JP2023110818A - Aqueous flexographic ink composition containing urea-based compound - Google Patents

Abstract

To provide an aqueous flexographic ink composition which has good flexographic printability and physical properties (bending resistance, re-solubility and coated film dryness) of a printing layer, and is excellent in plate cleaning property.SOLUTION: An aqueous flexographic ink composition contains an aqueous acrylic resin (A) and an urea-based compound (B), wherein the aqueous acrylic resin (A) contains a water-soluble acrylic resin (a1) and aqueous acrylic resin emulsion (a2), the content of the aqueous acrylic resin (A) is 10-45 mass% in the total mass of the aqueous flexographic ink composition, and the urea-based compound (B) is a compound represented by general formula (1).SELECTED DRAWING: None

Description

The present invention relates to a water-based flexographic ink composition containing a water-based acrylic resin and a urea-based compound.

In recent years, in water-based flexographic printing for packages, there are increasing cases of flexographic printing using an anilox roll with a high fine line and a low coating amount of ink (Patent Document 1). When the amount of ink applied is low, the ink coating film dries easily on the plate. In particular, water-based flexographic ink compositions containing water-based acrylic resins have a significant problem in washing the flexographic plate due to the solubility of the resin. In general, water-based flexographic ink compositions are required to have printing density, resolubility, and folding resistance.

Patent Document 2 discloses a water-based flexographic ink composition using a water-soluble acrylic resin and a water-based acrylic resin emulsion as a binder resin. However, the water-based flexographic ink, which has good physical properties in the printed layer and has a high print density, has a problem that water resistance tends to be insufficient. It is considered that this is related to the large amount of ammonia or the like used for neutralizing the water-based resin to make it water-soluble. On the other hand, in order to improve washability, the water solubility of the binder resin should be high. However, amine compounds such as ammonia cannot be used in large amounts by law, and cannot be used as means for improving the cleanability of plates.

Patent Documents 3 and 4 disclose inks using aqueous acrylic resin emulsions as binder resins and containing urea or urea derivatives. However, with the inks described in Patent Documents 3 and 4, the balance of physical properties such as drying properties of coating films and bending resistance of printed matter is insufficient.

JP 2021-167377 A JP 2019-108529 A Japanese Patent Publication No. 6-503370 Japanese Patent Publication No. 2012-506786

An object of the present invention is to provide a water-based flexographic ink composition which has good suitability for flexographic printing, good physical properties of the printed layer (bending resistance, re-solubility, coating film drying property), and excellent cleanability of the plate. .

The present inventors have found that the above problems can be solved by using the following water-based flexographic ink composition, and have completed the present invention.

［一般式（１）中、Ｒ^１は、酸素原子又は硫黄原子を表す。
Ｒ^２およびＲ^３は、それぞれ独立に、水素原子、置換基を有してもよい炭素数１～４のアルキル基、又は置換基を有してもよい炭素数６～９のアリール基を表す。
ただし、Ｒ^２とＲ^３とが、炭素数１～３のアルキレン基を介して環を形成してもよい。］ That is, the present invention is a water-based flexographic ink composition containing a water-based acrylic resin (A) and a urea-based compound (B),
The aqueous acrylic resin (A) comprises a water-soluble acrylic resin (a1) and an aqueous acrylic resin emulsion (a2),
The content of the water-based acrylic resin (A) is 10 to 45% by mass in the total mass of the water-based flexographic ink composition,
The present invention relates to an aqueous flexographic ink composition, wherein the urea-based compound (B) is a compound represented by the following general formula (1).
General formula (1)

[In general formula (1), R ¹ represents an oxygen atom or a sulfur atom.
R ² and R ³ each independently represent a hydrogen atom, an optionally substituted C 1-4 alkyl group, or an optionally substituted C 6-9 aryl group .
However, R ² and R ³ may form a ring via an alkylene group having 1 to 3 carbon atoms. ]

The present invention also relates to the water-based flexographic ink composition, wherein the content of the urea-based compound (B) in the total weight of the water-based flexographic ink composition is 1 to 10% by mass.

The present invention also relates to the water-based flexographic ink composition, wherein the mass ratio of the urea-based compound (B) and the water-based acrylic resin (A) is 5:95 to 40:60.

The present invention also relates to the water-based flexographic ink composition, wherein the water-soluble acrylic resin (a1) has an acid value of 150 to 350 mgKOH/g.

