Aqueous radical-cationic hybrid photocurable ink and use thereof

Abstract

The present application relates to the technical field of ink, in particular to a water-based radical-cation hybrid photocuring ink and application thereof.The cationic curing prepolymer is obtained by introducing alicyclic epoxy compound, acrylic ester and glycerol ether, and then the radical curing prepolymer, mixed monomer, water-based pigment, additive and other substances obtained are subjected to ultraviolet irradiation to obtain the ink.By introducing sulfonic acid group and rigid benzene ring group, the cured ink has good hardness and heat resistance;the ink obtained by adding the cationic curing prepolymer has high tensile strength and flexibility;the mixed monomer formed by mixing monomer and acrylic ester is used for diluting and curing the ink, and the ink has short curing time and high wear resistance;by changing the ratio of radical photoinitiator and cationic photoinitiator and introducing sesamin at the same time, the hardness of the cured ink is 4H and 5H;the photocuring ink prepared by the present application is suitable for screen printing of packaging materials of various material types.

Description

Technical Field

[0001] This invention relates to the field of ink technology, specifically to an aqueous free radical-cationic hybrid photocurable ink and its applications. Background Technology

[0002] UV ink, also known as ultraviolet ink, is a type of light-curing ink that, under ultraviolet light, undergoes a rapid photochemical reaction that polymerizes the prepolymers and monomers in the ink, curing them into a film. In response to environmental protection initiatives, inks have shifted from solvent-based to water-based. Water-based UV-curing inks offer advantages such as safety, reliability, high printing quality, and high curing efficiency, and are widely used in printing on various materials including mirror paper, posters, containers, plastics, and cigarette packs.

[0003] The UV curing process of water-based inks can be divided into three systems according to different polymerization mechanisms: free radical polymerization, cationic polymerization, and free radical-cationic hybrid systems. Free radical polymerization-dominated curing processes include chain initiation, chain propagation, and chain termination. It features high monomer reactivity, high polymerization rates, and low cost, but suffers from oxygen inhibition, incomplete curing, and significant volume shrinkage after curing. Cationic polymerization systems achieve deep curing of inks, do not exhibit oxygen inhibition, and have low shrinkage after curing. However, monomers used in cationic polymerization, such as epoxy monomers, have drawbacks such as high brittleness and poor fatigue resistance.

[0004] The free radical-cationic hybrid system combines the advantages of the two curing systems mentioned above. For example, patent CN201811332330.5 discloses "an aqueous free radical-cationic hybrid photocurable ink and its application." The ink obtained by curing oxygen-containing heterocyclic aqueous organosilicon-modified polyester oligomers has good water resistance and fast curing speed, but its hardness is low (2H and 3H) and its heat resistance is poor. In addition, water-based inks have problems with poor adhesion and low bonding strength to printing materials after curing. Patent CN202110316534.5 provides an "LED-UV curable offset printing ink," in which the ink components contain both cationic and free radical curable compounds. The ink used for printing has strong adhesion to securities.

[0005] Raw materials used in inks: Oligomers used in free radical photocuring are resins with unsaturated double bonds, while oligomers used in cationic photocuring are generally resins with epoxy or vinyl ether groups. Patent CN202111185113.X discloses "A fully bio-based thermosetting resin and its preparation method and application," which uses acrylates, unsaturated double-bonded diacids, and epoxy compounds to prepare a resin suitable for inks. This resin has good mechanical properties, heat resistance, and acid and alkali resistance, solving the problem of poor resin flexibility. Patent CN202210689110.8 discloses "A printing process and printing ink for environmentally friendly printing ink," where the printing ink contains water-based acrylates, polyurethane acrylates, and wear-resistant color-retaining fillers, resulting in an environmentally friendly ink that overcomes the disadvantage of poor ink wear resistance.

[0006] Existing water-based free radical-cationic hybrid photocurable inks also suffer from problems such as poor heat resistance, low hardness, low tensile strength and flexibility, poor abrasion resistance, long curing time, and weak bonding with printing materials.

[0007] To this end, a water-based free radical-cationic hybrid photocurable ink and its application are proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a water-based free radical-cationic hybrid photocurable ink and its application. A cationic curable prepolymer is obtained by reacting an alicyclic epoxy compound with acrylate and glycerol ether. This prepolymer is then cured with a modified free radical curable prepolymer, mixed monomers, water-based pigments, additives, and other substances under ultraviolet radiation to obtain the ink. By modifying the epoxy acrylate, introducing sulfonic acid groups and rigid benzene rings, and changing the composition of the free radical curable prepolymer in the system, the resulting photocurable ink has a hardness of 3H-5H and a TT. d10 The temperature ranges from 394 to 448℃. d90 The curing temperature is 530-589℃. A cationic curable prepolymer is obtained by further reacting alicyclic epoxy compounds with acrylates and glycerol ethers. The resulting ink has a tensile strength of 29.16-43.27 MPa and a flexibility of 2-3 mm. By synthesizing monomers and adding mixed monomers to the system, the curing time of the ink is 0.9-3.1 s, and the wear loss percentage of the cured ink is 8.9%-22.7%. Introducing a sesamin-containing free radical photoinitiator and a cationic photoinitiator results in a curing time of 1.0-4.5 s and a hardness of 4H and 5H for the cured ink. The water-based free radical-cationic hybrid photocurable ink exhibits adhesion grades 0 and 1 on five packaging materials. The ink prepared by this invention has advantages such as high hardness, good heat resistance, strong tensile and flexibility, short curing time, wear resistance, and suitability for screen printing on packaging materials.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] On one hand, the present invention provides an aqueous free radical-cationic hybrid photocurable ink, comprising the following preparation steps:

