JP7501587B2 - Water-based ink, printed matter and laminate using the same - Google Patents

Description

The present invention relates to water-based inks, and printed matter and laminates using the same.

Gravure inks and flexographic inks are widely used for printing patterns to impart beauty and functionality to printed materials, but in recent years, the demands on printing inks have become more diverse year by year, due to the diversity of packaging materials, the sophistication of packaging technology, and efforts to address environmental issues from the perspective of legal regulations such as organic solvents. For example, a shift from solvent-based inks to water-based inks has been proposed as a means of solving recent issues regarding environmental conservation and legal regulations, and water-based inks have been widely used for printing on general packaging paper, paper containers such as cardboard, plastic film substrates, and the like. However, compared to solvent-based inks, water-based inks still have many issues with coating film properties, printing effects, printability, and the like.

In addition, one way to achieve carbon neutrality (the amount of carbon dioxide emitted from combustion is the same as the amount of carbon dioxide absorbed and fixed by the growth of plants, etc.) is to use biomass-derived raw materials such as plant materials. In printing inks, the use of biomass-derived raw materials for the resins contained therein is also being considered (Patent Document 1).

As one of the biomass-derived raw materials, the use of rosin-based resin in water-based inks has been considered. For example, Patent Document 2 discloses an invention for a water-based flexographic ink that contains an acrylic resin having a polysaccharide-derived component and a resin not having a polysaccharide-derived component, and further contains a rosin-based resin. However, when the ink is printed on a substrate and the substrate is further laminated to form a laminate, there may be cases where the laminate strength and retort resistance are insufficient when using only rosin-based resin, or where the compatibility of the rosin-based resin with other components is low, resulting in low ink stability.

Furthermore, Patent Document 3 discloses an invention of an ink composition, a printed coating film, and a laminate containing an aqueous medium, a biomass-derived urethane resin, and a rosin-based resin. However, because a rosin-based resin with a high acid value is used, there are concerns that the compatibility between the aqueous urethane resin and the rosin-based resin and the resolubility of the rosin-based resin are insufficient, which may result in poor ink stability and printing defects. Furthermore, when a packaging bag is made using the ink and retorted, it is thought that the laminate strength will decrease due to the high acid value of the rosin resin.

International Publication No. 2018/199085 JP 2021-167377 A JP 2021-008569 A

The present invention aims to provide a water-based ink that has good pigment dispersibility, ink stability, and printing effect, and has good retort resistance when made into a printed matter or laminate.

As a result of extensive research, the inventors discovered that the problem in question could be solved by using the water-based ink described below, which led to the creation of the present invention.

That is, the present invention relates to an aqueous ink containing a pigment, an aqueous urethane resin, a rosin-based resin, and an acetylene glycol-based surfactant, in which the acid value of the rosin-based resin is 10 to 280 mg KOH/g.

The present invention also relates to the above water-based ink for flexographic printing or gravure printing.

The present invention also relates to the above water-based ink, in which the content of the acetylene glycol surfactant is 0.1 to 5 mass % based on the total mass of the water-based ink.

The present invention also relates to the above water-based ink, in which the rosin-based resin contains a water-soluble rosin resin and/or an emulsion-type rosin resin.

The present invention also relates to the above water-based ink, in which the water-based urethane resin contains structural units derived from polyether polyol and/or structural units derived from polyester polyol.

The present invention also relates to the above water-based ink, in which the water-based urethane resin contains structural units derived from a polyether polyol, and the polyether polyol contains at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

The present invention also relates to the above water-based ink, in which the water-based urethane resin contains structural units derived from a polyester polyol, the polyester polyol contains structural units derived from a dibasic acid, and the dibasic acid contains at least one selected from the group consisting of adipic acid, succinic acid, azelaic acid, and dimer acid.

The present invention also relates to a printed matter containing an ink layer made of the above-mentioned water-based ink and a substrate 1.

The present invention also relates to a laminate having, in this order, a substrate 1, an ink layer made of the above-mentioned water-based ink, and a substrate 2.

The present invention makes it possible to provide a water-based ink that has good pigment dispersibility, ink stability, and printing effect, and also has good retort resistance when made into a printed matter or laminate.

The following describes an embodiment of the present invention in detail. The following description of the components is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents as long as it does not exceed the gist of the invention.

In this specification, the above "water-based ink" may be referred to simply as "ink," and the above "water-based urethane resin" may be referred to simply as "urethane resin," but they are synonymous.

<Water-based ink>
The water-based ink of the present invention contains a pigment, a water-based urethane resin, a rosin-based resin, and an acetylene glycol-based surfactant, and the acid value of the rosin-based resin is 10 to 280 mgKOH/g. It is also preferable that the water-based ink contains additives and a liquid medium as necessary.

The ink of the present invention contains a rosin-based resin with an acid value of 10 to 280 mgKOH/g and an acetylene glycol-based surfactant, which effectively dissolves them in the water-based urethane resin, stabilizing the ink. Furthermore, the cohesive force of the ink layer formed by the water-based ink is increased, improving retort resistance when made into a printed matter or laminate.

Furthermore, the acetylene glycol surfactant improves the pigment adsorption ability of the aqueous urethane resin and the rosin resin, thereby providing an aqueous ink with excellent pigment dispersion stability.
In addition, the acetylene glycol surfactant improves the resolubility of the aqueous urethane resin and the rosin resin, and the resolubility of the rosin resin is particularly excellent, which improves printing effects such as leveling properties.
The above discussion of the mechanism is merely an example and is not intended to limit the present invention.

<Pigments>
The pigment contained in the water-based ink of the present invention may be, for example, an achromatic pigment such as carbon black, titanium oxide, calcium carbonate, or a chromatic organic pigment. Organic pigments such as yellow, magenta, cyan, and black are preferably blended in an amount of 5 to 30% by mass based on 100% by mass of the water-based ink. White titanium oxide is preferably blended in an amount of 10 to 60% by mass based on 100% by mass of the water-based ink.

Organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red; soluble azo pigments such as lithol red, helio bordeaux, pigment scarlet, and permanent red 2B; derivatives of vat dyes such as alizarin, indanthrone, and thioindigo maroon; phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green; quinacridone organic pigments such as quinacridone red and quinacridone magenta; perylene organic pigments such as perylene red and perylene scarlet; and isoindoli. Isoindolinone organic pigments such as non-yellow and isoindolinone orange, pyranthrone organic pigments such as pyranthrone red and pyranthrone orange, thioindigo organic pigments, condensed azo organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments such as quinophthalone yellow, isoindoline organic pigments such as isoindoline yellow, and other pigments include flavanthrone yellow, acylamide yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, and dioxazine violet.

Examples of organic pigments by color index (C.I.) number are C.I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, C.I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, C.I. C.I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, C.I. Pigment Violet 19, 23, 29, 30, 37, 40, 50, C.I. Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 60, 64, C.I. Pigment Green 7, 36, C.I. Pigment Brown 23, 25, 26, etc.

Specific examples of carbon black include Degussa's Special Black 350, 250, 100, 550, 5, 4, 4A, 6, Printex U, V, 140U, 140V, 95, 90, 85, 80, 75, 55, 45, 40, P, 60, L6, L, 300, 30, 3, 35, 25, A, G, and Cabot's REGAL 400R, 660R, 330R, 250R, and MOGUL E, L" and Mitsubishi Chemical's "MA7, 8, 11, 77, 100, 100R, 100S, 220, 230" and "#2700, #2650, #2600, #200, #2350, #2300, #2200, #1000, #990, #980, #970, #960, #950, #900, #850, #750, #650, #52, #50, #47, #45, #45L, #44, #40, #33, #332, #30, #25, #20, #10, #5, CF9, #95, #260".

Specific examples of titanium oxide include "Typeeque CR-50, 50-2, 57, 80, 90, 93, 95, 953, 97, 60, 60-2, 63, 67, 58, 58-2, 85," "Typeeque R-820, 830, 930, 550, 630, 680, 670, 580, 780, 780-2, 850, 855," "Typeeque A-100, 220," "Typeeque W-10," "Typeeque PF-740, 744," and "TTO-55 (A)" manufactured by Ishihara Sangyo Kaisha. ), 55(B), 55(C), 55(D), 55(S), 55(N), 51(A), 51(C)", "TTO-S-1, 2", "TTO-M-1, 2", Teika's "Titanix JR-301, 403, 405, 600A, 605, 600E, 603, 805, 806, 701, 800, 808", "Titanix JA-1, C, 3, 4, 5", DuPont's "Typure R-900, 902, 960, 706, 931", etc.

<Water-based urethane resin>
The water-based ink of the present invention contains a water-based urethane resin. The water-based urethane resin is preferably one having a hydroxyl group at the end, which is obtained by a condensation reaction between a polyol and a polyisocyanate. The urethane resin may also be a water-based urethane urea resin obtained by reacting a urethane prepolymer having an isocyanate group at the end, which is a condensation reaction product between a polyol and a polyisocyanate, with a chain extender.

The acid value of the aqueous urethane resin is 15 to 60 mgKOH/g, preferably 20 to 55 mgKOH/g, more preferably 25 to 50 mgKOH/g, and even more preferably 25 to 45 mgKOH/g. Within the above range, the acidic groups are neutralized with a base, resulting in sufficient dispersibility and solubility in water, and the ink is stable, while also providing excellent pigment dispersibility and printing stability. The acid value is the amount of acid in 1 g of resin calculated by titrating the acid with an alkali, converted into mg of potassium hydroxide, and is measured according to JIS K0070.

The hydroxyl value of the aqueous urethane resin is preferably 0.1 to 30 mgKOH/g, and more preferably 1 to 25 mgKOH/g. This is because the aqueous urethane resin has good solubility in water, which results in good ink stability and further laminate strength of the laminate. The hydroxyl value is the amount of hydroxyl groups in 1 g of resin calculated by esterifying or acetylating the hydroxyl groups in the resin and back titrating the remaining acid with an alkali, converted into mg of potassium hydroxide, and is measured according to JIS K0070.

The weight average molecular weight of the aqueous urethane resin is preferably 5,000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 20,000 to 70,000.

The content of the above water-based urethane resin is preferably 1 to 30% by mass, and more preferably 5 to 15% by mass, of the total mass of the ink.

<Polyol>
The aqueous urethane resin preferably contains a structural unit derived from a polyether polyol and/or a structural unit derived from a polyester polyol, and also preferably contains a structural unit derived from a polyol having a carboxyl group.

(Polyether polyol)
From the viewpoint of pigment dispersibility and ink stability, the polyether polyol preferably contains at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. The polyether polyol may be used alone or in a mixture of two or more kinds, and these may be copolymerized polyether polyols or may be used in combination with a single polyether polyol. It is also possible to use polyether polyols other than those mentioned above in combination. For example, polymers or copolymers of methylene oxide, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, etc. may be mentioned.
The polyether polyol is preferably derived from biomass from the viewpoint of the biomass content of the ink.

The content of the polyether polyol is preferably from 5 to 80 mass %, more preferably from 10 to 70 mass %, and even more preferably from 15 to 60 mass %, based on the total mass of the aqueous urethane resin.
The above range is preferable since it provides excellent solubility and lubricity of the ink and excellent printing effect of the ink.

(Polyester polyol)
The polyester polyol is preferably, for example, a condensate of a dibasic acid and a diol. From the viewpoint of ink stability and retort resistance, it is preferable that the dibasic acid contains at least one selected from the group consisting of adipic acid, succinic acid, azelaic acid, and dimer acid.

