Aqueous gravure printing ink composition

Abstract

To provide an aqueous gravure printing ink composition that offers excellent drying performance, blocking resistance, whitening prevention, and leveling properties, where the aqueous gravure printing ink composition incorporates a significant amount of carbon-neutral raw materials.SOLUTION: An aqueous gravure printing ink composition contains a pigment, a styrene-acrylic resin emulsion with a core-shell structure, a resin for pigment dispersion, and an aqueous medium, and satisfies specific conditions.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a water-based gravure printing ink composition. [Background technology]

[0002] Conventionally, water-based inks have been printed by gravure printing for cosmetic purposes on the exterior boxes of various products ranging from food products such as confectionery, tissues, and detergents to household goods, and on multi-pack packages for alcoholic beverages and beverages (see Patent Documents 1 and 2). However, the ink compositions described in Patent Documents 1 and 2 have room for improvement in drying properties, blocking resistance, leveling properties, and the like. As a result of intensive research into solving the above problems, the present inventors have proposed that the drying properties, blocking resistance, and leveling properties of an aqueous gravure printing ink composition for paper containers can be improved by using a specific amount of a hyperbranched polyether type wetting agent in combination with a specific printing modifier (see, for example, Patent Document 3). In recent years, there has been a demand for improved drying properties, blocking resistance, prevention of white spots, and leveling properties. In addition, environmental initiatives are becoming more active, and the packaging industry is also under pressure to develop inks that can reduce carbon dioxide emissions (become carbon neutral) by using raw materials that are not derived from fossil fuels, such as plant- and animal-derived materials. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-144334 A [Patent Document 2] JP 2017-128701 A [Patent Document 3] JP 2020-066653 A Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide an aqueous gravure printing ink composition that is excellent in drying properties, gloss, blocking resistance, prevention of white spots, resolubility, and leveling properties, and further to provide an aqueous gravure printing ink composition that uses a large amount of raw materials that can be carbon neutral. [Means for solving the problem]

[0005] Means of Solving the Problems The present inventors have conducted extensive research to solve the above problems and have discovered the following aqueous gravure printing ink composition, thereby completing the present invention. That is, the present invention provides: 1. An aqueous gravure printing ink composition comprising a pigment, a styrene-acrylic resin emulsion having a core-shell structure, a pigment dispersion resin, and an aqueous medium, and satisfying the following condition 1 or 2: Condition 1 The styrene-acrylic resin emulsion having a core-shell structure contains a structural unit derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms in the shell portion and / or the core portion, but does not contain a structural unit derived from a (meth)acrylate having a hydroxyl group. The aqueous gravure printing ink composition contains 3.0 to 22.0 mass % of a hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g based on the total solid content. Condition 2 The styrene-acrylic resin emulsion having a core-shell structure contains a structural unit derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms in the shell portion and / or the core portion, and also contains a structural unit derived from a (meth)acrylate having a hydroxyl group. The aqueous gravure printing ink composition does not contain a hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g, or contains it in an amount in the range of 0 mass % or more and 22.0 mass % or less in the total solid content. 2. The water-based gravure printing ink composition according to 1, which contains a rosin-based emulsion. 3. The aqueous gravure printing ink composition according to 1 or 2, wherein the hydroxyl group-containing acrylic copolymer has an acid value of 30 to 100 mgKOH / g and is a hydroxyl group-containing acrylic copolymer having a structural unit derived from a (meth)acrylate having a hydroxyl group. 4. The aqueous gravure printing ink composition according to any one of 1 to 3, wherein the styrene-acrylic resin emulsion having a core-shell structure has a mass ratio of the core part to the shell part of shell part:core part=40:60 to 60:40, and the shell part and / or the core part contains a structural unit derived from a (meth)acrylate having an alkyl group having 4 to 8 carbon atoms. 5. The aqueous gravure printing ink composition according to any one of 1 to 4, wherein the styrene-acrylic resin emulsion having a core-shell structure, when condition 2 above, contains a structural unit derived from a (meth)acrylate having a hydroxy group in the shell portion. 6. The aqueous gravure printing ink composition according to 3 or 5, wherein the (meth)acrylate having a hydroxy group is 2-hydroxyethyl (meth)acrylate. 7. The water-based gravure printing ink composition according to any one of 1 to 6, wherein the pigment dispersing resin contains an alkali-soluble water-soluble resin. 8. The water-based gravure printing ink composition according to any one of 1 to 7, wherein the pigment dispersing resin contains an (ethylene oxide / propylene oxide) block polymer. 9. The aqueous gravure printing ink composition according to any one of 1 to 8, wherein the aqueous medium contains water, 2-ethyl-1,3-hexanediol, and a lower alcohol having 1 to 4 carbon atoms. Regarding. Effect of the Invention

