JP2000219833A - Printing ink composition for flexo letterpress - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printing ink composition for flexo letterpress excellent in viscosity stability when printed with a printing machine and having good drying properties on a paper and clear color developing properties. SOLUTION: This composition contains glycerol in an amount of 3-80 wt.% based on the total amount of a solvent in the ink composition, water in an amount of 0-50 wt.% based on the total amount of the solvent in the ink composition and one or more kinds of solvents selected from the group of a glycol and a glycol derivative in an amount of 0-50 wt.% based on the total amount of the solvent in the ink composition in the ink composition for flexo letterpress used in a printing machine equipped with an ink feeder capable of storing an ink between an anilox roll and a squeeze roll or a doctor blade and then feeding the ink to a plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a printing machine equipped with an ink supply device for storing a small amount of ink between an anilox roll and a squeezing roll and supplying ink to a printing plate, thereby providing more vivid color formation. The present invention relates to a printing ink composition for flexographic letterpress having good properties, good on-machine viscosity stability and good on-paper drying properties.

[0002]

2. Description of the Related Art Conventionally, in the field of flexographic printing centering on cardboard, water-based ink compositions and glycol-type ink compositions have been selectively used taking advantage of their respective features. The aqueous ink composition can be printed at a high speed because it dries faster than the glycol type ink composition, but has poor cleaning properties, and once dried on a plate or the like, cleaning becomes difficult. . Therefore, the aqueous ink composition is
It is used when printing a large number of prints in a large lot, which allows continuous operation of the printing press at high speed for a long time.On the other hand, the glycol type ink composition is frequently used to stop the printing press and change ink or color. It has been used to produce many kinds of printed materials in small lots.

However, in the flexographic printing industry in recent years, the tendency of a small lot and a large variety of products has become stronger, and in the shortest case, printing of one lot is completed in several minutes. In this case, cleaning the printing press or changing the ink takes several times as long as the printing time, which causes a problem that the printing efficiency is extremely low.

Therefore, in order to solve the above-mentioned problem from the viewpoint of the printing mechanism, first, a small amount of ink is stored between the anilox roll and the squeezing roll, and a dam plate is provided to prevent the ink from flowing out. A printing machine without an ink circulation device, which is difficult to perform, has been devised.
No. 78435 describes the details. In a printing machine with such a mechanism, the parts to be washed when moving to the next printing are only the anilox roll and the squeezing roll,
In addition, at present, it is only necessary to change the bottle containing the ink, and it is possible to print various kinds of printed matter extremely efficiently.

[0005] On the other hand, since the ink circulation device is not provided, the supplied ink is always kept in contact with the atmosphere, and the solvent component evaporates without interruption. In particular, in this type of printing press, since printing is performed with the ink supply amount suppressed as much as possible, the viscosity increases as soon as the solvent component evaporates, making printing impossible.

Accordingly, the viscosity stability of the ink on a printing press is relatively good, and in order to speed up the drying on paper, for example, 50 to 95% by weight of glycol is added to the total amount of the solvent of the ink. An ink composition using 5 to 50% by weight of water is disclosed in JP-A-1-62373.

[0007]

However, such an ink composition does not provide clear color development, and as the amount of water used increases, especially when the amount of water used is around 50% by weight, printing is not possible. There is a problem that the viscosity stability on the machine is reduced. Accordingly, an object of the present invention is to provide a flexographic relief printing ink composition having sharper color developing properties, good viscosity stability on a printing press, and good on-paper drying properties when printing under the severe printing conditions as described above. It is to provide things.

[0008]

That is, the present invention is used in a printing press having an ink supply device for storing ink between an anilox roll and a squeezing roll or a doctor blade, and then supplying the ink to a plate. In the printing ink composition for flexographic relief printing, glycerin is added in an amount of 3 to 80% by weight and water is added in an amount of 0 to 0 based on the total amount of the solvent in the ink composition.
The present invention relates to a printing ink composition for flexographic relief printing plates, characterized in that the composition contains from 0 to 50% by weight, and from 0 to 50% by weight of one or more solvents selected from the group consisting of glycols and glycol derivatives.

The present invention is a flexographic printing ink composition comprising a pigment, a binder resin and a solvent as main components.

