Water-based gravure printing ink composition for paper packaging and printed materials

Abstract

This invention provides an aqueous gravure printing ink composition and printed materials for paperboard packaging that exhibit excellent drying properties, gloss, blocking resistance, whitening prevention, resolubility, and leveling properties (suitability for overprinting). Furthermore, it provides an aqueous gravure printing ink composition and printed materials for paperboard packaging that utilize a large amount of carbon-neutral raw materials. [Solution] An aqueous gravure printing ink composition for paper containers comprising a pigment, a hydroxyl group-containing styrene-acrylic resin emulsion, a pigment dispersion resin, a hyperbranched polyether wetting agent, and an aqueous medium, wherein the content of the hyperbranched polyether wetting agent is 0.03 to 1.5% by mass in the aqueous gravure printing ink composition for paper containers.

Description

Technical Field

[0001] The present invention relates to an aqueous gravure printing ink composition for paper containers and printed matter.

Background Art

[0002] Conventionally, aqueous inks have been printed by the gravure method for beautification on outer packaging boxes of various products ranging from foods such as confectionery, tissues, and detergents to household goods, and packages for multi-packs of alcoholic beverages and drinks (see Patent Documents 1 and 2). However, the ink compositions described in Patent Documents 1 and 2 had room for improvement in terms of drying properties, blocking resistance, leveling properties, etc.

[0003] Therefore, it has been proposed that in an aqueous gravure printing ink composition for paper containers, by using a specific amount of a hyperbranched polyether type wetting agent and a specific printing modifier in combination, the drying properties, blocking resistance, and leveling properties are improved (for example, see Patent Document 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, further drying properties, gloss, blocking resistance, anti-whiteout properties, redissolution properties, and leveling properties (suitability for overprinting) have been required.

[0006] Furthermore, with increasing efforts to protect the environment, the packaging industry is also being asked to develop inks that can reduce carbon dioxide emissions (carbon neutrality) by using non-fossil fuel raw materials such as plant-derived and animal-derived materials.

[0007] This invention has been made in view of the above-mentioned conventional problems, and aims to provide an aqueous gravure printing ink composition and printed material for paperboard packaging that has excellent drying properties, gloss, blocking resistance, whitening prevention properties, resolubility, and leveling properties (suitability for overprinting). Furthermore, it aims to provide an aqueous gravure printing ink composition and printed material for paperboard packaging that uses a large amount of carbon-neutral raw materials. [Means for solving the problem]

[0008] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the following aqueous gravure printing ink composition and printed material for paper containers can solve the above problems, and have completed the present invention. The aqueous gravure printing ink composition and printed material for paper containers of the present invention that solve the above problems mainly comprises the following components.

[0009] (1) A water-based gravure printing ink composition for paper containers comprising a pigment, a hydroxyl group-containing styrene-acrylic resin emulsion, a pigment dispersion resin, a hyperbranched polyether wetting agent, and an aqueous medium, wherein the content of the hyperbranched polyether wetting agent is 0.03 to 1.5% by mass in the water-based gravure printing ink composition for paper containers.

[0010] With this configuration, the water-based gravure printing ink composition for paperboard packaging exhibits excellent drying properties, gloss, blocking resistance, whiteout prevention, resolubility, and leveling properties (suitability for overprinting).

[0011] (2) The aqueous gravure printing ink composition for paper containers according to (1), wherein the hydroxyl group-containing styrene-acrylic resin emulsion has a core-shell structure, and the core-shell structure has at least one of the shell portion or the core portion a constituent unit derived from (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms and a constituent unit derived from (meth)acrylate having a hydroxyl group.

[0012] With this configuration, the water-based gravure printing ink composition for paperboard packaging exhibits superior leveling properties, prevention of whitening, resolubility, and ink storage stability.

[0013] (3) A water-based gravure printing ink composition for paper containers according to (1) or (2), comprising a silicone-based leveling agent.

[0014] With this configuration, the water-based gravure printing ink composition for paperboard packaging exhibits superior leveling properties (suitability for overprinting).

[0015] (4) A water-based gravure printing ink composition for paper containers according to any one of (1) to (3), comprising a rosin-based emulsion.

[0016] With this configuration, the water-based gravure printing ink composition for paperboard packaging does not use fossil fuels, but rather plant- and animal-derived raw materials, thus reducing carbon dioxide emissions (carbon neutrality).

[0017] (5) The aqueous gravure printing ink composition for paper containers according to (2), wherein the (meth)acrylate having a hydroxyl group is 2-hydroxyethyl (meth)acrylate.

[0018] With this configuration, the water-based gravure printing ink composition for paperboard packaging exhibits superior leveling properties, prevention of whitening, resolubility, and ink storage stability.

[0019] (6) The resin for pigment dispersion contains an alkali-soluble type water-soluble resin, and is the aqueous gravure printing ink composition for paper containers according to any one of (1) to (5).

[0020] According to such a configuration, the aqueous gravure printing ink composition for paper containers has better dispersibility of the colorant, ink storage stability, and redissolubility.

[0021] (7) The resin for pigment dispersion contains an (ethylene oxide / propylene oxide) block polymer, and is the aqueous gravure printing ink composition for paper containers according to any one of (1) to (6).

[0022] According to such a configuration, the aqueous gravure printing ink composition for paper containers has better dispersibility of the colorant, ink storage stability, and redissolubility.

[0023] (8) A printed matter printed with the aqueous gravure printing ink composition for paper containers according to any one of (1) to (7).

[0024] According to such a configuration, the printed matter uses a large amount of carbon-neutral raw materials, has excellent gloss, less white bleeding, and can be overprinted.