[0006] According to the present invention, it is possible to obtain a water-based gravure printing ink composition which is excellent in drying properties, leveling properties, gloss, blocking resistance and resolubility and which does not cause blank spots. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The water-based gravure printing ink composition of the present invention will be described in detail below. In the present invention, the acid value is a value measured in accordance with JIS K2501:2003, and the glass transition temperature (Tg) is a value measured in accordance with JIS K7121:2012. <Pigments> The pigment used in the aqueous gravure printing ink composition of the present invention may be any pigment that has been used in aqueous gravure printing inks. Specifically, the inorganic pigment may be a colored pigment such as titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, or graphite. The titanium oxide is preferably a titanium oxide surface-treated with at least silica and / or alumina. The organic pigment may be a soluble azo pigment, an insoluble azo pigment, an azo lake pigment, a condensed azo pigment, a copper phthalocyanine pigment, or a condensed polycyclic pigment. The above pigments may be used alone or in combination of two or more. The concentration of the pigment in the total solid content of the aqueous gravure printing ink composition is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, and preferably 60.0% by mass or less. In the case of normal organic pigments and carbon black, the concentration is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, and preferably 35% by mass or less, and more preferably 30.0% by mass or less.

[0008] <Items common to Condition 1 and Condition 2 for styrene-acrylic resin emulsions having a core-shell structure> The styrene-acrylic resin emulsion having a core-shell structure used in the water-based gravure printing ink composition of the present invention satisfies condition 1 or 2, and can be produced by a known method. (Items common to Conditions 1 and 2) The shell and / or core contain structural units derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms. The mass ratio of the core part to the shell part of the styrene-acrylic resin emulsion having a core-shell structure is shell part:core part=10:90 to 70:30, preferably 30:70 to 70:30, and more preferably 40:60 to 60:40. Moreover, the styrene-acrylic resin emulsion having a core-shell structure is more preferably made of a styrene-acrylic resin containing a structural unit derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 8 carbon atoms in the shell portion and / or the core portion. Furthermore, among the styrene-acrylic resin emulsions having a core-shell structure that satisfies condition 1, those that form a film at room temperature and are obtained by using a water-soluble acrylic resin that becomes the shell as a polymer emulsifier and copolymerizing a styrene monomer, a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, and, if necessary, a (meth)acrylate other than the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, can be preferably used.

[0009] Furthermore, the shell and core portions of the styrene-acrylic resin emulsion having a core-shell structure will be described in detail. The shell portion contains, per 100 parts by mass of the shell portion, 10 to 50 parts by mass of a structural unit derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, a structure derived from a carboxyl group-containing monomer, and a structural unit derived from a (meth)acrylate other than a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, and the theoretical acid value of the shell portion is preferably 40 to 120 mgKOH / g. In Table 2 below, the shell portion is formed from a polymer emulsifier. Examples of the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, and eicosyl (meth)acrylate, and it is preferable to contain butyl acrylate and / or 2-ethylhexyl (meth)acrylate. Examples of the carboxyl group-containing monomer include maleic acid monoester compounds having an aliphatic hydrocarbon group having 8 to 13 carbon atoms, such as acrylic acid, methacrylic acid, maleic acid (anhydride), monomethyl maleate, monoethyl maleate, monobutyl maleate, monohexyl maleate, monooctyl maleate, mono-2-ethylhexyl maleate, and monolauryl maleate; maleic acid monoester compounds having an aliphatic hydrocarbon group having 14 to 20 carbon atoms, such as monomyristyl maleate, monocetyl maleate, monostearyl maleate, monooleyl maleate, and monoeicosyl maleate; crotonic acid and its ester compounds; and itaconic acid and its ester compounds. Examples of (meth)acrylates other than (meth)acrylates having an aliphatic alkyl group having 4 to 24 carbon atoms include (meth)acrylates having an aliphatic hydrocarbon group, such as methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate; (meth)acrylamide, acrylonitrile, and olefin-based compounds; styrene-based monomers, such as styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, ethylstyrene, isopropylstyrene, t-butylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, and fluorostyrene; benzyl (meth)acrylate-based monomers, such as benzyl methacrylate and benzyl acrylate; and phenyl (meth)acrylate-based monomers, such as phenyl methacrylate and phenyl acrylate. It is preferable that the shell portion contains structural units derived from butyl acrylate and / or 2-ethylhexyl methacrylate, The core part preferably contains, per 100 parts by mass of the core part, 25 parts by mass or more of a structural unit derived from a styrene-based monomer, a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, and, as necessary, a (meth)acrylate other than the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms. In Table 2 below, the core part is formed from components other than the polymer emulsifier. Examples of the styrene monomer include styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, 4-methoxystyrene, and vinyltoluene. Examples of the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, and eicosyl (meth)acrylate, and it is preferable to contain butyl acrylate and / or 2-ethylhexyl (meth)acrylate. Examples of (meth)acrylates other than (meth)acrylates having an aliphatic alkyl group having 4 to 24 carbon atoms include (meth)acrylates having an aliphatic hydrocarbon group, such as methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate; (meth)acrylamide, acrylonitrile, olefin-based compounds; benzyl (meth)acrylate-based monomers, such as benzyl methacrylate and benzyl acrylate; and phenyl (meth)acrylate-based monomers, such as phenyl methacrylate and phenyl acrylate. By using a styrene-acrylic resin emulsion having such a core-shell structure, the aqueous gravure printing ink composition has good drying properties, blocking resistance and leveling properties, and when the surface tension is reduced, poor doctor cutting on the printing plate and the occurrence of misting can be further prevented even with a small amount of antifoaming agent or surfactant contained.