The present invention also relates to a printed material having a printed layer formed from the water-based flexographic ink composition on a substrate.

According to the present invention, it is possible to provide an aqueous flexo ink composition which has good suitability for flexographic printing, good physical properties of the printed layer (bending resistance, re-solubility, coating film drying property), and excellent cleanability of the plate. rice field.

The water-based flexographic ink composition of the present invention will be described in detail below.

(Aqueous acrylic resin (A))
In the present invention, the water-based acrylic resin (A) refers to water-soluble or dispersible acrylic resins, including water-soluble acrylic resins (a1) and water-based acrylic resin emulsions (a2).
Among the water-soluble acrylic resins (a1), water-soluble styrene-acrylic copolymer resins are preferred, and among the water-soluble acrylic resin emulsions (a2), styrene-acrylic copolymer resin emulsions are preferred.

The content of the aqueous acrylic resin (A) is preferably 10 to 45% by mass, more preferably 11 to 40% by mass, even more preferably 12 to 35% by mass, based on the total mass of the ink. .

The weight average molecular weight of the water-based acrylic resin (A) is preferably 1,500 to 1,500,000, more preferably 5,000 to 1,000,000, even more preferably 1,000 to 50,000.

(Water-soluble acrylic resin (a1))
The water-soluble acrylic resin in the present invention refers to an acrylic resin obtained by solution-polymerizing a monomer containing an acrylic monomer in an organic solvent, removing the solvent, and dissolving the solid resin under alkaline conditions.

Preferred examples of the acrylic monomer include acrylic acid esters and methacrylic acid esters. For example, acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethylaminoethyl acrylate, hydroxyethyl acrylate, hydroxylopyl acrylate, and glycidyl acrylate. and methacrylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and glycidyl methacrylate. is mentioned.
Carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid, or their anhydrides and half esters can also be used.
These may be used alone or in combination of two or more.

Among the above, acrylic monomers include methyl acrylate, ethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, hydroxyethyl methacrylate, It preferably contains hydroxypropyl methacrylate, acrylic acid, methacrylic acid, maleic acid, itaconic acid.

Further, the water-soluble acrylic resin (a1) is preferably a water-soluble styrene-acrylic copolymer resin obtained by copolymerizing an acrylic monomer and a styrene monomer. Examples include styrene and β-methylstyrene. These may be used alone or in combination of two or more.
Among them, the styrene monomer preferably contains α-methylstyrene.

The water-soluble acrylic resin (a1) preferably has an acid group, and when it has an acid group, the acid value is preferably 150 to 350 mgKOH/g, more preferably 200 to 300 mgKOH/g. more preferred. When the acid value of the water-soluble acrylic resin (a1) is within the above range, the washability of the plate and the anilox roll is improved.

(Aqueous acrylic resin emulsion (a2))
The aqueous acrylic resin emulsion (a2) in the present invention refers to an acrylic resin that is insoluble or sparingly soluble in an aqueous system, but is dispersed and stabilized with a surfactant or the like. The average particle size of the aqueous acrylic resin emulsion (a2) is preferably 10-500 nm, more preferably 30-200 nm.

The water-based acrylic resin emulsion (a2) preferably has an acid group, and when it has an acid group, the acid value is preferably 30 to 150 mgKOH/g, more preferably 40 to 100 mgKOH/g. more preferred.

The acid group of the aqueous acrylic emulsion (a2) having the acid group is preferably neutralized with a basic compound. Suitable basic compounds include, for example, amine compounds and alkali metals.

Examples of the amine compound include ammonia; alkylamines such as diethylamine, triethylamine and ethylenediamine; and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine and triethanolamine. Examples of the alkali metal include sodium hydroxide and potassium hydroxide. These may be used alone or in combination of two or more.

Acrylic monomers constituting the water-based acrylic resin emulsion (a2) preferably include acrylic acid esters and methacrylic acid esters. For example, acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and hexyl acrylate. , 2-ethylhexyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethylaminoethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, glycidyl acrylate, and methacrylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, Hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate. These may be used alone or in combination of two or more.

Carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid, or their anhydrides and half esters can also be used. These may be used alone or in combination of two or more.

Among the above, acrylic monomers include methyl acrylate, ethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, hydroxyethyl methacrylate, hydroxy It preferably contains propyl methacrylate, acrylic acid, methacrylic acid, maleic acid, itaconic acid.

