JP2023092680A - Coating agent for aqueous flexographic printing, and printed matter - Google Patents

Abstract

To provide a coating agent for aqueous flexographic printing which is applicable to a preprint type corrugated cardboard and other base materials, and is suitable for obtaining printed matter which has good glossiness and leveling property, has heat resistance required for corrugating processing, and is excellent in water resistance and abrasion resistance, when aqueous flexographic printing is performed.SOLUTION: A coating agent for aqueous flexographic printing contains an alkali-soluble type water-soluble resin, an aqueous emulsion resin (a), and an aqueous medium, wherein the aqueous medium contains a glycol-based compound having a boiling point of 140-290°C.SELECTED DRAWING: None

Description

The present invention relates to a coating agent for aqueous flexographic printing. In particular, it is a coating agent for water-based flexographic printing that can be used for flexographic printing on paper such as corrugated cardboard and carton paper. Especially, after printing on liner base paper, it is a pre-printing method that laminates the core and back liner paper with a corrugator. relates to a water-based flexographic printing coating agent used for corrugated board.

Flexographic printing and gravure printing are performed on corrugated cardboard, carton paper containers, and the like. In particular, flexographic printing is used for pre-printed corrugated board, and the water-based flexographic printing coating agent used in flexographic printing is used for the purpose of imparting a decorative appearance to the printed appearance and durability of the corrugated box. Demands for improved heat resistance, water resistance, and abrasion resistance are increasing.

Water-based flexographic printing coating agents for pre-printed cardboard have traditionally used water-based types, which are advantageous in terms of work environments such as environmental considerations, safety, and sanitation. It is known that when a styrene-based or styrene-acrylic copolymer resin emulsion having a refractive index is used, high glossiness and good physical properties of a coating film can be obtained in printing (Patent Documents 1 and 2).

In addition, corrugating is performed in a post-printing process, but if the heat resistance of the water-based flexographic printing coating agent is poor, when the water-based flexographic printing coating agent is rubbed against the hot plate of the corrugating machine, the water-based flexographic printing A certain degree of heat resistance is necessary because the coating agent for the product may peel off and impair the cosmetic properties (Patent Document 3).

Patent Document 4 discloses a water-based printing ink composition using a styrene-acrylic copolymer resin and a glycol ether. However, the combination of a water-soluble styrene-acrylic copolymer resin (Joncryl 678) and glycol ether was insufficient in coating film performance (friction resistance, heat resistance, water resistance, etc.).

In order to prevent the ink or varnish from peeling off when the water-based flexographic printing coating agent is rubbed against the hot plate of the corrugating machine, an anti-abrasion additive such as polyethylene wax, silicone or phosphate ester is added. Although it is common practice to use a release agent such as a release agent in combination with a binder resin, there are problems such as a problem in the slipperiness of printed matter and a decrease in water resistance (Patent Document 5).

Japanese Patent Application Laid-Open No. 2005-290078 Japanese Patent No. 6828978 JP 2018-158986 A JP-A-62-290772 Japanese Patent Publication No. 2007-510017

The object of the present invention is to be applicable to preprinted corrugated cardboard and other substrates, and to have good gloss and leveling properties, heat resistance necessary for corrugation, and water resistance when water-based flexographic printing is performed. To provide a coating agent for water-based flexographic printing suitable for obtaining printed matter of excellent quality in terms of durability and abrasion resistance.

As a result of intensive studies conducted by the present inventors to solve the above-described problems, the inventors found that the above-described problems can be solved by using the water-based flexographic printing coating agent described below.

That is, the present invention provides an aqueous flexographic printing coating agent containing an alkali-soluble water-soluble resin, an aqueous emulsion resin (a), and an aqueous medium,
It relates to a coating agent for water-based flexographic printing, wherein the water-based medium contains a glycol-based compound having a boiling point of 140 to 290°C.

The present invention also relates to the aqueous flexographic printing coating agent containing 9 to 30% by mass of the aqueous emulsion resin (a) in terms of solid content in the total weight of the aqueous flexographic printing coating agent.

In addition, the present invention further relates to the above coating agent for water-based flexographic printing, which contains a coloring agent.

The present invention also relates to the aqueous coating agent for flexographic printing, which contains 1.5 to 10% by mass of a glycol-based compound in the total mass of the aqueous coating agent for flexographic printing.

