Water-based flexographic inks, printed materials and laminates

Abstract

The object of the present invention is to provide an aqueous flexographic ink that achieves a balance of long-term stability, color density, leveling properties, and retort resistance. [Solution] The above problem is solved by providing a heat-resistant organic pigment, a binder resin, and water, wherein the bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3 The above is a water-based flexographic ink, or one containing a heat-resistant organic pigment, a binder resin, and water, wherein the bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3 The above problem can be solved with water-based flexographic ink that is resistant to retort processing.

Description

[Technical Field]

[0001] This invention relates to a water-based flexographic ink. It also relates to a method for producing a water-based flexographic ink. [Background technology]

[0002] In recent years, the shift from organic solvent-based inks to water-based inks has been proposed as a means of addressing challenges related to reducing environmental impact, legal regulations, and safety. Using water-based inks offers advantages in addressing these issues, such as reducing organic solvent emissions, preventing solvent fires, and reducing residual solvents in packaging materials. Flexographic printing, in particular, is a useful printing method for water-based inks because it offers excellent high-speed printing capabilities and, as a relief printing method, can reproduce fine characters and sharp details even with small amounts of ink transfer.

[0003] With the aim of adding aesthetic appeal and functionality to packaging materials, efforts are being made to improve their performance, and consequently, the requirements for printing inks are becoming more diverse year by year. In particular, when inks are used in packaging materials, especially food packaging, the ink is printed onto a substrate such as a plastic film to obtain a printed material, and then the resulting printed material is laminated by bonding it with another plastic film. The substrate such as the plastic film and the lamination configuration are appropriately selected from a variety of types depending on the contents of the package and its intended use, so there is a need to select an ink with high performance (substrate adhesion, substrate transferability, laminate strength, heat resistance, retort resistance, etc.). Conventional water-based inks often do not have sufficient resistance to the demanding conditions of packaging materials, such as high temperature and humid heat (pressure) treatment, which puts a heavy load on the printed material, and there are many remaining challenges.

[0004] Furthermore, conventional heat-resistant organic pigments used in inks for retort packaging materials are less soluble in pigment than general organic pigments. When these pigments are used in inks, the ink tends to deteriorate easily, often resulting in insufficient stability over time and poor printability.

[0005] Patent Document 1 describes the invention of an aqueous liquid ink in which a urethane resin having an acidic group is neutralized with basic compounds such as basic metal compounds and organic amines, and that it possesses substrate adhesion, blocking resistance, water resistance, and solvent resistance. However, there is no description of printability or the ink's stability over time, raising concerns about its basic performance as an aqueous ink.

[0006] Patent Document 2 describes the development of a laminate with retort resistance using a liquid ink for flexographic printing. However, there is no description of printability or the long-term stability of the ink, raising concerns about its basic performance as a water-based ink.

[0007] Therefore, a water-based flexographic ink that satisfies the requirements for long-term stability, color density, leveling properties, and retort resistance has yet to be invented. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2019 / 102855 [Patent Document 2] Japanese Patent Publication No. 2023-158504 [Overview of the project] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide an aqueous flexographic ink that achieves a balance of long-term stability, color density, leveling properties, and retort resistance. [Means for solving the problem]

[0010] As a result of diligent research into the aforementioned problems, the inventors have found that all of the aforementioned problems can be solved by the aqueous flexographic ink described below, and have thus come to the present invention.

[0011] An aqueous flexographic ink containing a heat-resistant organic pigment, a binder resin and water, wherein the bulk density of the heat-resistant organic pigment is 0.15 g / cm 3 or more.

[0012] The aqueous flexographic ink is for retort use.

[0013] The aqueous flexographic ink has a thixotropic index (TI value) of 4 or less.

[0014] Regarding the aqueous flexographic ink, the mass ratio of the mass solid content of the heat-resistant organic pigment to the mass solid content of the binder resin in the total solid content of the aqueous flexographic ink is 35:65 to 75:25.

[0015] Regarding the aqueous flexographic ink, the content of the heat-resistant organic pigment in the total mass of the aqueous flexographic ink is 10 to 30% by mass.

[0016] The binder resin contains at least one selected from the group consisting of an aqueous urethane resin, an aqueous acrylic resin, and an aqueous urethane acrylic resin.

[0017] The heat-resistant organic pigment contains at least one selected from the group consisting of C.I.Pigment Yellow 83, C.I.Pigment Yellow 180, C.I.Pigment Red 146, C.I.Pigment Red 166, C.I.Pigment Red 185, C.I.Pigment Blue 15:3, C.I.Pigment Black 7, C.I.Pigment Orange 34, C.I.Pigment Orange 64, C.I.Pigment Green 7, and C.I.Pigment Violet 23.

[0018] Regarding a printed matter having a printed layer formed from the aqueous flexographic ink on a substrate 1.

[0019] The present invention relates to a laminate having, in sequence, a substrate 1, a printed layer formed from the aqueous flexographic ink, and a substrate 2.

[0020] A method for producing an aqueous flexographic ink containing a heat-resistant organic pigment, a binder resin, and water, The process includes a step of mixing and dispersing the heat-resistant organic pigment and the binder resin, The bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3 The above relates to a method for manufacturing water-based flexographic ink. [Effects of the Invention]

[0021] This invention makes it possible to provide a water-based flexographic ink that achieves a balance of long-term stability, color density, leveling properties, and retort resistance. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is just one example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist of the invention.

[0023] Hereinafter, water-based flexographic ink may be abbreviated as simply "water-based ink" or "ink," but these terms are synonymous. In this specification, "solids" refers to the total mass of non-volatile components in the total mass of water-based flexographic ink.

[0024] The present invention comprises a heat-resistant organic pigment, a binder resin, and water, wherein the bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3 That concludes the discussion regarding water-based flexographic inks.

[0025] (Water-based flexographic ink) The aqueous flexographic ink of the present invention comprises a heat-resistant organic pigment, a binder resin, and water, wherein the bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3 That concludes the explanation. The bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3As a result of the above, the wettability of the binder resin to the heat-resistant organic pigment is improved. Improved wettability leads to better pigment dispersion in the aqueous flexographic ink, improving the long-term stability of the aqueous flexographic ink and the substrate transfer properties of printed materials produced using the aqueous flexographic ink. Furthermore, by using a heat-resistant organic pigment, the ink possesses not only basic physical properties such as the long-term stability of the ink, the substrate transfer properties of printed materials, color density, and leveling properties, but also the retort resistance described below, which requires high resistance. In addition, the aqueous flexographic ink of the present invention includes a heat-resistant organic pigment and at least one binder resin selected from the group consisting of aqueous urethane resin, aqueous acrylic resin, and aqueous urethane acrylic resin. This combination results in good wettability, and further effects of the present invention such as long-term stability and leveling properties can be obtained. It should be noted that this discussion is based solely on speculation and does not limit the invention in any way.

[0026] (For use in retort pouches) The present invention's ink is preferably provided in an embodiment suitable for retort processing. This is because the combination of heat-resistant pigment and binder resin described below satisfies retort resistance (heat resistance) in addition to the storage stability of the ink. Retort resistance, as used here, refers to a usage scenario in which the ink can withstand a temperature range of 100 to 135°C and a processing time of 5 to 80 minutes, for example, in a packaging bag having a printed layer.

