Yellowing-resistant UV ink for packaging and preparation method thereof

Abstract

The invention discloses a yellowing-resistant UV ink for packaging and a preparation method thereof, and belongs to the technical field of ink preparation, the yellowing-resistant UV ink comprises the following components by weight: 100 parts of an acrylate monomer and / or an acrylate prepolymer, 2-7 parts of a photoinitiator, 1-20 parts of a pigment, 4-24 parts of a yellowing-resistant filler, and 1-20 parts of an auxiliary agent; the anti-yellowing filler is prepared by taking ZIF-8 as a template and mixed salt of nickel and manganese as an etching agent and a coating material to prepare a nano material with a hollow structure, and then sequentially grafting amino and stilbene dicarboxylic acid on the surface to introduce a coating layer with a stilbene structure. The UV ink disclosed by the invention has good yellowing resistance while keeping an efficient drying rate.

Description

Technical Field

[0001] The present invention relates to the technical field of ink preparation, and particularly relates to a yellowing-resistant UV ink for packaging and a preparation method thereof. Background Art

[0002] UV ink is a kind of printing ink. Different from ordinary oil-based or water-based inks that can be cured by relying on the reaction of curing agents or the volatilization of solvents, UV ink is irradiated with a UV light source (usually a wavelength band centered on ultraviolet light of 365 nm). By irradiating the printed matter that has just left the impression cylinder with ultraviolet light, the photoinitiator contained in the system is stimulated by the UV light source, causing the photoinitiator molecules in the imprinted ink layer to decompose into highly activated atoms or atomic groups, thereby inducing a photochemical reaction of the ink components containing unsaturated bonds and promoting molecular cross-linking polymerization to form a cured film. UV ink has the characteristics of fast drying speed and high surface gloss, and is widely used in the field of packaging printing.

[0003] Due to the existence of photosensitive active initiator molecules, the cured UV ink is also prone to absorbing ultraviolet light in the environment, resulting in poor aging resistance and weather resistance of the ink layer, and easy yellowing. Yellowing will cause the gloss of the ink to decrease or even crack, affecting the packaging quality. And it is not feasible to add ordinary ultraviolet absorbers or light stabilizers like other oil-based or water-based inks, because when ultraviolet absorbers are added, the photoinitiator in the UV ink system may not be able to obtain sufficient energy to cure completely, and most of it is absorbed by the ultraviolet absorber and converted into heat energy. Summary of the Invention

[0004] In view of the above problems, the present invention provides a yellowing-resistant UV ink for packaging and a preparation method thereof.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A yellowing-resistant UV ink for packaging, by weight, comprises the following components: 100 parts of acrylate monomer and / or acrylate prepolymer, 2 - 7 parts of photoinitiator, 1 - 20 parts of pigment, 4 - 24 parts of yellowing-resistant filler, and 1 - 20 parts of auxiliary agent;

[0007] The preparation method of the yellowing-resistant filler comprises the following steps:

[0008] (1) Weigh zinc nitrate and dissolve it in a methanol solvent to obtain a zinc nitrate solution. Under stirring conditions, add the zinc nitrate solution to a methanol solution of 2-methylimidazole, stir well and incubate at room temperature for 12 - 24 h, separate the precipitate and wash it with an alcohol solvent, and then dry it under vacuum to obtain a template;

[0009] (2) Disperse the template in an alcohol solvent to obtain a dispersion solution; dissolve a soluble nickel salt and a soluble manganese salt in an alcohol solvent to obtain a salt solution. Under stirring conditions, mix the dispersion solution and the salt solution, put them into a high-pressure reaction kettle, and keep the reaction at 110 - 140 °C and autogenous pressure for 20 - 30 h. After the reaction is completed, separate the precipitate, wash it with deionized water and alcohol solvent respectively, and then dry it under vacuum to obtain the hollow nanomaterial;

[0010] (3) Disperse the hollow nanomaterial in an alcohol-water mixed solution of an amino silane coupling agent, and stir and react at 50 - 70 °C for 1 - 4 h. After the reaction is completed, separate the precipitate, wash it, and then disperse it again in an alcohol solvent. Add dicyclohexylcarbodiimide and 4,4'-stilbenedicarboxylic acid, and stir and react at 40 - 80 °C for 10 - 20 h. After the reaction is completed, separate the precipitate, wash it, and dry it under vacuum to obtain the product.

