UV inkjet printing ink, preparation method and application

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

Technical Field

[0001] The present application relates to the technical field of inkjet printing inks, and in particular to a UV inkjet printing ink, a preparation method and an application thereof. Background Art

[0002] As an environmentally friendly functional material, UV inkjet printing ink is widely used in packaging printing, electronic devices, advertising signs, and other fields due to its fast curing, low VOC emissions, high adhesion, and excellent color stability. The technical principle of UV inkjet printing ink is based on a photosensitive system. The main components are photosensitive resin, photoinitiator, reactive diluent, and pigment. Under ultraviolet light, the photoinitiator triggers a chain polymerization reaction, causing the liquid ink to solidify into a high-strength, highly durable solid film within seconds. When UV ink is used on flexible substrates, the products of flexible substrates are often stretched and folded during storage and application, which makes the ink layer prone to cracking, resulting in many shortcomings. Summary of the Invention

[0003] In response to the problem that traditional UV inks are prone to cracking on flexible substrates, the present application provides a UV inkjet printing ink, a preparation method and an application. A cross-linking monomer prepared from pentaerythritol tetrakis(3-mercaptopropionic acid) is designed, which extends outward through four-arm star-shaped branches 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.

[0004] To achieve the above objectives, this application adopts the following technical solutions:

[0005] In a first aspect, the present application provides a UV inkjet printing ink, comprising:

[0006] A cross-linking monomer, a reactive diluent, a first photoinitiator, a wetting dispersant and a pigment; the cross-linking monomer is prepared from pentaerythritol tetrakis(3-mercaptopropionic acid), and the cross-linking monomer is a four-arm star-shaped cross-linking monomer or a phosphate four-arm star-shaped cross-linking monomer;

[0007] The structural formula of the four-arm star-shaped cross-linked monomer is:

[0008] ;

[0009] The structural formula of the phosphate four-arm star-shaped crosslinking monomer is:

[0010] .

[0011] In a second aspect, the present invention provides a method for preparing a UV inkjet printing ink, comprising the following steps:

[0012] S1, using pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether, adding a second photoinitiator to prepare an intermediate product;

[0013] S2, adding 4,4'-diaminodiphenylmethane to the intermediate product to prepare a four-arm star-shaped cross-linking monomer;

[0014] S3, mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment, grinding and vacuum degassing to obtain the UV inkjet printing ink.

[0015] In a third aspect, the present application provides an application of UV inkjet printing ink in UV inkjet printing.

[0016] Beneficial technical effects:

[0017] In the UV inkjet printing ink provided by the present application, a cross-linked network is formed by the four-arm star structure of the cross-linked monomer, and its branches can provide sufficient cross-linking sites on the one hand, and on the other hand, the spatial extensibility of the branch structure has a certain spatial redundancy to release stress when folded; an amino alcohol structure is formed by epoxy and amino groups on the branch, and the hydrogen bonds formed on the surface of the amino alcohol structure substrate can enhance the interfacial adhesion, thereby having stronger adhesion on the substrate, and the flexible chain segments of the branches enable the ink to release stress through local slippage of the molecular chain when folded or stretched after drying; in addition, the branch structure on the phosphate-modified four-arm star cross-linked monomer molecule provides more cross-linking sites while avoiding excessive cross-linking through spatial steric hindrance, thereby maintaining flexibility. The four-arm star structure of the cross-linked monomer extends outward through four branches to form a uniform three-dimensional cross-linked network, and its spatial redundancy provides a flexible basis. The alkane flexible chain segments and the amino alcohol structure on the side chains release stress. The two methods work together to enhance flexibility while maintaining adhesion, thereby achieving the effect of avoiding ink cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the preparation method of UV inkjet printing ink of the present invention. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions, and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below with reference to the following examples. However, this should not be construed as limiting the scope of this application to the following examples. Without departing from the above-mentioned method concepts of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0020] In this application, the terms used in this application are for the purpose of describing specific embodiments only and are not intended to be limiting of the application.

