CN114196255B

CN114196255B - Water-based polyurethane ink for gravure printing

Info

Publication number: CN114196255B
Application number: CN202111649296.6A
Authority: CN
Inventors: 郭松海; 燕子; 钟琦
Original assignee: ZHEJIANG HUABAO INK CO Ltd
Current assignee: ZHEJIANG HUABAO INK CO Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2022-05-24
Anticipated expiration: 2041-12-30
Also published as: CN114196255A

Abstract

The present invention belongs to printing inkThe field especially relates to a gravure printing water-based polyurethane ink. The ink comprises: 16-21 wt% of three-component binder, 11-26 wt% of pigment, 0-5 wt% of functional additive and the balance of water; the three-component connecting material comprises acrylic emulsion A, acrylic emulsion B and polyurethane dispersion liquid; calculating a relative hydroxyl value Hv when the components of the three-component binder are mixed_rAnd controlling the relative hydroxyl value ratio Hv_rHv is more than or equal to 1.02_rLess than or equal to 1.45. According to the invention, through effective improvement and regulation of the formula and the proportion of the binder, the relative ratio of hydroxyl values in the binder and the dosage of acrylic emulsion with different hydroxyl values are strictly controlled, and the adhesive force and wettability of the ink can be comprehensively coordinated to reach a higher level.

Description

Water-based polyurethane ink for gravure printing

Technical Field

The invention belongs to the field of printing ink, and particularly relates to gravure printing waterborne polyurethane printing ink.

Background

Intaglio printing is called intaglio printing for short and is one of four printing modes. Intaglio printing is a direct printing method, which directly imprints the ink contained in the intaglio pits on a printing stock, wherein the shade level of the printed picture is determined by the size and the depth of the pits, if the pits are deeper, the contained ink is more, and the ink layer left on the printed matter after impressing is thicker; conversely, if the pit is shallow, the amount of ink contained is small, and the ink layer left on the substrate after the imprint is thin. The gravure printing occupies an extremely important position in the fields of printing packaging and graphic publishing by the advantages of bright color, high saturation, high printing plate printing durability, stable quality of printed products, high printing speed and the like.

However, the existing gravure printing also has certain defects. In particular, the gravure printing technology has the defects of high solvent volatilization of the printing ink, easy damage to human bodies and environmental pollution. Therefore, in addition to the solvent-based gravure inks, researchers have developed aqueous polyurethane inks containing water and alcohol as solvents, but the aqueous polyurethane inks can reduce the amount of volatilization, but the harmfulness of volatilization of organic solvents cannot be completely avoided, and the adhesion of the improved inks is significantly reduced compared to the solvent-based gravure inks.

In this regard, how to further improve the water-based polyurethane ink is a big research hotspot in the gravure printing industry.

Disclosure of Invention

The invention provides water-based polyurethane ink for gravure printing, aiming at solving the problems that the existing solvent-based gravure printing ink has large volatilization amount of organic solvent, causes harm to human bodies and pollutes the environment, and the existing alcohol-water system water-based polyurethane ink has a large adhesive force and the like.

The invention aims to:

firstly, organic solvent volatilization is reduced or even completely avoided;

and secondly, the bonding strength of the water-based ink and the printing stock is improved.

In order to achieve the purpose, the invention adopts the following technical scheme.

The gravure printing water-based polyurethane ink comprises the following components in percentage by mass:

16-21 wt% of three-component binder, 11-26 wt% of pigment, 0-8 wt% of functional additive and the balance of water;

the three-component connecting material comprises acrylic emulsion A, acrylic emulsion B and polyurethane dispersion liquid;

in the three-component binder, the mass ratio of the acrylic emulsion A is 18-25 wt%, the mass ratio of the acrylic emulsion B is 7-11 wt%, and the balance is polyurethane dispersion liquid;

the hydroxyl value of the acrylic emulsion A is 36-45 mgKOH/g;

the hydroxyl value of the acrylic emulsion B is 90-95 mgKOH/g;

