Water-based ink compositions, laminates, and packaging materials

Abstract

To provide an aqueous ink composition for gravure printing or flexographic printing that has excellent adhesion to polyolefin films, acid resistance, blocking resistance, and abrasion resistance that can withstand friction with rubber, and also has excellent storage stability, as well as laminates and packaging materials using the same. [Solution] An aqueous ink composition for gravure printing or flexographic printing, comprising (meth)acrylic resin emulsion (A), modified polypropylene resin emulsion (B), pigment (C), and aqueous medium (D), wherein the acid value of (A) is 60 mgKOH / g or less, the average particle size is 0.038 to 0.300 μm, the acid value of (B) is 60 mgKOH / g or less, the difference between the acid value of (A) and the acid value of (B) satisfies a specific relational expression, the solid content of (B) is 0.8 to 9.0% by mass, and the solid content mass ratio expressed as (B) / (A) is 0.050 to 0.500.

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition, a laminate, and a packaging material.

Background Art

[0002] In soft packaging materials such as plastic films used for packaging foods, daily necessities, etc., printing is performed by gravure printing or flexographic printing using ink or varnish for purposes such as information display, design, functionality, etc. Conventionally, oil-based types using organic solvents have been the mainstream for inks and varnishes for soft packaging, but in recent years, there has been a strong demand for water-based types from the perspective of environmental issues and the like.

[0003] One of the uses of soft packaging materials is a packaging label attached to containers such as plastic containers, metal containers, and paper containers. Examples of packaging labels include roll labels attached by wrapping around the container and fastening with an adhesive, and shrink labels attached by heating and shrinking to a shape suitable for the container. As a typical configuration of the packaging label, an ink layer serving as a pattern layer is laminated on the inner side of the plastic film, that is, on the container side, and a varnish layer for protecting the ink layer from contact with the container or the like is laminated on the surface of the ink layer. Also, in such a configuration, a typical example is a configuration in which a varnish layer for protecting the plastic film from external contact such as human hands or the like is further laminated on the outer side of the plastic film, that is, on the side opposite to the container. Further, in recent years, there is also known a configuration in which the outer varnish layer is a matte ink layer not only for the purpose of protecting the plastic film from external contact but also for improving the design. The varnish layer, ink layer, and matte ink layer are each coating films formed by printing using varnish, ink, and matte ink. Hereinafter, these are also collectively referred to as printing coating films or printing layers.

[0004] Examples of plastic films used for packaging labels with water-based inks include polyethylene terephthalate film (PET film), nylon film (NY film), and polystyrene film (PS film). In recent years, polyolefin films (PO films), such as polypropylene film (PP film), have been increasingly used for various reasons, including their high oxygen permeability, low moisture permeability, low specific gravity, flexibility, and low cost compared to other films. However, PO films have a lower wettability and lower solubility parameters compared to other films, which leads to poor adhesion between the PO film and the ink layer when using water-based inks.

[0005] Furthermore, since many of the environments in which packaging labels are used and the contents of the containers are acidic, the printed coating is frequently exposed to acidic substances. In addition, it is required to withstand friction under harsh conditions, such as when the printed coating peels off due to friction with the rubber rolls on the printing press. Moreover, it is required that the printed coating does not transfer to the opposite side of the material when the printed material is wound up after printing, preventing defects in appearance and processing. Therefore, the printed coating on packaging labels requires coating properties such as acid resistance, blocking resistance, and abrasion resistance. In particular, in the case of gravure printing or flexographic printing, the printing distance at one time is longer than in inkjet printing, resulting in a larger amount of printed material being wound up, which makes the printed material more susceptible to pressure, and the printed coating is more likely to transfer to the opposite side that comes into contact with it, thus requiring excellent blocking resistance.

[0006] Furthermore, water-based inks often use core-shell type resins with low hydrophilicity in the core to improve the properties of the coating film. However, depending on the usage and storage environment, problems can arise in water-based inks where the core-shell structure breaks down, leading to increased viscosity and gelation. Therefore, water-based inks are required to have excellent storage stability.

[0007] Conventionally, in order to improve adhesion to polypropylene film, studies have been conducted on incorporating a modified polypropylene resin emulsion into water-based inks that has a solubility parameter similar to that of polypropylene film and exhibits high affinity. For example, Patent Document 1 discloses an aqueous pigment dispersion containing a pigment, a (meth)acrylic resin, and a polypropylene resin. Patent Document 2 discloses an aqueous binder containing aqueous polyurethane, a modified polypropylene resin emulsion, and an aqueous acrylic resin. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2021-031616 [Patent Document 2] Japanese Patent Publication No. 2002-226758 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the aqueous pigment dispersion described in Patent Document 1 is intended for use as an inkjet recording ink. Therefore, the printed coating formed from the aqueous pigment dispersion described in Patent Document 1 does not satisfy the blocking resistance required for printed coatings formed by gravure printing or flexographic printing. Furthermore, the printed coating formed from the aqueous pigment dispersion described in Patent Document 1 does not satisfy the requirements for abrasion resistance with rubber or acid resistance. In addition, there is room for improvement in terms of storage stability and adhesion to PO film. The aqueous binder described in Patent Document 2 is intended for lamination. Printed coatings protected by lamination rarely require specific coating properties, and do not satisfy requirements such as acid resistance or abrasion resistance to rubber. Furthermore, storage stability is not sufficient, and there is room for improvement in adhesion to PO film and blocking resistance.

[0010] The present invention aims to provide an aqueous ink composition for gravure printing or flexographic printing that has excellent adhesion to polyolefin films, acid resistance, blocking resistance, and abrasion resistance that can withstand friction with rubber, as well as excellent storage stability, a laminate using the same, and packaging materials. [Means for solving the problem]

[0011] The present invention has the following aspects. [1] An aqueous ink composition for gravure printing or flexographic printing, comprising (meth)acrylic resin emulsion (A), modified polypropylene resin emulsion (B), pigment (C), and aqueous medium (D), The acid value of the (meth)acrylic resin emulsion (A) is 60 mg KOH / g or less, and the average particle size is 0.038 to 0.300 μm. The acid value of the modified polypropylene resin emulsion (B) is 60 mgKOH / g or less. The difference between the acid value of the (meth)acrylic resin emulsion (A) and the acid value of the modified polypropylene resin emulsion (B) satisfies the following formula (1) or (2): The amount of the modified polypropylene resin emulsion (B) in terms of solid content is 0.8 to 9.0% by mass relative to the total solid content of the aqueous ink composition. An aqueous ink composition having a mass ratio of 0.050 to 0.500 on a solid content basis, represented by the modified polypropylene resin emulsion (B) and the (meth)acrylic resin emulsion (A). When the acid value of (meth)acrylic resin emulsion (A) is greater than or equal to the acid value of modified polypropylene resin emulsion (B): Acid value of (meth)acrylic resin emulsion (A) - Acid value of modified polypropylene resin emulsion (B) ≤ 52 ···(1) Acid value of (meth)acrylic resin emulsion (A) < Modified polypropylene resin emulsion (B): Acid value of modified polypropylene resin emulsion (B) - Acid value of (meth)acrylic resin emulsion (A) ≤ 30 ···(2) [2] The aqueous ink composition according to [1], wherein the minimum film-forming temperature of the (meth)acrylic resin emulsion (A) is 50°C or less. [3] Further containing hydrocarbon wax (E), The aqueous ink composition according to [1] or [2], wherein the penetration of the hydrocarbon wax (E) is 12 or less and the average particle size is 6 μm or less. [4] Further containing a thickening agent (F), The aqueous ink composition according to any one of [1] to [3], wherein the thickening agent (F) is a polyurethane-associated thickening agent. [5] Further containing a hardening agent (G), The aqueous ink composition according to any one of [1] to [4], wherein the curing agent (G) is an aziridine-based curing agent. [6] A laminate comprising a plastic film and an ink layer formed on one surface of the plastic film using the aqueous ink composition described in any of [1] to [5] above. [7] The laminate according to [6], further comprising a varnish layer or a matte ink layer on the other surface of the plastic film for protecting the plastic film. [8] The laminate according to [6] or [7], further comprising a varnish layer on the surface of the ink layer for protecting the ink layer. [9] A packaging material comprising the laminate described in any of [6] to [8] above. [Effects of the Invention]

[0012] According to the present invention, an aqueous ink composition for gravure printing or flexographic printing is provided that can form a coating film with excellent adhesion to polyolefin films, acid resistance, blocking resistance, and abrasion resistance that can withstand friction with rubber, and also has excellent storage stability, as well as laminates and packaging materials using the same. [Brief explanation of the drawing]

[0013] [Figure 1] It is a cross-sectional view schematically showing an example of the laminate of the present invention. [Figure 2] It is a cross-sectional view schematically showing another example of the laminate of the present invention.