[0011] In some preferred embodiments, the molar ratio of zinc nitrate to 2-methylimidazole in step (1) is 1:4.

[0012] In some preferred embodiments, the mass ratio of the template to the soluble nickel salt and the soluble manganese salt in step (2) is 1:(1.1 - 1.5):(1 - 1.3).

[0013] In some preferred embodiments, the mass ratio of the hollow nanomaterial to the amino silane coupling agent, dicyclohexylcarbodiimide, and 4,4'-stilbenedicarboxylic acid in step (3) is 10:(0.4 - 0.7):(0.2 - 0.5):(3.5 - 5.2).

[0014] In some preferred embodiments, the amino silane coupling agent is one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, phenylaminomethyltrimethoxysilane, and phenylaminomethyltriethoxysilane.

[0015] In some preferred embodiments, the acrylate monomer is one or more of monofunctional acrylate with a chain hydrocarbon, monofunctional acrylate with a non-aromatic carbon ring, monofunctional acrylate with an aromatic carbon ring, monofunctional acrylate with an oxygen-containing heterocycle, and monofunctional acrylate with an alcohol or ether structure.

[0016] In some preferred embodiments, the photoinitiator is one or more of 1-hydroxy-cyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-phenylpropan-1-one, 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide, 2-hydroxy-2-methyl-4'-hydroxyethoxyphenylpropan-1-one.

[0017] In some preferred embodiments, the pigment is one or more of phthalocyanine pigments, carbon black, and titanium white.

[0018] In some preferred embodiments, the additives are one or more of dispersants, emulsifiers, stabilizers, softeners, preservatives, defoamers, pH regulators, adhesion promoters, antistatic agents, thickeners, and light absorbers.

[0019] The second aspect of the present invention is to provide a method for preparing the yellowing-resistant UV ink for packaging, comprising the following steps:

[0020] S1. Weigh each raw material according to the proportion for standby;

[0021] S2. Mix the acrylate monomer and / or acrylate prepolymer, the photoinitiator, and the additives, stir well until completely dissolved, then add the pigment and the yellowing-resistant filler, and continue to stir until evenly dispersed to obtain the yellowing-resistant UV ink for packaging.

[0022] The beneficial effects of the present invention are as follows:

[0023] Aiming at the problem that it is difficult for the existing UV inks to improve weather resistance and yellowing resistance simply by adding stabilizers, the present invention provides a yellowing-resistant UV ink for packaging through component improvement. The UV ink has good yellowing resistance while maintaining a high drying rate. Specifically, on the basis of a conventional acrylate ink system, the present invention introduces a modified filler with yellowing resistance. The yellowing-resistant filler uses metal-organic framework material ZIF-8 as a template, and a mixed salt of nickel and manganese as an etching agent and a coating material to prepare a nanomaterial with a hollow structure composed of nickel and manganese oxides and hydroxides. Then, through the coupling reaction of a silane coupling agent, an amino group is grafted on the surface, and after activation, it is grafted with stilbene dicarboxylic acid through amidation to introduce a coating layer with a stilbene structure on the surface of the hollow nanomaterial. Utilizing the multiple light reflection and scattering properties of the hollow nanostructure, it can reduce the absorption of ultraviolet light in the environment by the ink layer to improve the yellowing resistance. At the same time, by utilizing the photoisomerization response of the stilbene structure, on the one hand, it can reduce the absorption of ultraviolet light for initiation by the hollow nanomaterial, and on the other hand, the isomerized vinyl can participate in vinyl polymerization to improve the connection and stability between the ink layer and the filler. Detailed embodiments

[0024] The present invention is further described in conjunction with the following examples.

