JP2002292985A - Method of preventing stain of printed matter in flexographic letterpress printing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preventing a stain of a printed matter of water-based printing ink which enables immediate start of printing and prevents an anilox roller from being clogged with an ink-repellent material and which can maintain the effect of preventing the stain for a long time. SOLUTION: In the manufacture of the print of water-based printing ink by the flexographic letterpress printing system using a plate roller and the anilox roller, a stain-preventing agent containing the ink-repellent material and a water-based resin in the weight ratios of 2:8-8:2 is applied to both of a projecting part and an indented part of a letterpress plate and dried before printing and then, the stain-preventing agent being removed from the projecting part of the letterpress plate, the water-based printing ink is printed, according to the method of preventing the stain of the print of the water-based printing ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing contamination of a water-based printing ink print, and more particularly, to a method of applying an ink-based material to a plate surface in the production of a water-based printing ink print using a flexographic relief printing method. In addition, the present invention relates to a method for preventing stains on water-based printing ink prints, which can start printing immediately, can maintain the stain prevention effect for a long time, and can prevent clogging of the anilox roll with ink-based materials.

[0002]

2. Description of the Related Art In a relief printing method, an ink supply roll is brought into contact only with the surface of a convex portion (image portion) of a printing plate having irregularities to supply ink, and then the plate is brought into contact with a printing medium. This is a printing method for performing printing. Therefore, if the ink is supplied to the concave portion (non-image portion) of the printing plate, the ink adheres to a portion where there is no printed pattern, and the printed matter is stained.

[0003] In order to prevent such stains, an ink-based material is applied to the entire surface of the printing plate, and then the ink-based material having the convex portions is transferred to the printing medium and removed. A method is known in which the ink material is left in the concave portions as it is and the ink is adhered only to the convex portions. For example,
JP-A-52-13904, JP-A-53-6118
In the Japanese Patent Publication No.
There is disclosed a method of using a lipophilic ink material in the above-described method to prevent stains on printed matter.

[0004] Since oil-based inks have a relatively high viscosity, the ink supply roll, whose surface is covered with an ink film, is pressed against a hard plate material with a strong force, and the adhesion of the ink to the plate surface is determined by the cohesive force of the ink itself. A method is used in which ink is transferred only to a larger portion. In this case, while the convex portion on the plate comes into contact with the ink supply roll with high pressure,
Even if the recesses come into contact with each other, the pressure is low, and the ink is further covered with the ink material, so that the adhesive force of the ink is reduced and the ink can be relatively easily transferred only to the protrusions.

On the other hand, the printing method targeted by the present invention is a flexographic printing method for printing corrugated cardboard, paper bags, and the like mainly using water-based ink even in the same letterpress printing. It has a very low viscosity, and a rubbery elastic material is used as the plate material. Therefore, when the ink supply roll is pressed against the printing plate surface with a strong force, the ink is pushed out from the convex portions of the printing plate and is removed, so that the ink is not transferred.

Therefore, in the flexographic printing system, a method is used in which the ink accumulated in the concave portions is brought into contact with the plate with a very weak pressure to transfer by using an ink supply roll called an anilox roll having an uneven surface. However, there are many problems that need to be solved in order to prevent stains on printed matter using an ink-based material in this method.

For example, as compared with a printing method using oil-based ink, the projections are crushed by a slight pressure due to the flexibility of the plate material, the depressions are more likely to come into contact with the anilox roll, and the ink is transferred with a low viscosity. For example, the concave portions are required to have a higher ink repellency because they are easy to perform. On the other hand, the higher the effect as a reversible ink material, the longer the reproducibility of the ink on the protruding portions of the plate, and the more the material must be completely removed through more substrates to transfer the ink. There's a problem. In addition, in the flexographic printing method, since an anilox roll is used, if an ink material adheres to a concave portion of the surface, the ink is repelled and cannot be supplied to the plate, which causes a problem of poor printing. is there.

