A Highly Flexible UV Digital Ink and Its Preparation Method

Abstract

This invention discloses a high-flexibility UV digital ink and its preparation method, belonging to the field of ink technology. The method includes the following steps: In a nitrogen atmosphere, a monocarboxylic acid and epoxy resin are heated, condensed, refluxed, and stirred under the catalysis of a catalyst to obtain a modified epoxy resin; In a nitrogen atmosphere, polyethylene glycol and a catalyst are mixed, and isocyanate is added dropwise while stirring; the temperature is raised to 60°C, and 3-ethyl-3-oxabutane methanol is added dropwise while stirring; the temperature is raised to 70°C and held to obtain a modified polyurethane polymer; The modified polyurethane polymer and modified epoxy resin are mixed evenly, and a photoinitiator, carbon black, dispersant, and defoamer are added and mixed evenly to obtain the high-flexibility UV digital ink; Through chemical modification, flexible segments are chemically bonded into a rigid network, ultimately enabling the cured film to simultaneously possess high flexibility, high elongation at break, suitable tensile strength, practical hardness, and good stability, fully adapting to the application requirements of digital printing on flexible substrates.

Description

Technical Field

[0001] This invention belongs to the field of ink technology, specifically relating to a high-flexibility UV digital ink and its preparation method. Background Technology

[0002] With its core advantages such as fast curing speed, no volatile organic compound emissions, high printing precision, and low energy consumption, UV digital inks have been widely used in various fields, including packaging printing, label making, flexible substrate decoration, and electronic product casing printing. As the packaging industry moves towards lightweight and flexible designs, the popularization of smart labels, and the rise of flexible electronic devices, the market is placing higher demands on the performance of UV digital inks. Especially in terms of flexibility, the inks need to adapt to the bending, stretching, and curling deformations of the substrate to avoid cracking, peeling, and loss of gloss. Simultaneously, they must also consider comprehensive performance aspects such as adhesion, abrasion resistance, and curing rate.

[0003] UV digital ink formulations often use high-functionality resins, resulting in a rigid and brittle cured film. This makes the film prone to micro-cracks and even peeling off from flexible substrates after repeated bending, failing to meet the practical requirements of flexible packaging for folding and transport, and label adhesion deformation. While adding low-functionality resins or monofunctional reactive diluents can reduce crosslinking density and improve flexibility, it reduces film hardness and slows curing speed, affecting printing efficiency and making it difficult to balance overall performance. Summary of the Invention

[0004] The purpose of this invention is to provide a high-flexibility UV digital ink and its preparation method, which solves the problems of insufficient flexibility, limited toughening methods, and difficulty in balancing comprehensive performance of existing UV digital inks, thus failing to meet the practical application needs of flexible packaging, smart labels, flexible electronics and other fields.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a highly flexible UV digital ink includes the following steps:

[0007] S1. In a nitrogen atmosphere, a monocarboxylic acid and an epoxy resin are heated, condensed, refluxed, and stirred under the catalysis of a catalyst to obtain a modified epoxy resin.

[0008] S2. In a nitrogen atmosphere, polyethylene glycol and catalyst are mixed, and isocyanate is added dropwise while stirring. The temperature is raised to 60°C, and then 3-ethyl-3-oxabutane methanol is added dropwise while stirring. The temperature is raised to 70°C and kept at that temperature for 1-2 hours. The material is then cooled and discharged to obtain the modified polyurethane polymer.

[0009] S3. Take the modified polyurethane polymer and modified epoxy resin, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer and mix evenly to obtain the high flexibility UV digital ink.

[0010] As a preferred embodiment of the present invention, the photoinitiator includes at least one of triarylthionium salt and diaryliodonium salt.

[0011] As a preferred embodiment of the present invention, the dispersant includes at least one of BYK-190 and YB-401.

[0012] As a preferred embodiment of the present invention, the defoamer includes at least one of DAPRO DF7073 and TEGO FOAMEX1488.

[0013] As a preferred embodiment of the present invention, the catalyst in step S1 is tetraethylammonium bromide.

[0014] As a preferred embodiment of the present invention, the catalyst in step S2 is dibutyltin dilaurate.

[0015] As a preferred embodiment of the present invention, the monocarboxylic acid includes any one of butyric acid, hexanoic acid, octanoic acid, and decanoic acid.

[0016] As a preferred embodiment of the present invention, the average molecular weight of the polyethylene glycol is 800-2000 Da.

[0017] As a preferred embodiment of the present invention, the isocyanate is selected from at least one of isophorone diisocyanate, hexamethylene diisocyanate, and 1,6-hexamethylene diisocyanate.

[0018] A highly flexible UV digital ink prepared using the above-described preparation method.