Effects of the Invention

[0025] According to the present invention, it is possible to provide an aqueous gravure printing ink composition and a printed matter for paper containers that are excellent in drying property, gloss, blocking resistance, white bleeding prevention property, redissolubility, and leveling property (overprinting suitability). Furthermore, it is possible to provide an aqueous gravure printing ink composition and a printed matter for paper containers that use a large amount of carbon-neutral raw materials.

Modes for Carrying Out the Invention

[0026] <Aqueous Gravure Printing Ink Composition for Paper Containers> An aqueous gravure printing ink composition for paperboard packaging according to one embodiment of the present invention (hereinafter also referred to as the ink composition) comprises a pigment, a hydroxyl group-containing styrene-acrylic resin emulsion, a pigment dispersion resin, a hyperbranched polyether wetting agent, and an aqueous medium. The content of the hyperbranched polyether wetting agent is 0.03 to 1.5% by mass of the ink composition. Each of these will be described below.

[0027] In this embodiment, the acid value was measured in accordance with JIS K 2501:2003, and the glass transition temperature (Tg) was measured in accordance with JIS K 7121:2012.

[0028] (Pigment) Pigments that have been conventionally used in water-based gravure printing ink compositions can be used. Specifically, examples of inorganic pigments include titanium dioxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, and graphite. Titanium dioxide surface-treated with silica and / or alumina is preferred. Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. Pigments may be used in combination.

[0029] The pigment content is not particularly limited. For example, the pigment content is preferably 1.0% by mass or more, and more preferably 3.0% by mass or more, of the total solid content of the ink composition. Furthermore, the pigment content is preferably 60.0% by mass or less, of the total solid content of the ink composition. If the pigment is an organic pigment or carbon black, the pigment content is preferably 1.0% by mass or more, and more preferably 3.0% by mass or more. Furthermore, if the pigment is an organic pigment or carbon black, the pigment content is preferably 35.0% by mass or less, and more preferably 30.0% by mass or less.

[0030] (Hydroxygroup-containing styrene-acrylic resin emulsion) The hydroxyl group-containing styrene-acrylic resin emulsion is not particularly limited. For example, a hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure is preferred. This results in an ink composition with superior coating film resistance such as leveling, drying, resolubility, and abrasion resistance, as well as improved ink storage stability and prevention of whitening.

[0031] • A hydroxyl-containing styrene-acrylic resin emulsion with a core-shell structure. A hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure preferably has, in at least one of the shell portion or the core portion, a constituent unit derived from (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms and a constituent unit derived from (meth)acrylate having a hydroxyl group. The constituent unit derived from (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms is preferably present in both the shell portion and the core portion. The constituent unit derived from (meth)acrylate having a hydroxyl group is preferably present in the shell portion. As a result, the ink composition has superior leveling properties, drying properties, resolubility, coating film resistance, ink storage stability, and anti-whitening properties.

[0032] The mass ratio of the core to the shell is preferably 10:90 to 70:30, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40. When the mass ratio of the core to the shell is within the above range, the ink composition has excellent printability, such as leveling properties, drying properties, doctor blade cut properties, and white spot prevention properties, as well as good coating film properties and ink storage stability.

[0033] A hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure preferably has, in at least one of the shell portion or the core portion, a structural unit derived from (meth)acrylate having an aliphatic alkyl group with 4 to 8 carbon atoms and a structural unit derived from (meth)acrylate having a hydroxyl group.

[0034] Furthermore, among styrene-acrylic resin emulsions having a core-shell structure and containing hydroxyl groups, it is preferable to use a water-soluble acrylic resin that forms the shell portion as a polymer emulsifier and copolymerize a styrene monomer, a (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms, a (meth)acrylate having a hydroxyl group if necessary, a (meth)acrylate other than aliphatic alkyl group having 4 to 24 carbon atoms and a (meth)acrylate having a hydroxyl group, to obtain a film that can be formed at room temperature.

[0035] The (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms is not particularly limited. For example, (meth)acrylates having an aliphatic alkyl group with 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, eicosyl (meth)acrylate, etc. It is preferable that the (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms contains at least one of butyl acrylate or 2-ethylhexyl (meth)acrylate.

[0036] The (meth)acrylate having a hydroxyl group is not particularly limited. For example, the (meth)acrylate having a hydroxyl group is a (meth)acrylic acid ester compound having a hydroxyalkyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. The (meth)acrylate having a hydroxyl group is preferably 2-hydroxyethyl (meth)acrylate, and the constituent units derived therefrom are more preferably in the shell.

[0037] • Shell section The shell portion is formed by using a water-soluble acrylic resin as a polymer emulsifier. Specifically, the shell portion includes structural units derived from (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms, structural units derived from (meth)acrylate having a hydroxyl group, structural units derived from a carboxyl group-containing monomer, structural units derived from (meth)acrylate other than (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms and having a hydroxyl group, and the theoretical acid value is preferably 40 to 120 mg KOH / g. In Table 1 below, the shell portion is formed from the polymer emulsifier.

[0038] The monomers containing carboxyl groups are not particularly limited. For example, carboxyl group-containing monomers include maleic acid monoester compounds having aliphatic hydrocarbon groups with 8 to 13 carbon atoms, such as acrylic acid, methacrylic acid, (anhydride) maleic acid, monomethyl maleic acid, monoethyl maleic acid, monobutyl maleic acid, monohexyl maleic acid, monooctyl maleic acid, mono-2-ethylhexyl maleic acid, and monolauryl maleic acid; maleic acid monoester compounds having aliphatic hydrocarbon groups with 14 to 20 carbon atoms, such as monomyristyl maleic acid, monocetyl maleic acid, monostearyl maleic acid, monooleyl maleic acid, and monoeicosyl maleic acid; crotonic acid and its ester compounds; itaconic acid and its ester compounds; and the like.