[0025] Example 1

[0026] A yellowing-resistant UV ink for packaging, comprising, by weight, 35 parts of methyl acrylate, 20 parts of isobornyl acrylate, 10 parts of benzyl acrylate, 15 parts of cyclotrimethylolpropane formal acrylate, 20 parts of ethoxyethoxyethyl acrylate, 6 parts of photoinitiator, 5 parts of pigment, 17 parts of yellowing-resistant filler, 1 part of dispersant, and 0.6 parts of defoamer;

[0027] The preparation method of the yellowing-resistant filler comprises the following steps:

[0028] (1) Weighing zinc nitrate and dissolving it in a methanol solvent to obtain a zinc nitrate solution with a concentration of 0.12 mol / L, adding the zinc nitrate solution to a methanol solution of 2-methylimidazole (with a concentration of 0.48 mol / L) under stirring conditions, stirring sufficiently, incubating at room temperature for 24 hours, separating the precipitate, washing it with an alcohol solvent, and vacuum drying it to obtain a template; the molar ratio of the zinc nitrate to the 2-methylimidazole is 1:4;

[0029] (2) dispersing the template in an ethanol solvent to obtain a dispersed solution with a concentration of 7 g / L; dissolving nickel nitrate and manganese nitrate in an ethanol solvent to obtain a salt solution (the concentration of nickel ions and manganese ions are both 1 mol / L), mixing the dispersed solution and the salt solution under stirring conditions, placing the mixture in a high-pressure reactor, and reacting the mixture at 130° C. and autogenous pressure for 24 hours. After the reaction is completed, separating the precipitate, washing it with deionized water and ethanol solvent respectively, and vacuum drying it to obtain a hollow nanomaterial; the mass ratio of the template to the nickel nitrate and the manganese nitrate is 1:1.3:1.2;

[0030] (3) dispersing the hollow nanomaterial in a mixed solution of γ-aminopropyltrimethoxysilane and ethanol and water (v / v=9:1, coupling agent concentration is 1 g / L), stirring and reacting at 60° C. for 2 h, separating the precipitate after the reaction is completed, washing and dispersing it again in an ethanol solvent, adding dicyclohexylcarbodiimide and 4,4'-stilbene dicarboxylic acid (CAS No.: 100-31-2), stirring and reacting at 50° C. for 12 h, separating the precipitate after the reaction is completed, washing, and vacuum drying to obtain;

[0031] The mass ratio of the hollow nano material to the aminosilane coupling agent, the dicyclohexylcarbodiimide, and the 4,4'-stilbene dicarboxylic acid is 10:0.5:0.3:4;

[0032] The photoinitiator is 2-hydroxy-2-methyl-phenylpropan-1-one (1173); the pigment is titanium white; the dispersant is dispersant 5040; the defoamer is defoamer byk-028;

[0033] The preparation method of the yellowing-resistant UV ink for packaging comprises the following steps:

[0034] S1. Weigh each raw material according to the proportion for standby;

[0035] S2. Mix the methyl acrylate, isobornyl acrylate, benzyl acrylate, trimethylolpropane formal acetal acrylate, ethoxyethoxyethyl acrylate, the photoinitiator, the dispersant and the defoamer, stir fully until completely dissolved, then add the pigment and the yellowing-resistant filler, and continue to stir until uniformly dispersed to obtain the yellowing-resistant UV ink for packaging.

[0036] Example 2

[0037] A UV ink for packaging, by weight, comprises 35 parts of methyl acrylate, 20 parts of isobornyl acrylate, 10 parts of benzyl acrylate, 15 parts of trimethylolpropane formal acetal acrylate, 20 parts of ethoxyethoxyethyl acrylate, 6 parts of photoinitiator, 5 parts of pigment, 17 parts of hollow nanomaterial, 1 part of dispersant, and 0.6 part of defoamer;

[0038] The preparation method of the hollow nanomaterial comprises the following steps:

[0039] (1) Weigh zinc nitrate and dissolve it in a methanol solvent to obtain a zinc nitrate solution with a concentration of 0.12 mol / L. Under stirring conditions, add the zinc nitrate solution to a methanol solution of 2-methylimidazole (concentration: 0.48 mol / L), stir fully, incubate at room temperature for 24 h, separate the precipitate, wash it with an ethanol solvent, and vacuum dry it to obtain a template; the molar ratio of zinc nitrate to 2-methylimidazole is 1:4;