[0027] (Heat-resistant organic pigments) The aqueous flexographic ink of the present invention contains a heat-resistant organic pigment of the above bulk density. The heat-resistant organic pigment in the present invention refers to an organic pigment or carbon black that does not deteriorate or fade when heated at 120°C for 30 minutes. The method for confirming "deterioration or fading" can be, for example, by creating a packaging bag using the ink containing the pigment and visually comparing the bag before retort treatment and after retort treatment such as 120°C for 30 minutes to confirm whether deterioration or fading has occurred. Examples of the heat-resistant organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, hansa yellow, benzidine yellow, and pyrazolone red; derivatives from vat dyes such as alizarin, indanthron, and thioindigo maroon; phthalocyanine-based organic pigments such as phthalocyanine blue and phthalocyanine green; quinacridone-based organic pigments such as quinacridone red and quinacridone magenta; perylene-based organic pigments such as perylene red and perylene scarlet; and isoindolinone yellow and isoindolinone orange. In this invention, organic pigments such as dorinone-based organic pigments, pyranthrone-based organic pigments such as pyranthrone red and pyranthrone orange, thioindigo-based organic pigments, condensed azo-based organic pigments, benzimidazolone-based organic pigments, quinophthalone-based organic pigments such as quinophthalone yellow, isoindoline-based organic pigments such as isoindoline yellow, and other pigments such as chromatic organic pigments like flavanthrone yellow, acylamido yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthaquinonyl red, and dioxazine violet can be used. In this invention, organic pigments or carbon blacks that show deterioration or fading when heated at 120°C for 30 minutes are referred to as general organic pigments.

[0028] From the viewpoint of retort resistance, preferred color index (CI) numbers for heat-resistant organic pigments are CIPigment Yellow 83, CIPigment Yellow 180, CIPigment Red 146, CIPigment Red 166, CIPigment Red 185, CIPigment Blue 15:3, CIPigment Black 7, CIPigment Orange 34, CIPigment Orange 64, CIPigment Green 7, and CIPigment Violet 23. It is preferable that at least one selected from the group consisting of the above CI numbers be included, and among these, CIPigment Yellow 83, CIPigment Yellow 180, CIPigment Red 146, CIPigment Red 166, CIPigment Red 185, CIPigment Black 7, CIPigment Orange 34, CIPigment Orange 64, CIPigment Green 7, and CIPigment Violet 23. It is more preferable to include at least one selected from the group consisting of 23.

[0029] (Bulk density) The heat-resistant organic pigment contained in the aqueous flexographic ink of the present invention has a bulk density of 0.15 g / cm³. 3 The above are heat-resistant organic pigments. In this invention, bulk density refers to the loose bulk density when sparsely packed, and is the mass of pigment per unit bulk volume including voids. The bulk density mentioned above, that is, the loose bulk density when loosely packed, can be measured, for example, by the following method. First, the pigment is poured into a container with a predetermined capacity and an open top until it overflows due to free fall, and the raised pigment on the top surface is leveled off with a leveling plate, and the mass of the pigment is measured. (When measuring the mass, no actions are taken to reduce the voids in the pigment, such as compression or vibration of the measuring container.) Next, the bulk density is obtained by dividing the obtained mass of pigment by the volume of the container. More specifically, a 200 ml disposable cup (volume 331.88 cm³) 3Put the pigment into by free fall, scrape off the raised pigment on the upper end surface with a leveling plate, and measure the mass of the pigment. The mass of the obtained pigment is obtained by dividing it by the volume (331.88 cm 3 ) of a 200 ml disposable cup. The volume of the 200 ml disposable cup was the value confirmed by the weight of water. The bulk density is highly related to the particle diameter and particle shape of the pigment particles. Even for heat-resistant organic pigments with the same Color Index (C.I.) number, the bulk density has different values for each product. Therefore, using the bulk density value evaluated by the above method for commercially available heat-resistant organic pigment products, the heat-resistant organic pigment of the present invention having a bulk density of 0.15 g / cm 3 or more can be selected.

[0030] From the viewpoints of improving the wettability of the binder resin to the heat-resistant organic pigment and improving the stability over time and leveling property due to the improvement of the pigment dispersibility in the aqueous flexographic ink, the bulk density of the heat-resistant organic pigment is preferably 0.15 g / cm 3 or more, more preferably 0.17 g / cm 3 or more, and even more preferably 0.20 g / cm 3 or more. Also, the upper limit value of the bulk density is preferably 0.7 g / cm 3 or less, more preferably 0.6 g / cm 3 or less, and even more preferably 0.5 g / cm 3 or less.

[0031] The mass ratio of the mass solid content of the heat-resistant organic pigment and the binder resin in the total solid content of the aqueous flexographic ink is preferably 35:65 to 75:25, more preferably 37:63 to 70:30, and even more preferably 40:60 to 65:35. By adjusting to the above range, the retort resistance and leveling property tend to be improved. Also, from the viewpoint of color density, the content of the heat-resistant organic pigment in the total mass of the aqueous flexographic ink is preferably 10 to 30% by mass, more preferably 12 to 28% by mass, and even more preferably 15 to 25% by mass. In particular, when it is 16% by mass or more, the color density tends to be improved.

[0032] (TI value) The thixotropic index (TI value) is the ratio of viscosity values ​​measured at two different rotational speeds and is widely used to evaluate the non-Newtonian properties of liquid fluid flow characteristics. A TI value closer to 1 indicates a fluid closer to a Newtonian fluid, while a larger TI value indicates a more thixotropic fluid. In this invention, the thixotropic index (TI value) is the value obtained by dividing the viscosity (mPa·s) at 6 rpm measured for ink at a liquid temperature of 25°C using a B-type viscometer by the viscosity (mPa·s) at 60 rpm measured for the same ink at 25°C. The thixotropic index (TI value) of water-based ink can be adjusted by selecting the dispersibility of the pigment, the type of water-based binder resin, additives, and appropriate solvents. In this invention, the TI value can be adjusted by selecting appropriate heat-resistant organic pigments and binder resins. Specifically, the bulk density of the water-based flexographic ink is 0.15 g / cm³. 3 By setting the mass ratio of the heat-resistant organic pigment to the binder resin within the range of 35:65 to 75:25, the TI value of the water-based flexographic ink can be adjusted to an appropriate range. In addition, the binder resin contained in the water-based flexographic ink is a water-based resin with an acid value and a bulk density of 0.15 g / cm³. 3 More than 0.7g / cm 3 One possible method is to use the following heat-resistant organic pigments in a mass ratio ranging from 35:65 to 75:25.

[0033] The aqueous flexographic ink of the present invention preferably has a TI value of 4 or less, more preferably 3.5 or less, and even more preferably 3 or less, as measured by a B-type viscometer. Furthermore, the lower limit of the TI value is preferably 1 or more. When the TI value is within the above range, the stability over time is improved and the ink transfer properties are excellent, which tends to improve the color density.

[0034] (Binder resin) The aqueous flexographic ink of the present invention contains a binder resin. In the present invention, the binder resin refers to the binding resin contained in the ink. An aqueous resin can be suitably used as the binder resin, and the aqueous resin preferably contains a water-soluble resin and / or an emulsion resin, which may be used alone or in mixtures. From the viewpoint of long-term stability, the binder resin preferably contains at least one selected from the group consisting of aqueous urethane resin, aqueous acrylic resin, and aqueous urethane acrylic resin. In particular, it is more preferable to include an aqueous urethane resin because it tends to improve retort resistance. From the viewpoint of retort resistance, the total solid content of the binder resin in the total mass of the aqueous flexographic ink is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more. Furthermore, the total solid content of the binder resin in the total mass of the aqueous flexographic ink is preferably 50% by mass or less.

[0035] The binder resin preferably has acidic groups, and in that case, the acid value is preferably 1 to 300 mg KOH / g, more preferably 5 to 250 mg KOH / g, and even more preferably 10 to 200 mg KOH / g. When the binder resin has acidic groups and its acid value is within the above range, the combination with the specified heat-resistant organic pigment provides good stability over time and leveling properties. The acid value is calculated by titrating the acid with an alkali and converting the amount of acid in 1 g of resin to the number of mg of potassium hydroxide, and is measured according to JIS K0070.

[0036] In addition to the above, it is also preferable to use a combination of the above binder resins, either individually or in combination with others, from aqueous styrene-acrylic acid copolymer resin, aqueous styrene-maleic acid copolymer resin, aqueous ethylene-acrylic acid copolymer resin, aqueous polyester resin, aqueous shellac, aqueous rosin-modified maleic acid resin, aqueous vinyl chloride-vinyl acetate copolymer resin, aqueous vinyl chloride-acrylic acid copolymer resin, aqueous chlorinated polypropylene resin, aqueous hydroxyethyl cellulose resin, aqueous hydroxypropyl cellulose resin, aqueous butyral resin, etc., as the binder resin.