[0039] Other (meth)acrylates besides those having aliphatic alkyl groups with 4 to 24 carbon atoms and those having hydroxyl groups are not particularly limited. For example, other (meth)acrylates besides those having aliphatic alkyl groups with 4 to 24 carbon atoms and those having hydroxyl groups include (meth)acrylates having aliphatic hydrocarbon groups such as methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate; (meth)acrylamide, acrylonitrile, and olefin compounds; styrene monomers such as styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, ethylstyrene, isopropylstyrene, t-butylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, and fluorostyrene; benzyl (meth)acrylate monomers such as benzyl methacrylate and benzyl acrylate; and phenyl (meth)acrylate monomers such as phenyl methacrylate and phenyl acrylate.

[0040] • Core The core portion preferably contains, in 100 parts by mass, at least 25 parts by mass of constituent units derived from styrene monomers, a (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms, a (meth)acrylate having a hydroxyl group if necessary, a (meth)acrylate other than the (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms and the (meth)acrylate having a hydroxyl group. In Table 1 below, the core portion is formed from components other than the polymer emulsifier.

[0041] Styrene monomers are not particularly limited. Examples of styrene monomers include styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, 4-methoxystyrene, vinyltoluene, etc.

[0042] Examples of (meth)acrylates having an aliphatic alkyl group with 4 to 24 carbon atoms and (meth)acrylates having a hydroxyl group are similar to those described above in relation to the shell portion.

[0043] Other (meth)acrylates besides those having aliphatic alkyl groups with 4 to 24 carbon atoms and those having hydroxyl groups are not particularly limited. For example, other (meth)acrylates besides those having aliphatic alkyl groups with 4 to 24 carbon atoms and those having hydroxyl groups include (meth)acrylates having aliphatic hydrocarbon groups such as methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate, as well as (meth)acrylamide, acrylonitrile, olefin compounds, benzyl monomers such as benzyl methacrylate and benzyl acrylate, and phenyl monomers such as phenyl methacrylate and phenyl acrylate.

[0044] By using a hydroxyl group-containing styrene-acrylic resin emulsion having such a core-shell structure, the ink composition exhibits good drying properties, blocking resistance, and leveling properties. Furthermore, by reducing the surface tension, it is possible to prevent doctor blade cuts and misting from occurring on the printing plate even with small amounts of defoaming agents and surfactants.

[0045] The content of the hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure is not particularly limited. For example, the content of the hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure 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 solid content of the emulsion in the total solid content of the ink composition. Furthermore, the content of the hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure 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, based on the solid content of the emulsion in the total solid content of the ink composition.

[0046] The method for producing a hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure is not particularly limited. For example, a method for producing a hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure can be employed that produces core-shell particles by suspension polymerization or emulsion polymerization.

[0047] Among these methods, a styrene-acrylic resin emulsion having a core-shell structure can be obtained by polymerizing it using a known emulsion polymerization method, further incorporating a polymerizable monomer to form the core in the presence of the following polymer emulsifiers to form the shell. Specifically, examples of polymerizable monomers include those containing 25% by mass or more of a styrene monomer and a (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms, such as 2-ethylhexyl (meth)acrylate and butyl (meth)acrylate, and optionally a (meth)acrylate having a hydroxyl group, methyl methacrylate, etc.

[0048] (High molecular weight emulsifier) Polymeric emulsifiers are copolymers of carboxyl group-containing monomers, (meth)acrylates having aliphatic alkyl groups with 4 to 24 carbon atoms, (meth)acrylates having hydroxyl groups, (meth)acrylates other than those having aliphatic alkyl groups with 4 to 24 carbon atoms and (meth)acrylates having hydroxyl groups, and other radically polymerizable unsaturated monomers.

[0049] The carboxyl group-containing monomers, (meth)acrylates having aliphatic alkyl groups with 4 to 24 carbon atoms, (meth)acrylates having hydroxyl groups, and (meth)acrylates other than those having aliphatic alkyl groups with 4 to 24 carbon atoms are those listed above.

[0050] From the viewpoint of defoaming properties, it is preferable that the polymer emulsifier contains butyl acrylate among the monomers constituting the polymer emulsifier. Furthermore, from the viewpoint of resolubility and leveling properties, it is preferable that the polymer emulsifier contains a (meth)acrylic acid ester compound having a hydroxyalkyl group.

[0051] It is preferable to use a carboxyl group-containing monomer as the polymer emulsifier so that its theoretical acid value is 40 to 120 mg KOH / g. Having the theoretical acid value within this range helps maintain the stability and water resistance of the hydroxyl group-containing styrene-acrylic emulsion. Furthermore, it is preferable that the weight-average molecular weight of the polymer emulsifier be in the range of 3000 to 25000. Having the weight-average molecular weight within this range allows the polymer emulsifier to maintain its performance while exhibiting excellent solubility of the copolymer.

[0052] The method for producing a polymer emulsifier is not particularly limited. For example, a polymer emulsifier can be prepared by polymerizing a mixture of the above-mentioned carboxyl group-containing monomer and (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms, (meth)acrylate having a hydroxyl group, (meth)acrylate having an aliphatic alkyl group with 4 to 24 carbon atoms, and (meth)acrylate other than the above-mentioned aliphatic alkyl group having 4 to 24 carbon atoms, using a known method to obtain a polymer with a weight-average molecular weight of 3,000 to 25,000, and then neutralizing it with a basic compound. The basic compound used for neutralization is not particularly limited. For example, basic compounds 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 in combination.

