Low-migration UV inkjet ink and preparation method thereof

Abstract

The invention discloses low-migration UV ink-jet ink and a preparation method thereof, and belongs to the technical field of novel ink. Comprising the following components in parts by mass: 10-15 parts of a dynamic cross-linked polyurethane acrylate oligomer, 5-8 parts of an epoxy silicone resin oligomer, 2-3 parts of modified silicon dioxide, 4-5 parts of a photoinitiator, 15-20 parts of sorbic acid modified color paste, 1-2 parts of nano cerium oxide and 0.5-1 part of an antioxidant. The molecular chain of the dynamic cross-linked polyurethane acrylate oligomer prepared by the invention contains an active group capable of forming a cross-linked structure and a dynamic covalent bond. The groups and bonds promote molecular chain crosslinking when the ink is cured, a three-dimensional network is formed, and the molecular crosslinking density is improved. Through interaction of palmitic acid modified silicon dioxide and oligomer, the palmitic acid modified silicon dioxide is uniformly dispersed in a matrix and interferes molecular chain movement during curing, so that the crosslinking density is further improved, an ink film layer is more compact and firmer, the wear resistance and the scratch resistance are improved, and the tinting strength and the stability are indirectly enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of new ink, and particularly relates to a low-migration UV inkjet ink and a preparation method thereof. Background Art

[0002] Low migration means that when in contact with foods or the like, the finished products in the ink film formed after the ink dries will not migrate into the foods or the inner packaging of the foods. Currently, the purpose is mainly achieved by using macromolecular and highly safe initiators or increasing the molecular crosslinking density after curing.

[0003] Chinese Patent CN118755301B discloses a low-migration UV-curable digital printing label inkjet ink and a preparation method thereof. However, in the above patent, the oleic acid / linoleic acid with double-bond structure used in the modified silica is prone to oxidize to generate peroxides or aldehydes under light or high temperature, which may cause the ink to change color or the crosslinking to fail, resulting in the label being easily peeled off or blurred.

[0004] The migration rate test of this patent has limitations. It is only carried out at 50°C for 72 hours. However, in actual applications, the product may face higher temperatures or long-term storage, which will cause changes in material properties and unstable migration rates, affecting the product performance and quality.

[0005] Based on this, the present invention designs a low-migration UV inkjet ink and a preparation method thereof to solve the above problems. Summary of the Invention

[0006] In view of the above-mentioned drawbacks of the prior art, the present invention provides a low-migration UV inkjet ink and a preparation method thereof.

[0007] To achieve the above object, the present invention is realized through the following technical solutions: A low-migration UV inkjet ink, comprising the following components in parts by mass: 10-15 parts of a dynamic crosslinked polyurethane acrylate oligomer, 5-8 parts of an epoxy silicone resin oligomer, 2-3 parts of modified silica, 4-5 parts of a photoinitiator, 15-20 parts of a sorbic acid-modified color paste, 1-2 parts of nano-ceria, 0.5-1 part of an antioxidant; The dynamic crosslinked polyurethane acrylate oligomer is prepared by dynamically crosslinking hexamethylene diisocyanate, polytetrahydrofuran diol, dibutyltin dilaurate and cystine through dynamic disulfide bonds; The modified silica is obtained by grafting modification with palmitic acid after high-speed shearing with a silane coupling agent; The sorbic acid-modified color paste is formed by hydrogen bonding of a pigment and sorbic acid and adding a composite dispersant for grinding; The ink forms a crosslinked structure through a polymerization reaction of the dynamic crosslinked polyurethane acrylate oligomer and the epoxy silicone resin oligomer initiated by UV irradiation.

[0008] A preparation method of a low-migration UV inkjet ink as described above, comprising the following steps: S1: Preparation of a dynamically modified polyurethane acrylate oligomer; Mix hexamethylene diisocyanate and polytetrahydrofuran glycol, add dibutyltin dilaurate, and react at 55 - 60 °C; Add cystine, and raise the temperature to 66 - 73 °C for reaction; Block with hydroxyethyl acrylate and react at 74 - 80 °C to obtain a dynamically crosslinked polyurethane acrylate oligomer; S2: Preparation of modified silica; Add nano-silica and a silane coupling agent to a high-speed emulsifier, and shear and emulsify at 4000 - 5000 r / min at 55 - 60 °C to form a uniformly dispersed liquid; Add palmitic acid to the dispersion, raise the temperature to 75 - 80 °C, stir and react, and dry after centrifugal separation; S3: Preparation of sorbic acid-modified color paste; Stir the pigment and sorbic acid at 58 - 63 °C to form a hydrogen bond; Add a composite dispersant, stir and mix with dipropylene glycol diacrylate, and grind with a sand mill until the particle size < 1 μm; S4: Ink step-by-step mixing; Premix, mix the dynamically modified polyurethane acrylate oligomer and epoxy silicone resin oligomer, and the stirring speed is 150 - 200 r / min; Disperse, add modified silica and sorbic acid-modified color paste, and ultrasonically disperse; Final mix, add a photoinitiator, nano-ceria and an antioxidant, stir at high speed, then vacuum degas and filter to obtain a low-migration UV inkjet ink.