[0021] As used in this application, the singular forms "for," "or," "an," "any," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0022] In addition, the terms “first” and “second”, if used, are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0023] In a first aspect, the present application provides a UV inkjet printing ink, comprising:

[0024] A cross-linking monomer, a reactive diluent, a first photoinitiator, a wetting dispersant and a pigment; the cross-linking monomer is prepared from pentaerythritol tetrakis(3-mercaptopropionic acid), and the cross-linking monomer is a four-arm star-shaped cross-linking monomer or a phosphate four-arm star-shaped cross-linking monomer;

[0025] The structural formula of the four-arm star-shaped cross-linked monomer is:

[0026] ;

[0027] The structural formula of the phosphate four-arm star-shaped crosslinking monomer is:

[0028] .

[0029] In a feasible implementation scenario, the mass ratio of the four-arm star-shaped crosslinking monomer, the reactive diluent, the first photoinitiator, the wetting dispersant and the pigment is (58-63):(22-25):(2.3-2.6):(0.5-0.7):9.5.

[0030] Reactive diluents provide fluidity and participate in crosslinking. Too low a ratio results in incomplete curing, while too high a ratio reduces flexibility. Photoinitiators ensure sufficient photoinitiation efficiency. Too low a ratio leads to incomplete curing, while too high a ratio may cause excessive crosslinking and increase brittleness. A precise ratio is crucial to balance viscosity, cure rate, and mechanical properties.

[0031] In a feasible implementation scenario, the reactive diluent is one of 1,6-hexanediol diacrylate and tripropylene glycol diacrylate; the first photoinitiator is TPO-L; the wetting and dispersing agent is one of BYK-331 and Tego Wet270; and the pigment is one of phthalocyanine blue BGS, CI pigment red 122, and CI pigment yellow 74.

[0032] 1,6-Hexanediol diacrylate is a short-chain reactive diluent that provides high reactivity, while tripropylene glycol diacrylate is a long-chain reactive diluent that enhances flexibility. TPO-L has an absorption peak at 365nm, which matches UV light sources and provides high curing efficiency. BYK-331 and Tego Wet 270 optimize pigment dispersion and prevent agglomeration.

[0033] In a feasible implementation, the raw material of the four-arm star-shaped crosslinking monomer further includes a second photoinitiator, and the second photoinitiator is one of Irgacure 184, Irgacure 907 and Darocur 1173.

[0034] In a second aspect, the present invention further provides a method for preparing a UV inkjet printing ink, comprising the following steps:

[0035] S1, using pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether, adding a second photoinitiator to prepare an intermediate product;

[0036] S2, adding 4,4'-diaminodiphenylmethane to the intermediate product to prepare a four-arm star-shaped crosslinking monomer;

[0037] S3, mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment, grinding and vacuum degassing to obtain the UV inkjet printing ink.

[0038] In a feasible implementation scenario, the preparation of the intermediate product in S1 includes: mixing pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether in a molar ratio of 1:(4.2-4.4) to obtain a mixture, adding a second photoinitiator in an amount of 0.45% to 0.55% of the total mass of the mixture, and reacting in a water bath at 38-42°C under nitrogen protection for 2-3 hours to obtain the intermediate product.

[0039] Under the action of the second photoinitiator, the thiol group (-SH) of pentaerythritol tetrakis(3-mercaptopropionic acid) and the alkenyl group (C=C) of allyl glycidyl ether undergo a thiol-ene click addition reaction through a free radical chain reaction, forming a star-shaped structure with four active epoxy groups, providing sites for subsequent functional modification. The star-shaped structure can form a three-dimensional cross-linked network, avoiding the chain entanglement problem of the linear structure and enhancing the mechanical properties after curing. The spatial ductility of its branched structure gives the molecular chain segments moderate freedom of movement, thereby avoiding brittleness caused by excessive rigidity. Controlling the molar ratio ensures that the thiol group and the alkenyl group react fully and avoid residual unreacted monomer. The second photoinitiator accelerates the click reaction and avoids side reactions. The reaction formula is as follows:

[0040] .