Mode for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described in detail. The following embodiments are merely illustrative for explaining the present invention, and it is not intended to limit the present invention only to these embodiments. The present invention can be implemented in various modes without departing from its gist. In the present invention, "aqueous" in the aqueous ink composition means containing water as a medium. The proportion of water in the medium of the aqueous ink composition is preferably 50% by mass or more, more preferably 70% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass, based on the total mass of the medium. "Coating film" refers to the coating film formed by the aqueous ink composition. In particular, the coating film before drying is also referred to as a "coated film", and the coating film after drying is also referred to as an "ink layer". The coated film is obtained by coating the aqueous ink composition of the present invention on the coating target surface (for example, a plastic film, etc.) of the present invention. The ink layer is obtained by drying the coated film and removing volatile components such as the medium in the coated film. "Medium" means components that volatilize, such as water and organic solvents. Specifically, it means components other than the following solid components (volatile components). The "solid content" of the aqueous ink composition refers to the components (non-volatile components) excluding the medium among the components contained in the aqueous ink composition, and is the component that finally forms the ink layer. Even if a component other than the medium is liquid at room temperature, that component is not included in the medium but is included in the solid content. The solid content is measured in accordance with JIS K 5601-1-2:2008. The "total solid content" of the aqueous ink composition means the total mass (total amount) of the solid content contained in the aqueous ink composition. The content of components other than the medium in the aqueous ink composition is all in terms of solid content conversion. A "unit" is a general term for atomic groups derived from a single monomer molecule, which are directly formed by the polymerization of monomers, and atomic groups obtained by chemically transforming a part of the above atomic group. Note that a "monomer-based constituent unit" is sometimes simply called a "monomer unit." For example, a "propylene-based constituent unit" is also called a "propylene unit." "(Meth)acrylic" is a general term for "acrylic" and "methacrylic". "Water-based binder resin" is a general term encompassing both "water-soluble binder resin" and "water-dispersible binder resin." Examples of water-dispersible binder resins include emulsion type and dispersion type. The medium of the water-based binder resin is considered to be included in the medium of the water-based ink composition. The "~" symbol indicating a numerical range means that the numbers before and after it are included as the lower and upper limits, respectively. For example, A~B is equivalent to A or greater and B or less. The lower and upper limits of the numerical ranges disclosed herein can be combined in any way to create new numerical ranges.

[0015] The weight-average molecular weights of (meth)acrylic resin emulsion (A) and modified polypropylene resin emulsion (B) are weight-average molecular weights converted to standard polystyrene molecular weights, and are measured by gel permeation chromatography (GPC). The glass transition temperature of (meth)acrylic resin emulsion (A) is measured in accordance with JIS K 7121:2012 as follows: Using a differential scanning calorimeter, 10 mg of (meth)acrylic resin emulsion (A) is heated from -100°C to 160°C at a rate of 20°C / min. The glass transition temperature is determined from the intersection of the baseline and the tangent to the endothermic curve in the resulting curve (DSC curve). The acid values ​​of (meth)acrylic resin emulsion (A) and modified polypropylene resin emulsion (B) are expressed in milligrams as the amount of potassium hydroxide required to neutralize acidic groups such as carboxyl groups per gram of non-volatile matter in the sample, and are measured in accordance with JIS K 5601-2-1:1999. The average particle size of (meth)acrylic resin emulsion (A) and modified polypropylene resin emulsion (B) is the particle size at which the volume-based cumulative frequency reaches 50% (median diameter: D50), calculated from the volume-based particle size distribution obtained by dynamic light scattering. The minimum film-forming temperature of (meth)acrylic resin emulsion (A) is measured in accordance with JIS K 6828-2:2003. The average particle size of hydrocarbon wax (E) is the particle size at which the cumulative frequency of particles reaches 50% (median diameter: D50) is calculated from the particle size distribution obtained by measuring the particle size distribution on a number basis using the Coulter counter method. The Coulter counter method is a method of electrically measuring the particle size and particle size distribution of particles by passing particles dispersed in a medium through pores and observing the change in electrical signal as the particles pass through. The penetration of hydrocarbon wax (E) is determined in accordance with JIS K 2235:2022. The measurement temperature is 25°C.

[0016] [Water-based ink composition] The aqueous ink composition of this embodiment contains a (meth)acrylic resin emulsion (A), a modified polypropylene resin emulsion (B), a pigment (C), and an aqueous medium (D). The aqueous ink composition may further contain hydrocarbon wax (E). The water-based ink composition may further contain a thickening agent (F). The aqueous ink composition may further contain a curing agent (G). The aqueous ink composition may further contain other components (hereinafter also referred to as "other optional components") as necessary, insofar as they do not impair the effects of the present invention, other than (meth)acrylic resin emulsion (A), modified polypropylene resin emulsion (B), pigment (C), aqueous medium (D), hydrocarbon wax (E), thickener (F), and curing agent (G).

[0017] <(Meth)acrylic resin emulsion (A)> (Meth)acrylic resin emulsion (A) (hereinafter also referred to as "resin (A)") is an emulsion-type (meth)acrylic resin, a water-dispersible binder resin, specifically a type of water-dispersible (meth)acrylic resin. Resin (A) typically has a core-shell structure. The core portion of the core-shell structure is preferably a hydrophobic (meth)acrylic resin. The shell portion of the core-shell structure is preferably a hydrophilic (meth)acrylic resin. The core portion and the shell portion may be bonded together by a crosslinking agent.

[0018] The hydrophobic (meth)acrylic resin of the core is typically a resin containing constituent units based on (meth)acrylate monomers. Examples of such resins include homopolymers of (meth)acrylate monomers, copolymers of two or more (meth)acrylate monomers, and copolymers of (meth)acrylate monomers and monomers other than (meth)acrylate monomers. The (meth)acrylate monomer is preferably one that does not have a carboxyl group.

[0019] The hydrophilic (meth)acrylic resin of the shell portion is typically a resin containing constituent units based on carboxyl group-containing monomers. Examples of such resins include homopolymers of carboxyl group-containing monomers, copolymers of two or more carboxyl group-containing monomers, and copolymers of carboxyl group-containing monomers and monomers other than carboxyl group-containing monomers. The monomers other than carboxyl group-containing monomers can be any monomer that does not have a carboxyl group, and may be (meth)acrylate monomers or monomers other than (meth)acrylate-based monomers.

[0020] Examples of (meth)acrylate monomers include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. (Meth)acrylate monomers may be used individually or in combination of two or more.

[0021] Examples of monomers containing carboxyl groups include (meth)acrylic acid, maleic acid (maleic anhydride), fumaric acid, and itaconic acid (itaconic anhydride). Carboxyl group-containing monomers may be used individually or in combination of two or more.

[0022] Examples of monomers other than (meth)acrylate monomers and carboxyl group-containing monomers include conjugated diene compounds such as 1,3-butadiene, isoprene, and chloroprene; aromatic vinyl compounds such as styrene, α-methylstyrene, halogenated styrene, and divinylbenzene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide; and unsaturated carboxylic acid esters such as diethyl maleate, dibutyl maleate, dibutyl fumarate, diethyl itaconate, and dibutyl itaconate. These monomers may be used individually or in combination of two or more.

[0023] The resin (A) may be self-crosslinking. If resin (A) is self-crosslinking, resin (A) typically contains structural units based on reactive functional group-containing monomers. These structural units may be contained in the core, the shell, or both. Examples of monomers containing reactive functional groups include monomers containing alkoxysilyl groups, monomers containing hydrazine groups, monomers containing epoxy groups, monomers containing methylol groups, monomers containing alkoxymethyl groups, dihydrazide adipate, diacetone acrylamide, vinyl acetoacetate, allyl acetoacetate, and acetoacetoxyalkyl (meth)acrylate. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, 2,3-epoxycyclohexyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, and allyl glycidyl ether. Examples of acetoacetoxyalkyl (meth)acrylates include acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetoxybutyl (meth)acrylate, and 2,3-di(acetoacetoxy)propyl (meth)acrylate. Reactive functional group-containing monomers may be used individually or in combination of two or more.

[0024] In resin (A), the mass ratio of the core portion to the shell portion (core portion:shell portion) is preferably 20:80 to 80:20, more preferably 25:75 to 75:25, and even more preferably 30:70 to 70:30. When the mass ratio of the core portion to the shell portion is within the above range, the storage stability, film-forming properties, adhesion of the coating film to the substrate, blocking resistance, abrasion resistance, and water abrasion resistance of the aqueous ink composition are better. If the amount of core portion is greater and the amount of shell portion is less than the above range, the storage stability, film-forming properties, and adhesion of the coating film to the substrate of the aqueous ink composition are slightly reduced. If the amount of core portion is less and the amount of shell portion is greater than the above range, the blocking resistance, abrasion resistance, and water abrasion resistance of the coating film are slightly reduced.

[0025] The acid value of resin (A) (hereinafter also referred to as "(A) acid value") is 60 mgKOH / g or less, preferably 55 mgKOH / g or less, more preferably 50 mgKOH / g or less, and may also be 0 mgKOH / g or more, 1 mgKOH / g or more, 5 mgKOH / g or more, 10 mgKOH / g or more, 20 mgKOH / g or more, or 25 mgKOH / g or more. The above upper and lower limits can be combined as appropriate. If the acid value of (A) exceeds the above upper limit, the acid resistance, water friction resistance, and storage stability of the coating film will decrease.

[0026] The average particle size of resin (A) is 0.038 to 0.300 μm, preferably 0.039 to 0.250 μm, and more preferably 0.040 to 0.200 μm. If the average particle size of resin (A) is below the lower limit, the adhesion of the coating film to the substrate, acid resistance, and blocking resistance will decrease. If the average particle size of resin (A) exceeds the upper limit, the adhesion of the coating film to the substrate, abrasion resistance (especially abrasion resistance to rubber (hereinafter also referred to as "rubber abrasion resistance")), film-forming ability, and dispersion stability will decrease.

[0027] The glass transition temperature of resin (A) is preferably -10 to 90°C, more preferably -5 to 70°C, and even more preferably 0 to 60°C. If the glass transition temperature of resin (A) is below the lower limit, the water friction resistance and blocking resistance of the coating film will be slightly reduced. If the glass transition temperature of resin (A) exceeds the upper limit, the adhesion of the coating film to the substrate and the friction resistance (especially the rubber friction resistance) will be slightly reduced.