[0009] Further, the specific steps of S1 are: mix hexamethylene diisocyanate and polytetrahydrofuran glycol, add dibutyltin dilaurate, and react at 55 - 60 °C for 3 - 4 h; Add cystine, and raise the temperature to 66 - 73 °C for reaction for 2.5 - 3 h; Block with hydroxyethyl acrylate and react at 74 - 80 °C for 1 - 1.5 h to obtain a dynamically crosslinked polyurethane acrylate oligomer.

[0010] Further, the molar ratio of hexamethylene diisocyanate, polytetrahydrofuran glycol and dibutyltin dilaurate is 10 - 12:4 - 7:0.02 - 0.05.

[0011] Further, the S2 is specifically as follows: adding nano-silica and silane coupling agent KH560 into a high-speed emulsifier, shearing and emulsifying at 55 - 60 °C at 4000 - 5000 r / min for 2 - 3 h to form a uniformly dispersed liquid; Adding palmitic acid to the dispersed liquid, heating to 75 - 80 °C, stirring and reacting at 2000 - 3000 r / min for 3 - 4 h, centrifuging and then drying.

[0012] Further, the S3 is specifically as follows: stirring the pigment and sorbic acid at 58 - 63 °C for 30 - 40 min to form hydrogen bond binding; Adding a composite dispersant, stirring for 15 - 20 min and then mixing with dipropylene glycol diacrylate, grinding with a Pengyi intelligent pin - type high - efficiency nano - sand mill until the particle size < 1 μm; the mass ratio of the pigment, sorbic acid, composite dispersant and dipropylene glycol diacrylate is 16 - 21:2 - 7:5 - 10:68 - 72.

[0013] Further, the S4 is specifically as follows: mixing the dynamic modified polyurethane acrylate oligomer and epoxy silicone resin oligomer, with a stirring speed of 150 - 200 r / min and a time of 50 - 60 min.

[0014] Adding modified silica and sorbic acid - modified color paste, ultrasonically dispersing for 25 - 30 min; Adding a photo - initiator, nano - cerium oxide and an antioxidant, stirring at high speed for 40 - 45 min, vacuum degassing and then passing through a 1 - 10 μm filter membrane to obtain a low - migration UV inkjet ink.

[0015] Further, the zirconia beads of the sand mill have a diameter of 0.2 - 0.4 mm, a filling rate of 60 - 85%, a grinding chamber temperature of 15 - 25 °C, a cooling water flow rate ≥ 10 L / min, a feed viscosity of 300 - 800 mPa·s, an outlet particle size D90 < 1 μm, a circulation times ≥ 3 times, and a single - time grinding time ≤ 30 min.

[0016] The beneficial effects of the present invention compared with the prior art are as follows: 1. The present invention prepares a dynamically cross - linked polyurethane acrylate oligomer with hexamethylene diisocyanate, polytetrahydrofuran glycol, dibutyltin dilaurate and cystine. Its molecular chain contains active groups and dynamic covalent bonds that can form cross - linked structures. These groups and bonds promote the cross - linking of molecular chains during ink curing, forming a three - dimensional network and increasing the molecular cross - linking density.

[0017] 2. Through the interaction between silica modified by palmitic acid and the oligomer, the present invention is uniformly dispersed in the matrix, interfering with the movement of molecular chains during curing, further increasing the cross - linking density, making the ink film layer denser and stronger, improving the wear resistance and scratch resistance, and indirectly enhancing the coloring power and stability.