[0010] The content of the styrene-acrylic resin emulsion having a core-shell structure in the present invention is preferably 15.0% by mass or more, more preferably 20.0% by mass or more, and even more preferably 22.0% by mass or more, based on the total solid content of the aqueous gravure printing ink composition, and is preferably 57.0% by mass or less, more preferably 50.0% by mass or less, and even more preferably 45.0% by mass or less. As a method for producing the styrene-acrylic resin emulsion in the present invention, for example, a method for producing core-shell particles by suspension polymerization or emulsion polymerization can be adopted. Among these methods, the styrene-acrylic resin emulsion having a core-shell structure of the present invention can be obtained by blending a polymerizable monomer that will become the core portion, specifically, 25 mass % or more of a styrene-based monomer, a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, such as 2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, etc., and a polymerizable monomer having methyl methacrylate, etc. as necessary, in the presence of the below-mentioned polymer emulsifier that will become the shell portion, and polymerizing the blend by a known emulsion polymerization method.

[0011] <Items specific to condition 1 (when the styrene-acrylic resin emulsion particles having a core-shell structure do not have a structural unit derived from a (meth)acrylate having a hydroxyl group)> In the case of condition 1, the constituent units constituting the particles having a core-shell structure constituting the styrene-acrylic resin emulsion having a core-shell structure are the compounds described above. In addition, the constituent units derived from (meth)acrylate having a hydroxyl group are not contained, and therefore the following compounds are not included. (Meth)acrylic acid ester compounds having a hydroxyalkyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate.

[0012] <Items specific to condition 2 (when the styrene-acrylic resin emulsion particles having a core-shell structure have a structural unit derived from a (meth)acrylate having a hydroxyl group)> In the case of condition 2, the constituent units constituting the particles having a core-shell structure constituting the styrene-acrylic resin emulsion having a core-shell structure include compounds that satisfy the following conditions in addition to the compounds described above. Examples of the hydroxyalkyl group-containing (meth)acrylic ester compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate, and among these, 2-hydroxyethyl acrylate is preferred. Furthermore, the structural unit derived from a (meth)acrylate having a hydroxy group is preferably present in the shell portion of the styrene-acrylic resin emulsion having a core-shell structure, and the structural unit preferably present in the shell is more preferably a structural unit derived from 2-hydroxyethyl (meth)acrylate.

[0013] (polymer emulsifier) The above polymer emulsifier is a copolymer of a carboxyl group-containing monomer, a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, a (meth)acrylate other than the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, or another radically polymerizable unsaturated monomer. As the carboxyl group-containing monomer, the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, and the (meth)acrylate other than the (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms, those described above can be used.

[0014] It is preferable that the resulting polymer emulsifier contains butyl acrylate in the monomers constituting the polymer emulsifier from the viewpoint of antifoaming properties, and a (meth)acrylic acid ester compound having a hydroxyalkyl group from the viewpoints of resolubility, leveling properties, etc. In addition, it is preferable to use a carboxyl group-containing monomer for the polymer emulsifier so that the theoretical acid value is 40 to 120 mgKOH / g. If the theoretical acid value is less than 40 mgKOH / g, the stability of the styrene-acrylic emulsion may decrease, while if it is more than 120 mgKOH / g, the water resistance of the styrene-acrylic emulsion may decrease. In addition, the weight-average molecular weight of the polymer emulsifier is preferably in the range of 3000 to 25000. If the weight-average molecular weight is less than 3000, the function as a polymer emulsifier may decrease, while if it is more than 25000, the solubility of the copolymer may decrease. The polymer emulsifier may be a (meth)acrylate having the above-mentioned carboxyl group-containing monomer and the above-mentioned aliphatic alkyl group having 4 to 24 carbon atoms, or a (meth)acrylate having the above-mentioned aliphatic alkyl group having 4 to 24 carbon atoms. A mixture of (meth)acrylate and other (meth)acrylates is polymerized by a known method. The polymer may be prepared by combining the above-mentioned two components to obtain a polymer having a weight average molecular weight of 3,000 to 25,000, and then neutralizing the polymer with a basic compound. Examples of the basic compound used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and organic basic compounds such as triethylamine, monoethanolamine, dimethylethanolamine, triethanolamine, and triethylenediamine. These may be used alone or in combination of two or more.

