JP2018076431A - Aqueous flexographic printing ink composition for surface printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous flexographic printing ink composition for surface printing excellent in temporal stability at the time of storage, printability and coated film physical properties of a surface-printed printed matter, and to provide an aqueous flexographic printed matter for surface printing obtained by printing using the same.SOLUTION: An aqueous flexographic printing ink composition for surface printing contains (a) an acid group-containing resin emulsion partially or wholly neutralized with a volatile basic compound, (b) a hydrazine-based compound having at least two or more hydrazine residues in the molecule, (c) 0.1-1 equivalent of an aqueous polycarbodiimide compound with respect to 1 equivalent of the acid group of the acid group-containing resin emulsion, (d) a pigment, (e) a surfactant and (f) an aqueous medium.SELECTED DRAWING: None

Description

  The present invention relates to a water-based flexographic ink composition for surface printing excellent in stability over time during storage, printability, and coating film properties of printed materials printed on the surface, and surface printing produced by printing using the printing ink composition. The present invention relates to a water-based flexographic print.

For packaging of products such as confectionery, rice bags, breads, rice balls, etc., a simple configuration in which printing gravure printing ink is printed on the front side of the plastic film for decoration and surface protection and not printed on the back side in contact with food Printed material (referred to as surface printing method) is used.
As described above, since the printing ink for surface printing gravure is printed on the front side of the plastic film, the ink film is directly exposed to the outside, and a tough film physical property at the time of handling a product is required.
Conventionally, as a printing ink for surface printing gravure, an ink using an organic solvent has been used (for example, see Patent Documents 1 to 3).

  However, in recent years, environmentally friendly inks have been demanded, and water-based flexographic printing inks for surface printing have been attracting attention as environmentally friendly inks. Since water-based flexographic printing ink for surface printing does not use organic solvents, it is effective in reducing emissions of carbon dioxide and VOC generated during printing, and is effective in saving energy during printing due to the thin film unique to flexographic printing. . However, the obtained printed matter has a problem that the physical properties of the coating film are low.

JP 2009-114256 A JP2013-256551A JP 2013-234238 A

  The present invention relates to a water-based flexographic ink composition for surface printing that is excellent in stability over time during storage, printability, and coating film properties of a surface-printed printed material, and a water-based flexographic printed material for surface printing that is printed using the same. It is an issue to provide.

As a result of diligent studies to solve the above problems, the present inventors have invented the following water-based flexographic ink composition for surface printing, and water-based flexographic printed material for surface printing formed using the same. .
That is, the present invention
1.
a. Acid group-containing resin emulsion neutralized partly or entirely with a volatile basic compound b. Hydrazine compounds having at least two hydrazine residues in the molecule c. The aqueous polycarbodiimide compound is added in an amount of 0.1 to 1 equivalent d.1 to 1 equivalent of acid groups of the acid group-containing resin emulsion. Pigment e. Surfactant f. An aqueous flexographic ink composition for surface printing, which contains an aqueous solvent.
2.
The aqueous flexographic ink composition for surface printing according to 1, wherein the acid value of the resin of the acid group-containing resin emulsion is 10 to 100 mgKOH / g, and the acid group is a carboxyl group.
3.
The acid group-containing resin emulsion has a keto group and / or an aldo group obtained by emulsion polymerization of an ethylenically unsaturated monomer in an aqueous solvent using a water-soluble resin having a carboxyl group as a polymer emulsifier. 3. A water-based flexographic ink composition for surface printing according to 1 or 2.
The aqueous flexographic ink composition for surface printing according to any one of 1 to 3, wherein the volatile basic compound is ammonia.
5.
A water-based flexographic printed matter for surface printing, which is printed using the water-based flexographic ink composition for surface printing according to any one of 1 to 4.