[0018] 3. In the present invention, the dynamically crosslinked polyurethane acrylate oligomer is combined with palmitic acid-modified silica, and the two cooperate with each other. The crosslinked network of the oligomer provides a stable dispersion environment for the silica particles, enabling them to fully play the role of enhancing and restricting molecular migration; while the addition of the silica particles further improves the crosslinking density and network structure stability of the oligomer, resulting in a denser and more stable molecular network structure after the ink is cured. The tight network structure helps to improve the heat resistance and chemical resistance of the ink, reduce the molecular chain breakage and color change caused by external factors, thereby reducing the color difference and enhancing the coloring power to a certain extent, and enhancing the stability of the ink in a high-temperature environment. Detailed implementation mode

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0020] Example 1: This example provides a preparation method of a low-migration UV inkjet ink, including the following steps: S1: Preparation of a dynamically modified polyurethane acrylate oligomer; Hexamethylene diisocyanate and polytetrahydrofuran diol are mixed, and dibutyltin dilaurate is added. The molar ratio of hexamethylene diisocyanate, polytetrahydrofuran diol, and dibutyltin dilaurate is 12:7:0.05, and the reaction is carried out at 60 °C for 4 h; Cystine (containing dynamic disulfide bonds) is added, and the temperature is raised to 73 °C for 3 h; It is capped with hydroxyethyl acrylate and reacted at 80 °C for 1.5 h to obtain a dynamically crosslinked polyurethane acrylate oligomer; S2: Preparation of modified silica; Nanometer silica (50 nm) and silane coupling agent KH560 (8% of the mass of silica) are added to a high-speed emulsifier, and shearing emulsification is carried out at 60 °C at 5000 r / min for 3 h to form a uniform dispersion; Palmitic acid (15% of the mass of silica) is added to the dispersion, the temperature is raised to 80 °C, and stirring reaction is carried out at 3000 r / min for 4 h, followed by centrifugal separation and drying; It should be noted that in the present invention, the grafting of the silane coupling agent and the acid is achieved through high-speed shear emulsification, avoiding solvent immersion and reducing 90% of the waste liquid.

[0021] S3: Preparation of sorbic acid-modified color paste The pigment and sorbic acid are stirred at 63 °C for 40 min to form hydrogen bond binding; Add a composite dispersant (polyetheramine: Tego Dispers 760W = 2:1), stir for 20 min and then mix with dipropylene glycol diacrylate, and grind with a Pengyi intelligent rod pin type high-efficiency nano sand mill (the zirconia beads of the sand mill have a diameter of 0.4 mm, a filling rate of 85%, a grinding chamber temperature of 25 °C, a cooling water flow rate of 20 L / min, a feed viscosity of 800 mPa·s, an outlet particle size D90 < 1 μm, a circulation times of 4 times, and a single grinding time of 20 min) until the particle size < 1 μm; the mass ratio of the pigment (selected from Runba P5160 high-performance red-phase phthalocyanine blue PB15:6), sorbic acid, composite dispersant and dipropylene glycol diacrylate is 21:7:10:72; S4: Ink step mixing; Low-temperature premixing (40 °C): Mix 15 parts of dynamically modified polyurethane acrylate oligomer and 8 parts of epoxy silicone resin oligomer, with a stirring speed of 200 r / min and a time of 60 min; Medium-temperature dispersion (50 °C): Add 3 parts of modified silica and 20 parts of sorbic acid modified color paste, and ultrasonically disperse (frequency 40 kHz) for 30 min; High-temperature final mixing (60 °C): Add 5 parts of photoinitiator (selected from IGM Omnirad 2959 photoinitiator of Shanghai Kayin Chemical Co., Ltd., Omnirad 2959 is a photoinitiator allowed to be used through the FDA certification system and can be used in adhesives that are not in direct contact with food, with high safety), 2 parts of nano cerium oxide and 1 part of hindered phenol antioxidant, stir at high speed for 45 min, perform vacuum degassing (-0.08 MPa) and then pass through a 10 μm filter membrane to obtain a low-migration UV inkjet ink.