Further, the water-soluble acrylic resin is preferably a water-soluble styrene-acrylic copolymer resin, and examples of styrene monomers constituting the resin include styrene, α-methylstyrene, β-methylstyrene and the like. These may be used alone or in combination of two or more. Among them, the styrene monomer preferably contains α-methylstyrene.

The above-described solid content mass ratio of the water-based acrylic resin (A) and the water-based acrylic resin emulsion (a2) is that the water-based acrylic resin (A):water-based acrylic resin emulsion (a2) is 70:30 to 50:50. is preferred, 65:35 to 50:50 is more preferred, and 60:40 to 55:45 is even more preferred. This is for improving the flexographic printability and physical property balance of the printed layer. In particular, it is effective in improving bending resistance and remeltability.

(liquid medium)
The aqueous flexographic ink composition of the present invention preferably contains a liquid medium. The main component of the liquid medium is preferably water, but water-soluble organic solvents can be used in addition to water. Specifically, an alcohol-based organic solvent, a glycol-based organic solvent, or the like can be contained depending on the printing conditions (speed, plate depth, design, drying temperature). The content of the water-soluble organic solvent is preferably 30% by mass or less with respect to the total amount of the ink.
Here, in the present invention, that the main component is water means that the content of water is the largest in the liquid medium. A water-soluble organic solvent is a solvent that is liquid at 25°C and has a solubility in water at 25°C of 1% by mass or more.

Examples of alcoholic organic solvents include methanol, ethanol, propanol, isopropanol, isobutanol, normal butanol, tertiary butanol, hexanol, octanol, and decanol.
Glycol-based organic solvents include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monooctyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, Diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene Glycol Monobutyl Ether, Dipropylene Glycol, Dipropylene Glycol Monomethyl Ether, Dipropylene Glycol Monoethyl Ether, Dipropylene Glycol Monopropyl Ether, Dipropylene Glycol Monobutyl Ether, Tripropylene Glycol, Tripropylene Glycol Monomethyl Ether, Tripropylene Glycol Monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, dibutyl glycol and the like.
These may be used alone or in combination of two or more.

(pigment)
As the pigment used in the water-based flexographic ink composition of the present invention, those conventionally used in water-based flexographic printing ink compositions can be used. Specific examples of inorganic pigments include colored pigments such as titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, graphite, and extender pigments such as calcium carbonate and barium titanate. can. Examples of organic pigments include oil-soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. These may be used alone or in combination of two or more.
The content of the pigment is preferably 1 to 60% by mass in the total mass of the water-based flexographic ink composition.

(Additive)
Various additives can be used in the water-based flexographic ink composition of the present invention, if necessary. Examples include dispersants, waxes, extenders, leveling agents, antifoaming agents, film-forming aids, and the like.
Specifically, wax resin fine particle dispersions such as polyethylene wax are used to improve abrasion resistance, and calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay , Extender pigments such as talc, Inorganic fine particles and adhesive resins (acrylic resin, vinyl acetate resin) to provide anti-slip properties, Leveling agents to improve leveling properties, Anti-foaming properties to provide anti-foaming properties Various additives such as a basic compound such as sodium hydroxide and potassium hydroxide to impart re-solubility and a film-forming aid can be added.

(dispersant)
The water-based flexographic ink composition of the present invention may optionally contain a dispersant in addition to the dispersant that may be used for dispersing the water-based acrylic resin emulsion (a2). As a dispersant, it is preferable to use a surfactant such as a polyether compound or an acetylene glycol compound.

For example, a polyether-based compound is preferably a copolymerized polyether, and although not limited thereto, a compound in which polypropylene glycol (propylene oxide) and polyethylene glycol (ethylene oxide) are copolymerized is preferable. . The weight average molecular weight of the polypropylene glycol-polyethylene glycol copolymer resin is preferably 500 to 30,000. If the weight average molecular weight is more than 500, the pigment dispersibility is improved, and if it is less than 30,000, the leveling property is improved. The weight average molecular weight is more preferably in the range of 1000-5000. Also, the amount of ethylene oxide added is preferably 10 to 95% by mass based on the total molecule. When the added amount of ethylene oxide is higher than 10%, the dispersion stability is improved, and when it is lower than 95%, the water resistance and drying property are improved. From the viewpoint of achieving both dispersion stability, water resistance and drying property, the amount of ethylene oxide to be added is more preferably 30 to 90% by mass.