[0028] The minimum film-forming temperature of resin (A) is preferably 70°C or lower, more preferably 50°C or lower, even more preferably 30°C or lower, and particularly preferably 10°C or lower. If the minimum film-forming temperature of resin (A) exceeds the above upper limit, the film-forming properties of the aqueous ink composition, the adhesion of the coating film to the substrate, acid resistance, abrasion resistance, and water abrasion resistance will be slightly reduced.

[0029] The weight-average molecular weight of resin (A) is preferably 30,000 to 1,000,000, more preferably 50,000 to 900,000, and even more preferably 100,000 to 800,000. If the weight-average molecular weight of resin (A) is below the lower limit, the abrasion resistance (especially abrasion resistance to fabric (hereinafter also referred to as "fabric abrasion resistance") and rubber abrasion resistance), water abrasion resistance, and blocking resistance of the coating film will be slightly reduced. If the weight-average molecular weight of resin (A) exceeds the upper limit, the storage stability of the aqueous ink composition will be slightly reduced.

[0030] The resin (A) may be one manufactured by a known manufacturing method, or a commercially available product may be used. In the production of resin (A), the polymerization method of the monomer is not particularly limited, but examples include radical polymerization, anionic polymerization, cationic polymerization, etc., and as radical polymerization in particular, examples include bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. Among these, emulsion polymerization is preferred. Emulsion polymerization is a method of polymerization in which the monomers used for polymerization are polymerized in an aqueous medium in the presence of an emulsifier and a polymerization initiator. Resin (A) may be produced by compounding a core part and a shell part after producing them separately, or it may be produced by multi-step emulsion polymerization. The polymerization mode may be any of random copolymer, block copolymer, graft copolymer, etc.

[0031] Examples of commercially available resins (A) include the "Hyros-X" series manufactured by CHEMIPAZ Corporation, the "Joncryl" series manufactured by BASF Japan Ltd., and the "Neocryl" series manufactured by Covestro. Resin (A) may be used alone or in combination of two or more types.

[0032] <Modified polypropylene resin emulsion (B)> Modified polypropylene resin emulsion (B) (hereinafter also referred to as "resin (B)") is an emulsion-type modified polypropylene resin, which is typically a resin obtained by modifying a polypropylene resin, introducing functional groups, and then stabilizing it as an emulsion in water by using an emulsifier, self-emulsification, or formation of a core-shell structure. Resin (B) is a water-dispersible binder resin, specifically a type of water-dispersible modified polypropylene resin. Resin (B) is typically a resin containing propylene units and monomer units having a modified group. Resin (B) may also contain olefin units other than propylene units (hereinafter also referred to as "other olefins").

[0033] Other olefins include, for example, ethylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-octene, norbornene, 4-methyl-1-pentene, and 3-methyl-1-pentene. Other olefins may be used individually or in combination of two or more.

[0034] The content of other olefin units is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, when the total content of propylene units and other olefin units is taken as 100% by mass.

[0035] While there are no particular limitations on the modifying group, an acid-modified group is preferred from the viewpoint of storage stability of the aqueous ink composition and adhesion of the coating film to the substrate (particularly adhesion to polyolefin films such as polypropylene films (hereinafter also referred to as "PP films") (hereinafter also referred to as "PO films"). Specifically, an acid-modified monomer is preferred as the monomer having a modifying group, and an acid-modified polypropylene resin emulsion is preferred as the resin (B). Examples of acid-modified groups include carboxyl groups, acid anhydride groups, and sulfonic acid groups. Among these, carboxyl groups and acid anhydride groups are preferred.

[0036] Examples of monomers having an acid-modified group include unsaturated carboxylic acids. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, aconitic acid, fumaric acid, crotonic acid, citraconic acid, mesaconic acid, allylsuccinic acid, half-esters and half-amides of unsaturated dicarboxylic acids, ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic acid. Among these, maleic anhydride, acrylic acid, and methacrylic acid are preferred from the viewpoint of reactivity during copolymerization, with maleic anhydride being more preferred. Unsaturated carboxylic acids may be used individually or in combination of two or more.

[0037] The content of monomer units having a modifying group is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1.5 to 7 parts by mass, based on 100 parts by mass of the total content of propylene units and other olefin units. If the content of monomer units having a modifying group is below the lower limit, emulsification of the modified polypropylene resin becomes difficult. In addition, the adhesion of the coating film to the substrate (especially to PP film) is slightly reduced. If the content of monomer units having a modifying group exceeds the upper limit, the blocking resistance of the coating film is slightly reduced.

[0038] Resin (B) may further contain, as necessary, propylene units, other olefin units, and monomer units other than monomer units having a modified group (hereinafter also referred to as "other monomers"), as long as the effects of the present invention are not impaired. Other monomers are not particularly limited as long as they can copolymerize with ethylene.

[0039] The acid value of resin (B) (hereinafter also referred to as "acid value of (B)") is 60 mgKOH / g or less, preferably 55 mgKOH / g or less, more preferably 40 mgKOH / g or less, and may also be 0 mgKOH / g or more, 5 mgKOH / g or more, 10 mgKOH / g or more, or 15 mgKOH / g or more. The above upper and lower limits can be combined as appropriate. If the acid value of (B) exceeds the above upper limit, the adhesion of the coating film to the substrate (especially to PP film), acid resistance, water friction resistance, and friction resistance (especially rubber friction resistance) will decrease.

[0040] The difference between the acid value of (A) and the acid value of (B) satisfies either formula (1) or (2) below. If the acid value of (A) is greater than or equal to the acid value of (B): Acid value of (A) - Acid value of (B) ≤ 52 ···(1) If the acid value of (A) is less than the acid value of (B): Acid value of (B) - Acid value of (A) ≤ 30 ···(2)

[0041] The difference between the acid value of (A) and the acid value of (B) (hereinafter also referred to as the "difference in acid values ​​(AB)") is 52 or less, preferably 50 or less, more preferably 45 or less, even more preferably 40 or less, even more preferably 35 or less, particularly preferably 30 or less, most preferably 25 or less, and may also be 0 or more, 1 or more, 3 or more, 5 or more, or 10 or more. The above upper and lower limits can be combined as appropriate. If the difference in acid values ​​(AB) exceeds the above upper limit, the stabilization state of the emulsion of resin (A) and resin (B) in the aqueous ink composition is easily disrupted, gelation and thickening are more likely to occur, and the storage stability of the aqueous ink composition decreases. In addition, the water friction resistance of the coating film decreases.

[0042] The difference between the acid value of (B) and the acid value of (A) (hereinafter also referred to as the "difference in acid values ​​(BA)") is 30 or less, preferably 28 or less, more preferably 25 or less, even more preferably 23 or less, and even more preferably 20 or less. It may also be greater than 0, 1 or more, 3 or more, 5 or more, or 10 or more. The above upper and lower limits can be combined as appropriate. If the difference in acid values ​​(BA) exceeds the above upper limit, the stabilization state of the emulsion of resin (A) and resin (B) in the aqueous ink composition is easily disrupted, making gelation and thickening more likely, and reducing the storage stability of the aqueous ink composition. In addition, the water friction resistance of the coating film decreases.

[0043] The average particle size of resin (B) is preferably 0.001 to 0.250 μm, more preferably 0.001 to 0.150 μm, and even more preferably 0.001 to 0.100 μm. If the average particle size of resin (B) is below the lower limit, the blocking resistance of the coating film is slightly reduced. If the average particle size of resin (B) exceeds the upper limit, the adhesion of the coating film to the substrate (especially to PP film), film-forming ability, and dispersion stability are slightly reduced.

[0044] The resin (B) may be one manufactured by a known manufacturing method, or a commercially available product may be used. Resin (B) can be obtained, for example, by modifying a polypropylene resin to introduce functional groups, and then using an emulsifier or by self-emulsification. The method for modifying the modified polypropylene resin is not particularly limited, but examples include copolymerizing propylene with a monomer having a modifying group such as an unsaturated carboxylic acid and, if necessary, one or more selected from other olefins and other monomers; and introducing a monomer having a modifying group such as an unsaturated carboxylic acid into an unmodified polypropylene resin.

[0045] Unmodified polypropylene resin is a polymer obtained by homopolymerizing propylene, or a copolymer obtained by copolymerizing propylene with one or more other monomers selected from other olefins and other monomers. The method for introducing a monomer having a modifying group, such as an unsaturated carboxylic acid, into an unmodified polypropylene resin is not particularly limited, but examples include a method in which the unmodified polypropylene resin and the monomer having a modifying group are reacted by melting them at a temperature above the melting point of the unmodified polypropylene resin in the presence of a radical generator; and a method in which the monomer having a modifying group is graft copolymerized into an unmodified polypropylene resin in the presence of a radical generator.

[0046] Examples of commercially available resins (B) include the "Aptrock" series manufactured by Mitsubishi Chemical Corporation; the "Aurollen" series manufactured by Nippon Paper Industries Ltd.; the "Hardren" series manufactured by Toyobo MC Corporation; and "ZE-1224" manufactured by CHEMIPAZ Corporation. Resin (B) may be used alone or in combination of two or more types.

