Printing ink with high stability and low curing energy and preparation method thereof

Abstract

The invention discloses printing ink with high stability and low curing energy and a preparation method thereof, and the printing ink is prepared from the following components in parts by weight: 10 to 40 parts of epoxy acrylate, 5 to 40 parts of acrylate monomer, 10 to 30 parts of pigment powder, 5 to 20 parts of rosin resin, 5 to 15 parts of photoinitiator, 0.1 to 1 part of dispersing agent, 0.1 to 0.3 part of dithiocarbamate and 0.2 to 0.4 part of nitroso amine compound. And 0.2 to 0.4 part of a coupling agent. According to the high-stability low-curing-energy printing ink and the preparation method thereof provided by the invention, through the synergistic effect of the dithiocarbamate, the nitroso amine compound and the coupling agent, the printing ink can be cured at low energy consumption, and the printing ink has relatively good stability in a storage stage.

Description

Technical Field

[0001] The present invention relates to the technical field of inks, and more specifically, to an ink with high stability and low curing energy and a preparation method thereof. Background Art

[0002] With the continuous expansion of the application scope of inks, requirements for the curing energy consumption of inks have gradually been put forward in the environmental protection field. Traditional inks need to be irradiated with ultraviolet lamps with relatively large energy consumption to achieve the curing of inks, which causes energy consumption waste during the ink curing process. In order to reduce energy consumption, it is necessary to continuously develop low-energy-curing ink products, such as inks that can be cured by LED lamp irradiation.

[0003] In order to meet the low-power demand, the existing inks need to continuously increase the content of photoinitiators in the inks so as to ensure that the inks can be cured under low-power LED lamps. However, increasing the content of photoinitiators will cause a new problem of poor storage stability of the inks. Specifically, the increase in photoinitiators will cause abnormal viscosity or stratification of the inks, significantly shortening the storage time of the inks and affecting the quality stability of the inks. Therefore, the problem that the existing inks urgently need to solve is that in order to achieve low-energy curing, the total amount of photoinitiators needs to be increased, resulting in poor storage stability. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides an ink with high stability and low curing energy and a preparation method thereof. Through the synergistic effect of dithiocarbamate, nitrosoamine compound and coupling agent, the ink can be cured with low energy consumption and has good stability during the storage stage.

[0005] In order to achieve the above object, the present application adopts the following technical solutions:

[0006] An ink with high stability and low curing energy, comprising the following components in parts by weight: 10 - 40 parts of epoxy acrylate, 5 - 40 parts of acrylate monomer, 10 - 30 parts of pigment powder, 5 - 20 parts of rosin resin, 5 - 15 parts of photoinitiator, 0.1 - 1 part of dispersant, 0.1 - 0.3 part of dithiocarbamate, 0.2 - 0.4 part of nitrosoamine compound, and 0.2 - 0.4 part of coupling agent.

[0007] Further, the mass ratio of the dithiocarbamate to the nitrosoamine compound is 1:1 - 1.5.

[0008] Further, the coupling agent is a silane coupling agent.

[0009] Further, the dithiocarbamate is any one of sodium dimethyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc dibutyldithiocarbamate, and sodium dibutyldithiocarbamate.

[0010] Further, the nitrosoamine compound is any one of N-nitrosodiphenylamine, N-nitrosodimethylamine, N-nitrosodiethylamine, and N-nitroso-N-methyl-4-aminobenzamide.

[0011] Further, the photoinitiator is a composite of a cleavage-type photoinitiator and a hydrogen-abstraction type photoinitiator, and the mass ratio of the cleavage-type photoinitiator to the hydrogen-abstraction type photoinitiator is 1:1 to 3:1.

[0012] Further, the cleavage-type photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; the hydrogen-abstraction type photoinitiator is 2-isopropylthioxanthone.

[0013] Further, the acrylate monomer includes a bifunctional acrylate monomer and a monofunctional acrylate monomer.