[0015] <Hydroxy group-containing acrylic copolymer with acid value of 30 to 120 mg KOH / g> (Items common to Condition 1 and Condition 2 regarding hydroxyl group-containing acrylic copolymers with an acid value of 30 to 120 mg KOH / g) The hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g is an acrylic copolymer resin having an acid value of 30 to 120 mgKOH / g which contains a structural unit derived from a (meth)acrylate having a hydroxyl group, and preferably has an acid value of 40 mgKOH / g or more, more preferably 50 mgKOH / g or more, and preferably 100 mgKOH / g or less, more preferably 80 mgKOH / g or less. The alkali-soluble resin usable as the hydroxyl group-containing acrylic copolymer can be prepared by neutralizing a copolymer of a carboxyl group-containing monomer, a (meth)acrylic acid ester monomer having a hydroxyalkyl group, a (meth)acrylate monomer having an aliphatic alkyl group having 4 to 24 carbon atoms, and other radically polymerizable unsaturated monomers with a basic compound. The basic compound used for neutralization can be the same as those mentioned above.

[0016] Examples of the carboxyl group-containing monomer include those described above for the polymer emulsifier. Examples of the (meth)acrylic acid ester monomer having a hydroxyalkyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate, with 2-hydroxyethyl (meth)acrylate being preferred. Examples of the (meth)acrylate monomer having an aliphatic alkyl group having 4 to 24 carbon atoms include those described above for the polymer emulsifier. Other radically polymerizable unsaturated monomers include (meth)acrylates having an aliphatic hydrocarbon group, such as methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate; (meth)acrylamide, acrylonitrile, olefin-based compounds; benzyl (meth)acrylate-based monomers, such as benzyl methacrylate and benzyl acrylate; and phenyl (meth)acrylate-based monomers, such as phenyl methacrylate and phenyl acrylate.

[0017] <Items specific to condition 1 (when the styrene-acrylic resin emulsion particles having a core-shell structure do not have a structural unit derived from a (meth)acrylate having a hydroxyl group)> Under these conditions, the content of the hydroxyl group-containing acrylic copolymer in the present invention is 3.0% by mass or more, preferably 5.0% by mass or more, and more preferably 10.0% by mass or more, based on the total solid content of the aqueous gravure printing ink composition, and is 22.0% by mass or less, preferably 20.0% by mass or less, and more preferably 16.0% by mass or less. By incorporating 3.0 to 22.0 mass % of a hydroxy group-containing acrylic copolymer in the total solid content of the aqueous gravure printing ink composition, the aqueous gravure printing ink composition becomes excellent in drying properties, blocking resistance, prevention of white voids, and leveling properties.

[0018] <Items specific to condition 2 (when the styrene-acrylic resin emulsion particles having a core-shell structure have a structural unit derived from a (meth)acrylate having a hydroxyl group)> Under these conditions, the hydroxyl group-containing acrylic copolymer of the present invention is not contained, or its content is 0 mass% or more, preferably 2.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 8.0 mass% or more, based on the total solid content of the aqueous gravure printing ink composition, and is 22.0 mass% or less, preferably 20.0 mass% or less, more preferably 16.0 mass% or less, and even more preferably 13.0 mass% or less. By not containing a hydroxy group-containing acrylic copolymer in the total solids content of the aqueous gravure printing ink composition, or by containing a hydroxy group-containing acrylic copolymer in an amount in the range of 0 mass % or more and 22.0 mass % or less, the aqueous gravure printing ink composition becomes excellent in drying properties, blocking resistance, prevention of white voids, and leveling properties.

[0019] <Rosin-based emulsion> In order to realize an aqueous gravure printing ink composition that uses raw materials derived from plants and animals and is not derived from fossil fuels, and that can reduce carbon dioxide emissions (be carbon neutral), it is preferable to contain a rosin-based emulsion. The rosin-based emulsion is preferably a rosin-based resin emulsion having an acid value of 0 to 350 mgKOH / g. As the rosin-based resin emulsion having an acid value of 0 to 350 mgKOH / g, a rosin derivative such as rosin ester, which is made of a material obtained by extracting from a plant, or the like, or a rosin dispersed in water as fine particles in the presence of a low molecular weight emulsifier can be used.Specific examples include Hariestar SK218NS, SK370N, SK385NS, and SK501NS manufactured by Harima Chemical Industries, Ltd., Snowpack XW-2442, XW-2551, XW-2561, XW-2582, SE780G, and 100G manufactured by LAWTER, and Superester NS-121, NS-100H, and E-865NT manufactured by Arakawa Chemical Industries, Ltd. When a rosin-based emulsion is contained, the content of the solid content of the rosin-based resin emulsion having an acid value of 0 to 350 mgKOH / g in the total solid content of the aqueous gravure printing ink composition of the present invention is preferably 1.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 10.0 mass% or more. It is preferably 30.0 mass% or less. The raw material component that can be carbon neutral refers to a raw material component derived from a plant material.

[0020] <Pigment dispersion resin> The pigment dispersing resin used in the water-based gravure printing ink composition of the present invention is preferably an alkali-soluble water-soluble resin, and more preferably used in combination with an (ethylene oxide / propylene oxide) block polymer.