[0011] Concentrated sulfuric acid and ferric chloride were added to epoxy acrylate to obtain a reaction solution; 127.6-182.6 parts of sulfocarboxylic acid and triethylamine were added to the reaction solution and refluxed to obtain a product; the product was separated into layers, centrifuged and dried to obtain a free radical cured prepolymer;

[0012] Oxabicycloheptane, 2,5-divinyl, azobisisobutyronitrile and toluene were mixed evenly to obtain a reaction solution; 40.1-68.5 parts of acrylate were added to the reaction solution, and nitrogen gas was introduced to react and obtain an intermediate; glycidyl methacrylate was added to the intermediate, and the reaction and rotary evaporation were carried out to obtain a cationic cured prepolymer;

[0013] A pre-reacted monomer is obtained by mixing triethylenetetramine, 21.6-41.3 parts glycidyl methacrylate, THF, and phenol; the pre-reacted monomer is reacted to obtain a monomer; the monomer and tris(propylene glycol) diacrylate are mixed monomers in a mass ratio of 0-8:1-9.

[0014] A pre-cured ink precursor is obtained by reacting 40-90 parts of the free radical-cured prepolymer, 0-60 parts of the cationic-cured prepolymer, silane-PEG-carboxyl, hydroxyl-terminated silane, triethylamine, and hydrochloride for 12 hours. A pre-cured ink precursor is then obtained by uniformly mixing the pre-cured ink precursor, 32-46 parts of the mixed monomers, 1.9-4.5 parts of the free radical photoinitiator, 1.3-3.4 parts of the cationic photoinitiator, a red water-based pigment, sodium carboxymethyl cellulose, an antifoaming agent, water, and ethanol. The free radical photoinitiator, by mass percentage, consists of 0-45% sesamin and 55-100% benzophenone. The pre-cured ink is then subjected to an irradiation intensity of 50-80 mW / cm². 2 The aqueous free radical-cationic hybrid photocurable ink is obtained by irradiation and curing.

[0015] Preferably, the sulfonic acid is one of sulfonated CY7 carboxyl, sulfonated CY3 carboxylic acid, Alexa Fluor 647 carboxylic acid, sulfonated anthocyanin CY5 carboxylic acid, potassium 3-cyanobishexanoate, sulfonated bis-(N,N'-carboxylic acid)-CY5, CY7 diacid, and CY3 diacid.

[0016] Preferably, the acrylate is one of ethylene glycol dimethacrylate, 2-hydroxy-1,3-propanediol acrylate, pentanediol 1,5-dimethacrylate, 1,6-hexanediol dimethacrylate, 1,12-dodecanediol dimethacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.

[0017] Preferably, the cationic cured prepolymer is 35-60 parts; the cationic photoinitiator is a triarylthionium salt.

[0018] Preferably, the free radical cured prepolymer is 40-80 parts.

[0019] Preferably, the monomer and the tri(propylene glycol) diacrylate are arranged in a mass ratio of 2-8:1-5 to form the mixed monomer.

[0020] Preferably, the sesamin content is 40%-45%.

[0021] Preferably, the benzophenone content is 55-60%.

[0022] On the other hand, the present invention provides an application of a water-based free radical-cationic hybrid photocurable ink, wherein the water-based free radical-cationic hybrid photocurable ink is used in screen printing of packaging materials; the packaging materials include one of high-density polyethylene, low-density polyethylene, polyethylene terephthalate, polyvinyl chloride and polypropylene.

[0023] The application of the water-based free radical-cationic hybrid photocurable ink described above, wherein the water-based free radical-cationic hybrid photocurable ink contains a free radical curing prepolymer, a cationic curing prepolymer, silane-PEG-carboxyl, triethylamine, hydrochloride, mixed monomers, a free radical photoinitiator, a cationic photoinitiator, a red water-based pigment, sodium carboxymethyl cellulose, an antifoaming agent, water, and ethanol; by changing the type of sulfonyl carboxylic acid and the amount of the free radical curing prepolymer added, the resulting water-based free radical-cationic hybrid photocurable ink has a hardness of 3H-5H and a T d10 The temperature ranges from 394 to 448℃. d90The temperature range is 530-589℃; the tensile strength of the water-based free radical-cationic hybrid photocurable ink obtained by adding the cationic curing prepolymer is 29.16-43.27 MPa, and the flexibility is 2-3 mm; with the addition of the mixed monomer, the curing time of the water-based free radical-cationic hybrid photocurable ink is 0.9-3.1 s, and the wear loss percentage is 8.9%-22.7%; with the addition of the cationic photoinitiator and the free radical photoinitiator, the curing time of the water-based free radical-cationic hybrid photocurable ink is 1.0-4.5 s, and the hardness is 4H and 5H; the adhesion of the water-based free radical-cationic hybrid photocurable ink to the packaging material is grade 0 and grade 1.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. This invention modifies epoxy acrylate to obtain modified epoxy acrylate, which is then reacted with cationic curable prepolymer, mixed monomers, and initiator under ultraviolet light to form ink. By introducing functional groups containing sulfonic acid groups and rigid benzene rings, and by changing the content of the modified epoxy acrylate free radical curable prepolymer in the system, the obtained UV-curable ink has a hardness of 3H-5H; T d10 The temperature ranges from 394 to 448℃. d90 The temperature range is 530-589℃. Water-based free radical-cationic hybrid UV-curable inks have good hardness and heat resistance.