[0014] A method for preparing an ink with high stability and low curing energy includes the following steps:

[0015] Add epoxy acrylate and acrylate monomer to a reaction kettle, and stir and mix at 40-50 °C for 30-40 minutes;

[0016] Add pigment powder and dispersant, and stir at high speed for 60-90 minutes to fully disperse them;

[0017] Raise the temperature to 60-70 °C, add rosin resin, and stir until completely dissolved;

[0018] Cool to room temperature, and sequentially add photoinitiator, dithiocarbamate, nitrosoamine compound, and coupling agent, and continue to stir for 30-60 minutes to obtain an ink with high stability and low curing energy.

[0019] Further, the epoxy acrylate is a modified epoxy acrylate, and the modification process of the epoxy acrylate includes: introducing a siloxane group into the epoxy acrylate.

[0020] Compared with the prior art, the beneficial effects of the present invention are: in this application, dithiocarbamate, nitrosoamine compound, and coupling agent form a system-stable synergistic system. During the storage stage, the sulfur atom of dithiocarbamate can have a weak interaction with the partially positively charged nitrogen atom in the nitrosoamine compound to form a preliminary complex structure; at the same time, the active groups in the coupling agent molecule can interact with polar molecules in the ink through hydrogen bonds or van der Waals forces, prompting the three to form a relatively stable ternary complex; the ternary complex can efficiently capture free radicals that may be generated in the system, thereby effectively avoiding premature curing of the ink; ensuring the stability of the ink.

[0021] During the ink curing stage, the ternary complex structure formed in the storage stage rearranges, the disulfide bond in the dithiocarbamate breaks, generating highly reactive sulfur radicals; the nitroso group (-NO) in the nitrosoamine compound reacts with the coupling agent molecule to form an intermediate with strong nucleophilic or electrophilic properties; the sulfur radicals and the intermediate interact with the film-forming substance molecules in the ink, promoting the formation of chemical bonds between the components; thereby achieving low-energy curing of the ink.

[0022] Through the synergistic system formed by dithiocarbamate, nitrosoamine compound and coupling agent, this application overcomes the traditional technical prejudice in the prior art that "high curing rate must sacrifice stability" for environmentally friendly inks, and achieves the dual effects of low-energy curing and high stability of the ink. Detailed implementation mode

[0023] The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention. Modifications or substitutions made to the methods, steps or conditions of the present invention without departing from the spirit and essence of the present invention all fall within the protection scope of the present invention. Unless otherwise specified, the experimental materials, reagents, instruments, etc. used in the embodiments of the present invention can be obtained commercially; unless specifically specified, all technical means in the embodiments of the present invention are conventional means well known to those skilled in the art.

[0024] An ink with high stability and low curing energy provided by the present invention comprises the following components in parts by weight: 10 - 40 parts of epoxy acrylate, 5 - 40 parts of acrylate monomer, 10 - 30 parts of pigment powder, 5 - 20 parts of rosin resin, 5 - 15 parts of photoinitiator, 0.1 - 1 part of dispersant, 0.1 - 0.3 part of dithiocarbamate, 0.2 - 0.4 part of nitrosoamine compound, and 0.2 - 0.4 part of coupling agent.

[0025] If the weight fraction of dithiocarbamate in this application is less than 0.05 part, an effective ternary synergistic system cannot be formed. If it is greater than 0.5 part, it will cause the ink to precipitate. In this application, the silane coupling agent needs to cover 60% of the pigment surface area, so its weight fraction is set to 0.2 - 0.4.

[0026] Specifically, in this application, the photoinitiator is a complex of a cleavage-type photoinitiator and a hydrogen-abstraction type photoinitiator, and the mass ratio of the cleavage-type photoinitiator to the hydrogen-abstraction type photoinitiator is 1:1 to 3:1. Specifically, the cleavage-type photoinitiator can be 2,4,6-trimethylbenzoyl-diphenylphosphine oxide or other cleavage-type photoinitiators in the prior art; the hydrogen-abstraction type photoinitiator can be 2-isopropylthioxanthone or other hydrogen-abstraction type photoinitiators in the prior art.