[0021] (Alkali-soluble water-soluble resin) As the alkali-soluble water-soluble resin, there can be used without any particular limitation, as long as it is a resin obtained by polymerizing a monomer having an unsaturated double bond used in a typical aqueous gravure printing ink composition, or a resin obtained by a reaction between functional groups. Specifically, suitable examples of binder resins include water-soluble acrylic resins copolymerized with acrylic acid or methacrylic acid and their alkyl esters, or styrene or the like as the main monomer component, water-soluble styrene-acrylic resins, water-soluble styrene-maleic acid resins, water-soluble styrene-acrylic-maleic acid resins, water-soluble polyurethane resins, and water-soluble polyester resins. In addition, when the alkali-soluble water-soluble resin is also a hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g, the hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g in the present invention also includes this alkali-soluble water-soluble resin.

[0022] These alkali-soluble water-soluble resins are usually dissolved in water in the presence of a basic compound and used as a water-soluble resin varnish. Examples of the basic compound used to dissolve the alkali-soluble water-soluble resin in water include ammonia, organic amines, and alkali metal hydroxides. Specifically, the organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxides include sodium hydroxide and potassium hydroxide. Among them, those that are easily volatilized at room temperature or with slight heating are preferred in order to improve drying properties. The content of alkali-soluble water-soluble resin relative to the pigment is the solid content per 100 parts by mass of pigment. The content is preferably 20 to 1000 parts by mass, and more preferably 20 to 500 parts by mass.

[0023] (Ethylene oxide / propylene oxide) block polymer The (ethylene oxide / propylene oxide) block polymer may contain two or more blocks, and each block may be composed of polyethylene oxide or propylene oxide. The (ethylene oxide / propylene oxide) block polymer can be synthesized by a known method, for example, a polyethylene oxide polymer can be reacted with propylene oxide to form a poly(propylene oxide / ethylene oxide / propylene oxide) block polymer, or, as another method, a polypropylene oxide polymer can be reacted with ethylene oxide to form a poly(ethylene oxide / propylene oxide / ethylene oxide) block polymer. The poly(ethylene oxide / propylene oxide / ethylene oxide) block polymer that can be used in the present invention preferably has a weight average molecular weight in the range of 5,000 to 100,000. Commercially available examples include the Adeka Pluronic (registered trademark) series manufactured by ADEKA.

[0024] Moreover, the poly(ethylene oxide / propylene oxide / ethylene oxide) block polymer preferably has an HLB value of 8 to 20 from the viewpoint of stability in a solvent containing water. Here, the HLB value is used in the field of surfactants and represents the balance between the hydrophilic and lipophilic parts of a molecule (hydrophile-lipophile balance). The HLB value can be calculated by applying the Griffin formula shown below (a formula based on the experimental value obtained by measuring the emulsification efficiency for a certain oil and the weight fraction of the hydrophilic part). [Griffin formula] HLB = (100 / 5) x hydrophilic group weight / (hydrophilic group weight + hydrophobic weight) The content of the (ethylene oxide / propylene oxide) block polymer relative to the pigment is 0 to 10 parts by mass, and preferably 0.5 to 8 parts by mass, relative to 100 parts by mass of the pigment. The total content of the alkali-soluble water-soluble resin and the (ethylene oxide / propylene oxide) block polymer relative to the pigment is preferably 10 to 30 parts by mass relative to 100 parts by mass of the pigment.

[0025] (Antifoaming agent) As the defoaming agent that may be used in the present invention, a known defoaming agent can be adopted. Examples of such defoaming agents that can be used include hydrophobic polydimethylsiloxane-based defoaming agents, defoaming agents that combine a polysiloxane containing a long-chain alkyl group or an aralkyl group with a polyoxyalkylene chain-containing polysiloxane, defoaming agents mainly composed of a polysilcarbene siloxane consisting of a silcarbene unit and a siloxane unit, defoaming agents consisting of a reaction product of an alkylene oxide compound, a silicone having an alcoholic hydroxyl group, and an isocyanate compound, and defoaming agents consisting of a siloxane-glycol copolymer and polypropylene glycol. In particular, by using 20 to 50 parts by mass of a constituent unit derived from butyl acrylate per 100 parts by mass of the shell portion of the styrene-acrylic resin emulsion having a core-shell structure, the amount of defoaming agent used in the present invention can be made smaller than the amount of defoaming agent blended in normal inks, and further the surfactant content can be made smaller, thereby preventing poor doctor cutting and misting on the printing plate. The content of the defoaming agent is preferably 0.3% by mass or less, and more preferably 0.2% by mass or less, of the aqueous gravure printing ink composition.

[0026] <Aqueous medium> The aqueous medium used in the aqueous gravure printing ink composition of the present invention is water or a water-soluble organic solvent within a range that does not cause a decrease in the performance of the aqueous gravure printing ink composition of the present invention. The water-soluble organic solvent is an alcohol or polyhydric alcohol solvent, specifically, methanol, ethanol, propanol, butanol, hexanol, octanol, decanol, 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, glycerin, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol isobutyrate, 2-ethyl-1,3-hexanediol, 1,6-hexanediol diacetate, isoamyl acetate, and the like can be added. From the viewpoint of drying property and leveling property, the aqueous medium preferably contains water, 2-ethyl-1,3-hexanediol, and a lower alcohol having 1 to 4 carbon atoms. The preferred range of the content of 2-ethyl-1,3-hexanediol is 0.5 to 2.0 mass%. The lower alcohol having 1 to 4 carbon atoms is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, and isobutanol. The content of the lower alcohol having 1 to 4 carbon atoms in the water-based gravure printing ink composition of the present invention is preferably 1 to 30 mass %.