the hydroxyl value relative ratio is calculated by the following formula when the components of the three-component binder are mixed:

in the formula: hv_rIs the relative hydroxyl value ratio, omega_AIs the mass ratio of the acrylic emulsion A in the three-component binder, Hv_AIs the hydroxyl number, omega, of acrylic emulsion A_BIs the mass ratio of the acrylic emulsion B in the three-component binder, Hv_BIs the hydroxyl value of the acrylic emulsion B;

when the three-component connecting materials are mixed, the relative hydroxyl value ratio is controlled to meet 1.02≤Hv_rLess than or equal to 1.45. Wherein, the acrylic emulsion A and the acrylic emulsion B are respectively hydroxyl acrylic emulsion with different hydroxyl values.

In the technical scheme of the invention, the main technical innovation points are that three-component connecting materials are adopted, and the solvent is a pure water solvent, so that the organic solvent of the traditional solvent type gravure printing ink or an alcohol-water system solvent used by the existing commercially available water-based ink is replaced, and the volatilization hazard of the organic solvent can be completely avoided. In the ink system, pure water is used as a solvent, so that the problem of volatilization of the organic solvent of the existing ink can be effectively solved. However, the solvent of the aqueous system causes poor wettability of the ink, poor printing effect and poor ink adhesion in practical use, and thus improvement of the binder is required.

The binder is usually a single-component or two-component binder composed mainly of polyurethane and optionally added with acrylic acid. When the existing single-component or double-component binder is matched with a pure water solvent system for gravure printing, the problems of missing printing and incomplete printing can occur, and the printing effect of complex patterns/characters or large-depth printing is not good. Therefore, the invention improves the existing binder system to obtain a three-component binder which is specifically composed of acrylic emulsion with low hydroxyl value, acrylic emulsion with medium and high hydroxyl value and polyurethane resin.

The hydroxyl value of the acrylic acid actually influences the wettability and the adhesive force of the acrylic acid in an ink system, the acrylic acid with the low hydroxyl value can effectively increase the wettability of the ink so as to improve the actual printing effect and avoid the problems of missing printing or incomplete printing, but the adhesive force of images and texts after actual printing is poor, the adhesive force grade of the ink which adopts the acrylic acid with the low hydroxyl value can only reach 2 grades generally, and the adhesive force grade of the ink after the acrylic acid with the medium and high hydroxyl values is added can reach 0 grade, so that the adhesive force has excellent adhesive force, but the actual wettability is poor, and the problems of missing printing and incomplete printing are more obvious. Therefore, the acrylic acid content and the hydroxyl value thereof are respectively adjusted, and a one-factor orthogonal test proves that the acrylic emulsion with the hydroxyl value of 36-45 mgKOH/g and polyurethane can keep good wettability of the ink, effectively reduce the problems of missing printing and incomplete printing, and have relatively good adhesive force. And by adopting the acrylic emulsion with the hydroxyl value of 90-95 mgKOH/g to be matched with polyurethane, the high adhesive force grade can be ensured, and the polyurethane has relatively good wettability, so that after a researcher tries to mix the low-hydroxyl-value acrylic emulsion A and the medium-high-hydroxyl-value acrylic emulsion B, the adhesive force performance and wettability of the ink can be effectively balanced by the formed three-system connecting material.

However, after performing the multi-factor orthogonal test, it was found that the acrylic emulsion a and the acrylic emulsion B are not simply mixed to optimize the performance, and the fluctuation range of the wettability and the adhesion performance is large, and particularly, the adhesion performance exists in a large range from 2 grades to 0 grades.

Therefore, in order to balance the adhesive force performance and the wettability of the ink and ensure that the quality of the ink reaches a better balanced state, a large number of tests are carried out and a calculation formula of the relative hydroxyl value is summarized, the adhesive force can be ensured to reach at least level 1 by controlling the relative hydroxyl value, the market use standard is met, the missing printing rate is reduced to be less than or equal to 0.5%, and the excellent wettability and the adhesive force of the ink are ensured.