Acetylene glycol-based compounds are also preferred, and acetylene glycol-based compounds having ethylene oxide and/or propylene oxide are preferred. Surfynol series (manufactured by Air Products) are commercially available as acetylene glycol compounds.

The dispersant is preferably used in an amount of 0.1 to 10% by weight, more preferably 1 to 8% by weight, based on the total weight of the ink. This is for improving the gloss of the pigment and maintaining blocking resistance.

(Urea-based compound (B))
The aqueous flexographic ink composition of the present invention contains a urea-based compound (B) represented by the following general formula (1). As a result, drying on the plate and the anilox roller can be suppressed, and washability of the plate can be improved. This effect is considered to be derived from hydration of the urea-based compound (B) with water in the liquid medium in the water-based flexographic ink composition.

［一般式（１）中、Ｒ^１は、酸素原子又は硫黄原子を表す。
Ｒ^２およびＲ^３は、それぞれ独立に、水素原子、置換基を有してもよい炭素数１～４のアルキル基、又は置換基を有してもよい炭素数６～９のアリール基を表す。
ただし、Ｒ^２とＲ^３とが、炭素数１～３のアルキレン基を介して環を形成してもよい。］ General formula (1)

[In general formula (1), R ¹ represents an oxygen atom or a sulfur atom.
R ² and R ³ each independently represent a hydrogen atom, an optionally substituted C 1-4 alkyl group, or an optionally substituted C 6-9 aryl group .
However, R ² and R ³ may form a ring via an alkylene group having 1 to 3 carbon atoms. ]

Examples of substituents in the alkyl group having 1 to 4 carbon atoms which may have a substituent and the aryl group having 6 to 9 carbon atoms which may have a substituent include, for example, a hydroxy group, an amino group, A carboxyl group, a halogen atom, a cyano group, a thio group, a silyl group, and a nitro group can be mentioned, and among them, a hydroxy group is preferable.

Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group and tert-butyl group, among which methyl group and ethyl group. is preferred.

Examples of the aryl group having 6 to 9 carbon atoms include a phenyl group, a tolyl group and a xylyl group, with a phenyl group being preferred.

Examples of the alkylene group having 1 to 3 carbon atoms include methylene group, ethylene group and propylene group, and ethylene group is preferred.

Examples of the urea-based compound (B) represented by the general formula (1) include urea, 2-hydroxyethylurea, thiourea, 1,3-dimethylurea, and synthesized by reacting ammonium carbamate with a titanium catalyst. Urea derivatives such as ethylene urea and thiourea derivatives such as N-phenylthiourea. Among them, urea, 2-hydroxyethylurea and 1,3-dimethylurea are preferred, and urea and 1,3-dimethylurea are more preferred. These may be used individually by 1 type, and may combine 2 or more types.

The urea-based compound (B) is preferably used in the range of 1 to 10% by mass, more preferably in the range of 5 to 8% by mass, based on the total mass of the ink. The urea compound (B) preferably has a solubility in water at 25° C. of 20% by mass or more, more preferably 30% by mass or more. This is for suppressing drying of the ink film. Further, the mass ratio of the urea-based compound (B) and the aqueous acrylic resin (A) is preferably 5:95 to 40:60, more preferably 10:90 to 30:70, and 15:85. ~25:75 is more preferred.

(Method for producing water-based flexographic ink composition)
A method for producing the water-based flexographic ink composition of the present invention will be described. As a method for producing the water-based flexo ink composition of the present invention, for example, after stirring and mixing water, pigment, dispersant, water-soluble resin, etc. It can be obtained by dispersing the pigment using a lighter, a roll mill, etc., adding predetermined materials such as a resin emulsion, a water-soluble resin, a rosin-based resin, and additives, and stirring and mixing. A bead mill is preferably used for pigment dispersion.

(Flexographic printing method)
Flexographic printing methods include a two-roll method, a doctor method, and a doctor chamber method. In both the doctor method and the doctor chamber method, a water-based flexo ink composition is supplied to an anilox roll having cells formed on the surface, and a doctor blade is used to scrape off excess water-based flexo ink from the surface of the anilox roll. , and finally printed on a substrate. When the water-based flexographic ink composition of the present invention 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.

(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 cell shape includes a honeycomb pattern, a diamond pattern, a helical pattern, and the like, and any pattern can be 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 screen ruling of the anilox roll is preferably 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 flexographic 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.