The present invention also relates to the aqueous flexographic printing coating agent, wherein the aqueous emulsion resin (a) has a glass transition temperature of 30 to 100°C.

The present invention also relates to the aqueous flexographic printing coating agent, wherein the aqueous emulsion resin (a) is an acrylic emulsion resin having an acid value of 30 to 200 mgKOH/g.

The present invention also relates to the water-based flexographic printing coating agent, wherein the glycol-based compound is a compound represented by general formula (1) and/or general formula (2).
General formula (1)

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.)
general formula (2)

(In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.)

The present invention also relates to the water-based flexographic printing coating agent, wherein n in general formula (1) or general formula (2) is 3.

The present invention also relates to a printed material having a print layer formed of the water-based coating agent for flexographic printing on a substrate.

The present invention also relates to the above-mentioned printed matter formed by corrugating.

INDUSTRIAL APPLICABILITY According to the present invention, it can be applied to preprinted cardboard and other substrates, and when water-based flexographic printing is performed, it has good gloss and leveling properties, has heat resistance necessary for corrugation, has water resistance, It has become possible to provide a coating agent for water-based flexographic printing that is suitable for obtaining printed matter with excellent abrasion resistance.

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of embodiments of the present invention, and the present invention does not exceed the gist thereof. Content is not limited.
The present invention will be described in detail. In addition, the part used in the following description indicates a mass part.

The present invention will be specifically described below.

(Aqueous emulsion resin (a))
In the present invention, the aqueous emulsion resin (a) preferably has a weight average molecular weight of more than 100,000 and 1,000,000 or less, more preferably 200,000 to 800,000. Examples of resins constituting the aqueous emulsion resin (a) include styrene-acrylic resins, vinyl acetate resins, styrene-butadiene resins, butadiene resins, styrene resins, polyurethane resins, polyolefin resins, polyester resins, Examples include polyamide-based resins, polybutene-based resins, and various waxes. Among these, aqueous emulsion resins composed of styrene-acrylic resins are more preferably used in terms of gloss, fluidity and re-solubility.

The resin is subjected to radical polymerization in the presence of a surface active agent such as an anionic active agent, a nonionic active agent, or a polymer active agent such as an alkali-soluble water-soluble resin capable of protecting the dispersion of polymer particles. However, in the case of water-based varnishes, from the viewpoint of gloss, leveling, fluidity, and re-solubility, alkali-soluble water-soluble resins are used during emulsion polymerization. A wet emulsion is preferred.

The styrene-acrylic resin as the water-based emulsion resin (a) comprises a radically polymerizable vinyl monomer such as an acrylic copolymer, a styrene-acrylic copolymer, or a styrene-maleic acid copolymer as a polymerization initiator. and a copolymer polymerized with. The radically polymerizable vinyl monomer used is not particularly limited, and vinyl monomers such as common aromatic vinyl monomers, ethylenically unsaturated carboxylic acid esters, ethylenically unsaturated carboxylic acid amides, ethylenically unsaturated carboxylic acid A radically polymerizable vinyl monomer, such as , can be used by polymerizing it with a polymerization initiator.

Examples of aromatic vinyl monomers include styrenes such as styrene, α-methylstyrene and vinyltoluene, and these can be used singly or as a mixture of two or more.

Ethylenically unsaturated carboxylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth) acrylate. Alkyl (preferably C 1-22 alkyl) esters of (meth)acrylic acid, hydroxyl group-containing ethylenically unsaturated compounds such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate, glycidyl (meth) Epoxy group-containing ethylenically unsaturated compounds such as acrylates and methylglycidyl (meth)acrylates can be used.

Examples of ethylenically unsaturated carboxylic acid amides and derivatives thereof include N-methylol(meth)acrylamide, N-dimethylol(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N- ethoxymethyl (meth)acrylamide and the like. For example methyl (meth)acrylate, ethyl (meth)acrylate, hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, stearyl (meth)acrylate, styrene, α-methylstyrene, vinyl acetate, vinyl chloride, acrylonitrile and vinylidene chloride.

Ethylenically unsaturated carboxylic acids include (meth)acrylic acid, maleic acid, itaconic acid, fumaric acid, crotonic acid, and anhydrides thereof, and these can be used singly or as a mixture of two or more.