Preferably, the acrylic emulsion B is subjected to crosslinking modification with epoxy resin;

the specific modification process comprises the following steps:

adding 5.5-8.5 wt% of epoxy resin and 0.15-0.25 wt% of 2, 2-dimethylolbutyric acid into the acrylic emulsion B, and reacting for 8-10 h at 80-90 ℃.

During the course of the orthogonal tests and the ink development studies, the researchers found that with the addition of acrylic emulsion B, a major cause of poor ink wettability was that acrylic emulsion B having a higher force after printing had the property of rapid curing and caused a hindrance to the ink wetting on the substrate. This is mainly due to the fact that acrylic acid with a high hydroxyl value easily forms a three-dimensional network cross-linked structure. The epoxy resin is modified by crosslinking, so that the molecular structure of the epoxy resin is more ductile, the wettability is improved, and the ink can be better spread and printed on a printing stock.

Preferably, when the three-component connecting material is mixed:

firstly, mixing acrylic emulsion A and acrylic emulsion B according to a proportion to form mixed emulsion, dripping amino polystyrene microsphere dispersion into the mixed emulsion, stirring for 2-3 h at the temperature of 60-80 ℃, and adding polyurethane dispersion after the temperature is reduced to be less than or equal to 35 ℃.

In the multi-factor orthogonal test process, researchers find that if the acrylic emulsion a and the acrylic emulsion B are simply mixed, the advantages of the two may be mutually offset and the disadvantages may be amplified, so that the ink has neither good wettability nor good adhesion. Therefore, through research and improvement, researchers find that the addition of the amino polystyrene microspheres can effectively improve and strengthen the synergistic effect of the acrylic emulsion A and the acrylic emulsion B, so that the advantages of the acrylic emulsion A and the acrylic emulsion B can be better optimized.

Preferably, the solid content of the polyurethane dispersion liquid is 40-50 wt%.

The solid content is the solid content of the common polyurethane dispersion liquid, and the polyurethane dispersion liquid with the solid content has relatively excellent use effect and can be effectively applied to the technical scheme of the invention. Compared with the conventional ink, the invention adopts the commercial water dispersion system of the polyurethane resin as a polyurethane source, and can avoid the addition and the use of an organic solvent.

Preferably, the functional auxiliary agent includes, but is not limited to, at least one of a dispersant and/or a defoamer.

The functional additives are common ink dispersants and can be selected and used according to requirements.

Preferably, the dispersant is used in an amount of 0 to 3 wt%.

The dispersant may be selected according to actual requirements, and does not play a decisive role in the technical scheme of the invention. The dispersant used in the specific test process of the technical scheme of the invention is a commercial BYK-163 dispersant. It is characterized by non-volatility.

Preferably, the defoaming agent is organic modified silicone emulsion, and the dosage of the defoaming agent is 0-0.5 wt%.

The organomodified silicone emulsion is also a Defoamer commonly used in inks, while the specific Defoamer brand used in the present invention during the specific experimental study was the commercial Defoamer.

Preferably, the pigment is an organic and/or inorganic pigment useful for gravure printing.

The technical scheme of the invention has good applicability to common organic and/or inorganic pigments.

Preferably, the pigment comprises titanium dioxide and/or carbon black and/or copper gold powder and/or phthalocyanine blue and/or lithol red and/or iron red.

The above are the types of pigments examined by specific tests.

The invention has the beneficial effects that:

1) according to the invention, through effective improvement and regulation of the formula and the proportion of the binder, the relative ratio of hydroxyl values in the binder and the use amount of acrylic emulsion with different hydroxyl values are strictly controlled, so that the adhesive force and wettability of the ink can be comprehensively coordinated to reach a higher level;

2) the prepared ink has qualified or relatively excellent levels through the tests of a water resistance test, a volatilization test, an anti-adhesion test and the like.

Detailed Description

The present invention will be described in further detail with reference to specific examples. Those skilled in the art will be able to implement the invention based on these teachings. Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all those known to those skilled in the art.