The diol preferably includes a branched diol, and more preferably includes both a branched diol and a linear diol. A linear diol is a diol having two or more carbon atoms, such as alkylene glycol, dialkylene glycol, trialkylene glycol, or other diol. A branched diol is a diol in which at least one hydrogen atom of the hydrocarbon group of an alkylene glycol is substituted with a non-hydrogen atom.

Examples of the branched diol include 2-butyl-2-ethyl-1,3-propanediol (hereinafter also referred to as BEPG), 2-methyl-1,3-propanediol (hereinafter also referred to as MPO), 3-methyl-1,5-pentanediol (hereinafter also referred to as MPD), neopentyl glycol (hereinafter also referred to as NPG), 1,2-propylene glycol (hereinafter also referred to as PG), 2,4-diethyl-1,5-pentanediol, 1,3-butanediol, and dipropylene glycol.
The branched diol is also preferably derived from biomass in terms of the degree of biomass.

The linear diol is preferably an alkylene glycol, and examples of such compounds include ethylene glycol (also written as EG), diethylene glycol, 1,3-propanediol (also written as 1,3-PD), 1,4-butanediol (also written as 1,4-BD), 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, and triethylene glycol.
Among these, linear diols having 8 or less carbon atoms, preferably 6 or less carbon atoms, are preferred, and EG, 1,3-PD, 1,4-BD, 1,5-pentanediol, 1,6-hexanediol, and 1,8-octanediol are more preferred, and EG, 1,3-PD, and 1,4-BD are particularly preferred.
From the viewpoint of the degree of biomass, the linear diol is preferably derived from biomass.

The mass ratio of the branched diol and the linear diol in the diol contained in the polyester polyol (branched diol: linear diol) is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

The branched diol and the linear diol may each be present in one polyester polyol, or a polyester polyol containing only a branched diol and a polyester polyol containing only a linear diol may be used as a mixture raw material to produce an aqueous urethane resin.

The content of polyester polyol is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and even more preferably 15 to 60% by mass, based on the total mass of the aqueous urethane resin. This range is preferable because it provides excellent ink solubility and lubricity, and excellent printing stability of the ink.

(Polyol having a carboxyl group)
In order to dissolve or disperse the aqueous urethane resin in an aqueous medium, the aqueous urethane resin must be hydrophilic. The above-mentioned polyether polyols and polyester polyols are also hydrophilic, but it is preferable to use a polyol having a carboxyl group in combination. The carboxyl group is preferably neutralized with a basic compound.

Examples of polyols having a carboxyl group include dimethylolalkanoic acids such as dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, dihydroxypropionic acid, and dihydroxybenzoic acid. These carboxyl group-containing polyols can be used alone or in combination.
Among these, dimethylolpropionic acid and dimethylolbutanoic acid are preferable.

When a polyol having a carboxyl group is contained, the content of the polyol having a carboxyl group is preferably 1 to 50 mass %, more preferably 2 to 30 mass %, and even more preferably 3 to 15 mass %, of the total mass of the aqueous urethane resin.
The above range is preferable since it provides excellent ink stability, printing effect, and lamination strength of the laminate.

(Other polyols)
Other suitable polyols include polycarbonate polyols. Examples of polycarbonate polyols include those obtained by reacting polyols with carbonate compounds such as dialkyl carbonates, alkylene carbonates, and diaryl carbonates. The polyols constituting the polycarbonate polyols can be the polyols listed above as examples of components of polyester polyols. Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate, examples of alkylene carbonates include ethylene carbonate, and examples of diaryl carbonates include diphenyl carbonate.

(Chain extension reaction with polyamine)
In the synthesis of the aqueous urethane resin, a chain extension reaction using a polyamine may be carried out as necessary. In the chain extension reaction, a urethane prepolymer having an excess of isocyanate groups is synthesized, and then a diamine or other polyamine is reacted as a chain extender. From the viewpoint of a significant increase in viscosity of the resin solution, this reaction is preferably carried out when the resin is neutralized to make it aqueous. The chain extension makes it possible to further increase the molecular weight of the aqueous urethane resin. In addition, the introduction of urea bonds can be expected to further improve the cohesive force of the aqueous urethane resin.

Examples of polyamines include diamines such as hydrazine, ethylenediamine, propylenediamine, 1,4-tetramethylenediamine, 2-methyl-1,5-pentanediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, phenylenediamine, tolylenediamine, xylylenediamine, adipic acid dihydrazide, and isophthalic acid dihydrazide;
Triamines such as diethylenetriamine;
Diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, bis(β-hydroxyethyl)terephthalate, and xylylene glycol;
Triols such as trimethylolpropane;
Pentaols such as pentaerythritol;
Known chain extenders such as amino alcohols such as N-(β-aminoethyl)ethanolamine can be used.
By using a monofunctional monoamine or monool in combination, it is also possible to control the molecular weight by terminating the chain extension.

(Polyisocyanate)
The polyisocyanate in the present invention is preferably a diisocyanate, and various known aromatic, aliphatic, or alicyclic diisocyanates can be used as such compounds. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylsilyl diisocyanate, 1,3,4-trimethylsilyl diisocyanate, 1,4,5 ...4,5-trimethylsilyl diisocyanate, 1,4,5-trimethylsilyl diisocyanate, 1,4,5-trimethylsilyl Representative examples include methylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate in which the carboxyl group of a dimer acid is converted to an isocyanate group. These can be used alone or in combination of two or more. Among them, isophorone diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate are preferred, and isophorone diisocyanate is more preferred from the viewpoint of solubility.

<Method of manufacturing water-based urethane resin>
The method for producing the aqueous urethane resin is not particularly limited, and the resin is produced by a known method. For example, as described in Japanese Patent No. 4900136, a method of polymerizing a polyol and a polyisocyanate without using an organic solvent can be mentioned. More specifically, for example, after charging a polyol and a polyisocyanate, the atmosphere is replaced with dry nitrogen, and the reaction is carried out at 90°C to 220°C for 10 minutes to 5 hours. Thereafter, a neutralizing agent is added while cooling to obtain the resin.