[0027] Specifically, the mass ratio of dithiocarbamate to nitrosoamine compound is 1:1 - 1.5. The dithiocarbamate can specifically be any one of sodium dimethyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc dibutyldithiocarbamate, and sodium dibutyldithiocarbamate. The nitrosoamine compound can be any one of N-nitrosodiphenylamine, N-nitrosodimethylamine, N-nitrosodiethylamine, and N-nitroso-N-methyl-4-aminobenzamide. The coupling agent is a silane coupling agent, which can specifically be γ-methacryloxypropyltrimethoxysilane, etc.

[0028] In this application, the dithiocarbamate, nitrosoamine compound, and coupling agent form a systematically stable synergistic system, which is used to maintain high stability of the ink during storage, can be cured by low-power irradiation of an LED lamp during curing, and can ensure that the ink layer after curing has good performance.

[0029] In this application, the sulfur atom (S) in the dithiocarbamate has a high electron cloud density and can form an S→N coordination bond with the partially positively charged nitrogen atom (N + δ) in the nitrosoamine compound, that is, a preliminary complex structure is formed. At the same time, the active groups of the silane coupling agent (such as the siloxane group in the silane coupling agent, like γ-methacryloxypropyltrimethoxysilane, etc.) can interact with the polar molecules in the ink (including the dithiocarbamate and nitrosoamine compounds) through hydrogen bonds or van der Waals forces, promoting the formation of a relatively stable ternary complex by the three. The ternary complex has a special electron cloud distribution and can efficiently capture the free radicals that may be generated in the system. Its ability to capture free radicals is much stronger than the sum of the individual actions of the dithiocarbamate and nitrosoamine compounds, thus effectively avoiding premature curing of the ink.

[0030] In the ink curing stage, due to the action of light and photoinitiator, the structure of the ternary complex formed in the storage stage rearranges; the disulfide bond in the dithiocarbamate breaks, generating highly reactive sulfur free radicals. The nitroso group (-NO) in the nitrosoamine compound interacts with the oxygen atom in the siloxane group of the silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.) to generate an intermediate with strong nucleophilicity or electrophilicity. The coupling agent is a silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.), and the siloxane group (-Si-O-R) in its molecule has certain activity. The oxygen atom of the siloxane group has lone pair electrons and has certain nucleophilicity, while the nitrogen atom in the nitroso group (-NO) has a partial positive charge, and a nucleophilic substitution or similar reaction may occur between them, thereby generating an intermediate with strong nucleophilicity or electrophilicity.

[0031] Meanwhile, the nitroso group (-NO) in the nitrosoamine compound interacts with the carbon-carbon double bond in the silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.) to generate an intermediate with strong nucleophilicity or electrophilicity. The coupling agent contains a carbon-carbon double bond (for example, the methacryloxy part in γ-methacryloxypropyltrimethoxysilane contains a carbon-carbon double bond), and the nitroso group (-NO) can react with the carbon-carbon double bond. The nitroso group (-NO) can act as an electrophilic reagent to carry out an electrophilic addition reaction with the carbon-carbon double bond to generate a new nitrogen-containing compound and form an intermediate with special activity.

[0032] These newly generated sulfur free radicals and intermediates interact with the film-forming substance molecules in the ink, promoting the formation of chemical bonds between the components. Meanwhile, due to its special molecular structure, the silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.) forms a covalent bond at one end with the active sites on the surface of the inorganic filler or pigment, and at the other end is tightly connected to the organic polymer molecular chain through chemical bonds or physical entanglement, further promoting the ink curing and shaping, accelerating the curing and shaping efficiency, and reducing the curing and shaping power consumption. Among them, the special molecular structure of the silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.) is Y-R-SiX3. In this structure, X is a hydrolyzable group (such as methoxy, ethoxy), and in an aqueous environment, the hydrolyzable group hydrolyzes to generate a silanol group (-Si-OH), and the silanol group can undergo a dehydration condensation reaction with the hydroxyl group (-OH) on the surface of the inorganic filler or pigment to form a stable Si-O bond, thus realizing the covalent bond connection with the surface of the inorganic filler or pigment.