Unless otherwise specified, the acrylic emulsions A and B used in the examples of the present invention were obtained from Bayer, and the polyurethane dispersions used were obtained from Steyr.

The following examples are typical, relatively representative test records recorded during the course of the research and development of the inventive arrangements, but do not represent all such records and do not limit the scope of the invention. Unless otherwise specified, the specific preparation methods of the inks in the embodiments of the present invention all use conventional ink preparation processes, specifically: the pigment, the functional auxiliary agent and the water with the total dosage of about 1/3 are weighed according to the proportion for grinding, and then the three-component connecting material and the balance of water are added for stirring and mixing evenly. And under the condition of no special description, the three-component connecting material is prepared by directly and uniformly mixing the three subcomponents.

Example 1

The components and the proportion and the hydroxyl value of acrylic emulsion of the gravure water-based polyurethane ink are shown in the following table:

hv of the three-component vehicle used in the inks of this example was calculated_rThe value was 1.15.

Example 2

hv of the three-component vehicle used in the inks of this example was calculated_rThe value was 1.04.

Example 3

The components and the proportion and the hydroxyl value of the acrylic emulsion of the gravure aqueous polyurethane ink are shown in the following table:

hv of the three-component vehicle used in the inks of this example was calculated_rThe value was 0.98.

Example 4

hv of the three-component vehicle used in the inks of this example was calculated_rThe value was 1.29.

Example 5

hv of the three-component vehicle used in the inks of this example was calculated_rThe value was 1.22.

Test I

The inks obtained in examples 1 to 5 were subjected to adhesion test, wettability test and VOC content test.

The VOC content detection is 0.

The adhesion detection is carried out according to GB/T13217.7-2009, and the research and development process of the project is set as follows: the grade 0 is judged when the adhesive force is more than or equal to 98 percent, the grade 1 is judged when the adhesive force is more than or equal to 92 and less than 98 percent, and the grade 2 is judged when the adhesive force is less than 92 percent. The grade 0 adhesive force meets most of market use standards and belongs to printing ink with stronger adsorption force. Typically, a level 1 adhesion strength is also sufficient for normal gravure printing applications.

The wettability test usually uses surface tension as an index, the surface tension is detected by a ring pulling method, the surface tension of the ink is less than or equal to 38 except for example 3, the surface tension of example 3 is 41, and the actual Hv can be seen_rValue pair

The influence of surface tension. However, in the actual use process, the actual ink surface tension is small, and the printing performance is not necessarily excellent. Therefore, the present invention has conducted a specific printing test to further ensure the actual printing quality of the ink.

The printing test is as follows: the roll intaglio paper is used as a printing stock, the font of the text content of the printing content is Hiragino Sans font, the font size is 8pt, the line spacing is 0.5 character, the number of characters on a single page is more than or equal to 1000 characters, 200 pages are printed by the ink obtained in each embodiment, checking is carried out, the condition that the missing printing or the incomplete printing is obvious in vision on the whole page is judged to be OK, and if the condition is OK, the condition is NG. The yield of the actual printing performance was used as the wettability index, and the yield was OK number/(OK number + NG number).

The results of the measurements are shown in the following table.

As is apparent from the above table results, eachUnder the condition of not changing the component proportion, the Hv of the acrylic emulsion A and the acrylic emulsion B is changed_rThe values have a significant effect on the adhesion and wetting of the ink.

Further, the following inks of examples 6 to 9 were prepared by adjusting the component distribution ratio of the three-component vehicle with respect to the acrylic emulsion A having a hydroxyl value of 40mgKOH/g and the acrylic emulsion B having a hydroxyl value of 90mgKOH/g used in example 1.

Example 6

The specific components and components of the gravure printing aqueous polyurethane ink are the same as those in example 1, except that the component distribution ratio of the three-component binder is adjusted, and the specific components are shown in the following table:

hv calculated for the ink of this example_rThe value was 1.14.

