阅读说明：本技术 无溶剂紫外光固化凹版印刷油墨 (Solvent-free ultraviolet curing gravure printing ink ) 是由 解传红 李良 陈源 于 2020-12-31 设计创作，主要内容包括：本发明涉及凹版印刷油墨技术领域,提供了一种无溶剂紫外光固化凹版印刷油墨,包括连接料、光引发剂、色粉和光阻剂；连接料包括活性单体和反应性齐聚物,活性单体包括如下重量份数的组分：二丙二醇二丙烯酸酯70～99份、三羟甲基丙烷三丙烯酸酯30～1份。流动性好、基本不含VOCs、光引发剂含量低且专门用于氮气保护下紫外光固化凹版印刷。(The invention relates to the technical field of gravure printing ink, and provides solvent-free ultraviolet curing gravure printing ink which comprises a binder, a photoinitiator, toner and a photoresist; the binder comprises an active monomer and a reactive oligomer, wherein the active monomer comprises the following components in parts by weight: 70-99 parts of dipropylene glycol diacrylate and 30-1 parts of trimethylolpropane triacrylate. Good fluidity, basically no VOCs, low photoinitiator content and special application to ultraviolet curing gravure printing under the protection of nitrogen.)

1. The solvent-free ultraviolet curing intaglio printing ink is characterized by comprising a binder, a photoinitiator, toner and photoresist;

the connecting material comprises an active monomer and a reactive oligomer, wherein the active monomer comprises the following components in parts by weight: 70-99 parts of dipropylene glycol diacrylate and 30-1 parts of trimethylolpropane triacrylate.

2. The solvent-free uv-curable intaglio printing ink according to claim 1 wherein said reactive oligomer comprises polyester acrylic oligomers, polyurethane acrylic resins and modified polyurethane acrylic resins.

3. The solvent-free ultraviolet-curable gravure printing ink according to claim 2, wherein the reactive oligomer comprises the following components in parts by weight: 50-70 parts of polyester acrylic oligomer, 15-35 parts of polyurethane acrylic resin and 5-25 parts of modified polyurethane acrylic resin.

4. The solvent-free ultraviolet-curable gravure printing ink according to claim 1, wherein the reactive monomer comprises the following components in parts by weight: 88 parts of dipropylene glycol diacrylate and 12 parts of trimethylolpropane triacrylate.

5. The solvent-free ultraviolet-curable gravure printing ink according to claim 3, wherein the reactive oligomer comprises the following components in parts by weight: 60 parts of polyester acrylic oligomer, 25 parts of polyurethane acrylic resin and 15 parts of modified polyurethane acrylic resin.

6. The solvent-free ultraviolet-curable gravure printing ink according to claim 3, wherein the reactive oligomer comprises the following components in parts by weight: 65 parts of polyester acrylic oligomer, 20 parts of polyurethane acrylic resin and 15 parts of modified polyurethane acrylic resin.

7. The solvent-free uv-curable intaglio printing ink according to claim 1 wherein said photoinitiator comprises the following components in parts by weight: 40-60 parts of 2, 4, 6 (trimethylbenzoyl) diphenylphosphine oxide, 15-35 parts of 2-phenylbenzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone and 15-35 parts of 1-hydroxy-cyclohexyl monophenyl ketone.

8. The solvent-free uv-curable intaglio printing ink according to claim 1 wherein said photoinitiator comprises the following components in parts by weight: 30-50 parts of 2, 4, 6 (trimethylbenzoyl) diphenylphosphine oxide, 30-50 parts of 2-phenylbenzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone and 10-30 parts of 1-hydroxy-cyclohexyl-phenyl ketone.

9. The solvent-free uv-curable intaglio printing ink according to claim 1 wherein said photoinitiator comprises the following components in parts by weight: 60-90 parts of 2-benzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone and 10-40 parts of 1-hydroxy-cyclohexyl-phenyl ketone.

10. The solvent-free ultraviolet curing gravure printing ink as claimed in any one of claims 1 to 9, wherein the weight ratio of each raw material is: 65-75 parts of active monomer, 10-20 parts of reactive oligomer, 8-10 parts of toner, 2-5 parts of photoinitiator and 1-2 parts of photoresist.

Technical Field

The invention relates to the technical field of gravure printing ink, in particular to solvent-free ultraviolet curing gravure printing ink.