[0019] The beneficial effects of this invention are:

[0020] This invention is achieved through:

[0021] After modification with monocarboxylic acid, the epoxy resin retains one epoxy group and forms an ether-linked crosslinking network with 3-ethyl-3-oxabutane-methanol-terminated polyurethane through cationic polymerization. The rigid segments formed after the three-membered rings of the epoxy groups open constitute the network skeleton, providing tensile strength and practical hardness, and preventing strength collapse due to toughening. The long alkyl chains of the monocarboxylic acid are incorporated into the system as flexible side links, providing buffer space for film deformation. The long flexible polyethylene glycol segments in the modified polyurethane act as soft segments, which are chemically bonded to the epoxy network through end-capping, forming an alternating structure of hard segments-soft segments-hard segments, improving the flexibility of the film. Through chemical modification, the flexible segments are chemically bonded into the rigid network, ultimately enabling the cured film to simultaneously possess high flexibility, high elongation at break, suitable tensile strength, practical hardness, and good stability, fully meeting the application requirements of digital printing on flexible substrates. Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0023] Example 1

[0024] A method for preparing a highly flexible UV digital ink includes the following steps:

[0025] S1. In a nitrogen atmosphere, 1.15g of hexanoic acid and 3.74g of epoxy resin E51 were heated and refluxed at 90°C under the catalysis of 0.05g of tetraethylammonium bromide. When the acid value of the system was lower than 1mgKOH / g, the temperature was lowered to below 65°C and the material was discharged to obtain the modified epoxy resin.

[0026] S2. Under a nitrogen atmosphere, mix 0.8g of polyethylene glycol 800 and 0.06g of dibutyltin dilaurate, and add 4g of isophorone diisocyanate dropwise while stirring. Heat to 60℃, and then add 2.4g of 3-ethyl-3-oxabutane methanol dropwise while stirring. Heat to 70℃ and hold for 1-2 hours. Cool and discharge to obtain the modified polyurethane polymer.

[0027] S3. Take the modified polyurethane polymer and modified epoxy resin, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer, mix evenly, and the high flexibility UV digital ink is obtained; the mass ratio of the modified polyurethane polymer, modified epoxy resin, photoinitiator, carbon black, dispersant and defoamer is 45:12:2:5:0.4:0.1;

[0028] The photoinitiator is a mixture of triarylthionium salt and diaryliodonium salt in a mass ratio of 3:1; the dispersant is BYK-190; and the defoamer is DAPRO DF7073.

[0029] Example 2

[0030] A method for preparing a highly flexible UV digital ink includes the following steps:

[0031] S1. In a nitrogen atmosphere, 1.44g of octanoic acid and 3.74g of epoxy resin E51 were heated and refluxed at 95°C under the catalysis of 0.05g of tetraethylammonium bromide. When the acid value of the system was lower than 1mgKOH / g, the temperature was lowered to below 65°C and the material was discharged to obtain the modified epoxy resin.

[0032] S2. Under a nitrogen atmosphere, 1.2g of polyethylene glycol 1200 and 0.06g of dibutyltin dilaurate were mixed. While stirring, 4.5g of isophorone diisocyanate was added dropwise. The mixture was heated to 60℃, and then 2.4g of 3-ethyl-3-oxabutane methanol was added dropwise while stirring. The mixture was heated to 70℃ and held at that temperature for 1.5h. After cooling, the mixture was discharged to obtain the modified polyurethane polymer.

[0033] S3. Take the modified polyurethane polymer and modified epoxy resin, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer, mix evenly, and the high flexibility UV digital ink is obtained; the mass ratio of the modified polyurethane polymer, modified epoxy resin, photoinitiator, carbon black, dispersant and defoamer is 50:15:3:7:0.6:0.2.

[0034] The photoinitiator is a mixture of triarylthionium salt and diaryliodonium salt in a mass ratio of 3:1; the dispersant is BYK-190; and the defoamer is DAPRO DF7073.

[0035] Example 3

[0036] A method for preparing a highly flexible UV digital ink includes the following steps:

[0037] S1. In a nitrogen atmosphere, 1.72g of decanoic acid and 3.74g of epoxy resin E51 were heated and refluxed at 100°C under the catalysis of 0.05g of tetraethylammonium bromide. When the acid value of the system was lower than 1mgKOH / g, the temperature was lowered to below 65°C and the material was discharged to obtain the modified epoxy resin.

[0038] S2. Under a nitrogen atmosphere, 2.0 g of polyethylene glycol 2000 and 0.06 g of dibutyltin dilaurate were mixed. While stirring, 5 g of isophorone diisocyanate was added dropwise. The mixture was heated to 60°C and then 2.4 g of 3-ethyl-3-oxabutane methanol was added dropwise while stirring. The mixture was heated to 70°C and kept at that temperature for 2 hours. After cooling, the mixture was discharged to obtain the modified polyurethane polymer.

[0039] S3. Take the modified polyurethane polymer and modified epoxy resin, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer, mix evenly, and the high flexibility UV digital ink is obtained; the mass ratio of the modified polyurethane polymer, modified epoxy resin, photoinitiator, carbon black, dispersant and defoamer is 55:18:4:9:0.8:0.3.

[0040] The photoinitiator is a mixture of triarylthionium salt and diaryliodonium salt in a mass ratio of 3:1; the dispersant is BYK-190; and the defoamer is DAPRO DF7073.