[0027] (wax) Wax may be added to improve the stain resistance and abrasion resistance of the resulting printed matter. The wax to be used is in the range of 1.0 to 6.0 μm according to the Coulter counter method (the average particle size means the particle size measured by #1: Microtrac UPA manufactured by Honeywell). If the average particle size is smaller than 1.0 μm, the slipping property and blocking property are reduced, and if the average particle size is larger than 6.0 μm, the trapping property is reduced. When wax is contained, the content of the wax in the total solid content of the aqueous gravure printing ink composition is preferably in the range of 0.1 to 3.0 mass %. If the content is less than 0.1 mass %, the desired effect cannot be obtained, and if the content is more than 3.0 mass %, the gloss tends to decrease. The type of wax is not particularly limited. For example, the wax is polyethylene wax, polytetrafluoroethylene wax, etc.

[0028] (Other optional ingredients) The water-based gravure printing ink composition of this embodiment may contain optional components as appropriate. Examples of optional components include surfactants, waxes, wetting agents, defoamers, pH adjusters, viscosity adjusters, drying adjusters, gloss agents, crosslinking agents, and the like.

[0029] <Method for producing water-based gravure printing ink composition> The method for producing the aqueous gravure printing ink composition of this embodiment is not particularly limited. For example, the aqueous gravure printing ink composition is produced by mixing a colorant, a pigment dispersion resin, etc., stirring and kneading the mixture using a known ink production device (ball mill, attritor, sand mill, etc.), and then adding and mixing a hydroxyl group-containing acrylic copolymer, a styrene-acrylic resin emulsion having a core-shell structure, a rosin emulsion, an antifoaming agent, a wax, an aqueous solvent, and, if necessary, an alkali-soluble water-soluble resin, etc. Next, if dilution is required during printing, a solvent containing water is further added to obtain the aqueous gravure printing ink composition.

[0030] <Method for producing printed matter using aqueous gravure printing ink composition> In one embodiment of the method for producing a printed matter using the aqueous gravure printing ink composition, the printed matter can be produced by printing the aqueous gravure printing ink composition described in detail in the above embodiment on a paper substrate such as coated paper by a gravure method. Considering the production efficiency of the printed matter, the printing speed is preferably 150 m / min or more. In addition, in the production method of this embodiment, a drying step using various heating and drying devices may be adopted after printing. During printing, the viscosity of the aqueous gravure printing ink composition is preferably about 15 to 19 seconds as measured by Zahn Cup No. 3. If it is less than 15 seconds, the leveling property tends to decrease. On the other hand, if it exceeds 19 seconds, the printability tends to decrease. The aqueous gravure printing ink composition may also be stored in a concentrated state and used after being diluted with a diluent at the time of printing. EXAMPLES

[0031] The present invention will be described in more detail below with reference to the following examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".

[0032] The raw materials and preparation methods used are shown below. (Polymerizable monomers, etc.) AA: Acrylic acid MMA: Methyl methacrylate BA: Butyl acrylate 2-EHA: 2-Ethylhexyl acrylate St: styrene EA: Ethyl acrylate 2-HEMA: 2-hydroxyethyl methacrylate DMEA: Dimethylethanolamine

[0033] <Base ink (PB15:3), (PY14), (PR48:3), (PB7)> The base inks of each color were prepared by blending and mixing 30 parts by mass of each pigment (blue pigment (PB15:3), yellow pigment (PY14), red pigment (PR48:3), black pigment (PB7)), 45 parts by mass of the alkali-soluble resin listed below as a pigment dispersion resin, 1.4 parts by mass of poly(ethylene oxide / propylene oxide) block polymer (HLB value 14, MW 16000), and 23.6 parts by mass of water. The solids concentration of these base inks is 30 + (45 × 20.2%) + 1.4 = 40.49% by mass.

[0034] (Alkali-soluble water-soluble resin) 15 parts by mass of styrene, 60 parts by mass of methyl methacrylate, 10 parts by mass of lauryl methacrylate, and 15 parts by mass of acrylic acid were copolymerized by a conventional polymerization method to obtain a copolymer having an acid value of 80 mgKOH / g and a weight average molecular weight of 38000. This copolymer resin was neutralized with dimethylethanolamine (DMEA) water to obtain an alkali-soluble water-soluble resin with a solid content concentration of 20.2%.

[0035] (hydroxyl group-containing acrylic copolymers with acid values ​​of 30 to 120 mgKOH / g, hydroxyl group-free acrylic copolymers) The polymerizable monomers shown in Table 1 below were polymerized by a conventional method and neutralized with dimethylethanolamine (DMEA) water to obtain hydroxyl group-containing or hydroxyl group-free acrylic copolymers 1 to 10 (solid content 30 mass %) having the acid values ​​and molecular weights (MW) (weight average molecular weight) shown in Table 1 below.