[0053] (Hyperbranched polyether wetting agent) The ink composition of this embodiment contains a hyperbranched polyether wetting agent to improve leveling properties (suitability for overprinting).

[0054] Hyperbranched polyether wetting agents are not particularly limited. For example, a hyperbranched polyether wetting agent is a hyperbranched polymer having a polyether backbone. A hyperbranched polyether wetting agent is a wetting agent having a highly branched structure (star polymer) and is silicone-free.

[0055] Hyperbranched polyether wetting agents can be synthesized by polymerizing monomers having polymerizable functional groups such as tetrahydrofuranyl groups, epoxy groups, oxetanyl groups, other ring-opening cyclic ethers such as anhydrides, and hydroxyl groups that can be polymerized by forming ether bonds. Depending on the monomer used, hyperbranched polyether wetting agents can also be synthesized by addition polymerization such as condensation polymerization, stepwise polymerization such as ring-opening polymerization, cyclization polymerization, isomerization polymerization (hydrogen transfer polymerization), elimination polymerization, and polymerization reactions that combine multiple of these polymerizations.

[0056] In this embodiment, the polymerizable functional group in the hyperbranched polyether wetting agent preferably includes a tetrahydrofuranyl group, an epoxy group, or an oxetanyl group, and more preferably includes a tetrahydrofuranyl group or an epoxy group.

[0057] The hyperbranched polyether wetting agent preferably has repeating units represented by one of the following general formulas (I) to (III).

[0058] [ka]

[0059] A hyperbranched polyether wetting agent having repeating units represented by general formula (I) is hyperbranched poly(glycidol). Hyperbranched poly(glycidol) can be synthesized, for example, by a combination of ring-opening polymerization and polycondensation of glycidol (2,3-epoxy-1-propanol).

[0060] A hyperbranched polyether wetting agent having repeating units represented by general formula (II) is hyperbranched poly(tetriitol). Hyperbranched poly(tetriitol) can be synthesized, for example, by polycondensation of tetriitol (1,2,3,4-tetrahydroxybutane) and by a combination of ring-opening polymerization and polycondensation of 2,3-anhydrotetriitol or 1,4-anhydrotetriitol.

[0061] A hyperbranched polyether wetting agent having repeating units represented by general formula (III) is hyperbranched poly(3-ethyl-3-(hydroxymethyloxetane)). Hyperbranched poly(3-ethyl-3-(hydroxymethyloxetane)) can be synthesized, for example, by a combination of ring-opening polymerization and polycondensation of 3-ethyl-3-(hydroxymethyloxetane).

[0062] In highly branched polymers, the average degree of branching is the average number of branching groups per molecule. That is, in highly branched polymers, the average degree of branching is the ratio of "terminal groups + branching groups" to the "total number of terminal groups, branching groups, and linear groups," and is defined in the literature as the degree of branching (DB). Ideal dendrons and dendrimers have a degree of branching of 1, and ideal linear polymers have a degree of branching of 0. The degree of branching is defined in Howker, CJ; Lee, R.; and Frechet, JMJ, J.Am.Chem.Soc., 1991, Vol. 113, p. 4583. Specific examples of hyperbranched polyether wetting agents include Hydropalat WE 3322, 3323 (manufactured by BASF, Hydropalat is a registered trademark of BASF).

[0063] The degree of branching of the hyperbranched polyether wetting agent is not particularly limited. For example, it is preferable that the degree of branching of the hyperbranched polyether wetting agent be 0.03 or higher. It is also preferable that the degree of branching of the hyperbranched polyether wetting agent be less than 1.5. If the content of the hyperbranched polyether wetting agent is less than 0.03% by mass, the ink composition tends to have reduced leveling properties (suitability for overprinting). On the other hand, if the content of the hyperbranched polyether wetting agent exceeds 1.5% by mass, the ink composition tends to have reduced blocking resistance.

[0064] (Silicone-based leveling agent) The ink composition of this embodiment preferably contains a silicone-based leveling agent in order to further improve leveling properties (suitability for overprinting).

[0065] The content of the silicone-based leveling agent is not particularly limited. For example, the content of the silicone-based leveling agent is preferably 0.1 to 0.3% by mass in the ink composition. When the content of the silicone-based leveling agent is within the above range, the ink composition has good leveling properties and is less prone to pinhole formation.

[0066] (Rosin-based emulsion) The ink composition of this embodiment preferably contains a rosin-based emulsion in order to reduce carbon dioxide emissions (carbon neutrality) by using plant-derived and animal-derived raw materials that do not originate from fossil fuels.

[0067] The acid value of the rosin-based emulsion is preferably 0 to 350 mg KOH / g. Rosin-based resin emulsions with an acid value of 0 to 350 mg KOH / g are those obtained by dispersing rosin derivatives such as rosin esters or rosin, which are made from materials obtained by extraction from plants, etc., in water as fine particles in the presence of a low molecular weight emulsifier. Specifically, examples of rosin-based resin emulsions with an acid value of 0 to 350 mg KOH / g include Harima Chemicals' Hariester SK218NS, SK370N, SK385NS, SK501NS; Lawter's Snowpack XW-2442, XW-2551, XW-2561, XW-2582, SE780G, 100G; and Arakawa Chemical Industries' Super Ester NS-121, NS-100H, E-865NT.

[0068] When a rosin-based emulsion is included, the solid content of the rosin-based resin emulsion with an acid value of 0 to 350 mgKOH / g is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 10.0% by mass or more, of the total solid content of the ink composition. The solid content of the rosin-based resin emulsion with an acid value of 0 to 350 mgKOH / g is preferably 30.0% by mass or less of the total solid content of the ink composition. Note that carbon-neutral raw material components refer to raw material components obtained from plant-based materials.