[0041] Comparative Example 1

[0042] A method for preparing a highly flexible UV digital ink includes the following steps:

[0043] S1. Under a nitrogen atmosphere, 1.2g of polyethylene glycol 1200 and 0.06g of dibutyltin dilaurate were mixed. While stirring, 4.5g of isophorone diisocyanate was added dropwise. The mixture was heated to 60℃, and then 2.4g of 3-ethyl-3-oxabutane methanol was added dropwise while stirring. The mixture was heated to 70℃ and held at that temperature for 1.5h. After cooling, the mixture was discharged to obtain the modified polyurethane polymer.

[0044] S2. Take the modified polyurethane polymer and epoxy resin E51, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer, mix evenly, and the high flexibility UV digital ink is obtained; the mass ratio of the modified polyurethane polymer, epoxy resin E51, photoinitiator, carbon black, dispersant and defoamer is 50:15:3:7:0.6:0.2.

[0045] The photoinitiator is a mixture of triarylthionium salt and diaryliodonium salt in a mass ratio of 3:1; the dispersant is BYK-190; and the defoamer is DAPRO DF7073.

[0046] Comparative Example 2

[0047] A method for preparing a highly flexible UV digital ink includes the following steps:

[0048] S1. In a nitrogen atmosphere, 1.44g of octanoic acid and 3.74g of epoxy resin E51 were heated and refluxed at 95°C under the catalysis of 0.05g of tetraethylammonium bromide. When the acid value of the system was lower than 1mgKOH / g, the temperature was lowered to below 65°C and the material was discharged to obtain the modified epoxy resin.

[0049] S2. In a nitrogen atmosphere, mix 1.2g of polyethylene glycol 1200 and 0.06g of dibutyltin dilaurate, and add 4.5g of isophorone diisocyanate dropwise while stirring. Heat to 80℃ and keep warm for 1.5h. Cool and discharge to obtain polyurethane polymer.

[0050] S3. Take the polyurethane polymer and modified epoxy resin, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer, mix evenly, and the high flexibility UV digital ink is obtained; the mass ratio of polyurethane polymer, modified epoxy resin, photoinitiator, carbon black, dispersant and defoamer is 50:15:3:7:0.6:0.2.

[0051] The photoinitiator is a mixture of triarylthionium salt and diaryliodonium salt in a mass ratio of 3:1; the dispersant is BYK-190; and the defoamer is DAPRO DF7073.

[0052] Performance testing

[0053] Take the UV digital inks prepared in Examples 1-3 and Comparative Examples 1-2:

[0054] 1) Apply the UV digital inks to an 8mm × 115mm dumbbell-shaped mold using a wet film coater, and cure each UV digital ink using a UV-LED lamp with an energy of 600mJ / cm². 2 The curing time was 1.5 min, resulting in dumbbell-shaped test material; a tensile test was performed using a tensile testing machine at a tensile rate of 10 mm / min, applying a longitudinal tensile load until the material fractured;

[0055] 2) Apply each group of UV digital inks to tinplate using a film scraper, cure with a UV curing machine, and test the pencil hardness and flexibility of the cured film.

[0056] The test results are shown in Table 1 below.

[0057] Table 1

[0058]

[0059] The test results above show that the UV digital inks prepared in Examples 1-3 of this application have better overall performance after curing than the comparative examples, proving that the dual modification synergy of the present invention can take into account the comprehensive balance of the multi-dimensional performance of the film layer after UV digital ink curing.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a high flexibility UV digital ink, characterized in that, Includes the following steps: S1. In a nitrogen atmosphere, a monocarboxylic acid and an epoxy resin are heated, condensed, refluxed, and stirred under the catalysis of a catalyst to obtain a modified epoxy resin. S2. In a nitrogen atmosphere, polyethylene glycol and catalyst are mixed, and isocyanate is added dropwise while stirring. The temperature is raised to 60°C, and then 3-ethyl-3-oxabutane methanol is added dropwise while stirring. The temperature is raised to 70°C and kept at that temperature for 1-2 hours. The material is then cooled and discharged to obtain the modified polyurethane polymer. S3. Take the modified polyurethane polymer and modified epoxy resin, mix them evenly, add photoinitiator, carbon black, dispersant and defoamer and mix evenly to obtain the high flexibility UV digital ink.

2. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The photoinitiator includes at least one of triarylthionium salt and diaryliodonium salt.

3. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The dispersant includes at least one of BYK-190 and YB-401.

4. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The defoamer includes at least one of DAPRO DF7073 and TEGO FOAMEX 1488.

5. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The catalyst mentioned in step S1 is tetraethylammonium bromide.

6. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The catalyst mentioned in step S2 is dibutyltin dilaurate.

7. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The monocarboxylic acid includes any one of butyric acid, hexanoic acid, octanoic acid, and decanoic acid.

8. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The average molecular weight of the polyethylene glycol is 800-2000 Da.

9. The method for preparing a high-flexibility UV digital ink according to claim 1, characterized in that, The isocyanate is selected from at least one of isophorone diisocyanate, hexamethylene diisocyanate, and 1,6-hexamethylene diisocyanate.

10. A highly flexible UV digital ink prepared by the preparation method according to any one of claims 1-9.

Images