UV-LED curing ink-jet ink for food packaging and preparation method of UV-LED curing ink-jet ink

Abstract

The invention belongs to the technical field of UV-LED curing ink-jet materials, and particularly relates to UV-LED curing ink-jet ink for food packaging based on a nitrogen heterocyclic ring vinyl compound and a preparation method of the UV-LED curing ink-jet ink. According to the UV-LED curing ink-jet ink for food packaging, the reactive diluent, the acrylate oligomer, the photoinitiator, the pigment and the auxiliaries are used as an ink formula system, and the five-membered ring nitrogen heterocyclic ring vinyl compound is introduced into the ink formula, so that the surface curing level of the UV-LED ink-jet ink can be greatly improved, the ink transfer possibility is reduced, and the UV-LED curing ink-jet ink has the advantages that the UV-LED curing ink-jet ink can be applied to food packaging. Therefore, the device is more suitable for the field of food package printing.

Description

Technical Field

[0001] The present invention belongs to the technical field of UV-LED curable inkjet materials for food packaging, and particularly relates to a UV-LED curable inkjet ink for food packaging based on nitrogen-containing heterocyclic vinyl compounds and a preparation method thereof. Background Art

[0002] After traditional inks for food packaging materials are printed, the ink will migrate and transfer to the packaged food, resulting in potential food safety hazards. In the face of the easy occurrence of ink migration, one situation is that the food is in direct contact with the ink. However, since it is usually stipulated that food packaging inks are materials that do not come into direct contact with food, as long as the food packaging design is reasonable, the printed ink generally does not come into direct contact with the food. Another situation is that small molecule components remaining due to insufficient curing in the ink will penetrate and migrate through the food packaging substrate and enter the food. In response to this situation, more and more food packaging materials now adopt a multi-layer structure, and even an aluminized process in the middle, so as to eliminate the possibility of permeation migration to the greatest extent.

[0003] In fact, however, the most likely way for food packaging ink to migrate is during the printing process. This is mainly because during the winding process, the printed surface comes into contact with the non-printed surface, causing the ink to stick back to the non-printed surface. The non-printed surface is the inner surface of the packaging and comes into direct contact with the food. The ink components just enter the food through this transfer and migration method. Even if the most reasonable food packaging design is adopted, or the ink uses macromolecular photoinitiators that are not prone to migration, or the packaging adopts an aluminized multi-layer structure, it will be of no avail. This has also become an urgent problem to be solved in this field.

[0004] At present, a major trend in food packaging is to use inkjet printing technology for small-batch, multi-variety, and personalized customized printing. Among the types of inkjet inks used, UV-LED curable inkjet inks are gradually replacing traditional mercury lamp-cured UV curable inkjet inks and solvent-based inkjet inks that are prone to a large amount of solvent volatilization due to their advantages of low energy consumption and environmental protection. However, traditional UV-LED curable inkjet printing inks generally have an oxygen inhibition phenomenon and insufficient surface curing due to the fact that UV-LED curing only occurs in the wavelength range of 365 nm - 395 nm. For UV-LED curable inkjet inks for food packaging, insufficient surface curing will make the situation that ink components enter the packaged food through transfer and migration more serious. This is also the reason why ordinary UV-LED curable inkjet inks are not suitable for the food packaging field. Therefore, there is an expectation in this field to develop a UV-LED curable inkjet ink suitable for food packaging applications, which has positive significance for the development of the food packaging field. Summary of the Invention

[0005] To this end, the technical problem to be solved by the present invention is to provide a UV-LED curable inkjet ink for food packaging printing based on nitrogen-containing heterocyclic vinyl compounds, which can greatly improve the surface curing level of the UV-LED inkjet ink and reduce the possibility of ink transfer and migration to ensure the safety of inks for food, medicine, and cosmetics;

[0006] The second technical problem to be solved by the present invention is to provide a preparation method of the above-mentioned UV-LED curable inkjet ink for food packaging printing.