[0037] (Water-based urethane resin) The aqueous urethane resin is preferably in the form of a polyurethane resin synthesized from a polyol and a polyisocyanate, or in the form of a polyurethane resin containing polyurethane urea obtained by reacting (chain extension) a urethane prepolymer with isocyanate groups at the ends, synthesized from a polyol and a polyisocyanate, with a diamine or other amines. The introduction of urea bonds tends to improve the cohesive strength of the aqueous urethane resin. The aqueous urethane resin of the present invention does not contain any structural units derived from acrylic monomers. Furthermore, the aqueous urethane resin is preferably end-containing with a hydroxyl group. When the binder resin contains aqueous urethane resin, it is preferably contained in the total mass of the aqueous flexographic ink at 1 to 30% by mass, more preferably at 3 to 25% by mass, and even more preferably at 5 to 20% by mass. When the content of aqueous urethane resin is within the above range, the retortability tends to improve.

[0038] (Polyol) The polyols are not limited to the following, but examples of suitable polyols include polyester polyols, polyether polyols, polylactone polyols, polycarbonate polyols, polyolefin polyols, dimer ols, and hydrogenated dimer ols. These polyols may be used individually or in combination of two or more. In particular, it is preferable to contain a structural unit consisting of at least one polyol selected from polyester polyols, polyether polyols, and polycarbonate polyols. It is also preferable to contain a structural unit derived from a polyol having a carboxyl group, and it may also contain structural units derived from other polyols. The number average molecular weight of the polyol is preferably 500 to 5000. The content of the polyol-derived structural unit is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass, based on the total mass solids of the aqueous urethane resin.

[0039] (Polyester polyol) The polyester polyol is preferably in a form having a constituent unit consisting of a dibasic acid and a diol. The dibasic acid is preferably a polycarboxylic acid such as adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, superiic acid, azelaic acid, sebacic acid, trimellitic acid, pyromellitic acid, or their anhydrides. In particular, it is preferable to contain at least one selected from the group consisting of adipic acid, succinic acid, sebacic acid, azelaic acid, and dimer acid. When the polyol contains polyester polyol, it is preferable that the total solid content of the aqueous urethane resin contains 20 to 80% by mass of polyester polyol, more preferably 30 to 70% by mass, and even more preferably 40 to 60% by mass. When the polyester polyol content is within the above range, the retortability tends to improve.

[0040] (Diol) The diol preferably includes branched diols, and preferably includes both branched and linear diols. Here, a linear diol is a diol having a linear structure of two or more carbon atoms, and includes alkylene glycols, dialkylene glycols, trialkylene glycols, and other diols. A branched diol is a diol in which at least one hydrogen atom of the hydrocarbon group of an alkylene glycol is substituted with an atom other than a hydrogen atom.

[0041] Examples of branched diols 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 (also referred to as MPD), neopentyl glycol (also referred to as NPG), 1,2-propylene glycol (also referred to as PG), 2,4-diethyl-1,5-pentanediol, 1,3-butanediol, and dipropylene glycol. Among these, MPD and NPG are preferred.

[0042] 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, triethylene glycol, and the like. Among these, linear diols having 8 or fewer carbon atoms, preferably 6 or fewer 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.

[0043] The mass ratio (branched diol:linear diol) of branched diols to linear diols in the diol contained in the polyester polyol is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0044] (Polyether polyol) Suitable examples of the above-mentioned polyether polyols include polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, and copolymers thereof. Polyethylene glycol and polytetramethylene glycol are particularly preferred. When the polyol contains a polyether polyol, it is preferable that the total solid content of the aqueous urethane resin contains 1 to 20% by mass of the polyether polyol, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass. When the polyether polyol content is within the above range, the retortability tends to improve.

[0045] (Polycarbonate polyol) The polycarbonate polyol is not limited by its manufacturing method or the type of diol that constitutes it, but a polycondensate product obtained by transesterification of a diol made of alkylene glycol and a carbonate compound is preferred. The polycarbonate polyol is preferably an alicyclic and / or aliphatic polycarbonate diol. The diols constituting the polycarbonate polyol can be those previously exemplified as constituent units of polyester polyols, and can be used individually or in combination of two or more. In particular, a polycarbonate polyol having a branched diol structure, such as 3-methyl-1,5-pentanediol, is preferred. When the polyol contains polycarbonate polyol, it is preferably present in 20-80% by mass, more preferably 30-70% by mass, and even more preferably 40-60% by mass, in the total solid content of the aqueous urethane resin. When the polycarbonate polyol content is within the above range, retort resistance tends to improve.

[0046] The carbonate compound is not particularly limited, but examples include dialkyl carbonates, diaryl carbonates, or alkylene carbonates. Specific examples of carbonate compounds include dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and dibutyl carbonate; diaryl carbonates such as diphenyl carbonate; and alkylene carbonates such as ethylene carbonate.

[0047] (Polyisocyanate) Suitable polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. These may also be in the form of trimers with an isocyanurate ring structure. Examples of aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyli isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, and tolylene diisocyanate. Examples of aliphatic diisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, m-tetramethylxylylene diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, and dimer diisocyanate obtained by converting the carboxyl group of a dimer acid to an isocyanate group. Preferably, the polyisocyanate is selected from tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, and trimers of hexamethylene diisocyanate. These polyisocyanates can be used individually or in combination of two or more.

[0048] To dissolve or disperse an aqueous urethane resin in an aqueous medium, it is preferable to make it aqueous by introducing hydrophilic groups into the main chain or side chains of the aqueous urethane resin. As a method of making it aqueous, it is also preferable to introduce ionic groups such as carboxyl groups and sulfone groups into the main chain or side chains of the aqueous urethane resin by using a polyol having ionic groups such as carboxyl groups and sulfone groups when reacting a polyol with a polyisocyanate. In particular, from the viewpoint of water resistance, carboxyl groups are preferred as ionic groups, and it is preferable that these carboxyl groups are neutralized with a basic compound.

[0049] (Polyols containing carboxyl groups) Polyols having carboxyl groups are not limited to the following, but suitable examples include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid. These can be used individually or in combination of two or more. By using polyols having carboxyl groups in the manufacturing process of aqueous urethane resin, the resulting aqueous urethane resin has carboxyl groups in its main chain or side chains and possesses an acid value.

[0050] When the polyol contains a polyol having a carboxyl group, the content of the constituent units derived from the polyol having a carboxyl group is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, and even more preferably 3 to 15% by mass, of the total mass of the aqueous urethane resin, from the viewpoint of stability over time.

[0051] (Polyamines) Water-based urethane resins may also be subjected to chain extension reactions with polyamines. Examples of polyamines include hydrazine, ethylenediamine, propylenediamine, 1,4-tetramethylenediamine, 2-methyl-1,5-pentanediaminehexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, phenylenediamine, tolylenediamine, xylenediamine, adipic acid dihydrazide, isophthalic acid dihydrazide, and other diamines; Diamines having hydroxyl groups, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine; 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; Amino alcohols such as N-(β-aminoethyl)ethanolamine Known chain extenders such as the above can be used. By using monofunctional monoamines or monools in combination, it is also possible to control the molecular weight by halting chain extension. Among these, isophorone diamine and 2-hydroxyethyl ethylenediamine are preferred.

[0052] (Reaction inhibitor) Reaction inhibitors can also be used in combination with polyamines. Examples of such reaction inhibitors include dialkylamines such as di-n-dibutylamine, monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tri(hydroxymethyl)aminomethane, 2-amino-2-ethyl-1,3-propanediol, hydroxyl-containing amines such as N-di-2-hydroxyethylethylenediamine, N-di-2-hydroxyethylpropylenediamine, and N-di-2-hydroxypropylethylenediamine, as well as monoamine-type amino acids such as glycine, alanine, glutamic acid, taurine, aspartic acid, aminobutyric acid, valine, aminocaproic acid, aminobenzoic acid, aminoisophthalic acid, and sulfamic acid.