Therefore, at present, a technology is used that uses a commercially available emulsion of a material having an ink-repellent property, such as a silicon compound or a fluororesin, to apply a thin coating on a plate surface by a spray method or the like to prevent stains on printed matter. It is just that.

[0009]

However, the above method of thinly applying an emulsion of a silicone oil or a fluororesin to a plate surface has a poor persistence of the effect, and causes stains on printed matter immediately. . Also, if the plate surface is thickly applied to maintain the effect, it takes a lot of time and a printing medium to remove the emulsion applied to the convex portions, and the concave portions of the anilox roll are clogged, There is a problem that supply of ink becomes impossible.

Therefore, the problem to be solved by the present invention is that in the production of an aqueous printing ink print by the flexographic relief printing method, printing can be started immediately,
An object of the present invention is to provide a method for preventing stains on a water-based printing ink print, which can prevent the anilox roll from being clogged with an ink-based material and can maintain the stain-preventing effect for a long time.

[0011]

That is, the present invention provides:
In the production of a water-based printing ink print by a flexographic relief printing method using a plate roll and an anilox roll, before printing, both the convex portion and the concave portion of the relief plate are provided with an ink-based material: aqueous resin = 2: 8 to 8: 2. The present invention relates to a method for preventing stains on a water-based printing ink printed matter, comprising applying a water-based printing ink after applying and drying a stain-proofing agent contained in a weight ratio, and then removing the stain-proofing agent from the projections of the relief printing plate. It is.

The present invention also relates to a method for preventing stains on an aqueous printing ink print, wherein the ink-repellent material of the stain inhibitor is a silicon compound and / or a fluorine compound. Further, the invention of the present application, the ink-repellent material of the antifouling agent,
The present invention relates to a method for preventing stains on an aqueous printing ink print, which is an aqueous emulsion of a silicon compound and / or an aqueous emulsion of a fluorine compound.

[0013] Further, the invention of the present application is characterized in that the aqueous resin of the antifouling agent is a rosin-modified maleic resin having an acid value of 100 to 250 mgKOH / g, an acrylic resin, a styrene-acrylic resin, a styrene-maleic resin, a styrene resin. The present invention relates to a method for preventing stains on an aqueous printing ink print, which is at least one selected from the group consisting of acrylic-maleic acid-based resins.

Further, the present invention provides an aqueous emulsion of a silicon-based compound and / or an aqueous emulsion of a fluorine-based compound as an antifouling agent.
An aqueous resin varnish obtained by dissolving at least one aqueous resin selected from the group consisting of 250 mg KOH / g acrylic resin, styrene-acrylic resin, and styrene-maleic acid resin in water in the presence of a basic compound; 5. A method for preventing stains on a water-based printing ink print according to claim 1, wherein a stain inhibitor obtained by mixing is used. Hereinafter, the present invention will be described in detail.

According to the present invention, a stain preventive agent containing an ink repellent material and an aqueous resin is left only in the concave portions of the letterpress to prevent stains on printed matter. Here, as the available ink-based material, a material having an ink-based property with respect to an aqueous printing ink, and any material that can be mixed with an aqueous resin can be used. From the viewpoint of obtaining a high effect, an aqueous dispersion such as a silicon compound or a fluororesin can be suitably used.

Further, the silicone compound is a silicone oil which can be dispersed in water in the presence of an emulsifier, or a self-emulsifying type modified silicone oil modified with polyoxyethylene or the like. Foams and release agents can be used more preferably. As a preferred embodiment of the silicone oil, those having an emulsion form include, for example, KM70, KM71, KM7
2 series, KM73 series, KM-722A, KM
-740, KM-780, KM-782, KM-785
Etc. (both are trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), TS
M 7341, TSM 7343, TSM 730, TSM 7
32, TSM770, TSM775, etc. (all trade names, manufactured by GE Toshiba Silicone Co., Ltd.), FS Antifoam 013B, FS Antifoam 1233, FS Antifoam 1254, etc. (all trade names, Toray Dow Corning Silicone Co., Ltd.) ) Company-based).