Usual radical polymerization initiators such as persulfates such as ammonium persulfate and organic peroxides such as t-butyl peroxide can be used as the polymerization initiator. The appropriate amount to be used is 0.1 to 5 parts by weight per 100 parts by weight of the total weight of the monomers.

The weight average molecular weight of the aqueous emulsion resin (a) is preferably 50,000 or more, more preferably 80,000 or more, or 100,000 or more, in order to obtain coating film performance such as water resistance and abrasion resistance. be. The upper limit of the weight average molecular weight is preferably 5 million or less, more preferably 2 million or less, and still more preferably 1 million or less.
Here, the weight average molecular weight refers to a value obtained as a polystyrene equivalent molecular weight using a GPC (gel permeation chromatography) device.

The amount of aqueous emulsion resin (a) is preferably in the range of 9 to 30% by mass in terms of solid content in the total mass of the coating agent for aqueous flexographic printing. This is to ensure coating film performance such as water resistance and abrasion resistance, and fluidity of the ink.

The glass transition temperature (Tg) of the aqueous emulsion resin (a) is preferably in the range of 30 to 100°C, more preferably 50 to 100°C, from the viewpoint of sufficiently exhibiting necessary heat resistance. Within this range, it is also suitable for corrugator processing.
Here, the glass transition temperature is a calculated glass transition temperature obtained by the following Wood's formula.
Wood's formula:

1/Tg=W1/Tg1+W2/Tg2+W3/Tg3+...+Wx/Tgx

(Wherein, Tg1 to Tgx represent the glass transition temperature (absolute temperature) of the homopolymer, W1 to Wx represent the polymerization fraction, and Tg represents the calculated glass transition temperature)

The acid value of the aqueous emulsion resin (a) is preferably 30 to 200 mgKOH/g, and the lower limit is preferably 50 mgKOH/g or more from the viewpoint of obtaining sufficient fluidity and re-solubility.
Here, the acid value is the number of mg of potassium hydroxide required to neutralize the carboxyl groups contained in 1 g of the resin, and is a value calculated by performing potentiometric titration with a potassium hydroxide/ethanol solution according to JIS K2501. is.

(Alkali-soluble water-soluble resin)
In the present invention, the alkali-soluble water-soluble resin refers to a resin that is soluble in alkaline water even without a surfactant, and is distinguished from the water-based emulsion resin (a). The weight average molecular weight is preferably 1,000 to 100,000, more preferably 3,000 to 50,000, even more preferably 5,000 to 30,000. Examples of the alkali-soluble water-soluble resin include styrene-acrylic acid resins, styrene-maleic acid resins, acrylic resins, ethylene-acrylic acid resins, polyurethane resins, and polyester resins. Among them, styrene-acrylic acid-based resin, styrene-maleic acid-based resin, acrylic resin, etc. are preferable, and the monomers constituting the styrene-acrylic acid-based resin, styrene-maleic acid-based resin, and acrylic resin include the above aqueous emulsion resins. Those listed in (a) are preferably used.
The alkali-soluble water-soluble resin preferably has an acid value, preferably 100 to 400 mgKOH/g, more preferably 150 to 350 mgKOH/g, and more preferably 180 to 320 mgKOH/g. It is even more preferable to have This is for improving resolubility, fluidity, and water resistance. The glass transition temperature (Tg) of the alkali-soluble water-soluble resin is preferably 30 to 200°C, more preferably 50 to 150°C, still more preferably 60 to 120°C. This is for improving heat resistance.
In terms of solid content, the mass ratio of the aqueous emulsion resin (a) and the alkali-soluble water-soluble resin is preferably 30:70 to 99:1, and more preferably 40:60 to 97:3. is still more preferred, and 50:50 to 95:5 is even more preferred. This is to ensure leveling properties, fluidity, and resolubility in printing of a coating agent for water-based flexographic printing, and to obtain film-forming properties, water resistance, abrasion resistance, and heat resistance necessary for corrugating.