[0033] Y in the special molecular structure is an organic functional group, and common ones include amino group (-NH2), vinyl group (-CH=CH2), methacryloxy group (-CH2=C(CH3)-COO-), etc. Different organic functional groups can react with or entangle with different organic polymer molecular chains. For example, vinyl and methacryloxy groups can participate in free radical polymerization reactions and undergo addition reactions with the active free radicals in the organic polymer molecular chain to form chemical bonds; while groups such as amino groups, in addition to participating in some chemical reactions, their molecular structures can also physically entangle with the organic polymer molecular chain through weak interactions such as hydrogen bonds.

[0034] R in the special molecular structure is a carbon chain spacer with a certain length. Its existence not only ensures the effective reaction of the hydrolyzable group with the surface of the inorganic filler or pigment, but also enables the organic functional group to better interact with the organic polymer molecular chain, avoiding affecting the coupling effect due to factors such as steric hindrance. This special structure enables the silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.) molecules to build a bridge between inorganic and organic materials, further promoting the ink curing and shaping, accelerating the curing efficiency, and reducing the curing power consumption.

[0035] In this application, the acrylate monomers include difunctional acrylate monomers and monofunctional acrylate monomers. The difunctional acrylate monomer can be 1,6 - hexanediol diacrylate (HDDA), and the monofunctional acrylate monomer can be isobornyl acrylate (IBOA).

[0036] In this application, the dispersant can be sodium dodecylbenzenesulfonate.

[0037] The epoxy acrylate in this application is a modified epoxy acrylate. The specific modification methods include: incorporating siloxane groups into the epoxy acrylate. For example, siloxane groups can be introduced through a condensation reaction, or through a free - radical graft copolymerization method. The modified epoxy acrylate can enhance its compatibility with other components and at the same time improve the reaction activity under low - energy curing conditions.

[0038] This application also provides a preparation method of an ink with high stability and low curing energy, including:

[0039] Weigh the raw materials according to mass fractions;

[0040] Add the epoxy acrylate and acrylate monomers into a reaction kettle, and stir and mix at 40 - 50 °C for 30 - 40 minutes;

[0041] Add the pigment powder and the dispersant, and stir at high speed for 60 - 90 minutes to fully disperse them;

[0042] Raise the temperature to 60 - 70 °C, add rosin resin, and stir until completely dissolved;

[0043] Cool to room temperature, and sequentially add a photoinitiator, a dithiocarbamate, a nitrosoamine compound, and a coupling agent, and continue to stir for 30 - 60 minutes to obtain an ink with high stability and low curing energy.

[0044] Example 1

[0045] An ink with high stability and low curing energy provided by this embodiment comprises components in the following weight parts: 30 parts of epoxy acrylate, 30 parts of acrylate monomer, 20 parts of pigment powder, 15 parts of rosin resin, 8 parts of photoinitiator, 0.5 part of dispersant, 0.2 part of dithiocarbamate, 0.3 part of nitrosamine compound, and 0.3 part of coupling agent. Among them, the epoxy acrylate is an epoxy acrylate introduced with a siloxane group, and the acrylate monomer comprises a mixture of 1,6 - hexanediol diacrylate (HDDA) and isobornyl acrylate (IBOA) with a mass ratio of 1:1; the photoinitiator comprises a mixture of 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide and 2 - isopropylthioxanthone with a mass ratio of 1:1; the dispersant is sodium dodecylbenzenesulfonate; the dithiocarbamate is sodium dimethyldithiocarbamate; the nitrosamine compound is N - nitrosodiphenylamine; and the coupling agent is γ - methacryloxypropyltrimethoxysilane.

[0046] A preparation method of an ink with high stability and low curing energy provided by this embodiment includes:

[0047] Add the epoxy acrylate and the acrylate monomer into a reaction kettle, and stir and mix at 40 - 50 °C for 30 - 40 minutes;

[0048] Add the pigment powder and the dispersant, and stir at high speed for 60 - 90 minutes to fully disperse them;

[0049] Raise the temperature to 60 - 70 °C, add the rosin resin, and stir until it is completely dissolved;

[0050] Cool to room temperature, sequentially add the photoinitiator, dithiocarbamate, nitrosamine compound, and coupling agent, and continue to stir for 30 - 60 minutes to obtain the ink with high stability and low curing energy.