[0026] 2. An alicyclic epoxy heptane containing two unsaturated double bonds undergoes a condensation reaction with acrylates. The double bonds of the reaction product further react with glycidyl methacrylate to obtain a cationic curable prepolymer containing epoxy groups at both ends. The cationic curable prepolymer and other substances form a cured ink under initiator and ultraviolet irradiation conditions. By changing the type and amount of acrylate, introducing flexible ether bonds, and adjusting the content ratio of the cationic curable prepolymer in the precured ink, the alicyclic epoxy compound produces tertiary oxygen salt intermediates in addition to secondary oxygen salt intermediates during ultraviolet photopolymerization, resulting in high photopolymerization activity. The obtained ink has a tensile strength of 29.16-43.27 MPa, a flexibility of 2-3 mm, and good curing effect and mechanical properties.

[0027] 3. A stable monomer is formed by reacting triethylenetetramine with glycidyl methacrylate. This monomer is then mixed with tris(propylene glycol) diacrylate in a ratio of 2-8:1-5 to form a mixed monomer. The content of this mixed monomer in the pre-cured ink is adjusted to between 32-46 parts. The mixed monomer serves to dilute the reaction system and reduce its viscosity. Furthermore, under the action of a photoinitiator, it cures to form a dense cross-linked structure. The resulting ink has a curing time of 0.9-3.1 seconds and an abrasion loss percentage of 8.9%-22.7%. The ink exhibits short curing time and good abrasion resistance.

[0028] 4. By changing the ratio of free radical photoinitiator and cationic photoinitiator, and replacing part of benzophenone with sesamin in the free radical photoinitiator, the pre-cured ink was cured under different UV irradiation intensities. The excimer complex formed by sesamin generates free radicals by abstracting hydrogen, which promotes the polymerization and curing of modified epoxy acrylate and tris(propylene glycol) diacrylate, etc. The curing time of the ink is 1.0-4.5s, and the hardness is 4H and 5H. The ink has a short curing time and high hardness.

[0029] 5. The water-based free radical-cationic hybrid photocurable ink prepared according to this invention is used for screen printing on packaging materials, resulting in strong adhesion between the ink and the material. The ink exhibits adhesion between the ink and packaging materials of high-density polyethylene, low-density polyethylene, polyethylene terephthalate, polyvinyl chloride, and polypropylene types, ranging from grade 0 to 1. The prepared ink is suitable for printing on these types of packaging materials. Attached Figure Description

[0030] Figure 1 The graph shows the curing time and abrasion resistance test results of the water-based free radical-cationic hybrid photocurable ink of Example 32 of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figure 1 This invention provides an aqueous free radical-cationic hybrid photocurable ink and its application, the technical solution of which is as follows:

[0033] The material information involved in this invention is as follows:

[0034] Epoxy acrylate CAS: 71281-65-7; Sulfonic acid CY7 carboxyl CAS: 1251915-04-4; Sulfono CY3 carboxylic acid CAS: 146368-13-0; Alexa Fluor 647 Carboxylic Acid CAS: 2090339-69-6; Sulfonated Anthocyanin CY5 Carboxylic Acid CAS: 2183440-68-6; Potassium 3-Cyanobetaate CAS: 762260-71-9; Sulfonated Bis-(N,N'-Carboxylic Acid)-CY5 CAS: 2353410-10-1; CY7 Diacid CAS: 146368-12-9; CY3 Diacid CAS: 1034871-56-1; Oxabicycloheptan, 2,5-Divinyl CAS: 165727-60-6; ​​Azobisisobutyronitrile CAS: 78-67-1; Glycidyl Methacrylate CAS: 106-91-2; Ethylene Glycol Dimethacrylate CAS: 97-90-5; 2-Acrylic Acid-2-Hydroxy-1,3-Propanediate CAS: 1709-71- 3; 1,5-Dimethacrylate pentanediol CAS: 13675-34-8; 1,6-hexanediol dimethacrylate CAS: 6606-59-3; 1,12-dodecanediol dimethacrylate CAS: 121150-60-5; triethylene glycol dimethacrylate CAS: 109-16-0; tetraethylene glycol dimethacrylate CAS: 109-17-1; triarylthionyl sulfonium salt CAS: 8945-2-37-9; benzophenone CAS: 119-61-9; sesamin CAS: 607-80-7; tri(propylene glycol) diacrylate CAS: 42978-66-5; triethylenetetramine CAS: 112-24-3; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride CAS: 7084-11-9;

[0035] Silane-PEG-carboxyl, product number PM01844, was purchased from Shanghai Chuangsai Technology Co., Ltd.; hydroxyl-terminated silane was purchased from Shenzhen Jipeng Silicon Fluorine Materials Co., Ltd.; red water-based pigment, product number Pigmosol Red 3855, was purchased from BASF (China) Co., Ltd.; SN-DISPERSANT 5027 is a defoamer, purchased from Guangzhou Yachuang New Materials Co., Ltd.