A plurality of each of the aqueous emulsion resin (a) and the alkali-soluble water-soluble resin may be used. Even if it is an additive for imparting various physical properties, a resin that cannot be distinguished from the aqueous emulsion resin (a) or the alkali-soluble water-soluble resin is either the aqueous emulsion resin (a) or the alkali-soluble water-soluble resin. It is a resin that corresponds to

(Aqueous medium, glycol compound)
Aqueous flexographic printing coating agents comprise an aqueous medium. Examples of aqueous media include water and glycol compounds. The glycol-based compound used in the present invention has a boiling point range of 140 to 290°C. The glycol-based compound is said to improve film-forming properties when a coating film (also referred to as a film) is formed by flexographic printing of an aqueous flexographic printing coating agent containing an alkali-soluble water-soluble resin and an aqueous emulsion resin. It can be considered that the film is strengthened. It should be noted that the present invention is not limited in any way by consideration of the mechanism concerned.
Specifically, the glycol-based compound is preferably a compound represented by general formula (1) and/or general formula (2).
General formula (1)

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.)
general formula (2)

(In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.)

Compounds represented by general formula (1) or general formula (2) are represented by polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and glycerin. kind,
ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, ethylene glycol monohexyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monopentyl ether, propylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, Dipropylene glycol monopentyl ether, dipropylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol mono Ethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether and the like are preferred.
Among them, triethylene glycol ether and/or tripropylene glycol ether are preferably included. For example, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene Glycol monobutyl ether and the like are preferably mentioned.
Among them, a triethylene glycol skeleton or tripropylene glycol skeleton in which n in general formula (1) or general formula (2) is 3 is preferable. Furthermore, triethylene glycol monoalkyl ether is preferable, and triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether and the like are preferable.
Dialkyl ethers include diethylene glycol dimethyl ether (bp 162°C), triethylene glycol dimethyl ether (bp 216°C), diethylene glycol methylethyl ether (bp 176°C), and diethylene glycol diethyl ether (bp 188.9°C).

The glycol-based compound used in the present invention is preferably contained in an amount of 1.5 to 10% by mass in the total mass of the coating agent for water-based flexographic printing. The content is more preferably 2 to 9% by mass, more preferably 3 to 7% by mass. This is to obtain the film-forming property, water resistance, and abrasion resistance of the coating agent for water-based flexographic printing, as well as the heat resistance necessary for corrugating.

The water-based flexographic printing coating agent of the present invention may contain additives such as the essential constituents described above and, if necessary, antifoaming agents, surfactants, thickeners, leveling agents, and high-boiling solvents. Waxes such as paraffin waxes, polyethylene waxes, and carnauba waxes, fatty acid amides such as oleic acid amide, stearic acid amide, and erucic acid amide for imparting abrasion resistance and slipperiness, etc., and foaming during printing Silicon-based or non-silicon-based antifoaming agents for suppressing this and various dispersants for improving wettability of pigments can be used as appropriate.

(coloring agent)
The coating agent for water-based flexographic printing of the present invention may contain a coloring agent, and as the coloring agent, pigments such as inorganic pigments, organic pigments and extender pigments used in general water-based printing ink compositions are used. be able to. In this case, it can be handled in the same way as a so-called coating agent for water-based flexographic printing.
In the case of water-based flexographic printing coating agents containing pigments, dispersion is carried out using commonly used Eiger mills, sand mills, gamma mills, other bead mills, attritors, etc., and a predetermined viscosity is obtained. It is manufactured by adjusting to be

Pigments to be blended in the water-based flexographic printing coating agent of the present invention include organic pigments such as azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, Pigments such as quinophthalone-based, azomethine-azo-based, ditopyrrolopyrrole-based, and isoindoline-based pigments are included.
Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, and mica (mica).
From the viewpoint of cost and coloring power, it is preferable to use titanium oxide for white ink, carbon black for black ink, aluminum for gold and silver inks, and mica for pearl ink.

The coating agent for aqueous flexographic printing of the present invention can be produced by a known method.

(Base material)
Pulp-based fiber materials such as liner paper, white liner, and woodfree paper are preferable as the printing paper substrate used in the present invention. The pulp-based fiber material preferably includes base paper and recycled paper using bleached hardwood kraft pulp, bleached softwood kraft pulp, and the like as raw materials. These base papers include acid papers such as fine papers, medium quality papers, one-gloss papers and kraft papers, which are produced by known fourdrinier multi-cylinder paper machines, Fourdrinier Yankee paper machines, cylinder paper machines, etc. It includes paper, alkaline paper, and molded articles molded by a pulp mold molding machine. As the paper base, it is preferable to use a paper base selected from non-coated paper, single-glazed kraft paper treated on one side of the base, bleached kraft paper, unbleached kraft paper, and the like.