[0022] Example 2: This example provides a preparation method of a low-migration UV inkjet ink, including the following steps: S1: Preparation of dynamically modified polyurethane acrylate oligomer; Mix hexamethylene diisocyanate and polytetrahydrofuran glycol, add dibutyltin dilaurate, and the molar ratio of hexamethylene diisocyanate, polytetrahydrofuran glycol and dibutyltin dilaurate is 10:4:0.02, and react at 55 °C for 3 h; Add cystine (containing dynamic disulfide bonds), and raise the temperature to 66 °C to react for 2.5 h; Block with hydroxyethyl acrylate and react at 74 °C for 1 h to obtain a dynamically crosslinked polyurethane acrylate oligomer; S2: Preparation of modified silica; Add nano-silica (50 nm) and silane coupling agent KH560 (8% of the mass of silica) to a high-speed emulsifier, and shear and emulsify at 4000 r / min for 2 h at 55 °C to form a uniform dispersion; Add palmitic acid (15% of the mass of silica) to the dispersion, raise the temperature to 75 °C, stir and react at 2000 r / min for 3 h, and dry after centrifugal separation; S3: Preparation of sorbic acid modified color paste; Stir the pigment and sorbic acid at 58 °C for 30 min to form a hydrogen bond; Add a composite dispersant (polyetheramine: Tego Dispers 760W = 2:1), stir for 15 min and then mix with dipropylene glycol diacrylate, and grind with a Pengyi intelligent rod pin type high-efficiency nano sand mill (the zirconia beads of the sand mill have a diameter of 0.2 mm, a filling rate of 60%, a grinding chamber temperature of 15 °C, a cooling water flow rate of 10 L / min, a feed viscosity of 300 mPa·s, an outlet particle size D90 < 1 μm, a circulation times of 3 times, and a single grinding time of 30 min) until the particle size < 1 μm; the mass ratio of the pigment (Titanium Yellow P2240A of Dongguan Haigrui Chemical Co., Ltd.), sorbic acid, composite dispersant and dipropylene glycol diacrylate is 16:2:5:68; S4: Ink step mixing; Low-temperature premixing (40 °C): Mix 10 parts of dynamically modified polyurethane acrylate oligomer and 5 parts of epoxy silicone resin oligomer, with a stirring speed of 150 r / min and a time of 50 min; Medium-temperature dispersion (50 °C): Add 2 parts of modified silica and 15 parts of sorbic acid modified color paste, and ultrasonically disperse (frequency 40 kHz) for 25 min; High-temperature final mixing (60 °C): Add 4 parts of photoinitiator (selected from IGM Initiator of Shanghai Kayin Chemical Co., Ltd.), 1 part of nano-ceria and 0.5 part of antioxidant, stir at high speed for 40 min, vacuum degas (-0.08 MPa) and then pass through a 1 μm filter membrane to obtain a low-migration UV inkjet ink Example 3: This example provides a method for preparing a low-migration UV inkjet ink, including the following steps: S1: Preparation of dynamically modified polyurethane acrylate oligomer; Mix hexamethylene diisocyanate and polytetrahydrofuran glycol, and add dibutyltin dilaurate. The molar ratio of hexamethylene diisocyanate, polytetrahydrofuran glycol and dibutyltin dilaurate is 11:5:0.03, and react at 58 °C for 3 h; Add cystine (containing dynamic disulfide bonds), and raise the temperature to 70 °C and react for 2.5 h; It was capped with hydroxyethyl acrylate and reacted at 78 °C for 1.5 h to obtain a dynamically crosslinked polyurethane acrylate oligomer; S2: Preparation of modified silica; Nanosilica (50 nm) and silane coupling agent KH560 (8% of the mass of silica) were added to a high-speed emulsifier and sheared and emulsified at 56 °C at 4200 r / min for 2 h to form a homogeneous dispersion; Palmitic acid (15% of the mass of silica) was added to the dispersion, the temperature was raised to 77 °C, and the mixture was stirred and reacted at 2400 r / min for 3 h, followed by centrifugal separation and drying; S3: Preparation of sorbic acid-modified color paste; The pigment and sorbic acid were stirred at 60 °C for 35 min to form hydrogen bond binding; A composite dispersant (polyetheramine: Tego Dispers 760W = 2:1) was added, stirred for 18 min and then mixed with dipropylene glycol diacrylate, and ground to a particle size <1 μm by a Pengyi intelligent rod pin type high-efficiency nanosand mill (the zirconia beads of the sand mill had a diameter of 0.3 mm, a filling rate of 70%, a grinding chamber temperature of 21 °C, a cooling water flow rate of 15 L / min, a feed viscosity of 400 mPa·s, an outlet particle size D90 < 1 μm, a circulation times of 3 times, and a single grinding time of 30 min); the mass ratio of the pigment (Shandong Caizhiyuan Pigment Technology Pigment Red HF3C), sorbic acid, composite dispersant and dipropylene glycol diacrylate was 18:6:8:70; S4: Ink step mixing; Low-temperature premixing (40 °C): 12 parts of dynamically modified polyurethane acrylate oligomer and 7 parts of epoxy silicone resin oligomer were mixed, with a stirring speed of 180 r / min and a time of 50 min; Medium-temperature dispersion (50 °C): 2.3 parts of modified silica and 17 parts of sorbic acid-modified color paste were added, and ultrasonic dispersion (frequency 40 kHz) was carried out for 28 min; High-temperature final mixing (60 °C): 4.8 parts of photoinitiator (selected from IGM Ivoclar Vivadent photoinitiator of Shanghai Kayin Chemical Co., Ltd.), 1.2 parts of nano-ceria and 0.4 part of antioxidant were added, and the mixture was stirred at high speed for 45 min, vacuum degassed (-0.08 MPa) and then passed through a 2-μm filter membrane to obtain a low-migration UV inkjet ink.