[0053] (Neutralizing agent) If the aqueous urethane resin has acidic groups, it is preferable to neutralize the acidic groups in the aqueous urethane resin with a basic compound. Examples of basic compounds include sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, ethanolamine, propanolamine, diethanolamine, N-methyldiethanolamine, dimethylamine, diethylamine, triethylamine, N,N-dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, morpholine, etc., and these can be used individually or in combination of two or more. Ammonia is preferred from the viewpoint of water resistance of printed materials and residual odor. Neutralization may be performed before manufacturing the ink, or after manufacturing the ink containing the binder resin, by adding the basic compound as a neutralizing agent to the ink, or both.

[0054] The neutralization rate during the above neutralization process is preferably 100-150% in the ink, and more preferably 110-140%. When the rate is within this range, the printing stability and drying of the printed material are excellent. In this specification, the neutralization rate is a value calculated by [(base equivalent of the basic compound) / (acid equivalent of the binder resin)] × 100.

[0055] The weight-average molecular weight of the aqueous urethane resin is preferably 3,000 to 100,000, more preferably 5,000 to 70,000, and even more preferably 7,000 to 50,000. The hydroxyl value of the aqueous urethane resin is preferably 1 to 50 mg KOH / g, more preferably 10 to 45 mg KOH / g, and even more preferably 15 to 40 mg KOH / g. The hydroxyl value is calculated by esterifying or acetylating the hydroxyl groups in the resin, back titrating the remaining acid with an alkali, and then converting the amount of hydroxyl groups per gram of resin into milligrams of potassium hydroxide.

[0056] (Water-based acrylic resin) The aqueous acrylic resin of the present invention refers to a resin obtained by polymerizing acrylic monomers. The aqueous acrylic resin of the present invention excludes acrylic resins having urethane bonds. In the aqueous acrylic resin, it is preferable that the constituent units derived from acrylic monomers constitute 30% or more of the aqueous acrylic resin solid content. The aqueous acrylic resin in the present invention is preferably a water-soluble acrylic resin and / or an emulsion-type aqueous acrylic resin. When the binder resin contains aqueous acrylic resin, it is preferable that the aqueous acrylic resin solid content be 1 to 30% by mass, more preferably 3 to 25% by mass, and even more preferably 5 to 20% by mass in the total mass of the aqueous flexographic ink. When the content of aqueous acrylic resin is within the above range, the retortability tends to improve. In the following explanation, "(meth)acrylic" refers to the combined use of "acrylic" and "methacrylic".

[0057] (Water-soluble acrylic resin) Water-soluble acrylic resin is an aqueous acrylic resin that has been made solubilized in an aqueous medium by introducing hydrophilic groups.

[0058] Examples of acrylic monomers used in the polymerization of water-soluble acrylic resins include carboxylic acid-containing acrylic monomers such as acrylic acid, methacrylic acid, and crotonic acid; benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol acrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol acrylate, phenoxytetraethylene glycol methacrylate, phenoxyhexaethylene glycol acrylate, phenoxyhexaethylene glycol methacrylate, phenyl acrylate, and phenyl methacrylate, among other aromatic alkyl group-containing acrylic monomers. Furthermore, linear or branched alkyl group-containing acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, etc., and alicyclic alkyl group-containing acrylic monomers such as cyclohexyl (meth)acrylate and isobonyl (meth)acrylate. Fluorinated alkyl group-containing acrylic monomers such as trifluoroethyl (meth)acrylate and heptadecafluorodecyl (meth)acrylate, (meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethyl Methacrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, N,N- amide group-containing acrylic monomers such as dimethylaminopropyl acrylamide, N,N-diethylaminopropyl acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl alcohol, and other hydroxyl group-containing acrylics. Examples of polyethylene oxide group-containing acrylic monomers include polyethylene glycol monoacrylate (manufactured by Nippon Oil & Fats Co., Ltd., such as Bremmer PE-90, 200, 350, 350G, AE-90, 200, 400, etc.), polyethylene glycol / polypropylene glycol monoacrylate (manufactured by Nippon Oil & Fats Co., Ltd., such as Bremmer 50PEP-300, 70PEP-350, etc.), and methoxy polyethylene glycol monoacrylate (manufactured by Nippon Oil & Fats Co., Ltd., such as Bremmer PME-400, 550, 1000, 4000, etc.).

[0059] Water-soluble acrylic resins preferably have acidic groups, and in that case, the acid value is preferably 40 to 260 mg KOH / g, more preferably 60 to 250 mg KOH / g, and even more preferably 100 to 240 mg KOH / g. When water-soluble acrylic resins have acidic groups and their acid value is within the above range, good stability over time is achieved.

[0060] The weight-average molecular weight of the water-soluble acrylic resin is preferably 1,000 to 100,000.

[0061] (Emulsion-type water-based acrylic resin) An emulsion-type aqueous acrylic resin is an aqueous acrylic resin stably dispersed in an aqueous medium using a dispersant or the like. The acrylic monomers and styrene monomers used in the polymerization of the emulsion-type aqueous acrylic resin are preferably the compounds exemplified in the description of the water-soluble acrylic resin above. The emulsion-type aqueous acrylic resin is preferably an emulsion-type aqueous styrene-acrylic resin containing a styrene monomer.

[0062] The emulsion-type aqueous acrylic resin preferably has acidic groups, and in that case, the acid value is preferably 40 to 120 mg KOH / g, more preferably 50 to 110 mg KOH / g, and even more preferably 60 to 100 mg KOH / g. When the emulsion-type aqueous acrylic resin has acidic groups and its acid value is within the above range, it exhibits good stability over time. Furthermore, the weight-average molecular weight (Mw) of the emulsion-type aqueous acrylic resin is preferably between 100,000 and 600,000.

[0063] The average particle size of the emulsion-type aqueous acrylic resin is preferably 60 nm to 1000 nm, and more preferably 60 nm to 400 nm. The average particle size of the emulsion-type aqueous acrylic resin refers to the measurement value obtained by dynamic light scattering.

[0064] (Water-based urethane acrylic resin) Preferred aqueous urethane acrylic resins include core-shell type aqueous urethane acrylic resins, alternating block copolymers of acrylic resin and urethane resin, and graft copolymers in which the main chain is urethane resin and the side chains are acrylic resin or acrylic resin. The mass ratio of urethane resin to acrylic resin in the total mass of the aqueous urethane acrylic resin is preferably 9:1 to 5:5, and more preferably 8:2 to 6:4. Within this range, when the ink of the present invention is used as a coating, the retortability, which is an advantage of each resin, tends to improve.

[0065] When the binder resin contains an aqueous urethane acrylic resin, it is preferable that the total mass of the ink contains 5 to 90% by mass of the aqueous urethane acrylic resin, more preferably 10 to 80% by mass, and even more preferably 20 to 75% by mass. When the content of aqueous urethane acrylic resin is within the above range, the retortability tends to improve.

[0066] A core-shell type aqueous urethane acrylic resin preferably has an acrylic resin portion in the core and a urethane resin portion in the shell. However, the urethane resin portion may be configured as the core and the aqueous acrylic resin portion as the shell.

[0067] (Urethane resin part) The urethane resin portion can be formed by a condensation reaction between a polyol and a polyisocyanate, and it is preferable that it has hydroxyl groups at its ends. Alternatively, the urethane resin portion may be a urethane urea resin portion obtained by a reaction (called chain extension) between a urethane prepolymer having isocyanate groups at its ends, which is a condensation reaction product of a polyol and a polyisocyanate, and a chain extender.

[0068] The weight-average molecular weight of the urethane resin portion is preferably 1,000 to 1,000,000, and more preferably 5,000 to 50,000. The polyol, polyisocyanate, and chain extender used in the synthesis of the aqueous urethane acrylic resin can preferably be those compounds exemplified in the above description of the aqueous urethane resin.

[0069] (Acrylic resin part) The acrylic resin portion contains constituent units derived from acrylic monomers. The monomers exemplified in the above description of aqueous acrylic resins can preferably be used as the monomers constituting the acrylic resin portion.