[0051] Example 2

[0052] An ink with high stability and low curing energy provided by this embodiment comprises components in the following parts by weight: 10 parts of epoxy acrylate, 40 parts of acrylate monomer, 10 parts of pigment powder, 20 parts of rosin resin, 5 parts of photoinitiator, 1 part of dispersant, 0.1 part of dithiocarbamate, 0.4 part of nitrosamine compound, and 0.2 part of coupling agent. Among them, the epoxy acrylate is an epoxy acrylate introduced with a siloxane group, and the acrylate monomer comprises a mixture of 1,6 - hexanediol diacrylate (HDDA) and isobornyl acrylate (IBOA) with a mass ratio of 1:1; the photoinitiator comprises a mixture of 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide and 2 - isopropylthioxanthone with a mass ratio of 1:1; the dispersant is sodium dodecylbenzenesulfonate; the dithiocarbamate is zinc dibenzyldithiocarbamate; the nitrosamine compound is N - nitrosodimethylamine; and the coupling agent is γ - methacryloxypropyltrimethoxysilane.

[0053] A preparation method of an ink with high stability and low curing energy provided by this embodiment comprises:

[0054] Adding the epoxy acrylate and the acrylate monomer into a reaction kettle, and stirring and mixing at 40 - 50 °C for 30 - 40 minutes;

[0055] Adding the pigment powder and the dispersant, and stirring at high speed for 60 - 90 minutes to fully disperse them;

[0056] Raising the temperature to 60 - 70 °C, adding the rosin resin, and stirring until completely dissolved;

[0057] Cooling to room temperature, successively adding the photoinitiator, the dithiocarbamate, the nitrosamine compound, and the coupling agent, and continuing to stir for 30 - 60 minutes to obtain the ink with high stability and low curing energy.

[0058] Example 3

[0059] An ink with high stability and low curing energy provided by this embodiment includes the following components in parts by weight: 40 parts of epoxy acrylate, 5 parts of acrylate monomer, 30 parts of pigment powder, 5 parts of rosin resin, 15 parts of photoinitiator, 0.1 part of dispersant, 0.3 part of dithiocarbamate, 0.2 part of nitrosoamine compound, and 0.4 part of coupling agent. Among them, the epoxy acrylate is an epoxy acrylate introduced with a siloxane group, and the acrylate monomer includes a mixture of 1,6 - hexanediol diacrylate (HDDA) and isobornyl acrylate (IBOA) with a mass ratio of 1:1; the photoinitiator includes a mixture of 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide and 2 - isopropylthioxanthone with a mass ratio of 1:1; the dispersant is sodium dodecylbenzenesulfonate; the dithiocarbamate is sodium dibutyldithiocarbamate; the nitrosoamine compound is N - nitrosodiethylamine; and the coupling agent is γ - methacryloyloxypropyltrimethoxysilane.

[0060] A preparation method of an ink with high stability and low curing energy provided by this embodiment includes:

[0061] Add the epoxy acrylate and acrylate monomer into a reaction kettle, and stir and mix at 40 - 50 °C for 30 - 40 minutes;

[0062] Add the pigment powder and dispersant, and stir at high speed for 60 - 90 minutes to fully disperse them;

[0063] Raise the temperature to 60 - 70 °C, add the rosin resin, and stir until completely dissolved;

[0064] Cool to room temperature, and sequentially add the photoinitiator, dithiocarbamate, nitrosoamine compound, and coupling agent, and continue to stir for 30 - 60 minutes to obtain an ink with high stability and low curing energy.

[0065] Comparative Example 1

[0066] The difference from Example 1 is that: in Example 1, "0.2 part of dithiocarbamate, 0.3 part of nitrosoamine compound, 0.3 part of coupling agent" is replaced with "0.8 part of dithiocarbamate", and the rest is the same as Example 1.

[0067] Comparative Example 2

[0068] The difference from Example 1 is that: in Example 1, "0.2 part of dithiocarbamate, 0.3 part of nitrosoamine compound, 0.3 part of coupling agent" is replaced with "0.8 part of nitrosoamine compound", and the rest is the same as Example 1.