[0023] Comparative Example 1: The difference between this comparative example and Example 3 was that the dynamically crosslinked polyurethane acrylate oligomer was replaced with a polyurethane acrylate oligomer (Sartomer CU216NS); This comparative example provided a preparation method of a low-migration UV inkjet ink, including the following steps: S1: Preparation of modified silica; Add nano-silica (50 nm) and silane coupling agent KH560 (8% of the mass of silica) to a high-speed emulsifier, shear and emulsify at 4200 r / min for 2 h at 56 °C to form a homogeneous dispersion; Add palmitic acid (15% of the mass of silica) to the dispersion, raise the temperature to 77 °C, stir and react at 2400 r / min for 3 h, and dry after centrifugal separation; S2: Preparation of sorbic acid modified color paste; Stir the pigment and sorbic acid at 60 °C for 35 min to form hydrogen bond binding; Add a composite dispersant (polyetheramine: Tego Dispers 760W = 2:1), stir for 18 min and then mix with dipropylene glycol diacrylate, grind with a Pengyi intelligent rod pin type high-efficiency nano sand mill to a particle size < 1 μm; the mass ratio of the pigment (Shandong Caizhiyuan Pigment Technology Pigment Red HF3C), sorbic acid, composite dispersant and dipropylene glycol diacrylate is 18:6:8:70; S3: Ink step mixing; Low-temperature premixing (40 °C): Mix 12 parts of polyurethane acrylate oligomer and 7 parts of epoxy silicone resin oligomer, stirring speed 180 r / min, time 50 min; Medium-temperature dispersion (50 °C): Add 2.3 parts of modified silica and 17 parts of sorbic acid modified color paste, and ultrasonically disperse (frequency 40 kHz) for 28 min; High-temperature final mixing (60 °C): Add 4.8 parts of photoinitiator (selected from IGM photoinitiator of Shanghai Kayin Chemical Co., Ltd.), 1.2 parts of nano-cerium oxide and 0.4 part of antioxidant, stir at high speed for 45 min, vacuum degas (-0.08 MPa) and then pass through a 2 μm filter membrane to obtain a low-migration UV inkjet ink.

[0024] Comparative Example 2: The difference between this comparative example and Example 3 is that the palmitic acid in the modified silica is replaced by an organic composite acid, and the mass ratio of palmitic acid and linoleic acid in the organic composite acid is 1:1; This comparative example provides a preparation method of a low-migration UV inkjet ink, including the following steps: S1: Preparation of dynamically modified polyurethane acrylate oligomer; Mix hexamethylene diisocyanate and polytetrahydrofuran glycol, add dibutyltin dilaurate, and the molar ratio of hexamethylene diisocyanate, polytetrahydrofuran glycol and dibutyltin dilaurate is 11:5:0.03, react at 58 °C for 3 h; Add cystine (containing dynamic disulfide bond), raise the temperature to 70 °C and react for 2.5 h; It was capped with hydroxyethyl acrylate and reacted at 78 °C for 1.5 h to obtain a dynamically crosslinked polyurethane acrylate oligomer; S2: Preparation of modified silica; Nanosilica (50 nm) and silane coupling agent KH560 (8% of the mass of silica) were added to a high-speed emulsifier and sheared and emulsified at 56 °C at 4200 r / min for 2 h to form a uniformly dispersed liquid; An organic composite acid was added to the dispersion, and the mass ratio of palmitic acid to linoleic acid in the organic composite acid was 1:1 (15% of the mass of silica). The temperature was raised to 77 °C and stirred and reacted at 2400 r / min for 3 h, followed by centrifugal separation and drying; S3: Preparation of sorbic acid-modified color paste; The pigment and sorbic acid were stirred at 60 °C for 35 min to form a hydrogen bond; A composite dispersant (polyetheramine: Tego Dispers 760W = 2:1) was added, stirred for 18 min and then mixed with dipropylene glycol diacrylate, and ground with a Pengyi intelligent rod pin type high-efficiency nanosand mill to a particle size <1 μm; the mass ratio of the pigment (Shandong Caizhiyuan Pigment Technology Pigment Red HF3C), sorbic acid, composite dispersant and dipropylene glycol diacrylate was 18:6:8:70; S4: Ink step mixing; Low-temperature premixing (40 °C): 12 parts of dynamically modified polyurethane acrylate oligomer and 7 parts of epoxy silicone resin oligomer were mixed, with a stirring speed of 180 r / min and a time of 50 min; Medium-temperature dispersion (50 °C): 2.3 parts of modified silica and 17 parts of sorbic acid-modified color paste were added, and ultrasonic dispersion (frequency 40 kHz) was carried out for 28 min; High-temperature final mixing (60 °C): 4.8 parts of photoinitiator (selected from IGM photoinitiator of Shanghai Kayin Chemical Co., Ltd.), 1.2 parts of nano-ceria and 0.4 part of antioxidant were added, stirred at high speed for 45 min, vacuum degassed (-0.08 MPa) and then passed through a 2-μm filter membrane to obtain a low-migration UV inkjet ink.