[0036] It should be noted that, unless otherwise specified in the examples, conventional conditions were followed. All reagents or instruments used, unless otherwise specified, are commercially available, conventional products, and are of analytical grade.

[0037] Examples 1-7

[0038] 49 parts of epoxy acrylate were placed in a three-necked flask, and the temperature was set to 70°C. 3.2 parts of concentrated sulfuric acid and 3 parts of ferric chloride were added to the flask while stirring to obtain the reaction solution. 127.6-182.6 parts of sulfocarboxylic acid and triethylamine were added to the reaction solution and refluxed for 24 hours to obtain the product. The product was then subjected to layering, centrifugation, and drying to obtain modified epoxy acrylate, i.e., a free radical cured prepolymer.

[0039] 15.2 parts of oxabicycloheptane, 2,5-divinyl, 16.5 parts of azobisisobutyronitrile, and 50 parts of toluene were added to a reaction flask and mixed thoroughly to obtain a reaction solution. 68.5 parts of 1,12-dodecanediol dimethacrylate were added to the reaction solution, nitrogen gas was introduced for 30 min, and the mixture was reacted at 65 °C for 5 h to obtain an intermediate. 28.8 parts of glycidyl methacrylate were added to the intermediate, and the mixture was reacted for 3 h and then rotary evaporated to obtain acrylate, i.e., the cationic cured prepolymer.

[0040] 15.0 parts of triethylenetetramine, 21.6 parts of glycidyl methacrylate, 50 mL of THF and 1 mL of phenol were mixed evenly to obtain a pre-reacted monomer; the pre-reacted monomer was reacted at 45 °C for 5 h, and then separated, concentrated and dried to obtain the monomer; the monomer and tris(propylene glycol) diacrylate were mixed in a mass ratio of 2:1 to form a mixed monomer.

[0041] A pre-cured ink precursor was obtained by reacting 40-80 parts of the free radical-cured prepolymer, 40 parts of the cationic-cured prepolymer, 6.5 parts of silane-PEG-carboxyl, 3.2 parts of terminal hydroxyl silane, 1.0 part of triethylamine, 2.0 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 10 mL of THF at 70 °C for 12 h. A pre-cured ink precursor was obtained by uniformly mixing 60 parts of the pre-cured ink precursor, 38 parts of the mixed monomers, 3.9 parts of free radical photoinitiator, 2.6 parts of cationic photoinitiator, 28 parts of red water-based pigment, 1.5 parts of sodium carboxymethyl cellulose, 3.0 parts of SN-DISPERSANT 5027, 26 parts of water, and 12 parts of ethanol. The cationic photoinitiator was a triarylthionium salt. The free radical photoinitiator consisted of 43% sesamin and 57% benzophenone by mass percentage. The pre-cured ink was irradiated with an intensity of 80 mW / cm². 2 After irradiation and curing for 5 seconds, an aqueous free radical-cationic hybrid photocurable ink was obtained.

[0042] Specific details of the embodiments are shown in Table 1.

[0043] Table 1. Conditions for the preparation of modified epoxy acrylate and UV-curable inks

[0044]

[0045] Example 10

[0046] The water-based free radical-cationic hybrid photocurable inks prepared in Examples 1-9 and Comparative Example 1 were placed for 24 hours and then subjected to hardness testing. The heat resistance of the prepared water-based free radical-cationic hybrid photocurable inks was also tested. Hardness testing was performed according to GB / T 6739-2006 "Determination of Hardness of Paints and Varnishes by Pencil Method". The heat resistance test method is as follows: Cured graphite was scraped off the material and collected in a bowl, ground into powder, and 8 mg of ink powder was weighed and tested in a TGA4000 thermogravimetric analyzer. Nitrogen gas was introduced for protection during the test at a flow rate of 30 mL / min, a heating rate of 10 K / min, and a heating range of 30-600℃. d10 and T d90 The temperatures at which the ink weight loss rate was 10% and 90% were respectively tested, and the results are shown in Table 2.

[0047] Table 2 Performance test results of water-based free radical-cationic hybrid photocurable inks

[0048]

[0049]

[0050] As shown in Table 2, the hardness of the photocurable ink prepared by this invention is between 3H and 5H; T d10 The temperature ranges from 394 to 448℃. d90 The temperature range is 530-589℃. This invention introduces sulfonic acid groups into the system by covalently linking the hydroxyl groups of epoxy acrylate and the carboxyl groups of sulfonic acid, thereby improving the affinity of water-based inks for water. The ink exhibits good properties after curing. In Examples 1-3, as the number of unsaturated double bonds in the sulfonic acid increases, the hardness of the cured ink decreases. More double bonds impart elasticity and flexibility to the system. As shown in Example 1, its hardness is lower than that of Examples 2 and 3; however, the thermal stability of Example 1 is higher than that of Examples 2 and 3. d10 The temperature is 422℃, T d90The temperature was 559℃. Compared with other examples, Example 4 had higher hardness and better thermal stability due to the presence of more unsaturated six-membered rings in addition to benzene rings. The cured inks obtained in Examples 5-7 had good hardness. The hardness of the cured ink in Comparative Example 1 was reduced to only 3H. This was because, compared with Example 5, its structure did not contain sulfonic acid groups. Therefore, the modified epoxy acrylate used as a binder for the ink had reduced compatibility with water, resulting in a worse curing effect and ultimately a lower hardness. Comparing Example 5 with Example 2, it can be seen that due to the exposed unreacted carboxyl groups, it can continue to react with terminal hydroxyl silanes in subsequent reactions, introducing silicon elements, thus improving thermal stability. At the same time, the terminal hydroxyl silanes can also play a leveling and lubricating role in the system. Similarly, the thermal stability of the ink in Example 6 was higher than that in Example 3, and the thermal stability of the ink in Example 7 was higher than that in Example 1, but the hardness was reduced. In Examples 5-7, the photocurable ink T of Example 7... d10 The temperature was 429℃, T d90 The optimal temperature for thermal stability was 572℃. Comparative Example 1 showed a slight decrease in thermal stability compared to Example 5. Comparing the results of Examples 7-9, the ink prepared under the conditions of Example 7 exhibited the best hardness and heat resistance. Overall, the water-based free radical-cationic hybrid photocurable ink prepared according to this invention possesses good hardness and thermal stability.