<Rosin-based resin>
The water-based ink of the present invention contains a rosin-based resin having an acid value of 10 to 280 mgKOH/g.

The rosin-based resin includes rosin and/or a rosin derivative, and a rosin derivative is preferable.
Examples of rosin include gum rosin, tall oil rosin, and wood rosin. Rosin is a natural resin obtained as the main component of the sap of pine plants. Rosin is mainly composed of resin acids such as abietic acid, neoabietic acid, parathrylic acid, pimaric acid, isopimaric acid, sandaracopimaric acid, and dehydroabietic acid.

The rosin derivative is a compound obtained by modifying the rosin, and examples thereof include rosin ester, rosin-modified maleic acid resin, hydrogenated rosin, disproportionated rosin, rosin-modified phenolic resin, polymerized rosin, rosin-modified polyol, and maleic acid-modified rosin. These may be used alone or in combination of two or more.

The acid value of the rosin-based resin is 10 to 280 mgKOH/g, more preferably 15 to 270 mgKOH/g, even more preferably 20 to 260 mgKOH/g, and particularly preferably 25 to 250 mgKOH/g.

The softening point of the rosin-based resin is preferably in the range of 10 to 180°C, more preferably 30 to 150°C, and even more preferably 50 to 120°C, from the viewpoint of ink stability and printing effect. The softening point is a value measured by the ring and ball method specified in JIS K 5902.

From the viewpoints of pigment dispersibility, ink stability, printing effect, and retort resistance, it is preferable that the rosin-based resin is a water-soluble rosin resin and/or an emulsion-type rosin resin.

(Water-soluble rosin resin)
The water-soluble rosin resin is a rosin or a rosin derivative that has been solubilized in an aqueous medium by introducing a hydrophilic group into the rosin or the rosin derivative.
Specific examples of the water-soluble rosin resin include Harima Chemicals' products Harimac T-80, AS-5, Hariestar MSR-4, Tespol 1150, 1154, and 1158, and Arakawa Chemical Industries' products Malquid 31, 32, and 33. The water-soluble rosin resin is preferably neutralized with a basic compound, and is made water-soluble by the neutralization. Examples of the basic compound include ammonia, alkylamines, and other organic amines.

(Emulsion type rosin resin)
The emulsion type rosin resin is a rosin or a rosin derivative in which the rosin or the rosin derivative is stably dispersed in an aqueous medium using a dispersant or the like.
As the emulsion-type rosin resin, those obtained by dispersing rosin or a rosin derivative such as a rosin ester made from a non-fossil raw material such as rosin resin in the form of fine particles in water in the presence of a low molecular weight emulsifier, a polymeric emulsifier made of an acrylic copolymer, or other emulsifiers can be suitably used. Specific examples include Hariestar SK218NS, SK370N, SK385NS, and SK501NS manufactured by Harima Chemical Industries, Ltd., Snowpack XW-2442, XW-2551, XW-2561, XW-2582, SE780G, and 100G manufactured by Lawter, and Superester NS-121, NS-100H, and E-865NT manufactured by Arakawa Chemical Industries, Ltd.

The content of rosin-based resin is preferably 1 to 10% by mass, and more preferably 2 to 8% by mass, based on the total mass of the water-based ink.

The mass ratio of the aqueous urethane resin to the rosin-based resin contained in the aqueous ink is preferably 95:5 to 40:60, more preferably 90:10 to 50:50, and even more preferably 85:15 to 55:45.

<Acetylene glycol surfactant>
The aqueous ink of the present invention contains an acetylene glycol surfactant. The acetylene glycol surfactant is a nonionic surfactant containing a structural unit derived from an acetylene group. The acetylene glycol surfactant is preferably an acetylene glycol surfactant to which ethylene oxide has been added. By using the acetylene glycol surfactant in combination with an aqueous urethane resin and a rosin resin having an acid value of 10 to 280 mgKOH/g, the acetylene glycol surfactant improves the pigment adsorption ability and resolubility of the aqueous urethane resin and the rosin resin, contributing to improved pigment dispersibility, ink stability, and printing effect.

The content of the acetylene glycol surfactant is preferably 0.01 to 8 mass% of the total mass of the ink, more preferably 0.05 to 5 mass%, even more preferably 0.1 to 3 mass%, and particularly preferably 0.2 to 2 mass%.

Examples of commercially available acetylene glycol surfactants include Surfynol 61, 104, 420, 440, 465, 485, SE, SE-F, Dynol 604, 607, Olfin E1004, E1010, E1020, PD-001, PD-002W, PD-004, PD-005, EXP. 4001, EXP. 4200, EXP. 4123, and EXP. 4300 (manufactured by Nissin Chemical Industry Co., Ltd.). The above surfactants may be used alone or in combination of two or more kinds.

The HLB (hydrophile-lipophile balance) value of the acetylene glycol surfactant is preferably 1 or more and 8 or less. More preferably, it is 1 or more and 6 or less, and even more preferably, it is 1 or more and 4 or less. The above HLB value refers to the value calculated by the Griffin method.

<Additives>
Suitable additives that can be used in the water-based ink include a hardener, an antiblocking agent, a thickener, a rheology modifier, an antifoaming agent, a leveling agent, a preservative, a surface tension modifier, a neutralizing agent, polyolefin particles, and the like.

(Neutralizer)
In order to improve the resolubility of the resin in the aqueous ink, it is preferable to contain various neutralizing agents. Examples of basic compounds used as neutralizing agents include ammonia; organic amines such as monoethylamine, diethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, methyldiethanolamine, monoethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, N-methylmorpholine, and 2-amino-2-ethyl-1-propanol; and inorganic alkalis such as sodium hydroxide and potassium hydroxide, and these may be used alone or in combination of two or more. Among these, ammonia, triethylamine, and dimethylethanolamine are preferred.