(Printed Matter Having a Printed Layer Formed from an Aqueous Flexographic Ink Composition)
As a method for producing a printed matter having a printed layer formed from a water-based flexographic ink composition, printing on the surface of paper or resin, particularly paper containers such as paper containers such as paper cups and paper plates, or a resin layer on the surface. A method of printing on paper containers coated with , thin paper for food packages, or materials thereof using the aqueous flexographic ink composition with a flexographic printing machine can be exemplified.
At this time, the material to be printed includes food packages such as wrapping paper and paper bags, paper products such as paper containers having a resin layer such as polyolefin laminated on the surface, and resin layers such as a resin coating layer such as polyolefin on the surface. Paper products such as paper containers and paper products such as uncoated paper containers having no resin layer on the surface may be used.

(Base material)
Examples of substrates for printing (printing materials) include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and nylon, cellophane, paper, aluminum foil, and films and sheets made of composite materials thereof. In the present invention, a paper substrate is particularly preferred. The paper substrate is preferably a paper substrate selected from non-coated paper, single-glazed kraft paper treated on one side of the substrate, bleached kraft paper, unbleached kraft paper, and the like.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "%" means "% by mass" and "parts" means "parts by mass" unless otherwise specified. In addition, the number of the amount of each material in the table is also "mass part". The unit of hydroxyl value and acid value is mgKOH/g.

(acid value and hydroxyl value)
It was obtained according to JISK0070.

(Example 1) [Preparation of water-based flexographic ink composition S1]
Water 28 parts, PigmentBlack 7 18 parts, urea compound 5 parts, PEG-PPG (polyethylene glycol (PEG) and polypropylene glycol (PPG) copolymer resin weight average molecular weight 2800; PEG:PPG = 40:60; solid content 100%) After kneading and dispersing a mixture of 2 parts, 1 part of acetylene glycol (80% solid content of Surfynol SE manufactured by Nissin Chemical Industry Co., Ltd.), and 15 parts of water-soluble acrylic resin (acid value: 240 mgKOH/g, solid content: 28%) in a bead mill, 27 parts of an aqueous acrylic resin emulsion (hydroxyl value: 50 mgKOH/g, solid content: 47%), 3 parts of polyethylene wax, and 1 part of triethanolamine were added and mixed with stirring to obtain an aqueous flexographic ink composition S1. .

[Printing of water-based flexographic ink composition S1]
Unbleached kraft paper: unbleached kraft pulp was prepared by applying the water-based flexographic ink composition S1 obtained above with a small flexipple printing machine equipped with an anilox roll of 200 lines/inch and a photosensitive resin solid plate. Printing was performed at a printing speed of 50 m/s on the surface of the base material of the kraft paper used (Nippon Paper Industries Co., Ltd. both kraft K basis weight: 70 g/m ² ) to obtain a printed material.

(Examples 2 to 15) [Preparation of aqueous flexo ink compositions S2 to S15]
A water-based flexographic ink composition was obtained in the same manner as in Example 1, except that the raw materials and formulations shown in Table 1 were changed. In the table, numerical values without unit marks represent parts, and blanks indicate that they are not blended.

[Printing of water-based flexographic ink compositions S2 to S15]
Using the water-based flexo ink compositions S2 to S15 listed in Table 1, printing was carried out in the same manner as in Example 1 to obtain printed matter by a flexi proof printing machine.

(Comparative Examples 1 to 3) [Aqueous Flexographic Ink Compositions T1 to T3]
A water-based flexographic ink composition was obtained in the same manner as in Example 1, except that the raw materials and formulations listed in Table 1 were changed. In the table, numerical values without units indicate parts, and blanks indicate that the ingredients are not blended.

[Printing of water-based flexographic ink compositions T1 to T3]
Using the water-based flexo ink compositions T1 to T3 listed in Table 1, printing was performed in the same manner as in Example 1 to obtain prints by a flexi proof printer.

(evaluation)
The following evaluations were performed using the inks and printed matter obtained in the above Examples and Comparative Examples. The evaluation results are shown in Table 1.

(bending resistance)
Unbleached kraft paper: Kraft paper using unbleached kraft pulp (Nippon Paper Industries Co., Ltd. Ryoko Kraft K; basis weight 70 g/m ² ) Then, a color was developed, a coating film was formed, and the bending resistance was evaluated. The substrate was folded so that the printed surface was on the inside, and then the substrate was folded so that the printed surface was on the outside, and then the degree of cracking of the ink coating on the printed surface was evaluated. The criteria are as follows.
5: No creases on the printed surface.
4: Having bending resistance that is a level between 5 and 3.
3: Cracking of the printed layer occurs only at the crease portion of the printed surface.
2: Those with folding resistance that is an intermediate level between 3 and 1.
1: On the printed surface, the printed layer other than the crease portion is cracked or chipped.
The ratings for industrially applicable levels above are 3, 4 and 5.