[0041] In a feasible implementation scenario, the preparation method of the four-arm star-shaped cross-linked monomer described in S2 includes: adding 4,4'-diaminodiphenylmethane to the intermediate product, the mass ratio of the intermediate product to the 4,4'-diaminodiphenylmethane is 25:(10-12), the addition rate of the 4,4'-diaminodiphenylmethane is 3-5g / min, triethylamine is added dropwise during the reaction, the pH is maintained at 8±0.2, and the reaction is carried out at 70-80°C for 3.5-6h to obtain the four-arm star-shaped cross-linked monomer.

[0042] The epoxy group from allyl glycidyl ether undergoes a nucleophilic ring-opening reaction with the amino group of 4,4'-diaminodiphenylmethane to form an amino alcohol structure. Triethylamine is used to control the pH to prevent protonation of the amine group and ensure reaction efficiency. The hydroxyl group in the amino alcohol forms intermolecular hydrogen bonds with the amino group or ether bond oxygen atom of the adjacent chain segment, and also easily forms hydrogen bonds with the substrate, improving adhesion to the substrate. Allyl glycidyl ether acts as a flexible chain segment, allowing the ink to release stress through local slippage of the molecular chain when folded or stretched after drying, preventing cracking and improving flexibility. The benzene ring structure of 4,4'-diaminodiphenylmethane provides rigidity and maintains mechanical properties. Each 4,4'-diaminodiphenylmethane molecule reacts with the epoxy groups of two different four-arm star molecules through its two amino groups, expanding the crosslinking network and crosslinking density. The reaction formula is as follows:

[0043] .

[0044] In a feasible implementation scenario, the preparation method of the UV inkjet printing ink described in S3 includes: mixing the four-arm star-shaped cross-linking monomer, the first photoinitiator, the active diluent and the pigment at 35-40°C, grinding them in a sand mill to a fineness of ≤200nm, and vacuum degassing at 40-45°C for 30-60min to obtain the UV inkjet printing ink.

[0045] In a feasible implementation scenario, the preparation method of the UV inkjet printing ink also includes: mixing the four-arm star-shaped cross-linking monomer and di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:(11-11.5), and reacting in vacuum at 65-68°C for 2.5-3.5h to obtain a phosphate-modified four-arm star-shaped cross-linking monomer; mixing the phosphate-modified four-arm star-shaped cross-linking monomer, a first photoinitiator, an active diluent and a pigment, grinding and vacuum degassing to obtain the UV inkjet printing ink.

[0046] The four-arm star-shaped crosslinking monomer combines with the phosphate group of di[2-(methacryloyloxy)ethyl]phosphate through nucleophilic substitution to form a phosphate-functionalized structure, which enhances the molecular polarity and the interfacial bonding strength with the substrate. At the same time, the steric hindrance of the phosphate group can balance the rigidity and flexibility of the crosslinked network. The acrylate double bond of di[2-(methacryloyloxy)ethyl]phosphate can be used for UV curing crosslinking, and the carbonyl group C=O in the molecule can form hydrogen bonds with the substrate to enhance adhesion. The reaction formula is as follows:

[0047] .

[0048] In a third aspect, the present application provides an application of UV inkjet printing ink in UV inkjet printing.

[0049] The following will describe in detail a UV inkjet printing ink, preparation method and application provided by the present application in combination with different embodiments.

[0050] Example 1

[0051] like Figure 1 As shown, a method for preparing UV inkjet printing ink comprises the following steps:

[0052] 1. Pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether were mixed at a molar ratio of 1:4.2, and 0.45% of the total weight of the mixture was added as photoinitiator Irgacure 184. Under nitrogen protection, the mixture was stirred in a water bath at 38°C and 300 rpm for 2 h to obtain the intermediate product.

[0053] 2. Add 4,4'-diaminodiphenylmethane to the intermediate product at a mass ratio of 25:10. Control the addition rate of 4,4'-diaminodiphenylmethane to be 3 g / min. Stir the reaction at 200 rpm and 70°C for 6 h. During the reaction, triethylamine was added dropwise to maintain the pH at 7.8 to obtain a four-arm star-shaped crosslinked monomer.