(Polyolefin particles)
The water-based ink of the present invention preferably further contains polyolefin particles for the purposes of improving the rub resistance of the ink film and improving the drying properties of the water-based ink.

The melting point of the polyolefin particles is preferably 90 to 140°C, more preferably 95 to 135°C, and even more preferably 95 to 125°C. The average particle size of the polyolefin particles is preferably 0.5 to 10 μm, more preferably 0.5 to 8 μm, and even more preferably 0.5 to 5 μm. The average particle size is measured using the Coulter Counter method. Polyolefin particles with the above particle size and melting point form a strong ink coating that is compatible with water-based urethane resins and rosin-based resins, and promote improvement of water-friction resistance.

The content of polyolefin particles is preferably 0.5 to 5% by mass (solids) of the total mass of the water-based ink. Water-friction resistance is improved when the content is 0.5% by mass or more, and the stability of the water-based ink over time is also improved when the content is 5% by mass or less.

Commercially available polyolefin particles can be used as the polyolefin particles. For example, Chemipearl W100, W200, W300, W310, W306, W400, W401, W4005, W410, W500, WF640, W700, W800, W900, W950, WH201, and WP100 manufactured by Mitsui Chemicals, Inc. can be mentioned.

(Hydrazide additives)
The water-based ink of the present invention may contain a hydrazide additive for the purpose of improving adhesion to a substrate, room temperature crosslinking of the resin (in the case of containing a keto group), etc. An example of the hydrazide additive is adipic acid hydrazide.

<Liquid medium>
The aqueous ink preferably contains water as a liquid medium, and further contains a hydrophilic solvent for the purpose of controlling the wettability to the substrate and the drying property of the ink. From the viewpoint of the leveling property and drying property of the ink, the content of the hydrophilic solvent is preferably 1 to 10 mass % and more preferably 2 to 5 mass % in 100 mass % of the aqueous ink.

Examples of hydrophilic solvents include monohydric alcohol solvents such as ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol;
Glycol solvents such as ethylene glycol, 1,3-propanediol, propylene glycol, 1,2-butanediol, 1,4-butanediol, pentylene glycol, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, and tetraethylene glycol;
glycol ether-based solvents such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether;
Lactam solvents such as N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, and ε-caprolactam;
Examples of the amide solvent include formamide, N-methylformamide, N,N-dimethylformamide, Equamide M-100 and Equamide B-100 manufactured by Idemitsu.
These can be used alone or in combination of two or more.

<Water-based ink manufacturing method>
The aqueous ink can be produced by dissolving and/or dispersing (pigment dispersion) a resin and a coloring pigment in water and a specified amount of a solvent, as described in, for example, JP-A-2020-186344. Thereafter, the aqueous ink can be produced by blending additives, liquid media, etc., as necessary, with the obtained dispersion. As a dispersing machine used for dispersing the pigment, a commonly used machine such as a roller mill, a ball mill, a pebble mill, an attritor, a sand mill, etc. can be used. Among them, it is preferable to disperse the pigment with a sand mill, a gamma mill, or other bead mill.

The viscosity of the water-based ink produced by the above method is preferably in the range of 10 mPa·s or more from the viewpoint of preventing the pigment from settling and dispersing appropriately, and 1000 mPa·s or less from the viewpoint of workability during ink production and printing. The above viscosity is measured at 25°C using a B-type viscometer. Viscometers such as those manufactured by Tokimec Co., Ltd. can be used.

<Printed materials>
The printed matter in this embodiment has an ink layer formed on the surface of a substrate using the above-mentioned water-based ink. Depending on the intended printed matter, either the gravure printing method or the flexographic printing method can be used.

Both gravure printing and flexographic printing use a roll-up printing method, allowing for high-speed printing and excellent productivity.

(Gravure printing method)
Gravure printing is a printing method that typically uses a gravure plate with cells (recesses) on the circumferential surface of a cylindrical cylinder to represent pictures and/or letters, fills these cells with ink, and transfers the ink filled in the cells to the print medium by pressing the print medium (substrate) through the gap between the gravure plate and an impression cylinder, thereby reproducing the pictures and/or letters on the print medium.

(Flexographic printing method)
In flexographic printing, ink is supplied from an ink container directly or via an ink supply pump or the like to an anilox roller having an uneven surface. The ink supplied to the anilox roller is transferred to the plate surface by contact with the raised parts of the plate surface, and is then finally transferred to the substrate by contact between the plate surface and the substrate, forming a pattern and/or letters.

<Substrate>
The substrate is a roll with a specified width because it is a winding method. Therefore, it is different from a sheet of paper that is cut off one by one in advance. The width of the substrate is appropriately selected based on the plate width of the printing press to be used and the width of the image (picture) part of the gravure plate. When printing by overlapping multiple colors of ink, the order of printing of the inks is not particularly limited.

(Substrate 1)
The type and thickness of the substrate 1 are not particularly limited, but it is preferably a plastic substrate. Specific examples of the plastic substrate used for the printed matter include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, and polylactic acid; polyamide resins such as nylon 6 and nylon 12; polystyrene resins such as polystyrene, AS resin, and ABS resin, chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride; ethylene-vinyl alcohol copolymer resins; cellophane; paper; metal foils such as aluminum, stainless steel, and iron; or film or sheet-like materials made of composite materials thereof.
Among these, polyolefin resins and/or polyester resins are preferred.

The substrate 1 is preferably treated to facilitate adhesion on the surface to be printed (the surface in contact with the ink layer). Examples of such treatments include corona discharge treatment, ultraviolet/ozone treatment, plasma treatment, oxygen plasma treatment, and primer treatment. For example, corona discharge treatment produces hydroxyl groups, carboxyl groups, carbonyl groups, and the like on the substrate. These functional groups can form hydrogen bonds with the resin in the ink if it has functional groups such as hydroxyl groups.