[0040] (2) Disperse the template in an ethanol solvent to obtain a dispersion solution with a concentration of 7 g / L; dissolve nickel nitrate and manganese nitrate in an ethanol solvent to obtain a salt solution (the concentrations of nickel ions and manganese ions are both 1 mol / L). Under stirring conditions, mix the dispersion solution and the salt solution, put them into a high-pressure reaction kettle, keep the temperature at 120 °C and the self-generated pressure for 24 h. After the reaction is completed, separate the precipitate, wash it with deionized water and an ethanol solvent respectively, and vacuum dry it to obtain the hollow nanomaterial; the mass ratio of the template to nickel nitrate and manganese nitrate is 1:1.3:1.2;

[0041] The photoinitiator is 2-hydroxy-2-methyl-1-phenylpropan-1-one (1173); the pigment is titanium white; the dispersant is dispersant 5040; the defoamer is defoamer byk-028;

[0042] The preparation method of the UV ink is the same as that in Example 1.

[0043] Example 3

[0044] A UV ink for packaging, by weight, comprises 35 parts of methyl acrylate, 20 parts of isobornyl acrylate, 10 parts of benzyl acrylate, 15 parts of trimethylolpropane formal acrylate, 20 parts of ethoxyethoxyethyl acrylate, 6 parts of photoinitiator, 5 parts of pigment, 17 parts of calcium carbonate, 1.2 parts of light stabilizer, 1 part of dispersant, and 0.6 part of defoamer;

[0045] The light stabilizer is BASF light stabilizer 770; the photoinitiator is 2-hydroxy-2-methyl-1-phenylpropan-1-one (1173); the pigment is titanium white; the dispersant is dispersant 5040; the defoamer is defoamer byk-028;

[0046] The preparation method of the UV ink is the same as that in Example 1.

[0047] Example 4

[0048] A UV ink for packaging, by weight, comprises 35 parts of methyl acrylate, 20 parts of isobornyl acrylate, 10 parts of benzyl acrylate, 15 parts of trimethylolpropane formal acrylate, 20 parts of ethoxyethoxyethyl acrylate, 6 parts of photoinitiator, 5 parts of pigment, 17 parts of calcium carbonate, 1 part of dispersant, and 0.6 part of defoamer;

[0049] The photoinitiator is 2-hydroxy-2-methyl-1-phenylpropan-1-one (1173); the pigment is titanium white; the dispersant is dispersant 5040; the defoamer is defoamer byk-028;

[0050] The preparation method of the UV ink is the same as that in Example 1.

[0051] The performance of the UV inks described in Examples 1-4 was tested. For adhesion, the alcohol test method was used. A printed sheet was taken and placed on a clean flat work surface (with the ink surface facing up); a weight was wrapped with a cotton cloth and the white cotton cloth was moistened with an appropriate amount of alcohol; the printed surface was wiped 10-15 times (one round trip counted as one time) with the white cotton cloth moistened with alcohol; after wiping, it was checked whether there was any ink peeling on the printed surface and whether the surface of the white cotton cloth was ink-stained. The score ranged from 10 (no obvious ink peeling) as the highest to 0 (more than 80% ink peeling) as the lowest; for drying property, 0.125 mL of ink was used to prepare a color spreading sample on an aluminum cardboard. After irradiation with UV light (lamp power 100 W / cm, irradiation energy 20 mJ / (cm 2 ·time)), it was placed on a flat plate with the printed surface facing up, and the tail of a paper clip was used to scratch forcefully towards the edge. The ink mark in the blank part was inspected to judge the drying degree. The score ranged from 10 (fully cured) as the highest to 0 (not curable) as the lowest; for abrasion resistance, GB / T 3008-2008 was referred to; long-term sunlight was simulated by irradiating with an ultraviolet lamp, the irradiation energy was 3.8 J / (cm 2 ·time), and the irradiation times were 30 times. The yellowing resistance was evaluated by measuring its whiteness value and making a comparison; the measurement results were as follows:

[0052] Adhesion / minute Drying property / minute Abrasion resistance / grade Whiteness before irradiation / ° Whiteness after irradiation / ° Example 1 9 9 10 66 60 Example 2 9 6 10 65 31 Example 3 9 7 10 69 54 Example 4 9 9 10 69 36

[0053] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A yellowing-resistant UV ink for packaging, characterized in that: The composition comprises the following components by weight: 100 parts of acrylate monomer and / or acrylate prepolymer, 2-7 parts of photoinitiator, 1-20 parts of pigment, 4-24 parts of yellowing-resistant filler, and 1-20 parts of auxiliary agent; The preparation method of the yellowing-resistant filler comprises the following steps: (1) weighing zinc nitrate and dissolving it in a methanol solvent to obtain a zinc nitrate solution, adding the zinc nitrate solution to a methanol solution of 2-methylimidazole under stirring conditions, stirring sufficiently, and incubating at room temperature for 12-24 hours, separating the precipitate, washing it with an alcohol solvent, and vacuum drying it to obtain a template; (2) dispersing the template in an alcohol solvent to obtain a dispersed solution; dissolving a soluble nickel salt and a soluble manganese salt in an alcohol solvent to obtain a salt solution, mixing the dispersed solution and the salt solution under stirring conditions, placing the mixture in a high-pressure reactor, and reacting the mixture at 110-140° C. and autogenous pressure for 20-30 hours. After the reaction is completed, separating the precipitate, washing it with deionized water and an alcohol solvent respectively, and vacuum drying the mixture to obtain a hollow nanomaterial; (3) dispersing the hollow nanomaterial in an alcohol-water mixed solution of an aminosilane coupling agent, stirring and reacting at 50-70° C. for 1-4 hours, separating and precipitating after the reaction is completed, washing and dispersing again in an alcohol solvent, adding dicyclohexylcarbodiimide and 4,4'-stilbene dicarboxylic acid, stirring and reacting at 40-80° C. for 10-20 hours, separating and precipitating after the reaction is completed, washing, and vacuum drying to obtain the product.

2. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: The molar ratio of the zinc nitrate to the 2-methylimidazole in step (1) is 1:

4.

3. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: In step (2), the mass ratio of the template to the soluble nickel salt and the soluble manganese salt is 1:(1.1-1.5):(1-1.3).

4. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: In step (3), the mass ratio of the hollow nanomaterial to the aminosilane coupling agent, the dicyclohexylcarbodiimide, and the 4,4'-stilbene dicarboxylic acid is 10:(0.4-0.7):(0.2-0.5):(3.5-5.2).

5. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: The aminosilane coupling agent is one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, anilinomethyltrimethoxysilane and anilinomethyltriethoxysilane.

6. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: The acrylate monomer is one or more of monofunctional acrylate with chain hydrocarbon, monofunctional acrylate with non-aromatic carbon ring, monofunctional acrylate with aromatic carbon ring, monofunctional acrylate containing oxygen heterocycle, and monofunctional acrylate containing alcohol or ether structure.

7. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: The photoinitiator is one or more of 1-hydroxy-cyclohexyl benzophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-phenylacetone-1, 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide, and 2-hydroxy-2-methyl-p-hydroxyethyl ether phenylacetone-1.

8. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: The pigment is one or more of phthalocyanine pigment, carbon black and titanium dioxide.

9. The yellowing-resistant UV ink for packaging according to claim 1, characterized in that: The auxiliary agent is one or more of a dispersant, an emulsifier, a stabilizer, a softener, a preservative, a defoamer, a pH adjuster, an adhesion promoter, an antistatic agent, a thickener, and a light absorber.

10. The method for preparing a yellowing-resistant UV ink for packaging according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Weigh each raw material in proportion and set aside; S2. Mix the acrylate monomer and / or acrylate prepolymer, the photoinitiator and the auxiliary agent, stir them thoroughly until they are completely dissolved, then add the pigment and the yellowing-resistant filler, continue stirring until they are evenly dispersed, and obtain the yellowing-resistant UV ink for packaging.