  According to the water-based flexographic ink composition for surface printing of the present invention, a surface-printed printed material having excellent stability over time and printability, and having excellent coating film properties can be obtained. Can be obtained.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention are water-based printing ink compositions for surface printing containing a pigment, an aqueous resin emulsion, a crosslinking agent, a surfactant, and an aqueous solvent, An acid group-containing resin emulsion that is partially or completely neutralized with a volatile basic compound is used as a resin emulsion, and a hydrazine-based compound in which the crosslinking agent has at least two hydrazine residues in the molecule and an aqueous solution as a crosslinking agent By using a polycarbodiimide compound and containing an aqueous polycarbodiimide compound in a range of 0.1 to 1 equivalent with respect to 1 equivalent of the acid group of the acid group-containing resin emulsion, stability over time during storage, printability A surface-printed water-based flexographic ink composition having excellent coating film properties and printed using the printing ink composition It found that to obtain a printing aqueous flexographic printed matter, thereby completing the following invention.
Hereinafter, the water-based flexographic printing ink composition for surface printing of the present invention and the water-based flexographic printing material for surface printing obtained by printing the ink composition will be specifically described for each configuration.

<A. Acid group-containing resin emulsion partially or completely neutralized with volatile basic compound>
The acid group-containing resin emulsion obtained by neutralizing part or all of the volatile basic compound is preferably one having an acid value of 10 to 100 mgKOH / g.
Examples of the acid group-containing resin emulsion include acid group-containing polyurethane resin emulsions, acid group-containing acrylic resin emulsions, styrene-maleic acid resin emulsions, and ethylene-acrylic acid resin emulsions.
Specifically, an acid group-containing resin emulsion having a keto group and / or an aldo group obtained by emulsion polymerization of an ethylenically unsaturated monomer in an aqueous solvent using a water-soluble resin having a carboxyl group as a polymer emulsifier. It is.

A specific example of the acid group-containing resin emulsion obtained by neutralizing a part or all of the volatile basic compound will be described.
In order to obtain the acid group-containing resin emulsion in the present invention, the water-soluble resin having a carboxyl group is composed of i component: 2 to 50% by weight of carboxylic acid and / or acid anhydride having a radical polymerizable double bond, ii Component (used as necessary): 0 to 5% by weight of a ketone and / or aldehyde compound having a radical polymerizable double bond, and iii component: having a radical polymerizable double bond excluding components i and ii It is a copolymer resin obtained by copolymerizing 50 to 98% by weight of a compound and soluble in an alkaline aqueous solution. In the present invention, the i, ii and iii components are collectively referred to as the I component.

Here, as the carboxylic acid having a radically polymerizable double bond of the i component, monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, itaconic acid, and the like Examples of the acid anhydride include monoalkyl esters, monohydroxyalkyl esters, monoamides, maleic anhydride, citraconic anhydride, and itaconic anhydride.
Among these carboxylic acids or acid anhydrides having a radical polymerizable double bond, monocarboxylic acids, particularly acrylic acid or methacrylic acid are preferably used from the viewpoint of the emulsifying ability of the resulting polymer emulsifier.

Next, the ketone compound having a radically polymerizable double bond of component ii is a radically polymerizable compound having at least one keto group in the molecule, specifically, diacetone (meth) acrylamide, Examples include diacetone (meth) acrylate, acetonyl (meth) acrylate, and vinyl alkyl ketones.
Further, the aldehyde compound having a radically polymerizable double bond as the ii component is a radically polymerizable compound having at least one aldo group in the molecule, and is acrolein, formylstyrene, alkanal (meth) acrylates. Etc.

Next, as the iii component, for example, (meth) acrylic acid derivatives, styrene compounds and maleic acid derivatives described below can be used.
-(Meth) acrylic acid derivatives: (meth) acrylic acid alkyl ester having 1 to 18 carbon atoms, alkyl amide having 1 to 18 carbon atoms, hydroxyalkyl ester having 2 to 4 carbon atoms, etc. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, methyl (meth) ) Acrylamide, ethyl (meth) acrylamide, butyl (meth) acrylamide, hexyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate and the like.

Styrenic compound: Styrene and its derivatives having about 8 to 10 carbon atoms, and specific examples include α-methylstyrene, chlorostyrene, vinyltoluene and the like.
Maleic acid derivatives: dialkyl esters of maleic acid having 1 to 18 carbon atoms, dialkyl amides having 1 to 18 carbon atoms, dihydroxyalkyl esters having 2 to 4 carbon atoms, and specifically dimethyl Examples thereof include malate, diethyl malate, dibutyl malate, dioctyl malate, bis-2-hydroxyethyl maleate, maleic acid dimethylamide, maleic acid diethylamide, maleic acid dibutylamide and the like.