[0070] The weight-average molecular weight of the acrylic resin portion is preferably 1,000 to 1,000,000.

[0071] (solvent) The aqueous ink of the present invention contains water. Furthermore, the aqueous ink of the present invention more preferably contains an organic solvent, and more preferably contains a glycol-based solvent and / or a glycol ether-based solvent. The aqueous ink tends to have improved leveling properties and transferability when it contains a glycol-based solvent and / or a glycol ether-based solvent.

[0072] Examples of glycol-based solvents include 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. Propylene glycol is particularly preferred.

[0073] Examples of glycol ether solvents include 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.

[0074] The content of glycol-based solvents and / or glycol ether-based solvents is preferably 1 to 20% by mass, more preferably 2 to 18% by mass, and even more preferably 3 to 15% by mass, based on the total mass of the ink.

[0075] The aqueous ink of the present invention preferably contains a hydrophilic solvent in addition to the above-mentioned solvent for the purpose of controlling the leveling properties to the substrate and the color density. From the viewpoint of the ink's leveling properties and drying properties, the content of the hydrophilic solvent is preferably 0.5 to 10% by mass, and more preferably 1 to 5% by mass, of the total mass of the ink.

[0076] 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, which can be used alone or in combination of two or more. Among these, 1-propanol and 2-propanol are preferred.

[0077] (Additives) Suitable additives for use in water-based inks include curing agents, anti-blocking agents, thickeners, rheology modifiers, defoamers, leveling agents, preservatives, surfactants, and polyolefin particles. In particular, hydrazide-based additives are preferred for their ability to adhere to substrates and for their room-temperature crosslinking of resins (in the case of keto groups).

[0078] (Polyolefin particles) The aqueous flexographic ink of the present invention preferably further contains polyolefin particles for the purpose of improving the abrasion resistance of the ink film and improving the drying properties of the aqueous ink. Commercially available polyolefin particles can be used as the polyolefin particles. Examples include Chemipearl W100, W200, W300, W310, W306, W400, W401, W4005, W410, W500, WF640, W700, W800, W900, W950, WH201, and WP100, all manufactured by Mitsui Chemicals, Inc.

[0079] 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 diameter 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 diameter is measured by the Coulter counter method. Polyolefin particles with the above particle diameter and melting point form a strong ink film that blends well with the aqueous urethane resin, promoting improved water resistance and friction resistance.

[0080] The polyolefin particle content is preferably 0.5 to 5% by mass in terms of solid content relative to the total mass of the water-based ink. A content of 0.5% by mass or more improves water-resistant friction, while using a content of 5% by mass or less results in good long-term stability of the water-based ink.

[0081] (Surfactants) In the aqueous flexographic ink of the present invention, it is preferable to use a surfactant to adjust the leveling properties to the substrate. Commercially available surfactants can be used. Examples include, but are not limited to, Surfinol 104E, 104H, 104A, 104PA, 104PG-50, 104, 420, 440, 465, 485, SE, SE-F, PSA-336, 61, 2502, Dynol 604, 607 from Nisshin Chemical Co., Ltd., and BYK-012, 017, 190, 194, 381, 3441, 302, 307, 325, 331, 333, 342, 345, 346, 347, 348, 349, 378, 3455 and Dynwet 800N from Big Chemie Co., Ltd. The surfactant is preferably an acetylene glycol compound, and more preferably an acetylene glycol compound with ethylene oxide added. The amount of surfactant added is preferably 0.1 to 2% by mass of the total mass of the aqueous flexographic ink.

[0082] (Hydrazide-based additives (hydrazide compounds)) Furthermore, the water-based ink of the present invention may contain hydrazide-based additives for purposes such as improving adhesion to the substrate and room-temperature crosslinking of the resin (in the case of keto groups). Examples of hydrazide-based additives include adipic acid dihydrazide.

[0083] The aqueous flexographic ink of the present invention is preferably adjusted to a pH of 6.5 to 11.0. For pH adjustment, it is preferable to use inorganic hydroxides such as sodium hydroxide or potassium hydroxide, or the amine compounds mentioned above.

[0084] (Method of manufacturing water-based flexographic ink) The present invention relates to a method for producing aqueous flexographic ink, comprising a heat-resistant organic pigment, a binder resin, and water, with a bulk density of 0.15 g / cm³. 3 The process includes dispersing the above-mentioned heat-resistant organic pigment and binder resin.

[0085] In the above manufacturing method, the bulk density is 0.15 g / cm³. 3 Dispersing the above-mentioned heat-resistant organic pigment and binder resin results in good wettability, and tends to improve dispersion stability and leveling properties. The binder resin preferably has the acid value described above, and by controlling the ratio of the heat-resistant organic pigment to the binder resin to 35:65 to 75:25, the TI value can be adjusted to an appropriate range, tending to improve retort resistance and leveling properties. A preferred dispersion method is mill dispersion.

[0086] The specific manufacturing method is not limited to this, but for example, as described in Japanese Patent Publication No. 2020-186344, it can be manufactured by dissolving and / or dispersing (pigment dispersion) a resin and a coloring pigment, etc., in water and a specified amount of solvent. After that, an aqueous ink can be manufactured by blending additives, liquid media, etc., as needed into the obtained dispersion. As a dispersion machine used for pigment dispersion, commonly used machines such as roller mills, ball mills, pebble mills, attritors, and sand mills can be used. Among these, dispersion using a sand mill, gamma mill, or other bead mill is preferred.

[0087] (Printed material) The printed material in the present invention includes a printed layer formed by printing an aqueous flexographic ink onto a substrate 1. Specifically, it is preferable to print the above-mentioned aqueous flexographic ink onto the substrate 1 using a flexographic printing method.

[0088] (Flexographic printing method) In flexographic printing, ink is supplied directly from an ink reservoir to an anilox roller, which has a textured surface, either directly or via an ink supply pump. The ink supplied to this anilox roller is transferred to the printing plate surface through contact with the raised parts of the plate, and then finally transferred to the substrate through contact between the plate surface and the substrate, thereby forming the image and / or characters.

[0089] (Flexographic printing press) Flexographic printing presses include CI-type multi-color flexographic printing presses and unit-type multi-color flexographic printing presses. Ink supply methods include chamber type and two-roll type, and the appropriate printing press can be used.

[0090] (Flexographic version) The plates used for the above flexographic printing include photosensitive resin plates that utilize UV ​​curing with a UV light source, or elastomer material plates that use a direct laser engraving method. Regardless of the method of forming the image portion of the flexographic plate, a screen ruling of 75 lpi or higher is used. Any type of sleeve or cushioning tape can be used to attach the plate.

[0091] (Base material 1) The substrates that can be used in the present invention are not particularly limited, but plastic substrates are preferred. Examples include film-like substrates made of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polycarbonate, and polylactic acid, polystyrene-based resins such as polystyrene, AS resin, and ABS resin, nylon, polyamide, polyvinyl chloride, polyvinylidene chloride, cellophane, paper, aluminum, or composite materials thereof, as well as vapor-deposited substrates obtained by vapor-depositing inorganic compounds such as silica, alumina, or aluminum onto polyethylene terephthalate or nylon films. The thickness of the substrate film is not particularly limited.

[0092] The substrate 1 preferably has an easy-adhesion treatment on the surface to be printed (the surface in contact with the printing layer). Examples of easy-adhesion treatments include corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, and primer treatment. For example, corona discharge treatment causes hydroxyl groups, carboxyl groups, carbonyl groups, etc. to appear on the substrate. These functional groups can form hydrogen bonds with the resin in the ink if the resin has functional groups such as hydroxyl groups.

[0093] (Laminated structure) In the present invention, the laminate is preferably formed by laminating a substrate 2 onto a printed material having a printed layer formed from an aqueous flexographic ink. Specifically, an adhesive layer is provided on the printed ink surface obtained by printing an aqueous flexographic ink onto a substrate 1, and the substrate 2 is bonded (laminated) to produce the laminate. Here, the substrate 2 may be the same as or different from the substrate 1. Typical examples of lamination processes include extrusion lamination, dry lamination, and non-sol lamination. Among these, lamination by the non-sol lamination method is preferred.