<Laminate>
The laminate in this embodiment can be obtained by further laminating the ink layer of the printed matter. An anchor coat or adhesive is applied to the ink layer, dried, and then laminated to a substrate 2. The substrate 2 may be the same as or different from the substrate 1, and preferably has thermoplasticity (heat sealability). For example, an unstretched polyolefin substrate may be used.
In the laminate, the ink layer made of the water-based ink is positioned as an intermediate layer (for example, substrate 1/ink layer/adhesive layer/substrate 2).

The lamination method is preferably a non-sol lamination method, a dry lamination method, an extrusion lamination method, etc. Among them, lamination by the non-sol lamination method is preferable.

(Non-sol lamination method)
The non-solvent lamination method is a method in which a solvent-free adhesive is applied onto the ink layer of the obtained print, and then laminated by pressing with a sealant substrate. The most common adhesive is a two-part type consisting of polyol/isocyanate, and specific examples of suitable adhesives include EA-N373A/EA-N373B manufactured by Toyo-Morton Co., Ltd.

(Dry lamination method)
The dry lamination method is a method in which an adhesive is diluted to an appropriate viscosity with an organic solvent, applied onto the ink layer of the resulting printed matter, dried, and then laminated by pressure bonding with a sealant substrate. The most common adhesive is a two-liquid type of polyol/isocyanate, and specific examples include TM-250HV/CAT-RT86L-60, TM-550/CAT-RT37, and TM-314/CAT-14B manufactured by Toyo-Morton Co., Ltd.

(Extrusion lamination method)
The extrusion lamination method is a method in which a thermoplastic resin is melted and extruded into a film from a slit-shaped die called a T-die onto the ink layer side of the obtained print, and then laminated onto a substrate. An anchor coating agent is often applied to the ink layer side of the print before lamination. It is also possible to extrude molten resin onto the ink layer of the print, and then attach a sealant substrate from a separate unwinder. Anchor coating agents include imine-based, butadiene-based,
Isocyanate-based anchor coating agents can be used. Specific examples of suitable agents include EL-420 (imine-based), EL-452 (butadiene-based), EL-530A/B (isocyanate-based), and EL-540/CAT-RT32 (isocyanate-based), all manufactured by Toyo-Morton Co., Ltd. As the molten resin, low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and the like can be used. Specific examples of suitable agents include Novatec LD LC600A (low-density polyethylene), all manufactured by Japan Polyethylene Corporation.

The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the scope of the invention. In the examples, "parts" means "parts by mass" and "%" means "% by mass."

<Mass average molecular weight, number average molecular weight>
The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) and calculated using polystyrene as a standard. The measurement conditions are shown below.
GPC device: Showa Denko Shodex GPC-104
Columns: The following columns were used in series connection:
Showa Denko Shodex LF-404 x 2 Showa Denko Shodex LF-G x 2
Detector: RI (differential refractometer)
Measurement conditions: column temperature 40°C
Eluent: tetrahydrofuran Flow rate: 0.3 mL/min

<Acid value>
It was determined according to the method described in JIS K0070.

[Synthesis Example 1-1] (Synthesis of polyester polyol A1)
A round-bottom flask equipped with a stirrer, a thermometer, a water divider, and a nitrogen gas inlet tube was charged with 25 parts of neopentyl glycol (NPG), 20 parts of 1,3-propanediol (1,3-PD), 55 parts of adipic acid, and 0.002 parts of tetrabutyl titanate, and esterification was carried out for 8 hours at 230° C. under a nitrogen stream while removing water generated by condensation. After confirming that the acid value of the polyester was 15 or less, the degree of vacuum was gradually increased with a vacuum pump to terminate the reaction. This produced a polyester polyol (A1) with a number average molecular weight of 2000 and an acid value of 0.3 mgKOH/g.

[Synthesis Examples 1-2 to 1-8] (Synthesis of Polyester Polyols A2 to A8)
Polyester polyols A2 to A8 were obtained in the same manner as in Synthesis Example 1-1, except that the raw materials and charging ratios shown in Table 1 were used. The abbreviations for the raw materials shown in the table are as follows.
Bio-succinic acid: succinic acid (derived from biomass, biomass content 100%)
NPG: Neopentyl glycol 1,3-PD: 1,3-propanediol Bio-NPG: Neopentyl glycol (derived from biomass, biomass content 100%)

[Synthesis Example 2-1] (Synthesis of Water-Based Urethane Resin PU01)
In a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube, a stirrer, and a thermometer, 275.0 parts of polyester polyol (A1), 35.0 parts of 2,2-dimethylol butanoic acid (DMBA), and 250 parts of methyl ethyl ketone (MEK) were mixed and stirred while dropping 72.0 parts of isophorone diisocyanate (IPDI) over 1 hour, and reacted at 80 ° C. for 4 hours to obtain a terminal isocyanate prepolymer, and a terminal isocyanate prepolymer solution was obtained. A mixture of 3.0 parts of 2-aminoethylethanolamine (AEA) and 150 parts of isopropanol (IPA) was gradually added at room temperature to the obtained terminal isocyanate prepolymer, and reacted at 40 ° C. for 2 hours to obtain a solvent-based polyurethane resin solution. Next, 15.0 parts of 28% ammonia water and 800.0 parts of ion-exchanged water were gradually added to the above-mentioned solvent-based polyurethane resin solution to neutralize it and make it water-soluble, and then 0.5 parts of an antifoaming agent was added, and MEK and IPA were distilled off under reduced pressure, and water was added to adjust the solid content, thereby obtaining an aqueous urethane resin PU01 solution with a solid content of 30%. The acid value and mass average molecular weight of the aqueous urethane resin PU01 are shown in Table 2.