(Resolubility)
The inks obtained in Examples and Comparative Examples were spread on a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd. E5100; thickness 12 μm) with a corona discharge treatment on one side using a bar coater to form a coating film. Resolubility in the same ink composition was evaluated.
5: After wiping off, the ink coating film adhesion area ratio to the substrate is less than 1%.
4: After wiping off, the ink coating film adhesion area ratio to the base material is 1% or more and less than 5%.
3: After wiping off, the ink coating film adhesion area ratio to the base material is 5% or more and less than 10%.
2: After wiping off, the ink coating film adhesion area ratio to the base material is 10% or more and less than 30%.
1: After wiping off, the ink coating film adhesion area ratio to the base material is 30% or more.
The ratings for industrially applicable levels above are 3, 4 and 5.

(Paint film drying property)
The inks obtained in the Examples and Comparative Examples were spread on a flexographic resin plate using a Meyer bar (#4) to form a coating film. The criteria are as follows.
5: In the touched area, the ink coating film adhesion area ratio to the flexographic resin plate is 30% or more.
4: In the touched area, the ink coating film adhesion area ratio to the flexographic resin plate is 10% or more and less than 30%.
3: In the touched area, the ink coating film adhesion area ratio to the flexographic resin plate is 5% or more and less than 10%.
2: In the touched area, the ink coating film adhesion area ratio to the flexographic resin plate is 1% or more and less than 5%.
1: In the touched area, the ink coating film adhesion area ratio to the flexographic resin plate is less than 1%.
The ratings for industrially applicable levels above are 3, 4 and 5.

(Plate washability)
The inks obtained in Examples and Comparative Examples were spread on a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd. E5100; thickness 12 μm), which had been corona discharge treated on one side, by a bar coater to form a coating film, followed by drying. Water was dropped on the plate and wiped off, and the solubility of the dried coating film in water was evaluated to evaluate plate washability. The criteria are as follows.
5: After wiping off, the ink coating film adhesion area ratio to the substrate is less than 1%.
4: After wiping off, the ink coating film adhesion area ratio to the base material is 1% or more and less than 5%.
3: After wiping off, the ink coating film adhesion area ratio to the base material is 5% or more and less than 10%.
2: After wiping off, the ink coating film adhesion area ratio to the base material is 10% or more and less than 30%.
1: After wiping off, the ink coating film adhesion area ratio to the base material is 30% or more.
The ratings for industrially applicable levels above are 3, 4 and 5.

From the above results, it was confirmed that the water-based flexo ink composition of the present invention is excellent in flexographic printability, physical properties of the printed layer (bending resistance, resolubility, coating film drying property), and good plate washability. confirmed.

Claims (5)

A water-based flexographic ink composition comprising a water-based acrylic resin (A) and a urea-based compound (B),
The aqueous acrylic resin (A) comprises a water-soluble acrylic resin (a1) and an aqueous acrylic resin emulsion (a2),
The content of the water-based acrylic resin (A) is 10 to 45% by mass in the total mass of the water-based flexographic ink composition,
An aqueous flexographic ink composition, wherein the urea-based compound (B) is a compound represented by the following general formula (1).
General formula (1)

[In general formula (1), R ¹ represents an oxygen atom or a sulfur atom.
R ² and R ³ each independently represent a hydrogen atom, an optionally substituted C 1-4 alkyl group, or an optionally substituted C 6-9 aryl group .
However, R ² and R ³ may form a ring via an alkylene group having 1 to 3 carbon atoms. ] 2. The aqueous flexographic ink composition according to claim 1, wherein the content of the urea-based compound (B) in the total weight of the aqueous flexographic ink composition is 1 to 10% by mass. 3. The water-based flexographic ink composition according to claim 1, wherein the mass ratio of the urea-based compound (B) and the water-based acrylic resin (A) is 5:95 to 40:60. 3. The water-based flexographic ink composition according to claim 1, wherein the water-soluble acrylic resin (a1) has an acid value of 150 to 350 mgKOH/g. A printed matter having a printed layer formed from the water-based flexographic ink composition according to claim 1 or 2 on a substrate.