(printing)
In the printing of the water-based flexographic printing coating agent of the present invention, it can be printed by a known flexographic printing method. In the case of flexographic printing, since it is a letterpress printing method, compared to other printing methods, the water-based flexographic printing coating agent easily adheres to non-smooth paper substrates, and the roughness of the paper substrate surface There is a wide range of response to fleshing.

As the flexographic printing method, a two-roll method, a doctor method, and a doctor chamber method can be used. In either case, a coating agent for water-based flexographic printing is supplied to an anilox roll having cells formed on its surface, and the printing material is finally printed through a resin plate. When the present water-based flexographic printing coating agent is printed by a flexographic printing method, a printed matter having excellent cosmetic properties can be obtained even on a paper substrate having a rough surface.

The coating agent for water-based flexographic printing of the present invention has good gloss and leveling properties even when combined with water-based printing inks other than the present invention, and has excellent heat resistance, water resistance, and abrasion resistance necessary for corrugating. performance can be obtained. The water-based flexographic printing coating agent containing the coloring agent of the present invention alone has good gloss and leveling properties, and has the heat resistance necessary for corrugating. Best performance can be obtained by overcoating.

(Flexographic printing method; anilox roll)
As the anilox used for flexographic printing used in the method for producing a flexographic printed matter of the present invention, a ceramic anilox roll with cell engraving, a chromium-plated anilox roll, or the like can be used. The shape of the cells includes a honeycomb pattern, a diamond pattern, a helical pattern, and the like, and any pattern can be suitably used. Also, the role of the anilox is to uniformly receive the ink supplied from the doctor chamber (or fountain roll) and then transfer it to the printing plate. The anilox roll preferably has a screen ruling of 50 to 2000 lines/inch, more preferably 100 to 1200 lines/inch.

(Flexographic printing method; flexographic plate)
The plate used for flexographic printing used in the method for producing a flexographic printed matter of the present invention includes a photosensitive resin plate utilizing ultraviolet curing with a UV light source or an elastomer material plate using a direct laser engraving system. Any sleeve or cushion tape for attaching the plate can be used.
The screen ruling of the flexo plate is preferably 80 to 200 lines/inch, more preferably 125 to 175 lines/inch.

(Flexographic printing method; printing machine)
Flexographic printing machines include CI type multicolor flexographic printing machines, unit type multicolor flexographic printing machines, etc. As for the ink supply system, a chamber system and a two-roll system can be mentioned, and an appropriate printing machine can be used. can. The printing speed is preferably 50-500 m/min, more preferably 100-300 m/min.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. In the following examples and tables, "part" means "part by mass" and "%" means "% by mass".

(Example 1) Water-based flexographic printing coating agent Water-based resin emulsion (a) 60.0 parts of A1, alkali-soluble water-soluble resin (Joncryl63D, manufactured by BASF Japan, styrene-acrylic copolymer resin, solid content 30% , acid value 213, glass transition point 73 ° C., weight average molecular weight 8,000) 15.0 parts, glycol compound (b) C5 6.0 parts, polyethylene wax dispersion (manufactured by Mitsui Chemicals, Inc. "Chemipearl- W400", solid content 40%, average particle size 4 to 5 μm) 5.0 parts, silicone antifoaming agent (Toray Silicon Co., Ltd. "Toray Silicon SC5540" 0.2 parts, water 13.8 parts, The mixture was stirred with a disper to obtain a coating agent for water-based flexographic printing (1).The properties of the water-based resin emulsion are shown in Table 1. Water-based resin emulsions A1 to B2 in the table are manufactured by BASF Japan Ltd. Boiling points of glycol compounds are shown in Tables 2-1 and 2-2.

(Examples 2-18 and Comparative Examples 1-5)
Coating agents for water-based flexographic printing (2) to (18) and (23) to (27) were obtained in the same manner as in Example 1 according to the formulations in Tables 3-1 and 3-2.