[0047] <Pigment (C)> Pigment (C) may be any pigment known as a coloring agent, such as organic pigments or inorganic pigments. Examples of organic pigments include azo pigments such as monoazo and condensed azo; surene pigments such as anthraquinone, perinone, perylene, and thioindigo; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; quinacridone pigments; dioxazine pigments; isoindolinone pigments; pyrrolopyrrole pigments; aniline black; and organic fluorescent pigments. Examples of inorganic pigments include natural products such as clay, barite, mica, and talc; ferrocyanides such as Prussian blue and sulfides such as zinc sulfide; sulfates such as barium sulfate; oxides such as chromium oxide, zinc oxide, titanium dioxide, and iron oxide; hydroxides such as aluminum hydroxide; silicates such as calcium silicate and ultramarine; carbonates such as calcium carbonate and magnesium carbonate; carbon such as carbon black and graphite; metal powders such as aluminum powder, bronze powder, and zinc powder; and calcined pigments. Pigment (C) may be used alone or in combination of two or more types.

[0048] When the aqueous ink composition is used to make a white ink, titanium dioxide is preferred as the pigment (C). Titanium dioxide is not particularly limited. For example, it can be manufactured using either the chlorine method or the sulfuric acid method, and it can have either the anatase or rutile crystal structure. From the viewpoint of printability, the sulfuric acid method is preferred, and from the viewpoint of weather resistance, the rutile crystal structure is preferred. Titanium oxide is preferably surface-treated. Various surface treatment agents can be selected according to the required physical properties. Alumina treatment is preferred from the viewpoint of improving dispersibility and gloss, and silica treatment is preferred from the viewpoint of improving heat resistance and opacity. Titanium oxide may also have metal oxides added to it to suit the required properties. Aluminum oxide and zinc oxide are preferred metal oxides. Titanium dioxide may be used alone or in combination of two or more types.

[0049] The oil absorption of titanium dioxide is preferably 10-40 mL / 100g, and more preferably 15-30 mL / 100g. If the oil absorption of titanium dioxide is below the lower limit, the dispersibility will be slightly reduced, and if it exceeds the upper limit, the adhesion of the coating film to the substrate will be slightly reduced. The oil absorption capacity of titanium dioxide is determined in accordance with JIS K 5101-13-1:2004.

[0050] The average particle size of titanium dioxide is preferably 0.15 to 0.35 μm, and more preferably 0.20 to 0.30 μm. If the average particle size of titanium dioxide is below the lower limit, the opacity will be slightly reduced, and if it exceeds the upper limit, the printability and storage stability will be slightly reduced. The average particle size of titanium dioxide is determined by directly measuring the size of primary particles from images observed using a transmission electron microscope (TEM). Specifically, the particle size of 100 randomly selected primary particles is measured, and the average particle size of titanium dioxide is determined by averaging these particle sizes.

[0051] <Aqueous medium (D)> Examples of aqueous media (D) include water; and mixed solvents of water and organic solvents. The organic solvent is not particularly limited as long as it is soluble in water, but examples include alcohol-based solvents such as methanol, ethanol, n-propanol, i-propanol, n-butanol, and i-butanol; ketone-based solvents such as acetone; and glycol ether-based solvents such as propylene glycol monomethyl ether. One organic solvent may be used alone, or two or more may be used in combination. The aqueous medium (D) preferably contains substantially no organic solvent.

[0052] <Hydrogen wax (E)> To further improve the water resistance, abrasion resistance, and blocking resistance of the coating film, hydrocarbon wax (E) may be further added to the water-based ink composition. A water-based wax is preferred as the hydrocarbon wax (E). Aqueous wax is a wax that has been dispersed in water to form an emulsion or dispersion. The hydrocarbon wax dispersed in water may be any conventionally known wax, such as polyolefin wax, Fischer-Tropsch wax, paraffin wax, modified paraffin wax, or microcrystalline wax. Among these, polyolefin wax and Fischer-Tropsch wax are preferred, and polyolefin wax is more preferred. Hydrocarbon wax (E) may be used alone or in combination of two or more types.

[0053] Examples of polyolefin waxes include polyethylene wax and polypropylene wax. Among these, polyethylene wax is preferred. Examples of polyethylene waxes include high-density polymerized polyethylene, low-density polymerized polyethylene, oxidized polyethylene, acid-modified polyethylene, and special monomer-modified polyethylene. Fischer-Tropsch wax is a wax produced using carbon monoxide and hydrogen as raw materials by the Fischer-Tropsch process, and has a nearly saturated, unbranched, linear molecular structure.

[0054] The average particle size of the hydrocarbon wax (E) is preferably 10 μm or less, more preferably 6 μm or less, even more preferably 5 μm or less, and even more preferably 4 μm or less. It may also be 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 1.5 μm or more. If the average particle size of the hydrocarbon wax (E) exceeds the above upper limit, the adhesion of the coating film to the substrate, abrasion resistance, water abrasion resistance, and printability will be slightly reduced. If the hydrocarbon wax (E) is an aqueous wax, the average particle size of the dispersed particles in the aqueous wax can be considered as the average particle size of the hydrocarbon wax (E) in the aqueous ink composition.

[0055] The penetration (hardness) of the hydrocarbon wax (E) is preferably 15 or less, more preferably 12 or less, even more preferably 10 or less, even more preferably 5 or less, and particularly preferably 3 or less. If the penetration of the hydrocarbon wax (E) exceeds the above upper limit, the adhesion of the coating film to the substrate, water friction resistance, and friction resistance will decrease slightly.

[0056] <Thickening agent (F)> For the purpose of increasing the viscosity of the aqueous ink composition and improving its stability, a thickening agent (F) may be further added to the aqueous ink composition. Examples of thickeners (F) include polyurethane-based thickeners, polyacrylic-based thickeners, polyamide-based thickeners, cellulose-based thickeners, and clay minerals such as bentonite. Among these, polyurethane-based thickeners are preferred because they are excellent at improving the storage stability of aqueous ink compositions, and among these, associated polyurethane-based thickeners (hereinafter also referred to as "polyurethane associated thickeners") are particularly preferred.

[0057] Associative thickeners are polymers that have both hydrophobic and hydrophilic groups in their molecules. The hydrophobic groups of the thickener interact with each other or with hydrophobic substances such as resins through intermolecular interactions, forming a network structure and increasing the viscosity of the aqueous ink composition. Furthermore, the viscosity of the aqueous ink composition is also increased by the association of the hydrophilic groups of the thickener with the hydrophilic groups of the emulsion surface of resin (A) or resin (B). Examples of hydrophobic groups in association-type thickeners include alkyl groups and phenyl groups. Examples of hydrophilic groups in association-type thickeners include hydroxyl groups, amide groups, and carboxyl groups.

[0058] Examples of polyurethane-associated thickeners include urethane-modified polyethers and polyether polyol-based urethane prepolymers.

[0059] Examples of commercially available polyurethane-based thickeners include the "SN Thickener" series manufactured by Sunopco Corporation. The thickening agent (F) may be used alone or in combination of two or more types.

[0060] <Hardening agent (G)> Examples of curing agents (G) include aziridine-based curing agents, isocyanate-based curing agents, blocked isocyanate-based curing agents, carbodiimide-based curing agents, oxazoline-based curing agents, and epoxy-based curing agents. Among these, aziridine-based curing agents, isocyanate-based curing agents, and epoxy-based curing agents are preferred from the viewpoint of the water abrasion resistance of the coating film, with aziridine-based curing agents being more preferred. The hardening agent (G) may be used alone or in combination of two or more types.

[0061] Aziridine-based curing agents are compounds containing two or more aziridine groups in one molecule. The aziridine groups react with the carboxyl groups in resin (A), causing a crosslinking reaction (curing reaction) of resin (A). The number of aziridine groups (functional groups) contained in one molecule of the aziridine-based curing agent is preferably 3 or more, from the viewpoint of forming a network structure when a crosslinking reaction occurs with resin (A), which is expected to further improve physical properties, and preferably 4 or less, from the viewpoint of stability when added.

[0062] Examples of aziridine-based curing agents include 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], pentaerythritol-tris[3-(1-aziridinyl)propionate], and 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane.

[0063] Examples of commercially available aziridine-based curing agents include the "Chemitite" series manufactured by Nippon Shokubai Co., Ltd., and the "Picassian" series manufactured by Stahl. A aziridine-based curing agent may be used alone or in combination of two or more types.

[0064] <Other optional components> Other optional components include known additives. Examples of additives include binder resins other than resin (A) and resin (B) (hereinafter also referred to as "other binder resins"), defoaming agents, surfactants, anti-settling agents, UV absorbers, antioxidants, leveling agents, surface tension modifiers, rheology modifiers, light stabilizers, lubricants, dispersants, stabilizers, pH adjusters, fillers, antifungal agents, antistatic agents, metal nanoparticles, magnetic powders, etc. Other optional components may be used individually or in combination of two or more.

[0065] As other binder resins, aqueous binder resins other than resin (A) and resin (B) (hereinafter also referred to as "other aqueous binder resins") are preferred. Other aqueous binder resins are not particularly limited, but examples include water-soluble (meth)acrylic resins, dispersion-type (meth)acrylic resins, aqueous polyurethane resins, aqueous polyolefin resins, and aqueous polyester resins. Aqueous polyurethane resins, aqueous polyolefin resins, and aqueous polyester resins may each be of the following types: water-soluble, emulsion, or dispersion. Other binder resins may be used individually or in combination of two or more types.

[0066] <Content of each ingredient> The content of resin (A) on a solids basis is preferably 1 to 30% by mass, more preferably 2 to 26% by mass, and even more preferably 3 to 22% by mass, relative to the total mass of the aqueous ink composition. The content of resin (A) on a solids basis is preferably 1 to 50% by mass, more preferably 3 to 48% by mass, and even more preferably 5 to 46% by mass, relative to the total solids of the aqueous ink composition. If the content of resin (A) is below the lower limit, the coating's blocking resistance, abrasion resistance (especially rubber abrasion resistance), and water abrasion resistance will be slightly reduced. If the content of resin (A) exceeds the upper limit, the coating's adhesion to the substrate, acid resistance, and printability will be slightly reduced.

