method for preparing the same, and applications thereof.

Example 1

As shown in fig. 1, a method for preparing UV inkjet printing ink includes the following steps:

1. Mixing pentaerythritol tetra (3-mercaptopropionic acid) and allyl glycidyl ether according to a molar ratio of 1:4.2, adding a photoinitiator Irgacure 184 accounting for 0.45% of the total mass of the mixture, and stirring and reacting in a water bath at 38 ℃ and 300rpm for 2 hours under the protection of nitrogen to obtain an intermediate product;

2. Adding 4,4' -diaminodiphenyl methane into an intermediate product, controlling the mass ratio of the intermediate product to the 4,4' -diaminodiphenyl methane to be 25:10, controlling the addition rate of the 4,4' -diaminodiphenyl methane to be 3g/min, stirring at 200rpm at 70 ℃ for reaction for 6 hours, dropwise adding triethylamine in the process, and maintaining the pH=7.8 to obtain a four-arm star-shaped crosslinking monomer;

3. mixing a four-arm star-shaped crosslinking monomer with 1, 6-hexanediol diacrylate, TPO-L, BYK-331 and phthalocyanine blue BGS in a mass ratio of 58:25:2.6:0.7:9.5 at 35 ℃, grinding in a sand mill until the fineness is less than or equal to 200nm, and defoaming for 30min at 45 ℃ under-0.1 MPa by a vacuum defoaming machine to obtain the UV ink-jet printing ink.

Example 2

3. Mixing the four-arm star-shaped crosslinking monomer with di [2- (methacryloyloxy) ethyl ] phosphate in a mass ratio of 14:11, vacuumizing to the air pressure of-0.08 MPa at 65 ℃, and reacting for 3.5 hours to obtain a phosphate modified four-arm star-shaped crosslinking monomer;

4. Mixing phosphate modified four-arm star-shaped crosslinking monomer, 1, 6-hexanediol diacrylate, TPO-L, BYK-331 and phthalocyanine blue BGS according to a mass ratio of 58:25:2.6:0.7:9.5, grinding in a sand mill until the fineness is less than or equal to 200nm, and defoaming for 30min at 45 ℃ under-0.1 MPa by a vacuum defoaming machine to obtain the UV inkjet printing ink.

Example 3

1. Mixing pentaerythritol tetra (3-mercaptopropionic acid) and allyl glycidyl ether according to a molar ratio of 1:4.3, adding a photoinitiator Irgacure 907 accounting for 0.50% of the total mass of the mixture, and stirring and reacting in a water bath at 40 ℃ and 300 rpm for 2.5 hours under the protection of nitrogen to obtain an intermediate product;

2. Adding 4,4' -diaminodiphenyl methane into an intermediate product, controlling the mass ratio of the intermediate product to the 4,4' -diaminodiphenyl methane to be 25:11, controlling the adding rate of the 4,4' -diaminodiphenyl methane to be 3g/min, stirring at 200rpm at 75 ℃ for reaction for 5 hours, dropwise adding triethylamine in the process, and maintaining pH=8 to obtain a four-arm star-shaped crosslinking monomer;

3. Mixing the four-arm star-shaped crosslinking monomer with di [2- (methacryloyloxy) ethyl ] phosphate in a mass ratio of 14:11.2, vacuumizing to the air pressure of-0.08 MPa at 65 ℃, and reacting for 2.5 hours to obtain a phosphate modified four-arm star-shaped crosslinking monomer;

4. Mixing a phosphate modified four-arm star-shaped crosslinking monomer with tripropylene glycol diacrylate, TPO-L, BYK-331 and C.I. pigment red 122 according to a mass ratio of 58:25:2.6:0.7:9.5, grinding in a sand mill until the fineness is less than or equal to 200nm, and defoaming for 30min at 45 ℃ under-0.1 MPa by a vacuum defoaming machine to obtain the UV inkjet printing ink.

Example 4

1. Mixing pentaerythritol tetra (3-mercaptopropionic acid) and allyl glycidyl ether according to a molar ratio of 1:4.4, adding a photoinitiator Darocur 1173 accounting for 0.55% of the total mass of the mixture, and stirring and reacting in a water bath at 42 ℃ and 300rpm under the protection of nitrogen for 3 hours to obtain an intermediate product;

2. Adding 4,4' -diaminodiphenyl methane into an intermediate product, controlling the mass ratio of the intermediate product to the 4,4' -diaminodiphenyl methane to be 25:12, controlling the adding rate of the 4,4' -diaminodiphenyl methane to be 3g/min, stirring at 200rpm at 80 ℃ for 3.5 hours, dropwise adding triethylamine in the process, and maintaining the pH=8.2 to obtain a four-arm star-shaped crosslinking monomer;

3. mixing the four-arm star-shaped crosslinking monomer with di [2- (methacryloyloxy) ethyl ] phosphate in a mass ratio of 14:11.5, vacuumizing to the air pressure of-0.08 MPa at 68 ℃, and reacting for 2.5 hours to obtain a phosphate modified four-arm star-shaped crosslinking monomer;

4. Mixing the phosphate modified four-arm star-shaped crosslinking monomer with 1, 6-hexanediol diacrylate, TPO-L, tego Wet 270 and C.I. pigment yellow 74 according to the mass ratio of 58:25:2.6:0.7:9.5, grinding in a sand mill until the fineness is less than or equal to 200nm, and defoaming for 30min at 45 ℃ under the pressure of-0.1 MPa by a vacuum deaerator to obtain the UV inkjet printing ink.