As the fluororesin, similarly to the silicon compound, a polyfluorinated ethylene compound, a poly (ethylene-fluoroethylene) compound, a poly (ethylene-fluorinated ethylene) compound which can be dispersed in water in the presence of an emulsifier. propylene)
And the like. Examples of the fluorine-based aqueous resin emulsion include Unidyne TG-40
0, TG-490, TG-500, TG-590 (all trade names, manufactured by Daikin Industries, Ltd.), Lumiflon (trade name, manufactured by Asahi Glass Co., Ltd.), Fluonate FEM-
Aqueous types such as 500 and FEM-600 (both trade names, manufactured by Dainippon Ink and Chemicals, Inc.).

On the other hand, the aqueous resin which can be used in the antifouling agent of the present invention is usually used in aqueous flexographic relief printing inks, and a water-soluble resin in the presence of a basic compound is used. It is possible, rosin-modified maleic resin,
At least one copolymer resin selected from the group consisting of an acrylic resin, a styrene-acrylic resin, a styrene-maleic acid resin, and a styrene-acryl-maleic acid resin can be suitably used. Here, the acrylic resin is an acrylic monomer, the styrene-acrylic resin is a styrene monomer and an acrylic monomer,
A maleic acid resin is a styrene monomer and a maleic acid monomer, and a styrene-acrylic-maleic resin is a styrene monomer, a maleic acid monomer and an acrylic monomer. It is a copolymer resin used as a copolymer component.

Further, as the acrylic monomer, acrylic acid and methacrylic acid are used as a component for introducing a carboxyl group necessary for dissolving the resin in water into a resin molecule in the presence of a basic compound. Other possible copolymerizable acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2- (Meth) acrylic acid alkyl ester compounds such as ethylhexyl (meth) acrylate, lauryl (meth) acrylate and stearyl (meth) acrylate; and (meth) acrylic containing aromatic rings such as benzyl (meth) acrylate and naphthyl (meth) acrylate Acid ester compound, 2-hydroxyethyl (meta Acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) (meth) acrylic acid hydroxyalkyl ester compounds such as acrylates can be used.

As the styrene monomer, styrene, α
-Methylstyrene, vinyltoluene and derivatives thereof. The maleic acid-based monomer includes maleic anhydride (maleic anhydride) and maleic anhydride as components for introducing a carboxyl group required for dissolving the resin in water in the presence of a basic compound into the molecule of the resin. Monoalkyl esters of maleic acid such as monomethyl acrylate, monoethyl maleate, monopropyl maleate, monobutyl maleate, monohexyl maleate, monooctyl maleate, mono-2-ethylhexyl maleate, monolauryl maleate, monostearyl maleate, etc. Further, dialkyl maleate compounds such as dimethyl maleate, diethyl maleate and dibutyl maleate can be used.

Further, 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 aqueous resin obtained by polymerizing the above monomer components is 100 to 250 mgKOH /
g, more preferably 120 to 250 mgKOH / g. When the acid value of the resin is lower than 100 mgKOH / g, it is difficult to remove the resin from the convex portion when used as a stain preventive agent, and the resin tends to be easily clogged with an anilox roll, which is not preferable. On the other hand, when the acid value is 25
If it is higher than 0 mgKOH / g, the durability of the stain prevention effect tends to decrease, which is not preferable.

The above-mentioned aqueous resin is used by dissolving it in water in the presence of a basic compound. Examples of the usable basic compound include aqueous ammonia, sodium hydroxide, potassium hydroxide and ammonium hydroxide. Such as inorganic basic compounds, triethylamine, monoethanolamine,
Organic amine compounds such as triethanolamine can be mentioned.