[0067] The content of resin (B) on a solids basis is preferably 0.5 to 6.0% by mass, more preferably 0.8 to 3.2% by mass, and even more preferably 1.2 to 2.8% by mass, relative to the total mass of the aqueous ink composition. The content of resin (B) on a solids basis is 0.8 to 9.0% by mass, preferably 2.0 to 5.0% by mass, and more preferably 2.5 to 4.0% by mass, relative to the total solids of the aqueous ink composition. If the resin (B) content is below the lower limit, the adhesion of the coating film to the substrate (especially to PP film), acid resistance, and printability will decrease. If the resin (B) content exceeds the upper limit, the blocking resistance, abrasion resistance (especially to rubber abrasion), and water abrasion resistance of the coating film will decrease.

[0068] The mass ratio of resin (B) / resin (A) in terms of solid content (hereinafter also referred to as the "B / A ratio") is 0.050 to 0.500, preferably 0.080 to 0.500, and more preferably 0.100 to 0.490. If the B / A ratio is below the lower limit, the adhesion of the coating film to the substrate (especially to PP film) and acid resistance will decrease. If the B / A ratio exceeds the upper limit, the blocking resistance, abrasion resistance, and water abrasion resistance of the coating film will decrease.

[0069] The content of pigment (C) on a solid content basis is preferably 3 to 60% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 45% by mass, based on the total mass of the aqueous ink composition. The content of pigment (C) on a solids basis is preferably 20 to 85% by mass, more preferably 30 to 80% by mass, and even more preferably 35 to 75% by mass, relative to the total solids of the aqueous ink composition. If the pigment (C) content is below the lower limit, the opacity, color development, and blocking resistance of the coating film will be slightly reduced. If the pigment (C) content exceeds the upper limit, the storage stability, fluidity, adhesion of the coating film to the substrate, and water friction resistance of the water-based ink composition will be slightly reduced.

[0070] The content of the aqueous medium (D) is preferably 20 to 70% by mass, more preferably 25 to 65% by mass, and even more preferably 30 to 60% by mass, relative to the total mass of the aqueous ink composition. If the content of the aqueous medium (D) is below the lower limit, the fluidity and printability of the aqueous ink composition will be slightly reduced. If the content of the aqueous medium (D) exceeds the upper limit, the blocking resistance and drying properties of the coating film will be slightly reduced.

[0071] When the aqueous ink composition contains hydrocarbon wax (E), the content of hydrocarbon wax (E) on a solid content basis is preferably 0.1 to 5.0% by mass, more preferably 0.1 to 4.0% by mass, and even more preferably 0.1 to 3.0% by mass, based on the total mass of the aqueous ink composition. When the aqueous ink composition contains hydrocarbon wax (E), the content of hydrocarbon wax (E) on a solids basis is preferably 0.1 to 8.0% by mass, more preferably 0.3 to 6.0% by mass, and even more preferably 0.5 to 5.0% by mass, relative to the total solids of the aqueous ink composition. If the hydrocarbon wax (E) content is below the lower limit, the improvement in blocking resistance, abrasion resistance, and water abrasion resistance due to hydrocarbon wax (E) will not be fully realized. If the hydrocarbon wax (E) content exceeds the upper limit, printability and color development will be slightly reduced.

[0072] When the aqueous ink composition contains a thickener (F), the content of the thickener (F) on a solids basis is preferably 0.01 to 8.00% by mass, more preferably 0.05 to 6.00% by mass, and even more preferably 0.10 to 5.00% by mass, based on the total mass of the aqueous ink composition. When the aqueous ink composition contains a thickener (F), the content of the thickener (F) on a solids basis is preferably 0.05 to 1.00% by mass, more preferably 0.10 to 0.80% by mass, and even more preferably 0.20 to 0.50% by mass, relative to the total solids of the aqueous ink composition. If the content of the thickener (F) is below the lower limit, the viscosity-improving effect and storage stability-improving effect of the thickener (F) on the aqueous ink composition will not be fully realized. If the content of the thickener (F) exceeds the upper limit, the printability of the aqueous ink composition, as well as the color development, abrasion resistance, and water abrasion resistance of the coating film, will be slightly reduced.

[0073] When the aqueous ink composition contains a curing agent (G), the content of the curing agent (G) on a solid content basis is preferably 0.1 to 5.0% by mass, more preferably 0.5 to 4.0% by mass, and even more preferably 1.0 to 3.0% by mass, based on the total mass of the aqueous ink composition. When the aqueous ink composition contains a curing agent (G), the content of the curing agent (G) on a solids basis is preferably 0.5 to 8.0% by mass, more preferably 1.0 to 6.0% by mass, and even more preferably 2.0 to 4.0% by mass, relative to the total solids of the aqueous ink composition. If the content of hardener (G) is below the lower limit, the acid resistance, abrasion resistance, and water abrasion resistance of the coating film will be slightly reduced. If the content of hardener (G) exceeds the upper limit, the storage stability of the water-based ink composition will be slightly reduced.

[0074] The content of other optional components on a solids basis is not particularly limited as long as it does not impair the effects of the present invention, but for example, it is preferably 0 to 20% by mass, more preferably 0 to 15% by mass, and even more preferably 0 to 10% by mass relative to the total mass of the aqueous ink composition. If the aqueous ink composition contains other optional components, the content of these other optional components on a solids basis is preferably 0.01% by mass or more, more preferably 0.10% by mass or more, and even more preferably 0.50% by mass or more, relative to the total mass of the aqueous ink composition. If the content of these other optional components is below the above lower limit, the effects of these other optional components will not be fully realized.

[0075] <Manufacturing method> The aqueous ink composition of this embodiment can be obtained, for example, by mixing a resin (A), a resin (B), a pigment (C), optionally a further aqueous medium (D), optionally a hydrocarbon wax (E), optionally a thickener (F), optionally a curing agent (G), and optionally other optional components. The method of mixing each component is not particularly limited, and each component can be mixed by various methods. For example, one method is to dissolve or disperse resin (A), resin (B), pigment (C), optionally hydrocarbon wax (E), optionally thickener (F), optionally curing agent (G), and optionally other optional components in an aqueous medium (D). In particular, it is preferable to add the curing agent (G) immediately before using the aqueous ink composition.

[0076] The method for dissolving or dispersing each component in the aqueous medium (D) is not particularly limited and can be carried out using known dispersers. Examples of dispersers include paint shakers, ball mills, attritors, sand mills, bead mills, dyno mills, roll mills, ultrasonic mills, and high-pressure impact dispersers. In this case, the dispersion treatment may be performed once or multiple times using one type of disperser, or multiple dispersion treatments may be performed using two or more types of dispersers in combination.

[0077] <Effects and Effects> According to the aqueous ink composition of this embodiment described above, by containing the above-mentioned resin (A), resin (B), pigment (C), and aqueous medium (D), and having a solid content of resin (B) of 0.5 to 9.0% by mass, it is possible to form a coating film with excellent adhesion to the substrate (especially to PP film), acid resistance, blocking resistance, and abrasion resistance (especially to rubber abrasion resistance).

[0078] When using a modified polyethylene resin emulsion (hereinafter also referred to as "resin (B')") instead of resin (B), it is necessary to increase the solid content of resin (B') in the aqueous ink composition (specifically, to more than 9.0% by mass) in order to achieve the same level of adhesion as resin (B). However, increasing the resin (B') content reduces the coating's blocking resistance, abrasion resistance, and water abrasion resistance. With resin (B), sufficient adhesion can be imparted to the coating film without increasing the content (specifically, even at 9.0% by mass or less). Therefore, a good balance is achieved between adhesion to the substrate, blocking resistance, abrasion resistance, and water abrasion resistance.

[0079] In addition, the aqueous ink composition of this embodiment has excellent storage stability because the difference between the acid value of (A) and the acid value of (B) satisfies formula (1) or (2) above.

[0080] <Application> The aqueous ink composition of this embodiment is suitable as an ink for printing on the surface of any substrate, such as a plastic film (or, if any layer is formed on the surface of the substrate, on the surface of that layer). In particular, it is suitable as an ink for printing on the surface of the substrate or the surface of the aforementioned layer by gravure printing or flexographic printing. That is, the aqueous ink composition of this embodiment is especially suitable for gravure printing or flexographic printing. The aqueous ink composition of this embodiment may be used as ink as is, or a diluted solution obtained by diluting it with water or the like may be used as ink. The aqueous ink composition of this embodiment is printed on any substrate to form an ink layer. Hereinafter, the ink layer formed using the aqueous ink composition will also be referred to as the printed layer.

[0081] [Laminated structure] Figure 1 shows an example of a laminate according to one embodiment of the present invention. Note that the dimensional ratios in Figure 1 differ from those of the actual dimensions for the sake of explanation. The laminate 10 in Figure 1 is a printed material comprising a plastic film 11 which is a base material and an ink layer 12 provided on one surface of the plastic film 11. One side of the plastic film 11 is the back side of the laminate 10, that is, the container side when the laminate 10 is used to package food, daily necessities, etc. The other side of the plastic film 11 is the front side of the laminate 10, that is, the visible side when the laminate 10 is used to package a container.