[0025] Comparative Example 3: The difference between this comparative example and Example 3 is that the dynamically crosslinked polyurethane acrylate oligomer was replaced with a polyurethane acrylate oligomer, and at the same time, palmitic acid in the modified silica was replaced with an organic composite acid, and the mass ratio of palmitic acid to linoleic acid in the organic composite acid was 1:1; This comparative example provides a preparation method of a low-migration UV inkjet ink, including the following steps: S1: Preparation of modified silica; Add nano-silica (50 nm) and silane coupling agent KH560 (8% of the mass of silica) to a high-speed emulsifier, shear and emulsify at 4200 r / min for 2 h at 56 °C to form a homogeneous dispersion; Add an organic composite acid to the dispersion, and the mass ratio of palmitic acid to linoleic acid in the organic composite acid is 1:1 (15% of the mass of silica), heat up to 77 °C, stir and react at 2400 r / min for 3 h, and dry after centrifugal separation; S2: Preparation of sorbic acid-modified color paste; Stir the pigment and sorbic acid at 60 °C for 35 min to form a hydrogen bond; Add a composite dispersant (polyetheramine: Tego Dispers 760W = 2:1), stir for 18 min and then mix with dipropylene glycol diacrylate, grind with a Pengyi intelligent rod pin type high-efficiency nano sand mill until the particle size < 1 μm; the mass ratio of the pigment (Shandong Caizhiyuan Pigment Technology Pigment Red HF3C), sorbic acid, composite dispersant and dipropylene glycol diacrylate is 18:6:8:70; S3: Ink step mixing; Low-temperature premixing (40 °C): Mix 12 parts of polyurethane acrylate oligomer and 7 parts of epoxy silicone resin oligomer, stirring speed 180 r / min, time 50 min; Medium-temperature dispersion (50 °C): Add 2.3 parts of modified silica and 17 parts of sorbic acid-modified color paste, and ultrasonically disperse (frequency 40 kHz) for 28 min; High-temperature final mixing (60 °C): Add 4.8 parts of photoinitiator (selected from IGM photoinitiator of Shanghai Kayin Chemical Co., Ltd.), 1.2 parts of nano-ceria and 0.4 part of antioxidant, stir at high speed for 45 min, vacuum degas (-0.08 MPa) and then pass through a 2 μm filter membrane to obtain low-migration UV inkjet ink.

[0026] Control example: The UV inkjet ink was prepared by the method of Example 1 of Chinese Patent CN118755301B.

[0027] Experimental example: The inks prepared in Examples 1-3, Comparative Examples 1-3 and the control example were photocured, and printed on a PET film with a surface energy of 38 dynes using a printer with a Ricoh Gen5 print head. At a temperature of 45 °C, the rotational viscosity of the printed ink is 5-10 mPa·s at 30 rpm, and it is photocured using a UV-LED lamp (395 nm) at 20 W / cm 2 under light irradiation.

[0028] The migration amount test (mg / dm 2 ) was carried out successively according to the standard of GB / T 31604.1-2023; Color strength experiment: The color strength (R%) and color difference (ΔE) of Examples 1-3 and Comparative Examples 1-3 were detected according to the standard of GB / T 13217.1-2020; UV aging experiment: Wavelength 253.7 nm, power 30 W, distance 120 mm, intermittent irradiation for 112 h (irradiation for 8 h followed by an 8-h interval); High-temperature experiment: Steam sterilization at 121 °C for 30 minutes (simulating the high-temperature sterilization scenario of food packaging); After UV aging and high-temperature experiments, the color strength experiment and migration amount test were carried out by the above method.