In addition, the amount of i component used to obtain the water-soluble resin having a carboxyl group is preferably 2 to 50% by weight, more preferably 5 to 20% by weight, and the amount of ii component used is 0 to 5% by weight. More preferably, it is preferably 1 to 4% by weight, and the amount of the iii component used is preferably 50 to 98% by weight.
Here, when the amount of component i used is less than the above range, the water-soluble resin having a carboxyl group may not be sufficiently soluble in an aqueous alkali compound solution, and the stability of emulsion polymerization is further increased. There is a possibility that the dispersion stability of the ink may decrease, and the fluidity of the resulting printing ink may be poor. On the other hand, when the above range is exceeded, the water resistance and printability may be unfavorable.
Moreover, when the usage-amount of ii component exceeds the said range, the obtained flexographic ink composition for aqueous | water-based surface printing may cause the thickening and solidification with time, and the fall of printability.

As a method of copolymerizing the above component I to obtain a water-soluble resin having a carboxyl group, in the presence of a polymerization initiator in an organic solvent, after reacting the mixture of the compounds at a predetermined temperature and reaction time, A method of distilling off the organic solvent can be used.
Here, examples of the organic solvent that can be used include esters such as ethyl acetate and isopropyl acetate, ketones such as acetone and methyl ethyl ketone, lower alcohols, glycols, and derivatives thereof. Initiators include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, organic peroxides such as benzoyl hydroperoxide, azo compounds such as azobisisobutyronitrile, and if necessary And redox initiators combined with a reducing agent.

When this water-soluble resin having a carboxyl group is used as a polymer emulsifier, the preferred molecular weight (number average molecular weight, hereinafter the same) is in the range of 3,000 to 100,000, more preferably 5,000 to 30,000. It is. If the molecular weight is lower than 3,000, another means is required to give the resulting printing ink water resistance and blocking resistance, while if it exceeds 100,000, the resulting printing ink viscosity increases.
The acid value of the water-soluble resin having a carboxyl group is preferably 20 to 300 mgKOH / g. If the acid value is less than 20 mgKOH / g, sufficient solubility in an aqueous alkali compound solution cannot be obtained. On the other hand, if it exceeds 300 mgKOH / g, the water resistance and printability of the resulting printing ink tend to be lowered.

Next, as the compound II having a radical polymerizable double bond to be subjected to emulsion polymerization, an iv component (used as necessary): a ketone and / or aldehyde compound having a radical polymerizable double bond, v component: A compound having a radical polymerizable double bond excluding the iv component is used. In the present invention, the iv and v components are collectively referred to as the II component.
Here, examples of the iv component include ketones and aldehyde compounds having a radical polymerizable double bond shown as the ii component.

On the other hand, as the v component, the carboxylic acid and acid anhydride having the radical polymerizable double bond exemplified as the i component, the (meth) acrylic acid derivative, the styrene compound, the maleic acid derivative exemplified as the iii component In addition, other examples include vinyl esters of saturated carboxylic acids having 2 to 18 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl laurate, and vinyl stearate.
Among these v components, a (meth) acrylic acid derivative and a styrene compound are preferable from the viewpoint of the dispersibility of the aqueous resin emulsion and the performance of the obtained aqueous printing ink.

In the total amount of the above II component, the usage amount of the iv component is preferably 0 to 30% by weight, and the usage amount of the v component is preferably 70 to 100% by weight.
Here, when the amount of the iv component used exceeds 30% by weight, it may be unfavorable because thickening / solidification with time and deterioration of printability may occur.

  When a water-soluble resin having a carboxyl group is used as a polymer emulsifier and an aqueous resin emulsion is synthesized using the II component, the sum of the weights of the ii component and the iv component results in i to v total single amount. It is 0.5 to 25% by mass with respect to the sum of the weights of the body components. Here, if the sum of the weights of the ii component and the iv component is less than 0.5% by mass, the adhesion of the ink to the plastic film and the suitability for lamination are lowered, which is not preferable.