[0051] Examples 11-19

[0052] 49 parts of epoxy acrylate were placed in a three-necked flask, and the temperature was set to 70°C. 3.2 parts of concentrated sulfuric acid and 3 parts of ferric chloride were added to the flask while stirring to obtain the reaction solution. 156.1 parts of CY7 diacid and triethylamine were added to the reaction solution and refluxed for 24 hours to obtain the product. The product was then subjected to layering, centrifugation, and drying to obtain modified epoxy acrylate, i.e., a free radical cured prepolymer.

[0053] 15.2 parts of oxabicycloheptane, 2,5-divinyl, 16.5 parts of azobisisobutyronitrile, and 50 parts of toluene were added to a reaction flask and mixed thoroughly to obtain a reaction solution. 40.1-68.5 parts of acrylate were added to the reaction solution, nitrogen gas was introduced for 30 min, and the mixture was reacted at 65°C for 5 h to obtain an intermediate. 28.8 parts of glycidyl methacrylate were added to the intermediate, and the mixture was reacted for 3 h and then rotary evaporated to obtain the acrylate, i.e., the cationic cured prepolymer.

[0054] 15.0 parts of triethylenetetramine, 21.6 parts of glycidyl methacrylate, 50 mL of THF and 1 mL of phenol were mixed evenly to obtain a pre-reacted monomer; the pre-reacted monomer was reacted at 45 °C for 5 h, and then separated, concentrated and dried to obtain the monomer; the monomer and tris(propylene glycol) diacrylate were mixed in a mass ratio of 2:1 to form a mixed monomer.

[0055] A pre-cured ink precursor was obtained by reacting 60 parts of the free radical-cured prepolymer, 35-60 parts of the cationic-cured prepolymer, 6.5 parts of silane-PEG-carboxyl, 3.2 parts of terminal hydroxyl silane, 1.0 part of triethylamine, 2.0 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 10 mL of THF at 70 °C for 12 h. A pre-cured ink precursor was obtained by uniformly mixing 60 parts of the pre-cured ink precursor, 38 parts of the mixed monomers, 4.1 parts of free radical photoinitiator, 2.8 parts of cationic photoinitiator, 28 parts of red water-based pigment, 1.5 parts of sodium carboxymethyl cellulose, 3.0 parts of SN-DISPERSANT 5027, 26 parts of water, and 12 parts of ethanol. The cationic photoinitiator was a triarylthionium salt. The free radical photoinitiator consisted of 43% sesamin and 57% benzophenone by mass percentage. The pre-cured ink was irradiated with an intensity of 80 mW / cm². 2 After irradiation and curing for 6 seconds, an aqueous free radical-cationic hybrid photocurable ink was obtained.

[0056] The specific preparation information is shown in Table 3.

[0057] Table 3. Information on the preparation of cationic cured prepolymer and total addition amount

[0058]

[0059] Comparative Example 2

[0060] Unlike Example 19, the amount of cationic cured prepolymer added was 0 parts, and the amount of free radical cured prepolymer added was 90 parts.

[0061] Example 20

[0062] The water-based free radical-cationic hybrid UV-curable inks prepared in Examples 11-19 and Comparative Example 2 were subjected to tensile and flexibility tests. The specific test methods are as follows: Flexibility was tested according to GB / 1731-2020 "Determination of Flexibility of Paint Films and Putty Films"; for tensile testing, the pre-cured ink was placed in a tetrafluoroethylene mold, cured by UV irradiation, and the tensile properties were measured. The cured ink was tested using a universal testing machine. The two ends of the ink were fixed with the instrument's clamps, and the ink was stretched at a speed of 8 mm / min. The data at breakage was recorded. The final results are shown in Table 4.