Example 7

hv calculated for the ink of this example_rThe value was 1.01.

Example 8

hv calculated for the ink of this example_rThe value was 0.73.

Example 9

hv calculated for the ink of this example_rThe value was 1.58.

Test II

The inks prepared in examples 6 to 9 were subjected to the same test as test I.

The test results show that the VOC content of the ink is 0. The adhesion and wettability test results are shown in the table below.

As can be seen from the above table, by adjusting the content, Hv is affected_rThe value, too, has a great influence on the adhesion and wetting of the ink. In particular, it can be seen from examples 8 and 9 that, in the case of increasing the amount of the acrylic emulsion B, the actual adhesion should be strengthened but the adhesion is rather significantly reduced according to the characteristics of the acrylic emulsion with a medium or high hydroxyl value, and in the case of increasing the amount of the acrylic emulsion a, the wettability should be enhanced but the wettability is rather significantly reduced according to the characteristics of the acrylic emulsion with a low hydroxyl value. In the technical scheme of the invention, the acrylic emulsion A and the acrylic emulsion B are not two mutually independent components which act, and the synergistic effect of the two components changes the effect, so that the effect is relatively more difficult to expect after the components or the mixture ratio are simply changed.

After researchers perform a large number of orthogonal tests, test the adhesive force and preliminarily estimate the actual wettability effect by measuring the surface tension, determining the relationship of each factor to obtain the following formula:

and preliminarily obtaining Hv in the formula_rThe value should satisfy 0.99. ltoreq. Hv_rThe conclusion of less than or equal to 1.47, and continuously carrying out a field printing test near the upper and lower threshold ranges to refine to obtain Hv_rThe value should be 1.02 ≦ Hv_rAnd (3) the conclusion of less than or equal to 1.45, and the optimization of the ink performance can be realized by adjusting the dosage and the hydroxyl value of the acrylic emulsion A and the acrylic emulsion B in the three-component binder. Moreover, the best formula proportion is obtained by performing single-factor orthogonal tests on other factors: 16-21 wt% of three-component binder, 11-26 wt% of pigment, 0-5 wt% of functional assistant and the balance of water. The ink is adjusted in the formula proportion, and the usage amount of the three-component connecting material and the pigment is controlled to be in positive correlation adjustment, so that the relatively excellent performance of the ink can be ensured. The functional auxiliary agent can be selectively added and used according to the actual use requirement. However, the amounts of the three-component binder and the pigment are strictly controlled, the viscosity of the ink is excessively increased easily due to excessive use of the three-component binder, the drying speed is excessively high, the printing effect is influenced, and the drying speed requirement required by printing cannot be met due to too small use of the three-component binder. Too large pigment amount easily causes the problems of agglomeration and deposition of the printing ink in the printing and storage processes, and too small amount can not realize full-color printing.

Example 10

On the basis of the embodiment 2, the scheme is further improved. The specific improvement is that the acrylic emulsion B is modified, and the specific modification process comprises the following steps:

to the acrylic emulsion B, 8.5% by weight of an epoxy resin and 0.25% by weight of 2, 2-dimethylolbutyric acid were added and reacted at 90 ℃ for 8 hours.

Example 11

On the basis of the embodiment 2, the scheme is further improved. The specific improvement is that the acrylic emulsion B is modified, and the specific modification process is as follows:

5.5 wt% of the epoxy resin and 0.15 wt% of 2, 2-dimethylolbutyric acid were added to the acrylic emulsion B, and reacted at 80 ℃ for 8 hours.

Test III

The inks obtained in example 10 and example 11 were subjected to the same test as in test I and compared with example 2, and the results are shown in the following table.

Detecting an object	VOC content	Adhesion force	Wettability	Surface tension/(. times.10)⁵N/cm)
					Example 2	0	Level 1	99.0％	37
Example 10	0	Level 1	100％	32
					Example 11	0	Level 1	100％	34

It is obvious from the above tests that the acrylic emulsion B is further modified to further improve the wettability of the ink and reduce the surface tension thereof, so that the ink has more excellent specific use effect.