[0007] To solve the above technical problems, a UV-LED curable inkjet ink for food packaging according to the present invention, based on the total amount of the ink, comprises components with the following mass contents:

[0008]

[0009] Specifically, for the UV-LED curable inkjet ink for food packaging, the five-membered ring nitrogen-containing heterocyclic vinyl compound includes N-vinyl oxazolidinone N-vinyl-2-pyrrolidone or at least one of 5-methyl-3-vinyl-2-oxazoline and the like.

[0010] Preferably, the five-membered ring nitrogen-containing heterocyclic vinyl compound is 5-methyl-3-vinyl-2-oxazoline, and its dosage in the overall formulation is 10-35%.

[0011] Specifically, for the UV-LED curable inkjet ink for food packaging, the active diluent includes at least one of monofunctional acrylate or methacrylate monomers, difunctional acrylate or methacrylate monomers, or trifunctional acrylate or methacrylate monomers.

[0012] Specifically, in the UV-LED curable inkjet ink for food packaging:

[0013] The monofunctional acrylate or methacrylate monomer includes at least one of trimethylolcyclohexyl acrylate (TMCHA), benzyl acrylate (BZA), isobornyl acrylate (IBOA), 4-tert-butylcyclohexyl acrylate (TBCHA), lauryl acrylate (LA), cyclotrimethylolpropane formal acrylate (CTFA), benzyl methacrylate (BZMA), or cyclotrimethylolpropane formal methacrylate (CTFMA); and / or,

[0014] The bifunctional acrylate or methacrylate monomer includes at least one of neopentyl glycol propoxylate (2) diacrylate (NPGPODA), 3-methyl-1,5-pentanediol diacrylate (MPDDA), ethylene glycol dimethacrylate (EGDMA), triethylene glycol dimethacrylate (TEGDMA), or 1,4-butanediol dimethacrylate (BDDMA); and / or,

[0015] The trifunctional acrylate or methacrylate monomer includes at least one of glycerol propoxylate (4) triacrylate (GPTA), trimethylolpropane ethoxylate (3) triacrylate (TMP3EOTA), trimethylolpropane propoxylate (3) triacrylate (TMP3POTA), or trimethylolpropane trimethacrylate (TMPTMA);

[0016] Preferably, the reactive diluent includes a mixture of trimethylcyclohexyl acrylate (TMCHA), neopentyl glycol propoxylate (2) diacrylate (NPGPODA), and glycerol propoxylate (4) triacrylate (GPTA);

[0017] Preferably, the mass ratio of TMCHA, NPGPODA, and GPTA is 3-5:1-5:0-3.

[0018] Specifically, for the UV-LED curable inkjet ink for food packaging, the acrylate oligomer includes at least one of amine-modified polyester acrylate oligomer, polyester acrylate oligomer, or polyurethane acrylate oligomer;

[0019] Preferably, the acrylate oligomer includes a mixture of amine-modified polyester acrylate oligomer and polyester acrylate oligomer;

[0020] Preferably, the mass ratio of the amine-modified polyester acrylate oligomer and the polyester acrylate oligomer is 4-5:1-3.

[0021] Specifically, the amine-modified polyester acrylate oligomer includes Photomer5850, Photomer 5930, etc. of IGM Company, or CN550, CN551NS, etc. of Sartomer Company;

[0022] Specifically, the oligomer of the polyester acrylate includes Photomer 5429, Photomer5432, Photomer 5500, etc. of IGM Company, or CN2262, CN2270, CN2273, CN2302, CN2303, etc. of Sartomer Company;

[0023] Preferably, the acrylate oligomer is a mixture of Photomer5930 and CN2302, and more preferably, the weight ratio of the two is Photomer5930:CN2302=(4-5):(1-3).

[0024] Specifically, the UV-LED curable inkjet ink for food packaging:

[0025] The photoinitiator includes at least one of bifunctional photoinitiators or macromolecular photoinitiators for food packaging materials; and / or,

[0026] The pigment includes the basic CMYK four-color pigments required for color printing on food packaging materials; and / or,

[0027] The additives include at least one of dispersants, leveling agents or inhibitors.