[0063] Table 4. Test results of mechanical properties of cured inks

[0064] Example 11 31.85 2 Example 12 34.24 1 Example 13 32.50 1 Example 14 33.39 1 Example 15 35.71 1 Example 16 38.02 1 Example 17 40.65 1 Example 18 29.16 1 Example 19 43.27 1 Comparative Example 2 10.08 3

[0065] The water-based free radical-cationic hybrid photocurable ink prepared in the embodiments of the present invention has a tensile strength of 29.16-43.27 MPa and a flexibility of 1, 2 and 3 mm. A comparison of the results of Examples 11 and 12 shows that the tensile strength of Example 2 is higher than that of Example 1. This is because the hydroxyl groups of the acrylate react with the carboxyl groups of the silane-PEG-carboxyl group in Example 2, and the introduction of silane improves the flexibility of the system. A comparison of the results of Examples 11 and 13-15 shows that the tensile strength of the cured ink increases with the elongation of the molecular chain, with Example 15 having the highest tensile strength at 35.71 MPa. A comparison of the results of Examples 16 and 17 shows that Example 17 has a high tensile strength of 40.65 MPa, which is due to the increased stretchability of the ink caused by the ether bonds in the system. A comparison of the results of Examples 17-19 shows that the increased proportion of cationic cured prepolymer in the system further improves the stretchability of the system. Compared with other examples, Example 18 has the lowest tensile strength and the worst flexibility. The proportion of flexible groups in the system decreases, while the proportion of rigid groups in the free radical cured prepolymer increases, thus reducing performance. At the same time, the ink has good flexibility. In Comparative Example 2, due to the absence of cationic curing prepolymer, the tensile strength was only 10.08 MPa, and the flexibility was 1 mm. This was partly due to the low content of flexible groups in the system, and partly because the ink only had free radical curing properties, resulting in oxygen inhibition during curing and incomplete curing. Therefore, both the tensile strength and flexibility were reduced. In summary, the water-based free radical-cationic hybrid photocurable ink prepared in the embodiments of this invention exhibits good tensile strength and flexibility.

[0066] Examples 21-31 and Comparative Example 3

[0067] 49 parts of epoxy acrylate were placed in a three-necked flask, and the temperature was set to 70°C. 3.2 parts of concentrated sulfuric acid and 3 parts of ferric chloride were added to the flask while stirring to obtain the reaction solution. 156 parts of CY7 diacid and triethylamine were added to the reaction solution and refluxed for 24 hours to obtain the product. The product was then subjected to layering, centrifugation, and drying to obtain modified epoxy acrylate, i.e., a free radical cured prepolymer.

[0068] 15.2 parts of oxabicycloheptane, 2,5-divinyl, 16.5 parts of azobisisobutyronitrile, and 50 parts of toluene were added to a reaction flask and mixed thoroughly to obtain a reaction solution. 43.5 parts of 2-acrylate-2-hydroxy-1,3-propanediol were added to the reaction solution, nitrogen gas was introduced for 30 min, and the mixture was reacted at 65 °C for 5 h to obtain an intermediate. 28.8 parts of glycidyl methacrylate were added to the intermediate, and the mixture was reacted for 3 h and then rotary evaporated to obtain an acrylate, i.e., a cationic cured prepolymer.

[0069] 15.0 parts of triethylenetetramine, 21.6-44.6 parts of glycidyl methacrylate, 50 mL of THF and 1 mL of phenol were mixed evenly to obtain a pre-reacted monomer; the pre-reacted monomer was reacted at 45°C for 5 h, and then separated, concentrated and dried to obtain the monomer; the monomer and tris(propylene glycol) diacrylate were mixed in a mass ratio of 0-8:1-9 to form a mixed monomer;

[0070] A pre-cured ink precursor was obtained by reacting 55 parts of the free radical-cured prepolymer, 35 parts of the cationic-cured prepolymer, 6.5 parts of silane-PEG-carboxyl, 3.2 parts of terminal hydroxyl silane, 1.0 part of triethylamine, 2.0 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 10 mL of THF at 70 °C for 12 h. A pre-cured ink precursor was obtained by uniformly mixing 60 parts of the pre-cured ink precursor, 32-46 parts of the mixed monomers, 3.9 parts of free radical photoinitiator, 2.6 parts of cationic photoinitiator, 28 parts of red water-based pigment, 1.5 parts of sodium carboxymethyl cellulose, 3.0 parts of SN-DISPERSANT 5027, 26 parts of water, and 12 parts of ethanol. The cationic photoinitiator was a triarylthionium salt. The free radical photoinitiator consisted of 44% sesamin and 56% benzophenone by mass percentage. The pre-cured ink was irradiated with an intensity of 80 mW / cm². 2 After irradiation and curing, an aqueous free radical-cationic hybrid photocurable ink is obtained.

[0071] The specific preparation information for the examples and comparative examples is shown in Table 5.

[0072] Table 5. Preparation of mixed monomers and information on the amount of mixed monomers added.

[0073]

[0074]

[0075] Example 32

[0076] The water-based free radical-cationic hybrid photocurable inks prepared in Examples 21-31 and Comparative Example 3 were subjected to curing time and abrasion resistance tests. The abrasion resistance was tested using an NMC-II ink printing abrasion tester. The test results are as follows: Figure 1 As shown.