Background

In the existing traditional gravure printing technology, more than 90% of used gravure printing ink is solvent-based printing ink, which contains a large amount of Organic solvent, part of which belongs to low-toxicity solvent, and part of which has pungent smell, and in the preparation and use processes of the solvent-based printing ink, a large amount of VOCs (Volatile Organic Compounds) are discharged, which can affect the environment and cause serious environmental pollution; the long-term contact can affect the health of human bodies, which causes physical and psychological damage to operators; the printed matter produced by the printing ink has residual VOCs and is harmful to the body of a user.

The existing ultraviolet curing ink is mainly used for offset printing and flexography because the viscosity of the product is high, and an active diluent is required to be added in the use process for adjusting the viscosity of the ink, although the volatility of the active diluent is low, the pollution to the environment is small, the active diluent becomes a part of a coating after curing, but the ultraviolet curing process is difficult to completely cure the active diluent, the residual active diluent causes adverse effects on the safety, sanitation and long-term performance of the product, and the shrinkage rate of the coating is increased by adding the active diluent, so that the physical performance of the coating is reduced.

The existing ultraviolet light curing printing ink still has 1-2% of volatile organic compounds due to the use of high-viscosity monomers and a large amount of auxiliary agents, and a certain amount of VOCs (volatile organic compounds) are still discharged in the use process.

The existing ultraviolet curing printing ink for offset printing and flexo printing and the printing process thereof have a defect which can not be overcome: that is, the printed product has a special odor. The main reasons for this serious drawback are: firstly, the existing ultraviolet curing ink must have a high content of photoinitiator (5-8%), and most photoinitiators are unstable derivatives (such as benzophenone, tetraphenylmethyl and the like) containing benzene ring structures; secondly, the existing printing process of the UV light curing ink is carried out in an open atmospheric environment, when the UV ink is irradiated by an ultraviolet lamp to initiate the light curing reaction, the short-wave-band ultraviolet light with higher energy is firstly captured by oxygen in the air to form excited oxygen molecules to form ozone, and the formed ozone in turn reduces the transmittance of the ultraviolet light. Under the combined action of ozone and stronger ultraviolet light, the photoinitiator generates stronger and more complex free radical process side reactions, and finally benzene and other analogues are dissociated, so that the printed product has more aromatic hydrocarbon residues.

In order to further solve the problems that printed packages have special odor and VOCs are unqualified in detection, the occurrence of side reactions in the photocuring process needs to be reduced to the maximum extent on the premise of ensuring the printing quality, the dosage of a photoinitiator containing a benzene ring structure needs to be reduced, and UV ink specially used for intaglio printing under nitrogen protection needs to be developed.

Disclosure of Invention

The invention aims to provide solvent-free ultraviolet curing gravure printing ink suitable for nitrogen protection, which has good fluidity, does not contain VOCs basically, has low photoinitiator content and is specially used for ultraviolet curing gravure printing under nitrogen protection.

The invention is realized by the following technical scheme:

a solvent-free ultraviolet curing gravure printing ink comprises a binder, a photoinitiator, a toner and a photoresist; the binder comprises an active monomer and a reactive oligomer, wherein the active monomer comprises the following components in parts by weight: 70-99 parts of dipropylene glycol diacrylate and 30-1 parts of trimethylolpropane triacrylate.

The binder is the most basic and important component of the ink and is used for dispersing the pigment and endowing the ink with proper viscosity, fluidity and printing performance. The binder consists of reactive monomers and reactive oligomers (resins), which are film-forming substances in UV inks, the properties of which play an important role in the curing process and in the properties of the cured ink film.

The reactive monomer, also called a crosslinking monomer, is a functional monomer and has the function of adjusting the viscosity, curing speed and curing film performance of the ink. The reactive monomer contains a "C ═ C" unsaturated double bond in the structure. The combined active monomer selected by the invention has the effects of low viscosity, good adhesion performance and quick photochemical reaction rate.

The dipropylene glycol diacrylate has low viscosity, good dilution rate, excellent adhesion, good water resistance, heat resistance and chemical resistance, and high curing speed under UV illumination.

Trimethylolpropane triacrylate, a low-odor colorless or yellowish transparent liquid, is hardly soluble in water and soluble in general solvents.

Further, the reactive oligomer includes polyester acrylic oligomer, urethane acrylic resin and modified urethane acrylic resin.

Unsaturated polyesters are generally very high in molecular weight, and the unsaturated double bonds located in the middle of the main chain are slow to cure, and high molecular weight also causes high viscosity problems, and monomers are generally added to adjust viscosity and properties. The double bond of the polyester acrylate is positioned at the tail end of a molecular chain, so that the polyester acrylate has higher activity, and the lower molecular weight makes the rheology regulation easier. The polyester acrylate has lower viscosity and higher reactivity, and the polymerization degree can be adjusted according to needs, so that resin or oligomer with required performance can be obtained.