[0029] Crosslinking density determination experiment: Prepare a cured ink film (thickness about 100 μm) and cut it into standard size (10 mm × 10 mm); Weigh the mass of the dry film (W0), immerse it in tetrahydrofuran solvent, and let it stand in the dark for 48 hours until swelling equilibrium; Take out the swollen film, dry the surface solvent with filter paper and then weigh it (W s ), and then vacuum dry it to a constant weight (W d ); Calculate the crosslinking density (v):

[0030] Among them, ρ is the polymer density, M c is the molecular weight between crosslinking points, ρ s is the solvent density, ρ p is the polymer density.

[0031] The results are shown in the following table:

[0032] Data analysis: As can be seen from Comparative Example 1, the dynamic crosslinked polyurethane acrylate oligomer prepared from hexamethylene diisocyanate, polytetrahydrofuran glycol, dibutyltin dilaurate and cystine has reactive groups and dynamic covalent bonds that can form crosslinked structures in its molecular chain. During the ink curing process, these reactive groups and dynamic bonds will promote crosslinking reactions between molecular chains, forming a three-dimensional network-like crosslinked structure, thereby increasing the molecular crosslinking density. The dynamic crosslinked structure restricts the movement ability of molecular chains, limits the free diffusion and migration of ink molecules, and thus reduces the migration amount. At the same time, this tight network structure is beneficial to improving the heat resistance and chemical resistance of the ink, reducing the damage of molecular chains and color change caused by external factors, and thus improving the color strength to a certain extent.

[0033] As a saturated fatty acid, palmitic acid undergoes a chemical reaction between the long-chain alkyl part in its molecular structure and the hydroxyl groups on the surface of silica, forming stable chemical bonds. This enables the silica particles to be evenly dispersed in the oligomer matrix and tightly bind to the oligomer molecular chains. When the ink cures, the presence of the silica particles interferes with the movement of the oligomer molecular chains, making it more difficult for them to displace and deform, thereby further restricting the diffusion and migration of the molecular chains and increasing the overall molecular crosslinking density.

[0034] The addition of silica particles can also increase the viscosity and mechanical properties of the ink system, making the cured film layer of the ink denser and stronger, which helps to improve the abrasion resistance and scratch resistance of the ink, thereby indirectly enhancing the coloring power and stability.

[0035] The combination of the dynamically crosslinked polyurethane acrylate oligomer and the saturated palmitic acid-modified silica produces a synergistic effect in the ink system. The crosslinked network of the oligomer provides a stable dispersion environment for the silica particles, enabling the silica to fully exert its role in enhancing and restricting molecular migration; while the addition of the silica particles further increases the crosslinking density of the oligomer and the stability of the network structure.

[0036] This synergistic effect causes the ink to form a denser and more stable molecular network structure after curing. In this structure, the migration of the ink molecules is more restricted, the color difference is effectively controlled, and the coloring power is significantly improved. At the same time, the stability of the ink in a high-temperature environment is also enhanced because the increase in the molecular crosslinking density enhances the ink's resistance to temperature changes, making it less likely to experience a decline in performance or aging under high-temperature conditions, thereby extending the service life and application range of the ink.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A low-migration UV inkjet ink, characterized in that, It comprises components in the following parts by mass: 10 - 15 parts of dynamically crosslinked polyurethane acrylate oligomer, 5 - 8 parts of epoxy silicone resin oligomer, 2 - 3 parts of modified silica, 4 - 5 parts of photoinitiator, 15 - 20 parts of sorbic acid modified color paste, 1 - 2 parts of nano cerium oxide, 0.5 - 1 part of antioxidant; The dynamically crosslinked polyurethane acrylate oligomer is prepared by crosslinking hexamethylene diisocyanate, polytetrahydrofuran diol, dibutyltin dilaurate and cystine through dynamic disulfide bonds; The modified silica is obtained by graft modification with palmitic acid after high - speed shearing with a silane coupling agent; The sorbic acid modified color paste is formed by binding a pigment and sorbic acid through hydrogen bonds and adding a composite dispersant for grinding; The ink forms a cross - linked structure through the polymerization reaction of dynamically crosslinked polyurethane acrylate oligomer and epoxy silicone resin oligomer initiated by UV irradiation.