[0028] Specifically, the photoinitiator is a bifunctional photoinitiator or a macromolecular photoinitiator applicable to food packaging materials and having low migration characteristics. Among them, the bifunctional photoinitiators are such as Omnirad 819, Esacure KIP-150, Esacure KIP-160, Esacure ONE, Esacure1001M, etc.; the macromolecular photoinitiators having low migration characteristics and applicable to food packaging are such as Omnipol TX, Omnipol 910, Esacure A198, Esacure 3644, etc.

[0029] Preferably, the photoinitiator is a mixture of Omnirad 819, Esacure 1001M, Omnipol TX, Esacure3644 and Esacure A198, and more preferably, the weight ratio is: Omnirad 819:Esacure1001M:OmnipolTX:Esacure 3644:EsacureA198=(3-5):(2-4):(4-6):(4-6):(1-4).

[0030] The pigment includes the basic CMYK four-color pigments required for color printing, and the selected pigments can all be used in inks for food contact materials;

[0031] Among them, the C pigment can be C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:4, C.I. Pigment Blue 2, C.I. Pigment Blue 28, etc.;

[0032] Among them, the M pigment can be C.I. Pigment Red 122, C.I. Pigment Red 146, C.I. Pigment Violet 19, C.I. Pigment Violet 23, etc.;

[0033] Among them, the Y pigment can be C.I. Pigment Yellow 83, C.I. Pigment Yellow 93, C.I. Pigment Yellow 155, C.I. Pigment Yellow 215, etc.;

[0034] Among them, the K pigment can be C.I. Pigment Black 7.

[0035] Furthermore, the pigments in the present invention can also use spot color white such as C.I. Pigment White 6; or, spot color green such as C.I. Pigment Green 7 can be used; or, spot color orange such as C.I. Pigment Orange 16, C.I. Pigment Orange 36, C.I. Pigment Orange 61, C.I. Pigment Orange 71, etc. can be used.

[0036] As a preferred pigment scheme, the CMYK pigments are C.I. Pigment Blue 15:4, C.I. Pigment Red 122, C.I. Pigment Yellow 155 or C.I. Pigment Black 7.

[0037] In the scheme of the present invention, the additives can include at least one of a dispersant, a leveling agent or a polymerization inhibitor.

[0038] Specifically, the dispersant can be selected from BYKJET-9150, BYKJET-9151, BYKJET-9152, DISPERBYK-2200, DISPERBYK-2152, DISPERBYK-2205, etc. of BYK company, or, such as EFKAPX4350, EFKA PX4701, EFKAPX4703, EFKAPX4733, etc. of BASF company.

[0039] Specifically, the leveling agent can be selected from BYK-333, BYK-377, BYK-3500, BYK-3760, etc. of BYK company, or, such as EFKA FL3277, EFKA FL3745, EFKAFL3257, EFKAFL3883, etc. of BASF company.

[0040] Specifically, the polymerization inhibitor can be selected such as 2,6-di-tert-butyl-p-cresol (BHT), p-methoxyphenol (MEHQ), diphenylamine sulfide (PTZ), or, such as Omnistab IN 515, Omnistab IN 518, etc. of IGM company, or, such as Irgastab UV-22, Irgastab UV-25, etc. of BASF company.

[0041] As a preferred scheme, among the types of additives, the dispersant is BYKJET-9151, the leveling agent is BYK-3760, and the polymerization inhibitor is Omnistab IN 518, all of which can be used in inks for food contact materials.

[0042] The present invention also discloses a preparation method of the UV-LED curable inkjet ink for food packaging as described above, which includes the steps of mixing the five-membered nitrogen-containing heterocyclic vinyl compound, the reactive diluent, the acrylate oligomer, the photoinitiator, the pigment and the auxiliary agent according to the selected ratio, and filtering the obtained slurry.

[0043] In the specific preparation method, each component is mixed in a batching kettle, stirred at 1000 rpm for 1 hour, and filtered with a positive pressure filtering device. The aperture of the filter membrane is 1 μm. After filtration, the UV-LED curable inkjet ink containing the nitrogen-containing heterocyclic vinyl compound is obtained, which is suitable for food packaging printing.