[0077] Figure 1The results showed that the ink required for complete curing in the embodiments of the present invention ranged from 0.9 to 3.1 seconds, and the wear loss percentage ranged from 8.9% to 22.7%. In Examples 21-25, with the increase of glycidyl methacrylate addition, the curing time showed a trend of first decreasing and then stabilizing, while the wear resistance gradually improved. After the ring-opening of the epoxy group of tetramolecule glycidyl methacrylate, the hydroxyl group formed reacts with the amino group of one molecule of triethylenetetramine to form a stable monomer, which crosslinks with the system under the action of the subsequent initiator. With the increase of raw material content, the density of the formed ink increases and the curing time shortens. The wear resistance first increases and then decreases because the amount of initiator in the system is fixed, and the free radicals formed by the initiator are insufficient to cause the excessive functional groups to crosslink and cure. The comparison of the results of Examples 24 and 26-29 shows that with the increase of the mass ratio of monomer to tri(propylene glycol) diacrylate, the curing time gradually decreases, and the wear resistance first increases and then stabilizes. As shown in the figure, the results of Examples 24, 30, and 31 indicate that increasing the amount of mixed monomers leads to longer curing time, while mass loss initially decreases and then increases. The mixed monomers play two roles in the system: first, they dilute the reaction system, reducing its viscosity, thus increasing their addition leads to longer curing time; second, they cure under the action of the photoinitiator, and excessive addition results in incomplete curing and decreased wear resistance. Comparative Example 3, lacking any added monomers, exhibited the longest curing time and the worst wear resistance.

[0078] Examples 33-42

[0079] A pre-cured ink precursor was obtained by reacting 60 parts of the free radical-cured prepolymer prepared in Example 4, 40 parts of the cationic-cured prepolymer prepared in Example 17, 6.5 parts of silane-PEG-carboxyl, 3.2 parts of terminal hydroxyl silane, 1.0 part of triethylamine, 2.0 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and 10 mL of THF at 70 °C for 12 h; 60 parts of the pre-cured ink precursor, 41.5 parts of the mixed monomer, and 1.9-4.5 A pre-cured ink is prepared by uniformly mixing 1.3-3.4 parts of a free radical photoinitiator, 28 parts of a cationic photoinitiator, 1.5 parts of a red water-based pigment, 3.0 parts of sodium carboxymethyl cellulose, 26 parts of SN-DISPERSANT 5027, and 12 parts of water; the cationic photoinitiator is a triarylthionium salt; the free radical photoinitiator, by mass percentage, consists of 40% sesamin and 60% benzophenone; the pre-cured ink is subjected to an irradiation intensity of 50-75 mW / cm². 2 After irradiation and curing for 5 seconds, an aqueous free radical-cationic hybrid photocurable ink was obtained. Specific preparation information for the examples is shown in Table 6.

[0080] Table 6. Composition and dosage of photoinitiator and preparation of ink.

[0081]

[0082]

[0083] Example 43

[0084] The free radical photoinitiator consists of 45% sesamin and 55% benzophenone.

[0085] Comparative Example 4

[0086] The free radical photoinitiator consists only of benzophenone.

[0087] Example 44

[0088] The curing time and hardness of the inks prepared in Examples 33-43 and Comparative Example 4 were tested. The time required for the complete curing of the water-based free radical-cationic hybrid photocurable ink and the hardness after 1 day of storage after curing are recorded in Table 7.

[0089] The curing time of the ink was 1.0-4.5 s, and the hardness was 4H and 5H. In Examples 33-37, the ratio of free radical photoinitiator to cationic photoinitiator was fixed at 3:2. As the total amount of both increased, the curing time showed a trend of first decreasing and then increasing. The more active groups generated by the increased amount of photoinitiator, the shorter the curing time of the ink. The shortest curing time was 1.0 s in Example 36. In Example 37, the curing time increased with the increase of photoinitiator, possibly because the excess free radicals generated combined with each other, leading to a decrease in curing efficiency and a corresponding decrease in ink hardness. Comparing the results of Examples 38-40 with Example 36, the total amount of photoinitiator remained constant, but the curing time changed by changing the ratio of free radical photoinitiator to cationic photoinitiator. The curing processes initiated by free radical and cationic photoinitiators were inconsistent. Controlling the ratio of the two to 3:2 was beneficial to the curing process. In Example 38, the hardness decreased when the ratio of the two free radical initiators was 7:3. Comparing the results of Example 36 with those of Examples 41 and 42, the conclusion is that the curing time gradually shortens with increasing irradiation intensity. The test results of the examples show that using sesamin to replace benzophenone as an initiator is feasible. The results of the examples are superior to those of Comparative Example 4, possibly because sesamin combines with substances in the system to form excitocomplexes. These excitocomplexes generate free radicals by abstracting hydrogen, promoting the polymerization of modified epoxy acrylate and tris(propylene glycol) diacrylate.

[0090] Table 7 Ink Curing Time and Hardness

[0091] Example 33 2.5 5H Example 34 2.1 5H Example 35 1.2 5H Example 36 1.0 5H Example 37 1.3 4H Example 38 2.9 4H Example 39 1.5 5H Example 40 1.8 5H Example 41 2.1 5H Example 42 2.4 5H Example 43 1.1 5H Comparative Example 4 4.5 4H

[0092] Examples 45-49

[0093] The pre-cured ink prepared in Example 36 was mixed with ethanol and poured into one end of a screen printing plate to obtain pre-screen printing ink. The pre-squeegee was moved from one end to the other end of the screen printing plate, so that the pre-screen printing ink was squeezed from the mesh of the image area onto the packaging material by the squeegee during the movement. Then, it was subjected to ultraviolet irradiation with an intensity of 75 mW / cm². 2 The ink screen printing material is obtained after irradiation for 15 seconds. Specific types of packaging materials are shown in Table 8.