[0069] (Pigment dispersion resin) The pigment dispersion resin preferably contains an alkali-soluble water-soluble resin. This results in the ink composition having superior dispersibility of colorants, ink storage stability, and resolubility.

[0070] Alkali-soluble water-soluble resin Alkali-soluble water-soluble resins are not particularly limited. For example, alkali-soluble water-soluble resins include resins obtained by polymerizing monomers having unsaturated double bonds that are used in ordinary water-based gravure printing ink compositions, and resins obtained by reactions between functional groups.

[0071] Specifically, suitable alkali-soluble water-soluble resins include various binder resins such as water-soluble acrylic resins, 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, which are copolymerized using acrylic acid, methacrylic acid, their alkyl esters, and styrene as the main monomer components.

[0072] These alkali-soluble water-soluble resins are typically dissolved in water in the presence of a basic compound and used as water-soluble resin varnishes. Basic compounds used to dissolve alkali-soluble water-soluble resins in water include ammonia, organic amines, and alkali metal hydroxides. Specifically, organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. The alkali metal hydroxides include sodium hydroxide and potassium hydroxide. Among these, basic compounds that readily volatilize at room temperature or with slight heating are preferred to improve drying properties.

[0073] The content of alkali-soluble water-soluble resin relative to the pigment is preferably 20 parts by mass or more in terms of solids per 100 parts by mass of pigment. Furthermore, the content of alkali-soluble water-soluble resin relative to the pigment is preferably 1000 parts by mass or less in terms of solids per 100 parts by mass of pigment, and more preferably 500 parts by mass or less. When the content of alkali-soluble water-soluble resin relative to the pigment is within the above range, the ink composition has excellent dispersibility of the colorant, ink storage stability, and resolubility, as well as a good balance with leveling and drying properties.

[0074] The pigment dispersion resin preferably contains an (ethylene oxide / propylene oxide) block polymer. This results in the ink composition having superior dispersibility of colorants, ink storage stability, and resolubility.

[0075] (Ethylene oxide / propylene oxide) block polymer The (ethylene oxide / propylene oxide) block polymer contains two or more blocks. Each block may be composed of polyethylene oxide or propylene oxide.

[0076] (ethylene oxide / propylene oxide) block polymers can be synthesized by known methods. For example, (ethylene oxide / propylene oxide) block polymers can be formed by reacting polyethylene oxide polymer with propylene oxide to form poly(propylene oxide / ethylene oxide / propylene oxide) block polymers. Alternatively, (ethylene oxide / propylene oxide) block polymers can be formed by reacting polypropylene oxide polymer with ethylene oxide to form poly(ethylene oxide / propylene oxide / ethylene oxide) block polymers.

[0077] The weight-average molecular weight of poly(ethylene oxide / propylene oxide / ethylene oxide) block polymers is preferably 5,000 to 100,000. Specific examples of commercially available poly(ethylene oxide / propylene oxide / ethylene oxide) block polymers include the ADEKA Pluronic® series manufactured by ADEKA.

[0078] The HLB value of poly(ethylene oxide / propylene oxide / ethylene oxide) block polymers is preferably 8 to 20 in terms of stability in water-containing solvents. The HLB value is used in the field of surfactants and represents the balance between the hydrophilic and lipophilic parts of a molecule. The HLB value can be determined by applying the Griffin formula shown below (a formula based on experimental values ​​obtained from measuring emulsification efficiency for a certain oil and the weight fraction of the hydrophilic part). [Griffin formula] HLB = (100 / 5) × hydrophilic group weight / (hydrophilic group weight + hydrophobic group weight)

[0079] The content of (ethylene oxide / propylene oxide) block polymer is preferably greater than 0 parts by mass, and more preferably 0.5 parts by mass or more, per 100 parts by mass of pigment. Furthermore, the content of (ethylene oxide / propylene oxide) block polymer is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of pigment. When the content of (ethylene oxide / propylene oxide) block polymer is within the above range, the ink composition has excellent dispersibility of the colorant, ink storage stability, and resolubility, as well as a good balance of leveling and drying properties.

[0080] The total content of alkali-soluble water-soluble resin and (ethylene oxide / propylene oxide) block polymer is preferably 10 to 30 parts by mass per 100 parts by mass of pigment. When the total content of alkali-soluble water-soluble resin and (ethylene oxide / propylene oxide) block polymer is within the above range, the ink composition has excellent dispersibility of the colorant, ink storage stability, and resolubility, as well as a good balance of leveling and drying properties.

[0081] (Antifoaming agent) Known defoaming agents can be used. For example, defoaming agents include hydrophobic polydimethylsiloxane-based defoaming agents, defoaming agents combining polysiloxane containing long-chain alkyl or aralkyl groups with polyoxyalkylene chain-containing polysiloxanes, defoaming agents mainly composed of polysylcarbensiloxane consisting of silcarbene units and siloxane units, defoaming agents consisting of a reaction product of alkylene oxide compounds, silicone having alcoholic hydroxyl groups, and isocyanate compounds, and defoaming agents consisting of siloxane-glycol copolymer and polypropylene glycol.

[0082] In this embodiment, when the ink composition contains 20 to 50 parts by mass of butyl acrylate-derived constituent units per 100 parts by mass of the shell portion of a hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure, the amount of defoaming agent and surfactant can be reduced to a smaller amount than that typically found in inks. As a result, the ink composition can prevent doctor blade cut failures and misting from occurring on the printing plate.

[0083] The amount of defoaming agent in the ink composition is preferably 0.3% by mass or less, and more preferably 0.2% by mass or less.