[0044] The present invention also discloses the application of the UV-LED curable inkjet ink for food packaging in the field of food packaging printing.

[0045] The present invention also discloses a food packaging inkjet printing method, which includes the step of spraying the UV-LED curable inkjet ink as described above on the surface of a selected food packaging substrate, and the step of performing UV curing on the UV-LED curable inkjet ink by using a UV-LED having an emission wavelength between 360 and 400 nm.

[0046] As a curing method, the ink in the present invention is suitable for industrial piezoelectric nozzles such as Ricoh G5 nozzle and Konica Minolta M600SH. After the ink is printed by the industrial piezoelectric nozzle, it is cured by a 395 nm wavelength UV-LED with a light power of 16 W / cm 2 to achieve good surface curing. Further, the curing method can use a water-cooled 395 nm wavelength UV-LED curing lamp with a power of 16 W / cm 2 to achieve long-term stable use of the curing light source. Further, the curing method can use a water-cooled 395 nm wavelength UV-LED curing lamp with a power of 16 W / cm 2 and a water-cooled 365 nm wavelength UV-LED curing lamp with a power of 16 W / cm 2 for curing, which can achieve better surface curing and further reduce the possibility of transfer and migration of the food packaging material after ink printing and curing.

[0047] The present invention also discloses a food packaging obtained by inkjet printing according to the above method.

[0048] The UV-LED curable inkjet ink for food packaging of the present invention uses reactive diluents, acrylate oligomers, photoinitiators, pigments and additives as the ink formulation system. By introducing a five-membered nitrogen-containing heterocyclic vinyl compound into the ink formulation, the surface curing level of the UV-LED inkjet ink can be significantly improved, and the possibility of ink transfer and migration can be reduced, making the invention more suitable for the field of food packaging printing.

[0049] For the UV-LED curable inkjet ink for food packaging of the present invention, the photoinitiator used is a bifunctional or macromolecular photoinitiator suitable for food packaging materials and having low migration characteristics. The monomers, oligomers, additives, etc. used also meet the requirements of inks for food packaging. The UV-LED curable inkjet ink for food packaging of the present invention uses a five-membered nitrogen-containing heterocyclic vinyl compound in combination with acrylate monomers and oligomers, solving the problem of difficult surface curing when inkjet printing inks are cured by UV-LED. It has a fast curing speed, complete surface curing, and reduces the phenomenon of ink component transfer and migration after ink printing on food packaging materials.

[0050] The UV-LED curable inkjet ink for food packaging printing based on nitrogen-containing heterocyclic vinyl compounds of the present invention can achieve a high curing rate through UV-LED curing, and reduce the amount of ink transfer and migration to ensure the safety of inks for food, drugs, and cosmetics.

[0051] The UV-LED curable inkjet ink for food packaging printing based on nitrogen-containing heterocyclic vinyl compounds of the present invention can obtain a Newtonian fluid with a viscosity less than 10 cps within the shear rate range of 40°C and 100 - 1000 s, which can meet the viscosity range requirements of the inkjet print head. -1 Within the shear rate range, it can obtain a Newtonian fluid with a viscosity less than 10 cps, which can meet the requirements of the inkjet print head for the viscosity range.

[0052] For the UV-LED curable inkjet ink for food packaging printing based on nitrogen-containing heterocyclic vinyl compounds of the present invention, by directly contacting the printed surface after ink curing with food simulants, the test conditions for transfer and migration are more stringent. The samples of the UV-LED curable inkjet ink for food packaging of the present invention after curing have been subjected to migration tests for different types of food simulants such as acidic, alcohol-containing, and fat-containing foods, and can meet the requirements of the migration amounts in GB 31604.1-2015 "National Food Safety Standard General Rules for Migration Tests of Food Contact Materials and Articles" and GB 4806.14-2023 "National Food Safety Standard Inks for Food Contact Materials and Articles" of China. Detailed implementation methods

[0053] The present invention will be further described below by way of examples. The technical solutions shown in the embodiments of the present invention are only used to further illustrate the technical solutions and cannot be used as a limitation to the present invention. Any simple improvement to the technical solutions of the present invention under the premise of the concept of the present invention falls within the scope of protection required by the present invention.