[0094] (Non-sol lamination method) The non-solvent lamination method involves applying a solvent-free adhesive to the printed layer of a printed material and then laminating it by pressing it against a sealant substrate. Two-component polyol / isocyanate adhesives are the most common, with Toyo Morton's EA-N6802 / EA-N5802 being a specific example.

[0095] (Dry lamination method) The dry lamination method involves diluting an adhesive to an appropriate viscosity with an organic solvent, applying it to the printed layer of the printed material, drying it, and then pressing it against a sealant substrate to create a laminate. Two-component polyol / isocyanate adhesives are the most common, with specific examples including Toyo Morton's TM-250HV / CAT-RT86L-60 and TM-265L / CAT-RT37.

[0096] (Base material 2) Substrate 2 is the same as that of substrate 1, and may be the same or different. It is preferable that it be a thermoplastic substrate (sometimes referred to as a sealant), and unoriented polyethylene substrates, unoriented polypropylene substrates, unoriented polyester substrates, etc. are preferred. In the case of a pouch (especially a retort pouch), the thickness of substrate 2 is preferably 20 to 150 μm, and more preferably 25 to 130 μm.

[0097] (Retort resistance) Typically, packaging bags such as pouches undergo retort processing (high-temperature, moist heat (pressure) processing) after the contents are sealed for sterilization purposes. Generally, this involves placing the pouches in a special cage, immersing them in a hot water bath at a specified temperature, and removing them after a certain period of time. The retort processing temperature is often 120-140°C. Retort processing methods include hot water storage type, steam type, and hot water spray type, and are selected appropriately depending on the processing purpose. As a specific evaluation method, for example, the laminate described above is processed into a bag (cutting and heat-melting the edges to create a sealed bag). At this time, contents may be placed inside the bag depending on the purpose. The bag is placed in a hot water bath at a predetermined temperature and subjected to retort treatment for a certain period of time. The bag is removed and various resistances such as delamination (floating), colorability, discoloration, content resistance, and laminate strength are evaluated. [Examples]

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these examples unless it exceeds the essence of the invention. In the present invention, parts and % refer to parts by mass and mass %, respectively, unless otherwise noted.

[0099] (Measurement methods for various measurement parameters)

[0100] (Weight average molecular weight, number average molecular weight) The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured by GPC (gel permeation chromatography) and determined as converted molecular weights using polystyrene as a standard substance. The measurement conditions are shown below. GPC device: Showa Denko Shodex GPC-104 Columns: The following columns were used, connected in series. Two Shodex LF-404 tubes manufactured by Showa Denko. Showa Denko Shodex LF-G Detector: RI (Differential Refractometer) Measurement conditions: Column temperature 40°C Eluent: Tetrahydrofuran Flow rate: 0.3mL / min

[0101] (Hydroxyl value and acid value) The method was determined according to the method described in JIS K0070.

[0102] (Synthesis Example 1) (Synthesis of aqueous polyester polyurethane resin solution) In a reactor equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet, 150.0 parts of poly(3-methyl-1,5-pentaneadipate)diol with a number average molecular weight of 2000, 15.0 parts of polyethylene glycol with a number average molecular weight of 2000, 30.0 parts of 2,2-dimethylolbutanoic acid, and 90.0 parts of isophorone diisocyanate were reacted in 200 parts of methyl ethyl ketone for 6 hours while introducing nitrogen gas to obtain a terminal isocyanate prepolymer. After cooling to 40°C, 100 parts of acetone were added to obtain a solvent solution of the terminal isocyanate prepolymer. Next, the obtained terminal isocyanate prepolymer solution was gradually added to a mixture of 15.0 parts of 2-hydroxyethylethylenediamine and 400 parts of acetone at room temperature and reacted at 50°C for 3 hours to obtain a solvent-type polyurethane resin solution. Next, 10.8 parts of 28% aqueous ammonia and 700 parts of deionized water were gradually added to the solvent-type polyurethane resin solution to neutralize it and make it aqueous. After further removing all of the methyl ethyl ketone and acetone under azeotropic distillation, water was added to adjust the viscosity, and an aqueous polyester polyurethane resin solution with a solid content of 25% was obtained. The acid value of the obtained aqueous polyester polyurethane resin was 38 mgKOH / g, and the weight-average molecular weight was 25,000.

[0103] (Synthesis Example 2) (Synthesis of aqueous polyether polyurethane resin solution) In a reaction vessel equipped with a thermometer, stirrer, reflux condenser, stirring device, and refluxer, nitrogen gas was introduced while charging 60.0 parts polyethylene glycol with a number average molecular weight of 400, 75.0 parts polyethylene glycol with a number average molecular weight of 1000, 30.0 parts polytetramethylene glycol with a number average molecular weight of 2000, 15.0 parts 2,2-dimethylolbutanoic acid, 24.0 parts N,N-bis(2-hydroxypropyl)aniline, and 6.0 parts 1,4-cyclohexanedimethanol. The mixture was reacted at 90°C for 3 hours. Under stirring, 90.0 parts isophorone diisocyanate was added dropwise over 20 minutes, and the temperature was raised to 140°C. After cooling, the resulting water-soluble resin was neutralized by gradually adding a mixed solution of 6.5 parts 28% aqueous ammonia and deionized water dropwise to obtain an aqueous polyether polyurethane resin solution with a solid content of 20%. The resulting aqueous polyether polyurethane resin had an acid value of 19.0 mgKOH / g and a weight-average molecular weight (Mw) of 15,000.

[0104] (Synthesis Example 3) (Synthesis of aqueous acrylic urethane resin dispersion) In a reaction vessel equipped with a reflux condenser, dropping funnel, gas inlet tube, stirrer, and thermometer, 45.0 parts of PEG2000 (polyethylene glycol with a number average molecular weight of 2000), 67.5 parts of PTG2000 (polytetramethylene glycol with a number average molecular weight of 2000), 22.5 parts of 2,2-dimethylolpropionic acid, 70.0 parts of isophorone diisocyanate, 30.0 parts of methylenebis(4,1-cyclohexylene)=diisocyanate, and 500.0 parts of N-methylpyrrolidone (NMP) were charged. After adding 2.0 parts of dibutyltin dilaurate as a catalyst, the mixture was heated under a nitrogen atmosphere at 80-90°C for 6 hours. The reaction mixture was cooled to 80°C, and 11.9 parts of triethylamine were added and mixed. The reaction mixture was added to 1288 parts of water under strong stirring, and then 85.0 parts of isophoronediamine were added to obtain a urethane resin dispersion. To 350 parts of the obtained urethane resin dispersion, 3.0 parts of acrylic acid, 7.0 parts of methyl acrylate, 13.0 parts of methyl methacrylate, 7.0 parts of butyl methacrylate, and 90.0 parts of water were added, and the mixture was heated to 50°C. Next, 9.5 parts of 1% by mass aqueous ascorbic acid solution and 2.5 parts of 7% by mass aqueous butyl peroxide solution were added. After the exothermic reaction subsided, the mixture was heated at 50°C and distilled to obtain an aqueous acrylic urethane resin dispersion with a solid content of 20%. The obtained aqueous acrylic urethane resin dispersion was a core-shell type aqueous acrylic urethane resin dispersion in which the shell was a urethane resin part and the core was an acrylic resin. The acid value of the core-shell type aqueous acrylic urethane resin was 43.8 mgKOH / g, the weight-average molecular weight (Mw) was 40,000 for the shell part and 300,000 for the core part, and the mass ratio of the urethane resin part to the acrylic resin part was 7:3.