Moreover, the weight ratio of I component / II component is 20 / 80-80 / 20, Preferably it is the range used as 30 / 70-70 / 30.
Here, if the weight ratio of the component I is lower than 20/80, the re-solubility, fluidity and storage stability of the ink may be lowered. On the other hand, if the weight ratio is higher than 80/20, the water resistance of the ink may be decreased. May be reduced.

  The monomer composition of the acid group-containing resin emulsion in the present invention has a glass transition temperature of −40 to 50 ° C. when all the monomer components i to v used are copolymerized. It is preferable to be adjusted within the range. When the glass transition temperature of this polymer is lower than −40 ° C., another means is required for the obtained printing ink to have blocking resistance. On the other hand, when it exceeds 50 ° C., stagnation resistance and adhesiveness are required. A different means is required to give

As a method for producing an aqueous resin emulsion using an alkali-soluble resin obtained by copolymerizing the above I component, II component and an aqueous alkali solution, the alkali-soluble resin is dissolved in the alkaline aqueous solution, and then the II component A method in which a mixture of a polymerization initiator and a polymerization initiator is dropped and reacted at a predetermined temperature and reaction time can be used.
Here, as an alkaline substance used for dissolving the alkali-soluble resin in water, a volatile basic compound described later is used. In addition, as the usage-amount of an alkaline substance, about 100-120% of the neutralization amount of alkali-soluble resin is the most suitable amount, and the solubility of alkali-soluble resin shows a tendency to fall as the usage-amount becomes less than 100%, On the other hand, even if it exceeds 120%, the solubility is not further improved.
Moreover, as a polymerization initiator, the polymerization initiator used in order to manufacture the said alkali-soluble resin can be used.

(Volatile basic compounds)
Examples of the volatile basic compound in the present invention include ammonia, triethylamine, N, N-dimethylethanolamine, monoethanolamine, etc. Among them, ammonia is preferable. Insofar as the performance does not deteriorate, inorganic alkali compounds such as sodium hydroxide and potassium hydroxide, and non-volatile amine compounds such as triethylenediamine, diethanolamine, triethanolamine, diethylenetriamine and diazabicyclooctene can be used in combination.

<B. Hydrazine-based compound having at least two hydrazine residues in the molecule>
The hydrazine compound having at least two hydrazine residues in the molecule of the present invention is used as a crosslinking agent.
The hydrazine-based crosslinking agent having at least two or more hydrazine residues in the molecule is preferably a water-soluble polyhydrazine or hydrazide compound having two or more hydrazine residues, and includes hydrazine and the following general hydrazine compounds: An alkylene dihydrazine represented by the formula (1), or a dihydrazide compound of a saturated aliphatic dibasic acid or an unsaturated dibasic acid can be exemplified.
_{H 2 N-NH-X-} NH-NH 2 (1)
(Wherein X represents an alkylene group having 1 to 8 carbon atoms or a residue of a saturated or unsaturated dibasic acid having 1 to 10 carbon atoms).

Specific examples of the alkylene dihydrazine include methylene dihydrazine, ethylene dihydrazine, propylene dihydrazine, butylene dihydrazine, and the like. Specific examples of the dihydrazide compound of a saturated aliphatic dibasic acid include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, and sebacic acid dihydrazide. Specific examples of the dibasic acid dihydrazide compound include phthalic acid dihydrazide, fumaric acid dihydrazide, and itaconic acid dihydrazide.
The hydrazine-based crosslinking agent having at least two hydrazine residues in the molecule is preferably blended in the aqueous resin emulsion, and the amount used is 0.1 to 5% by mass in the aqueous resin emulsion. Preferably, 0.4 to 2.0 mass% is more preferable.

<C. Aqueous Polycarbodiimide Compound>
In the present invention, the aqueous polycarbodiimide compound is used as a crosslinking agent.
Examples of the aqueous polycarbodiimide compound include water-soluble types such as V-02, V-02-L2, SV-02, V-04, and V-10, and emulsion types such as E-02, E-03A, and E-05. (Both manufactured by Nisshinbo Chemical Co., Ltd.) can be used. The amount of the aqueous polycarbodiimide compound used is preferably in the range of 0.1 to 1 equivalent, more preferably 0.1 to 0.7 equivalent, relative to 1 equivalent of the acid group of the acid group-containing resin emulsion. . If the amount used is less than 0.1 equivalent, the coating strength tends to decrease, whereas if it is more than 1 equivalent, the pot life (stability over time) tends to decrease.