As the pigment used in the present invention, those usually used in aqueous and glycol type flexographic relief printing inks can be used as they are. Specifically, as the inorganic pigment, titanium oxide, cadmium yellow, Vengara, antimony red, cobalt blue, navy blue, ultramarine,
Color pigments such as carbon black and graphite, and extenders such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide and talc can be mentioned. Examples of the organic pigment include a soluble azo pigment, an insoluble azo pigment, an azo lake pigment, a condensed azo pigment, a copper phthalocyanine pigment, and a condensed polycyclic pigment.

These pigments are usually used in the ink composition in the range of about 1 to 50% by weight.

Next, as the binder resin used in the present invention, those usually used in aqueous and glycol type flexographic relief printing inks can be used as they are,
At least one copolymer resin selected from the group consisting of rosin-modified maleic resin, acrylic resin, styrene-acrylic resin, styrene-maleic resin, and styrene-acryl-maleic resin can be suitably used. .

The acrylic resin is an acrylic monomer, the styrene-acrylic resin is a styrene monomer and an acrylic monomer, and the styrene-maleic acid resin is a styrene monomer. And a maleic acid-based monomer, and a styrene-acrylic-maleic acid-based resin is a copolymer resin containing a styrene-based monomer, a maleic acid-based monomer and an acrylic-based monomer as a copolymer component. .

Further, as the acrylic monomer, acrylic acid and methacrylic acid can be used as a component for introducing a carboxyl group required for dissolving the resin in a solvent into the molecule of the resin. Examples of copolymerizable acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) acrylic acid alkyl ester compounds such as lauryl (meth) acrylate and stearyl (meth) acrylate; and (meth) containing aromatic rings such as benzyl (meth) acrylate and naphthyl (meth) acrylate
Hydroxyalkyl (meth) acrylate compounds such as acrylic ester compounds, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl (meth) acrylate can be used.

As the styrene monomer, styrene, α
-Methylstyrene, vinyltoluene and derivatives thereof.

As the maleic acid monomer, maleic anhydride, monomethyl maleate, and maleic acid are used as components for introducing a carboxyl group necessary for dissolving the resin in a solvent into the molecule of the resin. Monoethyl, monopropyl maleate, monobutyl maleate, monohexyl maleate, monooctyl maleate, mono-2-ethylhexyl maleate, monolauryl maleate,
Monoalkyl maleate such as monostearyl maleate can be mentioned, and dialkyl maleate compounds such as dimethyl maleate, diethyl maleate and dibutyl maleate can be used.

These copolymer resins may be used, if necessary, such as (meth) acrylamide, crotonic acid and its ester compound, itaconic acid and its ester compound, citraconic acid and its ester compound, acrylonitrile, olefin compound and the like. Other copolymerizable monomers may be used as copolymer components.

The acid value of the above binder resin is preferably 100 to 300 mgKOH / g, more preferably 150 to 250 mgKOH / g. When the acid value of the resin is lower than 100 mgKOH / g, the solubility of the resin in the solvent is reduced, while the acid value is 300 mgKOH / g.
If it is higher, the water resistance of the ink is undesirably reduced.

In the present invention, the binder resin is used as a binder resin varnish by dissolving it in a single or mixed solvent of glycerin, water, glycol, a glycol derivative or the like in the presence of a basic compound. Examples of the basic compound that can be used in the present invention include inorganic basic compounds such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide, and organic amine compounds such as triethylamine, monoethanolamine, and triethanolamine.
In particular, a high-boiling organic amine compound is preferred in the present invention from the viewpoint of suppressing the viscosity of the ink on a printing press.

These binder resins are usually used in the ink composition in the range of about 1 to 30% by weight.

Next, as a solvent of the ink composition of the present invention, glycerin is an essential component, and water, glycol, a glycol derivative and the like are selectively used in accordance with the printing environment. Here, as the glycol component, diol compounds such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol can be used,
As the derivatives, alkyl ether compounds such as methyl, ethyl, propyl, butyl, hexyl and octyl of the glycol, ester compounds such as acetic acid ester and butyric acid ester, and ester ether compounds can be used.