Example 5

4. mixing phosphate modified four-arm star-shaped crosslinking monomer, 1, 6-hexanediol diacrylate, TPO-L, BYK-331 and phthalocyanine blue BGS according to a mass ratio of 60:24:2.4:0.6:9.5, grinding in a sand mill until the fineness is less than or equal to 200nm, and defoaming for 45min at 40 ℃ under-0.1 MPa by a vacuum defoaming machine to obtain the UV inkjet printing ink.

Example 6

4. Mixing phosphate modified four-arm star-shaped crosslinking monomer, 1, 6-hexanediol diacrylate, TPO-L, BYK-331 and phthalocyanine blue BGS according to a mass ratio of 63:22:2.3:0.5:9.5, grinding in a sand mill until the fineness is less than or equal to 200nm, and defoaming for 60min at 45 ℃ under-0.1 MPa by a vacuum defoaming machine to obtain the UV inkjet printing ink.

Comparative example 1

The experimental procedure and parameters of the preparation method of the UV ink-jet printing ink are the same as those of example 5, except that the phosphate modified four-arm star-shaped crosslinking monomer is changed into an intermediate product.

Comparative example 2

The preparation method of the UV ink-jet printing ink has the same experimental steps and parameters as in example 5, except that the phosphate modified four-arm star-shaped crosslinking monomer is replaced by pentaerythritol tetra (3-mercaptopropionic acid) ester for direct use.

Performance test:

Viscosity the properties of the UV-curable inkjet materials obtained in examples 1 to 6 and comparative examples 1 to 2 above were measured according to the spin method described in the test of Standard GB/T10247-2008, at 40℃and 30rpm, and the test results are shown in Table 1.

And (3) performing performance test after photo-curing, namely respectively spraying the UV-curing ink-jet materials obtained in the examples and the comparative examples on a PVC soft film and a copper plate in an ink drop volume of 10pL, and performing irradiation curing by adopting an LED light source under the intensity of 120mW/cm < 2 >, until the materials are cured and molded, so as to form a photo-curing ink layer, wherein the test results are shown in Table 1.

The adhesion performance is that the adhesion of the photo-curing ink layer to the PVC soft film and the copper plate is measured by using a hundred grid test according to the test standard of the standard GBT 9286-1998, wherein the atmosphere is 0-5 level, the 0 level is optimal, the 5 level is worst, and the test result is shown in Table 1.

Flexibility after the PVC flexible film forming the photo-curable ink layer was folded 3 times, it was observed whether the photo-curable ink layer was cracked or not, and the test results are shown in Table 1.

Table 1 results of performance tests of example 1-example 6 and comparative example 1-comparative example 2

As shown in Table 1, the UV ink-jet printing inks prepared in examples 1-6 have a viscosity of 14.0-14.9cps, a low viscosity, are not easy to block nozzles during ink-jet printing, have adhesion grades of 1-2 on PVC soft films and copper plates, and the photo-curing ink layer formed on the PVC soft films is folded for 3 times without cracking, which indicates that the UV ink-jet printing ink has good adhesion and flexibility, and has an elongation of 110% -120% and is not easy to crack.

The UV ink-jet printing ink of the embodiment 2-embodiment 6 is added with the phosphate modified four-arm star-shaped crosslinking monomer, and in the structure, the acrylic ester double bond introduced by the di [2- (methacryloyloxy) ethyl ] phosphate has high reactivity and an interface enrichment effect with a photoinitiator TPO-L, so that a compact crosslinking layer is formed on the surface of the ink, an aromatic ring network of 4,4' -diaminodiphenyl methane can be used as a rigid supporting structure to provide mechanical strength and hardness of the ink, the phosphate can be deprotonated on the metal surface to form Fe-O-P bonds, and the Fe-O-P bonds are anchored on the plastic surface through C=O.H-O-P hydrogen bonds to realize strong adhesion. The steric hindrance of the four-arm star-shaped framework can inhibit pigment aggregation, and the steric hindrance cooperates with the solvation action of the active diluent to prolong the sedimentation time of the ink, thereby prolonging the storage period.