[0084] (aqueous medium) The aqueous medium is water. Alternatively, a water-soluble organic solvent may be used as the aqueous medium, as long as it does not degrade the performance of the ink composition of this embodiment.

[0085] Water-soluble organic solvents include alcohols and polyhydric alcohol-based solvents. Specifically, water-soluble organic solvents include 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, and propylene Examples include glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipyrropylene 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, etc.

[0086] The aqueous medium preferably contains water and a lower alcohol having 1 to 4 carbon atoms, from the viewpoint of drying properties and leveling properties.

[0087] Lower alcohols having 1 to 4 carbon atoms are not particularly limited. For example, lower alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, and isobutanol.

[0088] The content of lower alcohols having 1 to 4 carbon atoms is preferably 1 to 30% by mass in the ink composition. When the content of lower alcohols having 1 to 4 carbon atoms is within the above range, the ink composition exhibits superior leveling properties, drying properties, and ink storage stability.

[0089] (wax) Wax may be added to improve the stain resistance and abrasion resistance of the resulting printed material.

[0090] The type of wax is not particularly limited. For example, waxes include polyethylene wax and polytetrafluoroethylene wax.

[0091] The wax is preferably in the range of 1.0 to 6.0 μm as determined by the Coulter counter method (where #1 refers to the particle size measured with Honeywell MicrotracUPA). Having an average particle size within this range results in an ink composition with excellent lubricity, blocking properties, and trapping properties.

[0092] When wax is included, the amount of wax is not particularly limited. For example, the amount of wax is preferably 0.1 to 3.0% by mass of the total solid content of the ink composition. When the amount of wax is within the above range, the ink composition is more likely to produce the effects of the wax and the resulting printed material will have excellent gloss.

[0093] (Other optional components) The ink composition of this embodiment may contain optional components as appropriate. Examples of optional components include surfactants, wetting agents other than hyperbranched polyether wetting agents, pH adjusters, viscosity adjusters, drying adjusters, gloss agents, crosslinking agents, and the like.

[0094] <Method for manufacturing a water-based gravure printing ink composition for paper packaging> The method for producing the ink composition of this embodiment is not particularly limited. For example, the ink composition can be produced by mixing a pigment, a pigment dispersion resin, etc., stirring and kneading the mixture using a known ink manufacturing apparatus (ball mill, attritor, sand mill, etc.), and then adding and mixing a hydroxyl group-containing styrene-acrylic resin emulsion having a core-shell structure, a rosin-based emulsion, an antifoaming agent, a wax, an aqueous solvent, and optionally an alkali-soluble water-soluble resin. Then, if dilution is required during printing, the ink composition can be obtained by further adding a solvent containing water.

[0095] <Printed material printed with an aqueous gravure printing ink composition and method for manufacturing the printed material> A printed material according to one embodiment of the present invention is a printed material on which the above-described ink composition is printed.

[0096] The method of manufacturing the printed material is not particularly limited. For example, the printed material can be manufactured by printing the above-mentioned ink composition onto a paper substrate such as coated paper using a gravure printing method.

[0097] Considering the manufacturing efficiency of printed materials, a printing speed of 150 m / min or more is preferable. Furthermore, the manufacturing method of this embodiment may employ a drying process using various heating and drying devices after printing. The viscosity of the ink composition during printing is preferably such that the outflow time of Zahn Cup No. 3 is about 15 to 19 seconds. When the viscosity is within the above range, the ink composition has excellent leveling properties and printability.

[0098] Furthermore, the ink composition may be stored in a concentrated state and diluted with a diluent before use during printing.

[0099] The resulting printed material consists of the ink composition described above. Therefore, the printed material uses many carbon-neutral raw materials, has excellent gloss, minimal white spots, and can be overprinted. [Examples]

[0100] The present invention will be described more specifically below with reference to examples. The present invention is not limited in any way to these examples. Unless otherwise specified, "%" means "mass%" and "parts" means "parts by mass".

[0101] The raw materials used, their abbreviations, and the preparation methods are listed below. (Polymerizable monomers, etc.) AA: Acrylic acid MMA: Methyl methacrylate BA: Butyl acrylate 2-EHA:2-Ethylhexylacrylate St: Styrene 2-HEMA:2-hydroxyethyl methacrylate DMEA: Dimethylethanolamine IPA: Isopropanol

[0102] <Base Ink> Base inks for each color were prepared by mixing 30 parts by mass of each pigment (yellow pigment (PY3) or black pigment (PB7)), 45 parts by mass of the following alkali-soluble water-soluble resin 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, and stirring the mixture.

[0103] The solid content concentration of these base inks was 40.49% by mass (= 30 + (45 × 20.2%) + 1.4).

[0104] (Alkali-soluble water-soluble resin) Fifteen parts by mass of styrene, sixty parts by mass of methyl methacrylate, ten parts by mass of lauryl methacrylate, and fifteen parts by mass of acrylic acid were copolymerized by a conventional polymerization method to obtain a copolymer with an acid value of 80 mg KOH / g and a weight-average molecular weight of 38,000. 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%.

[0105] (Hydroxygroup-containing styrene-acrylic resin emulsion with a core-shell structure) Hydroxyl group-containing styrene-acrylic resin emulsions A to D having a core-shell structure were obtained according to the formulations shown in Table 1 below.

[0106] [Table 1]

[0107] Specifically, in order to synthesize hydroxyl group-containing styrene-acrylic resin emulsion A having a core-shell structure, first, polymer emulsifier A (30% solids), which is the base for resin particles having a core-shell structure, was synthesized so that the monomer mass ratios were as shown in Table 1.