[Synthesis Examples 2-2 to 2-14] (Synthesis of Polyurethane Resins PU02 to P14)
Aqueous urethane resins PU02 to PU14 were obtained in the same manner as in Synthesis Example 2-1, except that the raw materials and their charging ratios shown in Table 2 were used.
The abbreviations in the table stand for the following:
PTMG: Polytetramethylene glycol (number average molecular weight 2000)
PEG: polyethylene glycol (number average molecular weight 2000)
PPG: Polypropylene glycol (number average molecular weight 2000)
PPD: Polytrimethylene glycol (number average molecular weight 2000)
Bio-PTMG: Polytetramethylene glycol (number average molecular weight 2000, biomass-derived, biomass content 100%)
C-2090: MPD/HD/PC polycarbonate polyol (number average molecular weight 2000) manufactured by Kuraray

(Example 1) Production of water-based ink (INK1) and creation of printed matter (gravure printing)
Pigment [Toyo Color Co., Ltd. indigo pigment C.I. Pigment Blue 15:3] 30.0 parts, aqueous urethane resin (PU01) of Synthesis Example 1 35.0 parts, rosin resin-1 (rosin resin emulsion softening point 100 ° C., hydroxyl value 0 mg KOH / g, acid value 120 mg KOH / g, solid content 50 mass%) 8.0 parts, ion-exchanged water 19.0 parts, acetylene glycol surfactant [Surfynol 420 Nissin Chemical Industry Co., Ltd.] 0.4 parts, adipic acid hydrazide 0.3 parts, isopropanol 2.0 parts were added, and the mixture was stirred with a stirrer for 10 minutes, and then dispersed for 10 minutes using a bead mill dispersing machine Eiger Mill (Eiger Co., Ltd. Bead Mill) to obtain a pigment dispersion. To the pigment dispersion, 3.0 parts of Chemipearl W500 (solid content 40.0%) manufactured by Mitsui Chemicals, Inc. and 2.0 parts of 28% by mass ammonia water were added, and the mixture was kneaded to obtain the target water-based ink (INK1).

The ink INK1 obtained above was adjusted to 16 seconds using a Zahn cup #3 (Rigo Co., Ltd.) with a water/n-propanol mixed solvent (mass ratio 1/1), and printed on substrate 1 (polyethylene terephthalate substrate (PET) E5100, film thickness 12 μm) at a speed of 50 m/min using a gravure printing machine manufactured by Iwase Printing Machine Co., Ltd. to obtain a printout of 2000 m. The plate used was a corrosion 250 line plate with a depth of 15 μm solid plate.

(Examples 2 to 25 and Comparative Examples 1 to 6) Production of water-based inks (INK2 to 31) and creation of printed matter Except for using the raw materials and ratios shown in Tables 3 and 4, the same method as in Example 1 above was used. Dispersion treatment was carried out for 10 minutes using an Eiger mill (a bead mill manufactured by Eiger Co., Ltd.) to produce inks INK2 to 31 of Examples 2 to 25 and Comparative Examples 1 to 6. Printing was carried out using a gravure printing machine to obtain printed matters.

(Example 26) (Flexographic printing)
The above water-based ink (INK1) was printed on a substrate 1 (polyethylene terephthalate substrate (PET) E5100, film thickness 12 μm) at a speed of 300 m/ ^min for 2000 m using a flexographic printing machine (MIRAFLEX CM) equipped with a flexographic plate (photosensitive resin plate, KODAK Corporation, FLEXCEL NXH digital flexographic plate, plate thickness 1.14 mm, plate ruling 150 lpi) and an anilox roll (900 lpi, 3 cc/m2), to obtain a print.

(Examples 1 to 26 and Comparative Examples 1 to 6) Preparation of packaging bag using laminate TM250-HV manufactured by Toyo-Morton Co., Ltd. was applied as a urethane adhesive at 2 g/m2 onto the ink layer of the printed matter obtained ^above , and laminated with an aluminum foil substrate (manufactured by Toyo Aluminium Co., Ltd., film thickness 7 μm), and then laminated with ZK-207 (manufactured by Toray Industries, Inc., unoriented polypropylene (CPP) substrate, film thickness 60 μm) to obtain a laminate. This laminate was heat-sealed at the edges of the CPP surfaces at 190°C to form a bag, and a packaging bag was obtained. The content was water. A retort resistance test was performed using this packaging bag.
The abbreviations in the table stand for the following:
Rosin resin-1: Emulsion type rosin resin, softening point 100°C, hydroxyl value 0 mgKOH/g, acid value 120 mgKOH/g, solid content 50% by mass
Rosin resin-2: rosin modified maleic resin ammonium salt (water-soluble rosin resin) softening point 100°C, hydroxyl value 0 mgKOH/g, acid value 140 mgKOH/g, solid content 30% by mass
Rosin resin-3: Emulsion type rosin resin, softening point 100°C, hydroxyl value 0 mgKOH/g, acid value 10 mgKOH/g, solid content 50% by mass
Rosin resin-4: Emulsion type rosin resin, softening point 100°C, hydroxyl value 0 mgKOH/g, acid value 260 mgKOH/g, solid content 50% by mass
Rosin resin-5: Maleic acid rosin (not water-soluble rosin resin or emulsion-type rosin resin) Softening point 145°C, hydroxyl value 0 mgKOH/g, acid value 20 mgKOH/g, solid content 50% by mass
Rosin resin-6: Emulsion type rosin resin, softening point 100°C, hydroxyl value 0 mgKOH/g, acid value 5 mgKOH/g, solid content 50% by mass
Rosin resin-7: Emulsion type rosin resin, softening point 100°C, hydroxyl value 0 mgKOH/g, acid value 300 mgKOH/g, solid content 50% by mass
TIPAKEC CR80: Ishihara Sangyo Kaisha, Ltd. Titanium oxide Surfynol 420: Nissin Chemical Industry Co., Ltd. Acetylene glycol surfactant HLB value 4 Solid content 100% by mass
Surfynol SE-F: Acetylene glycol surfactant manufactured by Nissin Chemical Industry Co., Ltd. HLB value: 6 Solid content: 81% by mass
Surfynol 485: Acetylene glycol surfactant manufactured by Nissin Chemical Industry Co., Ltd. HLB value: 17 Solid content: 100% by mass
BYK333: Silicone surfactant manufactured by BYK-Chemie

The printed matter and packaging bags made of laminates using the water-based inks of Examples 1 to 26 and Comparative Examples 1 to 6 were evaluated for pigment dispersibility, ink stability, printing effect, and retort resistance using the methods described below.