[0069] Comparative Example 3

[0070] The difference from Example 1 is that: in Example 1, "0.2 parts of dithiocarbamate, 0.3 parts of nitrosamine compound, 0.3 parts of coupling agent" is replaced with "0.8 parts of coupling agent", and the rest is the same as Example 1.

[0071] Comparative Example 4

[0072] The difference from Example 1 is that: in Example 1, "0.2 parts of dithiocarbamate, 0.3 parts of nitrosamine compound, 0.3 parts of coupling agent" is replaced with "0.2 parts of dithiocarbamate, 0.6 parts of nitrosamine compound", and the rest is the same as Example 1. In this example, the mass ratio of dithiocarbamate to nitrosamine compound is 1:3.

[0073] Comparative Example 5

[0074] The difference from Example 1 is that: in Example 1, "0.2 parts of dithiocarbamate, 0.3 parts of nitrosamine compound, 0.3 parts of coupling agent" is replaced with "0.2 parts of dithiocarbamate, 0.6 parts of coupling agent", and the rest is the same as Example 1.

[0075] Comparative Example 6

[0076] The difference from Example 1 is that: in Example 1, "0.2 parts of dithiocarbamate, 0.3 parts of nitrosamine compound, 0.3 parts of coupling agent" is replaced with "0.3 parts of nitrosamine compound, 0.5 parts of coupling agent", and the rest is the same as Example 1.

[0077] Experimental Example

[0078] 1. Place the inks in Examples 1 - 3 and Comparative Examples 1 - 6 at 50 °C for the gelation promotion test. According to GB / T 1723 - 2019, detect the gelation time of the inks in each example and comparative example, and according to ISO2884 - 1, detect the viscosity change rate of the inks in each example and comparative example after 30 days at 25 °C. The conclusions are shown in Table 1.

[0079] Table 1 Gelation time of inks in each example and comparative example

[0080]

[0081] As can be seen from Table 1: The inks in Examples 1, 2, and 3 can be stored for more than one year; the inks in the comparative examples cannot be stably stored and will gel within one month.

[0082] The reason why the ink in this application can stably exist during the storage stage is mainly due to the synergistic effect of dithiocarbamate, nitrosamine compound, and coupling agent. The specific synergistic mechanism includes the following three aspects:

[0083] First: Formation of the intermolecular interaction network among dithiocarbamate, nitrosamine compound and coupling agent

[0084] (1) Sulfur-nitrogen weak coordination: The sulfur atom (S) in dithiocarbamate has a high electron cloud density and forms an S→N coordination bond (bond energy about 15 - 25 kJ / mol) with the partially positively charged nitrogen atom (N + δ) in the nitrosamine compound.

[0085] (2) Hydrogen bond network construction: The silanol group (Si-OH) in the silane coupling agent (such as γ-methacryloxypropyltrimethoxysilane, etc.) forms a hydrogen bond (bond energy about 8 - 12 kJ / mol) with the amino group (-NH-) of dithiocarbamate.

[0086] (3) Superposition of van der Waals forces: The van der Waals force interactions among the three molecules further stabilize the complex structure.

[0087] Second: Free radical capture mechanism

[0088] (1) Electron delocalization system: The ternary complex forms a conjugated π-π* electron delocalization system, enabling the unpaired electrons to delocalize rapidly.

[0089] (2) Free radical quenching efficiency: The measured capture rate constant (kq) of the ternary system for methyl radicals (M·) reaches 5.8×10 8 M -1 s -1 , which is 5 - 8 times that of a single component; ESR detection confirms that the capture efficiency of the ternary system for methyl radicals reaches 92%, while the highest for a single component is only 35%.

[0090] (3) Steric hindrance effect: The three-dimensional structure of the complex creates a "molecular cage" effect, physically isolating the free radicals.

[0091] Third: Dynamic equilibrium regulation

[0092] (1) Reversible bonding: Under the storage condition of 25°C, the dissociation-recombination equilibrium constant (Keq) of the complex remains in the range of 10 2 -10 3 M -1 .

[0093] (2) pH buffering capacity: The system maintains a microenvironment with a pH of 6.5 - 7.5 to prevent acidic / alkaline degradation. During accelerated aging at 50°C, the pH fluctuation range is ±0.3, while that of the control group reaches ±1.5.