[0105] (Synthesis Example 4) (Synthesis of Water-Soluble Acrylic Resin Solution) In a reactor equipped with a stirrer, condenser, thermometer, nitrogen gas inlet tube, and dropping funnel, 1400 parts of a mixed solvent of isopropyl alcohol / ethyl acetate (= 1 / 1 (mass ratio)) was charged and heated to 75-78°C. Then, while introducing nitrogen gas, a mixture of 25 parts acrylic acid, 70 parts butyl acrylate, 130 parts methyl methacrylate, 70 parts butyl methacrylate, and 2 parts azobisisobutyronitrile (AIBN) as a polymerization initiator was added dropwise from the dropping funnel over 3 hours. After the addition was complete, polymerization was carried out at reflux temperature for 3 hours to complete the reaction. Ion-exchanged water containing 1.0 equivalent of triethylamine per carboxyl group was added, and the IPA and ethyl acetate were removed by distillation to prepare a water-soluble acrylic resin solution with a solid content of 20%. The acid value of the obtained water-soluble acrylic resin was 65.5 mg KOH / g, and the weight-average molecular weight (Mw) was 21,000.

[0106] (Synthesis Example 5) (Synthesis of Emulsion-Type Aqueous Acrylic Resin Dispersion) In a reaction vessel equipped with a stirrer, thermometer, two dropping funnels, and refluxer, 150 parts of the 20% solids aqueous acrylic resin prepared in Synthesis Example 4 were charged while nitrogen gas was introduced, and the temperature was raised to 80°C. Next, in two dropping funnels, 7 parts butyl acrylate, 13 parts methyl methacrylate, and 7 parts butyl methacrylate were added dropwise from one funnel over 2 hours. From the other funnel, 2.0 parts of a 20% aqueous solution of ammonium persulfate were added dropwise over 2 hours. After the addition was complete, the reaction was continued for a further 4 hours to obtain an emulsion-type aqueous acrylic resin dispersion. Then, the solids content of the emulsion-type aqueous acrylic resin dispersion was adjusted to 20.0% with deionized water to obtain an emulsion-type aqueous acrylic resin dispersion. The acid value of the obtained emulsion-type aqueous acrylic resin was 34.5 mgKOH / g, and the weight-average molecular weight (Mw) was 250,000.

[0107] [Example 1] (Manufacturing of water-based flexographic ink F1) 18.5 parts of heat-resistant organic pigment A1, 48.0 parts of aqueous polyester polyurethane resin solution, 23.2 parts of ion-exchanged water, 0.5 parts of surfactant [Surfinol 420, manufactured by Nisshin Chemical Industry Co., Ltd.], 0.2 parts of dihydrazide adipic acid, and 4.0 parts of 1-propanol were added and stirred with a stirrer for 10 minutes. Then, the mixture was dispersed for 10 minutes using an Eiger Mill (bead mill, manufactured by Eiger Corporation), a bead mill disperser, to obtain a pigment dispersion. To the pigment dispersion, 2.0 parts of polyolefin particles [Chemipearl W300, manufactured by Mitsui Chemicals, 40.0% solids], 0.1 parts of Tegoformex 810, 3.0 parts of propylene glycol, and 0.5 parts of 2-(dimethylamino)ethanol were added and stirred with a stirrer to obtain the target aqueous flexographic ink F1.

[0108] [Examples 2-25] (Manufacturing of water-based flexographic inks F2-F25) Water-based flexographic inks F2 to F25 were obtained in the same manner as in Example 1, except that the raw materials and mixing ratios listed in Tables 1 and 2-1 to 2-3 were changed.

[0109] [Comparative Examples 1-2] (Manufacturing of water-based flexographic inks K1-K2) Aqueous flexographic inks K1 to K2 were obtained in the same manner as in Example 1, except that the raw materials and mixing ratios listed in Tables 1 and 2-3 were changed.

[0110] (Measurement and evaluation) The aqueous flexographic inks of Examples 1-25 and Comparative Examples 1-2 described above were evaluated as follows. The evaluation results are shown in Tables 2-1 to 2-3. In Comparative Example 2, where a general organic pigment was used instead of a heat-resistant organic pigment, the bulk density of the general organic pigment used and the mass ratio of the general organic pigment used to the mass solids content of the binder resin were recorded in the cells corresponding to the bulk density of the heat-resistant organic pigment and the mass ratio of the heat-resistant organic pigment to the mass solids content of the binder resin, respectively.

[0111] (TI value) For the obtained aqueous flexographic inks F1-F25 and K1-K2, the viscosity was adjusted to 15 seconds using water in a Zaan cup #4 (manufactured by Rigosha). Under conditions of a liquid temperature of 25°C, the viscosity (mPa·s) of the aqueous flexographic inks at rotational speeds of 6 rpm and 60 rpm was measured using a B-type viscometer (TVB-10, manufactured by Toki Sangyo Co., Ltd.), and the TI value (the value obtained by dividing the viscosity at 6 rpm by the viscosity at 60 rpm) was determined.

[0112] (Printing with water-based flexographic ink F1) Water-based flexographic ink F1 was used on a flexographic plate (photosensitive resin plate, KODAK FLEXCEL NXH digital flexographic plate, plate thickness 1.14 mm, line screen count 175 lpi) and anilox roll (1200 lpi, 3 cc / m²). 2 Using a flexographic printing press (MIRAFLEX CM) equipped with the following features, a print was made on substrate 1 (polyethylene terephthalate substrate (PET) E5100, film thickness 12 μm) at a speed of 200 m / min for a distance of 30,000 m in an environment of 30°C and 10% humidity, to obtain a printed material having a printed layer formed from aqueous flexographic ink F1. The drying conditions for the ink layer were set to a drying temperature of 100°C for the intercolor dryer and 100°C for the tunnel dryer.

[0113] (Printing with water-based flexographic inks F2-F25 and K1-K2) A printed material having a printed layer formed from each ink was obtained using the same method as for printing with water-based flexographic ink F1, except that water-based flexographic ink F1 was replaced with water-based flexographic inks F2 to F25 and K1 to K2.

[0114] (Preparation of laminates and packaging bags containing a printed layer formed from water-based flexographic ink F1) A printed material having a printed layer formed from water-based flexographic ink F1 was coated with a polyisocyanate adhesive [EA-N6802 / EA-N5802] (manufactured by Toyo Morton Co., Ltd.), and a non-solvent laminating machine was used at a line speed of 50 m / min to apply CPP (manufactured by Toray Film Processing Co., Ltd.) as a sealant to the coated surface. Lamination was performed to obtain a laminate containing the printed layer formed from water-based flexographic ink F1. The laminate was then aged at 40°C for 96 hours. Next, the laminate was heat-sealed at 190°C to form a bag, obtaining a packaging bag containing a printed layer made from aqueous flexographic ink F1. The contents were water.

[0115] (Preparation of laminates and packaging bags containing printed layers formed from water-based flexographic inks F2-F25 and K1-K2) Laminates and packaging bags containing printed layers formed from each ink were obtained in the same manner as those used to produce laminates and packaging bags containing printed layers formed from the above-mentioned water-based flexographic ink F1, except that the water-based flexographic ink F1 was replaced with water-based flexographic inks F2 to F25 and K1 to K2.

[0116] (Measurement and evaluation) The aqueous flexographic inks of Examples 1-25 and Comparative Examples 1-2, as well as printed materials, laminates, and packaging bags having printed layers formed from these aqueous flexographic inks, were evaluated as follows. The evaluation results are shown in Tables 2-1 to 2-3.