The content ratio of each of the above solvents is determined based on the total amount of the solvent in the ink composition.
0 to 80% by weight, water 0 to 50% by weight, one or more solvents 0 to 0 selected from the group of glycols and glycol derivatives
50% by weight. If the content of glycerin is less than the above range, an ink having good coloring properties cannot be obtained, while if the content is too large, the drying property on paper is undesirably low. On the other hand, if the water content exceeds 50% by weight, the viscosity stability of the ink on a printing press is undesirably reduced.
Further, from the viewpoint of vivid color development and viscosity stability on a printing press, it is advantageous to include more glycerin in the system than glycols, while from the viewpoint of drying properties, glycol is more preferable than glycerin. It is more advantageous to contain a large amount of such compounds. From these viewpoints, a more preferable solvent composition is about 15 to 60% by weight of glycerin, 10 to 40% by weight of water, and about 15 to 45% by weight of one or more solvents selected from the group of glycols and glycol derivatives. .

The dried form of the ink composition of the present invention may contain a basic compound in an amount equal to or more than the neutralized amount as in a general aqueous printing ink composition. Even in the form of volatilizing or penetrating into paper, such as glycol-type printing ink compositions,
Including less than the neutralization amount of the basic compound, after printing,
It may be in the form of a so-called moisture set in which the ink is set by moisture absorption. Therefore,
Regarding the relationship between the solvent composition of the ink and the content of the basic compound, when the content of water is large, the degree of neutralization of the basic compound with respect to the binder resin is preferably set to 100% or more. When the content of glycol or the like is high and the content of water is low, the degree of neutralization of the basic compound with respect to the binder resin may be less than 100%.

Further, the ink composition of the present invention may contain various additives such as a pigment dispersant, a wax, an antifoaming agent, a transferability improving agent, and a leveling agent.

As a method for producing an ink composition using the above materials, first, a pigment, a binder resin varnish,
After stirring and mixing the solvent and, if necessary, a pigment dispersant, a surfactant and the like, various meat processing machines, for example, a bead mill,
Ball mill, sand mill, attritor, roll mill,
A method of kneading meat using a pearl mill or the like and further adding and mixing the remaining ingredients is used.

The ink composition of the present invention is used in a printing machine equipped with an ink supply device for storing ink between an anilox roll and a squeezing roll or a doctor blade and then supplying the ink to a plate. . Printing machines of this type usually do not have an ink circulation device, but instead have shielding plates or air curtains at the valleys formed between the anilox roll and the squeezing roll or doctor blade to prevent the ink from flowing out. And a mechanism for storing ink in the valleys. Then, a small amount of ink contained in a bottle type container is poured into the valley by an ink supply device called a tubing device, and the entire printing operation is performed in a non-circulating state.

Accordingly, the ink composition is always kept in contact with the atmosphere, and the solvent component evaporates without interruption. However, by using glycerin as the solvent component, the viscosity stability of the ink on a printing press can be improved. It has excellent color development.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” represent “parts by weight” and “% by weight” unless otherwise specified.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preparation of Ink <Synthesis of Binder Resin> Binder Resin Production Example 1 In a four-necked flask equipped with a stirrer, a cooling pipe, and a nitrogen gas inlet pipe, 600 parts of ethyl acetate was charged and heated to 75 to 85 ° C. to remove nitrogen gas. While introducing methacrylic acid 128
Part, methyl methacrylate 92 parts, butyl acrylate 100 parts, styrene 80 parts, a mixture of ditertiary butyl peroxide 4 parts as an initiator was added dropwise over 1.5 hours, and further copolymerized for 2 hours while maintaining the same temperature. After that, the solvent was distilled off under reduced pressure to obtain an acid value of 180 mg KO.
A styrene-acrylic copolymer resin having a H / g of 40,000 and a weight average molecular weight of 40,000 (binder resin No. 1) was obtained.

Binder Resin Production Example 2 In a four-necked flask equipped with a stirrer, a cooling pipe, and a nitrogen gas introducing pipe, 600 parts of ethyl acetate was charged and heated to 75 to 85 ° C. while introducing nitrogen gas. 225 parts of maleic acid, 20 parts of maleic anhydride, 155 parts of styrene,
Ditertiary butyl peroxide 4 as an initiator
Part of the mixture was added dropwise over 1.5 hours, and further copolymerized for 2 hours while maintaining the same temperature. Then, the solvent was distilled off under reduced pressure to obtain an acid value of 234 mgKOH / g and a weight average molecular weight of 280.
Thus, a styrene-maleic acid-based copolymer resin of No. 00 (binder resin No. 2) was obtained.