<D. Pigment>
The pigments used in the water-based flexographic ink composition for surface printing of the present invention are inorganic pigments and organic pigments that can generally be used in water-based printing ink compositions. For example, usable inorganic pigments include titanium oxide, bengara, antimony red, cadmium red, cadmium yellow, cobalt blue, bitumen, ultramarine, carbon black, graphite, and the like, and organic pigments include soluble azo pigments and insoluble azo pigments. Examples thereof include pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. Furthermore, extender pigments such as calcium carbonate, kaolin clay, barium sulfate, aluminum hydroxide, and talc can be used in combination. As content of these pigments, 0.5-20.0 mass% is preferable in the water-based flexographic ink composition for surface printing of this invention, and it is more preferable to set it as 5.0-15.0 mass%.

<E. Surfactant>
From the viewpoint of improving printability, leveling properties and the like, it is preferable to contain 0 to 1.0% by mass of a surfactant in the aqueous flexographic ink composition for surface printing. As the surfactant, Surfynol 82, 104E, 104H, 104A, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, PSA-336, 61, 2502, Dinol 604, 607 Acetylene glycol and derivatives thereof (manufactured by Nissin Chemical Industry Co., Ltd.) and the like, BYK-381, 3441, 302, 307, 325, 331, 333, 342, 345, 346, 347, 348, 349, 378, 3455 ( Examples thereof include silicon surfactants such as Big Chemie Japan Co., Ltd., and fluorine surfactants.

<F. Aqueous solvent>
The aqueous solvent is water, and a water-miscible solvent such as lower alcohol such as methanol, ethanol, isopropanol, methoxypropanol or lower alkoxypropanol can be used as necessary.

<Other additives>
In addition, various additives such as a resin for dispersing pigment, a pigment dispersant, an anti-blocking agent, an antifoaming agent, and an antistatic agent can be added according to the necessity of ink performance. In particular, from the viewpoint of improving the pigment dispersibility, it is preferable to use a resin that is soluble in an alkaline aqueous solution as the pigment dispersing resin.

<Manufacture of water-based flexographic ink composition for surface printing>
As a method for producing an aqueous flexographic ink composition for surface printing using the above-mentioned various materials, a pigment, a binder resin, an aqueous solvent, and, if necessary, a pigment dispersant are mixed and kneaded, and further crosslinked. A method of adding and mixing the remainder of a predetermined material such as an agent is common.

<Printed matter>
The water-based flexographic printed matter for surface printing obtained by the above method can be printed on a plastic film by a flexographic printing method.
Examples of the plastic film on which the water-based flexographic ink composition for surface printing according to the present invention is printed include various plastic films such as polyolefin, polyester, and nylon, and particularly those subjected to surface treatment such as corona discharge treatment are more preferable. It is.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited only to these examples. Unless otherwise specified, “%” means “% by mass”, and “part” means “part by mass”. In addition, the numbers of the amounts of each material in the table are also “parts by mass”.

White Pigment Dispersion A mixture of 75 parts by mass of titanium oxide, 7 parts by mass of Solsperse 190, 1 part by mass of isobutanol and 17 parts by mass of water was kneaded with a bead mill to obtain a white pigment dispersion.

Indigo pigment dispersion 45 parts by weight of PB15: 4, 11 parts by weight of alkali-soluble pigment-dispersing water-soluble resin (MAA / MMA / SMA = 15/75/10, ammonia neutralized, solid content 28%), pigment A mixture of 2 parts by mass of a dispersant (Solsperse 27000), 2 parts by mass of isobutanol, and 16 parts by mass of water was kneaded with a bead mill to obtain an indigo pigment dispersion.