[0054] 3. A four-arm star-shaped crosslinking monomer was mixed 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°C, ground in a sand mill to a fineness of ≤200 nm, and degassed in a vacuum degassing machine at -0.1 MPa and 45°C for 30 min to obtain the UV inkjet printing ink.

[0055] Example 2

[0056] like Figure 1 As shown, a method for preparing UV inkjet printing ink comprises the following steps:

[0057] 1. Pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether were mixed at a molar ratio of 1:4.2, and 0.45% of the total weight of the mixture was added as photoinitiator Irgacure 184. Under nitrogen protection, the mixture was stirred in a water bath at 38°C and 300 rpm for 2 h to obtain the intermediate product.

[0058] 2. Add 4,4'-diaminodiphenylmethane to the intermediate product at a mass ratio of 25:10. Control the addition rate of 4,4'-diaminodiphenylmethane to be 3 g / min. Stir the reaction at 200 rpm and 70°C for 6 h. During the reaction, triethylamine was added dropwise to maintain the pH at 7.8 to obtain a four-arm star-shaped crosslinked monomer.

[0059] 3. The four-arm star-shaped crosslinking monomer was mixed with di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:11, and the mixture was evacuated to a pressure of -0.08 MPa at 65°C for 3.5 hours to obtain a phosphate-modified four-arm star-shaped crosslinking monomer;

[0060] 4. A phosphate-modified four-arm star-shaped cross-linking monomer was mixed 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°C, ground in a sand mill to a fineness of ≤200 nm, and degassed in a vacuum degassing machine at -0.1 MPa and 45°C for 30 min to obtain the UV inkjet printing ink.

[0061] Example 3

[0062] like Figure 1 As shown, a method for preparing UV inkjet printing ink comprises the following steps:

[0063] 1. Pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether were mixed at a molar ratio of 1:4.3, and 0.50% of the total weight of the mixture was added as photoinitiator Irgacure 907. Under nitrogen protection, the mixture was stirred in a water bath at 40°C and 300 rpm for 2.5 hours to obtain an intermediate product.

[0064] 2. Add 4,4'-diaminodiphenylmethane to the intermediate product at a mass ratio of 25:11. Control the addition rate of 4,4'-diaminodiphenylmethane to be 3 g / min. Stir the reaction at 200 rpm and 75°C for 5 h. During the reaction, triethylamine was added dropwise to maintain the pH at 8 to obtain a four-arm star-shaped crosslinked monomer.

[0065] 3. The four-arm star-shaped crosslinking monomer was mixed with di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:11.2, and the mixture was evacuated to a pressure of -0.08 MPa at 65°C for 2.5 hours to obtain a phosphate-modified four-arm star-shaped crosslinking monomer;

[0066] 4. A phosphate-modified four-arm star-shaped cross-linking monomer was mixed with tripropylene glycol diacrylate, TPO-L, BYK-331, and CI Pigment Red 122 in a mass ratio of 58:25:2.6:0.7:9.5 at 35°C, ground in a sand mill to a fineness of ≤200 nm, and degassed in a vacuum degassing machine at -0.1 MPa and 45°C for 30 min to obtain the UV inkjet printing ink.

[0067] Example 4

[0068] like Figure 1 As shown, a method for preparing UV inkjet printing ink comprises the following steps:

[0069] 1. Pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether were mixed at a molar ratio of 1:4.4, and 0.55% of the total weight of the mixture was added as a photoinitiator Darocur 1173. Under nitrogen protection, the mixture was stirred in a water bath at 42°C and 300 rpm for 3 h to obtain an intermediate product.

[0070] 2. 4,4'-diaminodiphenylmethane was added to the intermediate product at a mass ratio of 25:12. The addition rate of 4,4'-diaminodiphenylmethane was controlled at 3 g / min. The reaction was stirred at 200 rpm at 80°C for 3.5 hours. Triethylamine was added dropwise during the reaction to maintain the pH at 8.2 to obtain a four-arm star-shaped crosslinked monomer.