[0054] Example 1

[0055] In this example, based on the five-membered nitrogen-containing heterocyclic vinyl compound as the active ingredient, the CMYK four-color inkjet inks for UV-LED curing are respectively prepared. The specific formulations of the inks of different colors are shown in Table 1 below.

[0056] Table 1 Inkjet Ink Formulations

[0057]

[0058]

[0059] In this example, the preparation method of the inkjet ink includes: selecting the raw materials and their proportioning amounts according to Table 1, mixing each raw material component, stirring at 1000 rpm / min for 1 hour, and then filtering with a positive pressure filtration device. The pore size of the filter membrane is 1 μm. After filtration, the UV-LED curable inkjet ink for food packaging printing containing nitrogen-containing heterocyclic vinyl compounds is obtained.

[0060] Example 2

[0061] For the UV-LED curable CMYK four-color inkjet ink prepared in this example, the selection of raw materials and the proportioning ratio are the same as those in Example 1, and the only difference is that the five-membered nitrogen-containing heterocyclic vinyl compound is N-vinyl oxazolidinone.

[0062] Example 3

[0063] For the UV-LED curable CMYK four-color inkjet ink prepared in this example, the selection of raw materials and the proportioning ratio are the same as those in Example 1, and the only difference is that the five-membered nitrogen-containing heterocyclic vinyl compound is N-vinyl-2-pyrrolidone.

[0064] Example 4

[0065] The UV-LED curable inkjet ink for food packaging described in this example, based on the total amount of the ink, includes the following components in mass content:

[0066]

[0067]

[0068] Among them, the specific selected components of the reactive diluent, acrylate oligomer, photoinitiator, pigment, and additive, as well as the ratio between the specific components, are the same as those in Example 1.

[0069] The preparation method of the UV-LED curable inkjet ink for food packaging in this example is the same as that in Example 1.

[0070] Example 5

[0071] The UV-LED curable inkjet ink for food packaging in this example, based on the total amount of the ink, includes the following components by mass content:

[0072]

[0073] Among them, the specific selected components of the reactive diluent, acrylate oligomer, photoinitiator, pigment, and additive, as well as the ratio between the specific components, are the same as those in Example 1.

[0074] The preparation method of the UV-LED curable inkjet ink for food packaging in this example is the same as that in Example 1.

[0075] Comparative Example 1

[0076] For the UV-LED curable inkjet ink prepared in this comparative example, the raw material selection is the same as that in Example 1. The difference is only that the addition amount of the five-membered nitrogen-containing heterocyclic vinyl compound is 5 wt%, which is lower than the lower limit of the use of this type of substance defined in the present invention. At the same time, the use ratio of the reactive diluent is adaptively adjusted to reach a total of 100%.

[0077] Comparative Example 2

[0078] For the UV-LED curable inkjet ink prepared in this comparative example, the raw material selection is the same as that in Example 1. The difference is only that the addition amount of the five-membered nitrogen-containing heterocyclic vinyl compound is 40 wt%, which is higher than the upper limit of the use of this type of substance defined in the present invention. At the same time, the use ratio of the reactive diluent is adaptively adjusted to reach a total of 100%.

[0079] Comparative Example 3

[0080] For the UV-LED curable inkjet ink prepared in this comparative example, the raw material selection and the proportioning ratio are the same as those in Example 1 respectively. The difference is only that the five-membered nitrogen-containing heterocyclic vinyl compound is not added.

[0081] Comparative Example 4

[0082] The UV-LED curable inkjet ink prepared in this comparative example has the same raw material selection and ingredient ratio as those in Example 1, except that the five-membered nitrogen-containing heterocyclic vinyl compound is not added, and an equal amount of triethylene glycol divinyl ether (DVE-3), a vinyl compound containing a vinyl reactive group, is added.