In the above-mentioned antifouling agent containing an ink-based material and an aqueous resin material, the content ratio is as follows: ink-based material: aqueous resin = 2: 8 to 8: 2, preferably 3: 7.
It is an amount that results in a weight ratio of up to 7: 3. When the content ratio of the ink-repellent material is less than the above range, the stain prevention effect tends to decrease, which is not preferable. On the other hand, when the content ratio of the ink repellent material is increased, it is difficult to remove the material from the projections when used as a stain preventive agent, and it tends to be easily clogged with an anilox roll, which is not preferable. In view of the fact that the coating can be made thicker on the plate surface, it is advantageous that the combined content of both materials in the antifouling agent is higher, and in order to obtain an effect with a smaller coating amount or the number of coatings, 10% by weight is required. It is preferable that this is the case.

Further, various additives such as a water-miscible organic solvent, an antifoaming agent, a transferability improving agent, and a leveling agent can be added as other optional components to the antifouling agent of the present invention.

In the antifouling agent containing the above-mentioned materials, if the conditions for maintaining the required antifouling effect for a long time differ depending on the depth or area of the concave portion of the relief plate, the amount of the antifouling agent applied, It can be adjusted by the acid value of the aqueous resin and the content ratio between the ink-based material and the aqueous resin.

Next, as a method of applying the stain preventive agent to the surface of the flexographic relief plate, any method can be used as long as it can form a stain preventive agent film on the plate surface of the relief plate.
For example, the spray method is a low-viscosity antifouling agent,
In addition, if it is a high-viscosity antifouling agent, brush coating or a method of attaching it to the plate surface using a cloth or sponge can be used,
It is suitable in that the coating can be performed on the plate as it is or mounted on the plate cylinder. In addition, if the plate is in its original state, a method of applying a stain preventive agent on the plate surface and then uniformly applying it using a bar or a blade can also be used. This is preferable because it is relatively easy to scrape and reduce the amount of coating, and to coat the surface of the concave portion thickly, so that printing can be performed immediately and the effect can be maintained.

In the present invention, at first, the entire surface of the plate is covered with a stain preventive agent, and the stain preventive agent on the surface of the convex portion of the plate is transferred to the printing medium, and is completely removed before printing. Will be possible. Even if the antifouling agent is formed as a thick film, printing can be performed earlier than in the case where only the ink-based material is applied, and the ink-based material is clogged in the recesses of the anilox roll to supply the ink. This has the characteristic that the effect can be maintained for a long time without causing a problem of preventing the effect.

[0029]

EXAMPLES 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.

1. Preparation of antifouling agent Styrene-methacrylic acid-butyl acrylate copolymer (aqueous resin A), styrene-methacrylic acid-butyl acrylate copolymer obtained by copolymerizing a mixture having the monomer composition shown in Table 1. The amount of neutralization of monoethanolamine was determined for each of the copolymer (aqueous resin B), styrene-monobutyl maleate copolymer (aqueous resin C), and styrene-maleic anhydride-monobutyl maleate copolymer (aqueous resin D). The resultant was dissolved in the dissolved aqueous amine solution to obtain an aqueous resin varnish having a solid content of 38%. Further, as a silicone emulsion, KM740 (manufactured by Shin-Etsu Chemical Co., Ltd., solid content 3)
8%) and each of the aqueous resin varnishes were stirred and mixed in such an amount as to have a weight composition ratio shown in Table 2 to prepare antifouling agents 1 to 10. Further, only the silicone emulsion KM740 was used as an antifouling agent 11, and the one diluted 5 times with water was used as an antifouling agent 12.

[Table 1]

[Table 2]

2. Evaluation Flexo resin letterpress (AFP, manufactured by DuPont)
A rectangular solid portion is provided, a fine character portion is provided at a portion which is rearward of the solid portion from the direction of travel of the plate, and is in contact with the anilox roll surface which has contacted the solid portion after one rotation, and a plate cylinder shaft is provided for the solid portion. A pattern consisting of a line drawing part of a bar code was provided in the (horizontal) direction, and a relief for evaluation of printed matter having a test pattern in which the depth of a concave portion was 1 mm was prepared.