[0082] <Plastic film> Examples of resins constituting the plastic film 11 include plastic films (base films) made of polyolefins (e.g., polyethylene (PE), milky polyethylene, polypropylene (PP), etc.), polyesters (e.g., polyethylene terephthalate (PET), etc.), polystyrene (PS), stretched polypropylene (OPP), polyamide (NY), etc. Among these, polyolefins are preferred, and polypropylene is more preferred. In other words, a polyolefin film is preferred as the plastic film 11, and a polypropylene film is more preferred. These plastic films 11 may be used individually or two or more types may be laminated together.

[0083] The plastic film 11 may have a single-layer structure or a laminated structure. That is, the plastic film 11 may be a single-layer film or a laminated film. If the plastic film 11 is a laminated film, it may be a configuration in which two or more films of the same type are laminated together, or a configuration in which two or more films of different types are laminated together. If the plastic film 11 is a laminated film, it is preferable that at least the layer in contact with the ink layer 12 is a polyolefin film, and more preferably a polypropylene film.

[0084] The plastic film 11 may or may not be subjected to corona treatment. The thickness of the plastic film 11 (or the thickness after lamination if two or more types are used together) is not particularly limited and may be, for example, 10 to 50 μm.

[0085] <Ink layer> In the illustrated example laminate 10, the ink layer 12 is provided on one surface of the plastic film 11. The ink layer 12 is a layer formed using the aqueous ink composition of the present invention described above. The ink layer 12 may have a single-layer structure or a multi-layer structure. The ink layer 12 may be the pattern layer. The thickness of the ink layer 12 is not particularly limited and may be, for example, 0.1 to 1 μm. However, if the ink layer contains particles (for example, particles of hydrocarbon wax (E)) and some of the particles protrude above the surface of the ink layer, the thickness of the ink layer shall be the thickness of the portion where the particles do not protrude.

[0086] <Method for manufacturing laminates> The manufacturing method of the laminate 10 of this embodiment includes the step of forming an ink layer 12 on one surface of the plastic film 11 using the aqueous ink composition of the present invention. In the method for manufacturing the laminate 10 of the present invention, for example, the aqueous ink composition of the present invention is applied to one surface of a plastic film 11 to form a coating film which serves as a laminate precursor, and then the coating film is dried to form an ink layer 12. Alternatively, the aqueous ink composition of the present invention may be applied to one surface of a plastic film 11, the resulting coating film may be dried to form an ink layer 12, and then the aqueous ink composition of the present invention may be applied again (overcoated), and the resulting coating film may be dried, repeating this process one or more times to form a laminated ink layer. When applying multiple layers of the aqueous ink composition of the present invention, the color tones of each aqueous ink composition may be the same or different.

[0087] The method for forming the ink layer 12 may be any known printing method. For example, the ink layer 12 is formed by coating one surface of the plastic film 11 with the aqueous ink composition of the present invention and drying it. The coating method may be any known coating method, such as gravure printing, flexographic printing, brush coating, gravure coater, die coater, bar coater, spray coating, flow coating, dip coating, spin coating, and curtain coating. Among these, gravure printing and flexographic printing are preferred in terms of superior quality and productivity. Of these, flexographic printing is more preferred in terms of superior suitability for high-speed printing.

[0088] The drying method for the coated film is not particularly limited as long as the aqueous medium (D) contained in the aqueous ink composition coated on one surface of the plastic film 11 can be removed, and known drying methods can be used. For example, it may be air drying, or forced drying such as reduced pressure drying, pressurized drying, heat drying, or air drying. When drying by heating, the drying temperature is preferably 60-100°C.

[0089] <Effects and Effects> The laminate of this embodiment described above has an ink layer formed using the aqueous ink composition of the present invention described above on one surface of a plastic film, and exhibits excellent acid resistance, blocking resistance, and abrasion resistance (particularly rubber abrasion resistance). Furthermore, the ink layer has excellent adhesion to the plastic film.

[0090] <Application> The laminate of this embodiment is suitable as a packaging material, particularly as a packaging label. Packaging labels are attached to containers such as plastic containers, metal containers, and paper containers. Examples of packaging labels include roll labels, which are attached by wrapping them around the container and securing them with adhesive, and shrink labels, which are attached by applying heat to shrink them to a shape that fits the container. When a laminate is used for a packaging label, the ink layer side of the laminate faces the inside of the packaging label, i.e., the container side.

[0091] <Other Embodiments> The laminate is not limited to the embodiments described above. For example, in the laminate 10 shown in Figure 1, the ink layer 12 is provided over the entire surface of one side of the plastic film 11, but the ink layer 12 may also be provided on only a part of one side of the plastic film 11. That is, a part of one side of the plastic film 11 may be exposed from the ink layer 12.

[0092] Furthermore, as shown in Figure 2, for example, the laminate 10 may further include a varnish layer 13 on the surface of the ink layer 12 to protect the ink layer 12. That is, the laminate 10 may have the ink layer 12 and the varnish layer 13 formed in this order on one surface of the plastic film 11. The varnish layer 13 is a protective layer that protects the ink layer 12 from contact with the container, etc. The varnish layer 13 is a printed layer typically formed using varnish. The varnish may be any known varnish. The method for forming the varnish layer 13 may be a known printing method, similar to the method for forming the ink layer 12.

[0093] Furthermore, as shown in Figure 2, for example, the laminate 10 may further include another layer 14 on the other surface of the plastic film 11. The other layer 14 is a protective layer that protects the plastic film 11 from external contact such as human hands. Other layers 14 include, for example, a varnish layer and a matte ink layer. In particular, if the other layer 14 is a matte ink layer, a matte finish can be given to the laminate 10. The varnish layer on the other surface of the plastic film 11 is typically a printed layer formed using varnish. The varnish may be any known varnish. The matte ink layer is a printed layer typically formed using a matte ink. The matte ink may be any known matte ink. The matte ink typically contains a matting agent. The method for forming the other layers 14 may be a known printing method, similar to the method for forming the ink layer. Although the laminate 10 shown in Figure 2 comprises a varnish layer 13 and other layers 14 in addition to the plastic film 11 and ink layer 12, the laminate 10 may also comprise either the varnish layer 13 or the other layers 14 in addition to the plastic film 11 and ink layer 12.

[0094] [Packaging material] The packaging material of this embodiment comprises the laminate of the present invention as described above. Specific examples of the packaging material include, for instance, various packaging labels such as plastic labels attached to packaging containers for beverages, prepared foods and bento boxes, and daily necessities such as cosmetics. Among these, it is particularly suitable as a label for food and beverages. [Examples]

[0095] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Note that Example 14 is for reference only.

[0096] [Raw materials used] <(Meth)acrylic resin emulsion (A)> The following compounds were used as (meth)acrylic resin emulsion (A) or a comparable product thereof. · A-1: ​​Manufactured by CHEMIPAZ Corporation, product name "Hyros-X 430F", non-volatile content: 41.5% by mass, acid value: 33 mg KOH / g, average particle size: 0.040 μm, minimum film formation temperature: less than 5°C, glass transition temperature: 21°C. · A-2: Manufactured by BASF Japan Ltd., product name "Joncryl PDX-7511", non-volatile content: 45% by mass, acid value: 54 mg KOH / g, average particle size: 0.090 μm, minimum film formation temperature: less than 5°C, glass transition temperature: 9°C. · A-3: Manufactured by BASF Japan Ltd., product name "Joncryl PDX-7440", non-volatile content: 48.5% by mass, acid value: 1 mg KOH / g, average particle size: 0.250 μm, minimum film formation temperature: 50°C, glass transition temperature: 40°C. A-4: Manufactured by BASF Japan Ltd., product name "Joncryl PDX-7780", non-volatile content: 48% by mass, acid value: 46 mg KOH / g, average particle size: 0.100 μm, minimum film formation temperature: over 50°C. • A-5: Manufactured by CHEMIPAZ Corporation, product name "Hyros-X TE-1336", non-volatile content: 39% by mass, acid value: 64 mgKOH / g, average particle size: 0.150 μm, minimum film formation temperature: less than 5°C. A comparative product of resin (A). • A-6: Manufactured by CHEMIPAZ Corporation, product name "Hyros-X RE-218", non-volatile content: 40% by mass, acid value: 49 mg KOH / g, average particle size: 0.035 μm, minimum film formation temperature: less than 5°C, glass transition temperature: 0°C. A comparative product of resin (A). • A-7: Manufactured by CHEMIPAZ Corporation, product name "Hyros-X TE-1124", non-volatile content: 60% by mass, acid value: 25 mg KOH / g, average particle size: 0.330 μm, minimum film formation temperature: less than 5°C. A comparative product of resin (A).

[0097] <Modified polypropylene resin emulsion (B)> The following compounds were used as modified polypropylene resin emulsion (B) or its substitute. • B-1: Manufactured by Mitsubishi Chemical Corporation, product name "Aptrock BW-5550", non-volatile content: 30% by mass, acid value: 18 mg KOH / g. B-2: Manufactured by Nippon Paper Industries Co., Ltd., product name "Aurolene S-4891", non-volatile content: 30% by mass, acid value: 0 mgKOH / g. B-3: Manufactured by Nippon Paper Industries Co., Ltd., product name "Aurolene S Series", non-volatile content: 25% by mass, acid value: 26 mgKOH / g. B-4: Manufactured by Toyobo MC Co., Ltd., product name "Hardlen NA-3002", non-volatile content: 30% by mass, acid value: 33 mgKOH / g. • B-5: Manufactured by CHEMIPAZ Corporation, product name "ZE-1224", non-volatile content: 30% by mass, acid value: 50 mg KOH / g. • B-6: Manufactured by Sumitomo Seika Co., Ltd., product name "Zyxene AC", non-volatile content: 30% by mass, acid value: 62.2 mgKOH / g. A comparative product of resin (B).