[0083]

[0084] Comparative Example 5

[0085] The UV-LED curable inkjet ink prepared in this comparative example has the same raw material selection and ingredient ratio as those in Example 1, except that the five-membered nitrogen-containing heterocyclic vinyl compound is not added, and an equal amount of vinylcyclopentane, a vinyl compound containing a five-membered ring, is added.

[0086]

[0087] In the above Comparative Examples 1-5 of the present invention, black ink was taken as the experimental example, and the specific formula is shown in Table 2 below.

[0088] Table 2 Ink Formulation of Comparative Examples (K Color Ink)

[0089]

[0090]

[0091] In the above Comparative Examples 1-5, the preparation method of the inkjet ink includes: selecting raw materials and their proportioning amounts according to Table 2, mixing each raw material component, stirring at 1000 rpm for 1 hour, filtering with a positive pressure filtration device, the pore size of the filter membrane is 1 μm, and the UV-LED curable inkjet ink is obtained after filtration.

[0092] Experimental Example

[0093] 1. Physical Property Indexes of Ink

[0094] In this experimental example, the viscosities (at 40 °C, Anton Paar MCR102 rotational rheometer, taking the average value in the shear rate range of 100-1000 s -1 ), surface tensions (at 25 °C, KRUSS K100 surface and interface instrument, platinum ring method), and particle sizes (at 25 °C, Malvern NANO ZS laser particle size analyzer) of the UV-LED curable CMYK four-color inkjet inks prepared in Example 1 and Comparative Examples 1-5 were respectively tested, and the test results are shown in Tables 3-4 below.

[0095] Table 3 Results of Physical Property Indexes of Ink in Example 1

[0096] Index C Blue Ink M Red Ink Y Yellow Ink K Black Ink Viscosity, cps 8.5±0.5 8.9±0.5 9.1±0.5 9.2±0.5 Surface Tension, mN / m 21.6 22.8 21.5 22.8 Particle Size Z-Average, nm 135 125 142 105

[0097] Table 4 Results of Physical Property Indexes of Ink for Comparative Examples 1 - 5

[0098] Index Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Viscosity, cps 11.2±0.5 7.5±0.5 12.5±0.5 8.9±0.5 9.5±0.5 Surface Tension, mN / m 23.9 22.3 23.8 22.6 23.2 Particle Size Z-Average, nm 110 103 112 104 106

[0099] As can be seen from the viscosity value data shown in Table 3 above, the UV - LED curable CMYK four - color inkjet ink prepared by the present invention can meet the requirements of the inkjet print head for the viscosity range.

[0100] As can be seen from the surface tension value data shown in Table 3 above, the UV - LED curable CMYK four - color inkjet ink prepared by the present invention can meet the requirements of the inkjet print head for the surface tension range.

[0101] As can be seen from the particle size Z - Average value data shown in Table 3 above, the UV - LED curable CMYK four - color inkjet ink prepared by the present invention can meet the requirements of the inkjet print head for the ink particle size.

[0102] As can be seen from the viscosity value data shown in Table 4 above, for the UV - LED curable black inkjet ink in Comparative Examples 1 - 5, although the viscosity value can meet the requirements of the inkjet print head for the viscosity range, temperature adjustment is required to better meet the printing requirements.

[0103] As can be seen from the surface tension value data shown in Table 4 above, the UV - LED curable black inkjet ink in Comparative Examples 1 - 5 can meet the requirements of the inkjet print head for the surface tension range.

[0104] As can be seen from the particle size Z - Average value data shown in Table 4 above, the UV - LED curable black inkjet ink in Comparative Examples 1 - 5 can meet the requirements of the inkjet print head for the ink particle size.

[0105] 2. Curing Performance

[0106] Take the UV - LED curable CMYK four - color inkjet ink prepared in Example 1 respectively, and use the Ricoh print head GEN5 for printing, controlling the printing speed at 60 m / min. During the experiment, the printing fluidity of each color inkjet ink is good, and there is no ink - flying phenomenon.

[0107] After printing, directly use a water - cooled 16 / cm 2 395 nm wavelength UV - LED curing lamp with water cooling and then a water - cooled 16 W / cm 2 365 nm wavelength UV - LED curing lamp for curing. After curing, the surface of the printed pattern is completely cured, there is no phenomenon of incomplete curing and surface stickiness, the surface is dry, and there is basically no phenomenon of transferring ink components to the back of the printed matter.