The anti-smudge agents 1 to 11 are applied to the relief printing plate for evaluation of the printed matter in a coating amount such that the thickness of the anti-smudge agent on the convex portions is approximately 0.5 mm, and covers the entire plate surface. After drying, a water-based printing ink (NewFK MR-10, manufactured by Sakata Inx Co., Ltd.) was printed on coated paper (CRC, manufactured by Rengo Co., Ltd., 230 g / m ² ) using a flexo printing machine. The following evaluation was performed. Also,
After the antifouling agent 12 was sprayed and dried on the plate surface by a conventionally known spray method, printing was performed using the same printing machine, coated paper, and water-based printing ink as described above, and the following evaluation was performed. Table 3 shows the evaluation results.

[Table 3]

Early printability From the start of printing, the early printability was evaluated from the length of the coated paper required until the antifouling agent on the convex portions came into contact with and removed from the coated paper and the bar code could be read. A: The length of the coated paper is 10 m or less. B: The length of the coated paper exceeds 10 m and is 100 m or less. C: Coated paper having a length exceeding 100 m and not more than 500 m. D: A normal printed matter cannot be obtained even if the length of the coated paper exceeds 500 m.

Stain resistance Stain resistance was evaluated from the length of the coated paper that was printed before normal printing was obtained and stains occurred and the bar code could not be read. A: Coated paper having a length of 40000 m or more. B: The length of the coated paper exceeds 4000 m and is 40,000 m
What is the following. C: Coated paper having a length of more than 500 m and not more than 4000 m. D: Coated paper having a length of 500 m or less.

The presence / absence of clogging of the anilox roll surface After the normal printing is obtained, the presence or absence of ink supply when the anilox surface comes into contact with the fine print after one rotation is determined from the printability of the fine print. The presence or absence of clogging on the anilox roll surface was evaluated. A: The fine print portion is not blurred, and clogging of the anilox roll is not observed. B: Fine print portion is blurred, and clogging of the anilox roll is observed.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

As described above, according to the present invention, printing can be started immediately by using the antifouling agent containing the anti-inking agent according to the present invention. Therefore, the effect of preventing contamination can be maintained for a long time, and the anilox roll does not become clogged with the ink-based material. Therefore,
This is a method for preventing contamination of a water-based printing ink print, which can improve both workability and print quality.

Claims (5)

[Claims] (1) In the production of an aqueous printing ink print by a flexographic relief printing method using a plate roll and an anilox roll, before printing, both a convex portion and a concave portion of a relief plate are provided with an ink-based material: aqueous resin = 2: 8. A water-based printing ink, wherein the water-based printing ink is printed by applying the anti-stain agent contained in a weight ratio of about 8: 2 and drying, and then removing the anti-stain agent from the projections of the relief printing plate. How to prevent dirt. 2. The method according to claim 1, wherein the ink material of the stain inhibitor is a silicon compound and / or a fluorine compound. 3. The method according to claim 1, wherein the ink material of the stain inhibitor is an aqueous emulsion of a silicon compound and / or an aqueous emulsion of a fluorine compound. 4. The method according to claim 1, wherein the aqueous resin of the antifouling agent has an acid value of 100.
２５０250 mg KOH / g rosin-modified maleic resin,
The aqueous printing ink according to any one of claims 1 to 3, which is at least one selected from the group consisting of an acrylic resin, a styrene-acrylic resin, a styrene-maleic acid resin, and a styrene-acryl-maleic acid resin. How to prevent stains on printed matter. 5. An anti-fouling agent comprising an aqueous emulsion of a silicon compound and / or an aqueous emulsion of a fluorine compound, and an acid value of 100 to 250 mg KOH / g.
At least one selected from the group consisting of acrylic resins, styrene-acrylic resins, and styrene-maleic resins
A water-based printing ink printed matter according to any one of claims 1 to 4, wherein an aqueous resin of a kind is used in the presence of a basic compound, and an antifouling agent obtained by mixing an aqueous resin varnish dissolved in water. How to prevent dirt.