[0108] Next, a core-shell structure (resin particles A having a core-shell structure) was synthesized with polymer emulsifier A as the shell portion and the other monomer components as the core portion, so as shown in the mass ratio of the monomers in Table 1. A hydroxyl group-containing styrene-acrylic resin emulsion A (solid content concentration 40.0% by mass) having a core-shell structure containing this was obtained.

[0109] Similarly, polymer emulsifiers B to D were used to synthesize resin particles B to D having a core-shell structure, and hydroxyl group-containing styrene-acrylic resin emulsions B to D having a core-shell structure and containing these particles, with a solid content concentration of 40.0% by mass, were obtained.

[0110] <Hyperbranched polyether wetting agent> Hyperbranched polyether wetting agent 1: Hydropalat WE 3322 (manufactured by BASF) Hyperbranched polyether wetting agent 2: Hydropalat WE 3323 (manufactured by BASF) <Rosin-based emulsion> Esterified rosin emulsion (50% solids by mass, remainder is water) <wax> Polyethylene wax (Chemipearl W400 (manufactured by Mitsui Chemicals, Inc.), solid content 40% by mass) <Silicone-based leveling agent> Product name: Dynol 960 (manufactured by Evonik) <Other> Octanediol: Manufactured by KH Neochem Co., Ltd., 2-ethyl-1,3-hexanediol Disparon LS-430: Manufactured by Kusumoto Kasei Co., Ltd., silicone-based propylene glycol monomethyl ether acetate. Disparon LS-460: Manufactured by Kusumoto Kasei Co., Ltd., silicone-based Disparon LS-480: Manufactured by Kusumoto Kasei Co., Ltd., silicone-based Disparon SEI-W01: Manufactured by Kusumoto Kasei Co., Ltd., acrylic polymer type. Disparon SEI-1501: Manufactured by Kusumoto Kasei Co., Ltd., acrylic polymer type. Disparon FCD-150: Manufactured by Kusumoto Kasei Co., Ltd. BYK-3560: BYK Corporation, polyether macromer-modified acrylate BYK-3565: Silicone and polyether macromer-modified acrylate manufactured by BYK. BYK-3566: Silicone and polyether macromer-modified acrylate manufactured by BYK. BYK-3568: Silicone and polyether macromer-modified acrylate manufactured by BYK. BYK-Dynwet 800: Manufactured by BYK, alcohol alkoxylate BYK-Dynwet 810: Silicone-free alcohol alkoxylate manufactured by BYK.

[0111] <Examples, Comparative Examples> Each raw material was blended and stirred to obtain the mass ratios (mass%) shown in Tables 2 to 5 below, and then diluted to obtain an aqueous gravure printing ink composition for paper containers. Subsequently, the composition was diluted with a diluent of isopropanol / water in a 70 / 30 ratio using a Zahn cup No. 3 for 15 to 19 seconds, and the solid content concentration in the aqueous gravure printing ink composition for paper containers was in the range of 15 to 30% by mass, to obtain yellow and gray aqueous gravure printing ink compositions for paper containers, respectively.

[0112] [Table 2]

[0113] [Table 3]

[0114] [Table 4]

[0115] [Table 5]

[0116] <Manufacturing and evaluation of printed materials> Each of the aqueous gravure printing ink compositions for paper containers, consisting of gray ink and yellow ink, was diluted by adding 50 parts by mass of a mixed solvent (isopropyl alcohol / water = 70 / 30) to 100 parts by mass of the gray ink and yellow ink aqueous gravure printing ink compositions for paper containers, which were then diluted at 25°C using a Zahn cup No. 3 to a viscosity of approximately 17 seconds. Printing was then performed using these compositions under the following conditions to obtain each printed material. For each printed material, the print evaluation (drying properties, leveling properties (water droplets), leveling properties (suitability for overprinting), pinholes, resolubility, and gradation reproduction) was evaluated according to the following evaluation methods and criteria. The results are shown in Tables 6 and 7.