[0094] 2. The inks in Examples 1 - 3 and Comparative Examples 1 - 6 were irradiated with a 30W LED light source for 3 seconds, and it was observed whether the inks were cured and the adhesion of the inks after curing. The adhesion of the inks was detected by the cross - cut test method. The specific method is as follows:

[0095] Take 3 - 5 printed sheets. Place the sheets with the ink surface facing up flat on a clean platform working surface. Use a cross - cut knife to draw 1 - mm - wide square grids on the printed paper or product; (Note: When drawing the grids, just cut through the ink layer on the surface of the printed sheet or product); Stick a prepared tape flat on the printed sheet or product with the grids already drawn. Wipe the surface of the tape back and forth with an eraser for 30S - 90S, and then quickly peel the tape from the printed sheet or product at an angle of 180 degrees; Observe the condition of the ink peeling off in the grids with a magnifying glass, and judge the adhesion of the ink according to the standards of 5B, 4B, 3B, 2B, 1B, 0B required by ASTM. The curing conditions and adhesion of the inks in each example and comparative example are shown in Table 2.

[0096] Table 2 Curing conditions and adhesion of the inks in each example and comparative example

[0097]

[0098] As can be seen from Table 2: The inks in Examples 1, 2, and 3 can be completely cured when irradiated with a 30W LED light source for 3 seconds, and the adhesion of the cured inks meets the production requirements. While the inks in the comparative examples cannot be completely cured when irradiated with a 30W LED light source for 3 seconds, and the adhesion of the incompletely cured inks does not meet the production requirements.

[0099] Under 30W LED 405nm light irradiation, the minimum curing energy of traditional inks is 500 - 800mJ / cm 2 , and the minimum curing energy of the ink of this application is only 150mJ / cm 2 .

[0100] For the cured ink with a film thickness of 50μm, its curing time was measured. The surface curing time of traditional inks is 8 - 12s, and the surface curing time of the ink of this application is only 3s.

[0101] The ink of this application can be cured with low energy consumption (cured by a 30W LED light source in 3 seconds), mainly due to the synergistic effect of dithiocarbamate, nitrosamine compounds and coupling agents. The specific synergistic mechanism includes:

[0102] First: The photo - responsive dissociation process

[0103] (1) Homolytic cleavage of disulfide bond: Under LED illumination (wavelength 365 - 405 nm), the S-S bond of dithiocarbamate undergoes homolytic cleavage to generate sulfur radicals (·S-R); specifically, under 365 nm LED irradiation, the dissociation energy of the S-S bond decreases from 268 kJ / mol to 210 kJ / mol. Nitroso conversion: The NO group is converted into ·NO radicals under illumination, and the conversion efficiency reaches 85% (only 40% in the control group).

[0104] (2) Nitroso conversion: Nitroso (-NO) is converted into nitroxyl radicals (·NO) under illumination, and further reacts with the coupling agent to generate reactive intermediates.

[0105] In summary, sulfur radicals (·S-R) can directly initiate the polymerization of acrylates and promote the growth of molecular chains; nitroxyl radicals (·NO) can generate reactive intermediates and accelerate the cross-linking reaction.

[0106] Second: Curing promotion mechanism

[0107] (1) Initiation by sulfur radicals: The generated ·S-R can directly initiate the polymerization of acrylate double bonds, and the initiation efficiency is above 85%.

[0108] Third: Bridging effect of coupling agent

[0109] (1) Inorganic interface: The Si-OR group condenses with the hydroxyl groups on the pigment surface; Si-OH + HO-pigment → Si-O-pigment + H2O.

[0110] (2) Organic interface: Vinyl copolymerizes with the resin; CH2=CH- + resin radicals → CH2-CH-resin.

[0111] (3) Synergistic catalytic effect: The ternary system reduces the activation energy of the curing reaction by about 30%, and curing can be completed in 3 seconds under 30W LED.

[0112] Fourth: Network structure optimization

[0113] (1) Crosslinking density regulation: The ternary system makes the gel content of the final cured film reach 92 - 95%, while that of the control sample is only 75 - 80%;

[0114] (2) Stress release: The remaining dynamic bonds endow the material with an elastic deformation ability of 5 - 8%, avoiding brittle fracture.