[0036] [Table 1]

[0037] As shown in Table 2 below, styrene-acrylic resin emulsions A to D having a core-shell structure were obtained. In Table 2, polymer emulsifiers A to D (solid content 30%), which are the base for resin particles having a core-shell structure, were prepared by synthesizing AA: acrylic acid, MMA: methyl methacrylate, BA: butyl acrylate, and, if necessary, 2-HEMA: 2-hydroxyethyl methacrylate, in the monomer mass ratios shown in Table 2 below. Next, resin particles A to D having a core-shell structure in Table 2 below were synthesized by preparing the corresponding polymer emulsifiers A to D, St: styrene, 2-EHA: 2-ethylhexyl acrylate, and if necessary MMA: methyl methacrylate, in the monomer mass ratios shown in Table 2 below. For example, to synthesize resin particles A having a core-shell structure, first, 8.0 parts by mass of AA, 68.5 parts by mass of MMA, 18.5 parts by mass of BA, and 5 parts by mass of 2-HEMA were polymerized to obtain polymer emulsifier A. Next, in order to obtain resin particle emulsion A having a core-shell structure, 53.3 parts by mass of polymer emulsifier A (solid content), 13.8 parts by mass of St, 19.6 parts by mass of 2-EHA, and 13.3 parts by mass of MMA were polymerized to obtain the monomer ratio in Table 2, resulting in a core-shell structure in which polymer emulsifier A became the shell portion and a phase consisting of the other monomer components became the core portion. The solid content of the obtained resin particle emulsion A having a core-shell structure was 40.0% by mass. Similarly, polymer emulsifiers B to D were obtained, and then resin particle emulsions B to D having a core-shell structure and a solid content concentration of 40.0% by mass were obtained.

[0038] [Table 2]

[0039] <Preparation of Water-Based Gravure Printing Ink Composition> The components were blended to obtain the mass ratios (mass%) shown in Table 3 below, and mixed by stirring to obtain aqueous gravure printing ink compositions. The components were then diluted with a diluent of 70 / 30 isopropanol / water to a Zahn cup No. 3 viscosity of 15 to 19 seconds, so that the solids concentration in the aqueous gravure printing ink composition was in the range of 15 to 30 mass%, to obtain black, red, yellow, and blue aqueous gravure printing ink compositions, respectively.

[0040] <Production of printed matter and evaluation of printed matter> Using the aqueous gravure printing ink compositions of the Examples and Comparative Examples, printing was carried out under the following conditions to obtain printed matter. The aqueous gravure printing ink compositions and printed matter were evaluated for printing (drying property, leveling property, blocking resistance, prevention of white spots, gloss, resolubility) according to the following evaluation methods and evaluation criteria. The results are shown in Table 3.

[0041] (Printing conditions) Paper: Coated paper (CRC230, Rengo Co., Ltd.) Printing machine: Toshiba gravure printing machine Printing plate for printing water-based gravure printing ink composition: Helio 175 line / inch (pattern: gradation plate with halftone density of 5 to 100%) Printing speed: 150~200m / min Drying conditions: 80℃・80cm 3 / min Printing pressure: 2.2t Regarding the prevention of whiteout, the printing plate for printing the water-based gravure printing ink composition: Helio 150-200LPI all solid, printing speed is 80m / min

[0042] <Printing evaluation> (dryness) The aqueous gravure printing ink compositions of the Examples and Comparative Examples were printed and coated on a Toshiba gravure printing machine at different printing speeds, and when the printed surface or coated surface came into contact with the guide roll, the degree to which the ink adhered to and stained the guide roll was visually observed and evaluated according to the following evaluation criteria. Evaluation criteria ◯: No adhesion to the guide roll. Δ: The amount of adhesion to the guide roll was small. ×: A large amount of the toner adhered to the guide roll was observed.

[0043] (Leveling ability) The aqueous gravure printing ink compositions of the Examples and Comparative Examples were printed and coated using a Toshiba gravure printing machine, and the ink receptivity of the printed matter was visually evaluated according to the following evaluation criteria. Evaluation criteria ◯: Ink was applied evenly over the entire coating film. △: A small amount of unevenness and bleeding occurred throughout the entire coating film. ×: Unevenness and bleeding were observed throughout the entire coating film.

[0044] (Glossy) The gloss value (points) of the printed surface (solid area) of the printed matter evaluated for the above leveling property was measured at five points with a gloss meter (micro-gloss 60°, manufactured by BYK) with a dot density of 100%, the average was calculated, and the result was evaluated according to the following evaluation criteria. Evaluation criteria A: The gloss value was 30 points or more. Δ: The gloss value was 20 points or more and less than 30 points. ×: The gloss value was less than 20 points.