[0108] Another black inkjet ink prepared in Comparative Examples 1-5 was printed using a Ricoh GEN5 printhead, with the printing speed controlled at 60 m / min, and there was flying ink during printing. Immediately after printing, it was cured using a 395 nm wavelength UV-LED curing lamp with water cooling at 16 W / cm 2 and a 365 nm wavelength UV-LED curing lamp with water cooling at 16 W / cm 2 . The surface of the printed pattern was not fully cured, and there was insufficient curing, resulting in a sticky surface, and the phenomenon of transferring ink components to the back of the printed material occurred.

[0109] It can be seen that in Comparative Examples 1-3, due to the inappropriate dosage of the nitrogen-containing heterocyclic vinyl compound, and in Comparative Examples 4-5, although the same compound containing a vinyl photocuring group was used, but the structure was not a nitrogen-containing heterocyclic compound, both showed the phenomenon of insufficient surface curing.

[0110] In the scheme of Comparative Example 4, both DVE-3 and the used five-membered ring nitrogen-containing vinyl compound contain vinyl reactive groups, and even actually contain two reactive groups, but because they do not have a nitrogen-containing heterocyclic structure, after being added to the formulation, they do not have the effect of improving surface curing.

[0111] In the scheme of Comparative Example 5, the selected vinyl pentane structure was used as a comparative reference. Although this substance contains the same vinyl reactive group, its five-membered ring is not a nitrogen-containing heterocyclic structure, so it will not have the effect of improving surface curing either.

[0112] 3. Ink migration test

[0113] In this experimental example, according to the food contact material migration test method, for the samples after the ink was cured, the following migration tests were carried out for different types of food simulants. The test conditions and limits refer to China's GB 31604.1-2015 "National Food Safety Standard General Rules for Migration Tests of Food Contact Materials and Articles" and GB 4806.14-2023 "National Food Safety Standard Inks for Food Contact Materials and Articles", as well as the European Commission's AP(2004)1 resolution, (EU) No 10 / 2011 and its amending directive (EU) 2020 / 1245; among them,

[0114] (1) Acidic food simulant, 3% acetic acid aqueous solution (W / V) (first migration), soaking time 2 hours, soaking temperature 70 degrees Celsius, maximum allowable total migration amount 10 mg / dm 2 ;

[0115] (2) Food simulants with 20% (volume fraction) < ethanol ≤ 50% (volume fraction), 50% ethanol aqueous solution (V / V) (first migration), soaking time 2 hours, soaking temperature 70 °C, maximum allowable total migration amount 10 mg / dm 2 ;

[0116] (3) Food simulants with ethanol content > 50% (volume fraction), 95% ethanol aqueous solution (V / V) (first migration), soaking time 2 hours, soaking temperature 60 °C, maximum allowable total migration amount 10 mg / dm 2 ;

[0117] (4) Grease and foods with greasy surfaces food simulants, using isooctane (first migration), soaking time 0.5 hours, soaking temperature 40 °C, maximum allowable total migration amount 10 mg / dm 2 .

[0118] For the migration test method described in this experimental example, the printed surface after curing the CMYK four-color ink in Experimental Example 2 was directly contacted with each food simulant solution, which is more stringent than the test conditions for transfer migration. The specific migration amount test results are shown in Table 5 below.

[0119] Table 5 Ink Migration Test Results

[0120]

[0121] The above test results show that for the ink using the nitrogen-containing heterocyclic vinyl compound in the present invention, after UV-LED curing, even if the whole ink is subjected to an immersion migration test, the total migration amount of the ink is much less than the maximum allowable total migration amount requirement for food contact materials, indicating that the ink has a good surface curing level under the curing conditions described in the present invention and can be used as an ink for food packaging printing.

[0122] For the inks in the comparative examples 1-5 of the present invention, it can be determined from the above curing experiments that they cannot be used as inks for food packaging printing, so no migration tests were carried out.