[0098] <Other binder resins> The following compounds were used as other binder resins. • Water-soluble (meth)acrylic resin: Manufactured by CHEMIPAZ Corporation, product name "Hyros-X GL-2439", non-volatile content: 26% by mass, acid value: 110 mg KOH / g, glass transition temperature: 52°C. • Water-based polyurethane resin: Lubrizol, product name "Sancure 2710", non-volatile content: 40%, acid value: 14 mg KOH / g.

[0099] <Pigment (C)> The following compounds were used as pigment (C). C-1: Titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., product name "CR-90", non-volatile content: 100% by mass, average particle size: 0.25 μm, oil absorption capacity: 21 mL / 100 g). • C-2: Pigment Red 146 (manufactured by DIC Corporation, product name "Symuler Fast Red 4580", non-volatile content: 100% by mass).

[0100] <Aqueous medium (D)> The following media were used as the aqueous medium (D). D-1: 25% by mass aqueous solution of ammonia. D-2: Tap water.

[0101] <Hydrogen wax (E)> The following compounds were used as hydrocarbon wax (E). E-1: Polyethylene wax (manufactured by Mitsui Chemicals, Inc., product name "Chemipearl W-500", non-volatile content: 40% by mass, penetration: 10, average particle size: 2.5 μm). E-2: Polyethylene wax (manufactured by Mitsui Chemicals, Inc., product name "Chemipearl W-410", non-volatile content: 40% by mass, penetration: 3, average particle size: 9.5 μm). E-3: Polyethylene wax, non-volatile content: 100% by mass, penetration: 13, average particle size: 2.2 μm.

[0102] <Thickening agent (F)> The following compounds were used as thickeners (F). F-1: Polyurethane-associated thickener (manufactured by Sunopco Corporation, product name "SN Thickener 612", non-volatile content: 40% by mass). F-2: Polyacrylic thickener (manufactured by BASF Japan Ltd., product name "Rheovis AS1130", non-volatile content: 30% by mass).

[0103] <Hardening agent (G)> The following compounds were used as the curing agent (G). G-1: Aziridine-based curing agent (manufactured by Nippon Shokubai Co., Ltd., product name "Chemitight PZ-33", non-volatile content: 99% by mass). G-2: Epoxy-based hardener (manufactured by Nagase ChemteX Corporation, product name "Denacol EX-612", non-volatile content: 99% by mass).

[0104] <Other optional components> The following compounds were used as optional components other than the binder resin. • Dispersant: BYK Corporation, product name "DISPERBYK-2012", non-volatile content: 40% by mass. • Surfactant: Evonik brand, product name "TEGO WET 240", non-volatile content: 100% by mass. • Defoaming agent: Manufactured by BYK, product name "BYK-018", non-volatile content: 97% by mass.

[0105] [Evaluation Method] <Evaluation of adhesion> After applying cellophane tape (manufactured by Nichiban Co., Ltd.) to the surface of the ink layer of the laminate, the cellophane tape was promptly peeled off, and the condition of the ink layer remaining on the plastic film (OPP film) was visually inspected. The adhesion of the ink layer to the polyolefin film was then evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. 5: The ink layer has not peeled off at all. 4. The ratio of the area of ​​the peeled-off ink layer to the area of ​​the cellophane tape application is greater than 0% and less than or equal to 10%. 3: The ratio of the area of ​​the peeled-off ink layer to the area of ​​the cellophane tape application is greater than 10% and less than or equal to 30%. 2: The ratio of the area of ​​the peeled-off ink layer to the area of ​​the cellophane tape application is more than 30% and less than or equal to 50%. 1: The area of ​​the peeled-off ink layer exceeds 50% of the area of ​​the cellophane tape that was applied.

[0106] <Evaluation of acid resistance> The laminate was immersed in a 1% by mass hydrochloric acid aqueous solution and left to stand at 40°C for 24 hours. After that, the laminate was removed from the hydrochloric acid solution and the water droplets were wiped off. Subsequently, the surface of the ink layer of the laminate was subjected to a friction test using a JSPS-type friction fastness tester (manufactured by Tester Sangyo Co., Ltd., product name "AB-301"), with a black cloth (metal cloth No. 3) applied under a load of 200 gf and rubbed back and forth 10 times. The appearance of the ink layer after the friction test was visually inspected, and the acid resistance of the ink layer was evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. 5: The ink layer has not peeled off at all. 4. The ratio of the area of ​​the peeled ink layer to the total area of ​​the ink layer is greater than 0% and less than or equal to 10%. 3. The ratio of the area of ​​the peeled ink layer to the total area of ​​the ink layer is greater than 10% and less than or equal to 30%. 2: The ratio of the area of ​​the peeled ink layer to the total area of ​​the ink layer is greater than 30% and less than or equal to 50%. 1: The area of ​​the peeled-off ink layer exceeds 50% of the total area of ​​the ink layer.

[0107] <Evaluation of storage stability> The viscosity of the aqueous ink composition was measured at 25°C using a Zahn cup #4. After standing the aqueous ink composition at 40°C for one week, the viscosity was measured again at 25°C using the same Zahn cup #4, and the storage stability of the aqueous ink composition was evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. If the aqueous ink composition contained a curing agent (G), the storage stability was evaluated using the aqueous ink composition immediately before the addition of the curing agent (G). 5. The increase in viscosity after standing is 5 seconds or less compared to before standing. 4. The increase in viscosity after standing is more than 5 seconds but less than 10 seconds compared to before standing. 3. The increase in viscosity after standing is more than 10 seconds but less than 15 seconds compared to before standing. 2: The increase in viscosity after standing is more than 15 seconds but less than 30 seconds compared to before standing. 1. The viscosity increase after standing is more than 30 seconds compared to before standing. Alternatively, gelation is confirmed.

[0108] <Evaluation of blocking resistance> Two laminate precursors were prepared. Two laminate precursors are stacked so that the coated film side (printed side) of one laminate precursor is in contact with the plastic film (OPP film) side (unprinted side) of the other laminate precursor, and then 5 kg / cm² is applied. 2 The materials were subjected to a load and stored for 24 hours in a constant temperature chamber at 40°C and 50% humidity. Afterward, the two laminate precursors were separated, and the blocking resistance of the coating films was evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. Note that "ink removal" below refers to the situation where, during separation, the coating film of one laminate precursor remains attached to the opposing surface (in this evaluation, the non-printed surface of the other laminate precursor) while the coating film of the other laminate precursor peels off the plastic film. 5: No ink is absorbed onto the non-printed surface. 4. Ink removal to the non-printed surface is greater than 0% and less than or equal to 10% of the total area of ​​the coated film under load. 3: Ink removal to the non-printed surface is between 10% and 30% of the total area of ​​the coated film under load. 2: Ink removal to the non-printed surface is between 30% and 50% of the total area of ​​the coated film under load. 1: Ink removal to the non-printed surface exceeds 50% of the total surface area of ​​the coated film under load.

[0109] <Evaluation of water and friction resistance> The surface of the ink layer of the laminate was subjected to a friction test using a JSPS-type friction fastness tester (manufactured by Tester Sangyo Co., Ltd., product name "AB-301") by rubbing it back and forth 200 times with a water-moistened black cloth (Kanahaba No. 3) under a load of 200 gf. After the friction test, the appearance of the ink layer was visually inspected, and the water friction resistance of the ink layer was evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. 5: The area of ​​the ink layer that transferred to the black cloth (gold cloth No. 3) is 0% of the total area of ​​the ink layer that was rubbed. 4. The percentage of the ink layer area transferred to the black cloth (gold cloth No. 3) is greater than 0% and less than or equal to 5% of the total area of ​​the friction-affected ink layer. 3: The percentage of the ink layer area transferred to the black cloth (gold cloth No. 3) is between 5% and 10% of the total area of ​​the friction-affected ink layer. 2: The proportion of the ink layer area transferred to the black cloth (gold cloth No. 3) is between 10% and 30% of the total area of ​​the friction-affected ink layer. 1: The area of ​​the ink layer that transferred to the black cloth (gold cloth No. 3) exceeds 30% of the total area of ​​the ink layer that was rubbed.

[0110] <Evaluation of abrasion resistance: Evaluation of fabric abrasion resistance> The surface of the ink layer of the laminate was subjected to a friction test using a JSPS-type friction fastness tester (manufactured by Tester Sangyo Co., Ltd., product name "AB-301"), with a black cloth (metal cloth No. 3) applied under a load of 200 gf and rubbed back and forth 200 times. After the friction test, the appearance of the ink layer was visually inspected, and the friction resistance of the ink layer to the cloth was evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. 5: The area of ​​the ink layer that transferred to the black cloth (gold cloth No. 3) is 0% of the total area of ​​the ink layer that was rubbed. 4. The percentage of the ink layer area transferred to the black cloth (gold cloth No. 3) is greater than 0% and less than or equal to 5% of the total area of ​​the friction-affected ink layer. 3: The percentage of the ink layer area transferred to the black cloth (gold cloth No. 3) is between 5% and 10% of the total area of ​​the friction-affected ink layer. 2: The proportion of the ink layer area transferred to the black cloth (gold cloth No. 3) is between 10% and 30% of the total area of ​​the friction-affected ink layer. 1: The area of ​​the ink layer that transferred to the black cloth (gold cloth No. 3) exceeds 30% of the total area of ​​the ink layer that was rubbed.