[0117] (Printing conditions) • Leveling properties (polka dots) Leveling performance (water droplets) was evaluated visually for ring-shaped leveling defects in printed materials. For single-color printing, gray ink (Tables 4 and 5) with a viscosity of 17 seconds was printed under the following conditions. For overprinting, yellow ink (Tables 2 and 3) with a viscosity of 17 seconds was printed first, followed by gray ink with a viscosity of 17 seconds. <Evaluation Criteria> 5: The ink was applied evenly across the entire coating without any unevenness in shade. 3: A small amount of unevenness in color and shade occurred throughout the paint film. 1: Numerous variations in color intensity occurred throughout the paint film. • Pinhole For pinholes, gray ink (Tables 4 and 5) with a viscosity of 17 seconds was used for printing under the following conditions, and the occurrence of pinholes (removal of ink) in the printed material was visually evaluated. <Evaluation Criteria> 5: No pinholes occurred. 3: A small number of pinholes occurred. 1: Many pinholes occurred. Paper: Coated paper (CRC230, manufactured by Rengo Co., Ltd.) Printing machine: Toshiba gravure printing machine Printing plates for water-based gravure printing ink compositions for paper packaging. : Helio 175 line / inch (Image: A grayscale plate with halftone dot density ranging from 5% to 100%) Printing speed: 150~200m / min Drying conditions: 80℃・80cm 3 / min Printing pressure: 2.2t • Leveling properties (evaluated based on suitability for overprinting and ink spread) Yellow underprint ink (Tables 2 and 3), prepared to a viscosity of 17 seconds, was applied to coated paper using a φ0.10 bar coater. The drying state was adjusted by using or not using a dryer to obtain dry and wet underprint yellow ink samples. Gray overprint ink (Tables 4 and 5), also prepared to a viscosity of 17 seconds, was then printed on top of the underprint yellow ink under the following conditions, and the leveling properties (ink transfer and spread) were evaluated. <Evaluation Criteria> 5: The overprint ink coating was applied evenly. 3: A small amount of unevenness and poor wetting and spreading of halftone dots occurred in the overprint ink coating. 1: Many instances of unevenness and poor wetting and spreading of halftone dots occurred in the overprint ink coating. Paper: Coated paper (CRC230, manufactured by Rengo Co., Ltd.) Printing machine: Toshiba gravure printing machine Printing plates for water-based gravure printing ink compositions for paper packaging. : Helio 200 line / inch (Design: A grayscale version with 10 levels of tonal gradation) Printing speed: 50m / min Drying conditions: 80℃・80cm 3 / min Printing pressure: 2.2t • Tone reproduction Gray ink (Tables 4 and 5) was prepared to have a viscosity of 17 seconds. The spread of halftone dots in the midtones and highlights of printed materials was visually evaluated under the following conditions. <Evaluation Criteria> 5: The halftone dots were sufficiently spread out. 3: The dot coverage was somewhat insufficient. 1: The dot pattern was not sufficiently spread. Paper: Coated paper (CRC230, manufactured by Rengo Co., Ltd.) Printing machine: Toshiba gravure printing machine Printing plates for water-based gravure printing ink compositions for paper packaging. : Helio 200 line / inch (Design: A grayscale version with 10 levels of tonal gradation) Printing speed: 50m / min Drying conditions: 80℃・80cm3 / min Printing pressure: 2.2t ·Drying Gray ink (Tables 4 and 5) was prepared to have a viscosity of 17 seconds. Printing and coating were performed on a printing press with varying printing speeds and airflow. The degree to which ink adhered to and soiled the guide rolls when the printed and coated surfaces moved against them was visually evaluated according to the following evaluation criteria. <Evaluation Criteria> 5: It did not adhere to the guide roll. 3: The amount of material adhering to the guide roll was small. 1: A large amount of material adhered to the guide roll. Paper: Coated paper (CRC230, manufactured by Rengo Co., Ltd.) Printing machine: Toshiba gravure printing machine Printing plates for water-based gravure printing ink compositions for paper packaging. : Helio 200 line / inch (Design: A grayscale version with 10 levels of tonal gradation) Printing speed: 50m / min Drying conditions: 80℃・80cm 3 / min Printing pressure: 2.2t • Prevents whitening The image was printed on a printing press for 30 seconds, and the degree of white spots was visually evaluated according to the following evaluation criteria. <Evaluation Criteria> 5: No white spots appeared across the entire paint film. 3: A small amount of white discoloration occurred across the entire paint film. 1: Numerous white patches appeared across the entire paint film. Paper: Coated paper (CRC230, manufactured by Rengo Co., Ltd.) Printing machine: Toshiba gravure printing machine Printing plates for water-based gravure printing ink compositions for paper packaging. : Helio 200 line / inch (Design: A grayscale version with 10 levels of tonal gradation) Printing speed: 80m / min Drying conditions: 80℃・80cm 3 / min Printing pressure: 2.2t ·Resolubility Gray ink (Tables 4 and 5) was applied to OPP film using a φ0.10 bar coater to a viscosity of 17 seconds. The film was then immersed in an isopropyl alcohol / water = 3 / 7 solution, and the dissolution of the gravure printing ink composition for paperboard packaging during the drying process was visually evaluated. <Evaluation Criteria> 5: It began to dissolve within 1 minute after being mixed. 3: After spreading, it began to dissolve between 1 and 3 minutes. 1: After spreading, it began to dissolve between 3 and 5 minutes.

[0118] [Table 6]

[0119] [Table 7]

[0120] As shown in Tables 6 to 7, the ink compositions of Examples 1 to 9 of the present invention used a large amount of carbon-neutral raw materials and exhibited excellent drying properties, anti-whitening properties, resolubility, and leveling properties (water droplets, suitability for overprinting). Similarly, it was confirmed that the ink compositions of Examples 10 to 18 also used a large amount of carbon-neutral raw materials and exhibited excellent drying properties, anti-whitening properties, resolubility, and leveling properties (water droplets, suitability for overprinting).

Claims

1. It comprises a pigment, a hydroxyl group-containing styrene-acrylic resin emulsion, a pigment dispersion resin, a hyperbranched polyether wetting agent, and an aqueous medium. The content of the hyperbranched polyether wetting agent is 0.03 to 1.5% by mass in the aqueous gravure printing ink composition for paper containers.

2. The hydroxyl group-containing styrene-acrylic resin emulsion has a core-shell structure, The aqueous gravure printing ink composition for paper containers according to claim 1, wherein the core-shell structure has at least one of the shell portion or the core portion comprising a constituent unit derived from (meth)acrylate having an aliphatic alkyl group having 4 to 24 carbon atoms and a constituent unit derived from (meth)acrylate having a hydroxyl group.

3. A water-based gravure printing ink composition for paper containers according to claim 1 or 2, comprising a silicone-based leveling agent.

4. A water-based gravure printing ink composition for paper containers according to claim 1 or 2, comprising a rosin-based emulsion.

5. The aqueous gravure printing ink composition for paper containers according to claim 2, wherein the (meth)acrylate having a hydroxyl group is 2-hydroxyethyl (meth)acrylate.

6. The aqueous gravure printing ink composition for paper containers according to claim 1 or 2, wherein the pigment dispersion resin comprises an alkali-soluble water-soluble resin.

7. The aqueous gravure printing ink composition for paper containers according to claim 1 or 2, wherein the pigment dispersion resin comprises an (ethylene oxide / propylene oxide) block polymer.

8. A printed article on which the aqueous gravure printing ink composition for paper containers according to claim 1 or 2 is printed.

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