[0115] In the present application, a synergistic system formed by a dithiocarbamate, a nitrosoamine compound, and a coupling agent has its highest occupied molecular orbital (HOMO) mainly concentrated on the sulfur atom of the dithiocarbamate (-2.8 eV); the lowest unoccupied molecular orbital (LUMO) is distributed on the nitroso group of the nitrosoamine compound (-1.2 eV); the complexation reduces the HOMO-LUMO energy gap from 4.5 eV to 3.2 eV, improving the light responsiveness; meanwhile, in the synergistic system formed by the dithiocarbamate, the nitrosoamine compound, and the coupling agent, the three form an approximate triangular planar configuration with a dihedral angle Φ(S...N...Si) ≈ 120°, constituting the optimal conformation; meeting the orbital overlap requirements and forming a stable triangular planar structure. The ink formed by the synergistic system achieves the dual effects of high stability during the storage stage and low energy requirements during the curing stage through a unique intermolecular interaction mechanism; meanwhile, it solves the two traditionally contradictory technical problems of low-energy curing (curing in 3 seconds with a 30W LED light source) and high stability (no gelation for more than 365 days at 50°C).

[0116] It can be understood that the above embodiments only represent the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, all of which fall within the protection scope of the present invention; therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. An ink with high stability and low curing energy, characterized in that It comprises components in the following parts by weight: 10 - 40 parts of epoxy acrylate, 5 - 40 parts of acrylate monomer, 10 - 30 parts of pigment powder, 5 - 20 parts of rosin resin, 5 - 15 parts of photoinitiator, 0.1 - 1 part of dispersant, 0.1 - 0.3 part of dithiocarbamate, 0.2 - 0.4 part of nitrosamine compound, and 0.2 - 0.4 part of coupling agent.

2. The ink with high stability and low curing energy according to claim 1, characterized in that The mass ratio of the dithiocarbamate to the nitrosamine compound is 1:1 - 1.

5.

3. A high-stability and low-curing-energy ink according to claim 1, wherein The coupling agent is a silane coupling agent.

4. A kind of ink with high stability and low curing energy according to claim 1, characterized in that, The dithiocarbamate is any one of sodium dimethyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc dibutyldithiocarbamate, and sodium dibutyldithiocarbamate.

5. The ink with high stability and low curing energy according to claim 1, characterized in that, The nitrosamine compound is any one of N-nitrosodiphenylamine, N-nitrosodimethylamine, N-nitrosodiethylamine, and N-nitroso-N-methyl-4-aminobenzamide.

6. The ink with high stability and low curing energy according to claim 1, characterized in that The photoinitiator is a complex of a cleavage-type photoinitiator and a hydrogen-abstraction-type photoinitiator, and the mass ratio of the cleavage-type photoinitiator to the hydrogen-abstraction-type photoinitiator is 1:1 - 3:

1.

7. The ink with high stability and low curing energy according to claim 6, characterized in that The cleavage-type photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; the hydrogen-abstraction-type photoinitiator is 2-isopropylthioxanthone.

8. A high-stability and low-curing-energy ink according to claim 1, characterized in that, The acrylate monomer includes a bifunctional acrylate monomer and a monofunctional acrylate monomer.

9. A method for preparing an ink with high stability and low curing energy as described in any one of claims 1-8, characterized in that, It includes the following steps: Add the epoxy acrylate and the acrylate monomer into a reaction kettle, and stir and mix them at 40 - 50 °C for 30 - 40 minutes; Add the pigment powder and the dispersant, and stir at high speed for 60 - 90 minutes to disperse them; Raise the temperature to 60 - 70 °C, add the rosin resin, and stir until it is completely dissolved; Cool to room temperature, sequentially add the photoinitiator, the dithiocarbamate, the nitrosamine compound, and the coupling agent, and continue to stir for 30 - 60 minutes to obtain an ink with high stability and low curing energy.

10. The method according to claim 9, wherein The epoxy acrylate is a modified epoxy acrylate, and the modification process of the epoxy acrylate includes: introducing a siloxane group into the epoxy acrylate.

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