[0071] 3. The four-arm star-shaped crosslinking monomer was mixed with di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:11.5, and the mixture was vacuumed to a pressure of -0.08 MPa at 68°C for 2.5 hours to obtain a phosphate-modified four-arm star-shaped crosslinking monomer;

[0072] 4. A phosphate-modified four-arm star-shaped crosslinking monomer was mixed with 1,6-hexanediol diacrylate, TPO-L, Tego Wet270, and CI Pigment Yellow 74 in a mass ratio of 58:25:2.6:0.7:9.5 at 35°C, ground in a sand mill to a fineness of ≤200 nm, and degassed in a vacuum degassing machine at -0.1 MPa and 45°C for 30 min to obtain the UV inkjet printing ink.

[0073] Example 5

[0074] like Figure 1As shown, a method for preparing UV inkjet printing ink comprises the following steps:

[0075] 1. Pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether were mixed at a molar ratio of 1:4.4, and 0.55% of the total weight of the mixture was added as a photoinitiator Darocur 1173. Under nitrogen protection, the mixture was stirred in a water bath at 42°C and 300 rpm for 3 h to obtain an intermediate product.

[0076] 2. 4,4'-diaminodiphenylmethane was added to the intermediate product at a mass ratio of 25:12. The addition rate of 4,4'-diaminodiphenylmethane was controlled at 3 g / min. The reaction was stirred at 200 rpm at 80°C for 3.5 hours. Triethylamine was added dropwise during the reaction to maintain the pH at 8.2 to obtain a four-arm star-shaped crosslinked monomer.

[0077] 3. The four-arm star-shaped crosslinking monomer was mixed with di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:11.5, and the mixture was vacuumed to a pressure of -0.08 MPa at 68°C for 2.5 hours to obtain a phosphate-modified four-arm star-shaped crosslinking monomer;

[0078] 4. A phosphate-modified four-arm star-shaped cross-linking monomer was mixed with 1,6-hexanediol diacrylate, TPO-L, BYK-331, and phthalocyanine blue BGS in a mass ratio of 60:24:2.4:0.6:9.5 at 35°C, ground in a sand mill to a fineness of ≤200 nm, and degassed in a vacuum degassing machine at -0.1 MPa and 40°C for 45 minutes to obtain the UV inkjet printing ink.

[0079] Example 6

[0080] like Figure 1 As shown, a method for preparing UV inkjet printing ink comprises the following steps:

[0081] 1. Pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether were mixed at a molar ratio of 1:4.4, and 0.55% of the total weight of the mixture was added as a photoinitiator Darocur 1173. Under nitrogen protection, the mixture was stirred in a water bath at 42°C and 300 rpm for 3 h to obtain an intermediate product.

[0082] 2. 4,4'-diaminodiphenylmethane was added to the intermediate product at a mass ratio of 25:12. The addition rate of 4,4'-diaminodiphenylmethane was controlled at 3 g / min. The reaction was stirred at 200 rpm at 80°C for 3.5 hours. Triethylamine was added dropwise during the reaction to maintain the pH at 8.2 to obtain a four-arm star-shaped crosslinked monomer.

[0083] 3. The four-arm star-shaped crosslinking monomer was mixed with di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:11.5, and the mixture was vacuumed to a pressure of -0.08 MPa at 68°C for 2.5 hours to obtain a phosphate-modified four-arm star-shaped crosslinking monomer;

[0084] 4. A phosphate-modified four-arm star-shaped cross-linking monomer was mixed with 1,6-hexanediol diacrylate, TPO-L, BYK-331, and phthalocyanine blue BGS in a mass ratio of 63:22:2.3:0.5:9.5 at 40°C, ground in a sand mill to a fineness of ≤200 nm, and degassed in a vacuum degassing machine at -0.1 MPa and 45°C for 60 min to obtain the UV inkjet printing ink.

[0085] Comparative Example 1

[0086] A method for preparing UV inkjet printing ink, wherein the experimental steps and parameters are the same as those in Example 5, except that the phosphate-modified four-arm star-shaped cross-linking monomer is replaced by an intermediate product.

[0087] Comparative Example 2

[0088] A method for preparing a UV inkjet printing ink, wherein the experimental steps and parameters are the same as those of Example 5, except that the phosphate-modified four-arm star-shaped cross-linking monomer is replaced with pentaerythritol tetrakis(3-mercaptopropionate) directly.