The polyurethane molecular chain contains a large amount of urethane chain segments, and also contains active groups such as ether bonds, ester bonds, urea bonds and the like. The structure enables the polyurethane material to show good physical and mechanical properties, excellent elasticity, cold resistance, organic solvent resistance, good temperature adaptability and other properties. Polyurethane resin is a fast-developing polymer material since the 80 s of the 20 th century because of its excellent physical and chemical properties. Different raw materials and synthesis processes are selected to obtain polyurethane resins with different molecular structures and different performances through polycondensation, so that the polyurethane has a larger play space in the design of the molecular structure, and various new modified polyurethane acrylic resins can be generated.

Further, the reactive oligomer comprises the following components in parts by weight: 50-70 parts of polyester acrylic oligomer, 15-35 parts of polyurethane acrylic resin and 5-25 parts of modified polyurethane acrylic resin.

The reactive oligomer is composed of different types of resins, and the acryloyl group has the fastest photocuring speed under the same condition, so that the oligomer is mainly composed of different acrylic resins and derivatives thereof. The reaction oligomer prepared by mixing three different resin bases, namely polyester acrylic oligomer, polyurethane acrylic resin and modified polyurethane acrylic resin according to a certain proportion has the characteristics of low viscosity, excellent wear resistance, high surface hardness, excellent yellowing resistance and the like.

Preferably, the reactive monomer comprises the following components in parts by weight: 88 parts of dipropylene glycol diacrylate and 12 parts of trimethylolpropane triacrylate.

Preferably, for light-colored inks, the reactive oligomer comprises the following components in parts by weight: 60 parts of polyester acrylic oligomer, 25 parts of polyurethane acrylic resin and 15 parts of modified polyurethane acrylic resin.

Preferably, for dark color inks, the reactive oligomer comprises the following components in parts by weight: 65 parts of polyester acrylic oligomer, 20 parts of polyurethane acrylic resin and 15 parts of modified polyurethane acrylic resin.

Photoinitiators (PI) are key components of photocurable systems, and are concerned with whether oligomers and diluents rapidly change from liquid to solid upon exposure of the formulation to light, i.e., crosslink cure.

Photoinitiators play a direct and critical role in the curing speed of the inks. However, since the ink contains pigments, different pigments absorb, reflect and scatter ultraviolet light with different wavelengths to different degrees, so that the initiation efficiency of the photoinitiator is reduced, and the curing speed of the ink is affected. Therefore, both photoinitiators and pigments have a significant effect on the curing speed of UV inks and are synergistic. The cure speed of UV inks can only be effectively increased if the appropriate photoinitiator and pigment are selected and matched well.

The nitrogen protection photo-curing printing ink uses cheap nitrogen to isolate oxygen, so that the problem of oxygen inhibition caused by the existence of oxygen in the whole system is avoided. Oxygen inhibition not only limits the choice of photoinitiator species, but also affects free radical initiated polymerization, especially in acrylate based photopolymerization systems, where oxygen inhibition makes a significant difference between internal and surface curing of the coating. In order to reduce the oxygen inhibition, it is generally necessary to increase the concentration of the photoinitiator or to add a proportion of an auxiliary such as an organic amine or paraffin to the UV ink. The introduction of organic amine can increase VOC residue of a printed product, and other auxiliary agents can influence the film forming quality of the ink because the other auxiliary agents do not participate in a crosslinking reaction.

Further, the composite photoinitiator one: the photoinitiator comprises the following components in parts by weight: 40-60 parts of 2, 4, 6 (trimethylbenzoyl) diphenylphosphine oxide, 15-35 parts of 2-phenylbenzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone and 15-35 parts of 1-hydroxy-cyclohexyl monophenyl ketone.

2, 4, 6 (trimethylbenzoyl) diphenylphosphine oxide (TPO) is a highly efficient photoinitiator of the free radical (I) type, absorbing in the long wavelength range. Because of the wide absorption range, the effective absorption peak value is 350-400 nm, and the maximum absorption peak value can be about 420 nm. Its absorption peak is longer than that of conventional initiator, and after being illuminated, it can produce two free radicals of benzoyl and phosphoryl group, and can initiate polymerization, so that its photocuring speed is quick. It also has photobleaching action, and is suitable for deep curing of thick film. The initiated coating is not yellow, and has the characteristics of low volatilization, no residue, low post-polymerization effect and the like, and the TPO is particularly suitable for white and colorless systems. The excellent absorption performance and the quick drying speed make the UV ink particularly suitable for gravure, silk screen and flexible printing.