<Manufacture of Binder Resin Varnish> According to the formulation shown in Table 1, a binder resin was added with stirring to a solvent in which a basic compound was dissolved, and the temperature was raised to 80 ° C. to prepare binder resin varnishes A to E. .

[Table 1]

<Preparation of Base Ink> In accordance with the formulation shown in Table 2, 25 parts of a pigment (Lionol Blue FG-7330, manufactured by Toyo Ink Mfg. Co., Ltd.), a binder resin varnish and a solvent in such an amount that the viscosity becomes appropriate at the time of kneading are used. After kneading the mixture with a ball mill, the remaining materials were further added and mixed to prepare base inks A to E.

[Table 2]

<Preparation of Ink Composition> According to the formulation shown in Table 3, base ink, binder resin varnish, solvent, wax (Chemipearl W200, manufactured by Mitsui Chemicals, Inc.) and defoamer (KM-70, Shin-Etsu Chemical Co., Ltd.) Was mixed with stirring to prepare ink compositions of Examples 1 to 6 and Comparative Examples 1 to 4.

[Table 3]

2. Evaluation of Performance of Ink Composition The viscosity stability of the test inks on a printing press, the drying property on paper, and the coloring property were evaluated by the following methods, and the results are shown in Table 3.

<Viscosity Stability on Printing Machine> The viscosity of each test ink was adjusted using a diluent having the same solvent composition as each ink so that the viscosity of each ink was 0.1 Pa · s. Flexographic two-color printing press equipped with a mechanism to supply ink to the plate with a squeeze roll (manufactured by Higashiya Works)
Each test ink was poured between an anilox roll and a squeeze roll with a spoid, and the ink was run for 20 minutes, and then printed on a K liner (manufactured by Oji Paper Co., Ltd.). Then, the viscosity stability of the ink on a printing machine was evaluated from the state in which the printing paper adhered to the plate due to the increase in the viscosity of the ink. The test conditions were as follows: ambient temperature 20 ° C., relative humidity 60%,
The printing speed was 60 m / min, and the dryer temperature was 60 ° C. A: Printing is possible without the paper sticking to the plate surface at all. B: The paper adheres to the plate surface, but printing can be performed without causing paper peeling. C: Printing is impossible due to peeling of the paper.

<Dryability on paper> In the viscosity stability test on the printing press, the ink that was printable was evaluated for dryness on paper from the presence or absence of stains on the guide rolls in contact with the printing surface. A: The guide roll is not stained. B: The guide roll becomes dirty.

<Coloring Property> Inks having the same composition as Comparative Example 1 were used as standard inks, each test ink was spread on a K liner with a 0.15 mm Meyer bar, and the level of coloring property was visually observed. A: Among the inks whose color is clearly clearer than the standard ink, those at a higher level even when compared. B: Below the average level when compared among the inks whose color is clearly clearer than the standard ink. C: Sharpness is not recognized for the standard ink.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

As described above in detail with reference to Examples and Comparative Examples, the printing ink composition of the present invention stores ink between an anilox roll and a squeezing roll or a doctor blade. Next, when used in a printing press equipped with an ink supply device that supplies ink to the plate, it has the effect of excellent viscosity stability of the ink on the printing press, excellent drying properties on paper, and clear coloring. It is.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C250 DB02 DB08 4J039 AD03 AD10 AD14 AF01 BA03 BA04 BA13 BA16 BA18 BA23 BA30 BA31 BA32 BA35 BA38 BA39 BC07 BC09 BE01 BE12 CA03 CA04 EA10 EA44 GA01

Claims (1)

[Claims] 1. A flexographic relief printing ink composition used in a printing press equipped with an ink supply device for storing ink between an anilox roll and a squeezing roll or a doctor blade and then supplying ink to a plate.
Glycerin is used in an amount of 3 to 3 with respect to the total amount of the solvent in the ink composition.
80% by weight, 0 to 50% by weight of water, and 0 or more solvents selected from the group consisting of glycols and glycol derivatives.
A printing ink composition for flexographic relief printing, characterized in that the composition contains about 50% by weight.