[0089] Performance testing:

[0090] Viscosity: Viscosity was measured using the rotation method described in the performance testing of the UV-curable inkjet materials obtained in Examples 1 to 6 and Comparative Examples 1 and 2 according to GB / T 10247-2008. The test conditions were 40° C. and 30 rpm. The test results are shown in Table 1.

[0091] Performance testing after light curing: The UV-curable inkjet materials obtained in the above examples and comparative examples were spray-printed onto a PVC soft film and a copper plate, respectively, with a droplet volume of 10 pL. The materials were then irradiated and cured using an LED light source at an intensity of 120 mW / cm² until they were solidified and formed a light-cured ink layer. The test results are shown in Table 1.

[0092] Adhesion performance: The adhesion of the light-curing ink layer to the PVC soft film and copper plate was measured using a 100-grid test according to the test standard of GBT 9286-1998, with an atmosphere level of 0-5, where level 0 is the best and level 5 is the worst. The test results are shown in Table 1.

[0093] Flexibility: After folding the PVC soft film forming the light-curing ink layer three times, observe whether the light-curing ink layer cracks. The test results are shown in Table 1.

[0094] Table 1 Performance test results of Examples 1-6 and Comparative Examples 1-2

[0095]

[0096] As shown in Table 1, the UV inkjet printing inks prepared in Examples 1 to 6 have a viscosity of 14.0-14.9 cps, which is low and not prone to nozzle clogging during inkjet printing. The adhesion levels on both the PVC soft film and the copper plate are 1-2, and the photocurable ink layer formed on the PVC soft film does not crack after being folded three times, indicating good adhesion and flexibility. The elongation is 110%-120%, indicating that the ink is not prone to breakage.

[0097] The UV inkjet printing inks of Examples 2 to 6 of the present invention contain a phosphate-modified four-arm star-shaped crosslinking monomer. In its structure, the acrylate double bond introduced by di[2-(methacryloyloxy)ethyl]phosphate has high reactivity and the interfacial enrichment effect with the photoinitiator TPO-L allows a dense crosslinked layer to be quickly formed on the ink surface. The aromatic ring network of 4,4'-diaminodiphenylmethane can serve as a rigid support structure, providing mechanical strength and hardness to the ink. The phosphate can be deprotonated on the metal surface to form an Fe-OP bond, and on the plastic surface, it is anchored by C=O···HOP hydrogen bonds to achieve strong adhesion. The steric hindrance of the four-arm star skeleton can inhibit pigment aggregation and synergize with the solvation effect of the active diluent to prolong the ink sedimentation time, thereby extending the shelf life.

[0098] Comparative Example 1 uses an intermediate product to replace the phosphate-modified four-arm star-shaped cross-linking monomer. The resulting UV inkjet printing ink has decreased adhesion, poor flexibility, and elongation reduced to 108%. Ring-opening amination introduces amino-containing 4,4'-diaminodiphenylmethane to form intermolecular hydrogen bonds and cross-linking points, and phosphate modification further stabilizes the network. The lack of both leads to a significant decrease in cross-linking density, and deterioration of adhesion and flexibility. The lack of flexible chain segments leads to a loose cross-linking network, and the molecular chain cannot be effectively extended. Due to the lack of synergistic effects of amino and phosphate groups, UV inkjet printing ink cannot form strong adhesion to the polar surface of the copper plate.

[0099] Comparative Example 2, which directly uses pentaerythritol tetrakis(3-mercaptopropionic acid) ester, yields a UV inkjet ink with reduced adhesion, poor flexibility, and an elongation reduced to 101%. Unmodified pentaerythritol tetrakis(3-mercaptopropionic acid) ester, which has only thiol functional groups and cannot form a multidimensional cross-linked network, results in an adhesion of only grade 5 and poor flexibility. Furthermore, the unmodified monomer has a low molecular weight, making it difficult for the reactive diluent to effectively disperse, resulting in increased viscosity. Furthermore, the single functional group of pentaerythritol tetrakis(3-mercaptopropionic acid) ester limits the ductility of the molecular chain, resulting in a fragile cross-linked network and reduced extensibility.