[Pigment dispersibility]
The particle size distribution of the water-based ink obtained above was measured using a Microtrac MT-3000 (laser diffraction type particle size distribution measuring device) manufactured by Nikkiso Co., Ltd. The sample solution was diluted by sample loading so that the DV value (a concentration index using the integrated value of the scattered light amount from the sample received by the detector) was within an appropriate range, and then measured. The evaluation criteria are as follows.
[In the case of water-based inks containing indigo pigments]
A: The median diameter d50 is less than 300 nm. (Excellent)
B: Median diameter d50 is 300 nm or more and less than 500 nm (usable)
C: Median diameter d50 is 500 nm or more and less than 1000 nm. D: Median diameter d50 is 1000 nm or more (poor).
The smaller the d50, the better the pigment dispersibility is, and the practical level is rated as A to C.
[In the case of water-based inks containing white pigments]
A: Median diameter d50 is less than 500 nm (excellent)
B: Median diameter d50 is 500 nm or more and less than 1000 nm (good)
C: Median diameter d50 is 1000 nm or more and less than 1500 nm (usable)
D: Median diameter d50 is 1500 nm or more (poor)

[Ink stability]
The water-based ink obtained above was placed in a 100 ml bottle, capped, and allowed to stand at 40° C. for 5 days. The viscosity of the ink at the time of initial preparation was then compared with the viscosity after standing at 25° C., and the degree of viscosity increase was evaluated based on the difference in Zahn cup #4 outflow time. The evaluation criteria were as follows:
A: The ink viscosity change is less than 2 seconds using Zahn cup #4 (excellent)
B: The ink viscosity change is 2 seconds or more but less than 4 seconds using Zahn cup #4 (good)
C: Ink viscosity change is 4 seconds or more but less than 8 seconds using Zahn cup #4 (usable)
D: The ink viscosity change is 8 seconds or more using Zahn cup #4 (poor)
The practical level is rated as A to C.

[Printing effect] (leveling)
The leveling property of the printed matter obtained above was evaluated according to the following criteria.
A: No unevenness even when 100% halftone dot is held up to fluorescent light (Excellent)
B: There is unevenness visible through a fluorescent lamp in the 100% halftone dot area (good)
C: There are gaps up to 90% of the dots, and the solid formation is insufficient. The 100% dots are solid (usable).
D: There are defects in the 100% halftone dot area, and the solid formation is insufficient (poor)
The practical level is rated as A to C.

[Retort resistance]
A retort test was carried out at 120°C for 80 minutes for packaging bags using the laminates obtained in the above Examples and Comparative Examples, and the laminate strength immediately after retort was compared with the laminate strength before the retort test. Regarding the laminate strength, the laminate was cut to a width of 15 mm, and the ink layer and the substrate 2 were peeled off from each other, and the peel strength was evaluated using an Intesco 201 universal tensile tester. The evaluation criteria were as follows:
A: No decrease in peel strength was observed before and after retort, and the peel strength after retort was 2.0 N/15 mm or more (excellent)
B: A decrease in peel strength of less than 1.0 N/15 mm was observed before and after retort, and the peel strength after retort was 2.0 N/15 mm or more (good)
C: A decrease in peel strength of 1.0 N/15 mm or more was observed before and after retort, and the peel strength after retort was 1.0 N/15 mm or more and less than 2.0 N/15 mm (usable)
D: A decrease in peel strength of 1.0 N/15 mm or more was observed before and after retort, and the peel strength after retort was less than 1.0 N/15 mm (defective)
The practical level is rated as A to C.

<Evaluation Results>
As shown in Table 3, the examples provided water-based inks that were all at practical levels in terms of pigment dispersibility, ink stability, printing effect, and retort resistance. On the other hand, as shown in Table 4, the water-based inks of the comparative examples did not meet practical levels in any one or more of pigment dispersibility, ink stability, printing effect, and retort resistance.

Claims (10)

A water-based ink for plastic substrates , comprising a pigment, a water-based urethane resin, a rosin-based resin, a hydrazide-based additive, and an acetylene glycol-based surfactant,
The acid value of the rosin-based resin is 10 to 280 mgKOH/g.
Water-based ink for plastic substrates . The water-based ink for plastic substrates according to claim 1, which is for flexographic printing or gravure printing. The water-based ink for plastic substrates according to claim 1 or 2, which is for lamination. The water-based ink for plastic substrates according to claim 1 or 2, wherein the content of the acetylene glycol surfactant is 0.1 to 5 mass% based on the total mass of the water-based ink for plastic substrates . 3. The water-based ink for plastic substrates according to claim 1, wherein the rosin-based resin comprises a water-soluble rosin resin and/or an emulsion-type rosin resin. 3. The water-based ink for plastic substrates according to claim 1, wherein the water-based urethane resin contains structural units derived from a polyether polyol and/or structural units derived from a polyester polyol. The aqueous urethane resin contains a structural unit derived from a polyether polyol,
The water-based ink for plastic substrates according to claim 6 , wherein the polyether polyol contains at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. The aqueous urethane resin contains a structural unit derived from a polyester polyol,
The polyester polyol contains a structural unit derived from a dibasic acid, and the dibasic acid contains at least one selected from the group consisting of sebacic acid, adipic acid, succinic acid, azelaic acid, and dimer acid.
The water-based ink for plastic substrates according to claim 6 . A printed matter comprising a substrate 1 and an ink layer made of the water-based ink for plastic substrates according to claim 1 or 2. 3. A laminate comprising: a substrate 1; an ink layer comprising the water-based ink for plastic substrates according to claim 1 or 2; and a substrate 2, in this order.