(Example 19) Coating agent for water-based flexographic printing (indigo ink)
Indigo pigment (phthalocyanine blue (Lionol Blue FG-7330, manufactured by Toyocolor Co., Ltd.)) 42.0 parts, dispersion resin (Joncryl HPD-96J, manufactured by BASF Japan Co., Ltd., solid content 34%, acid value 240, 35.0 parts of a glass transition point of 102° C.), 0.3 parts of a silicone antifoaming agent (“Toray Silicon SC5540” manufactured by Toray Silicon Co., Ltd.), and 22.7 parts of water are stirred and mixed, and then dispersed in a sand mill to obtain a pigment. A dispersion was obtained.
Next, 40.0 parts of the resulting pigment dispersion, 30.0 parts of the aqueous resin emulsion (a) A1, alkali-soluble water-soluble resin (Joncryl63D, manufactured by BASF Japan Ltd., solid content 30%, acid value 213, glass transition point 73 ° C., weight average molecular weight 8,000) 5.0 parts, glycol compound (b) 6.0 parts C5, polyethylene wax dispersion (manufactured by Mitsui Chemicals, Inc. “Chemipearl-W400 ”, solid content 40%, average particle size 4 to 5 μm) 5.0 parts, silicon antifoaming agent (Toray Silicon Co., Ltd. “Toray Silicon SC5540” 0.2 parts, water 13.8 parts Then, a water-based flexographic printing coating agent (19) containing an indigo pigment was obtained.

(Examples 20-22 and Comparative Example 7)
According to the formulations in Tables 3-1 and 3-2, in the same manner as in Example 19, aqueous flexographic printing coating agents (20) to (22) and (29) containing indigo pigments were obtained.

(Example 23)
The water-based flexographic printing coating agent (1) obtained in Example 1 was diluted with water, and the viscosity was adjusted to No.4. It was adjusted to 12-13 seconds with a Zahn cup. Using a flexographic printing machine (“SOLOFLEX” manufactured by Windmuller & Hercher, anilox roll 165 lines/inch, cell capacity 26.8 cm ³ /m ² ), a paper base material having a basis weight of 120 g/m ² (K liner paper) to obtain a printed matter (1).

(Examples 24-40 and Comparative Examples 8-13)
Prints (2) to (18) and (32) to (37) were obtained in the same manner as in Example 23 according to the configurations described in Tables 4-1 and 4-2.

(Example 41)
The aqueous flexographic printing coating agent (19) containing the indigo pigment obtained in Example 19 was diluted with water, and the viscosity was adjusted to No.4. It was adjusted to 12-13 seconds with a Zahn cup. Using a flexographic printing machine (“SOLOFLEX” manufactured by Windmuller & Hercher, anilox roll 165 lines/inch, cell capacity 26.8 cm ³ /m ² ), a paper base material having a basis weight of 120 g/m ² (K liner paper) to obtain printed matter (19).

(Examples 42-44 and Comparative Example 14)
Prints (20) to (22) and (38) were obtained in the same manner as in Example 41 according to the configurations described in Tables 4-1 and 4-2.

(Example 45)
The indigo pigment-containing water-based flexographic printing coating agent (19) obtained in Example 19 and the water-based flexographic printing coating agent (1) obtained in Example 1 were diluted with water, and each viscosity was adjusted to No.4. It was adjusted to 12-13 seconds with a Zahn cup. Using a flexographic printing machine (“SOLOFLEX” manufactured by Windmuller & Hercher, anilox roll 165 lines/inch, cell capacity 26.8 cm ³ /m ² ), a paper base material having a basis weight of 120 g/m ² (K Indigo pigment-containing water-based flexographic printing coating agent (19) and water-based flexographic printing coating agent (1) were printed in this order on a liner paper) to obtain printed material (23).

(Examples 46-55), (Comparative Examples 15-17)
Printed matter (24) to (33) in the same manner as in Example 45 by combining the aqueous flexographic printing coating agent containing the indigo pigment and the aqueous flexographic printing coating agent described in Tables 4-1 and 4-2. , and (39)-(41) were obtained.

Using the resulting prints (1) to (41), gloss, leveling, abrasion resistance, water resistance and heat resistance were evaluated. Test methods and evaluation criteria are shown below. Table 4 shows the evaluation results.