2-phenylbenzyl-2-dimethylamine-1- (4-morpholinylbenzyl) butanone (BDMB), also known as photoinitiator 369. The ultraviolet photoinitiator has high light sensitivity range and high UV absorptivity, is used for initiating photopolymerization of free radicals, can be compounded with a proper coinitiator, and is used in UV curing ink and paint. BDMB benefits from its excellent absorption properties making it particularly suitable for the curing of UV-pigmented systems, especially blue and black pigmented systems UV-curing, even in systems containing UV-light absorbers.

1-hydroxy-cyclohexyl-phenyl-methanone (HCPK), also known as photoinitiator 184. Is a highly efficient free radical (I) type non-yellowing photoinitiator and is one of the most commonly used photoinitiators. The UV curing agent is mainly used for UV curing of acrylate varnish coatings on the surfaces of paper, wood, metal and plastics. The coating has good non-yellowing property, and the cured coating has very small yellowing degree even if exposed to the sun for a long time, so the coating is particularly suitable for coatings and printing ink with high requirement on yellowing degree. Is a free radical (I) type solid photoinitiator with high efficiency and no yellowing,

and a composite photoinitiator II: the photoinitiator comprises the following components in parts by weight: 30-50 parts of 2, 4, 6 (trimethylbenzoyl) diphenylphosphine oxide, 30-50 parts of 2-phenylbenzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone and 10-30 parts of 1-hydroxy-cyclohexyl-phenyl ketone.

And (3) a composite photoinitiator III: the photoinitiator comprises the following components in parts by weight: 60-90 parts of 2-benzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone and 10-40 parts of 1-hydroxy-cyclohexyl-phenyl ketone.

Photoinitiators are key components of photo-curable ink systems and are related to the rate at which reactive monomers and reactive oligomers can rapidly change from a liquid to a solid state upon exposure of the ink formulation to light. The content of photoinitiator in the existing common ultraviolet curing ink formula is higher (5-8%). In order to improve the safety performance of the ink and reduce the cost of the ink, the invention designs the composite photoinitiator formed by combining a plurality of photoinitiators, selects three groups of different composite photoinitiators and applies the composite photoinitiators to the ultraviolet curing ink with five different colors. Meanwhile, when the composite photoinitiator is dissolved, a traditional volatilizable solvent is not used, a combined active monomer which is one of the printing ink components is directly used, the composite photoinitiator solution is prepared by heating to 60 ℃ under the condition of keeping out of the sun, and the problem of VOCs pollution caused by the introduction of the volatilizable solvent in the production process is solved.

Preferably, the mass ratio of each component in the composite photoinitiator I is as follows: TPO: BDMD: HCPK is 50: 25: 25. the composite photoinitiator is suitable for being matched with cyan and black toner.

Preferably, the composite photoinitiator II comprises the following components in percentage by mass: TPO: BDMD: HCPK 40: 40: 20. the composite photoinitiator is suitable for being matched with yellow and white toner.

Preferably, the composite photoinitiator III comprises the following components in percentage by mass: BDMD: HCPK 75: 25. the composite photoinitiator is suitable for being matched with red toner.

Further, the weight ratio of the raw materials is as follows: 65-75 parts of active monomer, 10-20 parts of reactive oligomer, 8-10 parts of toner, 2-5 parts of photoinitiator and 1-2 parts of photoresist.

The binder and photoinitiator are decisive for the main printing properties of the ink, while the curing speed, which is one of the most important criteria of the ink, is determined by the binder, photoinitiator and pigment. The ink viscosity is determined by the binder composition and pigment concentration. In the existing ultraviolet light curing ink, the using amount of the pigment is usually 15-20%, and the viscosity (S) of the ink is more than or equal to 50 seconds. The solvent-free ultraviolet curing intaglio printing ink provided by the invention meets the requirements that the viscosity (S) of the ink is less than or equal to 30 seconds, the printing and curing speed on a machine is more than or equal to 150 m/min, and no diluent is added in the printing process, so that the solvent-free ultraviolet curing intaglio printing ink systematically explores the mutual influence of a photoinitiator and a pigment in the solvent-free ink under the condition that a binder is fixed.

The invention develops the combination optimization research of the formulas of the pigments and the photoinitiators of the red ink, the yellow ink, the white ink, the cyan ink and the black ink in the solvent-free ultraviolet curing gravure printing ink, and determines the proportion range of the formulas of the materials of the five color inks.