Comparative example 1 uses the intermediate product to replace phosphate to modify the four-arm star-shaped crosslinking monomer, the prepared UV ink-jet printing ink has the advantages of reduced adhesive force, poor flexibility and reduced elongation to 108 percent. The ring-opening amination further stabilizes the network by introducing 4,4' -diaminodiphenylmethane containing amino groups, forming intermolecular hydrogen bonds and crosslinking points, phosphate modifications. Both of these deletions lead to a significant decrease in crosslink density, and deterioration in adhesion and flexibility. The soft chain segments are lost, the crosslinked network is loose, and the molecular chains cannot be effectively extended. UV inkjet printing inks cannot form strong adhesion to the polar surface of copper plates due to the lack of synergy of amino and phosphate groups.

Comparative example 2 the prepared UV inkjet printing ink was reduced in adhesion, poor in flexibility, and reduced in elongation to 101% by directly using pentaerythritol tetrakis (3-mercaptopropionate). The unmodified pentaerythritol tetra (3-mercaptopropionic acid) has only mercapto functional groups, cannot form a multidimensional crosslinked network, has the adhesiveness of only grade 5 and poor flexibility, and the unmodified monomer has low molecular weight, and the reactive diluent cannot be effectively dispersed, so that the viscosity is increased. And the single functional group of pentaerythritol tetra (3-mercaptopropionic acid) limits the ductility of molecular chains, the cross-linked network is fragile, and the extensibility is reduced.

The foregoing shows and describes the basic principles and main features of the present application and the advantages of the present application.

It will be understood by those skilled in the art that the present application is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present application, and various changes and modifications may be made without departing from the spirit and scope of the application, which is defined in the appended claims. The scope of the application is defined by the equivalents of the appended claims.

Claims

1. A UV inkjet printing ink, comprising:

The four-arm star-shaped crosslinking monomer has the structural formula:

;

。

2. the UV inkjet printing ink according to claim 1, wherein the mass ratio of the four-arm star-shaped crosslinking monomer, reactive diluent, first photoinitiator, wetting dispersant and pigment is (58-63): 22-25): 2.3-2.6): 0.5-0.7): 9.5.

3. The UV inkjet printing ink according to claim 1, wherein the reactive diluent is one of 1, 6-hexanediol diacrylate and tripropylene glycol diacrylate, the first photoinitiator is TPO-L, the wetting dispersant is one of BYK-331, tego Wet 270, and the pigment is one of phthalocyanine blue BGS, c.i. pigment red 122, and c.i. pigment yellow 74.

4. The UV inkjet printing ink according to claim 1, wherein the starting material for the four-arm star-shaped crosslinking monomer further includes a second photoinitiator, the second photoinitiator being one of Irgacure 184, irgacure 907, and Darocur 1173.

5. A method of preparing a UV inkjet printing ink according to any one of claims 1 to 4, including the steps of:

6. The method for preparing the UV ink-jet printing ink according to claim 5, wherein S1 comprises the steps of mixing pentaerythritol tetra (3-mercaptopropionic acid) and allyl glycidyl ether in a molar ratio of 1 (4.2-4.4) to obtain a mixture, adding a second photoinitiator accounting for 0.45% -0.55% of the total mass of the mixture, and reacting for 2-3 hours in a water bath at 38-42 ℃ under the protection of nitrogen to obtain the intermediate product.

7. The method for preparing the UV ink-jet printing ink according to claim 5, wherein S2 comprises the steps of adding 4,4' -diaminodiphenyl methane into the intermediate product, wherein the mass ratio of the intermediate product to the 4,4' -diaminodiphenyl methane is 25 (10-12), the adding rate of the 4,4' -diaminodiphenyl methane is 3-5g/min, triethylamine is dropwise added in the reaction process, and the reaction is carried out for 3.5-6 hours under the condition that the pH=8+/-0.2,70-80 ℃ is maintained, so that the four-arm star-shaped crosslinking monomer is obtained.

8. The method for preparing the UV ink-jet printing ink according to claim 5, wherein the step S3 comprises the steps of mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment at 35-40 ℃, grinding the mixture in a sand mill until the fineness is less than or equal to 200nm, and performing vacuum defoaming at 40-45 ℃ for 30-60min to obtain the UV ink-jet printing ink.

9. The preparation method of the UV ink-jet printing ink according to claim 5, further comprising the steps of mixing the four-arm star-shaped crosslinking monomer with di [2- (methacryloyloxy) ethyl ] phosphate in a mass ratio of 14 (11-11.5), carrying out vacuum reaction for 2.5-3.5h at 65-68 ℃ to obtain the phosphate modified four-arm star-shaped crosslinking monomer, mixing the phosphate modified four-arm star-shaped crosslinking monomer, a first photoinitiator, a reactive diluent and pigment, and carrying out vacuum deaeration after grinding to obtain the UV ink-jet printing ink.

10. Use of a UV inkjet printing ink according to any one of claims 1 to 4 in UV inkjet printing.