[0094] Comparative Example 5

[0095] Unlike Example 45, the pre-cured ink prepared in Comparative Example 1 was screen-printed onto high-density polyethylene using ultraviolet light.

[0096] Example 50

[0097] The ink screen printing materials obtained in Examples 45-49 and Comparative Example 5 were subjected to ink adhesion tests, which were conducted according to the method in GB / T 9286-1998 "Paints and Varnishes, Paint Films - Cross-cut Test". The specific test results are shown in Table 8.

[0098] As shown in Table 8, the water-based free radical-cationic hybrid photocurable ink prepared by this invention exhibits adhesion between grades 0 and 1 after curing on packaging materials. Grade 0 indicates the best curing effect, with completely smooth cutting edges and no peeling, while grade 1 indicates the worst effect. The free radical-cured prepolymer, cationic-cured prepolymer, and monomers in the ink prepared by this invention contain unsaturated double bonds, rigid benzene rings, and ether bonds, exhibiting good adhesion to these packaging materials. Comparing the results of Comparative Example 5 and Example 45, it can be seen that the adhesion of the ink cured in the comparative example is lower than that in the example. The main reason is that high-density polyethylene has a certain degree of hygroscopicity, and the compatibility of the ink in the comparative example with water is lower than that in Example 45. Therefore, a water layer forms between the ink and the high-density polyethylene material, reducing the adhesion between the ink and the material. Overall, the water-based free radical-cationic hybrid photocurable ink prepared by this invention exhibits good adhesion to packaging materials, and the prepared ink is suitable for printing on packaging materials.

[0099] Table 8. Material Types and Adhesion Test Results

[0100] Example 45 High density polyethylene 0 Example 46 Low density polyethylene 0 Example 47 Polyethylene terephthalate 0 Example 48 Polyvinyl chloride 0 Example 49 Polypropylene 0 Comparative Example 5 High density polyethylene 1

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A water-based free radical-cationic hybrid photocurable ink, characterized in that: The preparation steps include the following: Concentrated sulfuric acid and ferric chloride were added to epoxy acrylate to obtain a reaction solution; 127.6-182.6 parts of sulfocarboxylic acid and triethylamine were added to the reaction solution and the mixture was refluxed to obtain the product; The product was layered, centrifuged, and dried to obtain a free radical-cured prepolymer. 2,5-Divinyl-7-oxabicyclo[4.1.0]heptane, azobisisobutyronitrile, and toluene were mixed evenly to obtain a reaction solution; 40.1-68.5 parts of acrylate were added to the reaction solution, and nitrogen gas was introduced to react and obtain an intermediate; glycidyl methacrylate was added to the intermediate, and after reaction and rotary evaporation, a cationic cured prepolymer was obtained. A pre-reacting monomer is obtained by mixing 15.0 parts of triethylenetetramine, 21.6-41.3 parts of glycidyl methacrylate, THF, and phenol; the pre-reacting monomer is reacted to obtain a monomer; the monomer and the tripropylene glycol diacrylate are mixed in a mass ratio of 2-8:1-5 to form a mixed monomer; the hydroxyl group formed after ring opening of the epoxy group of the glycidyl methacrylate reacts with the amino group of the triethylenetetramine to form a stable monomer; A pre-cured ink precursor is obtained by reacting 40-90 parts of the free radical-cured prepolymer, 35-60 parts of the cationic-cured prepolymer, silane-PEG-carboxyl, hydroxyl-terminated silane, triethylamine, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride for 12 hours. A pre-cured ink precursor is then obtained by uniformly mixing the pre-cured ink precursor, 32-46 parts of the mixed monomers, 1.9-4.5 parts of free radical photoinitiator, 1.3-3.4 parts of cationic photoinitiator, red water-based pigment, sodium carboxymethyl cellulose, defoamer, water, and ethanol. The free radical photoinitiator, by mass percentage, consists of 0-45% sesamin and 55-100% benzophenone. The pre-cured ink is then subjected to irradiation at an intensity of 50-80 mW / cm². 2 The aqueous free radical-cationic hybrid photocurable ink is obtained by irradiation with ultraviolet light and curing. The cationic photoinitiator is a triarylthionium salt; The sulfonocarboxylic acid is sulfonated anthocyanin CY5.5 carboxyl group.

2. The water-based free radical-cationic hybrid photocurable ink according to claim 1, characterized in that: The acrylate is one of ethylene glycol dimethacrylate, 2-acrylate-2-hydroxy-1,3-propanediol, 1,5-dimethacrylate-pentanediol, 1,6-hexanediol dimethacrylate, 1,12-dodecanediol dimethacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.

3. The water-based free radical-cationic hybrid photocurable ink according to claim 1, characterized in that: The free radical cured prepolymer is 40-80 parts.

4. The water-based free radical-cationic hybrid photocurable ink according to claim 1, characterized in that: The sesamin content is 40%-45%.

5. The water-based free radical-cationic hybrid photocurable ink according to claim 1, characterized in that: The benzophenone content is 55-60%.

6. An application of the water-based free radical-cationic hybrid photocurable ink as described in claim 1, characterized in that: The application of the water-based free radical-cationic hybrid photocurable ink in screen printing of packaging materials; the packaging materials include one of high-density polyethylene, low-density polyethylene, polyethylene terephthalate, polyvinyl chloride and polypropylene.

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