[0045] (Blocking resistance) The prints used to evaluate the leveling properties were cut into test pieces of 5 cm x 4 cm. The printed surfaces of these test pieces were placed together, and a backing paper (unprinted coated paper) was placed on the back side of the prints. The test pieces were then subjected to a pressure of 20 kg (1 kg / cm 2) was applied and the sample was left to stand for 24 hours in an environment of a temperature of 40°C and a humidity of 90%. The degree of blocking between the printed surfaces was evaluated by touch and visual inspection according to the following evaluation criteria. Evaluation criteria ○: There was no resistance when the printed surfaces were peeled off from each other, and no ink was transferred to the backing paper. △: There was some resistance when the printed surfaces were peeled away from each other, but there was no ink transfer to the backing paper. ×: There was resistance when the printed surfaces were peeled off from each other, and the ink transferred to the backing paper.

[0046] (Prevention of white spots) The aqueous gravure printing ink compositions of the Examples and Comparative Examples were printed on a Toshiba gravure press under the following printing conditions: Helio 150-200 LPI, all solid, printing speed 80 m / min, and a base paper CRC (230 g / m 2 ) for 25 seconds and the average number of white spots that occurred on the print was used for evaluation. Evaluation criteria ○: Less than 10 〇△: 10 or more and 20 or less △: More than 20 and less than 40 ×: More than 40 pieces

[0047] (Re-soluble) The aqueous gravure printing ink compositions of the Examples and Comparative Examples were applied to an OPP film using a bar coater (φ0.10 mm), which was then immersed in a solution of isopropanol / water=3 / 7, and the dissolution of the ink was visually evaluated. Evaluation criteria 〇: Dissolves within 1 minute after application △: Dissolves within 3 minutes or more after application. ×: Dissolves within 3 to 5 minutes after application.

[0048] Polyethylene wax: Chemipearl W-400 (Mitsui Chemicals) solid content 40% Rosin-based emulsion: acid value 100mgKOH / g solids 50%

[0049] [Table 3] TIFF2025010045000004.tif136170

[0050] According to the Examples which are examples according to the present invention, the water-based gravure printing ink composition was excellent in drying property, leveling property, gloss, blocking resistance and resolubility, and no blank spots occurred. In contrast, Comparative Example 1 is an example in which the content of the hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g is excessive, Comparative Example 2 is an example in which the styrene-acrylic resin emulsion having a core-shell structure does not have a structural unit derived from a (meth)acrylate having a hydroxyl group and does not contain a hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g, and Comparative Example 3 is an example in which no acrylic copolymer is contained, and white spots occurred in all cases.

Claims

1. An aqueous gravure printing ink composition comprising a pigment, a styrene-acrylic resin emulsion having a core-shell structure, a pigment dispersing resin, and an aqueous medium, and satisfying the following condition 1 or 2: Condition 1 The styrene-acrylic resin emulsion having a core-shell structure contains a structural unit derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms in the shell portion and / or the core portion, but does not contain a structural unit derived from a (meth)acrylate having a hydroxyl group. The aqueous gravure printing ink composition contains 3.0 to 22.0 mass % of a hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g based on the total solid content. Condition 2 The styrene-acrylic resin emulsion having a core-shell structure contains a structural unit derived from a (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms in the shell portion and / or the core portion, and also contains a structural unit derived from a (meth)acrylate having a hydroxyl group. The aqueous gravure printing ink composition does not contain a hydroxyl group-containing acrylic copolymer having an acid value of 30 to 120 mgKOH / g, or contains it in an amount in the range of 0 mass % or more and 22.0 mass % or less in the total solid content.

2. 2. The water-based gravure printing ink composition of claim 1, which contains a rosin-based emulsion.

3. 3. The aqueous gravure printing ink composition according to claim 1, wherein the hydroxyl group-containing acrylic copolymer has an acid value of 30 to 100 mgKOH / g and is a hydroxyl group-containing acrylic copolymer having a structural unit derived from a (meth)acrylate having a hydroxyl group.

4. 3. The aqueous gravure printing ink composition according to claim 1, wherein the styrene-acrylic resin emulsion having a core-shell structure has a mass ratio of the core part to the shell part of shell part=40:60 to 60:40, and the shell part and / or the core part contains a structural unit derived from a (meth)acrylate having an alkyl group having 4 to 8 carbon atoms.

5. The aqueous gravure printing ink composition according to claim 1 or 2, wherein the styrene-acrylic resin emulsion having a core-shell structure, in the case of condition 2, contains a structural unit derived from a (meth)acrylate having a hydroxy group in the shell portion.

6. 4. The water-based gravure printing ink composition according to claim 3, wherein the (meth)acrylate having a hydroxy group is 2-hydroxyethyl (meth)acrylate.

7. 3. The water-based gravure printing ink composition according to claim 1, wherein the pigment dispersing resin contains an alkali-soluble water-soluble resin.

8. 3. The water-based gravure printing ink composition according to claim 1, wherein the pigment dispersing resin contains an (ethylene oxide / propylene oxide) block polymer.

9. 3. The aqueous gravure printing ink composition according to claim 1, wherein the aqueous medium contains water, 2-ethyl-1,3-hexanediol, and a lower alcohol having 1 to 4 carbon atoms.

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