Example 12

On the basis of the embodiment 2, the scheme is further improved. Specifically, the three-component binder is prepared by mixing a unique process, which specifically comprises the following steps:

firstly, mixing acrylic emulsion A and acrylic emulsion B according to a proportion to form mixed emulsion, dripping amino polystyrene microsphere dispersion liquid accounting for about 0.5 wt% of the total mass of the mixed emulsion into the mixed emulsion, stirring for 3 hours at the temperature of 60 ℃, cooling to the temperature of less than or equal to 35 ℃, and then adding polyurethane dispersion liquid to be uniformly mixed.

Example 13

firstly, mixing acrylic emulsion A and acrylic emulsion B according to a proportion to form mixed emulsion, dripping amino polystyrene microsphere dispersion liquid accounting for about 0.75 wt% of the total mass of the mixed emulsion into the mixed emulsion, stirring for 2 hours at the temperature of 80 ℃, adding polyurethane dispersion liquid after the temperature is reduced to be less than or equal to 35 ℃, and uniformly mixing.

Test IV

The inks obtained in example 12 and example 13 were subjected to the same test as in test I and compared with example 2, and the results are shown in the following table.

Detecting an object	VOC content	Adhesion force	Wettability	Surface tension/(. times.10)⁵N/cm)
					Example 2	0	Level 1	99.0％	37
Example 12	0	Level 1	99.5％	36
					Example 13	0	Level 0	100％	36

The tests show that the technical effect of reinforcing the acrylic emulsion A and the acrylic emulsion B can be achieved by adding the amino polystyrene microspheres, and the adhesive force and the wettability of the ink can be further reinforced under the condition that the component proportion is not changed, so that the ink has a better using effect.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. The gravure printing water-based polyurethane ink is characterized by comprising the following components in percentage by mass:

16-21 wt% of three-component binder, 11-26 wt% of pigment, 0-5 wt% of functional additive and the balance of water;

the hydroxyl value of the acrylic emulsion A is 36-45 mgKOH/g;

the hydroxyl value of the acrylic emulsion B is 90-95 mgKOH/g;

when the three-component connecting materials are mixed, the relative hydroxyl value ratio is controlled to meet the requirement that Hv is more than or equal to 1.02_r≤1.45。

2. The gravure aqueous polyurethane ink according to claim 1, wherein the acrylic emulsion B is modified by crosslinking with an epoxy resin; the specific modification process comprises the following steps:

3. The gravure aqueous polyurethane ink as claimed in claim 1 or 2, wherein the three-component vehicle, when mixed: firstly, mixing acrylic emulsion A and acrylic emulsion B according to a proportion to form mixed emulsion, dripping amino polystyrene microsphere dispersion into the mixed emulsion, stirring for 2-3 h at the temperature of 60-80 ℃, and adding polyurethane dispersion after the temperature is reduced to be less than or equal to 35 ℃.

4. The gravure-printing aqueous polyurethane ink as claimed in claim 1, wherein the polyurethane dispersion has a solid content of 40 to 50 wt%.

5. The gravure aqueous polyurethane ink according to claim 1, wherein the functional auxiliary comprises a dispersant and/or a defoaming agent.

6. The gravure-printing aqueous polyurethane ink as claimed in claim 5, wherein the amount of the dispersant is 0 to 3 wt%.

7. The gravure-printing aqueous polyurethane ink as claimed in claim 5, wherein the defoaming agent is an organic modified silicone emulsion, and the amount of the defoaming agent is 0 to 0.5 wt%.

8. The gravure-printing aqueous polyurethane ink according to claim 1, wherein the pigment is an organic and/or inorganic pigment usable for gravure printing.

9. An aqueous polyurethane intaglio printing ink according to claim 1 or 8, characterized in that said pigments comprise titanium dioxide and/or carbon black and/or bronze powder and/or phthalocyanine blue and/or lithol red and/or iron red.