[0111] <Evaluation of abrasion resistance: Evaluation of rubber abrasion resistance> The surface of the ink layer of the laminate was subjected to a friction test using a JSPS-type friction fastness tester (manufactured by Tester Sangyo Co., Ltd., product name "AB-301"), with rubber (chloroprene rubber, thickness: 1 mm) applied under a load of 200 gf and rubbed back and forth 200 times. After the friction test, the appearance of the ink layer was visually inspected, and the rubber friction resistance of the ink layer was evaluated according to the evaluation criteria shown below. A score of 3 to 5 is considered acceptable. 5. The percentage of the ink layer area that migrated to the rubber side is 0% of the total area of ​​the friction-affected parts of the ink layer. 4. The percentage of the ink layer area that migrated to the rubber side is greater than 0% and less than or equal to 5% of the total area of ​​the friction-affected parts of the ink layer. 3. The proportion of the ink layer that migrated to the rubber side is more than 5% and 10% or less of the total area of ​​the friction-affected parts of the ink layer. 2: The proportion of the ink layer that migrated to the rubber side is more than 10% and 30% or less of the total area of ​​the friction-affected parts of the ink layer. 1: The area of ​​the ink layer that migrated to the rubber side exceeds 30% of the total area of ​​the ink layer that was rubbed.

[0112] [Examples 1-21, Comparative Examples 1-10] <Preparation of aqueous ink composition> According to the compositions shown in Tables 1-5, (meth)acrylic resin emulsion (A), modified polypropylene resin emulsion (B), other binder resins, pigment (C), aqueous medium (D), hydrocarbon wax (E), thickener (F), and other optional components were mixed, and the resulting mixture was kneaded in a paint shaker. A curing agent (G) was further added and kneaded in a paint shaker to obtain an aqueous ink composition. The curing agent (G) was added immediately before preparing the printing ink in the following <Lamination Preparation>.

[0113] <Fabrication of laminates> As the plastic film, a biaxially oriented polypropylene film (OPP film, manufactured by Futamura Chemical Co., Ltd., product name "FOR", thickness: 30 μm) with one side treated with corona discharge was used. For the corona discharge treatment, a corona discharge surface treatment device (manufactured by Wedge Co., Ltd., product name "CTW-0212") was used. The prepared aqueous ink composition was diluted with water to a viscosity of 15 seconds at 25°C, as measured using a Zahn cup #4, to prepare a printing ink. Using a flexographic hand proofer equipped with a 6cc cell volume anilox roll as the applicator, the coating amount after drying was 1.0g / m². 2 To achieve this, the prepared printing ink was applied to the corona discharge treated surface of a plastic film using a flexographic printing method, and a laminate precursor with a coated film formed on the plastic film was obtained. Next, the laminate precursor was dried at 20°C for 24 hours to obtain a laminate (printed material) with an ink layer of 0.5 μm thickness formed on the plastic film. Storage stability was evaluated using the aqueous ink composition, blocking resistance was evaluated using the laminate precursor (before drying), and adhesion, acid resistance, water friction resistance, and abrasion resistance were evaluated using the laminate (after drying). These results are shown in Tables 1 to 5.

[0114] [Table 1]

[0115] [Table 2]

[0116] [Table 3]

[0117] [Table 4]

[0118] [Table 5]

[0119] The amounts of each component in Tables 1-5, excluding aqueous media (D), are calculated on a solid content basis. A blank space in Tables 1-5 indicates that the ingredient is not included (0% by mass). In Tables 1-5, "residue" refers to the amount of water (D-2) added, adjusted so that the total amount (mass%) of all components in the aqueous ink composition equals 100% by mass. In Tables 1-5, "(A) acid value - (B) acid value" represents the acid value of (meth)acrylic resin emulsion (A) minus the acid value of modified polypropylene resin emulsion (B). Similarly, "(B) acid value - (A) acid value" represents the acid value of modified polypropylene resin emulsion (B) minus the acid value of (meth)acrylic resin emulsion (A). In Tables 1-5, "Content of (B)" refers to the content of modified polypropylene resin emulsion (B) on a solids basis relative to the total solids of the water-based ink composition, rounded to three decimal places. The "B / A ratio" in Tables 1-5 represents the mass ratio on a solid content basis, expressed as modified polypropylene resin emulsion (B) / (meth)acrylic resin emulsion (A), and is rounded to the fourth decimal place.

[0120] As is clear from the results in Tables 1-3, the aqueous ink compositions obtained in each example exhibited excellent storage stability. Furthermore, the coating films formed from these aqueous ink compositions exhibited excellent adhesion to polyolefin films, blocking resistance, acid resistance, fabric friction resistance, rubber friction resistance, and water friction resistance.

[0121] On the other hand, as is clear from the results in Tables 4 and 5, the coating film formed from the aqueous ink composition obtained in Comparative Example 1, which used a (meth)acrylic resin emulsion with an acid value of 64 mgKOH / g, was inferior in acid resistance and water friction resistance. The coating film formed from the aqueous ink composition obtained in Comparative Example 2, which used a modified polypropylene resin emulsion with an acid value of 62.2 mg KOH / g, exhibited poor adhesion to polyolefin films, as well as poor acid resistance and water friction resistance. The coating film formed from the aqueous ink composition obtained in Comparative Example 3, which used a (meth)acrylic resin emulsion with an average particle size of 0.035 μm, exhibited poor blocking resistance. The coating film formed from the aqueous ink composition obtained in Comparative Example 4, which used a (meth)acrylic resin emulsion with an average particle size of 0.330 μm, exhibited poor adhesion to polyolefin films and poor resistance to rubber friction. The aqueous ink composition obtained in Comparative Example 5, where the acid value of (A) minus the acid value of (B) was 54.0, and the aqueous ink composition obtained in Comparative Example 6, where the acid value of (B) minus the acid value of (A) was 32.0, exhibited poor storage stability. The coating film formed from the aqueous ink composition obtained in Comparative Example 7, which contained 0.67% by mass of modified polypropylene resin emulsion (B), exhibited poor adhesion to polyolefin film and poor acid resistance. The coating film formed from the aqueous ink composition obtained in Comparative Example 8, which contained 9.82% by mass of modified polypropylene resin emulsion (B), exhibited poor resistance to blocking, water friction, and rubber friction. The coating film formed from the aqueous ink composition obtained in Comparative Example 9, which had a B / A ratio of 0.044, exhibited poor adhesion to polyolefin film and poor acid resistance. The coating film formed from the aqueous ink composition obtained in Comparative Example 10, which had a B / A ratio of 0.583, exhibited poor resistance to blocking, water friction, fabric friction, and rubber friction. [Industrial applicability]

[0122] The aqueous ink composition of the present invention can form a coating film that has excellent adhesion, acid resistance, and blocking resistance to polyolefin films, as well as abrasion resistance that can withstand friction with rubber, and also has excellent storage stability, making it useful as an ink for packaging materials, especially for packaging labels. [Explanation of symbols]

[0123] 10 Laminate 11 Plastic film 12 Ink Layers 13 layers of varnish 14 Other layers

Claims

1. An aqueous ink composition for gravure printing or flexographic printing, comprising (meth)acrylic resin emulsion (A), modified polypropylene resin emulsion (B), pigment (C), and aqueous medium (D), The acid value of the (meth)acrylic resin emulsion (A) is 60 mg KOH / g or less, the average particle size is 0.038 to 0.300 μm, and the minimum film-forming temperature is 50°C or less. The acid value of the modified polypropylene resin emulsion (B) is 60 mg KOH / g or less. The difference between the acid value of the (meth)acrylic resin emulsion (A) and the acid value of the modified polypropylene resin emulsion (B) satisfies the following formula (1) or (2): The content of the modified polypropylene resin emulsion (B) on a solid content basis is 0.8 to 9.0% by mass relative to the total solid content of the aqueous ink composition. An aqueous ink composition having a mass ratio of 0.050 to 0.500 on a solid content basis, represented by the modified polypropylene resin emulsion (B) and the (meth)acrylic resin emulsion (A). When the acid value of (meth)acrylic resin emulsion (A) is greater than or equal to the acid value of modified polypropylene resin emulsion (B): Acid value of (meth)acrylic resin emulsion (A) - Acid value of modified polypropylene resin emulsion (B) ≤ 36 ... (1) Acid value of (meth)acrylic resin emulsion (A) < Modified polypropylene resin emulsion (B): Acid value of modified polypropylene resin emulsion (B) - Acid value of (meth)acrylic resin emulsion (A) ≤ 25 ... (2)

2. It further contains hydrocarbon wax (E), The aqueous ink composition according to claim 1, wherein the penetration degree of the hydrocarbon wax (E) is 12 or less, and the average particle size is 6 μm or less.

3. It further contains a thickening agent (F), The aqueous ink composition according to claim 1, wherein the thickening agent (F) is a polyurethane-associated thickening agent.

4. It further contains a hardening agent (G), The aqueous ink composition according to claim 1, wherein the curing agent (G) is an aziridine-based curing agent.

5. A laminate comprising a plastic film and an ink layer formed on one surface of the plastic film using the aqueous ink composition described in any one of claims 1 to 4.

6. The laminate according to claim 5, further comprising a varnish layer or a matte ink layer for protecting the plastic film on the other surface of the plastic film.

7. The laminate according to claim 6, further comprising a varnish layer on the surface of the ink layer for protecting the ink layer.

8. A packaging material comprising the laminate described in claim 7.

Images