Gloss: Measure the surface gloss of printed matter with a gloss meter (MICRO-TRI-GROSS).
◎: Gloss value over 10.0 ○: Gloss value 5.0 to 10.0
△: gloss value 3.0 to 5.0
x: Gloss value less than 3.0 Practical levels are ⊚, ◯ and Δ.

Leveling property: The extent of printed matter swimming and coating unevenness was visually evaluated.
◎: No swimming or uneven coating ○: Slight swimming and uneven coating △: Slight swimming and uneven coating ×: Significant swimming and uneven coating Practical levels are ◎, ○ and △.

Abrasion resistance: rubbed with high-quality paper 100 times with a 500g load using a Gakushin type friction tester,
The degree of removal of the indigo ink and overcoat varnish was visually evaluated.
⊚: No indigo ink or overcoat varnish was removed from the rubbed fine paper.
◯: Indigo ink and overcoat varnish were slightly adhered to the rubbed woodfree paper.
Δ: Slight adhesion of indigo ink and overcoat varnish to rubbed woodfree paper.
x: Indigo ink and overcoat varnish adhered to the entire surface of the rubbed woodfree paper.
The practical levels are .circleincircle., .largecircle. and .DELTA.

Water resistance: rubbed with a cotton cloth soaked with water five times with a 200g load using a Gakushin type friction tester,
The degree of removal of the indigo ink and overcoat varnish was visually evaluated.
⊚: No indigo ink or overcoat varnish was removed from the rubbed fine paper.
◯: Indigo ink and overcoat varnish were slightly adhered to the rubbed woodfree paper.
Δ: Slight adhesion of indigo ink and overcoat varnish to rubbed woodfree paper.
x: Indigo ink and overcoat varnish adhered to the entire surface of the rubbed woodfree paper.
The practical levels are .circleincircle., .largecircle. and .DELTA.

Heat resistance: Cover the printed surface with aluminum foil, use a heat seal tester (manufactured by Tester Sangyo Co., Ltd.), apply a pressure of 2 kg / cm ² for 3 seconds, and measure the temperature at which the varnish begins to be removed from the aluminum foil surface. measurement.
A: Adhesion of varnish to the surface of the aluminum foil is observed at temperatures exceeding 230°C.
○: Adhesion of varnish to the aluminum foil surface is observed at 190°C to 230°C.
Δ: Adhesion of varnish to the aluminum foil surface is observed at 160°C to 190°C.
x: Adhesion of varnish to the aluminum foil surface is observed at temperatures below 160°C.
The practical levels are .circleincircle., .largecircle. and .DELTA.

Claims (10)

An aqueous flexographic printing coating agent containing an alkali-soluble water-soluble resin, an aqueous emulsion resin (a), and an aqueous medium,
A coating agent for aqueous flexographic printing, wherein the aqueous medium contains a glycol compound having a boiling point of 140 to 290°C. The water-based flexographic printing coating agent according to claim 1, which contains 9 to 30% by mass of the aqueous emulsion resin (a) in terms of solid content in the total mass of the water-based flexographic printing coating agent. 3. The coating agent for water-based flexographic printing according to claim 1, further comprising a colorant. The water-based flexographic printing coating agent according to any one of claims 1 to 3, which contains 1.5 to 10% by mass of the glycol compound in the total mass of the water-based flexographic printing coating agent. The coating agent for water-based flexographic printing according to any one of claims 1 to 4, wherein the water-based emulsion resin (a) has a glass transition temperature of 30 to 100°C. 6. The coating agent for water-based flexographic printing according to claim 1, wherein the water-based emulsion resin (a) is an acrylic emulsion resin having an acid value of 30-200 mgKOH/g. The coating agent for water-based flexographic printing according to any one of claims 1 to 6, wherein the glycol-based compound is a compound represented by general formula (1) and/or general formula (2).
General formula (1)

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.)
general formula (2)

(In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.) 8. The coating agent for water-based flexographic printing according to claim 7, wherein n in general formula (1) and/or general formula (2) is 3. A printed material having a printing layer comprising the water-based coating agent for flexographic printing according to any one of claims 1 to 8 on a substrate. 10. The printed matter according to claim 9, which is corrugated.