2. A preparation method of the low-migration UV inkjet ink as described in claim 1, characterized in that, It includes the following steps: S1: Preparation of dynamically modified polyurethane acrylate oligomer; Mix hexamethylene diisocyanate and polytetrahydrofuran diol, add dibutyltin dilaurate, and react at 55 - 60 °C; Add cystine, and raise the temperature to 66 - 73 °C for reaction; Block with hydroxyethyl acrylate and react at 74 - 80 °C to obtain the dynamically crosslinked polyurethane acrylate oligomer; S2: Preparation of modified silica; Add nano - silica and a silane coupling agent to a high - speed emulsifier, shear and emulsify at 55 - 60 °C at 4000 - 5000 r / min to form a homogeneous dispersion; Add palmitic acid to the dispersion, raise the temperature to 75 - 80 °C, stir and react, and dry after centrifugal separation; S3: Preparation of sorbic acid modified color paste; Stir the pigment and sorbic acid at 58 - 63 °C to form hydrogen - bond binding; Add a composite dispersant, stir and then mix with dipropylene glycol diacrylate, and grind with a sand mill to a particle size < 1 μm; S4: Step - by - step mixing of the ink; Pre - mixing: Mix the dynamically modified polyurethane acrylate oligomer and epoxy silicone resin oligomer at a stirring speed of 150 - 200 r / min; Dispersion: Add the modified silica and sorbic acid modified color paste and perform ultrasonic dispersion; Final mixing: Add the photoinitiator, nano cerium oxide and antioxidant, stir at high speed, perform vacuum degassing and then filtration to obtain the low - migration UV inkjet ink.

3. The preparation method of the low-migration UV inkjet ink according to claim 2, wherein Specifically, S1 is as follows: Mix hexamethylene diisocyanate and polytetrahydrofuran diol, add dibutyltin dilaurate, and react at 55 - 60 °C for 3 - 4 h; Add cystine, raise the temperature to 66 - 73 °C and react for 2.5 - 3 h; Block with hydroxyethyl acrylate and react at 74 - 80 °C for 1 - 1.5 h to obtain the dynamically crosslinked polyurethane acrylate oligomer.

4. The preparation method of the low-migration UV inkjet ink according to claim 3, characterized in that The molar ratio of hexamethylene diisocyanate, polytetrahydrofuran diol and dibutyltin dilaurate is 10 - 12:4 - 7:0.02 - 0.

05.

5. The preparation method of the low-migration UV inkjet ink according to claim 2, characterized in that, Specifically, S2 is as follows: Add nano - silica and the silane coupling agent KH560 to a high - speed emulsifier, shear and emulsify at 55 - 60 °C at 4000 - 5000 r / min for 2 - 3 h to form a homogeneous dispersion; Palmitic acid was added to the dispersion liquid, and the temperature was raised to 75 - 80 °C. Stirring reaction was carried out at 2000 - 3000 r / min for 3 - 4 h, followed by centrifugal separation and then drying.

6. The preparation method of the low-migration UV inkjet ink according to claim 2, characterized in that, Specifically, S3 is as follows: The pigment and sorbic acid were stirred at 58 - 63 °C for 30 - 40 min to form hydrogen bond binding; A composite dispersant was added, and after stirring for 15 - 20 min, it was mixed with dipropylene glycol diacrylate and ground to a particle size < 1 μm by a Pengyi intelligent rod pin type high - efficiency nanosand mill; The mass ratio of the pigment, sorbic acid, composite dispersant and dipropylene glycol diacrylate is 16 - 21:2 - 7:5 - 10:68 - 72.

7. The preparation method of the low-migration UV inkjet ink according to claim 2, characterized in that, Specifically, S4 is as follows: The dynamic modified polyurethane acrylate oligomer and epoxy silicone resin oligomer were mixed, with a stirring speed of 150 - 200 r / min and a time of 50 - 60 min; Modified silica and sorbic acid - modified color paste were added and ultrasonically dispersed for 25 - 30 min; A photoinitiator, nano - cerium oxide and an antioxidant were added, and high - speed stirring was carried out for 40 - 45 min. After vacuum degassing, it was passed through a 1 - 10 μm filter membrane to obtain a low - migration UV inkjet ink.

8. The preparation method of the low-migration UV inkjet ink according to claim 2, characterized in that, The zirconium beads of the sand mill have a diameter of 0.2 - 0.4 mm, a filling rate of 60 - 85%, a grinding chamber temperature of 15 - 25 °C, a cooling water flow rate ≥ 10 L / min, a feed viscosity of 300 - 800 mPa·s, an outlet particle size D90 < 1 μm, a circulation number ≥ 3 times, and a single grinding time ≤ 30 min.

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