[0123] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A UV-LED curable inkjet ink for food packaging, characterized in that, Based on the total amount of the ink, it comprises components with the following mass contents:

2. The UV-LED curable inkjet ink for food packaging according to claim 1, characterized in that, The five-membered nitrogen-containing heterocyclic vinyl compound includes at least one of N-vinyl oxazolidinone, N-vinyl-2-pyrrolidone or 5-methyl-3-vinyl-2-oxazoline.

3. The UV-LED curable inkjet ink for food packaging according to claim 1 or 2, characterized in that The reactive diluent includes at least one of monofunctional acrylate or methacrylate monomers, difunctional acrylate or methacrylate monomers, or trifunctional acrylate or methacrylate monomers.

4. The UV-LED curable inkjet ink for food packaging according to claim 3, wherein: The monofunctional acrylate or methacrylate monomer includes at least one of trimethylolcyclohexyl acrylate (TMCHA), benzyl acrylate (BZA), isobornyl acrylate (IBOA), 4-tert-butylcyclohexyl acrylate (TBCHA), lauryl acrylate (LA), cyclotrimethylolpropane formal acrylate (CTFA), benzyl methacrylate (BZMA) or cyclotrimethylolpropane formal methacrylate (CTFMA); and / or, The difunctional acrylate or methacrylate monomer includes at least one of neopentyl glycol propoxylate (2) diacrylate (NPGPODA), 3-methyl-1,5-pentanediol diacrylate (MPDDA), ethylene glycol dimethacrylate (EGDMA), triethylene glycol dimethacrylate (TEGDMA) or 1,4-butanediol dimethacrylate (BDDMA); and / or, The trifunctional acrylate or methacrylate monomer includes at least one of glycerol propoxylate (4) triacrylate (GPTA), trimethylolpropane ethoxylate (3) triacrylate (TMP3EOTA), trimethylolpropane propoxylate (3) triacrylate (TMP3POTA) or trimethylolpropane trimethacrylate (TMPTMA); Preferably, the reactive diluent includes a mixture of trimethylolcyclohexyl acrylate (TMCHA), neopentyl glycol propoxylate (2) diacrylate (NPGPODA) and glycerol propoxylate (4) triacrylate (GPTA); Preferably, the mass ratio of TMCHA, NPGPODA and GPTA is 3-5:1-5:0-3.

5. The UV-LED curable inkjet ink for food packaging according to any one of claims 1-4, characterized in that The acrylate oligomer includes at least one of amine-modified polyester acrylate oligomer, polyester acrylate oligomer or polyurethane acrylate oligomer; Preferably, the acrylate oligomer includes a mixture of amine-modified polyester acrylate oligomer and polyester acrylate oligomer; Preferably, the mass ratio of the amine-modified polyester acrylate oligomer and the polyester acrylate oligomer is 4-5:1-3.

6. The UV-LED curable inkjet ink for food packaging according to any one of claims 1-5, wherein: The photoinitiator includes at least one of bifunctional photoinitiators or macromolecular photoinitiators for food packaging materials; and / or, The pigments include the basic CMYK four-color pigments required for color spraying on food packaging materials; and / or, The additives include at least one of a dispersant, a leveling agent or a polymerization inhibitor.

7. A preparation method of a UV-LED curable inkjet ink for food packaging according to any one of claims 1-6, characterized in that, It includes the steps of mixing the nitrogen-containing heterocyclic vinyl compound with a five-membered ring, an active diluent, an acrylate oligomer, a photoinitiator, pigments and additives according to a selected ratio, and filtering the obtained slurry.

8. Application of the UV-LED curable inkjet ink for food packaging according to any one of claims 1-6 in the field of food packaging printing.

9. A food packaging inkjet printing method, characterized in that, It includes the step of spraying the UV-LED curable inkjet ink according to any one of claims 1-6 on the surface of a selected food packaging substrate, and the step of UV-curing the UV-LED curable inkjet ink using a UV-LED having an emission wavelength between 360 and 400 nm.

10. A food packaging obtained by inkjet printing according to the method described in claim 9.

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