Aqueous flexographic ink composition for surface printing of Examples 1 to 12 and Comparative Examples 1 to 4 Aqueous resin emulsion

AA: acrylic acid MMA: methacrylic acid St: styrene 2HEA: 2-hydroxyethyl acrylate DAAM: diacetone acrylamide AV: acid value ADH: adipic acid dihydrazide NV: solid content mass concentration

Each material was mix | blended so that it might become a mixing | blending of Table 2, it stirred and mixed, and the water-based flexographic printing ink composition for surface printing of Examples 1-12 and Comparative Examples 1-4 was obtained. Surfynol 82 was used as the surfactant.
Subsequently, the water-based flexographic ink compositions for surface printing of Examples 1 to 12 and Comparative Examples 1 to 4 were printed with a flexographic printing machine, and pot life, substrate adhesion, water rub resistance, and blocking resistance were evaluated. .

<Pot life>
After preparing the water-based flexographic printing ink composition for surface printing, the coating suitability and the coating film properties after 3 days were evaluated.
Evaluation criteria A: There is no problem in coating suitability and physical properties of the coating film B: Coating suitability and physical properties of the coating film are deteriorated

<Base material adhesion>
Adhesiveness was evaluated from the degree to which the printed film peeled off from the film when Cellotape (registered trademark) was affixed to the printed surface and peeled off rapidly.
Evaluation criteria A: The printed film does not peel from the film at all B: Less than 20% peels from the film as the area ratio of the printed film C: 20% or more and less than 50% peels from the film as the area ratio of the printed film D: 50% or more peeled from the film as the area ratio of the printed film

<Water and friction resistance>
Using kanakin dipped in water in a friction surface on the printed surface, it was reciprocated 200 times with a load of 500 g using a Gakushin type testing machine (Daiei Kagaku Seiki Seisakusho). .
Evaluation criteria A: No ink dropout B: Ink falls off in a range of less than 20% C: Ink drops off in a range of 20% or more and less than 50% D: Ink drops off in a range of 50% or more

<Blocking resistance>
The printed surface and the non-printed surface were put together, tightened with a vise, and peeled off by hand after 1 day at 40 ° C., and blocking resistance was evaluated from the degree and strength of ink peeling.
Evaluation criteria A: There is no peeling of the ink film, and no peeling resistance is felt B: There is no peeling of the ink film, but a peeling resistance is felt C: The ink film is peeled a little, and the peeling resistance is felt strongly D : The ink film is almost peeled off and the peel resistance is felt strongly

According to Comparative Example 1 in which the aqueous carbodiimide compound was not added, the results were inferior in water and friction resistance. According to Comparative Example 2 in which the aqueous carbodiimide compound was added in an amount of 1.1 equivalent to 1 equivalent of the acid group of the acid group-containing resin emulsion, the pot life was short and the coating suitability and the coating film physical properties were lowered.
Moreover, according to Comparative Example 3 that does not contain a hydrazine-based compound having at least two hydrazine residues in the molecule, the substrate adhesion, water wear resistance, and blocking resistance were poor.
Furthermore, according to Comparative Example 4 in which neutralization of the acid groups of the acid group-containing resin emulsion was not performed with a volatile basic compound, the results were inferior in water and friction resistance.

Claims (5)

a. Acid group-containing resin emulsion neutralized partly or entirely with a volatile basic compound b. Hydrazine compounds having at least two hydrazine residues in the molecule c. The aqueous polycarbodiimide compound is added in an amount of 0.1 to 1 equivalent d.1 to 1 equivalent of acid groups of the acid group-containing resin emulsion. Pigment e. Surfactant f. An aqueous flexographic ink composition for surface printing, which contains an aqueous solvent.   The aqueous flexographic ink composition for surface printing according to claim 1, wherein the acid value of the resin of the acid group-containing resin emulsion is 10 to 100 mgKOH / g, and the acid group is a carboxyl group.   The acid group-containing resin emulsion has a keto group and / or an aldo group obtained by emulsion polymerization of an ethylenically unsaturated monomer in an aqueous solvent using a water-soluble resin having a carboxyl group as a polymer emulsifier. The aqueous flexographic ink composition for surface printing according to claim 1 or 2.   The aqueous flexographic ink composition for surface printing according to any one of claims 1 to 3, wherein the volatile basic compound is ammonia. A water-based flexographic print for surface printing, which is printed using the water-based flexographic ink composition for surface printing according to any one of claims 1 to 4.