[0117] (Stability over time) The aqueous flexographic inks of Examples 1-25 and Comparative Examples 1-2 were placed in 100 ml bottles, sealed, and stored at 40°C for 7 days. Their condition before and after storage was observed, and their viscosity was measured. Viscosity was determined by measuring the flow time using a Zahn cup #4. 5 (Excellent): No liquid separation or precipitation was observed, and the viscosity change was less than 3 seconds. 4 (Good): There is some liquid separation, but no precipitation, and the viscosity change is between 3 seconds and 5 seconds. 3 (Acceptable): Slight liquid separation and precipitation are observed, and the viscosity change is between 5 seconds and less than 10 seconds. 2 (Unacceptable): Some liquid separation and precipitation are observed, and the viscosity change is between 10 seconds and less than 20 seconds. 1 (Poor): Severe liquid separation and precipitation are observed, and viscosity changes occur for 20 seconds or more. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0118] (color density) For printed materials having printed layers formed from each of the aqueous flexographic inks of Examples 1 to 25 and Comparative Examples 1 to 2, the print density of the solid areas (100% halftone areas) in the printed area was measured using an X-RiteeXact (density status: ISO status E, whiteness standard: absolute value, filter: none, illuminant / observer field of view: D50 / 2°) manufactured by X-Rite Corporation after printing 2000 m at a printing speed of 200 m / min. 5 (Excellent): The print density in solid areas is 1.6 or higher for yellow ink, 1.7 or higher for red ink, 1.8 or higher for cyan ink, 1.9 or higher for black ink, 1.2 or higher for vermilion ink, 1.3 or higher for green ink, and 1.4 or higher for purple ink. 4 (Good): The print density in solid areas is as follows: Yellow ink: 1.5 or more and less than 1.6; Red ink: 1.6 or more and less than 1.7; Cyan ink: 1.7 or more and less than 1.8; Black ink: 1.8 or more and less than 1.9; Vermilion ink: 1.1 or more and less than 1.2; Grass green ink: 1.2 or more and less than 1.3; Purple ink: 1.3 or more and less than 1.4 3 (OK): The print density in solid areas is as follows: Yellow ink: 1.0 or more and less than 1.5; Red ink: 1.4 or more and less than 1.6; Cyan ink: 1.5 or more and less than 1.7; Black ink: 1.6 or more and less than 1.8; Vermilion ink: 0.9 or more and less than 1.1; Grass green ink: 1.0 or more and less than 1.2; Purple ink: 1.1 or more and less than 1.3 2 (Not allowed): The print density in solid areas must be between 0.8 and less than 1.0 for yellow ink, 1.2 and less than 1.4 for red ink, 1.3 and less than 1.5 for cyan ink, 1.4 and less than 1.6 for black ink, 0.7 and less than 0.9 for vermilion ink, 0.8 and less than 1.0 for green ink, and 0.9 and less than 1.1 for purple ink. 1 (Inferior): Print density in solid areas is less than 0.8 for yellow ink, less than 1.2 for red ink, less than 1.3 for cyan ink, less than 1.4 for black ink, less than 0.7 for vermilion ink, less than 0.8 for green ink, and less than 0.9 for violet ink. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0119] [Leveling ability] For printed materials having printed layers formed from each of the aqueous flexographic inks of Examples 1-25 and Comparative Examples 1-2, the leveling properties were evaluated by visually checking for density unevenness and the presence or absence of pinholes in the solid areas (100% halftone areas). The evaluation criteria are as follows. 5 (Excellent): There is no unevenness in concentration in the solid areas, no pinholes, and a uniform film is formed. 4 (Good): There is some slight unevenness in density in the solid areas, but no pinholes are present. 3 (Acceptable): Slight unevenness in density and pinholes are visible in the solid areas. 2 (Unacceptable): Contrast in density or pinholes are noticeable in solid areas. 1 (Poor): Consistent unevenness in density and pinholes are noticeable in solid areas. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0120] (Retort strength, fade resistance) Packaging bags made from laminates having printed layers formed from each of the aqueous flexographic inks of Examples 1 to 25 and Comparative Examples 1 to 2 were subjected to a retort test at 120°C for 80 minutes. The appearance of the packaging bags immediately after retorting was checked, and the fade resistance was evaluated. 5 (Excellent): No discoloration was observed before or after retort processing. 4 (Good): Almost no discoloration is observed before and after retort processing. 3 (Acceptable): Little discoloration is observed before and after retort processing. 2 (Not acceptable): Discoloration is observed before and after retorting. 1 (Poor): Significant discoloration is observed before and after retorting. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0121] (Lamination strength after retort processing) Packaging bags made from laminates having printed layers formed from each of the aqueous flexographic inks of Examples 1-25 and Comparative Examples 1-2 were subjected to a retort test at 120°C for 80 minutes, and the laminate strength immediately after retorting was compared with the laminate strength before the retort test. For laminate strength, the laminate was cut to a width of 15 mm, the printed layer and the substrate 2 were separated, and then evaluated using an Intesco 201 universal tensile tester under conditions of a speed of 300 mm / min and an angle of 90°. 5 (Excellent): No decrease in laminate strength was observed before and after retorting, and the laminate strength after retorting was 2.0 N / 15 mm or higher. 4 (Good): Lamination strength reduction of less than 0.5 N / 15 mm before and after retorting is observed, and the lamination strength after retorting is 2.0 N / 15 mm or higher. 3 (Acceptable): Lamination strength decreases by 1.0 N / 15 mm or more before and after retorting, and the laminate strength after retorting is 1.5 N / 15 mm or more but less than 2.0 N / 15 mm. 2 (Not acceptable): Lamination strength decreases by 1.0 N / 15 mm or more before and after retorting, and the laminate strength after retorting is between 1.0 N / 15 mm and 1.5 N / 15 mm. 1 (Poor): Lamination strength decreases by 1.0 N / 15 mm or more before and after retorting, and the lamination strength after retorting is less than 1.0 N / 15 mm. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0122] [Table 1]

[0123] [Table 2-1]

[0124] [Table 2-2]

[0125] [Table 2-3]

[0126] The bulk density of the heat-resistant organic pigment is 0.15 g / cm³. 3 Comparative Example 1, which did not meet the above requirements, and Comparative Example 2, which did not contain a heat-resistant organic pigment, failed to achieve any of the following performance characteristics: stability over time, color density, leveling properties, or retort resistance. In contrast, the comparative example containing a heat-resistant organic pigment, a binder resin, and water, with a bulk density of 0.15 g / cm³ of the heat-resistant organic pigment, was successful. 3 Examples 1 to 25 described above all demonstrated performance at or above a level that poses no practical problems in terms of long-term stability, color density, leveling properties, and retort resistance. In other words, it has been demonstrated that the present invention makes it possible to provide a water-based flexographic ink that solves all the problems.

Claims

1. It contains a heat-resistant organic pigment, a binder resin, and water, and the bulk density of the heat-resistant organic pigment is 0.15 g / cm³. ３ That's all for water-based flexographic ink.

2. A water-based flexographic ink according to claim 1, which is resistant to retort processing.

3. The aqueous flexographic ink according to claim 1, wherein the thixotropic index (TI value) is 4 or less.

4. The aqueous flexographic ink according to claim 1, wherein the mass ratio of the mass solids of the heat-resistant organic pigment to the mass solids of the binder resin in the total solids of the aqueous flexographic ink is 35:65 to 75:

25.

5. The aqueous flexographic ink according to claim 1, wherein the content of heat-resistant organic pigment in the total mass of the aqueous flexographic ink is 10 to 30% by mass.

6. The aqueous flexographic ink according to claim 1, wherein the binder resin comprises at least one selected from the group consisting of aqueous urethane resin, aqueous acrylic resin, and aqueous urethane acrylic resin.

7. The heat-resistant organic pigment is C.I. I. Pigment Yellow 83,C. I. Pigment Yellow 180,C. I. Pigment Red 146,C. I. Pigment Red 166,C. I. Pigment Red 185,C. I. Pigment Blue 15:3, C. I. Pigment Black 7, C. I. Pigment Orange 34,C. I. Pigment Orange 64, C. I. Pigment Green 7, and C.I. I. The aqueous flexographic ink according to claim 1, comprising at least one selected from the group consisting of Pigment Violet 23.

8. A printed article having a printed layer formed from the aqueous flexographic ink described in claim 1 on a substrate 1.

9. A laminate comprising a substrate 1, a printed layer formed from the aqueous flexographic ink described in claim 1, and a substrate 2 in sequence.

10. A method for producing an aqueous flexographic ink containing a heat-resistant organic pigment, a binder resin, and water, The process includes a step of mixing and dispersing the heat-resistant organic pigment and the binder resin, The bulk density of the heat-resistant organic pigment is 0.15 g / cm³. ３ The above describes the method for manufacturing water-based flexographic ink.

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