The technical scheme of the invention at least has the following advantages and beneficial effects:

(1) the solvent-free ultraviolet curing intaglio printing ink provided by the invention does not contain an organic solvent in the components, and does not need to add an active diluent in the printing process, thereby realizing zero emission of VOCs in the production and use processes. Various safety technical indexes of the gravure printing ink are superior to the national mandatory technical standard, and the product safety is higher.

(2) The solvent-free ultraviolet curing intaglio printing ink provided by the invention has stable viscosity and good fluidity, is suitable for a high-speed intaglio printing machine with nitrogen protection, has the ultraviolet curing time of less than or equal to 0.3 second, and has high brightness and surface strength of a printed ink film.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Examples

50 g of the ink (binder, pigment and photoinitiator) was charged into a 100ML round bottom flask according to the formulation ratio, then 30 g of 1.2mm zirconium beads were added, stirred and ground for 30 minutes, and then filtered through a 300 mesh filter cloth to obtain inks for testing, examples 1 to 8, as shown in the following table.

TABLE 1 examples 1-8 batch formulations

In examples 1 to 8, the toners were black, yellow, red, white, red, yellow, cyan, and black, respectively.

Comparative example

50 g of the ink (binder, pigment and photoinitiator) was charged into a 100ML round bottom flask according to the formulation ratio, 30 g of 1.2mm zirconium beads were added, stirred and ground for 30 minutes, and then filtered through a 300 mesh filter cloth to obtain comparative inks 1 to 3 for testing as shown in the following table.

TABLE 2 comparative examples 1-3 feed formulations

In comparative examples 1 to 6, the toners were red, yellow, white, cyan, black and red, respectively.

Experimental example 1

(1) And (3) measuring film forming strength:

the samples to be tested were tested in accordance with GB/T6739-2002 using a 291 pencil hardness tester (Erichsen, Germany) with 3 replicates per sample. The pencil hardness grade was 6 B.5B.4B.3B.2B.HB.F.H.2H.3H.4H.5H.6H.7H.8H.9H (grade 1-17), and the larger the value, the higher the hardness.

(2) And (3) adhesive force determination:

the paint film sample to be tested is placed in a Sheen Ref 750 grid-dividing device for grid dividing, and then the adhesion force of the ink layer to be tested is tested by using a 3M (600 type) adhesive tape according to the GB/T9286-1998 standard, and each sample is repeated for 3 times. The adhesive force is divided into 0-5 grades according to the adhesive force, and the adhesive force is better when the grade number is smaller.

(3) Viscosity measurement

The samples of examples 1 to 8 and comparative examples 1 to 3 were subjected to viscosity measurement using a viscometer.

(4) Determination of the curing speed

The curing speed was examined for examples 1 to 8 and comparative examples 1 to 3.

(5) Yellowing resistance assay

The samples of examples 1 to 8 and comparative examples 1 to 3 were placed in a bulb-type yellowing resistance test chamber, a 300w ultraviolet lamp was used to irradiate the sample at a temperature of 60 ℃ for 24 hours at an irradiation distance of 25cm, the sample was taken out and placed in a normal temperature environment for 30min, and the sample was compared with a blank pattern on a gray card paper to observe the yellowing.

The results of each experiment are recorded as shown in the following table:

TABLE 3 Experimental results Table

Test items	Speed of curing	Film formation Strength	Adhesion force	Viscosity of the oil	Resistance to yellowing
						Example 1	28	8	2	28	4 stage
Example 2	33	9	1	26	4 stage
						Example 3	35	11	0	24	4 stage
Example 4	32	10	1	22	4 stage
						Example 5	31	9	0	26	4 stage
Example 6	31	10	1	25	4 stage
						Example 7	30	10	1	25	4 stage
Example 8	32	11	0	24	4 stage
						Comparative example 1	15	5	3	30	Grade 3
Comparative example 2	12	6	4	29	Grade 3.5
						Comparative example 3	22	5	4	35	Grade 3.5
Comparative example 4	17	6	3	33	Grade 3.5
						Comparative example 5	14	6	2	23	Grade 3.5
Comparative example 6	13	6	4	35	Grade 3.5

As can be seen from the test results of table 3:

the curing speed, the film forming strength, the adhesive force, the viscosity and the yellowing resistance of the samples of the examples 1 to 8 are all superior to those of the samples of the comparative examples 1 to 6; therefore, the solvent-free ultraviolet curing intaglio printing ink provided by the invention has the advantages of high curing speed, low viscosity and high ink quality.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.