[0100] The above results show and describe the basic principles and main features of this application as well as the advantages of this application.

[0101] Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. Such changes and improvements are intended to fall within the scope of the present application. The scope of protection claimed in the present application is defined by the equivalents of the appended claims.

Claims

1. A UV inkjet printing ink, characterized in that: include: A cross-linking monomer, a reactive diluent, a first photoinitiator, a wetting dispersant and a pigment; the cross-linking monomer is prepared from pentaerythritol tetrakis(3-mercaptopropionic acid), and the cross-linking monomer is a four-arm star-shaped cross-linking monomer or a phosphate four-arm star-shaped cross-linking monomer; The structural formula of the four-arm star-shaped cross-linked monomer is: ； The structural formula of the phosphate four-arm star-shaped crosslinking monomer is: 。 2. A UV inkjet printing ink according to claim 1, characterized in that: The mass ratio of the four-arm star-shaped crosslinking monomer, the reactive diluent, the first photoinitiator, the wetting dispersant and the pigment is (58-63):(22-25):(2.3-2.6):(0.5-0.7):9.

5.

3. A UV inkjet printing ink according to claim 1, characterized in that: The active diluent is one of 1,6-hexanediol diacrylate and tripropylene glycol diacrylate; the first photoinitiator is TPO-L; the wetting and dispersing agent is one of BYK-331 and Tego Wet 270; and the pigment is one of phthalocyanine blue BGS, CI pigment red 122, and CI pigment yellow 74.

4. The UV inkjet printing ink according to claim 1, characterized in that: The raw materials of the four-arm star-shaped crosslinking monomer further include a second photoinitiator, and the second photoinitiator is one of Irgacure 184, Irgacure 907 and Darocur1173.

5. A method for preparing the UV inkjet printing ink according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, using pentaerythritol tetrakis(3-mercaptopropionic acid) ester and allyl glycidyl ether, adding a second photoinitiator to prepare an intermediate product; S2, adding 4,4'-diaminodiphenylmethane to the intermediate product to prepare a four-arm star-shaped crosslinking monomer; S3, mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment, grinding and vacuum degassing to obtain the UV inkjet printing ink.

6. The method for preparing a UV inkjet printing ink according to claim 5, characterized in that: The S1 comprises: mixing pentaerythritol tetrakis(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 in an amount of 0.45% to 0.55% of the total mass of the mixture, and reacting in a water bath at 38-42° C. for 2-3 hours under nitrogen protection to obtain the intermediate product.

7. The method for preparing a UV inkjet printing ink according to claim 5, characterized in that: The S2 comprises: adding 4,4'-diaminodiphenylmethane to the intermediate product, wherein the mass ratio of the intermediate product to the 4,4'-diaminodiphenylmethane is 25:(10-12), the addition rate of the 4,4'-diaminodiphenylmethane is 3-5 g / min, triethylamine is added dropwise during the reaction, the pH is maintained at 8±0.2, and the reaction is carried out at 70-80°C for 3.5-6 hours to obtain the four-arm star-shaped cross-linked monomer.

8. The method for preparing a UV inkjet printing ink according to claim 5, wherein: The S3 comprises: mixing the four-arm star-shaped crosslinking monomer, the first photoinitiator, the reactive diluent and the pigment at 35-40° C., grinding in a sand mill to a fineness of ≤200 nm, and vacuum degassing at 40-45° C. for 30-60 minutes to obtain the UV inkjet printing ink.

9. The method for preparing a UV inkjet printing ink according to claim 5, characterized in that: The preparation method of the UV inkjet printing ink also includes: mixing the four-arm star-shaped crosslinking monomer and di[2-(methacryloyloxy)ethyl]phosphate in a mass ratio of 14:(11-11.5), and reacting in vacuum at 65-68°C for 2.5-3.5 hours to obtain a 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 a pigment, grinding, and vacuum degassing to obtain the UV inkjet printing ink.

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

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